Optical detection method and system

Abstract

The present invention is applicable to the field of optical detection technology, and provides an optical detection method. The optical detection method comprises the following steps: obtaining the coordinates of a two-dimensional photoelectric sensor and an optical element to be measured, and constructing a mapping relationship between rectangular plane coordinates; respectively obtaining shearing interference patterns in the x and y directions of the two-dimensional photoelectric sensor, and respectively selecting 18 interference fringe patterns for phase extraction; unwrapping the phase extraction results, respectively obtaining differential wavefronts in the x and y directions, and reconstructing shearing interference wavefronts to obtain the wavefront of the optical system to be measured. The optical detection method of the present invention measures the wave aberration of the optical system to be measured, eliminates the influence of multi-order parasitic interference generated by the 0th order and the first ±19th order diffraction during the Ronchi shearing interferometer detection process, and improves the wave aberration detection accuracy of the optical system to be measured. The detection accuracy is at least 20 times higher than that of the existing eight-step phase shift method.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical detection, and in particular relates to an optical detection method and system. Background Art

[0002] Photolithography is one of the key technologies in the semiconductor manufacturing process. It involves using a light source to transfer a specific pattern to a silicon wafer through a mask. As the feature size of integrated circuits continues to shrink, the accuracy requirements for photolithography are becoming higher and higher. The performance of a photolithography machine depends largely on the performance of its core component, the projection lens. The wave aberration of the projection lens directly affects the resolution and alignment accuracy of the pattern during the photolithography process. Therefore, high-precision wave aberration detection is essential to ensure the quality of photolithography.

[0003] In the development of lithography technology, the detection technology of wavefront aberration of lithography projection objective has also undergone continuous innovation and improvement. Traditional detection methods include Zernike polynomial fitting, interferometer-based wavefront detection, etc. However, these methods have certain limitations when dealing with large numerical aperture (NA) and large-size optical systems. With the continuous advancement of semiconductor process nodes, the requirements for the accuracy of wavefront aberration detection of projection objective lenses are becoming higher and higher. In order to meet these requirements, researchers have developed a phase extraction method based on Ronchi shearing interferometer. This method places specific gratings on the object plane and the image plane, obtains multiple interference patterns using phase shifting interference technology, and then calculates the wavefront distortion of the optical system under test through complex algorithms. This method not only improves the accuracy of wavefront aberration detection, but also enhances the robustness to environmental changes, making it possible to perform high-precision detection of large optical systems in actual production environments. In addition, with the improvement of computing power and the optimization of algorithms, the wavefront aberration detection technology of lithography projection objective lenses is moving towards a more automated and intelligent direction to meet the semiconductor industry's demand for high efficiency and high yield.

[0004] With the development of lithography technology, the requirements for wave aberration detection accuracy are getting higher and higher, for example, it is required to reach below 0.5 nm (RMS). The current detection methods are often limited by system errors, while absolute detection technology can separate system errors and break through the accuracy limit, but there are challenges in realizing this technology. For lithography objectives with high numerical aperture (NA), the detection of wave aberration is more difficult. The phase extraction method based on Ronchi shearing interferometer plays a key role in the detection of wave aberration in high-precision optical systems, but it also faces some technical bottlenecks. In the Ronchi shearing interferometer, high-order diffracted light will produce parasitic interference in the interference field, which directly affects the accuracy of phase extraction. In order to solve this problem, researchers have proposed high-precision phase extraction algorithms, such as the ten-step phase shift algorithm, to eliminate the interference of high-order diffracted light in the overlapping area of ​​±1 order diffracted light, thereby improving the accuracy of shear phase extraction. Prior art 1 "Research on wave aberration detection technology of lithography projection objective lens based on Ronchi shearing interferometer" (China Laser, Wu Feibin) and prior art 2 "Phase extraction method based on Ronchi shearing interferometer" (Chinese patent CN104111120B) proposed an eight-step phase shift algorithm that can effectively eliminate ±3 and ±5 levels. Prior art 3 "Ronchi phase shift shearing interferometer and its phase extraction error analysis" (Acta Optica Sinica, Wu Feibin) and prior art 4 "Online detection device and detection method of projection objective lens wave aberration" (Chinese patent CN104166316B) further proposed a ten-step phase shift method that can effectively eliminate the influence of multi-level diffraction within ±9 levels. However, in the actual system, the diffraction level that has a significant impact on the phase extraction method based on Ronchi shearing interferometer reaches ±19 levels, so the existing eight-step phase shift algorithm and ten-step phase shift algorithm cannot eliminate diffraction interference, resulting in insufficient optical detection accuracy. Summary of the invention

