A super-high-resolution HTM wavefront detection module based on a metasurface and its calibration method and testing method

Abstract

The present application provides an ultra-high resolution HTM wavefront detection module based on a metasurface and its calibration method and test method. The ultra-high resolution HTM wavefront detection module based on a metasurface includes a laser, a three-dimensional displacement stage, a collimator, a metasurface structure and a camera. The laser is located on the three-dimensional displacement stage, and the light outlet of the laser is located on the focal plane of the collimator. The spherical wave emitted by the laser is collimated by the collimator and then introduced into a plane wavefront with different slopes. After intensity modulation by the metasurface structure, the grayscale information is recorded by the camera. The present application realizes a wavefront detection technology with high resolution and ultra-large dynamic range by modulating the light intensity distribution through the metasurface and calibrating the relationship between the grayscale ratio and the slope. It has a simple structure and stable function, and has broad application prospects in the field of high-precision and large dynamic range wavefront measurement.

Description

Technical Field

[0001] The present application belongs to the field of wavefront detection, and more specifically, to an ultra-high resolution HTM wavefront detection module based on a metasurface and a calibration method and a testing method thereof. Background Art

[0002] In the field of telescope, the wavefront of the beam determines the imaging quality of the detected target. In the field of high-energy laser, the wavefront of the beam determines the power density of the laser to the target; in the field of optical component surface detection, the wavefront carries the three-dimensional surface information of the component. In the field of telescope detection and high-energy laser, the wavefront is corrected by adaptive optical system to obtain good detection and strike effects. Whether it is wavefront correction or surface detection of optical components, wavefront detection technology is involved.

[0003] The existing wavefront sensors mainly include HTM wavefront sensors, radial shearing interferometers, lateral shearing interferometers, tetrahedral pyramid wavefront sensors, wavefront curvature sensors, etc. The above wavefront sensors have different advantages and disadvantages due to their different principles and are used in different technical fields.

[0004] HTM wavefront sensors are widely used in various fields such as medical treatment, telescopes, surface detection, and adaptive optics due to their simple structure, stable functions, strong anti-interference ability, and no requirements for beam coherence and polarization state. HTM wavefront sensors are composed of cameras and microlens arrays. The principle is that the microlens array divides the wavefront to be measured into multiple sub-wavefronts that are approximately planes, and focuses the sub-wavefronts on the detector. The slope of each sub-wavefront can be expressed by dividing the centroid coordinates of the light spot on the detector by the focal length of the microlens. The slope can be used to obtain the wavefront to be measured after the wavefront restoration algorithm. From the principle of the HTM wavefront sensor, it can be seen that the dynamic range and spatial resolution of the wavefront to be measured are limited by the relative aperture (D / f) of the microlens, and the dynamic range and spatial resolution are two contradictory quantities that are difficult to improve at the same time.

[0005] Limited by the processing level of microlenses, the spatial resolution of HTM wavefront sensors is difficult to exceed the order of one hundred times one hundred (lateral multiplied by vertical resolution). In addition, the more microlenses there are, the smaller the dynamic range and detection sensitivity will be, which limits its application in the fields of high-resolution, high dynamic range and high-precision wavefront detection. Summary of the invention

[0006] In order to solve the problems existing in the prior art, the technical solution adopted in this application is: on the one hand, an ultra-high resolution HTM wavefront detection module based on a metasurface is provided, including a laser, a three-dimensional translation stage, a collimator, a metasurface structure and a camera, wherein the laser is located on the three-dimensional translation stage, and the light outlet of the laser is located on the focal plane of the collimator. The spherical wave emitted by the laser is collimated by the collimator and then introduced into a plane wavefront with different slopes. After intensity modulation by the metasurface structure, the grayscale information is recorded by the camera.

[0007] Optionally, the super surface structure uses four camera pixels as a unit, and columns grow on the edge of each unit to form a "well"-shaped super surface structure.

[0008] Optionally, the “well”-shaped supersurface structure contains an array of superatomic structures.

[0009] Optionally, the three-dimensional translation stage is used to control the laser light outlet to perform translation with the same step length in the focal plane of the collimator.

[0010] On the second aspect, the present application provides a calibration method for an ultra-high-resolution HTM wavefront detection module based on a metasurface, in which a camera is used to record the relationship between the ratio of the grayscale of four pixels in each subunit and the slope of the wavefront after the plane wavefront with different slopes passes through the metasurface structure, and the ratio of the grayscale of the four pixels in each subunit is used as the horizontal and vertical coordinates to perform surface polynomial fitting on the slopes in the X and Y directions of the calibration wavefront, and the polynomial coefficients of each subunit are recorded to form a calibration file.

