| 摘要 |
PURPOSE:To eliminate influences of direction deviation of optical beams due to the variation of a light source by providing an optical element which inverts the passing position of one of two divided optical beams in the longitudinal direction. CONSTITUTION:One optical beam 8d divided by a beam splitter 2 passes an image rotator 3 and is irradiated to an object 6 to be examined together with the other optical beam 8c. If the beam 8a is varied by the variation of a light source 1 at this time, these optical beams are moved symmetrically with respect to an optical beam 8e and are moved symmetrically also on the light receiving face of a PSD (optical position detector) 9. Consequently, variation components of the light source in the division direction are eliminated. With respect to variation components of the light source in the direction orthogonal to said division direction, the fact that the passing position of the optical beam is inverted by the rotator 3 is used to invert the variation direction of an optical beam 8d', and this optical beam is shifted symmetrically to the optical beam which does not pass the rotator 3. Thus, horizontal and vertical variation components are compensated, and a certain output is obtained though the light source is varied in an optional direction. |
