Previous work shows the effectiveness of computer controlled polishing (CCP) with the ADAPT tool by Satisloh for correcting form errors in optics manufacturing. This method however has a risk of producing residual errors in the range of mid spatial frequency errors (MSFE). In order to prevent these errors the residual in feed direction is investigated as well as the behavior at different parameters.
{"title":"Mid-spatial frequency errors in feed direction occurring in ADAPT polishing","authors":"S. Killinger, J. Liebl, R. Rascher","doi":"10.1117/12.2528114","DOIUrl":"https://doi.org/10.1117/12.2528114","url":null,"abstract":"Previous work shows the effectiveness of computer controlled polishing (CCP) with the ADAPT tool by Satisloh for correcting form errors in optics manufacturing. This method however has a risk of producing residual errors in the range of mid spatial frequency errors (MSFE). In order to prevent these errors the residual in feed direction is investigated as well as the behavior at different parameters.","PeriodicalId":422212,"journal":{"name":"Precision Optics Manufacturing","volume":"93 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123481986","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
For Line-Laser sensor products that CCD images are unknown, we present a method for the calibration of Line-Laser sensor measurement system using multi-directional and non-featured planes, and a method for system calibration optimization using multi-angle standard spheres. By building a mathematical model, we convert the line laser sensor measurement data into CMM measurement points. According to the constraint relationships of planes or spheres, the point measured by the Line-Laser sensor and the CMM should conform to the same equation, then we can solve the calibration matrix of the line laser sensor and the coordinate measuring machine by nonlinear optimization. Both simulation analyses and real experiments were conducted. A line laser sensor was used to measure a frosted standard ball with a radius of 12.696 mm. The radius deviation measured by the line laser sensor system and the center deviation of the sphere comparing with the CMM were observed. The experimental results show that the radius deviation of the calibration laser sensor measurement system is less than 0.02mm, and the center distance deviation of the sphere is less than 0.02mm. This method utilizing non-featured planes simplifies the calibration equipment and can reduce the fitting error when using standard ball from multiple angles for calibration. This method is different from the method of calibrating the single direction of the laser sensor. It can simultaneously calibrate the rotation matrix and translation matrix of the two-dimensional line laser sensor to the coordinate measuring machine, and optimize the global optimal calibration parameters.
{"title":"A multi-axis space coordinate system calibration method for composite line laser measuring systems using non-feature planes and multi-angle spheres","authors":"C. Xu, X. Wei, Zhongzhi Zhang, Xiaoping Zhou","doi":"10.1117/12.2526009","DOIUrl":"https://doi.org/10.1117/12.2526009","url":null,"abstract":"For Line-Laser sensor products that CCD images are unknown, we present a method for the calibration of Line-Laser sensor measurement system using multi-directional and non-featured planes, and a method for system calibration optimization using multi-angle standard spheres. By building a mathematical model, we convert the line laser sensor measurement data into CMM measurement points. According to the constraint relationships of planes or spheres, the point measured by the Line-Laser sensor and the CMM should conform to the same equation, then we can solve the calibration matrix of the line laser sensor and the coordinate measuring machine by nonlinear optimization. Both simulation analyses and real experiments were conducted. A line laser sensor was used to measure a frosted standard ball with a radius of 12.696 mm. The radius deviation measured by the line laser sensor system and the center deviation of the sphere comparing with the CMM were observed. The experimental results show that the radius deviation of the calibration laser sensor measurement system is less than 0.02mm, and the center distance deviation of the sphere is less than 0.02mm. This method utilizing non-featured planes simplifies the calibration equipment and can reduce the fitting error when using standard ball from multiple angles for calibration. This method is different from the method of calibrating the single direction of the laser sensor. It can simultaneously calibrate the rotation matrix and translation matrix of the two-dimensional line laser sensor to the coordinate measuring machine, and optimize the global optimal calibration parameters.","PeriodicalId":422212,"journal":{"name":"Precision Optics Manufacturing","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126177479","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
With more and more industrial devices getting inter-connected the attack surface for cyber attacks is increasing steadily. In this paper the possible approach of an attacker who got access to the office network at the Institute for Precision Manufacturing and High-Frequency Technology (IPH) to attack one of the optic machines that reside in another network segment is presented. Based on known vulnerabilities from the Common Vulnerabilities and Exposures (CVE), like the shellshock exploit or remote code execution with PsExec, for devices identified in the network, an attacker can bypass the firewall between the office network and the laboratory network and get full access to the HMI of the target machine.
