Optical load dual-axis frame encoder accuracy measurement device and measurement method

Abstract

This invention relates to the field of encoder measurement technology, and more particularly to a measuring device and method for measuring the accuracy of a dual-axis frame encoder with an optical load. The measuring device includes a cubic mirror, a mounting base, a dual-axis frame load, a first reflecting mirror, a theodolite, and a second reflecting mirror. Both the cubic mirror and the dual-axis frame load are mounted on the mounting base. The first reflecting mirror is mounted on the dual-axis frame load, and its reflected light direction indicates the direction of the optical axis of the dual-axis frame load. When the theodolite is used to collimate the cubic mirror, it is positioned between the cubic mirror and the second reflecting mirror; when the theodolite is used to collimate the dual-axis frame load, it is positioned between the dual-axis frame load and the second reflecting mirror. The advantage of this invention is that by measuring the roll and pitch encoders of the dual-axis frame load using a single theodolite, the roll angle error of the roll encoder and the pitch angle error of the pitch encoder can be easily achieved, while maintaining high accuracy.

Description

Technical Field

[0001] The present invention relates to the technical field of encoder measurement, and in particular to a device and a method for measuring the accuracy of an optical load dual-axis frame encoder. Background Art

[0002] Aerial long-range high-resolution optical payloads are one of the important means to achieve real-time and accurate reconnaissance of high-value time-sensitive targets. The positioning accuracy of high-value time-sensitive targets directly determines the implementation effect of subsequent decisions and is the core indicator of aeronautical optical payloads. The positioning accuracy of aeronautical optical payloads on ground targets is directly related to POS (position positioning device) and gyro accuracy, positioning algorithm, frame shake and encoder accuracy. Among them, the gyroscope and encoder are sensors for line of sight pointing, and their accuracy is the basis of subsequent positioning algorithms, especially for aerial long-range high-resolution optical payloads. The pointing accuracy of gyroscopes and encoders has a particularly obvious impact on ground positioning errors. Therefore, for aerial long-range high-resolution payloads, the accuracy of their frame encoders must be measured to meet the reconnaissance needs of high-precision ground target positioning.

[0003] According to the calculation of the optical load positioning accuracy index, in order to achieve the target positioning accuracy index, the pointing accuracy of the frame needs to reach the range of 10″-20″. Therefore, the accuracy of the frame encoder is required to reach within 5″-10″. At present, the Chinese patent publication number is CN116481582A, the publication date is July 25, 2023, and the patent name is "A kind of incremental photoelectric encoder accuracy detection system" invention patent application, and the Chinese patent publication number is CN114485762A, the publication date is May 13, 2022, and the patent name is "A kind of manual-automatic encoder accuracy detection device" invention patent application. Both patents use proprietary instruments to perform indexing measurement on single-axis encoders, and the measurement method is relatively complicated. Summary of the invention

[0004] In view of this, the present invention aims to provide a device and method for measuring the accuracy of a dual-axis frame encoder of an optical load. By setting a theodolite between a cubic mirror and a second reflector, or setting a theodolite between a dual-axis frame load and a second reflector, the cubic mirror and the dual-axis frame load are aligned, and then the roll angle error of a roll encoder and the pitch angle error of a pitch encoder of the dual-axis frame load are measured by the theodolite. The accuracy of the roll encoder and the pitch encoder can be measured simultaneously, the calibration accuracy is high, the implementation method is simple, and the two axes are detected simultaneously, thereby realizing efficient and accurate encoder accuracy detection, and determining whether the encoder accuracy meets the index requirements.

[0005] To achieve the above-mentioned purpose, the technical solution created by the present invention is implemented as follows: a device for measuring the accuracy of an optical load dual-axis frame encoder, comprising a cubic mirror, a mounting seat, a dual-axis frame load, a first reflector, a theodolite and a second reflector; the cubic mirror and the dual-axis frame load are both arranged on the mounting seat, and the cubic mirror is arranged above the dual-axis frame load; the normal direction of the cubic mirror is parallel to the normal direction of the mounting seat; the first reflector is arranged on the dual-axis frame load, and indicates the optical axis direction of the dual-axis frame load by the direction of the reflected light; the cubic mirror and the dual-axis frame load are both arranged in front of the second reflector; when the theodolite is used to align the cubic mirror, the theodolite is arranged between the cubic mirror and the second reflector; when the theodolite is used to align the dual-axis frame load, the theodolite is arranged between the dual-axis frame load and the second reflector.

