| 摘要 |
PURPOSE:To make it possible to obtain a stable pattern detecting signal all the time by correcting the change in illuminance of a light source with a detected signal in first operation, and automatically setting the level of the detected signal in second operation. CONSTITUTION:Light emitted from a light source 1 is projected to a half mirror 2. A part of the light is guided to an optoelectronic element 4 through a detecting unit 3 as the transmitted light. The remaining part becomes the reflected light which is guided to an optoelectronic element 5. Then, the outputs of the elements 4 and 5 are amplified in amplifiers 6 and 7, respectively. The outputs (a) and (b) thereof are supplied into a divider 8. Then, the waveform (a) is divided by the waveform (b) in the divider 8, and a waveform (c) is obtained. In a sample hold circuit 10, the waveform (c) is sampled and held at the timing when a pattern is not present. Furthermore, a reference voltage 15 (Vs) is divided by a holding voltage Vh in a divider 12. The value of Vs/Vh is guided into a multiplier 11 and multiplied by the waveform (c), and a waveform (d) is obtained. High frequency noises are removed from the waveform (d) through an LPF 13, and a detected waveform (e) is obtained. |
