Wavefront Curvature Sensing Method Based on Rotating Pupil

Abstract

The present invention provides a wavefront curvature sensing method based on a rotating pupil, which includes: S1, placing a first cylindrical mirror and a second cylindrical mirror vertically arranged between a camera and a stepped element, and compressing the image formed by the incident light into a point light spot through the first cylindrical mirror and the second cylindrical mirror, and using this point light spot as the center of the image; S2, removing the second cylindrical mirror, imaging the incident light, registering the image formed by the incident light by using the center of the image, and obtaining the curvature perpendicular to the direction of the first cylindrical mirror; S3, rotating the first cylindrical mirror and the rotating stepped element to obtain curvatures in different directions; S4, splicing the wavefront based on the curvatures in different directions to obtain the wavefront phase. The present invention measures the curvature information in different directions successively, avoids interference between the curvature information in different directions, and uses the stepped element to generate a defocus amount without moving a large-aperture transmission element, thereby improving the measurement accuracy from two aspects.

Description

Technical Field

[0001] The present invention relates to the technical field of wavefront sensing, and particularly to a wavefront curvature sensing method based on a rotating pupil. Background Art

[0002] The curvature sensor was proposed by Roddier in 1988. Its basic principle is to estimate the wavefront curvature change through the light intensity distribution of the images before and after the focal point, and solve the wavefront information. Due to the advantages of simple structure, stable calculation, and small influence of aperture obstruction, the wavefront sensing technology based on wavefront curvature has become an important front-end basis for adaptive optics. Therefore, the wavefront phase of large-aperture transmissive elements can be measured based on curvature sensing.

[0003] Currently, traditional measurement methods require moving large-aperture transmissive elements to generate defocus amounts. However, the control accuracy of moving large-aperture transmissive elements is limited, and each acquisition includes curvature information in all directions. The curvature information in different directions interferes with each other, resulting in limited accuracy of existing measurement methods. Summary of the Invention

[0004] The purpose of the present invention is to solve the problem of limited accuracy in the wavefront phase measurement method for existing large-aperture transmissive elements, and to propose a wavefront curvature sensing method based on a rotating pupil.

[0005] To achieve the above purpose, the present invention adopts the following specific technical solutions:

[0006] The wavefront curvature sensing method based on a rotating pupil provided by the present invention uses an optical system to realize the wavefront measurement of a large-aperture transmissive element. The optical system is arranged in the transmission direction of the large-aperture transmissive element. The optical system includes a stepped element, a first cylindrical mirror, a second cylindrical mirror, and a camera equipped with a curvature sensor arranged in sequence along the transmission direction. The method includes the following steps:

[0007] S1. Place the first cylindrical mirror and the second cylindrical mirror placed vertically between the camera and the stepped element, and compress the image formed by the incident light into a point spot through the first cylindrical mirror and the second cylindrical mirror, and use this point spot as the center of the image;

[0008] S2. Remove the second cylindrical mirror, image the incident light, register the image formed by the incident light using the center of the image, and obtain the curvature perpendicular to the direction of the first cylindrical mirror;

[0009] S3. Rotate the first cylindrical mirror and the rotating stepped element to obtain curvatures in different directions;

[0010] S4. Stitch the wavefronts based on the curvatures in different directions to obtain the wavefront phase;

[0011]

[0012]

[0013] Among them, Φ(x, y) is the wavefront phase, is the discrete Fourier series coefficient, is the complex number of the discrete Fourier transform, n and m are integers, x and y are discrete space coordinates, I1(x, y) is the energy distribution before the focus, I2(x, y) is the energy distribution after the focus, I0 is the total light intensity value, and Δz is the defocus amount.

[0014] Compared with the prior art, the present invention first measures the curvature information in one direction, and then rotates the cylindrical mirror and the stepped element to measure the curvature information in the other direction, avoiding interference between the curvature information in different directions and improving the measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a schematic structural diagram of an optical system according to an embodiment of the present invention;

[0016] Figure 2 is a schematic flow diagram of a wavefront curvature sensing method based on rotating pupil according to an embodiment of the present invention.

[0017] The reference numerals therein include a stepped element 1, a first cylindrical mirror 2, a camera 3, and a large-aperture transmission element 4. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] In the following, embodiments of the present invention will be described with reference to the drawings. In the following description, the same modules are denoted by the same reference numerals. In the case of the same reference numerals, their names and functions are also the same. Therefore, their detailed descriptions will not be repeated.