[0011] On the third aspect, the present application also provides a testing method for an ultra-high-resolution HTM wavefront detection module based on a metasurface. The wavefront to be measured is divided into multiple 2*2 pixel-sized sub-units that approximate plane wavefronts through the metasurface structure. The slope of the wavefront to be measured is inverted according to the ratio of the grayscale values ​​in each sub-unit and the polynomial coefficients in the calibration file, and then the wavefront to be measured is obtained through a wavefront restoration algorithm.

[0012] The beneficial effect of the ultra-high-resolution HTM wavefront detection module based on metasurface provided in the present application is that, compared with the prior art, the present application can achieve different transmittances for light of different wavelength bands by changing the geometric parameters of the meta-atomic structural unit, realize single longitudinal mode filtering and frequency selection of the target wavelength, and improve the signal-to-noise ratio of wavefront detection.

[0013] The present application realizes wavefront detection technology with high resolution and ultra-large dynamic range by modulating the light intensity distribution through the metasurface and calibrating the relationship between the grayscale ratio and the slope. It has a simple structure and stable function, and has broad application prospects in the field of high-precision and large dynamic range wavefront measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0015] Figure 1 A schematic diagram of the structure of an ultra-high resolution HTM wavefront detection module and calibration system based on a metasurface provided in an embodiment of the present application;

[0016] Figure 2 Schematic diagram of the translational position distribution of the laser outlet on the collimator focal plane;

[0017] Figure 3 For and A schematic diagram of surface polynomial fitting of the X-direction slope of the calibration wavefront for the horizontal and vertical coordinates;

[0018] Figure 4 For and Schematic diagram of surface polynomial fitting of the Y-direction slope of the calibration wavefront for the horizontal and vertical coordinates. DETAILED DESCRIPTION

[0019] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application 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 application and are not used to limit the present application.

[0020] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0021] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0022] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0023] Please also read Figure 1-Figure 3 , the ultra-high resolution HTM wavefront detection module based on the metasurface provided in the embodiment of the present application is now described.

[0024] An ultra-high-resolution HTM wavefront detection module based on a metasurface includes a laser, a three-dimensional translation stage, a collimator, a metasurface structure and a camera. The laser is located on the three-dimensional translation stage, and the light outlet of the laser is located on the focal plane of the collimator. The spherical wave emitted by the laser is collimated by the collimator and then introduced into a plane wavefront with different slopes. After intensity modulation by the metasurface structure, the grayscale information is recorded by the camera.

[0025] In some embodiments of the present application, the metasurface structure is based on four camera pixels as a unit, and pillars grow on the edge of each unit to form a "well"-shaped metasurface structure. The "well"-shaped metasurface structure modulates the incident light so that the grayscale ratio of the four pixels in the subunit is a monotonic function of the wavefront slope.

[0026] In some embodiments of the present application, the "well"-shaped metasurface structure is an array of superatomic structures. By designing the geometric parameters of the superatomic structural unit, different transmittances of light in different bands can be achieved, single longitudinal mode filtering and frequency selection of the target wavelength can be achieved, and the signal-to-noise ratio of wavefront detection can be improved.

[0027] In some embodiments of the present application, the three-dimensional translation stage is used to control the laser light outlet to perform translation with the same step length in the focal plane of the collimator. The spherical wave emitted by the laser is collimated by the collimator to introduce plane waves with different slopes.

[0028] On the other hand, the present application provides a calibration method for an ultra-high resolution HTM wavefront detection module based on a metasurface, in which a camera records the grayscale ratio of four pixels in each subunit after the plane wavefront with different slopes passes through the metasurface structure ( , ) and the wavefront slope, and The surface polynomial fitting is performed on the slopes of the calibration wavefront in the X and Y directions for the horizontal and vertical coordinates respectively, and the polynomial coefficients of each subunit are recorded to form a calibration file.

[0029] Specifically, Figure 1As shown in the figure, the laser is placed on a three-dimensional translation stage, and the light outlet is located at the focal plane of the collimator. The three-dimensional translation stage is used to make the laser light outlet Figure 2 The position distribution shown is translated. Assuming that the movement step lengths in the X and Y directions are both L, the wavefront slope distribution introduced after the spherical wave is collimated by the collimator after moving m and n steps in the x and y directions respectively is: , , where f is the focal length of the collimator.

