Laser emission circuit and frequency modulation continuous wave laser radar

Abstract

The utility model provides a laser emission circuit and a frequency modulation continuous wave laser radar, and the laser emission circuit comprises a laser, a laser drive circuit, a bias voltage output circuit, a signal output circuit, a current sampling circuit, a beat frequency processing circuit, and an adjusting circuit. The adjusting circuit can obtain the output current of the laser driving circuit through the current sampling circuit, obtain the bandwidth of the optical signal through the beat frequency processing circuit, adjust the bias voltage output by the bias voltage output circuit based on the output current and adjust the amplitude of the triangular wave modulation signal of the signal output circuit based on the optical signal. Therefore, the quiescent current of the laser and the bandwidth of the optical signal are adjusted, the quiescent current of the laser is stabilized at the preset current, the bandwidth of the optical signal is locked at the preset bandwidth, the distance measurement module realizes distance measurement and speed measurement according to the adjusted optical signal, and the precision of laser distance measurement is improved.

Description

Technical Field

[0001] This utility model belongs to the field of lidar technology, and particularly relates to a laser emitting circuit and a frequency-modulated continuous wave lidar. Background Technology

[0002] Frequency-modulated continuous wave laser ranging can achieve high-precision ranging and measurement, and it has a very promising future in lidar ranging and speed measurement.

[0003] Among them, the accuracy and precision of frequency-modulated continuous wave laser ranging depend on the modulation bandwidth. When the modulation frequency is constant, the modulation bandwidth depends on the amplitude of the modulation signal and the wavelength of the laser. The wavelength of the laser is related to the operating current of the laser.

[0004] To improve ranging accuracy, conventional solutions typically adjust the amplitude of the modulation signal based on the bandwidth. This adjustment method is limited and cannot be effectively adjusted when the laser's operating current changes, leading to a decrease in ranging accuracy. Utility Model Content

[0005] The purpose of this invention is to provide a laser emitting circuit that aims to solve the problem of decreased ranging accuracy caused by the single ranging adjustment method in traditional methods.

[0006] A first aspect of this utility model provides a laser emitting circuit, comprising:

[0007] The laser emits an optical signal when triggered by the current driving current.

[0008] The bias voltage output circuit outputs a bias voltage of a corresponding magnitude based on the first adjustment signal.

[0009] The signal output circuit outputs a triangular wave modulated signal of corresponding size, which is subject to the second adjustment signal.

[0010] A laser driving circuit is connected to the bias voltage output circuit, the signal output circuit, and the laser, respectively. The laser driving circuit is used to superimpose the bias voltage and the triangular wave modulation signal to obtain a driving signal, and output the driving current that changes in correlation with the driving signal.

[0011] A current sampling circuit, connected to the laser driving circuit, is used to sample the current output by the laser driving circuit and output a current sampling signal;

[0012] A beat frequency processing circuit is used to acquire a portion of the optical signal from the laser, perform beam splitting and beat frequency processing to generate a beat frequency signal, and convert the beat frequency signal into an electrical signal.

[0013] The adjustment circuit is connected to the bias voltage output circuit, the signal output circuit, the current sampling circuit, and the beat frequency processing circuit, respectively. The adjustment circuit is triggered by the current sampling signal to output a first adjustment signal of a corresponding magnitude, and triggered by the electrical signal to output a second adjustment signal of a corresponding magnitude.

[0014] Optionally, the laser emitting circuit further includes:

[0015] A temperature detection circuit is connected to the adjustment circuit. The temperature detection circuit is used to detect the current ambient temperature and output a temperature detection signal to trigger the adjustment circuit to output a first adjustment signal and / or a second adjustment signal of corresponding magnitude.

[0016] Optionally, the laser driving circuit includes:

[0017] A signal superposition circuit is connected to the bias voltage output circuit and the signal output circuit respectively, and is used to superimpose the bias voltage and the triangular wave modulation signal to obtain the driving signal;

[0018] A driving circuit, connected to the signal superposition circuit and the laser, is used to receive the driving signal and output a driving current of a corresponding magnitude based on the driving signal.

