Three-dimensional self-alignment device and method for photodetectors

Abstract

This invention discloses a three-dimensional automatic alignment device and method for photodetectors, relating to the fields of photoelectric detection and precision instrument technology. To address the problems in existing technologies using small photosensitive surface detectors such as avalanche diodes, where high alignment accuracy is required, leading to difficult, time-consuming, and inefficient manual adjustments and inconsistent alignment results, the following technical solution is proposed: A three-dimensional automatic alignment device for photodetectors includes an optical path focusing module, a photodetector mounted on a three-dimensional adjustment mechanism, a driving device, and a control unit. The control unit is connected to the photodetector and the driving device to automatically search for and locate the position with the strongest signal strength. This method achieves rapid and accurate automatic alignment through a two-stage strategy of coarse adjustment with large-range scanning and fine adjustment with small-range optimization. This invention achieves fully automatic, rapid, and high-precision alignment of small photosensitive surface detectors, significantly improving the assembly efficiency and stability of the detection performance.

Description

Technical Field

[0001] This invention relates to the field of photoelectric detection and precision instrument technology, specifically to a three-dimensional automatic alignment device and method for a photoelectric detector. Background Technology

[0002] In the fields of biomedicine and chemical analysis, fluorescence detection is a key technology widely used in precision equipment such as flow cytometers and fluorescence PCR instruments. The core of these devices is a highly sensitive photodetector used to capture weak fluorescence signals. Currently, the main detectors used are photomultiplier tubes (PMTs) and avalanche diodes (APDs). PMTs have the advantage of a large photosensitive receiving surface (e.g., a diameter of up to 8 mm) and relatively low requirements for optical path alignment precision, but they are very expensive. In contrast, avalanche diodes (APDs) are much cheaper, but their photosensitive receiving surface is extremely small (e.g., a diameter of only 0.8 mm).

[0003] To control costs, many devices tend to use APDs as photodetectors. However, the small photosensitive surface of APDs also presents a series of significant technical challenges:

[0004] 1. Strict optical path alignment requirements: Due to the extremely small receiving surface, the front-end optical path system must accurately focus the collected fluorescence signal into a light spot with a diameter of less than 0.8 mm in order for it to be effectively received by the APD.

[0005] 2. Extremely high alignment precision is required: Simply focusing the light spot to the specified size is not enough; this tiny spot must also be precisely aligned with the exact center of the APD photosensitive surface. Any micrometer-level deviation will cause a significant attenuation of the received signal intensity, severely affecting the accuracy and sensitivity of the detection results.

[0006] 3. Practical difficulties: During the actual assembly of the equipment, due to factors such as the installation tolerances of optical components and the thermal expansion and contraction of the mechanical structure, the actual landing point of the light spot is difficult to completely match the theoretical design position. Relying on manual micron-level three-dimensional alignment is not only extremely time-consuming and inefficient, but also requires extremely high skills and experience from the operators, making it difficult to guarantee the consistency of product performance in mass production.

[0007] Therefore, how to achieve rapid, accurate, and automated alignment of small photosensitive surface detectors such as APDs has become a technical bottleneck restricting the performance improvement and cost control of related equipment. Summary of the Invention

[0008] The purpose of this invention is to provide a three-dimensional automatic alignment device for photodetectors, in order to solve the problems in the prior art where small photosensitive surface detectors such as avalanche diodes (APDs) have small receiving areas, resulting in difficulties in manual alignment of the optical path, long time consumption, and low accuracy, which in turn affect equipment performance and production efficiency.

[0009] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0010] A three-dimensional automatic alignment device for a photodetector includes an optical path focusing module, a photodetector, a three-dimensional adjustment mechanism, a drive device, a control unit, and a full-band laser;

[0011] The full-band laser is connected to the optical focusing module via optical fiber;

[0012] The optical focusing module converges the light signals emitted by the full-band laser to form a light spot;

[0013] The photodetector is fixedly mounted on the three-dimensional adjustment mechanism and receives the light spot converged by the optical path focusing module; the driving device is connected to the three-dimensional adjustment mechanism and drives the three-dimensional adjustment mechanism to move within its three-dimensional space.

[0014] The control unit's signal input terminal is connected to the photodetector, and its control output terminal is connected to the drive device.

[0015] The control unit acquires the electrical signal output by the photodetector corresponding to the light intensity of the light spot; and based on the electrical signal, controls the drive device to drive the three-dimensional adjustment mechanism to move, so as to automatically search for and locate the position where the electrical signal intensity is the greatest.

