Signal encoding apparatus, imaging system, and imaging method

Abstract

The invention provides signal coding equipment, an imaging system and an imaging method. The signal coding equipment comprises an array waveguide grating, a coding optical fiber, a delay optical fiber and an optical splitter, the array waveguide grating is configured to convert an initial signal emitted by the light source into multiple paths of target signals; the optical splitter is configured to combine multiple paths of target signals and then emit the combined signals; a plurality of paths of coding optical fibers and a plurality of paths of delay optical fibers with different lengths are arranged behind the array waveguide grating, and each path of delay optical fiber is connected to the coding optical fiber of the corresponding coding sequence; the delay optical fiber is configured to delay a transmitted target signal, and the coding optical fiber is configured to perform pulse coding on the transmitted target signal. According to the invention, the original pulse signal is coded by using the sequence code with good orthogonality, so that the signal processing accuracy is improved. And the delay optical fibers are grouped, so that the corresponding channels in each group of channels can be simultaneously transmitted, the signal transmitting time is shortened, the signal processing efficiency is improved, and the point acquisition rate can be improved while the fuzzy distance is expanded.

Description

Technical Field

[0001] The present application relates to the field of laser radar, and more specifically, to a signal coding device, an imaging system, and an imaging method. Background Art

[0002] When LiDAR measures target distance, there is a close and mutually constrained relationship between the fuzzy distance and the pulse repetition frequency. This relationship has become one of the key factors limiting the improvement of LiDAR performance, especially in the traditional single-pulse direct time-of-flight measurement system.

[0003] In a traditional single-pulse mechanism, the system calculates the target distance, or depth, by recording the time interval between the emission and reception of a single laser pulse. With this measurement method, when the target depth is less than the ambiguity distance, the system can accurately determine the temporal origin of the returning pulse, thereby precisely measuring the target distance, because the echo signal is received before the subsequent pulse is emitted. However, once the target distance exceeds the ambiguity distance, a phenomenon called "multiple echoes" occurs, where one pulse travels a longer distance and returns to the detector only after a second pulse has been emitted, making it difficult to determine the pulse's true temporal origin.

[0004] like Figure 1 As shown in the figure (where Tx and Rx are the reference signal and its corresponding echo signal, respectively), this leads to inaccurate distance measurement. In practical application scenarios, especially in the field of automotive LiDAR, this limitation poses a serious challenge. Taking automotive forward-looking LiDAR as an example, to ensure driving safety and accurately detect potential obstacles at a distance, it is generally required to have a detection range of at least 200m. However, if common single-pulse technology is used, while meeting the scanning speed required by automotive LiDAR, its fuzzy distance becomes very small, far below the 200m requirement. This means that when the echo signal of a distant target overlaps with the subsequently transmitted pulse signal in time, the system cannot accurately determine the target's true distance and may mistakenly identify a distant target as a nearby target, or even lose information about the distant target. This poses a serious threat to the decision-making and safety of the autonomous driving system. Summary of the Invention

[0005] In view of this, an object of the embodiments of the present application is to provide a signal encoding device, an imaging system, and an imaging method, which can increase the point acquisition rate while extending the blur distance.

[0006] In a first aspect, the embodiments of the present application provide a signal encoding device, comprising: an arrayed waveguide grating, an encoding optical fiber, a delay optical fiber, and an optical splitter; the arrayed waveguide grating is configured to convert an initial signal emitted by a light source into a plurality of target signals; the optical splitter is configured to emit the plurality of target signals after beam combining; wherein the arrayed waveguide grating is provided after the plurality of encoding optical fibers and the plurality of delay optical fibers with different lengths, each of the delay optical fibers is connected to the encoding optical fiber of a corresponding encoding sequence; the delay optical fiber is configured to delay the transmitted target signal, and the encoding optical fiber is configured to pulse encode the transmitted target signal.

[0007] In the above implementation process, the original pulse signal is encoded by using a sequence code with good orthogonality. Since the different sequence codes have good orthogonality, the target signal can be identified by matching filtering in the signal identification part. Therefore, the second pulse sequence can be transmitted when the first pulse sequence has not returned, without worrying about the signal being unable to be correspondingly identified, and the signal processing accuracy can be improved. In addition, a plurality of delay optical fibers with different lengths are used, and the delay optical fibers are grouped. The corresponding channels in each group of channels can be transmitted simultaneously, thereby greatly shortening the transmission time of the signal and improving the signal processing efficiency. The ambiguity distance can be expanded, and the point acquisition rate can be improved.

[0008] In one embodiment, wherein the arrayed waveguide grating is provided after the delay optical fibers with lengths in an arithmetic sequence; the arrayed waveguide grating is configured to convert the initial signal emitted by the light source into a plurality of target signals with equal delay intervals through the delay optical fibers.

[0009] In the above implementation process, the lengths of the delay optical fibers provided after the arrayed waveguide grating are in an arithmetic sequence. The initial signal emitted by the light source can be converted into a plurality of target signals with equal delay intervals through the delay optical fibers. Therefore, the target signals of the corresponding channels of the plurality of delay optical fibers can be transmitted simultaneously, and the overall signal processing efficiency can be improved.

[0010] In one embodiment, wherein the plurality of target signals are distributed in the plurality of delay optical fibers; the target signals in the same delay optical fiber group use different sequence codes; wherein the delay optical fibers with equal lengths belong to the same delay optical fiber group; and / or the target signals distributed in the same delay optical fiber group are transmitted simultaneously.

