Multi-event camera time synchronization method based on B code

Abstract

The invention discloses a multi-event camera time synchronization method based on a B code, and solves the problems that for an application scene that a plurality of event cameras need accurate time synchronization, a traditional hardware triggering mode is tedious in connection and single in triggering signal, and subsequent further processing of event data is not facilitated. Based on the time sequence characteristic of the B code, the B code is applied to time synchronization of n event cameras to be synchronized, standard time information is processed according to a B code encoding mode, encoding of the standard time information is completed, and then the standard time information is sent to the n event cameras to be synchronized in a pulse mode. The n to-be-synchronized event cameras realize event camera synchronization by aligning the decoded time information and the corresponding timestamps, the triggering mode is simple, the connection structure is simple, and subsequent event data processing is facilitated.

Description

Technical Field

[0001] The invention relates to a time synchronization method, and in particular to a time synchronization method for multiple event cameras based on B code. Background Art

[0002] In recent years, neuromorphic engineering that simulates human vision has made great progress. Among them, event cameras, as dynamic visual sensors, have great potential in visual perception technology. Event cameras are fundamentally different from traditional frame rate cameras. They do not rely on a fixed frame rate to capture images, but instead record events where the brightness of each pixel changes by more than a certain threshold. Each event contains the pixel coordinates, the direction of the brightness change (increase or decrease), and the timestamp of the event. This mechanism gives event cameras significant advantages in high dynamic range, low latency, and asynchronous event-driven, and has broad application prospects in machine vision, autonomous driving and other fields.

[0003] For application scenarios where multiple event cameras require precise time synchronization, the traditional hardware triggering method has cumbersome connections and a single trigger signal, which is not conducive to subsequent further data processing such as precise slicing operations on event data. Summary of the invention

[0004] In order to solve the technical problem in the prior art that, for application scenarios where multiple event cameras require precise time synchronization, the traditional hardware triggering method has cumbersome connections and a single trigger signal, which is not conducive to subsequent further processing of event data, the present invention provides a time synchronization method for multiple event cameras based on B code.

[0005] In order to achieve the above object, the present invention adopts the following technical solution:

[0006] A method for time synchronization of multiple event cameras based on B code is special in that it includes the following steps:

[0007] Step 1, n time encoding modules respectively encode the standard time information based on the B code encoding method to obtain n B code encoding sequences, and then send the n B code encoding sequences to n event cameras to be synchronized in the form of pulse signals; n ≥ 2 and is an integer;

[0008] Step 2: Each camera of the event to be synchronized receives the pulse signal respectively, generates a timestamp corresponding to the pulse signal, decodes the standard time information, and extracts the corresponding timestamp;

[0009] Step 3: Align the standard time information decoded by each event camera to be synchronized and its corresponding timestamp, so that multiple event cameras to be synchronized can achieve time synchronization.

[0010] Furthermore, step 1 is specifically as follows:

[0011] The n time coding modules are based on the B code coding method, take the time interval between pulses as an identifier, and binary encode the standard time information according to the preset timing format to obtain n B code coding sequences; then the n B code coding sequences are sent to the n event cameras to be synchronized in the form of pulse signals; the B code coding sequence is a binary time information sequence; the binary time information sequence includes multiple time unit groups; each time unit group corresponds to a preset timing format; each time unit group includes multiple time units.

[0012] Furthermore, step 2 is specifically as follows:

[0013] Each event camera to be synchronized receives a binary time information sequence in the form of a pulse signal and generates a timestamp corresponding to the pulse signal. The pulse intervals between adjacent time unit groups are the same, and the pulse intervals between adjacent time units in each time unit group are different. In this way, each time unit group and each time unit in each time unit group are distinguished from the binary time information sequence, and then each binary time unit is converted into a decimal system, and the corresponding standard time information is decoded according to a preset timing format, and the corresponding timestamp is extracted.

[0014] Furthermore, in step 1:

[0015] The time coding module includes FPGA and GPS;

[0016] The standard time information is provided by GPS.

[0017] Furthermore, in step 1:

[0018] The standard time information is a decimal time information sequence.

[0019] Furthermore, in step 1 and step 2:

[0020] The preset time sequence format is: second-minute-hour-day-year; each time unit group includes five time units, which are second, minute, hour, day and year.

[0021] Furthermore, in step 1, the n B-code encoding sequences are sent to the plurality of event cameras to be synchronized in the form of pulse signals, specifically:

[0022] The n B-code encoding sequences are respectively sent to a plurality of event cameras to be synchronized in the form of pulse signals through a trigger line.

[0023] Beneficial effects of the present invention:

[0024] The present invention is based on the time series characteristics of B code and applies it to the time synchronization of n event cameras to be synchronized. The standard time information is processed according to the B code encoding method, the encoding of the standard time information is completed, and then sent to the n event cameras to be synchronized in the form of pulses. The n event cameras to be synchronized achieve event camera synchronization by aligning the decoded time information and the corresponding timestamp. The triggering method and the connection structure are simple, which is conducive to subsequent event data processing. Moreover, B code is a standard event encoding method and can be applied to a variety of test and measurement equipment. The synchronization method based on B code is conducive to the time unification and data fusion comparison between the event camera and the data of a variety of test equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a flow chart of a method for time synchronization of multiple event cameras based on B code of the present invention;

[0026] Figure 2 is a hardware composition diagram of a time encoding module and an event camera to be synchronized in an embodiment of the present invention;

[0027] Figure 3 It is a coding diagram of the time coding module in an embodiment of the present invention. DETAILED DESCRIPTION

[0028] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] The embodiment of the present invention provides a method for synchronizing multiple event cameras based on B code, combined with Figure 1 and Figure 2 As shown, the time synchronization method includes the following steps:

[0030] Step 1, n time coding modules (including FPGA and GPS) are based on B code coding mode, with the time interval between pulse signals as the identifier, and the standard time information of GPS timing is binary-encoded according to the preset timing format of seconds-minutes-hours-days-years to obtain n B code coding sequences; then the n B code coding sequences are sent to n event cameras to be synchronized in the form of pulse signals through the trigger line; the standard time information is a decimal time information sequence; the B code coding sequence is a binary time information sequence; the binary time information sequence includes multiple time unit groups, each time unit group corresponds to a preset timing format; then each time unit group includes five time units, namely seconds, minutes, hours, days and years; n ≥ 2 and is an integer.

