Frequency-modulated continuous wave laser radar chip and frequency-modulated continuous wave laser radar ranging system

Abstract

The invention relates to the technical field of laser ranging, and discloses a frequency-modulated continuous wave laser radar chip and a frequency-modulated continuous wave laser radar ranging system.The chip comprises a measuring circuit, a modulation reference light path and a calibration circuit, the measurement path is used for performing frequency mixing processing on the laser signal and the first detection signal to obtain a ranging beat frequency signal and sending the ranging beat frequency signal to the signal processor; the modulation reference light path is used for extracting a modulation reference signal in the laser signal and outputting the modulation reference signal to the signal processor; and the calibration circuit is used for performing frequency mixing processing on the laser signal and the delayed light signal to obtain a calibration beat frequency signal, and outputting the calibration beat frequency signal to the signal processor, so that the signal processor calculates the distance of the target object according to the modulation reference signal, the calibration beat frequency signal and the distance measurement beat frequency signal. According to the invention, the capability of detecting a close-range target object is increased, the calibration precision is maintained, and the acoustic transducer modules are added in the calibration path and the measurement path, so that the precision can be adjusted.

Description

Technical Field

[0001] The present invention relates to the field of laser ranging technology, and in particular to a frequency modulated continuous wave laser radar chip and a frequency modulated continuous wave laser radar ranging system. Background Art

[0002] At present, Frequency Modulated Continuous Wave (FMCW) LiDAR has shown great advantages in real-time detection distance, speed, etc., thanks to its application of coherent detection technology and reasonable continuous modulation of the laser frequency. Among them, the method of modulating the laser is generally to continuously modulate the driving current of the laser through a hardware circuit, thereby realizing the continuous change of the laser output frequency and the modulation of the output power. However, since the output of the laser has a lower modulation frequency, in the signal spectrum, when the frequency of the short-range signal of the FMCW LiDAR is close to the modulation frequency, the lower modulation frequency will interfere with the peak search of the short-range signal, resulting in a blind spot in the short-range detection of the FMCW LiDAR. Summary of the invention

[0003] In view of this, the present invention provides a frequency modulated continuous wave laser radar chip and a frequency modulated continuous wave laser radar ranging system to solve the problem of blind spots in close-range detection of FMCW laser radar.

[0004] In the first aspect, the present invention provides a frequency modulated continuous wave laser radar chip for receiving a laser signal emitted by a semiconductor laser, wherein the laser signal is obtained by modulating the output signal of the semiconductor laser by a signal generator through a modulation signal, and the frequency modulated continuous wave laser radar chip comprises: a measurement path, a modulation reference optical path and a calibration path, wherein the calibration path is provided with an optical circuit of a preset length inside the frequency modulated continuous wave laser radar chip, the measurement path is used for mixing the laser signal and a first detection signal to obtain a ranging beat frequency signal, and sending the ranging beat frequency signal to a signal processor, wherein the first detection signal is a signal returned when the laser signal detects the distance to the target object; the modulation reference optical path is used for extracting the modulation reference in the laser signal signal, and outputs the modulation reference signal to the signal processor, so that the signal processor removes the modulation signal in the ranging beat signal according to the modulation reference signal to obtain a ranging correction signal, and calculates the distance of the target object according to the ranging correction signal, and the modulation reference signal corresponds to the modulation signal; the calibration circuit is used to mix the laser signal and the delayed optical signal to obtain a calibration beat signal, and outputs the calibration beat signal to the signal processor, so that the signal processor removes the modulation signal in the calibration beat signal according to the modulation reference signal to obtain a calibration correction signal, and calculates the distance of the target object according to the calibration correction signal and the ranging correction signal, and the delayed optical signal is obtained after the laser signal passes through the optical circuit of the preset length.

[0005] The frequency modulated continuous wave laser radar chip provided in the embodiment of the present invention includes a measurement path, a calibration path and a modulation reference optical path. If the semiconductor laser has a center frequency drift, even if the measurement path has a beat frequency error when measuring the distance of the target object, after the calibration path is provided, the calibration path and the measurement path will generate a common mode error. At this time, the error caused by the center frequency drift can be eliminated according to the ratio of the beat frequency signal of the measurement path to the beat frequency signal of the calibration path, thereby improving the accuracy of the distance measurement of the measurement path. In addition, the modulation reference optical path in the embodiment of the present invention can extract the ranging beat frequency signal from the laser signal. Therefore, the modulation reference signal is extracted from the laser signal through the modulation reference optical path, and the modulation signal in the ranging beat frequency signal and the calibration beat frequency signal is removed according to the modulation reference signal. At this time, the ranging correction signal and the calibration beat frequency signal do not contain the modulation signal. Therefore, when the distance of the target object is calculated according to the ranging correction signal and the calibration beat frequency signal, it will not be interfered by the modulation signal, and the calculation result is more accurate.

