Showing papers in "Optical Engineering in 1975"
TL;DR: The SBUV/TOMS instrument as discussed by the authors measures the atmospheric ozone vertical profile and the solar ultraviolet spectrum, and provides a total ozone map by means of a mechanical scan across the Nimbus track.
Abstract: The SBUV/TOMS measures the atmospheric ozone vertical profile and the solar ultraviolet spectrum, and provides a total ozone map by means of a mechanical scan across the Nimbus track. While the SBUV/TOMS instrument has noteworthy design features such as a state-of-the-art double monochromator and fixed optical components on a nonmetallic structure, its most significant characteristic is an optimum system design based on technology proven on the BUV instrument.
345 citations
TL;DR: The FLD-ll as discussed by the authors is a computing photometer that determines and displays real-time values of the luminescence and reflectance coefficients of scenes within its field of view.
Abstract: The FLD-ll is a computing photometer that determines and displays real-time values of the luminescence and reflectance coefficients of scenes within its field of view. It senses luminescence by limiting the spectral bandwidth of the received energy to the spectral half-bandwidth of a Fraunhofer line-an absorption feature in the solar spectrum-by means of a. solidetalon Fabry-Perot filter. The Fraunhofer lines of interest are generally very narrow (less than 0.1 nm) and are appreciably reduced in intensity from the continuum. The FLD-II can operate from either helicopter or fixed-wing air-craft. The sensitivity of the instrument permits detection of the luminescence of <0.3 ppb of rhodamine WT dye at the 589.0-nm Fraunhofer line. The FLD-II can perform the fol-lowing functions: (1) remote tracking of fluorescent dyes for the study of current flow and rate of dispersion in large bodies of water; (2) detection of oil spills and leaks; (3) de-tection of the luminescence of in vivo chlorophyll of stressed vegetation in order to identify geochemical anomalies in the soil and the onset of crop disease; and (4) detection and mon itoring of pollutants that exhibit an inherent luminescence, such as effluents from phosphate processing plants, laundry detergents containing luminescent brighteners, lignin sulfo nate (a pulp mill effluent waste product), and others. This paper presents both details of the airborne FLD (optical system) and it's extension to an orbiting imaging system with applications to earth resources studies.
219 citations
TL;DR: In this paper, a CdS photoconductor, CdTe light absorbing layer, a dielectric mirror, and a liquid crystal layer sandwiched between indium-tin-oxide transparent electrodes deposited on optical quality glass flats was developed for real-time coherent optical data processing.
Abstract: A new, high-performance device has been developed for application to real-time coherent optical data processing The new device embodies a CdS photoconductor, a CdTe light-absorbing layer, a dielectric mirror, and a liquid crystal layer sandwiched between indium-tin-oxide transparent electrodes deposited on optical quality glass flats The noncoherent image is directed onto the photoconductor; this reduces the impedance of the photoconductor, thereby switching the ac voltage that is impressed across the electrodes onto the liquid crystal to activate the device The liquid crystal is operated in a hybrid field effect mode It utilizes the twisted nematic effect to create a dark off-state and the optical birefringence effect to create the bright on-state The liquid crystal modulates the polarization of the coherent read-out light so an analyzer must be used to create an intensity modulated output beam
195 citations
TL;DR: In this article, the annular field optical system (AOSOS) is proposed to avoid the extreme complexity of conventional projection mask alignment objectives. But it is not suitable for the use of a large number of mirrors.
Abstract: A new concept (the annular field optical system) makes it possible to avoid the extreme complexity of conventional projection mask alignment objectives This has been done in a new, extremely simple, all-reflecting optical system that consists of two, concentric, spherical mirrors A monolithic block consisting of three mutually perpendicular plane mirrors is used to fold the system into a configuration that makes possible an inherently synchronous, simple scanning arrangement Partially coherent illumination is used to increase the effective MTF without decreasing the depth of focus
163 citations
TL;DR: A survey of the characteristics, technology and applications of holographic optical elements (HOEs), considered as general elements in an optical system, can be found in this paper, where the authors show that HOEs provide unique system functions and configurations, show a rapid variation of optical power and image characteristics with wavelength, have relatively large amounts of astigmatism and coma, and require special consideration of optical efficiency during system design.
