Abstract: A tunable permanently fixed diffraction grating is interposed in the path of an optical beam propagated in an integrated-optics device. Tuning is accomplished, for example, by establishing a variable electric field in the propagating medium to control its refractive index. In that way the effective grating spacing is changed. As a result tunable optical filters and intensity modulators are thereby realized.

Abstract: Optical filter combination removes two selected bands of light in order to improve the observed color discrimination between different colored objects. One of the filtered bands includes radiations of a wavelength of 580 nm and the other of the filtered bands includes radiations of a wavelength of 490 nm. Each of the filtered bands is preferably from 5 nm to 55 nm wide although the bands can be widened to 80 nm if desired.

Abstract: Optical filters are prepared from transparent glasses by the formation of multilayer streams of molten glass. The optical filter is formed by flowing molten first and second glass compositions substreams and interdigitating the substreams into a composite stream on a bath and shaping the composite stream that the interfaces of the substreams are parallel to the major surface of the composite stream. By choice of layer thickness reflection can be obtained in infrared, visible ultraviolet range.

Abstract: An optical filter element is provided which comprises a plastic resin containing a particulate dispersion of filter glass. In one preferred embodiment, the photocell of a photometric device, e.g., the automatic exposure control system of a photographic camera, is embedded in the glass-filled resinous element to provide necessary spectral correction filtration for the photocell.

Abstract: Periodic structures are used widely in integrated optics for input-output couplers, bandstop filters, modulators, directional couplers, and distributed feedback lasers. An analytical discussion and review of these devices is given based upon the coupled-mode transmission-line analysis. Experimental results and performance characteristics are presented to illustrate the special features of each type of device. Finally, the usefulness of transmission-line analysis to the understanding and the design of these devices is pointed out.

Abstract: The photoluminescence of color filter glasses (as typified by the complete Corning filter glass set) is characterized. Emission, excitation spectra, and decay times are determined, and quantum yield is estimated. For many of the filters, the quantum yield and range of excitation are such that fluorescence can be a (perhaps unrecognized) problem when these filters are used in a long-bandpass mode. Furthermore, interference filters are often not free from filter fluorescence because fluorescent glasses are commonly used as a substrate or as protection for the dielectric layers.

Abstract: We report on a new method for increasing the linear dynamic range of coherent-optical spatial filters, with special reference to holographic image-deblurring filters. In the filter-generating step, a transmission grating is placed in contact with the transparency representing the spread function of the blur. The spectrum of the spread function then appears in a series of equally spaced islands of different intensities, each occupying a different region of the nonlinear characteristic of the recording medium. Each spatial frequency can then be properly exposed somewhere on the filter, even with a film of limited dynamic range. In the image -processing step, the grating is superposed on the blurred image, the spectrum of which then falls on all the islands of the filter. In this way, the filtering operation is done in parallel channels, each with a different nonlinear characteristic. The channels are combined in the output plane by superposing a grating on the filtered aerial image and viewing this plane through an optical system that does not resolve the grating. Theory, computer simulations, and experimental results are presented. The results show in particular that a good transfer function can be achieved with a hologram-only filter.

Abstract: Optical filters comprised of a plastic film having incorporated therein a mixture of dyes including the compound 1,4,5,8tetracyclohexylaminoanthraquinone are substantially opaque to visible radiation but permit high transmission of wavelengths in the near infrared region.

Abstract: Optical transmission properties are described for two types of waveguides formed in AlxGa1−xAs–GaAs–Alx Ga1−xAs epitaxial layers. The first consists of long smooth‐walled mesas formed by a masking and etching procedure and the second are obtained using an additional etching step to selectively etch the GaAs layer. The latter structure is potentially useful in forming active devices such as modulators since this structure is self‐masking for contacting of the top layer by conventional evaporation techniques. The waveguide dimensions are typically 1–30 μm wide, [sine wave] 1 μm thick, and several mm in length. The transmission measurements are quite similar for both types of guides with attenuation as low as [inverted lazy s]2 cm−1 in wide ([inverted lazy s]20 μm) guides but with losses increasing with decreasing width. The loss appears to arise from imperfections and compositional inhomogeneities in the epitaxial layers.

