Vertical interferometer system integrated with multi-degree-of-freedom motion platform

Abstract

The invention discloses a vertical interferometer system integrated with a multi-degree-of-freedom motion platform, which comprises a motion platform and three groups of driving mechanisms for driving the motion platform to move vertically, and is characterized in that the motion platform is movably connected with lead screw nut seats of the three groups of driving mechanisms through bearing assemblies respectively; the bearing assembly comprises an X-direction rotating shaft, a Y-direction rotating shaft and a bearing seat, the axes of the X-direction rotating shaft and the Y-direction rotating shaft are perpendicular to each other, one end of the Y-direction rotating shaft is rotationally connected with the X-direction rotating shaft, the other end of the Y-direction rotating shaft is fixedly connected with the motion platform, the X-direction rotating shaft is rotationally connected with the bearing seat, the bearing seat is fixedly connected with the lead screw nut seat, and XY axial angle adjustment of the motion platform is achieved. The motion platform has an angle adjusting function, can replace a design scheme formed by stacking a vertical moving platform, an X-axis rotating mechanism and a Y-axis rotating mechanism in the prior art, and has the advantages that the structure is simple, adjustment is convenient, the height of the motion platform stacked on other mechanisms is reduced, and the light path measurement range is enlarged.

Description

Technical Field

[0001] This invention relates to the field of optical measurement technology, and in particular to a vertical interferometer system integrating a multi-degree-of-freedom motion platform. Background Technology

[0002] Vertical large-aperture interferometers are widely used for high-precision optical lens surface profile measurement, especially in the field of photolithography projection lenses. These lenses are not only large in size and have extremely high surface profile requirements, but also require vertical measurement to eliminate the effects of gravitational deformation. Optical lenses with different radii of curvature have different focal lengths; therefore, a moving platform is needed to align the focal point of the lens under test with the focal point of a standard mirror. Utilizing the principle of optical interferometry, the surface profile of the lens under test is measured non-contactly, and the radius of curvature is accurately measured.

[0003] Existing vertical large-aperture interferometer systems employ dual servo motors and ball screws for vertical motion platform drive. The upper surface of the platform is stacked with sequentially stacked X-axis translational motion mechanisms, Y-axis translational motion mechanisms, X-axis rotational motion mechanisms, and Y-axis rotational motion mechanisms to achieve angle and displacement adjustment. This multi-layered mechanism stacking not only results in a complex structure and increased adjustment difficulty, but also a rigid connection between the ball screw and the motion platform. It fails to consider that if the side plate deviates from the fixed linear guide, this rigid connection will generate installation stress, causing the ball screw and linear guide to buckle. This leads to high friction and heat generation during vertical movement, affecting the stability and motion accuracy of the linear guide and ball screw. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide a vertical interferometer system with an integrated multi-degree-of-freedom motion platform. This motion platform has an angle adjustment function, which simplifies the multi-layer stacked structure of the motion platform in the prior art, reduces installation stress, and improves the stability and accuracy of interferometric measurements.

[0005] Technical Solution: To achieve the above objectives, the present invention provides a vertical interferometer system integrating a multi-degree-of-freedom motion platform, comprising a motion platform and three sets of drive mechanisms for vertical movement of the motion platform. The motion platform and the lead screw and nut seats of the three sets of drive mechanisms are movably connected via bearing assemblies. The bearing assembly includes a pair of mutually perpendicular X-axis and Y-axis rotation axes, and a bearing seat. One end of the Y-axis rotation axis is rotatably connected to the X-axis rotation axis, and the other end is fixedly connected to the motion platform. The X-axis rotation axis is rotatably connected to the bearing seat, and the bearing seat is fixedly connected to the lead screw and nut seat, thereby realizing the XY-axis angle adjustment of the motion platform.

[0006] Preferably, the drive mechanism includes a servo motor, a reducer, a first coupling, and a drive shaft assembly. The drive shaft assembly is fixed to the reducer via the first coupling. The drive shaft assembly includes a second coupling connected to the first coupling, a ball screw connected to the output end of the second coupling, a fixed side of the ball screw, a supporting side of the ball screw, and a linear slider guide rail. The slider of the linear slider guide rail is fixedly connected to a bearing seat.