Abstract: This article is a survey of the characteristics, technology and applications of Holographic Optical Elements (HOEs), considered as general elements in an optical system HOEs function by diffraction of light from a generalized grating structure with nonuniform groove spacing HOEs provide a system of thin film optics They are capable of unique system functions and configurations, show a rapid variation of optical power and image characteristics with wavelength, have relatively large amounts of astigmatism and coma, and require special consideration of optical efficiency during system design Comparison of the aberrations of specific, f/33 elements shows that the on-axis HOE and the conventional glass lens element have similar aberration levels, while the off-axis HOE has four times as much astigmatism and twice as much coma We show that these grating aberrations, which appear for conjugate points that are different from the HOE construction points, are proportional to the average surface grating spatial frequency of an off-axis HOE HOE technology is similar to conventional optics technology, but is less developed The relative complexity of optical systems with HOEs, and the lack of a suitable aberration theory, produce a relince on computer-based raytracing for system design and development We give the basic raytracing equations and discuss the special requirements for hologram recording appara-tus and materials In applications, HOEs will usually provide unique capabilities rather than replace conventional elements, and will usually operate over narrow spectral bandwidths The use of HOEs in several types of laser optical systems, and in visual displays, appears to be not only advantageous, but also technically and economically feasible
145 citations
TL;DR: There are several methods for optically subtracting one image from another in order to detect differences between scenes or between photographs of scenes as discussed by the authors, including holographic, interferometric, coding, and positive-negative superposition methods.
Abstract: There are several methods for optically subtracting one image from another in order to detect differences between scenes or between photographs of scenes. There are many applications for such a technology, including earth resource studies, meteorology, automatic surveillance and/or inspection, pattern recognition, urban growth studies, and bandwidth compression. This paper presents an overview of several techniques for obtaining optical image subtraction, including holographic, interferometric, coding, and positive-negative superposition methods. As part of this review, a table is presented summa-rizing and comparing the characteristics of more than twenty-five approaches. An extensive bibliography is also given.
80 citations
TL;DR: The tuned response of this camera makes it well adapted for measuring lateral displacements of large incoherently lit structures by the moire grid technique, and the technique is compared to laser speckle photography.
Abstract: If a camera is to be used for the special purpose of recording periodic grid-like patterns, the range of spatial frequencies which it must handle is limited, and its imaging performance for a given range can be optimized by installing a suitably slotted mask inside the lens aperture. With this modification, a standard 35 mm single lens reflex camera has been found to resolve up to 600 lines/mm in both vertical and horizontal directions across the full format. The tuned response of this camera makes it well adapted for measuring lateral displacements of large incoherently lit structures by the moire grid technique. Some preliminary results are described, and the technique is compared to laser speckle photography.
67 citations
TL;DR: A review of speckle interferometry techniques can be found in this article, where the authors set the various techniques into context, point out their similarities, and delineate their differences.
Abstract: Since its discovery in 1969, speckle interferometry has be-come a very active area of research, so much so that there now exists quite a collection of techniques that are applicable to a wide variety of problems. Because of the surprising versatility offered by such a wide range of techniques, the potential user of such technology may become con-fused as to what can and cannot be done, and, further, what process is suitable for what task. This review is provided, therefore, to set the various techniques into context, point out their similarities, and delineate their differences.
64 citations
TL;DR: Holography is ideally suited for the study of dynamic three-dimensional particle fields, and its applications for this purpose are almost limitless as mentioned in this paper, with the most successful systems currently in use are combinations of holographic with conventional methods, with the hologram serving primarily as a storage device.
Abstract: Holography is ideally suited for the study of dynamic three-dimensional particle fields, and its applications for this pur-pose are almost limitless. The types and selection of configurations are described. A number of examples of current applications are given ranging from the study of micro organisms in biology to ice crystals in meteorology. It is concluded that ultimate image quality arising from a well-designed holography system will normally be slightly lower than the equivalent conventional photographic imaging method. However, such comparison can only be made when the precise object position is known a priori since only then is conventional photography applicable. Holography provides a method for examining, with high resolution, volumes several orders of magnitude larger than can be examined by photography. The most successful systems currently in use are combinations of holography with conventional methods, with the hologram serving primarily as a storage device.
