| 摘要 |
PURPOSE:To reduce errors in speed measurement due to a deviation in wavelength caused by temperature variation by detecting the temperature of a semiconductor laser and multiplying a speed measured value by a compensating coefficient corresponding to the temperature. CONSTITUTION:A laser beam from a semiconductor laser 2 is passed through a collimator lens 4 and split by a beam splitter 5 into two, and a moving body 1 is irradiated with those beams in the mutually opposite directions in crossing relation through mirrors 6a and 6c; and scattered light is inputted to a frequency tracking device 10 through a condenser lens 7, a photodetector 8, and an amplifier 9. The tracking device 10 detects a Doppler frequency and a speed computing element 11 computes the speed of the body 1. A heat-sensitive element 12, on the other hand, detects the temperature of the laser 2 and multiplies the speed measured value by a prescribed correcting coefficient corresponding to the temperature of a temperature correcting circuit 13. Consequently, the errors in speed measurement due to temperature variation are reducible.
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