Multi-channel camera exposure synchronization method, device, system and storage medium

Abstract

The present application relates to a method, device, system and storage medium for synchronizing exposure of multiple cameras. The method comprises: obtaining the imaging phases of a master camera and several slave cameras, each of which is synchronized with a mains synchronization signal; obtaining the phase difference between the imaging of the slave camera and the master camera based on the imaging phase of the slave camera and the master camera; adjusting the synchronization moment of the slave camera and the mains synchronization signal based on the phase difference, so that the exposure of the slave camera and the master camera is synchronized. The use of this method can eliminate network transmission errors, sampling response errors, synchronization signal fluctuation errors, etc. between the master and slave cameras, and the exposure synchronization is accurate. It is also suitable for the exposure synchronization of multi-frame rate camera systems, and does not require additional wiring. It has a simple structure, good versatility, and strong anti-interference ability.

Description

Technical Field

[0001] The present application relates to the field of imaging technology, and in particular to a method, device, system and storage medium for synchronizing exposure of multiple cameras. Background Art

[0002] In a multi-camera system, multiple cameras are often required to synchronize exposure to ensure that multiple cameras are exposed at the same time. For example, in the field of vehicle-road collaboration, since the scene of a single camera cannot cover the entire road section, multiple cameras are usually placed at different locations for image acquisition. At the same time, the data center performs splicing and recognition on the images of multiple cameras. The greater the shutter deviation between the cameras, the greater the impact on the recognition and tracking of the center end. Therefore, the exposure synchronization of multiple cameras is a key issue.

[0003] In traditional technologies, there are methods that output a synchronization signal from the main camera and synchronize the exposure of the sub-cameras according to the synchronization signal. There are also methods that automatically trigger multiple cameras through GPS signals. There are also methods that synchronize the exposure of multiple cameras through network timing. In addition, there are methods that synchronize the exposure of multiple cameras through AC power synchronization signals.

[0004] However, current traditional technologies have various shortcomings: For solutions that require the main camera to output a synchronization signal, the construction and wiring are difficult, and the greater the distance between devices, the higher the risk of interference and loss of the synchronization signal. For solutions that synchronize via GPS signals, in some scenarios, such as tunnels, the GPS signal is generally weak, so it is impossible to accurately synchronize and trigger the cameras by acquiring GPS signals, resulting in poor versatility. For solutions that synchronize via network timing, the synchronization accuracy depends on the network timing accuracy, and the timing error will vary with the network status, resulting in uncertain timing errors in the synchronized exposure between cameras. For solutions that synchronize via mains power, because the mains synchronization signal frequency is generally higher than the device frame rate, synchronization between multiple cameras cannot be guaranteed. Summary of the Invention

[0005] Based on this, it is necessary to provide a multi-channel camera exposure synchronization method, device, system and storage medium with simple structure, good versatility and small synchronization error to address the above technical problems.

[0006] In a first aspect, the present application provides a multi-channel camera exposure synchronization method, comprising:

[0007] Acquire the imaging phases of a master camera and several slave cameras, each of which is synchronized with a mains synchronization signal;

[0008] According to the imaging phase of the slave camera and the main camera, the phase difference between the imaging of the slave camera and the main camera is obtained;

[0009] The synchronization time of the slave camera and the mains synchronization signal is adjusted according to the phase difference value, so that the exposure of the slave camera is synchronized with that of the master camera.

[0010] In one embodiment, acquiring the imaging phases of a master camera and a plurality of slave cameras, each of which is synchronized with a mains synchronization signal, includes:

[0011] The master camera and the slave camera collect the time interval between their respective phase sampling moments and the adjacent exposure end moments or exposure start moments on the same side to obtain the corresponding imaging phase.

[0012] In one embodiment, obtaining the phase difference between the images of the slave camera and the main camera according to the imaging phases of the slave camera and the main camera includes:

[0013] Normalizing the imaging phases of the slave camera and the master camera to obtain a normalized phase;

[0014] The phase difference value is obtained according to the normalized phase between the slave camera and the master camera.

[0015] In one embodiment, obtaining the phase difference between the slave camera and the main camera according to the normalized phase between the slave camera and the main camera further includes:

[0016] When the frame rate of the slave camera is greater than the frame rate of the master camera, the normalized phase of the master camera is preprocessed according to the frame rate ratio of the slave camera to the master camera.

[0017] In one embodiment, adjusting the synchronization time of the slave camera and the mains synchronization signal according to the phase difference value includes:

[0018] The phase difference value is compared with the frame period of the mains synchronization signal to determine the number of synchronization periods that differ between the slave camera and the master camera, and the synchronization time of the slave camera and the mains synchronization signal is adjusted according to the number of synchronization periods, where the number of synchronization periods is based on the frame period of the mains synchronization signal.

[0019] In one embodiment, before acquiring the imaging phases of the master camera and the plurality of slave cameras that are synchronized with the mains synchronization signal, the method further includes:

[0020] The master camera initiates a phase sampling command through the network, or the slave camera initiates a phase sampling request through the network.