[0019] Optionally, the signal superposition circuit includes a first resistor, a second resistor, a third resistor, a fourth resistor, an operational amplifier, and a Zener diode;

[0020] The first end of the first resistor is used to input the bias voltage, the first end of the second resistor is used to input the triangular wave modulation signal, the second end of the first resistor is connected to the non-inverting input of the operational amplifier, the second end of the second resistor is connected to the inverting input of the operational amplifier, the third resistor is connected between the inverting input of the operational amplifier and the output of the operational amplifier, the operational amplifier is also connected to the first end of the fourth resistor, the second end of the fourth resistor is connected to the cathode of the Zener diode to form the output of the signal superposition circuit, and the anode of the Zener diode is grounded.

[0021] Optionally, the driving circuit includes a fifth resistor and an electronic switching transistor;

[0022] The first end of the fifth resistor is connected to the positive voltage terminal, the second end of the fifth resistor is connected to the first end of the electronic switch, the second end of the electronic switch constitutes the output terminal of the driving circuit, and the control terminal of the electronic switch constitutes the input terminal of the driving circuit.

[0023] Optionally, the beat frequency processing circuit includes:

[0024] The beat frequency optical path is used to acquire a portion of the light signal emitted by the laser and perform beam-splitting beat frequency generation to generate the beat frequency signal;

[0025] A photoelectric conversion circuit, connected to the beat frequency optical path, is used to photoelectrically convert the beat frequency signal into an analog electrical signal;

[0026] An analog-to-digital sampling circuit, connected to the photoelectric conversion circuit and the adjustment circuit, is used to sample the analog electrical signal and convert it into a digital electrical signal.

[0027] Optionally, the beat frequency optical path includes:

[0028] A beam splitter is used to acquire a portion of the optical signal emitted by the laser and split it into a first optical signal and a second optical signal.

[0029] A delay fiber, connected to the beam splitter, is used to input the first optical signal and output it after a delay;

[0030] An optical coupler, connected to the beam splitter and the delay fiber respectively, is used to input the second optical signal and the delayed first optical signal, perform beat frequency analysis, and generate a beat frequency signal.

[0031] Optionally, the photoelectric conversion circuit includes a balance detector, the input terminal and the output terminal of the balance detector constituting the input terminal and the output terminal of the photoelectric conversion circuit, respectively.

[0032] Optionally, the laser is either a DFB laser or a DBR laser.

[0033] A second aspect of this utility model provides a frequency-modulated continuous wave lidar, including a laser receiving circuit and a laser emitting circuit as described above, wherein the laser emitting circuit and the laser receiving circuit are arranged opposite to each other.

[0034] The beneficial effects of this utility model embodiment compared with the prior art are as follows: The above-mentioned laser emitting circuit includes a laser, a laser driving circuit, a bias voltage output circuit, a signal output circuit, a current sampling circuit, a beat frequency processing circuit, and an adjustment circuit. The adjustment circuit can obtain the output current of the laser driving circuit through the current sampling circuit and the bandwidth of the optical signal through the beat frequency processing circuit. Based on the output current, it adjusts the bias voltage output by the bias voltage output circuit and the amplitude of the triangular wave modulation signal of the signal output circuit based on the optical signal, thereby adjusting the static current of the laser and the bandwidth of the optical signal, so that the static current of the laser is stabilized at a preset current and the bandwidth of the optical signal is locked at a preset bandwidth. The ranging module realizes ranging and speed measurement according to the adjusted optical signal, thereby improving the accuracy of laser ranging. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 A schematic diagram of a first type of laser emitting circuit provided in an embodiment of this utility model;

[0037] Figure 2 A schematic diagram of a second mechanism for a laser emitting circuit provided in an embodiment of this utility model;

[0038] Figure 3 A schematic diagram of a third mechanism for a laser emitting circuit provided in an embodiment of this utility model;

[0039] Figure 4 A circuit diagram of the laser driving circuit provided in an embodiment of this utility model;

[0040] Figure 5 A schematic diagram of the beat frequency optical path provided in an embodiment of this utility model;

[0041] Figure 6 A schematic diagram of the mechanism of the frequency-modulated continuous wave lidar provided in this embodiment of the present invention. Detailed Implementation

[0042] To make the technical problems, technical solutions, and beneficial effects of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present utility model and are not intended to limit the present utility model.

