FMCW laser radar device for passively suppressing low-frequency interference and frequency modulation method

Abstract

The invention relates to the technical field of laser radars, and discloses an FMCW laser radar device capable of passively suppressing low-frequency interference and a frequency modulation method, and the method comprises the steps: firstly generating a modulation signal through a signal generator, and carrying out the continuous frequency modulation of an original laser signal generated by a laser; and secondly, light absorption processing is carried out through the nonlinear absorber, so that the second modulation laser signal is approximately constant in output and is irrelevant to the driving current, and the laser power fluctuation level input into the FMCW coherent detection device is passively inhibited. Then, the power of the second modulated laser signal can be in a saturation gain region of the optical amplifier through the optical amplifier, so that the optical power fluctuation level is further suppressed, and the laser power change caused by frequency modulation is suppressed. And finally, the suppressed target modulation signal is input to the FMCW coherent detection device and the distance detection of the target object is completed, so that the recognition capability of the laser radar on the close-range target is improved.

Description

Technical Field

[0001] The present invention relates to the field of laser radar technology, and in particular to an FMCW laser radar device and a frequency modulation method for passively suppressing low-frequency interference. Background Art

[0002] For FMCW (Frequency Modulated Continuous Wave Radar) laser radar, coherent detection is used to obtain information such as target distance and speed. This type of laser radar requires continuous modulation of the frequency of the laser. Taking the DFB semiconductor laser as an example, the continuous change of the laser output frequency is achieved by continuously changing the driving current of the laser. However, since the output power of the laser is usually related to the driving current, the frequency modulation of the laser is accompanied by the modulation of the laser output power. The frequency of this power modulation signal is generally low, and it will overlap with the reflection signal of the close-range target. After being converted into a frequency domain signal, it will interfere with the judgment and identification of the target signal, affecting the close-range performance of the FMCW laser radar, and is one of the reasons for the close-range "blind spot". Summary of the invention

[0003] In view of this, the present invention provides an FMCW laser radar device and a frequency modulation method for passively suppressing low-frequency interference, so as to solve the problem that the output power of the laser is modulated simultaneously with the frequency modulation of the laser, but the frequency of the power modulation signal is generally low, which will overlap with the reflection signal of the close-range target. After being converted into a frequency domain signal, it will interfere with the judgment and recognition of the target signal, thereby affecting the close-range performance of the FMCW laser radar.

[0004] In a first aspect, the present invention provides a FMCW laser radar device for passively suppressing low-frequency interference, the device comprising: a laser modulation device and an FMCW coherent detection device, the laser modulation device comprising a signal generator, a laser, a nonlinear absorber and an optical amplifier;

[0005] A signal generator is used to generate a modulation signal and output the modulation signal to a laser; a laser is used to generate an original laser signal, and based on the modulation signal, continuously frequency modulate the original laser signal to obtain a first modulated laser signal containing amplitude modulation information, and output the first modulated laser signal to a nonlinear absorber; the nonlinear absorber is used to absorb the first modulated laser signal to obtain a second modulated laser signal, and output the second modulated laser signal to an optical amplifier; the optical amplifier is used to amplify the power of the second modulated laser signal and then output a target modulation signal to an FMCW coherent detection device; the FMCW coherent detection device is used to detect a target object based on the target modulation signal to obtain a target detection distance.

[0006] The FMCW laser radar device for passively suppressing low-frequency interference provided by the present invention first generates a modulation signal through a signal generator and continuously frequency modulates the original laser signal generated by the laser. Secondly, the first modulated laser signal after modulation is subjected to light absorption processing by a nonlinear absorber, so that the second modulated laser signal can present an approximately constant output and is independent of the driving current. Further, the laser power fluctuation level of the input FMCW coherent detection device can be passively suppressed by the nonlinear absorber. Then, the power of the second modulated laser signal can be placed in the saturation gain region of the optical amplifier through an optical amplifier, thereby further suppressing the optical power fluctuation level, thereby suppressing the laser power change caused by frequency modulation. Finally, the suppressed target modulation signal is input to the FMCW coherent detection device and the distance detection of the target object is completed. Therefore, by implementing the present invention, while realizing continuous frequency modulation of the laser, the amplitude change of the laser radar input power is weakened, thereby reducing or even avoiding the introduction of low-frequency interference signals, suppressing the interference of low-frequency modulation on the actual target signal, and improving the laser radar's ability to identify close-range targets.

[0007] In an optional implementation, the FMCW coherent detection device includes: an FMCW coherent detection module and a signal acquisition and calculation module;

[0008] The FMCW coherent detection module is used to detect the target object based on the target modulation signal and generate a mixed signal carrying the target detection distance information; the signal acquisition and calculation module is used to obtain the waveform data of the mixed signal based on the synchronous trigger signal, and calculate the target detection distance based on the waveform data. The synchronous trigger signal is synchronously output to the signal acquisition and calculation module when the signal generator outputs the modulation signal.

