A "Nanosensor" is conceived and tested in which a 400 nanometer grating and Helium Neon multimode laser are used to resolve nanometer motions of a PZT. A multipass scheme is described which is capable of resolving 1/9 nanometer motions or 1/5695 of the source wavelength.
Diffraction effects of secondary mirror spiders upon telescope image quality can be important in certain imaging applications. However, rigorous analytical calculations are often unwieldy and virtually all commercially available optical design and analysis codes that have a diffraction analysis capability are based upon numerical Fourier transform algorithms which lack adequate sampling density to model very narrow spiders. A simple empirical equation is developed that allows accurate engineering calculations of fractional encircled energy to be made for arbitrary spider configurations. Characteristic design and evaluation curves are provided for use with this equation for a variety of obscuration ratios and spider widths. The results of this empirical equation are compared to those of rigorous calculations to determine its range of validity. Finally, parametric encircled energy curves are presented that provide insight into the diffraction effects of secondary mirror spiders.
A diffraction grating rhomb is an excellent candidate for both suppressing sideband instabilities in a free electron laser (FEL) and outcoupling the optical beam. A rhomb incorporating sinusoidal profile gratings exhibits many of the required performance characteristics for such an application. We present in some detail a description of such a rhomb and include a rhomb alignment sensitivity analysis.
Simple apodized (soft) apertures (AA) were fabricated for use in laser physics to avoid hard-edge Fresnel diffraction in the beam spatial-intensity profile. These AA of ≈ 2-45 mm diameter have approximately Gaussian and super-Gaussian transmission function in the visible and infrared band. They have high threshold for intensity damage.
Waveguide optics in combination with gratings for in- and out-coupling provide a potentially powerful combination for building light, compact optical systems. The gratings may be simple linear gratings or focusing gratings for creating converging beams. To understand these devices and design and analyze them, we must consider both waveguide optical properties and the more common two dimensional optical beams. This paper addresses the special problems of fitting in- and out-coupling features into the usual end-to-end laser modeling methodology.
This paper illustrates a technique to enhance the image resolution of an optical sensor beyond its Rayleigh diffraction limit. Calibration of the optics and suitable signal processing algorithms to solve the image conditions described herein readily provide imagery enhanced beyond the diffraction limit. A practical example is drawn from an optical experiment set up at Pacific-Sierra Research Corporation, using a video monitor and video camera, all under computer control. Calibration data was taken and the equations for enhanced imagery were solved to demonstrate imagery enhanced by a factor of x2 beyond the Rayleigh limit. Further enhancement is possible and appears to be limited only by the signal-to-noise ratio of the image.
We have developed a high numerical aperture grating-lens pair with large wavelength allowance. It has a new "center cross" structure, in which all rays cross the optical axis between the two grating lenses. Grating-lenses have concentric grating rings with radii set to cancel the diffraction angle changes caused by wavelength change. Wavelength allowance was estimated using RMS of wavefront aberration. An example calculation showed a wavelength allowance of 20 nm for a numerical aperture of 0.7. This value is sufficient for use with laser diodes with mode hopping or multimode.
Ellipsometric parameters for coated aluminum surfaces with roughnesses below 10 nm were measured using an infrared ellipsometer at null operation. The two-phase model was used to fit the ellipsometric data of multiple angles of incidence at a fixed wavelength. The complex dielectric constant, the complex index of refraction, and the deviations of fitting were found to exhibit linear dependency on roughness. These linear relationships can be used to characterize roughness as well as to determine the optical constants of material without ambiguity of roughness.
This paper deals with the development of a vapor leak sensor for plant inspection. The sensor requires the ability to selectively detect troubles in various circumstances. The method to detect vapor leak is based on the detection of scattered light. The experiment on polarization property shows that there is large difference between the scattered light from vapor and that from structures in a plant, and that the method is effective for the distinction of the two scattered lights. As a result of our experiment, it is confirmed that the sensor enables us to selectively detect the vapor leak with high sensitivity even in a plant and has high performance for plant inspection.
A potential problem encountered in the implementation of symbolic substitution logic (SSL) is addressed in this paper. It is shown that in the case of intensity-coded data, the pattern recognizer in the architecture for the optical symbolic substitution processor does not recognize the presence of an overlapping pattern of interest. On the other hand, the architecture identifies the overlapping pattern in the case of polarization-coded SSL. However, the recognition of the overlapping search patterns can cause problem in certain applications when we try to make use of the parallelism in the spatial dimension. The above cases are illustrated by suitable examples.
In this paper, all varieties of the optical stabilizing image methods have been summarized into an optical stabilization pattern, and a mathematical model of the optical stabilizing image are proposed. Some representative systems are analyzed by means of this model in orde to show how to use this model.
