Sensor external trigger control method and system and medium

Abstract

The invention discloses a sensor external trigger control method and system and a medium, and the control method comprises the steps: receiving an external trigger signal, and controlling a sensor to start the reading work of all pixel lines in sequence after the generation of line synchronization signals with the number corresponding to a first preset value; obtaining pixel line reading time, so that line-by-line exposure is started after reading of the first pixel line is completed; after the pixel row at the position corresponding to the second preset value is opened to be exposed, stopping driving the next pixel row to be exposed; receiving a new external trigger signal, and continuing to drive the next pixel row to perform exposure, so that the sensor is controlled to start reading work of all pixel rows in sequence after the row synchronization signals with the number corresponding to the first preset value are generated, and image information in a normal area of the sensor is obtained according to preset exposure time. According to the invention, no jitter of the exposure time can be realized under the condition that the external trigger period time is not determined, the maximum frame rate can be reached in the external trigger mode, and the settable exposure time range is improved.

Description

Technical Field

[0001] The present invention belongs to the field of machine vision, and particularly relates to a method, system and medium for controlling external triggering of a sensor. Background Art

[0002] Rolling shutter exposure is the core exposure mode of a CMOS image sensor. It controls the pixel array to reset, expose and read out row by row through a vertical shift register. Its working principle is as follows: the reset register clears the pixel charges row by row in sequence (interval time Trow). The start time of exposure for each row is synchronized with the reset. After a uniformly set exposure time, the read register outputs data row by row. This mechanism has the advantages of low cost, low power consumption and short exposure in the microsecond level, and is widely used in the field of machine vision.

[0003] As can be seen from the above, the actual exposure time of each row of the rolling shutter exposure sensor is the frame period time minus the reading time of each row. Therefore, in the free running mode of the sensor, the sensor frame period and reading time are set by the user, and it is easy to calculate the ideal sensor exposure time.

[0004] However, in the external trigger mode, the sensor starts the exposure and output of a frame of image when an external trigger signal is input. The interval between two trigger signals cannot be controlled, and there are large differences and instabilities, so the accurate frame period time cannot be obtained, and the accurate reading time cannot be set, thus the sensor exposure time cannot be accurately controlled.

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

[0006] The purpose of the present invention is to overcome the above problems existing in the prior art, and provide a method, system and medium for controlling external triggering of a sensor. For the technical problem that the sensor exposure time cannot be accurately controlled in the external trigger mode for a rolling shutter exposure sensor, by setting a first preset value to control the exposure of normal pixel rows, and cooperating with setting the pixel row reading time and a second preset value, the sensor exposure time can be accurately controlled.

[0007] To achieve the above technical purpose and reach the above technical effect, the present invention is realized through the following technical solutions: A method for controlling external triggering of a sensor, which uses an external trigger signal to determine the sensor exposure time. The control method includes: Receiving an external trigger signal, and controlling the sensor to start the reading work of all pixel rows in sequence after the generation of the row synchronization signals corresponding to the first preset value; Obtaining the pixel row reading time, so as to start row-by-row exposure after the reading of the first row of pixel rows is completed; Statistically count the number of pixel rows with continuous exposure starting from the first pixel row, so that after the pixel row at the corresponding position of the second preset value is exposed, drive the next pixel row for exposure to be paused; Receive a new external trigger signal and continue to drive the next pixel row for exposure, so that after the first preset value of line synchronization signals are generated, control the sensor to start the reading work of all pixel rows in sequence, thereby obtaining the image information within the normal area of the sensor according to the preset exposure time; Wherein, the exposure time value is equal to the sum of the first preset value and the second preset value.

[0008] Further, the time interval for progressive exposure and the start interval for reading all pixel rows are both equal to the generation interval of the line synchronization signal.

[0009] Further, the number of line synchronization signals corresponding to the pixel row reading time is greater than the number of sensor pixel rows.

[0010] Further, the sum of the number of line synchronization signals corresponding to the pixel row reading time and the second preset value is greater than the number of sensor pixel rows.

[0011] Further, the second preset value is less than the number of invalid pixel rows at the start end of the sensor scan.

[0012] Further, it also includes exposure time analysis: If the number of line 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 control the exposure time value to be equal to the second preset value; If the number of line synchronization signals corresponding to the exposure time is greater than the number of invalid pixel rows at the start end of the sensor scan, then control the exposure time value to be equal to the sum of the number of invalid pixel rows at the start end of the sensor scan and the first preset value.