[0009] The FMCW laser radar device for passively suppressing low-frequency interference provided by the present invention can generate a mixed signal carrying target detection distance information by detecting the target object using the modulated target modulation signal in the FMCW coherent detection module. At the same time, the signal acquisition and calculation module synchronously obtains the waveform data of the generated mixed signal according to the synchronous trigger signal and calculates the corresponding target detection distance. Therefore, by implementing the present invention, detection is performed by using the modulated target modulation signal, thereby improving the detection accuracy of close-range targets.

[0010] In an optional embodiment, the nonlinear absorber adopts a silicon-based waveguide delay line structure.

[0011] The FMCW laser radar device for passively suppressing low-frequency interference provided by the present invention can achieve integrated design and integration with the silicon photonic chip in the FMCW laser radar by adopting a nonlinear absorber with a silicon-based waveguide delay line structure.

[0012] In a second aspect, the present invention provides a frequency modulation method for passively suppressing low-frequency interference, which is used in a laser modulation device in an FMCW laser radar device for passively suppressing low-frequency interference according to the first aspect or any corresponding embodiment thereof; the method comprises:

[0013] A signal generator is used to generate a modulation signal; the modulation signal is used to control the laser driving current change to generate continuous frequency modulation and output a first modulated laser signal containing amplitude modulation information; the first modulated laser signal is processed by a nonlinear absorber and an optical amplifier respectively to obtain a target modulation signal.

[0014] The frequency modulation method for passively suppressing low-frequency interference provided by the present invention processes the laser signal through a nonlinear absorber and an optical amplifier. It can weaken the amplitude variation of the laser radar input power while realizing continuous frequency modulation of the laser, thereby reducing or even avoiding the introduction of low-frequency interference signals and suppressing the interference of low-frequency modulation on the actual target signal.

[0015] In an optional implementation, using a modulation signal to control the laser driving current to change to generate continuous frequency modulation and output a first modulated laser signal containing amplitude modulation information includes:

[0016] The voltage amplitude of the modulation signal and the modulation efficiency of the laser are obtained; the modulation bandwidth is determined based on the voltage amplitude and the modulation efficiency; based on the modulation bandwidth, the laser driving current is controlled by the modulation signal to generate continuous frequency modulation and output a first modulated laser signal containing amplitude modulation information.

[0017] The frequency modulation method for passively suppressing low-frequency interference provided by the present invention can determine the modulation bandwidth according to the voltage amplitude of the modulation signal and the modulation efficiency of the laser when using the modulation signal to control the change of the laser driving current to produce continuous frequency modulation.

[0018] In an optional implementation, the first modulated laser signal is processed by a nonlinear absorber and an optical amplifier respectively to obtain a target modulated signal, including:

[0019] The first modulated laser signal is subjected to light absorption processing by using a nonlinear absorber and a second modulated laser signal is output to an optical amplifier; the second modulated laser signal is amplified by using the optical amplifier to obtain a target modulated signal.

[0020] The frequency modulation method for passively suppressing low-frequency interference provided by the present invention absorbs light on the modulated first modulated laser signal through a nonlinear absorber, so that the second modulated laser signal can present an approximately constant output and is independent of the driving current. Furthermore, the nonlinear absorber can passively suppress the laser power fluctuation level of the input FMCW coherent detection device. Furthermore, the optical amplifier can make the power of the second modulated laser signal in the saturation gain region of the optical amplifier, thereby further suppressing the optical power fluctuation level, thereby suppressing the laser power change caused by frequency modulation.

[0021] In an optional embodiment, the method further includes:

[0022] The target modulation signal is output to the FMCW coherent detection device, so that the FMCW coherent detection device detects the target object based on the target modulation signal.

[0023] The frequency modulation method for passively suppressing low-frequency interference provided by the present invention improves the detection accuracy of close-range targets by inputting the modulated target modulation signal into an FMCW coherent detection device and completing the distance detection of the target object.

[0024] In a third aspect, the present invention provides a computer device, comprising: a memory and a processor, the memory and the processor being communicatively connected to each other, the memory storing computer instructions, and the processor executing the frequency modulation method for passively suppressing low-frequency interference of the above-mentioned second aspect or any corresponding embodiment thereof by executing the computer instructions.

[0025] In a fourth aspect, the present invention provides a computer-readable storage medium having computer instructions stored thereon, the computer instructions being used to enable a computer to execute the frequency modulation method for passively suppressing low-frequency interference according to the second aspect or any corresponding embodiment thereof.

