Proceedings Volume 2576

International Conference on Optical Fabrication and Testing

Toshio Kasai
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Proceedings Volume 2576

International Conference on Optical Fabrication and Testing

Toshio Kasai
View the digital version of this volume at SPIE Digital Libarary.

Volume Details

Date Published: 2 August 1995
Contents: 11 Sessions, 49 Papers, 0 Presentations
Conference: International Conferences on Optical Fabrication and Testing and Applications of Optical Holography 1995
Volume Number: 2576

Table of Contents

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Table of Contents

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  • Cutting I
  • Grinding
  • Devices
  • Surface Testing II
  • Surface Testing I
  • Surface Testing II
  • Surface Testing I
  • Surface Testing II
  • Measurement for Fabrication II
  • Figure Testing I
  • Measurement for Fabrication II
  • Figure Testing I
  • Figure Testing II
  • Measurement for Fabrication I
  • Measurement for Fabrication II
  • Measurement for Fabrication I
  • Figure Testing II
  • Measurement for Fabrication II
  • Measurement for Fabrication I
  • Figure Testing II
  • Measurement for Fabrication I
  • Figure Testing II
  • Measurement for Fabrication I
  • Figure Testing I
  • Figure Testing II
  • Polishing and Processing
  • Cutting II
  • Surface Testing II
  • Figure Testing I
Cutting I
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Recent achievements in closing the loop in interferometric tool setting on a pneumo-precision MSG325 diamond-turning lathe
Peter R. Hall, David A. Page, John K. Myler
On-machine laser unequal-path interferometry is used for setting the zero-point of the tool path in a single point diamond turning (SPDT) lathe. Experiments have been performed to determine the accuracy of such a technique, with the aim of using it to close the control loop. This would permit the complete tool-setting cycle to be performed under CNC control, and would result in significant man-power cost reductions. Also described is a novel form of optical system which uses the advantages of SPDT to create a zoom high power laser beam expander which is permanently aligned, has in-built reference planes and which has no moving dioptric components.
Influence of material removal models on the dynamics of cutting and grinding machines
Roger F. Gans
This paper discusses various simple models for nonlinear coupling of two standard second- order oscillators. The coupling is based on the idea of the van der Pol equation: small- amplitude disturbances grown and large disturbances decay. This paper examines the effects of discontinuity of coupling, and of the nature and closeness of coupling. the nature of nonlinear coupling is more important in determining the qualitative nature of the dynamics of these systems than the presence or absence of discontinuities. I observe coupled oscillator behavior with either or both oscillators active. In cases where both oscillators are active I find limit cycles and probable strange attractors (chaotic motion).
Grinding
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Ultraprecision grinding of optical materials and components applying ELID (electrolytic in-process dressing)
Hitoshi Ohmori
A grinding method which uses specific metallic bond fine grit wheels and electrolytic in- process dressing (ELID) is proposed for the effectual mirror surface grinding of brittle materials. Significant results such as high ground surface quality and ultraprecision grinding have been achieved through the use of this new grinding technique: `ELID-Grinding'. The ELID technique realizes efficient grinding by eliminating several grinding steps and interprocess dressings, in the general grinding operation. Applications to optical components have also started.
Characterization of fine abrasive particles for optical fabrication
Paul D. Funkenbusch, Y. Y. Zhou, Toshio Takahashi, et al.
Material removal during fine grinding operations is accomplished primarily by the action of individual abrasive particles on the glass surface. The mechanical properties of the abrasive are therefore important. Unfortunately it is difficult to directly measure the mechanical response of abrasives once they reach the scale of approximately 10 microns. As a result mechanical properties of fine abrasives are sometimes characterized in terms of an empirical `friability', based on the response of the abrasive to crushing by a metal ball in a vial. In this paper we report on modeling/experiments designed to more precisely quantify the mechanical properties of fine abrasives and ultimately to relate them to the conditions experienced by bound particles during grinding. Experiments have been performed on various types and sizes of diamond abrasives. The response of the particles is a strong function of the loading conditions and can be tracked by changing the testing parameters. Diamond size is also found to play a critical role, with finer diamonds less susceptible to fracture. A micromechanical model from the literature is employed estimate the forces likely to be seen during testing. We are also developing dynamic models to better predict the forces experienced during `friability' testing as a function of the testing parameters.
