Photoelectric detection device, laser radar including the same, and detection method using the same

Abstract

The present invention provides a photoelectric detection device comprising multiple pixels, at least one of which includes: multiple detectors configured to receive incident light signals and convert them into electrical signals, the multiple detectors having different photon detection efficiencies; and a processing unit coupled to the detectors to receive the electrical signals and configured to process and output the electrical signals. Embodiments of the present invention improve the dynamic range of a laser radar receiver and enhance its performance.

Description

Technical Field

[0001] The present invention generally relates to the field of optoelectronic technology, and in particular to a photoelectric detection device, a laser radar including the photoelectric detection device, and a detection method using the photoelectric detection device. Background Art

[0002] Single-photon detection technology offers the advantages of ultrahigh sensitivity and ultrafast response speed, capable of detecting particles of light with minimal energy, making it a relatively important detection method. The energy of a single photon is extremely small, and detecting single photons requires specialized optoelectronic devices. A single-photon avalanche diode (APD), also known as a Geiger-mode SPAD, specifically refers to an avalanche photodiode (APD) with an operating voltage higher than its breakdown voltage. SPADs, with their high avalanche gain, fast response speed, and low power consumption, are the optimal device for single-photon detection.

[0003] LiDAR can use SPADs arrays as the receiving end. The working principle of SPAD is that SPAD amplifies the photocurrent based on the physical mechanisms of impact ionization and avalanche multiplication, thereby improving the detection sensitivity. Existing SPADs arrays use the method of reducing the area of ​​the photosensitive surface of a single SPAD and increasing the number of SPAD units to improve detection accuracy. Each SPAD unit is connected to a readout circuit and uses a time-to-digital converter (TDC) to obtain the electrical signal. Using this process, the area of ​​each SPAD unit is evenly distributed in a fixed area, and then each SPAD performs TDC signal readout and data processing separately, which is the best effect. However, this makes the back-end TDC and data processing very resource-intensive.

[0004] A common resource-saving approach is to connect multiple SPADs to the same readout circuit to form a pixel. The superimposed signals from multiple SPADs within a pixel are then read out and processed, reducing the number of TDCs and the amount of data processing required. The photon detection efficiency (PDE) of all SPADs in existing SPAD arrays is consistent. However, SPADs are highly sensitive and easily saturated. A large PDE results in a low signal-to-noise ratio in strong ambient light conditions, while a small PDE is detrimental to long-range LiDAR detection. For example, if there are four SPADs in a pixel and the PDE is 5%, it is assumed that 20 photons can cause a SPAD avalanche and output a count. In this case, 80 photons can saturate the entire pixel, and the pixel cannot distinguish even a large number of photons (high light intensity).

[0005] The contents of the background technology section are merely the technologies known to the inventors and do not necessarily represent the existing technologies in this field. Summary of the Invention

[0006] The present invention solves the problem of small dynamic response range of SPADs array as the receiving end of laser radar by changing the area size of the photosensitive surface or the bias voltage loaded to make the dynamic responses of different SPADs inconsistent.

[0007] In view of at least one drawback of the prior art, the present invention provides a photodetection device comprising a plurality of pixels, wherein at least one pixel comprises:

[0008] a plurality of detectors configured to receive incident light signals and convert them into electrical signals, wherein the photon detection efficiencies of the plurality of detectors are not completely the same; and

[0009] The processing unit is coupled to the detector to receive the electrical signal and is configured to process the electrical signal and output the signal.

[0010] According to one aspect of the present invention, the detector is a single-photon avalanche photodiode.

[0011] According to one aspect of the present invention, the photosensitive surface areas of the plurality of detectors are not completely the same.

[0012] According to one aspect of the present invention, the bias voltages applied to the plurality of detectors are not completely the same.

[0013] According to one aspect of the present invention, the at least one pixel further comprises a plurality of bias applying units corresponding to the plurality of detectors, wherein the plurality of bias applying units are coupled to the corresponding detectors and are used to apply unequal bias voltages thereto.

