| 摘要 |
PURPOSE:To produce a stable binary image and to correctly inspect the configuration of an object even when the object is a transparent thin plate of a film. CONSTITUTION:A pair of polarizing plates 13, 14 are provided on an optical path 16 between a light source 11 and a diffusion plate 12 in a manner that the planes of polarization are orthogonal to each other. The diffusion plate 12 is located between the light source 11 and one polarizing plate 13. An object 10 to be inspected is introduced in between the polarizing plates 13 and 14 for inspection. Part of the light incident upon the object 10 enters slantwise and therefore, the direction of polarization of the light is changed. As a result, the light not passing the object 10 is completely shut by the polarizing plate 14, whereas part of the light passing the object 10 penetrates the polarizing plate 14. Accordingly, the amount of light observed by a photographing device 15 differs, so that the image of the object can be binarized in a stable manner. |
