| 摘要 |
PURPOSE:To easily correct the positional shift of a focal point between at the detecting side and at the shape measuring side by calibrating an output of a dividing photodetec tor when the focal point is adjusted on the basis of the image data as an output when the focal point is set. CONSTITUTION:A luminous flux projected from a light source 9 enters a dichroic mirror 13 through a beam splitter 11, and is reflected at 90 deg. at the mirror 13 to pass through an objective lens 5. Therefore, the luminous flux form the light source 9 is cast to the surface of a work W, forming a spot corresponding to the cross sectional shape of the light source 9. The luminous flux reflected at the work W is, after passing through the lens 5, reflected by the mirror 13 towards the splitter 11. If the luminous flux from the lens 5 is a visible light, the luminous flux passes through the mirror 13. If the luminous flux is an infrared light, it is reflected by the mirror 13. Therefore, both the visible light from the surface of the work W and an infrared light for focus adjustment enters a CCD camera 7. Spots of the surface shape of the work W and of the luminous flux for focus adjustment are displayed in an overlapping manner on a monitor screen of the camera 7. The shape of the spot illuminated by a four- dividing photodetector 17 is changed in accordance with the shift of the focus. |
