Low noise front end for LiDAR receiver and method for controlling the same

Abstract

A light signal detection system is disclosed, which includes a plurality of photodetectors configured to detect light signals reflected from an environment surrounding the light signal detection system and convert the light signals into electrical signals. The light signal detection system also includes an amplifier coupled to the plurality of photodetectors. The amplifier is shared by the plurality of photodetectors and is configured to generate an output signal by amplifying a single electrical signal converted by a corresponding photodetector. The light signal detection system also includes a multiplexing circuit configured to selectively establish a connection between one of the plurality of photodetectors and the amplifier to amplify the electrical signal converted by the photodetector.

Description

Technical Field

[0001] The present disclosure relates to an optical signal detection device such as a light detection and ranging (LiDAR) device, and more particularly, to a low noise amplifier for amplifying an electrical signal converted from an optical signal detected by the optical signal detection device. Background Art

[0002] Light signal detection systems such as LiDAR systems have been widely used in autonomous driving and making high-definition maps. For example, a typical LiDAR system measures the distance to a target by illuminating the target with a pulsed laser and measuring the reflected pulses with a sensor such as a photodetector. The laser return time difference and / or wavelength difference and / or phase difference can then be used to make a digital three-dimensional (3D) representation of the target. The laser used for LiDAR scanning can be ultraviolet, visible light, or near-infrared. Since the use of a narrow laser beam as the incident light can map physical features with very high resolution, LiDAR systems are particularly suitable for applications such as sensing in autonomous driving and / or high-definition map surveys.

[0003] Optical signals such as lasers detected by a LiDAR system can be converted into electrical signals by, for example, photodetectors, and then processed by other components of the LiDAR system. The electrical signals generated by photodetectors are typically very small and need to be amplified. When multiple photodetectors are used, conventional LiDAR systems use multiple amplifiers, such as one amplifier for each photodetector, to amplify these electrical signals. Using multiple amplifiers is costly and may cause other problems, such as high power consumption, large footprint, and inconsistencies between different amplifiers. Efforts to reduce the number of amplifiers have been unsuccessful because sharing an amplifier between multiple photodetectors is a challenge. For example, the noise associated with switching between different photodetectors is typically too high compared to the electrical signal that needs to be amplified.

[0004] Embodiments of the present disclosure solve the above-mentioned problems by providing a low noise amplifier shared by a plurality of photodetectors or a low noise multi-channel amplifier used in an optical signal detection system. Summary of the invention

[0005] An embodiment of the present disclosure provides an optical signal detection system. The optical signal detection system includes a plurality of photodetectors, which are configured to detect optical signals reflected from the environment surrounding the optical signal detection system and convert the optical signals into electrical signals. The optical signal detection system also includes an amplifier coupled to the plurality of photodetectors, wherein the amplifier is shared by the plurality of photodetectors and is configured to generate an output signal by amplifying a single electrical signal converted by the corresponding photodetector. The optical signal detection system also includes a multiplexing circuit, which is configured to selectively establish a connection between one of the plurality of photodetectors and the amplifier to amplify the electrical signal converted by the photodetector.

[0006] Embodiments of the present disclosure also provide a method for processing optical signals. The method includes detecting optical signals reflected from the environment surrounding the optical signal detection system by multiple photodetectors and converting the optical signals into electrical signals by the photodetectors. The method also includes selectively establishing a connection between one of the multiple photodetectors and an amplifier by a multiplexing circuit. The amplifier is coupled to the multiple photodetectors and is shared by the multiple photodetectors. The method also includes generating an output signal by the amplifier by amplifying a single electrical signal converted by the photodetector connected to the amplifier.

[0007] An embodiment of the present disclosure also provides a multi-channel operational amplifier circuit. The multi-channel operational amplifier circuit includes multiple input channels, and the multiple input channels are configured to receive input signals generated by multiple photodetectors. The multi-channel operational amplifier also includes an amplification unit, which is coupled to the multiple photodetectors through the multiple input channels. The amplification unit is shared by the multiple input channels and is configured to generate an output signal by amplifying a single input signal received by the corresponding input channel. The multi-channel operational amplifier circuit also includes a multiplexing circuit, which is configured to select one of the multiple input channels for the amplification unit to amplify the input signal received by the selected input channel.

[0008] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 A schematic diagram showing an exemplary vehicle equipped with a LiDAR optical signal detection system according to an embodiment of the present disclosure.

[0010] Figure 2 A block diagram of an exemplary LiDAR optical signal detection device having a transmitter and a receiver according to an embodiment of the present disclosure is shown.

[0011] Figure 3A circuit diagram showing an exemplary optical signal detection circuit with a shared amplifier according to an embodiment of the present disclosure.

