Optical grating displacement measurement system

Abstract

The application provides a grating displacement measurement system, which comprises a reading head module, a reference grating and a grating ruler. The reading head module comprises an X-direction displacement measurement structure, a Y-direction displacement measurement structure and an interpolation subdivision circuit. The X-direction displacement measurement structure comprises a first light source and a plurality of first detectors. The Y-direction displacement measurement structure comprises a second light source and a plurality of second detectors. The reference grating is arranged on the upper part of the reading head module. The reference grating comprises a first light transmission hole matched with the first light source, a first mask slit matched with the first detector, a second light transmission hole matched with the second light source and a second mask slit matched with the second detector. The transverse distance between any adjacent first mask slit and any adjacent second mask slit is nT+T / 4. The grating ruler is arranged above the reference grating, and the distance formed between the grating ruler and the reference grating is the Talbot imaging plane distance of the grating ruler. The system size can be effectively reduced under the premise of meeting the high-precision measurement requirement.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical measurement technology, and particularly relates to a grating ruler displacement measurement system. BACKGROUND

[0002] The high-precision grating ruler displacement measurement system is a technology for precise displacement measurement by using the grating diffraction principle, and is widely applied to modern industrial technical fields such as microelectronics and ultra-precision machining. With the development of science and technology, the grating ruler displacement measurement system is developing towards miniaturization and multi-dimension, and there is a contradiction between the requirements of large range, high precision and miniaturization.

[0003] At present, in order to meet the demand of high-precision measurement, a digital camera and an optical lens are often used to collect the grating ruler stripes, and the displacement movement is measured by the equal-intensity-position movement. However, the structure of using the digital camera and the optical lens cannot meet the application demand of miniaturization.

[0004] Therefore, finding a grating ruler displacement measurement system that can meet the demand of high precision and miniaturization has become a current research hotspot. SUMMARY

[0005] The present application provides a grating ruler displacement measurement system, which can effectively reduce the size of the grating ruler displacement measurement system and realize the miniaturization of the equipment under the premise of meeting the demand of high-precision measurement.

[0006] The application provides a grating ruler displacement measurement system, which comprises a reading head module, a reference grating and a grating ruler.

[0007] According to the grating ruler displacement measurement system provided by the application, the plurality of first detectors are symmetrically distributed along an arc direction with the first light source as the center.

[0008] According to the grating ruler displacement measurement system provided by the application, the plurality of second detectors are symmetrically distributed along an arc direction with the second light source as the center.

[0009] According to the grating ruler displacement measurement system provided by the application, the slit length of the first mask slit in the reference grating and / or the slit length of the second mask slit in the reference grating is greater than or equal to a first preset length and less than or equal to a second preset length, wherein the first preset length is determined according to the required light quantity of the grating structure Talbot image signal; and the second preset length is determined according to a preset tolerance angle and a grating period of the reference grating.

[0010] According to the grating ruler displacement measurement system provided by the application, the first mask slit in the reference grating and / or the second mask slit in the reference grating are arranged in the following manner: the first total light intensity intensity corresponding to the first mask slit received by the first detector is obtained, and the second total light intensity intensity corresponding to the second mask slit received by the second detector is obtained; based on the first total light intensity intensity and the second total light intensity intensity, a weak light intensity intensity detector is determined in the first detector and the second detector, and the weak light intensity intensity detector is arranged to have maximum light transmission, thereby obtaining a weak light intensity intensity detector with maximum light transmission; based on the total light intensity intensity received by the weak light intensity intensity detector with maximum light transmission, the number of slits and / or the length of slits of another detector are arranged, thereby obtaining another detector with target number of slits and / or target length of slits, so that the intensity difference between the total light intensity intensity received by the another detector with target number of slits and / or target length of slits and the total light intensity intensity received by the weak light intensity intensity detector with maximum light transmission is less than a preset value, wherein the another detector is a detector other than the weak light intensity intensity detector in the first detector and the second detector; the first mask slit in the reference grating and / or the second mask slit in the reference grating are arranged according to the another detector with target number of slits and / or target length of slits and the weak light intensity intensity detector with maximum light transmission.

[0011] According to the grating ruler displacement measurement system provided by the application, the first total light intensity intensity received by the first detector corresponding to the first mask slit is obtained in the following manner: under test light, first pixel data corresponding to the first mask slit received by the first detector is obtained; based on the first pixel data, the first total light intensity intensity received by the first detector corresponding to the first mask slit is obtained.