[0021] In one embodiment, before acquiring the imaging phases of the master camera and the plurality of slave cameras that are synchronized with the mains synchronization signal, the method further includes:

[0022] Check whether the mains synchronization signal is stable. When the mains synchronization signal is stable, the master camera and the slave camera start to collect imaging phases that are synchronized with the mains synchronization signal.

[0023] In a second aspect, the present application further provides a multi-channel camera exposure synchronization device, comprising: a master camera, and a plurality of slave cameras, wherein the master camera and the slave cameras are synchronized with the mains power, and the master camera and the slave cameras communicate with each other via a network;

[0024] The master camera and the slave camera are used to collect their own imaging phases synchronized with the mains synchronization signal;

[0025] The slave camera is also used to obtain the phase difference between the slave camera and the main camera according to the imaging phase of the slave camera and the main camera, and adjust the synchronization time of the slave camera and the main power synchronization signal according to the phase difference, so that the exposure of the slave camera and the main camera is synchronized.

[0026] In a third aspect, the present application also provides a multi-channel camera exposure synchronization system, including a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the steps of the multi-channel camera exposure synchronization method described in any one of the above embodiments are implemented.

[0027] In a fourth aspect, the present application further provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the multi-channel camera exposure synchronization method described in any one of the above embodiments.

[0028] The above-mentioned multi-channel camera exposure synchronization method, device, system and storage medium perform preliminary synchronization based on the mains synchronization signal and perform precise synchronization based on the camera's phase synchronization sampling. They retain the advantages of mains synchronization and can complete synchronization using the mains and the network without additional wiring. They have a simple structure, good versatility, and strong anti-interference ability. At the same time, they eliminate network transmission errors, sampling response errors, synchronization signal fluctuation errors, etc. between the master and slave cameras. Exposure synchronization is precise and is also applicable to exposure synchronization of multi-frame rate camera systems:

[0029] First, the mains sync signal is used as the camera synchronization reference, and the master and slave cameras communicate via the network. Network communication does not affect the synchronization of the cameras with the mains sync signal. Therefore, errors in network transmission will not be introduced into the exposure synchronization based on the mains sync signal, ensuring the accuracy of exposure synchronization.

[0030] Secondly, the master and slave cameras are each synchronized with the mains synchronization signal, but the synchronization time between the master and slave cameras may be different. This synchronization time is relatively fixed, specifically in units of the mains synchronization signal frame period. Therefore, adjusting the exposure synchronization based on the mains synchronization signal frame period at the synchronization time can eliminate network transmission errors between the master and slave cameras and sampling response errors caused by phase synchronization sampling, ensuring the accuracy of exposure synchronization.

[0031] Thirdly, the use of normalized phase to calculate the phase difference can eliminate the fluctuation error in the mains synchronization signal itself, that is, the calculation error introduced by the signal period fluctuation. At the same time, when the frame rates of the master camera and the slave camera are different, the imaging phase of the two is normalized to a dimensionless scalar, the phase difference is calculated, and the exposure synchronization calibration is completed, realizing the exposure synchronization of the multi-frame rate camera system. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the conventional technology, the following briefly introduces the drawings required for use in the embodiments or the conventional technology descriptions. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0033] Figure 1 Schematic diagram of the overall structure of a multi-channel camera system in one embodiment;

[0034] Figure 2 A schematic diagram of the internal structure of a master-slave camera in one embodiment;

[0035] Figure 3 A schematic diagram of the overall process of a multi-channel camera exposure synchronization method according to an embodiment;

[0036] Figure 4 1. A schematic diagram of a synchronization process initiated from a camera in a multi-channel camera exposure synchronization method according to an embodiment;

[0037] Figure 5 A schematic diagram of a synchronization process initiated by a master camera in a multi-camera exposure synchronization method according to one embodiment;

[0038] Figure 6 and Figure 7 Schematic diagram of exposure synchronization principle of a single frame rate device system in a multi-channel camera exposure synchronization method according to one embodiment;

[0039] Figure 8 and Figure 9 Schematic diagram of the exposure synchronization principle of a multi-frame rate device system in a multi-channel camera exposure synchronization method according to one embodiment. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solutions and advantages of this application more clear, the following further describes this application in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application.

[0042] It should be noted that when an element is considered to be "connected" to another element, it can be directly connected to the other element or connected to the other element through an intervening element. In addition, the "connection" in the following embodiments should be understood as "electrical connection", "communication connection", etc., if there is transmission of electrical signals or data between the connected objects.

[0043] When used herein, the singular forms "a", "an", and "the" may also include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "include / comprise" or "have" and the like specify the presence of stated features, integers, steps, operations, components, parts, or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof.

[0044] The multi-channel camera exposure synchronization method provided in the embodiment of the present application can be applied to Figure 1 In the application environment shown, the master camera communicates with the slave cameras via a network, and the master and slave cameras are powered by the same power grid through a distribution box. The master and slave cameras send instructions via the network, acquire their respective imaging phases synchronized with the mains synchronization signal, and transmit the acquired imaging phases via the network. The slave camera receives the imaging phase of the master camera, obtains a phase difference based on the imaging phases of the slave and master cameras, and adjusts the synchronization time of the slave camera with the mains synchronization signal based on the phase difference, so that the exposure of the slave camera and the master camera are synchronized. The master camera is one of the multiple cameras, and the other cameras are slave cameras. The master camera and the slave cameras are structurally the same. All slave cameras are calibrated based on the synchronization time of the master camera with the mains synchronization signal to achieve multi-channel camera exposure synchronization.

