Theodore T. Saito

Machining of optics: an introduction

This paper introduces machining of optics, presenting some of the history of machining progress, critical machining variables, material and geometrical capabilities, and some new results on optical evaluation of machined surfaces. A most significant development is electroplating of materials that are otherwise not presently machinable. For example, molybdenum has been electroplated with silver or gold and then successfully diamond turned. Research and development ideas for future machining studies will be briefly discussed.

Diamond Turning of Optics: The Past, the Present, and the Exciting Future

Diamond turning of optics has grown from obscurity to popularity. After giving a brief background of the diamond-turning accomplishments, we summarize the technical capabilities and availabilities. Infrared systems applications are the major current production diamond-turning requirements. We discuss ongoing R&D work which bridges the present to the future. The DoD planned manufacturing technology program of the Army, Navy, and ongoing work of the Air Force are discussed briefly.

Surface Finish Measurements Of Diamond-Turned Electroless-Nickel-Plated Mirrors

Surface roughness data are presented for a matrix of diamond-turned electroless nickel samples having a combination of six phosphorus contents and four heat treatments. Roughness measurements were conducted with commercial optical and stylus profilers (WYKO and Talystep). The results are discussed in terms of the material composition and heat treatment, plus other factors having an observed influence on the surface roughness. For the optimum material properties, full-length (665 itm) 20x WYKO scans yielded values of better than 10 A rms after correction for instrument roll-off.

Diamond turning of optics

Recent developments in diamond turning of optics are reviewed. Improved surface figure and surface finish have been achieved as well as metrology of the machined part. Reflectivities of diamond turned metals at various wavelengths are summarized. Application of diamond turned optics include laser resonator mirrors, x-ray microscopes, x-ray telescopes, missile optics, and scanner mirrors. The technology looks especially promising for present infrared requirements since both reflective, refractive, and transmittive components can be fabricated. Diamond turning of optics can be defined as the use of a diamond tool on a precision lathe under very precisely controlled machine and environmental conditions to fabricate a finished optical component. The specific application of precision machining principles to diamond turning has been led by the Lawrence Livermore Laboratory (LLL), Livermore, California and Union Carbide Y-12 Plant (Y-12), Oak Ridge, Tennessee.

Direct Machining Of A Non-Axisymmetric Phase Corrector

One of the most challenging optical components to fabricate is a non-axisymetric part. We at Lawrence Livermore National Laboratory recently used the Large Optics Diamond Turning Machine, (LODTM), to make a part called a phase corrector. The Phase corrector is an annular opical component that is used to generate a known spectrum of time varying aberration. If the corrector has the proper distribution of spatial frequencies and amplitudes it will function correctly. Since the frequencies and amplitudes were the important requirement on the surface figure, the surface of the part was specified in the Fourier domain. A surface profile was generated from the spectrum which contained spatial frequencies as high as 40 cycles per revolution. The spatial frequency maps into a time domain frequency for the z- axis tool bar that is dependent on the spindle speed. At 40 cycles per revolution, any reasonable spindle speed taxed the band width limits of the z-axis tool bar. In order to decrease the errors in the surface figure due to machine dynamics, a technique for compensating for the dynamics in the Fourier domain was developed. The non-axisymetric phase corrector was directly machined out of brass on the LODTM. Test measurements of the surface figure were made with an LVDT on LODTM and compared to the commanded profile both in the spatial and frequency domains. The surface quality was measured with a Wyco Model 1000P surface analyzer.

Design and Fabrication of a Nonlinear Waxicon

This paper describes the theory, design and fabrication of a complementary pair of cone-like mirrors which transform an annular collimated laser beam into a gaussian profiled collimated beam without obscuration. The details of a simple computer algorithm are revealed which explain the numerical procedure for computing the coordinates of the mirror surfaces. Also discussed is the procedure to diamond turn the nonlinear surfaces using the development lathe at the ERDA Y 12 Plant and the metrology of the first parts produced.

Wave-front correctors by diamond turning

The production of wave-front correctors by single-point diamond turning is reported. Interferograms are shown which demonstrate excellent agreement between the diamond-turned surface and the desired surface. It is concluded from this experiment that it is now feasible by means of single-point diamond turning to make generalized wave-front control surfaces or to produce any unusual surface desired by the optical designer. The maximum departure from the nearest regular surface is set by the dynamic range and maximum diamond point acceleration permitted by the machine.

Applications of Diamond Turning to Infrared Optical Systems

Diamond turning is immediately applicable to the fabrication of infrared optical components because presently available machines can meet the reduced absolute accuracies required at 10 micrometers. An initial survey of infrared sensor programs at the Honeywell Radiation Center has been conducted to predict the near term and future demand for diamond-turned optical components. Not only does the fabrication process promise significant cost savings as compared to conventional lapping and polishing methods, but, as in the case of aspheric lenses, wider applications are also sought to reduce weight and space requirements. In addition, broader usage of diamond-turned aspherics reduces total parts count and assembly and alignment time, provided proper tools and test equipment are employed. The potential cost savings of diamond-turned vs conventionally fabricated optics are summarized for contracts at the Radiation Center. The savings were calculated by subtracting the difference in fabrication costs and multiplying by the number of items expected to be produced into the mid-1980s. Technical fallout potential of the diamond-turning process is also noted in the apparent ability of a coated sample to pass a 24-hour salt fog test.

Applications of diamond turning to infrared optical systems

Diamond turning is immediately applicable to the fabrication of infrared optical components because presently available machines can meet the reduced absolute accuracies required at 10 micrometers. An initial survey of infrared sensor programs at the Honeywell Radiation Center has been conducted to predict the near term and future demand for diamond turned optical components. Not only does the fabrication process promise significant cost savings as compared to conventional lapping and polishing methods, but, as in the case of aspheric lenses, wider applications are also sought to reduce weight and space requirements. In addition, broader usage of diamond turned aspherics reduces total parts count and assembly and alignment time, provided proper tools and test equipment are employed. The potential cost savings of diamond turned vs conventionally-fabricated optics are summarized for contracts at the Radiation Center. The savings were calculated by subtracting the difference in fabrication costs and multiplying by the number of items expected to be produced into the mid-1980s. Technical fall-out potential of the diamond turning process is also noted in the apparent ability of a coated sample to pass a 24-hour salt fog test.

Frequency Stabilizing a HeNe Laser: A Joint Senior Design Project

Operation Stalactite was a senior project to design and build a frequency stabilized helium-neon laser. The project objectives, approach, and teaching techniques are reviewed. Insights into student interactions and efforts to focus an undergraduate education will be given. Stalactite required the students to organize, plan, propose, and execute research plan in accordance with a schedule and budget. Reactions, educational benefits, and results of a post-project survey will be given.