[0012] Figure 4A A circuit diagram showing an exemplary optical signal detection circuit with a multi-channel amplifier according to an embodiment of the present disclosure.

[0013] Figure 4B A circuit diagram showing another exemplary optical signal detection circuit with a multi-channel amplifier according to an embodiment of the present disclosure is shown.

[0014] Figure 5 A circuit diagram of an exemplary optical signal detection circuit with a multi-channel amplifier and a feedback network according to an embodiment of the present disclosure is shown.

[0015] Figure 6 A circuit diagram is shown of an exemplary optical signal detection circuit with a multi-channel amplifier for voltage sensing according to an embodiment of the present disclosure.

[0016] Figure 7 A flow chart showing an exemplary method for processing an optical signal according to an embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0017] Reference will now be made in detail to these exemplary embodiments, examples of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts.

[0018] An optical signal detection system such as a LiDAR system may use multiple detectors, such as a photodetector or a photodetector array, to detect an optical signal (e.g., a laser) reflected by an object. For example, a photodetector may convert an optical signal into an electrical signal such as a current signal or a voltage signal. The electrical signal may be amplified by an amplifier such as a transimpedance amplifier (TIA). To ensure a certain level of signal-to-noise ratio (SNR), the amplifier should have low noise. For example, the electrical signal to be amplified should not be less than the noise floor of the amplifier. A typical approach is to use multiple amplifiers (one for each photodetector) to amplify the electrical signal, and then use a multiplexer to select one of the amplified electrical signals to the output. However, this approach is subject to high power consumption, large footprint, and high material cost due to the use of a large number of amplifiers. Moreover, due to the large signal swing at the output of each amplifier, the requirements for the linearity of the multiplexer are usually strict.

[0019] Embodiments of the present disclosure provide an improved optical signal detection system having a low noise amplifier shared by multiple photodetectors to reduce the number of amplifiers required for a receiver front end (e.g., the portion of a receiver that converts an optical signal into an electrical signal and then amplifies it for subsequent processing). For example, the amplifier can be selectively connected to a single photodetector via a multiplexing circuit so that it is shared by multiple photodetectors. In another example, the amplifier can take the form of a multi-channel amplifier capable of receiving electrical signals from multiple connected photodetectors (e.g., from one photodetector at a time). Either way, the number of amplifiers required to amplify the electrical signal can be greatly reduced, thereby reducing material costs and reducing power consumption and device footprint.

[0020] Figure 1 A schematic diagram of an exemplary vehicle 100 equipped with a LiDAR optical signal detection system 102 (or simply LiDAR system 102) according to an embodiment of the present disclosure is shown. Consistent with some embodiments, the vehicle 100 may be an autonomous vehicle or a survey vehicle configured to acquire data for building high-definition maps or 3D building and city modeling.

[0021] like Figure 1 As shown, the vehicle 100 can be equipped with a LiDAR system 102 mounted to the body 104 via a mounting structure 108. The mounting structure 108 can be an electromechanical device mounted or otherwise attached to the body 104 of the vehicle 100. In some embodiments of the present disclosure, the mounting structure 108 can use screws, adhesives, or another mounting mechanism. The vehicle 100 can additionally be equipped with sensors 110 inside or outside the body 104 using any suitable mounting mechanism. The sensors 110 can include sensors used in navigation units, such as a global positioning system (GPS) receiver and one or more inertial measurement unit (IMU) sensors. It is contemplated that the manner in which the LiDAR system 102 or sensor 110 can be mounted on the vehicle 100 is not limited to Figure 1 The examples shown may be modified specifically depending on the type of LiDAR system 102 and sensor 110 and / or vehicle 100 to achieve desired sensing performance.

[0022] As with some embodiments, the LiDAR system 102 and the sensor 110 may be configured to capture data as the vehicle 100 moves along a track. For example, the transmitter of the LiDAR system 102 is configured to scan the surroundings and acquire a point cloud. The LiDAR system 102 may include one or more LiDAR sensing devices configured to measure the distance to a target by illuminating the target with a pulsed laser beam and measuring the reflected pulses with a receiver. The laser beam used by the LiDAR system 102 may be ultraviolet, visible, or near infrared. In some embodiments of the present disclosure, the LiDAR system 102 may capture a point cloud. The LiDAR system 102 may capture data continuously as the vehicle 100 moves along a track. Each set of data captured within a certain time frame is referred to as a data frame.

[0023] Figure 2 A block diagram of an exemplary LiDAR optical signal detection device 200 (or simply LiDAR device 200), such as a LiDAR optical signal detection device used in LiDAR system 102, is shown. LiDAR device 200 may include a transmitter 202 and a receiver 204. As transmitter 202 moves (e.g., rotates, swings, etc.), the transmitter may emit a laser beam within a scanning angle. Transmitter 202 may include one or more laser sources 206 and a scanner 210. In some embodiments, laser source 206 and scanner 210 may be separate devices or components. In other embodiments, laser source 206 and scanner 210 may be integrated into a single device / component.