[0045] See Figure 2 For the master camera and the slave camera, there is no difference in the system structure. They both include at least: a mains power processing unit, a coprocessor, a sensor, and a central processing unit. The mains power processing unit processes the AC power and generates a mains power synchronization signal. The coprocessor combines the mains power synchronization signal and the parameter output signal configured by the central processing unit to control the camera sensor imaging. The sensor outputs image data to the central processing unit.

[0046] It should be noted that the exposure times of different sensors vary to a certain extent. Therefore, for a multi-camera system, if all cameras ensure the same exposure start time or exposure end time, they can be considered to be synchronized exposure.

[0047] In one embodiment, Figure 3 As shown, a multi-channel camera exposure synchronization method is provided, which is applied to Figure 1 The following steps are described in the application environment shown in the figure:

[0048] S100: Acquire imaging phases of a master camera and several slave cameras, each of which is synchronized with a mains synchronization signal;

[0049] Specifically, both the master and slave cameras are synchronized with the mains synchronization signal, i.e., mains synchronization. Since they are powered by the same power grid, any differences in the mains synchronization signals between the cameras are negligible. This embodiment simultaneously triggers phase sampling of the master and slave cameras during the same time period. Specifically, this is accomplished by simultaneously triggering phase sampling of the master and slave cameras via network communication, which can be either a wired or wireless network. The imaging phase is the synchronization position of the camera on the mains synchronization signal, i.e., the moment at which the camera synchronizes to the mains synchronization signal.

[0050] Specifically, the mains synchronization signal can be obtained by rectifying and filtering the mains (AC power), sampling with an ADC, or using a comparator. The frequency of the mains synchronization signal is usually N times the mains power frequency, such as generating a 120Hz synchronization signal at a 60Hz power frequency.

[0051] Specifically, this embodiment uses the mains synchronization signal as the camera synchronization reference, and the master and slave cameras communicate through the network. The network communication will not affect the synchronization of the camera and the mains synchronization signal. Therefore, the error of network transmission will not be introduced into the exposure synchronization based on the mains synchronization signal, thereby ensuring the accuracy of exposure synchronization.

[0052] S200: Obtaining a phase difference between the imaging of the slave camera and the main camera according to the imaging phase of the slave camera and the main camera;

[0053] Specifically, the master camera sends its imaging phase to each slave camera via the network, and each slave camera calculates the phase difference between itself and the master camera. This phase difference can be directly the imaging phase difference, or it can be the imaging phase difference after normalization, i.e., the normalized phase difference. For a single-frame-rate camera system, that is, the master and slave cameras have the same frame rate, that is, the shooting exposure period between the cameras is the same. In this case, this embodiment can directly use the imaging phase difference or the normalized phase difference for exposure synchronization. For a multi-frame-rate camera system, that is, a device including two or more frame rates, which results in different shooting exposure periods between the cameras, in this case, this embodiment normalizes the imaging phases corresponding to cameras with different frame rates into a dimensionless scalar, i.e., the normalized phase, for exposure synchronization, thereby further calculating the phase difference, thereby achieving exposure synchronization of the multi-frame-rate camera system.

[0054] Specifically, the AC synchronization signal itself fluctuates, which causes the signal period to be unstable and introduces calculation errors during calculation. However, this embodiment uses normalized phase, that is, a dimensionless scalar, to calculate the phase difference, which can effectively eliminate the synchronization signal fluctuation error and ensure the accuracy of exposure synchronization.

[0055] S300: adjusting the synchronization time of the slave camera and the mains synchronization signal according to the phase difference value, so that the exposure of the slave camera is synchronized with that of the master camera.

[0056] Specifically, this embodiment determines the exposure phase difference between the slave camera and the master camera based on the above-mentioned phase difference value, that is, the phase difference between the synchronization moments of the master and slave cameras and the mains synchronization signal. The synchronization moment is the moment position on the mains synchronization signal corresponding to the exposure start moment or exposure end moment in each frame period of the camera. The master and slave cameras themselves are synchronized with the mains synchronization signal, but the corresponding synchronization moments may be different. Therefore, what is actually determined based on the phase difference value is the phase difference between the synchronization moments of the master and slave cameras. Taking the synchronization moment of the master camera and the mains synchronization signal as the reference, the synchronization moment of the slave camera and the mains synchronization signal is readjusted based on the phase difference value, so that the exposure of the slave camera and the master camera can be synchronized, that is, the synchronization moments are the same.