[0006] In an optional embodiment, the frequency modulated continuous wave laser radar chip provided in an embodiment of the present invention also includes a splitting structure for sending the laser signal to a measurement path, a calibration path and a modulated reference optical path respectively, and the splitting structure includes a first multi-mode interferometer and a directional coupler, the first multi-mode interferometer is used to split the laser signal into two paths, one path is input into the measurement path, and the other path is input into the directional coupler; the directional coupler is used to split the laser signal into two paths, one path is input into the calibration path, and the other path is input into the modulated reference optical path.

[0007] In an optional embodiment, the measurement path includes a second multimode interferometer, a polarization flip beam splitter, a spot converter, a third multimode interferometer and a first photoelectric balanced detector, the second multimode interferometer is used to divide the laser signal into two paths, one path enters the polarization flip beam splitter, and the other path enters the third multimode interferometer; after the laser signal passes through the polarization flip beam splitter and the spot converter, it is emitted from the frequency modulated continuous wave laser radar chip, and returns the first detection signal after reaching the target object; the polarization flip beam splitter is used to convert the polarization state of the first detection signal so that the polarization state of the first detection signal is a transverse electric wave, and the first detection signal is sent to the third multimode interferometer; the third multimode interferometer is used to mix the laser signal and the first detection signal to obtain a first beat frequency signal, and send the first beat frequency signal to the first photoelectric balanced detector; the first photoelectric balanced detector is used to convert the first beat frequency signal into an electrical signal to form a ranging beat frequency signal.

[0008] In an optional embodiment, the measurement path further includes a first acoustic transducer module, which is used to change the refractive index of the measurement path waveguide, thereby equivalently increasing the detection distance of the target object to increase the frequency of the distance signal peak in the first detection signal.

[0009] In an optional embodiment, the calibration path includes a fourth multi-mode interferometer, a fifth multi-mode interferometer and a second photoelectric balanced detector. The fourth multi-mode interferometer is used to divide the laser signal into two paths, one laser signal enters the fifth multi-mode interferometer, and the other laser signal passes through an optical loop of a preset length to form a second detection signal and enter the fifth multi-mode interferometer; the fifth multi-mode interferometer is used to mix the laser signal and the second detection signal to obtain a second beat frequency signal, and send the second beat frequency signal to the second photoelectric balanced detector; the second photoelectric balanced detector is used to convert the second beat frequency signal into an electrical signal to form a calibration beat frequency signal.

[0010] In an optional embodiment, the calibration path further includes a second acoustic transducer module, and the second acoustic transducer module is used to change the refractive index of the calibration path waveguide, thereby changing the preset length.

[0011] In a second aspect, an embodiment of the present invention provides a frequency modulated continuous wave laser radar ranging system, including: a signal generator, a semiconductor laser, a frequency modulated continuous wave laser radar chip, and a signal processor, wherein the signal generator is used to modulate the output signal of the semiconductor laser by a modulation signal so that the semiconductor laser outputs a laser signal; the semiconductor laser is used to transmit a laser signal to the frequency modulated continuous wave laser radar chip; the frequency modulated continuous wave laser radar chip includes a measurement path, a modulation reference light path, and a calibration path, the measurement path is used to mix the laser signal and the first detection signal to obtain a ranging beat frequency signal, the first detection signal is a signal returned when the laser signal detects the distance to the target object; the modulation reference light path The circuit is used to extract the modulation reference signal in the laser signal and output the modulation reference signal to the signal processor; the calibration circuit is used to mix the laser signal and the delayed optical signal to obtain the calibration beat signal, and output the calibration beat signal to the signal processor, wherein the delayed optical signal is obtained after the laser signal passes through the optical circuit of the preset length; the signal processor is used to receive the ranging beat signal, the calibration beat signal and the modulation reference signal, remove the modulation signal in the ranging beat signal according to the modulation reference signal to obtain the ranging correction signal; remove the modulation signal in the calibration beat signal according to the modulation reference signal to obtain the calibration correction signal; and calculate the distance of the target object according to the calibration correction signal and the ranging correction signal.

[0012] In an optional implementation, the signal processor includes an analog-to-digital acquisition conversion module, a differential operational amplifier module and an FPGA system-on-chip, the analog-to-digital acquisition conversion module is used to receive the ranging beat signal, the calibration beat signal and the modulation reference signal, and send the ranging beat signal, the calibration beat signal and the modulation reference signal to the differential operational amplifier module; the differential operational amplifier module is used to subtract the positive phase signal of the ranging beat signal and the calibration beat signal from the negative phase signal of the modulation reference signal, respectively, to obtain the ranging correction signal and the calibration correction signal, and send the ranging correction signal and the calibration correction signal to the FPGA system-on-chip; the FPGA system-on-chip is used to calculate the distance of the target object according to the calibration correction signal and the ranging correction signal.

