| 摘要 |
PURPOSE:To measure the speed of an object to be measured at a high accuracy with a simple equipment by removing a disturbed portion in the frequency of narrow band irregular ones among electrical signals converted from light passing through a spatial filter to determine the center frequency thereof. CONSTITUTION:Light from an object to be measured moving in a specific direction is introduced into a spatial filter and converted into an electrical signal (c) to be inputted into a waveform shaping circuit 1. The waveform shaping circuit 1 in which threshold is set for the positive and negative voltage respectively shapes the waveform of the input signal as shown by the drawing A. Then, output thereof is inputted into an absolute value circuit 2 to invert -V as shown by the drawing B. Then, the output of the circuit 2 is inputted into a low pass filter 3 to be converted into a signal as shown by the drawing C and inputted into a frequency counting circuit 4 to detect the frequency. Such a conversion of the waveform enables the removal of disturbances from narrow band irregular signals having a waveform as illustrated thereby assuring accurate measurement of regular frequency with a simple circuitry. |