{"title":"Hacking an optics manufacturing machine: You don't see it coming?!","authors":"Robert Wildenauer, K. Leidl, M. Schramm","doi":"10.1117/12.2526691","DOIUrl":"https://doi.org/10.1117/12.2526691","url":null,"abstract":"With more and more industrial devices getting inter-connected the attack surface for cyber attacks is increasing steadily. In this paper the possible approach of an attacker who got access to the office network at the Institute for Precision Manufacturing and High-Frequency Technology (IPH) to attack one of the optic machines that reside in another network segment is presented. Based on known vulnerabilities from the Common Vulnerabilities and Exposures (CVE), like the shellshock exploit or remote code execution with PsExec, for devices identified in the network, an attacker can bypass the firewall between the office network and the laboratory network and get full access to the HMI of the target machine.","PeriodicalId":422212,"journal":{"name":"Precision Optics Manufacturing","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125602015","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Microstructuring of glass optics enables a large variety of benefits for miscellaneous fields of application. From an enhancement of the performance of optical systems to the haptic improvement of coverglasses – the advantages of structured glass are obvious. Especially in the field of high-precision optics, microstructured optical surfaces can carry out important functions, such as beam shaping in laser systems or the correction of dispersive color alterations. Besides enhancements regarding optics of the visible light spectrum, microstructures can compensate disadvantages of infrared(IR)-transmissive lenses such as chalcogenide glasses. As these optics suffer high transmission losses due to their high refractive index the integration of an anti-reflective (AR) function is necessary. Moth-eye-structures are a promising way to avoid the currently used AR-coatings. So far, microstructures are brought into the lens’ surface by lithography mainly. The therefore additional processing step follows the previous shaping. An efficient production of the structured components is the key to success for applications aside science and research. The technology precision glass molding (PGM) is able to combine the contradicting aspects of high precision and high volume production. PGM is a replicative manufacturing method that allows the macroscopic molding and the manufacturing of microscopic structures to be carried out simultaneously. Based on a representative PGM process chain, the paper at hand describes differences, challenges and current research results regarding molding microstructures.
{"title":"Replicative manufacturing of glass optics with functional microstructures","authors":"C. Rojacher, T. Grunwald, T. Bergs","doi":"10.1117/12.2526733","DOIUrl":"https://doi.org/10.1117/12.2526733","url":null,"abstract":"Microstructuring of glass optics enables a large variety of benefits for miscellaneous fields of application. From an enhancement of the performance of optical systems to the haptic improvement of coverglasses – the advantages of structured glass are obvious. Especially in the field of high-precision optics, microstructured optical surfaces can carry out important functions, such as beam shaping in laser systems or the correction of dispersive color alterations. Besides enhancements regarding optics of the visible light spectrum, microstructures can compensate disadvantages of infrared(IR)-transmissive lenses such as chalcogenide glasses. As these optics suffer high transmission losses due to their high refractive index the integration of an anti-reflective (AR) function is necessary. Moth-eye-structures are a promising way to avoid the currently used AR-coatings. So far, microstructures are brought into the lens’ surface by lithography mainly. The therefore additional processing step follows the previous shaping. An efficient production of the structured components is the key to success for applications aside science and research. The technology precision glass molding (PGM) is able to combine the contradicting aspects of high precision and high volume production. PGM is a replicative manufacturing method that allows the macroscopic molding and the manufacturing of microscopic structures to be carried out simultaneously. Based on a representative PGM process chain, the paper at hand describes differences, challenges and current research results regarding molding microstructures.","PeriodicalId":422212,"journal":{"name":"Precision Optics Manufacturing","volume":"260 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115011993","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper provides general information about Magnetic-Abrasive Polishing (MAP) of high-precision surfaces of machines and instruments. The polishing process is performed by a ferroabrasive powder tool, formed by the magnetic field into an “elastic brush”. The magnetic field helps formation of the surface layer with a minimum of structure defects. MAP technologies are used for finishing operations of super-fine polishing of optics, lasers and electronics. The main characteristics of the program-controlled installation of the model A17 for MAP surfaces up to 200 mm in size are presented. The presented effective technology allows forming a surface nanorelief with a roughness parameter Ra of less than 5 angstroms. It allows to significantly increase the laser induced damage threshold of the active elements of optical and laser systems.