[0013] In an optional embodiment, the FPGA on-chip system includes: a frequency extraction module, used to determine the first distance signal frequency in the ranging correction signal, and the second distance signal frequency in the calibration correction signal; a distance calculation module, used to calculate the distance of the target object according to the ratio of the first distance signal frequency to the second distance signal frequency, and a preset length, the ratio of the first distance signal frequency to the second distance signal frequency is the same as the ratio of the preset length to the distance of the target object.

[0014] In an optional embodiment, a semiconductor laser and a frequency modulated continuous wave laser radar chip are packaged using co-packaging technology, and the semiconductor laser and the frequency modulated continuous wave laser radar chip are arranged on the first surface of the circuit lead-out patch, and an optical isolator, an optical lens and a wave plate are arranged between the semiconductor laser and the frequency modulated continuous wave laser radar chip in sequence; a semiconductor cooler module is arranged on the second surface of the circuit lead-out patch. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] 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.

[0016] Figure 1 is a schematic structural diagram of a frequency modulated continuous wave laser radar ranging system according to an embodiment of the present invention;

[0017] Figure 2 is a schematic diagram of the structure of a frequency modulated continuous wave laser radar chip according to an embodiment of the present invention;

[0018] Figure 3 is a schematic diagram of a ranging beat frequency signal including interference from a modulation signal;

[0019] Figure 4is a schematic diagram of a ranging beat frequency signal with modulation signal interference removed;

[0020] Figure 5 It is a schematic diagram of the ranging beat frequency signal after the low frequency signal is pulled up;

[0021] Figure 6 is a schematic structural diagram of another frequency modulated continuous wave laser radar ranging system according to an embodiment of the present invention;

[0022] Figure 7 is a schematic diagram of a packaging structure of a semiconductor laser according to an embodiment of the present invention;

[0023] Figure 8 is a schematic diagram of the structure of a signal processor according to an embodiment of the present invention. DETAILED DESCRIPTION

[0024] 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.

[0025] In the FMCW laser radar ranging system, Figure 1 As shown, the signal generator modulates the output signal of the laser to obtain a laser signal. When the distance of the target object is measured by the laser signal, the laser signal returns a detection signal after reaching the target object. The frequency modulated continuous wave lidar chip processes the detection signal and the laser signal, and outputs the processed signal to the signal processor. The signal processor calculates the signal to obtain the distance of the target object.

[0026] Since the signal generator modulates the output signal of the laser, the laser signal has a lower modulation frequency. When the frequency of the short-range signal of the FMCW lidar is close to the modulation frequency, the lower modulation frequency will interfere with the peak finding of the short-range signal, resulting in a blind spot in the short-range detection of the FMCW lidar.

[0027] In order to avoid the influence of modulation frequency on the ranging process, a frequency modulated continuous wave laser radar chip is provided in an embodiment of the present invention, such as Figure 2 As shown, it includes a measurement path, a modulated reference optical path and a calibration path. The calibration path is provided with an optical circuit of a preset length inside the frequency modulated continuous wave laser radar chip.

[0028] The measuring circuit is used to mix the laser signal and the first detection signal to obtain a ranging beat signal, and send the ranging beat signal to the signal processor. The first detection signal is a signal returned when the laser signal detects the distance to the target object.

[0029] If the distance between the target object and the FMCW laser radar chip is different, the frequency of the returned first detection signal will also be different.

[0030] In an optional embodiment, after the laser emits a laser signal, the laser signal enters the frequency modulated continuous wave laser radar chip, passes through a measurement path, and is emitted from the frequency modulated continuous wave laser radar chip, and returns a detection signal after contacting an obstacle.

[0031] The modulation reference optical path is used to extract the modulation reference signal from the laser signal and output the modulation reference signal to the signal processor, so that the signal processor removes the modulation signal from the ranging beat frequency signal according to the modulation reference signal to obtain a ranging correction signal, and calculates the distance of the target object according to the ranging correction signal. The modulation reference signal corresponds to the modulation signal.

[0032] In an optional embodiment, in the modulation reference optical path, the laser signal can be converted into an electrical signal by a photodiode (PD), thereby extracting the modulation reference signal in the laser signal. The signal generator modulates the output signal of the laser, so the laser signal carries the modulation signal, and the modulation reference signal extracted from the laser signal corresponds to the modulation signal.

