Abstract: This optical near-field scanning microscope comprises an "objective" (aperture) attached to the conventional vertical adjustment appliance and consisting of an optically transparent crystal having a metal coating with an aperture at its tip with a diameter of less than one wavelength of the light used for illuminating the object. Connected to the aperture-far end of the "objective" is a photodetector via an optical filter and an optical fiber glass cable. Scanning the object is done by appropriately moving the support along x/y-coordinates. The resolution obtainable with this microscope is about 10 times that of state-of-the-art microscopes.

Abstract: Single-mode fibre recirculating delay lines have been made on a single continuous loop of fibre with the use of fibre directional couplers. These devices have been demonstrated as bandpass filters and as notch filters at centre frequencies from 0.5 MHz to 1.3 GHz with a notch depth of over 45 dB.

Abstract: A portable laser system for remote detection of methane gas leaks and concentrations is disclosed. The system transmitter includes first and second lasers, tuned respectively to a wavelength coincident with a strong absorption line of methane and a reference wavelength which is weakly absorbed by methane gas. The lasers are aimed at a topographical target along a system axis and the beams successively interrupted by a chopper wheel. The system receiver includes a spherical mirror for collecting the reflected laser radiation and focusing the collected radiation through a narrowband optical filter onto an optial detector. The filter is tuned to the wavelength of the two lasers, and rejects background noise to substantially improve the signal-to-noise ratio of the detector. The output of the optical detector is processed by a lock-in detector synchronized to the chopper, and which measures the difference between the first wavelength signal and the reference wavelength signal.

Abstract: In optical multiplexers and demultiplexers which utilize interference filters and optical gratings losses and noise are reduced by converting the unpolarized light into linearly polarized light. This improves the efficiency of the filters and gratings and suppresses noise which is caused by fluctuations in the degree of polarization of unpolarized light because filters and gratings have different characteristics for the different polarization directions.

Abstract: An automated acousto-optic tunable filter infrared analyzer system useable in a variety of industrial and commercial control applications. The system relies upon a narrow band pass tunable acousto-optic filter which is selectively tuned by predetermined rf frequency signals to selectively transmit the narrow band pass of interest which corresponds to a specific molecular species for identification and analysis. The system includes a microcomputer and associated memory function to measure and compare detected signals from an infrared detector which converts the filtered infrared signal to an electrical signal. The memory provides control signals for the computer and for controlling the sequence and frequency of rf energy applied to tune the filter. In this way, the near to mid range infrared can be analyzed for absorption bands corresponding to predetermined molecular species such as combustion product gases, and a feedback signal generated to control the combustion process.

Abstract: The experimental development of an infrared multiple-cavity electrooptically tuned Fabry-Perot filter using LiNbO3 is described. This filter, designed for operation in the 3–5-μm spectral band, was demonstrated by angle scanning using a He–Ne laser at 3.39 μm. The multiple-cavity configuration increased the free-spectral range of the 2-A bandwidth filter from 67 to 670 A as observed in the increased angular spacing of transmission peaks. Because of the large halfwave voltage of LiNbO3 at these wavelengths, tuning was restricted to ~15% of the free-spectral range.

Abstract: A technique is presented for fabricating large numbers of evanescently coupled taps on a single-mode fibre. An output fibre can be adjusted between any of the taps, resulting in a discretely variable delay. The concept was demonstrated with a 7 tap device which had a 2.5 ns delay between taps and a tap uniformity of ± 1.6 dB. A technique for making continuously variable delay lines is presented.

Abstract: A fiber-optical measuring apparatus for measuring magnetic fields, current, position, and various mechanical quantities consists of a transducer connected to a measuring electronic unit via at least one optical fiber, and the transducer comprises a magneto-optical modulator with a domain-producing magnetic material. The transducer is provided with at least two optical filters, of which at least one filter is positioned in the ray path on one side of the magneto-optical modulator and at least one other filter is positioned in the ray path on the opposite side of the modulator.

Abstract: In order to produce individualized compensating filters for use with high energy x rays, a study was undertaken to study lead as a filter material using 10-MV x rays. As was expected, it was found that lead filters could be constructed for 10-MV x rays by extending concepts developed for cobalt-60 gamma rays. A quantity called the "effective attenuation coefficient" (mueff) was determined for a range of field sizes, initial depths in water, and lead thicknesses and for 100-cm SSD and 150-cm SSD treatment techniques. Slight variations of mueff with field area and filter thickness were discernable. However, a single value of this parameter could reproduce the original depth of missing tissue data with an rms error of 2 mm. Tests were then performed on filters whose shapes were calculated using the effective attenuation coefficient. Compensating filters restored the flatness of 10-MV x-ray beams to better than 5%, which was better than comparable filters using cobalt-60 gamma rays. The technique is presented as generally reliable for constructing compensating filters for use with high energy linear accelerators.

