An active optical system for high-precision correction of the mirror surface shape

Abstract

The present invention provides an active optical system for accurately correcting the surface shape of a reflecting mirror, which includes a wire-pulling pulley, a side wire, a side anchor point, a system bracket, a limiting arm, a fixing device, a bracket anchor point, a bottom wire, a mirror body, a force-applying component, and a wire anchor point at the lower end of the mirror body; a structure with multiple wires is adopted on the side and bottom of the mirror body to form a multi-point adjustment system, and the surface shape of the long-shaped mirror is corrected by independently adjusting the tension of each wire. It is used to correct and adjust the surface shape of the reflecting mirror during service, and reduce the deviation between the actual surface shape and the target surface shape. The support and clamping force of the mirror body of the present invention are completely decoupled from the wire force for adjusting the surface shape of the mirror body, which is conducive to the installation and debugging of the mirror body; the boundary conditions of the system are clear, the optimization target is clear, which is beneficial to the optimization design of the surface shape, and the structure is simple, not affected by the installation accuracy and deformation of the force-applying device, etc., and has high adjustment accuracy and good system stability.

Description

Technical Field

[0001] The present invention belongs to the field of active optics, and particularly relates to an active optical system for precisely correcting the surface shape of a reflecting mirror. Background Art

[0002] The focusing mirror is a core component in synchrotron radiation beamlines and is the simplest and most effective component for reducing the spot size and improving the flux density. The surface shape error is an important indicator for measuring the quality of the focusing mirror and determining its performance. However, due to the very small grazing incidence angle and the large scale of the focusing mirror (1000 mm), it requires a high cost to obtain an X-ray focusing mirror with extremely small surface shape error, and some cannot even be fabricated in China. In the focusing mirror, an elliptical surface shape is commonly used to achieve point-to-point focusing, or a parabolic surface shape is used to achieve a collimated beam. Due to the large scale of these mirror bodies, they will be affected by gravity, clamping force, etc. during use, so it is difficult for their actual surface shape to match the designed surface shape. In order to achieve the expected surface shape accuracy of the mirror surface, many beamlines are designed around active adjustment optical instruments. Among them, there are various design schemes for multi-point adjustment of the focusing mirror.

[0003] ALBA Light Source in Spain fabricated a multi-point adjustment prototype. This prototype consists of two parts: an error correction part and a bending mechanism. At the error correction part, a high-precision motor is used as a corrector, which can achieve nanometer-level resolution; the minimum force increment is 0.001 N, and the maximum correction force that can be applied is 40 N. The bending force range of the bending mechanism is from 0 to 500 N, the accommodated mirror body length range is from 300 to 1500 mm, and the width and thickness of the mirror body are 50 mm and 20 mm respectively. This technology can reduce the slope error of the focusing mirror caused by gravity from 0.87 μrad (rms) to 0.115 μrad (rms). The adjustment mechanism of the SOLEIL Light Source in France uses 10 motors in the middle to control the local surface shape of a mirror with a length, width, and thickness of 350 mm, 50 mm, and 8 mm respectively; the motor has a self-locking function, the strength range is ±30 N, and the repeatability accuracy is 10 mN. The adjustable elliptical surface shape range is p = 35 m, q = 0.3 m to ∞, where p represents the object distance and q represents the image distance. The slope error of the mirror surface can be adjusted to approximately 0.55 μrad (rms). The Spring-8 Light Source in Japan adjusts the mirror body by combining mechanical multi-point adjustment and piezoelectric deformation adjustment, and can achieve a relatively high adjustment effect. The multi-point adjustment work of domestic light sources is more limited to the theoretical aspect, and there is no relatively mature prototype yet. The collimating mirror bending system of the XAFS beamline (BL14W) in the Shanghai Light Source proposed a method of multi-point adjustment for gravity balance, and obtained the optimal action point and magnitude of the balance force through calculation. When calculating the self-weight balance with two-point, three-point, and four-point adjustments, the root mean square errors of the surface shape are 0.179, 0.067, and 0.032 μrad (rms) respectively.

[0004] All of the above multi-point adjustment devices use a force application mechanism such as a motor-driven lead screw. The force application method belongs to ultra-high-precision displacement rigid conduction, which requires high precision in assembly and debugging. When the assembly is poor, it is easy to cause the force direction of the mirror body not to follow the design direction. In addition, the force application at each point needs to be achieved through the ultra-high-precision displacement of the adjustment device, and the high cost of the adjustment mechanism itself will further increase the overall cost of the device. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention proposes an active optical system for high-precision correction of the reflecting mirror surface shape, which adjusts the undulation of the reflecting surface of the mirror body by changing the tiny tension applied by the wire rope, so as to achieve the purpose of correcting the surface shape.