[0033] For the measurement path, in general, the mixed signal obtained after the optical signal is transmitted and received will carry AC component information such as the distance to the target, and at the same time, it also contains the DC component information of the laser input light. The DC component contains a low-frequency signal whose power changes with the modulation signal. After the low-frequency signal is fast Fourier transformed, a low-frequency signal peak will be generated in the FMCW overall signal spectrum, thereby interfering with the detection of close-range targets and creating a blind spot for FMCW laser radar close-range detection. That is, in addition to the target distance signal peak, the spectrum of the mixed signal also contains the corresponding interference peak caused by the modulation signal, such as Figure 3 After removing the modulation reference signal, the signal obtained is as follows Figure 4 shown.

[0034] The frequency modulated continuous wave laser radar chip provided in the embodiment of the present invention includes a measurement path and a modulation reference optical path. The modulation reference optical path can extract a ranging beat frequency signal from a laser signal. Therefore, the modulation reference signal is extracted from the laser signal through the modulation reference optical path, and the modulation signal in the ranging beat frequency signal is removed according to the modulation reference signal to obtain a ranging correction signal. At this time, the ranging correction signal does not contain a modulation signal. Therefore, when calculating the distance of the target object according to the ranging correction signal, it will not be interfered by the modulation signal, and the calculation result will be more accurate.

[0035] The frequency modulated continuous wave laser radar chip provided in an embodiment of the present invention also includes a calibration path, and the calibration path is provided with an optical circuit of a preset length inside the frequency modulated continuous wave laser radar chip.

[0036] The calibration circuit is used to mix the laser signal and the delayed optical signal to obtain a calibration beat signal, and output the calibration beat signal to the signal processor, so that the signal processor removes the modulation signal in the calibration beat signal according to the modulation reference signal to obtain a calibration correction signal, and calculates the distance of the target object according to the calibration correction signal and the ranging correction signal. The delayed optical signal is obtained after the laser signal passes through the optical circuit of the preset length.

[0037] In an optional embodiment, when the signal processor calculates the distance of the target object based on the calibration correction signal and the ranging correction signal, it first determines the first distance signal frequency in the ranging correction signal and the second distance signal frequency in the calibration correction signal, and then calculates the distance of the target object based on the ratio of the first distance signal frequency to the second distance signal frequency and a preset length, and the ratio of the first distance signal frequency to the second distance signal frequency is the same as the ratio of the preset length to the distance of the target object.

[0038] In FMCW radar, the laser frequency changes in the form of linear frequency modulation (Chirp), and the frequency difference (beat frequency) between the transmitted signal and the received signal is directly proportional to the distance to the target:

[0039]

[0040] Among them, f b is the beat frequency, B is the modulation bandwidth, L is the measurement distance, c is the speed of light, and T is the modulation period.

[0041] According to the above formula, the ratio of the first distance signal frequency to the second distance signal frequency is the ratio of the distance of the target object to the preset length of the optical circuit in the calibration path, so that the distance of the target object is calculated based on the ratio of the first distance signal frequency to the second distance signal frequency and the preset length.

[0042] When the distance of the target object is detected by the laser signal emitted by the semiconductor laser, the semiconductor laser may have a center frequency drift, which will cause the slope of the modulation waveform to change. Taking the triangle wave linear frequency modulation as an example, when the center frequency of the laser drifts, the slope of the triangle wave of the linear frequency modulation will also change, thereby affecting the modulation bandwidth B, which in turn causes the beat frequency result of the measurement path to deviate. At this time, the beat frequency result of the calibration path will also be affected. This error that affects the results of the two is called the common mode error. In order to eliminate this influence, the frequency ratio method can be used, that is, the time domain signals of the two paths are known, the frequency is obtained by transformation, and then the ratio of the frequencies of the two paths is directly equal to the ratio of the distances for conversion, and the detection distance of the measurement path can be directly obtained, thereby avoiding the error in the distance measurement accuracy of the measurement path caused by calculating the bandwidth B.

[0043] Since the laser signal input into the calibration path will also be interfered by the modulation signal, before the ranging correction signal is corrected by the calibration beat frequency signal, the modulation signal in the calibration beat frequency signal also needs to be removed first.

[0044] In an alternative embodiment, if Figure 2 As shown, the FMCW laser radar chip provided in the embodiment of the present invention also includes a splitting structure for sending laser signals to the measurement path, the calibration path and the modulated reference optical path respectively. The splitting structure includes a first multi-mode interferometer (Multi-mode Inferometer, MMI) and a directional coupler (Directional Coupler, DC). Figure 5 In the illustrated embodiment, the first multi-mode interferometer is a 1X2 MMI.

[0045] After the laser signal enters the frequency modulated continuous wave lidar chip through the spot-size converter (SSC), the first multi-mode interferometer is used to split the laser signal into two paths, one is input into the measurement path, and the other is input into the directional coupler; the directional coupler is used to split the laser signal into two paths, one is input into the calibration path, and the other is input into the modulation reference optical path.