[0019] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not constitute a limitation to the present invention.

[0020] The wavefront curvature sensing method based on rotating pupil provided by the embodiment of the present invention uses an optical system to realize the wavefront measurement of a large-aperture transmission element, and the optical system is arranged in the transmission direction of the large-aperture transmission element.

[0021] Figure 1 is the structure of an optical system according to an embodiment of the present invention.

[0022] As Figure 1As shown, the optical system includes a stepped element 1, a first cylindrical mirror 2, a second cylindrical mirror, and a camera 4 arranged in sequence along the transmission direction. The stepped element 1 is located behind the large-aperture transmission element 4 and is used to generate a defocus amount for the incident light. The first cylindrical mirror 2 and the second cylindrical mirror are arranged perpendicular to each other and are used to compress the incident light into a point light spot. If one of the cylindrical mirrors is removed, the incident light is compressed into a line light spot. The camera 4 is equipped with a curvature sensor and is used to measure the curvature information of the large-aperture transmission element 4.

[0023] Figure 2 The flowchart of the wavefront curvature sensing method based on a rotating pupil according to an embodiment of the present invention is shown.

[0024] As Figure 2 shown, the wavefront curvature sensing method based on a rotating pupil provided by the present invention includes the following steps:

[0025] S1. Place the first cylindrical mirror and the second cylindrical mirror arranged perpendicular to each other between the camera and the stepped element, and compress the image formed by the incident light into a point light spot through the first cylindrical mirror and the second cylindrical mirror, and use this point light spot as the center of the image.

[0026] S2. Remove the second cylindrical mirror, image the incident light, register the image formed by the incident light using the center of the image, and obtain the curvature perpendicular to the direction of the first cylindrical mirror.

[0027] S3. Obtain curvatures in different directions by rotating the first cylindrical mirror and the stepped element.

[0028] S4. Stitch the wavefronts based on the curvatures in different directions to obtain the wavefront phase.

[0029]

[0030]

[0031] Among them, Φ(x, y) is the wavefront phase, is the discrete Fourier series coefficient, is the complex number of the discrete Fourier transform, n and m are integers, x and y are discrete spatial coordinates, I1(x, y) is the energy distribution before the focus, I2(x, y) is the energy distribution after the focus, I0 is the total light intensity, and Δz is the defocus amount.

[0032] The present invention first measures the curvature information in one direction, then rotates the cylindrical mirror and the stepped element to measure the curvature information in another direction, avoiding interference between the curvature information in different directions, and using the stepped element to generate a defocus amount without moving the large-aperture transmission element, improving the measurement accuracy from two aspects.

[0033] In the description of this specification, the descriptions referring to terms such as "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0034] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

[0035] The above specific implementation manners of the present invention do not constitute a limitation on the protection scope of the present invention. Any other corresponding changes and deformations made according to the technical concept of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A wavefront curvature sensing method based on a rotating pupil, which uses an optical system to measure the wavefront of a large-aperture transmissive element. The optical system is arranged in the transmission direction of the large-aperture transmissive element. The optical system includes a stepped element, a first cylindrical mirror, a second cylindrical mirror, and a camera equipped with a curvature sensor arranged in sequence along the transmission direction. It is characterized in that, The method includes the following steps: S1. Place the first cylindrical lens and the second cylindrical lens which are vertically arranged between the camera and the stepped element. Compress the image formed by the incident light into a point light spot through the first cylindrical lens and the second cylindrical lens, and use this point light spot as the center of the image; S2. Remove the second cylindrical lens, image the incident light, register the image formed by the incident light using the center of the image, and obtain the curvature perpendicular to the direction of the first cylindrical lens; S3. Rotate the first cylindrical lens and the rotating stepped element to obtain curvatures in different directions; S4. Stitch the wavefronts based on the curvatures in different directions to obtain the wavefront phase; where, Φ(x, y) is the wavefront phase, are the discrete Fourier series coefficients, are the complex numbers of the discrete Fourier transform, n and m are integers, x and y are discrete spatial coordinates, I1(x, y) is the energy distribution before the focus, I2(x, y) is the energy distribution after the focus, I0 is the total light intensity value, and Δz is the defocus amount.

Images