Stop-band filters were made from metallic crossed dipoles on two types of substrates. The dipoles were fabricated using electron beam lithography on a ZnSe substrate and a surface-modified ZnSe substrate. A thin film of CaF, modified the ZnSe surface by providing a buffer layer between the crossed dipoles and the ZnSe.
To resolve a re-entry vehicle (RV) from its associated wake, their emittances due to different temperatures are used as the basic foundation for development of an innovative optical method. This method consists of using a selective sensor and a cross-grating. The former selects a particular waveband to differentiate the radiation of the tip of the RV from that of the wake while the latter determines the angular location of the tip radiation. The temperatures of the tip and the wake are assumed to be 2500°K and 2000°K respectively. The sensor is made of CsTe/MgF2, sensitive only to the ultraviolet band of ~ O.l3μm to 0.3μm which is the waveband covered by the spectral emittance curve of the tip at temperature 2500°K and above the level of emittance of 5.76 x 10-7 watt/(m2-μm). All other wavebands are excluded by the sensor. The angular location of the selected radiation in terms of azimuth and elevation is determined by a cross-grating of perpendicular slits. The number of slits was selected to be 20,000 in 4 cm. The details of the theoretical and engineering points will be presented in this paper along with the pertinent questions.
Fiber optic delivery systems promise to extend the application of holography to severe environments by simplifying test configurations and permitting the laser to be remotely placed in a more benign location. However, the introduction of optical fiber leads to phase stability problems. Environmental effects cause the pathlengths of the fibers to change randomly, preventing the formation of stationary interference patterns which are required for holography. An active phase control system has been designed and used with an all-fiber optical system to stabilize the phase difference between light emitted from two fibers, and to step the phase difference by 90° without applying any constraints on the placement of the fibers. The accuracy of the phase steps is shown to be better than 0.02°, and a stable phase difference can be maintained for 30 min. This system can be applied to both conventional and electro-optic holography, as well as to any system where the maintenance of an accurate phase difference between two coherent beams is required.
Automatic hologram calculation of 3-interferogram-method in a computer-controlled holographic setup is theoretically and experimentally studied. With this method we have obtained all informations: the deformation quantity, direction and form of a deformed object surface. As practical examples, we have measured all informations of a pressure-measure drum and a tilted plate.
This article introduces a holographic wide-angle lens detecting instrument. This is a multiple image point holographic lens system. It can not only detect the quadrant of incidence light reaching system, but also provide incidence angle of laser. Authors made theoretical analysis and experimental works. The comparison between the experimental results and theoretical count shows that the data of experiment are nearly as same as that of theory. This technique has a great potential to replace the conventional quadrantal detectors inthe laser guidance and tracking.
We present in this paper a new type of light source with adjustable chromaticity coordinates. It is composed of a white light collimation system, acoustooptic tunable filter(AOTF) and a special driving power supply. The chromaticity changing range of this light source is much wider, it can be used as a complex light source with adjustable chromaticity or monochromatic light sources in visible light ranges. Operating principles of this light source are discussed, the circuit block diagram of the special driving power supply is given in this paper,and chromaticity changing ranges are measured in it.
A novel technique for measuring the spectral properties of single-mode, semiconductor lasers for use in coherent optical communication systems is being explored. Unlike conventional linewidth/lineshape measurements both amplitude and phase information is retained in a complex spectral correlation function. In principle this should give additional insight into both the amplitude noise and phase noise processes within the laser that determine lineshape. The paper discusses the method and the problems involved.
Side-pumped lasers such as flashlamp- or reactor-pumped lasers often have a nonuniform energy deposition in the gain medium, which can establish a significant transverse index gradient. This gradient significantly complicates energy extraction. A normalized resonator analysis method is developed that predicts resonator stability transitions and mode sizes for parabolic index fields. Parameter studies for some practical classes of resonators are presented, along with some design guidelines. Experimental comparison for a long-pulse gas laser shows good agreement with stability transition times. Two resonator-design approaches are presented for increasing the extraction efficiency in the presence of intracavity index gradients.
The present study investigates the mechanical properties (tensile testing) of the laser spot welding of single and multi core wires. In order to investigate the effect of wire diameter on the welding, three different sizes of wire were selected. It is found that at some power intensities the mechanical properties of the welds improve. In addition, a mathematical model for a nonconduction limited welding was introduced.
This paper presents a detailed analysis of a space-based telescope requiring an accuracy of 50 pico radians. A relationship between the geometric centroid of a diffraction image and wave aberrations is derived by a combination approach of diffraction optics and geometric optics. Based on sensitivity of the centroid, one-mirror and two-mirror aplanatic telescopes are investigated. The comparison among three telescopes, parabola, Schwartzschild and Ritchey-Chretien are quantitatively carried out in terms of their sensitivites to the systematic errors and random errors. The study shows that the Ritchey-Chretien design is the most preferable.
