A pose detection device and method based on array laser reflection focal spot monitoring

Abstract

The application discloses a pose detection device and method based on array laser reflection focus spot monitoring, three collimating lasers are arranged in an array, and an optical measurement method similar to an optical lever is adopted, when there is a height deviation of an optical element, three light spot positions simultaneously change by an equal amount on an imaging screen, when there is an angle deviation of the optical element, the interval of the light spots on the imaging screen changes, the change amount is related to a laser incidence angle, a beam interval distance and an element deflection angle, therefore, a light spot position image obtained by a light spot imaging vision camera can be used to reversely obtain pose information of the optical element on an optical element positioning tool, so that accurate online detection of vertical in-plane angle and height information of the optical element can be realized by bypassing a lateral field of view, and accurate grabbing of the optical element can be realized.

Description

Technical Field

[0001] This invention relates to the field of optical element pose detection technology, and specifically to a pose detection device and method based on array-type laser reflection focal spot monitoring. Background Technology

[0002] In the automated assembly process of terminal optical components such as second-harmonic crystals, third-harmonic crystals, and polarizing crystals, the incoming materials are horizontally packaged in boxes. Because the optical components are in uncovered boxes, there are error sources such as placement gaps, motion angle errors, and deformation of long cantilever mechanical parts under stress. Therefore, please refer to [the relevant documentation / reference]. Figure 1 The spatial orientation of optical components and tooling usually deviates from the ideal position, often manifested as a combination of angular and height deviations.

[0003] Due to the aforementioned sources of error, the spatial pose of optical components deviates from their ideal positions. When grasping optical components, relying solely on the repeatability of the mechanical motion mechanism cannot achieve the required assembly accuracy.

[0004] Therefore, to achieve accurate grasping of optical components, their pose must be detected simultaneously. However, since the optical components are inside the packaging box, their lateral field of view is obstructed by the sides of the box, and other mechanical parts occupy some space during assembly, making it difficult to directly observe the pose of the optical components using existing methods. Therefore, there is an urgent need to design an online pose detection method for optical components suitable for this scenario. Summary of the Invention

[0005] In view of this, the present invention provides a pose detection device and method based on array-type laser reflection focal spot monitoring.

[0006] The technical solution is as follows:

[0007] The first aspect of this application relates to a pose detection device based on array-type laser reflection focal spot monitoring, including a detection platform. An optical element positioning fixture is provided on the platform. A module bracket and a screen bracket are respectively located on both sides of the optical element positioning fixture on the platform. A pose detection module is installed on the top of the module bracket. An imaging screen facing the pose detection module is vertically installed on the top of the screen bracket. The pose detection module includes a module housing fixedly installed on the top of the module bracket, a spot imaging vision camera and three collimating lasers all installed on the module housing. The lens of the spot imaging vision camera faces the imaging screen. The three collimating lasers are distributed in an isosceles triangle around the spot imaging vision camera, wherein two collimating lasers are symmetrically distributed on both sides of the spot imaging vision camera in the horizontal direction.

[0008] Three collimated lasers can emit three parallel laser beams at an angle downward toward the optical element positioning fixture; the optical element located on the optical element positioning fixture can reflect the three laser beams toward the imaging screen, thereby forming three light spots on the imaging screen; the light spot imaging vision camera can record the three light spots on the imaging screen.

[0009] The second aspect of this application relates to a pose detection method based on array-type laser reflection focal spot monitoring, which uses the above-mentioned pose detection device and is performed according to the following steps:

[0010] S1. Position the optical element on the optical element positioning fixture;

[0011] S2. Three collimated lasers emit three parallel laser beams toward the optical element located on the optical element positioning fixture. The three laser beams are reflected by the upper surface of the optical element and form three light spots on the imaging screen. The light spot imaging vision camera takes a picture of the imaging screen to obtain the image of the light spot position.

[0012] S3. Based on the spot position image, the pose information of the optical element located on the optical element positioning fixture is obtained by inversion.

[0013] The above-mentioned pose detection device and method based on array-type laser reflection focal spot monitoring utilizes three collimated lasers arranged in an array. An optical measurement method similar to an optical lever is employed. When there is a height deviation in the optical element, the positions of the three laser spots change simultaneously and equally on the imaging screen. When there is an angular deviation in the optical element, the spacing between the laser spots on the imaging screen changes. The amount of change is related to the laser incident angle, the beam spacing, and the element deflection angle. Therefore, the laser spot position image captured by the laser spot imaging vision camera can accurately invert the pose information of the optical element located on the optical element positioning fixture. This allows for accurate online detection of the vertical in-plane angle and height information of the optical element, bypassing the lateral field of view, and ultimately enabling accurate grasping of the optical element. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the pose deviation of optical components;

[0015] Figure 2 This is a schematic diagram of a pose detection method based on array-type laser reflection focal spot monitoring.

