A device and method for small spot positioning and perpendicularity calibration

Abstract

The application discloses a device and method for small light spot positioning and perpendicularity calibration, and relates to the technical field of optical measurement and calibration; the device comprises a structure light inlet, a beam expander module, an aperture structure, an observation card and a scale coordinate system, and each structure is coaxially arranged along a calibration axis; a camera establishes a reference position through the structure light inlet; a laser beam enters the structure light inlet, is expanded by the beam expander module, and forms an enlarged light spot on the observation card and the scale coordinate system; the observation card and the scale coordinate system display the distribution difference of the light spot in the X-axis scale and the Y-axis scale direction; the aperture structure converts the center offset of the light spot into the edge defect change through the concentric contraction of the light inlet, and completes the center offset judgment and the coordinate offset calculation accordingly; and the unified processing of the small light spot center positioning and the perpendicularity calibration is realized.

Description

Technical Field

[0001] This invention relates to the field of optical measurement and calibration technology, and more specifically, to a device and method for small spot positioning and perpendicularity calibration. Background Technology

[0002] The display industry is gradually iterating from Mini LED to Micro LED. As chip sizes on processed objects such as wafers and PCBs continue to shrink, the impact of local height differences on processing positioning accuracy becomes more pronounced. Laser height sensors are widely used in high-precision processing equipment because they can acquire height information of the measured location. In use, the light spot projected by the laser height sensor onto the measured surface is typically at a tiny scale. If the center position of this light spot cannot be accurately determined, subsequent height measurement coordinates and camera positioning coordinates are prone to deviation, thus affecting the positioning accuracy of the equipment for chips, pads, or other tiny processed targets. Existing simpler methods typically infer the center of the light spot by identifying the location of abrupt changes in height data when the motion mechanism moves in the X and Y directions. However, this method relies on the height change boundaries of the measured surface and is easily affected by chip height differences, edge morphology, and motion sampling intervals, resulting in significant center positioning errors. Existing precision methods typically require the use of optical cameras, optical lens groups, and image processing algorithms to acquire and analyze light spot images. While this can improve light spot positioning accuracy, it increases equipment material costs, calibration and debugging time, and system complexity.

[0003] It is evident that the current small spot calibration process still faces the challenge of simultaneously achieving both the spot center positioning accuracy and the verticality calibration accuracy of the laser altimeter under conditions of low cost and simplified structure. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a device and method for small spot positioning and verticality calibration. By coordinating the beam expander module, aperture structure, observation card, and scale coordinate system, it solves the problem that existing small spot calibration processes struggle to simultaneously achieve both spot center positioning accuracy and laser altimeter verticality calibration accuracy under low cost and simplified structural conditions.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A device for positioning and calibrating the verticality of a small light spot includes a structural light inlet on the light inlet side, a beam expander module arranged in the light outlet direction of the structural light inlet, and the beam expander module having a lens group arranged along the incident light path.

[0007] An aperture structure is provided in the light output direction of the beam expander module. The aperture structure has a light-passing port that opens and closes around the center of the aperture. The aperture structure is connected to an aperture lever, and the aperture lever is driven by the opening and closing component of the light-passing port.

[0008] An observation card and a scale coordinate system are set in the light-emitting direction of the aperture structure. The observation card and scale coordinate system have an observation surface and scale coordinates set on the observation surface. The scale coordinates have a coordinate center and X-axis and Y-axis scales passing through the coordinate center.

[0009] The center of the light inlet of the structure, the optical axis of the beam expander module, the center of the aperture of the aperture structure, and the coordinate center of the scale coordinates are located on the same calibration axis.

[0010] Preferably, the structural light inlet has a top-view profile for camera recognition, and the geometric center of the top-view profile coincides with the center of the structural light inlet.

[0011] Preferably, the beam expander module is a Galilean beam expander module, and the lens group includes negative lenses and positive lenses arranged at intervals along the calibration axis. The negative lenses, positive lenses, aperture structure, observation card and scale coordinate system are arranged sequentially along the calibration axis.

[0012] Preferably, the aperture structure includes light-shielding components distributed around the center of the aperture, the light-shielding components forming a light-passing opening, the light-shielding components being connected to an opening and closing component, and the aperture lever driving the light-shielding components to contract or expand relative to the center of the aperture through the opening and closing component.