[0026] In a fifth aspect, the present invention provides a computer program product, comprising computer instructions for causing a computer to execute the frequency modulation method for passively suppressing low-frequency interference according to the second aspect or any corresponding embodiment thereof. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0028] Figure 1is a structural block diagram of an FMCW laser radar device for passively suppressing low-frequency interference according to an embodiment of the present invention;

[0029] Figure 2 is a schematic diagram of the relationship between the driving current and the output power of the laser according to an embodiment of the present invention;

[0030] Figure 3 is a schematic diagram of an FMCW coherent detection module according to an embodiment of the present invention;

[0031] Figure 4 is a flow chart of a frequency modulation method for passively suppressing low-frequency interference according to an embodiment of the present invention;

[0032] Figure 5 is a flow chart of another frequency modulation method for passively suppressing low-frequency interference according to an embodiment of the present invention;

[0033] Figure 6 is a flow chart of another frequency modulation method for passively suppressing low-frequency interference according to an embodiment of the present invention;

[0034] Figure 7 is a structural block diagram of an FMCW frequency modulated continuous wave laser radar device for passively suppressing low-frequency interference according to an embodiment of the present invention;

[0035] Figure 8 2 is a schematic structural diagram of a low-frequency interference passive suppression device applicable to silicon photonic chip integration according to an embodiment of the present invention;

[0036] Fig. 9 It is a schematic diagram of the hardware structure of a computer device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0038] An embodiment of the present invention provides an FMCW laser radar device that passively suppresses low-frequency interference. The laser signal is processed by a nonlinear absorber and an optical amplifier to achieve continuous frequency modulation of the laser while weakening the amplitude variation of the laser radar input power, thereby reducing or even avoiding the introduction of low-frequency interference signals and suppressing the interference of low-frequency modulation on the actual target signal.

[0039] In this embodiment, a FMCW laser radar device for passively suppressing low-frequency interference is provided. Figure 1 As shown, the FMCW laser radar device 1 for passively suppressing low-frequency interference includes: a laser modulation device 11 and a FMCW coherent detection device 12.

[0040] The laser modulation device 11 includes a signal generator 111 , a laser 112 , a nonlinear absorber 113 and an optical amplifier 114 .

[0041] Furthermore, the FMCW coherent detection device 12 includes: an FMCW coherent detection module 121 and a signal acquisition and calculation module 122 .

[0042] Optionally, the signal generator 111 is used to generate a modulation signal and output the modulation signal to the laser 112 .

[0043] The signal generator 111 represents a device that can provide electrical signals of various frequencies, waveforms and output levels.

[0044] Specifically, the signal generator 111 is an electronic device that can generate a specific waveform and frequency, has a high degree of accuracy and adjustability, and can generate various types of modulation signals according to different requirements, such as sine waves, square waves, triangle waves, etc. In this embodiment, the signal generator 111 is a dual-channel, one of which generates a modulation signal and sends the modulation signal output to the laser 112.

[0045] Optionally, the laser 112 is used to generate an original laser signal, and continuously frequency modulate the original laser signal based on the modulation signal to obtain a first modulated laser signal containing amplitude modulation information, and output the first modulated laser signal to the nonlinear absorber 113 .

[0046] Specifically, the laser 112 requires a stable DC drive (power supply) signal and a relatively small continuous AC signal for frequency modulation, which is provided by a signal generator; Figure 2 As shown, if the laser DC drive current is set at 450mA, the laser output power will be stabilized at 90mW (frequency is f0). At this time, a modulation current of Vpp=100mA (±50mA) is applied, and the total drive current of the laser will continuously change between 400 and 500mA, causing the laser output frequency to continuously change in a certain range (f0±D). At the same time, the output power also fluctuates continuously in a certain range (such as 90±10mW).

[0047] Therefore, the DC driving output of the laser 112 is the original laser signal generated.

[0048] Furthermore, the laser 112 generates continuous frequency modulation under the drive of the modulation signal, that is, after continuously frequency modulating the original laser signal, a first modulated laser signal containing amplitude modulation information can be output. Continuous frequency modulation can include both frequency modulation and amplitude modulation.

[0049] Finally, the laser 112 outputs the modulated first modulated laser signal containing amplitude modulation information and sends it to the nonlinear absorber 113 .

[0050] Optionally, the nonlinear absorber 113 is used to perform light absorption processing on the first modulated laser signal to obtain a second modulated laser signal, and output the second modulated laser signal to the optical amplifier 114 .

[0051] The nonlinear absorber 113 is a material with special optical properties, and has a material characteristic that the stronger the light, the stronger the absorption.

[0052] Specifically, the first modulated laser signal has amplitude modulation. Therefore, when the nonlinear absorber 113 receives the first modulated laser signal, it performs light absorption processing on the received first modulated laser signal. Further, after being processed by the nonlinear absorber 113, the lower light absorption is small, and the stronger light absorption is large, and it will eventually become a flat power output that is close to stable over time, that is, the second modulated laser signal finally output can present an approximately constant output. At the same time, nonlinear absorption is independent of frequency and will not affect the frequency modulation result. Therefore, the power of the second modulated laser signal output after the light absorption processing is stable over time, and the frequency modulation is the same as the original laser signal.

[0053] Finally, the second modulated laser signal whose output power is stable over time and whose modulation frequency is the same as that of the original laser signal is sent to the optical amplifier 114 .

