Cooperative target circle center verification device based on coaxial four-quadrant detector

Abstract

The utility model discloses a cooperation target circle center verification device based on coaxial four quadrant detector, including laser scanning module, cooperation target subassembly, signal acquisition and processing module, host computer controller, cooperation target subassembly includes cooperation target with annular high reflection material area, and four quadrant detector is arranged in the center of annular high reflection material area, coaxially, laser scanning module is used for projecting laser spot to cooperation target surface to the light spot that projects to the fitting cooperation target circle center coordinate position, signal acquisition and processing module are used for gathering respectively cooperation target on reflection signal and four quadrant detector feedback's current information, and to the information of gathering is handled, will handle result data send to host computer controller, and host computer controller is connected with laser scanning module and signal acquisition and processing module communication respectively.

Description

Technical Field

[0001] This utility model belongs to the field of cross-application of laser projection and photoelectric detection technology, and in particular relates to a cooperative target center verification device based on a coaxial four-quadrant detector. Background Technology

[0002] With the continuous development of laser scanning projection and 3D measurement technologies, their applications in industrial assembly, precision machining, augmented reality, and intelligent manufacturing are becoming increasingly widespread. To achieve high-precision spatial registration between the projected coordinate system and the workpiece coordinate system, cooperative targets are typically deployed on the target surface. By laser scanning the highly reflective area of ​​the cooperative target and fitting its geometric center, calibration points for coordinate transformation can be obtained, enabling high-precision calibration of the system.

[0003] Existing methods for extracting the center of a target circle often rely on continuous scanning paths, such as epicycloid scanning, rectangular grid scanning, and sunflower-shaped scanning. These methods acquire the target's reflectivity curve through full-coverage scanning, then combine this with threshold determination to extract boundary points, and finally fit the center coordinates using the least squares method. While these methods can theoretically guarantee a certain level of accuracy, they also have significant shortcomings: continuous scanning often requires a large number of sampling points to cover the target boundary, resulting in excessively long scanning times and increased computational costs, making it difficult to meet real-time requirements; during the data processing stage, setting the threshold usually requires retaining all scan points, increasing the computational burden and reducing overall efficiency; furthermore, these methods are highly dependent on the stability of ambient light, and in complex industrial environments or under strong light conditions, the determination of boundary points is easily affected, thus weakening the accuracy of the center fitting.

[0004] To overcome the aforementioned problems, Correlated Double Sampling (CDS) technology has been introduced in recent years. Although the CDS method significantly improves anti-interference capability and scanning efficiency, its results still rely on geometric fitting calculations and lack direct verification of whether the fitted circle center truly corresponds to the physical center of the cooperative target. Limited by the shape of the light spot, the uniformity of the target's reflective surface, and mechanical assembly errors, even with high fitting accuracy, the circle center result may still have a non-negligible deviation from the true geometric center, thus affecting the subsequent coordinate calibration accuracy and system robustness.

[0005] Therefore, although existing technologies have made some progress in anti-interference scanning and center extraction, there are still significant shortcomings in the verification of the authenticity of fitting results. There is an urgent need for a new method that combines hardware structure design and signal processing to provide dual guarantees of geometric fitting and physical feedback for the extraction of the center of the cooperative target. Summary of the Invention

[0006] To address the aforementioned problems in existing technologies, this invention provides a cooperative target center verification device based on a coaxial four-quadrant detector. A high-precision four-quadrant photodetector is embedded in the center of the cooperative target, and a mechanical structure ensures its strict concentricity with the surrounding high-reflectivity area. After scanning the high-reflectivity area and fitting the center with a laser, the laser spot is guided to the fitted center position. The deviation from the physical center can be determined in real time using the symmetrical response characteristics of the four-quadrant detector. This invention organically combines anti-interference scanning extraction technology with a physical feedback verification mechanism, not only improving the robustness of center extraction but also achieving direct confirmation of fitting accuracy, thereby effectively enhancing the system's calibration reliability and environmental adaptability.

[0007] The objective of this utility model is achieved through the following technical solution:

[0008] A cooperative target center verification device based on a coaxial four-quadrant detector is provided, characterized by comprising a laser scanning module, a cooperative target component, a signal acquisition and processing module, and a host computer controller; the cooperative target component includes a cooperative target with an annular high-reflectivity material region and a four-quadrant detector coaxially disposed at the center of the annular high-reflectivity material region; the laser scanning module is used to project a laser spot onto the surface of the cooperative target and to project a spot onto the fitted coordinate position of the cooperative target center; the signal acquisition and processing module is used to acquire the reflected signal on the cooperative target and the current information fed back by the four-quadrant detector, respectively, and to process the acquired information before sending it to the host computer controller; the host computer controller is communicatively connected to both the laser scanning module and the signal acquisition and processing module.