[0007] Preferably, the drive mechanism further includes a feedback grating, and the grating reading head of the feedback grating is fixedly connected to the bearing housing.

[0008] Preferably, the bearing housing is fixedly connected to the lead screw nut housing, the slider of the linear slider guide rail, or the grating reading head of the feedback grating via a mounting plate.

[0009] Preferably, the Y-axis rotation shaft is connected to the middle of the X-axis rotation shaft, and the bearing housing includes two sets, which are connected to both sides of the X-axis rotation shaft.

[0010] Preferably, the other end of the Y-axis rotation is a U-shaped clamp, which is fixed to the side of the motion platform.

[0011] Preferably, the three sets of drive mechanisms are arranged in an isosceles triangle, with two sets of drive mechanisms located on the same side of the motion platform and the other set of drive mechanisms located on the other side of the motion platform, forming the vertices of the isosceles triangle.

[0012] Preferably, when the two sets of drive mechanisms forming the base of the isosceles triangle are driven synchronously, the angle adjustment of the motion platform along the Y-axis is realized; when the drive mechanism forming the vertex of the isosceles triangle is driven synchronously with the drive mechanism forming any end of the base, the angle adjustment of the motion platform along the X-axis is realized.

[0013] Preferably, the three sets of drive mechanisms are installed on the sidewalls of the sealed cavity made of marble.

[0014] Beneficial effects: The present invention has the following advantages: 1. The motion platform of the present invention has an angle adjustment function, which can replace the design scheme of the prior art which is composed of a vertical moving platform, an X-axis rotation mechanism and a Y-axis rotation mechanism. It has the advantages of simple structure, convenient adjustment, reduced height of the motion platform superimposed with other mechanisms, and increased optical path measurement range; 2. It can compensate for the installation error of the side plate and the linear guide rail, reduce the generation of installation stress, improve the stability and accuracy of interferometric measurement, and reduce motion friction. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the system structure;

[0016] Figure 2 This is a schematic diagram of the drive shaft assembly structure;

[0017] Figure 3 This is a schematic diagram of the structure of the first and second bearing assemblies;

[0018] Figure 4 This is a schematic diagram of the third bearing assembly. Detailed Implementation

[0019] The technical solution of the present invention will be described in detail below with reference to the embodiments and accompanying drawings.

[0020] like Figures 1-4 As shown, the vertical interferometer system of the present invention includes a sealed cavity consisting of a top plate 1, left / right side plates 2, bottom plate 3, front / rear sealing plates 4, and a light source host 5. The light source host 5 is mounted on the top plate 1 and includes a laser, a beam expander, a beam splitter, a reflector, a collimator, a standard lens, etc. The point laser emitted by the laser is converted into parallel light of the required aperture by the beam expander, beam splitter, reflector, collimator, etc. The parallel light is converged into a point by the spherical standard lens or remains parallel light after passing through the planar standard lens. It enters the sealed cavity through the through hole on the top plate 1 and illuminates the lens to be tested on the motion platform 6.

[0021] In this embodiment, the top plate 1, left / right side plates 2, and bottom plate 3 are made of marble. Compared to steel, marble has extremely excellent surface flatness after grinding and very good dimensional stability. Compared to ceramic, it has a lower cost for the same weight and size. Since a larger mass results in a lower natural frequency, other non-metallic materials, due to their low density, have a too large volume for the same weight.

[0022] In this embodiment, the motion platform 6 is composed of a first drive mechanism 7, a second drive mechanism 8, and a third drive mechanism 9, which realize vertical movement, rotation around the X-axis, and rotation around the Y-axis. The first drive mechanism 7 and the second drive mechanism 8 are installed on the same side of the motion platform 6 and are arranged symmetrically relative to the X-axis. The third drive mechanism 9 is installed on the other side of the motion platform 6 and is located on the X-axis (the X-axis and Y-axis are a reference coordinate system defined on the motion platform 6 itself to describe the direction of its rotational movement).