[0054] Furthermore, the nonlinear absorber 113 may adopt a silicon-based waveguide delay line structure.

[0055] Specifically, the band gap of silicon material is 1.12eV, corresponding to an absorption cutoff wavelength of 1110nm, which means that silicon generally does not absorb light with a wavelength of 1550nm. The intrinsic absorption of silicon waveguide is very small. However, at high power, due to the increase in the energy density per unit volume of the light field, nonlinear effects such as two-photon absorption will be generated in the silicon waveguide. In this case, silicon material can absorb light of 1550nm. Therefore, the silicon waveguide delay line used in this embodiment operates in the nonlinear absorption region of high incident power.

[0056] Furthermore, by adopting a silicon-based waveguide delay line structure, it is also possible to achieve integrated design and integration with the silicon photonic chip in the FMCW lidar.

[0057] Optionally, the optical amplifier 114 is used to amplify the power of the second modulated laser signal and then output a target modulated signal to the FMCW coherent detection device 12 .

[0058] The optical amplifier 114 is a device that plays a key role in optical communication and optical systems, and can amplify input optical signals to enhance the intensity of the optical signals. It mainly achieves the amplification of optical signals by utilizing specific physical mechanisms, such as stimulated radiation.

[0059] Specifically, the nonlinear absorber 113 can suppress low-frequency amplitude modulation interference, but cannot adjust the optical power. Therefore, the optical amplifier 114 is required to amplify the flat output light to the required power in one step.

[0060] Therefore, when the optical amplifier 114 receives the second modulated laser signal, it amplifies the power of the received second modulated laser signal to the required power and then outputs and sends it to the FMCW coherent detection device 12. Through the processing of the optical amplifier 114, the optical power fluctuation level can be further suppressed, thereby suppressing the laser power change caused by frequency modulation.

[0061] Optionally, the FMCW coherent detection device 12 is used to detect the target object based on the target modulation signal to obtain the target detection distance.

[0062] Among them, the FMCW (Frequency Modulated Continuous Wave) coherent detection device 12 is an advanced optical detection technology device that can achieve high-precision distance measurement and speed measurement. Furthermore, the distance measurement principle of the FMCW technology is to send and receive continuous laser beams, use mixing detection to measure the frequency difference between the two, and then calculate the distance of the target object.

[0063] First, the target object is detected using the target modulation signal in the FMCW coherent detection module 121 and a mixed signal carrying target detection distance information is generated.

[0064] Specifically, after receiving the target modulation signal, Figure 3 As shown, the target modulated signal is divided into two parts in the FMCW coherent detection module 121, one part is used as the local oscillator light, and the other part is used as the outgoing light. The outgoing light irradiates the object to generate reflected light that returns to the coherent detection module. The returned light and the local oscillator light meet and interfere with each other inside the coherent detection module to generate a mixed signal carrying the target distance information.

[0065] Secondly, in the signal acquisition and calculation module 122, the waveform data of the mixed signal is acquired based on the synchronous trigger signal, and the target detection distance is calculated based on the waveform data.

[0066] The synchronous trigger signal is synchronously output to the signal acquisition and calculation module 122 when the signal generator 111 outputs the modulation signal.

[0067] Specifically, when the FMCW coherent detection module 121 generates a mixed signal using a target modulation signal, the signal acquisition and calculation module 122 synchronously acquires waveform data of the generated mixed signal under the drive of a synchronous trigger signal.

[0068] Furthermore, in the signal acquisition and calculation module 122, the target frequency is demodulated by a frequency demodulation algorithm such as Fourier transform according to the obtained waveform data of the mixed signal, and the corresponding target detection distance is obtained by conversion.

[0069] The FMCW laser radar device for passively suppressing low-frequency interference provided in this embodiment first generates a modulation signal through a signal generator and continuously frequency modulates the original laser signal generated by the laser. Secondly, the first modulated laser signal after modulation is subjected to light absorption processing by a nonlinear absorber, so that the second modulated laser signal can present an approximately constant output and is independent of the driving current. Further, the laser power fluctuation level input to the FMCW coherent detection device can be passively suppressed by the nonlinear absorber. Then, the power of the second modulated laser signal can be placed in the saturation gain region of the optical amplifier through an optical amplifier, thereby further suppressing the optical power fluctuation level, thereby suppressing the laser power change caused by frequency modulation. Finally, the suppressed target modulation signal is input to the FMCW coherent detection device and the distance detection of the target object is completed. Therefore, by implementing the present invention, while realizing continuous frequency modulation of the laser, the amplitude change of the laser radar input power is weakened, thereby reducing or even avoiding the introduction of low-frequency interference signals, suppressing the interference of low-frequency modulation on the actual target signal, and improving the laser radar's ability to identify close-range targets.