[0014] According to one aspect of the present invention, each of the plurality of pixels comprises:

[0015] a plurality of detectors configured to receive incident light signals and convert them into electrical signals, wherein the photon detection efficiencies of the plurality of detectors are not completely the same;

[0016] The processing unit is coupled to the detector to receive the electrical signal and is configured to process the electrical signal and output the signal.

[0017] According to one aspect of the present invention, the dynamic response ranges of the plurality of pixels are the same.

[0018] The present invention also relates to a laser radar, comprising:

[0019] a transmitting unit configured to transmit a detection laser beam for detecting a target object;

[0020] The photoelectric detection device as described in any one of the above items is configured to receive an echo after the detection laser beam is reflected on the target object.

[0021] The present invention also relates to a method for detection using the photoelectric detection device as described in any one of the above items, comprising:

[0022] emitting a detection laser beam;

[0023] receiving the echo of the detection laser beam after being reflected on the target object through the multiple detectors of the photoelectric detection device and converting it into an electrical signal;

[0024] The processing unit processes the electrical signal and outputs the signal.

[0025] An embodiment of the present invention arranges multiple SPAD units in a pixel, and makes the photon detection efficiency of different SPAD units different by changing the size of the photosensitive surface area or the loaded bias voltage, thereby improving the dynamic response range of a single pixel and the SPADs array, reducing the number of processing units, and thereby reducing the resources and power consumption occupied by data processing, thereby improving the performance of the lidar. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0027] Figure 1 A block diagram of a photoelectric detection device according to an embodiment of the present invention is shown;

[0028] Figure 2 shows a schematic diagram of multiple detectors according to one embodiment of the present invention;

[0029] Figure 3A A circuit diagram for applying a bias voltage to a detector according to an embodiment of the present invention is shown;

[0030] Figure 3B A schematic diagram showing bias voltage loading on multiple detectors according to one embodiment of the present invention is shown;

[0031] Figure 4 shows a block diagram of a laser radar according to one embodiment of the present invention; and

[0032] Figure 5 A flow chart of a detection method of a photoelectric detection device according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0033] Hereinafter, only certain exemplary embodiments are briefly described. As will be appreciated by those skilled in the art, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and description are to be considered as illustrative in nature and not restrictive.

[0034] In the description of the present invention, it should be understood that the terms "center," "longitudinal," "transverse," "length," "width," "thickness," "up," "down," "front," "back," "left," "right," "vertical," "horizontal," "top," "bottom," "inside," "outside," "clockwise," "counterclockwise," and the like, indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely for the purpose of facilitating the description of the present invention and simplifying the description. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation, and therefore should not be construed as limiting the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features indicated. Thus, features defined as "first" or "second" may explicitly or implicitly include one or more of the aforementioned features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0035] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood broadly. For example, they may refer to fixed, removable, or integral connections; mechanical, electrical, or intercommunication connections; direct or indirect connections through an intermediary; and internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0036] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may also include the first and second features not being in direct contact but being in contact via another feature between them. Furthermore, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or diagonally above the second feature, or may simply mean that the first feature is at a higher level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly above or diagonally above the second feature, or may simply mean that the first feature is at a lower level than the second feature.

[0037] The disclosure below provides many different embodiments or examples for realizing different structures of the present invention. In order to simplify the disclosure of the present invention, the components and settings of specific examples are described below. Of course, they are merely examples and are not intended to limit the present invention. In addition, the present invention may repeat reference numbers and / or reference letters in different examples. Such repetition is for the purpose of simplicity and clarity and does not in itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present invention provides examples of various specific processes and materials, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0038] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0039] Figure 1 A block diagram of a photoelectric detection device according to an embodiment of the present invention is shown below. Figure 1 The photodetection device 100 is described in detail. As shown in the figure, the photodetection device 100 includes multiple pixels, such as pixels 101, 102, 103, and 104, wherein at least one pixel includes multiple detectors and a processing unit. Taking pixel 101 as an example, pixel 101 includes detectors 11, 12, and 13, and a processing unit 10. The multiple detectors 11, 12, and 13 form a detector array configured to receive incident light signals and convert them into electrical signals. The photon detection efficiencies of the multiple detectors 11, 12, and 13 are not completely the same. The processing unit 10 is coupled to the detectors 11, 12, and 13, respectively, to receive the electrical signals and is configured to perform signal processing on the electrical signals and output them, such as an analog front-end circuit (AFE). A pixel can be connected to the same AFE and then to the same data processing circuit, such as a time-to-digital converter (TDC), to output a digital signal related to time and photon number. Furthermore, preferably, the photon detection efficiencies of the multiple (three in the figure) detectors of pixel 101 are completely different.

