WAVEFRONT MEASUREMENT APPARATUS AND WAVEFRONT MEASUREMENT METHOD

• US 20180073957A1
• Filed: 09/27/2017
• Published: 03/15/2018
• Est. Priority Date: 03/27/2015
• Status: Active Grant

• Current Assignee: Olympus Corporation
• Original Assignee: Olympus Corporation
• Inventors: SATO, Yosuke
• Granted Patent: US 10,444,112 B2
• Time in Patent Office: Days
• CPC Class Codes: G01M 11/0214 Details of devices holding the object to be tested
• CPC Class Codes: G01M 11/0242 by measuring geometrical properties or aberrations
• CPC Class Codes: G01M 11/0257 by analyzing the image formed by the object to be tested

Abstract

A wavefront measurement apparatus includes alight source unit, a holding unit, a light reception optical system, a wavefront measurement unit, and a wavefront data generation unit. The light source unit is configured to apply light beams toward the subject optical system. The wavefront measurement unit is configured to measure light beams transmitted through the subject optical system. The wavefront data generation unit is configured to generate wavefront aberration data from results of the measurement by the wavefront measurement unit. A neighborhood of the opening portion and a neighborhood of the wavefront measurement unit are made to be optically conjugate with each other by the light reception optical system. The measurement of the light beams includes at least measurement of the light beams in a state in which a center of the opening portion is separated away from the measurement axis by a predetermined distance.

Claims

1. A wavefront measurement apparatus, comprising:

a light source unit;

a holding unit;

a first moving mechanism;

a light reception optical system;

a wavefront measurement unit;

a wavefront data generation unit;

a second moving mechanism;

a pre-rotation wavefront data acquisition control unit;

a post-rotation wavefront data acquisition control unit; and

a wavefront change data analysis unit, wherein

the light source unit is disposed on one side of a measurement axis,

the wavefront measurement unit is disposed on the other side of the measurement axis,

the holding unit is disposed between the light source unit and the wavefront measurement unit,

the light reception optical system is disposed between the holding unit and the wavefront measurement unit,

the holding unit has an opening portion configured to hold a subject optical system,

the light source unit is configured to apply light beams to the subject optical system,

the wavefront measurement unit is configured to measure light beams transmitted through the subject optical system,

the wavefront data generation unit is configured to generate wavefront aberration data from results of the measurement by the wavefront measurement unit,

a neighborhood of the opening portion and a neighborhood of the wavefront measurement unit are made to be optically conjugate with each other by the light reception optical system,

the first moving mechanism is configured to move the subject optical system to a plurality of positions around the measurement axis,

a transmission region of the light beam in the subject optical system is different at each of the plurality of positions,

the wavefront measurement unit is configured to measure a light beam transmitted through the subject optical system at each of the plurality of positions,

the wavefront data generation unit is configured to generate the wavefront aberration data from a result of the measurement at each of the plurality of positions,

the second moving mechanism is configured to rotate the subject optical system,

a first state is a state before the rotation by the second moving mechanism is performed,

a second state is a state after the rotation by the second moving mechanism is performed,

the pre-rotation wavefront data acquisition control unit is configured to move, in the first state, the subject optical system with respect to the measurement axis in a revolution orbit and store therein wavefront aberration data acquired at each of the plurality of positions in the revolution orbit,

the post-rotation wavefront data acquisition control unit is configured to move, in the second state, the subject optical system with respect to the measurement axis in a revolution orbit and store therein wavefront aberration data acquired at each of the plurality of positions in the revolution orbit, and

the wavefront change data analysis unit is configured to acquire wavefront aberration change data associated with the rotation by setting the wavefront aberration data acquired in the first state as reference wavefront data and setting the wavefront aberration data acquired in the second state as measurement wavefront data.

2. The wavefront measurement apparatus according to claim 1, wherein the opening portion, the light reception optical system, and the wavefront measurement unit are positioned such that the opening portion is made conjugate with the wavefront measurement unit.