[0006] Furthermore, a parallelism error between a normal direction of the cubic mirror and a normal direction of the mounting seat is less than or equal to a first preset value.

[0007] Furthermore, the first preset value is 1″.

[0008] Furthermore, the size of the second reflector is larger than that of the first reflector.

[0009] Furthermore, the mounting seat includes a base and a mounting plate, wherein the mounting plate is vertically arranged on the base, and a mounting surface for mounting the cubic mirror and the dual-axis frame load is provided on the mounting plate.

[0010] A method for measuring the accuracy of an optical load dual-axis frame encoder is implemented using the above-mentioned optical load dual-axis frame encoder accuracy measuring device, and the specific steps are as follows:

[0011] S1: The cubic mirror and the biaxial frame load are both arranged on a mounting seat, and the biaxial frame load and the cubic mirror are arranged in front of the second reflecting mirror at a first preset distance.

[0012] S2: placing the theodolite at the first preset position, leveling the theodolite, and aligning the second reflector of the theodolite.

[0013] S3: Rotate the theodolite 180° and align the cubic mirror through the theodolite.

[0014] S4: Move the theodolite to the second preset position. After the theodolite aligns the second reflector again, set the pitch angle and roll angle of the theodolite to zero, so that the reference of the theodolite is consistent with that at the first preset position.

[0015] S5: The dual-axis frame load is adjusted to the positions of the preset roll angle β1 and the preset pitch angle θ1. The theodolite measures the roll angle β2 and the pitch angle θ2 of the optical axis of the dual-axis frame load through the first reflector. The encoder zero position in the dual-axis frame load is adjusted to make the roll angle β1 and the roll angle β2 equal, and the pitch angle θ1 and the pitch angle θ2 equal.

[0016] S6: Rotate the roll angle and pitch angle of the optical axis of the dual-axis frame load by 180°, repeat step S4, adjust the position of the theodolite again, and repeat step S4 to make the reference consistent with that at the first preset position; then align the first reflector through the theodolite to measure the roll angle of the optical axis of the dual-axis frame load as β3 and the pitch angle as θ3.

[0017] S7: Set the roll angle error between the first reflector and the roll frame of the dual-axis frame load to β f , the pitch angle error between the first reflector and the pitch frame of the dual-axis frame load is set to θ f , the roll angle error Δβ of the roll encoder in the dual-axis frame load, and the pitch angle error Δθ of the pitch encoder in the dual-axis frame load are obtained by calculation.

[0018] Furthermore, in step S3, the specific steps of the theodolite aligning the cubic mirror are as follows:

[0019] S31: The roll angle and the pitch angle of the theodolite are rotated 180 degrees, and the pitch angle and the roll angle of the cubic mirror are measured by the theodolite.

[0020] S32: Adjust the roll and pitch attitude of the mounting base so that the crosshairs emitted by the theodolite are projected onto the cubic mirror and returned through the cubic mirror. Use the eyepiece of the theodolite to observe the crosshairs and adjust the position of the cubic mirror so that the crosshairs observed by the eyepiece of the theodolite coincide with the cross of the eyepiece, thus completing the alignment of the cubic mirror.

[0021] Furthermore, the calculation formulas for the roll angle error Δβ and the pitch angle error Δθ are:

[0022] Δβ=β2+β f -(-β3-β f ) = β2-(-β3);

[0023] Δθ=θ2+θ f -θ3-θ f =θ2-θ3.

[0024] Furthermore, the dual-axis frame load is fixed at a preset roll angle, and the angle of the dual-axis frame load in the pitch direction is equally divided into n parts, and the error of the pitch encoder in the dual-axis frame load at each equally divided angle is measured in turn.

