| 摘要 |
An illumination system for telecentric illumination throughout a wide variation range of magnification while keeping a large distance to an object to be illuminated is disclosed. The telecentric illumination system comprises a first lens group which is convergent and remains fixed when the magnification is varied; a second lens group which is divergent and movable along the the optical axis; a third lens group which is convergent and movable along the optical axis; a fourth lens group which is convergent and remains fixed when the magnification is varied; and a light source located at the focal point of the fourth lens group. The second and third lens groups are moved along the optical axis in a determined relation so as to make an imge of the light source formed between the first and third lens groups thereby changing the state of illumination between that for high magnification and that for low magnification.
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