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This research is focused on the link between manufacturing parameters and the resulting mid-spatial frequency error in the manufacturing process of precision optics. The goal is to understand the generation mechanisms of mid-spatial frequency errors and avoid their appearance in the manufacturing process. Also, a simulation which is able to predict the resulting mid spatial frequency error from a manufacturing process is desired.

The aim of our research was to study middle spatial frequency errors (MSFE) on optical surfaces. We investigate the surfaces after manufacturing processes to find out the main affecting factors and to choose the proper processing parameters to minimize the size of the errors. To find an appropriate parameter window we have to be able not only to define the factors, which lead to MSFE, but also to analyze the change of the error after next following production steps.

This research is focused on the link between manufacturing parameters and the resulting mid-spatial frequency error in the manufacturing process of precision optics. This third publication focuses on strategies of avoidance and generation mechanisms of the mid-spatial frequency errors from the grinding process. The Goal is to understand the generation mechanisms of the mid-spatial frequency errors and avoid their appearance in the manufacturing process.

This research is focused on the link between manufacturing parameters and the resulting mid spatial frequency error in the manufacturing process of precision optics. This first publication focuses on the parameters of the grinding step. The Goal is to understand and avoid the appearance of the mid spatial frequency error and develop a simulation which is able to predict the resulting mid spatial frequency error for/of a manufacturing process.

ASPHERO5 is a funded German research project (project prime: Schneider OpticalMachines) with the goal of economic fabrication of high precision aspheres. The research is concentrated on the classical process chain consisting of grinding and polishing. The characterization of the incoming and outgoing surface quality is one issue to characterize the improvements. The variation of the local removal rate related to local curvature is one of the limiting factors of the polishing process. In this paper we report on first results characterizing the surface quality with a PSD (Power Spectral Density) algorithm and analyzing the local removal rates for the polishing step. In our research, two types of aspheres with 30 and 60 mm diameter were polished with a spinning tool process. The final deviation between simulation and experiment was less than 10 percent. That’s the starting point for further investigations within the project.

The fields of application for polymer optics are huge and thus the need for polymer optics is steadily growing. Most polymer optics are produced in high numbers by injection molding. Therefore molds and dies that fulfill special requirements are needed. Polishing is usually the last process in the common process chain for production of molds for polymer optics. Usually this process step is done manually by experienced polishers. Due to the small number of skilled professionals and health problems because of the monotonous work the idea was to support or probably supersede manual polishing. Polishing using an industrial robot as movement system enables totally new possibilities in automated polishing. This work focuses on the surface generation with a newly designed polishing setup and on the code generation for the robot movement. The process starts on ground surfaces and with different tools and polishing agents surfaces that fulfill the requirements for injection molding of optics can be achieved. To achieve this the attention has to be focused not only on the process itself but also on tool path generation. A proprietary software developed in the Centre for Optical Technologies in Aalen University allows the tool path generation on almost any surface. This allows the usage of the newly developed polishing processes on different surfaces and enables an easy adaption. Details of process and software development will be presented as well as results from different polishing tests on different surfaces.

For the Computer Controlled Polishing (CCP) process of aspheres and freeform shapes different kind of subaperture tools can be used. The selection of the best tool out of a wide range of possible and available tools is today based on the experience of the skilled operator. If the optical part is finished with sufficient quality in a reasonable time, the working procedure is fixed. Another approach is to put the tool choice on a scientific base, using a simulation to generate the wear function and a Power Spectral Density (PSD) analysis to describe the residual shape deviations. Based only on theoretical tool data and the geometric shape of the tool, the final result of the shape correction could be calculated and transferred to a NC machine code for various polishing machines.

In the manufacturing process of aspheric glass lenses, the polishing step plays a key role with respect to the final quality of the lens as well as to the manufacturing costs. Due to the changing radius of curvature sub aperture tools are used for polishing aspherical lens elements. Even with small tools the changing radius has a significant influence to the wear function [1] [2]. This paper describes a method to calculate the removal based only on the surface shape and the material parameters of the tool. The described method can be used for any kind of surface, e.g. for freeform shapes.

The first step of the polymer optics process chain after finishing the optical design is the mold fabrication. Typically the mold is fabricated by a number of process steps including ultra precision diamond turning or milling. Often a manual polishing is necessary to get rid of the turning or milling marks. In contrary to the existing mold manufacturing process chain we develop a new two step mold manufacturing process capable for freeform optics. It consists of a milling step followed by a Computer Controlled Polishing. First results of the new process chain for mold fabrication including the replicated polymer optics will be reported in this paper.

The two major process steps, grinding and polishing, of the classical process chain have to fulfill the following requirements: Grinding: low subsurface damage, no cutter marks and best shape accuracy Polishing: fast removal of subsurface damage by form preserving The goal for the polishing step is a flexible process capable of removing mm 3 /min by keeping the shape generated by the grinding process or improving the shape in parallel to the required specifications. To be fast a new polishing kinematics is applied. The improvement of the removal rate is in the order of 2-3 compared to a standard asphere polishing processes. The drawback is a huge spatial variation of the removal rate. By application of proper simulation procedures this shortcomings can be overcome, requiring a detailed understanding of the local removal rate. Furthermore an extensive set of analysis tools such as PSD based evaluation of 1 and 2D shape measurements and separation tools for grouping of surface errors are applied. They help to understand and optimize the local polishing action and to define the cut-off wavelength for the final correction step. Results of the simulation, evaluation and experimental results for 3 different kinds of aspheres will be presented to demonstrate the power of described approach.