51 citations
TL;DR: In this article, the authors describe the optical design and performance of the Landsat multispectral scanner (MSS) with two versions; one with four spectral bands from 0.5 to 1.1 microns, and one with five bands, the added band being 10.4 to 12.6 microns.
Abstract: The earth resources sensing Multispectral Scanner (MSS) for the Landsat satellite has two versions; one with four spectral bands from 0.5 to 1.1 microns, and one with five bands, the added band being 10.4 to 12.6 microns. This paper describes optical design and performance. The instrument uses a flat, object-space scanning mirror of near-linear motion, with a sensitive optical position monitor to detect mirror angular position. The 22.9-cm aperture telescope images the scene on an array of fiber optics, which dissect and transmit the scene energy to photomultiplier tubes detecting in Bands 1, 2, and 3, and silicon photodiodes detecting Band 4. Band 5 energy passes the fiber optic assembly and is reimaged on a radiatively cooled mercury cadmium telluride (HgCdTe) detector. The orbiting four-band scanner is furnishing data registered to better than 50-m band-to-band and resolving 80-m repetitive pattern over a 185-km swath width from 907-km altitude.
35 citations
TL;DR: Computer-generation of holograms allows introduction of general carrier configurations and there are convenient techniques for producing image plane holograms consisting of many narrow fringes similar to interferograms.
Abstract: Information about arbitrarily shaped wavefronts can be recorded as computer-generated holograms. There are convenient techniques for producing image plane holograms consisting of many narrow fringes similar to interferograms. These diffractive filters are suitable for realization of generalized elements for use in optical systems. These holograms can be applied to accomplish phase transformations, geometrical transformations, and combinations of phase and geometrical transformations. Computer-generation of holograms allows introduction of general carrier configurations. Examples of circular carrier recordings are shown.
TL;DR: The annulus is intermediate between the pinhole and the Fresnel zone plate with regard to both collection efficiency and the number of counts required for a given signal-to-noise ratio (SNR) and offers an improvement over pinhole apertures without demanding the increased count rate and resolution required of detectors when Fresnel Zone plate coded aperture are used.
Abstract: In the past, annular coded aperture images have been recon-structed by correlating an appropriately scaled annulus with the coded image. The basic improvement suggested in this paper is the addition of a linear radial frequency weighting in the Fourier plane. Reconstructions of point and disk objects were simulated with a computer program. The results show the advantage of this modification in the processing scheme. When the assumption is made that the detector is an Anger camera, the resolution obtained with the improved processing of the coded image is equal to that obtained with conventional apertures. An actual object consisting of the letter E was imaged with an annular aperture and a scintillation camera. The reconstruction with and without the improved processing is presented. In addition, the annulus is intermediate between the pinhole and the Fresnel zone plate with regard to both collection efficiency and the number of counts required for a given signal-to-noise ratio (SNR). It therefore offers an improvement over pinhole apertures without demanding the increased count rate and resolution required of detectors when Fresnel zone plate coded apertures are used.
TL;DR: In this article, infrared detectors are discussed in terms of an equivalent circuit consisting of a photocurrent generator in series with a gain mechanism, both shunted by the detector internal impedance.
Abstract: Infrared detectors are discussed in terms of an equivalent circuit consisting of a photocurrent generator in series with a gain mechanism, both shunted by the detector internal impedance. Detectivity, the usual measure of infrared detector sensitivity, is defined in terms of the parameters of this equivalent circuit. The properties and performance of the most common and best developed infrared sensitive photoconductors and photodiodes are then described in terms of these parameters. Both normal and low background performance are considered, with emphasis on maximum sensitivity in the low-to-moderate frequency region. Short discussions of the current status and recent developments in thermal detectors, high-speed detectors, and infrared detector arrays are included. The importance of preamplification is stressed throughout, and preamplifier principles and current practice for the various types of detector are separately discussed.
