CN217818617U

CN217818617U - Circumference measurement system

Info

Publication number: CN217818617U
Application number: CN202222016774.6U
Authority: CN
Inventors: 郝凌凌
Original assignee: Shanghai Yinguan Semiconductor Technology Co Ltd
Current assignee: Shanghai Yinguan Semiconductor Technology Co Ltd
Priority date: 2022-08-02
Filing date: 2022-08-02
Publication date: 2022-11-15
Anticipated expiration: 2032-08-02

Abstract

The utility model relates to a circumference measurement system, including laser interferometer, swivel work head, measurement module, the measurement module is further including measuring speculum, straight line guiding mechanism, driven adaptor and cam, circumference measurement system converts the circular motion of measured object article into the linear displacement who measures the speculum, and then comes the accurate linear displacement distance of measuring the speculum through the laser interferometer for the circular motion of measured object article can measure with the help of linear displacement measuring device and obtain, can realize measuring the high resolution high accuracy of measured object article.

Description

Circumference measurement system

Technical Field

The utility model relates to a measure technical field, specifically relate to a circumference measurement system.

Background

With the newer iteration of semiconductor fabrication equipment technology, there is an increasing circular motion that requires high resolution, high precision measurements. The dual-frequency laser interferometer can well realize high-resolution and high-precision linear motion measurement, but for circular motion measurement, as the measured reflecting mirror is fixedly connected to the measured moving table, when the measured moving table rotates, the measured reflecting mirror rotates, and the laser interferometer is stationary, when the measured reflecting mirror rotates at a certain angle, a measurement beam emitted by the laser interferometer cannot be emitted to the measured reflecting mirror, so that the problem of light loss occurs, and the measurement cannot be continued. Because the measured reflector or surface can lose light in the process of circular motion, the existing dual-frequency laser interferometer can not directly realize circular measurement.

In addition, the measurement of the circular motion angle in the semiconductor production field requires high precision, for example, a motion stage for carrying a silicon wafer needs to rotate the silicon wafer, and the rotation angle needs to be accurately measured, which usually needs to reach the micro-radian (μ rad) level, and the existing angle measurement mechanism cannot realize the angle measurement of the precision level. Although the prior art also adopts the scheme of matching the circular grating with the laser interferometer to measure the circular motion, the scheme has high cost, and the circular grating process is complex and has high cost. In addition, if the pitch of the circular grating needs to reach the micro-radian (μ rad) level, the manufacturing difficulty and cost of the circular scale machine and the mask plate for manufacturing the circular grating are exponentially increased. There is therefore a need for improvements to existing circumference measurement systems that can be adapted for use in semiconductor manufacturing.

SUMMERY OF THE UTILITY MODEL

The utility model aims at providing a circumference measurement system to being surveyed speculum or surface can't accomplish the measuring problem because of losing light in the circular motion when adopting laser interferometer to measure among the solution prior art.

In order to achieve the above purpose, the utility model adopts the following technical scheme:

a circumference measuring system comprises a laser interferometer, a rotary workbench and a measuring module, wherein the measuring module further comprises a measuring reflector, a linear guide mechanism, a driven adapter and a cam; the measuring reflector is fixed on the driven adapter, the driven adapter is movably arranged on the linear guide mechanism, and the linear displacement action can be carried out on the linear guide mechanism along the measuring light path of the laser interferometer; the rotary worktable is in driving connection with the cam, a rotating shaft of the cam and the rotating shaft of the rotary worktable are coaxially arranged, the cam is in contact connection with the driven adapter, and the rotating action of the cam drives the driven adapter to perform linear displacement action along a measuring light path of the laser interferometer; and the mirror surface of the measuring reflecting mirror always faces the measuring light path of the laser interferometer.

In one embodiment, the measuring module further comprises an elastic member; at least one end of the elastic piece is connected with the driven adapter piece, acts on the driven adapter piece, generates acting force for pushing the driven adapter piece to the cam, and enables the cam to be always abutted against the driven adapter piece.

In an embodiment, the measuring module further includes a guide bearing, the elastic member is sleeved on the guide bearing, and the guide bearing generates a guiding effect on the elastic member, which is over against the driven adaptor.

