| 摘要 |
This specification discloses a focusing screen adapted to be mounted in the range finder of a single lens reflex camera. A diffraction lattice is provided in the focus indicating part of the focusing screen. The diffraction lattice comprises a periodical arrangement of optically asymmetric unit structures in which +1st diffracted light and -1st diffracted light assume a color-complementing relation, and in the defocus (out of focus) condition, double images colored in two colors mutually having a color-complementing relation are produced. Further, this diffraction lattice structure is such that the period directions are opposite to each other in the upper and lower half areas of the focus indicating part and therefore, the manner of coloring is inversely symmetric in the upper and lower areas and color split occurs even at the bondary between these areas. These phenomena disappear when the focus condition is brought about.
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