| 摘要 |
PROBLEM TO BE SOLVED: To permit the measurement of the aberration of an image-forming optical system such as one to converge extremely intense energy by multiplying the size of a light source pinhole by (m) and providing a reducing optical system of a multiplication of 1/m after the light source pinhole. SOLUTION: Quasi-monochromatic light emitted from the same light source 1 as an exposure light source is transmitted through a mirror 2, a beam expander, etc., and is converged on a pinhole 4 by a converging lens 3. Here, the size of a light source pinhole is multiplied by (m), and a reducing optical system of a multiplication of 1/m is provided after the light source pinhole. By this, as the density of irradiation energy on the light source pinhole is reduced by a multiplication of 1/m, it is possible to prevent pinholes from destruction. The light diffracted by the pinhole 4 becomes ideal spherical waves and becomes incident onto a test optical system 6 as measuring light. The measuring light is magnified and brought into forming an image on a mask 11 via the first objective lens 7, a half mirror 8, and the second objective lens 9 and is divided into a plurality of beams of diffracted light. A reference wavefront and a test wavefront are superimposed to an image pickup device 13 by a lens 12 to form interference fringes.
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