[0043] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0044] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0045] 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 technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this utility model, "a plurality of" means two or more, unless otherwise explicitly specified.

[0046] A first aspect of this utility model provides a laser emitting circuit 100.

[0047] like Figure 1 As shown, in this embodiment, the laser emitting circuit 100 includes:

[0048] Laser 10 is triggered by the current driving current to emit an optical signal;

[0049] The bias voltage output circuit 20 outputs a bias voltage of a corresponding magnitude based on the first adjustment signal;

[0050] The signal output circuit 30 outputs a triangular wave modulation signal of corresponding size under the second adjustment signal;

[0051] The laser driving circuit 40 is connected to the bias voltage output circuit 20, the signal output circuit 30 and the laser 10 respectively. The laser driving circuit 40 is used to superimpose the bias voltage and the triangular wave modulation signal to obtain the driving signal, and output the driving current that changes in correlation with the driving signal.

[0052] The current sampling circuit 50 is connected to the laser driving circuit 40 and is used to sample the current output by the laser driving circuit 40 and output a current sampling signal.

[0053] The beat frequency processing circuit 60 is used to acquire part of the optical signal from the laser 10, perform beam splitting and beat frequency processing to generate a beat frequency signal, and convert the beat frequency signal into an electrical signal.

[0054] The adjustment circuit 70 is connected to the bias voltage output circuit 20, the signal output circuit 30, the current sampling circuit 50, and the beat frequency processing circuit 60, respectively. The adjustment circuit 70 is triggered by the current sampling signal to output a first adjustment signal of corresponding magnitude, and triggered by the power signal to output a second adjustment signal of corresponding magnitude.

[0055] In this embodiment, the laser 10 is triggered to emit a linearly frequency-modulated optical signal based on the received drive current. The bandwidth of the optical signal depends on the amplitude of the drive current, which is determined by the bias voltage and triangular wave modulation signal received by the laser drive circuit 40. The amplitude of the drive current is positively correlated with the amplitude of the triangular wave modulation signal, and the static current of the drive current is positively correlated with the bias voltage.

[0056] After the laser emitting circuit 100 is initially powered on, it quickly enters an initial steady state. The bias voltage output circuit 20 outputs an initial bias voltage, and the signal output circuit 30 outputs an initial triangular wave modulation signal. The initial bias voltage and the initial triangular wave modulation signal are superimposed in the laser driving circuit 40 to generate a driving signal. The laser driving circuit 40 also outputs a driving current of corresponding magnitude to the laser 10 according to the driving signal. The laser 10 emits a light signal, and the ranging module obtains the reflected light signal through the laser receiving component. Based on the frequency difference between the emission and reception of the light signal, it determines the distance and speed to be measured, thereby realizing the laser radar ranging function. The type of ranging module is not limited and can be composed of components such as optical receiving elements, photoelectric converters, power amplifiers, and control units.

[0057] The beat frequency processing circuit 60 obtains a beat frequency signal by splitting a portion of the optical signal from the laser 10 and performing beat frequency processing. The magnitude of the beat frequency signal characterizes the bandwidth of the optical signal. The beat frequency processing circuit 60 further performs photoelectric conversion on the beat frequency signal to obtain an electrical signal. Correspondingly, the magnitude of the electrical signal characterizes the bandwidth.

[0058] The current sampling circuit 50 detects the output current of the laser drive circuit 40, thereby sampling the static current of the laser 10, and outputs the current sampling signal to the adjustment circuit 70.

[0059] The adjustment circuit 70 converts and compares the received electrical signal and current sampling signal. It can determine the magnitude of the first adjustment signal and the second adjustment signal through signal comparison and parameter adjustment logic, and output the corresponding first adjustment signal to the bias voltage output circuit 20 and the second adjustment signal to the signal output circuit 30. This changes the magnitude of the bias voltage and the amplitude of the triangular wave modulation signal, thereby changing the bandwidth of the optical signal and stabilizing the optical signal bandwidth at the preset bandwidth, thus improving the ranging accuracy of the ranging module.