[0006] The technical solution of the present invention is as follows:

[0007] An active optical system for high-precision correction of the reflecting mirror surface shape, comprising a wire rope pulley, side wire ropes, side anchor points, a system support, a limiting arm, a fixing device, a support anchor point, a bottom wire rope, a reflecting mirror body, a force application component and a wire rope anchor point at the lower end of the mirror body; wherein, there are two of the limiting arms, the upper ends of which are fixedly connected and fixed through the fixing device, and the lower ends are respectively fixed on the system support; the reflecting mirror body is fixed between the two limiting arms and is stabilized on the system support through the limiting arms and the fixing device; a plurality of the side anchor points are evenly arranged on each side of the reflecting mirror body at the same interval; a plurality of independently adjustable side wire ropes pass through the wire rope pulley, and the two ends of the side wire rope are respectively connected to the side anchor points aligned on both sides of the reflecting mirror body to form multiple groups of side wire ropes; the wire rope pulley is connected to the force application component, and the force applied to the side wire rope on the wire rope pulley is adjusted through the force application component; the reflecting mirror body is connected to a plurality of the bottom wire ropes through a plurality of the wire rope anchor points at the lower end of the mirror body arranged at equal intervals, and the bottom wire ropes are fixedly connected to a plurality of the support anchor points on the system support.

[0008] Further, the side anchor points on both sides of the reflecting mirror body are on the same horizontal plane, and the side anchor points on both sides are aligned.

[0009] Further, the tension of the side wire rope is adjusted by the wire rope pulley, and the distances from the wire rope pulley to the side anchor points on both sides are equal, so as to ensure that the same tension can be applied to the side wire ropes on both sides with one force application point.

[0010] Further, each of the bottom wire ropes is fixedly connected vertically downward to a plurality of the support anchor points evenly arranged on the system support, so as to form a plurality of vertical bottom wire ropes.

[0011] Furthermore, the side stay cables and the bottom stay cables are flexible structures; both the side stay cables and the bottom stay cables are provided with stay cable force receiving terminals.

[0012] Furthermore, both the side anchor points and the support anchor points are bonded to the mirror body as a whole.

[0013] Furthermore, the force applying component is a locking bolt, which is assembled on the fixing device through a screw rod and transmits the adjusting force to the stay cable pulley. The locking bolt is arranged on the top of the stay cable pulley, and the two are connected through a spherical connecting piece.

[0014] Furthermore, the locking bolt drives the stay cable pulley to adjust the tension of the side stay cable through the up and down movement of the screw rod.

[0015] Furthermore, it further includes a surface shape monitoring and detection device and a mirror surface target value correction control software.

[0016] Furthermore, the force applying component adopts a cooperation mode of a permanent magnet column and an electromagnetic coil. The permanent magnet column and the electromagnetic coil control the electromagnetic force between the force applying component and the stay cable pulley by using the magnitude of the current to perform force application adjustment.

[0017] Advantageous effects:

[0018] The present invention provides an active optical system for high-precision correction of the surface shape of a reflecting mirror. It adopts a structure of multiple stay cables to form multi-point detection, and realizes the surface shape correction of a long-shaped reflecting mirror through independent tension adjustment of each stay cable. It is used to correct and adjust the surface shape of a reflecting mirror during service, and reduce the deviation between the actual surface shape and the target surface shape. The present invention adopts a simple force application method to control the surface shape of the mirror body, so that the force on the mirror body always acts along the direction of the stay cable, which is different from the traditional force application method brought by the displacement of the force application device. Therefore, the present invention does not use ultra-high-precision mechanical displacement devices, making the overall cost of the surface shape correction mechanism lower than the traditional method; the support and clamping force of the mirror body and the stay cable force for adjusting the surface shape of the mirror body are completely decoupled, which is easy for the installation and debugging of the mirror body; the boundary conditions of the system are clear and the optimization target is clear, which is beneficial for the optimization design of the surface shape. The structure of the present invention is simple, not affected by the installation accuracy, deformation, etc. of the force application device, and has high adjustment accuracy and good system stability. Description of the drawings

[0019] Figure 1 It is a schematic diagram of the active optical system for high-precision correction of the surface shape of a reflecting mirror according to the present invention;

[0020] Figure 2 It is a side cross-sectional view of the active optical system for high-precision correction of the surface shape of a reflecting mirror; among them, (a) is a schematic diagram of the side stay cable applying force; (b) is a schematic diagram of the bottom stay cable applying force.

[0021] Among them, 1 - wire-pulling pulley, 2 - side wire, 3 - side anchor point, 4 - system support, 5 - limiting arm, 6 - fixing device, 7 - support anchor point, 8 - bottom wire, 9 - mirror body, 11 - force-applying component, 12 - wire anchor point at the lower end of the mirror body. Specific implementation mode

[0022] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to 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. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other. The same reference numerals in the drawings always represent the same components.

