Takashi NOMURA,¹ Kazuhide KAMIYA,¹ Hiroshi MIYASHIRO,¹ Hatsuzo TASHIRO² and Kazuo YOSHIKAWA²

¹Department of Mechanical Systems Engineering, Faculty of Engineering, Toyama Prefectural University, Kosugimachi Toyama, 939-03 Japan, ²Department of Mechanical Systems Engineering, Faculty of Engineering, Toyama University, Gofuku, Toyama, 3190 Japan

(Accepted November 21, 1995)

A compact zone-plate interferometer is developed to measure the shape error of concave mirrors. A diffracted light of (0, 0) and that of (–1, –1) or (+1, +1) are used in the interferometer. The interferometer enables us to measure the shape error of mirrors with a large numerical aperture and a steep asphericity. The shape errors of a spherical mirror and a parabolic mirror are measured by the interferometer, and that of the former agrees well with that measured by Fizeau interferometer. Methods for adjustments of zone plates and the mirrors being tested are proposed to perform precise measurements of the mirror shapes.

Key words : zone-plate interferometer, shape measurement of mirror, on-machine measurement, computer generated hologram, large numerical aperture, aspherical mirror