Non-pixelated multi-target detection system and method based on position detector

Abstract

The invention discloses a non-pixelated multi-target detection system and method based on a position detector. The non-pixelated multi-target detection system comprises a high-frequency scintillation light source, a position sensitive detector and an imaging lens, the high-frequency scintillation light source is arranged at the front end of the imaging lens, so that the high-frequency scintillation light source is projected to a working area of the position sensitive detector; the high-frequency flickering light source is used for projecting a group of variable patterns consisting of a plurality of light spots to a working area of the position sensitive detector, and at each moment, only one light spot in the high-frequency flickering light source emits light, and the other light spots do not emit light; and according to the electric signal generated by the position sensitive detector, the horizontal coordinate and the vertical coordinate of the current luminous spot are determined.

Description

Technical Field

[0001] The present invention belongs to the technical field of optoelectronic devices, and specifically relates to a non-pixelated multi-target detection system and method based on a position detector. Background Art

[0002] Due to the principle of its unique lateral photoelectric effect, the photoelectric position-sensitive detector has the ability to detect the position of a single light spot with high resolution and no dead zone, and thus is widely used in the fields of target positioning, automatic control, robotics, and guidance. However, its mechanism also limits its positioning ability for multiple light spots, that is, it cannot simultaneously locate and track multiple light spots (multiple targets). When multiple light spots irradiate the detector simultaneously, the carrier distributions generated by each light spot will affect each other. At this time, the position-sensitive detector will output incorrect positioning information, that is, the output result is the geometric center of multiple light spots. This severely limits the application scope of the position-sensitive detector. Therefore, when performing multi-light spot positioning, an electric-coupled camera or a CMOS image sensor is often used as the main detection device. However, there is an inverse relationship between the imaging frame rate and the resolution during the operation of these two detectors. Therefore, it is difficult to accurately track a high-speed moving object. In addition, the data types output by the electric-coupled camera and the CMOS image sensor are graphic information, and additional subsequent processing is required to obtain the motion information of the target, which restricts the existing system in terms of target positioning speed, positioning accuracy, and real-time processing ability. Summary of the Invention

[0003] Object of the Invention: To solve the problem that a single position-sensitive detector cannot achieve multi-target tracking, the present invention discloses a non-pixelated multi-target detection system and method based on a position detector, which uses a high-speed position-sensitive detector to locate or track multiple target light sources, and improves the flexibility and adaptability of the target tracking system through a frequency-related processing method.

[0004] Technical Solution: A non-pixelated multi-target detection system based on a position detector includes: a high-frequency flashing light source, a position-sensitive detector, and an imaging lens; the high-frequency flashing light source is placed at the front end of the imaging lens, so that the high-frequency flashing light source projects onto the working area of the position-sensitive detector;

[0005] The high-frequency flashing light source is used to project a set of changing patterns composed of multiple light spots onto the working area of the position-sensitive detector. At each moment, only one light spot in the high-frequency flashing light source emits light, and the other light spots do not emit light; the duration of a single light spot signal satisfies:

[0006] Duration of a single light spot signal × Total number of light spots < Threshold time

[0007] Determine the abscissa and ordinate of the currently emitting light spot according to the electrical signal generated by the position-sensitive detector.

[0008] Furthermore, the high-frequency flashing light source includes: a main PCB, a single-chip microcomputer control circuit, and multiple light-emitting diode units; the single-chip microcomputer control circuit and multiple light-emitting diode units are soldered on the main PCB and the circuit connections of each component are realized, and the single-chip microcomputer control circuit is used to turn on or off the light-emitting diode units at specific positions.

[0009] Furthermore, the position-sensitive detector includes: a position-sensitive area as the working area and two sets of orthogonally distributed electrodes; when the high-frequency flashing light source projects onto the working area of the position-sensitive detector, the two sets of orthogonally distributed electrodes generate electrical signals.