In one embodiment, the linear guide mechanism includes: the linear sliding rail is arranged on the frame; the driven adapter is provided with a sliding block matched with the linear slide rail, or the driven adapter is fixedly installed on the sliding block matched with the linear slide rail.

In one embodiment, the frame has a first mounting surface and a second mounting surface which are perpendicular to each other, the linear slide rail is fixedly mounted on the first mounting surface, the guide bearing is parallel to the linear slide rail, a first end of the guide bearing is fixed on the driven adapter, and a second end of the guide bearing is movably connected to the second mounting surface; the elastic piece is sleeved on the guide bearing, and two ends of the elastic piece are connected with the driven adapter piece and the second mounting surface respectively.

In an embodiment, the second mounting surface is provided with a first hole, the first hole is internally provided with a first shaft sleeve, and the second end of the guide bearing is movably connected with the first shaft sleeve and movably connected to the second mounting surface through the first shaft sleeve.

In one embodiment, a central point of a contact part of the cam and the driven adapter is defined as A, a rotation central point of the cam is defined as B, and a straight line where the A point and the B point are located is arranged in parallel with a measurement light path of the laser interferometer; setting the maximum distance between the two points AB as LMAX and the minimum distance between the two points AB as LMIN, and then setting the length of the elastic piece as (LMAX-LMIN)/0.5-0.1.

In one embodiment, the cam is a turntable with an oval outer contour; assuming that the linear distance of the measuring reflecting mirror moving along the measuring optical path of the laser interferometer is x, the rotating angle of the rotating table is y, the semi-axis of the long axis of the cam is a, the semi-axis of the short axis of the cam is b, and the initial measuring position is at any vertex of the long axis or the short axis of the cam (44), the x and the y satisfy the following conditions within 1/4 period of the elliptic turntable:

y＝arctan(bsin(arccos((a-x)/a)/(a-x)))。

in an embodiment, a weight-reducing portion is arranged on a long shaft of the cam, and the weight-reducing portion is a groove or a through hole.

In one embodiment, the cam is a turntable with a symmetrical double-parabola external profile, the symmetrical double-parabola comprises a first parabola located in a first quadrant and a fourth quadrant and a second parabola located in a second quadrant and a third quadrant, and the open ends of the first parabola and the second parabola are connected and are symmetrically arranged along the X axis; and assuming that the linear distance of the measuring reflecting mirror (41) moving along the measuring optical path of the laser interferometer (1) is x1, the rotating angle of the rotating workbench (2) is y1, the initial position of measurement is any vertex or endpoint of the symmetrical double parabola of the cam (44), and within 1/4 period of the turntable of the symmetrical double parabola, x1 and y1 satisfy the following condition: y1= arcsin (sqrt (x 1, 4)).

The utility model adopts the above technical scheme, the beneficial effect who has is, the utility model provides a circular measurement system converts the circular motion of measured object article into the linear displacement who measures the speculum, and then comes the linear displacement distance of accurate measurement measuring speculum through the laser interferometer, and then calculates the rotation angle of measured object article, make the circular motion of measured object article can measure with the help of linear displacement measuring device (laser interferometer) and obtain, both solved measured speculum or surface because of losing the unable completion measuring problem of light in the circular motion, can realize the measurement of the high resolution accuracy to measured object article again. And compare in prior art, the technical scheme of the utility model is simpler, easy to realize, and the cost is low relatively.

Drawings

FIG. 1 shows a schematic diagram of a circumference measurement system in an exemplary embodiment;

FIG. 2 shows a side view of a rotating table and measurement module in an exemplary embodiment;

FIG. 3 shows a schematic view of the structure of the measuring module and the cam in an exemplary embodiment;

FIG. 4 shows an exploded view of a measurement module and cam in an exemplary embodiment;

FIG. 5 is a simplified schematic diagram of a cam having an elliptical outer profile in an exemplary embodiment;

fig. 6 shows a simple schematic of a cam with a double parabolic outer profile in a specific embodiment.

Description of reference numerals:

the device comprises a laser interferometer 1, a rotary worktable 2, a measurement module 4, a measurement reflector 41, a linear guide mechanism 42, a driven adapter 43, a cam 44, an elastic member 45, a guide bearing 46, a frame 421, a linear sliding rail 422, a weight reduction part 441, a first mounting surface 4211, a second mounting surface 4212 and a first hole 42121.