Observation and analysis of grinding scratch generation around the central part of a component
Michimasa Daito, Akira Kanai, Masakazu Miyashita
Ductile mode grinding (DMG) process, which can provide geometric accuracy of 0. 1 tm without cracks on the surface, is highly expected as a next stage machining process of brittle materials. DMG can be achieved when grain depth of cut in uncut chipthickness is controlled to under the ductile-brittle transition value, dc, dc 0. 1 pm for Si wafer'. It is required to develop both ultraprecision grinding machine (2) and truing technology of diamond wheels. In particular ,for realizing ductile mode grinding of brittle materials, the absolute requirement is that the grain depth of cut dg of all active cutting edges has to be smaller than the ductile-brittle transition value, do.. An extruded cutting edge (ECE) from the envelope of adjacent cutting edges causes a serious problem of scratch generation. The present paper deals with observation and analysis of grinding scratch generation around central part of 5, wafers ground with diamond wheels on rotary work-spindle machines.
Dynamic model for microgrinding spherical optical surfaces
Natarajan Venkataramanan, Roger F. Gans
Current research in microgrinding spherical optical surfaces shows that undesired marks are often produced on the ground surface. We speculate that vibrations during the microgrinding process may be the cause of these marks, and propose a model for the dynamics of the process, in an attempt to eliminate the cutter marks and improve the quality of the finished surface. We use Lagrangian mechanics to model the tool-workpiece system and evaluate the effects of simple forcing functions acting on the tool-workpiece system. In preparation for future full analyses we find that even simple non-axial vibrations can lead to intermittent tool- work contact.
Shear-mode grinding force criteria of Zerodur and Pyrex
Hiroshi Hashimoto, Kenichiro Imai
Experimental grinding of Zerodur and Pyrex demonstrated shear-mode grinding criteria (SM' GFC), which is a repeatable deterministic function of grinding conditions including materials and grinding wheels. Both criteria as with BK7 glass previously reported, are found to be the logarithmic function of removal rate.
Optics manufacturing: mechanics and materials issues
Paul D. Funkenbusch, John C. Lambropoulos, David J. Quesnel, et al.
To understand and further develop techniques for the deterministic microgrinding of glass, issues in both the materials science and mechanics fields need to be addressed. As part of our efforts at the Center for Optics manufacturing we are working with researchers from the center, other universities, government, and industry in both areas and at the interface between them. In this report we wish to give an overview of some of the efforts we are involved in, including specific examples of the experiments and analyses being performed.
New mirror-finish surface-grinding technology for the fabrication of optical device endfaces
Torahiko Kanda, Masashige Mitsuhashi, Tetsuji Ueda, et al.
This paper describes a mirror-finish slicing technology, and a spherical mirror-finish surface grinding technology. The former technology uses a thin metal bond micro-grain blade to which an electrolytic dressing is applied, for use with optical waveguide device endfaces. The latter technology uses a concave surface of metal bond micro-grain grinding wheel with electrolytic dressing, which produces convex spherical ferrule endfaces for Physical Control optical fiber connectors. They successfully produce mirror-finish endfaces of 0.06 micrometers Rmax directly, without the need for lapping. Endfaces produced with these technologies have sufficiently high optical light transmission characteristics.
Devices
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Soft x-ray optics for synchrotron radiation
Takeshi Namioka, Masato Koike, Hiroo Kinoshita, et al.
A new simulation method has been developed for evaluating the performance of soft x-ray optics for synchrotron radiation (SR) and for estimating tolerances for the fabrication and assembly errors of optics. The method is based on ray tracing and takes into account the surface figure error, thermal deformation, and SR source parameters. The method is applicable to aspheric mirrors and gratings with or without varied spacing and curved grooves. To evaluate the method, we applied it to the following two optical systems: (1) a Monk- Gillieson type monochromator on an undulator beamline of a third-generation SR source and (2) an extreme ultraviolet projection lithography system for SR from a superconducting compact electron storage ring. The results indicate that the method seems to provide realistic tolerances for the figure error (due to both polishing and heat load) and evaluation of the system performance, though more experimental data are needed to establish the validity of the method.
Optical approach for LCD inspection
Shigeki Terada, Yasuo Shono
Optical inspection technology is very fundamental for TFT (thin film transistor) array and cell processes of the LCD (liquid crystal display) manufacturing which is utilized in IQC (in-line quality control) process. This paper describes a general overview about LCD inspection items and our requirements, and show some optical technology for those inspection items.
