| 摘要 |
PROBLEM TO BE SOLVED: To ensure a required measurement accuracy of MTF by specifying fluctuation in the scanning position of a scanning slit and thereby the positional accuracy. SOLUTION: A light from a light source is passed through an emission side slit to an optical system to be inspected and a receiving side slit is located at the position of a slit image formed through the optical system to be inspected. While scanning any one of these slits, the quantity of light passing through the receiving side slit is measured and MTF of the optical system to be inspected is determined based on the measurements. A scanning slit is positioned to satisfy a following condition; 0.01.A>=(ε.ν/2.10<1/2> ), when the measurement accuracy of MTF is A%, the measuring frequency isνand fluctuation in the scanning position of the scanning slit is±ε.
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