[0023] As Figure 1 shown, the active optical system for high-precision correction of the mirror surface shape of the present invention includes a wire-pulling pulley 1, side wires 2, side anchor points 3, a system support 4, limiting arms 5, a fixing device 6, support anchor points 7, bottom wires 8, a mirror body 9, a force-applying component 11 and a wire anchor point 12 at the lower end of the mirror body. There are two limiting arms 5, the upper ends of which are connected and fixed through the fixing device 6, and the lower ends are respectively fixed on the system support 4. The mirror body 9 is fixed between the two limiting arms 5 and is stably positioned on the system support 4 through the limiting arms 5 and the fixing device 6. On each side of the mirror body 9, a plurality of the side anchor points 3 are uniformly arranged at the same interval, the side anchor points 3 on both sides are on the same horizontal plane, and the side anchor points 3 on both sides are aligned. A plurality of independently adjustable side wires 2 pass through the wire-pulling pulley 1, and the two ends of the side wire 2 are respectively connected to the aligned side anchor points 3 on both sides of the mirror body 9 to form multiple groups of side wires 2. The tension of the side wire 2 is adjusted by the wire-pulling pulley 1, and the distances from the wire-pulling pulley 1 to the side anchor points 3 on both sides are equal, so as to ensure that the same pulling force can be applied to the side wires 2 on both sides with one force application point. The wire-pulling pulley 1 is connected to the force-applying component 11, and the pulling force on the side wire 2 on the wire-pulling pulley 1 is adjusted through the force-applying component 11. A plurality of the bottom wires 8 are uniformly connected on the bottom axis of the mirror body 9, and each bottom wire 8 is vertically downward and fixedly connected to a plurality of the support anchor points 7 uniformly arranged on the system support 4, so as to form a plurality of vertical bottom wires 8.

[0024] The active optical system further includes a surface shape monitoring and detection device and a mirror surface target value correction control software.

[0025] Preferably, the side stay wires 2 and the bottom stay wires 8 are flexible structures, separating the force required for surface shape correction from the displacement and deformation of the force application and transmission components, and achieving an ideal surface shape correction mechanism. Both the side stay wires 2 and the bottom stay wires 8 are provided with stay wire force terminals. Both the side anchor points 3 and the support anchor points 7 are bonded to the mirror body 9 as a whole.

[0026] Preferably, the force application and transmission component 11 is a locking bolt, which is assembled on the fixing device 6 through a screw rod and transmits the adjusting force to the stay wire pulley 1. A spherical connecting piece is provided at the connection between the locking bolt and the stay wire pulley 1 to ensure that the stay wire pulley 1 can maintain its direction when the locking bolt rotates. The side stay wire 2 is adjusted in tension by screwing the locking bolt connected to the screw rod at the top of the stay wire pulley 1. The screwing is achieved manually or automatically. The force application and transmission component 11 drives the stay wire pulley 1 to adjust the side stay wire 2 through the up and down movement of the screw rod. When necessary, a sensor can be installed on the side stay wire 2 to monitor the tension in real time.

[0027] Preferably, the force application and transmission component 11 adopts a combination of a permanent magnet column and an electromagnetic coil. The permanent magnet column and the electromagnetic coil control the magnitude of the electromagnetic force between them and the stay wire pulley 1 by controlling the magnitude of the current to adjust the force application. When necessary, a sensor can be installed on the side stay wire 2 to monitor the tension in real time. The electromagnetic coil is wound around the permanent magnet column, and the magnitude and direction of the magnetic force on the permanent magnet column are adjusted by changing the magnitude and direction of the current on the electromagnetic coil. The permanent magnet column and the electromagnetic coil can replace the adjusting function of the screw rod. The magnitude of the magnetic force of the permanent magnet column can change the distance between the stay wire pulley and the permanent magnet column, thereby applying an adjusting tension to the stay wire pulley. To ensure the linear movement of the pulley, a sleeve can be added between the fixed end of the stay wire pulley 1 and the permanent magnet column.

[0028] Preferably, the material of the mirror body 9 is any material that can be used as a mirror.

[0029] The surface shape correction process of the active optical system of the present invention is as follows: When the surface shape monitoring and detection device measures that the surface shape of the mirror body 9 does not meet the design requirements, the displacement information of each section on the mirror body 9 is fed back to the mirror surface target value correction feedback control group software, and the tension adjustment values of each side stay wire 2 and bottom stay wire 8 required for the target surface shape are calculated. The final tension magnitude is controlled by multiple side stay wires 2 and bottom stay wires 8. The tension magnitude of the side stay wire 2 is adjusted by controlling the up and down movement of the stay wire pulley 1, while the force application magnitude of the bottom stay wire 8 can be changed by adjusting the up and down displacement of the support anchor point 7.