[0013] Further, 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.

[0014] Further, the sensor exposure mode is rolling shutter exposure.

[0015] The present invention also provides a sensor external trigger control system, including: A reading control module, configured to, after receiving an external trigger signal, control the sensor to start the reading work of all pixel rows in sequence after the first preset value of line synchronization signals are generated; An exposure start module, configured to obtain the pixel row reading time, so as to start progressive exposure after the first pixel row is read; An exposure control module is configured to count the number of pixel rows continuously exposed starting from the first pixel row, so that after the pixel row at the corresponding position of the second preset value is exposed, the driving of the next pixel row for exposure is paused; after receiving a new external trigger signal, the driving of the next pixel row for exposure is continued, so that after the generation of the line synchronization signals corresponding to the first preset value, the sensor is controlled to sequentially start the reading operation of all pixel rows, thereby obtaining the image information within the normal area of the sensor according to the preset exposure time.

[0016] The present invention also provides a computer-readable storage medium, including a computer program, and when the computer program is executed by a processor, the above control method is implemented.

[0017] The beneficial effects of the present invention are as follows: (1) The present invention can accurately control the exposure time of the sensor, avoiding the exposure time jitter caused by the differences and instabilities of external trigger intervals, specifically as follows: By receiving an external trigger signal and controlling the sensor to sequentially start the reading operation of all pixel rows after the generation of the line synchronization signals corresponding to the first preset value, a cycle can be formed with the first preset value corresponding to the normal exposure of subsequent normal pixel rows. Starting from each received external trigger signal, the distance between the reading time point of the first pixel row and the time point when any external trigger signal appears is a fixed value, avoiding the influence caused by the differences and instabilities of external trigger intervals; By obtaining the pixel row reading time to start row-by-row exposure after the first pixel row is read, the time for starting the next exposure after the current pixel row is read can be accurately determined according to the previously set pixel row reading time; By counting the number of pixel rows continuously exposed starting from the first pixel row, so that after the pixel row at the corresponding position of the second preset value is exposed, the driving of the next pixel row for exposure is paused. At this time, the number of continuously exposed pixel rows will be less than the number of invalid pixel rows at the starting end of the sensor scan. No matter when the new external trigger signal arrives, since the driving of the next pixel row for exposure has been paused at this time, the overexposure caused by the variable-length trigger interval time will only affect the pixel rows in the front part of the sensor, that is, the pixel rows corresponding to the second preset value, thereby fundamentally avoiding the possibility of overexposure of normal pixel rows; By receiving a new external trigger signal and continuing to drive the next pixel row for exposure, so that after the generation of the line synchronization signals corresponding to the first preset value, the sensor is controlled to sequentially start the reading operation of all pixel rows, the time points for starting and ending the exposure of normal pixel rows can be controlled to fall within the normal continuous line synchronization area, that is, excluding the variable-length trigger interval time, which ensures the normal image output of normal pixel rows in principle.

[0018] (2) The present invention can not only achieve jitter-free exposure time without determining the external trigger cycle time, but also adjust the relative relationships of the first preset value, the second preset value, and the pixel row reading time when the exposure time is relatively low, enabling the sensor to run at the maximum frame rate in the external trigger mode and allowing the exposure time to be adjusted arbitrarily according to actual needs, greatly expanding the adjustable exposure time range under external trigger. Description of the Drawings

[0019] The drawings described herein are used to provide a further understanding of the present invention and form a part of this application. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings: Figure 1 is a schematic diagram of the rolling shutter exposure principle in the prior art of the present invention; Figure 2 is a flowchart of the control method in the present invention; Figure 3 is a schematic diagram of the control method principle in the present invention; Figure 4 is a block diagram of the control system structure in the present invention. Detailed Embodiments

[0020] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a 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 those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0021] There are two common exposure methods for industrial area array cameras: global exposure and rolling shutter exposure. Global exposure is when the sensor starts and ends exposure simultaneously across the entire frame, and rolling shutter exposure is when the sensor exposes line by line. The sensor implemented by the rolling shutter exposure method can achieve a higher frame rate and lower cost, and has been widely used in industrial cameras. As Figure 1 shown, after the traditional rolling shutter exposure sensor receives the frame synchronization signal, it waits for a fixed number of line interval times before stopping exposure and starting to read data. After REG_TIME (i.e., the pixel row reading time), the current pixel row starts to be exposed. Similarly, the start exposure and start read times of the next row are delayed by one line interval time relative to the previous row. The external trigger function also belongs to the conventional function of industrial area array cameras. In the external trigger scenario, since the frame cycle time cannot be determined, it is impossible to obtain the determined exposure time for each pixel row in combination with the pixel row reading time.