[0060] The adjustment circuit 70 can be internally equipped with corresponding signal comparison circuits, controllers, and other structures. The adjustment circuit 70 can determine the magnitudes of the first adjustment signal and the second adjustment signal through data comparison and / or parameter reading, thereby changing the magnitudes of the bias voltage and the triangular wave modulation signal. It can also adjust the bias voltage based on the detected static current (positive or negative correlation) and / or determine the bandwidth based on the detected electrical signal, and adjust the amplitude of the triangular wave modulation signal based on the bandwidth (positive or negative correlation). The specific adjustment method can be selected and adjusted according to the relationship between the bandwidth of the optical signal and the changes in the static current and the amplitude of the triangular wave modulation signal.

[0061] The laser emitting circuit 100, by configuring a current sampling circuit 50 and a beat frequency processing circuit 60, can detect the current of the laser 10 and the bandwidth of the emitted optical signal, and configure two output circuits with adjustable output to adjust the bias voltage and the magnitude of the triangular wave modulation signal, thereby stabilizing the bandwidth of the optical signal at the preset bandwidth and improving the ranging accuracy.

[0062] The regulating circuit 70 can be set with corresponding static current threshold, bandwidth threshold, etc. When the corresponding static current and bandwidth are within the threshold range, the current bias voltage and triangular wave modulation signal output can be maintained. When the corresponding static current and bandwidth exceed the preset range, the magnitude of the bias voltage and / or triangular wave modulation signal can be changed.

[0063] When the static current of the laser 10 is within a set threshold, and the beat frequency processing circuit 60 detects that the bandwidth of the optical signal is less than the bandwidth threshold, the adjustment circuit 70 selects to increase the amplitude of the triangular wave modulation signal, thereby increasing the amplitude of the driving current, so as to increase the bandwidth of the emitted optical signal and stabilize the bandwidth at the preset bandwidth.

[0064] When the static current of the laser 10 is within a set threshold, and the bandwidth of the detected optical signal is greater than the bandwidth threshold, the adjustment circuit 70 selects to reduce the amplitude of the triangular wave modulation signal, thereby reducing the amplitude of the driving current, so as to reduce the bandwidth of the emitted optical signal, realize bandwidth negative feedback adjustment, and make the bandwidth stable at the preset bandwidth.

[0065] When the quiescent current is detected to be less than the current threshold, the adjustment circuit 70 selects to increase the magnitude of the bias voltage, thereby increasing the quiescent current of the drive current and stabilizing the quiescent current at the preset current.

[0066] When the quiescent current is detected to be greater than the current threshold, the regulating circuit 70 selects to reduce the magnitude of the bias voltage, thereby reducing the quiescent current of the drive current and stabilizing the quiescent current at the preset current.

[0067] Furthermore, in actual use, different environmental conditions, especially different temperature conditions, can cause changes in the response bandwidth of the laser, ultimately resulting in the laser ranging accuracy and precision failing to meet the requirements.

[0068] In an alternative embodiment, such as Figure 2 As shown, the laser emitting circuit 100 also includes:

[0069] Temperature detection circuit 80 is connected to adjustment circuit 70. Temperature detection circuit 80 is used to detect the current ambient temperature and output temperature detection signal to trigger adjustment circuit 70 to output a first adjustment signal and / or a second adjustment signal of corresponding magnitude.

[0070] The adjustment circuit 70 can be set with a corresponding temperature threshold. When the ambient temperature is within the temperature threshold, the current bias voltage and / or triangular wave modulation signal output can be maintained. When the ambient temperature exceeds the temperature threshold, the magnitude of the bias voltage and / or triangular wave modulation signal can be changed.

[0071] Regarding ambient temperature, the adjustment circuit 70 can set different correction parameters for bias voltage and / or different correction parameters for triangular wave modulation signals based on different ambient temperatures. After detecting different temperatures, it generates a corresponding bias voltage and / or a corresponding triangular wave modulation signal based on the temperature and the determined correction parameters, thereby changing the static current of the drive current and stabilizing the static current at the preset current, thus improving the ranging accuracy.

