| 摘要 |
<p>PROBLEM TO BE SOLVED: To obtain a clear-cut image of an interference fringe in an entire inspected plane surface.SOLUTION: An optical system 10 is used in a surface shape measurement device 100 measuring a shape of an inspected plane surface 5 on the basis of an interference fringe to be formed by interfering reference light with measurement light reflected upon the inspected plane surface 5, and is the optical system that converts the measurement light into parallel light having a diameter of a flux of light enlarged, and makes the converted measurement light incident to the inspected plane surface 5. The optical system is composed of, in order from the side distant from the inspected plane surface,: a lens group 3 that has a positive refractive power as a whole; and a concave surface reflection mirror 4 that reflects transmission light of the lens group 3 and converts the transmission light thereof into the parallel light and makes the converted transmission light incident to the inspected plane surface 5. Of the lens group 3, a lens closest to a condensing point of the measurement light is a concave lens for correcting a Petzval sum.</p> |