[0057] Specifically, since the synchronization moments of the camera and the mains synchronization signal are relatively fixed, specifically in units of the frame period of the mains synchronization signal, the phase difference between the synchronization moments of the master and slave cameras determined based on the phase difference is also in units of the frame period of the mains synchronization signal. Furthermore, the synchronization moment of the slave camera and the mains synchronization signal is adjusted in units of the frame period of the mains synchronization signal. Such exposure synchronization adjustment eliminates the above-mentioned network transmission error and sampling response error, thereby ensuring the accuracy of exposure synchronization.

[0058] The above-mentioned multi-channel camera exposure synchronization method performs preliminary synchronization based on the mains synchronization signal and performs precise synchronization based on the camera's phase synchronization sampling. It retains the advantages of mains synchronization and can complete synchronization using the mains and the network without additional wiring. It has a simple structure, good versatility, and strong anti-interference ability. At the same time, it eliminates network transmission errors, sampling response errors, synchronization signal fluctuation errors, etc. between the master and slave cameras. The exposure synchronization is precise and is also suitable for exposure synchronization of multi-frame rate camera systems.

[0059] In one embodiment, before acquiring the imaging phases of the master camera and the plurality of slave cameras that are synchronized with the mains synchronization signal, the method further includes: the master camera initiating a phase sampling command via a network, or the slave camera initiating a phase sampling request via a network.

[0060] Specifically, after power-on, there is uncertainty between the phases of the slave and the master. At the same time, during operation, if the slave synchronization signal is abnormal, it will also cause phase deviation from the master. Therefore, exposure synchronization is required in both cases. The master camera can initiate a phase sampling command through the network, or the slave camera can initiate a phase sampling request through the network to trigger phase synchronization sampling between the master and slave cameras.

[0061] Specifically, see Figure 4 The slave camera initiates a phase sampling request through the network to request the master and slave cameras to synchronize phase sampling. The slave camera initiates a phase sampling request to the master camera or an external host computer. The master camera or the external host computer acts as a synchronization control end and responds to the phase sampling request by sending a control signal to trigger the master and slave cameras to perform phase synchronization sampling. Figure 5 The master camera initiates a phase sampling command over the network to trigger phase sampling with the associated slave cameras. As the synchronization control terminal, the master camera can initiate phase sampling commands proactively, in response to requests from slave cameras, or in response to power-on signals. Furthermore, an external host computer can initiate phase sampling commands to the master and slave cameras to trigger phase synchronization sampling between them.

[0062] Furthermore, before the master camera initiates a phase sampling command through the network or the slave camera initiates a phase sampling request through the network, it is first detected whether the mains synchronization signal is stable to determine whether the synchronization relationship between the master and slave cameras and the mains synchronization signal is stable. Specifically, the stability of the signal can be judged according to the signal frequency. When the mains synchronization signal is stable, the master camera and the slave camera start to collect imaging phases synchronized with the mains synchronization signal. Otherwise, phase synchronization sampling will be started after the mains synchronization signal is stable.

[0063] In one embodiment, obtaining imaging phases of a master camera and a plurality of slave cameras that are each synchronized with a mains synchronization signal includes: obtaining corresponding imaging phases by collecting the time intervals between respective phase sampling moments of the master camera and the slave cameras and adjacent exposure end moments or exposure start moments on the same side.

[0064] Among them, the sensor in the camera converts the light signal into an electrical signal in an integral manner. The start time of integration is the start time of exposure, and the end time of integration is the end time of exposure. Generally, the start time of exposure and the end time of exposure can be used as the frame interval between two video image frames.

[0065] Specifically, to capture the imaging phase of each camera—that is, the moment at which the camera synchronizes to the mains synchronization signal—the cameras in this embodiment determine the corresponding imaging phase based on the time interval between the camera sampling moment and the previous or next exposure end moment. This means that the camera's imaging phase is determined by calculating the time interval between the camera sampling moment and the previous exposure end moment, using the camera sampling moment as a reference. Accordingly, the consistency of the exposure end moments serves as the criterion for synchronized exposure.

[0066] Specifically, the camera of this embodiment can also determine the corresponding imaging phase based on the time interval between the camera sampling moment and the previous or next exposure start moment. That is, the camera imaging phase is determined by calculating the time interval between the camera sampling moment and the previous or next exposure start moment, using the camera sampling moment as a reference. Accordingly, the consistency of the exposure start moments serves as the criterion for synchronized exposure.

[0067] In one embodiment, obtaining a phase difference between the imaging of the slave camera and the main camera according to the imaging phases of the slave camera and the main camera includes: normalizing the imaging phases of the slave camera and the main camera to obtain a normalized phase; and obtaining a phase difference according to the normalized phase between the slave camera and the main camera.

[0068] Specifically, the normalized phase of the master and slave cameras is:

[0069] P=phase / T_frame

[0070] Where P is the normalized phase, phase is the imaging phase, and T_frame is the frame period of the corresponding camera.

[0071] Specifically, in the case of a single frame rate system, that is, the frame rates of the master and slave cameras are the same, the phase difference value is obtained directly based on the normalized phase difference between the master camera and the slave camera. In the case of a multi-frame rate device system, that is, there are cameras with two or more frame rates in the system, since the frame rates of the master and slave cameras are different, before calculating the phase difference value, it is necessary to preprocess the normalized phase of the master camera according to the frame rate ratio of the slave camera to the master camera, and obtain the phase difference value based on the difference between the normalized phase of the preprocessed master camera and the original normalized phase of the slave camera, where the frame rate of the slave camera is greater than the frame rate of the master camera.