[0013] Preferably, the X-axis scale and the Y-axis scale are perpendicular to each other on the observation plane, and the X-axis scale and the Y-axis scale have equidistant scale lines located on both sides of the coordinate center.

[0014] Preferably, the observation card and scale coordinate system are detachably disposed in the light-emitting direction of the aperture structure, and the observation card and scale coordinate system include observation cards corresponding to different light spot wavelengths, and the scale coordinates are disposed on the observation surface of the observation card.

[0015] A method for small spot positioning and perpendicularity calibration, performed using the aforementioned small spot positioning and perpendicularity calibration device, includes:

[0016] S1. Fix the calibration device on the support platform, move the camera above the light inlet of the structure, and determine the position of the camera relative to the center of the calibration device based on the top view of the light inlet of the structure.

[0017] S2. Move the laser rangefinder to the center of the mechanism so that the laser beam emitted by the laser rangefinder enters the beam expander module through the light inlet of the structure, and adjust the light outlet of the aperture structure to the open state so that the light spot magnified by the beam expander module is projected onto the observation surface of the observation card and the scale coordinate system.

[0018] S3. Adjust the orientation of the laser rangefinder according to the shape difference of the light spot on the observation surface relative to the X-axis and Y-axis scales until the light spot on the observation surface is circular.

[0019] S4. Adjust the light passage of the aperture structure by using the aperture lever, observe the edge defect direction of the light spot on the observation surface, determine the side where the edge defect appears first as the over-position direction, and move the motion mechanism carrying the laser rangefinder in the opposite direction of the over-position direction.

[0020] S5. Repeat the adjustment of the light-transmitting aperture and the movement of the motion mechanism until the light spot on the observation surface becomes smaller and smaller as the light-transmitting aperture contracts;

[0021] S6. Record the X and Y coordinates of the motion mechanism when the light spot becomes uniformly smaller, and subtract the X and Y coordinates of the motion mechanism from the X and Y coordinates of the camera respectively to obtain the offset value of the small light spot center of the laser rangefinder relative to the camera.

[0022] Preferably, S3 includes:

[0023] When the length of the light spot on the observation surface in the X-axis scale direction is greater than its length in the Y-axis scale direction, the assembly posture of the laser rangefinder in the corresponding X-axis scale direction is adjusted.

[0024] When the length of the light spot on the observation surface in the Y-axis scale direction is greater than its length in the X-axis scale direction, the assembly posture of the laser rangefinder in the corresponding Y-axis scale direction is adjusted.

[0025] After adjustment, observe the shape of the light spot on the observation surface again until the length difference of the light spot in the X-axis and Y-axis scale directions is reduced to a circular state.

[0026] Preferably, S4 includes:

[0027] Move the aperture lever along the first opening and closing direction to change the light passage from the open state to the closed state;

[0028] When the light spot on the observation surface first shows edge defects on one of the positive X-axis side, negative X-axis side, positive Y-axis side, or negative Y-axis side, the side on which the edge defects first appear shall be taken as the over-displacement direction;

[0029] After moving the motion mechanism in the opposite direction to the over-position direction, move the aperture lever again and re-observe the direction of the edge defect of the light spot.

[0030] Preferably, S6 includes:

[0031] The state in which the light spot on the observation surface shrinks synchronously in the circumferential direction as the light-transmitting aperture contracts is used as the recorded state of the coordinates of the motion mechanism;

[0032] Read the X-coordinate and Y-coordinate of the motion mechanism in the recording state;

[0033] The X-axis offset value is obtained by subtracting the X-axis coordinate of the camera from the X-axis coordinate of the motion mechanism, and the Y-axis offset value is obtained by subtracting the Y-axis coordinate of the camera from the Y-axis coordinate of the motion mechanism.

[0034] Beneficial effects:

[0035] 1. By coaxially arranging the light inlet, beam expander module, aperture structure and scale coordinate system, the small spot offset state can be transformed into the change of aperture blocking edge and the difference of scale coordinates, thereby achieving spot center positioning and laser height sensor verticality calibration at the same time under low cost and simplified structure conditions.