[0023] When the three drive mechanisms drive the motion platform 6 to move synchronously, the motion platform 6 is translated in the vertical direction; when the first drive mechanism 7 and the second drive mechanism 8 remain stationary, and the third drive mechanism 9 moves upward or downward, the motion platform 6 rotates around the Y-axis (or the first drive mechanism 7 and the second drive mechanism 8 move synchronously and in the opposite direction to the third drive mechanism 9, or the third drive mechanism 9 remains stationary and the first drive mechanism 7 and the second drive mechanism 8 move upward or downward synchronously); when the third drive mechanism 9 remains stationary, and the first drive mechanism 7 and the second drive mechanism 8 move in opposite directions, the motion platform 6 rotates around the X-axis (or when the three drive mechanisms are moving synchronously and relatively stationary, the first drive mechanism 7 and the second drive mechanism 8 move in opposite directions).

[0024] The first drive mechanism 7, the second drive mechanism 8, and the third drive mechanism 9 each include a servo motor 701, a reducer 702, a first coupling 703, a drive shaft assembly 704, and a feedback grating 705. In each drive mechanism, the drive shaft assembly and the reducer are fixed together by the first coupling. The rotation of the servo motor and the reducer drives the drive shaft assembly to move up and down, and the feedback grating provides real-time position information.

[0025] The drive shaft assembly 704 includes a second coupling 7041, a lead screw fixed side 7042, a ball screw 7043, a linear slider guide rail 7044, a lead screw nut seat 7045, and a lead screw support side 7046. In each drive shaft assembly, the input end of the second coupling is connected to the output end of the first coupling in the corresponding drive mechanism via a connecting rod, and the output end of the second coupling is connected to the ball screw. In each drive mechanism, the reducer and the drive shaft assembly are flexibly connected through the first coupling and the second coupling. The drive shaft assembly of the third drive mechanism includes two sets of linear slider guide rails, symmetrically arranged on both sides of the ball screw.

[0026] The feedback grating 705 includes a linear grating 7051 and a grating reading head 7052.

[0027] The first drive mechanism 7 and the second drive mechanism 8 are mounted on the right side plate, and the third drive mechanism 9 is mounted on the right side plate (in this embodiment, left and right only indicate the relative positions of the two sets of side plates). The specific installation structure is as follows: the ball screw is mounted on the side plate through the screw fixing side and the screw support side, and the slide groove of the linear slider guide rail and the linear grating are mounted on the measuring plate, parallel to the ball screw. The screw nut seat of the first drive mechanism 7, the slider of the linear slider guide rail, and the grating reading head of the third drive mechanism 9 are connected to the motion platform 6 through the first bearing assembly 706, the second bearing assembly 806, and the third bearing assembly 906, respectively.

[0028] The first bearing assembly 706 and the second bearing assembly 806 have the same structure, including a shaft retaining ring I7061, a bearing I7062, a bearing housing I7063, an X-axis rotating shaft I7064, a shaft retaining ring II7065, a bearing housing mounting plate I7066, a Y-axis rotating shaft I7067, and a bearing II7068. One end of the Y-axis rotating shaft I is cylindrical and connected to the X-axis rotating shaft I, while the other end is a U-shaped clamping member fixed to the side of the motion platform 6. The main through holes of the two sets of bearing housings I are symmetrically rotated and fixed to both ends of the X-axis rotating shaft I through the bearings I. At the same time, the bottom of the two sets of bearing housings I is fixed to the bearing housing mounting plate I, so that the central axis of the X-axis rotating shaft I is parallel to the bearing housing mounting plate I, and the X-axis rotating shaft I can rotate around its own central axis. The X-axis rotating shaft I has a through hole in the middle, and the Y-axis rotating shaft I is rotatably fixed by bearing II. The Y-axis rotating shaft I is perpendicular to the central axis of the X-axis rotating shaft I, and the Y-axis rotating shaft I can rotate around its own central axis.

[0029] The other side of the bearing housing mounting plate I is fixed to the lead screw nut seat of the first drive mechanism 7 or the second drive mechanism 8, the slider of the linear slider guide rail, and the grating reading head.