[0072] Furthermore, when applied to a multi-frame rate device system, this embodiment designates the camera with the lowest frame rate as the master camera and other high-frame rate cameras as slave cameras, with the frame rate of the slave cameras being higher than that of the master camera. In this case, when calculating the phase difference value, this embodiment needs to pre-process the normalized phase of the master camera, using the following formula:

[0073] Y_a=(P_a*N)%1

[0074] Where Y_a is the normalized phase of the master camera after preprocessing, P_a is the normalized phase of the master camera before preprocessing, and N is the frame rate ratio of the slave camera to the master camera. For example, if the frame rate of the slave camera is 50 fps and the frame rate of the master camera is 25 fps, then N is 2. "%" is the remainder operator, and the purpose of "%1" is to retain decimal places and remove integer places.

[0075] Furthermore, when applied to a single-frame-rate device system, that is, the master and slave cameras have the same frame rate, the master camera of this embodiment can be any one of the cameras, and the remaining cameras are slave cameras. In this case, when calculating the phase difference value, this embodiment does not require the above preprocessing process, and directly calculates the phase difference value by subtracting the normalized phase of the master camera from the normalized phase of the slave cameras.

[0076] Furthermore, this embodiment obtains a phase difference value based on the imaging phases of the slave camera and the master camera. When applied to a single frame rate device system, the difference can be directly calculated without the above preprocessing.

[0077] In one embodiment, adjusting the synchronization moment of the slave camera and the mains synchronization signal according to the phase difference value includes: comparing the phase difference value with the frame period of the mains synchronization signal, determining the number of synchronization periods that differ between the slave camera and the master camera, and adjusting the synchronization moment of the slave camera and the mains synchronization signal according to the number of synchronization periods, wherein the number of synchronization periods is in units of the frame period of the mains synchronization signal.

[0078] Among them, the frame period of the mains synchronization signal is taken as one synchronization period, and the number of synchronization periods is the number of synchronization periods. The phase difference between the synchronization moments of the master and slave cameras is determined by the number of synchronization periods, that is, the adjustment amount corresponding to the synchronization moment of the slave camera and the mains synchronization signal.

[0079] Specifically, the phase difference value is compared with the frame period of the mains synchronization signal to determine the number of synchronization periods that differ between the slave camera and the master camera. Since the master camera controls the phase sampling of the slave camera, there is a time delay between the sampling of the master camera and the slave camera. Taking this time delay into account, the phase sampling time of the master camera in this embodiment will be earlier than the phase sampling time of the slave camera. That is, when the master and slave cameras are exposed synchronously, the imaging phase or normalized phase of the master camera will also be smaller than the imaging phase or normalized phase of the slave camera. Therefore, while ensuring that the time delay is less than the frame period of the mains synchronization signal, this embodiment uses "the imaging phase or normalized phase of the master camera is smaller than the imaging phase or normalized phase of the slave camera" and "the phase difference value is less than one synchronization period" as conditions to determine whether the master and slave cameras are exposed synchronously. Correspondingly, when the imaging phase or normalized phase of the master camera is greater than the imaging phase or normalized phase of the slave camera, it means that the master camera exposure is not synchronized. In this case, if the phase difference is less than one synchronization cycle, it means that the slave camera differs from the master camera by one synchronization cycle. If the phase difference is greater than one synchronization cycle but less than two synchronization cycles, it means that the slave camera differs from the master camera by two synchronization cycles. In this way, the number of synchronization cycles between the slave camera and the master camera is determined.

[0080] For example, if the mains synchronization signal has a frame period of 10ms and the phase difference between the slave camera and the master camera is -5.5ms, then the master and slave cameras are considered to be synchronized by one synchronization cycle, as -10ms < -5.5ms < 0ms. Based on the number of synchronization cycles, the slave camera's synchronization with the mains synchronization signal is readjusted by the number of synchronization cycles that differ, so that the master and slave cameras are synchronized with the mains synchronization signal. For example, if the mains synchronization signal has a frame period of 10ms and the phase difference between the slave camera and the master camera is 1.5ms, then the master and slave cameras are considered to be in exposure synchronization, as 0ms < 1.5ms < 10ms.

[0081] It is worth noting that the above-mentioned judgment method is only one implementation method of this embodiment. Similarly, if the sampling time of the slave camera is earlier than that of the master camera, the above-mentioned opposite condition can be used for judgment. Similarly, if a third party controls the master and slave cameras to perform phase sampling, that is, when the time delay between the phase sampling of the master and slave cameras is very small and less than half of the synchronization period, then whether the master and slave cameras are exposed synchronously can also be determined based on whether the absolute value of the phase difference is less than half of the synchronization period, and the number of synchronization periods can be determined by rounding. For example, if the phase difference is greater than 0.5 synchronization periods and less than 1 synchronization period, it is determined that the master and slave cameras differ by 1 synchronization period; if the phase difference is greater than 1 synchronization period and less than 1.5 synchronization periods, it is determined that the master and slave cameras differ by 1 synchronization period; if the phase difference is greater than 1.5 synchronization periods and less than 2 synchronization periods, it is determined that the master and slave cameras differ by 2 synchronization periods.