High-speed glass-molding method to mass produce precise optics
Shigeru Hosoe, Yoshiharu Masaki
We propose a newly developed mass-production molding method for precise glass optics. The aims of this batch-type glass-molding method are as follows: (1) reduction of the molding time; (2) high reproducibility of molding and (3) high reliability of a molding system. The following engineering techniques were developed to achieve these aims: (1) independent distribution layout of multi-molding cavities to reduce thermal capacity and inhomogeneity of the cavity temperature, (2) die-based assembly structure to reduce decentering of the optical axis of the molds, (3) compact and small RF (radio frequency) power supply for rapid heating, and (4) automatic control with high error-recovery rate routines by a computer. As a result, this molding process achieved (1) high-speed molding of small optics, (2) high reproducibility and high production yield, (3) mold life longer than 10,000 shots without any optical surface protective coating, (4) high repeatability of molding conditions, and (5) high reliability of a molding system. Consequently, an average wave aberration of less than 0.025 (lambda) rms of a molded aspheric collimator (NA0.40) for laser beam printers (phi) 6.8 mm X t 5.6 mm in size and 40 s/piece tact time were achieved in large-capacity production.
Surface Testing II
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Precise measurements of refractive index distribution and optical surfaces
Tadashi Morokuma
Described are the two frontier areas of interest, that is, the measurement of refractive index distribution in gradient index glasses and the precise evaluation and measurement of optical surfaces for high precision optics. Scanning total reflection method and interferometric methods are applied to the refractive index measurement with an accuracy of 10-4 to 10-5. An AFM is found very useful for the evaluation of non-conductive surfaces as well as multilayers for x-ray optics. Methods for absolute measurement of surface profiles are proposed in consideration of the deformation due to gravity and another method for large surfaces.
Surface Testing I
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Computerized interferometric measurement of surface microstructure
Nearly all modern high-quality measuring instruments now use micro computers for the collection and analysis of data. This paper describes a computerized interferometric microscope system for the measurement of surface microstructure. For the instrument described in this paper the surface microstructure can be measured at data array sizes as large as 739 X 484 points for measurement fields ranging from 30 X 25 microns to 8.2 X 6.1 mm. A repeatability of the surface height measurements of less than 0.1 nm can be obtained for smooth surfaces. Surfaces having height variances as large as 500 microns can be measured to within an accuracy of a few nanometers.
Influence of surface skewness on the zero-order light scatter for a given roughness
Jan H. Rakels
The results ofthis study are: 1 . Inthe surface roughness range Rq < O.08A. the surfaces without Skewness obey the 115 formula within 5%. 2. Skewness in the surface height distribution reduces the light scatter for a given surface roughness. The latter result is useful for the manufacture of optical surfaces. For instance, for a given surface roughness, a diamond turned optic will perform better than an optic produced by grinding. Also a diamond turning machine can produce complicatedly shaped optical components. Keywords: light scattering. total integrated scatter, surface finish, skewness,
Surface Testing II
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Scattering effects from residual optical fabrication errors
Scattering effects from residual optical fabrication errors limit the optical performance of many imaging systems. Residual surface roughness over a broad range of relevant spatial frequencies must be specified and controlled for many applications of interest. Wide-angle scatter from surface microroughness severely reduces contrast in extended images. However, small-angle scatter from `mid' spatial frequency surface irregularities that span the gap between the `figure' and `finish' errors will degrade the achievable resolution. Specifying the traditional surface `figure' and `finish' is thus inadequate for high resolution imaging systems or for optical elements fabricated by new automated optical manufacturing processes. A linear systems treatment of surface scatter theory will be presented and its implementation in a computer code for modeling the image degradation effects of residual surface irregularities over the entire range of relevant spatial frequencies will be demonstrated. Parametric performance predictions can then be used to determine realistic optical fabrication tolerances for a variety of applications.
Surface Testing I
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Quantitative surface evaluation using a synchronous Nomarski microscope
Xinkang Tian, Masahide Itoh, Toyohiko Yatagai
A simple zonal approach is proposed for estimating phase distribution on large grids. The estimation is based on phase differences that are precisely measured in two orthogonal directions by a lateral shearing interferometer. It requires only O(N2) operations for reconstructing a phase distribution on a N by N grid. Computer simulation and experimental results are demonstrated to show effectiveness of the new algorithm.
Surface Testing II
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Lateral and vertical dimension measurements by using laser scanning microscopy including an optical heterodyne function
A construction of surface profile measurement system for measuring lateral and vertical dimensions of submicron to micron size and its applications to industrial inspection are described. This system includes a laser scanning microscopy (LSM) and an optical heterodyne interferometry (OHI) functions in one and the same optical device. These two functions are used individually depending on the purpose of the measurement. OHI measures vertical dimensions, LSM measures lateral dimensions. The selection of the functions is performed by changing the intensity distribution of the probe light beam falled on a sample and signal processing system of the reflected light beam.
