CN113390337A - X-Y-theta three-degree-of-freedom measuring method based on field separation - Google Patents
X-Y-theta three-degree-of-freedom measuring method based on field separation Download PDFInfo
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- CN113390337A CN113390337A CN202110620152.1A CN202110620152A CN113390337A CN 113390337 A CN113390337 A CN 113390337A CN 202110620152 A CN202110620152 A CN 202110620152A CN 113390337 A CN113390337 A CN 113390337A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/002—Measuring arrangements characterised by the use of optical techniques for measuring two or more coordinates
Abstract
The invention discloses an X-Y-theta three-freedom-degree measuring method based on field separation, which comprises the following steps of: fixing a two-dimensional absolute position coding disc on a two-dimensional displacement table, wherein the two-dimensional absolute position coding disc moves in the X, Y direction and the Abbe angle theta direction along with the two-dimensional displacement table; coaxial light in the telecentric lens is vertically irradiated on the two-dimensional absolute position coding disc through the view field separating device to form two independent optical view fields with a certain distance, and the CCD camera acquires coded images in the two view fields and transmits the coded images to the image processing system through a data line; the image processing system performs modular processing on the received coded image to obtain an accurate two-dimensional absolute position value X, Y and an abbe angle θ. On the basis of the prior art, the invention improves the coding imaging system, separates the camera view field by adding the view field separation device, and can avoid the limitation of the size of a single view field on the measurement precision of the Abbe angle, thereby obtaining more accurate Abbe angle.
Description
Technical Field
The invention relates to the field of precision measurement, in particular to an X-Y-theta three-degree-of-freedom measuring method based on field separation.
Background
The absolute position sensor is a precision sensor which utilizes the photoelectric technology to carry out non-contact measurement, has the advantages of being capable of obtaining a result after being electrified, small in error, high in precision, strong in anti-interference capability and the like, and has an irreplaceable position in the field of precision measurement. With the vigorous development of the Chinese processing industry and the manufacturing industry, the development requirements of the absolute position measurement sensor tend to be more and more miniaturized, intelligent and integrated. In terms of two-dimensional measurement, measurement of position, angle, and motion trajectory is typically accomplished using a plurality of one-dimensional absolute position measurement sensors. This inevitably increases the cost of the required instrumentation, increases the complexity of the system, and introduces abbe errors, reducing the accuracy of the measurement. The measuring method and the measuring system applied to the X-Y-theta three-degree-of-freedom position are provided, system errors brought by respectively mounting one-dimensional sensors in the X motion axis direction and the Y motion axis direction in practical engineering application are reduced, and the method and the system have practical engineering values for measuring the plane motion of a precise multi-axis platform system, reducing the Abbe error of a measuring system and ensuring measurement and control precision.
Prior art patent numbers: 201710716611.X discloses a two-dimensional absolute coding three-degree-of-freedom motion platform measurement system, which illustrates a two-dimensional absolute coding code disc and a coding and decoding mode thereof, and discloses a process of motion errors of an image acquisition and processing device. The invention can obtain the Abbe angle of the two-dimensional motion platform by using the two-dimensional absolute encoder in the single view field, but the measurement precision of the Abbe angle is limited by the size of the single view field. In view of the above problems, the patent does not disclose any technical means required for solving the problems.
Disclosure of Invention
The invention aims to realize high-precision measurement of the X-Y-theta three-degree-of-freedom direction and solve the error problem in the prior art, and provides a high-precision measurement method of the X-Y-theta three-degree-of-freedom direction based on field separation on the basis of a two-dimensional absolute encoder.
In order to achieve the purpose, the technical scheme of the invention is as follows:
a three-freedom-degree X-Y-theta measuring method based on field separation comprises the following steps:
step 1, fixing a two-dimensional absolute position coding disc on a two-dimensional displacement table, wherein the two-dimensional absolute position coding disc moves in X, Y directions and in Abbe angle theta directions along with the two-dimensional displacement table;
step 2, the coaxial light in the telecentric lens is vertically irradiated on a two-dimensional absolute position coding disc through a visual field separating device to form two independent optical visual fields with a certain distance, and a CCD camera acquires coded images in the two visual fields and transmits the coded images to an image processing system through a data line;
and 3, modularizing the received coded image by the image processing system to obtain an accurate two-dimensional absolute position value X, Y and an accurate Abbe angle theta.