Detailed Description

The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings so that the objects, features and advantages of the invention can be more clearly understood. It should be understood that the embodiments shown in the drawings are not intended as limitations on the scope of the invention, but are merely illustrative of the true spirit of the technical solutions of the present invention.

In the following description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the various disclosed embodiments. One skilled in the relevant art will recognize, however, that the embodiments may be practiced without one or more of the specific details. In other instances, well-known devices, structures and techniques associated with this application may not be shown or described in detail to avoid unnecessarily obscuring the description of the embodiments.

Throughout the specification and claims, the word "comprise" and variations thereof, such as "comprises" and "comprising," are to be understood as an open, inclusive meaning, i.e., as being interpreted to mean "including, but not limited to," unless the context requires otherwise.

Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

As used in this specification and the appended claims, the singular forms "a", "an", and "the" include plural referents unless the context clearly dictates otherwise. It should be noted that the term "or" is generally employed in its sense including "and/or" unless the context clearly dictates otherwise.

In the following description, for the sake of clarity, the structure and operation of the present invention will be described with the aid of directional terms, but the terms "front", "rear", "left", "right", "outer", "inner", "outer", "inward", "upper", "lower", etc. should be understood as words of convenience and not as words of limitation.

Furthermore, the terms "horizontal", "vertical", "overhang" and the like do not imply that the components are required to be absolutely horizontal or overhang, but may be slightly inclined. For example, "horizontal" merely means that the direction is more horizontal than "vertical" and does not mean that the structure must be perfectly horizontal, but may be slightly inclined.

In the description of the present application, it should also be noted that, unless expressly stated or limited otherwise, the terms "disposed," "mounted," "connected," and "connected" are to be construed broadly and can include, for example, fixed connections, detachable connections, or integral connections; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in this application will be understood to be a specific case for those of ordinary skill in the art.

Referring to fig. 1-5, the present invention provides a circumference measuring system, which includes a laser interferometer 1, a rotary table 2, and a measuring module 4, wherein the measuring module 4 further includes a measuring reflector 41, a linear guide mechanism 42, a driven adapter 43, and a cam 44; the measuring reflector 41 is fixed on the driven adaptor 43, the driven adaptor 43 is movably mounted on the linear guide mechanism 42, and the linear guide mechanism 42 can perform linear displacement along the measuring optical path of the laser interferometer 1; the rotary table 2 is in driving connection with the cam 44, the rotating shaft of the cam 44 is coaxially arranged with the rotating shaft of the rotary table 2, the cam 44 is in contact connection with the driven adapter 43, and the rotating action of the cam 44 drives the driven adapter 43 to perform linear displacement action along the measuring optical path of the laser interferometer 1; the mirror surface of the measuring reflecting mirror 41 always faces the measuring optical path of the laser interferometer 1.

A laser beam emitted by a laser enters a laser interferometer, a measuring beam is emitted from the laser interferometer, the measuring beam irradiates a measured reflecting mirror and is reflected by the measured reflecting mirror to return to the laser interferometer, interference light is generated by interference of a reference light and the returned measuring light in the laser interferometer, and the interference light is resolved by an optoelectronic signal processing module of the laser interferometer to obtain displacement information of the measured reflecting mirror.

