US 8,570,532 B2Granted

Noncontact surface shape measuring method and apparatus thereof

AssigneeMitaka Kohki Co., Ltd.

InventorsKatsuhiro Miura, Hajime Hirose, Hideo Kotajima, Takao Tsukamoto, Minoru Ishima

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Abstract

Even if a return beam from a work to be measured does not agree with the center of a two-piece sensor, a correction value is calculated according to a voltage difference between two sensors of the two-piece sensor if the voltage difference is within a neighborhood range. The correction value is added to an actual position of an objective lens in an up-down direction, to calculate a movement amount of the objective lens up to a focused state (a state in which the return beam agrees with the center of the two-piece sensor).

Claims8

Dependent claims

A noncontact surface shape measuring method for carrying out autofocusing control by way of a laser probe in an up-down direction with respect to a surface of a work, continuously scanning the work in a horizontal direction, and measuring a surface shape of the work according to a displacement amount in the up-down direction of an objective lens in an autofocusing optical system that is controlled so that a return beam of the laser probe is received at the center of a two-piece sensor, the noncontact surface shape measuring method comprising:

detecting a voltage difference between two sensors of the two-piece sensor and detecting whether or not the detected voltage difference is within a neighborhood range in which a voltage difference is substantially proportional to a displacement from an in-focus position;
calculating, if the detected voltage difference is within the neighborhood range, a correction value for a position of an objective lens in the up-down direction with respect to the in-focus position;
and
adding the correction value to an actual position of the objective lens in the up-down direction, to calculate a movement amount of the objective lens in the up-down direction.

1 more element

A noncontact surface shape measuring apparatus for carrying out autofocusing control of a laser probe in an up-down direction with respect to a surface of a work to be measured and measuring a surface shape of the work according to a displacement amount in the up-down direction of an objective lens in an autofocusing optical system, comprising:

a scanner configured to continuously scan the work in a direction that is horizontal with respect to an optical axis of the objective lens;
and
a controller configured to control a movement amount of the objective lens in the up-down direction so that a return beam of the laser probe is received at the center of the two-piece sensor, wherein the controller:
detects a voltage difference between two sensors of a two-piece sensor and detects whether or not the detected voltage difference is within a neighborhood range in which a voltage difference is related to a displacement from an in-focus position;
calculates, if the detected voltage difference is within the neighborhood range, a correction value for a position of an objective lens in the up-down direction with respect to the in-focus position;
and
adds the correction value to an actual position of the objective lens in the up-down direction, to calculate a displacement amount of the objective lens in the up-down direction.

4 more elements

Dependencies are inferred from the claim text.