The optics industry has not followed the lead of the machining and electronics industries in applying advances In computer aided engineering (CAE), computer assisted manufacturing (CAM), automation or quality management techniques. Automationbased on computer integrated manufacturing (CIM) and flexible machining systems (FMS) has been widely implemented In these industries. Optics continues to rely on standalone equipment that preserves the highly skilled, labor intensive optical fabrication systems developed in the 1940's. This paper describes development initiatives at the Center for Optics Manufacturing that will create computer integrated manufacturing technology and support processes for the optical industry.

Precision finishing process of hard and brittle material components such as single crystal silicon wafer and magnetic head consists of lapping and polishing which depend too much on skilled labor. This process is based on the traditional optical production technology and entirely different from the automated mass production technique in automobile production. Instead of traditional lapping and polishing, the nanogrinding is proposed as a new stock removal machining to generate optical surface on brittle materials. By this new technology, the damage free surface which is the same one produced by lapping and polishing can be obtained on brittle materials, and the free carvature can also be generated on brittle materials. This technology is based on the motion copying principle which is the same as in case of metal parts machining. The new nanogrinding technology is anticipated to be adapted as the machining technique suitable for automated mass production, because the stable machining on the level of optical production technique is expected to be obtained by the traditional lapping and polishing.

The Kodak 2 .5m Ion Figuring System (IFS), intended for the final figuring of large optics using a directed inert neutralized ion beam, has been installed and is operational. Process development and production implementation efforts are currently underway. Thermal heating effects due to exposure to the ion beam removal function are discussed. Details of processing and results from an ion figuring correction of a 0.Sm lightweighted optic are presented.

In the next decades, we foresee the need for the fabrication of many large asphenc mirrors for space and astronomy applications. Itek Optical Systems has developed computer controlled optical surfacing for rapidly fabricating such optics. Recently, these operations have been improved with the development of a sheaf of new processes based on a greatly increased understanding of the physics of glass surfacing. These improvements have already produced a reduction of large optics surfacing time and the technology points towards further reduction.

This paper presents results on figuring aspheric optical surfaces by Plasma Assisted Chemical Etching (PACE) demonstrating rapid, predictable convergence to the final figure. The figuring data shows better than 95% convergence of the final figure in a single operation for large spatial errors (on the order of the plasma tool size and larger) and a high efficiency for correcting errors much smaller than the tool size (mid-spatial frequency range). Automated correction of arbitrary figure errors are made from surface metrology data. This technology can be scaled from small optics, millimeters in diameter, to large optics, meters in diameter. A PACE production capability is first being developed for relatively small optics, up to 12" diameter, that can have an anamorphic shape. The central feature of PACE is control of material removal regardless of surface shape. In addition, it is capable of high removal rates for a polishing process, one to two orders of magnitude larger than conventional pitch polishing. Thus, PACE can be used for figure generation as well as final figure correction. PACE intrinsically smoothes while removing material leaving a virgin surface free of process related contamination and subsurface damage.

This paper presents results on figuring aspheric optical surfaces by Plasma Assisted Chemical Etching (PACE) demonstrating rapid, predictable convergence to the final figure. The figuring data shows better than 95% convergence of the final figure in a single operation for large spatial errors (on the order of the plasma tool size and larger) and a high efficiency for correcting errors much smaller than the tool size (mid-spatial frequency range). Automated correction of arbitrary figure errors are made from surface metrology data. This technology can be scaled from small optics, millimeters in diameter, to large optics, meters in diameter. A PACE production capability is first being developed for relatively small optics, up to 12" diameter, that can have an anamorphic shape. The central feature of PACE is control of material removal regardless of surface shape. In addition, it is capable of high removal rates for a polishing process, one to two orders of magnitude larger than conventional pitch polishing. Thus, PACE can be used for figure generation as well as final figure correction. PACE intrinsically smoothes while removing material leaving a virgin surface free of process related contamination and subsurface damage.