Specifically, the laser interferometer 1 may be a single-frequency laser interferometer or a dual-frequency laser interferometer, but the dual-frequency laser interferometer is insensitive to a change in dc level caused by a change in light intensity and has a high interference resistance, so that measurement with high resolution and high accuracy can be realized, and therefore the laser interferometer 1 is preferably a dual-frequency laser interferometer. The measuring light path is defined by the measuring light beam of the laser interferometer 1, and taking a dual-frequency laser interferometer as an example, the displacement measuring principle of the laser interferometer 1 is as follows: the laser of the double-frequency laser interferometer generates left-handed circularly polarized light and right-handed circularly polarized light with two different frequencies, wherein the frequency of the left-handed circularly polarized light is f1, the frequency of the right-handed circularly polarized light is f2, the left-handed circularly polarized light and the right-handed circularly polarized light are converted into two mutually perpendicular linearly polarized light after passing through a 1/4 wave plate, and the linearly polarized light is divided into two paths by the spectroscope. One path becomes a reference beam with frequency f1-f2 after being polarized by a polarizer; the other path is divided into two paths after passing through a polarization beam splitter: one path becomes a beam containing only f1, and the other path becomes a beam containing only f 2. Wherein f2 is emitted toward the measuring mirror 41, when the measuring mirror 41 moves, the light beam containing f2 is reflected by the measuring mirror 41 to become a light beam containing f2 ± Δ f, Δ f is an additional frequency generated by doppler effect when the measuring mirror 41 moves, and the sign indicates the moving direction. The light beam and the light beam reflected by the fixed reflector and only containing the light of f1 are converged into a measuring beam of f1- (f 2 +/-delta f) after being polarized by the other polarizer. The measuring beam and the reference beam enter a subtracter for subtraction after passing through a photoelectric conversion element, an amplifier and a shaper respectively, and are output to be an electric pulse signal only containing +/-delta f. After counting by the reversible counter, equivalent conversion is carried out by an electronic computer (the multiplier of the equivalent depends on the design of the laser interferometer, and is commonly 1/2 or 1/4 of the laser wavelength), and then the displacement of the movable reflecting mirror can be obtained. From the above, it can be seen that the measurement optical path of the dual-frequency laser interferometer 1 is the outgoing direction of the beam f 2.

The measuring module 4 comprises a measuring mirror 41, a linear guide 42, a driven adapter 43 and a cam 44. The measuring reflector 41 is fixed on the driven adapter 43, and the driven adapter 43 is movably mounted on the linear guide mechanism 42, and can perform linear displacement motion on the linear guide mechanism 42 along the measuring optical path of the laser interferometer 1, so that the measuring reflector 41 can perform linear displacement motion along the measuring optical path of the laser interferometer 1 along with the driven adapter 43, and the mirror surface of the measuring reflector 41 always faces the measuring optical path of the laser interferometer 1.

The cam 44 is in contact with the driven adapter 43. The contact connection between the cam 44 and the driven adapter 43 can be a point contact connection or a line contact connection. In this embodiment, the cam 44 and the driven adaptor 43 are connected in a tangential contact manner, so as to realize a line contact connection between the cam 44 and the driven adaptor 43. In other alternative embodiments, a needle-like or point-like projection may also be provided on the driven adapter 43, by means of which projection the driven adapter 43 is in point-contact connection with the cam 44. The point contact has higher sensitivity and higher final measurement accuracy than the line contact, but the point contact is easy to wear over time, influences the final measurement accuracy and needs to be replaced regularly. Accordingly, the line contact connection has the advantages that the components are not easily worn and have longer service life. The cam 44 rotates the curved surface of the cam 44 by the contact connection between the cam 44 and the follower adapter 43 and the rotation of the cam 44, so that the follower adapter 43 is driven to perform linear displacement along the measurement optical path of the laser interferometer 1.

The rotary workbench 2 is used for placing an object to be measured, the rotary workbench 2 is in drive connection with the cam 44, a rotating shaft of the rotary workbench 2 is coaxially arranged with the rotating shaft of the cam 44, so that the cam 44 can be driven to rotate coaxially by rotation of the rotary workbench 2, the cam 44 drives the driven adapter 43 to drive the measuring reflector 41 to perform linear displacement along a measuring optical path of the laser interferometer 1, the axial rotation of the rotary workbench 2 is converted into linear displacement of the measuring reflector 41, the linear displacement distance of the measuring reflector 41 can be accurately measured through the laser interferometer 1 (such as a dual-frequency laser interferometer), and the rotating angle of the cam 44 can be obtained through conversion of relation between curved surface rotation and linear displacement of the cam 44, namely, the rotating angle of the object to be measured on the rotary workbench is also obtained.

In an embodiment, referring to fig. 3 and 4, the measuring module 4 further includes an elastic member 45, at least one end of the elastic member 45 is connected to the driven adaptor 43, where the connection between the elastic member 45 and the driven adaptor 43 may be a fixed connection or a contact connection. The elastic member 45 acts on the driven adapter 43, generates an acting force for pushing the driven adapter 43 to the cam 44, and enables the cam 44 to always abut against the driven adapter 43, so that the phenomenon that the cam 44 idles without driving the driven adapter 43 to perform linear displacement along a measuring optical path of the laser interferometer 1 is avoided, and the accuracy of the circumference measuring system for measuring a measured object is ensured. The elastic member 45 may be a spring or other elastic member with negative stiffness, such as a cylinder, a magnetic spring, etc., and the elastic member 45 is exemplified in the present embodiment.

