This PDF file contains the front matter associated with SPIE Proceedings Volume 9271, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

Diffractive optical elements offer a high degree of freedom for controlling phase and spectral behavior in optical designs. This enables new and compact optical sensors and measurement systems. We show several recent applications which bene t from unique properties of diffractive optical elements. The applications include: field aberration correction e.g. for microscopic projection applications through microscope objective lenses, a 200 channel microscope objective integrated optical addressing system, diffractive/refractive hybrid optics for high efficiency beam shaping and deflection angle enlargement of spatial light modulators.

Micro-nano optics and digital dot matrix hologram (DDMH) technique has been combined to code and fabricate glassfree 3D image. Two kinds of true color 3D DDMH have been designed. One of the design releases the fabrication complexity and the other enlarges the view angle of 3D DDMH. Chromatic aberration has been corrected using rainbow hologram technique. A holographic printing system combined the interference and projection lithography technique has been demonstrated. Fresnel lens and large view angle 3D DDMH have been outputted, excellent color performance of 3D image has been realized.

An angular spectrum holographic algorithm is proposed for generating three-dimensional (3D) reconstruction from multiple computational tomography (CT) slices. Objects consist of multiple slices can be easily modeled by the angular spectrum. So the 3D structure can be built through the superposition of computer generated phase holograms originally from parallel discrete planes at different depths. Then the superposed phase hologram is uploaded to the phase-only spatial light modulator (SLM). With the SLM illuminated by the coherent light, the 3D reconstruction is observed by a camera. The proposed method is more computationally efficient compared with the point source algorithm, and the angular spectrum holographic algorithm can process more large-capacity CT data for the 3D visualization. Experiment demonstrates the feasibility of reconstructing CT biological structure with holographic display.

We propose a novel gold nanosphere doped photopolymer for volume holography. Nanospheres with the diameter of 6-8 nm are evenly dispersed inside a thick photopolymer with thermo-polymerization method. The holographic properties can be greatly enhanced during the two-beam holographic exposure with the doping of the gold nanospheres. Both the photophysical and photochemical mechanism of the gold nanosphere doped photopolymer are analyzed and discussed during holographic grating formation. The applications of the photopolymer for volume holographic recording and reconstruction systems are also experimentally demonstrated.

Polarization-based all-optical logic operations were realized with dual-channel polarization holographic recording system. The polarization property of 9, 10-phenanthrenequinone-doped poly-methyl methacrylate (PQ/PMMA) photopolymer is investigated experimentally. To accurately represent the optical operations, the diffraction efficiency of parallel and orthogonal polarization recording in PQ/PMMA with the thickness of 1 mm are characterized for holographic recording and reconstruction process. A dual-channel polarization holographic recording system is set up for simultaneously recording two input pages. By changing the polarization state of the diffraction beam, all-optical logic OR and NAND operations are realized in the volume holograms. The polarization-based all-optical logic operations in the volume holographic photopolymer may pave a way for practical all-optical logic devices with high speed and large information capacity.

Phase is an important component of an optical wavefield bearing the information of the refractive index, optical thickness, or the topology of the specimen. Phase retrieval is a central problem in many areas of physics and optics since the phase of a wavefield is not accessible directly. The most well-established method for obtaining quantitative phase is through interferometry, such as digital holography. However, this class of methods relies on coherent illumination, therefore, plagued with problems of speckle that prevent the formation of high quality images. On a different note, quantitative phase can be retrieved by transport-of-intensity equation (TIE) using only object field intensities at multiple axially displaced planes. TIE has been increasingly investigated during recent years due to its unique advantages over interferometric techniques: it is non-interferometric, works with partially coherent illumination, computationally simple, no need to phase unwrapping, and does not require a complicated optical system. In this paper, we will review some recent new developments in TIE phase retrieval: including its numerical solution, treatment of boundary problem and the low-frequency artifacts, and configurations for dynamic phase imaging. We also reexamine TIE in terms of phase-space optics, demonstrating the effect of partially coherent illumination on phase reconstruction, and connecting it to light field imaging at the geometry optics limit.

An Airy beam is a non-diffractive wave which propagates along a ballistic trajectory without any external force. Although it is impossible to implement ideal Airy beams because they carry infinite power, so-called finite Airy beams can be achieved by tailoring infinite side lobes with an aperture function and they have similar propagating characteristics with those of ideal Airy beams. The finite Airy beam can be optically generated by several ways: the optical Fourier transform system with imposing cubic phase to a broad Gaussian beam, nonlinear generation of Airy beams, curved plasma channel generation, and electron beam generation. In this presentation, a holographic generation of the finite Airy beams will be discussed. The finite Airy beams can be generated in virtue of holographic technique by ‘reading’ a hologram which is recorded by the interference between a finite Airy beam generated by the optical Fourier transform and a reference plane wave. Moreover, this method can exploit the unique features of holography itself such as successful reconstruction with the imperfect incidence of reference beam, reconstruction of phase-conjugated signal beam, and multiplexing, which can shed more light on the characteristics of finite Airy beams. This method has an advantage in that once holograms are recorded in the photopolymer, a bulky optics such as the SLM and lenses are not necessary to generate Airy beams. In addition, multiple Airy beams can be stored and reconstructed simultaneously or individually.

We present multiple-powered phase masks to convert a plane wave beam into different shaped beams. With the squared phase mask, a hollow beam is obtained before the Fourier plane of the converging lens and a highly focused beam is obtained after the Fourier plane. With the fourth-power phase mask, a crosshair beam with highly focused point in the center is formed on the Fourier plane, then a beam lattice with strong light spots on the four corners is generated after the Fourier plane and the beam lattice has different size on different observing distances. With the fifth-power phase mask, a self-bending beam is generated over long propagation distances.

