Desktop type installation and adjustment platform for extreme ultraviolet coaxial optical system and method thereof

Abstract

The invention discloses a desktop type installation and adjustment platform for an extreme ultraviolet coaxial optical system and a method of the desktop type installation and adjustment platform, and belongs to the field of optical system precision installation and adjustment devices.The installation and adjustment platform comprises a photoelectric auto-collimator, an electric rotary table, an image acquisition module, a light source and a lens set adjustment mechanism, and the optical axis of the photoelectric auto-collimator coincides with the rotating shaft of the electric rotary table; the optical platform is fixed on the base and serves as a reference axis of the adjustment platform, the electric rotary table is fixed on the optical platform, the plane reflector is fixed on the surface of the electric rotary table, the photoelectric auto-collimator is arranged on one side of the plane reflector, and the image acquisition module is arranged between the plane reflector and the photoelectric auto-collimator. The traditional installation and adjustment scheme is limited in applicable optical system and lacks flexibility and integration, but the installation and adjustment platform is an independent system with complete functions, integrates optical path calibration, attitude regulation and control and image analysis units, does not need external auxiliary equipment, can be flexibly arranged according to the relation between the aperture and the object image of the optical system to be installed and adjusted, and is convenient to install and adjust. And rapid adaptive precision adjustment is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optical system precision assembly and adjustment device, and particularly relates to a desktop assembly and adjustment platform for an extreme ultraviolet coaxial optical system and a method thereof. BACKGROUND

[0002] The extreme ultraviolet waveband (10-124 nm) covers the main atomic resonance lines and absorption edges of most low and medium atomic number elements, so that the extreme ultraviolet optical technology has important application value in the fields of chemical element analysis, plasma diagnosis, biological microscopic imaging, space astronomical observation and extreme ultraviolet lithography. Since all materials have strong absorption in this waveband, a transmissive optical system cannot work, and a reflective system based on multilayer film mirrors must be used. Among them, the coaxial reflective optical system has the characteristics of good symmetry, small aberration, compact structure and high resolution, and becomes the mainstream technical scheme, and a typical representative is the Schwarzschild structure. However, in order to realize ideal imaging or accurate focusing, the mirrors of this kind of system must be strictly coaxial and the mirror spacing must be accurately controllable, and any slight tilt, eccentricity or spacing error will introduce an aberration that is difficult to compensate, so high requirements are put forward for the assembly and adjustment precision. The traditional assembly and adjustment method relies on fixed devices and external separate equipment, and the operation is complex and flexible, which is difficult to meet the high-efficiency and high-precision assembly and adjustment requirements of different specifications of extreme ultraviolet coaxial systems.

[0003] The assembly and adjustment of the existing extreme ultraviolet coaxial optical system (such as the Schwarzschild system) mainly relies on a centering instrument to adjust the center deviation of each optical element. However, this method has obvious limitations: on the one hand, it cannot effectively monitor and calibrate the key parameter of mirror spacing; on the other hand, when the curvature radius of the mirror to be assembled and adjusted is too large or too small, it is difficult to make the convergence point of the centering instrument and the curvature center of the mirror surface accurately coincide in a limited space, resulting in a decrease in assembly and adjustment precision or even failure. Therefore, the traditional centering instrument scheme has insufficient applicability to optical systems with special numerical aperture or extreme mirror curvature, which limits its application in high-precision and diversified extreme ultraviolet optical assembly and adjustment. SUMMARY

[0004] The purpose of the present application is to provide a desktop assembly and adjustment platform for an extreme ultraviolet coaxial optical system and a method thereof to solve the problems mentioned in the background.

[0005] In order to achieve the above object, the application provides a desktop adjustment platform for an extreme ultraviolet coaxial optical system, comprising a photoelectric autocollimator, a motorized turntable, an image acquisition module, a light source and a mirror group adjustment mechanism, the optical axis of the photoelectric autocollimator coincides with the rotation axis of the motorized turntable and serves as a reference axis of the adjustment platform, the motorized turntable is fixed on an optical platform, a plane mirror is fixed on the surface of the motorized turntable, the photoelectric autocollimator is arranged on one side of the plane mirror, the image acquisition module is arranged between the plane mirror and the photoelectric autocollimator, the light source is located at a target object distance on the reference axis, and the mirror group adjustment mechanism is fixedly connected with the surface of the motorized turntable and stably rotates together with the motorized turntable.

