| 摘要 |
PURPOSE:To measure with a high accuracy an inclination and a displacement of a surface to be measured, by reflecting an emitted light which has been emitted hourly and alternately from two pieces of light sources, by the surface to be measured, and calculating an output of a position detecting element by this reflected light. CONSTITUTION:A voltage signal outputted by a light emission of a light source 13 and a light source 14, and a voltage signal which is not emitted by the light sources 13, 14 but has been outputted from a position detecting element 7 by being influenced by a disturbance light and has been amplified are brought to a digital conversion by A/D converters 21, 22 by a time division and inputted to an arithmetic circuit. When outputs of the position detecting element 7 by a light emission of the light source 13 are denoted as i1H, i2H, an outputs when both the light sources 13, 14 do not emit light are denoted as i1L, i2L, an operation corresponding to i1=i1H-i1L, and i2=i2H-i2L is executed in the arithmetic circuit, E=i1/(i1+i2) is calculated, and by correcting the derived E, a displacement l1 is derived. By i1H-i1L, and i2H-i2L, an influence by a disturbance light, etc., can be eliminated. In the same way, a displacement l2 is derived by a light emission of the light source 14. Also, an inclination alphato a reference surface of the surface to be measured can be derived by an operation.
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