[0010] Furthermore, the position-sensitive area consists of a substrate and a position-sensitive material disposed on the upper surface of the substrate, and the position-sensitive material forms an electrical contact with the substrate.

[0011] Furthermore, determining the abscissa and ordinate of the currently emitting light spot according to the electrical signal generated by the position-sensitive detector is expressed as:

[0012]

[0013] In the formula, x is the projection position of the high-frequency flashing light source, λ n is the diffusion distance, n 0 is the initial carrier concentration in the substrate, K is a constant, and L is the distance between the electrodes in the same set of orthogonal electrodes.

[0014] The present invention discloses a non-pixelated multi-target detection method based on a position detector, including the following steps:

[0015] Place the high-frequency flashing light source at the front end of the imaging lens so that the high-frequency flashing light source projects onto the working area of the position-sensitive detector;

[0016] The high-frequency flashing light source projects a set of changing patterns composed of multiple light spots onto the working area of the position-sensitive detector. At each moment, only one light spot in the high-frequency flashing light source emits light, and the rest of the light spots do not emit light; the duration of the single light spot signal satisfies:

[0017] Duration of single light spot signal × Total number of light spots < Threshold time

[0018] Determine the abscissa and ordinate of the currently emitting light spot according to the electrical signal generated by the position-sensitive detector to achieve target detection.

[0019] Further, the high-frequency flashing light source includes: a main body PCB, a single-chip microcomputer control circuit, and multiple light-emitting diode units; the single-chip microcomputer control circuit and the multiple light-emitting diode units are soldered on the main body PCB to realize the circuit connection of each component, and the single-chip microcomputer control circuit is used to turn on or off the light-emitting diode units at specific positions.

[0020] Further, the position-sensitive detector includes: a position-sensitive area serving as the working area and two groups of orthogonally distributed electrodes; when the high-frequency flashing light source projects onto the working area of the position-sensitive detector, the two groups of orthogonally distributed electrodes generate electrical signals.

[0021] Further, based on the electrical signals generated by the position-sensitive detector, the abscissa and ordinate of the currently emitting light spot are determined, expressed as:

[0022]

[0023] In the formula, x is the projection position of the high-frequency flashing light source, λ n is the diffusion distance, n 0 is the initial carrier concentration in the substrate, K is a constant, and L is the distance between the electrodes in the same group of orthogonal electrodes.

[0024] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0025] (1) The present invention uses a position-sensitive detector with fast photoelectric response and a high-frequency flashing light source to realize the method of multi-target trajectory tracking. By combining the fast light response of the position-sensitive detector and the high-frequency flashing light source, the positioning and tracking of multiple light spots are realized simultaneously;

[0026] (2) The method of the present invention has unique advantages and broad application prospects in the fields of real-time motion capture, autonomous driving, and machine vision compared with CMOS image sensors or charge-coupled cameras. Description of the Drawings

[0027] Figure 1 is a schematic diagram of a non-pixelated multi-target detection system based on a position detector proposed by the present invention;

[0028] Figure 2 is a schematic structural diagram of the position-sensitive detector proposed by the present invention;

[0029] Figure 3 is a schematic structural diagram of the high-frequency flashing light source used in Embodiment 1;

[0030] Figure 4 is a schematic diagram of the light response characteristics of the position-sensitive detector to the high-frequency flashing light source;

[0031] Figure 5 Schematic diagram of the optical response characteristics of the position-sensitive detector for Example 1;

[0032] Figure 6 Schematic diagram of the structure of the high-frequency flashing light source used in Example 2;

[0033] Figure 7 Schematic diagram of the optical response characteristics of the position-sensitive detector for Example 2. Specific implementation manners

[0034] To make the objectives, technical solutions, and advantages of the present invention clearer, the following will further describe a non-pixelated multi-target detection system and method based on a position detector proposed by the present invention in conjunction with the accompanying drawings and embodiments.