[0072] Meanwhile, after temperature-based adjustment, its bandwidth may deviate slightly from the set bandwidth, or during long-term use, the structure and parameters of the components may change, causing the bandwidth of the emitted optical signal to change. In this case, the adjustment circuit 70 can further adjust the bias voltage and / or triangular wave modulation signal according to the static current and bandwidth detected after adjustment, so that its bandwidth reaches the set bandwidth.

[0073] The laser 10 can be of different types. In an optional embodiment, the laser 10 is either a DFB laser 10 or a DBR laser 10. The DFB laser 10 can maintain single-mode characteristics even during high-speed modulation and can be used for long-distance transmission.

[0074] The laser driving circuit 40 can employ corresponding superposition circuits, conversion circuits, etc., as shown in an optional embodiment, such as... Figure 3 As shown, the laser driving circuit 40 includes:

[0075] The signal superposition circuit 41 is connected to the bias voltage output circuit 20 and the signal output circuit 30 respectively, and is used to superimpose the bias voltage and the triangular wave modulation signal to obtain the driving signal.

[0076] The driving circuit 42, connected to the signal superposition circuit 41 and the laser 10, is used to receive the driving signal and output a driving current of a corresponding magnitude based on the driving signal.

[0077] In this embodiment, the signal superposition circuit 41 receives the bias voltage and the triangular wave modulation signal respectively, and superimposes the two into a driving signal. The center value of the bias voltage and the driving signal are equal or in a preset ratio. The amplitude of the triangular wave modulation signal is equal or in a preset ratio to the amplitude of the driving signal. The driving signal is output to the driving circuit 42. The driving circuit 42 performs voltage-to-current conversion and outputs a driving current. The center value of the driving current, i.e., the static current, changes positively with the bias voltage. The amplitude of the driving current changes positively with the amplitude of the triangular wave modulation signal.

[0078] When the triangular wave modulation signal remains unchanged, increasing the bias voltage increases the center value of the driving signal, and correspondingly, the static current of the driving current increases. Conversely, decreasing the bias voltage decreases the center value of the driving signal, and correspondingly, the static current of the driving current decreases, and the bandwidth of the optical signal decreases. Therefore, the static current of the driving current can be changed by changing the bias voltage.

[0079] Similarly, when the bias voltage remains constant and the amplitude of the triangular wave modulation signal is increased, the amplitude of the driving signal increases, the amplitude of the driving current increases, and the bandwidth of the optical signal increases. Conversely, when the triangular wave modulation signal is decreased, the amplitude of the driving signal decreases, the amplitude of the driving current decreases, and the bandwidth of the optical signal emitted by the laser 10 decreases. Therefore, the bandwidth of the optical signal can be changed by changing the amplitude of the triangular wave modulation signal.

[0080] The signal superposition circuit 41 can adopt the structure of operational amplifier U1, coupler, etc., and the driving circuit 42 can adopt the structure of power transistor, electronic switch Q1, etc. In an optional embodiment, such as Figure 4 As shown, the signal superposition circuit 41 includes a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, an operational amplifier U1, and a Zener diode ZD1;

[0081] The first end of the first resistor R1 is used to input the bias voltage, the first end of the second resistor R2 is used to input the triangular wave modulation signal, the second end of the first resistor R1 is connected to the non-inverting input of the operational amplifier U1, the second end of the second resistor R2 is connected to the inverting input of the operational amplifier U1, the third resistor R3 is connected between the inverting input of the operational amplifier U1 and the output of the operational amplifier U1, the operational amplifier U1 is also connected to the first end of the fourth resistor R4, the second end of the fourth resistor R4 is connected to the cathode of the Zener diode ZD1 to form the output of the signal superposition circuit 41, and the anode of the Zener diode ZD1 is grounded.

[0082] The drive circuit 42 includes a fifth resistor R5 and an electronic switch Q1;

[0083] The first end of the fifth resistor R5 is connected to the positive voltage terminal VCC, and the second end of the fifth resistor R5 is connected to the first end of the electronic switch Q1. The second end of the electronic switch Q1 constitutes the output terminal of the drive circuit 42, and the control terminal of the electronic switch Q1 constitutes the input terminal of the drive circuit 42.