[0012] According to the grating ruler displacement measurement system provided by the application, the second total light intensity intensity received by the second detector corresponding to the second mask slit is obtained in the following manner: under test light, second pixel data corresponding to the second mask slit received by the second detector is obtained; based on the second pixel data, the second total light intensity intensity received by the second detector corresponding to the second mask slit is obtained.

[0013] According to the grating ruler displacement measurement system provided by the application, the grating ruler comprises a two-dimensional measurement grating and zero-position variable grating pitch gratings, wherein a plurality of zero-position variable grating pitch gratings are symmetrically distributed on both sides of the two-dimensional measurement grating, and the zero-position variable grating pitch gratings located on the same side of the two-dimensional measurement grating are orthogonally arranged.

[0014] According to the grating displacement measurement system provided by the present application, the read head module further comprises a zero mark signal measurement structure, wherein the zero mark signal measurement structure is matched with the zero variable grating pitch grating, and the zero mark signal measurement structure comprises at least a plurality of zero detectors; wherein, when the grating moves, the zero variable grating pitch grating initiates a signal to the zero detector, so that the zero detector performs reference positioning on the grating movement when receiving the signal.

[0015] According to the grating displacement measurement system provided by the present application, the zero mark signal measurement structure further comprises a zero light source, and the reference grating further comprises a zero light hole matched with the zero light source and a zero mask slit matched with the zero detector.

[0016] The grating displacement measurement system provided by the present application comprises a read head module, a reference grating and a grating, wherein the read head module comprises an X direction displacement measurement structure, a Y direction displacement measurement structure and an interpolation subdivision circuit, the X direction displacement measurement structure comprises a first light source and a plurality of first detectors, the Y direction displacement measurement structure comprises a second light source and a plurality of second detectors, the reference grating is arranged on the upper part of the read head module, and the reference grating comprises a first light hole matched with the first light source, a plurality of first mask slits matched with the plurality of first detectors, a second light hole matched with the second light source and a plurality of second mask slits matched with the plurality of second detectors, wherein the transverse distance between any adjacent first mask slit and any adjacent second mask slit is nT+T / 4, T is the mask slit period of the first mask slit and the second mask slit, the grating is arranged above the reference grating, and the distance formed between the grating and the reference grating is the Talbot imaging plane distance of the grating, wherein, during the movement of the grating, the light emitted by the first light source and the second light source in the read head module passes through the first light hole and the second light hole in the reference grating to reach the grating, is diffracted and reflected by the grating, and forms a grating structure Talbot image signal at the reference grating, so that the grating structure Talbot image signal passes through the first mask slit and the second mask slit to reach the first detector and the second detector, and the grating structure Talbot image signal is transmitted to the interpolation subdivision circuit based on the first detector and the second detector, so that the interpolation subdivision circuit differentially processes the grating structure Talbot image signal to obtain a differential sinusoidal signal, and determines the displacement value of the grating based on the differential sinusoidal signal. The size of the grating displacement measurement system can be effectively reduced to realize the miniaturization of the equipment under the premise of meeting the high-precision measurement requirement. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to make the technical solutions in the present application or the prior art clearer, the accompanying drawings needed in the embodiments or the prior art description will be briefly introduced. Obviously, the accompanying drawings in the following description are only some embodiments of the present application, and other accompanying drawings can be obtained by those of ordinary skill in the art without any creative effort.

[0018] Figure 1 is a structural schematic diagram of a grating ruler displacement measurement system provided by the present application.

[0019] Figure 2 is a structural schematic diagram of a reading head module provided by the present application.

[0020] Figure 3 is a structural schematic diagram of a reference grating provided by the present application.

[0021] Figure 4 is one of simulation result diagrams of the grating ruler displacement measurement system in a reference state provided by the present application.

[0022] Figure 5 is another simulation result diagram of the grating ruler displacement measurement system in a reference state provided by the present application.

[0023] Figure 6 is a third simulation result diagram of the grating ruler displacement measurement system in a reference state provided by the present application.

[0024] Figure 7 is a fourth simulation result diagram of the grating ruler displacement measurement system in a reference state provided by the present application.

[0025] Figure 8 is a flowchart for setting a first mask slit in a reference grating and / or a second mask slit in the reference grating provided by the present application.

[0026] Figure 9 is a structural schematic diagram of a grating ruler provided by the present application.

