DISTANCE MEASUREMENT BY CHARP ECHO AND DISTANCE MEASURING APPARATUS THEREBY

摘要

PURPOSE: To measure the radial velocity of an reflecting object by utilizing a Doppler frequency shift by detecting the relative magnitude between echo signals of adjacent frequency bands by means of a frequency, compressing means for received signals. CONSTITUTION: A continuous beam 2 from a laser l is modulated into a beam 20 having a frequency which linearly changes with time by means of a modulator 10 through a chirp encoding circuit 9. Echo signals are passed through the modulator 10, heterodyne-detected by means of a detector 41, and made incident to a surface acoustic wave chirp pulse compressing filter 45. The output-side transducer of the filter 45 covers all bands having a desired frequency by means of the output sections 64-67 of an independent transducer stage having a band which is nearly equal to the band of the chirp modulation. The radial speed of a reflecting object can be found through prescribed arithmetic operation by only using one chirp pulse based on the relative magnitude between short echoes which are simultaneously generated from adjacent ones of the output sections 64-67 by a Doppler shift.