[0024] In some embodiments, the emitter 202 may emit a series of pulsed laser beams in different directions within its scanning angle as it moves (e.g., rotates, swings, etc.). Figure 2 As shown. The laser source 206 can be configured to provide a laser beam 207 (also referred to as a "native laser beam") to the scanner 210 in a corresponding incident direction. In some embodiments, the laser source 206 can be disposed within the scanner 210 or integrated with the scanner 210 (for example, the scanner 210 forms a rotator for scanning the environment). In some embodiments of the present disclosure, the laser source 206 can generate a pulsed laser beam in the ultraviolet, visible, or near infrared wavelength range.

[0025] In some embodiments of the present disclosure, the laser source 206 may include a pulsed laser diode (PLD), a vertical cavity surface emitting laser (VCSEL), a fiber laser, etc. For example, the PLD may be a semiconductor device that generates a laser beam at the junction of a diode similar to a light emitting diode (LED). In some embodiments of the present disclosure, the PLD includes a PIN diode, in which the active region is located in the intrinsic (I) region, and carriers (electrons and holes) are pumped into the active region from the N region and the P region, respectively. Depending on the specific semiconductor material, the wavelength of the incident laser beam 207 provided by the PLD may be less than 1,100 nm, such as 405 nm, between 445 nm and 465 nm, between 510 nm and 525 nm, 532 nm, 635 nm, between 650 nm and 660 nm, 670 nm, 760 nm, 785 nm, 808 nm, or 848 nm. It should be understood that any suitable laser source may be used as the laser source 206 that emits the laser beam 207.

[0026] The scanner 210 can be configured to emit a laser beam 209 toward the object 212 in a first direction. In some embodiments, when a scanner (e.g., a MEMS scanner) is not used or when a rotator scanner is integrated with the laser source 206, the laser beam 209 can be the same as the laser beam 207. The object 212 can be made of a variety of materials, including, for example, non-metallic objects, rocks, rain, compounds, aerosols, clouds, and even single molecules. The wavelength of the laser beam 209 can vary depending on the composition of the object 212. In some embodiments, at each time point during the scan, the scanner 210 can emit the laser beam 209 toward the object 212 in a certain direction within the scanning angle by rotating the micromechanical mirror assembly and rotating the moving part 200, because the incident angle of the incident laser beam 207 can be fixed. In some embodiments of the present disclosure, the scanner 210 can also include an optical component (e.g., a lens, a mirror, etc.) capable of focusing the pulsed laser into a narrow laser beam to increase the scanning resolution and the range of the scanned object 212.

[0027] In some embodiments, receiver 204 can be configured to detect a returning laser beam 211 returning from object 212. Returning laser beam 211 can be in a different direction than beam 209. Receiver 204 can collect the laser beam returning from object 212 and output an electrical signal reflecting the intensity of the returning laser beam. Upon contact, the laser light can be reflected by object 212 through backscattering, such as Rayleigh scattering, Mie scattering, Raman scattering, and fluorescence. Figure 2As shown, receiver 204 may include lens 214 and photodetector 216. Lens 214 may be configured to collect light from various directions in its field of view (FOV). At each time point during the scan, return laser beam 211 may be collected by lens 214. Return laser beam 211 may be returned from object 212 and have the same wavelength as laser beam 209.

[0028] The photodetector 216 may be configured to detect a returning laser beam 211 returning from the object 212. In some embodiments, the photodetector 216 may convert the laser light (e.g., the returning laser beam 211) collected by the lens 214 into an electrical signal 218 (e.g., a current or voltage signal). The electrical signal 218 is generated when a photon is absorbed into a photodiode included in the photodetector 216. In some embodiments of the present disclosure, the photodetector 216 may include a PIN detector, a PIN detector array, an avalanche photodiode (APD) detector, an APD detector array, a single photon avalanche diode (SPAD) detector, a SPAD detector array, a silicon photomultiplier tube (SiPM / MPCC) detector, a SiP / MPCC detector array, and the like.

[0029] Although the scanner 210 is described herein as part of the transmitter 202, it should be understood that in some embodiments, the scanner 210 may also be included in the receiver 204, for example, disposed in the optical path before the photodetector 216. Including the scanner 210 in the receiver 204 can ensure that the photodetector 216 only captures light from a desired direction, such as a return laser beam 211, thereby avoiding interference from other light sources, such as the sun and / or other LiDAR systems. By increasing the aperture of the receiver 204, the sensitivity of the photodetector 216 can also be increased.