The OPTECAL testbed has been fabricated for the purposes of developing and evaluating control algorithms for active, closed loop control of optical systems. The testbed has the capacity for controlling up to 84 degrees of freedom, including deformable mirrors and segmented mirrors. Evaluation of optical performance is provided by either a phase measuring interferometer, shearing interferometer or image based sensor (IBS). The modular design of the operational software allows for easy implementation of new control algorithms. An accurate software simulation of the optical prescription is also incorporated to facilitate initial algorithm develoment. One imagebased algorithm and one wavefront based algorithm have been successfuly evaluated. Future plans include the investigation of other optical control algorithms, such as phase retrieval techniques and extended scene measurements.
MTF is considered as performance target when either making automatic optical design or tolerancing optical system recently. Therefore, it is very useful to give calculation expressions of MTF differentiation to structure parameters and tolerances of an optical system in optical design. The aim of this paper is to resolve the problem in this aspect.
The tolerances affect both of the cost and the performance of an optical system very much. This paper describes a mathematical model of making optical tolerances considering cost and performance. An example is given which was computed using the optimizing computer program we maked. The sensitive coefficient can be calculated either by optical path tracing or by using the partial derivatives of MTF with respect to the parameters r, d and n, and eccentric difference δ, partial optical ring AN. In the suggested method, the table of man - hour quota In optical manufacture is used.
LITE (Lidar In-space Technology Experiment) is a Langley Research Center project which will provide engineering data that can be used for future space-based lidar systems. The optical system consists of three science channels (the 355 nm PMT, the 532 nm PMT, and the 1064 nm APD channels) and one active alignment channel (the 532 nm QUAD channel) as aft optics to a Ritchey Chretien telescope. The purpose of this paper is to present the results of a study done to generate a tolerance budget for LITE using a combination of manual and Monte Carlo tolerancing techniques using the SYNOPSYStm optical analysis program.
In this article we have theoretically and experimentally dicussed how scanning interference fringes are automatically recorded with a ccd camera and a computer. This new measure technique can be used to any length measurement by interferomtry. As a practical example, we have automatically in real-time measured the shrinking of 2- components adhesive in a hardening process.
An automatic procedure of ordering fringes of the in-plane moire and the isochromatic patterns is proposed. The rotational mismatch is used in moire test and a bending beam is superimposed on the photoelastic specimen to generate straight-line carriers before the deformation. The in-plane displacement and the relative retardation of birefringence are encoded respectively as the modulation to the carriers. The resultant fringes are digitally processed by autotracking, interpolation and demodulation to number the fringe-order and to realize a whole-field compensation automatically.
The moire interferometry of high sensitivity is used in the solution of the load distribution on the boundary of semi-infinite plane. The displacement components normal to the edge or their partial derivatives with respect to the boundary coordinate are obtained from experimental data and then applied respectively to linear equations to solve the contact stresses.
An interferometer utilizing a multielement photodetector has been developed to conduct fast and accurate measurement of the thickness of ultra-thin films and small spacing between two separated surfaces. The thickness of a magnetic film on a metallic substrate was measured. In addition, the spacing between a magnetic recording head and a glass disk surface was demonstrated. By examining the spectral intensity of the interference pattern, the film thickness or the spacing is calculated. The entire visible spectrum of the interference light beam is obtained simultaneously with the multielement photodetector. The spectral efficiencies of the light source and the diffraction grating as well as the spectrum response of the photodetector are measured for the calibration. Substrate effects are minimized by fist examining the reflection spectrum intensity of the substrate. A numerical filtering technique used in the experiments significantly reduces the noise, thereby yielding a good signal to noise ratio. An optical thickness of L/10 ( L is the wavelength ) is obtained by a carefully numerical analysis of the measured data, which is significantly less than the limitation, L/4, by the conventional method.
This paper describes the optical hand-held scanner designed for use as an input device to the Kurzweil reading machine for the blind and visually-impaired. This device has numerous advantages over other scanners, chief among which are its high resolution, one-inch field of view, bidirectional capabilities, and compact block-shape. The device allows the user to scan single sheets as well as bound books and magazines. During its three-year development, the major emphasis has been on refining the design to make the device easy to use. This paper addresses the technical issues associated with the human-factors considerations that led us to this design.
In an earlier paper entitled "Regression Analysis of Zernike Polynomials, Proceedings of SPIE, Vol. 18, pp. 392-398, the least squares fitting process of Zernike polynomials was examined from the point of view of linear statistical regression theory. Among the topics discussed were measures for determining how good the fit was, tests for the underlying assumptions of normality and constant variance, the treatment of outliers, the analysis of residuals and the computation of confidence intervals for the coefficients. The present paper is a continuation of the earlier paper and concerns applications of relatively new advances in certain areas of statistical theory made possible by the advent of the high speed computer. Among these are: 1. Jackknife - A technique for improving the accuracy of any statistical estimate. 2. Bootstrap - Increasing the accuracy of an estimate by generating new samples of data from some given set. 3. Cross-validation - The division of a data set into two halves, the first half of which is used to fit the model and the second half to see how well the fitted model predicts the data. The exposition is mainly by examples.