A brief historical review is given of the earliest attempts to form optical images with x-rays with special emphasis on grazing incidence optics. Some mention will be made of other approaches to x-ray image formation such as holography and zone plates and how they were developed in an educational context. Comments are made concerning modern solutions to x-ray optical problems which seemed insurmountable in the early days of x-ray opt

The fabrication of large optical surfaces is accompanied by a considerable amount of mathematical analysis and modeling aimed at assisting in the measurement of the optic, refining the grinding operation and speeding up the polishing process. A summary of such recent efforts provides a good indication of the state of the overall process.

The Large Optical Generator (LOG) recently completed the generating of six off-axis aspheres. It was decided to use the non-traditional technique of three-axis contouring to solve many of the fabrication and mounting problems. The process and the solutions it provides are discussed, as well as the resultant figure errors and how these compare to the traditional two-axis generating that LOG has done in the past.

The Large Optical Generator (LOG) recently completed the generating of six off-axis aspheres. It was decided to use the non-traditional technique of three-axis contouring to solve many of the fabrication and mounting problems. The process and the solutions it provides are discussed, as well as the resultant figure errors and how these compare to the traditional two-axis generating that LOG has done in the past.

A large supersmooth precision cylindrical scanning mirror has been designed and in- stalled in beam-line BL-5 at Beijing Electron Positron Collider (BEPC) for synchro- tron radiation soft x-ray photolithography experimental station. Soft x-ray at wave length 4-20A collimated passing through cylindrical mirror is sent into experimental station at distance of 33 m from the source. Horizotal acceptance angle and grazing incidence angle are 7.5 mrad and 1.5 degree, respectively. The cylindrical mirror is made of aluminium alloy LD2 and its dimension and radius are 24OX110X30 mm and 527.5 mm, respectively. High accuracy figuring and supersmooth surface of the mirror are required in order to reduce energy lo$s as less as posible. Thj paper describts the fabrication technique and test method of the cylindrical mirror. The blank made of aluminium alloy is machined and formed precisely and then the surface of cylindrical mirror is plated by means of electronless nickel plating, and grinded precisely and polished superprecisely special fine grinding abrasive on cylindrical mirror fabreationmechinemodified. Finally Au coat is coated on the slit'- face of cylinbrocal mirror by coating machine under UHV condition 1O0 torr • The fi guring error of surface of the mirror is tested by test glass and interferometor; surface roughness of the mirror is tested by means of the scattering method and in terferometry. The s1op error, figuring error and roughnes of the surface of the cy lindeical mirror are less than 10 arc second, /1O and 1OA RMS, respectively. Per formence as mentioned above meets requirements of design.

Minimization of aberrations of a microlithographic projection lens is one of the more important processes in manufacturing a wafer stepper. It is difficult to optimize a Deep UV (249 nm) projection lens without a DUV interferometer. This paper will present the technique and result of testing and optimizing a DUV projection lens with a Twyman-Green interferometer which employs a HeCd laser (442 nanometers ) for a source. Testing the DUV lens with a visible wavelength interferometer inevitably degrades the sensitivity and accuracy of the interferometric testing process due to a large change in wavelength. The minimum aberration tested and optimized by the HeCd Twyman-Green interferometer will not correspond to the best performance of the DUV projection lens. This is because there is a residue of aberrations caused by testing the lens at a wavelength other than the 249 nm wavelength for which it was designed. To solve this problem, a synthetic wavefront predicted by a lens design program at 442 nm was generated and converted to Zernike polynomial coefficients. The true aberrations of the projection lens are obtained by subtracting the synthetic wavefront from the measured wavefront.

A gage is being developed to make precision measurements of moving surfaces in a manufacturing environment. A prototype has demonstrated submicron repeatability and accuracy at the 2- to 6-micron level as well as the ability to measure parts moving at about 1 in./min. The system is described, and the means to make the accuracy comparable to the repeatability and to increase part velocity to more than 200 in./min are indicated.