[0036] 2. The beam expander module magnifies small light spots, making the center shift and shape differences of light spots that were originally difficult to distinguish clearly visible on the observation surface, thus improving the resolvability of positioning.

[0037] 3. The aperture structure, which is concentrically set around the calibration axis, transforms the eccentric state of the light spot into a change in the direction of edge defects during the narrowing of the light aperture, thus achieving low-complexity determination of the direction of the light spot center offset.

[0038] 4. By observing the card and using the scale coordinate system, the magnified light spot is spatially mapped to a reference, so that changes in the shape of the light spot can correspond to deviations in the X / Y directions, thus achieving an intuitive and quantitative expression of the perpendicularity calibration results. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the structure of the device of the present invention;

[0040] Figure 2 This is a cross-sectional view of the device of the present invention;

[0041] Figure 3 This is a top view of the light inlet of the device of the present invention;

[0042] Figure 4 This is a schematic diagram showing the center positioning of the light spot under the condition of aperture blocking according to the present invention;

[0043] Figure 5 This is a flowchart of the method of the present invention;

[0044] Reference numerals: 1. Structural light inlet; 2. Aperture lever; 3. Observation card and scale coordinate system; 10. Mounting body; 11. Beam expander module; 12. Aperture structure; 21. Top view of the light inlet; 31. Observation surface; 32. Scale coordinates; 33. Coordinate center; 34. X-axis scale; 35. Y-axis scale; 111. Negative lens; 112. Positive lens; 121. Light passage; 122. Light-shielding component; L. Calibration axis. Detailed Implementation

[0045] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0046] Reference Figures 1 to 5 This embodiment provides a small spot positioning and verticality calibration device and a method for small spot positioning and verticality calibration using the device. It is applicable to calibration scenarios between laser rangefinders and cameras in wafer processing equipment, PCB board processing equipment, or display chip processing equipment. The device includes a mounting body 10, on which are provided a structural light inlet 1, a beam expander module 11, an aperture structure 12, an aperture lever 2, and an observation card and a scale coordinate system 3. The center of the structural light inlet 1, the optical axis of the beam expander module 11, the aperture center of the aperture structure 12, and the coordinate center 33 of the observation card and scale coordinate system 3 are located on the same calibration axis L. The calibration axis L is a geometric reference line representing the coaxial relationship between the above centers or optical axes and is not a physical component.

[0047] Before using the device, fix the main body 10 on the marble platform or the equipment calibration position, so that the structural light inlet 1 faces the side where the camera to be calibrated and the laser rangefinder are located, and the observation card and scale coordinate system 3 are located on the light-emitting side of the device; the structural light inlet 1, the beam expander module 11, the aperture structure 12 and the observation card and scale coordinate system 3 are arranged in sequence along the beam propagation direction, so that the beam entering the structural light inlet 1 can pass through the beam expander, the light outlet limitation and the observation display in sequence along the calibration axis L; through the above coaxial arrangement, the device forms a unified mechanical and optical calibration reference, and the subsequent camera center alignment, rangefinder verticality judgment and small spot center positioning are all completed based on the same calibration axis L.

[0048] Reference Figure 1 and Figure 3When aligning the camera with the device center, the camera moves above the light inlet 1 of the structure, and the top view profile 21 of the light inlet 1 enters the camera's field of view. The top view profile 21 of the light inlet has a geometric boundary that can be recognized by the camera, and the geometric center of the top view profile 21 of the light inlet coincides with the center of the light inlet 1 of the structure. The center of the light inlet 1 of the structure is located on the calibration axis L. After the camera recognizes the top view profile 21 of the light inlet, it obtains the position of the device's mechanism center and records the X and Y coordinates of the camera in the alignment state. Since there is a center correspondence between the top view profile 21 of the light inlet and the calibration axis L, the camera's recognition result of the light inlet 1 of the structure can be used as a reference for subsequent calculation of the laser rangefinder spot center offset.