[0025] Furthermore, the dual-axis frame load is fixed at a preset pitch angle, the angle of the dual-axis frame load in the roll direction is equally divided into m parts, and the error of the roll encoder in the dual-axis frame load at each equally divided angle is measured in turn.

[0026] Compared with the prior art, the invention can achieve the following beneficial effects: the second reflector and the cubic mirror are aligned at a first preset position by a single theodolite, and the dual-axis frame load is aligned at a second preset position by the theodolite, so that the references of the theodolite at the two preset positions are consistent, and then the roll encoder and the pitch encoder of the dual-axis frame load are measured by a single theodolite, so that the roll angle error of the roll encoder and the pitch angle error of the pitch encoder can be easily measured with high precision. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The drawings constituting part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments and descriptions of the present invention are used to explain the present invention and do not constitute an improper limitation on the present invention. In the drawings:

[0028] Figure 1 2 is a schematic diagram of the structure of a device for measuring the accuracy of an optical load dual-axis frame encoder provided in an embodiment of the present invention;

[0029] Figure 2 The present invention is a flowchart of a method for measuring the accuracy of an optical load dual-axis frame encoder provided in accordance with an embodiment of the present invention.

[0030] The reference numerals include: 1. cubic mirror; 2. mounting base; 3. dual-axis frame load; 4. first reflector; 5. screw; 6. theodolite; 7. second reflector. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solution and advantages of the invention more clear, the invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described here are only used to explain the invention and do not constitute a limitation of the invention.

[0032] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0033] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0034] In the description of the invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the invention can be understood according to specific circumstances.

[0035] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments.

[0036] like Figure 1 As shown, an optical load dual-axis frame encoder precision measuring device provided by an embodiment of the present invention comprises a cubic mirror 1, a mounting seat 2, a dual-axis frame load 3, a first reflector 4, a theodolite 6 and a second reflector 7. The cubic mirror 1 and the dual-axis frame load 3 are both arranged on the mounting seat 2, and the cubic mirror 1 is located above the dual-axis frame load 3. The normal direction of the cubic mirror 1 is parallel to the normal direction of the mounting seat 2.

[0037] The first reflector 4 is arranged on the dual-axis frame load 3, and indicates the optical axis direction of the dual-axis frame load 3 by the direction of the reflected light. The dual-axis frame load 3 is arranged in front of the second reflector 7 at a first preset distance. When the theodolite 6 is used to align the cubic mirror 1, the theodolite 6 is arranged between the cubic mirror 1 and the second reflector 7. When the theodolite 6 is used to align the dual-axis frame load 3, the theodolite 6 is arranged between the dual-axis frame load 3 and the second reflector 7.

[0038] In this embodiment, the dual-axis frame load 3 can rotate in two directions of the roll axis and the pitch axis. The dual-axis frame load 3 is a spherical load, including a roll encoder, a pitch encoder, a roll frame and a pitch frame.

[0039] Define the geodetic coordinate system O C X C Y C Z C , define the mount 2 coordinate system O A X A Y A Z A , the mounting seat 2 rolls around the axis O A X A Rotation, the pitch axis of the mounting base 2 is around O A Z A Rotate.

[0040] The normal direction is a specific direction, which refers to the direction of a line perpendicular to a plane or surface. In geometry and physics, the normal direction is often used to describe the behavior of light interacting with surfaces, such as reflection and refraction of light.

[0041] In this embodiment, the normal direction of the cubic mirror 1 is O c X C direction, the normal direction of the biaxial frame load 3 is O A X A , the normal direction O of cubic mirror 1 c X C The direction is the same as the normal direction of the biaxial frame load 3 (O A X A ) has a parallelism error less than or equal to a first preset value, the first preset value is 1″, that is, the normal direction of the cubic mirror 1 (O c X C ) and the normal direction of the biaxial frame load 3 (O A X A ) has a parallelism error of less than or equal to 1″.