[0022] The existing or relatively easy-to-implement solution is that after the camera receives an external trigger signal, it sends two frame synchronization signals to the sensor. 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 obtain an image with normal exposure output. The method of using two frame synchronization signals to output one image for each external trigger signal requires controlling the two frame synchronization signals to maintain a sufficient distance. Otherwise, the image output by the second frame synchronization signal will be an overexposed image. Therefore, at least the distance between the two frame synchronization signals must be greater than or equal to the time for reading the image data. In this logic, the external trigger cannot reach the maximum frame rate and can only reach at most half of the maximum frame rate.

[0023] Since the rolling shutter exposure of each row of the sensor starts to be driven and enabled by the line valid signal, after the previous row starts to be exposed, it will wait until the next line valid signal arrives to start the exposure of the next row, and there are several rows at the top and bottom of the sensor image that belong to invalid output rows, and these rows are not actually used in the output image. In order to effectively utilize the above characteristics of the sensor and solve the above problems to obtain the determined exposure time for each pixel row, as Figure 2 and Figure 3 shown, this embodiment first provides a method for controlling external trigger of a sensor to determine the exposure time of the sensor by using an external trigger signal. The control method includes: Receiving an external trigger signal and controlling the sensor to sequentially start the reading work of all pixel rows after the generation of the line synchronization signals corresponding to the first preset value. Define the first preset value as NUM1. This logic means that after receiving the external trigger signal, first give NUM1 line synchronization signals, and then start the reading work of all pixel rows.

[0024] Obtaining the pixel row reading time so as to start row-by-row exposure after the first pixel row is read. The pixel row reading time is REG_TIME. The end of the exposure time of each pixel row corresponds to the start of the pixel row reading time, and the end of the pixel row reading time corresponds to the start of the exposure time of that pixel row.

[0025] Count the number of pixel rows that are continuously exposed starting from the first pixel row of the statistical self-report. After the pixel row at the corresponding position of the second preset value is turned on for exposure, pause driving the next pixel row for exposure. Define the second preset value as NUM2. You can either adjust the REG_TIME value and the NUM2 value separately or directly give the sum of the REG_TIME value and the NUM2 value. By synchronously adjusting the REG_TIME value to obtain the NUM2 value, the total number of all pixel rows before the pixel row at the corresponding position of the second preset value corresponds to NUM2 line synchronization signals. Since the external trigger signal will arrive within a certain period of time in the future, and this time is the variable-length trigger interval time, the exposure time of the first NUM2 pixel rows will include the variable-length trigger interval time. The introduction of the variable-length trigger interval time will cause overexposure due to long-time exposure. However, since there are several invalid pixel rows at the starting end 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 end of the sensor scan, it will not affect the image output of the normal pixel rows.

[0026] Receive a new external trigger signal and continue to drive the next pixel row for exposure, so that after the generation of the line synchronization signals corresponding to the first preset value, control the sensor to start the reading work of all pixel rows in sequence, so as to obtain the image information in the normal area of the sensor according to the preset exposure time. Since the first preset value, that is, the NUM1 value, is set in advance, after starting the reading work of all pixel rows in sequence, starting from the (NUM2 + 1)-th pixel row, the exposure time of all subsequent pixel rows will become a fixed value and does not include the variable-length trigger interval time.

[0027] At this time, the exposure time value is equal to the sum of the first preset value and the second preset value.

[0028] The key to the design of the present invention lies in controlling the start and end exposure time points of the normal pixel rows to fall within the normal continuous line synchronization area, that is, not including the variable-length trigger interval time, corresponding to Figure 3 the NUM1 area in, so that a normal image with a normal exposure time can be obtained. 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, to increase the exposure time, it can be achieved by increasing the NUM1 or NUM2 time. If the sum of the REG_TIME value and the NUM2 value is directly given, it can also be achieved by increasing the sum of the REG_TIME value and the NUM2 value or decreasing the REG_TIME time.

[0029] To better ensure the effective control of the above control method, the sensor exposure method is rolling shutter exposure. Combining the characteristics of rolling shutter exposure can effectively implement the above control method, so as to obtain an accurate exposure time.

