| 摘要 |
PURPOSE:To prevent the malfunction due to noise by dividing variably the quantity of electricity of an electric signal being generated by a signal generating means into two, and supplying these divided quantities of electricity to a pair of input terminals of a comparing means, individually. CONSTITUTION:For the purpose of controlling the offset of a photodetector device, the light from a light source (omitted in the figure) is irradiated to three photodetectors A1, A2, and B simultaneously. Then, currents generated by photodetectors A1 and A2 flow to resistances RL1 and RL2, and the current generated by the photodetector B is divided in accordance with the reciprocal of a resistance value ratio of a variable resistance VR divided by a slide contact (c). After the control of the offset, the device performs the photodetecting operation to output photodetection signals corresponding to quantities of light which photodetectors A1 and A2 receive. That is, a comparator OP outputs signal '1' if the potential at a point (a) is higher than that at a point (b), and the comparator OP outputs signal '0' if the former is lower than the latter. As the result, noise rating quantities in the non-inverted input terminal and the inverted input terminal of the comparator OP are equalized.
|
