A detailed fluid mechanics and optical analysis has been completed for the TRW CL XV chemical laser nozzle. This nozzle configuration incorporates contoured supersonic "trip flows" to enhance the mixing of the two streams. The results presented were obtained from a two-part study, the first of which investigated the detailed fluid mechanics and chemistry of the gain regions with simplified optics and the second of which included a detailed physical optics analysis with a simplified fluid mechanics model. In the former, the LAMP computer code was utilized and in the latter the MRO and BLAZER codes were used. The chief interaction between the two parts was the development of the fluid mechanics model in the MRO/BLAZER computer codes from the results of the detailed fluid mechanics analysis. The results obtained compare favorably with measurements which have been made in experiments at TRW. These include small signal gain profiles, chemiluminescence results, power distributions and the flow field pressure measurements.
Optical design and engineering of the electro-optical (E0) system used for automatic tracking and laser designating tares from high-performance aircraft require consideration of many aspects of the total system; for example, large look-back capability, max-imum aperture, accurate boresight, and high transmission. First and second generation EQ pods have been designed and manufactured using a multifunction objective lens that combines apertures for a dual field of view (FOV)/dual wavelength camera system, laser designator, laser ranger, and laser spot tracker. A. diffraction-limited telephoto objective lens with an FOV capability of 1, 1.5, and 6 degrees is the heart of the optical system. The design provides good image quality while meeting the needs of the laser functions and allowing ease of maintenance through modular construction. The engineering of the optical bed for mounting the components in the pod in a dynamic environment required detailed analysis, using both optical deflection tolerances and structural characteristics. A mathematical model of the optical bed provided a means for determining stiffness requirements to meet the needs of imagery and boresight. The silicon target vidicon sensor allows a unique capability for automatic, in-flight boresight.
The effects of dispersion and gas flow on the operation of the ring laser gyro are summarized. The theory is shown to predict a dimple in the anomalous dispersion properties of the atomic transition. Experiments were carried out using a 43.4 cm and 21.7 cm visible laser gyro. Scale factor and nullshift results showed consistency and confirmed the existence of the dimple. The peak-peak relative magnitude of the scale factor dimple was found to be approximately 25 x 10-6. Gas flow was varied by unbalancing the discharge currents in the two legs of the laser gyro. A nullshift sensitivity of 0.0066 deg/hr/mamp of unbalance was found. Analysis of the data showed the nullshift sensitivity to velocity flow to be 4.4 deg/hr/cm/sec of velocity unbalance.
A single axis rotation sensor, utilizing a 200 m single mode optical fiber in a 30 cm diameter coil has been constructed and tested in the laboratory. A HeNe laser is the light source for the Sagnac interferometer-mode sensor. The outputs of Si detectors viewing two complementary interference patterns are electronically differenced to obtain a rotation dependent signal. Linear response over a rotation rate range of about 10-4 to 10-1 rad s-1 was obtained.
This paper describes some general features of a computer-controlled laser system for noncontact measurements of dimensions of objects. The laser beams are scanned over the object and a system of detectors mounted behind the object detects whether the beams are shadowed by the object or not. The detector signals are converted to digital values and transferred to a minicomputer, where they are processed. This may require special software to allow the dimensional data to be presented in real time. An ex-perimental system with a HeNe laser and controlled by an HP 21MX minicomputer has been built and tested. At a rate of 100 measurements per second the systematic error is in the order of 1 mm for absolute measurements and 0.1 mm for relative measurements. The imprecision is about 0.1 mm for both cases.
An optical method to compare the shape and the contours of optically opaque test objects with those of a master is proposed, analyzed and demonstrated. A grid pattern is projected onto the test sample and the diffusely scattered light is imaged onto a mask, fabricated to yield zero transmission for ideal samples. Deviations in shape or depth from the master result in light transmitted through the mask. Resolution is in the range of a few micrometers.