[0016] Figure 3 This is a schematic diagram illustrating how the imaging results change with deviation.

[0017] Figure 4 This is a schematic diagram of a pose detection device based on array-type laser reflection focal spot monitoring.

[0018] Figure 5 for Figure 4 Enlarged view of point A in the middle;

[0019] Figure 6 A schematic diagram of the dual-axis tilt angle of an optical element;

[0020] Figure 7 This is a schematic diagram illustrating the effect of the light spot on the imaging screen.

[0021] Figure 8 This is a schematic diagram showing the effect of the light spot on the imaging screen after the optical components are leveled.

[0022] Figure 9 For characteristic quantity The fitting trend plot;

[0023] Figure 10 For characteristic quantity The fitting trend plot;

[0024] Figure 11 Measured values ​​and characteristic quantities The fitting trend plot. Detailed Implementation

[0025] The present invention will be further described below with reference to the embodiments and accompanying drawings.

[0026] Example 1:

[0027] like Figure 4 and Figure 5 As shown, a pose detection device based on array-type laser reflection focal spot monitoring mainly includes a detection platform 1. An optical element positioning fixture 2 and module brackets 3 and screen brackets 4 are respectively located on both sides of the optical element positioning fixture 2.

[0028] Among them, the optical element positioning fixture 2 is used to reliably position the optical element, the top of the module bracket 3 is equipped with the pose detection module 5, and the top of the screen bracket 4 is vertically equipped with the imaging screen 6 facing the pose detection module 5.

[0029] In this embodiment, the pose detection module 5 includes a module housing 5a fixedly installed on the top of the module bracket 3, a spot imaging vision camera 5b and three collimating lasers 5c all installed on the module housing 5a. The lens of the spot imaging vision camera 5b faces the imaging screen 6. The three parallel collimating lasers 5c are distributed in an isosceles triangle around the spot imaging vision camera 5b. Two of the collimating lasers 5c are symmetrically distributed on both sides of the spot imaging vision camera 5b in the horizontal direction, and the other collimating laser 5c is located above or below the lens facing the imaging screen 6.

[0030] Three collimated lasers 5c can emit three parallel laser beams at an angle downward toward the optical element positioning fixture 2; the optical element located on the optical element positioning fixture 2 can reflect the three laser beams toward the imaging screen 6, thereby forming three light spots on the imaging screen 6; the light spot imaging vision camera 5b can record the three light spots on the imaging screen 6.

[0031] Therefore, please see Figure 2 and Figure 3 By arranging three collimated lasers 5c in an array and employing an optical measurement method similar to an optical lever, when there is a height deviation in the optical element, the positions of the three light spots change simultaneously and equally on the imaging screen 6. When there is an angular deviation in the optical element, the spacing between the light spots on the imaging screen 6 changes. The amount of change is related to the laser incident angle, the beam spacing distance, and the element deflection angle. Therefore, the position image of the light spot obtained by the light spot imaging vision camera 5b can accurately invert the pose information of the optical element located on the optical element positioning fixture.

[0032] Example 2:

[0033] Please see Figure 2 and Figure 3 A pose detection method based on array-type laser reflection focal spot monitoring, using the pose detection device of Example 1, is performed according to the following steps:

[0034] S1. Transfer the optical element to the optical element positioning fixture 2 so that the optical element is reliably positioned by the optical element positioning fixture 2.

[0035] S2. Three collimated lasers 5c emit three parallel laser beams toward the optical element located on the optical element positioning fixture 2. The three laser beams are reflected by the upper surface of the optical element and form three light spots on the imaging screen 6. The light spot imaging vision camera 5b takes a picture of the imaging screen 6 to obtain the light spot position image.

[0036] S3. Based on the spot position image, the pose information of the optical element located on the optical element positioning fixture 2 is obtained by inversion.

[0037] Specifically, step S3 includes:

[0038] Establish a mathematical model for the location of the light spot.

[0039] To calculate the impact of spot pose on the imaging results, the imaging results of a single spot are first analyzed.

[0040] The upper surface of the optical element is the reflective surface. The world coordinate system is defined as follows: the shooting direction facing the light spot imaging vision camera 5b is the Z-axis direction, the horizontal direction perpendicular to the Z-axis direction is the X-axis direction, and the vertically downward direction is the Y-axis direction.

