| 摘要 |
1,152,854. Photo-electric distance measurement. ALBISWERK ZURICH A.G. 24 Nov., 1966 [25 Nov., 1965], No. 52601/66. Heading H4D. Relates to photo-electric distance measurement wherein the phase of the amplitude modulation of an echo from the reflector is compared with that of the modulation of the wave on transmission. According to the invention the phase difference measurement is performed at a lower, e.g. audio frequency by mixing the transmitted and echo modulation signals with an oscillator 10. A simple narrow band phase measuring device 13 may be employed if the frequency of oscillator 10 is caused to follow that (F) of modulation oscillator 3 by a known means 14. Oscillator 10 may provide two frequencies at equal frequency differences one above and one below F; by switching between those two frequencies and averaging the phase measurements receiver phase distortion is eliminated. |
