Abstract: A flexible optical marker is applied to an optical scale substrate to make an optical scale assembly for an optical position encoder. The marker may be a limit marker, index marker, or other type of marker. The marker substrate may be a plastic film such as polyester, singulated from a “recombine” roll created by a web process. The marker has a microstructured pattern on one surface that is covered with a reflective metal coating. The marker also has an adhesive layer and is affixed to the optical scale substrate by a process of aligning the marker to an edge of the scale and then applying pressure to the upper surface of the marker. The marker may be applied with a handle portion that is separated from the marker after the marker is affixed. The marker may be especially useful with a flexible scale substrate such as a metal tape substrate.

Abstract: An optical encoder includes a source of a light beam, an optical grating that generates a spatial pattern of interference fringes, and an optical detector which includes generally elongated detector elements that sample the interference fringe pattern at spatially separated locations along the direction of motion of the grating. Each detector element has one or more segments slanted along the direction of motion of the grating by an integer multiple of the period of an undesirable harmonic component of the fringe pattern, thereby spatially integrating the harmonic component and suppressing its contribution to an output of the detector. One specific detector type includes parallel elongated rectangular elements in a rectangular array that is rotated slightly about a Z axis; another type includes detector elements arranged to form a non-rectangular parallelogram.

Abstract: An optical encoder includes a sensor head, an encoder scale, and an optical wavefront dividing element. The sensor head includes a substrate, a light source, a first optical detector, and a second optical detector. The light source, the first optical detector, and the second optical detector are disposed on the substrate. The scale includes a first track and a second track. The optical wavefront dividing element is disposed between the sensor head and the scale. A light beam emitted by the light source is divided into a first beam and a second beam by the wavefront dividing element. The first beam is incident on the first track and the second beam is incident on the second track. Light from the first beam diffracted by the first track is incident on the first optical detector. Light from the second beam diffracted by the second track is incident on the second optical detector.

Abstract: An optical encoder includes an optical source, a scale, an optical detector and signal processing circuitry. The scale is operative with a light beam from the source to generate an optical pattern such as a line pattern extending in an X direction of relative movement between the scale and the source. The detector generates analog detector output signals indicative of the location of the optical pattern on the detector in an alignment direction orthogonal to the X direction. The detector may include two bi-cell elements spaced apart in the X direction, each element including two cells of complementary shape, such as a sharks-tooth. The signal processing circuitry operates in response to the detector output signals to generate an alignment value indicating a polarity and a magnitude of misalignment between the detector and the scale in the alignment direction.

Abstract: There is provided a measurement system in which the calibration data is easily incorporated into or obtained by the position sensing and/or displacement sensing system's processing unit. A scale-based encoder has a signal processor that corrects for scale inaccuracy based on a limited set of correction coefficients. The correction coefficients are the slopes and offsets that define a piecewise linear correction curve corresponding to the errors inherent in the scale. Several ways for communicating the coefficients to the processor are envisioned. Correction is applicable to linear or rotary encoders.

Abstract: An optical encoder includes a sensor head, an encoder scale, and an optical wavefront dividing element. The sensor head includes a substrate, a light source, a first optical detector, and a second optical detector. The light source, the first optical detector, and the second optical detector are disposed on the substrate. The scale includes a first track and a second track. The optical wavefront dividing element is disposed between the sensor head and the scale. A light beam emitted by the light source is divided into a first beam and a second beam by the wavefront dividing element. The first beam is incident on the first track and the second beam is incident on the second track. Light from the first beam diffracted by the first track is incident on the first optical detector. Light from the second beam diffracted by the second track is incident on the second optical detector.

Abstract: There is provided a measurement system in which the calibration data is easily incorporated into or obtained by the position sensing and/or displacement sensing system's processing unit. A scale-based encoder has a signal processor that corrects for scale inaccuracy based on a limited set of correction coefficients. The correction coefficients are the slopes and offsets that define a piecewise linear correction curve corresponding to the errors inherent in the scale. Several ways for communicating the coefficients to the processor are envisioned. Correction is applicable to linear or rotary encoders.

