| 摘要 |
PURPOSE:To eliminate the influence of fluctuations of temperature and a secular change of a light source by controlling the quantity of light of the light source so that the sum of output signals of photodetecting elements is constant through a reflactive position detector which uses a quantity-of-light controlling means and two photodetecting elements. CONSTITUTION:Light from a light emitting element 14 reaches two photodetecting elements 15 and 16 through slits 12 and 13 of a light shielding plate 11. The circuit including operational amplifiers 18 and 19 converts output currents of photodetecting elements 15 and 16 into voltages V1 and V2, whose mean value V0=(V1+V2)/2 appears at a terminal 25. This output corresponds to a difference in diode current 9 by signal light and varies with the position X of the photodetecting element. An output V2 is inverted by inverters 19, 28, and 32 and added to V1 by adders 26, 33, and 27 to obtain the sum of the outputs of those two photodetecting elements. So that this sum output is constant, the current of the light emitting element is brought under feedback control, thereby preventing the output V0 from being influenced by fluctuations of temperature and deterioration of the ligh source. |