[0070] According to an embodiment of the present invention, an embodiment of a frequency modulation method for passively suppressing low-frequency interference is provided. It should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and although a logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0071] In this embodiment, a frequency modulation method for passively suppressing low-frequency interference is provided, which can be used for the laser modulation device 11 in the FMCW laser radar device 1 for passively suppressing low-frequency interference provided in the above embodiment of the present invention. Figure 4 is a flow chart of a frequency modulation method for passively suppressing low frequency interference according to an embodiment of the present invention. Figure 4 As shown, the process includes the following steps:

[0072] Step S401: Generate a modulation signal using a signal generator.

[0073] The specific process can refer to the functional description of the signal generator 111 in the laser modulation device 11 in the above embodiment, which will not be repeated here.

[0074] Step S402: Using a modulation signal to control the laser driving current to generate continuous frequency modulation and output a first modulated laser signal containing amplitude modulation information.

[0075] The specific process can refer to the functional description of the laser 112 in the laser modulation device 11 and the description of the interaction process between the signal generator 111 and the laser 112 in the above embodiment, which will not be repeated here.

[0076] Step S403: Process the first modulated laser signal through a nonlinear absorber and an optical amplifier to obtain a target modulated signal.

[0077] For the specific process, reference may be made to the functional description of the nonlinear absorber 113 and the optical amplifier 114 in the laser modulation device 11 and the corresponding interaction process description in the above embodiment, which will not be repeated here.

[0078] In an optional embodiment, if Figure 5 As shown, the above step S403 includes:

[0079] Step S4031: Utilize a nonlinear absorber to perform light absorption processing on the first modulated laser signal and output a second modulated laser signal to an optical amplifier.

[0080] The specific process can refer to the functional description of the nonlinear absorber 113 in the laser modulation device 11 and the description of the interaction process between the nonlinear absorber 113, the laser 112 and the optical amplifier 114 in the above embodiment, which will not be repeated here.

[0081] Step S4032: Amplify the second modulated laser signal using an optical amplifier to obtain a target modulated signal.

[0082] The specific process can refer to the functional description of the optical amplifier 114 in the laser modulation device 11 in the above embodiment, which will not be repeated here.

[0083] The frequency modulation method for passively suppressing low-frequency interference provided in this embodiment processes the laser signal through a nonlinear absorber and an optical amplifier. It can weaken the amplitude variation of the laser radar input power while realizing continuous frequency modulation of the laser, thereby reducing or even avoiding the introduction of low-frequency interference signals and suppressing the interference of low-frequency modulation on the actual target signal.

[0084] In this embodiment, a frequency modulation method for passively suppressing low-frequency interference is provided, which can be used for the laser modulation device 11 in the FMCW laser radar device 1 for passively suppressing low-frequency interference provided in the above embodiment of the present invention. Figure 6 is a flow chart of a frequency modulation method for passively suppressing low frequency interference according to an embodiment of the present invention. Figure 6 As shown, the process includes the following steps:

[0085] Step S601: Generate a modulation signal using a signal generator. Figure 4 Step S401 of the illustrated embodiment will not be described in detail here.

[0086] Step S602: Using the modulation signal to control the laser driving current to generate continuous frequency modulation and output a first modulated laser signal containing amplitude modulation information.

[0087] Specifically, the above step S602 includes:

[0088] Step S6021, obtaining the voltage amplitude of the modulation signal and the modulation efficiency of the laser.

[0089] Specifically, the voltage amplitude of the modulation signal can determine the degree of modulation of the laser 112: when the voltage amplitude of the modulation signal is small, the modulation effect on the laser 112 is relatively weak. This may cause the optical signal output by the laser to change inconspicuously and carry limited information. For example, in optical communication, the data rate of transmission may be reduced, affecting communication efficiency.

[0090] Furthermore, the modulation efficiency of the laser 112 can reflect the responsiveness of the laser 112 to the modulation signal: high modulation efficiency means that the laser 112 can more effectively convert the modulation signal into the change of the optical signal. This can improve the performance of the optical communication system and reduce energy consumption. For example, under the same modulation signal input, a laser with high modulation efficiency can output a stronger modulated optical signal, thereby improving the transmission distance and quality of the signal.

[0091] Furthermore, the modulation efficiency of the laser 112 can be obtained by measuring the relationship between the input electrical signal and the output optical signal, or can be estimated based on the specification parameters of the laser.

[0092] Step S6022, determining the modulation bandwidth based on the voltage amplitude and the modulation efficiency.

[0093] Generally speaking, a higher voltage amplitude can achieve a wider modulation range. This is because a larger voltage change can cause a greater change in the laser output characteristics, thereby expanding the modulatable frequency range. For example, when the voltage amplitude increases, it may cause more significant changes in the laser output light intensity, frequency or phase parameters, thereby widening the modulation bandwidth.

[0094] Further, according to the description of step S6021, high modulation efficiency means that the laser can respond to the modulation signal more effectively and convert the electrical signal into the change of the optical signal. If the modulation efficiency is high, a wider modulation bandwidth may be achieved even at a lower voltage amplitude. On the contrary, low modulation efficiency may limit the modulation bandwidth, and it is difficult to obtain a larger modulation range even with a higher voltage amplitude.