A novel optical profiler is described in this paper for measurement of surface profiles of synchrotron radiation (SR) mirrors. The measurement is based on a combination of an optical heterodyne technique and a precise phase measurement procedure without a reference surface. A Zeeman two-frequency He-Ne laser is employed as the light source. The common-path optical system, which uses a birefringent lens as the beam splitter, minimizes the effects of air turbulence, sample vibration and temperature variation. A special autofocus system allows the profiler to measure the roughness and shape of a sample surface. The optical system is mounted on a large linear air-bearing slide, and is capable of scanning over distances covering the spatial period range from several microns to nearly one meter with a high measurement accuracy.

The paper indicates the emerging requirements for profilometry instruments for use in the fabrication and characterisation of modern optical systems. Important design principles are covered, together with some of the problems which can be experienced. Examples of a number of systems recently developed are given both stand alone systems and those which operate insitu to the machining process.

There is a critical need for new metrology tools for bridging the gap between mechani cal profilometry and high-resolution Interterometry in the manufacture of advanced optical components. A new class of instruments is becoming available because of the rapid advances In laser diode technology. Properties of modern index-guIded laser diodes include wavelength tunability, multiple wavelength operation, excellent spatial coherence and low unit cost. These properties can be used for absolute distance measurement on polished and unpolished optical surfaces during fabrication.

Measurement of an optical surface by a figure measuring device allows one to make an estimate of the shape of the surface. The absolute accuracy in locating the "true" surface depends on the sources of error in the measurement process - both random errors and systematic errors. Analysis procedures have been developed to extract surface figure information from optical profiler measurements on large mirrors. Rigid-body orientation effects are important in analyzing the shape of the off-axis ellipsoidal reflectors used as grazing incidence mirrors in soft-x-ray synchrotron instrumentation. Knowledge of the noise level and optical aberration function of the Long Trace Profiler allow us to place error bars smaller than lambda/100 on measurements of surfaces that are more than 500mm long.

Minimization of aberrations of a microlithographic projection lens is one of the more important processes in manufacturing a wafer stepper. It is difficult to optimize a Deep UV (249 nm) projection lens without a DUV interferometer. This paper will present the technique and result of testing and optimizing a DUV projection lens with a Twyman-Green interferometer which employs a HeCd laser (442 nanometers ) for a source. Testing the DUV lens with a visible wavelength interferometer inevitably degrades the sensitivity and accuracy of the interferometric testing process due to a large change in wavelength. The minimum aberration tested and optimized by the HeCd Twyman-Green interferometer will not correspond to the best performance of the DUV projection lens. This is because there is a residue of aberrations caused by testing the lens at a wavelength other than the 249 nm wavelength for which it was designed. To solve this problem, a synthetic wavefront predicted by a lens design program at 442 nm was generated and converted to Zernike polynomial coefficients. The true aberrations of the projection lens are obtained by subtracting the synthetic wavefront from the measured wavefront.

The measurement of circularity of cylindrical grazing incidence optics is a formidable task, because required fabrication accuracies are typically on the order of several micro-inches, with resulting measurement accuracies on the order of a micro-inch or less. Such demanding accuracy requirements have evolved as the need for high resolution extreme ultraviolet and X-ray systems has increased. Current measurement approaches involve rotating the element (or one or more measurement probes) about the element's axis, and sensing the surface runout. Sensing can be mechanical or interferometric, but in either case the approach is clearly sensitive to runout in the rotation itself. Even when multiple probes are used to eliminate repeatable runout errors, nonrepeatable runout errors or drifts in probe position can severely degrade accuracy. In this paper we discuss a new, noncontacting approach (patent pending) that involves measuring the local circumferential curvature of the test piece by simultaneously measuring its circumferential slope at two slightly displaced locations. As the pair of sensing beams is scanned along the circumference, a profile of curvature is built, from which the circularity profile is deduced. The sensing of curvature not only makes the approach insensitive to all types ofvibration and drift (both in surface height and in surface slope), but also makes it insensitive to runout errors in the relative rotation. Thus, one can achieve absolute accuracies that are orders of magnitude smaller than typical drifts and runouts. We summarize the special qualities of this approach which make it well suited to measuring cylindrical optics, and which make it able to accommodate radii as small as twenty millimeters, working on either the inside (concave) or the outside (convex) surface. Finally, we discuss some preliminary experimental results and compare them with typical accuracy requirements.