[0011] In the above implementation process, the target signals in the delay optical fibers with equal lengths use different sequence codes, and the target signals distributed in the delay optical fibers with equal lengths are transmitted simultaneously. The target signals in the plurality of delay optical fibers can be transmitted simultaneously, and the target signals transmitted simultaneously can be identified independently. The signal processing efficiency is improved, and the signal identification accuracy is improved.

[0012] In one embodiment, the sequence code is a short coding sequence family.

[0013] In the implementation process, by setting the sequence code as a short coding sequence family, the code weight number is reduced, only the same number of optical fibers as the code weight is needed, and the expensive high-speed coding device in other coding schemes is not needed to realize pulse signal coding, which can reduce the cost and improve the performance of the signal coding device.

[0014] In a second aspect, the embodiments of the present application also provide an imaging system, comprising: a light source, a ranging device, and the signal coding device in the first aspect or any possible implementation manner of the first aspect; the light source is configured to emit an initial signal and transmit the initial signal to the ranging device and the signal coding device; the signal coding device is configured to convert the initial signal into a plurality of target signals, and emit the target signals after pulse coding to a target object; and the ranging device is configured to receive a reflected signal of the target signal reflected by the target object and the initial signal, and determine distance information of the target object according to the reflected signal and the initial signal.

[0015] In the implementation process, by setting the signal coding device in the imaging system, the coded pulse signal has the advantage of accurate identification of the corresponding pulse signal while transmitting and receiving simultaneously, which makes it possible to transmit the signals simultaneously, further shortens the idle listening time, improves the point acquisition rate of the laser radar, and improves the signal identification accuracy.

[0016] In one embodiment, the ranging device comprises: a signal scanning module and a signal receiving module; the signal scanning module is arranged between the signal receiving module and the signal coding device; the signal receiving module is arranged between the light source and the signal scanning module; the signal scanning module is configured to emit the target signal transmitted by the signal coding device to the target object; and the signal receiving module is configured to receive the reflected signal reflected by the target object and the initial signal, and determine the distance information of the target object according to the reflected signal and the initial signal.

[0017] In the implementation process, by setting the signal receiving module, the initial signal and the reflected signal are received, and then the distance information of the target object is determined according to the initial signal and the reflected signal, the structure of the whole system is simple, and the cost is low. The cost of the imaging system can be reduced while the target object is being ranged.

[0018] In one embodiment, the signal scanning module comprises a double-axis scanning device and a dispersive element; the double-axis scanning device is arranged between the signal encoding device and the dispersive element, and the dispersive element is arranged between the signal encoding device and the target object; the double-axis scanning device is configured to perform two-dimensional spatial scanning; and the dispersive element is configured to diffract the target signal to different spatial positions.

[0019] In the implementation process, the double-axis scanning device and the dispersive element are arranged in the signal scanning module, so that spectral and spatial scanning can be performed and the scanning efficiency is improved.

[0020] In one embodiment, the signal receiving module comprises a detector and a signal processor; the detector is connected to the signal processor; the detector is configured to receive the reflected signal and send the reflected signal to the signal processor; and the signal processor is configured to process the reflected signal and the initial signal, and determine the distance information of the target object according to the processed reflected signal and the processed initial signal.

[0021] In the implementation process, the detector and the signal processor are arranged, so that the reflected signal and the initial signal can be processed, the distance information of the target object is determined according to the reflected signal and the initial signal, and the accuracy of the distance information determination is improved.

[0022] In a third aspect, the embodiments of the present application further provide an imaging method, which is applied to the imaging system in the second aspect or any possible implementation manner of the second aspect, and the method comprises the following steps: an initial signal is emitted by a light source to a ranging device and a signal encoding device in the imaging system; the initial signal is converted into a plurality of target signals by an arrayed waveguide grating in the signal encoding device, and the target signals are delayed and pulse encoded by corresponding delay optical fibers and encoding optical fibers; the encoded target signals are combined by a beam combiner in the signal encoding device and then emitted to the ranging device; the target signals transmitted by the signal encoding device are emitted to the target object by the ranging device; the ranging device receives reflected signals of the target signals reflected by the target object, and determines distance information of the target object according to the reflected signals and the initial signal.

[0023] In the implementation process, the initial signal is converted into multiple target signals by the arrayed waveguide grating, and the target signals are delayed and pulse coded by corresponding delay optical fibers and coding optical fibers. Only a sequence code with good orthogonality is needed to code the initial signal. Since the orthogonality between different sequence codes is good, the signal can be identified by matching filtering in the signal identification part. The second pulse sequence can be transmitted when the first pulse sequence has not returned, without worrying about the signal being unable to be correspondingly identified, so as to improve the signal identification accuracy. In addition, under the condition of maintaining the same transmission period, the expansion multiple of the ambiguity distance is the same as the number of orthogonal sequence codes, so that the ambiguity distance can be expanded, and the point acquisition efficiency of the imaging system can be improved.

[0024] In one embodiment, before the coded target signals are combined and emitted to the ranging device by the splitter of the signal coding device, the method further comprises: simultaneously transmitting the target signals distributed in the same delay optical fiber group; and the delay optical fibers with equal lengths are the same delay optical fiber group.

[0025] In the implementation process, different sequence codes are used for the target signals, and the target signals distributed in delay optical fibers with equal lengths are simultaneously transmitted, so that the target signals in multiple delay optical fibers can be simultaneously transmitted, and the simultaneously transmitted target signals can be independently identified, thereby improving the signal processing efficiency and the signal identification accuracy.