[0095] Therefore, the modulation bandwidth can be calculated based on the obtained voltage amplitude and modulation efficiency data combined with theoretical models or empirical formulas. Different types of lasers may have different calculation methods, which need to be selected according to the specific situation.

[0096] Step S6023: Based on the modulation bandwidth, the laser driving current is controlled by the modulation signal to generate continuous frequency modulation and output a first modulated laser signal containing amplitude modulation information.

[0097] Specifically, based on the obtained modulation bandwidth, the modulation signal is used to control the laser driving current change to generate continuous frequency modulation and output a first modulated laser signal containing amplitude modulation information. The specific control process can refer to the functional description of the laser 112 in the laser modulation device 11 in the above embodiment, which will not be repeated here.

[0098] Step S603: Process the first modulated laser signal through a nonlinear absorber and an optical amplifier to obtain a target modulated signal. Figure 5 Step S403 of the illustrated embodiment will not be described in detail here.

[0099] Step S604: output the target modulation signal to the FMCW coherent detection device, so that the FMCW coherent detection device detects the target object based on the target modulation signal.

[0100] For the specific process, reference may be made to the description of the interaction process between the optical amplifier 114 in the laser modulation device 11 and the FMCW coherent detection device 12 in the above embodiment, as well as the functional description of the FMCW coherent detection device 12, which will not be repeated here.

[0101] The frequency modulation method for passively suppressing low-frequency interference provided in this embodiment can determine the modulation bandwidth according to the voltage amplitude of the modulation signal and the modulation efficiency of the laser when using the modulation signal to control the change of the laser driving current to generate continuous frequency modulation. Furthermore, the modulation signal is used to control the change of the laser driving current to generate continuous frequency modulation. Furthermore, by processing the laser signal through a nonlinear absorber and an optical amplifier, the amplitude change of the laser radar input power can be weakened while achieving continuous frequency modulation of the laser, thereby reducing or even avoiding the introduction of low-frequency interference signals, and suppressing the interference of low-frequency modulation on the actual target signal.

[0102] In one embodiment, a FMCW laser radar device is provided for passively suppressing low-frequency interference, such as Figure 7 As shown, it includes a signal generator, a laser, a nonlinear absorber, an optical amplifier, a FMCW coherent detection module and a signal acquisition and calculation module.

[0103] Specifically, the signal generator is used to provide a modulation waveform to the laser and provide a synchronization trigger signal to the signal acquisition and calculation module.

[0104] Furthermore, the laser generates continuous frequency modulation when driven by a modulation signal, and at the same time carries amplitude modulation information into the nonlinear absorber.

[0105] Furthermore, based on the material property of nonlinear absorbers that the stronger the light, the stronger the absorption. After passing through the nonlinear absorber, the laser will present an approximately constant output, regardless of the driving current. Subsequently, it is further amplified to the required power through an optical amplifier and connected to the FMCW coherent detection module. The signal acquisition and calculation module synchronously collects the signal waveform through the trigger signal, calculates and completes the detection of the target object in real time. Since the input power fluctuation caused by the frequency modulated driving current is suppressed, the low-frequency interference of the FMCW system is suppressed, and the performance of the lidar for close-range detection is improved.

[0106] The FMCW frequency-modulated continuous wave laser radar device for passively suppressing low-frequency interference provided in this example can weaken the amplitude variation of the laser radar input power while realizing continuous frequency modulation of the laser, thereby reducing or even avoiding the introduction of low-frequency interference signals, suppressing the interference of low-frequency modulation on the actual target signal, and improving the laser radar's ability to recognize close-range targets.

[0107] In an optional embodiment, a low-frequency interference passive suppression solution suitable for silicon photonic chip integration is provided, such as Figure 8 As shown, the semiconductor DFB laser is integrated on a silicon photonic chip with a wavelength of 1550nm. Channel 1 of the multi-channel signal generator provides a periodic triangle wave modulation signal of 100kHz to control the laser drive current change to produce continuous frequency modulation. The modulation bandwidth is determined by the modulation signal voltage amplitude V1 and the laser modulation efficiency. Figure 2 As shown in the figure, the laser operating current is 400mA, and the modulation signal voltage increases the laser driving current to 500mA. The frequency modulation also causes the laser output power to produce 100kHz amplitude modulation, and the power fluctuation reaches 22mW. Then it enters the silicon waveguide delay line. Since silicon material is a typical direct bandgap semiconductor, it exhibits a significant two-photon absorption effect for 1550nm light. This nonlinear effect leads to nonlinear changes in optical power, such as Figure 2 As shown. After passing through the silicon waveguide delay line, for the modulated signal range (driving current 400mA ~ 500mA), the output power fluctuation is reduced to 2.2mW, which is reduced by about 10 times. However, the overall output power also decreases. Therefore, the light continues to be input into the subsequent on-chip integrated semiconductor optical amplifier to increase the optical power to the required optical power level. Considering that optical amplification will also amplify the degree of optical power fluctuation, a suitable optical amplifier can be designed to make the incident light power in the saturation gain region of the optical amplifier, thereby further suppressing the optical power fluctuation level, thereby suppressing the laser power change caused by frequency modulation.