[0030] In some embodiments, the LiDAR device 200 may include a signal processor 220 configured to process the electrical signal 218. For example, the signal processor 220 may include an analog-to-digital converter to convert the electrical signal 218, which may be an analog signal, into a digital signal. In another example, the signal processor 220 may include one or more filters, noise reducers, signal enhancers, etc. to improve the signal-to-noise ratio (SNR) of the electrical signal 218. The signal processor 220 may include a microprocessor, a digital signal processor (DSP), a microcontroller, a field programmable gate array (FPGA), and / or other suitable devices or chips capable of processing the electrical signal 218.

[0031] Figure 3A circuit diagram of an exemplary optical signal detection circuit 300 with a shared amplifier (eg, TIA) according to an embodiment of the present disclosure is shown. When used in a LiDAR device, the circuit 300 may also be referred to as a LiDAR receiver front end 300 . Figure 3 The circuit 300 shown may be part of the receiver 204 and may be configured for the receiver 204 to process the electrical signal 218 generated based on receiving / detecting the return laser beam 211. In some embodiments, the electrical signal 218 converted by the photodetector 216 of the receiver 204 may be further converted (e.g., from a current signal to a voltage signal) and / or amplified to a larger electrical signal for processing by other parts of the LiDAR device 200. For example, the amplified electrical signal of the electrical signal 218 may be used to generate a point cloud or data frame reflecting the surrounding environment of the LiDAR device 200.

[0032] Unlike a typical multi-channel LiDAR receiver front end in which each channel includes a single amplifier (e.g., TIA), the LiDAR receiver front end 300 can employ a multiplexing circuit (also referred to as a multiplexer) before the common TIA (e.g., the multiplexer is built into the LiDAR receiver front end 300). Since the TIA is connected to the output of the multiplexer, the number of TIAs required is reduced compared to a typical multi-channel LiDAR receiver front end (e.g., only one TIA is shared by all channels). Therefore, the power consumption, system size, and bill of materials of a LiDAR system employing the LiDAR receiver front end 300 can be reduced. Moreover, due to the potential large signal swing at the TIA output, using a multiplexer before the common TIA instead of after each of the multiple TIAs can significantly reduce the requirements for the linearity of the multiplexer.

[0033] like Figure 3 As shown, the LiDAR receiver front end 300 may include a plurality of detectors (e.g., a photodetector array 302), a multiplexer 304, and an operational amplifier 306 (e.g., a TIA operational amplifier). The photodetector array 302 may include a plurality of photodetectors for detecting / receiving reflected laser light (e.g., a return laser beam 211) reflected by the object 212. For example, the photodetector array 302 may include N (e.g., N is greater than 1, 2, 3, 5, 10, 20, etc.) photodetectors arranged in a row or in any suitable manner for detecting the return laser light. The number of photodetectors in the photodetector array 302 may depend specifically on the scanning range and the scanning mechanism of the LiDAR system (e.g., full coaxial or semi-coaxial, etc.).

[0034] The photodetectors in the photodetector array 302 may be configured to detect a return laser beam 211 returning from the object 212. Each photodetector in the photodetector array 302 may convert the return laser light (e.g., the return laser beam 211) collected by the lens 214 into an electrical signal 218 (e.g., a current or voltage signal). For example, when a photon is absorbed into a photodiode of one of the photodetectors, a current signal may be generated. In some embodiments of the present disclosure, each photodetector of the photodetector array 302 may also be an avalanche photodiode (APD), such as a single photon avalanche diode (SPAD) or a photon avalanche diode array, or a silicon photon multiplier (SiPM).

[0035] The multiplexer 304 can be electrically connected to the photodetector array 302 and the operational amplifier 306. In some embodiments, the multiplexer 304 can be an electronic multiplexer or a digital multiplexer that selects among several input signals (e.g., a current input from one of the photodetectors in the photodetector array 302 or a digital input from one of the N input channels) and forwards an output generated based on the selected input to the operational amplifier 306 for subsequent processing, such as amplification of the signal. For example, the multiplexer 304 can establish a connection between the selected photodetector or input channel and the amplifier 306, so that the signal can pass through the multiplexer 304 and reach the input of the amplifier 306. In some other embodiments, the multiplexer 304 can also be a multiple-input single-output switch, in which only one input from the N input channels can be selected and output to the operational amplifier 306 for subsequent processing.

[0036] In some embodiments, operational amplifier 306 may be a DC-coupled high-gain voltage amplifier configured to amplify the differential input V + and V - For example, the output of operational amplifier 306 can be given by equation (1):

[0037] V out =A g *(V + -V - ) (1)

[0038] Among them A g is the gain of operational amplifier 306, (V + -V - ) is the differential input voltage of the operational amplifier 306.