Abstract: A color cathode ray tube screen structure, having means for enhancing the absorption of ambient light and providing improvement in the contrast of the image display, is comprised of a basic multi-windowed webbing of substantially opaque material having optical filter elements disposed in the window areas thereof. A process is provided for fabricating patterns of these diversely-hued filters whereof a coating of heat formable optical filter material is applied and transformed by heat. Light exposure through an apertured pattern mask polymerizes like areas of two superposed layers of diverse negative photo-resist materials separately applied thereover to provide protective means for defining the filter element areas and expediting discrete removal of the extraneous filter materials. The process provides for the deposition of one or more patterns of filter elements, such being related to the respective window patterns of the web-like structure and compatibly associated with specific color-emitting phosphor components of the patterned screen.

Abstract: The effects of absorption on the theoretical accuracy of the turning value method of film thickness monitoring in the production of thin-film all-dielectric narrow band optical filters are investigated. It is shown that the performance of the method is at least as good as it is in the absence of absorption, although care must be taken in the interpretation of the monitoring signals for certain critical layers.

Abstract: The techniques considered make it possible to construct high performance low-pass wide-band, and medium-band filters at wavelengths in the range from 25 to 300 micrometers. Short wavelength rejection without appreciable loss at long wavelengths is achieved by means of small particle scattering. Spectral definition in the far infrared is obtained by cooling one or more crystalline materials to liquid-He or liquid-nitrogen temperatures. The problem of reflection losses at the various surfaces is solved by a new antireflection coating technique.

Abstract: In satellite-to-helicopter communications, interference exists on the incoming signal when the receiving antenna is located below the rotor blades. A bound is established for the performance of a coherent fixed-tone ranging system operating at L band in this interference environment. The scalar diffracted field beneath the rotating blades, at L band and above, is found to satisfy the criterion of Fresnel diffraction, and is computed using the techniques of Fourier optics. The diffracted field is expressed in terms of a narrow-band signal. The amplitude and phase components are calculated from a Fourier Series expansion using the FFT algorithm. The significant harmonics of the phase component of the interference combine with the baseband of the narrow-band, phase-modulated ranging signal. This results in CW interference, and in rearrangement of the first-order, sideband, ranging-tone channel powers. The degradation in ranging accuracy is evaluated by computing the signal-to-interference (SIR) ratio for a set of ranging tones. The post-detection (SIR)PD at the output of the correlator is shown to be a function of the amplitude of the phase harmonics of the interference, the relative difference between the ranging tone and interference center frequencies (a function of rotor speed), the rangetone modulation indices, and the post-detection filter noise bandwidth.

Abstract: This invention relates to an optical detection of ballistics device using satellites emitting beams of neutral molecules in a specified direction. Intense optical radiation will be reflected off insulated surfaces of nose cones and detected by narrow band optical filters on the satellite.

Abstract: The optimum design of synthetic aperture radar (SAR) systems intended to classify randomly reflecting areas, such as agricultural fields, characterized by a reflectivity density spectral density is studied. Assuming areas of known shape and location, the binary case, and a certain Gaussian signal field property, and ignoring interfield interference, the problem solution is given. The optimum processor includes conventional matched filter processing, but is nonlinear; a coherent optical system realization is outlined. The performance is approximated using a x2 assumption and bounded by the Cernov bound. A fundamental design problem involves the system bandwidth analogously, in a special case, as in diversity communication systems; a solution is given based on the Cernov bound. A set of summary design curves is given and exemplified by a satellite SAR system design. Also discussed is the measurement of reflectivity spectral density amplitude with imaging sidelooking (synthetic or ?brute-force?) radars and the maximum likelihood estimator's accuracy and realization with a coherent optical system. It is also shown that a CW modulation is useable if the random reflectivity is, effectively, isotropic. Finally, the reflectivity density spectral density amplitude, when constant over the spatial bandpass of the measuring system, is related to the scattering cross-section density commonly measured.

