Abstract: Disclosed is a passive ring resonator and a control scheme for correcting bias effects due to intensity variations of waves propagating within the resonator.

Abstract: Disclosed is an apparatus for obtaining an output signal from a dithered ring laser angular rate sensor devoid of dither spill over into the output signal. For a single sensor, the output signal is sampled at two points separated in time by one half of the dither period. Also disclosed is an inertial sensor system in which each of the sensors are sampled about a common strobe pulse and separated in time corresponding to one half of their respective dither periods.

Abstract: Disclosed is an apparatus for inspecting negatives which is provided with a laser beam generating source, a scanner for scanning the laser beam, a holding device for holding a negative having a pattern formed in a reflective area on a first surface of a transparent plate and transferring the negative in a direction perpendicular to the scanning direction of the laser beam, a first converging lens for converging the laser beam on said first surface, a second converging lens for converging on a first photocell the beam transmitted through the negative, a third converging lens for converging on a second photocell the beam reflected by the first surface of the negative, and a comparator for comparing a first signal stream put out from the first photocell and a second signal stream put out from the second photocell and detecting an undesirable adhering matter.

Abstract: A sensor is described for detecting the difference in phase of a pair of returned light pulse components, such as the two components of a light pulse of an optical gyro. In an optic gyro, the two light components have passed in opposite directions through a coil of optical fiber, with the difference in phase of the returned light components determining the intensity of light shining on the sensor. The sensor includes a CCD (charge coupled device) that receives the pair of returned light components to generate a charge proportional to the number of photons in the received light. The amount of the charge represents the phase difference between the two light components. At a time after the transmission of the light pulse and before the expected time of arrival of the interfering light components, charge accumulating in the CCD as a result of reflections from optical components in the system, are repeatedly removed from the CCD, by transferring out charges in the CCD and dumping these charges.

Abstract: The present invention relates to a gas flow cell for spectrophotometric analysis of chemical compounds, consisting of a longish preferably cylindrical body (1) with a longitudinal central channel (2) which at the ends of the body (1) is limited by mutually parallel windows (3, 4) which are tightfitting against the channel (2) and transparent for the radiation used at the analysis. The channel (2) communicates at one end with connections (7, 8) for carrier gas and for injection of compounds and has at the other end an outlet (10) for the compounds and the carrier gas. Significant for the invention is that parallel with and at a distance from the mentioned channel (2) runs a second channel (11) serving for separation and connected between the connections (7, 8) and said end of the first mentioned channel (2). In this channel (11) there is a replaceable column tube (12) with filling of known composition.

Abstract: A ring laser for a ring laser type of gyro having a block with an optical resonator cavity therein and three corner mirrors and an amplifier element for optical frequencies. The amplifier element is adjustable and alignable with respect to the block in such a way that it is adaptable mechanically to the beam path resulting from the mirror arrangement determined by the production technology. The production depends basically on arranging the mirrors in such a way that a resonant beam path results. As tolerances with regard to the accuracy of the position of the amplifier element are considerably lower than those with regard to the positions of the mirrors, the position of the amplifier element is specified.

Abstract: An angle-sensitive interferometer includes a first beam splitter for splitting a beam of coherent radiation into two portions and a second beam splitter for recombining the two beam portions to produce an interference pattern. It also includes reflecting mirrors and lenses for recombining the two beam segments in such a manner that an angle of deviation in the incident beam results in the recombined beams diverging from the interferometer axis to create a wedge angle. A corner cube reflector, cat's eye reflector, or a telescope with either convex lenses or concave mirrors are used for this purpose. The invention also includes a mirror in one of the beam portion paths to reflect it out of alignment with that beam portion path emerging from the first beam splitter so that the second beam splitter where the beam portions are recombined does not produce feed back into the radiation source.

Abstract: In order to provide an calibration plate having both known reflectance and known luminescence characteristics for calibrating and proving a radiometer, which calibration plate exhibits a near-Lambertian surface reflectance, a ceramic or glass coating containing a rare earth photoluminescent material is bonded to a surface of a rigid substrate, such as a steel plate, and the ceramic coating is thereafter sandblasted with a fine abrasive in good condition.

Abstract: An apparatus for automatically measuring the depth and rate of etching of a semiconductor body (10) comprises an interferometer (18) and a counter circuit (28). The interferometer (18) directs light towards the semiconductor body (10) and detects the intensity of the light reflected therefrom which varies periodically during etching. The counter circuit (28) is responsive to the periodically varying intensity of the reflected light and automatically determines the number of cycles and the frequency thereof to compute the etch depth and etch rate therefrom.

Abstract: An apparatus for measuring a thickness of an object transparent to light utilizing an interferometric method includes a light source for generating a coherent light beam to which an object to be measured is transparent, an illumination unit for radiating onto the object the incident light beam as scanned over a range of angle of incidence varying from a predetermined angle of incidence .theta..sub.A to another predetermined angle of incidence .theta..sub.B, and a photosensor unit for detecting light intensity changes resulting from changing of the optical path difference between two light beams reflected by the upper and lower surfaces of the object. A count circuit receives an output signal from the photosensor unit and counts the difference between an order of interference fringes obtained for one scan of incident light beam having the predetermined angle of incidence .theta..sub.A to that having the other predetermined angle of incidence .theta..sub.