We propose a method for generating axial multifocal spots (AMS) with a high numerical aperture (NA) objective. The AMS is generated by using phase-only modulation at the back aperture of the objective. Without using any iteration algorithm, the modulated phase distribution is directly calculated by an additional phase analytical formula with different focal distances. By dividing the back aperture of the objective into multi sectorial zones and applying the corresponding additional phase with different focal distances, the AMS can be created. Numerical simulation shows that the numbers of the axial focus depends solely on the different phase distribution calculated by different focal distances. By engineering the phase pattern with different focal distances, axial multifocal spots with different spacing can be realized. Furthermore, combined with vortex phase, the AMS with specific shape spots also can be created. In addition, the AMS focused by incident beams of circular polarization, radial polarization and angular polarization are also studied. This kind of AMS may be found applications in optical imaging, especially in three-dimensional (3D) biological imaging, and also be attractive in mult-plane optical trapping.

A new method is suggested to transform a Gaussian laser beam to a Top-hat distribution using a kinoform. An iterative dummy area method is used to uniform the distribution in the top region of the Top-hat distribution for the design of the kinoform. Simulation results show that a plane-wave-neared Top-hat distribution can be obtained. In addition, the quality dependence of Top-hat distribution is also simulated on the relationship between the Gaussian radius and the size of the kinoform.

Normally, it requires a huge amount of spatial information to increase the number of views and to provide smooth motion parallax for natural three-dimensional (3D) display similar to real life. To realize natural 3D video display without eye-wears, a huge amount of 3D spatial information is normal required. However, minimum 3D information for eyes should be used to reduce the requirements for display devices and processing time. For the 3D display with smooth motion parallax similar to the holographic stereogram, the size the virtual viewing slit should be smaller than the pupil size of eye at the largest viewing distance. To increase the resolution, two glass-free 3D display systems rear and front projection are presented based on the space multiplexing with the micro-projector array and the special designed 3D diffuse screens with the size above 1.8 m× 1.2 m. The displayed clear depths are larger 1.5m. The flexibility in terms of digitized recording and reconstructed based on the 3D diffuse screen relieves the limitations of conventional 3D display technologies, which can realize fully continuous, natural 3-D display. In the display system, the aberration is well suppressed and the low crosstalk is achieved.

In this paper, we develop a binocular three-dimensional measurement system using a Dammann grating. A laser diode and a Dammann grating are employed to generate a regular and square laser spot array. Dammann array illuminator is placed between two cameras and narrowband-pass filters are embedded in the project lens to eliminate the interference of background light. During the measurement, a series of laser spot arrays are projected toward the target object and captured by two cameras simultaneously. Similar to stereo vision of human eyes, stereo matching will be performed to search the homologous spot which is a pair of image points resulting from the same object point. At first, the sub-pixel coordinates of the laser spots are extracted from the stereo images. Then stereo matching is easily performed based on a fact that laser spots with the same diffraction order are homologous ones. Because the system has been calibrated before measurement, single frame three-dimensional point cloud can be obtained using the disparity of homologous points by triangulation methods. Finally, three-dimensional point clouds belong to different frame which represent different view of the object will be registered to build up an integral three-dimensional object using ICP algorithm. On one hand, this setup is small enough to meet the portable outdoor applications. On the other hand, measurement accuracy of this system is better than 0.3 mm which can meet the measurement accuracy requirements in most situations.

We demonstrate a 3D holographic imaging system that composed 1. Recording stage, 2. Processing and transmission stage and 3 Reconstruction stage. First, we record the hologram of a diffusely reflective object using optical scanning holography without speckle noise as well as twin image and background noises. Second, we convert the hologram into an off-axis horizontal-parallax-only (HPO) hologram. Third, we reconstruct the off-axis HPO hologram using amplitudeonly SLM. To the best of our knowledge, this is the first demonstration that records and displays an HPO hologram of a diffusely reflective object optically.

In spite of the developments of various autostereoscopic three-dimensional (3D) technologies, the inferior resolution of the realized 3D image is a severe problem that should be resolved. For that purpose, a time-sequential 3D display is developed to provide 3D images with higher resolution and attracts much attention. Among them, a method using a directional backlight unit (DBLU) is an effective way to be adopted in liquid crystal display (LCD) with higher frame rate such as 120Hz. However, in the conventional time-sequential system, the insufficient frame rate results a flicker problem which means a recognizable fluctuation of image brightness. A dot dithering method can be a good solution for reducing that problem but it was impossible to observe the 3D image in side lobes because the image data and the directivity of light rays from the DBLU do not match in side lobes. In this paper, we propose a new vertical line dithering method to expand the area for 3D image observation by utilizing the side lobes. Since the side lobes locate in the left and right position of the center lobe, it is needed to arrange the image data in LCD panel and directivity of the light rays from the DBLU to have continuity in horizontal direction. Although the observed 3D images in side lobes are flipped ones, the utilization of the side lobes can increase the number of observers in horizontal direction.

Compressive sensing has been successfully applied in digital holography (DH), which formulated holography as a compressive sensing problem, thus the reconstruction of hologram is inverted as the decompress and solving the minimization problem. The original information can be reconstructed accurately when the reconstruction conditions are guaranteed in different physical scheme and optical recording set-up. In this paper, the reconstruction conditions are investigated both theoretically and experimentally in near-field Fresnel propagation regime. The effect of recording distance on the physical properties of Fresnel wave propagation is demonstrated, and then show their effect on reconstructed image quality.

It is well known that holographic display can provide 3D scenes with continuous viewpoints and is free of accommodation-convergence conflict. So far most of the research in this area focuses on the display end, leaving the acquisition end merely explored. For holographic content acquisition, one needs to capture the scene in 3D. Ways to do this include the traditional optical holography and integral imaging. However, optical holography suffers from serious speckle while integral imaging has a long march to increase the resolution. In this paper, we propose a technique based on a variation of the transport of intensity equation to calculate the “phase” information of a scene from its defocusd intensity captured by a color camera under white light illumination. With the defocused phase and intensity data at hand, we can calculate the infocused wavefront of the scene, and further encode it into a computer generated hologram for subsequent holographic display. We demonstrate the proposed technique by simulation and experimental results. Compared with existing 3D acquisition techniques for holographic display, our method may provide better viewing experience due to the free of speckle in the acquisition stage, as well as the fact that the resolution does not limited by the microlenslet.

