| 摘要 |
PURPOSE:To produce a reflection mirror where a projection image is prevented from being double reflected, by forming many narrow annular grooves on the reflection surface on the front side of an approximately plane mirror body to form the reflection surface so that set slopes of sections of these grooves have one focal length. CONSTITUTION:A rear face 11 of an approximately plane resin mirror body 10 having a set thickness of a reflection mirror 3' is formed into an optical plane, and many narrow annular grooves 13 having a set size are close formed on a front face 12 in concentric circles at a prescribed pitch in the diametral direction. Respective grooves 13 have one focus 14, and an incident light 7' of parallel rays to the mirror 3' forms one focus 14 by grooves 13. if this mirror 3' is applied to an overhead projector 1', the incident light is made incident and reflected on the front face of the mirror 3' on a base 2, namely, grooves 13 on the front face 12 and passes a projection mirror 8, and an expanded image is projected on a screen omitted in the figure by a projection lens 9. The incident light and the reflected light which are transmitted through an original picture 5 are projected on the screen without forming a double image.
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