This PDF file contains the front matter associated with SPIE Proceedings Volume 10448, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

One of the major developments in optics industry recently is the commercial manufacturing of freeform surfaces for optical mid- and high performance systems. The loss of limitation on rotational symmetry enables completely new optical design solutions – but causes completely new challenges for the manufacturer too. Adapting the serial production from radial-symmetric to freeform optics cannot be done just by the extension of machine capabilities and software for every process step. New solutions for conventional optics productions or completely new process chains are necessary.

A groundbreaking new approach [1] for the fabrication of complex photonic systems, especially such with off-axis optics, has been invented based on planar mounting in combination with a novel folding approach.

Up to now volume production of photonic systems has been optimized for on-axis lens based optical systems. Chromatic aberration limits the usage or spectral range of these systems. Applying mirrors instead of lenses may help to suppress chromatic aberrations and wavelength depending absorption. The assembly of reflective optics, often in an off-axis configuration, is a complex process. So far most tools for volume production apply stacking of components in planar technology. Off-axis systems are typically assembled by more or less manually alignment of the components, which is not in favor for mass and low cost production of these systems.

The novel approach utilizers a planar substrate featuring preprocessed bending lines. A high accuracy tool for planar assembly places the components onto the substrate. Then the sides of the substrate are bent leading to a predefined three dimensional body. The off-axis optical path inside is generated automatically.

This concept is not limited to rectangular shapes but can also be applied to more complex systems, for example the so called “W-configuration” for a Czerny-Turner spectrometer.

First tests of the “bend and place assembly” have been performed successfully on a camera setup to prove the working principle.

The surface figure control of the conventional annular polishing system is realized ordinarily by the interaction between the conditioner and the lap. The surface profile of the pitch lap corrected by the marble conditioner has been measured and analyzed as a function of kinematics, loading conditions, and polishing time. The surface profile measuring equipment of the large lap based on laser alignment was developed with the accuracy of about 1μm. The conditioning mechanism of the conditioner is simply determined by the kinematics and fully fitting principle, but the unexpected surface profile deviation of the lap emerged frequently due to numerous influencing factors including the geometrical relationship, the pressure distribution at the conditioner/lap interface. Both factors are quantitatively evaluated and described, and have been combined to develop a spatial and temporal model to simulate the surface profile evolution of pitch lap. The simulations are consistent with the experiments. This study is an important step toward deterministic full-aperture annular polishing, providing a beneficial guidance for the surface profile correction of the pitch lap.

The APS 3D system performs polishing and form correction in one step in order to reduce overall process time, reduce the number of polishing steps required and eliminate the need for highly skilled operators while providing a repeatable polishing process. This new 3D Polishing system yields better surface quality, and a better slope error, automatically determining the optimum speeds, feed rates and polish pressures to achieve a deterministic process based on the required quality parameters input by the operator. The process flow is always the same to ensure consistent quality and target quality values are defined before polishing begins.

Many optical system designs rely on high numerical aperture (NA) optics, including lithography and defense systems. Lithography systems require high-NA optics to image the fine patterns from a photomask, and many defense systems require the use of domes. The methods for manufacturing such optics with large half angles have often been treated as proprietary by most manufacturers due to the challenges involved. In the past, many high-NA concave surfaces could not be polished by magnetorheological finishing (MRF) due to collisions with the hardware underneath the polishing head. By leveraging concepts that were developed to enable freeform raster MRF capabilities, QED Technologies has implemented a novel toolpath to facilitate a new high-NA rotational MRF mode. This concept involves the use of the B-axis (rotational axis) in combination with a “virtual-axis” that utilizes the geometry of the polishing head. Hardware collisions that previously restricted the concave half angle limit can now be avoided and the new functionality has been seamlessly integrated into the software. This new MRF mode overcomes past limitations for polishing concave surfaces to now accommodate full concave hemispheres as well as extend the capabilities for full convex hemispheres. We discuss some of the previous limitations, and demonstrate the extended capabilities using this novel toolpath. Polishing results are used to qualify the new toolpath to ensure similar results to the “standard” rotational MRF mode.

Hard ceramic optical materials such as sapphire, ALON, Spinel, PCA, or Silicon Carbide can present a significant challenge in manufacturing precision optical components due to their tough mechanical properties. These are also the same mechanical properties that make them desirable materials when used in harsh environments. Slow processing speeds, premature tool wear, and poor surface quality are common results of the tough mechanical properties of these materials. Often, as a preparatory stage for polishing, the finish of the ground surface greatly influences the polishing process and the resulting finished product. To overcome these challenges, OptiPro Systems has developed an ultrasonic assisted grinding technology, OptiSonic, which has been designed for the precision optics and ceramics industry. OptiSonic utilizes a custom tool holder designed to produce oscillations, in microns of amplitude, in line with the rotating spindle. A software package, IntelliSonic, is integral to the function of this platform. IntelliSonic can automatically characterize tooling during setup to identify and select the ideal resonant peak which to operate at. Then, while grinding, IntelliSonic continuously adjusts the output frequency for optimal grinding efficiency while in contact with the part. This helps maintain a highly consistent process under changing load conditions for a more precise surface. Utilizing a variety of instruments, tests have proven to show a reduction in force between tool and part by up to 50%, while increasing the surface quality and reducing tool wear. This paper will present the challenges associated with these materials and solutions created to overcome them.

The fabrication of small size aspheric optical surface, which made of hard brittle materials, usually uses optical cold processing. However, it is difficult to achieve the ideal requirements of the surface accuracy and roughness. In order to solve this problem, the masked ion beam figuring method is used to etch the one-dimension structure on the plat surface which made of hard brittle material. The results show that the expected surface profile is acquired and meanwhile mainly kept the original roughness and mid-frequency. It provides a possible way for fabricating small size aspheric optics which made of hard brittle materials.

The production of complex glass components with 2.5D or 3D-structures involves great effort and the need for advanced CNC-technology. Especially the final surface treatment, for generation of transparent surfaces, represents a timeconsuming and costly process. The ultrasonic-assisted grinding procedure is used to generate arbitrary shaped components and freeform-surfaces. The special kinematic principle, containing a high-frequency tool oscillation, enables efficient manufacturing processes. Surfaces produced in this way allow for application of novel smoothing methods, providing considerable advantages compared to classic polishing. It is shown, that manufacturing of transparent glass surfaces with low roughness down to R_q = 10 nm is possible, using an ultra-fine grinding process. By adding a CO₂-laser polishing process, roughness can be reduced even further with a very short polishing time.

Sample finishing data from a broad range of materials — glasses, sapphire, silicon carbide, silicon, zirconium oxide, lithium tantalate, and flooring materials — are shown effectively processed with Trizact™ Diamond Tile (TDT). This data should provide the reader with an understanding of what to expect when using TDT on hard to grind or brittle materials. Keys to maintaining effective TDT pad wear rates, and therefore cost effect and stable processes, are described as managing 1) the proper lubricant flow rate for glasses and silicon-type materials and 2) the conditioning particle concentration for harder-to-grind materials

We have selected and characterized 2 cerium oxide slurries. We have then modified their pH to polish fused silica samples. The material removal rate, roughness, surface defects density and morphology have been observed as a function of pH. We noticed that while roughness and surface defect density don’t seem to be very affected by slurry pH, the latter has an influence on material removal rate and width of the scratches generated during polishing.

This paper describes the manufacturing steps necessary to manufacture hemispherical concave aspheric mirrors for high- NA systems. The process chain is considered from generation to final figuring and includes metrology testing during the various manufacturing steps. Corning Incorporated has developed this process by taking advantage of recent advances in commercially available Satisloh and QED Technologies equipment. Results are presented on a 100 mm concave radius nearly hemispherical (NA = 0.94) fused silica sphere with a better than 5 nm RMS figure. Part interferometric metrology was obtained on a QED stitching interferometer. Final figure was made possible by the implementation of a high-NA rotational MRF mode recently developed by QED Technologies which is used at Corning Incorporated for production. We also present results from a 75 mm concave radius (NA = 0.88) Corning ULE sphere that was produced using sub-aperture tools from generation to final figuring. This part demonstrates the production chain from blank to finished optics for high-NA concave asphere.

