| 摘要 |
PURPOSE:To improve reading accuracy of Ronchi fringes and to measure the abberation of a nonspherical surface optical element quantitatively, automatically, and highly accurately, by intermittently moving an optical grating, which is arranged at or near the focal point of the nonspherical surface to be checked, detecting the optical intensity of a plurality of interference fringes, which are yielded at least at one fixed point on a projected surface, and judging the unevenness at the position of nonspherical surface based on the change in optical intensity with respect to a reference value. CONSTITUTION:Light from a point light source 3 is made to be parallel light 5 through a collimator 4. The parallel light is projected on a nonspherical surface lens 1 to be checked. A Ronchi grating 2 is placed at the position of paraxial focus. The Ronchi grating 2 is moved by a stage 6, which is controlled by a pulse motor, and the phase of the Ronchi grating 2 is changed. The Ronchi pattern is detected by a TV camera or a two dimensional image sensor 7, and undergoes A/D conversion by an image memory 8. The result is inputted to a computer 9. The phase of the Ronchi grating is changed and N sheets of the Ronchi patterns are recorded. Fringes are analyzed by a Fringe Scanning method. Then a traverse abberation pattern (linear differential of wavefront abberation) of the nonspherical surface lens 1 to be checked is obtained. The wavefront abberation is obtained by the integration of the patterns. |