Referring to fig. 3 and 4, the measurement module 4 further includes a guide bearing 46, the elastic member 45 is sleeved on the guide bearing 46, the guide bearing 46 generates a guiding action on the elastic member 45 against the driven adaptor 43, so that the elastic member 45 generates an acting force perpendicular or approximately perpendicular to the driven adaptor 43 on the driven adaptor 43, and the acting force perpendicular or approximately perpendicular to the driven adaptor 43 can be maintained when the elastic member 45 extends and retracts, so as to ensure that the cam 44 is always in contact with the driven adaptor 43, and the driven adaptor 43 is smoother in the process of performing linear displacement along the measurement optical path of the laser interferometer 1, and meanwhile, the driven adaptor 43 is prevented from shifting in the displacement process.

In one embodiment, referring to fig. 3 and 4, the linear guide mechanism 42 includes a frame 421 and a linear guideway 422, and the linear guideway 422 is fixedly mounted on the frame 421. The driven adapter 43 is provided with a sliding block matched with the linear slide rail 422, that is, the driven adapter 43 itself is used as the sliding block matched with the linear slide rail 422, and can directly slide on the linear slide rail 422, and the measuring reflector 41 is equivalently directly and fixedly installed on the sliding block of the linear slide rail 422.

Or, the driven adaptor 43 is fixedly mounted on a sliding block matched with the linear sliding rail 422. Namely, the linear slide rail 422 is provided with a sliding block matched with the linear slide rail 422, the driven adapter 43 is fixedly mounted on the sliding block through a fixing part such as a screw, and the sliding block enables the driven adapter 43 to perform linear displacement along the linear slide rail 422. The driven adaptor 43 is linearly positioned through the linear slide rail 422, so that the offset of the driven adaptor 43 in the linear displacement process can be reduced (the offset is mainly determined by the precision of the linear slide rail), meanwhile, the resistance of the driven adaptor 43 in the displacement process can be reduced by means of the sliding friction or rolling friction between the sliding block and the linear slide rail 422, and the cam 44 can also push the driven adaptor 43 to perform the linear displacement motion with smaller force.

Referring again to fig. 3, the frame 421 has a first mounting surface 4211 and a second mounting surface 4212 arranged perpendicular to each other, and the frame 421 in fig. 3 is an L-shaped sheet metal part. The linear sliding rail 422 is fixedly installed on the inner side of the first installation surface 4211, the guide bearing 46 is arranged in parallel with the linear sliding rail 422, a first end of the guide bearing 46 is fixed on the driven adapter 43, and a second end of the guide bearing 46 is movably connected to the second installation surface 4212; the elastic piece 45 is sleeved on the guide bearing 46, and two ends of the elastic piece 45 are respectively connected with the driven adapter piece 43 and the second mounting surface 4212, so that the elastic piece 45 generates acting force on the driven adapter piece 43 along the linear displacement direction of the elastic piece, and the cam 44 is enabled to be in contact with the driven adapter piece 43 all the time, and meanwhile, the driven adapter piece 43 can slide on the linear slide rail 422 more smoothly. The connection between the two ends of the elastic member 45 and the driven adapter 43 and the second mounting surface 4212 may be a fixed connection, or may be a contact connection (e.g., an abutting connection). Referring to fig. 3 again, the second mounting surface 4212 is provided with a first hole 42121, a first shaft sleeve (not shown in the figure) is arranged in the first hole 42121, a second end of the guide bearing 46 is movably connected with the first shaft sleeve and is movably connected to the second mounting surface 4212 through the first shaft sleeve, the first shaft sleeve supports the second end of the guide bearing 46, the guide bearing 46 is in clearance fit with the first shaft sleeve, so that the guide bearing 46 can linearly displace along with the driven adapter 43, the first shaft sleeve and the linear slide rail 422 jointly limit the displacement direction of the driven adapter 43, the driven adapter 43 can linearly displace more accurately, the linear displacement distance of the measuring reflector 41 is more accurate, and the final measuring result is more accurate.