[0046] In an alternative embodiment, if Figure 2 As shown, in the frequency modulated continuous wave laser radar chip provided by the embodiment of the present invention, the measurement path includes a second multimode interferometer, a polarizing beam reversal splitter (polarizing beam reversal splitter, PBRS), a spot size converter (Spot-size Converter, SSC), a third multimode interferometer and a first balanced photodetector (Balanced Photo Detector, BPD), Figure 2In the illustrated embodiment, the second multi-mode interferometer is a 1X2MMI, and the third multi-mode interferometer is a 2X2MMI.

[0047] The second multimode interferometer is used to split the laser signal into two paths, one path enters the polarization flip beam splitter, and the other path enters the third multimode interferometer.

[0048] After passing through the polarization flip beam splitter and the spot converter, the laser signal is emitted from the frequency modulated continuous wave lidar chip and returns the first detection signal after reaching the target object.

[0049] The polarization flipping beam splitter is also used to convert the polarization state of the first detection signal so that the polarization state of the first detection signal is a transverse electric wave, and send the first detection signal to the third multi-mode interferometer.

[0050] The third multi-mode interferometer is used to send the laser signal and the first beat frequency signal of the first detection signal to the first photoelectric balanced detector.

[0051] The first photoelectric balance detector is used to convert the first beat frequency signal into an electrical signal to form a distance measurement beat frequency signal.

[0052] exist Figure 2 In the embodiment shown, the optical signal in the measurement path passes through the 1X2 MMI and then passes through the PBRS and SSC structures for coaxial transmission and reception of detection signals. In addition to the splitting function, the PBRS structure also makes the polarization state of the returned optical signal consistent with the signal polarization of the local light, that is, the polarization state of the transverse magnetic wave (TM) light is converted into the transverse electric wave (TE) light after passing through the PBRS, thereby avoiding the loss of the received optical signal and fundamentally improving the final signal-to-noise ratio of the signal.

[0053] In an alternative embodiment, if Figure 2 As shown, in the FMCW laser radar chip provided in the embodiment of the present invention, the measurement circuit also includes a first acoustic transducer module (Acoustic Interdigital Transducer, AcousticIDT). Figure 2 In the illustrated embodiment, the first acoustic transducer module is Acoustic IDT 1 .

[0054] The first acoustic transducer module is used to change the refractive index of the measuring path waveguide, thereby equivalently increasing the detection distance of the target object to increase the frequency of the distance signal peak in the first detection signal. When the distance of the target object is subsequently calculated, the calculation can be performed based on the frequency of the distance signal peak. Since the frequency of the distance signal peak is far away from the low-frequency area, it will not be interfered by the low-frequency signal at this time, and the distance calculation result obtained is more accurate.

[0055] In order to solve the problem that the ranging beat frequency signal of the measurement path may be interfered by low frequencies, an Acoustic IDT structure is designed in the embodiment of the present invention. The process of the Acoustic IDT structure is mainly to deposit an AlScN piezoelectric film layer on the buried oxide layer of the Silicon-on-Insulator Chip (SOI), and to make gold interlaced finger electrodes on the AlScN piezoelectric film layer. The RF signal output by an external radio frequency (RF) signal source is applied to the electrodes of the Acoustic IDT structure, and the structure will generate surface acoustic waves and propagate on the buried oxide layer, causing the refractive index of the optical waveguide at the rear end of the PBRS to change, and the change is proportional to the change in the acoustic wave. At the same time, the change in the refractive index will modulate the phase of the light in the waveguide, that is, the frequency of the output signal and the coaxial return detection signal can be modulated at high frequencies, and finally the returned detection signal is kept away from the low-frequency region in the spectrum, thus avoiding low-frequency interference. Figure 3 The signal spectrum with interference peaks at close distance is shown as Figure 5 The signal spectrum after passing through the Acoustic IDT structure is shown in Figure 1. Figure 3 , Figure 5 It can be seen that after the Acoustic IDT structure, the distance signal peak is far away from the low-frequency interference peak. At this time, when the distance to the target object is calculated based on the distance signal peak, the result obtained is more accurate.

[0056] In an optional embodiment, in the frequency modulated continuous wave laser radar chip provided by the embodiment of the present invention, Figure 2 As shown, the calibration circuit includes a fourth multi-mode interferometer, a fifth multi-mode interferometer, a second acoustic transducer module and a second photoelectric balance detector. Figure 2 In the illustrated embodiment, the fourth multi-mode interferometer is 1X2MMI and the fifth multi-mode interferometer is 2X2MMI.