TL;DR: Holographic flow visualization has been studied extensively in the literature as discussed by the authors, and the most significant recent contributions in the field comprise solution of practical engineering problems, refinement in analytical and interpretive methods, and an increasing list of current and potential applications.
Abstract: The combination of the techniques of holography with those of flow visualization has resulted in one of the most wide-spread uses of holography. The most significant recent contributions in the field comprise solution of practical engineering problems, refinement in analytical and interpretive methods, and an increasing list of current and potential applications. The purpose of this paper is to summarize the meth-1 ods and state-of-the-art of holographic flow visualization. Holographic interferometry, like conventional interferometry, provides a measurement of optical path length between points of space. This can be applied to determine gas density or to observe density gradients and their movement throughout a volume. Moreover, a holographic image of a space is not just limited to interferometric analysis. Such images are amenable to a broad class of optical analysis, including three-dimensional photography and optical filtering methods such as schlieren photography.
TL;DR: In this article, a discussion of holographic recording materials in current use is examined along with a few of their applications, and a convenient summation of some material properties is presented in tabular form.
Abstract: Holographic recording materials in current use are examined along with a few of their applications. Some experimental media are also studied. No effort is made to rank the commercial materials, since satisfactory results can be obtained with any of them. The discussion covers silver halide plates and films, photoresists, thermoplastics, photopolymers, dichromated gelatin, photochromic materials, electrooptical crystals, styryl free radical film, and TEP film. A convenient summation of some material properties is presented in tabular form.
TL;DR: In this paper, an oblique-incidence interferometer for testing the flatness of fine-ground surfaces is described, which uses reflecting diffraction gratings to divide and recombine the beams, resulting in a very compact optical system.
Abstract: An oblique-incidence interferometer for testing the flatness of fine-ground surfaces is described. This uses reflecting diffraction gratings to divide and recombine the beams, resulting in a very compact optical system. In addition, the relative amplitudes of the interfering beams can be adjusted, by a suitable choice of the grating orders used, to give fringes of excellent visibility with surfaces having a wide range of refleetances.
TL;DR: In this paper, the principles and methods of scanned transmitter-receiver and scanned object microwave holography and their use in high resolution microwave imaging are discussed, together with a discussion of potential applications in radar-like imag-ing of remote moving objects and in the visualization of internal structures.
Abstract: The principles and methods of scanned transmitter-receiver and scanned object microwave holography and their use in high resolution microwave imaging are discussed. Results of laboratory experiments demonstrating the capabilities of this scanned mode of microwave imaging are presented together with a discussion of potential applications in radar-like imag-ing of remote moving objects and in the visualization of internal structures.
TL;DR: A nephelometer has been developed for airborne measurement of polar scattering diagrams of atmospheric aerosols as discussed by the authors, which has been used for airborne measurements on a pressurized aircraft using outside air ducted through a 5-cm diameter airflow tube.
Abstract: A nephelometer has been developed for airborne measurement of polar scattering diagrams of atmospheric aerosols. The nephelometer light source is a modulated heliumneon laser; a digital synchronous photon counter is utilized to measure scattered-light intensity. The system has been designed for airborne measurements on a pressurized aircraft using outside air ducted through a 5-cm diameter airflow tube; the sample volume is that which is common to the intersection of the collimated source beam and the detector field of view within the airflow tube. The instrument has been flown on the NASA Convair 990 airborne laboratory to obtain data on the complex index of refraction of atmospheric aerosols. Particle sizing devices were operated simultaneously to determine the aerosol size-number distribution. Calculated values of the angular variation of scattered-light intensity were obtained by applying Mie scattering theory to the observed size distribution function and assuming different values of the complex index of refraction of the particles. The calculated values were then compared with data on the actual variation of the scattered-light intensity obtained with the polar nephelometer. The most probable value of the complex refractive index was taken to be that which provided the best fit between the experimental light-scattering data and the polar scattering diagrams calculated from the observed size distribution function.
TL;DR: A new method for controlling the shape of an optical mirror which does not require any reaction against a support structure is described and the required distribution of control points established.
