PURPOSE: To obtain a laser Doppler speedometer of which the adjustment of alignment of each optical component is dispensed with and which is excellent in vibration resistance.
CONSTITUTION: A laser Doppler speedometer is constructed of an interference unit 1 wherein a semiconductor laser 4, a photodiode 5, optical waveguides 6, 7 and 8 and 3dB couplers 9 and 10 are integrated and formed integrally on a semiconductor base 3, and of a measuring unit 2 which measures an output signal subjected to heterodyne detection optically in the photodiode 5. A laser light emitted from the semiconductor laser 4 is made to branch by the 3dB coupler 9. One branch light is emitted toward a moving body 11 and a reflected light therefrom enters the optical waveguide 7, while the other is propagated through the optical guide 8 and, with the direction of advance changed, is made to enter the optical waveguide 7 through the 3dB coupler 10. This laser light is synthesized with the above-mentioned reflected light in the optical waveguide 7 and a synthesized light thus formed is sensed by the 5.
NAKAMURA AKIHIKO
OKUDA HIROSHI
