The collimator lens turns the light emitted from the semiconductor laser into a parallel beam that the diffraction grid separates into two beams. After each beam passes through the lens, it is applied to the E/O frequency shifter to establish a difference in frequency. The two beams with differentiated frequencies are both refracted and applied to the moving object of measurement. A photo diode collects the dispersed light reflected from the object measured. Because the Doppler signal for the light that includes the speed information obtained here does not depend on the laser light wavelength, stable, highly accurate and wide-ranging speed measurement is possible, as s measurement from a still state.