[0026] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the following embodiments are specifically described below, and the detailed description is made below by combining with the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0028] Figure 1 The schematic diagram of the reference signal and the echo signal in the prior art; Figure 2 The schematic diagram of the signal coding device provided by the embodiments of the present application; Figure 3 The schematic diagram of the signal coding device provided by the embodiments of the present application; Figure 2 The schematic diagram of the sequence code generated by the signal coding device shown; Figure 4 The schematic diagram of the imaging system provided by the embodiments of the present application; Figure 5 The flowchart of the imaging method provided by the embodiments of the present application.

[0029] Description of the drawings: 100 - arrayed waveguide grating, 110 - time-delay optical fiber, 120 - coded optical fiber, 200 - optical splitter, 300 - light source, 410 - signal scanning module, 411 - dual-axis scanning device, 412 - dispersion element, 413 - collimator, 414 - reflector, 415 - lens, 420 - signal receiving module, 421 - detector, 422 - signal processor, 20 - target object. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be described below in conjunction with the accompanying drawings in the embodiments of the present application.

[0031] It should be noted that similar reference numerals and letters represent similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings. At the same time, in the description of this application, the terms "first", "second", etc. are only used to distinguish the description and should not be understood as indicating or implying relative importance.

[0032] Real-time, high-resolution 3D imaging is crucial in a variety of fields, including drones and autonomous driving. LiDAR is an active detection technology that uses a laser source to illuminate a target object and collect the returned echo signals, thereby accurately acquiring the target's 3D information. Compared to structured light imaging and stereo vision, LiDAR offers unique advantages in complex lighting environments, high precision, and long-range 3D imaging. It is widely used in aerospace, autonomous driving, and other fields.

[0033] To maximize the point acquisition rate, the academic community has proposed a variety of scanning methods. For example, acousto-optic scanning can achieve a scanning rate of MHz, and combined with spectral scanning, it can reach tens of MHz. For traditional LiDAR systems, such as pulsed LiDAR, achieving a higher point acquisition rate requires a higher laser repetition frequency. However, the maximum detectable distance, i.e., the fuzzy distance, is limited by the laser repetition frequency, i.e.: ; in, is the speed of light in vacuum, is the laser repetition rate. That is, the higher the laser repetition rate, the smaller the detection system's ambiguity distance. Specifically, the laser can only emit subsequent pulses after the first pulse emitted by the laser source is received by the detector. Otherwise, the receiver will not be able to accurately distinguish when the received signal was transmitted, and thus will not be able to identify the corresponding signal's time of flight, resulting in ghost imaging. However, reducing the laser repetition rate to achieve a larger ambiguity distance will limit the system's scanning speed.

[0034] Overcoming these basic limitations and further improving the performance of lidar has always been a hot spot in the field. For example, the frequency of the transmitted laser chirps linearly with time in the frequency-modulated continuous-wave lidar, and the target distance is calculated by measuring the frequency difference between the transmitted signal and the return signal. Since the frequency difference is proportional to the target distance, and is not limited by the pulse repetition period, the range ambiguity problem can be effectively avoided. However, this requires a long modulation period and a frequency bandwidth greater than 1GHz to achieve high resolution, which is costly and difficult to implement in hardware. In addition, multi-wavelength parallel lidar uses multiple lasers of different wavelengths to transmit simultaneously, and by analyzing the return signals of different wavelengths, more distance information can be obtained to solve the range ambiguity problem that may occur with a single wavelength laser. However, this solution is costly, as it requires multiple lasers of different wavelengths, as well as the corresponding optical devices and drive circuits, which significantly increases the manufacturing cost of the lidar. Moreover, the performance and stability of lasers of different wavelengths need to be precisely matched and controlled. At the same time, this solution increases the complexity of the optical system design. In order to transmit and receive multiple wavelengths of light simultaneously, a complex optical system needs to be designed, including beam splitters, filters, etc.

[0035] Therefore, the signal encoding device provided by the present application encodes the original pulse signal by using a sequence code with good orthogonality. Since different sequence codes have good orthogonality, they can be identified by matching filtering in the signal recognition part. That is, the second pulse sequence can be transmitted before the first pulse sequence returns without worrying about the inability to correspond to the identification of the signal, which can improve the accuracy of signal processing. In addition, a plurality of delay optical fibers with different lengths are grouped, and the corresponding channels in each group of channels are transmitted simultaneously, thereby greatly shortening the transmission time of the signal and improving the efficiency of signal processing. The fuzzy distance can be expanded while the point acquisition rate is improved.

[0036] In order to facilitate the understanding of the present embodiment, first, a signal encoding device disclosed by the present application is introduced in detail.

[0037] As shown in Figure 2 , it is a schematic diagram of the signal encoding device provided by the present application, which comprises an arrayed waveguide grating 100, a coded optical fiber 120, a delay optical fiber 110 and a beam splitter 200.

[0038] Among them, the arrayed waveguide grating 100 is provided with multiple coded optical fibers 120 and multiple delay optical fibers 110 with different lengths, and each delay optical fiber 110 is connected to a corresponding coded optical fiber 120 with a coded sequence. The arrayed waveguide grating 100 is configured to convert the initial signal emitted by the light source 300 into multiple target signals.

[0039] The delay optical fiber 110 is configured to delay the target signal, and the encoding optical fiber 120 is configured to pulse encode the target signal.

[0040] The above-described optical splitter 200 is configured to combine the target signals and emit the combined target signals.

[0041] In an embodiment, the initial signal is a pulse signal.

[0042] It can be understood that, after the initial signal enters the arrayed waveguide grating 100, the initial signal is divided into multiple target signals by wavelength division multiplexing, and the target signals are combined by wavelength division multiplexing after passing through the delay optical fibers 110 with different lengths.

