초록 ▼

A closed loop optical gauge directs a laser beam toward an object whose radial velocity, instantaneous position, and/or shape are to be measured, and utilizes the Doppler frequency shift of the reflected beam to make measurements. A reference sample of the original direct beam has its frequency shif

A closed loop optical gauge directs a laser beam toward an object whose radial velocity, instantaneous position, and/or shape are to be measured, and utilizes the Doppler frequency shift of the reflected beam to make measurements. A reference sample of the original direct beam has its frequency shifted by an acoustooptical modulator. A closed loop system is created by sensing the difference in frequency between the reflected beam and the shifted reference beam. The amount of frequency modulation is then controlled so that the frequency of the shifted reference beam continuouly tracks that of the reflected beam, preferably with a fixed offset of frequency. The output can be integrated with respect to time to obtain position or shape information. Absolute distance to the object is measured by transmitting a train of pulses of light toward the object and receiving reflected light pulses back. The round trip time of the light pulses is ascertained by measuring the phase displacement of the envelope of the reflected signals relative to the envelope of the transmitted light signals, with the aid of a phase locked loop. The oscillator of the phase locked loop is locked to the envelope of a reference sample of the transmitted signal, and can operate selectively at the fundamental frequency or a higher harmonic frequency of that envelope. A selected harmonic from the oscillator can be compared as to phase with the corresponding harmonic of the reflected light pulses. With calibration, the system can measure flight time, and therefore distance to the object, with high resolving power at the higher harmonic frequencies.

대표청구항 ▼

A closed loop optical gauge comprising: laser means for producing a first beam; means for directing at least a portion of said first beam toward a target from which a beam is reflected; means for providing a reference beam having the frequency of said first beam; frequency shift means receiving said

A closed loop optical gauge comprising: laser means for producing a first beam; means for directing at least a portion of said first beam toward a target from which a beam is reflected; means for providing a reference beam having the frequency of said first beam; frequency shift means receiving said reference beam and receiving a modulation input signal, for providing a shifted reference beam whose frequency is shifted from that of the reference beam in accordance with the modulation input signal; means for producing interference of said shifted reference beam and said reflected beam to produce a beat frequency signal; negative feedback means for utilizing said beat frequency signal to control the frequency of said modulation input signal; whereby the frequency of said shifted reference beam tracks the reference of said reflected beam and has a known relationship to the radial component of velocity of said target.