[0035] Example 1:

[0036] This example proposes a non-pixelated multi-target detection method based on a position detector to achieve the positioning and tracking of multiple targets and multiple light sources, which mainly includes:

[0037] Prepare or select a position-sensitive detector, such as Figure 2 As shown, the position-sensitive detector includes: a substrate, a position-sensitive material, and two sets of orthogonally distributed electrodes. The substrate is made of a material that absorbs light. The position-sensitive material is placed on the upper surface of the substrate. The two sets of orthogonally distributed electrodes form an electrical contact with the position-sensitive material. The substrate used in this example is a silicon substrate or a germanium substrate. The position-sensitive material is silicon, amorphous silicon, graphene channel material, or gallium arsenide channel material. Among the two sets of orthogonally distributed electrodes, the length range of each electrode is 10 nm to 10 cm, and the bias voltage applied to the electrodes ranges from 0 mV to 10 V. The position-sensitive detector prepared in this example has a fast optical response time, that is, the voltage or current signal of the detector reaches the peak within 10 ms after being illuminated.

[0038] Objectively, the position-sensitive detector prepared or selected in this example needs to respond to the optical signal of the high-frequency flashing light source and needs to have a fast optical response time, that is, the duration of a single light spot signal × the total number of light spots < the threshold time. Therefore, in order to achieve this purpose, the position-sensitive detector is designed (including the structure of the position-sensitive detector and the material characteristics of the position-sensitive area) to have a high-speed optical response time. Since this example mainly introduces the target detection method rather than the specific position detection device, the specific device structure, material characteristics, and physical mechanisms are not described, but only a device performance requirement suitable for this detection method is proposed.

[0039] Prepare or select a high-frequency flashing light source, which is composed of multiple independent and controllable LED or laser light sources and can generate multiple light points. Perform corresponding switching, pointing, and light intensity control processing according to the importance, purpose, and type characteristics of the detected target. The high-frequency flashing light source can be an independent structure, or the high-frequency flashing light source can be placed on the detected target. The high-frequency flashing light source can also be the light source reflected by projecting onto the surface of the detected object;

[0040] Prepare or select an imaging system for projecting the high-frequency flashing light source completely onto the surface of a high-speed position-sensitive detector. Using the following formula, the relationship between the signal of the position-sensitive detector and the position projected by the light source is given:

[0041]

[0042] In the formula, x is the position projected by the high-frequency flashing light source, λ n is the diffusion distance, n 0 is the initial carrier concentration in the substrate, K is a constant, and L is the distance between the electrodes among the same group of orthogonal electrodes of the position-sensitive detector.

[0043] Although it can be known from the above formula that the electrical signal measured by a single electrode shows an exponential decay trend with distance, and the signal difference between the symmetric electrodes shows a linear relationship with the position projected by the high-frequency flashing light source, it can therefore be used for position detection.

[0044] Set the duration of the single light point signal of the high-frequency flashing light source to satisfy:

[0045] Duration of single light point signal × Total number of light points < Threshold time

[0046] The value of the threshold time is determined according to the specific application scenario.

[0047] Now, perform high-speed and high-resolution trajectory tracking on a group of moving targets with a total of 20 target light points. As Figure 1 shown, use a high-frequency flashing light source 1 with an independent structure, an imaging lens 2, and a high-speed position-sensitive detector 3; the high-frequency flashing light source 1 is placed at the front end of the imaging lens 2 and projects the high-frequency flashing light source 1 completely into the working area of the high-speed position-sensitive detector 3.