The Advanced X-Ray Astrophysical Facility (AXAF) is part of NASA's Great Observatory program, and is scheduled for launch in the late 1 990's. A Wolter Type I grazing incidence telescope, it is planned to study high energy astronomical phenomena which emit in the x-ray spectrum from 0.1 -1 0 KeV (1 24 - 1 .24 A). The telescope consists of 6 nested, confocal parabola/hyperbola pairs, with the conic figure polished on the inside surfaces of cylindrical substrates. The 1 2 cylindrical elements are 1 meter in length and range in diameter from 0.5 - 1.2 meters. The specifications for the AXAF optics place strict requirements on the metrology instrumentation used to guide the fabrication process; in general, the accuracy of the measurements must be an order of magnitude better than the quality of the finished product. This is true for each of the measured parameters, which include axial figure, circumferential figure, inner diameter, and surface microroughness. Axial figure, circumferential figure, and inner diameter data are used to form maps of the inside surface of the optics, and form the basis for the subsequent fabrication cycle. Surface microroughness is used to determine the scattering performance of the system. This paper describes the facility used for the measurement of circumferential figure and inner diameter. This facility, the Circularity and Inner Diameter Station (CIDS), measures inner diameters of over 40 inches to within 70 microinches and acquires circularity data which is accurate to better than 1 microinch rms after averaging and the removal of systematic errors.

Recent developnients in the technology of surface generation are directed towards higher quality and reduced costs using an everincreasing range of optical materials. These goals require the use of objective methods of measurement to ensure that the desired end- points are within thresholds of acceptance at the instant these occur. This paper reviews progress in the development of methods of measurement of surface roughness, waviness and flaws which are likely to be suitable for on-machine use which could be traceable to National Standards, and which might provide outputs suitable for linking the process of design, manufacture and testing necessary to ensure total quality management. Results from recent laboratory assessments on a variety of surface characteristics are presented to illustrate the potential of the methods described.

We present the results of an extensive study of X-ray reflectivities of dip lacquered and Au coated Al foils. The measurements are performed at four different energies from 0.71 keV to 8.1 keV. The foils span a range of fabrication parameters. We show, that two of three examined versions of a density variation model are able to explain the data. We fmd a strong dependence on the microroughness of thickness of the Au coating and of the Au deposition rates. We present data suggesting important correspondence between X-ray measurements and scanning tunneling microscopy measurements. We fmd no dependence on curing temperatures (70°C to 130°C). Finally, we have performed an energy scan of one of the foils, in the range 6 keV to 12 keV.

Three kinds of deposition methods : ECR ( Electron Cycloiron Resonance ) sputtering, Ion Beam Sputtering (IBS) and conventional Vacuum Evaporation (VE) are compared to obtain highly reflective X-ray mirrors. ECR sputtered platinum film shows the highest X-ray reflectivity, because it exhibits the smallest surface roughness, a. The surface roughness and morphology of Pt films are investigated using SEM, STM and X-ray reflectivity measurements. The surface roughness of VE films is more than 0.8 nm. ECR and lBS films have optimum thicknesses which yield minimum surface roughness. The minimum surface roughness of the ECR film is 0.30 nm and X-ray reflectivity of this film does not vary before and after baking ( 250°C x 40 hours). ECR sputtered film is therefore the best one for preparing high quality X-ray mirrors.

