A planar optical element alignment system based on moire diffraction optical elements

Abstract

The present application relates to a kind of plane optical element alignment system based on moire diffraction optical element, the system includes: the plane optical element to be aligned, continuous spectrum light source, multispectral camera and optical subsystem, wherein: the optical subsystem, the subsystem is based on moire diffraction optical element MODEs optical subsystem, for the polychromatic light generated by the continuous spectrum light source is focused to the surface of the plane optical element to be aligned at different depths, and the reflected light reflected by the surface is returned to the multispectral camera, to obtain the imaging of the same magnification of the surface at multiple different depths, by adjusting the moire diffraction optical element MODEs, when the imaging is all clear image, the alignment of the plane optical element to be calibrated is completed.Compared with prior art, the present application has the beneficial effects of high alignment accuracy, simple structure, rich functions and the like.

Description

Technical Field

[0001] This invention relates to the field of optical system assembly and adjustment technology, and in particular to a planar optical element alignment system based on moiré diffraction optical elements. Background Technology

[0002] With the rapid development of micro-nano fabrication technologies for optical components such as electron beam lithography, ultraviolet lithography, and laser direct writing, planar optical components with special surface microstructures, such as gratings and metasurfaces, have become a major research hotspot. These planar optical components typically exhibit strong angular sensitivity and often require multiple components to be cascaded. Therefore, achieving high-precision alignment of planar optical components is a key technology for assembling and adjusting such optical systems.

[0003] The challenge in solving the above technical problems lies in how to simultaneously achieve clear imaging of multiple surface alignment markers with a spacing of millimeters at the same magnification. Currently, there is no good alignment system to achieve this function. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a planar optical element alignment system based on moiré diffraction optical elements that has high alignment accuracy, simple structure, and rich functions.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A planar optical element alignment system based on moiré diffraction optical elements includes: a planar optical element to be aligned, a continuous spectrum light source, a multispectral camera, and an optical subsystem. The optical subsystem, which is an optical subsystem based on moiré diffraction optical elements (MODEs), is used to focus multicolor light generated by the continuous spectrum light source onto the surface of the planar optical element to be aligned at different depths, and to return the reflected light from the surface to the multispectral camera to obtain images of the surface at multiple different depths with the same magnification. By adjusting the moiré diffraction optical elements (MODEs), the alignment of the planar optical element to be aligned is completed when all images are clear.

[0007] Preferably, the optical subsystem includes a beam splitter, moiré diffraction optical elements (MODES), a fixed-focus lens, and a microscope objective. The multicolor light generated by the continuous spectrum light source sequentially enters the beam splitter, the moiré diffraction optical elements (MODES), the fixed-focus lens, and the microscope objective before being projected onto the surface of the planar optical element to be aligned. After reflection, the light projected onto the surface of the planar optical element to be aligned sequentially enters the microscope objective, the fixed-focus lens, the moiré diffraction optical elements (MODES), and the beam splitter before entering the multispectral camera.

[0008] More preferably, the moiré diffractive optical elements (MODES) include a cascaded first diffractive optical element and a second diffractive optical element.

[0009] More preferably, both the first diffractive optical element and the second diffractive optical element are diffractive optical elements with adjustable rotation angles.

[0010] More preferably, the first diffractive optical element and the second diffractive optical element are phase-conjugated diffractive optical elements.

[0011] More preferably, the distance between the microscope objective and the moiré diffraction optical elements (MODES) is equal to the focal length of the microscope objective.

[0012] More preferably, when the distance between the microscope objective and the moiré diffraction optical elements (MODES) is equal to the focal length of the microscope objective, the magnification of the images of the plurality of surfaces at different depths is the same.

[0013] More preferably, the multispectral camera has multiple camera channels; the number of images acquired by the multispectral camera is equal to the number of camera channels.

[0014] More preferably, the system further includes: adjusting the spacing between focal planes by adjusting the rotation angle of the moiré diffraction optical elements MODEs, and completing the alignment of the plane optical element to be calibrated when all images are clear.

[0015] Preferably, the system further includes a sample stage for placing the planar optical element to be aligned.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] (1) High alignment accuracy: In the planar optical element alignment system provided by the present invention, multiple planes are aligned by observing multiple focal planes with the same magnification at the same time. The angle between two diffractive optical elements is changed by rotation, thereby adjusting the position of different focal planes. The focal plane spacing can reach the millimeter level, which effectively improves the alignment accuracy of planar optical elements.

[0018] (2) Simple structure: The optical path structure of the planar optical element alignment system provided by the present invention is the same as that of the traditional microscope, which is simple and has a low implementation cost.

