A high spatial frequency modulation transfer function (MTF) of a lens has been obtained by scanning a line image with a knife edge. Practical limit of the spatial frequency for a camera lens is about lOO/mm at the utmost. However, this apparatus, aiming at measuring high resolution lenses, can measure MTF's at the spatial frequency up to 1, 000 1ines/mm. To design this apparatus, the following components have been developed a knife edge using 18-carat gold, a moving coil type scanner, a digital-to-analogue converter type scanner driver circuit and a slit. The MTF was measured at the spatial frequency of 500 1ines/mm on the axis of the lens under test within 5% discrepancy to the calculated value.

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We designed a sensibility-variable flatness tester by use of interference by the obliquely impinging light. Its purpose was to test the flatness of emulsion layer coated on a glass substrate. In searching for the testing method, we considered the following requirements; (1) to test the emulsion surface, (2) to use in the mass production process. We adopted a method utilizing interference fringes of equal thickness by obliquely impinging light, the source of which was a He-Ne laser and as the standard surface was used a base surface of an isosceles prism. The sensibility is varied by exchanging the several kinds of prisms having different sensibility. Because of a long coherence length of the laser light, the interference fringes between the emulsion surface and the rear surface of the glass substrate of the emulsion appear with equal visibility to the interference fringes between the emulsion surface and the standard surface. To remove the undesirable interference frings, there is used a combination of the converging optical system and a rotating diffusing plate, and the visibility of noise interference fringes could exclusively decreased. The difference of the reflection characteristics between the standard surface and the test surface including the state of the polarization of the obliquely impinging light becomes the cause of reduction in the visibility of the interference fringes. This problem was solved by adjusting the state of polarization of the impinging elliptic polarized light and by using an analyzer. This flatness tester is capable of wide application not only testing flatness of emulsion surface but to many kinds of surfaces.

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