[0027] Figure 10 is an enlarged side view structural diagram of a measurement grating of the grating ruler provided by the present application.

[0028] Figure 11 is one of enlarged front view structural diagrams of a measurement grating of the grating ruler provided by the present application.

[0029] Figure 12 is another enlarged front view structural diagram of a measurement grating of the grating ruler provided by the present application.

[0030] Reference signs:

[0031] 1: reading head module; 2: reference grating; 3: grating ruler; 1071: zero position light source;

[0032] 1072: zero position detector; 1081: first light source; 1082: first detector;

[0033] 1091: second light source; 1092: second detector; 2011: zero position light passing hole;

[0034] 2012: zero position mask slit; 2021: first light passing hole; 2022: first mask slit;

[0035] 2031: second light passing hole; 2032: second mask slit; 301: two-dimensional measurement grating;

[0036] 302: zero position variable grating; 3011: grating line; 3012: etching part;

[0037] 105: interpolation subdivision circuit. DETAILED DESCRIPTION

[0038] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions in the present application will be described clearly and completely below in combination with the drawings in the present application. Obviously, the described embodiments are some embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0039] The grating ruler displacement measurement system provided by the present application realizes high-precision multi-dimensional long-stroke displacement measurement, and through tolerance design, the reasonable layout design of the detector and the reference grating is enhanced, the uniformity of the detection light intensity is enhanced, the alignment tolerance design value is larger, and the actual application scene is better adapted. Moreover, the grating ruler displacement measurement system has simple structure, and the miniaturization and higher alignment tolerance design index of the device can improve the installation and adjustment of the sensor in actual application.

[0040] It should be noted that the grating ruler displacement measurement system provided by the present application can be a sensor. In the present embodiment, the grating ruler displacement measurement system can be described as a sensor. The grating ruler displacement measurement system can be used to measure the displacement in the X and Y axis directions. The X and Y directions can be the coordinate axis directions in the rectangular coordinate system. In an example, the horizontal direction can be taken as the X axis direction, and the vertical direction can be taken as the Y axis direction.

[0041] Figure 1 is a structural schematic diagram of the grating ruler displacement measurement system provided by the present application; Figure 2 is a structural schematic diagram of the read head module provided by the present application; Figure 3This is a schematic diagram of the reference grating provided by the present invention. The following will be combined with... Figures 1 to 3 The structure of the grating ruler displacement measurement system provided by the present invention will be described.

[0042] In an exemplary embodiment of the present invention, combined with Figures 1 to 3 As can be seen, the grating ruler displacement measurement system may include a read head module 1, a reference grating 2, and a grating ruler 3. Each component will be described in detail below.

[0043] In one embodiment, the read head module 1 may include an X-direction displacement measurement structure, a Y-direction displacement measurement structure, and an interpolation subdivision circuit 105. The X-direction displacement measurement structure may include a first light source 1081 and a plurality of first detectors 1082; the Y-direction displacement measurement structure may include a second light source 1091 and a plurality of second detectors 1092. In one embodiment, there may be four first detectors 1082 and four second detectors 1092. In this embodiment, four first detectors 1082 and four second detectors 1092 will be used as an example for explanation.

[0044] In another embodiment of the present invention, the reference grating 2 can be disposed on the upper part of the read head module 1. In one example, the reference grating 2 can be fixed to the read head module 1 by adhesive or a housing. The reference grating 2 may include a first light-transmitting aperture 2021 matching the first light source 1081, a plurality of first mask slits 2022 matching the plurality of first detectors 1082, a second light-transmitting aperture 2031 matching the second light source 1091, and a plurality of second mask slits 2032 matching the plurality of second detectors 1092. The lateral distance between any two adjacent first mask slits 2022 is nT+T / 4, where T is the mask slit period of the first mask slit 2022; the lateral distance between any two adjacent second mask slits 2032 is nT+T / 4, where T is the mask slit period of the second mask slit 2032. By setting the lateral distance between any two adjacent first mask slits 2022 to nT+T / 4 and the lateral distance between any two adjacent second mask slits 2032 to nT+T / 4, the signal phase difference between the four first detectors 1082 is 90°, and the signal phase difference between the four second detectors 1092 is 90°.

