Eccentricity measuring method and eccentricity measuring apparatus

• US 20050128468A1
• Filed: 11/09/2004
• Published: 06/16/2005
• Est. Priority Date: 11/28/2003
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Murata, Yasunori
• Granted Patent: US 7,307,708 B2
• Time in Patent Office: Days
• US Class Current: 356/127
• CPC Class Codes: G01M 11/0221 by determining the optical axis or position of lenses
• CPC Class Codes: G01M 11/0257 by analyzing the image formed by the object to be tested

Abstract

A surface to be tested and an optical system for projecting an index to an apparent spherical center position of the surface to be tested are moved relative to each other and an eccentric quantity of the surface to be tested is calculated from an movement quantity. A focal distance of an optical system is changed according to an apparent radius of curvature of each surface to be tested, which is calculated in advance. A reflection image on a surface to be tested, which is to be measured, is determined from the apparent radius of curvature of each surface to be tested, which is calculated in advance. Thus, an eccentric quantity of the entire lens system is accurately measured.

Claims

1. An eccentricity measuring method, comprising:

projecting an index to an apparent spherical center position of at least one surface to be tested through an optical system;

relatively moving the surface to be tested and the optical system based on a state of a reflection image of the index on the surface to be tested; and

calculating an eccentric quantity of the surface to be tested from a relative movement quantity between the surface to be tested and the optical system.

2. An eccentricity measuring method according to claim 1, wherein the projecting step, the moving step, and the calculating step are executed on each of a plurality of surfaces to be tested to calculate an eccentric quantity of each of the surfaces to be tested.

3. An eccentricity measuring method according to claim 1, wherein a focal distance of the optical system is changed based on an apparent radius of curvature of the surface to be tested when the index is projected to the apparent spherical center position of the surface to be tested through the optical system.

4. An eccentricity measuring method, comprising:

projecting an index to an apparent spherical center position of a surface to be tested through an optical system; and

calculating an eccentric quantity of the surface to be tested based on a state of a reflection image of the index on the surface to be tested,

wherein a focal distance of the optical system is changed based on an apparent radius of curvature of the surface to be tested when the index is projected to the apparent spherical center position of the surface to be tested through the optical system.

5. An eccentricity measuring method, comprising:

projecting an index to an apparent spherical center position of at least one surface to be tested through an optical system; and

calculating an eccentric quantity of the surface to be tested based on a state of a reflection image of the index on the surface to be tested,

wherein the projecting step and the calculating step are executed on each of a plurality of surfaces to be tested to calculate an eccentric quantity of each of the surfaces to be tested, and

wherein a reflection image to be measured on a surface to be tested is determined from an apparent radius of curvature of each of the surfaces to be tested, which is calculated in advance.

6. An eccentricity measuring apparatus, comprising:

means for calculating an apparent radius of curvature of a surface to be tested in advance; and

an optical system for projecting an index to an apparent spherical center position of the surface to be tested, a focal distance of the optical system being changeable based on an apparent radius of curvature of the surface to be tested, which is calculated in advance,

wherein the eccentricity measuring apparatus calculates an eccentric quantity of the surface to be tested based on a state of a reflection image of the index on the surface to be tested.

7. An index for an eccentricity measuring method of projecting the index to an apparent spherical center position of a surface to be tested through an optical system and calculating an eccentric quantity of the surface to be tested based on a state of a reflection image of the index on the surface to be tested, the index comprising:

cross lines having a first line and a second line which cross each other;

a one mark having a symmetric shape with respect to the first line; and

a one mark having a symmetric shape with respect to the second line.

8. An index according to claim 7, wherein a plurality of marks each having the symmetric shape with respect to the first line have sizes different from each other and a plurality of marks each having the symmetric shape with respect to the second line have sizes different from each other.

9. An index according to claim 8, wherein a first mark of the plurality of marks having the different size further from an intersection of the first line and the second line is larger than a second mark of the plurality of marks having different sizes closer to the intersection of the first line and the second line.