Fresnel incoherent correlation holography (FINCH) is one of the 3D imaging techniques which records holograms under incoherent illumination. A spatial light modulator (SLM) is used to split the incoherent light reflected/emitted from each object point into two self-coherent spherical beams with different curvatures, and the interference fringes is recorded by a CCD. This technology has been well used in white light reflection imaging and 3D fluorescence microscope imaging. We present a new idea of 4D imaging including three-dimensional spatial information and one-dimensional spectral information on the basis of FINCH. A mathematical model of 4D FINCH system using dual diffractive lenses on a spatial light modulator has been established. We obtained the specific forms of the point spread function, the axial magnification and the reconstruction distance. The experimental results of 3D FINCH imaging are given and one example of 4D imaging with three channels is numerically simulated. And we discussed the key problems of 4D imaging at last.

Unavoidable speckle noise on reconstructed image in laser-based holographic system has been a serious problem in holographic display, due to both temporal and spatial coherence of laser. Employing partially coherent light into optics experiment is an effective way to reduce the speckle noise and thus enhance the signal-to-noise ratio. We will show you the analysis on the coherence of input light, which will affect the quality of the reconstructed image by computer generated hologram (CGH). LED light source with band-pass filters and spatial filters is used to achieve different levels of coherence. The experimental results show high agreement with our analysis. We will also show you how to eliminate the unexpected fringes by employing fast Fourier transform, which can overcome the drawback in our previous proposal with a full analytical algorithm for encoding the CGH of polygonal model. In conclusion, we propose the LED-based holographic imaging system, in order to improve the quality of the holographic imaging.

This paper proposes a new method for three-dimensional dynamic holographic display that combines computer generated holography (CGH) and holographic stereogram. Theoretically, three-dimensional (3D) dynamic holographic display can be achieved by using CGH alone, however the application of CGH is still limited because large amounts of data processing and complex mathematical calculation of off-axis diffracted light field. A new method combining CGH and stereogram is proposed, since stereogram uses a set of 2D images instead of a 3D object, both the complexity of the calculation and the resolution requirements of spatial light modulator (SLM) is reduced. To prove the feasibility of this method, experiments of making hologram using this method is carried out and the result shows that 3D displaying with a view angle of 28 is achieved.

Digital in-line holography (DIH) is a lensless imaging technique that can be used to build low-cost and compact imaging systems. In DIH, the in-line hologram is recorded by a CMOS or CCD sensor and later used to reconstruct the image of the sample. The imaging resolution is determined by the system numerical aperture provided that the pixel size is smaller than the required Nyquist criteria for sampling distance. In the case of short sample-to-sensor distance, pixel size is often a limiting factor for the resolution. To solve this problem, we propose to use iterative method along with data interpolation for the holographic reconstruction. Proof-of-concept numerical simulations have been done to show the effectiveness of our method. In our algorithm, the optical field is propagated back and forth between the sample plane and the sensor plane while using the measured intensity and a priori information about the sample as constraints, following Gerchberg-Saxton and Fienup’s methods. The iteration will converge and we can get both intensity and phase information of the sample. Before the iteration, the intensity data matrix measured by the sensor is interpolated to enlarge the matrix dimension and thus effectively reduce the pixel size. During the iteration, we apply the sensor plane constraints on only the measured intensity location but not the interpolated data location. In our simulation, we observed that during the iteration, the interpolated data will be changed reasonably and we can finally reconstruct the sample image with better resolution.

An automatic angular-spectrum filtering for the phase reconstruction of dual-wavelength digital holograms in a common-path configuration is presented. The major procedure of this automatic angular-spectrum filtering consists of excluding the zero-order region of Fourier spectrums and locating the center of order +1 region of the angular spectrums for two individual wavelengths. The phase map of the object is retrieved with the automatic angular spectrum-filtering algorithm in dual-wavelength digital holographic system, which demonstrates that the automatic angular spectrum-filtering algorithm is feasible and effective. It provides an efficient solution for angular-spectrum filtering in real time dual wavelength digital holographic microscopy.

Incoherent digital holographic adaptive optics (IDHAO) is a new technology of wavefront sensing and correction. However, the process of the holographic wavefront sensing needs to record digital holograms of object and a guide star independently which reduces the speed of sensing. We present a method for enhancing the operation speed of the IDHAO in this paper. The effects of the size of guide star hologram and the minimum resolvable size of discrete object on compensation of wavefront aberration are discussed. We find that for a discrete object, the hologram of guide star can be extracted from the hologram of the incoherent object. The operation speed of IDHAO system can be enhanced for discrete object by this method. This study improves the potential applications of IDHAO in the field of astronomical observation and so on.

The phase-only liquid crystal spatial light modulator (SLM) is a real-time electro-optic device capable of modulating the phase of an optical wavefront in space. SLMs have been harnessed for beam shaping. In this paper, an accelerated GS phase retrieval and iteration algorithm is used for designing the SLM phases which transformed a single-mode He-Ne laser into a ring-shaped pattern. These generated ring beams are investigated experimentally and the phenomena of the added prism phases are also observed. The experimental results showed that a given single-mode laser beam could be converted into a ring-shaped intensity distribution which corresponds to our designation.

We propose a lensless microscopic imaging technique based on iteration algorithm with known constraint for image reconstruction in digital in-line holography. In our method, we introduce a constraint on the sample plane as known part in the lensless microscopy for iteration algorithm in order to eliminate the twin-image effect of holography and thus lead to better performance on microscopic imaging. We evaluate our method by numerical simulation and built a prototype in-line holographic imaging system and demonstrated its capability by preliminary experiments. In our proposed setup, a carefully designed photomask used to hold the sample is under illumination of a coherent light source. The in-line hologram is then recorded by a CMOS sensor. In the reconstruction, the known information of the illumination beam and the photomask is used as constraints in the iteration process. The improvement of image quality because of suppression of twin-images can be clearly seen by comparing the images obtained by direct holographic reconstruction and our iterative method.