Aspherical lenses offer advantages over spherical optics by improving image quality or reducing the number of elements necessary in an optical system. Aspheres are no longer being used exclusively by high-end optical systems but are now replacing spherical optics in many applications. The need for a method of production-manufacturing of precision aspheres has emerged and is part of the reason that the optics industry is shifting away from artisan-based techniques towards more deterministic methods. Not only does Magnetorheological Finishing (MRF) empower deterministic figure correction for the most demanding aspheres but it also enables deterministic and efficient throughput for series production of aspheres. The Q-flex MRF platform is designed to support batch production in a simple and user friendly manner. Thorlabs routinely utilizes the advancements of this platform and has provided results from using MRF to finish a batch of aspheres as a case study. We have developed an analysis notebook to evaluate necessary specifications for implementing quality control metrics. MRF brings confidence to optical manufacturing by ensuring high throughput for batch processing of aspheres.

Improvements to sensing hardware and image processing for airborne optical systems have inspired designers to propose new optics and windows which may be any of: more precise, conformal/freeform and multi-functional. Manufacture of these optics has required innovations in machining, polishing and metrology. The performance requirements and manufacturing methods demand more from conventional optical materials, while also driving development of new formulations with tailored optical and mechanical properties. We describe innovations in manufacturing and adaptations for optical materials selected for end-use performance, though some such materials may present unusual challenges related to their composition, how they are produced, and/or the design geometry. Our desire is to share some observations with the optical designer, who may be able to incorporate some tips into parts “designed for manufacture.”

Optical system designers are well-versed in optimizing the performance of a system. The impact of the optical and optomechanical assembly, however, poses a significant challenge to attaining the modelled performance in practice. The system engineers are tasked with designing tooling, fixtures and procedures that minimize such impacts, employing well known modeling and analysis techniques. Despite these efforts the resulting system performance often exhibits errors that can be directly related to the assembly process.

In the face of lost system performance, the optical designer can compensate with more stringent component and alignment specifications. Alternatively, at the risk of a more complex design, she can consider active compensation, or the addition of compensation components. Yet another path is correcting the components after assembly to regain the original optical performance.

MRF is well known for its ability to produce state of the art optical components, lenses, mirrors, etc. In this paper we will explore and demonstrate its application to correcting errors induced by various assembly techniques by reviewing several examples, their respective challenges and the results of the post assembly corrections.

For modern production of micro lens systems, such as cementing of doublets or more lenses, precise centering of the lens edge is crucial. Blocking the lens temporarily on a centering arbor ensures that the centers of all optical lens surfaces coincide with the lens edge, while the arbor’s axis serves as reference for both alignment and edging process.

This theoretical assumption of the traditional cementing technology is not applicable for high-end production. In reality cement wedges between the bottom lens surface and the arbor’s ring knife edge may occur and even expensive arbors with single-micron precision suffer from reduced quality of the ring knife edge after multiple usages and cleaning cycles. Consequently, at least the position of the bottom lens surface is undefined and the optical axis does not coincide with the arbor’s reference axis!

In order to overcome this basic problem in using centering arbors, we present a novel and efficient technique which can measure and align both surfaces of a lens with respect to the arbor axis with high accuracy and furthermore align additional lenses to the optical axis of the bottom lens. This is accomplished by aligning the lens without mechanical contact to the arbor. Thus the lens can be positioned in four degrees of freedom, while the centration errors of all lens surfaces are measured and considered. Additionally the arbor’s reference axis is not assumed to be aligned to the rotation axis, but simultaneously measured with high precision.

Additive manufacturing of optical elements is known but still new to the field of optical fabrication. In 3D printers, the parts are deposited layer-by-layer approximating the shape defined in optics design enabling new shapes, which cannot be manufactured using conventional methods. However, the layered structure also causes surface roughness and subsurface scattering, which decrease the quality of optical elements. Illuminating a flat sample with a laser beam, different light distributions are generated on a screen depending on the printing orientation of the sample. Whereas the laser beam is mainly diffused by the samples, a line shaped light distribution can be achieved for a special case in which the laser light goes parallel to the layer structure. These optical effects of 3D printed parts are analyzed using a goniometric setup and fed back into the optics simulation with the goal to improve the design considering the characteristics of the real sample. For a detailed look on the effect, the total scattering is split up into surface contributions and subsurface scattering using index matching techniques to isolate the effects from each other. For an index matched sample with negligible surface effects the line shaped distribution turns into a diffraction pattern which corresponds to the layer thickness of the printer. Finally, an optic simulation with the scattering data is set up for a simple curved sample. The light distribution measured with a robot-based goniophotometer differs from the simulation, because the curvature is approximated by the layer structure. This makes additional analysis necessary.

Additive manufacturing, or 3D printing, has become widely used in recent years for the creation of both prototype and end-use parts. Because the parts are created in a layer-by-layer manner, the flexibility of additive manufacturing is unparalleled and has opened the design space to enable features like undercuts and internal channels which cannot exist on traditional, subtractively manufactured parts. This flexibility can also be leveraged for optical applications. This paper outlines some of the current uses of 3D printing in the optical manufacturing process at Optimax. Several materials and additive technologies are utilized, including polymer printing through fused deposition modeling, which creates parts by depositing a softened thermoplastic filament in a layerwise fashion. Stereolithography, which uses light to cure layers of a photopolymer resin, will also be discussed. These technologies are used to manufacture functional prototypes, fixtures, sealed housings, and other components. Additionally, metal printing through selective laser melting, which uses a laser to melt metal powder layers into a dense solid, will be discussed due to the potential to manufacture thermally stable opticalmechanical assembly frameworks and functional optics. Examples of several additively manufactured optical components will be shown.

A standard way of tolerancing optical elements or systems is to perform a Monte Carlo based analysis within a common optical design software package. Although, different weightings and distributions are assumed they are all counting on statistics, which usually means several hundreds or thousands of systems for reliable results. Thus, employing these methods for small batch sizes is unreliable, especially when aspheric surfaces are involved. The huge database of asphericon was used to investigate the correlation between the given tolerance values and measured data sets. The resulting probability distributions of these measured data were analyzed aiming for a robust optical tolerancing process.

Manufactured system performance analysis routines are built into several optical design software programs. These programs have limited abilities to change the probability distribution function of the tolerances. At Corning Incorporated, Advanced Optics, in-house analysis software is used which allows the distribution function of different tolerances to be customized. These simulation tools are capable of accurately modeling the distribution functions from the internal optical fabrication capabilities of Corning. This case study demonstrates the change in performance outcomes due to distribution functions and the importance of knowing the manufacturing distribution functions of the optical fabrication house used.

Optical systems must perform under environmental conditions including thermal and mechanical loading. To predict the performance in the field, integrated analysis combining optical and mechanical software is required. Freeform and conformal optics offer many new opportunities for optical design. The unconventional geometries can lead to unconventional, and therefore unintuitive, mechanical behavior. Finite element (FE) analysis offers the ability to predict the deformations of freeform optics under various environments and load conditions. To understand the impact on optical performance, the deformations must be brought into optical analysis codes. This paper discusses several issues related to the integrated optomechanical analysis of freeform optics.