[0006] Preferably, the mirror group adjustment mechanism is a combination of a high-precision three-axis displacement table, a pitch table and an arc swing table.

[0007] Preferably, the extreme ultraviolet coaxial optical system is composed of a series of extreme ultraviolet multilayer film mirrors, the reflecting surfaces of all the mirrors are symmetrical to the optical axis of the system, and the vertex normals of all the optical elements coincide with the optical axis of the extreme ultraviolet coaxial optical system.

[0008] Preferably, the mirror group adjustment mechanism is fixedly connected with the surface of the motorized turntable and stably rotates together with the motorized turntable.

[0009] Preferably, the light source is a visible light source or an extreme ultraviolet light source matched with the optical system.

[0010] Preferably, the image acquisition module is an industrial camera matched with the wave band of the light source.

[0011] The application further provides an adjustment method, the reference axis of the adjustment platform is established by means of self-collimation adjustment, and the method comprises the following steps: S1, fixing the motorized turntable, installing a plane mirror on the surface of the motorized turntable, marking a mark point on the surface of the plane mirror for indicating the center of the turntable, and making the reflecting surface of the plane mirror parallel to the mounting surface of the motorized turntable; S2, adjusting the photoelectric autocollimator to a first working distance to make the photoelectric autocollimator emit collimated light, adjusting the pitch and yaw angles of the photoelectric autocollimator, and making the cross-shaped wire image received by the photoelectric autocollimator and reflected by the plane mirror coincide with the reference cross-shaped wire built in the photoelectric autocollimator; S3, adjusting the photoelectric autocollimator to a second working distance to make the photoelectric autocollimator clearly image on the surface of the plane mirror, adjusting the horizontal and vertical positions of the photoelectric autocollimator, and making the mark point image on the surface of the plane mirror coincide with the reference cross-shaped wire built in the photoelectric autocollimator; S4, rotate the electric rotary table for one circle, and switch the working distance of the photoelectric autocollimator between the first working distance and the second working distance alternately, fine-tune the attitude and position of the photoelectric autocollimator, until the cross-shaped wire image reflected by the plane mirror and the mark point image on the surface of the photoelectric autocollimator are always coincident with the reference cross-shaped wire at any angle, at this time, the optical axis of the photoelectric autocollimator is coincident with the rotation axis of the electric rotary table, and thus the establishment of the reference axis of the platform is completed.

[0012] Preferably, the optical axis of the extreme ultraviolet coaxial optical system is adjusted by the mirror group adjustment mechanism until it is coincident with the reference axis of the platform, and the adjustment precision is judged by the electric rotary table and the image acquisition module.

[0013] Preferably, the adjustment method of the light source is that the photoelectric autocollimator is focused to the target working distance, the light source is adjusted until the center of the light outlet of the light source is coincident with the reference cross-shaped wire built in the photoelectric autocollimator.

[0014] Therefore, the desktop type platform for the extreme ultraviolet coaxial optical system and the method thereof have the following beneficial effects: 1. High precision and comprehensiveness: the present application can realize the precise adjustment and verification of the coaxial precision and the mirror spacing of the extreme ultraviolet coaxial optical system at the same time by establishing a high-precision reference axis and combining the autocollimator and image analysis, and overcomes the defect that the traditional method can only adjust the center deviation.

[0015] 2. High flexibility and versatility: the platform can be configured with light sources and cameras of different wavebands, which can be used for safe and convenient initial adjustment by visible light, and final verification by extreme ultraviolet light, and has wide applicability; compared with the traditional centering instrument scheme which has poor applicability to optical systems with special numerical aperture or extreme mirror curvature, the present application scheme can flexibly adapt to various optical systems with different numerical apertures and object-image relationships, and breaks through the limitation of traditional equipment on special curvature mirrors.