[0030] The third bearing assembly 906 includes a shaft retainer III 9061, a bearing III 9062, a bearing housing II 9063, an X-axis rotating shaft II 9064, a shaft retainer IV 9065, a bearing housing mounting plate II 9066, a Y-axis rotating shaft II 9067, and a bearing IV 9068. One end of the Y-axis rotating shaft II is cylindrical and connected to the X-axis rotating shaft II, while the other end is a U-shaped clamping member fixed to the other side of the motion platform 6.

[0031] The main through holes of the two sets of bearing housings II are symmetrically rotated and fixed at both ends of the X-axis rotating shaft II via bearings III. Simultaneously, the bottoms of the two sets of bearing housings II are fixed to the bearing housing mounting plate II, thus ensuring that the central axis of the X-axis rotating shaft II is parallel to the bearing housing mounting plate II, and that the X-axis rotating shaft II can rotate around its own central axis. A through hole is provided in the middle of the X-axis rotating shaft II, through which a Y-axis rotating shaft II is rotatably fixed via bearing IV. The Y-axis rotating shaft II is perpendicular to the central axis of the X-axis rotating shaft II, and can rotate around its own central axis.

[0032] The other side of the bearing housing mounting plate II is fixed to the lead screw nut seat of the third drive mechanism 9, the sliders of the two linear slider guides, and the grating reading head.

[0033] Under the above structural design, the motion platform 6 has two movable connection points on one side with the right side plate, which are symmetrically located on both sides of the X-axis of the motion platform 6. The other side of the motion platform 6 has one movable connection point with the left side plate, and this connection point is located on the X-axis of the motion platform 6. Therefore, when the lead screw nut seats of the three drive mechanisms move synchronously vertically under the drive of the servo motor, the motion platform 6 also moves vertically under the constraint of the three movable connection points. The linear slider guide rail plays a guiding role, and the feedback grating monitors the movement position of the connected bearing seat mounting plate II in real time.

[0034] When the motion platform 6 needs to tilt around its Y-axis at a certain angle, the lead screw nut seats of the first drive mechanism 7 and the second drive mechanism 8 move synchronously upward (or downward) under the drive of the servo motor, and the lead screw nut seat of the third drive mechanism 9 moves downward (or upward) under the drive of the servo motor. When the motion platform 6 needs to tilt around its X-axis at a certain angle, the lead screw nut seats of the first drive mechanism 7 and the third drive mechanism 9 move synchronously upward (or downward) under the drive of the servo motor, and the lead screw nut seat of the second drive mechanism 8 moves downward (or upward) under the drive of the servo motor. The specific flipping direction and angle are set according to the adjustment requirements of the lens under test. The moving direction and distance of the drive mechanism are then determined. Assuming the vertical distance *a* between the third bearing assembly 906 and the first bearing assembly 706 (or the second bearing assembly 806) along the X-axis of the motion platform 6, and the distance *b* between the first bearing assembly 706 and the second bearing assembly 806 along the Y-axis of the motion platform 6, and the real-time position values ​​*c*, *d*, and *e* of the feedback gratings of the first drive mechanism 7, the second drive mechanism 8, and the third drive mechanism 9, then the angle of rotation of the motion platform 6 around the X-axis can be calculated as follows: The angle of rotation around the Y-axis is Based on this method, it can be deduced that when the motion platform 6 is adjusted to the set rotation angle, the bearing seat mounting plates of the first drive mechanism 7, the second drive mechanism 8, and the third drive mechanism 9 are adjusted in position by the servo motor.

[0035] In addition, the bearing assemblies (706, 806, 906) movably connect the motion platform 6 and the drive shaft assembly 704, making the ball screw and the motion platform a flexible connection. If there is a deviation in the side plate when fixing the linear guide, this connection method can compensate for the installation error, reduce the installation stress, improve the adjustment accuracy, and reduce motion friction.

[0036] The motion platform 6 described in this invention has an angle adjustment function, which can replace the existing design scheme consisting of a vertical moving platform, an X-axis rotation mechanism and a Y-axis rotation mechanism. It has advantages such as simple structure, convenient adjustment, reduced height of the motion platform with other mechanisms, and increased measurement range.