[0049] Reference Figure 2 After the camera center alignment is completed, the laser rangefinder is moved above the light inlet 1 of the structure, so that the beam emitted by the laser rangefinder enters the mounting body 10 through the light inlet 1 of the structure. The light inlet 1 of the structure limits the initial position of the beam before it enters the beam expander module 11, so that the small light spot entering the device enters the beam expander module 11 along the calibration axis L. At this time, the light passage 121 of the aperture structure 12 is adjusted to the open state, so that the beam processed by the beam expander module 11 can completely reach the observation surface 31 of the observation card and the scale coordinate system 3.

[0050] Reference Figure 2 The beam expander module 11 is positioned in the light-emitting direction of the light inlet 1 of the structure. The beam expander module 11 adopts a Galilean beam expander module. The lens group includes a negative lens 111 and a positive lens 112 arranged sequentially at intervals along the calibration axis L. After the small light spot formed by the laser rangefinder enters the beam expander module 11, it is first diverged by the negative lens 111, and then collimated or shaped by the positive lens 112 before propagating to the aperture structure 12. Through the combination of the negative lens 111 and the positive lens 112, the small light spot is magnified before being projected onto the observation surface 31, so that the outline, roundness difference and edge defect changes of the light spot that were originally difficult to directly identify can be observed.

[0051] Reference Figure 2 and Figure 4 The observation card and scale coordinate system 3 are set in the light-emitting direction of the aperture structure 12. The observation card and scale coordinate system 3 include an observation surface 31 and scale coordinates 32 set on the observation surface 31. The scale coordinates 32 have a coordinate center 33, an X-axis scale 34 and a Y-axis scale 35. The coordinate center 33 is located on the calibration axis L. The X-axis scale 34 and the Y-axis scale 35 are perpendicular to each other and pass through the coordinate center 33. After the light spot magnified by the beam expander module 11 is projected onto the observation surface 31, the operator compares the outline of the light spot with the X-axis scale 34 and the Y-axis scale 35 respectively. If the length of the light spot in the X-axis scale 34 direction and the Y-axis scale 35 direction are close, the light spot is circular. If there is a difference in the length in the two directions, it indicates that the laser rangefinder is tilted in the corresponding direction relative to the calibration axis L.

[0052] During the perpendicularity calibration process, if the length of the light spot on the observation surface 31 in the X-axis scale 34 direction is greater than the length in the Y-axis scale 35 direction, the assembly posture of the laser rangefinder in the X-axis direction is adjusted; if the length of the light spot on the observation surface 31 in the Y-axis scale 35 direction is greater than the length in the X-axis scale 34 direction, the assembly posture of the laser rangefinder in the Y-axis direction is adjusted; after each adjustment, the shape difference of the light spot relative to the X-axis scale 34 and Y-axis scale 35 is re-observed until the light spot on the observation surface 31 is close to a circle; through the observation card and scale coordinate system 3, the optical axis tilt state of the laser rangefinder is converted into the difference in the roundness and directional size of the light spot on the observation surface 31, thereby completing the perpendicularity calibration.

[0053] Reference Figure 1 , Figure 2 and Figure 4 After completing the verticality calibration, the center of the small light spot is located using the aperture structure 12. The aperture structure 12 is located between the beam expander module 11 and the observation card and scale coordinate system 3. The aperture structure 12 has a light-passing port 121 that opens and closes around the center of the aperture. The center of the light-passing port 121 is located on the calibration axis L. The aperture lever 2 is driven by the opening and closing components of the aperture structure 12. When the operator moves the aperture lever 2, the light-blocking component 122 in the aperture structure 12 contracts or expands around the center of the aperture, causing the opening range of the light-passing port 121 to change.

[0054] When locating the center of the small light spot, the operator moves the aperture lever 2 to gradually retract the light passage 121 from the open state and observes the direction of the defect at the edge of the light spot on the observation surface 31. Since the light passage 121 retracts concentrically around the calibration axis L, when the center of the small light spot of the laser rangefinder is offset relative to the calibration axis L, the light spot on the observation surface 31 will first show edge defects on one side during the retraction of the light passage 121. If the light spot first shows defects on one side of the positive X-axis, negative X-axis, positive Y-axis, or negative Y-axis, then the side that first shows defects is determined as the over-position direction.

