Abstract: A magneto-optic optical disc system which uses the magneto-optic differential data detection channel, with addition only a low pass filter, to also detect focus error. The differential data detection channel includes a pair of photodetectors, the first photodetector being located a predetermined distance within the focal length of the detector lens associated with that photodetector and the second photodetector being located beyond the focal length of the detector lens associated with that photodetector. The output of a differential amplifier receiving the photodetector outputs is the data signal and the output of a low pass filter connected to the output of the differential amplifier is the focus error signal. The dual functionality of the differential data detection channel eliminates a separate optical focus channel, and relative to separate astigmatic focus and data detection channels elmininates a quadrature detector, several optical elements, several electrical elements, and the space they occupy.

Abstract: A process for measuring the temperature of a body by optical detection is disclosed wherein the body is heated by a modulated light beam and the radiation coming from the object is detected. The modulated component of the detected signal is measured and the temperature of the body is extracted by signal processing.

Abstract: A method for determining parameters, especially pressure, temperature, concentration, number of particles and particle size distribution, of gaseous substances present in combustion processes and other high temperature processes, comprises transmitting spectrally broad-band light through an object (2) of measurement, spectrally dividing the light transmitted through said object, and recording the spectral distribution of the light in the studied wavelength range a large number of times. Each recording occurs sequentially in that the spectrally divided light is swept relative to a one-channel detector and for such a short time that the total light intensity of the entire wavelength range is constant during each recording.

Abstract: A system for tracking a randomly moving object using a laser beam and first and second beam steering assemblies. The steering assemblies pivot, respectively, about substantially perpendicular and intersecting X and Y axes and direct the laser beam along an R axis, which is perpendicular to the X axis and intersects the X and Y axes. Along the R axis, the laser beam is intercepted by a retroreflector, which is coupled to the moving object and which returns the laser beam to a quadrant detector via the steering assemblies. The quadrant detector generates an error signal representative of the object's movement relative to the X and Y axes, and this signal is transmitted to two motors which pivot the steering assemblies about the X and Y axes to reduce the error to zero. The system includes an interferometer to determine the distance of the object from a reference location. The first beam steering assembly includes two prisms which redirect the laser beam through three 90.degree.

Abstract: A high optical efficiency dual spectra pyrometer for measuring the temperature of a target includes an optical guide for collecting and guiding a target optical beam to a detection module which comprises an interference filter and photodetectors adjustably positioned to provide efficient coupling of the target optical beam thereto. The pyrometer additionally includes a signal processor which receives the signals from the photodetectors, as well as signals indicative of an estimated fireball equivalent black body temperature and the spectral width difference between the two detector signals, and provides a compensated temperature signal.

Abstract: The invention is a temperature sensor which uses the variation in the critical angle between two optically transparent media, at least one of which has an index of refraction variable as a function of temperature, to variably refract and reflect portions of a spectrum incident on the junction of the media at angles less than and greater than the critical angle to produce an optical signal variable as a function of temperature.

Abstract: A radiation thermometer comprises two radiation detectors for detecting radiation in wavelength bands centered on two different wavelengths .lambda..sub.1,.lambda..sub.2 (where .lambda..sub.1 >.lambda..sub.2) from a rotating body such as a gas turbine motor and for generating first and second signals S.sub.1,<S.sub.2 >respectively related to the radiance profile around said body and the average radiance around said body. A time averaging circuit generates a signal <S.sub.1 >representing an average value of said first signal. A dividing circuit generates a signal related to the ratio of <S.sub.1 >to <S.sub.2 >; and a monitor monitors at least one of said signals, predetermined arithmetic combinations of said signals, and quantities related thereto and provides corresponding output signals.

Abstract: A temperature detection pyrometer for determining the temperature of a turbine blade detects radiation reflected and emitted from the turbine blade. The reflected radiation is a result of flame and hot carbon particles rather than the emission representing the blade temperature. The radiation is divided into two channels, each of which detects radiation in different, but preferrably overlapping wavelength bands, to detectors providing currents proportional to the radiation intensity in the respective channel. The signal from one channel is weighted with respect to the signal from the other by a constant that is equal to the ratio of the radiation in the two channels which is the attributable to the reflected radiation. The difference between the signals, after weighting the one signal by the constant provides an output that is a function of blade temperature only so the blade temperature may be obtained from a calibration curve or a look-up table.

