Abstract
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.
