| 摘要 |
PURPOSE:To obtain a light detector in which index signals of full intensity are obtained on all points of a focusing plate by forming light emitting end surfaces on both corner parts of a planar light conducting body and equipping the respective light emitting end surfaces with light receiving surfaces made of photoelectric converting elements. CONSTITUTION:Both end corner part of an upper end side 14a of a rectangular focusing plate 14 are cut to form light emitting end surfaces 14c. Photodiodes 13 and 13 are disposed on these light emitting end surfaces 14c so that light receiving surfaces 13a face each other. The light-receiving surfaces 13a of the photodiodes 13 and 13 are disposed to become perpendicular to imaginary straight lines coming from a central point (c) of a lower end side 14b of the focusing plate 14. In this composition, because index signals of full strength are obtained on all points of the focusing plate 14, a contrast of an image at the time of black level regeneration can be improved with a small beam current when the focusing plate 14 is used in a beam index type color picture tube.
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