Instant Photogrammetry With a Grid The term photogrammetry is usually associated with photography from the air, but in the strict sense of the word, it refers to any photographic technique in which measurements are made. Properly calibrated, even the simplest of cameras is capable of making measurements to respectable accuracies. In those cases where the accuracy requirements are not too excessive, instant-developing films offer the advantage of providing data quickly and at the same time allowing the photogrammetrist the opportunity to check his results while still in the field. The technique to be described in this article is limited to measurements taken on level areas, namely inside buildings and on streets and other flat exterior grounds. It utilizes a transparent perspective grid, Figure I, that is superimposed with the resulting picture to indicate scale) The method has application in plant layout surveys, accident investigations, architectural studies, traffic surveys, etc.
An economical method of fabricating aspherics and optical design flexibility for an even broader family of optical shapes is now possible through precision machining of optics. One of the most exciting developments over the past few years has been in the area of diamond turning of optics. Diamond turning is now a recognized and sought-after technology.
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.
The development of precision machines for generating aspheric optical surfaces at. Bell & Howell Company, which were the ancestors of many of today's diamond turning machines, is outlined together with present machine capability. A practical procedure for compensating for repeatable machine position errors based upon measurement of a best-fit sphere is described. Applications of diamond turning to reflective and transmissive (germanium and silicon) infrared optical elements are illustrated.
A technique to improve the adherence of multilayer dielectric coatings to diamond-turned copper mirror surfaces was developed. The method employs carefully controlled ion polishing, vacuum annealing, and in situ coating of the mirror substrates. It was found that ion polishing the substrates, with as little as 100 A removed, prior to coating improved the film adhe-sion significantly. All of the samples prepared in this manner passed all of the standard ASTM mechanical tests while control samples produced by conventional methods failed the tests. Additional coating evaluation such as reflectivity and laser damage threshold measurements at 10.6 pm, auger analysis for contaminants in the films and at interfaces, SEM characterization, and x-ray energy dispersive analysis are also discussed.
This paper describes the best large-aperture single-point diamond-turned copper mirrors currently available. The state of the art is progressing rapidly. At present, for 400-mm diam, f/16.5 spherical surfaces, the peak-to-valley figure can be held to two visible fringes in a center of curvature test, and the surface roughness is better than 50 mm peak-to-valley. Since the time of Galileo attempts have been made to machine optical components. With very few exceptions these attempts have failed. Recently 1,2 however, much careful atttention has been paid to the numerous fine details such as vibration isolation, uniformity of spindle and tool drive, temperature control, tool shaprness, etc. Components of infrared quality are being produced in large numbers. The advantages of machined optics are a generally lower price, a higher production rate, a higher damage threshold (on the order of 11 J/cm2, the intrinsic limit, for 1-ns, 10-um pulses),3 and greater resistance to corrosion and tarnishing than can be achieved through conventional optic production. It is the combination of these advantages which made single-point diamond-turned (SPDT) optical components a key element in the current and projected Los Alamos Scientific Laboratory (LASL) CO2 laser systems. There are two operating large pulsed CO21 lasers at LASL; the TBS or Two-Beam System, and Helios, the Eight-beam System. Helios has a nominal energy of 10 kJ at 1 ns, while the TBS has a nominal energy of 2.5 kJ at 1 ns. The Antares CO2 laser at LASL will have an energy of 105 J in 1 ns and consist of 6 beams of 12 segments, each of which is essentially an independent beam train. In addition to numerous smaller optics, a single segment of the beam train will contain nine elements with a characteristic diameter of 40 cm or larger. There will be 72 such beam trains and 1500 elements. Completion of the laser is scheduled for 1982. Timely and reliable fabrication will be essential. Thus, single-point diamond turning forms an integral part of the CO2 lase
A fabrication process is now available that can manufacture focusing mirrors for the 10-kJ laser fusion experiment being conducted by the Los Alamos Scientific Laboratory. Techniques have been developed for satisfactory metal preparation, copper electroplating, single-crystal diamond turning, and optical inspection. Fabrication of these mirrors by these techniques, and a post diamond-turning polish, resulted in diffraction-limited optics at a wavelength of 10.6 pm.
