| 摘要 |
PROBLEM TO BE SOLVED: To accurately, easily and consecutively change a focal distance by changing the thickness of a lens so that a refraction degree may be gradually changed from one end to the other end of a lens long sideways. SOLUTION: The convex lens 1 of this variable focal distance lens is formed to be semicylindrical, and its front surface is round and its back surface is smooth. The reflection degree of the lens 1 is different between both ends but the difference is not stepwise and is made by gradual change. A normal image is not obtained by such a lens 1, but an image having no obstacle in practical use is obtained by combining two lenses so that both lenses correct a shortcoming each other. Since both lenses 1 are bonded at a B part 3, the focal distance is the longest, and when both lenses 1 are shifted and bonded at an A part 2, the focal distance is the shortest. Furthermore, the focal distance is changed and selected by stopping the lens 1 in the midst of shifting.
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