Six-degree-of-freedom optical measurement integrated system

Abstract

The present application relates to a kind of six degrees of freedom optical measurement integrated systems, by placing diffraction grating special target on the measured object, multiple use the light reflected by the diffraction grating special target on the measured object and the diffracted light, realize the measurement of the rotation angle of X, Y, Z three directions and the displacement along the direction of Z axis, simultaneously measure the displacement of X, Y axis direction by visual imaging mode, to obtain the six degrees of freedom motion state of measured object comprehensively and accurately.The present application has the advantages of high measurement precision, high integration, high measurement efficiency and non-contact measurement, and can provide a kind of high-precision, high-efficiency non-contact measurement method and integrated system for six degrees of freedom measurement in industrial manufacturing, robot, aerospace and other fields.

Description

TECHNICAL FIELD

[0001] The present application relates to a six-degree-of-freedom optical measurement integrated system, in particular, by placing a diffraction grating special target on the measured object, using its reflected light and diffracted light to measure the rotation angles of X, Y, Z three directions and the displacement along the Z axis direction of the measured object, and measuring the displacement to X, Y axis by visual method, relates to the field of laser triangulation and visual measurement. BACKGROUND

[0002] Six-degree-of-freedom measurement refers to comprehensive and accurate measurement of the position and attitude of an object (translation and rotation in three-dimensional space). In the fields of industrial manufacturing, robotics, aerospace, etc., six-degree-of-freedom measurement is the basis and prerequisite for accurate measurement and control of object motion state. At present, traditional mechanical measurement methods have great limitations in measurement accuracy, integration, measurement efficiency, non-contact measurement, etc., and cannot meet the precise requirements of six-degree-of-freedom measurement. Therefore, it is of great significance to research and develop a high-precision and high-efficiency six-degree-of-freedom measurement method and integrated system.

[0003] In recent years, with the development of science and technology, optical measurement technology has gradually become an important means of non-contact measurement. Among them, optical triangulation and visual measurement technology are widely used in kinematics and dynamics measurement in the fields of industrial manufacturing, robotics, aerospace, etc. However, traditional optical measurement methods can only realize the measurement of part of the degrees of freedom of the measured object, and cannot comprehensively and accurately obtain its six-degree-of-freedom motion state. Therefore, an optical measurement method and integrated system capable of comprehensively and accurately measuring the six-degree-of-freedom motion state of the measured object is needed. SUMMARY

[0004] The six-degree-of-freedom optical measurement method and integrated system of the present application places a diffraction grating special target on the measured object, uses the reflected light and diffracted light of the diffraction grating special target on the measured object multiple times to realize the measurement of the rotation angles of X, Y, Z three directions and the displacement along the Z axis direction, and measures the displacement to X, Y axis by visual imaging method, thereby comprehensively and accurately obtaining the six-degree-of-freedom motion state of the measured object. The present application has the advantages of high measurement accuracy, high integration, high measurement efficiency and non-contact measurement, etc., and can provide a high-precision and high-efficiency non-contact measurement method and integrated system for six-degree-of-freedom measurement in the fields of industrial manufacturing, robotics, aerospace, etc.

[0005] The purpose of the present application is achieved as follows:

[0006] The application discloses a six-degree-of-freedom optical measurement integrated system, which is divided into a first optical system, a second optical system and a third optical system according to the differences of the measured degrees of freedom, and common devices included in the above three systems are a laser, a collimating and expanding lens, a diffraction grating special target and a computer processing system; the first optical system further includes a first light splitting prism, a first focusing lens and a first photoelectric detector; the second optical system further includes a second light splitting prism, a long working distance objective lens and a CCD camera; and the third optical system further includes a second focusing lens, a second photoelectric detector, a third light splitting prism, a third focusing lens and a third photoelectric detector.

[0007] The laser beam output by the laser passes through the collimating and expanding lens, becomes a parallel light beam and irradiates on the diffraction grating special target, and generates reflected light and first-order diffraction light.

[0008] The first optical system measures the rotation angles of the measured object in the X and Y axial directions based on the autocollimation principle and by using the reflected light; the reflected light enters the first focusing lens via the first light splitting prism, is focused, forms a light spot on the first photoelectric detector on the focal plane, and the rotation angle change of the measured object is measured by measuring the position change of the light spot in the X and Y axial directions.

[0009] The second optical system adopts a visual imaging mode, images and positions the measured object, and further measures the displacement of the measured object in the X and Y axial directions; the reflected light enters the long working distance objective lens via the second light splitting prism, is imaged to the image plane of the CCD camera, and the displacement change is measured through image positioning processing.