A procedure is described for the use of diamond-impregnated pitch and silicone oil which has produced surfaces which appear to be as smooth as 5 Angstrom rms on small flat samples removing the objectionable diffraction-producing grooves that sometimes accompany diamond turning. Possible mechanisms are described together with the procedures and equipment used to polish an x-ray microscope and a UV telescope.
This paper presents a simple method of axisymmetric wear pattern calculation covering all cases normally encountered on con-ventional polishing machines. The techniques were developed for use with small programmable calculators to make them available to the small-shop personnel for whom this paper is written. Polishing pad design and drives are also discussed.
Diamond turning of optics uses a single-point diamond tool on a precision lathe under precisely controlled machine and environmental conditions to fabricate an optical component. The technology has been used to make many high precision optics. The F-111 windscreen is in the shape of an oblique frustrated right circular cone, a geometry compatible with diamond turning. Phase I of the feasibility study demonstrated the machinability and polishability of the F-111 windscreen material. Two flat 15 cm square samples of the F-111 windscreen material were diamond turned and then polished. The diamond turning was performed on a Moore machine at Union Carbide's Y-12 plant. The Lawrence Livermore Laboratory polished the sample with Lustralox Plastic Grade on Polytex Supreme. Extensive pre-machining and postmachining tests are described, including the lateral shearing interferometric techniques developed by one of the authors. Optical distortion and haze were significantly reduced after machining and polishing. Diamond turning of windscreens may offer attractive cost savings by reducing shrinkage during fabrication and allowing recycling of windscreens rejected because of excess haze. Diamond turning may also provide revolutionary optical designs to reduce distortion through decentering techniques. The plans for phase II of the feasibility study, to machine and polish actual curved windscreen sections, will also be described.
Various instruments to measure the refractive state of the eye have been built based on a servosystem concept. This paper describes the optical system of the Dioptron automatic objective refractor. This autorefractor measures the modulation of a grating image formed on the retina while being controlled by a digital computer. The optical subsystems include the image projecting system, the image detecting system, the patient fixation target, and the patient alignment system. Accuracy is obtained by controlling the patient's accommodation and eliminating "instrument" myopia. The overall system is designed to be compact while maintaining very good signal-to-noise ratio and minimum operator controls.
A variety of reflectance techniques have been developed to determine the thickness of thin transparent films on silicon substrates 1,2 These techniques are based on the way incident radiation is reflected from air-film and film-substrate interfaces. These reflectance techniques are ideally suited to measuring films ranging in thickness from approximately 500 A to many thousands of angstroms. The absolute reflectivity technique measures the reflectance at several wavelengths and, by matching the curve as measured to the theoretical, the actual film thickness can be determined. A refined version of the absolute reflectivity technique is the Brewster's angle spectrophotometer. This article describes the development phase for an automatic Brewster's angle spectrophotometer and discusses the performance of the instrument. The optical and mechanical layouts and photographs depict the choice of implementation.
Threshold effects are examined for a real-time image correlator in the absence of geometric distortion. Images obtained from two different television sensors are sampled and quantized to two levels. The correlation algorithm is then implemented as an "exclusive OR" followed by summation. For a KxL reference array the correlation algorithm produces an output between zero and KL. This paper examines the effect of choosing a threshold No above which the images are considered to be correlated. Probability of false alarm is found to be dependent on the total number of pixels used in the correlation algorithm. Probability of detection is found to depend also on the video signal-to-noise ratios and is computed for Gaussian, uniform and bimodal image distributions.