[0043] Optionally, the delay optical fiber 110 can be a spiral optical fiber, a ring structure, a folded optical fiber, a delay line, or the like, and the structure of the delay optical fiber 110 can be selected according to actual conditions.

[0044] It should be understood that, because the lengths of the optical fibers in the delay optical fibers 110 are different, the transmission times of the target signals in the delay optical fibers 110 can be different, and thus the target signals passing through the delay optical fibers 110 form corresponding time delays.

[0045] It can be understood that, by setting the corresponding encoding optical fiber 120 for each delay optical fiber 110, the target signal delayed by the delay optical fiber 110 is pulse encoded by the encoding optical fiber 120, and the target signal with the corresponding encoding is formed. In this way, when multiple target signals are emitted, because each target signal has a corresponding sequence code, because the different sequence codes have good orthogonality, the signals can be identified by matching filtering in the signal identification part, and the second pulse sequence can be emitted when the first pulse sequence has not returned, without worrying about the signals being unable to be identified.

[0046] The above-described encoding optical fiber 120 can be connected to a corresponding control unit, and the control unit can transmit a corresponding sequence code to the corresponding encoding optical fiber 120, and thus pulse encode the target signal transmitted in the encoding optical fiber 120.

[0047] Optionally, the target signals in different delay optical fibers 110 can be transmitted simultaneously, at different times, or partially simultaneously, and the transmission times of the target signals in different delay optical fibers 110 can be selected according to actual conditions.

[0048] For the convenience of understanding, the working process of the signal encoding device in the embodiment of the present application is described below through a specific example. The initial signal enters the arrayed waveguide grating 100. Behind the arrayed waveguide grating 100, H delay fibers 110 of varying lengths are positioned. Wavelength division multiplexing (WDM) is performed on the arrayed waveguide grating 100 to generate H target signals. These signals then pass through N delay fibers 110 before being combined and converted into H optical signals with corresponding time intervals. These H optical signals are then pulse-coded. First, the H optical signals are divided into M groups, each containing N channels (H = M × N). These channels are connected to different delay fibers 110 and then combined using a 1-to-N optical splitter 200. These N channels share the same code set and are transmitted at corresponding times.

[0049] like Figure 2 As shown, taking the GOLD code as an example, the GOLD sequence code is a pseudo-random sequence widely used in communication systems (such as CDMA, GPS, etc.), known for its good cross-correlation characteristics and a large number of sequences, and can be generated through programming. The specific encoding implementation method of the GOLD sequence code in the imaging system is: the non-zero bit of the sequence code is connected to the corresponding length of the delay fiber 110, and the combined signal will become a series of pulse sequences corresponding to the coding sequence, such as Figure 3 As shown, there are M such sequence codes, corresponding to M groups of independently combined channels. These codes are mutually orthogonal, and the corresponding channels in each group (for example, the first channel in each group) are transmitted simultaneously. Compared to non-coded schemes, this significantly shortens the transmission time for all channels. Due to the good orthogonality between the sequence codes, the receiver can still accurately identify the corresponding signals.

[0050] In the above implementation, the original pulse signal is encoded using a highly orthogonal sequence code. Due to the high orthogonality between different sequence codes, matched filtering can be used in the signal recognition process to identify the signal. Therefore, the second pulse sequence can be transmitted before the first pulse sequence returns without worrying about signal recognition errors, thereby improving signal processing accuracy. Furthermore, by utilizing multiple delay fibers 110 of varying lengths and grouping these delay fibers 110, corresponding channels within each group can be transmitted simultaneously, significantly shortening signal transmission time and improving signal processing efficiency. This can extend the fuzzy distance while increasing the point acquisition rate.

[0051] In a possible implementation, a delay optical fiber 110 having a length in an arithmetic progression is provided after the arrayed waveguide grating 100 .

[0052] The arrayed waveguide grating 100 is configured to convert the initial signal emitted by the light source 300 into multiple target signals with equal delay intervals through the delay optical fiber 110 .

[0053] It can be understood that, by setting the lengths of the delay optical fibers 110 behind the arrayed waveguide grating 100 in an arithmetic sequence, the lengths of the delay optical fibers 110 in the arrayed waveguide grating 100 can be substantially consistent, and the initial signal emitted by the light source 300 can be converted into target signals with equal delay intervals by the delay optical fibers 110.

[0054] Exemplarily, the initial signal enters the arrayed waveguide grating 100, and the arrayed waveguide grating 100 is provided with H pieces of delay optical fibers 110 with unequal lengths but equal differences. The arrayed waveguide grating 100 generates H pieces of target signals with equal wavelength intervals through wavelength division demultiplexing, and then the H pieces of target signals are combined through wavelength division multiplexing after passing through N pieces of delay optical fibers 110. The series of target signals are converted into H pieces of optical signals with fixed time intervals. Then, the H pieces of optical signals are pulse coded. First, the H pieces of optical signals are divided into M groups, and each group has N channels (H=M×N). These channels are connected to different delay optical fibers 110, and then combined through a 1-to-N optical splitter 200. The N channels share the same code and are transmitted at different times.

[0055] In the above implementation process, by setting the lengths of the delay optical fibers 110 behind the arrayed waveguide grating 100 in an arithmetic sequence, the initial signal emitted by the light source 300 can be converted into target signals with equal delay intervals by the delay optical fibers 110, and then the target signals in the corresponding channels of the multiple delay optical fibers 110 can be transmitted simultaneously, thereby improving the overall efficiency of signal processing.