[0030] Super surface structure such as Figure 1 As shown in the figure, four camera pixels are used as units, and strip-shaped columns are grown around them. Each unit forms a "well"-shaped structure. The metasurface structure modulates the intensity distribution of the incident light, making the grayscale ratio of the four pixels in each sub-unit ( , ) is distributed as a monotonic function with the slope of the incident wavefront.

[0031] The system is calibrated by a large number of plane wavefronts with different slopes, and the grayscale value of the camera records the light intensity distribution during calibration, such as Figure 1 The grayscale distribution values ​​of the four pixels (Pixel_A, Pixel_B, Pixel_C, Pixel_C) of each unit are A, B, C, and D, and the slope of the incident wavefront during calibration is recorded at the same time. , And the grayscale ratio of each unit pixel , ,by , are the horizontal and vertical coordinates, respectively , Perform polynomial surface fitting of formula (1), the polynomial fitting diagram is shown in Figure 3 Figure 4 As shown, the mesh represents the fitted surface. ” indicates the measured , Record the polynomial coefficients (a1, a2, a3, ...) of each unit to form a calibration file.

[0032] (1)

[0033] Among them, Z is the vector height of the polynomial fitting surface, and x and y are the coordinate axes of two orthogonal coordinate systems of the polynomial fitting.

[0034] On the other hand, the present application also provides a test method for an ultra-high resolution HTM wavefront detection module based on a metasurface. The wavefront to be measured is divided into a plurality of 2*2 pixel-sized sub-units of approximately plane wavefronts by the metasurface structure, and the slope of the wavefront to be measured is inverted according to the ratio of the grayscale value in each sub-unit and the polynomial coefficient in the calibration file, and then the wavefront to be measured is obtained by a wavefront restoration algorithm.

[0035] Specifically, the wavefront test module is composed of a metasurface structure and a camera. When the wavefront to be tested enters the metasurface structure, it is divided into multiple plane wavefronts with different slopes. According to the calibration file, the incident wavefront has a certain functional relationship with the grayscale ratio of the four pixels of the camera in each unit. The light intensity ratio of each unit is calculated through the grayscale distribution of the camera. , , under the premise of knowing the polynomial coefficients, the distribution of the wavefront slope to be measured can be obtained by substituting it into the polynomial formula.

[0036] The wavefront distribution to be measured can be obtained from the wavefront slope distribution through the traditional HTM wavefront restoration algorithm (regional method or pattern method).

[0037] The present application realizes wavefront detection technology with high resolution and ultra-large dynamic range by modulating the light intensity distribution through the metasurface and calibrating the relationship between the grayscale ratio and the slope. It has a simple structure and stable function, and has broad application prospects in the field of high-precision and large dynamic range wavefront measurement.

[0038] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. An ultra-high resolution HTM wavefront detection module based on a metasurface, characterized in that: The invention comprises a laser, a three-dimensional displacement stage, a collimator, a metasurface structure and a camera. The laser is located on the three-dimensional displacement stage, and the light outlet of the laser is located on the focal plane of the collimator. The metasurface structure takes four camera pixels as units, and a column grows on the edge of each unit to form a "well"-shaped metasurface structure. The "well"-shaped metasurface structure contains an array composed of super-atomic structures. The spherical wave emitted by the laser is collimated by the collimator to introduce plane wavefronts with different slopes, and the plane wavefronts with different slopes are recorded by the camera. The relationship between the ratio of the grayscale values ​​of the four pixels in each sub-unit and the slope of the wavefront after the wavefront passes through the metasurface structure is calculated. The slopes of the calibration wavefront in the X and Y directions are fitted with surface polynomials using the ratio of the grayscale values ​​of the four pixels in each sub-unit as the horizontal and vertical coordinates, and the polynomial coefficients of each sub-unit are recorded to form a calibration file. The wavefront to be measured is divided into multiple sub-units of 2*2 pixels by the metasurface structure. The slope of the wavefront to be measured is inverted according to the ratio of the grayscale values ​​in each sub-unit and the polynomial coefficients in the calibration file, and then the wavefront to be measured is obtained through the wavefront restoration algorithm.

2. The ultra-high resolution HTM wavefront detection module based on a metasurface as claimed in claim 1, characterized in that: The three-dimensional translation stage is used to control the laser light outlet to perform translation with the same step length on the focal plane of the collimator.

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