| 摘要 |
PURPOSE:To enhance measuring accuracy by sequentially reading the digital values corresponding to the charnge in the sweeping position of luminous flux in response to the sweeping of the luminous flux, and latching the readings when the luminous flux crosses the edges of an object to be measured. CONSTITUTION:The luminous flux 2 from a light source 1 is swept by a deflecting device 3 in the direction Y at a constant frequency. The edges A1 and A2 are detected by a light receiving device 6. The luminous flux also reaches a light receiving device 27 through semitransparent mirrors 21 and 25. A circuit 30 functions as a PLL circuit and sequentially reads the data from a memory 35 during one period of a received light of the light receiving device 27. A data is the digital value which is obtained by sampling the one period of the time domain waveform of the sweeping position of the luminous flux 2 in the direction Y. A pulse generator 40 operates first and second latches 41 and 42 in response to the edges A1 and A2 of the object to be measured. Therefore, the sweep position data of the luminous flux 2 at the instance the edge A1 or A2 is latched. Subtraction 43 is performed for both data and the size of the object to be measured is obtained. |