In one embodiment, referring to fig. 5, a central point of the contact point between the cam 44 and the driven adapter 43 is defined as a, a rotational central point of the cam 44 is defined as B, and a straight line where the two points a and B are located is parallel to the measurement optical path of the laser interferometer 1. The maximum distance between the two points AB is set to be LMAX, the minimum distance between the two points AB is set to be LMIN, and the length of the elastic member 45 is (LMAX-LMIN)/0.5-LMAX-LMIN)/0.1, so that the acting force of the elastic member 45 on the driven adapter 43 can enable the cam 44 to be always abutted against the driven adapter 43.

In the present embodiment, the cam 44 is a dial having an elliptical outer profile. Assuming that the linear distance of the measuring mirror 41 moving along the measuring optical path of the laser interferometer 1 is x, the angle of rotation of the rotary table 2 is y, the semi-axis of the long axis of the cam 44 is a, the semi-axis of the short axis is b, and the initial measurement position is at any vertex of the long axis or the short axis of the cam 44, within 1/4 period of the elliptical rotating disk (i.e. the rotation angle of the rotary table 2 does not exceed 90 °), x and y satisfy: y = arctan (bsin ((a-x)/a)/(a-x))) and the correspondence between x and y is established by sequentially calibrating the values for each 1/4 cycle. The linear distance x over which the measuring mirror 41 is moved along the measuring beam path of the laser interferometer 1 can be accurately measured by means of the laser interferometer 1, the semi-axis a of the long axis of the cam 44 being constant, so that the angle y over which the rotary table 2 is rotated can be calculated by the formula y = arctan (bsin (arccos ((a-x)/a)/(a-x))), whereas if the angle of rotation of the rotary table 2 exceeds 1/4 period, i.e. exceeds 90 °, the angle corresponding to the period is complemented in the calculation structure, e.g. the angle calculated by the formula is 13.5 °, and the rotary table is rotated over 1/2 period, i.e. the actual angle of rotation of the rotary table is 13.5 ° +180 ° =193.5 °. That is, the circular motion is converted into the linear displacement by the circular measuring system provided by the embodiment, and the linear displacement distance is measured by the laser interferometer 1 having the accurate measuring effect on the linear displacement, so that the rotation angle of the object to be measured can be accurately calculated, and the purpose of accurately measuring the circular motion is achieved.

Referring to fig. 3, the long axis of the cam 44 is provided with a weight reduction portion 441, the weight reduction portion 441 is a groove or a through hole, since the mass of the elliptical cam in the long axis direction is greater than the mass of the elliptical cam in the short axis direction, a certain vibration can be generated to the rotating shaft during the circular motion, in order to ensure the stable rotation of the rotating shaft, the weight reduction portion is arranged in the long axis direction of the elliptical turntable to reduce the weight in the long axis direction, so as to ensure the weight matching between the long axis direction and the short axis direction of the ellipse, so as to ensure the dynamic balance during the motion of the cam, and especially, in the high-speed rotation process, the vibration caused by the uneven weight distribution of the cam can be greatly applied to the measured result.

In an alternative embodiment, referring to fig. 6, the cam 44 is a rotating disk with an outer contour of a symmetrical double parabola, the symmetrical double parabola includes a first parabola located in the first and fourth quadrants and a second parabola located in the second and third quadrants, and the open ends of the first parabola and the second parabola are connected and are symmetrically arranged along the X-axis. Assuming that the linear distance of the measurement mirror 41 moving along the measurement optical path of the laser interferometer 1 is x1, the angle of rotation of the rotary table 2 is y1, and the initial position of measurement is at any vertex or end point of the symmetrical double parabola of the cam 44, x1 and y1 satisfy the following conditions within 1/4 period of the turntable of the double parabola (i.e. the rotation angle of the rotary table 2 does not exceed 90 °): y1= arcsin (sqrt (x 1, 4)), and the correspondence between x1 and y1 is established by sequentially calibrating the values of each 1/4 cycle. The vertex of the double parabola means the vertex of the first parabola or the second parabola, and the end point of the double parabola means any connection point of the first parabola and the second parabola. The linear distance x1 over which the measuring mirror 41 is moved along the measuring beam path of the laser interferometer 1 can be accurately measured by means of the laser interferometer 1, so that the angle y1 of rotation of the rotary table 2 can be calculated by the formula y1= arcsin (sqrt (x 1, 4)), whereas if the angle of rotation of the rotary table 2 exceeds 1/4 of the period, i.e. exceeds 90 °, the angle of the corresponding period is complemented in the calculation structure, e.g. the angle calculated by the formula is 13.5 °, and the rotary table is rotated over 1/4 of the period, i.e. the actual angle of rotation of the rotary table is 13.5 ° +90 ° =103.5 °. That is, the circular motion is converted into the linear displacement by the circular measuring system provided by the embodiment, and the linear displacement distance is measured by the laser interferometer 1 having the accurate measuring effect on the linear displacement, so that the rotation angle of the object to be measured can be accurately calculated, and the purpose of accurately measuring the circular motion is achieved.