[0039] In some embodiments, operational amplifier 306 may be an open loop amplifier where a very large amplitude A is desired. g(eg, a gain of 100,000). For example, operational amplifier 306 may include a voltage maintained at a reference voltage (eg, V + =0) at the non-inverting input Bias , and the input voltage applied to the inverting input (e.g., the single output of the multiplexer 304) can be amplified to the maximum extent (e.g., the maximum positive value if the input voltage is positive or the maximum negative value if the input voltage is negative). In these embodiments, the operational amplifier 306 can be used as a comparator to compare the electrical signal 218 to 0V.

[0040] In some embodiments, because the electrical signal 218 (e.g., the input to the multiplexer 304) is predictable, the operational amplifier 306 can include negative feedback (disclosed in more detail below) by applying a portion of the output voltage of the operational amplifier 306 to the inverting input using a feedback network. This feedback transforms the operational amplifier into a transimpedance amplifier (TIA). Negative feedback can be used to control gain. For example, the gain A of the TIA g,TIA can be controlled primarily by the design of the feedback network, in this case Rfb. The gain A of the operational amplifier 306 can be given by equation (2): g,TIA :

[0041] A g,TIA =R fb (2)

[0042] In some embodiments, instead of holding the non-inverting input at a reference voltage (e.g., V + =0), the operational amplifier 306 may include a buffer 308 for further controlling and stabilizing the gain A of the operational amplifier 306 g .

[0043] Figure 4A-4B FIG. 1 is a circuit diagram of an exemplary optical signal detection circuit with a multi-channel amplifier according to an embodiment of the present disclosure. Figure 4A As shown, the optical signal detection circuit 400 may include a plurality of input branches 402 arranged in parallel. Each of the plurality of input branches may be coupled to one of the plurality of photodetectors. In some embodiments, each input branch may include an input transistor 404 and a switch 406. The plurality of switches 406 may form a multiplexing circuit that is configured to selectively establish a connection between one of the photodetectors and an amplifier of the circuit 400 (e.g., via the differential input of the input transistor M1). The switch 406 may be configured to control the connection between one of the photodetectors and the amplifier of the circuit 400. For example, when the i-th input branch (M3 ) is turned on, the switch 406 is selected to be coupled to the input transistor M1 The electrical signal converted by the photodetector at the gate end is amplified.

[0044] In one example, if Figure 4A As shown, the input transistor 404 and the switch 406 can be N-type metal oxide semiconductor logic (NMOS) devices. The input transistor 404 can be electrically coupled to one of the photodetectors in the photodetector array 302. The switch 406 can be arranged in series with the input transistor in the input branch. When one of the photodetectors in the photodetector array 302 detects the returning laser beam 211 (e.g., photons reflected by the object 212) returning from the object 212, the receiving photodetector can convert the received photons into an electrical signal 218 (e.g., a current signal and / or a voltage signal) and transmit the electrical signal 218 to the gate terminal of the input transistor 404. When the switch 406 connected in series with the input transistor in the same input branch is turned on, the electrical signal 218 at the gate terminal of the input transistor 404 can be selected for amplification. The switches 406 of the input branch can be turned on one at a time to control the selection of the corresponding input transistor 404, thereby establishing a connection between the corresponding photodetector and the amplifier. In some embodiments, the order in which the different switches 406 are turned on and off is predetermined or pre-programmed based on the scanning mode of the LiDAR device 200 .

[0045] In some embodiments, the optical signal detection circuit 400 may further include a non-inverting input branch 410, which includes at least one NMOS device to generate another input for the operational amplifier 306 (eg, the differential inverting input V + In some embodiments, the circuit 400 may also include an active P-type metal oxide semiconductor logic (PMOS) current mirror load (e.g., Figure 5 For example, the PMOS current mirror load can be configured to convert the differential output of the circuit 400 (eg, the differential current output 408) into a single-ended output.

[0046] Figure 4B Another optical signal detection circuit 400' is shown. Figure 4B As shown, input transistor 404' and switch 406' can be PMOS devices, where input transistor 404' is electrically coupled to one of the photodetectors in photodetector array 302, and switch 406' is electrically coupled to the output of modified N-way input branch 402'. Switch 406' can be arranged in series with the input transistor in the input branch. When one of the photodetectors in photodetector array 302 detects a returning laser beam 211 returning from object 212 (e.g., a photon reflected by object 212), the photodetector can convert the received photon into an electrical signal 218 (e.g., a current signal and / or a voltage signal) and transmit the electrical signal 218 to the gate terminal of input transistor 404', which can be selected for amplification. Figure 4A Similar to the N-channel input of the built-in multiplexer 400 shown, when the switch 406' connected in series with the input transistor in the same input branch is turned on, the electrical signal 218 at the gate terminal of the input transistor 404' can be selected for amplification. The switches 406' of the input branch can be turned on one at a time to control the selection of the corresponding input transistor 404', thereby establishing a connection between the corresponding photodetector and the amplifier. In some embodiments, the order of turning on and off the different switches 406' is predetermined or pre-programmed based on the scanning mode of the LiDAR device 200.