[0041] The plane equation of the reflecting surface of the optical element is defined as follows:

[0042] ;

[0043] In the above formula, A, B, C, and D are all planar parameters.

[0044] Set the emission point position of the laser beam from one of the collimating lasers 5c. The incident beam equation of the laser beam is then expressed as:

[0045] ;

[0046] In the above formula, Let be the three-dimensional vector of the coordinates of a point on the laser beam of collimated laser 5c in the world coordinate system; assume that the laser beam emitted by collimated laser 5c is parallel to the principal beam surface and has an incident angle relative to the horizontal plane of . Then the beam direction vector ; To describe the relationship between this point on the laser beam and A scalar of distance.

[0047] The upper surface of the optical element is a reflecting surface, using an angle and angle For the biaxial tilt angle of the reflecting surface, please refer to [link / reference]. Figure 6 ,horn In the XOY plane of the world coordinate system, the angle between the line of intersection of the reflecting surfaces and the X-axis is given. Figure 6 The angle shown The direction is negative, the angle Let be the angle between the line of intersection of the reflecting surface and the Z-axis in the YOZ plane of the world coordinate system. Figure 6 The angle shown If the direction is positive, then the expression for the corresponding reflection surface normal vector n is:

[0048] ;

[0049] The height deviation h of the optical element is defined as the distance from the reflecting surface to the lower point in the world coordinate system. Then the plane parameters can be obtained:

[0050] ;

[0051] The position of the reflection point can be obtained by using the equation of the incident beam and the equation of the plane of the reflecting surface. :

[0052] ;

[0053] According to the vector form of the law of reflection, the unit vector of the reflected laser beam is obtained as follows:

[0054] ;

[0055] Based on the location of the reflection point and the unit vector of the emitted beam Establish the equation for the emitted beam:

[0056] ;

[0057] In the above formula, To describe the three-dimensional vector of the coordinates of a point on the incident beam in the world coordinate system, To describe the relationship between this point on the laser beam and A scalar of distance;

[0058] Assuming that imaging screen 6 coincides with the YOZ plane of the world coordinate system, the plane equation of imaging screen 6 is: Its normal vector Let the plane equation of the imaging screen 6 be... Then the plane parameters Thus, the coordinates of the light spot are obtained. for:

[0059] ;

[0060] As can be seen from the above derivation, any point on the incident laser beam of the collimated laser 5c will not affect the position of the laser spot. To simplify the calculation, we assume that the emission point of the laser beam of the collimated laser 5c is located at... If the light spot is located in the XOY plane of the world coordinate system, then the coordinates of the light spot are... for:

[0061] ;

[0062] In the above formula, parameters A, B, and C are all determined by the biaxial tilt angle of the reflecting surface of the optical element relative to the horizontal plane (i.e., angle). and angle The value of h is determined by the angle deviation, which reflects the influence of the angle deviation. h is the height deviation of the optical element. Under the condition that other system parameters are determined, the imaging result is only affected by the above deviation.

[0063] Furthermore, to simplify the calculation, the incident angle of the laser beam of the collimated laser 5c relative to the horizontal plane is designed to be 45°.

[0064] The two collimated lasers 5c, symmetrically distributed horizontally on both sides of the spot imaging visual camera 5b, form two light spots on the imaging screen 6, which are represented as spot 1 and spot 3, respectively. The remaining light spot is represented as spot 2. Please refer to [link to relevant documentation]. Figure 7The difference between the mean Y-coordinates of spot 1 and spot 3 in the world coordinate system and the Y-coordinate of spot 2 in the world coordinate system is expressed as a characteristic quantity. The difference between the Y-coordinates of spot 1 and spot 3 in the world coordinate system is expressed as a characteristic quantity. The mean value of the Y-coordinates of spot 1, spot 2, and spot 3 in the world coordinate system is expressed as a characteristic quantity. .

[0065] The imaging process for the three light spots is the same; the only difference lies in the initial position of each collimating laser 5c. The imaging results are as follows: Figure 7 As shown, the imaging screen 6 coincides with the XOZ plane of the world coordinate system. Therefore, the emission point coordinates of the laser beams of the collimated laser 5c corresponding to spots 1, 2, and 3 are respectively:

[0066] ;

[0067] Therefore, the following correspondence exists:

[0068] ;

[0069] Feature quantities were identified from the image of the light spot location. Measured values, characteristic quantities Measured values ​​and characteristic quantities The measured values ​​are as follows. The algorithm for accurately identifying the coordinates of the three light spots on the imaging screen 6 based on vision is very mature and is common knowledge to those skilled in the art, so it will not be elaborated here.