[0009] Furthermore, the laser scanning module includes a laser, a dual-axis galvanometer, and a galvanometer control unit; the galvanometer control unit is communicatively connected to the host computer controller, and receives instructions sent by the host computer controller to control the deflection of the dual-axis galvanometer, so that the laser beam output by the laser is deflected by the dual-axis galvanometer and projected onto the surface of the cooperative target according to a preset discontinuous scanning path.

[0010] Furthermore, the signal acquisition and processing module includes a photodiode, a transimpedance amplifier, an analog-to-digital converter, and a related dual-sampling circuit. The photodiode, acting as a front-end photosensitive element, converts the received reflected light intensity into a current signal when the laser is projected onto the target surface. This current is then converted into a voltage signal by the transimpedance amplifier and subsequently enters the related dual-sampling circuit for differential sampling processing to obtain a net reflected signal free from ambient light interference. The net reflected signal is then sent to the analog-to-digital converter for digital acquisition, and the converted net reflected signal is then sent to the host computer controller for further processing. The current signal output by the four-quadrant photodetector is also converted into a voltage signal by the transimpedance amplifier, and then converted to digital by the analog-to-digital converter. The voltage signal obtained from the analog-to-digital conversion is then sent to the host computer controller for further processing.

[0011] Furthermore, the host computer controller includes an STM32 controller and a data communication module; the data communication module communicates with the STM32 controller via a serial port protocol, and the data communication module also communicates with the laser scanning module and the signal acquisition and processing module.

[0012] This utility model has the following beneficial effects:

[0013] This invention provides a cooperative target center verification device based on a coaxial four-quadrant detector. It combines anti-interference related dual-sampling scanning technology with the physical feedback mechanism of a four-quadrant photodetector. This significantly reduces the number of scanning points and improves boundary recognition efficiency while effectively suppressing the impact of ambient light interference on the accuracy of center extraction. By embedding and strictly coaxially mounting a four-quadrant detector at the center of the cooperative target, real-time physical verification of the geometrically fitted center is achieved, effectively avoiding the systematic deviation between the fitted results and the true center in traditional methods. This device improves the accuracy and robustness of cooperative target center extraction, providing higher reliability and stability for subsequent coordinate calibration and system registration, and meeting the high-precision requirements for laser projection and positioning in complex industrial environments.

[0014] This invention is not only applicable to laser projection calibration systems, but can also be extended to the calibration and alignment processes of laser ranging and lidar. It also has application potential in the automatic alignment of optical communication receivers. In the field of precision manufacturing and assembly, this device can be used to detect and verify the geometric accuracy of workpiece positioning points. In optical experimental and scientific research equipment, it can serve as an auxiliary detection module for precise alignment of laser spots. Attached Figure Description

[0015] Figure 1 This is a schematic diagram illustrating the composition principle of a cooperative target center verification device based on a coaxial four-quadrant detector, as described in an embodiment of this utility model.

[0016] Figure 2This is a schematic diagram of the main structure of the cooperative target component described in this embodiment of the present invention;

[0017] Figure 3 This is an isometric structural diagram of the cooperative target component described in this embodiment of the present invention;

[0018] Figure 4 This is a schematic diagram illustrating the working principle of an embodiment of the present invention.

[0019] Figure 5 This is a schematic diagram illustrating the working principle of the four-quadrant detector described in this embodiment of the present invention. Detailed Implementation

[0020] The technical solution of this utility model is further described below with reference to the accompanying drawings and embodiments:

[0021] Example

[0022] This embodiment is a cooperative target center verification device based on a coaxial four-quadrant detector, such as... Figures 1 to 3 As shown, the device includes a laser scanning module, a cooperative target component, a signal acquisition and processing module, and a host computer controller. The cooperative target component includes a cooperative target with an annular high-reflectivity material region and a quadrant detector (QD) coaxially positioned at the center of the annular high-reflectivity material region. The laser scanning module is used to project laser spots onto the surface of the cooperative target according to a preset discontinuous scanning path, and to project laser spots onto the fitted coordinates of the cooperative target's center, according to instructions from the host computer controller. The signal acquisition and processing module is used to acquire the reflected signals from the cooperative target and the current information fed back by the quadrant detector, process the acquired information, and send the processed data to the host computer controller. The host computer controller is communicatively connected to both the laser scanning module and the signal acquisition and processing module.

