| 摘要 |
PURPOSE:To obtain a lens which is small in size and has its spherical aberration, coma aberration, curvature of field, and distortion aberration compensated by using a homogeneous sphere, a homogeneous hemisphere, and a flat plate which has a refractive index distribution. CONSTITUTION:Concave spherical surfaces 4 are formed in one surface of a 1st flat plate 31 which has the refractive index distribution in its depth direction nearby the surface an both surfaces of a 2nd flat plate 32 which has the refractive index distribution, the homogeneous sphere 1 which provides high refraction is sandwiched between the 1st and 2nd flat plates 31 and 32 in contact with the concave spherical surfaces 4, and the homogeneous hemisphere 2 is embedded in the other concave spherical surface 4; and the flat plate heterogeneous parts 31' and 32' of the 1st and 2nd flat plates 31 and 32 on the side of the homogeneous sphere 1 are increased in refractive index toward the homogeneous sphere 1 to compensate the spherical aberration and compensate the coma aberration by its distribution allotment, and the heterogeneous part 33' of the 2nd flat plate 32 on the side of the homogeneous hemisphere 2 is decreased in refractive index toward the homogeneous hemisphere 2 to the contrary to compensate the total curvature of field. Then the refractive index of the homogeneous hemisphere 2 is set low to compensate the distortion aberration. |