[0005] The purpose of the embodiments of the present invention is to provide an optical detection method, aiming to solve the problem of insufficient optical detection accuracy.

[0006] The embodiment of the present invention is implemented as follows: an optical detection method, the optical detection method comprising the following steps:

[0007] Obtain the coordinates of the two-dimensional photoelectric sensor and the optical element to be measured, and construct a mapping relationship of rectangular plane coordinates;

[0008] Obtain the shearing interference pattern in the x direction of the two-dimensional photoelectric sensor, select 18 interference fringe patterns, and use the following algorithm to perform phase extraction:

[0009]

[0010] in, is the phase of the measured wavefront in the x direction, representing the gradient information of the measured wavefront in the x direction; the motion control module controls the image plane grating translation stage to move the chessboard grating along the x direction, moving 23 times, so that the image plane grating moves 1 / 24 grating period each time, and after each movement, the two-dimensional photoelectric sensor collects a shearing interference pattern ,in ;

[0011] Obtain the shearing interference pattern in the y direction of the two-dimensional photoelectric sensor, select 18 interference fringe patterns, and use the following algorithm to perform phase extraction:

[0012]

[0013] in, is the phase of the measured wavefront in the y direction, representing the gradient information of the measured wavefront in the y direction; the motion control module controls the image plane grating translation stage to move the chessboard grating along the y direction for 23 times, so that the image plane grating moves 1 / 24 of the grating period each time, and after each movement, the two-dimensional photoelectric sensor collects a shearing interference pattern ,in ;

[0014] The phase extraction result is unwrapped to obtain differential wavefronts in the x direction and the y direction respectively, and shearing interferometry wavefront reconstruction is performed to obtain the wavefront of the optical system under test.

[0015] Furthermore, the coordinates of the two-dimensional photoelectric sensor and the optical element to be measured are obtained, and a mapping relationship of rectangular plane coordinates is constructed, and then the following steps are included:

[0016] Adjust the rotation angle of the polarizer to change the polarization direction of the transmitted light;

[0017] Adjust the scattering optical element close to the object plane grating so that the object plane grating is evenly illuminated;

[0018] The positions of the two-dimensional photoelectric sensor and the image plane grating are adjusted, thereby adjusting the collected interference fringe pattern.

[0019] Furthermore, after performing phase extraction on the shearing interferogram in the x direction, before performing phase extraction on the shearing interferogram in the y direction, the following steps need to be performed: the object plane grating is controlled to rotate 90 degrees so that the direction of the object plane grating transparent units is parallel to the x direction and is periodically distributed in the y direction.

[0020] Another object of an embodiment of the present invention is an optical detection system, the optical detection system comprising:

[0021] An optical detection device, used for detecting the surface of an optical element;

[0022] A motion control module, used to control the object plane grating displacement stage and the image plane grating displacement stage in the optical detection device;

[0023] A signal acquisition and analog-to-digital conversion module, used for acquiring optical interference image data of a two-dimensional photoelectric sensor in the optical detection device;

[0024] The computer device is used to control the motion control module, obtain the optical interference image data of the signal acquisition and analog-to-digital conversion module, and execute the optical detection method.

