Sensor external trigger control method, system and medium

Abstract

The present invention discloses a sensor external trigger control method, system and medium. The control method includes: receiving an external trigger signal, and controlling the sensor to sequentially start reading all pixel rows after a number of row synchronization signals corresponding to a first preset value are generated; obtaining the pixel row reading time so that row-by-row exposure is started after the first row of pixel rows is read; after the pixel row at a position corresponding to a second preset value is exposed, pausing the drive of the next pixel row for exposure; receiving a new external trigger signal, and continuing to drive the next pixel row for exposure, so that after a number of row synchronization signals corresponding to the first preset value are generated, controlling the sensor to sequentially start reading all pixel rows, thereby obtaining image information within the normal area of the sensor according to the preset exposure time. The present invention can not only achieve exposure time jitter-free under uncertain external trigger cycle time, but also achieve full maximum frame rate in external trigger mode and increase the configurable exposure time range.

Description

Technical Field

[0001] The present invention belongs to the field of machine vision, and in particular relates to a sensor external trigger control method, system and medium. Background Art

[0002] Rolling shutter exposure is a core exposure mode in CMOS image sensors. It uses a vertical shift register to control the sequential reset, exposure, and readout of the pixel array row by row. Its operating principle is as follows: the reset register clears the pixel charge row by row (at interval Trow). The start of each row exposure is synchronized with the reset, and after a uniformly set exposure time, the readout register outputs the data row by row. This mechanism offers the advantages of low cost, low power consumption, and short exposure times in the microsecond range, making it widely used in machine vision.

[0003] As can be seen above, the actual exposure time for each row of a rolling shutter sensor is the frame period minus the readout time for each row. Therefore, in the sensor's free-running mode, where both the sensor frame period and readout time are user-defined, it's easy to calculate the ideal sensor exposure time.

[0004] However, in external trigger mode, the sensor starts exposing and outputting a frame of image when a trigger signal is input externally. The interval between the two trigger signals cannot be controlled, and there is a large difference and instability. It is impossible to obtain an accurate frame cycle time, and it is also impossible to set an accurate reading time, and thus it is impossible to accurately control the sensor exposure time.

[0005] Therefore, in order to accurately control the exposure time of a sensor, the present invention provides a sensor external trigger control method, system and medium. Summary of the Invention

[0006] The purpose of the present invention is to overcome the above-mentioned problems existing in the prior art and provide a sensor external trigger control method, system and medium. To solve the technical problem that the rolling shutter exposure sensor cannot accurately control the sensor exposure time in the external trigger mode, the first preset value is set to control the normal pixel row exposure, and the pixel row reading time and the second preset value are set to accurately control the sensor exposure time.

[0007] In order to achieve the above technical objectives and the above technical effects, the present invention is implemented through the following technical solutions:

[0008] A sensor external trigger control method utilizes an external trigger signal to determine the sensor exposure time. The control method includes:

[0009] receiving an external trigger signal and controlling the sensor to start reading all pixel rows in sequence after a number of row synchronization signals corresponding to a first preset value are generated;

[0010] Get the pixel row reading time so that the row-by-row exposure can be started after the first row of pixels is read;

[0011] Counting the number of pixel rows that are continuously exposed starting from the first pixel row, so that after the pixel row at a position corresponding to the second preset value starts exposure, the exposure of the next pixel row is stopped;

[0012] Receive a new external trigger signal and continue to drive the next pixel row for exposure, so that after a number of row synchronization signals corresponding to the first preset value are generated, the sensor is controlled to start reading all pixel rows in sequence, thereby obtaining image information within the normal area of the sensor according to the preset exposure time;

[0013] The exposure time value is equal to the sum of the first preset value and the second preset value.

[0014] Furthermore, the time interval of the row-by-row exposure and the read-on interval of all pixel rows are both equal to the generation interval of the row synchronization signal.

[0015] Furthermore, the number of row synchronization signals corresponding to the pixel row reading time is greater than the number of sensor pixel rows.