{"title":"Magnetic-abrasive polishing: opportunities and prospects","authors":"M. Khomich, Viachaslau Bitkasha, Kseniya Yurasava","doi":"10.1117/12.2528703","DOIUrl":"https://doi.org/10.1117/12.2528703","url":null,"abstract":"This paper provides general information about Magnetic-Abrasive Polishing (MAP) of high-precision surfaces of machines and instruments. The polishing process is performed by a ferroabrasive powder tool, formed by the magnetic field into an “elastic brush”. The magnetic field helps formation of the surface layer with a minimum of structure defects. MAP technologies are used for finishing operations of super-fine polishing of optics, lasers and electronics. The main characteristics of the program-controlled installation of the model A17 for MAP surfaces up to 200 mm in size are presented. The presented effective technology allows forming a surface nanorelief with a roughness parameter Ra of less than 5 angstroms. It allows to significantly increase the laser induced damage threshold of the active elements of optical and laser systems.","PeriodicalId":422212,"journal":{"name":"Precision Optics Manufacturing","volume":"2000 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128275636","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Sebastian Sitzberger, J. Liebl, J. Reitberger, R. Rascher
Zero point clamping systems are an integral part of the manufacturing industry. They have only yet to find their way into the optical industry. This article compares the hydraulic expansion holder, a clamping system currently used in the optical industry with a zero-point clamping system. The achievable accuracies of both systems are compared over several measurement series. In addition, the process capability evaluation is used for the comparison. Finally, the results are summarized to provide every researcher and practitioner with a foundation for assessing whether zero point clamping systems meet the requirements for the use in optical manufacturing.
{"title":"Zero-point clamping systems in optical production","authors":"Sebastian Sitzberger, J. Liebl, J. Reitberger, R. Rascher","doi":"10.1117/12.2528774","DOIUrl":"https://doi.org/10.1117/12.2528774","url":null,"abstract":"Zero point clamping systems are an integral part of the manufacturing industry. They have only yet to find their way into the optical industry. This article compares the hydraulic expansion holder, a clamping system currently used in the optical industry with a zero-point clamping system. The achievable accuracies of both systems are compared over several measurement series. In addition, the process capability evaluation is used for the comparison. Finally, the results are summarized to provide every researcher and practitioner with a foundation for assessing whether zero point clamping systems meet the requirements for the use in optical manufacturing.","PeriodicalId":422212,"journal":{"name":"Precision Optics Manufacturing","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130096546","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Driven by the wide range of applications in the fields of laser technology, biomedicine and consumer electronics, etc., the demand for high-quality lenses with complex geometries and small dimensions is rapidly rising. Since grinding and polishing of such lenses is neither practically nor economically viable, Precision Glass Molding (PGM) has become a popular production method. PGM is a replicative technology for producing high-precision optical lenses in medium or high volumes. During the one-cycle molding process, a glass preform is heated until the viscous state and afterwards pressed into the desired shape using two high-precise molding tools. This process permits the direct and efficient manufacture of high shape accuracy and surface quality optics without any mechanic post-processing step. The efficiency of PGM processes depend primarily on the lifetime of the high-precision molding tools. Therefore, various investigations focus on enhancing the molding tool lifetime. This work focuses on the evaluation of suitable mold materials for PGM, whereby different substrate materials as well as protective coatings are considered. At this, three different kinds of glass with varying molding temperature were investigated: common optical glass, infrared transmissive chalcogenide glass, and fused silica. The molding temperature of common optical glass ranges from 400°C to 700°C, whereas chalcogenide glass is molded at around 250°C. Fused silica requires a more challenging molding temperature of about 1400°C. Due to the varying molding temperatures, different mold materials can be evaluated for each of the investigated glasses.