[0025] Furthermore, the optical detection device includes, in sequence along the propagation direction of the light beam of the light source: a light source, a focusing lens, a polarizer, a scattering optical element, an object plane grating, an object plane grating displacement stage, an optical system to be measured, an image plane grating, an image plane grating displacement stage and a two-dimensional photoelectric sensor;

[0026] The object plane grating is placed on the object plane grating displacement stage and is located on the object plane of the optical system under test; the polarizer is located at the light outlet of the focusing lens; the scattering optical element is located above the object plane grating; the image plane grating is placed on the image plane grating displacement stage and is located on the image plane of the optical system under test; the two-dimensional photoelectric sensor is located below the image plane grating and is connected to the computer device through the signal acquisition and analog-to-digital conversion module; the object plane grating displacement stage and the image plane grating displacement stage are respectively connected to the computer device through the motion control module.

[0027] Furthermore, the object plane grating is periodic One-dimensional diffraction grating with a duty cycle of 50%, the grating period is equal to the interval between adjacent light-transmitting units and light-shielding units; the direction of the object plane grating light-transmitting units is parallel to the y-axis direction and is periodically distributed in the x-direction;

[0028] The image plane grating has a chessboard layout, which is a square with the same size of light-transmitting units and light-shielding units. Each light-transmitting unit is surrounded by 4 light-shielding units, and each light-shielding unit is surrounded by 4 light-transmitting units. The period of the image plane grating is The diagonal length of the image plane grating light-transmitting unit and the light-shielding unit are parallel to the x-axis and y-axis directions.

[0029] Furthermore, the object plane grating is periodic One-dimensional diffraction grating with a duty cycle of 25%, grating period is equal to the interval between adjacent light-transmitting units; the direction of the object plane grating light-transmitting unit is parallel to the y-axis direction;

[0030] The image plane grating has a chessboard layout, which is a square with the same size of light-transmitting units. The light-shielding units are located around the light-transmitting units, and the light-transmitting units are arranged alternately in the diagonal direction. The period of the image plane grating is It is equal to the interval length in the diagonal direction of two adjacent light-transmitting units; the diagonal direction of the image plane grating light-transmitting unit and the light-shielding unit is parallel to the x-axis and y-axis directions.

[0031] Furthermore, the object plane grating is periodic One-dimensional diffraction grating with a duty cycle of 25%, grating period is equal to the interval between adjacent light-transmitting units; the direction of the object plane grating light-transmitting unit is parallel to the y-axis direction;

[0032] The image plane grating has a chessboard layout, which is a square with the same size of light-transmitting units. The light-transmitting parts along the x-direction and y-direction are arranged at a distance of twice or an integer multiple of the diagonal length of the light-transmitting unit. The period of the image plane grating is It is equal to twice or an integer multiple of the diagonal length of the light-transmitting unit of the light-transmitting part along the x-direction and the y-direction; the diagonal direction of the image plane grating light-transmitting unit and the light-shielding unit is parallel to the x-axis and the y-axis directions.

[0033] An embodiment of the present invention proposes an optical detection method to measure the wave aberration of the optical system under test, eliminate the influence of multi-order diffraction light of the image plane grating on the phase extraction accuracy during the Ronchi shearing interferometer detection process, eliminate the influence of multi-order parasitic interference generated by the 0th order and the first ±19 orders of diffraction, and improve the wave aberration detection accuracy of the optical system under test. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 A diagram of an application environment of the optical detection method provided by an embodiment of the present invention;

[0035] Figure 2 A structural diagram of an optical detection system provided by an embodiment of the present invention;

[0036] Figure 3 Object plane grating provided by the embodiment of the present invention Figure 1 ;

[0037] Figure 4 Image plane grating provided by the embodiment of the present invention Figure 1 ;

[0038] Figure 5 Object plane grating provided by the embodiment of the present invention Figure 2 ;

[0039] Figure 6 Image plane grating provided by the embodiment of the present invention Figure 2 ;

[0040] Figure 7 Image plane grating provided by the embodiment of the present invention Figure 3 ;

[0041] Figure 8 A flow chart of an optical detection method provided by an embodiment of the present invention;

[0042] Fig. 9 A flow chart of an optical detection method provided by an embodiment of the present invention;

[0043] Fig.10 A flow chart of an optical detection method provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0045] Figure 1 FIG. 1 is an application environment diagram of the optical detection method provided by an embodiment of the present invention. Figure 1 As shown, in this application environment, it includes an optical detection device, a motion control module, a signal acquisition and analog-to-digital conversion module and a computer device.