A laser scanning device can be used for contour or pattern reconstruction with associated image processing or recognition algorithm. For a better accuracy or accommodating to a high efficiency algorithm, the laser beam often needs reshaping to a specific pattern, such as a line beam, or homogenization so as to reduce the spatial variation of the device performance. In addition, a scanning mechanics is normally inevitable. Both beam shaping and scanning module take quite a volume in the whole system, which could be an issue for the applications in which miniature device is highly desired. In this paper, a holographic scanner has been proposed to perform both laser beam shaping and scanning function. A pure phase modulation liquid crystal on silicon (LCoS) device is used for implementing the dynamic hologram. The LCoS has a pixel size of 3.74μm, and provides 16 phase level with a full phase depth of 2π. A line beam with 20mm and uniformity up to 70% is generated and it is scanned back and forth in the orthogonal direction of the line with a stroke of 20mm. The scanning line pattern is generated based on iterative Fourier transform algorithm (IFTA) and the first diffraction order pattern is exploited with the zero order being blocked and absorbed so that the noise in the scanning line pattern is minimized. The proposed scheme is a compact and versatile solutions for patterned laser beam scanning devices.

The paper considers the dynamic holographic interferometry schemes with amplification (multiplication) of holographic fringes and with correction for distortions, imposed by the interferometer scheme elements. The use of digital microscope and of the matrix light modulator with direct addressing provides the completely digital closed-loop performance of the overall system for real-time evaluation of nano-scale objects size. Considered schemes were verified in the laboratory experiment, using the Michelson micro-interferometer, equipped by the USB-microscope and digital holography stage, equipped by the Holoeye spatial light modulator.

Various quantitative phase microscopy (QPM) techniques for noninvasive and quantitative analysis of samples proposed based on imaging interferometry techniques over the last decade [1-4]. A phase image can be obtained with a single set of interference data in some types of phase microscopes such as diffraction phase microscope [5, 6]. They are suitable for studying rapidly varying phenomena with reduced concern for systematic and sample variations that may occur during the acquisition of the raw data. Dispersion measurements of a sample carry more information than refractive index of measurements at a single wavelength [7]. Knowledge of the optical dispersion for phase objects such as optical fibers, biological cells and micro-particles can provide very useful information about their property. In this work, we report on a common-path and dual wavelength quantitative phase microscope that simultaneously acquires two phase images at different wavelengths. The simultaneous dual-wavelength measurement was performed with a diffraction phase microscope based on a transmission grating and a spatial filter that form a common-path imaging interferometer. With a combined laser source that generates two-color light continuously, a different diffraction order of the grating was utilized for each wavelength component so that the dual-wavelength interference pattern could be distinguished by the distinct fringe frequencies. The refractive index profiles of fiber in both wavelengths were measured adequately by our DW-DPM system.

This paper will report our recent works on fabrication, evaluation, and applications of gratings. We are using the Dammann parallel laser writing facility for fabrication of gratings. High-efficiency reflective gratings and large-sized grating are fabricated. We have fabricated high-power reflective laser vortex grating with expectation of a new laser drilling effect for laser fusion in the future, which is just evaluated by our developed method. These gratings are essential elements for high-power laser systems and other high-demanding metrology applications.

Diffraction gratings are key elements of chirped pulse amplification laser systems. In these applications, the gratings should have high diffraction efficiency, high laser induced damage threshold (LIDT), and large spectral bandwidth. Gratings consist of grooves etched into a substrate and coated with first a highly-reflecting metallic layer and then a multilayer dielectric thin-film stack may meet these requirements. However, in reality after each layer is deposited, the new top surface of the grating deviates from the previous one, and at the end the final top surface of the grating may be significantly different from the initial substrate surface in both groove shape and groove depth. The deformation of layer interface profiles reduces the diffraction efficiency and affects the LIDT of gratings. In this work, the deformation process for a particular thin-film deposition method was studied by means of scanning electron microscopy. On the basis of the experimental data, a profile evolution model was proposed. Diffraction efficiency and bandwidth performance of metal/multilayer-dielectric coated gratings were numerically optimized for various initial substrate grating profiles by changing the dielectric layer thicknesses.

Beam splitters are widely used in various optical modern systems for separating optical wave into different directions. We have proposed a novel slanted grating for beam splitter at the central wavelength of 1550nm, which can be used in the optical communication. With the simulated annealing algorithm, beam splitter slanted grating can be optimized by using the rigorous coupled wave analysis (RCWA). The diffraction process can be analyzed by the simplified modal method. The simplified modal method, without complicated calculation, reduces the difficult diffraction process into a vividly and physical modal. We have derived an analytical expression which can provide an insightful physical description of the simplified modal method for the slanted grating. Compared with the rectangular grating, the slanted grating has the asymmetric physical structure. Therefore, the odd grating mode can also be excited in the slanted grating under normal incidence. The odd grating mode, which only exists in the asymmetric structure, plays the role of breaking the symmetric field distribution in the output plane. The physical analytical expression of mode conversion and coupling for the slanted grating can be obtained to interpretation the asymmetric field distribution. Numerical results obtained by the rigorous coupled wave analysis verified the validity of the simplified modal method. We expect the modal method for the slanted grating set forth in this work should be helpful for the tremendous potential application of the slanted grating.

A 3×3 high divergent 2D-grating with period of 3.842μm at wavelength of 850nm under normal incidence is designed and fabricated in this paper. This high divergent 2D-grating is designed by the vector theory. The Rigorous Coupled Wave Analysis (RCWA) in association with the simulated annealing (SA) is adopted to calculate and optimize this 2D-grating.The properties of this grating are also investigated by the RCWA. The diffraction angles are more than 10 degrees in the whole wavelength band, which are bigger than the traditional 2D-grating. In addition, the small period of grating increases the difficulties of fabrication. So we fabricate the 2D-gratings by direct laser writing (DLW) instead of traditional manufacturing method. Then the method of ICP etching is used to obtain the high divergent 2D-grating.

