Showing papers in "Optical Engineering in 1972"

The Use of Solid Etalon Devices as Narrow Band Interference Filters

Abstract: The fabrication of Fabry-Perot Etalon Filters with spacer elements of solid fused silica is described. Typically spacer thicknesses of 120pm are used to provide filters with .05nm to .07nm FWHM at 656.3nm centre wavelength. More complex devices having two coherently coupled cavities are described. The effect of optical system parameters on the spectral performance of the solid etalon filters is discussed and suitable operating parameters are suggested. The performance of solid etalon filters is compared with the birefringent filters of the Lyot type.

C W Pumped Dye Lasers

Abstract: A review is given of fundamental information about CW-pumped dye lasers that is most useful to users of these lasers. The important attribute of continuous tunability is discussed and limits suggested for the following: Wavelength ranges, linewidth, mode purity, polarization and power output. The physics of operation of the dye laser is described and rate equations are solved for the dye solution flowing through a focused pump beam. A detailed discussion is given of the design limitations, on efficiency and on wavelength selectivity, that are imposed by considerations of geometrical and physical optics. It is shown that tradeoffs may have to be made between high power output and efficiency, and high wavelength selectivity. Finally, there is brief mention of the chemistry of the dye solution.

A relative performance analysis of atmospheric laser Doppler velocimeter methods.

Abstract: A performance analysis is presented that compares two remote-sensing atmospheric laser Doppler velocimeter systems, one using dual-scatter and the other local-oscillator illuminating techniques. The comparison results show that there exist specific parameter ranges and conditions whereunder the performance of one of the systems is superior to that of the other. A procedure providing a quantitative basis for a judicious system selection is proposed.

A Low-Light-Level Objective Lens with Integral Laser Channel

Abstract: A high performance, f/1.5 objective lens of 229 mm (9 inches) focal length has been designed and produced for use in a variety of military low light level systems. The latest version of this lens has an integral coaxial 10X beam expander for a 1.06//m laser beam. This allows the lens to be used in a laser rangefinder/target designator role as well as to produce an ambient light image of a 20° field of view for intensification in a direct-view periscope. In this paper, the configuration and optical performance of this new objective lens are described, and the means used to solve some of the unique problems associated with transmission of the laser beam are discussed.

The Design and Application of a Surface-Measuring Interferometer

Abstract: The most common method of surface evaluation in optical production uses optical test plates. The main objections to test plates concern the possibility of damage to the surface through contact and the need for a different test plate for every different surface. A surface measuring interferometer is described which is capable of measuring the radius of curvature and the surface irregularity independently. The process of evaluating surface irregularity is simplified since all power error can be nulled out. Other useful applications of the interferometer are also described.

Scanners and Recorders for Imagery Transmission

Abstract: The current trend toward higher bandwidths, finer resolutions, and the desire for dry rapid film processing will require new approaches toward scanning and recording of imagery. This paper will first discuss present technology in high bandwidth, high resolution laser recording. These devices can achieve resolutions up to 200 lp/mm at recording rates up to 340 X 10 6 Hz. It will be shown that little improvement can be expected over today's technology due to fundamental component and physics limitations. The remainder of the paper will describe a new approach that employs integrated optics in the development of modulators and scanners. An integrated optic scanner could conceivably scan light at information rates exceeding 1 gbs (109 bits/sec) without any mechanical motion.

Multichannel television coupling modulation experiments using a CO2 laser.

Abstract: Experiments are described in which a carbon dioxide laser oscillating at 28.4 THz has been modulated simultaneously by three commercial television signals with carriers at 54, 66, and 82 MHz. Signal-to-noise degradation in the system was measured to be less than 1 dB, corresponding to modulator drive power of 1 W. This combination of wide bandwidth and low power consumption was made possible by the application of coupling modulation. This technique employs an intracavity electrooptic crystal to which the modulating fields are applied. Despite the fact that the crystal is positioned inside the laser cavity, the maximum bandwidth attainable is independent of both the cavity Q and the laser transition linewidth, and is limited only by modulator characteristics and optical transit time. Rigrod's (1965) method has been adapted to obtain an expression for the power coupled out of the laser. Modulator frequency response and drive power requirements are also summarized. It is seen that the noise bandwidth performance of the system would allow simultaneous modulation by 17 color television channels, or equivalently, more than a 300-megabit/sec capacity.

