The 5D-alignment of multi-element assemblies within a single barrel by adhesive bonding represents a powerful alternative to the sub-cell mounting concept. A bifocal autocollimation head offers efficient and simultaneous monitoring of the single element’s tilt and shift within the cell and minimizes the impact of error propagation. The described process allows for production of mounted lenses with an outstanding alignment precision below 1 μm in all dimensions in less than 3 minutes per lens element. The automated process greatly simplifies the transfer of existing, conventional optomechanical designs to higher performance independent of the number of lens elements in the assembly.
Modern high-performance optical systems require new technologies for alignment and joining processes. With the established OptiCentric® Bonding 5D TRIOPTICS offers a technology that provides high-precision lens mounting based on adhesive bonding. With innovative alignment bonding in 5 dimensions, the lens surfaces are aligned to the tube with accuracies below 1 μm in x, y, z direction and below 2 arcsec in Θx and Θy direction. This fine-adjustment method doesn’t dependent on mechanical tolerances because the lens can move freely in the frame. By using high-resolution autocollimators as well as tactile and optical distance sensors the accuracy of each lens is checked after each step of machining. This procedure facilitates the stacking of several lenses into one tube without further costly alignment steps of sub-cells. This reduces the process steps and makes the multilens mounting into a tube more efficient. Furthermore, glue bonded lenses without sub-cells save space and weight due to waiver of set-screws and shims. Integrated into the production line this technology allows a greater degree of accuracy of optical systems and new design opportunities for more compact and higher-quality lenses. The highly flexible OptiCentric® Bonding 5D can be quickly converted to other types of lenses. This technology is also suitable for clean room applications.
The 5D-alignment of multi-element assemblies within a single barrel by adhesive bonding represents a powerful alternative to the so-called “poker-chip assembly” where the barrel is populated with sub-cells. This way, the single element’s lateral and axial position can be precisely controlled. The described process allows for production of mounted lenses with an outstanding alignment precision below 1 µm in all dimensions in less than 3 minutes per lens element.
The fully automated process greatly simplifies the transfer of existing, conventional optomechanical designs to higher performance and allows for smaller and lighter barrel designs compared to the established poker chip assembly.
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.
Today's optical systems require up-to-date assembly and joining technology. The trend of keeping dimensions as small as possible while maintaining or increasing optical imaging performance leaves little to no room for mechanical lens adjustment equipment that may remain in the final product. In this context active alignment of optical elements opens up possibilities for the fast and cost-economic manufacturing of lenses and lens assemblies with highest optical performance.
Active alignment for lens manufacturing is the precise alignment of the optical axis of a lens with respect to an optical or mechanical reference axis (e.g. housing) including subsequent fixation by glue. In this contribution we will describe different approaches for active alignment and outline strengths and limitations of the different methods. Using the SmartAlign principle, highest quality cemented lenses can be manufactured without the need for high precision prealignment, while the reduction to a single alignment step greatly reduces the cycle time. The same strategies can also be applied to bonding processes. Lenses and lens groups can be aligned to both mechanical and optical axes to maximize the optical performance of a given assembly. In hybrid assemblies using both mechanical tolerances and active alignment, SmartAlign can be used to align critical lens elements anywhere inside the system for optimized total performance. Since all geometrical parameters are re-measured before each alignment, this process is especially suited for complex and time-consuming production processes where the stability of the reference axis would otherwise be critical. For highest performance, lenses can be actively aligned using up to five degrees of freedom. In this way, SmartAlign enables the production of ultra-precise mounted lenses with an alignment precision below 1 μm.
For the manufacturing of high performance optical systems, centered alignment of the optical surfaces within the assembly is becoming increasingly important.
In this contribution, we will present a system for the automated alignment of optical surfaces for the high-throughput manufacturing of cemented doublets (and triplets) with optimized imaging performance. First of all, different concepts for the alignment of doublets etc. are discussed. Standard methods for cementing evaluate mechanical features, such as the outer barrel of one element as reference axis. Using this procedure the optical performance of the assembly that can be achieved is limited by imperfections in the collinearity of the element’s barrel axis and its optical axis. Instead, using the optical axis of the bottom element as target axis opens up perspectives for the production of multiplets with perfect symmetric imaging performance. For this concept, all three center of curvature positions of the optical surfaces are measured. Then, the top surface is aligned to the bottom element's optical axis using high-precision actuators.
In order to increase the throughput of this procedure, the system is equipped with a novel measurement head that acquires autocollimation images of all three surfaces of a doublet at the same time. Thus, the positions of all surfaces are measured simultaneously during just a single rotation, avoiding both additional rotations and focus movements.
Using this approach, cycle times can significantly be reduced from an average of 1 min to less than 10 seconds (w/o curing time). The system is reconfigurable in order to support a wide range of sample designs and enables cementing of high quality optics with centering errors below 2 μm.
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