[0045] In yet another embodiment, the grating ruler 3 can be arranged above the reference grating 2, and the distance formed between the grating ruler 3 and the reference grating 2 is the Talbot imaging plane distance of the grating ruler 3. In the application process, the distance from the grating ruler 3 to the reference grating 2 is the distance from the grating ruler 3 to its Talbot imaging plane, which makes the reference grating 2 just located on the Talbot imaging plane of the grating ruler 3. Thus, the displacement value of the grating ruler can be determined based on the Talbot imaging principle. The grating ruler displacement measurement system provided by the application realizes the miniaturization of the grating ruler displacement measurement system by arranging the reading head module, the reference grating and the grating ruler, while meeting the high-precision measurement requirement.

[0046] In yet another embodiment, based on the grating ruler displacement measurement system provided by the application, during the movement of the grating ruler 3, the light emitted by the first light source 1081 and the second light source 1091 in the reading head module 1 passes through the first light transmission hole 2021 and the second light transmission hole 2031 in the reference grating 2 to reach the grating ruler 3, is diffracted and reflected by the grating ruler 3, and then forms a grating structure Talbot image signal at the reference grating 2, so that the grating structure Talbot image signal passes through the first mask slit 2022 and the second mask slit 2032 to reach the first detector 1082 and the second detector 1092, and the grating structure Talbot image signal is transmitted to the interpolation subdivision circuit 105 based on the first detector 1082 and the second detector 1092, so that the interpolation subdivision circuit 105 differentially processes the grating structure Talbot image signal to obtain a differential sinusoidal signal, and the displacement value of the grating ruler 3 is determined based on the differential sinusoidal signal.

[0047] In yet another embodiment, light can be emitted by the first light source 1081 and the second light source 1091 in the reading head module 1, pass through the first light transmission hole 2021, the zero light transmission hole 2011 and the second light transmission hole 2031 on the reference grating 2 to reach the grating ruler 3, and after being diffracted and reflected by the grating ruler 3, reach the first mask slit 2022 and the second mask slit 2032 of the reference grating 2, and the imaging (corresponding to the grating structure Talbot image) passes through the first mask slit 2022 and the second mask slit 2032 to reach each detector. Among them, the four first detectors 1082 and the four second detectors 1092 respectively receive four light intensity signals (corresponding to the grating structure Talbot image signal), and the phases of the four signals are respectively different by 90°. The four signals are differentially processed to obtain two sinusoidal signals with a phase difference of 90°, and the two differential signals are subdivided for subsequent displacement calculation. The miniaturized grating ruler displacement measurement system can realize high-precision displacement measurement.

[0048] The grating ruler displacement measurement system provided by this invention includes a read head module, a reference grating, and a grating ruler. The read head module includes an X-direction displacement measurement structure, a Y-direction displacement measurement structure, and an interpolation subdivision circuit. The X-direction displacement measurement structure includes a first light source and multiple first detectors; the Y-direction displacement measurement structure includes a second light source and multiple second detectors. The reference grating is disposed on the upper part of the read head module and includes a first light-transmitting aperture matching the first light source, multiple first mask slits matching the multiple first detectors, a second light-transmitting aperture matching the second light source, and multiple second mask slits matching the multiple second detectors. The lateral distance between any two adjacent first mask slits and any two adjacent second mask slits is nT + T / 4, where T is the distance between the first mask slit and the second mask slit. The mask slit period of the slit is defined. A grating ruler is positioned above a reference grating, and the distance between the grating ruler and the reference grating is the distance to the Talbot imaging plane of the grating ruler. During the movement of the grating ruler, light emitted from the first and second light sources in the readhead module passes through the first and second light-passing holes in the reference grating and reaches the grating ruler. After diffraction and reflection by the grating ruler, a Talbot image signal of the grating structure is formed at the reference grating. This Talbot image signal then passes through the first and second mask slits to reach the first and second detectors. Based on the first and second detectors, the Talbot image signal is transmitted to the interpolation subdivision circuit. The interpolation subdivision circuit performs differential processing on the Talbot image signal to obtain a differential sine signal, and determines the displacement value of the grating ruler based on the differential sine signal. This achieves a reduction in the size of the grating ruler displacement measurement system while meeting high-precision measurement requirements, thus realizing equipment miniaturization.

[0049] In yet another exemplary embodiment of the present invention, the following combination continues... Figure 2 To explain, multiple first detectors 1082 are symmetrically distributed along an arc-shaped direction with the first light source 1081 as the center. This ensures the uniformity of the optical signal obtained based on the first light source.