[0042] In order to measure the angle relationship between the cubic mirror 1 and the optical axis of the biaxial frame load 3 pointing to the second reflector 7, the theodolite 6 first aligns the second reflector 7 at the first preset position, and then aligns the cubic mirror 1. The crosshairs emitted by the theodolite 6 are projected onto the second reflector 7, and the crosshairs are returned through the second reflector 7. The crosshairs are observed with the eyepiece of the theodolite 6, and the position of the theodolite 6 is adjusted so that the crosshairs observed by the eyepiece of the theodolite 6 coincide with the cross of the eyepiece, thus completing the alignment of the second reflector 7.

[0043] After completing the alignment of the second reflecting mirror 7, rotate the roll angle and pitch angle of the theodolite 6 by 180° to align the cubic mirror 1. The crosshairs emitted by the theodolite 6 are projected onto the cubic mirror 1, and the crosshairs are returned through the cubic mirror 1. The crosshairs are observed through the eyepiece of the theodolite 6, and the position of the cubic mirror 1 is adjusted so that the crosshairs observed through the eyepiece of the theodolite 6 coincide with the cross of the eyepiece, thereby completing the alignment of the cubic mirror 1.

[0044] The theodolite 6 aligns the second reflector 7 again at the second preset position, and then aligns the optical axis of the dual-axis frame payload 3 to point to the second reflector 7 .

[0045] The method for theodolite 6 to collimate the second reflector 7 again at the second preset position is the same as the method for theodolite 6 to collimate the second reflector 7 at the first preset position, and will not be described again here.

[0046] The first reflector 4 is set on the theodolite 6. After the theodolite 6 aligns the second reflector 7 again at the second preset position, the roll angle and pitch angle of the theodolite 6 are rotated 180° to align the dual-axis frame load 3. The crosshairs emitted by the theodolite 6 are projected onto the first reflector 4 of the dual-axis frame load 3, and the crosshairs are returned through the first reflector 4. The crosshairs are observed with the eyepiece of the theodolite 6, and the pitch angle and roll angle of the dual-axis frame load 3 are adjusted so that the crosshairs reflected by the first reflector 4 point to the second reflector 7, that is, the optical axis of the dual-axis frame load 3 points to the second reflector 7, thereby completing the alignment of the dual-axis frame load 3.

[0047] Since the field of view of a single theodolite 6 is limited, the theodolite 6 needs to be moved during the two alignments, so a large-sized second reflector 7 is needed to calibrate the two alignments so that the theodolite 6 can establish a unified reference at the first preset position and the second preset position. The size of the second reflector 7 is larger than that of the first reflector 4.

[0048] By collimating the cubic mirror 1 and the second reflector 7, the reference of the cubic mirror 1 is transferred to the second reflector 7. At the same time, through the mounting surface of the mounting seat 2, the mounting reference of the dual-axis frame load 3 is made consistent with the mounting reference of the cubic mirror 1. Therefore, through this reference transfer, the reference of the dual-axis frame load 3 is consistent with the second reflector 7.

[0049] The position where the theodolite 6 is set between the cubic mirror 1 and the second reflector 7 is defined as a first preset position, and the position where the theodolite 6 is set between the dual-axis frame load 3 and the second reflector 7 is defined as a second preset position.

[0050] Furthermore, the mounting seat 2 includes a base and a mounting plate. The mounting plate is vertically arranged on the base, and a mounting surface for mounting the cubic mirror 1 and the dual-axis frame load 3 is provided on the mounting plate.

[0051] A method for measuring the accuracy of an optical load dual-axis frame encoder is implemented using the above-mentioned optical load dual-axis frame encoder accuracy measuring device, and the specific steps are as follows:

[0052] S1: The cubic mirror 1 and the biaxial frame load 3 are both arranged on the mounting seat 2, and the biaxial frame load 3 is arranged in front of the second reflecting mirror 7 at a first preset distance.

[0053] S2: placing the theodolite 6 at the first preset position, leveling the theodolite 6 , and aligning the second reflecting mirror 7 of the theodolite 6 .

[0054] The crosshairs emitted by the theodolite 6 are projected onto the second reflector 7, and the crosshairs are returned through the second reflector 7. The crosshairs are observed with the eyepiece of the theodolite 6, and the position of the theodolite 6 is adjusted so that the crosshairs observed by the eyepiece of the theodolite 6 coincide with the cross of the eyepiece, thereby completing the alignment of the second reflector 7.

