| 摘要 |
PURPOSE:To measure the speed with a high precision, by subjecting the translation signal of the speckle pattern of the moving object, which is irradiated with the interferable light, to Fourier conversion and by measuring the frequency of the waveform obtained by sampling values in a specific space frequency. CONSTITUTION:In respect to measurement for the speed of moving object 6 which is irradiated with the interferable light, the translation motion of speckle pattern 7 focused onto CCD image sensor 5 is converted photoelectrically to obtain odd element signal (a) and even element signal (b). Signal (a) is sample-held in 8 and has the phase matched to that of signal (b) to obtain signal (c), and the difference between signals (c) and (b) is operated by subtractor 11 to obtain signal (d), and this signal (d) is amplified by 12 and is multiplied by cosine wave (e) from signal generator 13 to obtain signal (f), and this signal (f) is integrated during one scanning period T of the CCD by integrator 15 to obtain signal (g), and the integral value in its specific space frequency mu0 is extracted by sample hold circuit 8 and A/D converter 17 and is stored in 18. Since the period of output (h) obtained by plotting Fourier conversion values which are obtained by repeating this sampling is equal to the time when the speckle pattern is moved by one pitch of the space filter, this period is measured and averaged by calculator 21 to measure the speed with a high precision, and the speed is displayed on 22. |