Measurement for Fabrication II
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Indicatrix measurement based on birefringence retardation using phase modulation technology
Yoshihiro Mochida
The measurement of 3D anisotropy, which is the measurement of an indicatrix nx, ny, nz is made by the birefringence measurement with normal and inclined incidence of the light beam. Birefringence retardation contains a fast and a slow axis which are caused by the phase difference of two orthogonal light waves. Information obtained will be different, depending on whether the inclination of a sample is made around the fast axis or the slow axis. Also, depending on the sample to be measured, it is sometimes necessary to incline the sample by changing the azimuthal angle of the sample. Taking into account the recent developments mentioned above, an automatic measuring system of an indicatrix is discussed.
Figure Testing I
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Aspherical wavefront testing with several defocusing steps
A deep aspheric wavefront produces many interference fringes even when the optimum defocusing term is selected. The large number of fringes imposes a limit to the degree of asphericity that may be measured. A procedure using several interferograms with several defocusing values is described.
Measurement for Fabrication II
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Technique of recording and judging the sign of tilt in one interferogram
Koji Tenjimbayashi
How to record and judge the sign of tilt, that is the sign of configuration error, in one interferogram where the fringes are frozen is presented. If a flat surface is tested by a Twyman-Green interferometer without an imaging lens, not only usual straight and equally spaced fringes but also the extra curved fringes are caused. We can judge the sign of tilt by knowing which direction the extra fringes are curved. The application of this technique to a lateral shearing interferometer is also shown.
Figure Testing I
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Absolute measurement of spherical surfaces using phase-conjugate waves
Osami Sasaki, Yuuichi Takebayashi, Takamasa Suzuki
A new method for absolute measurement of spherical surfaces is described which does not require the rotation of the test surface. It requires the rotation of the diverger lens and the phase-conjugate waves. The alignment of the lens is easy because the two lights reflected by the two surfaces of the lens can be utilized for the alignment. In addition, the phase-conjugate waves can also be used. We analyze the alignment of the diverger lens, and also the alignments of the mirror to be set in the catseye position and the test surface. The experimental results show clearly the usefulness of the method.
Figure Testing II
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Considerations on the interferometric testing of convex hyperboloidal surfaces
Zacarias Malacara, Daniel Malacara-Hernandez
Two methods for hyperbolic secondary telescope mirror testing have been proposed for interferometrical testing. In the traditional one, a compensator is used to correct for the most significative aberrations. Other method calls for the use of an appropriate capture and analysis software, and the need for a compensator is eliminated. On a computation based system, some other restrictions appear. Both analysis methods are reviewed and compared.
Testing the 8.3-meter telescope optics
W. Scott Smith
The optical tests used for qualifying the Subaru optics are discussed along with their development on other programs. For the primary mirror five separate tests of the optical surface are performed at various stages of the fabrication process. The secondary mirrors will be qualified with a Simpson-Hindle test. Error budgets and calibration techniques are discussed.
Measurement for Fabrication I
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Light source with orthogonally linear polarized two-frequency beam from laser diode and its application
Yukitoshi Otani, Atsushi Tanahashi, Toru Yoshizawa
A novel light source using a laser diode is proposed for the optical heterodyne interferometry. The light from this source has two frequency beams whose polarization directions are orthogonal. The light source consists of a laser diode and some optical elements. The laser diode is easy to give frequency modulation by the injection current modulation. Two- frequency waves are made by giving time difference due to a different optical path. A Mach- Zehnder interferometer using polarizing beam splitters and a right angle prism makes orthogonal linear polarized two-frequency light. In order to compensate the power fluctuation by injection current modulation and to keep the total power constant, an incoherent laser diode is added. This light source is suitable for practical application and can produce a small unit compared with a light source using a Zeeman laser or an acousto optic modulator. Three dimensional surface profilometry by a differential interferometer is demonstrated as its application.
Measurement for Fabrication II
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Interferometers without fringe patterns
There are some optical arrangements closely resembling interferometric configurations. These, however, do not produce fringe patterns. An important characteristic of this device is that they do not have two different outputs with complementary patterns, but only one. Two of these configurations are described.
Measurement for Fabrication I
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Sinusoidal phase-modulating laser diode interferometer using a self-pumped phase-conjugate mirror
Takamasa Suzuki, Jyunzi Hasegawa, Osami Sasaki, et al.
A sinusoidal phase-modulating laser diode interferometer using a self-pumped phase-conjugate mirror is proposed. Since the laser diode has some attractive features in size, power waste, and wavelength tunability compared with the ordinary gas lasers, it is suitable for the light source of the interferometers. But to our knowledge, the interferometer which is constructed with a self-pumped phase-conjugate mirror and a laser diode is not well examined, although various applications of self-pumped phase-conjugate mirror has been proposed. Especially, the phase-conjugate wave goes back into the light source, it is important to examine the influences of the feedback effect for laser diode. We have examined the characteristics of the phase- conjugate interferometer and carried out the wave-front measurements using a sinusoidal phase-modulating interferometry.