[0019] (3) Rich in functions: When using a continuous spectrum light source and a multispectral camera, the planar optical element alignment system provided by this invention can also realize the function of a stereo microscope. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the planar optical element alignment system based on moiré diffraction optical elements in an embodiment of the present invention;

[0021] Figure 2 This is a schematic diagram of the phase distribution of two cascaded diffractive optical elements (DOEs) in an embodiment of the present invention.

[0022] in, Figure 2 (a) is the phase distribution diagram of the first diffractive optical element. Figure 2 (b) is the phase distribution diagram of the second diffractive optical element;

[0023] Figure 3 This is a schematic diagram of the surface alignment mark imaging results of the three channels of the RGB camera in an embodiment of the present invention;

[0024] in, Figure 3 (a)~ Figure 3 (c) Schematic diagrams of the alignment mark imaging results for the R, G, and B channels, respectively.

[0025] The numbers in the diagram are as follows:

[0026] 1. Planar optical element to be aligned; 2. Continuous spectrum light source; 3. Multispectral camera; 4. Optical subsystem.

[0027] 41. Spectroscopic element; 42. Moiré diffraction optical element (MODES); 43. Fixed-focus lens; 44. Microscope objective.

[0028] 421. First diffractive optical element; 422. Second diffractive optical element. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0030] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0031] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0032] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of this invention is usually placed during use. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0033] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0034] This invention provides a planar optical element alignment system based on Moiré Diffractive Optical Elements (MODES), such as... Figure 1 As shown, the alignment system includes: a planar optical element to be aligned 1, a continuous spectrum light source 2, a multispectral camera 3, and an optical subsystem 4, wherein:

[0035] Optical subsystem 4 is an optical subsystem based on moiré diffraction optical elements MODEs. It is used to focus the multicolor light generated by the continuous spectrum light source 2 onto the surface of the planar optical element 1 to be aligned at different depths, and return the reflected light from the surface to the multispectral camera 3 to obtain images of multiple surfaces at different depths with the same magnification. By adjusting the moiré diffraction optical elements MODEs, the alignment of the planar optical element to be aligned is completed when all images are clear.

[0036] The optical subsystem 4 described above will be introduced in detail below:

[0037] Optionally, the aforementioned optical subsystem 4 includes: a beam splitter 41, a moiré diffraction optical element MODEs 42, a fixed-focus lens 43, and a microscope objective 44. Multicolor light generated by the continuous spectrum light source 2 sequentially enters the beam splitter 41, the moiré diffraction optical element MODEs 42, the fixed-focus lens 43, and the microscope objective 44 before being projected onto the surface of the planar optical element 1 to be aligned. After reflection, the light projected onto the surface of the planar optical element 1 to be aligned sequentially enters the microscope objective 44, the fixed-focus lens 43, the moiré diffraction optical element MODEs 42, and the beam splitter 41 before entering the multispectral camera 3.

[0038] Optionally, the aforementioned moiré diffraction optical elements MODEs42 include a cascaded first diffraction optical element (DOE1) 421 and a second diffraction optical element (DOE2) 422.

[0039] Optionally, the first diffractive optical element (DOE1) 421 and the second diffractive optical element (DOE2) 422 are both diffractive optical elements (DOEs) with adjustable rotation angles.

[0040] Optionally, the first diffractive optical element (DOE1) 421 and the second diffractive optical element (DOE2) 422 are phase-conjugated diffractive optical elements.

[0041] Understandably, due to the significant dispersion capability of diffractive optical elements (DOEs), light of different wavelengths is focused onto the surface of the planar optical element to be aligned at different depths, thus achieving "rainbow depth illumination" in image space. Each wavelength corresponds to a clear image at its focal plane, and the relative positions of these focal planes can be flexibly changed by altering the focal length of the MDOEs.

[0042] Optionally, the distance between the aforementioned microscope objective 44 and the moiré diffraction optical element MODEs 42 is equal to the focal length of the microscope objective 44.

[0043] Optionally, when the distance between the microscope objective 44 and the moiré diffraction optical element MODEs 42 is equal to the focal length of the microscope objective 44, the magnification of the images of the multiple surfaces at different depths is the same.

[0044] It is understandable that the magnification β in the above alignment system satisfies the following relationship:

[0045]

[0046] Among them, l image f1 is the distance between the camera and the MDOEs, and f1 is the focal length of the microscope objective.

[0047] Therefore, when the distance between the microscope objective 44 and the moiré diffraction optical element MODEs 42 is equal to the focal length of the microscope objective 44, the magnification of the images of the multiple surfaces at different depths is the same.

[0048] Optionally, the multispectral camera 3 has multiple camera channels, and the number of images acquired by the multispectral camera 3 is equal to the number of camera channels.