Abstract: A new method for controlling the shape of an optical mirror which does not require any reaction against a support structure is described. A computer analysis has been made for a sample case of a simple, thin disc, and the required distribution of control points established for direct control of the first ten terms of a Zernike polynominal expansion describing the surface shape.
TL;DR: A highly corrected three-mirror telescope has been designed for space application as discussed by the authors, which is free of spherical aberration, coma, astigmatism and field curvature, and the rms-spot size within a 40 arc min field is equal to or better than.025 arc sec.
Abstract: A highly corrected three-mirror telescope has been designed for space application. It is free of spherical aberration, coma, astigmatism and field curvature. The rms-spot size within a 40 arc min field is equal to or better than .025 arc sec. The full field cannot be utilized in its entireness. A number of subfields for different instruments can be folded out radially.
TL;DR: In this article, an electronically scannable electron-beam-pumped semicon-ductor laser device is described which provides laser emission from more than 1000 X 1000 randomly addressable spots.
Abstract: An electronically scannable electron-beam-pumped semicon-ductor laser device is described which provides laser emission from more than 1000 X 1000 randomly addressable spots. The device consists of a permanently sealed electron beam tube about 50 cm long. Attached to the inside of the face-plate is a 30 um thick cadmium sulfide single crystal wafer with typical lateral dimensions of 28 mm X 28 mm, which serves as the active laser element. Using a 50 ns pulsed elec-tron beam current of up to 2 mA, with an accelerating poten-tial of about 50 keV, laser emission is produced in a direction essentially coaxial with the pumping electron beam. A laser spot diameter of 25 um can be achieved with these devices. The emitted radiation is typically confined to a symmetric cone with a half angle less than 0.1 rad. The laser tube is capable of operation at room temperature or, for greater power output, may be conveniently cooled with conventional refrigeration to about -50°C. At this temperature, peak power outputs in excess of 5 watts have been produced from CdS at 515 nm wavelength. In preliminary tests, laser tubes have been operated at repetition rates up to 400 kHz for more than 2000 hours without significant decrease in laser emission. Applications of such devices include display, COM/CIM, and optically addressed holographic memories.
TL;DR: Some examples of applications of holographic interferometry to structures are presented in this paper, arranged in increasing order of quantitative or interpretive sophistication.
Abstract: Some examples of applications of holographic interferometry to structures are presented in this paper. Some of the reconstruction techniques are novel and have not been reported previously, in particular the moire and blink projection methods to be described. The applications are arranged in increasing order of quantitative or interpretive sophistication. The dis-cussion of the actual holographic technique in each instance is very brief, the details being available in the literature. . . . nothing more can be attempted than to establish the beginning and the direction of an infinitely long road. The pretension of any systematic and definitive completeness would be, at least, a self-illusion. Perfection can here be ob-tained by the individual student only in the subjective sense that he communicates everything he has been able to see." Georg Simmel
TL;DR: The theory behind the aberration correction of holographic concave diffraction grating is discussed in this article, where applications in instrumentation design are described, including Spectrophotometry, Spectrofluorimetry, Raman, Polychromators, etc.
Abstract: The theory behind the aberration correction of holographic concave diffraction grating is discussed. From these results, applications in instrumentation design are described. The fields include Spectrophotometry, Spectrofluorimetry, Raman, Polychromators, etc. The new design options are then discussed by comparing the possible available solution for in-strument improvement before and after the advent of the holographic gratings.
TL;DR: The Optical Telescope Assembly (OTA) as mentioned in this paper was installed in the LST spacecraft and the vertex-to-vertex spacing of the primary and secondary mirror is 193 inches, and this spacing must be maintained constant to a precision of -±11.1 for observation periods up to 10 hours.