[0055] S3: Rotate the theodolite 6 by 180° and align the cubic mirror 1 through the theodolite 6 .

[0056] The specific steps are:

[0057] S31: Rotate the roll angle and the pitch angle of the theodolite 6 by 180°, and measure the pitch angle and the roll angle of the cubic mirror 1 through the theodolite 6 .

[0058] S32: Adjust the roll attitude and pitch attitude of the mounting base 2 so that the crosshairs emitted by the theodolite 6 are projected onto the cubic mirror 1, and the crosshairs are returned through the cubic mirror 1. The crosshairs are observed through the eyepiece of the theodolite 6, and the position of the cubic mirror 1 is adjusted so that the crosshairs observed through the eyepiece of the theodolite 6 coincide with the crosshairs of the eyepiece, thus completing the alignment of the cubic mirror 1. At this time, the cubic mirror 1 is parallel to the second reflector 7.

[0059] In this embodiment, the accuracy of the theodolite 6 is less than or equal to 1″, so the parallelism between the second reflector 7 of the theodolite 6 aligned at the first preset position and the cubic mirror 1 is less than or equal to a first preset value, which is 1″.

[0060] The mounting base 2 is fixed by a plurality of screws 5. When the pitch angle and roll angle of the measuring cubic mirror 1 need to be adjusted, the screws 5 are loosened to adjust the height of the mounting base 2 and the rotation angle of the mounting base 2. A X A Rotate the angle and adjust the mount 2 around O A Z A The angle of rotation is such that the cross hairs returning from the cubic mirror 1 coincide with the cross hairs of the eyepiece, and then the frame skip mount 2 is fixed with screws 5.

[0061] S4: Move the theodolite 6 to the second preset position. After the theodolite 6 aligns the second reflector 7 again, set the pitch angle and roll angle of the theodolite 6 to zero, so that the reference of the theodolite 6 is consistent with that at the first preset position.

[0062] When the theodolite 6 aligns the second reflector 7 at the first preset position, its pitch angle and roll angle are displayed as zero degrees, forming an initial reference state. When the theodolite 6 aligns the second reflector 7 at the second preset position, due to the change in position, the pitch angle and roll angle of the theodolite 6 have a certain angle. In order to maintain the accuracy and consistency of the measurement, the pitch angle and roll angle of the theodolite 6 at the second preset position are adjusted to zero. That is, the reference of the theodolite 6 at the second preset position is the same as the reference at the first preset position, thereby ensuring the consistency and accuracy of measurements at different positions.

[0063] S5: Adjust the optical axis of the dual-axis frame load 3 to the positions of the preset roll angle β1 and the preset pitch angle θ1. The theodolite 6 measures the roll angle β2 and the pitch angle θ2 of the optical axis of the dual-axis frame load 3 through the first reflector 4. By adjusting the encoder zero position in the dual-axis frame load 3, the roll angle β1 and the roll angle β2 are equal, and the pitch angle θ1 and the pitch angle θ2 are equal.

[0064] S6: Rotate the roll angle and pitch angle of the optical axis of the dual-axis frame load 3 by 180°, that is, the roll angle is (180°+β1) and the pitch angle is -θ1, adjust the position of theodolite 6 again, and repeat step S4 to make the reference of theodolite 6 consistent with that at the first preset position. Then, align the first reflector 4 through theodolite 6 to measure the roll angle of the optical axis of the dual-axis frame load 3 as β3 and the pitch angle as θ3.

[0065] S7: Set the roll angle error between the first reflector 4 and the roll frame of the biaxial frame load 3 to β f , the pitch angle error between the first reflector 4 and the pitch frame of the biaxial frame load 3 is set to θ f , the roll angle error of the roll encoder in the dual-axis frame load 3 is calculated to be Δβ=β2+β f -(-β3-β f ) = β2-(-β3). The pitch angle error of the pitch encoder in the dual-axis frame load 3 is Δθ = θ2 + θ f -θ3-θ f =θ2-θ3.