Figure Testing II
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Testing of progressive spectacle lenses by coded optical correlation
Liren Lin
An incoherent optical correlator is developed to contour-map progressive power lenses, and the beam deviations across the aperture of a tested lens can be read by the disfocal shifting of one mask. A modelling of a local area of progressive lens to an extended sphere-cylindric lens is suggested to calculate the optical properties from the measured deviations in the local area. Thus the optical properties across the whole aperture can be achieved.
Measurement for Fabrication II
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Straightness measurement using laser beam straight datum
Junichi Uchikoshi, Shoichi Shimada, Naoya Ikawa, et al.
Using the direction stabilized laser beam as a physical straight datum, instead of the tangible reference surface, a method is proposed for the measurement of an error motion of a slide table and/or surface profile of mechanical components. A specially designed 2D position sensor/compensator for laser beam center is developed combining a quadrant photo-diode (QPD) position sensor for beam center and the piezo-compensator which compensates the beam shift from the center of QPD. By the use the sensor/compensator proposed, the positional and angular fluctuations of laser beam path is evaluated with nanometric resolution. Combining the sensor with the piezo-driven mirror compensator, the directional stabilizer for the laser beam is also designed in the same manner as the sensor/compensator. The stabilized He-Ne laser beam can be used as the metrological datum of straightness within the accuracy of 2 X 10 -8 rad. By mounting the position sensor/compensator on a slide table, the carriage with working distance of 1 m is so designed and built as to move straight along the stabilized laser beam. The carriage can be used as a mechanical straight datum with the accuracy equivalent to the laser beam stability.
Measurement for Fabrication I
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Use of power spectral density (PSD) functions in specifying optics for the National Ignition Facility
David M. Aikens, C. Robert Wolfe, Janice K. Lawson
In the second half of the 1990's, LLNL and others will be designing and beginning construction of the National Ignition Facility. This new laser will be capable of producing the worlds first controlled fusion ignition and burn, completing a vital milestone on the path of Fusion Energy. This facility will use more than 7,000 optical components, most of which have a rectangular aperture, which measure greater than 600 mm on the diagonal. In order to optimize the performance versus cost of the laser system, we have determined that specifications based on the Power Spectral Density (PSD) functions are the most effective for controlling mid-spatial wavelength errors. The draft optics specifications based on a combination of PSD and conventional roughness and P-V requirements are presented, with a discussion of their origins. The emphasis is on the application of a PSD function for transmitted wavefront optical specifications, and the benefits thereof. The PSD function is the most appropriate way to characterize transmitted wavefront errors with spatial frequencies ranging from several centimeters to a few hundred nanometers, with amplitudes in the (lambda) /100 regime. Such errors are commonly generated by cost effective, deterministic finishing technologies, and can be damaging to the laser, as well as causing unnecessary energy loss and inability to focus, in a high energy laser application. In addition, periodic errors can occur as a result of errors at other steps in the fabrication process, such as machine vibration in a fixed abrasive step, or material homogeneity ripple. The control of such errors will be essential to the construction of future high energy lasers.
Figure Testing II
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Parabolic liquid mirrors: reference surfaces in interferometry
Nathalie M. Ninane
A parabolic liquid mirror can be made by rotating a bath of mercury. The mirror focal length f is related to the angular speed of rotation (omega) and the gravity g by the formula: f equals g/2(DOT)(omega) 2. Good quality mirrors having a diameter up to 3 meters have been built and, telescopes and lidar based on this technology are running. The greatest advantage of liquid mirrors is the cost. For a big mirror the cost is 1 or 2 orders of magnitude less than a conventional glass mirror and its cell. The idea developed here is that if a good parabolic mirror can be produced at low cost, this one can be useful in optical shop testing as reference mirror and can fill the lack of aspheric reference. The liquid mirror can be used to test null correctors, to make holographic references or to control any system developed to test parabolic mirrors.