[0016] 3. High integration and convenience: all functional units required for adjustment are highly integrated in an independent system, without the need for external auxiliary equipment, which realizes rapid deployment and precise adjustment in a standard laboratory, and greatly improves the adjustment efficiency and the convenience of operation.

[0017] The technical solutions of the present application will be further described in detail below with reference to the drawings and embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a structural schematic diagram of an extreme ultraviolet focusing Schwarzschild system; Figure 2 is a schematic diagram of the reference axis establishment method of the adjustment platform; Figure 3Real-time photos taken during the establishment of the reference axis for the assembly and adjustment platform using a photoelectric autocollimator. Figure 4 A schematic diagram of the assembly and adjustment platform for the extreme ultraviolet focusing Schwarzschild system; Figure 5 A real-life image showing the focusing results of the Schwarzschild system; Figure Labels 1. Light source; 2. Secondary mirror; 3. Primary mirror; 4. Focal spot; 5. Motorized turntable; 6. Plane mirror; 7. Photoelectric autocollimator; 8. Reference axis; 9. Visible light CCD; 10. Lens tube; 11. Three-dimensional adjustment frame. Detailed Implementation

[0019] 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, not all, of the embodiments of the present invention. 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. Therefore, the following detailed description of the embodiments of the present 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 present invention without inventive effort are within the scope of protection of the present invention.

[0020] 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.

[0021] To address the precision assembly and adjustment requirements of extreme ultraviolet (EUV) coaxial optical systems, this invention provides a desktop assembly and adjustment platform for EUV coaxial optical systems. The platform includes an optoelectronic autocollimator 7, a motorized turntable 5, an image acquisition module, a light source 1, and a lens adjustment mechanism. The optical axis of the optoelectronic autocollimator 7 coincides with the rotation axis of the motorized turntable 5, serving as the reference axis 8 of the assembly and adjustment platform. The motorized turntable 5 is fixed to the optical platform, and a plane mirror 6 is fixed to its surface. The optoelectronic autocollimator 7 is positioned on one side of the plane mirror 6, and the image acquisition module is positioned between the plane mirror 6 and the optoelectronic autocollimator 7. The lens adjustment mechanism is a combination of a high-precision three-axis displacement stage, a pitch stage, and a swing stage, allowing the EUV coaxial optical system to be adjusted to various angles via this mechanism.

[0022] The extreme ultraviolet coaxial optical system consists of a series of extreme ultraviolet multilayer mirrors. The reflecting surfaces of all mirrors are symmetrical about the optical axis of the system, and the vertex normals of all optical elements coincide with the optical axis of the extreme ultraviolet coaxial optical system.

[0023] Light source 1 is located at the target distance on the reference axis 8.

[0024] The lens assembly adjustment mechanism is fixedly connected to the surface of the electric turntable 5 and can rotate stably together with the electric turntable 5.

[0025] Light source 1 is a visible light source or an extreme ultraviolet light source matched with the optical system; the image acquisition module can selectively use an industrial camera that matches the wavelength of light source 1.

[0026] "Desktop type" is defined as: the platform is a fully functional independent assembly and adjustment platform that integrates all the functional units required for assembly and adjustment, such as optical path calibration, attitude control and image analysis. It does not require external auxiliary equipment and can be flexibly arranged in the laboratory according to the aperture and object-image relationship of the extreme ultraviolet optical system to be assembled and adjusted, so as to achieve rapid and adaptive precision assembly and adjustment.