[0050] In yet another exemplary embodiment of the present invention, the following combination continues... Figure 2 To illustrate, multiple second detectors 1092 are symmetrically distributed along an arc-shaped direction, centered on the second light source 1091. This ensures the uniformity of the optical signal obtained based on the second light source.

[0051] It should be noted that, since the reference grating 2 includes a first light-transmitting aperture 2021 that matches the first light source 1081, a plurality of first mask slits 2022 that match the plurality of first detectors 1082, a second light-transmitting aperture 2031 that matches the second light source 1091, and a plurality of second mask slits 2032 that match the plurality of second detectors 1092, that is, the reference grating 2 is symmetrically designed, and the mask slits (including the plurality of first mask slits 2022 and the plurality of second mask slits 2032) are all designed with a curved layout, the uniformity of the probe light can be enhanced, thereby improving the alignment tolerance design value during the equipment installation process.

[0052] In yet another exemplary embodiment of the present invention, the slit length of the first mask slit 2022 in the reference grating 2 and / or the slit length of the second mask slit 2032 in the reference grating 2 are greater than or equal to a first preset length and less than or equal to a second preset length, wherein,

[0053] The first preset length is determined based on the amount of light transmission required for the Taber image signal of the grating structure;

[0054] The second preset length is determined based on the preset tolerance angle and the grating period of the reference grating 2.

[0055] Taking the first mask slit 2022 as an example, the distance between the two slits along their length is D1. When the angle between the fringes and the slits is α = arctan((1 / 2T) / D1), the phase of the interference fringes on the two slits is consistent, no longer differing by 180°. This causes the loss of effective signal information during differential signaling, making the two differential signals inaccurate and unable to provide effective signals for subsequent processing. It should be noted that the fringe refers to one of the interference fringes generated at the reference grating 2 after the grating ruler 3 deflects around the Z-axis. The α mentioned earlier is the RZ deflection dead angle. Therefore, by limiting the slit length, the length of D1 can be reduced, increasing the angle of the α deflection dead angle, making it outside the tolerance design angle range.

[0056] To ensure the sensor can still measure displacement even when there is an angular deviation between the read head module 1 and the grating ruler 3, the slit lengths of the first mask slit 2022 and / or the second mask slit 2032 in the reference grating 2 can be set according to a first preset length and a second preset length. The slit length is greater than or equal to the first preset length and less than or equal to the second preset length. The first preset length can be determined based on the light transmission required for the Taber image signal of the grating structure; the second preset length can be determined based on the preset tolerance angle α (i.e., α mentioned above) and the grating period T of the reference grating, and can be obtained by α = arctan((1 / 2T) / D1).

[0057] Figure 4This is one of the simulation results of the grating ruler displacement measurement system provided by the present invention under a reference state; Figure 5 This is the second simulation result diagram of the grating ruler displacement measurement system provided by the present invention under the reference state; Figure 6 This is the third simulation result diagram of the grating ruler displacement measurement system provided by the present invention under the reference state; Figure 7 This is the fourth simulation result of the grating ruler displacement measurement system provided by this invention under reference conditions. The following will be combined with... Figures 4 to 7 Please provide an explanation.

[0058] Combination Figures 4 to 7 It is known that the image reaches each detector after passing through the mask slit. The four first detectors 1082 and the four second detectors 1092 respectively receive four light intensity signals, with each signal having a 90° phase difference. The grating ruler 3 moves one cycle in each of the X and Y measurement directions, thus obtaining four sinusoidal signals with sequentially 90° phase differences. The measured signals are as follows: Figures 4 to 7 As shown. Among them, Figure 4 DataY1, dataY2, dataY3, and dataY4 represent the signals received by the four second detectors 1092. Figure 5 DataX1, dataX2, dataX3, and dataX4 are the signals received by the four first detectors (1082). Differential processing of the four signals yields two sinusoidal signals with a 90° phase difference. Figure 6 In the example, dataYY1 is obtained by differencing dataY3 and dataY1, and dataYY2 is obtained by differencing dataY2 and dataY4. Figure 7 In the diagram, dataXX1 is obtained by differentiating dataX3 and dataX1, and dataXX2 is obtained by differentiating dataX2 and dataX4. The two differential signals are then further subdivided for subsequent displacement calculations to obtain the grating ruler displacement value. During movement, when the zero-position variable-pitch grating 302 passes through the read head module 1, the zero-position detector 1072 receives the zero-position signal, achieving reference positioning functionality for displacement in the X and Y directions.