Measurement for Fabrication I
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Fabrication of a highly variable curvature mirror: testing and results
Marc Ferrari, Silvio P. Mazzanti, Gerard R. Lemaitre
A variable curvature mirror is a powerful device that can increase the field of view of optical interferometers. Such a mirror is being developed for the coherent combined focus of the European Southern Observatory Very Large Telescope Interferometer. The variable focal length permits positioning of the pupil image of an individual telescope at a precise location after the delay-line. This property is necessary to exactly remap homothetically the output pupil configuration at the image beamcombiner. Given the large zoom range that is needed in the delay line, when the mirror is not stressed the optical surface is a plane while it is convex with f/2.5 at maximum stress. The mirror itself is a very small stainless steel meniscus, with a 300 micrometers thickness, because only the high elasticity of such material allows to achieve the full domain of curvature. The thickness distribution of the meniscus is calculated using elasticity theory and a set of non-linear equations valid for the case of a large deformation. The realization of this micro-optic active device requires advanced techniques in optical fabrication and in particular high precision manufacturing with numerical command lathe. This article also presents the testing of this highly Variable Curvature Mirror and the surface quality obtained within the full curvature range.
Figure Testing II
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Interferometry for measuring large aspherical surfaces with holographic optical elements made by two steps
Takashi Mizobuchi, Hiroaki Ueda, Toshihiro Kubota, et al.
Interferometry with a holographic optical element for measuring the shape of large aspherical surfaces is reported. The interference fringe pattern between a parallel reference beam and a reconstructed wavefront from a master zone plate which has a very precise pattern drawn by an electron beam drawing machine is recorded on a hologram plate with an off-axis optical arrangement. The hologram plate used as the standard element is reconstructed by the conjugate beam in a modified Twyman-Green interferometer. Insufficient parallelism of commercial hologram plates and the difference in reflection ratio between a sample and the reference mirror can be compensated by this method. Not only rotationally symmetric lenses but also nonrotationally symmetric samples are available. It is also easy to make replicas. Some experimental results are also presented.
Measurement for Fabrication I
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Applications of computer-generated holograms for interferometric measurement of large aspheric optics
James H. Burge
Interferometric optical testing using computer-generated holograms (CGH's) has proven to give highly accurate measurements of aspheric surfaces. New applications of CGH interferometry were developed to support the fabrication of the large, steep mirrors required by the next generation ground-based telescopes. A new test to certify null correctors was designed and implemented that uses small CGH's fabricated onto flat surfaces. This test solves the difficult problem of verifying the accuracy of the null correctors that are used for measuring primary mirrors. Several new techniques for hologram fabrication have been explored for this application. A second new use of CGH's was developed for measuring convex secondary mirrors using test plates with holograms fabricated onto concave spherical reference surfaces. This test provides efficient and accurate measurement of large aspheric convex mirrors. A polar coordinate laser writing machine was built for fabricating these patterns onto curved optical surfaces up to 1.8 meters in diameter and as fast as f/1. These powerful new techniques have been implemented and optimized at the Steward Observatory Mirror Laboratory to guide mirror polishing for large telescope projects. They can also be readily applied for measuring small aspheres to high accuracy.
Figure Testing I
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Common path interferometer for flat surface measurement
Katsuyuki Okada, Shigeki Kawabata, Toshio Honda
In this paper, we propose a new common path interferometer, that needs only typical beam splitters to split and couple the reference and object beams. Some experiments show the common path configuration reduces the influence of vibration of the mirror effectively.
Figure Testing II
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Toroidal surfaces compared with spherocylindrical surfaces
Toroidal and sphero-cylindrical optical surfaces are two different kinds of surfaces (Menchaca and Malacara, 1986), but they are almost identical in the vicinity of the optical axis. The separation between these two surfaces increases when the distance to the optical axis increases. In this work the separation between these two surfaces outside of the central region is analytically studied.
Polishing and Processing
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Super-smooth polishing on aspherical surfaces (I): high-precision coordinate measuring and polishing systems
Mahito Negishi, Manabu Ando, Masafumi Takimoto, et al.
For the purpose of fabricating free-form optical elements with the accuracy of 80 nm PV, the Canon Super-Smooth Polisher has been developed. It has a high resolution on-machine coordinate measuring system that utilizes a contact probe. A unique probe structure is proposed, by which both inclination and motion errors of the probe are simultaneously compensated. The flaw problem is discussed from an experimental point of view, and it is found that the major cause of flaws is dirt on the probe or the workpiece. Fourteen axes interferometers are used to compensate for mechanical motion errors. The scanning speed of 4 mm/s is achieved by speeding up the force controller. The measurement results show good repeatabilities of 3 nm RMS for a 540 mm line measurement, and 9 nm RMS for a (phi) 500 mm aspherical surface measurement.
Super-smooth polishing on aspherical surfaces (II): achievement of a super-smooth polishing
Manabu Ando, Mahito Negishi, Masafumi Takimoto, et al.