[0084] In this embodiment, the operational amplifier U1 performs signal superposition and outputs a drive signal through its output terminal. The drive signal is a voltage signal. The bias voltage is equal to or in a preset ratio to the center value of the voltage signal. The amplitude of the triangular wave modulation signal is equal to or in a preset ratio to the amplitude of the voltage signal. The electronic switch Q1 performs voltage-to-current conversion. When the center value of the voltage signal received by the electronic switch Q1 changes, the static current of the output drive current changes positively correlated, thereby changing the wavelength and bandwidth of the emitted optical signal.

[0085] Furthermore, when the amplitude of the voltage signal received by the electronic switch Q1 changes, the amplitude of the output drive current changes in a positive correlation, thereby altering the bandwidth of the optical signal.

[0086] The electronic switch Q1 can be selected from corresponding switching devices. In one optional embodiment, the electronic switch Q1 is a MOS transistor, and the drain, source and gate of the MOS transistor constitute the first terminal, the second terminal and the control terminal of the electronic switch Q1, respectively.

[0087] The MOSFET turns on and off according to the received drive signal and outputs a drive current with the same bandwidth and corresponding proportional change as the drive signal.

[0088] The beat frequency processing circuit 60 is used to detect and convert the beat frequency signal, determine the bandwidth based on the beat frequency signal, and then output an electrical signal representing the bandwidth. Correspondingly, the beat frequency processing circuit 60 can adopt a corresponding optical path, conversion circuit, etc. In an optional embodiment, such as... Figure 3 As shown, in an optional embodiment, the beat frequency processing circuit 60 includes:

[0089] Beat frequency optical path 61 is used to acquire part of the light signal emitted by laser 10 and perform beam splitting and beat frequency generation to generate a beat frequency signal;

[0090] The photoelectric conversion circuit 62 is connected to the beat frequency optical path 61 and is used to photoelectrically convert the beat frequency signal into an analog electrical signal.

[0091] The analog-to-digital sampling circuit 63 is connected to the photoelectric conversion circuit 62 and the adjustment circuit 70, and is used to sample analog electrical signals and convert them into digital electrical signals.

[0092] In this embodiment, the beat frequency optical path 61 can acquire part of the optical signal through the corresponding optical path, or through structures such as optical fibers and mirrors. At the same time, the beat frequency optical path 61 processes the optical signal to obtain two beat frequency signals with phase difference. The beat frequency signal contains the bandwidth information of the optical signal. The beat frequency signal is converted into an analog electrical signal by the photoelectric conversion circuit 62, and then sampled and converted into a digital electrical signal by the analog-to-digital sampling circuit 63. The digital electrical signal also contains the bandwidth information of the optical signal. The adjustment circuit 70 can determine the bandwidth of the current optical signal based on the received digital electrical signal, compare it with the bandwidth threshold, and output a second adjustment signal to the signal output circuit 30, thereby adjusting the amplitude of the triangular wave modulation signal, thereby changing the driving current and the bandwidth of the optical signal, stabilizing its bandwidth at the preset bandwidth, and improving the ranging accuracy.

[0093] Among them, the beat frequency optical path 61 can adopt a corresponding delay fiber 612 or other structure, and the photoelectric conversion circuit 62 can adopt a corresponding photoelectric conversion device, photodiode, or other structure. In an optional embodiment, such as Figure 5 As shown, the beat frequency optical path 61 includes:

[0094] Beam splitter 611 is used to acquire part of the optical signal emitted by laser 10 and split the light to output the first optical signal and the second optical signal.

[0095] The delay fiber 612 is connected to the beam splitter 611 and is used to input the first optical signal and output it after a delay.

[0096] Optical coupler 613 is connected to beam splitter 611 and delay fiber 612 respectively, and is used to input the second optical signal and the delayed first optical signal, perform beat frequency, and generate beat frequency signal.

[0097] The photoelectric conversion circuit 62 includes a balanced detector, and the input and output terminals of the balanced detector constitute the input and output terminals of the photoelectric conversion circuit 62, respectively.