In the semiconductor field, a multi-dimensional motion table is generally used, some multi-dimensional motion tables have a full-stroke rotational degree of freedom in the Rz direction, high-precision measurement needs to be carried out on the multi-dimensional motion tables, and measurement of the linear degree of freedom is generally carried out by adopting a laser interferometer. For the measurement of 360 degrees of rotational freedom, the circumference measurement system of the present embodiment may be adopted to convert the circular motion into the linear motion for measurement. The circumference measurement system of the embodiment solves the problem that the measured reflector or surface cannot be measured due to light loss in the circumferential motion, and can realize high-resolution and high-precision measurement of the multidimensional motion platform. And the circumference measurement system of this embodiment simple structure easily realizes, and is with low costs.

The outer contour of the cam 44 is selected to be elliptical or symmetrical double parabolic shape for the following purposes:

1. the cam contour conforming to the two situations can be directly processed by the existing precision machining equipment to obtain the cam conforming to the measurement precision of the circumference measurement system of the embodiment, and basic guarantee is provided for the measurement precision of the circumference measurement system to reach the micro radian level.

2. The elliptic or double-parabolic curve selected in the embodiment can be expressed by a clear analytic expression, so that the position relation between the motion track of the cam and the rotation angle of the motion table can be accurately calculated, interpolation can be performed according to the relational expression provided by the scheme during calibration to realize calibration with higher resolution, but if the cam with any curve is selected, the analytic expression is unclear, and the interpolation precision during calibration is not very high.

3. The cam contour profiles according with the two situations are characterized by axial symmetry, easy arrangement of weight reduction parts, reduction of the load weight of the rotary worktable (the rotary angle of the rotary worktable capable of measuring smaller loads), realization of dynamic balance and contribution to high-speed circumference measurement.

In one embodiment, the device further comprises a circular grating; the circle grating set up in the periphery of swivel work head 2, just the circle grating with swivel work head 2 coaxial setting. The data of the circular grating is in one-to-one correspondence with the cam positions on the rotary table 2, and the current position is obtained after the position data of the circular grating is read before measurement is started each time, and then measurement is performed. Or the rotary table 2 is rotated so that the reading of the circular grating is zero, i.e. the cam position on the rotary table 2 is at the proximal end limit position.

Preferably, the pitch of the circular grating is greater than 20um. The circular grating on the rotary worktable 2 can be roughly positioned, the current position is conveniently confirmed to be in the specific direction of the elliptical rotating disk, the manufacturing cost of the circular grating with the grating pitch larger than 20um is low, and the total cost of the circumference measuring system provided by the embodiment cannot be greatly increased.

The preferred embodiments of the present invention have been described in detail, but it should be understood that various changes and modifications can be made by those skilled in the art after reading the above teachings of the present invention. Such equivalents are intended to fall within the scope of the claims appended hereto.

Claims

1. A circumference measuring system, characterized by: the device comprises a laser interferometer (1), a rotary workbench (2) and a measuring module (4), wherein the measuring module (4) further comprises a measuring reflector (41), a linear guide mechanism (42), a driven adapter (43) and a cam (44); the measuring reflector (41) is fixed on the driven adapter (43), the driven adapter (43) is movably mounted on the linear guide mechanism (42), and the linear displacement action can be carried out on the linear guide mechanism (42) along the measuring optical path of the laser interferometer (1); the rotary worktable (2) is in driving connection with the cam (44), a rotating shaft of the cam (44) and a rotating shaft of the rotary worktable (2) are coaxially arranged, the cam (44) is in contact connection with the driven adapter (43), and the rotating action of the cam (44) drives the driven adapter (43) to perform linear displacement action along a measuring optical path of the laser interferometer (1); the mirror surface of the measuring reflecting mirror (41) always faces the measuring optical path of the laser interferometer (1).