[0016] Furthermore, the sum of the number of row synchronization signals corresponding to the pixel row reading time and the second preset value is greater than the number of sensor pixel rows.

[0017] Furthermore, the second preset value is smaller than the number of invalid pixel rows at the start end of the sensor scan.

[0018] Furthermore, it also includes exposure time analysis:

[0019] If the number of row synchronization signals corresponding to the exposure time is less than or equal to the number of invalid pixel rows at the start end of the sensor scan, then controlling the exposure time value to be equal to the second preset value;

[0020] If the number of row synchronization signals corresponding to the exposure time is greater than the number of invalid pixel rows at the start of the sensor scan, the exposure time value is controlled to be equal to the sum of the number of invalid pixel rows at the start of the sensor scan and the first preset value.

[0021] Furthermore, the sum of the first preset value, the second preset value and the pixel row reading time value is less than the minimum interval time of the external trigger signal.

[0022] Furthermore, the sensor exposure mode is rolling shutter exposure.

[0023] The present invention also provides a sensor external trigger control system, comprising:

[0024] A reading control module is used to control the sensor to start reading all pixel rows in sequence after receiving an external trigger signal and generating a number of row synchronization signals corresponding to a first preset value;

[0025] An exposure start module is used to obtain the pixel row reading time so that row-by-row exposure can be started after the first row of pixels is read;

[0026] The exposure control module is used to count the number of pixel rows that are continuously exposed starting from the first pixel row, so that after the pixel row at the position corresponding to the second preset value starts to be exposed, the driving of the next pixel row for exposure is suspended; after receiving a new external trigger signal, the driving of the next pixel row for exposure is continued, so that after the number of row synchronization signals corresponding to the first preset value are generated, the sensor is controlled to start reading all pixel rows in sequence, thereby obtaining image information within the normal area of the sensor according to the preset exposure time.

[0027] The present invention also provides a computer-readable storage medium, comprising a computer program, wherein the computer program implements the above control method when executed by a processor.

[0028] The beneficial effects of the present invention are:

[0029] (1) The present invention can accurately control the sensor exposure time and avoid exposure time jitter caused by external trigger interval differences and instability, as follows:

[0030] By receiving an external trigger signal and controlling the sensor to sequentially start reading all pixel rows after a number of row synchronization signals corresponding to a first preset value are generated, a cycle can be formed with the first preset value corresponding to the normal exposure of subsequent normal pixel rows. With each received external trigger signal as the starting point, the distance between the reading time point of the first pixel row and the time point of the appearance of any external trigger signal is constant, thus avoiding the influence caused by the difference and instability of the external trigger interval;

[0031] By obtaining the pixel row reading time, the row-by-row exposure can be started after the first row of pixel rows is read. The time to start the next exposure after the current row of pixel rows is read can be accurately determined according to the pre-set pixel row reading time.

[0032] By counting the number of pixel rows continuously exposed starting from the first pixel row, the exposure of the pixel row corresponding to the second preset value is started, and then the exposure of the next pixel row is suspended. At this time, the number of pixel rows continuously exposed will be less than the number of invalid pixel rows at the beginning of the sensor scan. Regardless of when a new external trigger signal arrives, the exposure of the next pixel row has been suspended. Therefore, the overexposure caused by the indefinite trigger interval will only affect the front pixel rows of the sensor, that is, the number of pixel rows corresponding to the second preset value, thereby fundamentally avoiding the possibility of overexposure of normal pixel rows.

[0033] By receiving a new external trigger signal and continuing to drive the next pixel row for exposure, the sensor is controlled to start reading all pixel rows in sequence after the number of row synchronization signals corresponding to the first preset value is generated. The time points for starting and ending exposure of normal pixel rows can be controlled to fall within the normal continuous row synchronization area, that is, excluding the indefinite-length trigger interval time, which in principle ensures the normal image output of normal pixel rows.

