| 摘要 |
PURPOSE:To raise a detection accuracy by measuring a signal of the quantity of light according to a linear variation of the quantity of light of the light beam end part, and calculating a light beam position from an output level which is about a prescribed level. CONSTITUTION:An image sensor S is placed at the position where a light beam B which has been obstructed by a displacement body M is detected, a photodetection signal is outputted as a series pulse signal by supporting a clock pulse CP from the driving circuit 1, a pulse signal exceeding a prescribed level is outputted by the amplifier 2 and the level comparator 3, and a counter output is obtained through the counter 4. Also, as for a linear variation of the quantity of light at the end part of the light beam B, its quantity of light is measured by the image sensor S, is amplified, it is sent to the sampling and holding circuit 5 and the A/D converter 6, and an AD conversion value is obtained. And, the counter output and the AD conversion value are inputted to the operator 7, an intermediate position of the image sensor pit is calculated, and a signal showing the light beam position is outputted. According to such a constitution, it is possible to raise the resolution of the sensor and elevate the detection accuracy. |