[0046] An optical detection device, used for detecting the surface of an optical element;

[0047] A motion control module, used to control the object plane grating displacement stage 6 and the image plane grating displacement stage 9 in the optical detection device;

[0048] A signal acquisition and analog-to-digital conversion module, used to acquire optical interference image data of the two-dimensional photoelectric sensor 10 in the optical detection device;

[0049] A computer device is used to control the motion control module and obtain the optical interference image data of the signal acquisition and analog-to-digital conversion module. The computer device can be a smart phone, a tablet computer, a laptop computer, a desktop computer, a smart speaker or a smart watch, etc., but is not limited thereto. The motion control module, the signal acquisition and analog-to-digital conversion module and the computer device can be connected via a network, and the present invention is not limited thereto.

[0050] In one embodiment, Figure 2 The structure diagram of the proposed optical detection system is shown in FIG. 1 , and an optical detection system is proposed, which includes Figure 1The optical detection device includes, in order along the propagation direction of the light beam of the light source 1: a light source 1, a focusing lens 2, a polarizer 3, a scattering optical element 4, an object plane grating 5, an object plane grating displacement stage 6, an optical system to be measured 7, an image plane grating 8, an image plane grating displacement stage 9 and a two-dimensional photoelectric sensor 10;

[0051] The object plane grating 5 is placed on the object plane grating displacement stage 6 and is located on the object plane of the optical system 7 under test; the polarizer 3 is located at the light outlet of the focusing lens 2; the scattering optical element 4 is located above the object plane grating 5; the image plane grating 8 is placed on the image plane grating displacement stage 9 and is located on the image plane of the optical system 7 under test; the two-dimensional photoelectric sensor 10 is located below the image plane grating 8 and is connected to the computer device through the signal acquisition and analog-to-digital conversion module; the object plane grating displacement stage 6 and the image plane grating displacement stage 9 are respectively connected to the computer device through the motion control module.

[0052] In this embodiment, the specific details of the components of the optical detection system are as follows:

[0053] The focusing lens 2 is an optical lens assembly used to focus the light beam emitted by the light source 1 onto the object plane grating 5 .

[0054] The polarizer 3 is an optical lens used to adjust the polarization state of the light beam emitted by the light source 1. The polarizer 3 is orthogonal to the direction of the light path, and the polarizer 3 used is an adjustable linear polarizer, which has the characteristic of high transmittance within a specific wavelength range; by changing the angle of the polarizer 3, the contrast of the optical system can be optimized; by adjusting the angle of the polarizer 3, the polarization direction of the transmitted light can be changed.

[0055] The scattering optical element 4 is an optical element such as frosted glass or a microlens array, which makes the illumination light beam uniformly illuminate within the numerical aperture of the optical system 7 to be measured.

[0056] The object plane grating 5 and the image plane grating 8 are both phase gratings or amplitude gratings. There are three ways to combine the two:

[0057] The first one, such as Figure 3 As shown, the object plane grating 5 is periodic One-dimensional diffraction grating with a duty cycle of 50%, the grating period is equal to the interval between adjacent light-transmitting units and light-shielding units; the light-transmitting units of the object plane grating 5 are parallel to the y-axis direction and are periodically distributed in the x-direction. Figure 4 As shown, the image plane grating 8 has a chessboard layout, where the light-transmitting units and the light-shielding units are all squares of the same size, each light-transmitting unit is surrounded by 4 light-shielding units, and each light-shielding unit is surrounded by 4 light-transmitting units; the period of the image plane grating 8 is Equal to the diagonal length of the square; the diagonal directions of the light-transmitting units and the light-shielding units of the image plane grating 8 are parallel to the x-axis and y-axis directions.