[0048] The high-speed position-sensitive detector in this embodiment is as Figure 2 shown. Use a silicon-based high-speed position-sensitive detector with a detection area of 14 mm × 14 mm. It mainly includes: a position photosensitive area 4, an upper orthogonal electrode 5, a left orthogonal electrode 6, a right orthogonal electrode 7, and a lower orthogonal electrode 8; when the light spot irradiates the position photosensitive area 4, the upper orthogonal electrode 5, the left orthogonal electrode 6, the right orthogonal electrode 7, and the lower orthogonal electrode 8 respectively output voltages Vy1 , V x1 , V x2 , V y2 , the horizontal position coordinate and the vertical position coordinate projected by the high-frequency flashing light source 1 are expressed as:

[0049]

[0050] The high-frequency flashing light source adopted in this embodiment is as Figure 3 shown. This is a light source form with an independent structure, which mainly includes: a main body PCB 9, a single-chip microcomputer control circuit 10 and a light-emitting diode (LED) unit 11; the single-chip microcomputer control circuit 10 and the 10×10-sized light-emitting diode unit 11 are soldered on the main body PCB 9, and the circuit connections of each component are realized. Through the control of the single-chip microcomputer program, the lighting 12 and turning off 13 of a specific position and a specific light-emitting diode unit 11 are realized.

[0051] Through the single-chip microcomputer control circuit 10, the pattern of the high-frequency flashing light source is set as follows: the high-frequency flashing light source projects a set of changing patterns composed of 20 light points. At any moment, only one light point in the high-frequency flashing light source is in the working state, and the rest of the light points do not emit light. The formation of the pattern is achieved through the rapid switching and coordination between light points. The switching frequency of the light points is 2800 Hz, that is, the residence time of each light point is about 360 μs. In this embodiment, the light response time of the high-speed position-sensitive detector is 16 μs. The light response characteristics of the position-sensitive detector to the high-frequency flashing light source are as Figure 4 shown. It can reach the peak value during the light source information duration and realize the accurate detection and tracking of the light source information; if another non-high-speed position-sensitive detector is used, that is, the response time is greater than 360 μs, then the device does not meet the speed requirement of the light response ( Figure 4 shown by the short dash line), so the function described in this embodiment cannot be realized.

[0052] In this embodiment, the electrical signals generated by the high-speed position-sensitive detector are as Figure 5 shown, which respectively represent the abscissa and ordinate of the light point at this time, so the light point can be positioned. Due to the extremely fast light response speed of the high-speed position-sensitive detector, the flashing process of the high-frequency flashing light source can be clearly captured. The high-frequency flashing light source completed the process of gradually transitioning from an 'X' shape to a 'diamond' shape within 30 milliseconds, and this process includes 3 intermediate frames.

[0053] The duration of a single light point signal × 20 < threshold time

[0054] Among them, the threshold time is the maximum frame duration of consecutive images that the human eye can perceive. The human eye requires a minimum of 24 frames per second for a smooth image, so the maximum frame duration of consecutive images is 41.67 milliseconds. It can be obtained that the duration of a single light spot in the high-frequency flashing light signal should be less than 2.1 milliseconds at this time. This result shows that the movement trends of these 20 light spots are completely captured and recorded by the high-speed position-sensitive detector, and continuous capture at 143 frames per second is achieved. This result far exceeds the 60 Hz refresh rate of ordinary displays.

[0055] Embodiment 2:

[0056] Now, a non-pixelated multi-target detection method based on a position detector proposed in Embodiment 1 is applied to track the trajectory of a human target. The specific operations include:

[0057] As Figure 6 shown, the high-frequency flashing light source 1 is placed on the target to be measured and at the front end of the imaging lens 2, and the high-frequency flashing light source 1 is completely projected onto the working area of the high-speed position-sensitive detector 3.

[0058] The electrical signals generated by the high-speed position-sensitive detector in this embodiment are as Figure 7 shown, which respectively represent the abscissa and ordinate of the light spot at this time, so the light spot can be positioned. Since the light response speed of the high-speed position-sensitive detector is extremely fast, the process of the high-frequency flashing light source flashing can be clearly captured. The high-frequency flashing light source completes the capture of human movements within 20 milliseconds.

[0059] Single light spot signal duration × 15 < 20 (milliseconds)

[0060] This result shows that the movement trend of the person is completely captured and recorded by the high-speed position-sensitive detector, and continuous capture at 50 frames per second is achieved.