Abstract: Method and apparatus for measuring a distance to an object includes directing first and second laser beams having frequencies .omega..sub.11 and .omega..sub.12 toward the object. A first reference signal is derived having a beat frequency .omega..sub.1 =.omega..sub.11 -.omega..sub.12. A first reflected light beam reflected from the object is detected and has the beat frequency .omega..sub.1 and a first phase difference with respect to the first reference signal. The first phase difference is then extracted from the first reference signal and the first reflected light beam and a first plurality of distance nodes is calculated from the first phase difference. Then, the frequency of the second laser beam is changed to .omega..sub.13. A second reference signal having a beat frequency of .omega..sub.2 =.omega..sub.11 -.omega..sub.13 is then derived. A second reflected light beam reflected from the target is detected and has the beat frequency of .omega..sub.

Abstract: Apparatus and method is disclosed for determining position with light by providing input light at an input light port of an optical cavity having a variable length dimension and detecting light which has traversed the variable length dimension at an output light port of the optical cavity and determining the present length of the variable length dimension using the detected light as a measure.

Abstract: A method and an apparatus for determining distance by the use of laser beam is disclosed. An optical measuring system which derives a measuring beat wave in a known manner is combined with an optical reference system which derives a reference beat wave for allowing the distance to be determined to a higher precision. An optical measuring system causes laser beam to be reflected from an object being determined and also causes the laser beam to be reflected from a standard reflector which is spaced by a given distance. The both reflected beams are superimposed upon each other to produce a measuring beat wave. The optical reference system causes the laser beam to be refected from a first and a second reference reflector, which are spaced by given distances, to provide reflected beams, which are superimposed upon each other to produce a reference beat wave.

Abstract: A laser interferometer wherein a laser beam emitted from a laser device at a fixed position impinges on an optical lens mounted on a movable member, and interference fringes are produced on a semitransparent mirror formed at an end of the optical lens opposite to the laser device. The interference fringes on the semitransparent mirror are converted to electrical signals by a photoelectric transducer including a bundle of optical fibers arranged along concentric circles and photodiodes located opposed to the end surface of the bundle of optical fibers. Based on the electrical signals from the photoelectric transducer, the number of the interference fringes passing by and the direction of movement of the interference fringes are detected to determine a relative distance between the laser device and the optical lens.

Abstract: A light beam is projected on a reference plane and an object to-be-measured, a phase difference between reflected lights from them is changed by a phase shifter, a drive voltage for causing the change of the phase difference is applied to the phase shifter, a magnitude of phase shift of the phase of the reflected lights is detected by a phase shift detector on the basis of the drive voltage at a point of time at which the change of the phase difference of the reflected lights has been compensated, and an up pulse or down pulse is generated by an up-down pulse generator upon detecting a discontinuous change in the magnitude of phase shift attributed to the displacement of the object to-be-measured, while a pulse is generated by another pulse generator upon sensing a change in brightness of an interference signal of the reflected lights attributed to the displacement of the object to-be-measured.

Abstract: A method and apparatus for calculating the equivalent blackbody color temperature of incandescent lamps. A lamp analyzer having photosensors which detect the red and blue components of lamp radiation and convert the components to analog currents. The currents pass through a multiplex system and are converted into a signal with voltages proportional to the photosensor currents. A signal conditioner circuit removes switching transients, damped oscillations and cell noise from the circuit, and an automatic gain controller system insures linearity in the signal. The ratio of the blue component of the signal to the red component is then determined by a ratio computer, producing an output which is linearized and scaled by a translator to display the corresponding color temperature of the lamp in Kelvins.

Abstract: A super resolution imaging system employing coherent radiation comprises transmitting, receiving and processing means to provide complex amplitude image data. The image data is processed by a weight function generator to provide a weight function. The weight function has values at individual image pixels consisting of a background or clutter intensity term added to a pixel intensity dependent term. The latter term is non-zero for pixel intensities exceeding a threshold level well above background. A computer generates singular functions from the weight function and system impulse response, and employs the singular functions to decompose the image data and subsequent object reconstruction. This provides enhanced resolution compared to that available from the image data alone. An iteration controller employs the reconstructed object data to iterate resolution enhancement until no significant improvement is obtained.