[0056] In a possible implementation, the multiple target signals are configured to be distributed in the multiple delay optical fibers 110; the target signals in the same group of delay optical fibers 110 use different sequence codes; and / or the target signals distributed in the same group of delay optical fibers 110 are transmitted simultaneously.

[0057] The delay optical fibers 110 with equal lengths are the same group of delay optical fibers 110.

[0058] It can be understood that the multiple delay optical fibers 110 can be divided into multiple channel groups according to lengths. The delay optical fibers 110 in the same channel group have different lengths, and the delay optical fibers 110 with equal lengths in each channel group can be regarded as the same channel.

[0059] The target signals in the delay optical fibers 110 with equal lengths have the same time delay, and if the target signals in the delay optical fibers 110 with equal lengths are transmitted at the same time, the transmission and reception of multiple target signals can be completed at the same time, thereby greatly shortening the transmission time of all channels and improving the signal processing efficiency. Considering that the target signals may affect each other, the encoding optical fibers 120 are arranged, and the delay optical fibers 110 with equal lengths are connected to different encoding optical fibers 120, so that the target signals in the delay optical fibers 110 with equal lengths use different sequence codes. Since the sequence codes have good orthogonality, the receiving end can still accurately identify the corresponding signals, thereby providing signal identification accuracy.

[0060] In the above implementation process, by arranging the target signals in the delay optical fibers 110 with equal lengths to use different sequence codes and transmitting the target signals in the delay optical fibers 110 with equal lengths at the same time, the target signals in multiple delay optical fibers 110 can be transmitted at the same time, and the target signals transmitted at the same time can be independently identified, thereby improving the signal processing efficiency and the signal identification accuracy.

[0061] In a possible implementation, the sequence code is a short coding sequence family.

[0062] The short coding sequence family here refers to a sequence set with a relatively short length and a specific coding rule or biological function.

[0063] Alternatively, the sequence code can be an m-sequence, a Walsh code, a short code in a CDMA system, etc. The sequence code can be selected according to actual conditions.

[0064] The selection of the sequence code described above can be adjusted according to the fastest speed of the scanning device. Different sequence codes can be implemented through different lengths of the encoding optical fibers 120, which are suitable for different laser radar ranging systems. The delay optical fibers 110 correspond to the period of the scanning device, which maximizes the scanning rate of the scanning device and improves the point acquisition rate of the overall system. Taking the scanning rate of an acousto-optic deflector as an example, which can reach several MHz, through H=40 spectral multiplexing, the system point acquisition rate can easily reach more than 100 MHz.

[0065] In an embodiment, the sequence code is less than or equal to 50 bits.

[0066] It should be understood that the sequence code is less than or equal to 50 bits, the sequence code has fewer code weight bits, and the implementation of coding only needs the same number of optical fibers as the code weight, without the need for expensive high-speed coding devices in other coding schemes to implement pulse signal coding, and has good performance.

[0067] In the implementation process, by setting the sequence code as a short coding sequence family, the code weight bits are reduced, only the same number of optical fibers as the code weight need to be set, and the expensive high-speed coding device in other coding schemes is not needed to realize pulse signal coding, which can reduce the cost and improve the performance of the signal coding device.

[0068] As shown in Figure 4 Fig. 1 is a schematic diagram of an imaging system provided by an embodiment of the present application, which includes a light source 300, a ranging device, and a signal coding device in the above embodiment.

[0069] The light source 300 is arranged between the ranging device and the signal coding device. The light source 300 is configured to emit an initial signal and transmit the initial signal to the ranging device and the signal coding device.

[0070] Optionally, the light source 300 can be a super-continuum laser, a wide-spectrum laser, a random fiber laser, etc., which can be selected according to actual needs.

[0071] The signal coding device is arranged between the light source 300 and the ranging device. The signal coding device is configured to convert the initial signal into a plurality of target signals and emit the target signals after pulse coding to the target object 20.

[0072] Optionally, the signal coding device can be independent of the light source 300 and the ranging device, and be a separate module. The signal coding device can also be arranged integrally with the ranging device, and the signal coding device and the ranging device are two parts of the same device. The arrangement of the signal coding device can be selected according to actual conditions.

[0073] It should be understood that when the signal coding device is a separate module, it can be adapted to a variety of laser radar systems. When the signal coding device is needed, the signal coding device only needs to be connected between the light source 300 and the scanning module, and the code weight and code length of the sequence code are adjusted according to the light frequency and the response time of the signal scanning module 410, so that the signal coding device can be adapted to the laser radar system and realize the functions of expanding the ambiguity distance and improving the scanning point acquisition rate.

[0074] It can be understood that for a non-coded pulse laser radar, it is necessary to ensure that the echo signal of the first beam of light signal has been received when the second beam of light signal is emitted. Therefore, the higher the laser repetition frequency of the non-coded pulse laser radar, the lower the ambiguity distance. In the embodiment of the present application, the coding scheme only needs to code the original pulse signal with a sequence code with good orthogonality. Since different sequence codes have good orthogonality, they can be identified by matching filtering in the signal recognition part, that is, the second pulse sequence can be emitted when the first pulse sequence has not returned without worrying about the signal being unable to be correspondingly identified.

[0075] The signal coding device is configured to transmit the target signal to the target object 20.

[0076] The ranging device is configured to receive the reflected signal and the initial signal, and determine the distance information of the target object 20 according to the reflected signal and the initial signal.

[0077] The distance information can be determined according to the time difference or the phase difference between the reflected signal and the initial signal received by the ranging device.

