| 摘要 |
A device for establishing the magnitude of irregularities at a surface includes a laser directing a beam of light, obliquely towards said surface, a photodetector mounted so as to catch a beam of light reflected from an irregularity at said surface, and a diffraction grating mounted in the path of a beam, mirror-image reflected from said surface and movable in relation thereto. The photodetector is provided with means for measuring the frequency and the amplitude of the time-dependent photocurrent caused by the interaction between the beam reflected from the irregularity and a further beam deflected by the diffraction grating from the mirror-image reflected beam. In a modified version the device may be used for measuring flow velocity, the laser and the photodetector being mounted to opposite sides of a flow path defined by transparent walls. |