[0047] In some embodiments, the optical signal detection circuit 400' may further include a non-inverting input branch 410', which includes at least one PMOS device to generate another input for the operational amplifier 306 (eg, the differential inverting input V + In some embodiments, the circuit 400' may also include an active NMOS current mirror load (eg, Figure 5 For example, the NMOS current mirror load can be configured to convert the differential output of the circuit 400' (eg, the differential current output 408') into a single-ended output.

[0048] Because the input multiplexing function is achieved without a series switch at the "gate" end of the input transistor 404, each of the N switchable input branches provides the same low noise amplification performance as a conventional single differential input operational amplifier. On one side, the N input branches are connected at the transistor M1 The “source” terminals of the optical signal detection circuit 404 are connected together, which is the low impedance “virtual ground” node of the optical signal detection circuit 404. On the other side, the N input branches are connected in transistor M3. The "drain" terminals of Figure 5 In the illustrated embodiment, this node is connected to a diode-connected PMOS transistor M5, which also provides a low impedance at the connection point. The presence of low impedance nodes on both sides of the N-way input branch makes the impact of multiple parallel branches on the bandwidth of the optical signal detection circuit 400 negligible. Overall, this will reduce noise and improve the signal-to-noise ratio of the circuit 400, thereby improving the overall performance of the optical detection (e.g., LiDAR) system.

[0049] Figure 5 FIG. 5 shows an optical signal detection circuit 500 having a feedback network 502 according to an embodiment of the present disclosure. The feedback network 502 may include a plurality of feedback branches connected in parallel. The plurality of feedback branches may be electrically connected to the inverting input branch 410 (e.g., the differential inverting input V - ) to further control and stabilize the gain A of the operational amplifier 306 g In some embodiments, the feedback network 502 may include a resistor-capacitor network for filtering out undesired signals and N parallel branches, each of which includes a first switch M9 and a second switch M10. In some embodiments, switches M9 and M10 may be at least one of an NMOS or a PMOS device. In some embodiments, switches M9 and M10 may be of the same type (e.g., both M9 and M10 are NMOS or PMOS), or switches M9 and M10 may be of different types (e.g., M9 may be NMOS and M10 may be PMOS or vice versa). For example, each of the N parallel branches is electrically connected to one of the N input channels (e.g., a node at the "gate" terminal of the input transistor 404).

[0050] When the switch 406' connected in series with the input transistor in the same input branch is turned on, the electrical signal 218 at the gate terminal of the input transistor 404' can be selected for amplification. The switches 406 of the input branch can be turned on one at a time to control the selection of the corresponding input transistor 404, thereby establishing a connection between the corresponding photodetector and the amplifier. The switch M9 of the input branch is turned on, and the switch M10 of the input branch is turned off. Thus, a feedback branch is formed for the input branch. On the other hand, the remaining branches of the N-way input channel, whose switches 406 are turned off, the switch M9 of the branch will be closed, and the switch M10 of the branch will be turned on. Thus, the branch with the switch 406 turned off will be divided into keeping the switch M10 of the branch to the ground line, or in some other embodiments, keeping the switch M10 of the branch to the buffer.

[0051] Figure 6 FIG. 6 is a circuit diagram of an exemplary optical signal detection circuit 600 having a multi-channel amplifier for voltage sensing according to an embodiment of the present disclosure. In some embodiments, as Figure 6 As shown, the input from the photodetector of the photodetector array 302 may be a voltage signal. For example, each of the N input channels may include a resistor R in , and the feedback network may include a resistor R Bias By adjusting the resistor R in and R Bias The circuit 600 can convert the voltage signal into a current signal and process the current signal in a manner similar to that disclosed in the above embodiments.

[0052] Figure 7 A flowchart of an exemplary method for processing an optical signal according to an embodiment of the present disclosure is shown. In step S702, an optical signal reflected by the environment around the optical signal detection system (e.g., photons of the returning laser beam 211 reflected by the object 212) may be detected by a plurality of photodetectors of the receiver 204 (e.g., an avalanche photodiode array or a silicon photomultiplier or a photodetector array 302).

[0053] In step S704, the optical signal may be converted into an electrical signal (e.g., a current signal or a voltage signal) by a plurality of photodetectors. For example, when a photon is absorbed in a photodiode of a photodetector, the photodetector array 302 may generate a current. The photodetector array 302 may then transmit the electrical signal (e.g., the electrical signal 218) to a multiplexing circuit (e.g., multiplexer 304) as an input to the multiplexing circuit.