[0078] In the implementation process, the coded pulse signal has the advantage of accurate identification of the corresponding pulse signal while transmitting and receiving simultaneously by setting the signal coding device in the imaging system. This makes it possible to transmit signals simultaneously that originally had to be transmitted sequentially, further shortens the idle listening time, improves the point acquisition rate of the laser radar, and improves the signal recognition accuracy.

[0079] In one possible implementation, the ranging device comprises a signal scanning module 410 and a signal receiving module 420.

[0080] The signal scanning module 410 is arranged between the signal receiving module 420 and the signal coding device, and the signal receiving module 420 is arranged between the light source 300 and the signal scanning module 410.

[0081] The signal scanning module 410 is configured to transmit the target signal transmitted by the signal coding device to the target object 20.

[0082] In one embodiment, the signal scanning module 410 can expand the ranging capability from a single point to two-dimensional or three-dimensional space perception by dynamically controlling the pointing angle of the laser beam.

[0083] Optionally, the signal scanning module 410 can be a double-axis scanning device 411, a double-axis galvanometer, a rotating mirror, etc. The structure of the signal scanning module 410 can be selected according to actual conditions.

[0084] The signal receiving module 420 is configured to receive the reflected signal and the initial signal, and determine the distance information of the target object 20 according to the reflected signal and the initial signal.

[0085] It should be understood that the light source 300 transmits the initial signal to the signal coding device and the ranging device at the same time. The initial signal transmitted to the ranging device is received by the signal receiving module 420. In addition, after the target signal is transmitted to the target object 20 by the signal scanning module 410, the target object 20 reflects the target signal, and the reflected target signal is also received by the signal receiving module 420.

[0086] The signal receiving module 420 can determine the distance information of the target object 20 according to the time difference or phase difference between the initial signal and the reflected signal after receiving the initial signal and the corresponding reflected signal.

[0087] Optionally, the signal receiving module 420 can be an oscilloscope, a processor, an electronic device, etc., and the structure of the signal receiving module 420 can be selected according to actual conditions.

[0088] In the above implementation process, by setting the signal receiving module 420 for receiving the initial signal and the reflected signal, and then determining the distance information of the target object 20 according to the initial signal and the reflected signal, the structure of the entire system is simple and the cost is low. The cost of the imaging system can be reduced while the distance of the target object 20 is measured.

[0089] In a possible implementation, the signal scanning module 410 includes a dual-axis scanning device 411 and a dispersive element 412.

[0090] The dual-axis scanning device 411 is arranged between the signal encoding device and the dispersive element 412, and the dispersive element 412 is arranged between the signal encoding device and the target object 20.

[0091] The dual-axis scanning device 411 here is a device capable of dynamic scanning in a two-dimensional plane (X-axis and Y-axis), which realizes the coordinated movement of two perpendicular directions through a mechanical or optical system, thereby covering the detection / scanning requirements of a plane or a curved surface. The dual-axis scanning device 411 is configured to perform two-dimensional spatial scanning.

[0092] The dispersive element 412 described above is an optical component for decomposing composite light into different wavelength monochromatic light, and its core function is to realize the dispersion of light through physical mechanisms such as refraction, diffraction or reflection. The dispersive element 412 is configured to diffract the target signal to different positions in space.

[0093] As can be understood, the initial signal emitted by the light source 300 is transmitted to the arrayed waveguide grating 100 through an optical fiber, and through wavelength division multiplexing, the arrayed waveguide grating 100 generates multiple paths of target signals with equal wavelength intervals. Each path in the arrayed waveguide grating 100 is then subjected to wavelength division multiplexing and beam combining by the arrayed waveguide grating 100 after passing through the delay optical fiber 110 with an arithmetic sequence of lengths. This series of target signals with equal wavelength intervals are converted into multiple paths of discrete pulsed light signals with fixed time intervals. After two-dimensional spatial scanning by the dual-axis scanning device 411, the multiple paths of discrete pulsed light signals are diffracted and dispersed to different positions in space by the dispersive element 412, thereby realizing spectral-time-space multidimensional mapping (i.e., spectral scanning). The multiple signals obtained by spectral scanning can be independently edited to achieve ultra-high-speed scanning.

[0094] Optionally, the signal scanning module 410 can further include one or more elements such as a collimator 413, a mirror 414, a lens 415, etc. The elements in the signal scanning module 410 can be selected according to actual conditions.

[0095] It should be understood that in the distance measuring device, the laser repetition frequency corresponds to the delay of each sequence code group, that is, when a larger repetition frequency is used, a shorter delay optical fiber 110 is used to additionally delay the code group, so that the superfast point acquisition rate can be achieved. When a smaller repetition frequency is switched, a longer delay optical fiber 110 is used to additionally delay the code group, so that the fuzzy distance is expanded by several times. That is, in the embodiment of the present application, the additional delay can be flexibly adjusted by the delay optical fiber 110, and different functions (i.e., improving the scanning rate or expanding the fuzzy distance) can be achieved according to different use scenarios.

[0096] In the above implementation process, by setting the signal scanning module 410 to include the dual-axis scanning device 411 and the dispersion element 412, spectral and spatial scanning can be achieved, and the scanning efficiency can be improved.

[0097] In a possible implementation, the signal receiving module 420 includes a detector 421 and a signal processor 422.

[0098] The detector 421 is connected to the signal processor 422.

[0099] The detector 421 is configured to receive the reflected signal and send the reflected signal to the signal processor 422.

[0100] In an embodiment, the detector 421 can also convert the received optical signal into an electrical signal.