[0034] (2) The present invention can not only realize exposure time jitter-free under the condition of uncertain external trigger cycle time, but also adjust the relative relationship between the first preset value, the second preset value and the pixel row reading time when the exposure time is low, so that the sensor can run at the maximum frame rate in the external trigger mode, and can also adjust the exposure time at will according to actual needs, thereby greatly improving the range of exposure time that can be set under external triggering. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0036] Figure 1 It is a schematic diagram of the rolling shutter exposure principle in the prior art of the present invention;

[0037] Figure 2 It is a flow chart of the control method in the present invention;

[0038] Figure 3 It is a schematic diagram of the control method principle in the present invention;

[0039] Figure 4 It is a structural block diagram of the control system in the present invention. DETAILED DESCRIPTION

[0040] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0041] There are two common exposure methods for industrial area scan cameras: global exposure and rolling exposure. Global exposure starts and ends the exposure of the entire sensor frame at the same time, while rolling exposure exposes the sensor line by line. Sensors using rolling exposure can achieve higher frame rates and lower costs, and have been widely used in industrial cameras. Figure 1As shown in the figure, after receiving the frame synchronization signal, a traditional rolling shutter exposure sensor waits for a fixed number of row intervals before stopping exposure and starting data readout. After REG_TIME (i.e., the pixel row readout time), the current pixel row begins exposure. Similarly, the start of exposure and readout of the next row is delayed by one row interval relative to the previous row. External triggering is also a common feature of industrial area scan cameras. In this scenario, since the frame cycle time cannot be determined, it is impossible to combine the pixel row readout time to determine the exposure time for each pixel row.

[0042] An existing, or relatively easy-to-implement, solution is for the camera to send two frame synchronization signals to the sensor after receiving an external trigger signal. The image data output after the first frame synchronization signal is discarded, and the exposure time is controlled by the distance between the two frame synchronization signals to produce a properly exposed image. This method, in which each external trigger signal uses two frame synchronization signals to output a single image, requires maintaining a sufficient distance between the two frame synchronization signals. Otherwise, the image output by the second frame synchronization signal will be overexposed. Therefore, the distance between the two frame synchronization signals must be at least equal to the image data readout time. Under this logic, the external trigger cannot achieve the maximum frame rate, and can only reach half the maximum frame rate at best.

[0043] Since the rolling shutter exposure of each row of the sensor is driven by the row valid signal, after the previous row is exposed, it will wait until the next row valid signal arrives to start the next row exposure. In addition, there are several rows above and below the sensor image that are invalid output rows. These rows are not used in the actual output image. In order to effectively utilize the above characteristics of the sensor and solve the above problems, the exposure time determined by each pixel row is obtained, such as Figure 2 and Figure 3 As shown, this embodiment first provides a sensor external trigger control method, which uses an external trigger signal to determine the sensor exposure time. The control method includes:

[0044] Receives an external trigger signal and controls the sensor to sequentially initiate reading of all pixel rows after generating a number of row synchronization signals corresponding to a first preset value. Define the first preset value as NUM1. This logic indicates that after receiving the external trigger signal, NUM1 row synchronization signals are generated, and then the reading of all pixel rows is initiated.

[0045] Get the pixel row read time so that row-by-row exposure can start after the first row of pixel rows has been read. The pixel row read time is REG_TIME. The end of each pixel row exposure time is the start of the corresponding pixel row read time, and the end of the pixel row read time is the start of the corresponding pixel row exposure time.

[0046] The number of pixel rows exposed continuously starting from the first pixel row is counted, so that after the pixel row corresponding to the second preset value starts exposure, the exposure of the next pixel row is paused. The second preset value is defined as NUM2. The REG_TIME value and NUM2 value can be adjusted separately, or the sum of the REG_TIME value and NUM2 value can be directly given. By synchronously adjusting the REG_TIME value to obtain the NUM2 value, the total number of pixel rows before the pixel row corresponding to the second preset value corresponds to NUM2 row synchronization signals. Since the external trigger signal will arrive within a certain period of time later, this time is the variable-length trigger interval. Therefore, the exposure time of the first NUM2 pixel rows will include the variable-length trigger interval. The introduction of the variable-length trigger interval will result in long exposure and overexposure. However, since several pixel rows are invalid at the starting point of the sensor scan, as long as the number of overexposed pixel rows is less than the number of invalid pixel rows at the starting point of the sensor scan, the image output of the normal pixel rows will not be affected.