{"title":"Evaluation of mold materials for precision glass molding","authors":"M. Friedrichs, T. Grunwald, T. Bergs","doi":"10.1117/12.2526769","DOIUrl":"https://doi.org/10.1117/12.2526769","url":null,"abstract":"Driven by the wide range of applications in the fields of laser technology, biomedicine and consumer electronics, etc., the demand for high-quality lenses with complex geometries and small dimensions is rapidly rising. Since grinding and polishing of such lenses is neither practically nor economically viable, Precision Glass Molding (PGM) has become a popular production method. PGM is a replicative technology for producing high-precision optical lenses in medium or high volumes. During the one-cycle molding process, a glass preform is heated until the viscous state and afterwards pressed into the desired shape using two high-precise molding tools. This process permits the direct and efficient manufacture of high shape accuracy and surface quality optics without any mechanic post-processing step. The efficiency of PGM processes depend primarily on the lifetime of the high-precision molding tools. Therefore, various investigations focus on enhancing the molding tool lifetime. This work focuses on the evaluation of suitable mold materials for PGM, whereby different substrate materials as well as protective coatings are considered. At this, three different kinds of glass with varying molding temperature were investigated: common optical glass, infrared transmissive chalcogenide glass, and fused silica. The molding temperature of common optical glass ranges from 400°C to 700°C, whereas chalcogenide glass is molded at around 250°C. Fused silica requires a more challenging molding temperature of about 1400°C. Due to the varying molding temperatures, different mold materials can be evaluated for each of the investigated glasses.","PeriodicalId":422212,"journal":{"name":"Precision Optics Manufacturing","volume":"11171 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129874645","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Deggendorf Institute of Technology (DIT) and its Faculty of Applied Natural Sciences and Industrial engineering transfer a broad spectrum of knowledge to the students. The clarification of the interrelations that exist between seemingly isolated fields of knowledge is a permanent process. In order to put this into practice, a telescope construction project was started. The base of the in-house student project is the Technology Campus in Teisnach, which bundles capacities for process development, production and measurement of high-precision optics, including telescope optics. A first optical design, which is based on a subset of the parameter space published in 1989 by M. Brunn1, 2 (later built by D. Stevick as f/12-system3 ), made use of a primary mirror M1 with a diameter of 400 mm. An f/8-system provide a Strehl ratio SR ≥ 0.8 over an entire field of view of 0.7° deg. Even if this seems to be sufficient, manufacturing tolerances, adjustment tolerances, thermal drift and positional changes considerably reduce the Strehl ratio. In order to obtain reliable values of acceptable tolerances, statistical Monte Carlo analyses had been carried out. As consequences, the tube design was changed and the design of new mirror mounts started. This was done to achieve the required stiffness. The new tube designs, one based on carbon-fiber-reinforced polymer (CFRP) and one based on FeNi36, had been tested by using FEM analysis. In addition, the practicability of deep learning based aberration detection was tested. Zernike polynomials obtained by analyzing the star images with a Convolutional Neuronal Network (CNN). The current state of the development is described.
{"title":"Alignment and thermal drift aspects of a four-tilted-mirror student project telescope","authors":"G. Fütterer, M. Wagner, L. Bauer, S. Wittl","doi":"10.1117/12.2530076","DOIUrl":"https://doi.org/10.1117/12.2530076","url":null,"abstract":"The Deggendorf Institute of Technology (DIT) and its Faculty of Applied Natural Sciences and Industrial engineering transfer a broad spectrum of knowledge to the students. The clarification of the interrelations that exist between seemingly isolated fields of knowledge is a permanent process. In order to put this into practice, a telescope construction project was started. The base of the in-house student project is the Technology Campus in Teisnach, which bundles capacities for process development, production and measurement of high-precision optics, including telescope optics. A first optical design, which is based on a subset of the parameter space published in 1989 by M. Brunn1, 2 (later built by D. Stevick as f/12-system3 ), made use of a primary mirror M1 with a diameter of 400 mm. An f/8-system provide a Strehl ratio SR ≥ 0.8 over an entire field of view of 0.7° deg. Even if this seems to be sufficient, manufacturing tolerances, adjustment tolerances, thermal drift and positional changes considerably reduce the Strehl ratio. In order to obtain reliable values of acceptable tolerances, statistical Monte Carlo analyses had been carried out. As consequences, the tube design was changed and the design of new mirror mounts started. This was done to achieve the required stiffness. The new tube designs, one based on carbon-fiber-reinforced polymer (CFRP) and one based on FeNi36, had been tested by using FEM analysis. In addition, the practicability of deep learning based aberration detection was tested. Zernike polynomials obtained by analyzing the star images with a Convolutional Neuronal Network (CNN). The current state of the development is described.","PeriodicalId":422212,"journal":{"name":"Precision Optics Manufacturing","volume":"11171 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130046701","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Henkel, A. Barz, J. Bliedtner, Carolin Lampert, Dietmar Gräfe, Kurt Kleinen, C. Kleinen
In many optical applications plane optical elements are needed for deflection or splitting of light. The functionality of these parts is usually reduced to one certain task and manufacturing of them needs a big amount of effort to achieve high precision. A new optical element is presented, which can fulfill different optical functions simultaneously, is simply built and robust. It is based on glass cuboids joined together under a certain angle while introducing the possibility of fine adjusting the angle in the manufacturing process. The basic components can be modified to offer a lot of different applications. A technological process development is presented as well for more efficient machining of these new parts and existing part geometries. Novel manufacturing processes like ultrasonic grinding, ultrafine grinding and diffusion joining are experimentally investigated, since they promise significant improvements compared to conventional methods. Finally, an appropriate process chain is developed.