From October 1986 to April 1988 Carl Zeiss has fabricated the 3.5m primary mirror of the "New Technology Telescope" (NY!') for the European Southern Observatory (ESO). This was the first time at Carl Zeiss that at no stage of manufacturing a skilled optician was necessary for doing manual corrections on the mirror. In the contrary, all the shaping and fine correction was done by computer controlled machine work. Computerized interferometry was the tool to deliver the necessary data for closing the loop1'2. As a rule of thumb, in a sound fabrication process the logarithm of the rms-values of the remaining figure-errors drops linearly with time. For the LOT (Large Optical Telescope, Iraq) 3.6m-primary mirror with an f-number of 3.5, which was fabricated at Carl Zeiss in a traditional way and finished in 1984, the rms-value was brought down by a factor of two in about 81 days. For the ESO-N1T the time for cutting the rms-value to half was 35 days3. Next month the fabrication of another 3.5m mirror, the primary for the Telescopio Nationale Galileo (TNG), will start. Although the NTE' was a very big success, we have used the time since 1988 to further improve our measuring techniques. First we will report on the metrology applied during fabrication of the NTT, then we will describe the tremendous improvements in resolution and speed now ready for the TNG.

ABSTRACT A new technique for fringe-pattern analysis is described. The technique, based on the Hilbert transform, is highly accurate and computationally efficient.

In this paper we define a versatile new noncontacting profilometry approach that offers significant advantages in terms of accuracy, robustness, and flexibility over conventional interferometric or slope measuring approaches. The approach involves measuring the local curvature of the test piece by simultaneously measuring its slope at two slightly displaced locations. As the pair of sensing beams is scanned along the test piece, a profile of curvature is built, from which the height profile is deduced. The sensing of curvature eliminates the need for an interferometric reference surface, and makes the approach insensitive to all types of vibration and drift, both in surface height and in surface slope. Thus, the approach is extremely robust. We have already demonstrated sub-Angstrom accuracy for typical mid-spatial period ranges extending from a fraction of a millimeter to tens of millimeters. In this paper, however, we emphasize several extensions of the measurement technique that make it an extremely versatile profiling approach for a variety of metrology needs. These extensions include beam expansion to make very long scans possible; measurement of circularity and cone angle of near cylindrical optics; and measurement of absolute flatness. We summarize our experimental results obtained to date, and define expected performance levels for these extended measurement functions.

One of the unique properties of deformable mirrors is their ability to be shaped. The as-assembled mirror figure can vary greatly, depending on the adjustment capability of the actuators used to shape it. Due to these variations, it is difficult to directly interpret progress during the mirror-polishing cycle when the interpretation is based only upon the metrology mterferometric readings. An in-process figure qualification procedure, which has been developed at Hughes Danbury Optical Systems, is described in this paper. By facilitating the real time monitoring of progress, the application of this procedure will accelerate the fabrication process of large deformable mirrors.

An essential component in laser diode array systems is the micro-optic system used for collimation and shaping of the output beams from indMdual elements of the laser array. Candidate micro-optic technologies include photolithic arrays, gradient-index optics, binary optics, and laser-assisted techniques. For the present work, a Mach Zender interferometer was constructed for evaluating wavefront quality. This instrument was used to select a lensiet array for an external cavity phase locking öxpement involving a 2 x 5 element monolithic surtace-emlthng laser diode array.

A new algorithm for designing an illuminator in a proximity exposure system is discussed. A relation between aberration of an irradiating lens and the irradiance distribution is studied and it is found that the lens has to satisfy the expression:h =f tan 0 to achieve uniform distribution. We designed a new-type illuminator with irradiating lens based on this expression and used a Fresnel lens as a collimator. This illuminator has high uniformity in the distribution within over an exposure area of 650mm x 650 mm. It has a collimation angle which is desirable fOr high resolution; and, experimentally, a resolution of 5 p.m line and space pattern was observed with a gap of 50 p.m.

The precision metrology mount is the structural "backbone" that supports all AXAF metrology at Hughes Danbury Optical Systems. This mount is currently designed to support P1 and Hi optics, the two outermost elements of the High Resolution Mirror Assembly (HRMA)1 . The mount must offload the mirror deterministically in a one-g field with tolerances established on the gram level. The intent of this paper is to quantify the requirements placed on the metrology mount and then to describe the design philosophy used to meet these demanding performance requirements. Finally and most importantly, the paper describes how each of the metrology mount's specifications were addressed and met from a design vantage point.

