| 摘要 |
PURPOSE:To resolve the problem that the precision of the normalized position signal of the calculation result of a normalizer deteriorates when an input fluctuation is generated on the normalizer by the fluctuation of the light quantity of the spot light on the photoelectric face of a position detecting element. CONSTITUTION:The added signal of position signals AS, BS of the first and second I/V converters 2, 3 is outputted from an adder 6, the added signal is converted into the added digital signal, and the gain switching signal is outputted from a decoder 8. Amplification factors of the first and second variable amplifiers 4, 5 are switched by the gain switching signal, and amplification position signals A, B keeping the level of the sum of the position signals AS, BS nearly constant are obtained. Amplification position signals A, B are inputted to a normalizer 9, and the position normalized signal of the spot light is obtained.
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