[0023] The laser scanning module includes a laser, a dual-axis galvanometer, and a galvanometer control unit. The galvanometer control unit is communicatively connected to the host computer controller. The galvanometer control unit receives commands from the host computer controller and controls the deflection of the dual-axis galvanometer, so that the laser beam output from the laser is deflected by the dual-axis galvanometer and projected onto the target surface along a preset discontinuous scanning path. The galvanometer control unit consists of a drive circuit and a timing control circuit, used to receive galvanometer deflection control commands from the host computer controller and ensure that the dual-axis galvanometer operates stably along the set trajectory.

[0024] The four-quadrant detector consists of four symmetrically distributed photosensitive units. When a laser spot illuminates the detector surface, each quadrant receives different amounts of light energy, generating corresponding current signals.

[0025] The four-quadrant detector is electrically connected to the signal acquisition and processing module, and sends the current signal to the signal acquisition and processing module for subsequent signal processing.

[0026] The signal acquisition and processing module includes a photodiode, a transimpedance amplifier, an analog-to-digital converter (ADC), and a correlated double sampling (CDS) circuit. The photodiode, acting as a front-end photosensitive element, converts the received reflected light intensity into a current signal when the laser is projected onto the target surface. This current is then converted into a voltage signal by the transimpedance amplifier and subsequently enters the CDS circuit for differential sampling to obtain a net reflected signal free from ambient light interference. The net reflected signal is then sent to the ADC for digital acquisition, and the converted net reflected signal is sent to the host computer controller for further processing. Similarly, the current signal output by the four-quadrant photodetector is also converted into a voltage signal by the transimpedance amplifier, then converted to digital by the ADC, and finally sent to the host computer controller for further processing.

[0027] The related dual sampling circuit includes a sample-and-hold capacitor, an analog switch, a differential amplifier, and a reset switch.

[0028] The host computer controller includes an STM32 controller and a data communication module. The data communication module communicates with the STM32 controller via a serial port protocol, and also communicates with the laser scanning module and the signal acquisition and processing module. The host computer controller is used to set up scanning tasks, issue laser scanning commands, fit the geometric center coordinates of the cooperative target, and calculate the deviation between the fitted center of the cooperative target and the actual physical center.

[0029] The working principle of this utility model embodiment is described below:

[0030] This embodiment verifies the center of the cooperative target circle, such as... Figure 4 As shown, it includes the following steps:

[0031] Step 1: The host computer controller's host control module generates a scanning task instruction based on calibration requirements and sends the scanning instruction to the STM32 controller via a serial port protocol through the data communication module. The controller drives the dual-axis galvanometer of the laser scanning module according to the scanning instruction, so that the laser transmits a laser beam along a preset discontinuous scanning path to the surface of the cooperative target. The scanning path covers the boundary of the annular high-reflectivity area of ​​the cooperative target to facilitate the rapid extraction of boundary points.

[0032] Step 2: Signal Acquisition and Processing

[0033] As a front-end photosensitive element, the photodiode converts the intensity of the received reflected light into a current signal when the laser is projected onto the surface of the target.

[0034] The current signal is first converted into a voltage signal by a transimpedance amplifier. The voltage signal then enters the CDS circuit for differential sampling: when the laser is off, the first sample-and-hold unit samples and holds the background light signal, meaning the CDS circuit acquires the ambient background light intensity; after the laser is on, the second sample-and-hold unit samples and holds the "background light + reflected light" signal, meaning the CDS again acquires the signal superimposed with laser reflected light and ambient light. The two sampled voltage signals are input to the positive and negative ports of the differential amplifier, respectively. After subtraction, the net reflected signal, free from ambient light interference, is obtained. By differentiating the two sampling results, ambient light interference is effectively eliminated, retaining only the effective signal generated by the high-reflectivity area of ​​the cooperative target. This process ensures accurate determination of whether the laser has hit the cooperative target even in complex lighting environments. To prevent residual capacitor charge from affecting sampling accuracy, a reset switch is included in the circuit to periodically release capacitor charge, ensuring sampling consistency and stability.

[0035] The net reflection signal output by the CDS circuit is then sent to the analog-to-digital converter (ADC) to complete digital acquisition, obtain the reflected light intensity data of the scanning area on the surface of the cooperative target, and send it to the host computer controller for the microcontroller to perform normalization calculations and subsequent boundary point extraction.