[0047] After receiving a new external trigger signal and continuing to drive the next pixel row for exposure, the sensor controls the sequential reading of all pixel rows after generating a number of row synchronization signals corresponding to the first preset value, thereby obtaining image information within the sensor's normal area according to the preset exposure time. Because the first preset value, NUM1, is set in advance, after sequentially starting the reading of all pixel rows, the exposure time for all subsequent pixel rows, starting with pixel row NUM2+1, becomes a constant, excluding the variable-length trigger interval.

[0048] At this time, the exposure time value is equal to the sum of the first preset value and the second preset value.

[0049] The key to the design of the present invention is to control the time points of the normal pixel row exposure start and end to fall within the normal continuous row synchronization area, that is, excluding the indefinite length trigger interval time, corresponding to Figure 3 The NUM1 area in the image is used to obtain a normal image with a normal exposure time. Since the exposure time value is equal to the sum of the first preset value and the second preset value, when the exposure time is relatively small, if you want to increase the exposure time, you can increase NUM1 or NUM2 to achieve control. If the sum of REG_TIME and NUM2 is directly given, you can also increase the sum of REG_TIME and NUM2 or decrease REG_TIME to achieve control.

[0050] In order to better ensure the effective control of the above control method, the sensor exposure mode is rolling exposure. Combined with the characteristics of rolling exposure, the above control method can be effectively implemented to obtain accurate exposure time.

[0051] To ensure precise and stable control of the entire system, the time interval between line-by-line exposure and the read-on interval for all pixel rows are equal to the generation interval of the line synchronization signal. The generation interval of the line synchronization signal is the line interval time, which is used as the basic reference unit. For example, the general line interval time is 7.2us.

[0052] like Figure 3 As shown in the figure, to consistently obtain a properly exposed image, it is necessary to ensure that all pixel rows within the NUM1 region can start and end exposure according to the scheduled exposure time. As long as the number of row synchronization signals corresponding to the pixel row read time is greater than the number of sensor pixel rows, that is, the readout of all pixel rows within the REG_TIME region is included, the normal exposure time for all normal pixel rows can be fully guaranteed. Assuming the number of sensor pixel rows is N, it is ensured that REG_TIME>N.

[0053] Similarly, in order to always obtain a normal image with normal exposure, even if the REG_TIME area cannot include the reading of all pixel rows, as long as the REG_TIME+NUM2 area includes the reading of all pixel rows, the normal exposure time of all normal pixel rows can also be guaranteed, that is, the sum of the number of row synchronization signals corresponding to the pixel row reading time and the second preset value is greater than the number of sensor pixel rows, that is, REG_TIME+NUM2>N.

[0054] Regarding the adjustable range of exposure time: Since exposure time T = NUM1 + NUM2, or T = NUM1 + (NUM2 + REG_TIME) - REG_TIME, external triggering typically involves increasing exposure time by increasing NUM1, increasing NUM2, increasing NUM2 + REG_TIME, and decreasing REG_TIME. To maximize the adjustable exposure time range, we need to set each parameter appropriately, but we must also consider the mutual constraints between parameters due to overexposure.

[0055] When the exposure reaches a certain level, you cannot reduce the REG_TIME time or increase the NUM2 time. Otherwise, the exposure time of the pixel rows in front of the normal image will cause the current row to be overexposed due to the indefinite trigger interval time, resulting in a white edge on the upper side of the image. Therefore, it is necessary to set the second preset value to be less than the number of invalid pixel rows at the beginning of the sensor scan, such as Figure 3 As shown, at this time, all pixel rows containing variable-length trigger intervals belong to invalid pixel rows at the starting end of the sensor scan, and do not involve any normal pixel rows, which will effectively avoid the exposure time corresponding to the normal pixel rows including the variable-length trigger interval.