[0108] Subsequently, the laser with stable power is connected to the FMCW coherent detection module. The signal acquisition and calculation module synchronously collects the time domain waveform of the mixing signal inside the FMCW coherent detection module under the 100kHz square wave trigger signal output by the signal generator, and solves it through FFT calculation to obtain information such as the distance and speed corresponding to the detected target.

[0109] Specifically, ideally, for a general FMCW coherent detection module, its optical path mixing signal is converted into an electrical signal by the detector and contains both DC and AC components, wherein the DC component carries the amplitude information of the laser input light, and the AC component contains information such as the distance of the detection target. In fact, due to the power change caused by frequency modulation, the DC component here often carries a low-frequency AC signal with the same frequency as the frequency modulated signal. Mathematically, the triangular wave can be regarded as the superposition of a series of sine and cosine signals of different frequencies: f(x) = 2A / π*(sin(x)+1 / 3sin(3x)+1 / 5sin(5x)+…).

[0110] Furthermore, after FFT transformation, a series of low-frequency interference signal peaks will be generated in the low-frequency region of the spectrum. For the detection target, its signal frequency is proportional to the distance. For long-distance detection targets, its spectrum signal peak is far away from the low-frequency region, and the signal peak search is almost unaffected; while for close-range detection targets, its spectrum signal peak will overlap with the low-frequency interference peak, making it impossible to accurately judge, and even causing the detection target signal to be lost, thus affecting the close-range performance of the FMCW lidar.

[0111] Therefore, the laser power fluctuation level of the input FMCW coherent detection module is passively suppressed through nonlinear absorption to keep it basically constant, and the FFT spectrum only contains the reflected signal peak of the detection target, so that the low-frequency interference signal caused by the laser power fluctuation can be passively suppressed.

[0112] The embodiment of the present invention also provides a computer device for executing the above Figures 4 to 6 The laser frequency modulation method for passively suppressing low-frequency interference is shown.

[0113] See also Fig. 9 , Fig. 9 is a schematic diagram of the structure of a computer device provided by an optional embodiment of the present invention, such as Fig. 9 As shown, the computer device includes: one or more processors 10, a memory 20, and interfaces for connecting various components, including high-speed interfaces and low-speed interfaces. Various components are connected to each other using different buses for communication, and can be installed on a common mainboard or installed in other ways as needed. The processor can process the instructions executed in the computer device, including instructions stored in or on the memory to display the graphical information of the GUI on an external input / output device (such as, a display device coupled to the interface). In some optional embodiments, if necessary, multiple processors and / or multiple buses can be used together with multiple memories and multiple memories. Similarly, multiple computer devices can be connected, and each device provides some necessary operations (for example, as a server array, a group of blade servers, or a multi-processor system). Fig. 9 A processor 10 is taken as an example.

[0114] The processor 10 may be a central processing unit, a network processor or a combination thereof. The processor 10 may further include a hardware chip. The hardware chip may be a dedicated integrated circuit, a programmable logic device or a combination thereof. The programmable logic device may be a complex programmable logic device, a field programmable gate array, a general purpose array logic or any combination thereof.

[0115] The memory 20 stores instructions executable by at least one processor 10, so that at least one processor 10 executes the method shown in the above embodiment.

[0116] The memory 20 may include a program storage area and a data storage area, wherein the program storage area may store an operating system, an application required for at least one function; the data storage area may store data created according to the use of the computer device, etc. In addition, the memory 20 may include a high-speed random access memory, and may also include a non-transient memory, such as at least one disk storage device, a flash memory device, or other non-transient solid-state storage device. In some optional embodiments, the memory 20 may optionally include a memory remotely arranged relative to the processor 10, and these remote memories may be connected to the computer device via a network. Examples of the above-mentioned network include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and combinations thereof.

[0117] The memory 20 may include a volatile memory, such as a random access memory; the memory may also include a non-volatile memory, such as a flash memory, a hard disk or a solid state drive; the memory 20 may also include a combination of the above types of memory.

[0118] The computer device further comprises a communication interface 30 for the computer device to communicate with other devices or a communication network.

[0119] The embodiment of the present invention also provides a computer-readable storage medium. The method according to the embodiment of the present invention can be implemented in hardware, firmware, or can be implemented as a computer code that can be recorded in a storage medium, or can be implemented as a computer code that is originally stored in a remote storage medium or a non-temporary machine-readable storage medium and will be stored in a local storage medium through a network download, so that the method described herein can be stored in such software processing on a storage medium using a general-purpose computer, a dedicated processor, or programmable or dedicated hardware. Among them, the storage medium can be a magnetic disk, an optical disk, a read-only storage memory, a random access memory, a flash memory, a hard disk or a solid-state hard disk, etc.; further, the storage medium can also include a combination of the above types of memories. It can be understood that a computer, a processor, a microprocessor controller, or programmable hardware includes a storage component that can store or receive software or computer code. When the software or computer code is accessed and executed by a computer, a processor, or hardware, the method shown in the above embodiment is implemented.