[0058] The second type, such as Figure 5 As shown, the object plane grating 5 is periodic One-dimensional diffraction grating with a duty cycle of 25%, grating period is equal to the interval between adjacent light-transmitting units; the direction of the light-transmitting units of the object plane grating 5 is parallel to the y-axis direction. Figure 6 As shown, the image plane grating 8 has a chessboard layout, where the light-transmitting units are all squares of the same size, the light-shielding units are located around the light-transmitting units, and the light-transmitting units are arranged alternately in the diagonal direction; the period of the image plane grating 8 is It is equal to the interval length in the diagonal direction of two adjacent light-transmitting units; the diagonal directions of the light-transmitting units and the light-shielding units of the image plane grating 8 are parallel to the x-axis and y-axis directions.

[0059] The third type, such as Figure 5 As shown, the object plane grating 5 is periodic One-dimensional diffraction grating with a duty cycle of 25%, grating period is equal to the interval between adjacent light-transmitting units; the direction of the light-transmitting units of the object plane grating 5 is parallel to the y-axis direction. Figure 7 As shown, the image plane grating 8 has a chessboard layout, where the light-transmitting units are squares of the same size, and the light-transmitting parts along the x-direction and y-direction are arranged at a distance of twice or an integer multiple of the diagonal length of the light-transmitting units. The period of the image plane grating 8 is It is equal to twice or an integer multiple of the diagonal length of the light-transmitting unit of the light-transmitting part in the x-direction and the y-direction; the diagonal direction of the light-transmitting unit and the light-shielding unit of the image plane grating 8 is parallel to the x-axis and the y-axis directions.

[0060] The period of the image plane grating 8 is With the period of the object plane grating 5 satisfy Relationship, wherein M is the imaging magnification of the optical system 7 under test; the numerical aperture of the optical system 7 under test is NA, and the imaging magnification is M:1.

[0061] The object plane grating displacement stage 6 is a displacement stage for moving the object plane grating 5 into the object optical path of the optical system 7 to be measured, and is a three-dimensional displacement stage for driving the image plane grating 8 to move stepwise along the x direction and along the y direction.

[0062] The image plane grating displacement stage 9 is used to move the image plane grating 8 into the image-side optical path of the optical system 7 to be measured, and is a three-dimensional displacement stage that drives the image plane grating 8 to move stepwise along the x direction and along the y direction.

[0063] The two-dimensional photoelectric sensor 10 is a camera, a CCD, a CMOS image sensor or a two-dimensional photodetector array, and the shearing interference fringes generated by the image plane grating 8 are received on its detection surface.

[0064] The object plane grating displacement stage 6 and the image plane grating displacement stage 9 are connected to the motion control system module, and are three-dimensional displacement stages used to carry the object plane grating 5 and the image plane grating 8 into the detection optical path respectively, and to drive the object plane grating 5 and the image plane grating 8 to move in steps along the x direction, the y direction and the z direction; the encoder on the three-dimensional motion control platform is used to provide feedback signals so that the system can monitor the position and posture of the platform in real time and perform closed-loop control.

[0065] The signal acquisition and analog-to-digital conversion module is used to acquire the optical interference image data of the two-dimensional photoelectric sensor 10 in the optical detection device.

[0066] The computer equipment is used for the interference detection process and storage of measurement data, and processes and analyzes the optical interference image data collected by the two-dimensional photoelectric sensor 10. The seven-wave aberration stitching imaging of the measured optical system can be performed based on the optical interference image data collected by the two-dimensional photoelectric sensor 10 and the spatial position information fed back by the three-dimensional motion control platform.

[0067] An optical detection system provided in this embodiment can measure the wave aberration of the optical system 7 under test, eliminate the influence of multi-order diffraction light of the image plane grating on the phase extraction accuracy during the Ronchi shearing interferometer detection process, eliminate the influence of multi-order parasitic interference caused by the 0th order and the first ±19th order diffraction, and improve the wave aberration detection accuracy of the optical system 7 under test.