3. The wavefront measurement apparatus according to claim 1, wherein the opening portion, the light reception optical system, and the wavefront measurement unit are positioned such that a rear principal point of the subject optical system is conjugate with the wavefront measurement unit.

4. The wavefront measurement apparatus according claim 1, wherein

the light reception optical system includes at least a front optical system located closest to the light source unit and a rear optical system located closest to the wavefront measurement unit, and

a rear focus position of the front optical system and a position of front focal point of the rear optical system are aligned with each other or conjugate with each other.

5. The wavefront measurement apparatus according to claim 1, further comprising a light projection optical system between the light source unit and the holding unit.

6. The wavefront measurement apparatus according to claim 1, wherein the light projection optical system is coaxial with the light reception optical system.

7. The wavefront measurement apparatus according to claim 1, wherein the light projection optical system is configured to generate condensed light beam.

8. The wavefront measurement apparatus according to claim 1, wherein the light projection optical system and the holding unit are positioned such that a position of condensing point of the condensed light beam is aligned with a position of front focal point of the subject optical system.

9. The wavefront measurement apparatus according to claim 1, wherein the light projection optical system is capable of being driven in a direction of the measurement axis.

10. The wavefront measurement apparatus according to claim 1, wherein the light projection optical system is a zoom lens.

11. The wavefront measurement apparatus according to claim 1, wherein the first moving mechanism is configured to rotate the subject optical system to change the transmission region.

12. The wavefront measurement apparatus according to claim 1, wherein

the first moving mechanism is configured to move the subject optical system with respect to the measurement axis in a revolution orbit, and

the wavefront measurement unit is configured to acquire the wavefront aberration data while the subject optical system moves in the revolution orbit.

13. The wavefront measurement apparatus according to claim 1, wherein the wavefront change data analysis unit is configured to perform Zernike fitting on the wavefront aberration change data acquired at each of the plurality of positions, and acquire Zernike wavefront aberration change data at each acquisition position.

14. The wavefront measurement apparatus according to claim 13, further comprising an aberration component amount extraction and analysis unit, wherein

the aberration component amount extraction and analysis unit is configured to, for Zernike wavefront aberration change data obtained in each of the states, subtract Zernike coefficients having pupil coordinates of even order in Zernike polynomials and add Zernike coefficients having pupil coordinates of odd order in Zernike polynomials between Zernike wavefront aberration change data that are symmetric about the measurement axis by 180 degrees to extract aberration components.

15. The wavefront measurement apparatus according to claim 1, further comprising a front-back inverting mechanism, wherein

the front-back inverting mechanism is configured to rotate the subject optical system around a rotation axis that is an axis orthogonal to the measurement axis.

16. The wavefront measurement apparatus according to claim 1, further comprising a rotation axis reference eccentricity amount calculation unit, wherein

the rotation axis reference eccentricity amount calculation unit is configured to calculate an eccentricity amount of the subject optical system with reference to a rotation axis from an analyzed displacement amount of each degree of freedom of eccentricity of each surface of the subject optical system.

17. A wavefront measurement method, comprising:

a step of making a neighborhood of a subject optical system and a neighborhood of a wavefront measurement unit to have an optically conjugate relation;

an eccentricity driving step of driving the subject optical system to be eccentric with respect to a measurement axis of a wavefront measurement apparatus; and

a wavefront data acquisition step of acquiring, by the wavefront measurement unit and a wavefront data generation unit, wavefront aberration data on a light beam transmitted through the subject optical system;

wherein

at the wavefront data acquisition step, acquisition of the wavefront aberration data is executed at a first state and a second state,

at the first state, the subject optical system is moved with respect to the measurement axis in a revolution orbit in a state before rotation,

at the second state, the subject optical system is moved with respect to the measurement axis in a revolution orbit in a state after rotation,

a wavefront aberration change data associated with rotation is acquired by setting a wavefront aberration data acquired in the first state as reference wavefront data, and setting a wavefront aberration data acquired in the second state as measurement wavefront data.