Small grinding and polishing tools are useful for certain applications since they can closely follow the curve of an aspheric surface and are less affected by workpiece distortion than larger tools. Also, the use of a computer to control the action of grinding and polishing tools can increase the efficiency and accuracy of the process. The computer controlled polisher (CCP) takes adantage of both features, moving a tool assembly with small pads over the workpiece under computer control. By varying the amount of time the machine works any region, a controlled amount of material may be removed. The best tool configuration for any figuring operation is determined by use of co puter modeling, while the proper operating parameters are obtained from ex perimentation. The process has been used to fabricate a nu her of difficult mirrors; as a result of this work, the CCP will be used on important future fabrication efforts.
A new machine tool now in the final stages of development at the Pacific Northwest Laboratory uses a unique tool motion to produce diamond-turned surfaces of exceptionally high quality. The cutting tool is computer programmed to move in 4-nm increments along two axes: an X axis and an Omega axis. Exceptionally stiff and accurate control of the tool is possible with this "Omega-X" system. Copper surfaces of revolution have been produced with a 12.3-A rms surface finish and a contour accuracy of 75 nm. In conjunction with a unique thermally stabilized air bearing spindle and machine calibration equipment, the computer-controlled Omega-X system permits a significant advance in the fabrication of optical-quality surfaces.
The use of moire interference fringes in biostereometrical applications has the advantage that contour fringes on the surface of an object are visible to the unaided eye and that these fringes may be recorded photographically. The movement of such fringes as would accompany the motion of the human body can be recorded by movie or video camera when the fringes are used to study human subjects. One of the limitations of this moire method using noncollimated light is that the value of the contour interval increases with the increase of the order number of the fringes as counted from the grating. To overcome this limitation, a new moire technique using parallel light has been developed. An optical system, which includes a field lens, provides the parallel light which makes it possible to obtain equal valued contour intervals, independent of fringe order. Any desired contour interval is obtained by choosing a grating with suitable pitch and/or an appropriate angle of incidence for the parallel light at the grating. Analogue data from the moire pattern is automatically fed into the central processing unit of a computer by means of a TV camera and an A/D converter. Examples of the line printer output of this conversion system are given.
A method of using the SIMS (the Selective Modulation Interferometric Spectrometer) to measure the difference between the spectral content of two optical beams is given. The differencing is done optically; that is, the modulated detector signal is directly proportional to the difference between the two spectra being compared. This optical differencing minimizes the dynamic-range requirements of the electronics and requires only a simple modification of the basic cyclic SIMS spectrometer. This technique can be used to suppress background radiation for the enhancement of target detection and tracking. Laboratory measurements demonstrating the application of this technique are reported.
CO2 and N2 jets issuing into air from small rectangular channels of 2 x 25 mm cross section were investigated. Concentration measurements were obtained by cw laser Raman spectroscopy; gradients larger than 10 vol. %/100 pm could easily be resolved; spatial resolution was better than 10-2 mm3 and the measured fluctuations of the Raman signals show satisfactory agreement with Poisson statistics. Axial and radial profiles are reported for single and multiple jets and comparison with theory is given, where possible.
Solar flux is inherently of very high thermodynamic quality (low entropy). However, the terrestrial use of solar heat at high temperature can be achieved only by means of solar concentrators of the reflecting or refracting type. It is the purpose of this paper to describe the three major design variables of concentrators optical efficiency, heat loss coefficient and heat removal factor. The optical efficiency no embodies many important concentrator properties including mirror surface reflectance and slope, tracking accuracy, receiver transmittance and adsorptance and solar beam incidence angle effects. The heat loss coefficient Uc of a solar concentrator represents its thermal performance and depends upon the relative magnitudes of convection and conduction flux rates, surface emittances of receiver components and operating temperature relative to the environment. The third design parameter-the heat removal factor FR-is a measure of the efficiency of the receiver when viewed as a heat exchanger. Its value is governed by working fluid properties and flow rates as well as by the thermal properties of the receiver material. The principal factors which determine the value of no, Uc and FR are described in the paper.
