Patent ID: 9279667
Filing Date: 2016-03-08
CPC Classification: G01B,G01M,G02B

Claim Text:
1. An aspheric surface measuring method of measuring a profile of a measurement object aspheric surface using output from a light-receiving sensor to which a measurement light projected onto and reflected by the measurement object aspheric surface is introduced through an optical system, the method comprising: a step of providing a reference aspheric surface whose profile has been measured; a step of calculating (a) a positional magnification distribution of rays of a reference light, which is projected onto and reflected by the reference aspheric surface and is introduced to the light-receiving sensor through the optical system, using a distance on the light-receiving sensor from a position corresponding to an optical axis of the optical system to an incident position of each of the rays and a distance on a sensor conjugate surface from a position corresponding to the optical axis to an incident position of that ray, the sensor conjugate surface being located at a position conjugate with the light-receiving sensor with respect to the optical system and (b) an angular magnification distribution of the rays of the reference light using a change amount of a reflection angle in a meridional plane on the sensor conjugate surface with respect to a tilt of the reference surface and a change amount of an incident angle in a meridional plane on the light-receiving sensor with respect the tilt of the reference surface; a step of measuring a first wavefront of the reference light on the light-receiving sensor using the output from the light-receiving sensor; a step of calculating a second wavefront of the reference light on the light-receiving sensor using a parameter of the optical system; a calibration step of moving at least two movable elements among part of the optical system, the reference aspheric surface and the light-receiving sensor so that a difference between rotationally symmetric components of the first and second wavefronts becomes smaller than a predetermined value; a step of measuring, after the calibration step, a third wavefront of the reference light on the light-receiving sensor using the output from the light receiving sensor; a step of measuring, after the calibration step, a fourth wavefront of the measurement light on the light-receiving sensor using the output from the light receiving sensor; and a step of calculating the profile of the measurement object aspheric surface using the third wavefront, the fourth wavefront, the positional magnification distribution, the angular magnification distribution and the profile of the reference aspheric surface.