[0059] Figure 8 This is a schematic diagram of the process of setting the first mask slit in the reference grating and / or the second mask slit in the reference grating according to the present invention.

[0060] The following will combine Figure 8 The process of setting the first mask slit in the reference grating and / or the second mask slit in the reference grating is described.

[0061] In an exemplary embodiment of the present invention, combined with Figure 8As can be seen, the layout setting of the first mask slit in the reference grating and / or the second mask slit in the reference grating may include steps 810 to 850, and each step will be described below.

[0062] In step 810, the first total light intensity received by the first detector corresponding to the first mask slit is obtained.

[0063] In step 820, the second total light intensity received by the second detector corresponding to the second mask slit is obtained.

[0064] In one embodiment, a first total light intensity received by a first detector corresponding to a first mask slit can be obtained, and a second total light intensity received by a second detector corresponding to a second mask slit can be obtained.

[0065] In yet another exemplary embodiment of the present invention, obtaining the first total light intensity received by the first detector corresponding to the first mask slit can be achieved in the following manner:

[0066] Under test light, acquire the first image data received by the first detector corresponding to the first mask slit;

[0067] Based on the first image data, the first total light intensity received by the first detector corresponding to the first mask slit is obtained.

[0068] In one embodiment, image data of the first detector 1082 corresponding to the first mask slit 2022 can be obtained respectively, and the total light intensity of the first detector 1082 corresponding to the first mask slit 2022 can be obtained by adding the image data of each image data, that is, the first total light intensity is obtained.

[0069] Based on the same inventive concept, the second total light intensity received by the second detector corresponding to the second mask slit can be obtained in the following manner:

[0070] Under test light, acquire the second image data received by the second detector corresponding to the second mask slit;

[0071] Based on the second image data, the second total light intensity received by the second detector corresponding to the second mask slit is obtained.

[0072] In step 830, based on the first total light intensity and the second total light intensity, a weak light intensity detector is determined from the first detector and the second detector, and the weak light intensity detector is set to the maximum light transmittance to obtain a weak light intensity detector with the maximum light transmittance.

[0073] In one embodiment, the total light intensity of the two detectors can be compared. Under the condition of satisfying the RZ deflection dead angle limit, the mask on the side with weaker light intensity can be set to the maximum transmittance within the detector range to improve light utilization. That is, based on the first and second total light intensity, the weak light intensity detector can be determined among the first detector 1082 and the second detector 1092, and the weak light intensity detector can be set to the maximum transmittance to obtain the weak light intensity detector with the maximum transmittance.

[0074] In step 840, based on the total light intensity received by the weak light intensity detector with maximum light transmittance, the number of slits and / or the slit length of another detector are arranged to obtain another detector with a target number of slits and / or a target slit length, so that the intensity difference between the total light intensity received by the other detector with the target number of slits and / or the target slit length and the total light intensity received by the weak light intensity detector with maximum light transmittance is less than a preset value.

[0075] In step 850, the first mask slit and / or the second mask slit in the reference grating are arranged according to another detector having the target number of slits and / or the target slit length, and a weak light intensity detector with the maximum light transmittance.

[0076] In another embodiment, the number of slits and / or the slit length of another detector can be arranged based on the total light intensity received by the weak light intensity detector with the maximum light transmittance, resulting in another detector with a target number of slits and / or a target slit length. This ensures that the intensity difference between the total light intensity received by the other detector with the target number of slits and / or the target slit length and the total light intensity received by the weak light intensity detector with the maximum light transmittance is less than a preset value. Here, the other detector is the detector other than the weak light intensity detector among the first and second detectors.

[0077] It is understandable that if the weak light intensity detector is the first detector, then the other detector is the second detector, and if the weak light intensity detector is the second detector, then the other detector is the first detector.

[0078] Furthermore, the first mask slit and / or the second mask slit in the reference grating can be arranged according to another detector having the target number of slits and / or the target slit length, and a weak light intensity detector with maximum light transmission. That is, the first mask slit and / or the second mask slit in the reference grating are respectively set as another detector having the target number of slits and / or the target slit length, and a weak light intensity detector with maximum light transmission.