[0070] Feature quantities are established based on the mathematical model of the light spot position. Mathematical models and characteristic quantities Mathematical model and characteristic quantity The mathematical model.

[0071] Feature quantity The mathematical model is as follows:

[0072] ;

[0073] Feature quantity The mathematical model is as follows:

[0074] ;

[0075] Feature quantity The mathematical model is as follows:

[0076] ;

[0077] feature quantity Measured values, characteristic quantities Measured values, characteristic quantities Substituting the measured values, the emission point coordinates of the three collimated lasers 5c, and the incident angles relative to the horizontal plane into the characteristic quantity... Mathematical models and characteristic quantities Mathematical model and characteristic quantity The mathematical model is solved to obtain the biaxial tilt angle of the optical element.

[0078] Specifically, feature quantity , characteristic quantity , characteristic quantity And the emission point coordinates of the three collimated lasers 5c , , and the angle of incidence relative to the horizontal plane All values ​​are known; substitute them. Mathematical models and characteristic quantities Mathematical model and characteristic quantity In the mathematical model, parameters A, B, and C can be solved because:

[0079] ;

[0080] Substituting parameters A, B, and C into the above equation, the biaxial tilt angle of the optical element can be obtained: angle and angle .

[0081] Please see Figure 8 Based on the obtained dual-axis tilt angle, the optical element on the optical element positioning fixture 2 is leveled.

[0082] The average Y-coordinate of spot 1, spot 2, and spot 3 after optical element leveling in the world coordinate system is represented as a characteristic quantity. And the feature quantity is identified from the spot position image. The measured value of this feature quantity The height deviation h of the optical element is equal to the height deviation h of the optical element. Then, the height of the optical element on the optical element positioning fixture 2 is adjusted according to this height deviation h.

[0083] Similarly, feature quantities are identified from the image of the light spot location. The measured values ​​are as follows. The algorithm for accurately identifying the coordinates of the three light spots on the imaging screen 6 based on vision is very mature and is common knowledge to those skilled in the art, so it will not be elaborated here.

[0084] The theoretical accuracy analysis of the pose detection device and method based on array-type laser reflection focal spot monitoring is given below:

[0085] With other parameters remaining constant, its characteristic quantity with horns Relationship such as Figure 9 As shown, characteristic quantity with horns Relationship such as Figure 10 As shown, the calculation results were obtained by linear fitting, which is considered to reflect the trend of change relatively well.

[0086] The inherent errors of the 5b spot-image vision camera, the spot center localization error, and the camera calibration error, after optical path magnification, result in errors in the spot center coordinates obtained in the world coordinate system. This error directly affects the pose calculation. Assuming a deviation of 0.5 pixels in a single direction of the image coordinate system, after magnification, with the 5b spot-image vision camera's working distance of 800mm, the corresponding error in the real world is approximately 0.04mm. The transfer coefficient corresponding to the fitted slope is approximately 0.77° / mm, which corresponds to an angle measurement error of approximately 0.031°. The corresponding transfer coefficient is approximately 0.28° / mm, resulting in an angle measurement error of approximately 0.011°. The cost of decoupling angle and height is a sharp decrease in the transfer coefficient of the Y-axis angle, thus amplifying the measurement error. The ratio of their transfer coefficients is approximately 2.76, which is close to the ratio of the standard deviations of the errors in the actual measurement results.

[0087] Feature quantity The relationship between it and its height deviation h is as follows Figure 11 As shown, the two exhibit a completely linear relationship, with a corresponding measurement error of approximately 0.02 mm. Since the angle deviation is calculated first after decoupling the angle deviation and height deviation, the height deviation will be affected by the angle deviation.

[0088] It should be noted that the slope in the above measurements is obtained when other values ​​are zero. For example, the mean Y-coordinate of the light spot changes with the height deviation, and only when the plane is completely parallel to the ideal plane does it have exactly a twofold relationship. When the element has a tilt angle, its coefficient will change very little.

[0089] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention. Those skilled in the art, under the guidance of the present invention, can make various similar representations without departing from the spirit and claims of the present invention, and such modifications all fall within the protection scope of the present invention.

