An optical interferometer of the coherent light type with which distances are measured by counting the total number of interference fringes produced when one reflector of a pair in the interferometer is moved through the distance to be measured. The movable reflector which is also translatable normal to the direction of measurement, is a roof prism having its reflective surfaces elongated in this direction. Photoelectric detectors are provided on opposite sides of a beam splitter for each providing a pair of phase displaced sinusoidal interference signals. The outputs of the detectors are combined to produce a single pair of phase displaced sinusoidal interference signals having an average D.C. level of zero volts. Electronic logic circuitry is provided for producing a digital signal representing the amount and direction of the displacement of the movable reflector along the axis of measurement. This circuitry includes a weighted summing means, including an operational amplifier, for providing at least one sinusoidal signal pair from the combined detector outputs, which is a weighted sum of these outputs and which is squared by Schmitt triggers and combined with these outputs in accordance with a predetermined signal pair condition.
An optical interferometer, particularly for use in measurements of length, employs a light transmissive splitting cube which is provided with three beam splitting faces in parallel to each other. A light bundle entering the splitting cube is split into two partial light bundles. After passage of an optical path within the splitting cube both partial light bundles interfere with each other and produce an interference pattern. Light portions of said interference pattern interfere with each other after having passed separate light paths. Both interference patterns so produced are 90.degree. phase-shifted relative to each other. This phase shift permits a unique determination of direction in variations of length.
A work locating system having temperature and other compensation capabilities wherein the work member is mounted for controlled movement with respect to the work tool. Two sets of two laser interferometers are utilized to generate distance measuring light beams such that the beams of each set are coaxial and the beams of the respective sets are orthogonal and intersect at the work tool reference axis to thereby instantaneously and continuously determine the location of four reference points on the work member and compensate for all expansions or contractions of the work member or changes in the laser measuring system during the programmed work operation.
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.1 to the nearest integer and the accurate distance L is calculated according to the equation: ##EQU2##
An interferometer, preferably of the Michelson type, is disclosed, in which the reflectors associated with the interferometer arms are stationary, and scanning is accomplished by displacement of a single wedge-shaped refractive element in one of the arms. The reflectors are preferably retro-reflectors rather than flat mirrors in order to minimize the effects of chromatic dispersion. A Moire scale may be used to measure the position of the wedge-shaped refractive element.
A non-storage type image pick-up tube line scans a sample for picking up the fringes. A circuit responds to the maximum and minimum values of the output from the image pick-up tube generating a signal corresponding to the brightness of the fringes, signals corresponding to the positions of the bright and/or dark spots of the fringes, and signals corresponding to the spacings between a reference point and the positions of the bright and/or dark spots of the fringes.