[0079] In another embodiment, the number and length of the mask slits on the side with stronger light intensity (corresponding to the mask slits of the other detector) can be set as variables to construct digital mask matrices. The detector data matrix is ​​then multiplied by the mask matrix, and the total light intensity after multiplication is calculated. Further, the absolute value of the difference between the total light intensity of the detector corresponding to the mask slit on the side with weaker light intensity (corresponding to the weak light intensity detector with the maximum transmittance mentioned earlier) and the total light intensity of another detector (corresponding to another detector with the target slit number and / or target slit length) under different slit number and length layouts is selected, and the layout with the smallest absolute value is chosen. Through this embodiment, the overall layout of the mask slit light intensity uniformity of the reference grating 2 can be completed.

[0080] Figure 9 This is a schematic diagram of the structure of the grating ruler provided by the present invention; Figure 10 This is a magnified side view of the grating measuring grating structure provided by the present invention; Figure 11 This is one of the magnified front view structural diagrams of the grating ruler measurement grating provided by the present invention; Figure 12 This is the second magnified front view of the grating ruler measurement grating structure provided by the present invention.

[0081] The following will combine Figures 9 to 12 The structure of the grating ruler is explained.

[0082] In an exemplary embodiment of the present invention, the grating ruler 3 may include a two-dimensional measuring grating 301 and a plurality of zero-position variable gratings 302, wherein the plurality of zero-position variable gratings 302 are symmetrically distributed on both sides of the two-dimensional measuring grating 301, and the zero-position variable gratings 302 located on the same side of the two-dimensional measuring grating 301 are orthogonally arranged.

[0083] In one embodiment, combined with Figures 10 to 11 It can be seen that the two-dimensional measurement grating 301 can be a grating with a uniform period, the grating period is L1, the width of the grating line 3011 is L2, the width ratio of the grating line 3011 to the etched portion 3012 is 1:1, and the etching depth is L3.

[0084] As a variation, such as Figure 12 As shown, the two-dimensional measurement grating 301 can also be a cross-shaped type, and its grating structure is similar to... Figure 11 The etched portion 3012 and the grating line 3011 of the rectangular array grating shown have opposite structures. It should be noted that the two-dimensional measurement grating 301 is not limited to a rectangular structure.

[0085] In another exemplary embodiment of the present invention, the read head module 1 may further include a zero-position marker signal measurement structure, wherein the zero-position marker signal measurement structure is matched with the zero-position variable-pitch grating 302, and the zero-position marker signal measurement structure includes at least a plurality of zero-position detectors 1072. When the grating ruler 3 moves, the zero-position variable-pitch grating 302 sends a signal to the zero-position detectors 1072, so that the zero-position detectors 1072, upon receiving the signal, perform reference positioning for the movement of the grating ruler 3. That is, when the grating ruler 3 moves, and the zero-position variable-pitch grating 302 passes through the read head module 1, the zero-position detectors 1072 receive the zero-position signal, thereby enabling reference positioning for displacement in the X and Y directions.

[0086] In another exemplary embodiment of the present invention, the zero-position marker signal measurement structure may further include a zero-position light source 1071, and the reference grating 2 may further include a zero-position light-passing aperture 2011 matching the zero-position light source 1071, and a zero-position mask slit 2012 matching the zero-position detector 1072. It is understood that the zero-position mask slit 2012 is centered on the zero-position light-passing aperture 2011, wherein the distribution characteristics of the zero-position mask slit 2012 are dependent on the distribution characteristics of the zero-position variable-pitch grating, and the two slits are orthogonal to each other.

[0087] As described above, the grating ruler displacement measurement system provided by this invention has a simple structure and a small optical measurement structure size, which can realize non-contact high-precision two-dimensional displacement measurement and meet the application requirements of equipment miniaturization and large rotation tolerance.

[0088] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.

[0089] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A grating ruler displacement measurement system, characterized in that, The grating ruler displacement measurement system includes a readhead module, a reference grating, and a grating ruler. The read head module includes an X-direction displacement measurement structure, a Y-direction displacement measurement structure, and an interpolation subdivision circuit. The X-direction displacement measurement structure includes a first light source and multiple first detectors. The Y-direction displacement measurement structure includes a second light source and multiple second detectors. The reference grating is disposed on the upper part of the read head module. The reference grating includes a first light-transmitting aperture matching the first light source, a plurality of first mask slits matching a plurality of first detectors, a second light-transmitting aperture matching the second light source, and a plurality of second mask slits matching a plurality of second detectors. The lateral distance between any two adjacent first mask slits and any two adjacent second mask slits is nT+T / 4, where T is the mask slit period of the first mask slit and the second mask slit. The grating ruler is disposed above the reference grating, and the distance formed between the grating ruler and the reference grating is the Talbot imaging plane distance of the grating ruler. During the movement of the grating ruler, the light emitted by the first and second light sources in the read head module passes through the first and second light-transmitting holes in the reference grating and reaches the grating ruler. After being diffracted and reflected by the grating ruler, a grating structure Talbot image signal is formed at the reference grating. This grating structure Talbot image signal then passes through the first and second mask slits to reach the first and second detectors. Based on the first and second detectors, the grating structure Talbot image signal is transmitted to the interpolation subdivision circuit. The interpolation subdivision circuit performs differential processing on the grating structure Talbot image signal to obtain a differential sine signal, and determines the displacement value of the grating ruler based on the differential sine signal.