Abstract: A color cathode ray tube screen structure, having means for enhancing the absorption of ambient light and providing improvement in the contrast of the image display, is comprised of three superimposed substantially continuous window-defining layers of optical filter materials. The primary, secondary and tertiary filter layers have discretely disposed window areas formed therein to expose a pattern of filter areas representing the respective filter materials. The filter windows are of a shaping similar to that of the apertures in a spatially related pattern mask member. Each window exhibits a uniform periphery free of indentations, being so defined by a uniform opaque interstitial encompassment homogeneously made up of the three distinct layers of filter materials. Disposed over the filter windows is a patterned screen of cathodoluminescent phosphor elements, which upon electron excitation produces color-emissions that are colormetrically related to the respective filter windows therebeneath.

Abstract: The influence of additional filters upon the output of an optical correlator is studied for the case of a spatial filter measuring the size of rectangles. Addtional filters leading to increased sensitivity are derived by means of a series expansion. One type of additional filter, consisting of several transparent slits, yields a linear relation between output signal and the deviation from the desired size. The other additional filter, effecting a quadratic output characteristic, is a properly dimensioned bandpass. Experimental results demonstrate the enhancement of sensitivity achieved with additional filters. As this method can easily be extended to a correlator measuring the diameter of circular apertures, additional filters may be of interest in the field of automatic production control.

Abstract: Designing microwave bandpass filters attenuation poles at finite frequencies as well as group delay requirements can be achieved by providing additional couplings between non-adjacent resonators. The paper deals with the synthesis procedure, a possible way of realization using TEM-resonators and measurement results of narrowband linear phase filters in the 1 GHz range with and without attenuation poles at finite frequencies.

Abstract: A device for achieving optical mixing in optical waveguides which is not dependent upon a precise and uniform waveguide thickness. This result is accomplished by using an almost symmetric waveguide geometry, narrow waveguide widths and the lowest order TE or TM modes. Such systems are used for harmonic generation, parametric oscillation, and upconversion of radiation.

Abstract: Analysis of signal characteristics observed in the receiving plane of an optical beam has yielded information about the turbulence characteristics and cross winds over the propagation path. The measurements are generally made over relatively short paths, near the ground, with a laser at one end and one or more detectors situated at the opposite end of the propagation path. In some cases it may be desirable to have the laser and detectors at the same location. This can be accomplished by use of a reflector at the far end of the path to direct the transmitted energy back to the detectors. In a previous publication, the characteristics were developed for the optical filter function appropriate to a high-frequency plane wave propagating over a folded path. The purpose of this communication is to extend the previous analysis to the case of a spherical wave propagating over a folded path. In particular, an expression is developed showing the dependence of the observed amplitude covariance on the spectral density of the turbulence and the path geometry.

Abstract: Optical viewing systems have been well designed for specific applications. However, partial coherence evaluation of the optical viewer illustrates potential for control of the frequency response to phase and amplitude components of the photographic image (where the phase component is due to the emulsion relief image). The complex image formed by the partially coherent system contains a separable response to the phase and amplitude components for a low contrast object. Optical frequency response control is applied to the complex image by design of a variable source size condensing system and by inserting an attenuation filter in the pupil of the imaging lens. Illustrations are given to show the adaptability of the system response to low contrast images.

Abstract: The optical control of thin films by the « static ratio » method avoids the necessity of the operator having a knowledge of the « machine's sensitivity ». This method is applied to controlling the deposition of films of optical thickness H=λ1/4 an B=λ2/4 in the visible, for the fabrication of optical filters for the near infrarouge and near ultraviolet. We show by approximate calculation that the controlling radiations used converge to a limiting value.

Abstract: Calculations were made to determine the effects which contrast elements of various thicknesses have in Lyot filters. A filter which is significantly narrower than the line at which it is looking produces the best results. Therefore, if the filter is broad the addition of as thick an element as possible is desired. However, if the filter is already narrow, a contrast element whose thickness equals that of the second Lyot element will produce the best performance.

Abstract: : Grating targets of different spatial frequency and with square and sine wave luminance distributions were presented to male subjects who wore ophthalmic filters that are frequently used by aviators, namely, neutral gray, yellow, and rose-colored. Threshold light modulation that permitted detection of the grating pattern was determined. Average luminance levels from bright to dim were used. Although contrast sensitivity was found to vary with luminance level, it has not been possible to demonstrate the clear-cut superiority of one colored sunglass filter over another in this experiment. The differences that are seen are related to the luminous transmittances of the filter and not to their intrinsic colorations. (Author)