[0027] The present invention also provides an assembly and adjustment method, wherein the reference axis 8 of the assembly and adjustment platform is established through a self-collimation assembly and adjustment method, including the following steps: S1. Fix the electric turntable 5 and install a plane reflector 6 on its surface. The plane reflector 6 has markings for indicating the center of the turntable, and its reflective surface is parallel to the mounting surface of the electric turntable 5. S2. Focus the photoelectric autocollimator 7 to the first working distance (A) so that it emits collimated light. Adjust the pitch and yaw angles of the photoelectric autocollimator 7 so that the crosshair image received by it and reflected back by the plane mirror 6 coincides with the reference crosshair built into the photoelectric autocollimator. S3. Focus the photoelectric autocollimator 7 to the second working distance (B) so that it is clearly imaged on the surface of the plane mirror 6. Adjust the horizontal and vertical positions of the photoelectric autocollimator 7 so that the marked point image on the surface of the plane mirror 6 coincides with the reference crosshairs built into the photoelectric autocollimator 7. S4. Rotate the electric turntable 5 one revolution and alternately switch the working distance of the photoelectric autocollimator 7 between the first working distance A and the second working distance B, fine-tuning its attitude and position until, at any rotation angle, the crosshair image reflected back by the plane mirror 6 and the surface mark point image always coincide with the reference crosshair. At this time, the optical axis of the photoelectric autocollimator 7 coincides with the rotation axis of the electric turntable 5, thus the reference axis 8 of the assembly and adjustment platform is established.

[0028] The optical axis of the extreme ultraviolet coaxial optical system is adjusted by the lens assembly adjustment mechanism until it coincides with the reference axis 8 of the assembly and adjustment platform. The accuracy of the assembly and adjustment is determined by the electric turntable 5 and the image acquisition module.

[0029] The adjustment method for light source 1 is as follows: focus the photoelectric autocollimator to the target working distance, and adjust light source 1 until the center of its light outlet coincides with the reference crosshairs built into the photoelectric autocollimator 7.

[0030] Example 1 This embodiment uses an extreme ultraviolet (EUV) focusing Schwarzschild system as an example, demonstrating its assembly and adjustment via an assembly platform. The Schwarzschild system, as a typical EUV coaxial optical system, employs a two-mirror reflection structure to achieve focusing or magnified imaging. For example... Figure 1 As shown, the optical system includes a primary mirror 3 and a secondary mirror 2 disposed on one side of the primary mirror 3. The primary mirror 3 is a convex spherical reflector and the secondary mirror 2 is a concave spherical reflector with a central opening. The centers of curvature and geometric centers of the primary mirror 3 and the secondary mirror 2 are collinear, forming the optical axis of the system. The incident light is reflected sequentially by the primary mirror 3 and the secondary mirror 2, and then focused behind the primary mirror 3.

[0031] The specific optical structure parameters of the assembly and adjustment platform in this embodiment are shown in Table 1.

[0032] Table 1 Specific optical structural parameters of the assembly and adjustment system

[0033] This optical system is a focusing Schwarzschild structure with a magnification of up to 150x, capable of focusing a 3mm aperture light source to a 20μm focal spot. The system operates in the 13.5nm extreme ultraviolet band, and both the primary mirror and the secondary mirrors are coated with Mo / Si multilayer films. Due to the extremely high magnification, the assembly and adjustment tolerances are stringent: the adjustment accuracy of the distance between the two mirrors and the image distance must reach the micrometer level, and the eccentricity of each mirror must reach the sub-micrometer level. The assembly and adjustment platform of this invention is designed to meet these high-precision assembly and adjustment requirements, enabling rapid and precise assembly and adjustment.

[0034] The method for establishing the reference axis 8 is as follows: Figure 2 As shown. First, the electric turntable is fixed to the optical platform by a bracket, and a plane mirror 6 with the center mark of the electric turntable is tightly attached to its surface. The photoelectric autocollimator 7 is placed facing the mirror. The reference axis 8 is established as follows: First, the photoelectric autocollimator 7 is focused to the first working distance (outgoing parallel light), and its pitch and yaw adjustment knobs are adjusted so that the crosshair image reflected back by the plane mirror 6 coincides with the center of the reference crosshair built into the photoelectric autocollimator 7, such as... Figure 3 (a) At this point, the optical axis of the autocollimator is parallel to the normal of the mirror, that is, parallel to the axis of rotation of the turntable. Then, the photoelectric autocollimator 7 is focused to the second working distance (aligned with the surface of the mirror), and its lateral and vertical positions are adjusted by the three-dimensional adjustment frame 11 placed under the photoelectric autocollimator 7 until the marked point image on the surface of the plane mirror 6 coincides with the center of the reference crosshairs, such as... Figure 3(b) Finally, rotate the electric turntable 5 one revolution and alternately switch the working distance of the photoelectric autocollimator 7 between the two states mentioned above. The returned crosshair image and the marker point image always coincide with the built-in reference crosshair line, indicating that the optical axis of the photoelectric autocollimator 7 and the rotating axis of the electric turntable have been precisely coincided at this time. This coincident axis is the reference axis 8 of the assembly and adjustment platform.