Beam expander optical and structural characteristics can be utilized to desensitize line of sight (LOS) jitter. The overall LOS jitter for a given disturbance spectrum is largely dependent on the optical alignment sensitivity and the resonance mode shapes of the beam expander. By properly selecting the beam expander configuration design, "nodes" can be generated in terms of the LOS where no, or minimum, participation can be expected for certain frequency bands. By adopting such a design approach, the overall LOS jitter for a given disturbance can be reduced significantly.
By using a low power laser beam to pass through a beam splitter to illuminate the system which functions as a right angle reflector, the incident beam is reflected several times in the interval between the beam splitter and the system. The reflections will result in multiple beams to emerge from the system to the screen. The two principal ones of these beams will interfere each other to generate a zone plate pattern. When the centers of the beams are not coincided, unsymmetrical fringe pattern will be observed. By adjusting the system to get symmetrical pattern, perpendicularity of setting of the system will be gotten. In testing, deviation of perpendicularity of the angle to be tested can be estimated from the symmetry of the interference pattern. It is very easy to get five arc seconds accuracy both in setting and testing.
A new static IR horizon earth sensor is used in Indian Remote Sensing (IRS) satellite for precision attitude determination. Due to a large subtended angle of the Earth at 904 km IRS satellite's polar orbit, the static earth sensor has a unique design consisting of four telescopes mounted on a pyramid shaped base. Each of the telescopes contains an IR optics and thermopile detectors of special geometry. These detectors are positioned precisely and aligned with respect to earth's image at the horizon. Sensitive axis of each telescope is defined at sub-assembly level using extended area black body source and a two-axis indexing table. This sensitive axis is transferred to an alignment mirror mounted on each telescope. The four telescopes carrying individual alignment mirrors are finally aligned to a central optical cube on an integrated sensor assembly. This alignment is carried out using a two-axis servo-table and an alignment facility. In addition, there are four sun interference sensors mounted on the main base and aligned to sensitive axis of the individual telescope. This alignment is carried out using a sun simulator and a two-axis servo table. The alignment of integrated static sensor is counter-checked using the large earth simulator both for altitude and null angles, and calibration is carried out for roll and pitch measurements. The central optical cube is finally used for aligning the sensor with respect to the satellite reference axes and in turn to the camera systems on the satellite. This paper discusses the methodology used for the alignment of individual telescopes, four telescopes on the main base and sun interference sensors.
An automated fiber alignment, fixing, and sealing process was developed for optoelectronic devices produced by BT&D Technologies. The products -- transmitters, receivers, etc. -- were developed simultaneously with the process, allowing development of common technologies and submodule "building blocks." This approach has many advantages: sufficient manufacturing volume to justify automation, quick response to new product variations, and uniform quality. This paper describes the development of a patented laser-based manufacturing system for pigtailing optoelectronic devices.
A relatively simple technique was devised to precisely align the components of a diagnostic instrument which recorded the first neutron images of imploding laser fusion targets. Alignment was achieved using a laser, a 2 mm diameter glass sphere, and a pair of lenses. With this technique, a 6 cm long aperture was pointed with an accuracy of 68 microradians and coaxially aligned with a target and detector separated by 10.5 meters. The alignment technique is described and critical features are discussed.
This paper describes a technique for verifying with high accuracy and repeatability the alignment of optical components and subassemblies. Using as an example the work done at Martin Marietta Electronic Systems to implement the testing of an optical laser pattern encoder operating in conjunction with a zoom optics and a CO2 laser, we show how relatively simple alignment tools simulating optical components can be utilized, both in the laboratory and in the factory, to position the components on their test beds and predict their performance prior to installation in the system. This simulator method can shorten dramatically the time required to align, check-out and troubleshoot optical components.
The major problems faced in spaceborne multielement optical systems used for high resolution imagery and remote sensing applications are the stability of optical and mechanical configurations under Shock, Vibration and Thermal cycling environments. The critical parameters to be achieved in a housing design for such situations are the decentering limits and separation limits for temperature variations. In this paper, a new technique for mounting optical elements for such applications is discussed.
A 19-element serial hill-climbing adaptive optical system is introduced. By using a 19-element deformable mirror, a detector for sharpness of the focal spot and a dither control system, it can correct static and slowly varying dynamic wavefront errors. The hill-climbing control algorithm, experimental setup and correction effect are reported. Experimental result shows that this system can be used in large laser engineering system for wavefront error compensation and far-field sharpness improvement.