| 摘要 |
PROBLEM TO BE SOLVED: To take a photograph having a great depth of field, in which an image of a subject being several centimeters apart from a lens, including a distant view, is clear. SOLUTION: A subject image which has passed an objective lens of which the ratio f/D of a focal length f to an aperture D is low is projected on an imaging surface by a projection lens placed a prescribed distance apart from the objective lens. Though a photographic image is equivalent to an image photographed by a reduction image of the projection lens formed by the objective lens, photographing with the objective lens and the projection lens is equivalent to photographing with a wide angle lens having a very small aperture in the case that a low reduction magnification is given, and close-up photographing with a great depth of field is possible. Either of a convex lens and a concave lens can be used as the objective lens, and a convex lens is preferable when the objective lens is more approximated to the subject, and a concave lens is used for making an erect image visible on a finder when this lens system is attached to a single lens reflex camera. COPYRIGHT: (C)2006,JPO&NCIPI
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