| 摘要 |
PURPOSE:To detect a peak value accurately at high speed through an MTF inspecting machine which detects the peak value of the sampled and held value of a video signal based upon a slit-projected image, by reading the sample holding value corresponding to the intermediate value between the leading and trailing edge of an comparison output of the sample holding value with a reference value through a memory. CONSTITUTION:A video signal obtained by a sensor 30 by projecting a slit image is held by a sample holding circuit 40 and A/D-converted and the resulting signal is written in an RAM60 through an address counter 70 which is driven synchronously with the circuit 40. The contents of the circuit 40, on the other hand, are compared by a comparator 100 with a reference value from a system controller 80a. Its comparison output is passed through an inverter 110, delay circuit 120, delay circuit 130, and AND gates 140 and 150 to detect the leading and trailing edges of the comparison output, which are stored in registers 160 and 170; and the controller 80a calculates the intermediate value of both edges, and this is set in the counter 70 to read the RAM60. Thus, a peak value is read out accurately at a high speed through simple processing. |
