| 摘要 |
PURPOSE:To prevent the change of the luminous intensity characteristic and the spectral characteristic even if the illumination intensity is varied, by providing an aperture varying the quantity of passing light and a light diffusing means on an optical path. CONSTITUTION:An aperture 15 which controls variably the quantity of illuminating light, a focusing lens 16 which focuses a narrowed light, and a diffusing plate 17 placed in the focus position are provided on the optical path between an illuminating lamp 12 and a condenser lens 14. The quantity of passing light of the aperture 15 is adjusted variably automatically or manually. The light narrowed by the aperture 15 is focused on the diffusing plate 17 by the focusing lens 16, and most of the light is condensed by the condenser lens 14 and is irradiated to the incidence end of a light guide 10. Thus, the luminous intensity characteristic and the spectral characteristic of the light irradiated to the object side from the exit end of the light guide 10 are kept constant independently of the adjustment of the quantity of light.
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