[0049] Understandably, the aforementioned multispectral camera 3 can observe multiple image planes at once, and the position of the image planes is adjustable, with the maximum spacing reaching the millimeter level.

[0050] Understandably, the alignment system adjusts the spacing between focal planes by adjusting the rotation angle of the moiré diffraction optical element MODEs42, and completes the alignment of the optical element to be calibrated when all images are clear.

[0051] Optionally, the alignment system may further include a sample stage for placing the planar optical element 1 to be aligned.

[0052] In the above scheme, images formed by different wavelengths correspond to planes at different depths, and the spacing can be adjusted by adjusting the rotation angle of the two DOEs in the moiré diffraction optical element MDOEs42. When clear images are obtained on different surfaces at the same time, the calibration of the planar optical element is achieved.

[0053] Understandably, the alignment system described above can also function as a stereomicroscope when using a continuous spectrum light source and a multispectral camera.

[0054] The following example uses a common RGB camera to align a planar optical element 1 containing three surfaces. The three channels of the RGB camera have wavelengths of 420nm, 525nm, and 635nm.

[0055] Specifications of microscope objective 44: magnification 5×, numerical aperture NA = 0.10, focal length f1 = 25.4 mm, and f1 is equal to the distance D between microscope objective 44 and MDOEs;

[0056] MDOEs consist of two phase conjugate DOEs with variable rotation angles, and their phase distributions are shown in the attached figure. Figure 2 As shown, with a rotation angle θ = 30°, the focal length of the MDOEs is f0 ≈ 114.3 mm;

[0057] The RGB three channels respectively obtained images of the alignment marks on three optical surfaces, and the imaging results are shown in the attached figure. Figure 3 As shown. Under the conditions of this embodiment, the image plane spacing is: ΔL1 = 1.129 mm, ΔL2 = 1.183 mm.

[0058] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A planar optical element alignment system based on a moiré diffraction optical element, characterized in that, The system includes a planar optical element to be aligned, a continuous spectrum light source, a multispectral camera, and an optical subsystem, wherein: The optical subsystem, which is an optical subsystem based on moiré diffraction optical elements (MODEs), is used to focus the multicolor light generated by the continuous spectrum light source onto the surface of the planar optical element to be aligned at different depths, and return the reflected light from the surface to the multispectral camera to obtain images of the surface at multiple different depths with the same magnification. By adjusting the moiré diffraction optical elements (MODEs), the alignment of the planar optical element to be aligned is completed when all the images are clear. The optical subsystem includes a beam splitter, moiré diffraction optical elements (MODEs), a fixed-focus lens, and a microscope objective. The multicolor light generated by the continuous spectrum light source is sequentially incident on the beam splitter, the moiré diffraction optical elements (MODEs), the fixed-focus lens, and the microscope objective before being projected onto the surface of the planar optical element to be aligned. After being reflected, the light projected onto the surface of the planar optical element to be aligned enters the microscope objective, the fixed-focus lens, the moiré diffraction optical element (MODES), and the beam splitter in sequence before entering the multispectral camera.

2. The planar optical element alignment system based on a moiré diffraction optical element according to claim 1, characterized in that, The moiré diffraction optical elements (MODES) include a cascaded first diffraction optical element and a second diffraction optical element.

3. The planar optical element alignment system based on a moiré diffraction optical element according to claim 2, characterized in that, Both the first diffractive optical element and the second diffractive optical element are diffractive optical elements with adjustable rotation angle.

4. The planar optical element alignment system based on a moiré diffraction optical element according to claim 2, characterized in that, The first diffractive optical element and the second diffractive optical element are phase-conjugated diffractive optical elements.

5. A planar optical element alignment system based on a moiré diffraction optical element according to claim 1, characterized in that, The distance between the microscope objective and the moiré diffraction optical elements (MODES) is equal to the focal length of the microscope objective.

6. The planar optical element alignment system based on a moiré diffraction optical element according to claim 5, characterized in that, When the distance between the microscope objective and the moiré diffraction optical elements (MODES) is equal to the focal length of the microscope objective, the magnification of the images of the plurality of surfaces at different depths is the same.

7. The planar optical element alignment system based on a moiré diffraction optical element according to claim 1, characterized in that, The multispectral camera has multiple camera channels; the number of images acquired by the multispectral camera is equal to the number of camera channels.

8. A planar optical element alignment system based on a moiré diffraction optical element according to claim 1, characterized in that, The system further includes: adjusting the spacing between focal planes by adjusting the rotation angle of the moiré diffraction optical elements MODEs, and completing the alignment of the optical elements to be aligned when all images are clear.

9. A planar optical element alignment system based on a moiré diffraction optical element according to claim 1, characterized in that, The system also includes: A sample stage is used to place the planar optical element to be aligned.

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