Abstract: Recirculating delay lines have been made using loops of single mode fiber that are closed, without splices, using one or more single mode fiber directional couplers. The use of an all single mode fiber system allows the accurate storage of high frequency analog or digital signals for long delay periods. Such devices can be used as wideband transient or buffer memories. Recirculating fiber loops are also useful as transversal filters that can exhibit uniform notch and bandpass filter characteristics over a wide range of frequencies from 1 MHz to 1.3 GHz.© (1982) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Abstract: Fiber-optical sensor for detecting electric arc-discharges. An optical waveguide serves to detect electric arc-discharges in an enclosed space, this waveguide being designed, in its detecting or active zone, as a heavily curved spiral. Testing light is fed in at the beginning of the optical waveguide, from a source of testing light. An optical filter, matched to the testing light, is located at the exit from the optical waveguide, this filter directing the light, resulting from a fault, and coming from the arc, up to a first photo-receiver. Sound waves, which are likewise emitted from the arc-discharge, modulate the testing light in the interior ofthe spiral. The modulated testing light passes to a second photoreceiver. The changes in the luminous intensity at the two photoreceivers are recorded in an electronic evaluator, and the time-difference is determined.

Abstract: A family of optical methods are developed for the measurement of slope and curvature of flexed plate surfaces. Slope and curvature contour fringes are generated by using gratings as filters in the light path emerging from the flexed surface. General field equations are derived for gratings placed anywhere in the field. Depending upon the pitch and the position and the number of gratings used, a variety of techniques are obtained for the contouring of slopes or curvatures. When a low density grating is used, the resulting shadowgram yields slope contour fringes if it is placed at the real focal plane of the field lens. Otherwise, the shadow gram fringes are not slope contours. However, slope contours can be obtained if a double-exposure technique or a double grating is used to generate the moire fringes. If a grating of sufficiently high frequency is used, the resulting pattern is a curvature pattern, for which a monochromatic light source is needed. A successive plotting method is also proposed for curvature contouring whereby white light and a grating of arbi-trary pitch can be used. The methods are verified by a series of experiments using cantilever beams and clamped circular plates. Applications to a variety of other problems, including flexure wave propagation, are also demonstrated.

Abstract: Computer modeling studies indicate that planar dielectric waveguides clad with silicon exhibit a damped periodic oscillation in their attenuation and phase characteristics. The effect is due to a periodic coupling between the lossy, guided modes in the silicon film and the TE 0 mode of the dielectric waveguide. Experimental confirmation of the periodic coupling for a wavelength of 632.8 nm is presented. Propagation characteristics for a wavelength of 1150 nm were investigated for application in integrated optical modulators. Frequency filtering properties of silicon-clad waveguides are also examined and it is shown that the silicon thickness controls the filter response curve.

Abstract: An improved soft focus optical filter is provided and comprises a plurality of effective filter areas on a transparent substrate. The filter areas are designed specifically to modify the modulation transfer function of the filter so that a selective soft focus effect is achieved only for transmitted green light.

Abstract: A hardware median filter is described which is designed to filter imagery at a real-time rate of 10X106 pixels/second. The data is windowed with line buffers, and propagates through n pipe lined stages where n is the number of bits in a pixel. The algorithm described is a form of the radix method of Atamanl modified to reduce the decisionmaking at each stage. Each stage is nearly identical thus making the filter very structured and modular. The filter can be implemented with available logic components and would be useful as a preprocessor in a pattern recognition system.© (1982) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Abstract: The absorptivity of soot and methylene blue particles collected on Teflon filters is derived from photoacoustic measurements by least squares fitting a simple expression based on Beer’s law to the experimental data. Refinements of the expression take into account the diffuse reflection of light by the filter substrate, yielding a base 10 absorptivity at 600 nm for soot of 3.00 ± 0.37 m2/g. This value is in close agreement with the result of transmission measurements performed on the same samples (3.08 ± 0.05 m2/g).

Abstract: An optical power supply switching apparatus by which a battery power can be connected to or disconnected from at least one electric appliance provided for an automotive vehicle without generating electromagnetic noise or electromagnetic interference between the electric appliance and other audio equipment. The optical power supply switching apparatus according to the present invention comprises at least one light-emitting element, one optical fiber, at least one photoelectric transducer, at least one semiconductor contactless switching element, and a plurality of optical directional-couplers and optical filters where necessary, in addition to a special low-impedance coaxial power distribution line.