[0056] In the actual control process, in order to fully consider the relationship between the exposure time T and the number of invalid pixel rows X at the start of the sensor scan, assuming the total number of sensor pixel rows is h, the exposure time needs to be analyzed as follows:

[0057] If the number of row synchronization signals corresponding to the exposure time is less than or equal to the number of invalid pixel rows at the start of the sensor scan, the exposure time is set to a second preset value. In this case, T ≤ X, and NUM1 is fixed to 0. NUM2 + REG_TIME = X + h is used to obtain the current maximum frame rate. REG_TIME = h + XT is used to set the exposure time, i.e., T = NUM2.

[0058] If the number of row synchronization signals corresponding to the exposure time is greater than the number of invalid pixel rows at the start of the sensor scan, the exposure time is controlled to be equal to the sum of the number of invalid pixel rows at the start of the sensor scan and the first preset value. In this case, T>X, REG_TIME=h, NUM2+REG_TIME=X+h, and NUM1=TX to set the exposure time, that is, T=NUM1+X.

[0059] From the above, it can be seen that the sum of the first preset value, the second preset value and the pixel row reading time value is equivalent to a fixed frame period. In order to be unaffected by trigger signals with different time intervals, it is necessary to make the sum of the first preset value, the second preset value and the pixel row reading time value less than the minimum interval time of the external trigger signal, that is, the new external trigger signal will not arrive until the pixel row corresponding to the position NUM2 starts to be exposed. This means that Figure 3 The actual range of the indefinite-length trigger interval is equal to the difference between the minimum interval and the maximum interval of the external trigger signal.

[0060] like Figure 4 As shown, the second aspect of the present invention further provides a sensor external trigger control system, comprising:

[0061] A reading control module is used to control the sensor to start reading all pixel rows in sequence after receiving an external trigger signal and generating a number of row synchronization signals corresponding to a first preset value;

[0062] An exposure start module is used to obtain the pixel row reading time so that row-by-row exposure can be started after the first row of pixels is read;

[0063] The exposure control module is used to count the number of pixel rows that are continuously exposed starting from the first pixel row, so that after the pixel row at the position corresponding to the second preset value starts to be exposed, the driving of the next pixel row for exposure is suspended; after receiving a new external trigger signal, the driving of the next pixel row for exposure is continued, so that after the number of row synchronization signals corresponding to the first preset value are generated, the sensor is controlled to start reading all pixel rows in sequence, thereby obtaining image information within the normal area of the sensor according to the preset exposure time.

[0064] A third aspect of the present invention further provides a computer-readable storage medium comprising a computer program, wherein the computer program implements the above-mentioned control method when executed by a processor.

[0065] In practical applications, computer-readable storage media may take the form of any combination of one or more computer-readable media. Computer-readable media may be computer-readable signal media or computer-readable storage media. Computer-readable storage media may be, but are not limited to, electrical, magnetic, optical, electromagnetic, infrared, or semiconductor systems, devices, or components, or any combination thereof. More specific examples of computer-readable storage media may include: an electrical connection having one or more wires, a portable computer disk, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination thereof. In this embodiment, a computer-readable storage medium may be any tangible medium containing or storing a program that can be used by or in conjunction with an instruction execution system, device, or component.

[0066] A computer-readable signal medium may include a data signal propagated in baseband or as part of a carrier wave, which carries computer-readable program code. Such propagated data signals may take various forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination thereof. A computer-readable signal medium may also be any computer-readable medium other than a computer-readable storage medium that can transmit, propagate, or transport a program for use by or in conjunction with an instruction execution system, apparatus, or device.