[0035] Remove the plane mirror 6 to allow light to pass through the center of the motorized turntable 5. Focus the photoelectric autocollimator 7 to the target object distance and place an LED light source with a 2.5mm aperture at that position; according to the theoretical calculation of the Schwarzschild system, the focal spot 4 size is 16.7μm. Mount the lens barrel 10, which houses the primary mirror 3 and the secondary mirror 2, onto the surface of the motorized turntable 5, with both the primary mirror 3 and the secondary mirror 2 in a free state in space. The primary mirror 3 is positionally adjusted using the three-dimensional adjustment frame 11, which is rigidly connected to the motorized turntable 5; the secondary mirror 2 is finely adjusted using the bolt pull mechanism on the side wall of the lens barrel 10. Place a visible light CCD 9 (i.e., the image acquisition module) between the motorized turntable 5 and the photoelectric autocollimator 7, ensuring that its photosensitive surface coincides with the theoretical image point of the system. All axial spacing measurements and calibrations are performed using the photoelectric autocollimator 7. At this point, the layout of the assembly platform is complete, and the overall arrangement is as follows: Figure 4 As shown.

[0036] During the assembly and adjustment process, the focused spot is monitored in real time using a visible light CCD 9 with a pixel size of 2.2μm. The attitudes of the primary and secondary mirrors 2 and the distance between them are adjusted until the focused spot on the CCD is minimized. The motorized turntable 5 is rotated, and the focus is checked for movement or defocusing during rotation. If the focus spot moves or defocuses, it indicates that the mirror centers of the two mirrors are not aligned with the reference axis 8. Further adjustments are made based on the focus spot during rotation. The assembly and adjustment are complete when the motorized turntable 5 rotates and the focused spot 4 remains at its minimum size and does not move. Figure 5 The result of the adjusted focal spot 4 is approximately 7 to 8 pixels in diameter, which corresponds to an actual focal spot size of 15.4 μm to 17.6 μm, consistent with the theory. At the same time, the objective lens group is rotated using a turntable, and the position of focal spot 4 remains unchanged, thus completing the adjustment.

[0037] During the assembly and adjustment process, the focused spot morphology output by the visible light CCD9 real-time monitoring system was monitored. The pixel size of this CCD is 2.2μm. By adjusting the attitude of the primary and secondary mirrors 2 and precisely controlling the distance between the two mirrors, the system was gradually optimized until the spot size in the CCD's field of view was minimized. Subsequently, the motorized turntable 5 was rotated one revolution, and the changes in the spot during the rotation were observed. If the spot showed positional drift or defocusing, it indicated that the coaxial state of the optical lens group was not fully established, and the mirror center was not precisely aligned with the reference axis 8. Iterative fine-tuning of the lens group attitude was required based on the direction of the spot's shift and the degree of defocusing. Finally, when the motorized turntable 5 rotated within a 360° range, the focal spot 4 remained at its minimum size and in a stable position without movement, indicating that the coaxial assembly and adjustment of the system was complete. Figure 5 The image of focal spot 4, acquired after assembly and adjustment, is shown. Its diameter is approximately 7-8 pixels, corresponding to an actual size of 15.4μm-17.6μm, which is in good agreement with the theoretical design value (16.7μm). Further verification by rotating the electric turntable 5 showed that the position of focal spot 4 did not shift at all, fully demonstrating the assembly and adjustment accuracy and stability, marking the completion of the entire assembly and adjustment process.

[0038] Therefore, the present invention adopts the above-mentioned desktop assembly and adjustment platform and method for extreme ultraviolet coaxial optical systems, which highly integrates all the functional units required for assembly and adjustment into an independent system without the need for external auxiliary equipment. This enables rapid deployment and precise assembly and adjustment in a standard laboratory, greatly improving assembly and adjustment efficiency and ease of operation.