Flat-field concave diffraction grating is the key component of a portable grating spectrometer, which integrates three optical properties: dispersion, imaging, and flat spectral image in a single device. In recent years, fabricating concave grating has attracted much attention. However, the distance between two exposure light sources in the fabrication light system are often short, which makes it difficult to build the fabrication structure, sometimes even impossible. In order to solve this problem, two methods have been adopted. One is using special microscope objectives, but it reduces the system’s ability of eliminating of aberrations. The other way is building spatial filters respectively, but this adds the difficulty of the system installing and adjustment, furthermore, it makes it impossible to fabricate wide spectrum FCDG. In this paper, a method to increase the distance between the two exposure light sources is proposed by using a compensation mirror. The use of compensation mirror can not only reduce the difficulty of fabricating grating, but also achieve results almost as better as that of the two original exposure points. We calculated the two new exposure points position with Matlab, and then performed system modeling, simulation and optimization in the Zemax software. A theoretical analysis is given to show that the proposed method can ensure the spectral image quality and greatly reduce the fabrication difficulty.

Optical encoders and laser interferometers are two primary solutions in nanometer metrology. As the precision of encoders depends on the uniformity of grating pitches, it is essential to evaluate pitches accurately. We use a CCD image sensor to acquire grating image for evaluating the pitches with high precision. Digital image correlation technique is applied to filter out the noises. We propose three methods for determining the pitches of grating with peak positions of correlation coefficients. Numerical simulation indicated the average of pitch deviations from the true pitch and the pitch variations are less than 0.02 pixel and 0.1 pixel for these three methods when the ideal grating image is added with salt and pepper noise, speckle noise, and Gaussian noise. Experimental results demonstrated that our method can measure the pitch of the grating accurately, for example, our home-made grating with 20μm period has 475nm peak-to-valley uniformity with 40nm standard deviation during 35mm range. Another measurement illustrated that our home-made grating has 40nm peak-to-valley uniformity with 10nm standard deviation. This work verified that our lab can fabricate high-accuracy gratings which should be interesting for practical application in optical encoders.

Femtosecond laser technology is one of the frontiers in the fields of nonlinear optics, advanced manufacturing etc. The method of femtosecond pulse compression is an important research content. To compress the femtosecond pulse, we need to use negative dispersive elements to compensate the positive dispersion of Ti: sapphire crystal and other optical elements. For this purpose, we propose a miniature double-line-density grating pair in which the line density of the second grating is twice of the first one, the output pulse propagates along the way back. The density of the gratings is high, which will have a high diffraction efficiency and can compensate a high GVD ( group velocity dispersion ) in a small distance. The first grating is transmitted and the second one is reflective, the device will not occlude the beam propagation. With the pair of the gratings, the input positive chirped 89fs pulse is neatly compressed into the Fourier transform limited 44fs pulse with no spectral spatial walkoff and dispersion. It can be used for compression in laser cavity or out of the cavity. The gratings are easy to adjust and the structure is simple and compact, which has widespread interest in practical applications.

A new method of single-track absolute position encoding based on spatial frequency of stripes is proposed. Instead of using pseudorandom-sequence arranged stripes as in conventional situations, this kind of encoding method stores the location information in the frequency space of the stripes, which means the spatial frequency of stripes varies with position and indicates position. This encoding method has a strong fault-tolerant capability with single-stripe detecting errors. The method can be applied to absolute linear encoders, absolute photoelectric angle encoders or two-dimensional absolute linear encoders. The measuring apparatus includes a CCD image sensor and a microscope system, and the method of decoding this frequency code is based on FFT algorithm. This method should be highly interesting for practical applications as an absolute position encoding method.

As optical spectroscopy plays a vital role in many of modern science and engineering, there is a growing need for developing an inexpensive and miniature spectrometers. Many attempts have been tried to solve the issue. Grating-Fresnel is a hybrid device that fuses the functions of a grating and Fresnel lens into a single device. In this paper, we try to simulate reflection type and transmission type G-Fresnel device in ZAMAX. And with the aids of ZEMAX, we try to optimize the Fresnel lens, grating pattern. A better alignment for the CCD detector could also improve sensitivity of the system as well. In order to improve the resolution and sensitivity, the length between Fresnel lens and gratings will be optimized.

The resolution of spectrometer can be increased by using multiple detectors. But for the portable spectrometer, the relatively wide edge that used to fix the detector can seriously influence the imaging quality. And the multiple detectors will increase the difficulty of the circuit part. In this paper, a novel method is introduced to increase the resolution by using one detector. The whole waveband is divided into two wavebands in this new structure. And the long waveband will be reflected by a mirror to the definitely location in which the short wave is located. This structure will not only solve the influence of the detector’s edge but also lower the cost of circuit part. By the simulation of the ZEMAX, the resolution of the spectrometer using the new method is better than the current works using one detector in the whole waveband.

In this paper, a quite effective method is proposed for designing the diffractive optical element (DOE) to generate a pattern with large diffraction angle. Through analyze the difference between the non-paraxial Rayleigh Sommerfeld integral and the paraxial Fraunhofer diffraction integral, we modify the desired output intensity distribution with coordinate transformation and intensity adjustment. Then the paraxial Fraunhofer diffraction integral can be used to design the DOE, which adopts the fast-Fourier-transform (FFT) algorithm to accelerate the computation. To verify our method, the simulation and the experiments are taken. And the result shows that our method can effectively rectify the pillow distortion and can achieve the exact diffraction angle.

One method of realizing color holographic imaging using one thin diffractive optical element (DOE) is proposed. This method can reconstruct a two-dimensional color image with one phase plate at user defined distance from DOE. For improving the resolution ratio of reproduced color images, the DOE is optimized by combining Gerchberg-Saxton algorithm and compensation algorithm. To accelerate the computational process, the Graphic Processing Unit (GPU) is used. In the end, the simulation result was analyzed to verify the validity of this method.

A phase-only hologram (POH) has two major advantages. First, it can be displayed with a single phase-only SLM. Second, the reconstructed image is brighter, and free from the zeroth-order diffraction and the twin image. In this paper, four modern methods for the generation of POH, are reviewed. Being different from some existing approach that involved multiple epochs of evaluation in the generation of POH, the methods describe in this paper are non-iterative and computationally efficient. Moreover, these works also share the common feature that the holograms generated can be displayed directly on the phase-only SLM, hence simplifying the optical setup.