[0068] In one embodiment, Figure 8 The flowchart of the optical detection method shown in FIG. 1 is a flowchart of the optical detection method shown in FIG. 1 , and an optical detection method is proposed. This embodiment mainly applies this method to the above Figure 1 and Figure 2 The optical detection method includes the following steps S102 to S108:

[0069] Step S102, obtaining the coordinates of the two-dimensional photoelectric sensor 10 and the optical element to be measured, and constructing a mapping relationship of rectangular plane coordinates;

[0070] Step S104, obtaining the shearing interference pattern in the x direction of the two-dimensional photoelectric sensor 10, selecting 18 interference fringe patterns, and using the following algorithm to perform phase extraction:

[0071]

[0072] in, is the phase of the measured wavefront in the x direction, representing the gradient information of the measured wavefront in the x direction; the motion control module controls the image plane grating displacement stage 9 to move the chessboard grating along the x direction, moving 23 times, so that the image plane grating 8 moves 1 / 24 grating period each time, and after each movement, the two-dimensional photoelectric sensor 10 collects a shearing interference pattern ,in ;

[0073] Step S106, obtaining the shearing interference pattern in the y direction of the two-dimensional photoelectric sensor 10, selecting 18 interference fringe patterns, and using the following algorithm to perform phase extraction:

[0074]

[0075] in, is the phase of the measured wavefront in the y direction, representing the gradient information of the measured wavefront in the y direction; the motion control module controls the image plane grating displacement stage 9 to move the chessboard grating along the y direction, moving 23 times, so that the image plane grating 8 moves 1 / 24 grating period each time, and after each movement, the two-dimensional photoelectric sensor 10 collects a shearing interference pattern ,in ;

[0076] Step S108, unpacking the phase extraction result to obtain differential wavefronts in the x direction and the y direction respectively, performing shearing interferometry wavefront reconstruction to obtain the wavefront of the optical system under test.

[0077] In this embodiment, the wave aberration of the optical system 7 under test is measured to eliminate the influence of the multi-order diffraction light of the image plane grating on the phase extraction accuracy during the Ronchi shearing interferometer detection process. The influence of the multi-order parasitic interference generated by the 0th order and the first ±19th order diffraction can be eliminated, thereby improving the wave aberration detection accuracy of the optical system 7 under test.

[0078] The above method of this embodiment is compared with the existing eight-step phase shift method, ten-step phase shift method and thirteen-step phase shift method. The eight-step phase shift method can eliminate the influence of ±3 and ±5 diffraction parasitic interference, and the theoretical PV value of the phase extraction error is 0.0110λ (λ is the wavelength), and the RMS value is 0.0033λ. The ten-step phase shift method can eliminate the influence of diffraction parasitic interference within ±9 levels, and the theoretical PV value of the phase extraction error is 0.0038λ, and the RMS value is 0.0012λ. The thirteen-step phase shift method can eliminate the influence of ±15-level diffraction parasitic interference, and the theoretical PV value of the phase extraction error is 0.0019λ, and the RMS value is 0.00062λ (the above data refer to the paper: Method for designing phase-retrieval algorithms for Ronchi phase-shifting lateral-shearing interferometry, Optical Society of America, FEIBINWU, 2019.4.25). The method of this embodiment can eliminate the influence of diffraction parasitic interference within ±19 levels. Theoretically, the PV value of the phase extraction error is about 0.0005λ, and the RMS value is 0.00013λ. The detection accuracy is at least 20 times higher than that of the existing eight-step phase shift method.

[0079] In one embodiment, Fig. 9 As shown, an optical detection method is proposed, including steps S102 to S108, wherein steps S202 to S206 are further included between step S102 and step S104:

[0080] Step S202, adjusting the rotation angle of the polarizer 3 to change the polarization direction of the transmitted light;

[0081] Step S204, adjusting the position of the scattering optical element 4 close to the object plane grating 5 so that the object plane grating 5 is evenly illuminated;

[0082] Step S206, adjusting the positions of the two-dimensional photoelectric sensor 10 and the image plane grating 8, and further adjusting the collected interference fringe pattern.

