JPS6415631A - Apparatus for measuring scattering rate of reflecting mirror - Google Patents

Abstract

PURPOSE:To shut out ghost, by forming a light outputting port and a light detecting body so that their shapes are approximately the same as the luminous fluxes of a beam at positions corresponding to light path lengths from the emitting position of the beam to an introducing port and to a measuring surface. CONSTITUTION:A body to be measured 13 and a photodetector 14 are provided in a symmetrical pattern on both sides of a central point C on the diameter of a reflecting body 10, whose inner surface is a semispherical mirror. A laser beam L from a laser oscillator 12 is made to pass through an introducing port 15 and inputted into the body to be measured 13. The reflected light is outputted to the outside through a light passing out port 16. A diameter D2 of the outputting port 16 and a diameter D3 of the photodetector are set as shown in the Expression in the Figure. The scattered light at a measuring surface is reflected with a semispherical mirror 11. The diameter of the luminous flux of each scattered light at the position of the photodetector 14 becomes the same as the diameter of the luminous flux of the beam L at the measuring surface 13a. Thus the light is condensed. When a diameter D1 of the beam is made to be the same as the diameter D3 of the photodetector, ghost, which does not go out of the reflecting body 10 through the port 16, advances at the outside of the photodetector 14 and is not detected.