Abstract: A tracking system for measuring at least the spatial coordinates of a target and possibly the angular orientation of the target. A collimated beam is directed to the target and a mirror attached to the target reflects this beam back to a tracking point. Photosensors attached to the tracking or target point provide error signals to a servo system which controls optics at the tracking or target points to provide the direction necessary to accomplish the coincidence of the beams. An interferometer interferes the source beam with the beam that has travelled twice between the tracking and target points in order to measure the separation. By measuring the directions of the beams relative to structure attached to the tracking and target points, the target point can be located in spatial coordinates and additionally the orientation of the target structure can be determined.

Abstract: The temperature of a thermally emitting target which radiates over a band of wavelengths which includes first and second spaced wavelengths and which has an unknown emissivity characteristic at which the emissivity at one wavelength may but does not necessarily differ from the emissivity of another wavelength is read remotely by [a] deriving signals from those portions of the thermal radiation at these two wavelengths; [b] deriving signals from the reflected portions of two beams of radiation at these wavelengths which strike the target; and [c] by using these derived signals to compute the temperature.

Abstract: A reflection corrected radiosity optical pyrometer includes an optical guide for receiving a target optical beam from a turbine blade in a jet engine. The target optical beam is provided to a detector module that divides the target optical beam into two beams, one having a spectral width selected to be less than the target optical beam spectral width. A signal processor receives signals from the detector module indicative of the energy of the two beams, calculates a reflection corrected energy signal directly therefrom and provides a correct target temperature signal.

Abstract: A system for measuring angles, including a lens or antenna for focusing the radiation from an object scene onto an image sensor which is shifted by a clock, thereby producing the real time imaging of the object scene wherein each element of the object scene is detected as a pulse, representing the element angular displacement from the lens, at the output of the image sensor. A system for measuring angles of objects relative to the centerline of a lens or antenna. A goniometer for measuring the bearing of objects. A system for measuring the vector speed of objects. A velocity meter for measuring the speed of objects. A system for tracking objects. A system for motion compensation. A search, track or track-while-scan detection system. Without the lens or antenna, a system for recording and reproducing halograms.

Abstract: An interferometer having a beam generating section and a reflecting section. Mechanisms are provided to direct a beam from the generating section to the reflecting section even when the reflecting section moves freely in three dimensions. Mechanisms are also provided to direct the beam back from the reflecting section to the generating section even when the reflecting section moves freely in three dimensions. A method is presented that enables the absolute distance between the generating and reflecting sections to be determined.

Abstract: In a semiconductor color sensor circuit with two photodiodes having mutually different wavelength sensitivity characteristics, the ratio of numbers or areas of two types of transistors for logarithmic compression of signals from these photodiodes is adjusted so that errors in output voltage due to changes in temperature can be reduced and the dynamic range of illuminance of incident light can be enlarged.

Abstract: A novel dual spectra optical pyrometer is characterized by a serial array of photodetectors. The first photodetector absorbs a spectral portion of a target optical beam incident thereto, and passes the remainder optical beam to the second photodetector. Signals from both photodetectors are provided along with signals indicative of the first detector's spectral absorption and an estimate of the equivalent black body temperature of a fireball to a signal processor which provides a compensated temperature signal therefrom.

Abstract: Fiber optic probe apparatus usable for measuring temperatures with increased dynamic range and frequency domain response and desirable measurement accuracy. A black body signal source, fiber optic signal coupling, and extension of the transducer dynamic range with optical multiplexing are employed; the instrument operates in the range of 1.6 micrometers of optical energy wavelength and preferably employs recently improved indium gallium arsenide photodiode transducer devices and transducer frequency domain compensation. Use of the instrument in measuring combustion flame transient temperatures is disclosed.

Abstract: A method for determining range by correlating the relationship between the distance of a diffraction grating from a monochromatically illuminated target surface with the respective relative displacements of higher order diffraction images from the position of the zero order image as observed through the diffraction grating. An apparatus suggested for embodying the aforesaid method.

Abstract: A velocity interferometer has a continuously variable sensitivity and is particularly applicable to the study of the movement of reflecting polished surfaces or back-scattered rough surfaces. The interferometer is a Michelson interferometer with a widened field comprising in a per se known manner a light splitter and two light reflectors, one of which is associated with a medium having parallel faces. The medium is constituted by a fluid in which the associated reflector is immersed and displaceable in translation parallel to the path of the light falling on it, the other reflector also being displaceable in translation parallel to the path of the light falling thereon.

