| 摘要 |
<p>PURPOSE:To provide a device for accurately detecting a focal point on the surface of an object that is transparent to visible light. CONSTITUTION:An infrared beam from an infrared source 12 is passed through a field lens 2 to a slit member 3, and the image of the slit is passed through an object lens 4A and formed on the surface 5a of a glass substrate 5. The slit image on the surface 5a is passed through an object lens 4B and formed on a slit member 6. Light passing through the slit of the slit member 6, which is vibrating, is received by a photodetector 8 through a collector lens 7. Infrared ray is absorbed in the substrate 5, thus suppressing the internal reflection toward the surface 5a.</p> |