As a preferable mode of the present invention, the two-dimensional absolute position code disk includes a flat glass plate and a two-dimensional code sequence engraved on the flat glass plate, the two-dimensional code sequence is formed by combining a pseudo-random sequence and a binary sequence, and each line or column a of the two-dimensional code sequence1a2…anAccording to formula bi＝ai^d1ai+1^d2ai+2^…^dhai+hA transformation is obtained, where ^ represents a bit XOR operation, d1,d2,…,dhIs 0 or 1, d1,d2,…,dhThere are and only odd number of 1, each bit biIs formed by aiAnd subsequent logical operation of successive h bits, biSatisfies the following conditions: (1) the odd term or even term is m sequence, if the m sequence is j order, its cycle length is 2 j-1; (2) the even terms or the odd terms are a segment sequence representing the value size, 2j-1 is taken as the cycle length, and the value size represented by the latter segment is 1 larger than that represented by the former segment.
As a preferred scheme of this scheme, the visual field separation device includes a right-angle prism and two reflectors, the reflectors are respectively disposed on two sides of the right-angle prism and respectively parallel to a vertical plane of the right-angle prism, and the visual field separation process specifically includes: coaxial light emitted by the telecentric lens irradiates on two vertical planes of the right-angle optical prism, then is reflected to the left reflector and the right reflector respectively, and is reflected by the reflectors to vertically irradiate the two-dimensional absolute position coding disc, and finally two independent optical fields with a certain distance are formed on the two-dimensional absolute position coding disc.
As a preferred scheme of this scheme, the image processing system includes an image acquisition and preprocessing module, a position identification and subdivision module, an abbe angle measurement module, an error correction module, and a two-dimensional absolute position and abbe angle result output module, and the encoded image modularization processing process is as follows: the image acquisition and preprocessing module receives an image sent by a CCD camera, median filtering and binarization processing are carried out on a coded image, the position identification and subdivision module decodes a two-dimensional absolute coding value identified in the image to obtain current two-dimensional position information, sub-pixel subdivision is carried out on the coded image to obtain more accurate position information, the Abbe angle measurement module reads image position information of two areas to obtain an Abbe angle between a two-dimensional coding disc and the CCD camera, the error correction module compensates the two-dimensional position information according to the obtained Abbe angle to finally obtain accurate three-degree-of-freedom coordinate information, and then the two-dimensional absolute position and Abbe angle result output module outputs accurate three-degree-of-freedom coordinate information.
As a preferred scheme of the present scheme, the method for acquiring accurate coordinate information of three degrees of freedom specifically includes:
two fields of view A and B obtained by a coded imaging system, a position recognition and subdivision module uses a decoding algorithm and reads the position values (X) of the two images respectively after subdivision1,Y1) And (X)2,Y2) When the Abbe angle theta is
The error correction module compensates the two-dimensional position information according to the obtained Abbe angle to obtain a two-dimensional absolute position value correction result
The invention has the beneficial effects that:
on the basis of the prior art, the coding imaging system is improved, the field of view separating device is added, the field of view of the camera is separated, the limitation of the size of a single field of view on the measurement precision of the Abbe angle can be avoided, the more accurate Abbe angle can be obtained, and the high-precision measurement in the X-Y-theta three-degree-of-freedom direction can be realized. The method can be applied to the measurement of the planar motion of a precise multi-axis platform system, the measurement of the errors of the positioning, the straightness and the rotation angle of a linear displacement platform, the measurement of the rotation angle of a rotation axis system and the radial error motion thereof, and the like.
Drawings
FIG. 1 is a schematic structural diagram of an X-Y-theta three-degree-of-freedom measurement system based on field separation according to the present invention;
FIG. 2 is a schematic view of a view field separation device of the X-Y-theta three-degree-of-freedom measurement method based on view field separation according to the present invention;
FIG. 3 is a schematic view of Abbe angle measurement of an X-Y-theta three-degree-of-freedom measurement method based on field separation.