A high-resolution full-parallax computer-generated hologram (CGH) is created to reconstruct a photorealistic threedimensional (3D) scene. Fully-computed holographic stereogram is introduced to generate the CGH, which integrates physically based method and holographic stereogram based method to produce accurate depth information as well as view-dependent effects. Accurate accommodation cue and occlusion effect can be created, and computer graphics rendering techniques can be employed in the CGH generation to enhance the image fidelity. A high-resolution hologram with 400 million pixels is fabricated by a lithography system, and the viewing angle is above 30 degrees during optical reconstruction.

Ultrafast lasers, emitting ultra-short pulses of light, generally of the order of femtoseconds to ten picoseconds, are widely used in micro-processing with the advantage of very little thermal damage. Parallel micro-processing is seen significant developments in laser fabrication, thanking to the spatial light modulator (SLM) which can concert single beam to multiple beams through computer generate holograms (CGHs). However, without synchronization control, on the conditions of changing different holograms or processing on large area beyond scanning galvo’s ability, the fabrication will be interrupted constantly for changing holograms and moving the stages. Therefore, synchronization control is very important to improve the convenience and application of parallel micro-processing. A synchronization control method, carried out through two application software: SAMLight (or WaveRunner) and Labview, is presented in this paper. SAMLight is used to control the laser and the scanning galvo to implement microprocessing, and the developed program with Labview is used to control the SLM and motion stages. The synchronization signals, transmitted between the two software, are utilized by a National Instruments (NI) device USB-6008. Using optimal control methods, the synchronized system can easily and automatically accomplish complicated fabrications with minimum time. A multi-drilling application is provided to verify the affectivity of the synchronized control method. It uses multiple annular beams, generated by superimposing multi-beam CGH onto a diffractive axicon CGH, to drill multiple holes at one time, and it can automatically finish different patterns based on synchronization control. This drilling way is an optical trepanning and it avoids huge laser energy waste with attenuation. The multi-beam CGHs, generated by the Grating and Lens algorithm, are different for different patterns. The processing is over 200 times faster than traditional mechanical trepanning, moving a small laser spot in a larger orbit.

Reduced-phase dual-illumination interferometer (RPDII) is an off axis, single shot and single wavelength phase imaging technique to measure large objects without using unwrapping algorithms. Two beams of this interferometer illuminate a sample at different incident angles, two phases of the different incident angles and their phase difference are recorded. The phase difference between two beams can be controlled by adjusting the incident angles. The angle accuracy that decrease the RPDII accuracy have been studied. We have shown, the groove spacing of the grating and magnification of the lens system before sample, determine the incident angle accuracy. The ability of RPDII to unwrap large phases is shown by reconstructing phase of a step object without using unwrapping algorithms. The reconstructed image shows that the total inaccuracy is much more than the inaccuracy caused by incident angles.

A novel retina-like image sensor based on space-variant lens array is proposed, in which a space-variant lens array is used for performing log-polar mapping. Firstly, the mathematical models are developed and verified. Secondly, the relationships among the parameters of the space-variant lens have been simulated and discussed. Finally, some conclusions are deduced, which will help to result in a retina-like image sensor with the characteristics of high speed, large resolution, high sensitivity and big planar array, etc.

A series of LiNbO₃:Hf:Ce:Cu crystals with various level of Hf doping were prepared using the Cz equipment with a resistance furnace. The crystal storage properties with optical damage resistance ability, sensitivity and dynamic range were measured by means of two-beam coupling light path. The defect structure is also discussed, accounting for the optical damage resistance. Based on optimal one of these crystals as storage medium, one thousand of holograms were recorded in a public coherent volume of 0.073 cm³. The result shows that storage density arrives10.7Gbits/cm3 and the crystal has potential application in the future high density storage..

An effective approach to measure image motion is presented based on joint transform correlator(JTC), in order to measure the sub-pixel image motion caused by satellite attitude instability or vibration. Firstly, the high-speed CCD is used to capture image sequences, which are preprocessed by wavelet edge detection. Next the acquired image edge sequences are optically calculated by JTC, and an improved correlation peak is obtained. Lastly a modified centroid algorithm is proposed to get more accurate motion measurement. Motion measurement based on optical correlation is discussed, and the optical experiment system is also set up. The experimental results show that the measurement error is as low as 0.02 pixels, the accuracy is improved greatly.

We propose and present a planar plasmonic lens formed by an array of spatially varying sub-wavelength rectangular annular patterned in the upper Au film of a metal-insulator-metal (MIM) structure. It is found that the reflected phase and amplitude can be well controlled by manipulating the width of the annular gaps and the length of the MIM cavity, in which localized surface plasmonic resonances occur. A reflective planar plasmonic lens that can generate a spherical wave-front in the reflected field has been realized through an optimized design at wavelength 1.55μm. Numerical results using the Finite Difference Time Domain (FDTD) method show that the focal length can be precisely controlled with a beam spot size at focal plane being close to the diffraction limits, and the focusing efficiency is up to 50%. It provides a great potential for applications in advanced nanophotonic devices and integrated photonic systems.

Blazed grating is a key diffractive optical element in spectrometer. Different from the traditional holographic ion beam etching method, blazed grating has been fabricated on a novel polymer with cyclic-azobenzene pendants (Pcyclic-azoMMA) by all optical fabrication with two steps in this paper. Firstly, use two interfering Kr+ laser beams with the most efficient RCP+LCP polarization to inscribe symmetric surface relief gratings on polymer film. After that, make a single laser beam with polarization perpendicular to the grating grooves irradiate slantly to induce blazed asymmetric structure. The distribution of the near field of the grating while single linearly polarized beam irradiate slantly at different angles was simulated. The calculation demonstrates that -1st order diffraction efficiency of blazed gratings is similar to that of triangle blazed grating.

It is difficult to dectect and recognize moving target for optical correlator owing to the image information containing various rotation and scale variation, though optical processing owns the advantage of high-speed, large capacity and real-time. An efficient approach was proposed to impove correlation peak and enhance recognition performance of target based on Fourier-Mellin transform, by which optical correlator is not sensitive to the distortion of image information, and it will alleviate greatly the complexity of image recognition. We have also constructed an detection and recognition system based on optical joint correlator, the computer simulations and experimental results show that the proposed method has got sharp corrlation peak and improved the detection performance.