[0031] B code is a time information encoding method, which is widely used in the fields of electricity, communication, aviation, etc. It transmits time information through a time string code of one frame per second. Its basic code elements include 0 code element, 1 code element and position code element P, and each code element has a different pulse width. The timing format of B code is seconds-minutes-hours-days, and each time unit is represented in binary code form. This encoding method enables B code to provide accurate time signals, which is suitable for occasions that require a high-precision time reference.

[0032] This embodiment designs a time code sequence according to the B code encoding method. The time sequence format of the B code is second-minute-hour-day-year, and each time unit is represented in binary coding form. According to the decimal standard time information of GPS timing, binary coding is performed in the time sequence format of second-minute-hour-day-year. For example, if the "second" time unit of the standard time information is 10 in decimal, the first nine bits are 0, the tenth bit is 1, and so on, the decimal time information sequence is converted into a binary time information sequence.

[0033] According to the binary coding of the time sequence format of seconds-minutes-hours-days-years, each time unit needs to be distinguished by a position code element similar to the B code for subsequent decoding processing. Therefore, the time interval between pulse signals is used as an identifier to distinguish each time unit. The first pulse of the encoding is a high level, which serves as the pulse reference. Then the pulse interval within each time unit group is the same, and the pulse interval between different time units is different.

[0034] Step 2: Each event camera to be synchronized obtains a binary time information sequence in the form of a pulse signal and generates a timestamp corresponding to the pulse signal. The pulse intervals between adjacent time unit groups are the same, and the pulse intervals between adjacent time units in each time unit group are different. In this way, the binary sequence is distinguished into each time unit group and each time unit in each time unit group. The binary of each time unit is then converted into decimal, and the corresponding time information is decoded according to the time sequence format of seconds-minutes-hours-days-years, and the corresponding timestamp is extracted.

[0035] The camera for the event to be synchronized records the binary time information sequence of the pulse signal and the timestamp generated inside the camera, distinguishes each time unit in the binary time information sequence according to the time interval of the pulse, and then converts the binary of each time unit into decimal, decodes the corresponding time information according to the time sequence format of seconds-minutes-hours-days-years, and extracts the corresponding timestamp.

[0036] Step 3: Align the time information decoded by each event camera to be synchronized and its corresponding timestamp, so that multiple event cameras to be synchronized can achieve time synchronization.

[0037] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for time synchronization of multiple event cameras based on B code, characterized in that: The following steps are involved: Step 1, n time encoding modules respectively encode the standard time information based on the B code encoding method to obtain n B code encoding sequences, and then send the n B code encoding sequences to n event cameras to be synchronized in the form of pulse signals; n ≥ 2 and is an integer; Step 2: Each camera of the event to be synchronized receives the pulse signal respectively, generates a timestamp corresponding to the pulse signal, decodes the standard time information, and extracts the corresponding timestamp; Step 3: Align the standard time information decoded by each event camera to be synchronized and its corresponding timestamp, so that multiple event cameras to be synchronized can achieve time synchronization.

2. The method for time synchronization of multiple event cameras based on B code according to claim 1, characterized in that: Step 1 is as follows: The n time coding modules are based on the B code coding method, take the time interval between pulses as an identifier, and binary encode the standard time information according to the preset timing format to obtain n B code coding sequences; then the n B code coding sequences are sent to the n event cameras to be synchronized in the form of pulse signals; the B code coding sequence is a binary time information sequence; the binary time information sequence includes multiple time unit groups; each time unit group corresponds to a preset timing format; each time unit group includes multiple time units.

3. The method for time synchronization of multiple event cameras based on B code according to claim 2, characterized in that: Step 2 is as follows: Each event camera to be synchronized receives a binary time information sequence in the form of a pulse signal and generates a timestamp corresponding to the pulse signal. The pulse intervals between adjacent time unit groups are the same, and the pulse intervals between adjacent time units in each time unit group are different. In this way, each time unit group and each time unit in each time unit group are distinguished from the binary time information sequence, and then each binary time unit is converted into a decimal system, and the corresponding standard time information is decoded according to a preset timing format, and the corresponding timestamp is extracted.

4. The method for time synchronization of multiple event cameras based on B code according to claim 2 or 3, characterized in that: In step 1: The time coding module includes FPGA and GPS; The standard time information is provided by GPS.

5. The method for time synchronization of multiple event cameras based on B code according to claim 4, characterized in that: In step 1: The standard time information is a decimal time information sequence.

6. The method for time synchronization of multiple event cameras based on B code according to claim 5, characterized in that: In steps 1 and 2: The preset time sequence format is: second-minute-hour-day-year; each time unit group includes five time units, which are second, minute, hour, day and year.

7. The method for time synchronization of multiple event cameras based on B code according to claim 6, characterized in that: In step 1, the n B-code encoding sequences are sent to a plurality of event cameras to be synchronized in the form of pulse signals, specifically: The n B-code encoding sequences are respectively sent to a plurality of event cameras to be synchronized in the form of pulse signals through a trigger line.

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