| 摘要 |
A method of and an arrangement for measuring the velocity and/or length of moving objects using the Doppler principle. Measurement of the velocity of objects over a wide range imposes stringent requirements on the bandwidth of the electronic apparatus which process the Doppler shift. The velocity and/or length are measured accurately using simple, narrow-band electronic processing circuits by imparting a pre-shift to the frequency of the electromagnetic wave directed towards the object to be measured. This pre-shift is opposite to the Doppler shift generated by the movement of the object and is realized by imaging a light beam originating from a laser onto the object via a rotating phase grating. The rate of rotation of the phase grating is controlled so that the total Doppler shift measured is always constant.
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