2. The circumference measurement system according to claim 1, wherein: the measuring module (4) also comprises an elastic piece (45); at least one end of the elastic member (45) is connected with the driven adapter member (43), acts on the driven adapter member (43), generates acting force for pushing the driven adapter member (43) to the cam (44), and enables the cam (44) to be always abutted against the driven adapter member (43).

3. The circumference measurement system according to claim 2, wherein: the measuring module (4) further comprises a guide bearing (46), the elastic piece (45) is sleeved on the guide bearing (46), and the guide bearing (46) has a guide effect on the elastic piece (45) and is over against the driven adapter piece (43).

4. The circumference measurement system of claim 3, wherein: the linear guide mechanism (42) includes: the device comprises a frame (421) and a linear slide rail (422), wherein the linear slide rail (422) is arranged on the frame (421); the driven adapter (43) is provided with a sliding block matched with the linear sliding rail (422), or the driven adapter (43) is fixedly installed on the sliding block matched with the linear sliding rail (422).

5. The circumference measurement system of claim 4, wherein: the frame (421) is provided with a first mounting surface (4211) and a second mounting surface (4212) which are perpendicular to each other, the linear sliding rail (422) is fixedly mounted on the first mounting surface (4211), the guide bearing (46) is arranged in parallel with the linear sliding rail (422), a first end of the guide bearing is fixed on the driven adapter piece (43), and a second end of the guide bearing is movably connected to the second mounting surface (4212); the elastic piece (45) is sleeved on the guide bearing (46), and two ends of the elastic piece (45) are connected with the driven adapter piece (43) and the second mounting surface (4212) respectively.

6. The circumference measurement system according to claim 5, wherein: the second mounting surface (4212) is provided with a first hole (42121), a first shaft sleeve is arranged in the first hole (42121), and the second end of the guide bearing (46) is movably connected with the first shaft sleeve and movably connected to the second mounting surface (4212) through the first shaft sleeve.

7. The circumference measurement system according to claim 2, wherein: the center point of the contact part of the cam (44) and the driven adapter piece (43) is defined as A, the rotation center point of the cam (44) is defined as B, a straight line where the two points A and B are located is arranged in parallel with a measuring light path of the laser interferometer (1), the maximum distance between the two points AB is set to be LMAX, the minimum distance between the two points AB is set to be LMIN, and then the length of the elastic piece (45) is (LMAX-LMIN)/0.5-LMAX-LMIN)/0.1.

8. The circumference measurement system according to claim 1, wherein: the cam (44) is a turntable with an oval outer contour; assuming that the linear distance of the measuring reflecting mirror (41) moving along the measuring optical path of the laser interferometer (1) is x, the angle of rotation of the rotary table (2) is y, the semi-axis of the long axis of the cam (44) is a, the semi-axis of the short axis is b, and the initial measuring position is at any vertex of the long axis or the short axis of the cam (44), x and y are satisfied within 1/4 period of the elliptic turntable:

y＝arctan(bsin(arccos((a-x)/a)/(a-x)))。

9. the circumference measurement system according to claim 8, wherein: a weight reduction part (441) is arranged on a long shaft of the cam (44), and the weight reduction part (441) is a groove or a through hole.

10. The circumference measurement system according to claim 1, wherein: the cam (44) is a turntable with a symmetrical double-parabola external profile, the symmetrical double-parabola comprises a first parabola located in a first quadrant and a fourth quadrant and a second parabola located in a second quadrant and a third quadrant, open ends of the first parabola and the second parabola are connected and are symmetrically arranged along an X axis, assuming that a straight line distance of the measuring reflecting mirror (41) moving along a measuring optical path of the laser interferometer (1) is X1, a rotating angle of the rotary worktable (2) is y1, an initial measuring position is any vertex or endpoint of the symmetrical double-parabola of the cam (44), and within 1/4 period of the turntable of the symmetrical double-parabola, X1 and y1 satisfy: y1= arcsin (sqrt (x 1, 4)).