Abstract: As spaceborne optical systems increase in diameter to achieve improved resolution, the stability requirements imposed on structures approach values which were unthinkable only several years ago. To achieve the capabilities of these apertures optical path errors must not exceed a specific fraction of the wavelength of light, and this fraction, typically x/20 rms in the focal plane, is independent of system size. Thus, from a percentage error basis, large optical support structures represent a far more formidable development task than do smaller systems. The Large Space Telescope (LST) sponsored by MSFC/NASA is a case in point. The Optical Telescope Assembly (OTA) is shown (Fig. 1) installed in the LST spacecraft. The vertex-to-vertex spacing of the primary and secondary mirror is 193 inches. To achieve satisfactory optical performance, this spacing must be maintained constant to a precision of -±11.1 for observation periods up to 10 hours. During this time it may be necessary to alter the spacecraft attitude with respect to the sun, which would change the temperature levels and gradients within the structures. It is believed that by exploiting the use of graphite-epoxy in a novel manner, the stringent alignment require-ments can be satisfied with a nominally passive structure.
Abstract: Substantial improvements in the thermal imaging state-of-the-art are occurring in forward-looking infrared (FLIR) system technology. These far infrared imaging systems have achieved broadcast television standards for frame rate, resolution, and signal-to-noise ratio, and are moving toward the standardization and volume production necessary for wider dissemination of the technology. Current techniques permit a single-detector system to approach within a factor of two the theoretical limit of thermal sensitivity using a photon detector. FLIR systems now use mechanical scanners and the mini-mum number of detectors necessary to achieve the needed performance, but performance requirements are increasing, and future systems may use mosaics of self scanned detec-tors. Then problems of element-to-element nonuniformities and of background substraction must be solved.
TL;DR: In this article, a portable battery-powered spectroradiometer has been constructed for the measurement of the apparent directional reflectance of natural targets, and a silicon detector that is tripod mounted and positioned to monitor a horizontally oriented reference panel determines the target irradiance.
Abstract: A portable battery-powered spectroradiometer has been constructed for the measurement of the apparent directional reflectance of natural targets. A silicon detector that is tripod mounted and positioned to monitor a horizontally oriented reference panel determines the target irradiance. A second detector for measurement of target radiance is mounted on the tripod swivel head. Electronic switching provides alter-nate detector references for the determination of apparent directional reflectance. Snap-on interference filters allow measurement in desired spectral bands. Equipment calibration procedures are discussed and typical experimental radiation data are given.
TL;DR: In this paper, a computer program for straylight suppression system design and analysis was developed to analyze various proposed LST stray light suppression systems, and experimental measurements were made on a simplified LST suppression system in a unique facility.
Abstract: A computer program for straylight suppression system design and analysis was developed to analyze various proposed LST straylight suppression systems. Simultaneously, experimental measurements are being made on a simplified LST straylight suppression system in a unique facility. The experimental measurements are being used to verify and improve the computer program. The facility represents the state-of-the-art in straylight suppression measurements, and transmission factors of 10 to the minus 12th power have been measured.
TL;DR: In this article, the authors outline the motivation for applying coherent optics to topographic mapping, present some additional applications not included in Ref. 1, and further discuss some applications developed in that reference.
Abstract: Several potential applications of coherent optics in the field of topographic mapping have been identified.1 This paper outlines the motivation for applying coherent optics to topographic mapping, presents some additional applications not included in Ref. 1, and further discusses some applications developed in that reference.
TL;DR: The state of the art in manufacturing large one piece metal mirrors has advanced dramatically in the past 10 years, following important pioneer work by NASA's Jet Propulsion Laboratory in 1965 as mentioned in this paper, and several additional large solar simulator mirrors have been manufactured.
Abstract: The state of the art in manufacturing large one piece metal mirrors has advanced dramatically in the past 10 years, following important pioneer work by NASA's Jet Propulsion Laboratory in 1965. Since that time, several additional large solar simulator mirrors have been manufactured. Careful mechanical and thermal design analysis and structure material selection are important elements in a successful finished product. Manufacturing techniques for mirror structure fabrication borrow from the heavy metal industry, while optical processing still follows relatively classical methods. Requirements for electroless nickel plating, sea transportation, and improved long term optical surface protection are challenges that have resulted in innovative practical solutions. The recently completed 5.5 meter (18 foot) diameter mirror for the Japanese National Space Development Agency's new space center at Tsukuba, Japan, exemplifies much of the technical advancement achieved over the last 10 years.