[0010] The third optical system adopts a laser triangulation method, utilizes the first-order diffraction light to be divided into two paths to measure the displacement and the Z-direction rotation angle of the measured object; the first-order diffraction light is split by the third light splitting prism and enters the second focusing lens and the third focusing lens respectively, is focused to the second photoelectric detector and the third photoelectric detector respectively, the Z-direction rotation angle of the measured object is further calculated by the light spot coordinates on the second photoelectric detector, and the displacement of the measured object in the Z direction is further calculated by the light spot displacement on the third photoelectric detector.

[0011] The first optical system, the second optical system and the third optical system are integrated through the common devices, and the six-degree-of-freedom non-contact simultaneous measurement of the measured object is realized through the synchronous processing of the computer processing system.

[0012] Further, the diffraction grating special target is a square diffraction grating with high reflectivity and high precision, and has a mark pattern processed through precision machining on the surface, is placed on the surface of the measured object and ensures the measurement precision and stability.

[0013] Further, the second optical system is used for image positioning of the mark pattern on the special target of the diffraction grating, and according to the constant position relationship between the special target of the diffraction grating and the measured object, the displacement of the measured object in the X and Y axis directions is measured.

[0014] Further, the first, second and third photoelectric detectors are PSD photoelectric position sensors.

[0015] Further, the elements of the third optical system and the placement position of the laser should satisfy the Scheimpflug condition, so that the signal is clear.

[0016] Further, the integrated system further comprises a computer processing system, and the light signals collected by the first, second and third photoelectric detectors are converted into electrical signals and transmitted to the computer, and the computer processes the electrical signals and the images obtained by the CCD camera through an algorithm to obtain the six-degree-of-freedom motion state of the measured object.

[0017] The beneficial effects of the present application are that by placing the special target of the diffraction grating on the measured object, the reflected light and the diffraction light of the special target of the diffraction grating on the measured object are used multiple times to measure the rotational angle displacement in the three-axis direction and the displacement along the Z-axis direction, and the displacement in the X and Y axis directions is measured by visual imaging, so that the six-degree-of-freedom motion state of the measured object is accurately obtained. The present application has the advantages of high measurement accuracy, high integration, high measurement efficiency and non-contact measurement, and can provide a high-precision and high-efficiency non-contact measurement method and integrated system for six-degree-of-freedom measurement in the fields of industrial manufacturing, robots, aerospace, etc. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a general schematic diagram of a six-degree-of-freedom optical measurement integrated system according to the present application.

[0019] Figure 2 is a first optical system schematic diagram of a six-degree-of-freedom optical measurement integrated system according to the present application.

[0020] Figure 3 is a second optical system schematic diagram of a six-degree-of-freedom optical measurement integrated system according to the present application.

[0021] Figure 4 is a third optical system schematic diagram of a six-degree-of-freedom optical measurement integrated system according to the present application.

[0022] In the figure: 1-laser, 2-collimating beam expander, 3-first light splitting prism, 4-first focusing lens, 5-first photodetector, 6-CCD camera, 7-long working distance objective, 8-second light splitting prism, 9-diffraction grating special target, 10-second photodetector, 11-second focusing lens, 12-third light splitting prism, 13-third focusing lens, 14-third photodetector, 15-computer processing system. DETAILED DESCRIPTION

[0023] The embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0024] A device schematic diagram of an embodiment of a six-degree-of-freedom optical measurement integrated system is shown in Figure 1 A diffraction grating special target is mounted on the object to be measured, and the reflected laser light is used to measure the rotational angle displacement of the object to be measured in the X and Y axial directions and the displacement along the Z axial direction, and the displacement in the X and Y axial directions is measured by visual imaging. A first optical system schematic diagram is shown in Figure 2 A second optical system schematic diagram is shown in Figure 3 A third optical system schematic diagram is shown in Figure 3

[0025] According to different degree-of-freedom measurement requirements, the system can be divided into three different optical systems. The first optical system is composed of the first focusing lens 4 and the first photodetector 5, and is mainly used to measure the rotational angle of the object to be measured in the X and Y axial directions by using reflected light. The second optical system is composed of the CCD camera 6 and the long working distance objective 7, and is used to measure the displacement of the object to be measured in the X and Y axial directions by using reflected light. The third optical system is composed of the second photodetector 10, the second focusing lens 11, the third light splitting prism 12, the third focusing lens 13, and the third photodetector 14, and is mainly used to measure the displacement and rotational angle of the object to be measured in the Z axial direction by using first-order diffraction light.