Abstract: Position of a diffusely scattering surface is detected by interfering backscattered light from respective input beams which illuminate a common spot. Through polarization of the input beams and appropriate filtering, backscattered light is isolated from specularly reflected light and interfered to form a fringe pattern on a detector. The position sensor has particular applicability as a push pin sensor in a hard disk servo system.

Abstract: A displacement measuring apparatus is disclosed, one embodiment of which employs two diffractive code disks, attached to a shaft, and a sensing head which need not contact the shaft. The head includes a light source with beam shaping optics, which creates two individual beamlets and pre-cranks the beamlets so that they reach the first grating at proscribed angles. Two diffracted orders from the first grating are allowed, preferably through free space propagation, to strike the second grating and to be rediffracted by the second grating. A phased-array detector, or equivalent array of detecting elements, are positioned beyond the second grating and in a region of natural interference between rediffracted orders of the incident diffracted orders, to detect the interference fringes which are generated there. The change in phase of the fringes is proportional to the relative displacement between the first and second gratings.

Abstract: The apparatus disclosed herein employs a grating (13) which concentrates light at a preselected wavelength into the positive (33) and negative (35) first orders while minimizing the zeroth order (31). The grating (13) is illuminated with monochromatic light of the selected wavelength and a poly-phase periodic detector (25) has its sensing plane spaced from the grating a distance less than ##EQU1## where W is the width of the illuminated region of the grating. The period of the poly-phase detector is equal to P/2 so that each detector element (51) or phase responds principally to the natural interference between the positive and negative first orders without requiring magnification or redirection of the diffracted light. Preferably, the distance of the sensing plane from the grating (13) is greater than ##EQU2## so that the detector response does not include substantial components from diffraction orders higher than the first.

Abstract: The apparatus disclosed herein employs a grating or scale which concentrates light at a preselected wavelength into the positive and negative first orders while minimizing the zeroth order. The scale is illuminated with monochromatic light of the selected wavelength and a poly-phase periodic detector has its sensing plane spaced from the scale a distance less than ##EQU1## where W is the width of the illuminated region of the scale. The period of the poly-phase detector is equal to P/2 so that each detector element or phase responds principally to interference between the positive and negative first orders without requiring magnification or redirection of the diffracted light. Preferably, the distance of the sensing plane from the scale is greater than ##EQU2## so that the detector response does not include substantial components from diffraction orders higher than the first.

Abstract: The apparatus disclosed herein employs a grating (13) which concentrates light at a preselected wavelength into the positive (33) and negative (35) first orders while minimizing the zeroth order (31). The grating (13) is illuminated with monochromatic light of the selected wavelength and a poly-phase periodic detector (25) has its sensing plane spaced from the grating a distance less than ##EQU1## where W is the width of the illuminated region of the grating. The period of the poly-phase detector is equal to P/2 so that each detector element (51) or phase responds principally to the natural interference between the positive and negative first orders without requiring magnification or redirection of the diffracted light. Preferably, the distance of the sensing plane from the grating (13) is greater than ##EQU2## so that the detector response does not include substantial components from diffraction orders higher than the first.

Abstract: A method and apparatus for geophysical exploration wherein a seismic wave is passed through a bore hole so at to sequentially detonate a plurality of explosive charges disposed within said bore hole at spaced intervals. A preselected seismic wave magnitude represented by a stored voltage is compared with signals generated by electro-acoustic sensors associated with each charge. When the magnitude of a seismic wave in the bore hole equals the preselected magnitude, a voltage stored on a capacitor discharges into a detonator. Means are provided for varying the stored voltage representing the preselected magnitude from the surface of the bore hole and for detonating any unexploded charges which may after the initial seismic wave passes through the bore hole. A firing circuit is armed substantially simultaneously with the initiation of the seismic wave in the bore hole. The firing circuit is armed for only approximately 0.1 to 0.5 seconds thereby preventing late detonation which destroys seismic data.