[0040] Pixel 102, pixel 103, and pixel 104 may also include multiple detectors and processing units. For each pixel, the photon detection efficiency of the multiple detectors therein may be the same, or they may be different, as in the case of pixel 101. All of these are within the scope of the present invention. In addition, Figure 1The four pixels 101, 102, 103, and 104 are shown as having respective processing units 10, 20, 30, and 40. It is readily apparent to those skilled in the art that two or more processing units may be integrated together. For example, the photodetection device 100 may preferably include a processing unit having multiple input channels connected to the outputs of the detectors in the pixels 101, 102, 103, and 104, respectively, to process the output electrical signals of the detectors in each pixel simultaneously or in a predetermined time sequence.

[0041] Those skilled in the art will understand that the photoelectric detection device 100 can include more pixels as needed, and each pixel can also include more detectors as needed, for example, 6 or 8 or even dozens to hundreds of detectors. In addition, the number of detectors included in different pixels can be the same or different, which are all within the scope of protection of the present invention.

[0042] According to a preferred embodiment of the present invention, the detector is a single-photon avalanche photodiode (APD). A single-photon avalanche diode (APD), also known as a Geiger-mode SPAD, specifically refers to an avalanche photodiode (APD) with an operating voltage higher than its breakdown voltage. With its high avalanche gain, fast response speed, and low power consumption, SPADs are the optimal device for single-photon detection.

[0043] Figure 2 A schematic diagram of multiple detectors according to one embodiment of the present invention is shown. As shown in pixel 101, it includes four detectors, namely detector 11, detector 12, detector 13, and detector 14. The photosensitive surface areas of the four detectors are not identical. Detectors 11, 12, 13, and 14 each have photosensitive surfaces of different sizes, so the number of photons they receive is not identical, resulting in four different photon detection efficiencies. Detectors with larger photosensitive surfaces (e.g., single-photon avalanche diodes) have relatively higher photon detection efficiencies and are more likely to receive incident photons and generate electrical output signals, facilitating detection in low-light environments. Detectors with smaller photosensitive surfaces have relatively lower photon detection efficiencies and are less likely to receive incident photons and generate electrical output signals, resulting in less saturation and facilitating detection in high-light environments. The different photon detection efficiencies of the detectors within pixel 101 improve the dynamic response range of pixel 101. By varying the photosensitive surface area of ​​each detector within each pixel, the dynamic response range of each pixel can be improved, thereby expanding the dynamic response range of the photoelectric detection device 100.

[0044] According to a preferred embodiment of the present invention, the photosensitive areas of the multiple detectors in each pixel are set to be completely different, for example Figure 2 As shown, the photosensitive surface areas of the detectors 11, 12, 13, and 14 are set to increase in sequence. Increasing the photosensitive surface area is equivalent to increasing the photosensitive surface. Therefore, the photon detection efficiency corresponding to the detector with a large photosensitive surface area is higher. Compared with the solution in the existing process of evenly distributing the area of ​​each SPAD unit and connecting each SPAD to a readout circuit, this embodiment uses multiple SPADs to form a pixel and connects to the same processing unit, which reduces the resources occupied by data processing and is conducive to reducing the power consumption of the laser radar. Compared with the solution in the existing process of multiple SPADs of the same area to form a pixel and connect to a readout circuit, the multiple SPAD photosensitive surfaces in a pixel of this embodiment are different in size, and the corresponding photon detection efficiency is different, so a larger dynamic response range can be obtained within the same pixel area, thereby improving the detection capability of the laser radar.

[0045] In addition to providing multiple detectors with different photosensitive surfaces within a single pixel, the photon detection efficiencies of the detectors can also be made different by applying different bias voltages to the multiple detectors. Figure 3A A circuit diagram showing a bias voltage applied to one of the detectors is shown. Figure 3B A schematic diagram of loading bias voltage on multiple detectors according to an embodiment of the present invention is shown.