{"title":"Development of adjustable multifunctional optical elements for deflection, splitting, and shaping of light beams","authors":"S. Henkel, A. Barz, J. Bliedtner, Carolin Lampert, Dietmar Gräfe, Kurt Kleinen, C. Kleinen","doi":"10.1117/12.2526505","DOIUrl":"https://doi.org/10.1117/12.2526505","url":null,"abstract":"In many optical applications plane optical elements are needed for deflection or splitting of light. The functionality of these parts is usually reduced to one certain task and manufacturing of them needs a big amount of effort to achieve high precision. A new optical element is presented, which can fulfill different optical functions simultaneously, is simply built and robust. It is based on glass cuboids joined together under a certain angle while introducing the possibility of fine adjusting the angle in the manufacturing process. The basic components can be modified to offer a lot of different applications. A technological process development is presented as well for more efficient machining of these new parts and existing part geometries. Novel manufacturing processes like ultrasonic grinding, ultrafine grinding and diffusion joining are experimentally investigated, since they promise significant improvements compared to conventional methods. Finally, an appropriate process chain is developed.","PeriodicalId":422212,"journal":{"name":"Precision Optics Manufacturing","volume":"48 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115258881","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
An interferometric problem is the limited fringe density, which is due to the limited allowed slope difference of superimposed wave fronts. Thus, the angular dynamic range of measurable surfaces and objects under test is limited. In other words, all shapes that deviate from a plane surface or a sphere represent a measuring problem in interferometers, or require an individually adapted null optics, which might cost e.g. 10 k∈ or more. In addition, ground surfaces cannot be measured in standard interferometers, except by using Speckle interferometry, which is limited in resolution. Freeform optics are very problematic. Even when polished, only tactile or confocal coordinate measurement might work. Several interferometers address the problem of the angular deviation to a sphere. For instance, lateral stitching on a curved surface, which is equivalent to the best-fit sphere, or longitudinal stitching is used. To use a tilted wave interferometer for asphere metrology is another option, which provides versatile measurement configurations. The approach discussed here is to use optical filters. The development of this technique is part of a project most recently started at the Technology Campus in Teisnach. The surface under test (SUT) is imaged onto an optical filter, which has a calibrated angular selectivity. Thus, the angles of the local wave front normal vectors are transferred into an intensity distribution. A set of angular measurements enables reduced uncertainty of the wave front measurement. Aspects as e.g. the working principle, boundary conditions and the identification of practical filters are discussed in the paper.
{"title":"Wave front sensing for metrology by using optical filter","authors":"G. Fütterer","doi":"10.1117/12.2530013","DOIUrl":"https://doi.org/10.1117/12.2530013","url":null,"abstract":"An interferometric problem is the limited fringe density, which is due to the limited allowed slope difference of superimposed wave fronts. Thus, the angular dynamic range of measurable surfaces and objects under test is limited. In other words, all shapes that deviate from a plane surface or a sphere represent a measuring problem in interferometers, or require an individually adapted null optics, which might cost e.g. 10 k∈ or more. In addition, ground surfaces cannot be measured in standard interferometers, except by using Speckle interferometry, which is limited in resolution. Freeform optics are very problematic. Even when polished, only tactile or confocal coordinate measurement might work. Several interferometers address the problem of the angular deviation to a sphere. For instance, lateral stitching on a curved surface, which is equivalent to the best-fit sphere, or longitudinal stitching is used. To use a tilted wave interferometer for asphere metrology is another option, which provides versatile measurement configurations. The approach discussed here is to use optical filters. The development of this technique is part of a project most recently started at the Technology Campus in Teisnach. The surface under test (SUT) is imaged onto an optical filter, which has a calibrated angular selectivity. Thus, the angles of the local wave front normal vectors are transferred into an intensity distribution. A set of angular measurements enables reduced uncertainty of the wave front measurement. Aspects as e.g. the working principle, boundary conditions and the identification of practical filters are discussed in the paper.","PeriodicalId":422212,"journal":{"name":"Precision Optics Manufacturing","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125282507","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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