[0067] Program code embodied on a computer readable medium may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber cable, RF, etc., or any suitable combination of the foregoing.

[0068] Computer program code for performing the operations of the present application may be written in one or more programming languages, or a combination thereof, including object-oriented programming languages such as Java, Smalltalk, C++, and conventional procedural programming languages such as "C" or similar programming languages. The program code may be executed entirely on the user's computer, partially on the user's computer, as a stand-alone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer via any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., via the Internet using an Internet service provider).

[0069] Throughout this specification, references to terms such as "one embodiment," "example," and "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0070] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention, and such changes and modifications fall within the scope of the invention as claimed.

Claims

1. A sensor external trigger control method, which uses an external trigger signal to determine the sensor exposure time, characterized in that: Control methods include: receiving an external trigger signal and controlling the sensor to start reading all pixel rows in sequence after a number of row synchronization signals corresponding to a first preset value are generated; Get the pixel row reading time so that the row-by-row exposure can be started after the first row of pixels is read; Counting the number of pixel rows that are continuously exposed starting from the first pixel row, so that after the pixel row at a position corresponding to the second preset value starts exposure, the exposure of the next pixel row is stopped; Receive a new external trigger signal and continue to drive the next pixel row for exposure, so that after a number of row synchronization signals corresponding to the first preset value are generated, the sensor is controlled to start reading all pixel rows in sequence, thereby obtaining image information within the normal area of the sensor according to the preset exposure time; The exposure time value is equal to the sum of the first preset value and the second preset value.

2. A sensor external trigger control method according to claim 1, characterized in that: The time interval of the row-by-row exposure and the read-on interval of all pixel rows are equal to the generation interval of the row synchronization signal.

3. A sensor external trigger control method according to claim 2, characterized in that: The number of row synchronization signals corresponding to the pixel row reading time is greater than the number of sensor pixel rows.

4. A sensor external trigger control method according to claim 2, characterized in that: The sum of the number of row synchronization signals corresponding to the pixel row reading time and the second preset value is greater than the number of sensor pixel rows.

5. A sensor external trigger control method according to any one of claims 1 to 4, characterized in that: The second preset value is smaller than the number of invalid pixel rows at the start end of the sensor scan.

6. A sensor external trigger control method according to claim 5, characterized in that: Also includes exposure time analysis: If the number of row synchronization signals corresponding to the exposure time is less than or equal to the number of invalid pixel rows at the start end of the sensor scan, then controlling the exposure time value to be equal to the second preset value; If the number of row synchronization signals corresponding to the exposure time is greater than the number of invalid pixel rows at the start of the sensor scan, the exposure time value is controlled to be equal to the sum of the number of invalid pixel rows at the start of the sensor scan and the first preset value.

7. A sensor external trigger control method according to claim 6, characterized in that: The sum of the first preset value, the second preset value, and the pixel row reading time value is less than the minimum interval time of the external trigger signal.

8. A sensor external trigger control method according to claim 7, characterized in that: The sensor exposure mode is rolling shutter exposure.

9. A sensor external trigger control system, characterized in that: include: A reading control module is used to control the sensor to start reading all pixel rows in sequence after receiving an external trigger signal and generating a number of row synchronization signals corresponding to a first preset value; An exposure start module is used to obtain the pixel row reading time so that row-by-row exposure can be started after the first row of pixels is read; The exposure control module is used to count the number of pixel rows that are continuously exposed starting from the first pixel row, so that after the pixel row at the position corresponding to the second preset value starts to be exposed, the driving of the next pixel row for exposure is suspended; after receiving a new external trigger signal, the driving of the next pixel row for exposure is continued, so that after the number of row synchronization signals corresponding to the first preset value are generated, the sensor is controlled to start reading all pixel rows in sequence, thereby obtaining image information within the normal area of the sensor according to the preset exposure time.

10. A computer-readable storage medium comprising a computer program, characterized in that When the computer program is executed by a processor, the control method according to any one of claims 1 to 8 is implemented.

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