Abstract: A dual spectra optical pyrometer having an air pressure sensitive shutter for measuring the temperature of a turbine blade includes a sight tube located in the jet engine receiving an optical beam from the turbine blade. Located within the sight tube is a shutter responsive to the jet engine air pressure and providing the turbine blade optical beam only above a selected threshold magnitude of said air pressure. A detection module receives and divides the turbine blade optical beam and provides signals to a signal processor. From these signals and signals indicative of an estimated fireball equivalent black body temperature and the spectral width difference between the two detector signals, the signal processor provides a signal indicative of a compensated turbine blade temperature.

Abstract: A novel dual spectra optical pyrometer for use in in-flight control of jet engines includes an optical probe containing a shutter sensitive to the air pressure within the jet engine. The shutter provides an optical beam from rotating turbine blades to an optical fiber only above a threshold pressure. A serial array of photodetectors receives the optical beam and provides first and second signals therefrom. A signal processor receives the first and second signals as well as signals indicative of the energy ratio therebetween, and provides reflection corrected energy signals from the difference between the first signals and the product of the energy ratio signals and the second signals.

Abstract: The disclosed apparatus provides a point optical radiation source (i.e. point light source), at one or more distant points, the three-dimensional coordinates of which are to be measured relative to a known frame of reference. Each point light source emits light waves of a known wavelength which are received by the front plate of a multiple-beam interferometer means having a known angle of light acceptance. With respect to the light waves transmitted by each point light source and received by the interferometer means, a set of non-localized multiple-beam interference fringes are created within the interferometer means. A photo-electric detection means is provided a known distance from the back plate of the multiple-beam interferometer means and is positioned so that the interferometer means and photo-electric detection means have a common optical center axis.

Abstract: An apparatus for measuring bath temperature of metallurgical furnaces through a tuyere is disclosed. The apparatus comprises a periscope adapted to be inserted into a tuyere, a fiber optic cable having one end connected to the periscope for receiving radiation entering the tuyere from the bath of a furnace, and a two wavelength pyrometer connected to the other end of the fiber optic cable for analysing the radiations transmitted through the fiber optic cable to provide an indication of the temperature of the bath.

Abstract: An optical instrument (10), such as a stability monitor or a target range finder, uses an unstabilized laser (12) to project a composite optical signal of coherent light having two naturally occurring longitudinal mode components. A beamsplitter (24) divides the signal into a reference beam (26) which is directed toward one photodetector (28) and a transmitted beam (42) which illuminates and is reflected from a distant target (44) onto a second photodetector (52) optically isolated from the first photodetector. Both photodetectors are operated on the square law principle to provide electrical signals modulated at a frequency equal to the separation between the frequencies of the two longitudinal mode components of the optical signal projected by the laser (12).

Abstract: The brazing wand comprises a hollow helically wound electrically conductive tubular member for conducting an electrical current and for conducting a coolant therethrough. The electrical current is used to heat a member to be brazed while the coolant is used to control the temperature of the brazing wand. The brazing wand also comprises an optical sensing device for determining and controlling the brazing temperature.

Abstract: An optical video signal processor which produces a two-dimensional cross-correlation in real time of images received by a stereo camera system. The optical image of each camera (12, 14) is projected on respective liquid crystal light valves (28, 48). The images on the liquid crystal valves (28, 48) modulate light produced by an extended light source (32). This modulated light output becomes the two-dimensional cross-correlation when focused onto a video detector (42) and is a function of the range of a target (1) with respect to the stereo camera (10). Alternate embodiments utilize the two-dimensional cross-correlation to determine target movement and target identification.

Abstract: A passively Q-switched laser system uses a common Q-switch cell to control two lasers. The first laser to turn on Q-switches the other laser.

Abstract: A range imaging system in which a periodic pattern is projected onto the scene to be imaged. Three frames of intensity values are collected as the pattern shifts 120.degree.. The phase by which variations in range cause portions of the pattern to shift are determined from the three frames of data as being proportional to range. To generate the phase information, the intensity value for each pixel in the third frame is subtracted from intensity values of the same pixel of the first and second frames. The arc tangent of a function of these difference values represents the phase shift, and thus range.

Abstract: In a method of and apparatus for making remote measurements of temperature and pressure in a gas, laser beams are transmitted through the gas to a reflecting target, which may be either a solid surface or particulate matter in gas or the gas molecules and the return beams are measured to determine the amount of energy absorbed by the gas. For temperature measurements, the laser beam has a wavelength whereat the gas exhibits a relatively temperature sensitive and pressure insensitive absorption characteristic, whereas for pressure measurements, the laser beam has a wavelength whereat the gas has a relatively pressure sensitive and temperature insensitive absorption characteristic. To reduce the effects of scattering on the absorption measurements, a reference laser beam having a weak absorption characteristic is transmitted colinearly with the data beam having a strong absorption characteristic. The two signals are processed as a ratio to eliminate back scattering that is common to the two beams.

