Patent RU-94018593-A (RU)
Inventor: PASYNKOV S A
IPC: G01P3/36
Filed: 1994-05-23
Abstract: FIELD: measurement technology; electronic and optical instruments used for determination of parameters of motion of object or unit of mechanism; method may be employed in quick-acting remote measurement systems, orientation and control systems of space vehicles and other flying vehicles, as well as in instruments and devices of navigational and geodetic systems. SUBSTANCE: light radiation from source 1 is directed by objective 2 through narrow-band light filter 3, polarizer 4, optical plate 5 and light analyzer 6 and photodetector 7. Light filter and polarizer are used to obtain plane-polarized monochromatic narrow beam from standard beam radiated by source or reflected by object. Optical plate is made from crystal possessing birefringence of light, for example, from calcite ((CaCO)). Angle between optical axis of crystal 00' and plane of polarization of light polarizer 00" is equal to 45 deg; that is why, light wave falls into two orthogonally polarized indivisible in space components Eo and Ee which are equal in amplitude and have similar frequency but propagating at different phase velocities. Oscillations of light waves of standard beam Eo and non-standard beam Ee come to one plane in analyzer - plane of analyzer polarization which is parallel to polarization plane of polarizer. As a result, interference takes place and resultant wave Ea is formed which will have initial frequency and its amplitude will depend on difference of phases between "O" wave and "E" wave. Amount of Doppler shift of initial frequency of light radiation of "O" wave and "E" wave is different; it depends upon refractive indices nand nof optical plate. Due to interference of "O" wave and "E" wave, resultant light wave is formed in analyzer which is just product of low-frequency component by high-frequency component. As a result, pulsation of light signal will take place at photodetector input at frequency νwhich is proportional to velocity V of optical plate relative to source of light radiation and will be found from expression given in Description. Speed of motion of object is determined by magnitude of frequency of pulsation of light signal in accordance with formula given in Description with the aid of computer-converter 8. Device for realization of this method operates as follows: standard light reflected from object or radiated by source comes to optical birefringent crystal of velocity sensor 5 through objective 2, narrow-band (interference) light filter 3, light polarizer 4 and semireflecting mirror 11. Natural light is converter to monochromatic plane-polarized narrow beam. Light polarized at 45 deg to optical axis of crystal, falls in optical crystal into two orthogonally polarized components "O" beam and "E" beam which are equal in amplitude and indivisible in space. Phase velocities of light waves "O" and "E" beams are different. Their magnitudes depend on natural crystalline anisotropy. Having passed through optical crystal, one part of light flux E1 passes through semireflecting mirror and light analyzer and comes to photodetector of first conversion channel. Second part of light flux E2 reflects from semireflecting mirror and passes through optical crystal 5 in opposite direction; it reflects from semireflecting mirror at angle of 45 deg, then passes through light analyzer and comes to photodetector of second conversion channel. During motion of optical crystal 5 together with receiving and recording devices and light source 1, light signal will be furnished to photodetector input in accordance with expression (1) frequency of pulsation of this signal and phase of its low-frequency component are in proportion to crystal velocity. The same light signal will be furnished to input of photodetector 5, but phase of this signal will be constant, i. e. its magnitude is independent on crystal velocity. That is why, the second reflected light flux and conversion channel are used as reference values for determination of sign of velocity. Photodetectors are used for demodulation of light signal and for conversion of this signal into voltage or current. Bell-like signals are fed from output of photodetectors to input of amplifiers-limiters where signals are amplified and are limited in amplitude in order to separate section at maximum rate of rise. Optimal magnitude of gain factor is set by means of automatic gain control unit which is operated from computer. Trapezoidal signals are furnished from output of amplifiers-limiters to mark former input. Mark former performs function of comparison circuit. Fed to second input of mark formers from reference voltage source is reference voltage whose magnitude is equal to half amplitude of voltage of signals fed from amplifiers- limiters. Mark formers generate pulses of short duration - marks M1 and M2 as soon as magnitude of voltage at information input gets equal to reference voltage. Sequences of marks M1 and M2 are fed to computer unit 7 which performs measurement and conversion of mark repetition period and time shift of marks M1 relative to marks M2 into digital code; computer unit also performs static processing of information and calculation of magnitude and sign of object speed. EFFECT: enhanced efficiency.