[0054] In step S706, the multiplexing circuit can selectively establish a connection between one of the photodetectors in the photodetector array 302 and an amplifier (e.g., operational amplifier 306). For example, the multiplexing circuit can include a modified N-way input branch and a differential current output that compares a single output of the multiplexing circuit (e.g., a multiple-input single-output circuit) and an inverting input of the amplifier. In some embodiments, each of the N-way input branches can include an input transistor (e.g., a first switch) electrically connected to each of the photodetector array 302, and a second switch for controlling each of the N-way input branches to be turned on and off. The N-way input branches are electrically connected in parallel to each other. A single output of the multiplexing circuit can be used as an input for the operational amplifier 306 (e.g., one of the differential inputs V + ) for subsequent processing.

[0055] In step S708, the electrical signal converted by the selected photodetector (e.g., its switch is turned on) can be amplified by an amplifier to generate an output signal. For example, the amplifier (e.g., operational amplifier 306) can use the output of the multiplexing circuit as one of its non-inverting inputs (e.g., differential non-inverting input V + ), and the other inverting input (e.g., the differential inverting input V-) is held at ground or connected to a buffer for subsequent control and stabilization purposes (e.g., controlling the gain A of the amplifier). g ). The amplifier can then be switched to gain A g Amplifies the differential non-inverting input V + and the inverting input V-.

[0056] In some embodiments, the operational amplifier may be an open loop amplifier where a very large amplitude of A is desired. g (e.g., a gain of 100,000). For example, the operational amplifier may include a V + / V - = 0) The resistor R is kept at the reference voltage Bias , and the input voltage applied to the other input can be amplified to the maximum extent (e.g., the maximum positive value if the input voltage is positive or the maximum negative value if the input voltage is negative). In these embodiments, the amplifier can be used as a comparator to compare the electrical signal generated by the detector (e.g., electrical signal 218) with 0V. In some embodiments, as described above in conjunction with Figure 3 As discussed, the amplifier may be a closed loop amplifier including negative feedback.

[0057] In some embodiments, method 700 may further include feeding the output signal of the amplifier to the output terminal of at least one of the photodetectors when the multiplexing circuit establishes a connection between the at least one of the photodetectors and the amplifier. For example, a feedback network (e.g., feedback network 502) may be electrically connected to one of the N input channels at a low impedance node (e.g., a node at the "source" terminal of an input transistor of the multiplexing circuit) to further control and stabilize the gain A of the amplifier. g . In some embodiments, wherein the feedback network may include a resistor-capacitor network for filtering out undesired signals and N parallel branches, each of which includes a first and a second switch. The first and second switches may be arranged in parallel and connected to a common point connected to a low impedance node (e.g., a node at the "source" end of an input transistor of a multiplexing circuit). In some embodiments, the first and second switches may be at least one of an NMOS or PMOS device. For example, each of the N parallel branches of the feedback network may be electrically connected to one of the N input channels at a low impedance node (e.g., a node at the "source" end of an input transistor of a multiplexing circuit). When the input transistor of one of the N input channels is selected to be turned on (e.g., a connection is established between a corresponding photodetector and an amplifier), the first switch of the branch may be turned on and the second switch of the branch may be turned off. Thus, a feedback branch of the input branch of the branch is formed. On the other hand, the first switches of the remaining branches of the N input channels may be turned off, and the second switches of the branches may be turned on. Thus, the branch is divided into being grounded or connected to a buffer via the second switch of the branch.

[0058] It will be apparent to those skilled in the art that various modifications and variations may be made to the disclosed systems and related methods.Other embodiments will be apparent to those skilled in the art by reference to the specification and practice of the disclosed systems and related methods.

[0059] It is intended that the specification and examples be considered exemplary only, with a true scope being indicated by the following claims and their equivalents.