Acousto-optic devices have been developed for implementing advanced signal processing functions required for real-time and near-real-time analysis of both high-frequency radar signals and low-frequency sonar signals. These devices use the Bragg interaction between laser beams and surface acoustic waves (SAWs) to perform waveform convolution and correlation, achieving time-bandwidth products of 3000 to 10,000 with dynamic bandwidths of several hundred megahertz. Using these devices, wideband (about 100 MHz) signals have been extracted from extremely noisy environments (-30 dB signal-to-noise ratio) and a real-time Fourier transformation with a linear dynamic range exceeding 60 dB has been performed. A programmable correlator and a programmable filter have been demonstrated that use the newly discovered acousto-photorefractive memory effect. This effect is based on a nonlinear interaction between intense, short-duration laser pulses permanent index-of-refraction pattern corresponding to the SAW signal. An implementation of the triple-product convolver architecture (proposed by Whitehouse et al.) for perform-ing either a long one-dimensional or a two-dimensional discrete Fourier transform can be obtained by combining an acousto-optic convolver with many CCD chirp-Z transform modules. This triple-product convolver would have extremely rapid data handling capability and large dynamic range, and would be useful for applications such as "w-k" beamforming for sonar signal process-ing. Further, a programmable 1-, 2-, 3-dimensional beamformer with a one second update capability may be feasible if the acousto-photorefractive memory effect is used to store SAW signals corresponding to the position of nonstationary sensors.
The design of present-day color-sensing devices (such as color TV cameras) is generally based on Young's 1801 trichromatic theory as quantified in the CIE system of color mixture. But the actual makeup of the human color-vision mechanism remains unknown to this day. There exists significant evidence that neural hue signals originate from direct rod-cone interaction. We describe a simple opto-electronic device which models a possible neural mechanism for generating such retinal hue signals. The device produces a pulse train simulating the neural hue signal. The frequency of the pulse train varies with changes in stimulus wavelength in a manner similar to the way retinal hue signals are believed to vary. Thus these signals represent primitive hue information extracted from the stimulus.
The Limb Infrared Monitor of the Stratosphere (L[MS), an experiment on the NIMBUS-7 satellite, is designed to scan the earth's limb vertically and measure spectral emission profiles of trace atmospheric gases believed to be important in processes controlling the stratospheric ozone distribution. Experiment objectives are reviewed and several analyses and measurements are described which were performed to determine the adequacy of the system for satisfying these objectives. Adequate spatial-frequency response for all the spectral channels is required to provide, through inversion of the measured limb-radiance profiles, important information about the temperature, structure, and composition of the atmosphere. From the LIMS design-model data, the MTF was calculated for the optical system, the detector field mask, the electronics, and the overall system, for each channel. The signal output performance of the instrument was predicted from the system MTF data and model input radiance data for each channel. MTF measurements made on the flight sensor confirmed the analytical results. The predictions indicate that the instrument can satisfy the basic measurement objectives of the experiment.
A dynamic beam pointing system capable of stabilization of beam motion has been assembled and partly tested. The system uses bismuth photopot position detectors, closed loop control elec-tronics, and a two-axis active mirror/mount. The system is capable of automatically maintaining a preset optical alignment. Measurements are presented that represent the system (position detector, electronics, and the dynamic mirror/mount) perfor-mance in terms of ability to stabilize a moving infrared beam in one axis (dc - 300 Hz). In addition, the frequency response and phase delay for the detectors tested are presented. A CO2 laser provided an infrared signal at 10.6 microns with adjustable power between .25 -1.0 watt. Controlled amounts of beam direction change (beam jitter) were induced by a second two-axis dynamic mirror/mount.
For seven and a half years, it has been difficult to think of Optical Engineering without thinking of its outstanding editor, Professor John B. DeVelis. With this issue, Dr. DeVelis is retiring as editor to devote a larger fraction of his time to his distinguished research career.