[0057] The fourth multi-mode interferometer is used to divide the laser signal into two paths, one laser signal enters the fifth multi-mode interferometer, and the other laser signal is calibrated and delayed modulated by the second acoustic transducer module to form a second detection signal and enter the fifth multi-mode interferometer; the fifth multi-mode interferometer is used to send the second beat signal of the laser signal and the second detection signal to the second photoelectric balanced detector; the second photoelectric balanced detector is used to convert the second beat signal into an electrical signal to form a calibrated beat signal.

[0058] In the embodiment of the present invention, a second acoustic transducer module (Acoustic IDT structure) is integrated in the calibration path. The function of this structure for the calibration path is to change the refractive index of the waveguide of the calibration path, thereby equivalently changing the length of the calibration path; the closer the length of the calibration path is to the length of the measurement path, the more synchronized the optical signal transmission of the calibration path and the measurement path, that is, the time for error extraction of the system through the calibration path is more matched with the detection time of the measurement path, so that the high-precision result of the measurement path will be better. Therefore, although there is a calibration path of fixed physical length on the chip, its functional length in actual application can be adjusted by adjusting the refractive index of the waveguide, that is, by adjusting the functional length of the calibration path, the final detection distance accuracy of the entire system can be adjusted.

[0059] In an optional embodiment, although the calibration path and the measurement path are modulated by the Acoustic IDT, if the beat frequency signals of the measurement path and the calibration path output an unbalanced result in the BPD, the low-frequency signal in the DC component still exists, which will interfere with the application of the system in point cloud peak finding. Therefore, the modulation reference optical path is to make a difference between the final beat frequency signal and the reference modulation signal to remove the modulation information, so as to ensure that the subsequent beat frequency signal has no modulation information, thereby eliminating application risks.

[0060] The embodiment of the present invention also provides a frequency modulated continuous wave laser radar ranging system, such as Figure 1 As shown, it includes: a signal generator, a semiconductor laser, a frequency modulated continuous wave laser radar chip, and a signal processor.

[0061] The signal generator is used to modulate the output signal of the semiconductor laser through a modulation signal so that the semiconductor laser outputs a laser signal.

[0062] Semiconductor lasers are used to transmit laser signals to the frequency modulated continuous wave lidar chip.

[0063] The frequency modulated continuous wave laser radar chip includes a measurement path, a modulation reference optical path and a calibration path. The measurement path is used to mix the laser signal and the first detection signal to obtain a ranging beat signal. The first detection signal is a signal returned when the laser signal detects the distance of the target object; the modulation reference optical path is used to extract the modulation reference signal in the laser signal and output the modulation reference signal to the signal processor; the calibration path is used to mix the laser signal and the delayed optical signal to obtain a calibration beat signal, and output the calibration beat signal to the signal processor. The delayed optical signal is obtained after the laser signal passes through the optical circuit of the preset length;

[0064] The signal processor is used to receive a ranging beat signal, a calibration beat signal and a modulation reference signal, remove the modulation signal in the ranging beat signal according to the modulation reference signal to obtain a ranging correction signal; remove the modulation signal in the calibration beat signal according to the modulation reference signal to obtain a calibration correction signal; and calculate the distance of the target object according to the calibration correction signal and the ranging correction signal.

[0065] In an optional embodiment, in order to match the frequency modulated continuous wave laser radar chip, the semiconductor laser needs to be co-packaged with the silicon photonic chip. The semiconductor laser and the frequency modulated continuous wave laser radar chip are arranged on the first surface of the circuit lead-out patch. An optical isolator, an optical lens and a wave plate are sequentially arranged between the semiconductor laser and the frequency modulated continuous wave laser radar chip. The optical lens and the wave plate perform optical polarization and coupling confirmation on the output light of the laser to ensure that the optical coupling of the semiconductor laser enters the silicon photonic chip. In order to ensure the stability of the overall device after co-packaging, a semiconductor refrigerator (Thermo Electric Cooler, TEC) module must be added below the device package on the circuit lead-out patch for temperature control protection, such as Figure 7 shown.

[0066] The present invention adopts co-packaging technology to make the frequency modulated continuous wave laser radar ranging system highly integrated, which greatly reduces the size of the frequency modulated continuous wave laser radar ranging system, makes the frequency modulated continuous wave laser radar ranging system large-scale and batch-produced, and has lower production cost; at the same time, silicon photonics integration technology makes the frequency modulated continuous wave laser radar ranging system consume less power, have stronger functional expansion capability, be less affected by the external environment, and have more reliable performance.

[0067] In an alternative embodiment, if Figure 6 As shown, the frequency modulated continuous wave laser radar ranging system provided by the embodiment of the present invention also includes a radio frequency signal source.