Abstract: The apparatus and method include adjusting two single frequency lasers to separate longitudinal modes of an interferometer, the plates of which are separated by a distance to be measured. A rough estimate of the distance is made using a tape measure or the like. The rough estimate, together with the frequency distance (.DELTA.F) of the lasers adjusted to the longitudinal modes of the interferometer is used to solve the equation: ##EQU1## where c is the speed of light and L.sub.1 is the rough estimate. The parameter k then calculated by rounding k.sub.

Abstract: A range imaging system in which a moving periodic pattern is projected onto the scene to be imaged. The phase by which variations in range cause portions of the pattern to shift are monitored to develop range data. A television camera offset from the axis of illumination generates four frames of intensity values. The moving pattern shifts one-quarter cycle with respect to the pattern between each of the frames. The data from the third frame is subtracted from the first frame and the data from the fourth frame is subtracted from the data of the second frame to cancel the effects of background illumination. The first difference represents a sine signal and the second difference represents a cosine signal. The arc tangent of the quotient of these values represents the phase, and thus the relative range of various points in the image. The moving pattern can be generated by either a translating plate or rotating disk which has a periodic variation in transmissiveness.

Abstract: The disclosed heterodyne measurement apparatus utilizes a single coherent light source to simultaneously measure the location of a number of points on a surface. The coherent light is split into two parts by a Bragg Cell. One part, after being spatially split into a plurality of beams by a second Bragg Cell, fed to a plurality of reflectors on the surface, and recombined by the second Bragg Cell, is heterodyned with the second part. The heterodyned signal is fed to a photodetector and further processed to produce a signal representative to the distance to the points of interest on the surface.

Abstract: A measuring arrangement is disclosed for measuring the contour of a two or three dimensional surface in which a redundant configuration of distance measuring systems is positioned above the surface being measured. Each distance measuring system monitors distance measurements to a point proximate the surface as the measuring point is moved across the surface. The distance measurements are taken from a sufficient number of points on the surface such that a sufficient quantity of data is obtained to define the system geometry and also to define the position of each measurement point. The data is transformed by recognized mathematical techniques into the coordinate positions of all of the measured points on the surface.In one embodiment for measuring the contour of a three dimensional surface, a tetrahedral arrangement of four distance measuring interferometers includes three interferometers positioned in a planar array above the measured surface and a fourth interferometer positioned at a central apex thereof.

Abstract: A beam director for an optical ranging system for measuring relative distance changes between first and second retroreflectors in which a beam of radiation is introduced between the first and second retroreflectors by a steering beam splitter pellicle positioned obliquely therebetween. A portion of the beam is reflected by the pellicle onto the first retroreflector, which reflects it back through the pellicle onto the second retroreflector, which in turn reflects it back onto the pellicle where it interferes with the radiation beam being initially introduced thereon. The pellicle is rotatable about two axes positioned substantially perpendicular to the radiation beam reflected between the first and second retroreflectors and steers the beam to compensate for relative movements of the retroreflectors. The arrangement is such that translation of the pellicle along any of three axes does affect the optical path difference between the retroreflectors.

Abstract: The present invention teaches a unique laser radiometer capable of accurately measuring the radiation temperature of a radiant surface and independently measuring the surface's emissivity. A narrow-band radiometer is combined with a laser reflectometer to measure concurrently radiance and emissivity of a remote, hot surface. Together, radiance and emissivity yield the true surface temperature of the remote target. A narrow receiver bandwidth is attained by one of two methods; (a) heterodyne detection or (b) optical filtering. A direct measurement of emissivity is used to adjust the value obtained for the thermal radiation signal to substantially enhance the accuracy of the temperature measurement for a given subject surface. The technique provides substantially high detection sensitivity over a very narrow spectral bandwidth.

Abstract: A laser range meter utilizing a mode locked laser for transmitting ultrashort pulses toward a target and a receiver for cross correlating the pulses returned from a target with corresponding reference pulses derived from the transmitted pulses is disclosed. Cross correlation is accomplished with a nonlinear element which responds to the return and reference pulses by producing secondary radiation of longer duration and of an intensity indicative of the time correlation of the pulses. The secondary radiation is sensed with a photodetector whose output signal is supplied to an output device.