Claims

1. An optical signal detection system, comprising: a plurality of photodetectors configured to detect light signals reflected from an environment surrounding the light signal detection system and convert the light signals into electrical signals; a transimpedance amplifier coupled to the plurality of photodetectors, wherein the transimpedance amplifier is shared by the plurality of photodetectors and is configured to generate an output signal by amplifying a single electrical signal converted by a corresponding photodetector; a multiplexing circuit configured to selectively establish a connection between one of the plurality of photodetectors and the transimpedance amplifier to amplify an electrical signal converted by the photodetector; and Feedback network, wherein the transimpedance amplifier comprises a plurality of input branches arranged in parallel, each of the plurality of input branches comprises an input transistor, a gate of the input transistor being coupled to one of the plurality of photodetectors, The multiplexing circuit includes a plurality of switches, at least one of the plurality of switches being arranged in one of the plurality of input branches in series connection with an input transistor and configured to control a connection between one of the plurality of photodetectors and the transimpedance amplifier, The feedback network comprises a plurality of feedback branches connected in parallel, at least one of the plurality of feedback branches comprises a pair of switches connected in series, wherein an output terminal of at least one of the photodetectors is connected between the pair of switches, The pair of switches are configured as: feeding back the output signal to an output terminal of at least one of the photodetectors when the multiplexing circuit establishes a connection between at least one of the photodetectors and the transimpedance amplifier; and When the multiplexing circuit does not establish a connection between at least one of the photodetectors and the transimpedance amplifier, an output terminal of at least one of the photodetectors is grounded.

2. The optical signal detection system according to claim 1, wherein: At least one of the plurality of switches includes an N-type metal oxide semiconductor field effect transistor or a P-type metal oxide semiconductor field effect transistor.

3. The optical signal detection system according to claim 1, wherein: The plurality of input branches are connected to a low impedance node of the amplifier.

4. The optical signal detection system according to claim 1, wherein: The electrical signal includes at least one of a voltage signal or a current signal.

5. The optical signal detection system according to claim 1, wherein: The pair of switches includes a first switch connected between the output terminal of the corresponding photodetector and the output terminal of the transimpedance amplifier, and a second switch connected between the output terminal of the photodetector and ground.

6. A method for processing an optical signal, comprising: Detecting, by a plurality of photodetectors, optical signals reflected from the environment surrounding the optical signal detection system; The plurality of photodetectors convert the optical signals into electrical signals; selectively establishing, by a multiplexing circuit, a connection between one of the plurality of photodetectors and a transimpedance amplifier, wherein the transimpedance amplifier is coupled to and shared by the plurality of photodetectors; generating an output signal by the transimpedance amplifier by amplifying a single electrical signal converted by a photodetector connected to the transimpedance amplifier; and The output signal is fed back to the output end of the photodetector connected to the transimpedance amplifier by a feedback network. wherein the transimpedance amplifier comprises a plurality of input branches arranged in parallel, each of the plurality of input branches comprises an input transistor, a gate of the input transistor being coupled to one of the plurality of photodetectors, The multiplexing circuit includes a plurality of switches, at least one of the plurality of switches being arranged in one of the plurality of input branches in series connection with an input transistor and configured to control a connection between one of the plurality of photodetectors and the transimpedance amplifier, The feedback network comprises a plurality of feedback branches connected in parallel, at least one of the plurality of feedback branches comprises a pair of switches connected in series, wherein an output terminal of at least one of the photodetectors is connected between the pair of switches, The pair of switches are configured as: feeding back the output signal to an output terminal of at least one of the photodetectors when the multiplexing circuit establishes a connection between at least one of the photodetectors and the transimpedance amplifier; and When the multiplexing circuit does not establish a connection between at least one of the photodetectors and the transimpedance amplifier, an output terminal of at least one of the photodetectors is grounded.

7. The method according to claim 6, wherein: The plurality of input branches are connected to a low impedance node of the amplifier.

8. A multi-channel operational amplifier circuit comprising: a plurality of input channels configured to receive input signals generated by the plurality of photodetectors; an amplification unit coupled to the plurality of photodetectors via the plurality of input channels, wherein the amplification unit is shared by the plurality of input channels and is configured to generate an output signal by amplifying a single input signal received by a corresponding input channel; a multiplexing circuit configured to select one of the plurality of input channels for the amplification unit to amplify an input signal received by the selected input channel; and Feedback network, wherein the transimpedance amplifier comprises a plurality of input branches arranged in parallel, each of the plurality of input branches comprises an input transistor, a gate of the input transistor being coupled to one of the plurality of photodetectors, The multiplexing circuit includes a plurality of switches, at least one of the plurality of switches being arranged in one of the plurality of input branches in series connection with an input transistor and configured to control a connection between one of the plurality of photodetectors and the transimpedance amplifier, The feedback network comprises a plurality of feedback branches connected in parallel, at least one of the plurality of feedback branches comprises a pair of switches connected in series, wherein an output terminal of at least one of the photodetectors is connected between the pair of switches, The pair of switches are configured as: feeding back the output signal to an output terminal of at least one of the photodetectors when the multiplexing circuit establishes a connection between at least one of the photodetectors and the transimpedance amplifier; and When the multiplexing circuit does not establish a connection between at least one of the photodetectors and the transimpedance amplifier, an output terminal of at least one of the photodetectors is grounded.

9. The multi-channel operational amplifier circuit according to claim 8, wherein: The plurality of input branches are connected to low impedance nodes of the amplification unit.

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