[0083] In this embodiment, the object plane grating 5 is placed on the object plane grating displacement stage 6 and located on the object plane of the optical system 7 under test. The object plane grating displacement stage 6 is moved to move the object plane grating 5 into the object field point position of the optical system 7 under test, and the direction of the light-transmitting units of the object plane grating 5 is parallel to the y-axis direction and is periodically distributed in the x-direction. The image plane grating 8 is placed on the image plane grating displacement stage 9 and located on the image plane of the optical system 7 under test. The image plane grating displacement stage 9 is moved to move the image plane grating 8 into the image-side optical path of the optical system 7 under test, and the diagonal directions of the light-transmitting units and the light-shielding units of the image plane grating 8 are parallel to the x-axis and y-axis directions.

[0084] In step S202, the rotation angle of the polarizer 3 is adjusted to change the polarization direction of the transmitted light. For example, the polarizer 3 is adjusted so that the state of the light beam irradiated by the light source 1 onto the object plane grating 5 is an s-polarization state.

[0085] In step S206, the calibrated two-dimensional photoelectric sensor 10 is installed below the image plane grating 8. The distance between the two-dimensional photoelectric sensor 10 and the image plane grating 8 needs to be adjusted according to the collected interference fringe pattern, so that the 0th order and ±1st order diffraction light in the interference fringe pattern can be completely collected, and ensure that the interference pattern of the 0th order and ±1st order diffraction light occupies most of the position of the two-dimensional photoelectric sensor 10, thereby ensuring sufficient data clarity and obtaining a better interference fringe pattern on the detection surface.

[0086] In one embodiment, Fig.10 As shown, an optical detection method is proposed, including steps S102~S108, wherein step S302 is further included between step S104 and step S106: controlling the object plane grating 5 to rotate 90 degrees so that the direction of the light-transmitting units of the object plane grating 5 is parallel to the x direction and is periodically distributed in the y direction.

[0087] The object plane grating of the prior art includes gratings in both the x-direction and the y-direction, and the object plane grating has a large area. The object plane grating 5 of this embodiment is provided with a grating in one direction, and the interference pattern detection in the x-direction and the y-direction is realized by rotating 90 degrees, which is simpler and more convenient.

[0088] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0089] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An optical detection method, the optical detection method is applied to a Ronchi shearing interferometer, characterized in that: The optical detection method comprises the following steps: Obtain the coordinates of the two-dimensional photoelectric sensor and the optical element being measured in the Ronchi shearing interferometer, and construct the mapping relationship of the rectangular plane coordinates; Obtain the shearing interference pattern in the x direction of the two-dimensional photoelectric sensor, select 18 interference fringe patterns, and use the following algorithm to perform phase extraction: ； in, is the phase of the measured wavefront in the x direction, representing the gradient information of the measured wavefront in the x direction; the motion control module in the Ronchi shearing interferometer controls the image plane grating translation stage to move the chessboard grating along the x direction for 23 times, so that the image plane grating moves 1 / 24 of the grating period each time, and after each movement, the two-dimensional photoelectric sensor collects a shearing interference pattern ,in ; Obtain the shearing interference pattern in the y direction of the two-dimensional photoelectric sensor, select 18 interference fringe patterns, and use the following algorithm to perform phase extraction: ； in, is the phase of the measured wavefront in the y direction, representing the gradient information of the measured wavefront in the y direction; the motion control module controls the image plane grating translation stage to move the chessboard grating along the y direction for 23 times, so that the image plane grating moves 1 / 24 of the grating period each time, and after each movement, the two-dimensional photoelectric sensor collects a shearing interference pattern ,in ; The phase extraction results in the x-direction and the y-direction are unwrapped to obtain the differential wavefronts in the x-direction and the y-direction respectively, and the shearing interferometer wavefront reconstruction is performed to obtain the wavefront of the optical system under test.

2. The optical detection method according to claim 1, characterized in that: The step of obtaining the coordinates of the two-dimensional photoelectric sensor and the optical element to be measured in the Ronchi shearing interferometer and constructing a mapping relationship of rectangular plane coordinates further includes the following steps: Adjust the rotation angle of the polarizer to change the polarization direction of the transmitted light; Adjust the scattering optical element close to the object plane grating so that the object plane grating is evenly illuminated; The positions of the two-dimensional photoelectric sensor and the image plane grating are adjusted, thereby adjusting the collected interference fringe pattern.