Abstract: A temperature pattern distribution measuring method and apparatus by which portions of light from parts of an area of an object whose temperature distribution pattern is to be measured, and whose parts are in a predetermined pattern, are passed through first and second optical filters which respectively pass different wavelengths of light. The level of engery passed by the respective filters for the respective portions of light are determined by scanning the light from the filters with a pickup device or devices and, by using the determined energy levels, an arithmetic unit carries out a two-color temperature determining operation for the respective parts of the area for determining the temperature on each part of the area of the object. The temperature pattern of the area of the object can thereby be determined from the temperatures of the parts of the area.

Abstract: Methods and systems for measuring the temperature and spectral factors of a number of specimens (or radiators). The radiant flux from the specimens are spectrally analyzed with respect to effective wavelengths from M different channels (M being greater than or equal to 3). A relation among the spectral radiant flux intensity, approximated spectral factor (depending only on wavelength) and the temperature is determined for each channel by using Planck's radiation law with the condition that a relation N+K=M is kept among M of the number of channels, N of the number of specimens with unknown temperature values and K of the number of unknown terms of the approximated spectral factor of the specimens. Strict algebraic development of such relation is employed to cancel out all of the unknown terms of the spectral factor to obtain a one-dimensional equation concerning the sole temperature.

Abstract: A combustion technique and control is provided by the use of an optical pyrometer by means of which combustion control is afforded in accordance with the inspection of the combustion flame. The preferred optical pyrometer takes the form of an optical pyrometer having a single measurement cell which is alternately exposed to the flame through different filters arranged on a rotating disc driven by a motor. The circuit associated with the optical pyrometer, for purposes of generating control signals, features the use of a synchronous D. C. restorer which establishes a reference level for minimum signal distortion. Also employed is an AGC circuit by means of which one of the signals derived from one of the aforementioned filters is utilized to minimize undesired variations in the results. Gating logic is used to separate the two channels derived from the different filters and actually demultiplexes the two separate channels.

Abstract: A temperature pattern measuring device for obtaining the surface temperature distribution of an object. The device receives an image of the measured object and two different wavelength components of light emitted from the object. The device performs a two color temperature process for each minute area within a visual field of the image pickup, detecting the temperature at a portion on the surface of the corresponding measured object, thereby obtaining the temperature pattern thereof. The above minute areas can be set by an electrical method using photoelectric conversion means. Also, a supervision unit for the weld zone at an electrically seamed pipe, may employ the temperature pattern measuring unit of the present invention, the supervision unit producing a composite display of the form of the weld zone and the temperature pattern thereof.

Abstract: A pyrometer system for the measurement of the temperature of a primary source of heat which might be contaminated by radiation from a transient spurious source of heat at a higher temperature, and in which the presence of radiation from the spurious source can be detected or identified by spectral discrimination. The received radiation is separated into two spectral components of which a second component comprises a significantly higher proportion of radiation emitted by the spurious source than does the first component. The ratio of, or the difference between, the magnitudes of the radiation in the second and first components is used to identify or detect the presence of spurious radiation and to produce an error, or flag, signal which is used to inhibit operation of the pyrometer or to cause it to hold the last received `good` reading before the occurrence of the spurious radiation.

Abstract: A radiation absorbing cone (34) affixed to an infrared pyrometer (31) has a pair of lateral apertures (36--36) therein through which a continuously moving heated wire (11) passes. The cone (34) blocks stray ambient radiation while substantially eliminating any reflected radiation from the wire (11) from impinging on the pyrometer (31) to provide an accurate and repeatable measurement of the wire temperature.

Abstract: A method for measuring the velocity of earth surface motion utilizing coherent light energy which comprises steps of generating and directing a coherent light beam toward a selected earth surface position, reflecting said beam from a stationary reflector located at the earth surface position, and simultaneously reflecting said beam from a reflector at said earth surface position which moves with earth surface motion; and, detecting the reflected beam, including both the reflection path components, to derive an instantaneous difference frequency that is proportional to the velocity of the earth surface motion.

Abstract: A fiber optical temperature measuring apparatus is based on the ability of certain materials to change color in dependence on changes in temperature. Visible or invisible light having at least two different wavelengths is supplied to the material and the light emanating from the material is detected for determining the changes in the absorption characteristic of the material at the emitted wavelengths by determining the quotient between the detected signals from the material.