| 摘要 |
PURPOSE:To take a measurement at one point in a rotatable lens to be inspected in a short time by mounting the rotatable lens to be inspected, and the 2nd and the 1st positioning tables which move a Ronchi grating with a scanner in optical-axis directions respectively on the 2nd rotary table. CONSTITUTION:Parallel light exiting from a light source 100 is focused nearby the surface of the Ronchi grating through the lens 18 to be inspected. When the Ronchi grating 41 is scanned forth and back once as shown by an arrow (a) in said state, a measuring instrument 43 detects the peak value A and bottom value B of the output waveform of the photoelectric conversion part 21 of a photodetecting device 98. Those values and position data on the 1st positioning table 36 are used to calculate an MTF value. A radial Ronchi grating pattern and a tangential Ronchi grating pattern can be scanned by the single-time reciprocation of the Ronchi grating 41, so a radial MTF value is measured in the reciprocation and a tangential MTF value is measured in the return motion. Thus, the MTF values at one point in the object lens 18 are measured during the single-time reciprocation of the Ronchi grating 41. |