This paper discusses super-smooth polishing technology for excimer lasers, soft X-rays, and other short-wavelength light applications. Short-wavelength light elements require surface quality and contour accuracy superior to traditional specifications, as well as free-form contours. For this reason, our target for free-form contours of a 500 mm diameter was set to 0.08 mm PV for contour accuracy, and 0.2 nm RMS for surface roughness. To improve surface quality we employed local pitch polishing, utilizing a flexible tool laminated with an elastic sheet, which adapts well to various contours. For greater contour accuracy, we developed the CSSP (Canon Super-Smooth Polisher), which polishes 500 mm diameter optical elements. The CSSP polishing process achieves a contour accuracy of 0.078 mm PV and a surface roughness of 0.13 nm RMS on a 500 mm diameter fused silica toroidal mirror. We also fabricated both CaF2 and CVD-SiC, materials widely used in short-wavelength light elements.
Fabrication and characterization of optical super-smooth surfaces
Dirk-Roger Schmitt, Frank Kratz, Gabriele A. Ringel, et al.
Intercomparison roughness measurements have been carried out at supersmooth artefacts fabricated from BK7, fused silica, and Zerodur. The surface parameters were determined using a special prototype of the mechanical profiler Nanostep (Rank Taylor Hobson), the Optical Heterodyne Profiler Z5500 (Zygo), and an Atomic Force Microscope (Park Scientific) with an improved acquisition technique. The intercomparison was performed after the range of collected spatial wavelength for each instrument was adjusted using digital filtering techniques. It is demonstrated for different roughness ranges that are applied superpolishing techniques yield supersmooth artefacts which can be used for more intercomparisons.
Influence of polishing fluid on ultrasmoothness polishing of Al-Mg alloy plate
Heiji Yasui, Ryuji Matsunaga, Hisashi Inao, et al.
In the ultra smoothness polishing of a kind of Al-Mg alloy plate with alumina and colloidal silica abrasives, the influence of the hydrogen exponent of polishing fluids on the removal rate and the smoothness are examined and discussed by polishing in four hydrogen exponent of fluids of pH equals 2.3 (acid), pH equals 7.3 (neutral), pH equals 9.7 (middle alkaline) and pH equals 11.7 (strong alkaline). In case of polishing with alumina abrasives, the acid fluid has better influence on the removal rate and the surface smoothness than the neutral and the alkaline fluid. The removal rate and the smoothness for alumina-polishing in the neutral fluid are extremely small and worse than those before polishing. The best micro-area smoothness obtained by alumina-polishing in the acid fluid is about 13 nm (P-V). In case of polishing with colloidal silica abrasives, the alkaline fluid has better influence on the removal rate but the hydrogen exponent of fluid has little influence on the smoothness. The best micro-area smoothness is about 5 nm (P-V) for silica-polishing but that excluding pits of about 5 nm in depth becomes below 2 nm. In the silica-polishing of pure aluminum plate, the pit is not formed on the polished surface.
Magnetorheological finishing: a deterministic process for optics manufacturing
Stephen D. Jacobs, Donald Golini, Yuling Hsu, et al.
Finish polishing of optics with magnetic media has evolved extensively over the past decade. Of the approaches conceived during this time, the most recently developed process is called magnetorheological finishing (MRF). In MRF, a magnetic field stiffens a fluid suspension in contact with a workpiece. The workpiece is mounted on the rotating spindle of a computer numerically controlled machine. Driven by an algorithm for machine control that contains information about the MRF process, the machine deterministically polishes out the workpiece by removing microns of subsurface damage, smoothing the surface to a microroughness of 10 angstroms rms, and correcting surface figure errors to less than 0.1 micrometers p-v. Spheres and aspheres can be processed with the same machine set-up using the appropriate machine program. This paper describes MRF and gives examples which illustrate the capabilities of a pre-prototype machine located at the Center for Optics Manufacturing.
Optomechanical switches for fiber optic communication systems
Shinji Nagaoka
This paper describes the design, performance, and application of newly developed latching type 1 X 2 single-mode fiber switch. The switch has been successfully fabricated using a micromachine technology. It exhibits excellent optical and mechanical characteristics. The optical loss is < 0.5 dB, the switching time is < 2 ms, and the driving power is only 9 mw. Switching operation was stable over 108 switchings. A 1 X 4 single-mode fiber switch constructed using three 1 X 2 switches exhibited practical characteristics. Several examples of possible switch application are briefly presented.
Cutting II
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Molecular dynamics analysis on microstructure of diamond-turned surfaces
Shoichi Shimada, Ryosuke Inoue, Junichi Uchikoshi, et al.