The Twyman effect refers to the fact that, when a thin optical plate has one side ground, the plate bends with the ground side becoming convex, i.e. as if the ground side is in a residual compressive stress. Such deformation often shows up as “power” on form measurements of the other (usually polished) plate surface. For thin flat optics, Twyman effects become important at aspect ratios of 1:25 or thinner. In this case, the optic bends throughout its surface with a constant curvature, i.e. bending extends over the whole surface. Here we discuss Twyman effects for mildly or highly curved thin axisymmetric optics such as cylinders, spheres, and shallow lenses or mirrors. We also outline extensions to more complex geometries, such as ogives. We show that the deformation in thin curved optics is significantly different from flat plates: In curved optics, deformation consists of a simple stretching contribution, valid over the largest portion of the optic, plus a complex, spatially-dependent bending contribution in a boundary layer, valid near the free edges of the optic.

Ultra-precision diamond turning enables the manufacturing of parts with mirror-like surfaces and highest form accuracies out of non-ferrous, a few crystalline and plastic materials. Furthermore, an ultrasonic assistance has the ability to push these boundaries and enables the machining of materials like steel, which is not possible in a conventional way due to the excessive tool wear caused by the affinity of carbon to iron.

Usually monocrystalline diamonds tools are applied due to their unsurpassed cutting edge properties. New cutting tool material developments have shown that it is possible to produce tools made of nano-polycrystalline diamonds with cutting edges equivalent to monocrystalline diamonds. In nano-polycrystalline diamonds ultra-fine grains of a few tens of nanometers are firmly and directly bonded together creating an unisotropic structure. The properties of this material are described to be isotropic, harder and tougher than those of the monocrystalline diamonds, which are unisotropic. This publication will present machining results from the newest investigations of the process potential of this new polycrystalline cutting material.

In order to provide a baseline with which to characterize the cutting material cutting experiments on different conventional machinable materials like Cooper or Aluminum are performed. The results provide information on the roughness and the topography of the surface focusing on the comparison to the results while machining with monocrystalline diamond. Furthermore, the cutting material is tested in machining steel with ultrasonic assistance with a focus on tool life time and surface roughness. An outlook on the machinability of other materials will be given.

A wide range of materials including metals and alloys, ceramics, glasses, semiconductors and composites are manufactured to meet service requirements to a given geometry, accuracy, finish and surface integrity. Metals and alloys in general are easier to machine because of their high fracture toughness, low hardness, non-directional bonding, low porosity, large strain to fracture and high impact energy. Non-metals, on the other hand, such as ceramics, semiconductors and optical crystals are characterized by covalent or ionic bonding, limited slip systems for plastic deformation, high hardness and low fracture toughness. It is due to these major differences that ceramics, semiconductors and optical crystals are considered more challenging to machine.

The need for increasingly complex optics and the demand for freeform optics with ultra-high precision specifications is growing rapidly for numerous applications. Achieving the required accuracies in freeform manufacturing still demands very long machining times, high production costs, a need for experienced, highly skilled operators as well as numerous manual interventions, tying up valuable resources while machining a small number of parts. By utilizing fully integrated optical measurement features, high accuracy long stroke fast tool, an advanced software package with built in tool path calculation and analysis as well as corrective machining functions the UPC 300 eliminates these burdens.

Recently, freeform surface widely using to the optical system; because it is have advance of optical image and freedom available to improve the optical performance. For freeform optical fabrication by integrating freeform optical design, precision freeform manufacture, metrology freeform optics and freeform compensate method, to modify the form deviation of surface, due to production process of freeform lens ,compared and provides more flexibilities and better performance. This paper focuses on the fabrication and correction of the free-form surface. In this study, optical freeform surface using multi-axis ultra-precision manufacturing could be upgrading the quality of freeform. It is a machine equipped with a positioning C-axis and has the CXZ machining function which is also called slow tool servo (STS) function. The freeform compensate method of Zernike polynomials results successfully verified; it is correction the form deviation of freeform surface. Finally, the freeform surface are measured experimentally by Ultrahigh Accurate 3D Profilometer (UA3P), compensate the freeform form error with Zernike polynomial fitting to improve the form accuracy of freeform.

Atmospheric Plasma Jet Machining is a non-conventional deterministic sub-aperture surface processing technique that employs a local chemical etching process for material removal. It was shown to have great technological potential for the manufacturing and correction of precision optical surfaces made preferably from fused silica, ULE(R), silicon, or silicon carbide. A plasma based processing chain suitable for freeform generation or surface correction comprises high-rate plasma etching for freeform generation (removal rate 1-30 mm³/min), bonnet polishing for smoothing, plasma fine correction (removal rate 0.01-1 mm³/min) to achieve minimal surface figure error and a post-polishing step utilizing a soft tool. Since plasma jets are not only a source of reactive species but also of heat, the chemical reaction during processing depends on the resulting local surface temperature distribution. A coupled model involving finite elements for temperature field analysis and sophisticated dwell time calculation algorithms has been developed to simulate the complex interplay of surface heating and material removal. With it, the convergence of the etching process is significantly increased. Sub-aperture polishing on freeforms suffers from inhomogeneities in material removal depending on local surface curvatures. An analytical approach has been chosen to estimate the material removal during polishing and appropriate measures have been undertaken to preserve the plasma-generated surface shape. By combination of the processing steps and applying the theoretical modeling fast and efficient precision freeform manufacturing aiming at residual errors of less than 30 nm PV becomes possible.

Recently, the desire to use freeform optics has been increasing. Freeform optics can be used to expand the capabilities of optical systems and reduce the number of optics needed in an assembly. The traits that increase optical performance also present challenges in manufacturing. As tolerances on freeform optics become more stringent, it is necessary to continue to improve methods for how the grinding and polishing processes interact with metrology.

To create these complex shapes, OptiPro has developed a computer aided manufacturing package called PROSurf. PROSurf generates tool paths required for grinding and polishing freeform optics with multiple axes of motion. It also uses metrology feedback for deterministic corrections. ProSurf handles 2 key aspects of the manufacturing process that most other CAM systems struggle with. The first is having the ability to support several input types (equations, CAD models, point clouds) and still be able to create a uniform high-density surface map useable for generating a smooth tool path. The second is to improve the accuracy of mapping a metrology file to the part surface. To perform this OptiPro is using 3D error maps instead of traditional 2D maps. The metrology error map drives the tool path adjustment applied during processing. For grinding, the error map adjusts the tool position to compensate for repeatable system error. For polishing, the error map drives the relative dwell times of the tool across the part surface. This paper will present the challenges associated with these issues and solutions that we have created.

To use its proven abilities in gradient based surface measurement of aspherical lenses in transmission, we adapted the principle of experimental ray tracing (ERT) to measure the gradient field of specular freeform surfaces. In this work we present a new application for ERT and propose a setup for this application.

Using gradient based measurements improves the efficiency of the used channel capacity of a measurement. Also, the measurement can be performed relatively and has not to be performed absolutely. This leads to a higher accuracy of the measurements compared to direct height measurements. Additionally, most of the common measurement techniques are using lenses. These lenses may introduce deviations to the results that cannot be traced back to its source.

In this work, we propose a new measurement technique to measure freeform optics without any optical component between the device under test (DUT) and the measuring sensor. For this, we introduce a narrow laser beam under a certain angle into the measurement system. After being reflected from the freeform surface, the direction and the position of the ray on the sensor are detected. By moving the DUT, the whole surface is investigated. From knowledge about the direction of the beam introduced into the measurement system and the directions of the reflected beams for the known surface positions, the gradient field of the surface is determined. Common surface reconstruction methods can be applied to these data.

Recently the use of freeform surfaces have become a realization for optical designers. These non-symmetrical optical surfaces have allowed unique solutions to optical design problems. The implementation of freeform optical surfaces has been limited by manufacturing capabilities and quality. However over the past several years freeform fabrication processes have improved in capability and precision. But as with any manufacturing, proper metrology is required to monitor and verify the process. Typical optics metrology such as interferometry has its challenges and limitations with the unique shapes of freeform optics. Two contact metrology methods for freeform metrology are presented; a Leitz coordinate measurement machine (CMM) with an uncertainty of ± 0.5 μm and a high resolution profilometer (Panasonic UA3P) with a measurement uncertainty of ± 0.05 μm. We are also developing a non-contact high resolution technique based on the fringe reflection technique known as deflectometry. This fast non-contact metrology has the potential to compete with accuracies of the contact methods but also can acquire data in seconds rather than minutes or hours.