[0066] According to the formulas of Δβ and Δθ, it can be seen that the optical axis of the dual-axis frame load 3 points to the first reflector 4, and the angular errors of the pitch axis and the roll axis between the first reflector 4 and the dual-axis frame load 3 are offset during the calculation process. Therefore, there is no need to calibrate the angular errors of the pitch axis and the roll axis of the first reflector 4 relative to the dual-axis frame load 3, and the roll angle error of the roll encoder and the pitch angle error of the pitch encoder in the dual-axis frame load 3 can be obtained.

[0067] Furthermore, the roll angle of the dual-axis frame load 3 is fixed, and the angle of the dual-axis frame load 3 in the pitch direction is equally divided into n parts, and the error of the pitch encoder in the dual-axis frame load 3 at each equally divided angle is measured in turn.

[0068] In this embodiment, the roll angle of the dual-axis frame load 3 is fixed at 90°. By rotating the pitch axis system of the dual-axis frame load 3, each increase of 10° in the pitch angle is used as a measurement point. The error of each equally divided angle of the pitch encoder can be measured in turn, and a total of 36 points are measured (i.e., starting from 0° and ending at 350°, and measured every 10°).

[0069] Biaxial frame load 3 at O C Y C Z C In-plane winding O C X C When rotating, the biaxial frame load 3 optical axes and O C Y C When overlapped, it is defined as zero degree, and the biaxial frame load 3 optical axes are around O C X C The roll angle is positive when rotating clockwise. C X C The roll angle when rotating counterclockwise is negative. The roll angle of the biaxial frame load 3 is fixed at 90°, which means that the optical axis of the biaxial frame load 3 rotates around O C X C Rotate 90° clockwise.

[0070] Furthermore, the pitch angle of the dual-axis frame load 3 is fixed, and the angle of the dual-axis frame load 3 in the rolling direction is equally divided into m parts, and the error of the rolling encoder in the dual-axis frame load 3 at each equally divided angle is measured in turn.

[0071] In this embodiment, the pitch angle of the dual-axis frame load 3 is fixed at 90°. By rotating the roll axis system of the dual-axis frame load 3, each increase of 10° in the roll angle is used as a measurement point. The error of each equally divided angle of the roll encoder can be measured in turn, and a total of 36 points are measured (i.e., starting from 0° and ending at 350°, and measured every 10°).

[0072] Biaxial frame load 3 at O C YC X C In-plane winding O C Z C When rotating, the biaxial frame load 3 optical axes and O C X C When overlapped, it is defined as zero degree, and the biaxial frame load 3 optical axes are around O C Z C The pitch angle is positive when rotating clockwise, and the pitch angle is positive when rotating around O C Z C The pitch angle when rotating counterclockwise is negative. The pitch angle of the biaxial frame load 3 is fixed at 90°, which means that the optical axis of the biaxial frame load 3 rotates around O C Z C Rotate 90° clockwise.