[0082] Specifically, for the comparison of the phase difference value and the frame period of the mains synchronization signal, if the phase difference value is obtained based on the imaging phase, the object of comparison is the frame period of the mains synchronization signal itself; if the phase difference value is obtained based on the normalized phase, the object of the corner is the frame period of the mains synchronization signal after normalization, specifically based on the normalization of the frame period of the slave camera. For example, if the frame period of the mains synchronization signal is 10ms and the frame period of the slave camera is 20ms, then the frame period of the mains synchronization signal is 0.5 after normalization.

[0083] This embodiment will now be described in detail in conjunction with application scenarios, but is not limited thereto.

[0084] Application scenario 1: Single frame rate device system, that is, the frame rate of the master and slave cameras is the same, see Figure 6 Assume that the system includes a master A and a slave B. The mains power is 50Hz, the mains synchronization signal is 100Hz, and the frame rate of camera A and camera B are both 25fps. Currently, both are synchronized with the mains power, but at different times. The master camera is synchronized to the synchronization signal N_1, and the synchronization reference of the slave camera is N-2. The system performs exposure synchronization:

[0085] 1) The master camera initiates phase synchronization at a certain system moment. The master camera transmits the phase sampling command to the slave camera through the network, and the master and slave cameras perform phase synchronous sampling. Due to the existence of network transmission errors, the master and slave cameras actually perform phase sampling in sequence, and the slave camera samples later than the master. Therefore, phase synchronous sampling needs to be performed under stable network transmission conditions, that is, the network transmission error is within the allowable range;

[0086] 2) See Figure 6, based on the time interval from the end moment of the last exposure of the master camera to the current phase sampling moment, the master camera captures an imaging phase of phase_a = 26 ms, and the slave camera captures an imaging phase of phase_b = 20.5 ms;

[0087] 3) The master camera sends the imaging phase phase_a to the slave camera;

[0088] 4) The slave camera calculates the phase difference value diff_phase = phase_b - phase_a = -5.5 ms according to the difference between the imaging phases of the slave camera and the master camera;

[0089] 5) The slave camera judges the phase difference value. Since -10 ms < diff_phase < 0 ms, it can be known that the slave camera lags behind the master camera by one synchronization period. Therefore, the slave camera processes the mains synchronization signal and retains the signal moment of serial number 1 as the synchronization moment of the slave camera and the mains synchronization signal, making the synchronization moments of the master and slave cameras the same as that of the mains synchronization signal.

[0090] After the above exposure synchronization adjustment, the above steps can be executed again to verify the result of the exposure synchronization adjustment: Refer to Figure 7 , after the exposure synchronization adjustment, the imaging phases phase_a = 26 ms and phase_b = 27.5 ms are obtained by phase synchronous sampling, and the phase difference value is diff_phase = 1.5 ms. Since 0 ms < diff_pahse < 10 ms, it can be considered that the phases of the master and slave cameras are consistent, and both the adjusted master and slave cameras are synchronized to the synchronization signal N_1 in the mains synchronization signal.

[0091] Application scenario 2: A multi-frame rate device system, that is, there are devices with 2 or more frame rates in a system. The low-frame rate camera is used as the master camera, and the high-frame rate camera is used as the slave camera. Refer to Figure 8 , assuming that the system includes a host A and a slave B, the mains power is 50 Hz, the mains synchronization signal is 100 Hz, the frame rate of the host is 25 fps, and the frame rate of the slave is 50 fps. Currently, both are synchronized with the mains power, but the synchronization moments are different. The master camera is synchronized to the synchronization signal N_1, and the synchronization references of the slave camera are N-2 and N-4. The system performs exposure synchronization:

[0092] 1) The master camera initiates phase synchronization at a certain system moment. The master camera sends the phase sampling command to the slave camera through the network, and the master and slave cameras perform phase synchronous sampling. Due to the existence of network transmission errors, in fact, the master and slave cameras perform phase sampling in sequence, and the slave sampling is later than the master. Therefore, phase synchronous sampling needs to be carried out under the condition of stable network transmission, that is, the network transmission error is within the allowable range;

[0093] 2) Refer to Figure 8Based on the time interval from the last exposure end of the main camera to the current phase sampling time, the normalized phase collected by the main camera is phase_a = 26ms / 40ms = 0.65, and the normalized phase collected by the slave camera is phase_b = 0.5ms / 20ms = 0.025;

[0094] 3) The master camera sends the imaging phase phase_a to the slave camera;

[0095] 4) Preprocess the normalized phase of the master camera from the slave camera:

[0096] Phase_a=(phase_a*N)%1=0.65*2%1=1.3%1=0.3, N=40ms / 20ms=2.

[0097] 5) The slave camera calculates a phase difference value based on the normalized phase difference between the slave camera and the master camera: diff_phase=0.025–0.3=−0.275.

