Large single crystals, up to 200 mm in diameter, of high optical quality germanium have been grown by the Czochralski technique. Post-growth thermal treatment improves the optical homogeneity and reduces optical losses, as shown by measurements of refractive index gradients and modulation transfer function (MTF). A new approach for the piecewise combination of interferograms, as well as a polychromatic treatment of MTF, is presented.
A recently published system for determining the spacing and direction of speckle photography fringes is tested for accuracy and computer run time through a computer simulation that includes the degradation of data by noise. Compared with a previously published processing method, the algorithm used in the new system determines fringe direction with higher accuracy and reduced computational effort. From the evaluation of fringe spacing, displacement components are also determined as a function of fringe density, visibility, and image resolution. Errors in displacement components are compared with those obtained using other algorithms.
The design of a four-spherical-mirror zoom telescope is presented. By use of third order aberration theory the system is determined to satisfy the aplanatic condition at every point on the zooming locus. From examination of spot diagrams, a system with Cassegrainian-Cassegrainian configuration is found satisfactory. The design data are presented.
Some simple image processing techniques are suggested that can be used for enhancing the contrast of real-time digital speckle pattern interferometry fringes. The techniques have been developed for the commercial Intellect 100 image processing system interfaced to a PDP-1 1 /23+ microcomputer, but they can be adapted to any commercial image processing system with slight modifications, if necessary, depending on the hardware configuration of the system.
In the May 15, 1989, issue of The Wall Street Journal, the lead editorial addressed an activity that is taking place in the United States but one that should send chills up the spines of scientists and engineers around the world.
Optical Nonlinearities and Instabilities in Semiconductors is a collection of 16 review chapters written by some of the leading experts in nonlinear optical phenomena and the related optical instabilities in semiconductors.
This paper describes an approach to 3-D surface reconstruction that integrates the information provided by two different sources: stereo vision and local shading analysis. In our scheme a sparse depth map, obtained by a binocular stereo technique, provides an estimate of surface shape that can be refined by local shading information (an orientation map), extracted from one of the stereo pair of intensity images. The proposed local shading analysis is simplified. In fact, illumination direction and line of sight are coincident. This seems to provide better results on surface orientation estimates than do more general methods. The integration process consists of two phases: First, the scene is segmented in connected regions by means of a raw needle map. Second, the surface interpolation is obtained using information extracted from the segmentation process and the sparse depth map. The result of the integrated approach is a good quality, dense depth map. The functionality of the approach has been tested on synthetic data and real data.
A multiple microcomputer system for digital signal and image processing applications is presented. A simple ring structure is employed to organize the multiple microcomputers. The data flow in the ring structure is unidirectional. A task can be partitioned and distributed among the microcomputers, making possible pipelined execution of a task. Implementation with the use of the TMS32010 signal processing CPU and IBM PC is demonstrated. A design to ensure the program synchronization is also shown. Algorithms for carrying out infinite impulse response filtering, the fast Fourier transform, and the McClellan transform method of 2-D finite impulse response filters are developed. Experimental results are presented.
This paper presents an algorithm to detect road lines on digitized map images. This algorithm detects road lines based on object shape (line thickness) and gray level values. The road detection process is accomplished in two steps: road line extraction and road tracking. The road line extraction consists of level slicing, morphological filtering, and connected component analysis. The road tracking routine is capable of connecting broken road lines caused by the overlapping of text labels. The algorithm has been implemented on an IBM PC/AT-based image processing system and applied to various map images.
The characteristics of an omnidirectional vision navigation system were studied to determine position accuracy for the navigation and path control of a mobile robot. Experiments for calibration and other parameters were performed using an industrial robot to conduct repetitive motions. The accuracy and repeatability of the experimental setup and the alignment between the robot and the sensor provided errors of less than 1 pixel on each axis. Linearity between zenith angle and image location was tested at four different locations. Angular error of less than 1° and radial error of less than 1 pixel were observed at moderate speed variations. The experimental information and the test of coordinated operation of the equipment provide understanding of characteristics as well as insight into the evaluation and improvement of the prototype dynamic omnivision system. The calibration of the sensor is important since the accuracy of navigation influences the accuracy of robot motion. This sensor system is currently being developed for a robot lawn mower; however, wider applications are obvious. The significance of this work is that it adds to the knowledge of the omnivision sensor.
