Detection and/or filtering of optical scenes by analog techniques usually requires separate filters for amplitude and phase. The Vander Lugt (holographic) filter provides the phase correction and the same filter can provide some amplitude correction if the nonlinearity of the film processing is used judiciously. This study shows how the control parameters, namely, exposure time and reference beam-to-signal ratio, can be chosen to modify the amplitude of the effective filter. The distortion is characterized in terms of a transfer curve which maps the input filter into the effective filter. Some experimental results are presented to demonstrate the theory.
When an object being tested and its holographic image are 'superimposed for real time holographic interferometry studies a distorted fringe field is normally observed as a result of emulsion shrinkage on the hologram plate. A liquid gate is commonly employed to eliminate emulsion shrinkage effects. This paper describes an alternative technique for reducing these effects which requires only that the plate be overexposed and underdeveloped.
In this paper, we introduce a dynamic coherent optical system capable of yielding coherent images without the usual coherent artifacts such as noise and speckle. In addition, the dynamic coherent system will possess a bandwidth twice that of the corresponding coherent system. The system has been successfully applied to zoom stereoscope for viewing aerial images using illumination from an Argon Laser.
The application of Fraunhofer (far- field) holography to the study of particulates in environmental situations is described. The use of the technique is illustrated with single and multiple exposure holograms of particles of ground talc containing both tremolite and asbestos. Size, velocity and behavior of the particles as they fall through air is obtained. Future uses of this technology are outlined.
Color-encoded images can be recorded on black-and-white film through the use of synthetically generated diffraction gratings. This technique has applications in the display and interpretation of multispectral information generated by airborne or spaceborne line scan sensors and color scanners in facsimile systems. A color facsimile system based on this principle has been implemented using a white light color transparency scanner and a laser beam recorder. In system tests, good color recognition, 20-line pair/millimeter resolution, and 7, grey level steps have been achieved.
This paper discusses the measurement and correction of line spacing errors in laser recorders caused by residual fabrication tolerances in the face-axis angles of multi-faceted mechanical scanners. These residual angular errors are typically the chief source of line to line spacing errors in systems employing multi-faceted scanners. Apart from the fact that a periodic line structure produced in the film which is objectionable from an aesthetic viewpoint, the spacing errors decrease the MTF of systems having 10 micron line spacing, or less, which is becoming increasingly common in current equipment. A new application of a previously known art is used to correct angular errors in a multi-faceted scanner to an accuracy of 0.1 arc-second (1 part in 2,000,000). The correction technique appears to be limited only by the resolution of the measurement.
Integrated optical circuits formed from thin dielectric films on a substrate offer the potential for scanners and recorders which are free of the limitations in spinner dynamics or in electron focusing which, at present, curtail the applicability of contemporary scanners in future high bandwidth systems. The integrated optical circuits operate as optical waveguides and couplers. Transmission through one guide and coupling (transition) to the adjacent guide are each low loss processes. An integrated assembly can be made in which the guides and couplers are so located and so equipped with electrodes that an electrically controllable switching tree is formed. Such a tree is able to commutate among 2n output ports, where n is the number of logic levels. The scanning among the output ports of the tree is inertialess and has a rate determined by the frequency of the pumping of the last logic level. Lasser film recorders are seen as devices which will emerge early from integrated optics technology.
An instrument for performing film sensitometry with coherent sources is described. The instrument utilizes the diffraction properties of a periodic structure to generate an array of images at various energy levels. Relative measurements depend only on the properties of the optical system and are therefore very repeatable. Results are presented for exposures on 3404 film with a pulsed ruby laser.
In previous papers" we have shown that phase aberrations due to both simulated and excised human cataracts can be removed by utilizing holographic techniques. All of the experiments reported to date have utilized holograms made in the transmission mode. In order for the technology to be useful in a clinical environment it will be necessary to form the hologram in vivo. With this application in mind we extended the previous work" to the reflection mode for both the object derived reference beam and the image holographic systems. In this letter we describe the results obtained with these reflection experiments.
In the last editorial, I brought to your attention some new and expanded policies of the editorial staff of Optical .Engineering. At that time, we expressed the desire that future issues of the Journal would include specials featuring optical engineering at various major industrial and private institutions. The May-June 1973 issue will include in addition to other papers, a special section of five papers describing "Optical Engineering at the National Bureau of Standards". In addition, we are in the process of soliciting papers for a special feature dealing with microdensitometric techniques and their applications, and we hope to bring this to fruition in a later issue this year. Our readers can look forward to future specials such as Optical Engineering at Avco-Everett, Optical Testing and Fabrication, Environmental Optics, Optical Engineering at the Retina Foundation, and Electro-O ptics.