| 摘要 |
PURPOSE: To obtain an optical system which is capable of illuminating a visual field range of a wide angle to be observed with more uniformly distributed light from its center to its periphery and has less loss of the light quantity by Fresnel reflection by consisting this optical system of one positive lens and forming this positive lens so is to satisfy specific conditions when rays parallel with the optical axis of the positive lens are made incident on the positive lens. CONSTITUTION: This optical system consists of the one positive lens. The positive lens is so formed as to satisfy the two following conditions;|W(y1 )|,|W(y3 )|>=|W(y2 )|and 0<|y1|<|2|<|y3|<ED when the rays parallel with the optical axis of the positive lens are made incident on the positive lens. In the equation, y1 to y3 denote the ray heights before the rays parallel with the optical axis are made incident on the positive lens when the optical axis is taken as x-axis and the direction perpendicular to the optical axis as y-axis; W(y1 ), W(y2 ), W(y3 ) respectively denote the angles with the optical axis when the rays of the ray heights y1 to y3 parallel with the optical axis are emitted after passage through the lens and ED denotes the effective radius of the positive lens.
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