[0073] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for measuring the accuracy of an optical load dual-axis frame encoder, characterized in that: The method is realized by using a measuring device for the precision of a dual-axis frame encoder of an optical load, the measuring device comprising a cubic mirror, a mounting seat, a dual-axis frame load, a first reflector, a theodolite, and a second reflector; the cubic mirror and the dual-axis frame load are both arranged on the mounting seat, and the cubic mirror is arranged above the dual-axis frame load; the normal direction of the cubic mirror is parallel to the normal direction of the mounting seat; the first reflector is arranged on the dual-axis frame load, and indicates the optical axis direction of the dual-axis frame load by the direction of the reflected light; the cubic mirror and the dual-axis frame load are both arranged in front of the second reflector; when the theodolite is used to collimate the cubic mirror, the theodolite is arranged between the cubic mirror and the second reflector; when the theodolite is used to collimate the dual-axis frame load, the theodolite is arranged between the dual-axis frame load and the second reflector; The specific steps of the measuring method are as follows: S1: placing the cubic mirror and the biaxial frame load on the mounting seat, and placing the biaxial frame load and the cubic mirror in front of the second reflector at a first preset distance; S2: placing the theodolite at a first preset position, leveling the theodolite, and aligning the second reflector with the theodolite; S3: rotating the theodolite by 180°, and aligning the cubic mirror by the theodolite; S4: moving the theodolite to a second preset position, and after the theodolite aligns the second reflector again, setting the pitch angle and roll angle of the theodolite to zero, so that the reference of the theodolite is consistent with that at the first preset position; S5: adjusting the dual-axis frame load to a position of a preset roll angle β1 and a preset pitch angle θ1, the theodolite measures the roll angle β2 and the pitch angle θ2 of the optical axis of the dual-axis frame load through the first reflector, and adjusting the encoder zero position in the dual-axis frame load to make the roll angle β1 and the roll angle β2 equal, and the pitch angle θ1 and the pitch angle θ2 equal; S6: rotating the roll angle and pitch angle of the optical axis of the dual-axis frame load by 180°, repeating step S4, adjusting the position of the theodolite again, and repeating step S4, so that the reference is consistent with that at the first preset position; and then measuring the roll angle of the optical axis of the dual-axis frame load as β3 and the pitch angle as θ3 by aligning the first reflector with the theodolite; S7: Set the roll angle error between the first reflector and the roll frame of the dual-axis frame load to β f , the pitch angle error between the first reflector and the pitch frame of the dual-axis frame load is set to θ f , the roll angle error Δβ of the roll encoder in the dual-axis frame load and the pitch angle error Δθ of the pitch encoder in the dual-axis frame load are obtained by calculation.

2. The method for measuring the accuracy of the optical load dual-axis frame encoder according to claim 1, characterized in that: In step S3, the theodolite aligns the cubic mirror in the following specific steps: S31: rotating the roll angle and the pitch angle of the theodolite by 180°, and measuring the pitch angle and the roll angle of the cubic mirror by the theodolite; S32: Adjust the roll and pitch attitude of the mounting seat so that the crosshairs emitted by the theodolite are projected onto the cubic mirror and the crosshairs are returned through the cubic mirror. The crosshairs are observed through the eyepiece of the theodolite, and the position of the cubic mirror is adjusted so that the crosshairs observed through the eyepiece of the theodolite coincide with the cross of the eyepiece, thereby completing the alignment of the cubic mirror.

3. The method for measuring the accuracy of the optical load dual-axis frame encoder according to claim 2, characterized in that: The calculation formulas for the roll angle error Δβ and the pitch angle error Δθ are: Δβ=β2+β f -(-β3-β f )=β2-(-β3); Δθ=θ2+θ f -θ3-θ f =θ2 -θ3.

4. The method for measuring the accuracy of an optical load dual-axis frame encoder according to claim 1, characterized in that: The dual-axis frame load is fixed at a preset roll angle, and the angle of the dual-axis frame load in the pitch direction is equally divided into n parts, and the error of the pitch encoder in the dual-axis frame load at each equally divided angle is measured in turn.

5. The method for measuring the accuracy of the optical load dual-axis frame encoder according to claim 1, characterized in that: The dual-axis frame load is fixed at a preset pitch angle, the angle of the dual-axis frame load in the roll direction is equally divided into m parts, and the error of the roll encoder in the dual-axis frame load at each equally divided angle is measured in turn.

6. The method for measuring the accuracy of the optical load dual-axis frame encoder according to claim 1, characterized in that: A parallelism error between a normal direction of the cubic mirror and a normal direction of the mounting seat is less than or equal to a first preset value.

7. The method for measuring the accuracy of an optical load dual-axis frame encoder according to claim 6, characterized in that: The first preset value is 1″.

8. The method for measuring the accuracy of an optical load dual-axis frame encoder according to claim 1, characterized in that: The size of the second reflector is larger than that of the first reflector.

9. The method for measuring the accuracy of an optical load dual-axis frame encoder according to claim 1, characterized in that: The mounting seat comprises a base and a mounting plate, wherein the mounting plate is vertically arranged on the base, and a mounting surface for mounting the cubic mirror and the dual-axis frame load is provided on the mounting plate.

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