[0101] The signal processor 422 described above has a certain signal processing capability, and is configured to process the reflected signal and the initial signal, and determine the distance information of the target object 20 according to the processed reflected signal and the processed initial signal.

[0102] It should be understood that the working principle of the signal receiving module 420 is that the detector 421 receives the reflected signal of the laser signal hitting the target object 20 and then transmits the reflected signal to the signal processor 422 (such as an oscilloscope), the signal processor 422 converts the optical signal (i.e., the reflected signal) transmitted by the detector 421 into an electrical signal, and synchronously saves the pulse sequence signal (i.e., the initial signal) emitted by the light source 300 as a reference signal. Then, the two signals are matched and filtered and the optical path delay is corrected, and then the time difference between the reflected signal and the initial signal, that is, the flight time, is calculated, and the distance information of the target object 20 is obtained.

[0103] In the signal receiving module 420 block, the initial signal initially transmitted by the signal source and the reflected signal returned after irradiating on the object are cross-correlation detected (such as matched filtering), the sequence code is kept as short as possible (that is, the transmission time is shortened, and the scanning rate is improved), and the corresponding sequence code can be well detected, the transmission time and the error code rate can be balanced, the anti-noise interference ability is strong, the signal-to-noise ratio is high, and the design is simple.

[0104] In the above implementation process, by setting the detector 421 and the signal processor 422, the reflected signal and the initial signal can be processed, and the distance information of the target object 20 is determined according to the reflected signal and the initial signal, thereby improving the accuracy of the distance information determination.

[0105] The imaging system in the embodiment can be used to execute each step in the imaging method provided in the embodiments of the present application. The implementation process of the imaging method will be described in detail through several embodiments.

[0106] Please refer to Figure 5 , which is a flowchart of the imaging method provided in the embodiments of the present application. The specific process shown in Figure 5 will be described in detail.

[0107] Step S201, the light source 300 transmits an initial signal to the ranging device and the signal coding device in the imaging system.

[0108] The initial signal here is a pulse signal emitted by the light source 300.

[0109] It should be understood that the light source 300 transmits the initial signal to the ranging device and the signal coding device at the same time. That is, the ranging device and the signal coding device acquire the initial signal at the same time.

[0110] Step S202, the arrayed waveguide grating 100 in the signal coding device converts the initial signal into multiple target signals, and delays and pulse encodes the target signals through the corresponding delay optical fiber 110 and coding optical fiber 120.

[0111] Here, the arrayed waveguide grating 100 is provided with multiple coding optical fibers 120 and multiple delay optical fibers 110 with different lengths. After the initial signal is transmitted into the arrayed waveguide grating 100, it is converted into multiple target signals. Each target signal is transmitted through the corresponding coding optical fiber 120 and length optical fiber to generate a corresponding delay and generate a corresponding pulse code.

[0112] Step S203, the beam combiner 200 of the signal coding device transmits the coded target signal to the ranging device after beam combining.

[0113] Step S204, by the ranging device, emitting the target signal transmitted by the signal encoding device to the target object 20.

[0114] The target signal is spectrally and spatially scanned by a two-axis scanning device 411 and a dispersive element 412 in the ranging device.

[0115] Step S205, by the ranging device, receiving the reflected signal of the target signal reflected by the target object 20, and determining the distance information of the target object 20 according to the reflected signal and the initial signal.

[0116] The reflected signal is received by a detector 421 in the ranging device, and the signal processor 422 in the ranging device processes the signal and determines the distance information of the target object 20.

[0117] In the above implementation process, the initial signal is converted into multiple target signals by the arrayed waveguide grating 100, and the target signals are delayed and pulse coded by the corresponding delay optical fiber 110 and coding optical fiber 120. Only a sequence code with good orthogonality is needed to encode the initial signal. Since the orthogonality between different sequence codes is good, it can be identified by matching filtering in the signal recognition part. The second pulse sequence can be transmitted when the first pulse sequence has not returned, without worrying about the inability to correspond to the identification of the signal, which can improve the accuracy of signal recognition. In addition, under the condition of maintaining the same transmission period, the number of orthogonal sequence codes is the same as the multiple of the expanded ambiguity distance. The ambiguity distance can be expanded while improving the point acquisition efficiency of the imaging system.

[0118] In a possible implementation, before step S203, the method further includes: simultaneously transmitting the target signals distributed in the same delay optical fiber 110 group.

[0119] The delay optical fibers 110 with equal lengths are the same delay optical fiber 110 group.

[0120] In the above implementation process, by using different sequence codes for the target signals and simultaneously transmitting the target signals distributed in the delay optical fibers 110 with equal lengths, the target signals in multiple delay optical fibers 110 are simultaneously transmitted, and the simultaneously transmitted target signals can be independently identified. The signal processing efficiency is improved, and the accuracy of signal recognition is improved.

[0121] In several embodiments provided in the present application, it should be understood that the disclosed apparatus and method can also be implemented by other means. The apparatus embodiments described above are only illustrative, for example, the flowcharts and block diagrams in the drawings show the possible implementation architecture, function and operation of the apparatus, method and computer program product according to the embodiments of the present application. In this regard, each block in the flowchart or block diagram can represent a module, program segment or part of code, which contains one or more executable instructions for implementing the specified logic function. It should also be noted that in some alternative implementations, the functions noted in the blocks can occur in different order from that noted in the drawings. For example, two consecutive blocks can actually be executed substantially in parallel, and sometimes they can be executed in reverse order, depending on the functions involved. It should also be noted that each block in the block diagram and / or flowchart, and the combination of blocks in the block diagram and / or flowchart, can be implemented by a dedicated hardware-based system for performing the specified functions or actions, or can be implemented by a combination of special-purpose hardware and computer instructions.

