# US 7,609,389 B2 · Measurement apparatus for measuring surface map

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- Number: US 7,609,389 B2
- Document ID: US7609389B2
- Status: Granted
- Kind: B2
- Application number: 12/022,368
- Filed: 2008-01-30
- Published: 2008-08-07
- Granted: 2009-10-27
- Earliest claimed: 2008-01-30
- Assignees: Canon Kabushiki Kaisha
- Inventors: Saori Hasegawa
- Web page: https://patentgrep.com/patent/US7609389B2

## CPC

- G01B 9/02039: {by matching the wavefront with a particular object surface shape}
- G01B 9/02057: {by using common path configuration, i.e. reference and object path almost entirely overlapping}
- G01B 9/02087: {Combining two or more images of the same region}
- G01B 11/306: {for measuring evenness}
- G01B: MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS

## Abstract

A measurement apparatus for measuring a surface map comprises an image sensor, an optical system including a reference surface and arranged to form an interferogram of a reflected wavefront from a test surface and that from the reference surface on an image sensing surface of the image sensor and a calculation unit which calculates a surface map of the measurement target based on the interferogram. The calculation unit calculates the surface map of the measurement target by utilizing first data which expresses, by a first coordinate system, data in a state in which a central axis of the test surface is at a first angle to an optical axis of the optical system, and second data which expresses, by a second coordinate system obtained by shifting the first coordinate system, data in a state in which the central axis is at a second angle to the optical axis.

## Claims

### Claim 1

A measurement apparatus for measuring a surface map, the apparatus comprising:
an image sensor;
an optical system including a reference surface and arranged to form an interferogram of a reflected wavefront from a test surface of a measurement target and that from said reference surface on an image sensing surface of said image sensor; and
a calculation unit which calculates a surface map of the measurement target based on the interferogram,
wherein said calculation unit calculates the surface map of the measurement target by utilizing first data which expresses, by a first coordinate system, data on an image taken by said image sensor in a state in which a central axis of the test surface is at a first angle to an optical axis of said optical system, and second data which expresses, by a second coordinate system obtained by shifting the first coordinate system, data on an image taken by said image sensor in a state in which the central axis of the test surface is at a second angle to the optical axis of said optical system,
wherein each of the first coordinate system and the second coordinate system comprises a coordinate system in which an angle is uniformly divided, that is, a unit scale is equal to an angle obtained by uniformly dividing an angle formed by the optical axis of said optical system and a marginal ray.

### Claim 2 (depends on 1)

The apparatus according to claim 1, wherein the state of the first angle comprises a state in which the central axis of the test surface coincides with the optical axis of said optical system.

### Claim 3 (depends on 1)

The apparatus according to claim 1, wherein a surface of the measurement target comprises a spherical surface.