| 摘要 |
PURPOSE:To obtain an interferogram with a good S/N ratio, by checking whether the error of the moving speed of a scanning mirror is within a permissible range or not all the time and inhibiting the integration of measurement data by the scan at the time when abnormality of the moving speed of the scanning mirror is detected. CONSTITUTION:An AC waveform A obtained by a photodetector D1 is shaped W to obtain a rectangular signal B with a duty cycle which is about 50% of one period of the alternating current. Then, the pulse width of this signal B is measured by using clock pulses of high frequency to detect the moving speed of the scanning mirror M, which is compared with a reference speed to find the high- speed error, discriminating whether this speed error is within the permissible range or not. A computer 3 when deciding on that the error exceeds the permissible range excludes measurement data by the scan at the time from the integration of an interferogram. |