[0068] The RF signal source is used to transmit a RF signal to the first acoustic transducer module so that the first acoustic transducer module changes the refractive index of the measuring path waveguide, thereby equivalently increasing the detection distance of the target object and increasing the frequency of the distance signal peak in the first detection signal.

[0069] The RF signal source is also used to transmit a RF signal to the second acoustic transducer module so that the second acoustic transducer module changes the refractive index of the calibration path waveguide, thereby changing the preset length so that the preset length is close to the actual distance of the target object, thereby ensuring that no matter how far the target object is measured using the frequency modulated continuous wave lidar ranging system, a higher measurement accuracy can be obtained.

[0070] In an alternative embodiment, if Figure 8As shown, in the frequency modulated continuous wave laser radar ranging system provided in an embodiment of the present invention, the signal processor includes an analog-to-digital acquisition conversion module, a differential operational amplifier module and an FPGA chip system.

[0071] The analog-to-digital acquisition conversion module is used to receive the ranging beat frequency signal, the calibration beat frequency signal and the modulation reference signal, and send the ranging beat frequency signal, the calibration beat frequency signal and the modulation reference signal to the differential operational amplifier module.

[0072] The differential operational amplifier module is used to subtract the positive phase signal of the ranging beat signal and the calibration beat signal from the negative phase signal of the modulation reference signal to obtain the ranging correction signal and the calibration correction signal, and send the ranging correction signal and the calibration correction signal to the FPGA on-chip system.

[0073] The FPGA on-chip system is used to calculate the distance of the target object based on the calibration correction signal and the ranging correction signal.

[0074] In an optional embodiment, in the frequency modulated continuous wave laser radar ranging system provided in the embodiment of the present invention, the FPGA chip system includes:

[0075] A frequency extraction module, used to determine the first distance signal frequency in the ranging correction signal and the second distance signal frequency in the calibration correction signal;

[0076] The distance calculation module is used to calculate the distance of the target object according to the ratio of the first distance signal frequency to the second distance signal frequency and a preset length, and the ratio of the first distance signal frequency to the second distance signal frequency is the same as the ratio of the preset length to the distance of the target object.

[0077] Of course, the calibration path has other functions that can improve the ranging accuracy of the system, such as extracting the nonlinear error parameters of the system through the calibration path for calibration, which will not be elaborated here.

[0078] 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 frequency modulated continuous wave laser radar chip, characterized in that: The FMCW laser radar chip is used to receive a laser signal emitted by a semiconductor laser. The laser signal is obtained by modulating the output signal of the semiconductor laser by a signal generator through a modulation signal. The FMCW laser radar chip includes: a measurement path, a modulation reference optical path and a calibration path. The calibration path is provided with an optical circuit of a preset length inside the FMCW laser radar chip. The measuring circuit is used to mix the laser signal and the first detection signal to obtain a ranging beat signal, and send the ranging beat signal to a signal processor, wherein the first detection signal is a signal returned when the laser signal detects the distance to the target object; The modulation reference optical path is used to extract the modulation reference signal from the laser signal, and output the modulation reference signal to the signal processor, so that the signal processor removes the modulation signal from the ranging beat frequency signal according to the modulation reference signal to obtain a ranging correction signal; The calibration circuit is used to mix the laser signal and the delayed optical signal to obtain a calibration beat signal, and output the calibration beat signal to the signal processor, so that the signal processor removes the modulation signal in the calibration beat signal according to the modulation reference signal to obtain a calibration correction signal, and calculates the distance of the target object according to the calibration correction signal and the ranging correction signal. The delayed optical signal is obtained after the laser signal passes through the optical circuit of the preset length.

2. The chip according to claim 1, characterized in that: It also includes a splitter structure for sending the laser signal to the measurement path, the calibration path and the modulated reference optical path respectively, and the splitter structure includes a first multimode interferometer and a directional coupler. The first multi-mode interferometer is used to divide the laser signal into two paths, one path is input into the measurement path, and the other path is input into the directional coupler; The directional coupler is used to divide the laser signal into two paths, one path is input into the calibration path, and the other path is input into the modulation reference optical path.

3. The chip according to claim 1, characterized in that: The measuring path includes a second multimode interferometer, a polarization flip beam splitter, a mode spot converter, a third multimode interferometer and a first photoelectric balance detector. The second multi-mode interferometer is used to split the laser signal into two paths, one path enters the polarization flip beam splitter, and the other path enters the third multi-mode interferometer; After passing through the polarization flip beam splitter and the spot converter, the laser signal is emitted from the frequency modulated continuous wave laser radar chip, and returns a first detection signal after reaching the target object; The polarization flip beam splitter is used to convert the polarization state of the first detection signal so that the polarization state of the first detection signal is a transverse electric wave, and send the first detection signal to the third multi-mode interferometer; The third multi-mode interferometer is used to mix the laser signal and the first detection signal to obtain a first beat frequency signal, and send the first beat frequency signal to the first photoelectric balance detector; The first photoelectric balance detector is used to convert the first beat frequency signal into an electrical signal to form the ranging beat frequency signal.