By the use of molecular dynamics computer simulation, a feasibility study is made for the quest of ultimate quality of machined surface attainable in diamond microturning of copper and aluminum with a fine cutting edge under hypothetically perfect machine motion. Based on the analyses, the surface generation process and microstructure of worksurface are well understood from atomistic point of view. In cutting of monocrystalline copper, the worksurface which has nearly perfect lattice structure can be obtained and ultimate surface roughness is estimated to be less than 1 nm. The quality of worksurface of aluminum is worse than that of copper, especially machined by the cutting edge with large radius. In cutting of polycrystalline copper, nanometric distorted layer inevitably remains on worksurface. However, the ultimate surface roughness is estimated to be at the same level as that of monocrystalline copper.
Flatness and surface roughness of diamond-turned surface
Osamu Horiuchi, Shyunji Itoh
In this study, investigated are the relationships between machining accuracy and motion errors of the machine tool. Moreover a method of compensating for the relative motion errors between tool and workpiece has been developed and its capability for improving the form accuracy has been experimentally evaluated. Flatness of diamond turned surface can be analytically divided to circular flatness and radial straightness. The circular flatness is mainly influenced by motion errors of the work spindle, i.e. axial motion error and angular motion error. Because of high repeatability of the motion errors, the circular profile is dependent on the radius and the rotational angle. The radial straightness depends upon straightness of locus of the diamond tool or motion errors of the carriage. These relationships have been demonstrated by experiments. The method of compensation of relative motion errors between the tool and work was effective to improve the flatness. Surface roughness of the diamond turned surface was greater than theoretical surface roughness. The differences between the actual surface roughness and the theoretical one were due to inaccuracies in copying the tool profile, anisotropy of the work material and vibrations of the machine tool.
Ultrasonic vibration turning of optical plastics
Jeong-Du Kim, Il Woo Choi
Mirror-surface machining is a very important technology to manufacture precision parts, especially optical parts. So far, those are produced by multi-processes, grinding and polishing, which are inefficient. In this study, the ultrasonic vibration cutting as a substitute for them in the precision machining of optical plastics (CR-39) which have been used for optical lens is suggested and experimented. To analyze the characteristics of surfaces machined by the ultrasonic vibration cutting in the ductile mode, the wavelength spectrum analysis is carried out and the micro-texture is compared with that of a conventional cutting. As a result, in micro cutting of the optical plastics by the ultrasonic vibration, it is confirmed that the surfaces of ductile cutting is obtained in depth of cut less than 2.7 micrometers .
Assessment of the precision and cost effectiveness of direct machining hybrid type optical surfaces for IR applications
Paul Shore
The investigations described in this paper highlight some important aspects of diamond turning `hybrid' type IR optics. Three commonly used IR substrate materials are assessed for their machinability into diffractive `hybrid' type elements. The influence of various machining and tooling parameters on surface quality are discussed. Achievable lens precision, surface quality and machining rates are provided.
Behavior of various cracks in the machining of glass
Junji Shibata
Today, high quality free-from-crack surfaces of brittle materials are expected to be machined by ductile mode chip formation. Firstly, abrasions and cracks formed on or beneath the machined surface were observed through turning tests with diamond cutting tools and it was discussed that the crack-free machining of glass would be possible. Secondly, the turning tests of glass with single crystal diamond conical indenters, tip radius of which are 5, 10 and 100 micrometers respectively, were performed for the purpose of investigating the criteria for crack- free chip formation, especially paying attention to the effect of indenter's tip radius. As a result, some crack-free grooves formed on the glass surface were observed, and it was concluded that one of the most important factors for ductile mode chip formation is the radius of tip curvature and suppression of a median crack.
Surface Testing II
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Optical metrology for small zone measurement
Guan-chang Jin, Nai-Keng Bao, Po Sheun Chung
A novel technique in optical metrology is developed for small zone measurement. The technique consists of a double lenses optical arrangement and an improved digital speckle correlation technique. This new method provides the possibility of high sensitivity for deformation measurements. A theoretical analysis and an experimental result confirmed that a 2 nm resolution can be realized. Some application examples are presented in the paper.
Figure Testing I
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Analysis of the measurement range in Fizeau phase-stepping interferometry using the moire effect
Benito Vasquez Dorrio, Jesus Blanco-Garcia, Angel F. Doval, et al.
In this work, the phase evaluation of multiple-beam Fizeau interferograms is carried out by the usual phase-stepping algorithms by superimposing the interferogram on a Ronchi grid located at the interferometer image plane. The phase modulation, required for phase measurement, is obtained by translating the grid in its own plane, while a slight defocusing in the image acquisition system provides a suitable sinusoidal intensity pattern. An estimation of the measurable range of surface slopes is calculated and experiments on a spherical surface have been realized in order to analyze the validity of the obtained results.