[0037] In practical applications, the motion platform 6 of this invention can be directly superimposed with X-direction translational motion mechanisms and Y-direction translational motion mechanisms, with the lens to be tested mounted on the Y-direction translational motion mechanism. If the lens to be tested is a spherical mirror, the vertical position of the motion platform 6 can be adjusted by the driving mechanism, etc. (If the real-time feedback position values ​​of the feedback gratings of the first driving mechanism 7, the second driving mechanism 8, and the third driving mechanism 9 are c, d, and e, then the center position O (Z-axis) value of the motion platform is: O = The X-axis and Y-axis translation mechanisms, combined with each other, ensure that the focal point of the lens under test coincides with the focal point of the beam converged by the spherical standard lens. The reference light from the spherical standard lens and the light being measured from the lens surface share a common optical path and are reflected into the camera for final interference imaging. If the lens under test is a plane mirror, the motion platform angle is adjusted via the drive mechanism to make the lens under test parallel to the plane standard lens. In this case, the reference light from the plane standard lens and the light being measured from the lens surface share a common optical path and are reflected into the camera for final interference imaging.

Claims

1. A vertical interferometer system integrating a multi-degree-of-freedom motion platform, comprising a motion platform (6) and three sets of drive mechanisms for driving the vertical movement of the motion platform, characterized in that, The motion platform (6) and the lead screw nut seats of the three sets of drive mechanisms are movably connected through bearing assemblies. The bearing assembly includes a pair of X-axis and Y-axis rotating shafts with mutually perpendicular axes, and a bearing seat. One end of the Y-axis rotating shaft is rotatably connected to the X-axis rotating shaft, and the other end is fixedly connected to the motion platform (6). The X-axis rotating shaft is rotatably connected to the bearing seat, and the bearing seat is fixedly connected to the lead screw nut seat, so as to realize the XY axis angle adjustment of the motion platform (6).

2. The vertical interferometer system according to claim 1, characterized in that, The drive mechanism includes a servo motor, a reducer, a first coupling, and a drive shaft assembly. The drive shaft assembly is fixed to the reducer via the first coupling. The drive shaft assembly includes a second coupling connected to the first coupling, a ball screw connected to the output end of the second coupling, a fixed side of the ball screw, a supporting side of the ball screw, and a linear slider guide rail. The slider of the linear slider guide rail is fixedly connected to a bearing seat.

3. The vertical interferometer system according to claim 1, characterized in that, The drive mechanism also includes a feedback grating, and the grating reading head of the feedback grating is fixedly connected to the bearing housing.

4. The vertical interferometer system according to any one of claims 1 to 3, characterized in that, The bearing housing is fixedly connected to the lead screw nut housing, the slider of the linear slider guide rail, or the grating reading head of the feedback grating via a mounting plate.

5. The vertical interferometer system according to claim 1, characterized in that, The Y-axis rotation shaft is connected to the middle of the X-axis rotation shaft, and the bearing housing includes two sets, which are connected to both sides of the X-axis rotation shaft.

6. The vertical interferometer system according to claim 1, characterized in that, The other end of the Y-axis rotation axis is a U-shaped clamp, which is fixed to the side of the motion platform (6).

7. The vertical interferometer system according to claim 1, characterized in that, The three sets of drive mechanisms are arranged in an isosceles triangle, with two sets of drive mechanisms located on the same side of the motion platform (6) and the other set of drive mechanisms located on the other side of the motion platform (6), forming the apex of the isosceles triangle.

8. The vertical interferometer system according to claim 7, characterized in that, When the two sets of drive mechanisms that form the base of the isosceles triangle drive synchronously, the angle adjustment of the motion platform (6) along the Y-axis is realized. When the drive mechanism that forms the vertex of the isosceles triangle drives synchronously with the drive mechanism that forms any end of the base, the angle adjustment of the motion platform (6) along the X-axis is realized.

9. The vertical interferometer system according to claim 1, characterized in that, The three sets of drive mechanisms are installed on the side walls of the sealed cavity made of marble.

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