| 摘要 |
PURPOSE:To allow even reflected light from a lustrous sample to reache a photodetection surface, by arranging a refraction optical system for illuminating the sample between a light source and the sample at such an angle that the reflected light from the sample is made incident to the photodetection surface. CONSTITUTION:A Fresnel lens 5 has a flat surface as its front surface 5a and concentrical grooves in its rear surface 5b so that the section is in a sawtooth shape. Incident light 9 to the Fresnel lens 5 is refracted by the lens 5 and radiated as shown by projection light 10. Light 4a radiated from a light source 4 illuminates the sample 7 through the Fresnel lens 5 and reflected; all specularly- reflected components of the reflected light are made incident to the photodetecting element 6 because the light 4a from the light source 4 illuminates the sample 7 at the angle through the Fresnel lens 5. Therefore, not only diffused components, but also the specularly reflected components are measured, so the reflectance is measured regardless of the characteristics of the sample. |