[0098] 6) The slave camera determines the phase difference. The synchronization period is 10ms, and the frame period of the slave camera is 20ms. The normalized phase of one synchronization period relative to the frame period of the slave camera is 0.5. Since 0>diff_phase>-0.5, it can be seen that the slave camera differs from the master camera by one synchronization period. Therefore, the slave camera processes the mains synchronization signal and retains the signal times of sequence numbers 1 and 3 as the slave camera's processing of the mains synchronization signal, so that the master and slave cameras are synchronized with the mains synchronization signal at the same time.

[0099] After the above exposure synchronization adjustment, you can also perform the above steps again to verify the results of the exposure synchronization adjustment: See Figure 9 After exposure synchronization adjustment, phase synchronization sampling obtains the normalized phases phase_a = 26ms / 40ms = 0.65, phase_b = 10.5ms / 20ms = 0.525. After preprocessing, the normalized phase of the master camera is Phase_a = (phase_a*N)%N=0.65*2%1=1.3%1=0.3, and the phase difference is diff_phase=0.525–0.3=0.225. Since 0.5>diff_phase>0, it can be assumed that the phases of the master and slave cameras are consistent. After adjustment, the master and slave cameras are both synchronized to the synchronization signal N_1 in the mains synchronization signal.

[0100] It should be understood that, although the various steps in the flowcharts involved in the various embodiments described above are displayed in sequence according to the instructions of the arrows, these steps are not necessarily executed in sequence in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order restriction on the execution of these steps, and these steps can be executed in other orders. Moreover, at least a portion of the steps in the flowcharts involved in the various embodiments described above can include multiple steps or multiple stages, and these steps or stages are not necessarily executed and completed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily to be carried out in sequence, but can be executed in turn or alternately with other steps or at least a portion of steps or stages in other steps.

[0101] Based on the same inventive concept, embodiments of the present application also provide a multi-channel camera exposure synchronization device for implementing the multi-channel camera exposure synchronization method described above. The solution provided by this device is similar to the solution described in the method described above. Therefore, the specific limitations of one or more embodiments of the multi-channel camera exposure synchronization device provided below can be found in the limitations of the multi-channel camera exposure synchronization method described above and will not be repeated here.

[0102] In one embodiment, Figure 1 and Figure 2 As shown, a multi-channel camera exposure synchronization device is provided, comprising: a master camera, and several slave cameras, wherein the master camera and the slave cameras are synchronized with the mains power, and the master camera and the slave cameras communicate with each other via a network;

[0103] The master camera and the slave camera are used to collect their own imaging phases synchronized with the mains synchronization signal;

[0104] The slave camera is also used to obtain the phase difference between the slave camera and the main camera according to the imaging phase of the slave camera and the main camera, and adjust the synchronization time of the slave camera and the main power synchronization signal according to the phase difference, so that the exposure of the slave camera and the main camera is synchronized.

[0105] In one embodiment, the master camera and the plurality of slave cameras collect imaging phases that are each synchronized with a mains synchronization signal, including:

[0106] The master camera and the slave camera collect the time interval between their respective phase sampling moments and the adjacent exposure end moments or exposure start moments on the same side to obtain the corresponding imaging phase.

[0107] In one embodiment, obtaining the phase difference between the images of the slave camera and the main camera according to the imaging phases of the slave camera and the main camera includes:

[0108] Normalizing the imaging phases of the slave camera and the master camera to obtain a normalized phase;

[0109] The phase difference value is obtained according to the normalized phase between the slave camera and the master camera.

[0110] In one embodiment, obtaining the phase difference between the slave camera and the master camera according to the normalized phase between the slave camera and the master camera further includes:

[0111] When the frame rate of the slave camera is greater than the frame rate of the master camera, the normalized phase of the master camera is preprocessed according to the frame rate ratio of the slave camera to the master camera.

[0112] In one embodiment, adjusting the synchronization time of the slave camera and the mains synchronization signal according to the phase difference value includes:

[0113] The phase difference value is compared with the frame period of the mains synchronization signal to determine the number of synchronization periods that differ between the slave camera and the master camera, and the synchronization time of the slave camera and the mains synchronization signal is adjusted according to the number of synchronization periods, where the number of synchronization periods is based on the frame period of the mains synchronization signal.

[0114] In one embodiment, before the master camera and the slave camera acquire imaging phases synchronized with the mains synchronization signal, the method further includes:

[0115] The master camera initiates a phase sampling command through the network, or the slave camera initiates a phase sampling request through the network.

[0116] In one embodiment, before the master camera and the slave camera acquire imaging phases synchronized with the mains synchronization signal, the method further includes:

[0117] Check whether the mains synchronization signal is stable. When the mains synchronization signal is stable, the master camera and the slave camera start to collect imaging phases that are synchronized with the mains synchronization signal.

[0118] In one embodiment, a computer device is provided, including a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, it implements any of the multi-channel camera exposure synchronization methods described in the above embodiments. For detailed descriptions, please refer to the corresponding descriptions of the methods, which will not be repeated here.