A Large Multiple Mirror Telescope (MMT) Project

Abstract: The University of Arizona and Smithsonian Astrophysical Observatory are jointly undertaking the development of the concept of a multiple-mirror telescope for astronomical uses. The system consists of six 1.8-m-aperture cassegrainian telescopes combined to produce a common focal surface in the center of the telescope. The early form of the telescope will provide for automatic alignment of the six independent systems. The telescope will be constructed to facilitate later extension of the alignment subsystem to include aperture synthesis (phasing) by methods proposed by Meinel and Shannon. The light-gathering power of the combination is equal to a standard telescope of 180-in. aperture, but the construction will cost very much less. The mounting will be of the alt-azimuth type. The telescope will be located at an elevation of 8,600 ft at the SAO's Mt. Hopkins Observing Station near Tucson.

The Moon Camera and Its Lenses

Abstract: A Hasselblad camera has been used during all NASA lunar landings from Apollo 11 through Apollo 16. A few basic changes make it different from Hasselblad equipment used in previous space flights

A Tunable Semiconductor Laser for Pollution Studies

Abstract: Tunable semiconductor lasers have been utilized for detecting and measuring atmospheric pollutants. By adjusting the stoichiometry of the junction, one can fabricate diodes that oscillate in desired wavelength ranges. Experiments have shown that it is possible to use such lasers to detect typical pollutants, in concentrations ranging from parts per million to parts per billion, by measuring the infrared absorption spectrum of a sample.

HF Laser Flow Visualization with an Infrared Television System

Abstract: This paper describes an infrared television system used for observing HF continuous chemical laser gas flows. The prime goal for these experiments was the flow visualization of the supersonic free jets provided by the IR HF emissions which were generated by the reaction of hydrogen and fluorine flowing out of selected nozzle configurations. The spatial flow patterns for three IF laser configurations were observed and monitored with this IR television system. The mechanical configuration, optics, and operating parameters associated with each configuration are discussed in this report. The uniformity of the laser medium and the properties of the jet are also described.

Modulation Measurement Applied to the Focusing of Aerial Cameras

Abstract: Photoelectric measurement of aerial image modulation at a single spatial frequency has been applied to the focusing of lenses in aerial cameras. Using an automated apparatus to provide a plot of modulation through focus, the settings are made in a fraction of the time and with much greater confidence than by the photographic resolving power method. It is pointed out that the focus for a single well-chosen frequency can be a good index of the focus for all frequencies in the photographically-important region of the MTF of the lens, also that a through-focus plot of modulation at one or two important frequencies is often of greater value to the camera manufacturer than the usual MTF plot at one focus position. The well-known difficulty in focusing some lenses by high contrast resolving power is explained in terms of their decreased sensitivity to focus setting above a certain frequency; in some cases this effect cannot be eliminated by moderate stopping down. Although primarily designed for measuring relative modulation on axis, the apparatus can be calibrated to read absolute modulation to a useful degree of accuracy, can be used off-axis, and has many photo-optical applications.

Editorial and Forum

Abstract: One of the good things that could come out of the hard times of the past few years is the coalescence of several of the smaller technical societies, to form larger groups that can more effectively serve the interests of related fields. Such associations can benefit a field in several ways.

Estimation and Measurement of the Frequency of Coarse Gratings by Moire Fringe Techniques

Abstract: Moire fringes are obtained when two gratings of about same frequency are superposed on each other. Normally the two gratings are of special geometrical curves. For the present particular application, one grating is assumed to be a grating of constant but unknown frequency. The other grating which is the measuring grating consists of different types of curves. The theory of the resulting pattern and how it is used to measure the frequency is presented.

A Selected Bibliography on Optical Spatial Filtering

Abstract: A bibliography has been compiled concerning optical spatial filtering The citations are listed chronologically and followed by an author index

Fabrication of Flexible Conforming Laps

Abstract: A method of fabricating flexible laps with predictable deflection behavior is described. Rates of deflection versus loading show a nominally linear deformation of 15X with 400-g loading for a 5-cm diam lap.

Image Intensifier Systems and their Applications to Astronomy

Abstract: The rapid and intensive development of the field of electro-optics over the last decade has resulted in the production of a wide range of sensitive, photoelectronic imaging devices for applications in astronomical research. It is five years since Livingston) reviewed the applications of image intensifiers to astronomy but since that time existing devices have been further developed and new devices have been introduced. A wide range of devices is currently in use-this review will describe those devices which have found a wide measure of acceptance amongst observational astronomers and will mention some recently developed devices which show considerable potential.