Volume Moiré Tomography (VMT) is an important technique to diagnose the flow field. In this Letter, the characteristic of temporal phase-shifting is analyzed for VMT. When the distance between two cross gratings is not on the Talbot distance, the phase-shifting factors are existed between moiré patterns of different orders. Especially, when the distance conforms to the sub-Talbot distance, the phase-shifting factors are maximum. This characteristic of temporal phaseshifting could be used for real 3-D flow fields reconstruction in the future.

With the intrinsic advantages of high diffraction efficiency, signal to noise ratio, wavelength and angle selectivity, and low scattering and absorption, volume phase holographic gratings (VPHGs) have been widely used for spectroscopy, telecommunications, astronomy and ultra-fast sciences. In this paper, a novel kind of beam splitter which is consisted of a transmission VPHG and a reflection VPHG as core components and used in near-infrared waveband is proposed. The design idea of the device is described in detail. Based on the Bragg condition and the rigorous coupled wave analysis (RCWA), diffraction properties in near-infrared waveband of the transmission and reflection VPHGs recorded in dichromated gelatin (DCG) are studied theoretically. As an example, two wavebands that need to be separated in near infrared spectrum region are taken into account. One that from 1.574μm to 1.617μm centered at 1.596μm will be diffracted by the reflection grating, and the other that from 1.636μm to 1.682μm centered at 1.659μm will be diffracted by the transmission grating. The diffraction efficiencies of the gratings are calculated and optimized by applying Kogelnik's coupled wave theory and G-solver software, respectively. The recording setup is also designed for further experiments. The effects of the recording and reconstruction setup parameters, the amplitude of the index modulation (Δn) and the thickness of the gelatin layer (d), and the polarization state of reconstruction beams on the diffraction efficiency properties of the gratings are calculated and analyzed. This kind of beam splitter is prospected to be used in spectrometers for greenhouse gases monitoring.

An encryption method combining optical digital holography with digital decryption on computer is proposed, which avoid the precise setup of optical devices. A digital hologram of three-dimensional (3D) object and a hologram of key information are recorded by optical method in the encryption process. The 3D object is reconstructed by filtering in spectrum domain and simple numerical calculation. The quality of reconstructed object is improved by reducing speckle noise. The robustness against occlusion and noise attacks of the system has also been analyzed. Optical experiments results are presented.

Autostereoscopic displays are a promising three dimensional display technology for its convenience and compatibility with current display systems which has attracted considerable attention. We describe in detail an autostereoscopic display system with full-parallax using a directional light-guide device with continuously variable spatial frequency sub-micron grating structures. The optimization process of parameters of the multi-direction light-guide is given. A method of implementing sub-micron grating pixels (SMGPs) based on an ultraviolet continuously variable spatial frequency photolithography process has been proposed. The process aims to provide low cost fabrication of variable spatial frequency grating pixels with high efficiency. We fabricate 2 inch backlight plate with nine viewing directions, and the pitch of each diffractive pixel varies between 441 nm and 578 nm. The properties of SMGPs are investigated by the measurement of diffraction efficiency dependence on viewing angle under a collimated 650 nm LED light source at an incidence angle of 60°. The variation of diffraction efficiency with regards to viewing angle is weak. The measured diffraction efficiency is around 6%, which is in good agreement with the simulated value.

Three-dimensional (3D) tabletop display is a kind of display with wide range of potential applications. An auto-stereoscopic 3D tabletop display system is designed to provide the observers with high level of immersive perception. To improve the freedom of viewing position, the eye tracking system and a set of active partially pixelated masks are utilized. To improve the display quality, large number of images is prepared to generate the stereo pair. The light intensity distribution and crosstalk of parallax images are measured respectively to evaluate the rationality of the auto-stereoscopic system. In the experiment, the high immersive auto-stereoscopic tabletop display system is demonstrated, together with the system architectures including hardware and software. Experimental results illustrate the effectiveness of the high immersive auto-stereoscopic tabletop display system.

An experimental comparison of four methods of wavefront reconstruction is presented. We considered two iterative and two holographic methods with differences in mathematical models and reconstruction algorithms. The first two of these methods do not use the reference wave in the recording scheme that reduces the need of setup stability. A set of spatial intensity measurements of a volume scattered field plays the main role in phase retrieval in such methods. The obtained data are sequentially used for iterative wavefront reconstruction. Iterative approach involves numerical wavefront propagation between various planes of the volume scattered fiels. Throughout this procedure the phase information of the wavefront is retained while the calculated amplitudes is replaced by the square root of the intensity distributions measured in corresponding planes. In the first compared phase retrieval method (FRIM), a two-dimensional Fresnel transform and iterative calculation in the object plane are used as a mathematical model. In the second method (SBMIR), the angular spectrum is used for numerical wavefront propagation, and iterative calculation is made only between closely spaced planes for data registration. Two methods of digital holography, which we compared, differ from each other in algorithm of a waverfont reconstruction. The first holographic method (CWR-DH) uses the conception of spatial phase steps for complex wave retrieval, and the second method (FT-DH) is a widespread Fourier transformation method. All methods provide satisfactory capacity for image reconstruction. The results of the comparison showed that FRIM produces better quality of reconstruction, but a diffraction artifacts takes place at the boundaries of the reconstructed image. Taking this into account we can conclude that the CWR-DH method is the best among considered.

Fresnel incoherent correlation holography (FINCH) is one of the methods for recording digital holograms of 3D samples under incoherent illumination. This method has been successfully applied to white reflective holographic imaging and 3D microscopic imaging. In this article, the processes of optical recording, digital reconstruction and the point spread function of the classic FINCH system are described in detail. The reconstruction images of three letters of “Z”, “W” and “F”, each of which has a different distance from the collimating lens, are simulated. The expression of the resolution of FINCH system has been deduced, which shows that the resolution of the optimal FINCH is beyond the Rayleigh resolution. Effect of the background light on the resolution is analyzed through two groups of contrast experiments when introducing the polarizer in FINCH system and changing phase masks on the SLM.