Recent advances in polishing and metrology have addressed many of the challenges in the fabrication and metrology of freeform surfaces, and the manufacture of these surfaces is possible today. However, achieving the form and mid-spatial frequency (MSF) specifications that are typical of visible imaging systems remains a challenge. Interferometric metrology for freeform surfaces is thus highly desirable for such applications, but the capability is currently quite limited for freeforms. In this paper, we provide preliminary results that demonstrate accurate, high-resolution measurements of freeform surfaces using prototype software on QED’s ASI™ (Aspheric Stitching Interferometer).

Testing micro optics, i.e. lenses with dimensions down to 0.1mm and less, with high precision requires a dedicated design of the testing device, taking into account propagation and wave-optical effects. In this paper, we discuss testing methods based on Shack-Hartmann wavefront technology for functional testing in transmission and for the measurement of surface shape in reflection. As a first example of more conventional optics testing, i.e. optics in the millimeter range, we present the measurement of binoculars in transmission, and discuss the measured wave aberrations and imaging quality. By repeating the measurement at different wavelengths, information on chromatic effects is retrieved. A task that is often tackled using Shack-Hartman wavefront sensors is the alignment of collimation optics in front of a light source. In case of a micro-optical collimation unit with a 1/e² beam diameter of ca. 1mm, we need adapted relay optics for suitable beam expansion and well-defined imaging conditions. In this example, we will discuss the alignment process and effects of the relay optics magnification, as well as typical performance data. Oftentimes, micro optics are fabricated not as single pieces, but as mass optics, e.g. by lithographic processes. Thus, in order to reduce tooling and alignment time, an automated test procedure is necessary. We present an approach for the automated testing of wafer- or tray-based micro optics, and discuss transmission and reflection measurement capabilities. Exemplary performance data is shown for a sample type with 30 microns in diameter, where typical repeatabilities of a few nanometers (rms) are reached.

Aspheric surfaces can provide substantial improvements to optical designs, but they can also be difficult to manufacture cost-effectively. Asphere metrology contributes significantly to this difficulty, especially for high-precision aspheric surfaces. With the advent of computer-controlled fabrication machinery, optical surface quality is chiefly limited by the ability to measure it. Consequently, understanding the uncertainty of surface measurements is of great importance for determining what optical surface quality can be achieved.

We measured sample aspheres using multiple techniques: profilometry, null interferometry, and subaperture stitching. We also obtained repeatability and reproducibility (R&R) measurement data by retesting the same aspheres under various conditions. We highlight some of the details associated with the different measurement techniques, especially efforts to reduce bias in the null tests via calibration. We compare and contrast the measurement results, and obtain an empirical view of the measurement uncertainty of the different techniques. We found fair agreement in overall surface form among the methods, but meaningful differences in reproducibility and mid-spatial frequency performance.

Advancements in optical manufacturing technology allow optical designers to implement steep aspheric or high departure surfaces into their systems. Measuring these surfaces with profilometers or CMMs can be difficult due to large surface slopes or sharp steps in the surface. OptiPro has developed UltraSurf to qualify the form and figure of steep aspheric and diffractive optics. UltraSurf is a computer controlled, non-contact coordinate measuring machine. It incorporates five air-bearing axes, linear motors, high-resolution feedback, and a non-contact probe. The measuring probe is scanned over the optical surface while maintaining perpendicularity and a constant focal offset. Multiple probe technologies are available on UltraSurf. Each probe has strengths and weaknesses relative to the material properties, surface finish, and figure error of an optical component. The measuring probes utilize absolute distance to resolve step heights and diffractive surface patterns. The non-contact scanning method avoids common pitfalls with stylus contact instruments. Advancements in measuring speed and precision has enabled fast and accurate non-contact metrology of diffractive and steep aspheric surfaces. The benefits of data sampling with twodimensional profiles and three-dimensional topography maps will be presented. In addition, accuracy, repeatability, and machine qualification will be discussed with regards to aspheres and diffractive surfaces.

Conventional interferometry is widely used to measure spherical and at surfaces with nanometer level precision but is plagued by back reflections. We describe a new method of isolating the measurement surface by controlling spectral properties of the source (Spectrally Controlled Interferometry - SCI). Using spectral modulation of the interferometer's source enables formation of localized fringes where the optical path difference is non-zero. As a consequence it becomes possible to form white-light like fringes in common path interferometers, such as the Fizeau. The proposed setup does not require mechanical phase shifting, resulting in simpler instruments and the ability to upgrade existing interferometers. Furthermore, it allows absolute measurement of distance, including radius of curvature of lenses in a single setup with possibility of improving the throughput and removing some modes of failure.

In Advanced Optical Instrumentation, Aspherics provide an effective performance alternative. The aspheric fabrication and surface metrology, followed by aspheric design are complementary iterative processes for Precision Aspheric development. As in fabrication, a holistic approach of aspheric surface characterization is adopted to evaluate actual surface error and to aim at the deliverance of aspheric optics with desired surface quality. Precision optical surfaces are characterized by profilometry or by interferometry. Aspheric profiles are characterized by contact profilometers, through linear surface scans to analyze their Form, Figure and Finish errors. One must ensure that, the surface characterization procedure does not add to the resident profile errors (generated during the aspheric surface fabrication). This presentation examines the errors introduced post-surface generation and during profilometry of aspheric profiles. This effort is to identify sources of errors and is to optimize the metrology process. The sources of error during profilometry may be due to: profilometer settings, work-piece placement on the profilometer stage, selection of zenith/nadir points of aspheric profiles, metrology protocols, clear aperture – diameter analysis, computational limitations of the profiler and the software issues etc. At OPTICA, a PGI 1200 FTS contact profilometer (Taylor-Hobson make) is used for this study. Precision Optics of various profiles are studied, with due attention to possible sources of errors during characterization, with multi-directional scan approach for uniformity and repeatability of error estimation. This study provides an insight of aspheric surface characterization and helps in optimal aspheric surface production methodology.

SUN is a test bench developed by Safran Reosc to measure spherical or aspherical surface errors of litho-grade lenses with sub-nanometer accuracy. SUN provides full aperture high resolution interferometric measurements. Measurements are performed at the center of curvature using high precision transmission sphere (TS), and Computer Generated Holograms (CGH) for aspheres, in order to light the surface at normal incidence. SUN can measure lenses with diameter up to 350mm and a radius of curvature varying from 60 to 3000 mm.

We describe a method of finding the optical axis of an aspheric surface by looking at an annulus of the surface as the surface is rotated in azimuth. The method uses either an autostigmatic microscope or an interferometer to view the annulus. Distinctive features of the reflected spot movement, or the changes in Zernike coefficients found with interferometry while the surface is rotated in azimuth permits the separation of decenter from tilt. The method appears to be suitable for use with any aspheric surface.

With aspheres being incorporated in optical designs across all industry fields, there is high demand for fast and flexible metrology solutions for aspheric lenses. While many systems support measuring the surface topography, the process is limited to a specific design or based on a time-consuming scanning process. Centration measurement with such systems requires additional probes or the inclusion of external reference surfaces in the measurement process.

