MEASUREMENT METHOD, MEASUREMENT APPARATUS, AND METHOD OF MANUFACTURING OPTICAL SYSTEM
First Claim
1. A measurement method of measuring a light beam wavefront formed by a measurement target object using a measurement apparatus which includes an optical system having a reference surface and a detection unit having a detection surface, and detects, by the detection unit, an interference pattern, between a test light beam from one of the measurement target object and a standard surface and a reference light beam from the reference surface, formed on the detection surface by the optical system, the method comprising:
- a first measurement step of measuring a wavefront error attributed to the optical system by arranging the standard surface and detecting an interference pattern between a test light beam from the standard surface and a reference light beam from the reference surface by the detection unit;
a second measurement step of measuring a light beam wavefront formed by the measurement target object by arranging the measurement target object and detecting an interference pattern between a test light beam from the measurement target object and a reference light beam from the reference surface by the detection unit;
a first calculation step of calculating a first phase transfer characteristic which is a transfer characteristic of a phase of a light beam traveling through an optical path from the standard surface to the detection unit via the reference surface, and depends on a distance between the standard surface and the reference surface;
a second calculation step of calculating a second phase transfer characteristic which is a transfer characteristic of a phase of a light beam traveling through an optical path from the measurement target object to the detection unit via the reference surface, and depends on a distance between the measurement target object and the reference surface;
a third calculation step of calculating a first power spectrum density by Fourier-transforming the wavefront error measured in the first measurement step;
a fourth calculation step of calculating a second power spectrum density by Fourier-transforming the light beam wavefront which is formed by the measurement target object and measured in the second measurement step;
a fifth calculation step of calculating a reference power spectrum density of the wavefront error attributed to the optical system in the first measurement step based on the first phase transfer characteristic calculated in the first calculation step and the first power spectrum density calculated in the third calculation step;
a sixth calculation step of calculating a third power spectrum density of the wavefront error attributed to the optical system in the second measurement step based on the reference power spectrum density calculated in the fifth calculation step and the second phase transfer characteristic calculated in the second calculation step; and
a correction step of correcting the light beam wavefront, which is formed by the measurement target object and measured in the second measurement step, by separating the third power spectrum density calculated in the sixth calculation step from the second power spectrum density calculated in the fourth calculation step.
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Abstract
The present invention provides a measurement method of measuring a light beam wavefront formed by a measurement target object using a measurement apparatus which includes an optical system having a reference surface and a detection unit having a detection surface, and detects, by the detection unit, an interference pattern, between a test light beam from one of the measurement target object and a standard surface and a reference light beam from the reference surface, formed on the detection surface by the optical system.
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Citations
10 Claims
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1. A measurement method of measuring a light beam wavefront formed by a measurement target object using a measurement apparatus which includes an optical system having a reference surface and a detection unit having a detection surface, and detects, by the detection unit, an interference pattern, between a test light beam from one of the measurement target object and a standard surface and a reference light beam from the reference surface, formed on the detection surface by the optical system, the method comprising:
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a first measurement step of measuring a wavefront error attributed to the optical system by arranging the standard surface and detecting an interference pattern between a test light beam from the standard surface and a reference light beam from the reference surface by the detection unit; a second measurement step of measuring a light beam wavefront formed by the measurement target object by arranging the measurement target object and detecting an interference pattern between a test light beam from the measurement target object and a reference light beam from the reference surface by the detection unit; a first calculation step of calculating a first phase transfer characteristic which is a transfer characteristic of a phase of a light beam traveling through an optical path from the standard surface to the detection unit via the reference surface, and depends on a distance between the standard surface and the reference surface; a second calculation step of calculating a second phase transfer characteristic which is a transfer characteristic of a phase of a light beam traveling through an optical path from the measurement target object to the detection unit via the reference surface, and depends on a distance between the measurement target object and the reference surface; a third calculation step of calculating a first power spectrum density by Fourier-transforming the wavefront error measured in the first measurement step; a fourth calculation step of calculating a second power spectrum density by Fourier-transforming the light beam wavefront which is formed by the measurement target object and measured in the second measurement step; a fifth calculation step of calculating a reference power spectrum density of the wavefront error attributed to the optical system in the first measurement step based on the first phase transfer characteristic calculated in the first calculation step and the first power spectrum density calculated in the third calculation step; a sixth calculation step of calculating a third power spectrum density of the wavefront error attributed to the optical system in the second measurement step based on the reference power spectrum density calculated in the fifth calculation step and the second phase transfer characteristic calculated in the second calculation step; and a correction step of correcting the light beam wavefront, which is formed by the measurement target object and measured in the second measurement step, by separating the third power spectrum density calculated in the sixth calculation step from the second power spectrum density calculated in the fourth calculation step. - View Dependent Claims (2, 3, 4, 5, 6, 7, 9, 10)
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8. A measurement apparatus which includes an optical system having a reference surface and a detection unit having a detection surface, and measures a light beam wavefront formed by a measurement target object by detecting, by the detection unit, an interference pattern, between a test light beam from one of the measurement target object and a standard surface and a reference light beam from the reference surface, formed on the detection surface by the optical system, the apparatus comprising:
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a control unit configured to perform control so as to measure a wavefront error attributed to the optical system by arranging the standard surface and detecting an interference pattern between a test light beam from the standard surface and a reference light beam from the reference surface by the detection unit, and so as to measure a light beam wavefront formed by the measurement target object by arranging the measurement target object and detecting an interference pattern between a test light beam from the measurement target object and a reference light beam from the reference surface by the detection unit; and a processing unit configured to perform a process associated with calculation of the light beam wavefront formed by the measurement target object, wherein said processing unit calculates a first phase transfer characteristic which is a transfer characteristic of a phase of a light beam traveling through an optical path from the standard surface to the detection unit via the reference surface, and depends on a distance between the standard surface and the reference surface, calculates a second phase transfer characteristic which is a transfer characteristic of a phase of a light beam traveling through an optical path from the measurement target object to the detection unit via the reference surface, and depends on a distance between the measurement target object and the reference surface, calculates a first power spectrum density by Fourier-transforming the wavefront error measured, calculates a second power spectrum density by Fourier-transforming the light beam wavefront which is formed by the measurement target object and measured, calculates a reference power spectrum density, when the wavefront error attributed to the optical system is measured, based on the first phase transfer characteristic and the first power spectrum density, calculates a third power spectrum density of the wavefront error attributed to the optical system, when the light beam wavefront formed by the measurement target object is measured, based on the reference power spectrum density and the second phase transfer characteristic, and corrects the light beam wavefront, which is formed by the measurement target object and measured, by separating the third power spectrum density from the second power spectrum density.
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Specification