A Dammann grating coupling method and corresponding coupling condition are proposed. The different diffractive efficiency of the traditional 3x3 Dammann grating are analyzed by using both the scalar diffraction theory and the Fourier Modal Method (FMM). One new 3x3 Dammann grating is designed by using FMM in association with the simulated annealing optimization (SAO), and its diffraction efficiency and uniformity are about 40% and 15%, respectively. The new 3x3 grating and one traditional 64x64 Dammann grating are then coupled and analyzed numerically. The diffractive efficiency and the uniformity of the final 192x192 dense spots array are 30% and 18%, respectively. As the reference object, one 121x121 beam-splitting grating is designed, whose uniformity and overall diffractive efficiency are 50% and 85%, respectively. Numerical results show that the Dammann grating coupling method is more economical and applicable way to generate dense spots array.

With the development of infrared optics, infrared optical imaging systems play an increasingly important role in modern optical imaging systems. Infrared optical imaging is used in industry, agriculture, medical, military and transportation. But in terms of infrared optical imaging systems which are exposed for a long time, some contaminations will affect the infrared optical imaging. When the contamination contaminate on the lens surface of the optical system, it would affect diffraction. The lens can be seen as complementary multiple circular holes screen happen Fraunhofer diffraction. According to Babinet principle, you can get the diffraction of the imaging system. Therefore, by studying the multiple circular holes Fraunhofer diffraction, conclusions can be drawn about the effect of infrared imaging. This paper mainly studies the effect of multiple circular holes Fraunhofer diffraction for the optical imaging. Firstly, we introduce the theory of Fraunhofer diffraction and Point Spread Function. Point Spread Function is a basic tool to evaluate the image quality of the optical system. Fraunhofer diffraction will affect Point Spread Function. Then, the results of multiple circular holes Fraunhofer diffraction are given for different hole size and hole spacing. We choose the hole size from 0.1mm to 1mm and hole spacing from 0.3mm to 0.8mm. The infrared wavebands of optical imaging are chosen from 1μm to 5μm. We use the MATLAB to simulate light intensity distribution of multiple circular holes Fraunhofer diffraction. Finally, three-dimensional diffraction maps of light intensity are given to contrast.

Large-size autostereoscopic 3D LED displays are commonly used in outdoor or large indoor space, and have the properties of long viewing distance and relatively low light intensity at the viewing distance. The instruments used to measure the characteristics (crosstalk, inconsistency, chromatic dispersion, etc.) of the displays should have long working distance and high sensitivity. In this paper, we propose a methodology for characteristics measurement based on a distribution photometer with a working distance of 5.76m and the illumination sensitivity of 0.001 mlx. A display panel holder is fabricated and attached on the turning stage of the distribution photometer. Specific test images are loaded on the display separately, and the luminance data at the distance of 5.76m to the panel are measured. Then the data are transformed into the light intensity at the optimum viewing distance. According to definitions of the characteristics of the 3D displays, the crosstalk, inconsistency, chromatic dispersion could be calculated. The test results and analysis of the characteristics of an autostereoscopic 3D LED display are proposed.

A polarization-multiplexing off-axis dual-wavelength digital holography is presented. The structure of a groove grating is measured by using the polarization-multiplexing dual-wavelength digital holographic system with a co-path optical configuration. Two holograms of the grating is recorded at the wavelengths 671nm and 656nm by using a pair of CCDs, and then their two phase maps are reconstructed by numerical simulation of diffraction process of the holograms, respectively. The synthetic phase image is obtained by subtracting two phase images directly. Thus, the unwrapping phase map of the grating is achieved by using the polarization-multiplexing dual-wavelength digital holography in the off-axis optical setup.

In most cases of the generation of computer-generated hologram, a zero-valued dummy area is usually added to the desired object in order to avoid the disturbance of high order reconstruction. The high order reconstruction not only disturbs the zero order reconstruction but also decreases the zero order reconstruction diffraction efficiency. In this study, we show a method to improve the zero order reconstruction diffraction efficiency by using a finite dummy area. According to the structure of a general computer-generated hologram, that is each calculated computer-generated hologram point has the same square size, then the high order reconstruction is the product of the zero order reconstruction and a sampling function with a scale factor. We use computer simulation to show the effect of dummy area in the improvement of the zero order reconstruction diffraction efficiency. According to our simulation results, we find that the zero order reconstruction diffraction efficiency increases as increasing the size of dummy area. In addition, we also find that the on-axis reconstruction has a higher reconstruction diffraction efficiency that the off-axis ones.

In this paper, a dual-core polymer-filled photonic crystal fiber (PCF) is designed for broadband dispersion compensation. Large negative dispersion value from −255 to −823 ps/(nm•km) over the entire C band is achieved. Furthermore, the effective refractive index of the polymer-filled outer core can be well tuned by changing the temperature. This PCF can be used for the dynamical dispersion compensation in wavelength-division-multiplexing (WDM) systems.

Varied line spacing plane gratings have the features of self-focusing , aberration-reduced and easy manufacturing ,which are widely applied in synchrotron radiation, plasma physics and space astronomy, and other fields. In the study of diffracting imaging , the optical path function is expanded into maclaurin series, aberrations are expressed by the coefficient of series, most of the aberration coefficients are similar and the category is more, can't directly reflects image quality in whole. The paper will study on diffraction imaging of the varied line spacing plane gratings by using computer simulation technology, for a method judging the image quality visibly. In this paper, light beam from some object points on the same object plane are analyzed and simulated by ray trace method , the evaluation function is set up, which can fully scale the image quality. In addition, based on the evaluation function, the best image plane is found by search algorithm .

Based on Thom’s elliptic umbilical singularity, we design pivotal phase-only masks to generate accelerating regular polygon beams. By using the diffractive phase grey-scale map written onto a spatial light modulator, we experimentally obtain optical regular accelerating triple-cusp beams and quinary-cusp beams. Their optical propagation characteristics are investigated subsequently. It will provide useful information for their future potential applications.