[0036] Step 3: Extract boundary points and fit the geometric center of the target circle based on the reflected light intensity data of the scanned area on the surface of the cooperative target.

[0037] The STM32 controller normalizes the reflected light intensity data of the surface scanning area of ​​the cooperative target obtained in step two, identifies boundary points, records and uploads the coordinates of the identified boundary points one by one, and the trajectory calculation unit of the upper control module receives the boundary point coordinate data and uses the least squares method to fit the point set to obtain the geometric center coordinates of the cooperative target.

[0038] Step 4: The STM32 controller re-drives the dual-axis galvanometer of the laser scanning module based on the fitted geometric center coordinates of the cooperative target. The laser beam output by the laser is adjusted by the dual-axis galvanometer so that the laser spot accurately hits the geometric center position of the fitted cooperative target.

[0039] Step 5: Calculate the deviation between the fitted center of the cooperative objective and the actual physical center, and provide feedback on the results:

[0040] A four-quadrant detector is coaxially embedded at the center of the cooperative target. When the light spot is incident on the cooperative target, the four-quadrant detector generates four current signals. When the light spot is at the actual physical center of the cooperative target, the current in the four quadrants should be approximately equal; if the light spot is offset, the current distribution will show obvious asymmetry, and its direction and amplitude can reflect the displacement of the light spot relative to the actual center.

[0041] After the four current signals are sampled by the signal acquisition and processing module, the STM32 controller performs baseline subtraction and normalization operations to calculate the two-dimensional normalized offset of the light spot relative to the physical center of the cooperative target in real time. and These two parameters, as quantitative indicators, directly characterize the magnitude of the deviation between the fitted circle center and the physical center. For example... Figure 5 As shown, if the light spot is located at the geometric center of the detector, the currents in all four quadrants are equal; if the light spot is offset, the currents are asymmetrical. The two-dimensional offset of the light spot (fitted center) relative to the actual physical center can be obtained through normalization calculation. , The calculation formula is as follows:

[0042]

[0043] Finally, the normalized offset is... and Perform analysis, upload error data, and output verification results.

Claims

1. A cooperative target center verification device based on a coaxial four-quadrant detector, characterized in that, The system includes a laser scanning module, a cooperative target component, a signal acquisition and processing module, and a host computer controller. The cooperative target component includes a cooperative target with a ring-shaped high-reflectivity material region and a four-quadrant detector coaxially positioned at the center of the ring-shaped high-reflectivity material region. The laser scanning module projects a laser spot onto the surface of the cooperative target and projects the spot onto the fitted coordinates of the cooperative target's center. The signal acquisition and processing module collects the reflected signals from the cooperative target and the current information fed back by the four-quadrant detector, processes the collected information, and sends it to the host computer controller. The host computer controller is communicatively connected to both the laser scanning module and the signal acquisition and processing module.

2. The cooperative target center verification device based on a coaxial four-quadrant detector as described in claim 1, characterized in that, The laser scanning module includes a laser, a dual-axis galvanometer, and a galvanometer control unit. The galvanometer control unit is communicatively connected to the host computer controller. The galvanometer control unit receives instructions from the host computer controller and controls the dual-axis galvanometer to deflect, so that the laser beam output by the laser is deflected by the dual-axis galvanometer and projected onto the surface of the target object according to a preset discontinuous scanning path.

3. The cooperative target center verification device based on a coaxial four-quadrant detector as described in claim 1, characterized in that, The signal acquisition and processing module includes a photodiode, a transimpedance amplifier, an analog-to-digital converter, and a related dual-sampling circuit. The photodiode, as a front-end photosensitive element, converts the intensity of the received reflected light into a current signal when the laser is projected onto the surface of the target. This current is then converted into a voltage signal by the transimpedance amplifier and subsequently enters the related dual-sampling circuit for differential sampling processing to obtain a net reflected signal that has removed ambient light interference. The net reflected signal is then sent to the analog-to-digital converter to complete digital acquisition, and then the net reflected signal after analog-to-digital conversion is sent to the host computer controller for further processing.

4. The cooperative target center verification device based on a coaxial four-quadrant detector as described in claim 1, characterized in that, The host computer controller includes an STM32 controller and a data communication module. The data communication module communicates with the STM32 controller via a serial port protocol, and also communicates with the laser scanning module and the signal acquisition and processing module.

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