Detailed Description
The technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.
As shown in fig. 1-2, the X-Y- θ three-degree-of-freedom measurement system based on field separation includes two parts, namely, a coded imaging system 5 and an image processing system 7, wherein the coded imaging system 5 and the image processing system 7 perform data communication through a USB 3.0. The code imaging system 5 includes: the two-dimensional displacement platform comprises a two-dimensional absolute position coding disc 1, a two-dimensional absolute position coding disc 2, a view field separating device 3, a coaxial light telecentric lens 4 and a CCD camera 6, wherein the view field separating device comprises a right-angle prism and two reflectors, and the reflectors are respectively arranged on two sides of the right-angle prism and are respectively parallel to a vertical plane of the right-angle prism. The image processing system 7 includes: the device comprises an image acquisition and preprocessing module 8, a position identification and subdivision module 9, an Abbe angle measuring module 10, an error correction module 11 and a two-dimensional position and Abbe angle result output module 12. Fixing a two-dimensional absolute position coding disc on a two-dimensional displacement table, wherein the two-dimensional absolute position coding disc moves in the X, Y direction and the Abbe angle theta direction along with the two-dimensional displacement table; coaxial light in the telecentric lens is vertically irradiated on the two-dimensional absolute position coding disc through the view field separating device to form two independent optical view fields with a certain distance, and the CCD camera acquires coded images in the two view fields and transmits the coded images to the image processing system through a data line; the image processing system performs modular processing on the received coded image to obtain an accurate two-dimensional absolute position value X, Y and an abbe angle θ.
The two-dimensional absolute position coding disc comprises a plane glass plate and a two-dimensional coding sequence engraved on the plane glass plate, the two-dimensional coding sequence is formed by combining a pseudorandom sequence and a binary sequence, and each row or column a of the two-dimensional coding sequence1a2…anAccording to formula bi＝ai^d1ai+1^d2ai+2^…^dhai+hA transformation is obtained, where ^ represents a bit XOR operation, d1,d2,…,dhIs 0 or 1, d1,d2,…,dhThere are and only odd number of 1, each bit biIs formed by aiAnd subsequent logical operation of successive h bits, biSatisfies the following conditions: (1) the odd term or even term is m sequence, if the m sequence is j order, its cycle length is 2 j-1; (2) the even terms or the odd terms are a segment sequence representing the value size, 2j-1 is taken as the cycle length, and the value size represented by the latter segment is 1 larger than that represented by the former segment.
As shown in fig. 2, the field separation process specifically includes: coaxial light emitted by the telecentric lens irradiates on two vertical planes of the right-angle optical prism, then is reflected to the left reflector and the right reflector respectively, and is reflected by the reflectors to vertically irradiate the two-dimensional absolute position coding disc, and finally two independent optical fields with a certain distance are formed on the two-dimensional absolute position coding disc. Here, the dashed lines represent the path of the imaging light through the telecentric lens, and the proposed reflective imaging system enables the splitting of a single continuous field of view of the camera into two separate fields of view at a distance, in contrast to the ordinary optical path marked with dashed lines.
As shown in fig. 1, the encoding image modularization processing process specifically includes: the image acquisition and preprocessing module receives an image sent by a CCD camera, median filtering and binarization processing are carried out on a coded image, the position identification and subdivision module decodes a two-dimensional absolute coding value identified in the image to obtain current two-dimensional position information, sub-pixel subdivision is carried out on the coded image to obtain more accurate position information, the Abbe angle measurement module reads image position information of two areas to obtain an Abbe angle between a two-dimensional coding disc and the CCD camera, the error correction module compensates the two-dimensional position information according to the obtained Abbe angle to finally obtain accurate three-degree-of-freedom coordinate information, and then the two-dimensional absolute position and Abbe angle result output module outputs accurate three-degree-of-freedom coordinate information.