4. The chip according to claim 3, characterized in that: The measuring circuit also includes a first acoustic transducer module, The first acoustic transducer module is used to change the refractive index of the measuring path waveguide, thereby equivalently increasing the detection distance of the target object to increase the frequency of the distance signal peak in the first detection signal.

5. The chip according to claim 1, characterized in that: The calibration circuit includes a fourth multi-mode interferometer, a fifth multi-mode interferometer and a second photoelectric balance detector. The fourth multi-mode interferometer is used to divide the laser signal into two paths, one path of the laser signal enters the fifth multi-mode interferometer, and the other path of the laser signal forms a second detection signal after passing through an optical loop of a preset length and enters the fifth multi-mode interferometer; The fifth multi-mode interferometer is used to mix the laser signal and the second detection signal to obtain a second beat frequency signal, and send the second beat frequency signal to the second photoelectric balanced detector; The second photoelectric balanced detector is used to convert the second beat frequency signal into an electrical signal to form the calibration beat frequency signal.

6. The chip according to claim 5, characterized in that: The calibration circuit also includes a second acoustic transducer module, The second acoustic transducer module is used to change the refractive index of the calibration path waveguide, thereby changing the preset length.

7. A frequency modulated continuous wave laser radar ranging system, characterized in that: include: Signal generator, semiconductor laser, frequency modulated continuous wave laser radar chip, signal processor, The signal generator is used to modulate the output signal of the semiconductor laser by means of a modulation signal so that the semiconductor laser outputs a laser signal; The semiconductor laser is used to transmit a laser signal to the frequency modulated continuous wave laser radar chip; The frequency modulated continuous wave laser radar chip comprises a measurement path, a modulation reference optical path and a calibration path, wherein the measurement path is used to mix the laser signal and the first detection signal to obtain a ranging beat frequency signal, wherein the first detection signal is a signal returned when the laser signal detects the distance to the target object; The modulation reference optical path is used to extract the modulation reference signal from the laser signal, and output the modulation reference signal to the signal processor; the calibration path is used to mix the laser signal and the delayed optical signal to obtain a calibration beat signal, and output the calibration beat signal to the signal processor, wherein the delayed optical signal is obtained after the laser signal passes through an optical circuit of a preset length; The signal processor is used to receive the ranging beat signal, the calibration beat signal and the modulation reference signal, remove the modulation signal in the ranging beat signal according to the modulation reference signal to obtain a ranging correction signal; remove the modulation signal in the calibration beat signal according to the modulation reference signal to obtain a calibration correction signal; and calculate the distance of the target object according to the calibration correction signal and the ranging correction signal.

8. The system according to claim 7, characterized in that The signal processor includes an analog-to-digital acquisition conversion module, a differential operational amplifier module and an FPGA chip system. The analog-to-digital acquisition conversion module is used to receive the ranging beat frequency signal, the calibration beat frequency signal and the modulation reference signal, and send the ranging beat frequency signal, the calibration beat frequency signal and the modulation reference signal to the differential operational amplifier module; The differential operational amplifier module is used to respectively subtract the positive phase signal of the ranging beat signal and the calibration beat signal from the negative phase signal of the modulation reference signal to obtain the ranging correction signal and the calibration correction signal, and send the ranging correction signal and the calibration correction signal to the FPGA on-chip system; The FPGA on-chip system is used to calculate the distance of the target object according to the calibration correction signal and the ranging correction signal.

9. The system according to claim 8, characterized in that The FPGA system-on-chip comprises: A frequency extraction module, used to determine the first distance signal frequency in the ranging correction signal and the second distance signal frequency in the calibration correction signal; A distance calculation module is used to calculate the distance of the target object according to the ratio of the first distance signal frequency to the second distance signal frequency and the preset length, and the ratio of the first distance signal frequency to the second distance signal frequency is the same as the ratio of the preset length to the distance of the target object.

10. The system according to claim 7, characterized in that The semiconductor laser and the frequency modulated continuous wave laser radar chip are packaged using co-packaging technology. The semiconductor laser and the frequency modulated continuous wave laser radar chip are arranged on the first surface of the circuit lead-out patch, and an optical isolator, an optical lens and a wave plate are sequentially arranged between the semiconductor laser and the frequency modulated continuous wave laser radar chip; A semiconductor cooler module is arranged on the second surface of the circuit lead-out patch.

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