[0055] After determining the overshoot direction, the motion mechanism carrying the laser rangefinder is moved in the opposite direction of the overshoot direction; after moving, the aperture lever 2 is moved again to make the light port 121 retract, and the direction of the edge defect of the light spot is observed again; the process of retracting the light port 121, observing the defect direction, and moving the motion mechanism in the opposite direction is repeated until the light spot on the observation surface 31 no longer shows a unilateral preferential defect, but becomes smaller uniformly around the coordinate center 33 as the light port 121 retracts; at this time, the center of the small light spot of the laser rangefinder, the center of the light port 121, and the coordinate center 33 tend to coincide; through the concentric blocking characteristics of the aperture structure 12, the offset of the small light spot center is converted into an observable edge defect change, avoiding the inference of the light spot center based solely on the position of the height change in the X or Y direction.

[0056] As the light spot shrinks uniformly as the light port 121 contracts, the current X-coordinate and Y-coordinate of the motion mechanism carrying the laser rangefinder are recorded, and the camera X-coordinate and camera Y-coordinate recorded during the aforementioned camera alignment process are read. The current X-coordinate of the motion mechanism is subtracted from the camera X-coordinate to obtain the X-axis offset value. The current Y-coordinate of the motion mechanism is subtracted from the camera Y-coordinate to obtain the Y-axis offset value. The X-axis offset value and the Y-axis offset value together represent the offset relationship between the center of the small light spot of the laser rangefinder and the center of the camera.

[0057] When calibrating light spots of different wavelengths, the observation card and scale coordinate system 3 can be detachably installed in the light-emitting direction of the aperture structure 12. After changing the corresponding observation card according to the light source wavelength of the laser rangefinder, the coordinate center 33 of the scale coordinate 32 is still coincident with the calibration axis L. Then, the perpendicularity calibration and small light spot center positioning are performed according to the above process. In this way, the same device can adapt to the observation needs of light spots of different wavelengths, while maintaining the concentric calibration relationship between the structural light inlet 1, the beam expander module 11, the aperture structure 12 and the observation card and scale coordinate system 3.

[0058] Through the above implementation process, the light inlet 1 establishes a reference relationship between the camera and the center of the device mechanism in the initial stage of use. After the beam enters, the beam expander module 11 magnifies the small light spot into an observable light spot. The observation card and scale coordinate system 3 display the difference in the roundness and directional size of the light spot during the verticality calibration stage. The aperture structure 12 converts the center offset of the light spot into the direction of the edge defect during the center positioning stage. The motion mechanism moves in the opposite direction according to the defect to obtain the center position of the small light spot. Finally, the offset value is obtained by subtracting the coordinates of the motion mechanism from the coordinates of the camera. Each structure participates in the calibration process in sequence under the same calibration axis L, so that the center positioning of the small light spot and the verticality calibration of the laser rangefinder can be completed in the same simplified device.

[0059] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A device for small spot positioning and verticality calibration, characterized in that, It includes a structural light inlet on the light inlet side, a beam expander module in the light outlet direction of the structural light inlet, and a lens group arranged along the incident light path. An aperture structure is provided in the light output direction of the beam expander module. The aperture structure has a light-passing port that opens and closes around the center of the aperture. The aperture structure is connected to an aperture lever, and the aperture lever is driven by the opening and closing component of the light-passing port. An observation card and a scale coordinate system are set in the light-emitting direction of the aperture structure. The observation card and scale coordinate system have an observation surface and scale coordinates set on the observation surface. The scale coordinates have a coordinate center and X-axis and Y-axis scales passing through the coordinate center. The center of the light inlet of the structure, the optical axis of the beam expander module, the center of the aperture of the aperture structure, and the coordinate center of the scale coordinates are located on the same calibration axis.

2. The device for small spot positioning and perpendicularity calibration according to claim 1, characterized in that, The structure's light inlet has a top-view profile for camera recognition, and the geometric center of the top-view profile coincides with the center of the structure's light inlet.

3. The device for small spot positioning and perpendicularity calibration according to claim 1, characterized in that, The beam expander module is a Galilean beam expander module. The lens group includes negative lenses and positive lenses arranged at intervals along the calibration axis. The negative lenses, positive lenses, aperture structure, observation card and scale coordinate system are arranged sequentially along the calibration axis.