A wavelength that lies within a Fraunhofer line (a spectral interval of reduced solar emission) can carry optical communications in the atmosphere and space with reduced interference from direct or reflected background sunlight. Suitable Fraunhofer lines are located within the tuning range of good candidate laser sources. The laser should be tunable dynamically to track Doppler shifts in the sunlight incident on any solar system body that may appear in the background as viewed by the receiver, or in earthlight for ground-based daylight reception. The Fraunhofer filter used with a direct-detection receiver should be tuned to match the Doppler shifts of the source. The required tuning is calculated here for various situations. A typical Saturn-to-Earth data link can reduce its source power requirement from 8.8 W to 2 W of laser output by employing a Fraunhofer filter instead of a conventional multilayer dielectric filter.
Interferometric measurements of the transient refractive index in electron-beam-pumped Ne/Xe/NF3, Ne/Xe, and Ne/NF3 mixtures are reported. The measured fringe shift in the Ne/Xe/NF3 laser mixture at 351 nm is + 5 rad over a 2 m path at an energy loading of 70 J/f, indicating an increase in the refractive index. Energy flow pathway kinetics used in conjunction with fringe shift measurements suggest that the observed shift is due to XeF(B2I1,2). The implications of these measurements for obtaining near- diffraction-limited beam quality in an electron-beam-pumped XeF laser are discussed.
The operating characteristics of a discharge-excited XeCI laser, which uses a screen electrode and UV preionization behind the screen, are reported. An output energy of 250 mJ and an efficiency of 2% were measured. The uniformity of the laser beam cross section extends to 60% of the total area with a 5% variation of the energy.
Near-field irradiance distributions of a deuterium fluoride laser system are obtained using infrared presensitization photography. This represents the shortest wavelength region to employ this technique thus far.
Integrated optical signal processing devices can be implemented through the use of passive structures. A wide variety of devices and functions can be developed from a few fundamental elements. Possible device designs and applications are discussed.
A technique is presented for calculating the aberrations induced by misalignment of elements of an imaging system with a segmented primary mirror. The misalignment-induced aberration function, derived in terms of a set of five vectors representing small displacements from the aligned position of each element, represents changes in optical path along each ray for the displacement under consideration. This aberration function can be used to conduct parametric tolerance studies of such segmented systems. The behavior of the optical system can be analyzed for variable location of the image plane and at selected points within it. These studies are difficult to conduct with conventional ray trace programs since they involve extensive data processing and great attention to proper se-lection of coordinate systems and transformations. We present results to illustrate the precision levels that should be met in the alignment and metrology of imaging systems with segmented primary mirrors to be operated at visible wavelengths. These precision levels are challenging but achievable with state-of-the-art technology.
Moire contours are seen on a curved surface viewed through a grating when the surface is illuminated with a matched grating. We have been able to replace both the projection and viewing physical gratings with gratings of variable spacing generated in acousto-optic (AO) cells and have been able to observe and record moire contours. The gratings are generated by amplitude modulating 70 MHz AO cells with a 1 to 10 MHz square wave. The gratings become visible on the curved object when the illuminating laser beam is strobed with 50 ns pulses by means of an AO modulator. We give data showing the variation in grating spacing with AO modulation frequency. Figures show the variation of the moire contour spacing with the AO modulation frequency and with target contour. The results for an angled flat plate target are compared with those in the literature.
A new method of calibrating tomodensitometric systems for spatial distortions, developed at Laval University, is based on the concept that each image represents parallel projection geometry for the sectional plane it represents. Scale affinity and inherent distortions are mathematically modeled. A series of parallel consecutive images taken of an object placed in a specially designed plastic cube gives a cost-effective solution. The results obtained indicate a standard error of about ±0.2 mm in each of three dimensions.