| 摘要 |
PURPOSE:To reduce the size of an optical system, eliminate the need for adjustment between a lens and lighting optical part in the stage of constituting the optical system and to form the lighting part which is stable with a secular change by injecting or diffusing a material having the refractive index different from the light refractive index of a light transmittable part to at least part of said member thereby forming a refractive index distribution region having a lens effect. CONSTITUTION:A wavelength plate 1 is formed by diffusing thermally the material (for example, zinc) having the refractive index higher than the refractive index of a conventional wavelength plate 2 to the plate 2 to the radial concn. distribution from the center as shown by dots in the figure (a) to build a distributed refractive index region 3 therein. The material is so diffused into the region 3 as to maintain the refractive index difference (ne-n0) where the normal refractive index of the plate 2 is designated as n0 and the abnormal refractive index as ne. The n0, ne refractive index characteristic of the wavelength 1 exhibits the arc shape distribution in which the refractive index difference is maintained within the region 3 and is max. in the central position as shown by the solid line in the figure (b). The refractive index distribution plays consequently the same role as the role of a lens. The wavelength plate 2 is thus made into the constitution in which the wavelength plate 1 and the lens are united to one body.
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