[0046] Figure 3A The schematic diagram shows the circuit of a passively quenched detector 11, wherein the detector (single photon avalanche diode, SPAD) 11 is loaded with a voltage greater than the breakdown voltage V BD Bias voltage V bias , V bias The cathode of the SPAD is loaded through the quenching resistor RL, and the anode of the SPAD is grounded through the sampling resistor Rs. The avalanche pulse signal Vout generated by the incident photon is drawn from Rs. Before the photon arrives, the voltage across the SPAD is V bias , in the active state. Once a photon arrives to trigger an avalanche, the instantaneous increase in avalanche current causes a large voltage drop on RL, and the voltage on the SPAD is reduced to V BD Below, the avalanche is quenched; after that, V bias The SPAD is then charged and restored to the active detection state. bias Different photon detection efficiencies can be obtained. Generally, the greater the bias voltage, the higher the photon detection efficiency.

[0047] like Figure 3BAs shown, taking pixel 101 as an example, the pixel 101 includes four detectors, namely detector 11, detector 12, detector 13 and detector 14. By loading bias voltages of different magnitudes on each detector in a pixel in the above manner, the photon detection efficiency of different detectors in each pixel can be increased or decreased respectively, so that the dynamic response range of each pixel of the photoelectric detection device 100 is expanded. Figure 3B In the embodiment, the photosensitive surface areas of the four detectors are set to be the same, and the bias voltages loaded on the four detectors are not exactly the same, so the four detectors have not exactly the same photon detection efficiency, thereby improving the dynamic response range of the pixel 101.

[0048] According to an embodiment of the present invention, the bias voltages loaded on the multiple detectors within each pixel are set to be completely different, and the dynamic response ranges of different pixels can be set to be consistent.

[0049] According to one embodiment of the present invention, in order to apply a bias voltage to the detector, the at least one pixel further includes a plurality of bias application units corresponding to the plurality of detectors, the plurality of bias application units being coupled to the corresponding detectors and configured to apply different bias voltages thereto. The bias application unit may, for example, include a voltage-type digital-to-analog converter that receives a digital pulse sequence and generates an analog voltage output signal based on the digital pulse sequence for providing a bias voltage for the corresponding detector. The plurality of detectors in a pixel may be connected to the same processing unit, such as an analog front-end circuit (AFE), and then to the same data processing circuit, such as a time-to-digital converter (TDC), to output a digital signal related to time and photon number. By providing different bias voltages to the detectors, the photon detection efficiency of each detector in a pixel is different, thereby improving the overall dynamic response range of the pixel.

[0050] According to one embodiment of the present invention, each of the plurality of pixels comprises a plurality of detectors and a processing unit, for example Figure 1 As shown, each of pixel 101, pixel 102, pixel 103, and pixel 104 includes three detectors and a processing unit, wherein the three detectors are respectively coupled to the processing unit. The multiple detectors in each pixel are configured to receive incident light signals and convert them into electrical signals, and the photon detection efficiencies of the multiple detectors are not completely the same. The processing unit is coupled to the detectors to receive the electrical signals and is configured to process and output the electrical signals. According to one embodiment of the present invention, the multiple pixels have the same dynamic response range.

[0051] Two embodiments of changing the dynamic response range of a pixel are described above, which are respectively achieved by making the multiple detectors in the pixel have different photosensitive surface areas and by changing the bias voltage of the detector. Those skilled in the art can also conceive of combining the two schemes together. For example, the interior of each of the multiple pixels can be configured so that the photosensitive surface areas of the multiple detectors are different in size, or the bias voltages applied to the multiple detectors are different in size. It can also be configured so that the photosensitive surface areas of the multiple detectors are different in size and different bias voltages are loaded on them respectively. This can further increase the dynamic response range of each pixel.

[0052] The present invention also relates to a laser radar, such as Figure 4 The block diagram of a laser radar 400 according to an embodiment of the present invention is shown, and the laser radar 400 includes a transmitting unit 410 and the photoelectric detection device 100, wherein the transmitting unit 410 is configured to transmit a detection laser beam L1 for detecting a target object OB; the photoelectric detection device 100 is configured to receive an echo L1' after the detection laser beam L1 is reflected on the target object OB.