In this paper, we present AspheroCheck UP [1], a highly automated lens testing system based on the well-established AspheroCheck principle. The paraxial centering errors of both optical surfaces are measured in reflection using a focusing autocollimator. This centration measurement is combined with a fully motorized, non-contact distance sensor that measures the aspheric surface run-out. All three measurements can be performed in parallel during a single rotation of the sample, greatly reducing overall measurement time. The sensor can also be used for referencing to outer diameter, flange and/or interlock surfaces and even double-aspheric lenses. A five-axis motorized table enables the automatic alignment of the optical axis of the sample to the rotation axis. This significantly reduces setup time and allows for fully automatic testing without user interaction, ensuring both high measurement accuracy and high repeatability independent of the operator.

A full cycle time of less than 1 minute including loading and unloading is possible, enabling applications in both R&D and production environments. In addition to supporting ISO and Q-type polynomial surfaces, the system supports most other rotationally symmetric surface types, including Fresnel and diffractive surfaces.

A problem of interferometers is the elimination of parasitic reflections. Parasitic reflections and modulated intensity signals, which are not related to the reference surface (REF) or the surface under test (SUT) in a direct way, can increase the measurement uncertainty significantly. In some situations standard methods might be used in order to eliminate reflections from the backside of the optical element under test. For instance, match the test object to an absorber, while taking the complex refractive index into account, can cancel out back reflections completely. This causes additional setup time and chemical contamination.

In some situations an angular offset might be combined with an aperture stop. This reduces spatial resolution and it does not work if the disturbing wave field propagates in the same direction as the wave field, which propagates from the SUT. However, a stack of surfaces is a problem.

An increased spectral bandwidth might be used in order to obtain a separation of the plane-of-interest from other planes. Depending on the interferometer used, this might require an optical path difference of zero or it might cause a reduction of the visibility to V < 0.5.

Contrary to these methods, a tailored complex degree of mutual coherence can be used. High visibility is obtained for a single plane-of-interest. Wave fields of interest are shifted against each other. The reduction of the measurement uncertainty, as well as the embodiment of a modified interferometer, will be discussed.

In this paper, a test method based on oblique incidence is practically implemented in the interferometric measurement process. Three sets of wavefront data are achieved through cavity interference measurement with a Fizeau interferometer and one oblique incidence measurement. An iterative algorithm is applied to retrieve the matrix of transmission flatness and reference flatness. The new method can not only calibrate the reference flat error of large aperture interferometer, but also provide the absolute measurement method for large rectangular optical components applied in high power laser systems.

Reproducible manufacturing especially of large diffraction gratings using two-beam laser interference lithography gives rise to exceptional requirements on the stability of environmental conditions like temperature, air pressure, humidity, vibrations as well as a robust exposure setup using stable components, a highly coherent, frequency-stable laser and highquality optics. In our contribution, these requirements are reviewed systematically. The influences of atmospheric refractive index, laser frequency fluctuations, and thermomechanical drifts on the exposed dose contrast and hence on profile variations for surface-corrugated gratings are discussed. Moreover, mid-spatial frequency surface-errors of the used optical elements are identified as a main cause for local dose variations. Reasonable specifications for series manufacturing of grating masters are given and real-world measurement data from a holography laboratory is presented to illustrate the interplay between these different influences. This experimental data includes atomic force microscope scans of highgroove density resist gratings, spatially resolved diffraction efficiency measurements and moiré-interferometric measurements of the fringe stability. The results of our analysis are also useful for other holographic manufacturing facilities, including the manufacturing of surface and volume holographic optical elements of any kind.

When manufacturing precision optical surfaces of relatively larger sizes it is critical to understand the thermal stability of the substrate material. The material properties associated with thermal homogenization are commonly reviewed and soak schedules are created. These schedules ensure a surface under test is in a stable state and is ready for wavefront measurement with an interferometer. However with some materials such as N-BK7, standard soak schedules may not be enough. This paper shows the thermal challenges associated with manufacturing precision optical surfaces when the substrate material is N-BK7, and how the issue can be easily confused with poor metrology. Throughout the manufacturing of precision optical surfaces, the substrates are exposed to varying heat sources and loads. During the manufacturing of lenses greater than 4 inches in diameter we have observed permanent deformation of the optical surface as a result of exposure to temperatures well below the glass strain point. While the reasons why the change occurs is not yet well understood, the result is well documented and was recently observed during the manufacturing of a 15 inch diameter spherical mirror. We use this lens as a case study highlighting the challenges associated with this phenomenon.

Many scientific lasers and increasingly industrial laser systems operate in <500W and kW output power regime, require high-performance optical isolators to prevent disruptive light feedback into the laser cavity. The optically active Faraday material is the key optical element inside the isolator. SYNOPTICS has been supplying the laser market with Terbium Gallium Garnet (TGG - Tb₃Ga₅O₁₂) for many years. It is the most commonly used material for the 650-1100nm range and the key advantages for TGG include its cubic crystal structure for alignment free processing, little to no intrinsic birefringence, and ease of manufacture. However, for high-power laser applications TGG is limited by its absorption at 1064nm and its thermo-optic coefficient, dn/dT. Specifically, thermal lensing and depolarization effects become a limiting factor at high laser powers. While TGG absorption has improved significantly over the past few years, there is an intrinsic limit. Now, SYNOPTICS is commercializing the enhanced new crystal Potassium Terbium Fluoride KTF (KTb₃F₁₀) that exhibits much smaller nonlinear refractive index and thermo-optic coefficients, and still exhibits a Verdet constant near that of TGG. This cubic crystal has relatively low absorption and thermo-optic coefficients. It is now fully characterized and available for select production orders. At OPTIFAB in October 2017 we present recent results comparing the performance of KTF to TGG in optical isolators and show SYNOPTICS advances in large volume crystal growth and the production ramp up.

Although many optical-quality glass materials are available for use in optical systems, the range of polymeric materials is limited. Polymeric materials have some advantages over glass when it comes to large-scale manufacturing and production. In smaller scale systems, they offer a reduction in weight when compared to glass counterparts. This is especially important when designing optical systems meant to be carried by hand. We aimed to expand the availability of polymeric materials by exploring both crown-like and flint-like polymers. In addition, rapid and facile production was also a goal. By using UV-cured thiolene-based polymers, we were able to produce optical materials within seconds. This enabled the rapid screening of a variety of polymers from which we down-selected to produce optical flats and lenses. We will discuss problems with production and mitigation strategies in using UV-cured polymers for optical components. Using UV-cured polymers present a different set of problems than traditional injection-molded polymers, and these issues are discussed in detail. Using these produced optics, we integrated them into a modified direct view optical system, with the end goal being the development of drop-in replacements for glass components. This optical production strategy shows promise for use in lab-scale systems, where low-cost methods and flexibility are of paramount importance.

The paper will describe application of Brilluoin spectroscopy to obtain Young modulus, stress, and thermal history of different glass parts as well as mechanical properties of polymer coating on optical fibers. We demonstrate that use of empirical relationships between Brilluoin frequency and stress and thermal history in glass can provide useful information about different glass products like optical fibers, ion-exchanged glass and others. In addition, similar approach for polymers can serve as a tool to obtain degree of cure or Young modulus for multilayered products such optical fiber.

In this paper, authors present a new application of speckle shearing interferometry (shearography) to a phenomenon known as creep compliance, which is an important mechanical property of viscoelastic materials. Two different sealing elastomers were tested in a short-term creep experiment, applying a constant tensile stress to a specimen. An experimental in-plane shearography setup was implemented to measure directly the in-plane creep strains produced in the tested object. In order to show the effectiveness of shearography for the assessment of this mechanical property, results were compared to that obtained with an equipment of Digital Image Correlation (DIC). It was demonstrated that shearography can be potentially and successfully applied to the creep analysis of these kind of materials. Finally, advantages and limitations of this measurement method are discussed.