The Solar-A Soft X-Ray telescope will be launched aboard the Japanese Solar-A Satellite in 1991, to study the sun during the next period of sunspot activity. The mechanical and optical design of this monolithic, near 2 arc-sec image quality Nariai Telescope was developed previously as explained in reference 1 and depicted in Figure 2.0. Successful achievement of the aggressive performance goals for this design required precision manufacturing and assembly, and accurate metrology to verify results. In fact, more than three-fourths of the error budget was allocated to manufacturing and meirology errors because of the recognized difficulty in producing and measuring the precision grazing-incident optical surfaces. To obtain the anufacturing precision and metrology accuracy desired, specialized tooling had to be designed to support and mount the optical substrate during the fabrication, surface metrology, alignment and assembly processes. The design considerations, the substantiating structural analyses performed and the resulting successful application of this specialized tooling are reported here in to show the difficulties often encountered in developing "support" equipment to achieve desired results in the final product.

Using RTV rubber as an interface between mirror elements and their supporting structures during grinding and polishing was proposed for the Advanced X-ray Astrophysics Facility (AXAF) for glass safety concerns. This paper shows that the mirror performance is quite sensitive to the compression modulus of GE RTV-60 which, like all other rubber-like materials, is very difficult to characterize by testing and even more difficult to characterize analytically. Consequently, using representative RTV properties in mirror analyses only produces nominal performance predictions. The envelope of the range of performance has to be determined by using both extremes of the RTV compression modulus. This paper also presents a comparison between compression moduli generated via testing and that from semi-empirical formulas. The agreement is satisfactory when mean values of the test data are used for comparison and the shape factor is modified to include partially constrained surfaces. The scatter ranges from 7.6% to 23.0% depending upon the way the RTV samples were cast. Using an error of about 16.2, we were still able to meet the error budget requirements for the Glass Support Fixture (GSF).

Thermal-structural errors are inherently present during AXAF metrology. These include gravity release, random alignment, thermal, and vibro acoustic errors. The impact of each of these sources on AXAF metrology is presentedin this paper.

Four new optical system configurations (-÷-++--, +÷-++-, -+-+- and +-++-) are concieved for a laser scanning lens from fundamental thifl lens equations and optimized for diffraction limited performance. The speciality of these designs is the absence of thick meniscus concentric (1) elements. Also the article explains the circumstances forcing the use of thick meniscus elements. The six-element designs are having small rms spot sizes. These spot sizes are relatively insensitive to the position errors as compared to the other published/communicated ones (2, 3 and 4). The rms spot sizes at various zones are compared to understand the relative merits of the present designs with the published ones. In this study, percentage position errors at the respective zones, telecentricity, efl and bfl are retained at the same values as those of published ones. When the rms spot sizes are of the same order in both the designs under comparison, then design with less distance between the aperture stop and image is found to be better. Out of the two six-element types, one having configuration (++-+÷-) showed better performance compared to the other in all respects. Also in this design, the rms spot sizes are practically unchanged when position error is changed from 0.90% to 0.006%. Two four element configurations (+-+- and -++-) are also optimized and compared with the one (-++-) recieved (5). The two published (2, 3) configurations (-++++- and -+++-) are considered along with the above. The characteristics of the resulting seventeen designs are discussed in the later part of the paper.

This paper examines the transition between brittle and ductile mode in loose abrasive microgrinding (grinding with micron and sub-micron sized abrasives). The work was directed specifically at understanding loose abrasive grinding dependency on slurry fluid chemistry and the swlace stresses that are introduced in the grInding process. Several slurry fluids were investigated including water, a homologous series of n-alcohols, and several other organics selected for various properties including molecular size and dielectric constant. Chemistry was found to play a major role in the process; in fact, by simply changing slurry fluid composition, it was possible to induce the transition from brittle fracture to ductile mode grinding in ULE (Corning Code 7971 Titanium Silicate Low Expansion Glass). Data revealed that the dependency ofloose abrasive grinding on slurry chemistry can best be explained as Rebinder-Westwood chemo-mechanical effects [1,2,3,4]. It was also observed that the grinding surface stresses, known as the Twyman effect, increased dramatically in the transition from brittle to ductile mode grinding.