[0053] Figure 5 1 is a flow chart showing a detection method of a photoelectric detection device according to an embodiment of the present invention. Figure 4 The photoelectric detection device 100 shown in FIG. detects the target object OB at a certain distance from the photoelectric detection device 100. Figure 5 The detection method 500 of the photoelectric detection device is described in detail. As shown in the figure, the detection method 500 includes the following steps:

[0054] In step S501: emit a detection laser beam. Figure 4 The transmitting unit 410 of the laser radar 400 transmits a detection laser beam L1 to the surrounding environment where the target object OB is located to detect the target object OB.

[0055] In step S502, the multiple detectors of the photoelectric detection device receive the echo of the probe laser beam after it reflects off the target object and convert it into an electrical signal. The probe laser beam emitted in step S501 undergoes diffuse reflection upon encountering the target object OB. The reflected partial echo L1' is received by the multiple detectors of the photoelectric detection device 100, as described above, and the echo signal is converted into an electrical signal.

[0056] In step S503, the processing unit processes the electrical signal and outputs the processed signal, and calculates the number of photons actually detected based on the electrical signal.

[0057] By varying the photosensitive surface area of ​​multiple detectors within at least one pixel of a photodetector and / or the bias voltage applied thereto, the present invention achieves a uniform photon detection efficiency across the various detectors, thereby improving the dynamic response range of the entire photodetection device. Compared to conventional photodetection devices, embodiments of the present invention expand the dynamic response range of the laser radar receiver and enhance the detectability of echo signals.

[0058] When ambient light noise is constant, detectors with high photon detection efficiency are more likely to saturate, while detectors with low photon detection efficiency are less likely to saturate and can still detect valid signals. Detectors with low photon detection efficiency are better for detection in strong light, while detectors with high photon detection efficiency are better for detection in weak light. When ambient light is low, detectors with high photon detection efficiency are more likely to detect valid signals. When ambient light is strong, detectors with high photon detection efficiency are more likely to saturate and fail to detect targets, but detectors with low photon detection efficiency, because they are not saturated, can still detect valid signals. Therefore, using detectors with different photon detection efficiencies to form the pixels of a photoelectric detection device, and then the photoelectric detection device at the LiDAR receiver, can improve the dynamic response range of the photoelectric detection device, thereby enhancing the LiDAR's detection capabilities for targets at different distances under varying ambient light conditions.

[0059] The embodiments of the present invention can measure accurate signals for echoes of different strengths, reduce the influence of ambient light, and improve the detection accuracy of the laser radar.

[0060] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A laser radar comprising: a transmitting unit configured to transmit a detection laser beam for detecting a target object; a photoelectric detection device configured to receive an echo of the detection laser beam after it is reflected on a target object, The photodetection device includes a plurality of pixels, wherein each pixel includes a plurality of detectors, each detector is configured to receive incident photons and convert them into electrical signals, and the photon detection efficiencies of the plurality of detectors within a pixel are not completely the same. The fact that the photon detection efficiencies of the multiple detectors within a pixel are not completely the same includes: the photosensitive surface areas of the multiple detectors within a pixel are not completely the same, and / or the bias voltages applied to the multiple detectors within a pixel are not completely the same. The multiple detectors included in one pixel are connected to the same data processing circuit.

2. The laser radar as claimed in claim 1, wherein the detector is a single photon avalanche photodiode.

3. The laser radar as claimed in claim 1, wherein at least one pixel further comprises a plurality of bias application units corresponding to the plurality of detectors, the plurality of bias application units being coupled to the corresponding detectors and used to apply unequal bias voltages thereto.

4. The laser radar as claimed in claim 1, wherein the dynamic response ranges of the multiple pixels are the same.

5. A method for detection using the laser radar according to any one of claims 1 to 4, comprising: emitting a detection laser beam; receiving the echo of the detection laser beam after being reflected on the target object through the multiple detectors of the photoelectric detection device and converting it into an electrical signal; The electrical signal is processed by a processing unit and outputted.

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