Abstract: A method and apparatus for geophysical exploration wherein a seismic wave is passed through a bore hole so as to sequentially detonate a plurality of explosive charges disposed within said bore hole at spaced intervals. A preselected seismic wave magnitude represented by a stored voltage is compared with signals generated by electro-acoustic sensors associated with each charge. When the magnitude of a seismic wave in the bore hole equals the preselected magnitude, a voltage stored on a capacitor discharges into a detonator. Means are provided for varying the stored voltage representing the preselected magnitude from the surface of the bore hole.

Abstract: Digital apparatus for approximating the logarithmic equation of the form: X= W Log.sub.z (Y)+ K where W and K are selected constants, employs basically a three counter, one comparator logarithmic digital calculator assembly. A source provides a selected train of time spaced pulses to a divide by N counter, which drives a first counter. The clock pulses also go to a second counter. The comparator at each clock pulse compares the counts of the first and second counters. If the count of the second counter is greater than that of the first counter, an output pulse is produced, which resets the second counter and including an output circuit.

Abstract: In the roll-furling mainsail arrangement disclosed herein, the clew of the sail is trimmed to a boom by means of a car which is freely slidable along the boom. An outhaul line rigged to pull aft from the tip of the boom passes forward through a block on the car, thence through a block at the clew of the sail and then back to the car where it is secured. The balance of forces on the car automatically bias it to a position providing an advantageous drawing angle for shaping the mainsail, even at varying stages of partial furling.

Abstract: In the mainsail roll-furling system disclosed herein, the mainsail is roller-furled inside a tubular compartment in the mast itself, the sail being drawn out through an aft-facing slot in the mast. A swivel is utilized between the halyard and the luff of the mainsail and a guide is provided on the halyard side of the swivel which both positively prevents rotation of the halyard during furling of the sail and positions the upper end of the sail luff essentially in the middle of the sail storage compartment.

Abstract: The gooseneck fitting disclosed herein carries a reel adapted for roll-furling a mainsail along its luff edge, the reel being positioned within a hollow mast with which the gooseneck fitting is used so the mainsail can be rolled up within the mast. The gooseneck fitting incorporates also a sheave for turning a line being drawn horizontally off the reel in a downwardly direction to a point of exit from the gooseneck fitting beneath the boom.

Abstract: This invention describes an apparatus and method for generating seismic waves in the earth for seismic geophysical prospecting. It involves a slender pipe open at the lower end, which can be driven into the earth to a shallow depth. The upper end is closed. Means are provided for introducing oxygen and acetylene through a pair of control valves and check valves, for a selected period of time. The oxygen and acetylene are mixed in the pipe and flow downward through the pipe and through the perforations into the earth, and fill the voids and fissures in the shallow sediments. Means are provided in the top end of the pipe to detonate the gas mixture. The detonation wave travels down the pipe and eventually reaches the openings at the lower end, and detonates the gas in the pores and fissures of the earth. The resulting explosion opens up the fissures and provides a larger void space than was there before.

Abstract: A mechanical and electronic apparatus for integrating gas flow charts for determining gas volume. The mechanical apparatus includes a motor driven disc on which a recorded flow chart can be placed, with suitable pen arms, and operating arms, so that an operator can simultaneously vary the angular position of each of two pens, so that the pens may trace or scan simultaneously, the two recorded traces of pressure and differential pressure, as the disc and chart rotate under a motor drive. Optical encoders convert the rotation of the disc and the angles of swing of the pen arms to digital values. The outputs of the encoders are scaled to the particular charts and chart arms. The result of the scaled pulses go to an up/down counter for interpretation of total angle of each of the pen arms. The digital numbers representing the angles of the two pen arms then have their square roots extracted, the two outputs of square roots of pressure (P & A) and differential pressure H go to a multiplier and an accumulator.