[0030] To ensure precise and stable control of the entire system, the time interval between sequential exposures and the read start interval for all pixel rows are both equal to the generation interval of the line synchronization signal. The generation interval of the line synchronization signal is the line interval time, which serves as the basic reference unit. For example, the general line interval time is 7.2 us.

[0031] As Figure 3 shown, to continuously obtain normal images with normal exposures, it is necessary to ensure that all pixel rows within the NUM1 area can start and end exposures according to the predetermined exposure time. As long as the number of line synchronization signals corresponding to the pixel row read time is greater than the number of sensor pixel rows, that is, the REG_TIME area contains the reading of all pixel rows, it can fully ensure the normal exposure time of all normal pixel rows. Let the number of sensor pixel rows be N, that is, ensure REG_TIME > N.

[0032] Similarly, to continuously obtain normal images with normal exposures, even if the REG_TIME area does not contain the reading of all pixel rows, but as long as it is ensured that the REG_TIME + NUM2 area contains the reading of all pixel rows, it can also ensure the normal exposure time of all normal pixel rows, that is, the sum of the number of line synchronization signals corresponding to the pixel row read time and the second preset value is greater than the number of sensor pixel rows, that is, ensure REG_TIME + NUM2 > N.

[0033] Regarding the adjustable range setting of the exposure time: Since the exposure time T = NUM1 + NUM2, or T = NUM1 + (NUM2 + REG_TIME) - REG_TIME, there are usually the following methods in the case of external triggering: increasing NUM1, increasing NUM2, increasing NUM2 + REG_TIME, and decreasing REG_TIME to increase the exposure time. To be able to increase the adjustable range of the exposure time as much as possible, we need to reasonably set the parameter values, but at the same time, we need to consider that the parameters are mutually restricted due to the problem of line overexposure.

[0034] When the exposure reaches a certain level, the REG_TIME time cannot be further decreased or the NUM2 time cannot be further increased, otherwise the exposure time of the pixel rows in front of the normal image will include an indefinite-length trigger interval time, resulting in overexposure of the current row and 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 start of the sensor scan. As Figure 3 shown, at this time, the number of pixel rows containing the indefinite-length trigger interval time all belong to the invalid pixel rows at the start of the sensor scan and do not involve any normal pixel rows, effectively avoiding the exposure time corresponding to the normal pixel rows from including the indefinite-length trigger interval time.

[0035] In the actual control process, in order to fully consider the association between the exposure time T and the number of invalid pixel rows X at the starting end of the sensor scan, assuming the total number of sensor pixel rows is h, the exposure time also needs to be analyzed as follows: If the number of line synchronization signals corresponding to the exposure time is less than or equal to the number of invalid pixel rows at the starting end of the sensor scan, then control the exposure time value to be equal to the second preset value. At this time, T ≤ X, fix NUM1 = 0; control NUM2 + REG_TIME = X + h, and the current maximum frame rate can be obtained; control REG_TIME = h + X - T to set the exposure time, that is, T = NUM2.

[0036] If the number of line synchronization signals corresponding to the exposure time is greater than the number of invalid pixel rows at the starting end of the sensor scan, then control the exposure time value to be equal to the sum of the number of invalid pixel rows at the starting end of the sensor scan and the first preset value. At this time, T > X, fix REG_TIME = h, NUM2 + REG_TIME = X + h, control NUM1 = T - X to set the exposure time, that is, T = NUM1 + X.

[0037] As can be seen from the above, 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 when facing 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, a new external trigger signal will arrive only after the pixel row corresponding to NUM2 starts to be exposed. This means that Figure 3 the actual range of the variable-length trigger interval time in [] is equal to the difference between the minimum interval time and the maximum interval time of the external trigger signal.

[0038] As Figure 4 shown, the second aspect of the present invention also provides a sensor external trigger control system, including: A reading control module, configured to control the sensor to sequentially start the reading work of all pixel rows after receiving an external trigger signal and generating the number of line synchronization signals corresponding to the first preset value; An exposure start module, configured to obtain the pixel row reading time to start progressive exposure after the first row of pixel rows is read; An exposure control module, configured to count the number of pixel rows continuously exposed starting from the first row of pixel rows, so as to pause driving the next pixel row for exposure after the pixel row corresponding to the second preset value starts to be exposed; after receiving a new external trigger signal, continue to drive the next pixel row for exposure, so that after generating the number of line synchronization signals corresponding to the first preset value, control the sensor to sequentially start the reading work of all pixel rows, thereby obtaining the image information within the normal area of the sensor according to the preset exposure time.