Abstract: In a chemical analyzing apparatus of a colorimetric type in which a light flux transmitted through a test liquid is made incident upon a light receiving element through an optical filter having a predetermined transmission spectrum range and a measurement signal is obtained by processing a photoelectrically converted signal, a plurality of optical filters having different transmission spectrum ranges and arranged side by side and a solid state image sensor having a plurality of light receiving elements each having a photoelectric converting element and a static induction transistor are arranged one upon the other. An analytical result is obtained by calculating output signals selectively derived from light receiving elements which are arranged behind a particular optical filter having a transmission spectrum range related to a wavelength determined by a test item to be studied. Since use is made of a static induction transistor, it is not necessary to change the optical filters mechanically and is possible to read out the necessary output signals having high S/N selectively in a prompt manner, while the levels of output signals can be monitored.

Abstract: In a system of real-time coherent optical filtering of visual imagery having a Fabry-Perot interferometer for use as a variable bandpass spatial filter, the improvement of having the pair of mirrors of the interferometer mounted in spaced parallel relationship to one another for rotation about a common axis. The mirrors each have a reflectivity value which changes as a function of rotation. Thus, the bandwidth of the interferometer in acting as a filter can be adjusted by merely rotating one or both of the mirrors.

Abstract: Considerable interest has been shown in recent years in electronic systems of photography which use no film. In 1972, for instance, Texas Instruments filed a patent for an electronic camera(1) and in 1980 Polaroid introduced their concept of an instant electronic camera.(2)

Abstract: The horizon sensor is intended to monitor the attitude of spacecraft and capable of locating the Earth-space discontinuity using photosensitive elements 1 - 8 operating in the visible band of the spectrum. The photosensitive elements are charge transfer devices (CTDs) which are combined with an optical focusing system. The latter consists of at least one lens 11 for focusing the radiation on to the sensitive surfaces of the CTDs and an optical filter 12 placed before the lens in order to limit the radiation received by the optical system to the visible band of the spectrum (0.4 - 0.9 mu m).

Abstract: An optical filter is formed by exposing a photosensitive material to directnd retroreflected coherent optical radiation. These radiations set up standing waves in the material such that, when the material is fixed, variations in parallel, equally spaced layers of some optical property of the material remain. The optical property may be reflectance, index of refraction, or optical density. The layers are spaced apart one-half wavelength of the coherent radiation and act as an interference filter. The material may be capable of being erased and a new filter formed, if desired.

Abstract: Method and apparatus for conversion of digital multistate signals, represing a numerical value, to an optical output signal having an amplitude analogous to the numerical value. A controllable density optical transmission device provides plural optical signals representative of the digital states of components of the input signal. The plural optical signals are weighted and summed by optical filters to provide the desired analogous optical output representing the input numerical value. The use of phase shifting filters enables the conversion of negative and complex numbers. A two dimensional liquid crystal array may be used as the controllable optical transmission device to enable conversion of a plurality of numerical values simultaneously.

Abstract: PURPOSE:To obtain a small-sized and light-weight Doppler speedometer capable of real-time detection, by irradiating the light of a light source from two differenct positions through optical fibers and detecting the Doppler-shifted reflected light from an object. CONSTITUTION:Laser beams from both ends of a laser light source 17 of a light source 7 are transmitted to lenses 9 and 9 of a supporting member 15, which forms a head, through optical fibers 10 and 10, and a material 16 moving in a speed V is irradiated with laser beams from two different positions of incident angles theta1 and theta2. The reflected scattered light from the material 16 which is Doppler-shifted in accordance with the speed V is received by a photodetector through an optical filter 12 and a lens 11 of the member 15. Thus, oscillation components DELTAf of the frequency based on expressionIappears in a detector 8, and the movement speed of the material 16 is measured by a processing part 13 provided with an HPF 23 for eliminating DC components, an amplifier 24, a frequency counter or frequency-voltage converter 25, etc., and a small-sized and light-weight laser Doppler speedometer which is separated from the light source or the like and makes the real-time measurement possible is obtained. In expression, lambda is a laser beam wavelength.

Abstract: PURPOSE:To make it possible to perform external inspection under the illumination for dark field of view and automatic focal point adjustment simultaneously, by performing the external inspection and the automatic focal point adjustment by light beams having different wavelengths. CONSTITUTION:A first optical system projects a focal point detecting pattern 2 on a wafer 5 which is a material to be measured through a lens 4. A second optical system forms the image of the reflected pattern from the material to be measured 5 on a contrast detector 7' through a lens 4 and optical filters 3 and 13. A third optical system irradiates the light, whose wavelength is different from the wavelength region passing the optical filters 3 and 13, to the material to be measured 5 from the slant direction. The light for illuminating the dark field of view, which is generated by the third optical system comprising a light source 10 and parabolic concave mirrors 11 and 12, is stopped by the optical filters so as not to influence the contrast detector 7'. In this constitution, the external inspection and automatic focal point adjustment are simultaneously performed by the light beams having the different wavelengths.