[0016] Furthermore, the photodetector is an avalanche diode.

[0017] Furthermore, the driving device includes a first driving motor and a second driving motor. The first driving motor is used to drive the three-dimensional adjustment mechanism to perform reciprocating movement in the first dimension; the second driving motor is used to drive the photodetector on the three-dimensional adjustment mechanism to perform fine adjustment in the second and third dimensions.

[0018] Furthermore, the three-dimensional adjustment mechanism includes a guide rail and an adjustment mechanism base plate. The first drive motor drives the transmission belt to move the adjustment mechanism base plate back and forth on the guide rail, and the other end of the transmission belt is fixed by a synchronous pulley.

[0019] Furthermore, it also includes a fixing magnet; before performing automatic search, the control unit controls the fixing magnet to be energized and attracted to fix the part to be adjusted of the three-dimensional adjustment mechanism; after the search and positioning is completed, the control unit controls the fixing magnet to be de-energized and released.

[0020] Furthermore, the control unit is a field-programmable gate array (FPGA).

[0021] A method for automatic three-dimensional alignment of a photodetector includes the following steps:

[0022] S1: The optical signal is focused to form a light spot through the optical path focusing module;

[0023] S2: The control unit obtains the electrical signal strength output by the photodetector at the current position;

[0024] S3: The control unit runs a preset algorithm to generate drive commands;

[0025] S4: The drive unit drives the three-dimensional adjustment mechanism to move to a new position according to the drive command;

[0026] S5: Repeat steps S2 to S4 until the photodetector moves to the position with the strongest electrical signal.

[0027] Furthermore, the execution in S3 and S4 involves two steps:

[0028] Coarse adjustment step: Control the drive device to perform a large-scale scan with a preset coarse adjustment step size to find an initial optimal position with the strongest signal strength;

[0029] Fine-tuning steps: Starting from the initial optimal position, the control drive device performs small-range optimization with a preset fine-tuning step size until the signal strength change is less than the preset threshold, thereby determining the final optimal position.

[0030] Furthermore, the fine-tuning step employs a gradient descent algorithm to determine the next movement direction by calculating the signal gradient at adjacent positions.

[0031] The present invention has the following beneficial effects:

[0032] This invention achieves fully automatic, high-precision alignment of a photodetector through a motor-driven three-dimensional adjustment mechanism and a closed-loop control system based on the detector's own signal feedback. It effectively solves the technical challenges of difficult, time-consuming, and unreliable manual alignment caused by the small photosensitive surface of avalanche diodes (APDs). This device not only significantly improves the assembly efficiency and automation level of the equipment but also maximizes signal collection efficiency by ensuring the light spot is precisely focused at the center of the detector, guaranteeing the stability and reliability of the equipment's detection performance. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of a three-dimensional automatic alignment device for a photoelectric detector.

[0034] Figure 2 This is a schematic diagram of the three-dimensional adjustment mechanism of a three-dimensional automatic alignment device for a photoelectric detector.

[0035] Figure 3This is a schematic diagram of a three-dimensional automatic alignment method for a photoelectric detector.

[0036] Figures 1 to 3 The reference numerals in the attached figures are respectively: 1-optical path focusing module, 2-photodetector, 21-connector, 3-three-dimensional adjustment mechanism, 31-first drive motor, 32-second drive motor, 33-guide rail, 34-adjustment mechanism base plate, 35-synchronous wheel, 4-drive device, 5-control unit, 6-fixed magnet, 7-full-band laser, 8-base plate. Detailed Implementation

[0037] The technical solution 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.

[0038] Please refer to Figure 1 This embodiment provides a three-dimensional automatic alignment device for a photodetector, including an optical path focusing module 1, a photodetector 2, a three-dimensional adjustment mechanism 3, a driving device 4, and a control unit 5.

[0039] In this embodiment, the optical focusing module 1 is used to receive fluorescence signals generated by the front end (such as a flow cytometer or fluorescence detection device). It consists of a dichroic mirror, a filter, and a focusing lens (such as a plano-convex lens). Its function is to accurately focus fluorescence signals of a specific wavelength into a light spot with a diameter of less than 0.8 mm to match the receiving surface size of the photodetector 2.

[0040] Photodetector 2: In this embodiment, photodetector 2 is an avalanche diode (APD), which is characterized by its low cost and extremely small photosensitive area (e.g., 0.8 mm in diameter). This photodetector 2 is used to sense the light energy of the light spot and outputs an electrical signal proportional to the light intensity as a feedback signal for subsequent automatic alignment.