[0030] Preferably, the surface shape monitoring and detecting device is used to monitor and detect the surface shape change of the mirror body 9 under the action of multiple external forces formed by the plurality of side tension wires 2 and the bottom tension wire 8, and transmit the surface shape information to the mirror target value correction control component.

[0031] Preferably, the mirror target value correction control component gives new correction adjustment values of the side tension wire 2 and the bottom tension wire 8 according to the processing calculation result until the correction amount of the mirror target value converges to the expected range.

[0032] In the present invention, a plurality of anchor points of the side tension wire 2 and the bottom tension wire 8 are set by equidistantly arranging points at the bottom center line of the mirror body 9 and at positions close to the mirror surface on the side surface of the mirror body 9. The number of anchor points still needs to be further determined by an optimization algorithm. The detection of the surface shape can be obtained by scanning the height and height error of the surface shape along the length direction of the mirror body 9 by a long-range profiler (LTP) or a laser interferometer. The displacement of the mirror surface generated by the tensile force at each point on the mirror body 9 can be calculated to obtain the response surface function of the mirror surface. The response surface functions at each point are linearly independent, so the error between the actual surface shape and the target surface shape can be corrected by using the method of linear superposition. Figure 2 Specifically, a method for applying force to the side tension wire 2 and the bottom tension wire 8 is given. The bottom tension wire 8 is adjusted by a bolt at the bracket anchor point 7, and the side tension wire 2 is adjusted by screwing a locking bolt at the top of the tension wire pulley 1. Of course, the present invention is not limited to bolt adjustment, and other methods such as the attraction and repulsion of electromagnetic fields or adjusting levers can also be used.

[0033] It is easy for those skilled in the art to understand that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An active optical system for high-precision correction of the shape of a reflecting mirror, characterized in that: It includes a guy wire pulley, side guy wires, side anchor points, a system support, a limit arm, a fixing device, a support anchor point, a bottom guy wire, a mirror body, a force application component, and a mirror body lower end guy wire anchor point; wherein, there are two limit arms, the upper ends of which are fixedly connected through the fixing device, and the lower ends are respectively fixed on the system support; the mirror body is fixed between the two limit arms and is stabilized on the system support through the limit arms and the fixing device; on each side of the mirror body, a plurality of the side anchor points are evenly arranged at the same interval; a plurality of independently adjustable side guy wires pass through the guy wire pulley, and the two ends of the side guy wire are respectively connected to the side anchor points aligned on both sides of the mirror body to form multiple groups of side guy wires; the guy wire pulley is connected to the force application component, and the force applied to the side guy wire on the guy wire pulley is adjusted through the force application component; the mirror body is connected to a plurality of the bottom guy wires through a plurality of the mirror body lower end guy wire anchor points arranged at uniform intervals, and the bottom guy wires are fixedly connected to a plurality of the support anchor points on the system support.

2. The active optical system according to claim 1, characterized in that: The side anchor points on both sides of the mirror body are on the intersection line of the plane parallel to the mirror surface and the mirror body.

3. The active optical system according to claim 1, characterized in that: The tension of the side guy wire is adjusted by the guy wire pulley, and the distances from the guy wire pulley to the side anchor points on both sides are equal, so as to ensure that the same tension can be applied to the side guy wires on both sides with one force application point.

4. The active optical system according to claim 1, wherein: Each bottom guy wire is fixedly connected vertically downward to a plurality of the support anchor points evenly arranged on the system support, so as to form a plurality of vertical bottom guy wires.

5. The active optical system according to claim 1, wherein: The side guy wire and the bottom guy wire are flexible structures; both the side guy wire and the bottom guy wire have guy wire force receiving terminals.

6. The active optical system according to claim 1, wherein: Both the side anchor point and the support anchor point are bonded to the mirror body as a whole.

7. The active optical system according to claim 1, characterized in that: The force application component is a locking bolt, which is assembled on the fixing device through a screw rod and transmits the adjusting force to the guy wire pulley. The locking bolt is arranged at the top of the guy wire pulley, and the two are connected through a spherical connecting piece.

8. The active optical system according to claim 7, characterized in that: The locking bolt drives the guy wire pulley to adjust the tension of the side guy wire through the up and down movement of the screw rod.

9. The active optical system according to claim 1, wherein: It also includes a surface shape monitoring and detection device and a mirror surface target value correction control software.

10. The active optical system according to claim 1, wherein: The force application component adopts a mode of cooperation between a permanent magnet column and an electromagnetic coil. The permanent magnet column and the electromagnetic coil control the magnitude of the electromagnetic force between the force application component and the guy wire pulley by using the magnitude of the current to adjust the force application.

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