[0122] In addition, each functional module in the embodiments of the present application can be integrated together to form an independent part, or each module can exist independently, or two or more modules can be integrated to form an independent part.

[0123] If the functions are implemented in the form of software function modules and sold or used as independent products, they can be stored in a computer readable storage medium. Based on this understanding, the technical solutions of the present application essentially or the parts that make contributions to the prior art or parts of the technical solutions can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present application. The aforementioned storage medium includes: a U disk, a mobile hard disk, a read-only memory (ROM, Read-Only Memory), a random access memory (RAM, Random Access Memory), a magnetic disk or an optical disk, and various media that can store program codes. It should be noted that in this paper, relationship terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between the entities or operations. Moreover, the terms "include", "contain" or any other variants thereof are intended to cover non-exclusive inclusion, so that the processes, methods, articles or devices that include a series of elements not only include those elements, but also include other elements not explicitly listed or inherent to such processes, methods, articles or devices. Without more limitations, the elements defined by the statement "include" do not exclude the presence of other identical elements in the processes, methods, articles or devices that include the elements. The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application. It should be noted that similar reference numbers and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0124] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application. It should be noted that similar reference numbers and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application. It should be noted that similar reference numbers and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

Claims

1. A signal encoding device, characterized in that include: Arrayed waveguide gratings, coded optical fibers, time-delay optical fibers, and optical splitters; The arrayed waveguide grating is configured to convert an initial signal emitted by a light source into a multi-path target signal; The optical splitter is configured to combine the multiple target signals into a beam and then transmit the beam; Among them, multiple coding optical fibers and multiple delay optical fibers of different lengths are arranged behind the arrayed waveguide grating, and each delay optical fiber is connected to the coding optical fiber of the corresponding coding sequence; the delay optical fiber is configured to delay the transmitted target signal, and the coding optical fiber is configured to pulse encode the transmitted target signal.

2. The signal encoding device according to claim 1, characterized in that in, A delay optical fiber with an arithmetic progression of lengths is arranged behind the arrayed waveguide grating; The arrayed waveguide grating is configured to convert an initial signal emitted by a light source into multi-path target signals with equal delay intervals through the delay optical fiber.

3. The signal encoding device according to claim 2, characterized in that in, The multiple target signals are configured to be distributed among the multiple delay optical fibers; The target signals in the same delay optical fiber group use different sequence codes; wherein the delay optical fibers of equal length belong to the same delay optical fiber group; and / or The target signals allocated to the same delay optical fiber group are sent simultaneously.

4. The signal encoding device according to any one of claims 1 to 3, characterized in that: in, The sequence code is a family of short coding sequences.

5. An imaging system, characterized in that: include: A light source, a distance measuring device, and a signal encoding device according to any one of claims 1 to 4; The light source is configured to emit an initial signal and transmit the initial signal to the ranging device and the signal encoding device; The signal encoding device is configured to convert the initial signal into a multi-path target signal, and pulse encode the target signal before transmitting it toward the target object; The distance measuring device is configured to receive a reflected signal of the target signal after being reflected by the target object and the initial signal, and determine the distance information of the target object according to the reflected signal and the initial signal.

6. The imaging system according to claim 5, wherein: The distance measuring device includes: a signal scanning module and a signal receiving module; The signal scanning module is arranged between the signal receiving module and the signal encoding device; the signal receiving module is arranged between the light source and the signal scanning module; The signal scanning module is configured to transmit the target signal transmitted by the signal encoding device toward the target object; The signal receiving module is configured to receive a reflected signal and the initial signal after being reflected by the target object, and determine distance information of the target object according to the reflected signal and the initial signal.

7. The imaging system according to claim 6, wherein: The signal scanning module includes: a dual-axis scanning device and a dispersion element; The biaxial scanning device is arranged between the signal encoding device and the dispersive element, and the dispersive element is arranged between the signal encoding device and the target object; The biaxial scanning device is configured to perform two-dimensional spatial scanning; The dispersive element is configured to diffract the target signal to different locations in space.

8. The imaging system according to claim 6, wherein: The signal receiving module includes: a detector and a signal processor; The detector is connected to the signal processor; The detector is configured to receive the reflected signal and send the reflected signal to the signal processor; The signal processor is configured to process the reflected signal and the initial signal, and determine the distance information of the target object according to the processed reflected signal and the processed initial signal.

9. An imaging method, characterized in that: Applied to the imaging system according to any one of claims 5 to 8, the method comprising: The light source transmits an initial signal to the ranging device and the signal encoding device in the imaging system; The arrayed waveguide grating in the signal encoding device converts the initial signal into a multi-path target signal, and delays and pulse encodes the target signal through corresponding delay optical fibers and coding optical fibers; The optical splitter of the signal encoding device combines the encoded target signal into a beam and transmits the combined signal to the ranging device; The ranging device transmits the target signal transmitted by the signal encoding device toward the target object; The distance measuring device receives a reflected signal of the target signal after being reflected by the target object, and determines the distance information of the target object according to the reflected signal and the initial signal.

10. The method according to claim 9, characterized in that Before the optical splitter of the signal encoding device combines the encoded target signal into a beam and transmits the combined signal to the ranging device, the method further includes: Simultaneously sending the target signals distributed in the same delay optical fiber group; Among them, delay optical fibers with equal lengths are the same delay optical fiber group.

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