Non-thoriated rare-earth fluoride based coating solutions involving DyF₃ and YbF₃ based films as well as non-wetting fluorohydrocarbon cap layers on such films, have been deposited, analyzed and partly optimized. Intermediate results for DyF₃ based films from ion assisted e-gun deposition with O₂ and N₂ alone and as base for the non-wetting to-player as well as for YbF3 starting material with or without admixtures of CaF₂ are discussed for low-loss LWIR and multispectral solutions.

The purpose of this paper is to present concepts for an improved control of plasma ion assisted deposition (PIAD) processes which are employed for the production of optical interference coatings. While the well established PIAD technique typically comprises methods for in situ monitoring of thin film properties, there is no detailed knowledge about plasma parameters which are the foundation of magnitude and stability of plasma assistance, however. We adopt optical emission spectroscopy (OES) and active plasma resonance spectroscopy (APRS) and present schemes for controlling radiance and electron density on a batch coater equipped with an Advanced Plasma Source (APS). In a repeatability experiment of a 5-layer quarterwave stack (QWS, SiO₂/TiO₂), characteristics of two plasma based control schemes are compared to those of a conventional approach. For the conventional process we find systematic drifts and shifts in time traces of monitored plasma paramaters which correlate to properties of the layer stack. By using the novel concepts, stability of plasma paramaters can be improved by a factor of up to 6, while repeatability of in situ QWS transmission is strongly enhanced, exhibiting no spectral shift and minimal variation in reflectivity.

Ion beam sputtering is well established in research and industry, despite its relatively low deposition rates compared to electron beam evaporation. Typical applications are coatings of precision optics, like filters, mirrors and beam splitter. Anti-reflective or high-reflective multilayer stacks benefit from the high mobility of the sputtered particles on the substrate surface and the good mechanical characteristics of the layers. This work gives the basic route from single layer optimization of reactive ion beam sputtered Ta2O5 and SiO2 thin films towards complex multilayer stacks for high-reflective mirrors and anti-reflective coatings. Therefore films were deposited using different oxygen flow into the deposition chamber Afterwards, mechanical (density, stress, surface morphology, crystalline phases) and optical properties (reflectivity, absorption and refractive index) were characterized. These knowledge was used to deposit a multilayer coating for a high reflective mirror.

Optical choppers are widely used in laser systems – for light modulation and/or attenuation. In their most used and wellknown configuration, they are built as a rotational wheel with windows, which transforms a continuous-wave laser beam into a series of impulses with a certain frequency and profile. We briefly present the analysis and design we have completed for the classical chopper wheels (i.e., with windows with linear margins) for both top-hat and Gaussian laser beams. Further on, novel chopper wheels configurations, with outward or inward semi-circular (or with other non-linear shaped) margins of the windows is pointed out; we completed for them both analytic functions and simulations, for both top-hat and Gaussian beams, in order to deduce their transmission functions (i.e., the time profile of the laser impulses generated by the device). The stress of the presentation is put on the novel choppers with shafts (patent pending); their transmission functions are pointed out for top-hat laser beams. Finally, an example of such choppers is considered, with regard to the necessary Finite Element Analysis (FEA) that has to be performed for their rotational shaft. Both the mechanical stress and the deformations in the shaft have to be taken into account, especially at high rotational speeds of the mobile element.

Single crystal calcium fluoride (CaF₂) is the excellent transparent optical substance that has extremely good permeability and refractive index from 120nm wavelength ultraviolet range to 12μm wavelength infrared range and it has widely used in the applications of various advanced optical instrument, such as infrared optical systems (IR), short wavelength optical lithography systems (DUV), as well as high power UV laser systems. Nevertheless, the characteristics of CaF₂ material, including low fracture toughness, low hardness, low thermal conductivity and high thermal expansion coefficient, result in that the conventional pitch polishing techniques usually expose to lots of problems, such as subsurface damage, scratches, digs and so on. Single point diamond turning (SPDT) is a prospective technology for manufacture the brittle material, but the residual surface textures or artifacts of SPDT will cause great scattering losses. Meanwhile, the roughness also falls far short from the requirement in the short wavelength optical systems. So, the advanced processing technologies for obtaining the shape accuracy, roughness, surface flaw at the same time need to put forward. In this paper, the authors investigate the Magnetorheological Finishing (MRF) technology for the high precision processing of CaF₂ material. We finish the surface accuracy RMS λ/150 and roughness Rq 0.3nm on the concave aspheric from originate shape error 0.7λ and roughness 17nm by the SPDT. The studying of the MRF techniques makes a great effort to the processing level of CaF₂ material for the state-of-the-art DUV lithography systems applications.

An optimized method to calculate error correction capability of tool influence function (TIF) in certain polishing conditions will be proposed based on smoothing spectral function. The basic mathematical model for this method will be established in theory. A set of polishing experimental data with rigid conformal tool is used to validate the optimized method. The calculated results can quantitatively indicate error correction capability of TIF for different spatial frequency errors in certain polishing conditions. The comparative analysis with previous method shows that the optimized method is simpler in form and can get the same accuracy results with less calculating time in contrast to previous method.

The poker chip assembly with high precision lens barrels is widely applied to ultra-high performance optical system. ITRC applies the poker chip assembly technology to the high numerical aperture objective lenses and lithography projection lenses because of its high efficiency assembly process. In order to achieve high precision lens cell for poker chip assembly, an alignment turning system (ATS) is developed. The ATS includes measurement, alignment and turning modules. The measurement module is equipped with a non-contact displacement sensor (NCDS) and an autocollimator (ACM). The NCDS and ACM are used to measure centration errors of the top and the bottom surface of a lens respectively; then the amount of adjustment of displacement and tilt with respect to the rotational axis of the turning machine for the alignment module can be determined. After measurement, alignment and turning processes on the ATS, the centration error of a lens cell with 200 mm in diameter can be controlled within 10 arcsec. Furthermore, a poker chip assembly lens cell with three sub-cells is demonstrated, each sub-cells are measured and accomplished with alignment and turning processes. The lens assembly test for five times by each three technicians; the average transmission centration error of assembly lens is 12.45 arcsec. The results show that ATS can achieve high assembly efficiency for precision optical systems.

Roughness, shape and structure of a surface offer information on the state, shape and surface characteristics of a component. Particularly the roughness of the surface dictates the subsequent polishing of the optical surface. The roughness is usually measured by a white light interferometer, which is limited by the size of the components. Using a moulding method of surfaces that are difficult to reach, an imprint is taken and analysed regarding to roughness and structure. This moulding compound method is successfully used in dental technology. In optical production, the moulding compound method is advantageous in roughness determination in inaccessible spots or on large components (astrological optics).

The "replica method" has been around in metal analysis and processing. Film is used in order to take an impression of a surface. Then, it is analysed for structures. In optical production, compound moulding seems advantageous in roughness determination in inaccessible spots or on large components (astrological optics). In preliminary trials, different glass samples with different roughness levels were manufactured. Imprints were taken from these samples (based on DIN 54150 „Abdruckverfahren für die Oberflächenprüfung"). The objective of these feasibility tests was to determine the limits of this method (smallest roughness determinable / highest roughness). The roughness of the imprint was compared with the roughness of the glass samples. By comparing the results, the uncertainty of the measuring method was determined.

The spectrum for the trials ranged from rough grind (0.8 μm rms), over finishing grind (0.6 μm rms) to polishing (0.1 μm rms).

