| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a reflection type image formation optical system in which a small f-stop number (FNO) and a short optical path are compatible with each other. <P>SOLUTION: In the reflection type image formation optical system having an image formation system composed, successively in the order from an image formation face side, of 3 reflection mirrors which are a first reflection mirror having a form of rotational symmetry face of which the concave face is directed toward the image formation face, a second reflection mirror having a form of rotational symmetry aspherical face of which the convex face is directed toward a luminous flux emitted from the first reflection mirror, a third reflection mirror having a form of rotational symmetry aspherical face of which the convex face is directed toward a luminous flux emitted from the second reflection mirror, the total power of the reflection type image formation system is denoted by ϕ, the powers of the first, the second and the third reflection mirrors are denoted by ϕ1, ϕ2 and ϕ3, respectively, and the Petzval sum is denoted by P, then conditions 0.01<ϕ1/ϕ<0.1...(1), ϕ3/ϕ<ϕ2/ϕ<0...(2), and 0.1<|P/ϕ|<0.5...(3) are satisfied. <P>COPYRIGHT: (C)2004,JPO |
