| 摘要 |
PURPOSE:To equlize quantities of light at the center and periphery of a visual field, by providing a blocking plate for blocking a part of luminous flux to the center (on the optical axis) of the visual field increased in quantity of light from the periphery thereof. CONSTITUTION:A blocking plate 14 is arranged on the optical axis between lenses 11, 12. When luminous fluxes by the light at the center of a visual field and light having an angle theta to the optical axis at the periphery of the visual field are cobserved at the position between the lens 12 and an image pick-up tube 13, said luminous fluxes come to shapes shown by numerals 17a, 17b, 17c as go to the periphery of the visual field from the center thereof. These luminous fluxes form images at positions 18a, 18b, 18c on the surface of the image pick-up tube 13. the light intensity distribution on the surface of the image pick-up tube is reduced and uniformized by the effect of the blocking plate 14 so that the quantity of light at the center of the visual field becomes equal to the quantity theta of light (relative ratio) at the periphery thereof. This blocking plate 14 is constituted so that the diameter of the outer periphery of the outer circle 14a thereof is same to that of each of the lenses 11, 12 and arranged at the center of the optical axis by connecting a blocking inner circle 14b by a connection part 14c.
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