Abstract: A method and apparatus for automatically detecting defects on the surfaces of semiconductor wafers and chips which provides a 100% inspection capability. The entire surface of each wafer is scanned by use of a low magnification, low resolution detector such as a photodiode array. Whenever a defect occurs, encoders on the supporting XY table are triggered, such that the location of a defect on the wafer is recorded. After the event coordinates have been determined, the XY table positions each defect directly under a high magnification detector to determine the nature of the detected event. Since only the locations of the detected events are stored, 100% of the processed wafers can be scanned for defects.

Abstract: An interferometric device for measuring an angular rotational speed comprising an amplifying photo refractive crystal placed in the path of optical guide means forming a closed loop. Two signal waves penetrate into said crystal so as to obtain two contrarotating waves of different optical frequencies and of amplitudes restored by amplification in the crystal, moving in said closed loop.

Abstract: A photoelectric device for use as a radiation thermometer capable of measuring the temperature of a target without being in contact therewith is provided. The photoelectric device can include a photovoltaic cell of germanium that is suitable for a radiation thermometer capable of measuring the temperature of a target between 200 degrees C. to 800 degrees C. The electrical output of the photovoltaic cell corresponding to the intensity of radiation is made independent of any change of the characteristic of the cell resulting from temperature.

Abstract: A ring laser particularly for a ring laser type of gyro in which the ring ser includes three corner mirrors and a separate gas discharge tube arranged in a recess in a block. The gas discharge tube is mounted on the block longitudinally of the beam path by at least one piezo electric drive. The modulation amplitude of the separated beam portion is measured by a control circuit and is converted into a high voltage adjustment signal for the drive as a function of the modulation amplitude. Two drives may be spaced apart in the longitudinal direction of the gas discharge tube and these can be controlled independently of each other. Although the beam path may be displaced as a result of thermal expansion and/or bending of the block, the gas discharge tube may be kept exactly coaxial with the beam which traverses it.

Abstract: A low Q ring laser gyro-dither motor assembly which is responsive to a wide range of frequency components of a drive signal having a randomly varying frequency such that the dither imparted to the gyro is frequency modulated by the drive. The frequency modulated dither varies the lock-in rate of the gyro as a function of the random drive signal to eliminate errors in the gyro output due to lock-in. The drive signal may be random in frequency only or random in both frequency and amplitude to provide the frequency modulation. Fixed frequency modulation may also be employed. The low Q assembly need not be driven at the natural frequency thereof so that a common drive circuit may be employed for a plurality of low Q gyro-dither motor assemblies forming an instrument cluster.

Abstract: An interferometer/spectroradiometer that uses a beamsplitter means for dividing an input beam into two separate beams and presents the resultant beams to a rotary refractive window from symmetrically oriented optical elements such that the optical path differences through the refractive window as it rotates are additive and non-linearities are subtracted. The beams are returned through the refractive window to the beamsplitter for dividing the input beam, where fringes are generated for application to appropriate detectors. The detector output is applied to Fourier transform computer equipment for digitizing and processing for presentation on a spectrum display device.

Abstract: A ring laser gyroscope may be oscillated or dithered about its sensing axis to the known `lock-in` effect. The diether motion can comprise an alternating component plus a random component generated by a random noise generator, e.g. a noise diode. The use of a true random noise generator may not always be practicable. Herein, there is proposed the dithering of a ring laser gyroscope with a motion including a component having a specifically Gaussian probability density. Such a component can be formed using a so-called pseudo-random sequence generator based on a shift-register.

Abstract: A ring laser gyroscope having apparatus for compensating a gyroscope output signal for optical power variations in accordannce with variations of a dihedral frequency. A scaler quantity is determined based on operational data and it is used to compensate the gyroscope output signal. Alternatively, a gyroscope output signal is compensated via a feedback network by adjusting the gain medium in the laser gyroscope in accordance with variations in the dihedral frequency.

Abstract: A rotation rate measuring instrument for measuring the rotation rate of a fiber gyro having a light source, a series of beam splitters, a phase modulator, a coiled optical waveguide and an evaluating circuit provides a first and second light beam which traverse the coiled optical waveguide in opposite directions. At least one of the light beams is modulated at an angular frequency .omega.m in the phase modulator while at least one of the light beams is further modulated at a second frequency .omega.s. The frequencies are distinguishable in the evaluating circuit permitting the suppression of signal components caused by light reflected at the boundaries of the phase modulator.

Abstract: An interferometer wherein detected local oscillator beam power is variable without varying detected target-reflected return beam power. A P-polarized beam of energy is produced along a predetermined path. First and second waveplates are serially disposed in the predetermined path. Also included are a beamsplitter disposed in the path between the first and second waveplates, and a polarization analyzer disposed in the path between the beam producing means and the first waveplate. A first portion of the P-polarized beam couples through the first waveplate, the beamsplitter and the second waveplate, and is transmitted to a target, the first and second waveplates altering the polarization of the transmitted beam to circular polarization.