[0041] Specifically, such as Figure 2 As shown, the three-dimensional adjustment mechanism 3 and the driving device 4 are connected. The photodetector 2 is fixedly mounted on the connector 21 of the three-dimensional adjustment mechanism 3. The driving device 4 is mechanically connected to the three-dimensional adjustment mechanism 3 and is used to drive its movement. The driving device 4 includes a first driving motor 31 and multiple second driving motors 32. In this embodiment, the first driving motor 31 is a 28-type stepper motor. The base of the three-dimensional adjustment mechanism 3 is mounted on a guide rail 33 on the base plate 8. The first driving motor 31 drives the entire base to move back and forth along the guide rail 33 in a large range. This movement is mainly used to switch the alignment device to the working position of different channels in a multi-channel system.

[0042] In this embodiment, the second drive motor 32 consists of three 20-type stepper motors integrated on an adjustment mechanism base plate 34. These three motors control the photodetector 2 to perform micron-level precision movements in the front-back, up-down, and small-range left-right directions, i.e., fine-tuning in the second and third dimensions. To ensure absolute stability of the platform during fine-tuning, the device also includes a fixed magnet 6, preferably an electromagnet. When preparing for fine alignment of a channel, the control unit 5 controls the fixed magnet 6 to be energized, firmly attracting its adjustment base to eliminate any potential shaking. After alignment is completed, the magnet is de-energized and released.

[0043] In this embodiment, the core of the control unit 5 is a field-programmable gate array (FPGA). The FPGA is connected to the signal output terminal of the photodetector 2 (via an ADC analog-to-digital converter) and the motor driver of the drive device 4. It is responsible for receiving and processing the detector signals, executing the preset alignment algorithm, and generating pulse and direction signals to precisely control the movement of the first drive motor 31 and the second drive motor 32.

[0044] As attached Figure 3 As shown, a three-dimensional automatic alignment method for a photodetector includes the following steps:

[0045] S1: Spot formation. When the system is working, the full-spectrum laser at the front end emits laser light, which is then used to excite the sample after passing through the optical fiber and collimator. The generated fluorescence signal is collected and processed by the optical path focusing module 1, and finally a tiny spot is formed in the predetermined focal area.

[0046] S2: High-precision electrical signal acquisition and processing. Each cycle begins with signal acquisition. The control unit 5 first reads the light spot intensity received by the photodetector 2 at its current position and converts it into an electrical signal value that can be analyzed. To ensure the accuracy of the judgment, the system performs preliminary processing on the raw signal to obtain a stable and reliable intensity value, avoiding misjudgments caused by instantaneous signal fluctuations.

[0047] S3: After generating a movement command and obtaining a stable signal value, the preset algorithm inside control unit 5 begins to work to determine the next movement direction and distance. This algorithm adopts a two-stage strategy:

[0048] Coarse-tuning search: The goal of this stage is to quickly locate the approximate area of ​​the light spot. Control unit 5 controls the second drive motor 32 to perform a two-dimensional grid scan within a large range (e.g., ±3mm) with a preset large step size (e.g., 0.5mm). At each grid point, the system acquires the signal strength. After the scan is complete, control unit 5 finds the coordinates of the point with the strongest signal, which is used as the "initial optimal position".

[0049] Fine-tuning and optimization: After finding the initial optimal position, the system enters the fine-tuning phase. Starting from this position, the control unit 5 controls the second drive motor 32 to perform optimization within a small range using a fine-tuning step size much smaller than the coarse-tuning step size (e.g., 0.01 mm). The goal of this step is to precisely lock the energy center of the light spot. When the change in signal intensity is less than a preset convergence threshold, the control unit 5 determines that the final optimal position has been found and stops moving.

[0050] S4: The drive mechanism performs the movement, and the movement command generated by S3 is sent to the drive device 4. The drive device 4 then precisely controls the connected motor, driving the three-dimensional adjustment mechanism 3 to perform physical movement, thereby moving the photodetector 2 to the new position specified by the algorithm.

[0051] S5: Loop. After completing one movement (i.e., S4), the system does not stop but immediately returns to execute S2, measuring the signal strength at the new position, thus forming a continuous loop. Control unit 5 determines whether the stopping condition is met in each loop. This loop only terminates when the fine-tuning algorithm confirms that the signal peak point has been found (i.e., any small movement in any direction will no longer amplify the signal). At this point, the system determines that alignment is complete, and photodetector 2 is precisely positioned at the center of the light spot.

