Canon Kabushiki Kaisha

Yoshiki Maeda

Yasunori Furukawa

Yumiko Osaki

The method includes: calculating positional and angular magnification distributions of rays reflected by a reference aspheric surface on a light-receiving sensor and on a sensor conjugate surface; measuring a first wavefront of a reference light on the sensor; and calculating a second wavefront of the reference light on the sensor based on a parameter of an optical system. The method includes: moving at least two movable elements for calibration such that a difference between rotationally symmetric components of the first and second wavefronts becomes small; measuring, after the calibration, a third wavefront of the reference light on the sensor; measuring, after the calibration, a fourth wavefront of the measurement light on the sensor; and calculating the profile of the measurement object aspheric surface by using the third and fourth wavefronts, the positional and angular magnification distributions, and the profile of the reference aspheric surface.

Aspheric surface measuring method, aspheric surface measuring apparatus, optical element producing apparatus and optical element

The method for measuring profile of an aspheric surface projects an illumination light onto the aspheric surface and introduces a reflected light reflected by the aspheric surface to a sensor through an optical system. The method provides, to a wavefront of the illumination light, a curvature bringing an absolute value of an angle of the reflected light to a smaller value than a maximum value of absolute values of angles of optical system side peripheral rays, locates an exit pupil such that the absolute value of the reflected light angle is smaller than the maximum value, provides, to a sensor conjugate surface, a curvature and a position causing rays of the reflected light not to intersect on the sensor conjugate surface. The sensor conjugate surface, the wavefront of the illumination light and the aspheric surface have a same one of convex and concave surfaces toward a same direction.

The method includes: measuring a first wavefront of a reference light on a sensor by using the sensor; calculating a second wavefront of the reference light on the sensor by using a parameter of an optical system; changing an optical system parameter in calculation such that a difference between rotationally symmetric components of the first and second wavefronts becomes smaller; calculating, by using the changed parameter, a magnification distribution of rays of the reference light between on the sensor and on a sensor conjugate surface; measuring a first ray angle distribution of the reference light by using the sensor, and measuring a second ray angle distribution of a measurement light by using the light-receiving sensor. The method calculates the profile of the measurement object aspheric surface by using the profile of the reference aspheric surface, the first and second ray angle distributions and the magnification distribution.

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Utsunomiya, Japan

Yoshiki Maeda