[0098] In this embodiment, the optical signal output by the laser 10 passes through the first beam splitter 611, and one path is delayed by the delay fiber 612 and input to the second input terminal of the optical coupler 613, while the other path is directly input to the first input terminal of the optical coupler 613. The optical coupler 613 is used to realize the superposition and coupling of the two optical signals, generating two beat frequency signals with a phase difference of 180 degrees. The beat frequency signals are converted into electrical signals by the balanced detector. The balanced detector forms coherent light from the two input optical signals and outputs a differential current signal to the signal analog-to-digital sampling circuit 63. The analog-to-digital sampling circuit 63 performs analog-to-digital sampling and outputs a digital electrical signal to the adjustment circuit 70.

[0099] The output current of the balanced detector changes with the frequency of the laser 10, meaning its output current has a corresponding optical curve to the frequency of the laser 10. The balanced detector is an unbalanced Mach-Zehnder interferometer.

[0100] Let the length difference between the two paths be L, the refractive index of the optical fiber be n, the speed of light be C, the frequency modulation bandwidth be B, the frequency modulation period be T, and the beat frequency be F. Then the following mathematical relationship exists:

[0101]

[0102] Therefore, the current bandwidth can be obtained simply by obtaining the frequency of the beat frequency signal.

[0103] The analog-to-digital sampling circuit 63 can be an ADC sampling chip or other digital-to-analog converter structure.

[0104] The beneficial effects of this utility model embodiment compared with the prior art are as follows: The laser emitting circuit 100 mentioned above includes a laser 10, a laser driving circuit 40, a bias voltage output circuit 20, a signal output circuit 30, a current sampling circuit 50, a beat frequency processing circuit 60, and an adjustment circuit 70. The adjustment circuit 70 can obtain the output current of the laser driving circuit 40 through the current sampling circuit 50 and the bandwidth of the optical signal through the beat frequency processing circuit 60. Based on the output current, it adjusts the bias voltage output by the bias voltage output circuit 20 and the amplitude of the triangular wave modulation signal of the signal output circuit 30 based on the optical signal, thereby adjusting the bandwidth of the optical signal. This stabilizes the static current of the laser at a preset current and locks the bandwidth of the optical signal at a preset bandwidth. The ranging module realizes ranging and speed measurement according to the adjusted optical signal, improving the accuracy of laser ranging.

[0105] This utility model also proposes a frequency-modulated continuous wave lidar 1, such as... Figure 6 As shown, the frequency-modulated continuous wave lidar 1 includes a laser receiving circuit 200 and a laser emitting circuit 100. The specific structure of the laser emitting circuit 100 is as described in the above embodiments. Since this frequency-modulated continuous wave lidar 1 adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, and will not be described in detail here. The laser emitting circuit 100 and the laser receiving circuit 200 are arranged opposite to each other.

[0106] In this embodiment, the laser receiving circuit 200 and the laser emitting circuit 100 form a frequency-modulated continuous wave lidar 1. The laser receiving circuit 200 can receive the light signal reflected back from the target object by the laser reflecting circuit and perform photoelectric conversion to obtain the echo electrical signal. The laser receiving circuit 200 can determine the distance and speed information based on the frequency difference of the light signal. Alternatively, the frequency-modulated continuous wave lidar 1 can also be equipped with a control module, which is connected to the laser reflecting circuit and the laser receiving circuit 200 respectively. The control module receives the echo electrical signal and determines the distance and speed information based on the frequency difference of the signal. Alternatively, the echo electrical signal can be directly output to the adjustment circuit 70 of the laser emitting circuit 100, and the adjustment circuit 70 of the laser emitting circuit 100 determines the distance and speed information.

[0107] The above-described embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although this utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this utility model, and should all be included within the protection scope of this utility model.