The grinding process is the primary technology for curvature generation (CG) on glass optics. The higher material removal rate (MRR) leads to deeper sub-surface damage (SSD) on lens surface. The SSD must be removed by following lapping and polishing processes to ensure the lens quality. However, these are not an easy and an efficient process to remove the SSD from ground surface directly for aspheric surfaces with tens or hundreds microns departure from bestfit- sphere (BFS). An efficient fabrication procedure for large aspheric departure on glass materials must be considered. We propose 3-step fabrication procedures for aspheric surface with larger departure. 1st step is to generate a specific aspheric surface with depth less than 10 μm of SSD residual. 2nd step is to remove SSD and keep the aspheric form by using Zeeko polisher with higher MRR pad. Final step is to figure and finish the aspheric surface by using QED MRF machine. In this study, we focus on the 1st step to investigate the residual depth of SSD after grinding process on different abrasion materials. The materials of tested part are fused silica, S-NPH2, and S-PHM52. The cross grinding would be configured and depth of SSD/surface roughness would be evaluated in this study. The characteristic of SSD could be observed after etching by confocal microscope. The experimental results show the depth of SSD below 31.1 μm with #400 grinding wheel. And the near 10 μm depth of SSD would be achieved with #1,000 grinding wheel. It means the aspherization polishing on large parts with large departure from best fit sphere would be replaced. The fabrication of large aspheric part would be efficient.

The efficient production of complex glass components is often not possible with classical manufacturing methods. In order to obtain glazed three-dimensional quartz glass moldings, the alternative method of selective laser beam sintering is investigated.

Using synthetic and natural silica powders enables an additive production by high-temperature selective laser sintering (HT-SLS). Particle-diameters in the range of 19...78 μm and spheroidal and vitrified particle-shapes allow to manufacture green bodies. For this purpose, an experimental set up as well as material-specific scan and parameter concepts are developed. Component densities of ρ_R = 65 % and surface roughness of Ra = 32.21 μm are achieved. Subsequently a glassy, opaque molded body is produced by temperature pressure sintering. The component density increases to ρ_R = 96 % with a shrinkage of 16%. In order to use the glazed molded body as glass fiber preform, polishing of the shell surface is necessary. Surface roughness of Ra = 10.4 nm can be realized by laser beam polishing.

Basically, HT-SLS is an alternative method to the classical isostatic pressing of glass powder. In particular, an increase in efficiency with regard to the producible component geometry of the green bodies can be achieved.

We apply the Hydroxide Catalysis Bonding (HCB) technique to phosphate glass and measure the reflectivity and Light Induced Damage Threshold (LITD) of the newly formed interface. HCB is a room temperature, high performing process which was designed for astronomical research glass assemblies and played a key role in the detection of gravitational waves, a breakthrough in contemporary science. The bonds have numerous assets including mechanical strength, stability, no outgassing and resistance to contamination which are of high interest in the precision optics industry. However only little research has been done on their optical properties and mostly on silica based materials. In this paper, we use HCB to bond phosphate glass at room temperature with the goal of designing composite components for solid state laser gain media. We change the solution parameters to identify how they influence the final properties of the bonds: the LIDT at 1535 nm in long pulse regime and the reflectivity at 532 nm are investigated. The measurement of the incidence dependent reflectance allows estimating the thickness and refractive index of the bond in a non destructive process. The best performing set of parameters yields a LIDT of 1.6 GW/cm² (16 J/cm²) and a reflectivity below 0.03 % which makes it suitable for use in high power lasers. The bond thickness is derived both from Scanning Electron Microscopy and the reflectivity measurements and is in the range of 50-150 nm depending on the parameters. Finally, the bonds survive cutting and polishing which is promising for manufacturing purpose.

A newly patented process for completing the spectral light array emitted by LED bulbs provides a low-cost method for producing better human centered lighting (HCL). This process uses non-luminescent colorant filters, filling out the jagged LED spectral emission into a full, white light array. While LED bulbs have the distinct economic advantages of using less energy, producing less heat and lasting years longer than traditional incandescent bulbs, the persistent metameric failure of LED bulbs has resulted in slower, and sometimes reluctant, adoption of LED lighting by the residential, retail and architectural markets. Adding missing wavelengths to LED generated bulbs via colorant filters increases the aesthetic appeal of the light by decreasing current levels of metameric failure, reducing the ‘flatness’, ‘harshness’, and ‘dullness’ of LED generated light reported by consumers. LED phosphor-converted light can be successfully tuned to "whiter" white light with selective color filtering using permanent, durable transparent pigments. These transparent pigments are selectively applied in combination with existing manufacturing technologies and utilized as a final color-tuning step in bulb design. The quantity of emitted light chosen for color filtering can be adjusted from 1% to 100% of emitted light, creating a custom balance of light quantity with light quality. This invention recognizes that “better light” is frequently chosen over “more light” in the consumer marketplace.

The demands on optical metrology such as Fizeau interferometers increase steadily. Typically, a Fizeau lens design consists exclusively of several spheres. Since there is a growing need for larger measuring ranges as well as higher NA of Fizeau lenses, classical spherical Fizeau lenses increasingly reaching their limits. In this paper, a prototype of an innovative transmission sphere comprising aspheric surfaces is introduced and some results and new findings of the manufacturing and testing are presented.

The many industries and research fields have demands for small scale optical systems. To satisfy the demands, many studies are conducted and the miniaturization technologies have been developed. The optical lens is directly related to the optical systems and a key component for the miniaturization. So the aspheric surface which can replace multispherical lenses is applied to the optical lens. And fabrication methods to reduce the diameter of the lens have been developed. The glass molding pressing (GMP) process is an attractive method to fabricate aspheric lens among the lens manufacturing processes. Because the GMP process has advantages of productivity, repeatability and so on. In this study, a 3 mm diameter aspheric plano-convex lens was fabricated using the GMP process. The GMP process was divided into heating, pressing, annealing and cooling. And the process was conducted using a commercial glass molding machine. Mold tools consist of an upper and a lower mold insert, an inner and an outer guide. The aspheric and the flat surfaces of the mold inserts were coated with ta-C to prevent the sticking of the glass to the mold. The surfaces of molded lens were measured by white interferometry and surface profilometer. The height and the diameter were measured using optical microscopy. As results, the aspheric surface of the lens was 5.1187 nm in Ra and 0.242 um in Pt. And the flat surface was 2.6697 nm in Ra and 0.13 um in Pt. The height and the diameter were 1.935 mm and 3.002 mm respectively.

Experimental ray tracing (ERT) is a proven method for transmission testing of various optical components providing a wide range of optical performance parameters from a single measurement. In this work, we demonstrate how this technique can be enabled for testing strongly curved specular surfaces in reflection with an emphasis on increased dynamic range. The surface under test (SUT) is scanned by a beam of light. The direction of the beam after reflection from the surface is detected from intersection with two parallel imaging planes yielding a gradient that will be transferred to a set of surface slopes and finally yield the actual surface profile. Dynamic range can be increased by using multiple beams in an appropriate arrangement to cover different slopes regimes of the surface shape by different beams. The derivation from ray slope to surface profile is discussed in detail as well as a suitable method to determine the angle of the incident ray, which is needed in the analysis. Simulations of strong spheres and extreme apsheres are used to demonstrate the functionality of the introduced method. The discussion is finished with the first results from an experimental setup.

As optical systems get more complex and compact the use of freeform components is becoming ever more present. With their nontraditional geometry freeform optics can not only improve image quality over a greater field of view but they can also reduce the physical space requirements of the optical components in a system. On top of increased performance conformal shapes can match the shape of platform they reside on to reduce drag while still maintaining optical functionality. As the demand for these shapes increases manufacturing and metrology techniques need to be developed to achieve the specifications as well reduce the cost of fabrication. On top of those challenges the optical tolerances used for traditional optics are not always relevant or practical to an optic with a freeform prescription.

OptiPro Systems has been a pioneer in the field of optics manufacturing and freeform geometry is no exception. We have improved our existing grinding and polishing platforms to facilitate easier fabrication of optics with complex shapes and difficult materials as well created our own software packages specifically tailored to these processes. In this paper we will discuss some of the challenges associated with complex shapes and some of the techniques and technologies we use to overcome them. We will discuss some of the difficulties associated with the qualification and tolerancing of these freeform prescriptions as well as some possible solutions to reduce manufacturing costs while still fabricating effective parts. Examples these difficult shapes will be provided alongside of results and data from processing.