Claims

1. A pose detection method based on array-type laser reflection focal spot monitoring, characterized in that, The pose detection device is used, which includes a detection platform. An optical element positioning fixture is provided on the platform. The platform is characterized by having a module bracket and a screen bracket located on both sides of the optical element positioning fixture. A pose detection module is installed on the top of the module bracket, and an imaging screen facing the pose detection module is vertically installed on the top of the screen bracket. The pose detection module includes a module housing fixedly installed on the top of the module bracket, a spot imaging vision camera and three collimating lasers all mounted on the module housing. The lens of the spot imaging vision camera faces the imaging screen, and the three collimating lasers are distributed in an isosceles triangle around the spot imaging vision camera, with two collimating lasers symmetrically distributed on both sides of the spot imaging vision camera in the horizontal direction. Three collimated lasers can emit three parallel laser beams at an angle downward toward the optical element positioning fixture; the optical element located on the optical element positioning fixture can reflect the three laser beams toward the imaging screen, thereby forming three light spots on the imaging screen; the light spot imaging vision camera can record the three light spots on the imaging screen. The pose detection method is performed according to the following steps: S1. Position the optical element on the optical element positioning fixture; S2. Three collimated lasers emit three parallel laser beams toward the optical element located on the optical element positioning fixture. The three laser beams are reflected by the upper surface of the optical element and form three light spots on the imaging screen. The light spot imaging vision camera takes a picture of the imaging screen to obtain the image of the light spot position. S3. Based on the spot position image, the pose information of the optical element located on the optical element positioning fixture is obtained by inversion. Step S3 includes: S31. Establish a mathematical model for the position of the light spot; S32. Represent the two collimated lasers symmetrically distributed on both sides of the spot imaging vision camera along the horizontal direction as spot 1 and spot 3 on the imaging screen. Represent the remaining spot as spot 2. Represent the difference between the average Y-coordinate of spot 1 and spot 3 in the world coordinate system and the Y-coordinate of spot 2 in the world coordinate system as a characteristic quantity. The difference between the Y-coordinates of spot 1 and spot 3 in the world coordinate system is expressed as a characteristic quantity. The mean value of the Y-coordinates of spot 1, spot 2, and spot 3 in the world coordinate system is expressed as a characteristic quantity. ; S33. Identify feature quantities from the light spot position image. Measured values, characteristic quantities Measured values ​​and characteristic quantities The measured value; S34. Establish feature quantities based on the mathematical model of the light spot position. Mathematical models and characteristic quantities Mathematical model and characteristic quantity Mathematical model; S35, Feature quantities Measured values, characteristic quantities Measured values, characteristic quantities Substituting the measured values, the emission point coordinates of the three collimated lasers, and the incident angles relative to the horizontal plane into the characteristic quantity... Mathematical models and characteristic quantities Mathematical model and characteristic quantity The mathematical model was solved to obtain the biaxial tilt angle of the optical element; S36. Based on the dual-axis tilt angle obtained in step S35, level the optical element on the optical element positioning fixture; S37. The average Y-coordinate of spot 1, spot 2, and spot 3 after the optical element is leveled is expressed as a characteristic quantity. And the feature quantity is identified from the spot position image. The measured value of this feature quantity Equal to the height deviation h of the optical element; S38. Based on the height deviation h obtained in S37, adjust the height of the optical element on the optical element positioning fixture.

2. The pose detection method according to claim 1, characterized in that, Step S31 includes: The upper surface of the optical element is the reflecting surface. The plane equation of the reflecting surface of the optical element is defined as follows: ； In the above formula, A, B, C, and D are all planar parameters; Set the emission point position of the laser beam from one of the collimated lasers. The incident beam equation of the laser beam is then expressed as: ； In the above formula, Let be the three-dimensional vector of the coordinates of a point on the laser beam of the collimated laser in the world coordinate system; assume that the laser beam emitted by the collimated laser is parallel to the principal plane and has an incident angle relative to the horizontal plane of . Then the beam direction vector ; To describe the relationship between this point on the laser beam and A scalar of distance; Use angle and angle Let the biaxial tilt angle of the reflecting surface represent the angle of inclination. Then, the expression for the corresponding normal vector n of the reflecting surface is: ； The height deviation h of the optical element is defined as the distance from the reflecting surface to the lower point in the world coordinate system. Then the plane parameters can be obtained: ； Since any point on the incident laser beam of a collimated laser will not affect the position of the laser spot, it is assumed that the emission point of the collimated laser beam is located at... If the light spot is located in the XOY plane of the world coordinate system, then the coordinates of the light spot are: ； In the above formula, parameters A, B, and C are all determined by the biaxial tilt angle of the reflecting surface of the optical element relative to the horizontal plane.

3. The pose detection method according to claim 2, characterized in that, In step S32, the coordinates of the emission points of the laser beams of the collimated lasers corresponding to light spots 1, 2, and 3 are as follows: ； Therefore, the following correspondence exists: 。 4. The pose detection method according to claim 3, characterized in that, In step S34, the feature quantity The mathematical model is as follows: ； Feature quantity The mathematical model is as follows: ； Feature quantity The mathematical model is as follows: 。

Images