[0026] The specific measurement steps are as follows:

[0027] First, the laser 1 expands the laser beam through the collimating beam expander 2 and then parallelly enters the diffraction grating special target 9, and the reflected light passes through the first light splitting prism 3 and the first focusing lens 4, enters the first photodetector 5, and the position change and the formula

[0028]

[0029] Thus, the rotational angle of the object to be measured in the X and Y axial directions is realized. ​measurement. Another reflected light beam is imaged to the CCD camera 6 through the second beam splitter prism 8 and the long working distance objective 7, and the displacement of the measured object in the X and Y axis directions is measured according to the visual imaging method. When the measured object rotates and displaces in the Z axis direction, the diffracted light on the diffraction grating special target 9 also rotates and moves, and is separated by the third beam splitter prism 12 and focused on the second photoelectric detector 10 and the third photoelectric detector 14, respectively. According to the formula

[0030]

[0031]

[0032] the rotation angle of the measured object in the Z axis direction is measured and the displacement in the Z direction . Wherein is the first-order diffraction angle of the diffraction grating special target, and the incident laser wavelength and the grating constant satisfy

[0033]

[0034] The above measurement results are summarized and processed by the computer processing system 15, and the six-degree-of-freedom motion state of the measured object, including the displacement in the X, Y and Z axis directions and the rotation angle in the X, Y and Z axis directions, is obtained.

[0035] The above only describes the embodiments of the present application, and does not limit the patent scope of the present application. Any equivalent device or equivalent method transformation using the content of the specification and drawings, or direct or indirect application in other related technical fields, is also included in the patent protection scope of the present application.

Claims

1. A six-degree-of-freedom optical measurement integrated system, characterized in that, The system is divided into a first optical system, a second optical system, and a third optical system according to the difference in the degrees of freedom measured. The common components included in the above three systems are: a laser, a collimating and expanding lens, a diffraction grating target, and a computer processing system. The first optical system also includes a first beam splitter, a first focusing lens, and a first photodetector. The second optical system also includes a second beam splitter, a long working distance objective lens, and a CCD camera. The third optical system also includes a second focusing lens, a second photodetector, a third beam splitter, a third focusing lens, and a third photodetector. The laser beam output by the laser is collimated and expanded by a collimating lens, becoming a parallel beam that illuminates the target for the diffraction grating, producing reflected light and first-order diffracted light. The first optical system is based on the principle of self-collimation and uses reflected light to measure the rotation angle of the object under test in the X and Y directions. The reflected light enters the first focusing lens through the first beam splitter, and after focusing, forms a light spot on the first photodetector on the focal plane. The rotation angle change of the object under test is measured by measuring the position change of the light spot in the X and Y directions. The second optical system uses a visual imaging method to image and locate the object under test, and further measures the displacement of the object under test in the X and Y axis directions. The reflected light enters the long working distance objective lens through the second beam splitter and is imaged onto the image plane of the CCD camera. The displacement change is measured after image positioning processing. The third optical system employs laser triangulation, which uses first-order diffraction light to split into two paths to measure the displacement and rotation angle of the object under test along the Z-axis. The first-order diffraction light is split by the third beam splitter and enters the second and third focusing lenses respectively, and is focused onto the second and third photodetectors respectively. The rotation angle of the object under test is further calculated from the coordinates of the light spot on the second photodetector, and the displacement of the object under test along the Z-axis is further calculated from the displacement of the light spot on the third photodetector. The first, second, and third optical systems are integrated by sharing components and achieve non-contact simultaneous measurement of the six degrees of freedom of the object under test through synchronous processing by a computer processing system.

2. The six-degree-of-freedom optical measurement integrated system according to claim 1, characterized in that, The diffraction grating target is a square diffraction grating with high reflectivity and high precision, and it has a precision-machined marking pattern on it. It is placed on the surface of the object being measured to ensure measurement accuracy and stability.

3. The six-degree-of-freedom optical measurement integrated system according to claim 2, characterized in that, The second optical system performs image positioning on the marking pattern on the diffraction grating target as described in claim 2, and then measures the displacement of the object under test in the X and Y axes based on the constant positional relationship between the diffraction grating target and the object under test.

4. The six-degree-of-freedom optical measurement integrated system according to claim 1, characterized in that, The first, second, and third photodetectors are PSD photoelectric position sensors.

5. The six-degree-of-freedom optical measurement integrated system according to claim 1, characterized in that, The placement of the components of the third optical system and the laser should satisfy Scheimpflug's law to ensure a clear signal.

6. The six-degree-of-freedom optical measurement integrated system according to claim 1, characterized in that, The integrated system also includes a computer processing system that converts the light signals collected by the first, second, and third photodetectors into electrical signals and transmits them to the computer. The computer processes the electrical signals and the images obtained by the CCD camera through algorithms to determine the six-degree-of-freedom motion state of the object under test.

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