ASPHERO5 is a funded research project (project prime: Schneider OpticalMachines) with the goal of economic fabrication of high precision aspheres. The research is concentrated on the classical process chain consisting of grinding and polishing. The mid spatial artefacts are one of the limiting factors for grinding, whereas for polishing the variation of the local removal rate depends on the local curvature. In this paper first results of minimizing mid spatial artefacts for the grinding step and analyzing local removal rates for the polishing step are reported. Based on the results of our research, aspheres with local radii from 200 mm to 10 mm are polished to 25 nm rms final surface error. Nevertheless, to perform the different process steps in an economic way is still a challenge.

The Center of Optics Technology at the University of Applied Science, founded in 2003, is part of the School of Optics and Mechatronics. It completes the existing optical engineering department with a full optical fabrication and metrology chain and serves in parallel as a technology transfer center, to provide area industries with the most up-to-date technology in optical fabrication and engineering. Two examples of research work will be presented. The first example is the optimizing of the grinding process for high precision aspheres, the other is generating and polishing of a freeform optical element which is used as a phase plate.

It is widely expected that 193 nm lithography will be the technology of choice for volume production of the 0.10 micrometer device generation. For this purpose the PAS5500/1100TM Step & Scan system, the second generation ArF tool, was developed. It is based on the PAS5500/900TM, the body of which has been adapted to fit the new 0.75 NA StarlithTM projection optics. This high NA enables mass manufacturing of devices following the 0.10 micrometer design rule. The system features a 10 W 2 kHz ArF laser and the AERIALTM II illuminator that can be equipped with a QUASARTM (multipole) option. In order to minimize wafer processing influences on overlay performance ATHENATM off- axis alignment with phase modulator is implemented. The usage of Reticle Blue Alignment will further improve overlay as well as increase the system stability. In this paper the PAS5500/1100TM system layout is discussed and the first imaging and overlay results are presented. Imaging performance is illustrated by SEM pictures of 0.10 micrometer dense lines, 0.15, 0.13 and 0.12 micrometer dense contact holes, 0.10 micrometer DRAM isolation patterns, image plane deviation and system distortion fingerprints. Alignment reproducibility and single machine overlay results demonstrate the overlay capability.

High throughput and/or high resolution imaging telescopes for x-ray energies up to 8 keV are part of several space based astronomic missions to study small and faint cosmic x-ray objects. High throughput telescopes are applied for spectroscopy missions, high resolution telescopes to detect and analyze small X-ray sources. Depending on the goal and the constraints of the mission some of the various parameters such as resolution, throughput, number of nested shells or weight etc. are optimized. The production technology has to match to the mission goals and constraints to obtain an optimum balance between scientific performance, production time and costs. The entire production process of XMM mirror shells at Carl Zeiss and Medialario (Italy) respectively will be presented in this paper. This technology will be compared with the ones of other x-ray telescopes such as EINSTEIN, EXOSAT, ROSAT, JET-X, AND AXAF; and EUV telescopes such as CDS and EUVE regarding potentials and limitations of the manufacturing processes and optical performances.

The High Throughput X-Ray Spectroscopy Mission (XMM) is a `Cornerstone' Project in the ESA long-term Programme for Space Science. The satellite observatory uses three grazing incidence mirror modules coupled to reflection grating spectrometers and X-ray CCD cameras. In order to achieve a large effective area, each XMM mirror module shall consist of 58 Wolter I mirrors which are nested in a coaxial and cofocal configuration. This high packing density requires the production and integration of very thin mirror shells with diameters included between 300 and 700 mm. In 1991-93, a development program was run which aims to demonstrate the feasibility of such mirrors. Demonstration models which integrate mirrors having different sizes were manufactured using CFRP replication and Nickel electroforming technologies. These were X-ray tested. The proposed paper summarizes the activities and the test results obtained during this program.

The Joint European X-Ray Telescope, JET-X, is one of the core instruments of the scientific payload of the Russian SPECTRUM-X astrophysics mission due for launch in 1995. JET-X is designed to study the emission from X-ray sources in the band from 0.3 to 10 keV, particularly to meet primary scientific goals in cosmology and extragalactic astronomy. JET-X consists of two identical, coaligned X-ray imaging telescopes, each with a spatial resolution of 30 arcsecond (Half Energy Width, HEW) or better. Each telescope is composed of a nested array of 12 mirrors with an aperture of 0.3 m and a focal length of 3.5 m. The mirror shells have Wolter I geometry and are replicated by an electroforming process for which Carl Zeiss manufactured the 12 monolithic Nickel coated aluminum mandrels. In order to determine the mandrel limited HEW, several measurement and analysis steps including raytracing calculations are performed. The major contributions to the error budget, axial slopes and roundness errors, as well as the position of the focus are investigated. The results are reported and discussed.