[0120] A part of the present invention may be applied as a computer program product, such as a computer program instruction, which, when executed by a computer, can call or provide the method and / or technical solution according to the present invention through the operation of the computer. Those skilled in the art should understand that the existence of the computer program instruction in a computer-readable medium includes, but is not limited to, a source file, an executable file, an installation package file, etc., and accordingly, the way in which the computer program instruction is executed by the computer includes, but is not limited to: the computer directly executes the instruction, or the computer compiles the instruction and then executes the corresponding compiled program, or the computer reads and executes the instruction, or the computer reads and installs the instruction and then executes the corresponding installed program. Here, the computer-readable medium may be any available computer-readable storage medium or communication medium accessible to the computer.

[0121] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A FMCW laser radar device for passively suppressing low-frequency interference, characterized in that: The device comprises: a laser modulation device and a FMCW coherent detection device, wherein the laser modulation device comprises a signal generator, a laser, a nonlinear absorber and an optical amplifier; The signal generator is used to generate a modulation signal and output the modulation signal to the laser; The laser is used to generate an original laser signal, and to continuously frequency modulate the original laser signal based on the modulation signal to obtain a first modulated laser signal containing amplitude modulation information, and to output the first modulated laser signal to the nonlinear absorber; The nonlinear absorber is used to perform light absorption processing on the first modulated laser signal to obtain a second modulated laser signal, and output the second modulated laser signal to the optical amplifier; The optical amplifier is used to amplify the power of the second modulated laser signal and then output a target modulated signal to the FMCW coherent detection device; The FMCW coherent detection device is used to detect the target object based on the target modulation signal to obtain the target detection distance.

2. The device according to claim 1, characterized in that The FMCW coherent detection device comprises: an FMCW coherent detection module and a signal acquisition and calculation module; The FMCW coherent detection module is used to detect the target object based on the target modulation signal and generate a mixed signal carrying target detection distance information; The signal acquisition and calculation module is used to obtain the waveform data of the mixed signal based on a synchronous trigger signal, and calculate the target detection distance based on the waveform data. The synchronous trigger signal is synchronously output to the signal acquisition and calculation module when the signal generator outputs the modulated signal.

3. The device according to claim 1, characterized in that The nonlinear absorber adopts a silicon-based waveguide delay line structure.

4. A frequency modulation method for passively suppressing low-frequency interference, characterized in that: A laser modulation device in a FMCW laser radar device for passively suppressing low-frequency interference as claimed in any one of claims 1 to 3; the method comprising: Generate a modulation signal using a signal generator; Using the modulation signal to control the laser driving current to produce continuous frequency modulation and output a first modulated laser signal containing amplitude modulation information; The first modulated laser signal is processed by a nonlinear absorber and an optical amplifier respectively to obtain a target modulated signal.

5. The method according to claim 4, characterized in that Using the modulation signal to control the laser driving current change to generate continuous frequency modulation and output a first modulated laser signal containing amplitude modulation information, comprising: Acquiring the voltage amplitude of the modulation signal and the modulation efficiency of the laser; determining a modulation bandwidth based on the voltage amplitude and the modulation efficiency; Based on the modulation bandwidth, the laser driving current is controlled by the modulation signal to generate continuous frequency modulation and output the first modulated laser signal containing amplitude modulation information.

6. The method according to claim 4, characterized in that The first modulated laser signal is processed by a nonlinear absorber and an optical amplifier respectively to obtain a target modulated signal, comprising: Using the nonlinear absorber to absorb the first modulated laser signal and output a second modulated laser signal to an optical amplifier; The optical amplifier is used to amplify the second modulated laser signal to obtain a target modulated signal.

7. The method according to claim 4, characterized in that The method further comprises: The target modulation signal is output to a FMCW coherent detection device, so that the FMCW coherent detection device detects the target object based on the target modulation signal.

8. A computer device, characterized in that: include: A memory and a processor, wherein the memory and the processor are communicatively connected to each other, the memory stores computer instructions, and the processor executes the laser frequency modulation method for passively suppressing low-frequency interference as described in any one of claims 4 to 7 by executing the computer instructions.

9. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer instructions, and the computer instructions are used to enable a computer to execute the laser frequency modulation method for passively suppressing low-frequency interference according to any one of claims 4 to 7.

10. A computer program product, characterized in that The method comprises computer instructions, wherein the computer instructions are used to cause a computer to execute the laser frequency modulation method for passively suppressing low-frequency interference according to any one of claims 4 to 7.

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