2. The grating ruler displacement measurement system according to claim 1, characterized in that, The plurality of first detectors are symmetrically distributed along an arc-shaped direction with the first light source as the center.

3. The grating ruler displacement measurement system according to claim 1, characterized in that, The plurality of second detectors are symmetrically distributed along an arc-shaped direction with the second light source as the center.

4. The grating ruler displacement measurement system according to any one of claims 1 to 3, characterized in that, The slit length of the first mask slit in the reference grating and / or the slit length of the second mask slit in the reference grating are greater than or equal to a first preset length and less than or equal to a second preset length, wherein, The first preset length is determined based on the amount of light transmission required for the Taber image signal of the grating structure; The second preset length is determined based on the preset tolerance angle and the grating period of the reference grating.

5. The grating ruler displacement measurement system according to any one of claims 1 to 3, characterized in that, The first mask slit and / or the second mask slit in the reference grating are arranged in the following manner: Obtain the first total light intensity received by the first detector corresponding to the first mask slit, and Obtain the second total light intensity received by the second detector corresponding to the second mask slit; Based on the first total light intensity and the second total light intensity, a weak light intensity detector is determined among the first detector and the second detector, and the weak light intensity detector is set to the maximum light transmittance to obtain a weak light intensity detector with the maximum light transmittance. Based on the total light intensity received by the weak light intensity detector with the maximum light transmittance, the number of slits and / or slit length of another detector are arranged to obtain another detector with a target number of slits and / or a target slit length, so that the intensity difference between the total light intensity received by the other detector with the target number of slits and / or the target slit length and the total light intensity received by the weak light intensity detector with the maximum light transmittance is less than a preset value, wherein the other detector is the detector other than the weak light intensity detector among the first detector and the second detector; The first mask slit and / or the second mask slit in the reference grating are arranged according to another detector having the target number of slits and / or the target slit length, and the weak light intensity detector with the maximum light transmittance.

6. The grating ruler displacement measurement system according to claim 5, characterized in that, The first total light intensity received by the first detector corresponding to the first mask slit is obtained in the following manner: Under test light, acquire the first image data received by the first detector corresponding to the first mask slit; Based on the first image data, the first total light intensity received by the first detector corresponding to the first mask slit is obtained.

7. The grating ruler displacement measurement system according to claim 5, characterized in that, The second total light intensity received by the second detector corresponding to the second mask slit is obtained in the following manner: Under test light, acquire the second image data received by the second detector corresponding to the second mask slit; Based on the second image data, the second total light intensity received by the second detector corresponding to the second mask slit is obtained.

8. The grating ruler displacement measurement system according to claim 1, characterized in that, The grating ruler includes a two-dimensional measuring grating and multiple zero-position variable gratings, wherein the multiple zero-position variable gratings are symmetrically distributed on both sides of the two-dimensional measuring grating, and the zero-position variable gratings located on the same side of the two-dimensional measuring grating are orthogonally arranged.

9. The grating ruler displacement measurement system according to claim 8, characterized in that, The readhead module further includes a zero-position marker signal measurement structure, wherein the zero-position marker signal measurement structure is matched with the zero-position variable-pitch grating, and the zero-position marker signal measurement structure includes at least a plurality of zero-position detectors; wherein... As the grating ruler moves, the zero-position variable-pitch grating sends a signal to the zero-position detector, so that the zero-position detector can use the signal to reference the movement of the grating ruler.

10. The grating ruler displacement measurement system according to claim 9, characterized in that, The zero-position marker signal measurement structure further includes a zero-position light source, and the reference grating further includes a zero-position light-passing hole that matches the zero-position light source, and a zero-position mask slit that matches the zero-position detector.

Images