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Measurement method and measurement apparatus

  • US 9,297,646 B2
  • Filed: 12/12/2011
  • Issued: 03/29/2016
  • Est. Priority Date: 12/17/2010
  • Status: Active Grant
First Claim
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1. A measurement method of measuring a surface shape of a measurement target surface using a measurement apparatus including a first optical system that illuminates the measurement target surface including an aspherical surface using light emitted by a light source, and a second optical system that guides the light traveling from the measurement target surface to a detection unit having a detection surface, the method comprising:

  • a first step of arranging a reference surface having a known aspherical shape on a plane conjugate to the detection surface, and detecting, with the detection unit at each coordinate in a coordinate system having a predetermined number of coordinates defined on the detection surface, angles of light traveling from the reference surface at which the light enters the detection surface;

    a second step of arranging the measurement target surface on the conjugate plane and detecting, with the detection unit at each of the coordinates in the coordinate system defined on the detection surface, angles of light traveling from the measurement target surface at which the light enters the detection surface;

    a third step of converting coordinates in the coordinate system defined on the detection surface that indicate positions where light traveling from the measurement target surface enters the detection surface into coordinates in a coordinate system defined on the measurement target surface;

    a fourth step of converting angle differences between the angles detected in the first step and the angles detected in the second step at each of the coordinates in the coordinates system defined on the detection surface into angle differences at each of a plurality of coordinates in the coordinate system defined on the measurement target surface that correspond to each of the coordinates in the coordinate system defined on the detection surface; and

    a fifth step of obtaining a difference shape between the surface shape of the measurement target surface and the known aspherical shape by integral calculation using the coordinates in the coordinate system defined on the measurement target surface that have been converted in the third step and the angle differences at the plurality of coordinates in the coordinate system defined on the measurement target surface that have been converted in the fourth step, and adding the difference shape to the known aspherical shape to calculate the surface shape of the measurement target surface.

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