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Shape measurement apparatus and shape measurement method

  • US 8,310,536 B2
  • Filed: 07/18/2008
  • Issued: 11/13/2012
  • Est. Priority Date: 07/18/2007
  • Status: Active Grant
First Claim
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1. A shape measurement apparatus comprising:

  • a light transmission element configured to transmit light to a chamfer processed end part of a disk-shaped measurement target from a direction substantially parallel to respective front and rear surfaces of the measurement target;

    an image pickup device configured to pick up a projection image of an end surface of the measurement target from a direction opposite to the light transmitting direction;

    a rotation supporting mechanism configured to rotatably support the measurement target in a circumferential direction thereof;

    a rotation control device configured to support the measurement target by the rotation supporting mechanism in a range from a first supporting position rotated by a predetermined first set angle with respect to a predetermined reference supporting position to a second supporting position rotated by a predetermined second set angle having an opposite positive or negative sign with respect to the first set angle at two or more supporting positions including the first supporting position and the second supporting position;

    an image pickup control device configured to pick up by the image pickup means the projection image of the end surface of the measurement target supported by the rotation control means at the two or more supporting positions;

    an index value calculation device configured to calculate an index value of an end surface shape by executing a previously set image processing for each of a plurality of projection images obtained through a processing by the image pickup control device; and

    a measurement value derivation device configured to derivate a measurement value for the shape of the end surface of the measurement target corresponding to the reference supporting position by selecting one representative value based on the plurality of index values calculated by the index value calculation device or calculating one aggregate value while following a previously set rule, wherein in a case where the first set angle is denoted by +δ

    1 and the second set angle is denoted by −

    δ

    2, the δ

    1 and the δ

    2 satisfy the following expression;


    δ

    1≧

    cos

    1
    ((r−

    k
    )/r)
    δ

    2≧

    cos

    1
    ((r−

    k
    )/r)r;

    Radius of the measurement targetk;

    Chamfer width of the end surface of the measurement target.

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