Claims

1. A laser emitting circuit, characterized in that, include: The laser emits an optical signal when triggered by the current driving current. The bias voltage output circuit outputs a bias voltage of a corresponding magnitude based on the first adjustment signal. The signal output circuit outputs a triangular wave modulated signal of corresponding size, which is subject to the second adjustment signal. A laser driving circuit is connected to the bias voltage output circuit, the signal output circuit, and the laser, respectively. The laser driving circuit is used to superimpose the bias voltage and the triangular wave modulation signal to obtain a driving signal, and output the driving current that changes in correlation with the driving signal. A current sampling circuit, connected to the laser driving circuit, is used to sample the current output by the laser driving circuit and output a current sampling signal; A beat frequency processing circuit is used to acquire a portion of the optical signal from the laser, perform beam splitting and beat frequency processing to generate a beat frequency signal, and convert the beat frequency signal into an electrical signal. The adjustment circuit is connected to the bias voltage output circuit, the signal output circuit, the current sampling circuit, and the beat frequency processing circuit, respectively. The adjustment circuit is triggered by the current sampling signal to output a first adjustment signal of a corresponding magnitude, and triggered by the electrical signal to output a second adjustment signal of a corresponding magnitude.

2. The laser emitting circuit as described in claim 1, characterized in that, The laser emitting circuit also includes: A temperature detection circuit is connected to the adjustment circuit. The temperature detection circuit is used to detect the current ambient temperature and output a temperature detection signal to trigger the adjustment circuit to output a first adjustment signal and / or a second adjustment signal of corresponding magnitude.

3. The laser emitting circuit as described in claim 1, characterized in that, The laser driving circuit includes: A signal superposition circuit is connected to the bias voltage output circuit and the signal output circuit respectively, and is used to superimpose the bias voltage and the triangular wave modulation signal to obtain the driving signal; A driving circuit, connected to the signal superposition circuit and the laser, is used to receive the driving signal and output a driving current of a corresponding magnitude based on the driving signal.

4. The laser emitting circuit as described in claim 3, characterized in that, The signal superposition circuit includes a first resistor, a second resistor, a third resistor, a fourth resistor, an operational amplifier, and a Zener diode; The first end of the first resistor is used to input the bias voltage, the first end of the second resistor is used to input the triangular wave modulation signal, the second end of the first resistor is connected to the non-inverting input of the operational amplifier, the second end of the second resistor is connected to the inverting input of the operational amplifier, the third resistor is connected between the inverting input of the operational amplifier and the output of the operational amplifier, the operational amplifier is also connected to the first end of the fourth resistor, the second end of the fourth resistor is connected to the cathode of the Zener diode to form the output of the signal superposition circuit, and the anode of the Zener diode is grounded.

5. The laser emitting circuit as described in claim 3, characterized in that, The driving circuit includes a fifth resistor and an electronic switch. The first end of the fifth resistor is connected to the positive voltage terminal, the second end of the fifth resistor is connected to the first end of the electronic switch, the second end of the electronic switch constitutes the output terminal of the driving circuit, and the control terminal of the electronic switch constitutes the input terminal of the driving circuit.

6. The laser emitting circuit according to any one of claims 1 to 5, characterized in that, The beat frequency processing circuit includes: The beat frequency optical path is used to acquire a portion of the light signal emitted by the laser and perform beam-splitting beat frequency generation to generate the beat frequency signal; A photoelectric conversion circuit, connected to the beat frequency optical path, is used to photoelectrically convert the beat frequency signal into an analog electrical signal; An analog-to-digital sampling circuit, connected to the photoelectric conversion circuit and the adjustment circuit, is used to sample the analog electrical signal and convert it into a digital electrical signal.

7. The laser emitting circuit as described in claim 6, characterized in that, The beat frequency optical path includes: A beam splitter is used to acquire a portion of the optical signal emitted by the laser and split it into a first optical signal and a second optical signal. A delay fiber, connected to the beam splitter, is used to input the first optical signal and output it after a delay; An optical coupler, connected to the beam splitter and the delay fiber respectively, is used to input the second optical signal and the delayed first optical signal, perform beat frequency analysis, and generate a beat frequency signal.

8. The laser emitting circuit as described in claim 6, characterized in that, The photoelectric conversion circuit includes a balance detector, and the input and output terminals of the balance detector constitute the input and output terminals of the photoelectric conversion circuit, respectively.

9. The laser emitting circuit as described in claim 1, characterized in that, The laser is either a DFB laser or a DBR laser.

10. A frequency-modulated continuous wave lidar, characterized in that, It includes a laser receiving circuit and a laser emitting circuit as described in any one of claims 1 to 9, wherein the laser emitting circuit and the laser receiving circuit are arranged opposite to each other.

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