[0039] The third aspect of the present invention also provides a computer-readable storage medium, including a computer program, where when the computer program is executed by a processor, the above control method is implemented.

[0040] In practical applications, the computer-readable storage medium can adopt any combination of one or more computer-readable media. The computer-readable medium can be a computer-readable signal medium or a computer-readable storage medium. The computer-readable storage medium can be, but is not limited to, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination of the above. More specific examples of the computer-readable storage medium can include: an electrical connection with one or more wires, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the above. In this embodiment, the computer-readable storage medium can be any tangible medium that contains or stores a program, and this program can be used by or combined with an instruction execution system, apparatus, or device.

[0041] The computer-readable signal medium can include a data signal propagated in a baseband or as part of a carrier wave, which carries the computer-readable program code. Such a propagated data signal can take various forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination of the above. The computer-readable signal medium can also be any computer-readable medium other than the computer-readable storage medium, and this computer-readable medium can send, propagate, or transmit a program for use by or in combination with an instruction execution system, apparatus, or device.

[0042] The program code contained on the computer-readable medium can be transmitted by any appropriate medium, including but not limited to wireless, wire, optical cable, RF, etc., or any suitable combination of the above.

[0043] Computer program code for performing the operations of this application can be written in one or more programming languages or combinations thereof. The programming languages include object-oriented programming languages such as Java, Smalltalk, C++, and also include conventional procedural programming languages such as the "C" language or similar programming languages. The program code can be executed entirely on the user's computer, partially on the user's computer, executed 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 can be connected to the user's computer through any kind of network, including a local area network (LAN) or a wide area network (WAN), or it can be connected to an external computer (for example, by using an Internet service provider to connect through the Internet).

[0044] In the description of this specification, the descriptions referring to terms such as "one embodiment", "example", "specific example", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0045] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. The above embodiments and the descriptions in the specification only illustrate the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed.

Claims

1. A method for externally triggering and controlling a sensor, which uses an external trigger signal to determine the exposure time of the sensor, is characterized in that, The control method includes: Receiving an external trigger signal, and after the generation of the line synchronization signals corresponding to the first preset value, controlling the sensor to sequentially start the reading operation of all pixel rows; Obtaining the pixel row reading time so as to start progressive exposure after the first pixel row is read; Counting the number of pixel rows 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, driving the next pixel row for exposure is paused; Receiving a new external trigger signal and continuing to drive the next pixel row for exposure, so that after the generation of the line synchronization signals corresponding to the first preset value, the sensor is controlled to sequentially start the reading operation of all pixel rows, thereby obtaining the image information in the normal area of the sensor according to the preset exposure time; Wherein, the exposure time value is equal to the sum of the first preset value and the second preset value.

2. The sensor external trigger control method according to claim 1, wherein The time interval of progressive exposure and the start interval of reading all pixel rows are both equal to the generation interval of the line synchronization signals.

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

4. The sensor external trigger control method according to claim 2, characterized in that, The sum of the number of line 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 method for externally triggering and controlling a sensor according to any one of claims 1-4, characterized in that, The second preset value is less than the number of invalid pixel rows at the start end of the sensor scan.

6. The method for externally triggering and controlling a sensor according to claim 5, wherein It also includes exposure time analysis: If the number of line 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, controlling the exposure time value to be equal to the second preset value; If the number of line synchronization signals corresponding to the exposure time is greater than the number of invalid pixel rows at the start end of the sensor scan, controlling the exposure time value to be equal to the sum of the number of invalid pixel rows at the start end of the sensor scan and the first preset value.

7. A method for externally triggering and controlling a sensor 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 signals.

8. A method for externally triggering and controlling a sensor according to claim 7, wherein The exposure mode of the sensor is rolling shutter exposure.

9. A sensor external trigger control system, characterized in that, It includes: A reading control module, configured to, after receiving an external trigger signal, control the sensor to sequentially start the reading operation of all pixel rows after the generation of the line synchronization signals corresponding to the first preset value; An exposure start module, configured to obtain the pixel row reading time so as to start progressive exposure after the first pixel row is read; An exposure control module, configured to count the number of pixel rows 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, driving the next pixel row for exposure is paused; after receiving a new external trigger signal, continue to drive the next pixel row for exposure, so that after the generation of the line synchronization signals corresponding to the first preset value, the sensor is controlled to sequentially start the reading operation of all pixel rows, thereby obtaining the image information in 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, it implements the control method according to any one of claims 1-8.

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