Claims

1. A non-pixelated multi-target detection system based on a position detector, characterized in that: include: A high-frequency flickering light source, a position-sensitive detector and an imaging lens; the high-frequency flickering light source is placed at the front end of the imaging lens so that the high-frequency flickering light source is projected onto the working area of ​​the position-sensitive detector; The high-frequency flickering light source is used to project a set of changing patterns consisting of multiple light spots to the working area of ​​the position sensitive detector. At each moment, only one light spot in the high-frequency flickering light source emits light, and the other light spots do not emit light; the duration of a single light spot signal satisfies: Single light spot signal duration × total number of light spots < threshold time According to the electrical signal generated by the position sensitive detector, the horizontal and vertical coordinates of the current luminous light spot are determined.

2. The non-pixelated multi-target detection system based on position detector according to claim 1, characterized in that: The high-frequency flashing light source includes: a main body PCB, a single-chip control circuit and a plurality of light-emitting diode units; the single-chip control circuit and the plurality of light-emitting diode units are welded on the main body PCB, and the circuit connection of each component is realized, and the light-emitting diode unit at a specific position is lit or turned off by using the single-chip control circuit.

3. The non-pixelated multi-target detection system based on position detector according to claim 1, characterized in that: The position sensitive detector comprises: a position photosensitive area as a working area and two groups of orthogonally distributed electrodes; when a high-frequency flickering light source is projected onto the working area of ​​the position sensitive detector, the two groups of orthogonally distributed electrodes generate electrical signals.

4. The non-pixelated multi-target detection system based on position detector according to claim 3, characterized in that: The position sensitive region is composed of a substrate and a position sensitive material arranged on the upper surface of the substrate, and the position sensitive material forms an electrical contact with the substrate.

5. The non-pixelated multi-target detection system based on position detector according to claim 3, characterized in that: The abscissa and ordinate of the current luminous spot are determined according to the electrical signal generated by the position sensitive detector, which is expressed as: Where x is the projection position of the high-frequency flickering light source, λ n is the diffusion distance, n0 is the initial carrier concentration in the substrate, K is a constant, and L is the distance between electrodes in the same set of orthogonal electrodes.

6. A non-pixelated multi-target detection method based on a position detector, characterized in that: The following steps are involved: A high-frequency flickering light source is placed at the front end of the imaging lens so that the high-frequency flickering light source is projected onto the working area of ​​the position sensitive detector; The high-frequency flickering light source projects a set of changing patterns consisting of multiple light spots to the working area of ​​the position sensitive detector. At each moment, only one light spot in the high-frequency flickering light source emits light, and the other light spots do not emit light; the duration of a single light spot signal satisfies: Single light spot signal duration × total number of light spots < threshold time According to the electrical signal generated by the position sensitive detector, the horizontal and vertical coordinates of the current luminous light spot are determined to achieve target detection.

7. The non-pixelated multi-target detection method based on position detector according to claim 6, characterized in that: The high-frequency flashing light source includes: a main body PCB, a single-chip control circuit and a plurality of light-emitting diode units; the single-chip control circuit and the plurality of light-emitting diode units are welded on the main body PCB, and the circuit connection of each component is realized, and the light-emitting diode unit at a specific position is lit or turned off by using the single-chip control circuit.

8. The non-pixelated multi-target detection method based on position detector according to claim 6, characterized in that: The position sensitive detector comprises: a position photosensitive area as a working area and two groups of orthogonally distributed electrodes; when a high-frequency flickering light source is projected onto the working area of ​​the position sensitive detector, the two groups of orthogonally distributed electrodes generate electrical signals.

9. The non-pixelated multi-target detection method based on position detector according to claim 8, characterized in that: The abscissa and ordinate of the current luminous spot are determined according to the electrical signal generated by the position sensitive detector, which is expressed as: Where x is the projection position of the high-frequency flickering light source, λ n is the diffusion distance, n0 is the initial carrier concentration in the substrate, K is a constant, and L is the distance between electrodes in the same set of orthogonal electrodes.

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