| 摘要 |
Light horizontally output from a light source 50 passes through a projection lens 51 and reaches a half mirror 52 . The light reflected by the half mirror 52 coaxially reaches the measurement object 43 through a objective lens 53 . The light reflected by the objective lens 53 provides an image at a image-taking unit 56 through a telecentric optical system on an object side comprising the objective lens 53 and an aperture stop 54 . The light to be input to the image-taking unit 56 passes through a spectral filter provided in a multi-spectral filter 55 . Here, the light source 50 and the aperture stop 54 are in an image-forming relation and the object 43 and the image-taking unit 56 are in the image-forming relation. In addition, a numerical aperture on an image side in a light-projecting optical system is greater than a numerical aperture on an object side in a light-receiving optical system, and the light source 50 outputs light which has a certain degree of divergence and forms an image having uniform light intensity at the aperture stop 54.
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