Microchannel plates are widely used today in military night vision devices. Their successful application has prompted widespread interest in many laboratories and in the industry for use in diagnostic tools. Of particular interest are the applications as: (a) an electro-optical ion detector to enhance the sensitivity of a mass spectrometer for clinical environment and chemical analysis, (b) an electron collimator for subpicosecond x-ray and visible streak camera tubes, and (c) particle detectors in spaceborne instrumentation. Many of these applications required the development of strip multichannel arrays (SMCA) ranging in active area from 1 mm x 15 mm up to 1 mm x 360 mm. Also described herein is the state of the art of high resolution and increased detection efficiency multichannel arrays.
An "inchworm"-type piezoelectric displacement device has been tested for operation in a vacuum. Comparative data are given for its operation at two pressures (1 atmosphere and 10-6 to 1O-7 torr), three loads (0, 8, 15 N), and four speeds in the range 0.5 to 50 micrometers per second. The results are such that the device is now being applied successfully to drive an X-Y stage in a scanning electron microscope (SEM).
An automated system for scanning missile domes under computer control at an arbitrary number of points and determining both forward scattering and transmittance from 0 degrees to over 60 degrees from the dome axis is now in operation. Measurements at 3.39 pm have been made on both new and used domes, artificially eroded domes, and also on pieces of spinel, which is a possible replacement for the magnesium fluoride now used as an infrared dome material. A total of 18 new, 1 used, and 2 artificially eroded domes have been measured. Data indicate that (1) the scattering and transmission is nearly uniform as a function of angle away from the dome axis for the used dome as well as for new domes, (2) the scatter from the used dome was higher than that from 16 of the 18 new domes, but less than that for two of the new domes (26% more scatter than the average of all the new domes), and (3) a sample of press-forged, single-crystal spinel scattered five times less than the average of the new domes, while a fusion-cast polycrystalline spinel sample scattered 2.5 times more than the average.
A digital video image processor (VIP) has been constructed and is presently being tested and used in a variety of preclinical medical imaging situations. Details of its design are discussed. The VIP can digitize, store and process images from a conventional radiographic TV fluoroscopy system. From these images a variety of subtraction images can be formed and displayed in real time at video rates. These subtraction images include: K-edge images, time dependent subtraction images, tomographic, and K-edge tomographic images. Examples of in vivo K-edge and time-dependent subtraction images are presented.
A large diameter lightweight elliptical plastic mirror was developed for use with an airborne laser sensor system. The plastic mirror, of moderate optical quality, is about one-third the weight and cost of an aluminum mirror of comparable size. This paper discusses the fabrication and optical characteristics of a honeycomb constructed plastic scanning mirror.
Finely detailed striae in astronomical images can be important in formulation of theory. Examples are studies of streamers in the solar corona and of dust tails in comets. In both instances, conventional observations fail to reveal much of the structural detail. Digital image processing has been used at Los Alamos Scientific Laboratory (LASL) for enhancing these images. The corona images have tremendous variations in film density which must be eliminated before fine striae can be seen. These variations can be removed by means of numerical modeling of their spatial relation to the sun. This model can be thought of as a surface of background film density. In the comet images the overall variation is less severe. Further, the large number of comet images makes it infeasible to model them individually. Hence, an extreme low-pass filter was used to create an image which can be used as the background surface. In both cases, the background surface is divided into the original image pixel by pixel. This quotient image is then frequency-filtered for edge enhancement or noise control. Nonlinear density transformations are then used to enhance contrast. For both types of images, heretofore unmeasurable details become readily visible for analysis.
Single heterojunction photodiodes suitable for the 1.0 to 1.3 pm spectral region of interest for fiber optics communication have been prepared from lattice-matched p-type epilayers of the quaternary III-V alloy semiconductor InGaAsP on n-type InP substrates. The characteristics of these heterojunctions are demonstrated by mesa photodiodes made from Zn-doped epilayers of composition In0.84Ga0.16Aso.34P0.66 on Sn-doped InP. Their room temperature spectral response extends from the ~0.96 um self-filtering cutoff of the InP substrate to (~1.13 um determined by the bandgap of this particular quaternary composition. Responsivities of 0.46 A/W and external quantum efficiencies of 0.54 are measured at 1.05 um.