3. The optical detection method according to claim 1, characterized in that: After performing phase extraction on the shearing interferogram in the x direction, before performing phase extraction on the shearing interferogram in the y direction, the following steps need to be performed: the object plane grating is controlled to rotate 90 degrees so that the direction of the object plane grating transmission unit is parallel to the x direction and is periodically distributed in the y direction.

4. An optical detection system, characterized in that: The optical detection system comprises: An optical detection device, used for detecting the surface of an optical element; A motion control module, used to control the object plane grating displacement stage and the image plane grating displacement stage in the optical detection device; A signal acquisition and analog-to-digital conversion module, used for acquiring optical interference image data of a two-dimensional photoelectric sensor in the optical detection device; A computer device is used to control the motion control module, obtain the optical interference image data of the signal acquisition and analog-to-digital conversion module, and execute the optical detection method described in any one of claims 1-3.

5. The optical detection system according to claim 4, characterized in that: The optical detection device comprises, in order along the propagation direction of the light beam of the light source: a light source, a focusing lens, a polarizer, a scattering optical element, an object plane grating, an object plane grating displacement stage, an optical system to be measured, an image plane grating, an image plane grating displacement stage and a two-dimensional photoelectric sensor; The object plane grating is placed on the object plane grating displacement stage and is located on the object plane of the optical system under test; the polarizer is located at the light outlet of the focusing lens; the scattering optical element is located above the object plane grating; the image plane grating is placed on the image plane grating displacement stage and is located on the image plane of the optical system under test; the two-dimensional photoelectric sensor is located below the image plane grating and is connected to the computer device through the signal acquisition and analog-to-digital conversion module; the object plane grating displacement stage and the image plane grating displacement stage are respectively connected to the computer device through the motion control module.

6. The optical detection system according to claim 5, characterized in that: The object plane grating is periodic One-dimensional diffraction grating with a duty cycle of 50%, the grating period is equal to the interval between adjacent light-transmitting units and light-shielding units; the direction of the object plane grating light-transmitting units is parallel to the y-axis direction and is periodically distributed in the x-direction; The image plane grating has a chessboard layout, which is a square with the same size of light-transmitting units and light-shielding units. Each light-transmitting unit is surrounded by 4 light-shielding units, and each light-shielding unit is surrounded by 4 light-transmitting units. The period of the image plane grating is The diagonal length of the image plane grating light-transmitting unit and the light-shielding unit are parallel to the x-axis and y-axis directions.

7. The optical detection system according to claim 5, characterized in that: The object plane grating is periodic One-dimensional diffraction grating with a duty cycle of 25%, grating period is equal to the interval between adjacent light-transmitting units; the direction of the object plane grating light-transmitting unit is parallel to the y-axis direction; The image plane grating has a chessboard layout, which is a square with the same size of light-transmitting units. The light-shielding units are located around the light-transmitting units, and the light-transmitting units are arranged alternately in the diagonal direction. The period of the image plane grating is It is equal to the interval length in the diagonal direction of two adjacent light-transmitting units; the diagonal direction of the image plane grating light-transmitting unit and the light-shielding unit is parallel to the x-axis and y-axis directions.

8. The optical detection system according to claim 5, characterized in that: The object plane grating is periodic One-dimensional diffraction grating with a duty cycle of 25%, grating period is equal to the interval between adjacent light-transmitting units; the direction of the object plane grating light-transmitting unit is parallel to the y-axis direction; The image plane grating has a chessboard layout, which is a square with the same size of light-transmitting units. The light-transmitting parts along the x-direction and y-direction are arranged at a distance of twice or an integer multiple of the diagonal length of the light-transmitting unit. The period of the image plane grating is It is equal to twice or an integer multiple of the diagonal length of the light-transmitting unit of the light-transmitting part along the x-direction and the y-direction; the diagonal direction of the image plane grating light-transmitting unit and the light-shielding unit is parallel to the x-axis and the y-axis directions.

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