[0052] Furthermore, in the fine-tuning optimization of S3, a gradient descent algorithm (and gradient ascent when searching for the maximum value) is employed. At each step of the fine-tuning, the control unit 5 controls the second drive motor 32 to move a tiny distance in both the X and Y directions of the current point and measures the signal. The intensity gradient at the current position is calculated based on the change in the signal value. Then, the control unit 5 commands the motor to move one fine-tuning step along the steepest direction indicated by the gradient. Through repeated iterations, the photodetector 2 can move very precisely to the peak point of the light intensity.

[0053] After alignment is complete, the control unit 5 illuminates the success indicator and releases the fixing magnet 6. For applications requiring permanent fixation, the operator can then apply adhesive to the adjustment mechanism for secure fixation. Upon receiving a manual confirmation signal, the system can drive the first drive motor 31 to move to the next channel and repeat the entire alignment process described above.

[0054] The above description is only 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 three-dimensional self-alignment device for photodetectors, characterized by, It includes an optical path focusing module (1), a photodetector (2), a three-dimensional adjustment mechanism (3), a drive device (4), a control unit (5), and a full-band laser (7). The full-band laser (7) is connected to the optical path focusing module (1) via an optical fiber. The optical path focusing module (1) focuses the optical signal emitted by the full-band laser (7) to form a light spot; The photodetector (2) is fixedly mounted on the three-dimensional adjustment mechanism (3) and receives the light spot converged by the optical path focusing module (1); the driving device (4) is connected to the three-dimensional adjustment mechanism (3) and drives the three-dimensional adjustment mechanism (3) to move in its three-dimensional space; The signal input terminal of the control unit (5) is connected to the photodetector (2), and its control output terminal is connected to the drive device (4); The control unit (5) acquires the electrical signal output by the photodetector (2) that corresponds to the light intensity of the light spot; Based on the electrical signal, the drive device (4) is controlled to drive the three-dimensional adjustment mechanism (3) to move, so as to automatically search and position to the position where the electrical signal strength is the greatest; it also includes a fixed magnet (6); before the automatic search is performed, the control unit (5) controls the fixed magnet (6) to be energized and attracted to fix the part to be adjusted of the three-dimensional adjustment mechanism (3), and after the search and positioning is completed, the fixed magnet (6) is de-energized and released; Automatic search includes two steps: coarse adjustment step: control the drive device (4) to perform a large-scale scan with a preset coarse adjustment step size to find an initial optimal position with the strongest signal strength; Fine-tuning step: Starting from the initial optimal position, control the drive device (4) to perform small-range optimization with a preset fine-tuning step size until the signal strength change is less than the preset threshold, thereby determining the final optimal position. The fine-tuning step adopts the gradient descent algorithm to determine the next movement direction by calculating the signal gradient of adjacent positions.

2. The three-dimensional self-alignment device of a photodetector according to claim 1, wherein, The photodetector (2) is an avalanche diode.

3. The three-dimensional self-alignment device of photodetectors according to claim 1, characterized in that, The driving device (4) includes a first driving motor (31) and a second driving motor (32). The first driving motor (31) is used to drive the three-dimensional adjustment mechanism (3) to perform reciprocating movement in the first dimension; the second driving motor (32) is used to drive the photodetector (2) on the three-dimensional adjustment mechanism (3) to perform fine adjustment in the second and third dimensions.

4. The three-dimensional self-alignment device of photodetectors according to claim 3, characterized in that, The three-dimensional adjustment mechanism (3) includes a guide rail (33), an adjustment mechanism base plate (34), a transmission belt, and a synchronous pulley (35). The first drive motor (31) drives the transmission belt to move the adjustment mechanism base plate (34) back and forth on the guide rail (33). The other end of the transmission belt is fixed by the synchronous pulley (35).

5. The three-dimensional self-alignment device of photodetectors according to claim 1, wherein, The control unit (5) is a field-programmable gate array (FPGA).

6. A three-dimensional automatic alignment method for a photodetector, implemented based on the three-dimensional automatic alignment device for a photodetector according to any one of claims 1-5, characterized in that, Includes the following steps: S1: The optical signal is focused to form a light spot through the optical path focusing module (1); S2: The control unit (5) obtains the electrical signal strength output by the photodetector (2) at the current position; S3: The control unit (5) runs a preset algorithm to generate drive instructions; S4: The driving device (4) drives the three-dimensional adjustment mechanism (3) to move to a new position according to the driving command; S5: Repeat steps S2 to S4 until the photodetector (2) moves to the position with the strongest electrical signal.

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