[0119] In one embodiment, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, any of the multi-channel camera exposure synchronization methods described in the above embodiments is implemented. For detailed descriptions, please refer to the corresponding descriptions of the methods, which will not be repeated here.

[0120] Those skilled in the art will appreciate that all or part of the processes in the above-mentioned embodiment methods can be implemented by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, database or other media used in the embodiments provided in this application may include at least one of non-volatile and volatile memory. Non-volatile memory may include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory may include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM). The database involved in the various embodiments provided herein may include at least one of a relational database and a non-relational database. Non-relational databases may include, but are not limited to, distributed databases based on blockchains. The processor involved in the various embodiments provided herein may be, but are not limited to, a general-purpose processor, a central processing unit, a graphics processing unit, a digital signal processor, a programmable logic unit, a data processing logic unit based on quantum computing, and the like.

[0121] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0122] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present application shall be determined by the appended claims.

Claims

1. A method for synchronizing exposure of multiple cameras, characterized in that: include: Acquire the imaging phases of a master camera and several slave cameras, each of which is synchronized with a mains synchronization signal; The imaging phase refers to the time interval between the phase sampling moment and the exposure end moment or exposure start moment adjacent to the same side; the mains synchronization signal is the camera synchronization reference; the master camera and the slave camera communicate over the network; Obtaining a phase difference between the imaging of the slave camera and the main camera according to the imaging phase of the slave camera and the main camera; Adjusting the synchronization moment of the slave camera and the mains synchronization signal according to the phase difference value so that the slave camera is exposed synchronously with the master camera; the synchronization moment is the position of the exposure start moment or exposure end moment on the mains synchronization signal corresponding to the exposure start moment or exposure end moment in each frame period of the camera; The step of adjusting the synchronization time between the slave camera and the mains synchronization signal according to the phase difference value includes: Compare the phase difference value with the frame period of the mains synchronization signal, determine the number of synchronization periods that differ between the slave camera and the master camera, and adjust the synchronization moment of the slave camera and the mains synchronization signal according to the number of synchronization periods, wherein the number of synchronization periods is in units of the frame period of the mains synchronization signal.

2. The method according to claim 1, characterized in that The acquiring of imaging phases of a master camera and a plurality of slave cameras, each of which is synchronized with a mains synchronization signal, comprises: The master camera and the slave camera collect the time interval between their respective phase sampling moments and the exposure end moments or exposure start moments adjacent to each other on the same side to obtain the corresponding imaging phase.

3. The method according to claim 1, characterized in that The obtaining, according to the imaging phases of the slave camera and the master camera, a phase difference between the imaging of the slave camera and the master camera comprises: Normalizing the imaging phases of the slave camera and the master camera to obtain a normalized phase; The phase difference value is obtained according to the normalized phase between the slave camera and the master camera.

4. The method according to claim 3, characterized in that The obtaining of the phase difference value according to the normalized phase between the slave camera and the master camera further includes: In a case where the frame rate of the slave camera is greater than the frame rate of the master camera, the normalized phase of the master camera is preprocessed according to a frame rate ratio of the slave camera to the master camera.

5. The method according to any one of claims 1 to 4, characterized in that Before acquiring the imaging phases of the master camera and the plurality of slave cameras, each of which is synchronized with the mains synchronization signal, the method further includes: The master camera initiates a phase sampling command through a network, or the slave camera initiates a phase sampling request through a network.

6. The method according to any one of claims 1 to 4, characterized in that Before acquiring the imaging phases of the master camera and the plurality of slave cameras, each of which is synchronized with the mains synchronization signal, the method further includes: It is detected whether the mains synchronization signal is stable. When the mains synchronization signal is stable, the master camera and the slave camera start to collect imaging phases that are respectively synchronized with the mains synchronization signal.

7. A multi-channel camera exposure synchronization device, characterized in that: include: A master camera and several slave cameras, wherein the master camera and the slave cameras are synchronized with the mains power supply and the master camera and the slave cameras communicate with each other via a network; The master camera and the slave camera are respectively used to collect imaging phases synchronized with the mains synchronization signal; the imaging phase refers to the time interval between the phase sampling moment and the adjacent exposure end moment or exposure start moment on the same side; the mains synchronization signal is the camera synchronization reference; The slave camera is further configured to obtain a phase difference between the imaging of the slave camera and the main camera based on the imaging phase of the slave camera and the main camera, and to adjust the synchronization time of the slave camera and the mains synchronization signal based on the phase difference, so that the exposure of the slave camera is synchronized with that of the main camera; the synchronization time is the time position on the mains synchronization signal corresponding to the exposure start time or exposure end time within each frame period of the camera; The slave camera is further used to compare the phase difference value with the frame period of the mains synchronization signal, determine the number of synchronization periods that differ between the slave camera and the master camera, and adjust the synchronization moment of the slave camera and the mains synchronization signal according to the number of synchronization periods, wherein the number of synchronization periods is in units of the frame period of the mains synchronization signal.

8. A multi-channel camera exposure synchronization system, characterized in that: The method comprises a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the steps of the method according to any one of claims 1 to 6 are implemented.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 6 are implemented.

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