| 摘要 |
PURPOSE:To enable high-speed sampling to be performed for a zone having a small measurement area such as a water scale division by using a semiconductor laser beam as an illuminant. CONSTITUTION:Linearly polarized light 2 from a semiconductor laser 1 is converted to circularly polarized light 21 via a collimator 3 and a 1/4 wavelength plate 4. The circularly polarized light 21 passes a beam displacing prism 22, and becomes parallel laser beams 26 and 27 with optical axes relatively displaced for P- and S-polarized light. The laser beam 26 and 27 collides with the surface of a printing plate 6, and the quantity of regular reflected light for both P- and S-waves is branched into a half with a half-mirror 23, and separated into the light receiving side of the P-polarized light wave 26 and the light receiving side of the S-polarized light wave 27. Light receiving constitution for the P-wave interrupts the S-wave and, therefore, the voltage signal 31 of a P-wave component is obtained by a receiver lens 24 and a laser detecting element 25. Light receiving constitution for the S-wave also interrupts the P-wave and permit the passage of only the S-wave. The voltage signal 32 of a S-wave component is obtained by a receiver lens 7 and a laser detecting element 8. Also, the voltage signals 31 and 32 are calculated from the voltage signals of the P- and S-waves by a signal processor 9, thereby calculating the thickness of a water screen on the plate 6. |