New applications for light pipes include waveguiding solar concentrators. For practical applications, achieving high optical transmission is critical so low-absorption glass is preferred over other materials, and the fabrication approach must show promise for scalability and low manufacturing costs. We present results for fabricated fused silica light pipes using femtosecond laser irradiation followed by chemical etching. After compensating for Fresnel losses and averaging over incident angles (in air) from 0° to 25°, transmission efficiencies of 96% and higher were measured for light pipes up to 20mm in length and 1mm2 cross-sectional area. The feasibility of creating glass light pipes with advanced geometries such as angled facets, tapering of the cross-section along the length, and combiners with micron-scale precision is also demonstrated. Tapered light pipes with concentrating factors up to 7x were fabricated, as well as cascaded structures with 45°-angled facets to couple light from multiple lens array elements into a common light pipe.

Single Point Diamond Turning (SPDT) has the potential to cost-effectively manufacture optical materials such as metals and plastic types. However, SPDT generally leaves tool marks on the machined surfaces, which creates problems that can deteriorate the optical performance. Several processes have been studied to eliminate the tool marks caused by SPDT, but it was difficult to carry out without the additional defects like sub-surface damages and other tool marks. To overcome this weakness, we investigated the Magneto-Rheological Finishing (MRF) process to effectively remove the periodic micro structures without surface deterioration for optical performance. The workpiece used in the experiment is a mirror plated with electroless nickel-phosphorus. Through the processing of the SPDT, an initial surface gets periodic tool marks, which have a height of 1.1 μm and a pitch of 20 μm. We studied on the reduction rate of the turning marks by the MRF process with some different conditions of uniform removal. The quantitative analysis of the surface roughness and residual marks was performed using a scanning low-coherence interferometer and through the Power Spectral Density (PSD) respectively. The results showed that reduction rates of tool marks depend on the angles (0, 45, and 90 degs) between the turning direction of the tool marks and the rotation direction of MR wheel. In the case of 45 degs, it indicated the fastest reduction rate.

Besides the wavelength used, there is another factor that we have to notice in designing an optical system. It is material used which is correct for the spectral bands determined. Basically, due the limitation of the available range and expensive, choosing and determining materials for Infra Red (IR) wavelength are more difficult and complex rather than visible spectrum. We also had the same problem while designing our thermal IR camera equipped with two microbolometers sharing aperture.

Two spectral bands, 3 - 4 μm (MWIR) and 8 - 12 μm (LWIR), have been decided to be our thermal IR camera spectrum to address missions, i.e., peat land fire, volcanoes activities, and Sea Surface Temperature (SST). Referring those bands, we chose the appropriate material for LAPAN's IR camera optics. This paper describes material of LAPAN's IR camera equipped with two microbolometer in one aperture.

First of all, we were learning and understanding of optical materials properties all matters of IR technology including its bandwidths. Considering some aspects, i.e., Transmission, Index of Refraction, Thermal properties covering the index gradient and coefficient of thermal expansion (CTE), the analysis then has been accomplished. Moreover, we were utilizing a commercial software, Thermal Desktop/Sinda Fluint, to strengthen the process. Some restrictions such as space environment, low cost, and performance mainly durability and transmission, were also cared throughout the trade off the works. The results of all those analysis, either in graphs or in measurement, indicate that the lens of LAPAN's IR camera with sharing aperture is based on Germanium/Zinc Selenide materials.

We study the propagation of light in order to efficiently redirect the reflected light on photocatalytic samples placed inside a commercial solar simulator, and we have designed a small-scale prototype of Cycloidal Collectors (CCs), resembling a compound parabolic collector. The prototype consists of either cycloidal trough or cycloidal collector having symmetry of rotation, which has been designed considering an exact ray tracing assuming a bundle of rays propagating parallel to the optical axis and impinging on a curate cycloidal surface, obtaining its caustic surface produced by reflection.

In this work, an optical method to characterize a turbulent liquid will be presented; it comes to measuring the content of a suspension in a liquid by laser scattering.

A laser beam transmitted through a transparent rectangular glass container including the emulsion of plaster is imaged using CCD camera, and the resulting image is processed to calculate the scattering intensity. Thus, a relationship between the concentration of the particles in the liquid and the full width at half maximum (FWHM) of the intensity profile of the scattered laser will be determined.

Furthermore, a measure of the contrast of an interference pattern obtained by Mach-Zehnder interferometer is achieved; the object beam passes through the glass container comprising the turbulent liquid. A correlation between the FWHM determined above and the contrast of the interference pattern as a function of the concentration of the emulsion will be deduced.

Yb³⁺/Er³⁺ co doped SrTiO₃ ceramic have been prepared through solid state reaction route and then x-ray diffraction, upconversion photoluminescence properties of the sample are investigated. The variation of upconversion intensities with external temperature exhibits a well-fashioned pattern, which suggests that the ²H _{1 ½} and ⁴S_3⁄2 levels of Er³⁺ ion are thermally coupled. The upconversion mechanism is well explained in terms of phonon-assisted cooperative sensitization. Based on the above upconversion properties the ceramic sample is suggested for near infrared laser based optical imaging and solid state lighting areas.

We report fabrication of optical volume grating inside the quartz glass and PDMS sample using femtosecond laser based micromachining system with 10μm grating period and areaof 2mm x 6mm x 2mm thickness. The wavelength of femtosecond (fs) laser system is 775nm, repetition rate and pulse width of the system is 1 KHz and 100 fs respectively. Both embedded micro gratings are successfully demonstrated under same fabrication parameters. The comparison of diffraction efficiency and angle of diffraction up to the third order of diffraction for grating inside the quartz glass and PDMS has been examined at 632.8 nm, 532 nm and 447 nm respectively. The change in R.I of laser modified region was obtained ~10^-3.

The chemical mechanical polishing (CMP) is a key process during the machining route of plane optics. To improve the polishing efficiency and accuracy, a new CMP model and machine tool were developed. Based on the Preston equation and the axial run-out error measurement results of the m circles on the tin plate, a CMP model that could simulate the material removal at any point on the workpiece was presented. An analysis of the model indicated that lower axial run-out error led lower material removal but better polishing efficiency and accuracy. Based on this conlusion, the new CMP machine was designed, and the ultra-precision gas hydrostatic guideway and rotary table as well as the Siemens 840Dsl numerical control system were incorporated in the new CMP machine. To verify the design principles of new machine, a series of detection and machining experiments were conducted. The LK-G5000 laser sensor was employed for detecting the straightness error of the gas hydrostatic guideway and the axial run-out error of the gas hydrostatic rotary table. A 300-mm-diameter optic was chosen for the surface profile machining experiments performed to determine the CMP efficiency and accuracy.

Beam steering optical arrangement needs less volume envelope for same field of regard than other gimbal approaches. Both for imaging and four quadrant missile applications, volume is critical parameter limiting system performance. Therefore, a conceptual design of beam steering method has been focused on both imaging and four quadrant missiles. In this study; four different optical designs have been made by using both beam steering and regular method for mid-wave infra-red imaging and four quadrant systems. Optical designs performances have been illustrated in simulation results. By using manufactured Risley prisms, some experimental results are conducted to compare simulations results.

Drag force effect is an important aspect of range performance in missile applications. Depending on domes geometry, this effect can be decreased. Hemispherical domes have great image uniformity but more drag force has an effect on it. Four and eight faceted domes decrease drag force. However, environment reflections cause a noise in a system. Also depending on the faceted domes shape, sun and other sources in the environment are deformed in the face of them and these deformed objects result in a false target in an image. In this study; hemispherical, four faceted and eight faceted domes are compared with respect to drag force. Furthermore, images are captured by using these manufactured domes. To compare domes effects on images, scenarios are generated and automatic target acquisition algorithm is used.