| 摘要 |
PROBLEM TO BE SOLVED: To provide an inexpensive optical system consisting of the small number of optical elements by providing a 1st prism and a 2nd prism formed of a medium whose refractive index is larger than a specified value and forming the system of an image-forming system where the 2nd prism is arranged nearer to an image side than the 1st prism and which does not form an intermediate image. SOLUTION: This system is provided with the 1st and the 2nd prisms 10 and 20 formed of the medium whose refractive index is larger than 1.3, and formed of the image-forming system where the 2nd prism 20 is arranged nearer to the image side than the 1st prism 10 and which does not form the intermediate image. The 2nd prism 20 is provided with four optical action surfaces to transmit or reflect luminous flux, and at least, either of the 2nd surface 22 and the 3rd surface 23 has curved surface shape to give power to the luminous flux, and the curved surface shape has rotationally asymmetric surface shape to compensate aberration caused by eccentricity. The 1st prism 10 has a reflection surface to reflect the luminous flux in one-surface prism, and the reflection surface gives the power to the luminous flux and has the rotationally asymmetric surface shape to compensate the aberration caused by the eccentricity.
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