[0039] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A desktop assembly platform for an extreme ultraviolet coaxial optical system, characterized in that: The system includes an optoelectronic autocollimator, a motorized turntable, an image acquisition module, a light source, and a lens adjustment mechanism. The optical axis of the optoelectronic autocollimator coincides with the rotation axis of the motorized turntable and serves as the reference axis for the assembly and adjustment platform. The motorized turntable is fixed on the optical platform, and a plane mirror is fixed on the surface of the motorized turntable. The optoelectronic autocollimator is located on one side of the plane mirror, and the image acquisition module is located between the plane mirror and the optoelectronic autocollimator. The light source is located at the target object distance on the reference axis. The lens adjustment mechanism is fixedly connected to the surface of the motorized turntable and rotates stably together with the motorized turntable.

2. The desktop assembly platform for an extreme ultraviolet coaxial optical system according to claim 1, characterized in that: The mirror assembly adjustment mechanism is a combination of a high-precision three-axis displacement stage, a pitch stage, and an arc swing stage.

3. A desktop assembly platform for an extreme ultraviolet coaxial optical system according to claim 1, characterized in that: The extreme ultraviolet coaxial optical system consists of a series of extreme ultraviolet multilayer mirrors. The reflecting surfaces of all mirrors are symmetrical about the optical axis of the system, and the vertex normals of all optical elements coincide with the optical axis of the extreme ultraviolet coaxial optical system.

4. A desktop assembly platform for an extreme ultraviolet coaxial optical system according to claim 1, characterized in that: The light source is a visible light source or an extreme ultraviolet light source matched with the optical system.

5. A desktop assembly platform for an extreme ultraviolet coaxial optical system according to claim 1, characterized in that: The image acquisition module is an industrial camera that matches the wavelength of the light source.

6. An assembly and adjustment method, applied to a desktop assembly and adjustment platform for an extreme ultraviolet coaxial optical system as described in any one of claims 1-5, characterized in that: The reference axis of the assembly and adjustment platform is established through a self-collimation assembly and adjustment method, including the following steps: S1. Fix the electric turntable and install a plane reflector on the surface of the electric turntable. The surface of the plane reflector is engraved with markings to indicate the center of the turntable, and the reflective surface of the plane reflector is parallel to the mounting surface of the electric turntable. S2. Focus the photoelectric autocollimator to the first working distance so that the photoelectric autocollimator emits collimated light. Adjust the pitch and yaw angles of the photoelectric autocollimator so that the crosshair image received by the photoelectric autocollimator and reflected back by the plane mirror coincides with the reference crosshair built into the photoelectric autocollimator. S3. Focus the photoelectric autocollimator to the second working distance so that the photoelectric autocollimator can clearly image the plane mirror surface. Adjust the horizontal and vertical positions of the photoelectric autocollimator so that the marked point image on the plane mirror surface coincides with the reference crosshairs built into the photoelectric autocollimator. S4. Rotate the electric turntable one revolution and alternately switch the working distance of the photoelectric autocollimator between the first working distance and the second working distance. Fine-tune the attitude and position of the photoelectric autocollimator until, at any angle, the crosshair image reflected back by the plane mirror and the image of the marked point on the surface of the photoelectric autocollimator always coincide with the reference crosshair. At this time, the optical axis of the photoelectric autocollimator coincides with the rotation axis of the electric turntable, and the reference axis of the assembly and adjustment platform is established.

7. The assembly and adjustment method according to claim 6, characterized in that: The optical axis of the extreme ultraviolet coaxial optical system is adjusted by the lens assembly adjustment mechanism until it coincides with the reference axis of the assembly platform. The accuracy of the assembly is determined by the electric turntable and the image acquisition module.

8. The assembly and adjustment method according to claim 7, characterized in that: The method for adjusting the light source is as follows: focus the photoelectric autocollimator to the target working distance, and adjust the light source until the center of the light source's output port coincides with the reference crosshairs built into the photoelectric autocollimator.

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