As shown in fig. 3, the method for obtaining accurate coordinate information of three degrees of freedom specifically includes:
two fields of view A and B obtained by a coded imaging system, a position recognition and subdivision module uses a decoding algorithm and reads the position values (X) of the two images respectively after subdivision1,Y1) And (X)2,Y2) When the Abbe angle theta is
The error correction module compensates the two-dimensional position information according to the obtained Abbe angle to obtain a two-dimensional absolute position value correction result
The described embodiments are only some embodiments of the invention, not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Claims (5)
1. A three-freedom-degree X-Y-theta measuring method based on field separation is characterized by comprising the following steps of:
step 1, fixing a two-dimensional absolute position coding disc on a two-dimensional displacement table, wherein the two-dimensional absolute position coding disc moves in X, Y directions and in Abbe angle theta directions along with the two-dimensional displacement table;
step 2, the coaxial light in the telecentric lens is vertically irradiated on a two-dimensional absolute position coding disc through a visual field separating device to form two independent optical visual fields with a certain distance, and a CCD camera acquires coded images in the two visual fields and transmits the coded images to an image processing system through a data line;
and 3, modularizing the received coded image by the image processing system to obtain an accurate two-dimensional absolute position value X, Y and an accurate Abbe angle theta.
2. The field-of-view separation-based X-Y-theta three-degree-of-freedom measurement method as claimed in claim 1, wherein the two-dimensional absolute position code disk comprises a planar glass plate and a two-dimensional code sequence engraved on the planar glass plate, the two-dimensional code sequence is formed by combining a pseudo-random sequence and a binary sequence, and each row or column a of the two-dimensional code sequence1 a2 … anAccording to formula bi＝ai ∧d1ai+1∧d2ai+2∧…∧dhai+hIs transformed into∧Representing a bit XOR operation, d1，d2，…，dhIs 0 or 1, d1，d2，…，dhThere are and only odd number of 1, each bit biIs formed by aiAnd subsequent logical operation of successive h bits, biSatisfies the following conditions: (1) the odd term or even term is m sequence, if the m sequence is j order, its cycle length is 2 j-1; (2) the even terms or the odd terms are a segment sequence representing the value size, 2j-1 is taken as the cycle length, and the value size represented by the latter segment is 1 larger than that represented by the former segment.
3. The method as claimed in claim 1, wherein the field-of-view separation device comprises a right-angle prism and two mirrors, the mirrors are respectively disposed at two sides of the right-angle prism and are respectively parallel to a vertical plane of the right-angle prism, and the field-of-view separation process specifically comprises: coaxial light emitted by the telecentric lens irradiates on two vertical planes of the right-angle optical prism, then is reflected to the left reflector and the right reflector respectively, and is reflected by the reflectors to vertically irradiate the two-dimensional absolute position coding disc, and finally two independent optical fields with a certain distance are formed on the two-dimensional absolute position coding disc.
4. The method as claimed in claim 1, wherein the image processing system comprises an image acquisition and preprocessing module, a position identification and subdivision module, an abbe angle measurement module, an error correction module, and a two-dimensional absolute position and abbe angle result output module, and the modularization processing procedure of the coded image is as follows: the image acquisition and preprocessing module receives an image sent by a CCD camera, median filtering and binarization processing are carried out on a coded image, the position identification and subdivision module decodes a two-dimensional absolute coding value identified in the image to obtain current two-dimensional position information, sub-pixel subdivision is carried out on the coded image to obtain more accurate position information, the Abbe angle measurement module reads image position information of two areas to obtain an Abbe angle between a two-dimensional coding disc and the CCD camera, the error correction module compensates the two-dimensional position information according to the obtained Abbe angle to finally obtain accurate three-degree-of-freedom coordinate information, and then the two-dimensional absolute position and Abbe angle result output module outputs accurate three-degree-of-freedom coordinate information.
5. The method for measuring three degrees of freedom X-Y-theta based on field separation as claimed in claim 4, wherein the method for obtaining accurate three degrees of freedom coordinate information is specifically:
two fields of view A and B obtained by a coded imaging system, a position recognition and subdivision module uses a decoding algorithm and reads the position values (X) of the two images respectively after subdivision1,Y1) And (X)2,Y2) When the Abbe angle theta is
The error correction module compensates the two-dimensional position information according to the obtained Abbe angle to obtain a two-dimensional absolute position value correction result
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