4. The device for small spot positioning and perpendicularity calibration according to claim 1, characterized in that, The aperture structure includes light-shielding components distributed around the center of the aperture, forming a light-passing opening. The light-shielding components are connected to an opening and closing component, and the aperture lever drives the light-shielding components to contract or expand relative to the center of the aperture through the opening and closing component.

5. The device for small spot positioning and verticality calibration according to claim 1, characterized in that, The X-axis scale and the Y-axis scale are perpendicular to each other on the observation plane, and the X-axis scale and the Y-axis scale have equidistant scale lines located on both sides of the coordinate center.

6. The device for small spot positioning and perpendicularity calibration according to claim 1, characterized in that, The observation card and scale coordinate system are detachably disposed in the light-emitting direction of the aperture structure. The observation card and scale coordinate system include observation cards corresponding to different light spot wavelengths, and the scale coordinates are disposed on the observation surface of the observation card.

7. A method for locating small light spots and calibrating their perpendicularity, characterized in that, Performed using the device for small spot positioning and perpendicularity calibration as described in any one of claims 1 to 6, comprising: S1. Fix the calibration device on the support platform, move the camera above the light inlet of the structure, and determine the position of the camera relative to the center of the calibration device based on the top view of the light inlet of the structure. S2. Move the laser rangefinder to the center of the mechanism so that the laser beam emitted by the laser rangefinder enters the beam expander module through the light inlet of the structure, and adjust the light outlet of the aperture structure to the open state so that the light spot magnified by the beam expander module is projected onto the observation surface of the observation card and the scale coordinate system. S3. Adjust the orientation of the laser rangefinder according to the shape difference of the light spot on the observation surface relative to the X-axis and Y-axis scales until the light spot on the observation surface is circular. S4. Adjust the light passage of the aperture structure by using the aperture lever, observe the edge defect direction of the light spot on the observation surface, determine the side where the edge defect appears first as the over-position direction, and move the motion mechanism carrying the laser rangefinder in the opposite direction of the over-position direction. S5. Repeat the adjustment of the light-transmitting aperture and the movement of the motion mechanism until the light spot on the observation surface becomes smaller and smaller as the light-transmitting aperture contracts; S6. Record the X and Y coordinates of the motion mechanism when the light spot becomes uniformly smaller, and subtract the X and Y coordinates of the motion mechanism from the X and Y coordinates of the camera respectively to obtain the offset value of the small light spot center of the laser rangefinder relative to the camera.

8. The method for small spot positioning and perpendicularity calibration according to claim 7, characterized in that, S3 includes: When the length of the light spot on the observation surface in the X-axis scale direction is greater than its length in the Y-axis scale direction, the assembly posture of the laser rangefinder in the corresponding X-axis scale direction is adjusted. When the length of the light spot on the observation surface in the Y-axis scale direction is greater than its length in the X-axis scale direction, the assembly posture of the laser rangefinder in the corresponding Y-axis scale direction is adjusted. After adjustment, observe the shape of the light spot on the observation surface again until the length difference of the light spot in the X-axis and Y-axis scale directions is reduced to a circular state.

9. The method for small spot positioning and perpendicularity calibration according to claim 7, characterized in that, S4 includes: Move the aperture lever along the first opening and closing direction to change the light passage from the open state to the closed state; When the light spot on the observation surface first shows edge defects on one of the positive X-axis side, negative X-axis side, positive Y-axis side, or negative Y-axis side, the side on which the edge defects first appear shall be taken as the over-displacement direction; After moving the motion mechanism in the opposite direction to the over-position direction, move the aperture lever again and re-observe the direction of the edge defect of the light spot.

10. The method for small spot positioning and perpendicularity calibration according to claim 7, characterized in that, S6 includes: The state in which the light spot on the observation surface shrinks synchronously in the circumferential direction as the light-transmitting aperture contracts is used as the recorded state of the coordinates of the motion mechanism; Read the X-coordinate and Y-coordinate of the motion mechanism in the recording state; The X-axis offset value is obtained by subtracting the X-axis coordinate of the camera from the X-axis coordinate of the motion mechanism, and the Y-axis offset value is obtained by subtracting the Y-axis coordinate of the camera from the Y-axis coordinate of the motion mechanism.

Images