CN110868584A - Focal length calibration method and device of image acquisition device - Google Patents

Abstract

The embodiments of the present invention provide a focal length calibration method and device for an image acquisition device. The focal length calibration method of the image acquisition device includes: detecting the current sharpness value of the image on the imaging plate every preset period; according to the preset sharpness value and the current sharpness value, judging whether the back focus of the image acquisition device is not Offset occurs; when the back focus of the image acquisition device deviates, adjust the position of the imaging plate to calibrate the focal length, automatically detect, judge and adjust, reduce the burden of manual adjustment, reduce the burden of maintenance personnel, and improve maintenance efficiency. The clarity of the image is guaranteed.

Description

A focal length calibration method and device of an image acquisition device

technical field

The present invention relates to the technical field of image acquisition, and in particular, to a focal length calibration method and device of an image acquisition device.

Background technique

With the development of society, the use of image acquisition technology has become more and more popular. Among them, PTZ cameras are widely used in large-scale projects such as safe cities, high-speed monitoring, and forest fire prevention, and are installed on commanding heights such as roofs and signal towers.

The existing camera is a combination of multiple components. When the temperature changes greatly or the vibration for a long time, it is easy to cause the optical back focus to be shifted, and finally it will appear as the original preset virtual focus. Once a problem occurs, due to its installation location and the complexity of components, maintenance is difficult, maintenance time is long, and efficiency is low. At the same time, it will also affect its monitoring function, which may lead to monitoring errors and omissions.

SUMMARY OF THE INVENTION

In order to improve the above problems, the purpose of the present invention is to provide a focal length calibration method and device of an image acquisition device.

In order to achieve the above purpose, the technical solutions adopted in the embodiments of the present invention are as follows:

In a first aspect, an embodiment of the present invention provides a method for calibrating a focal length of an image acquisition device, including:

Detect the current clear value of the image on the imaging plate every preset period;

Wherein, the current sharpness value is the sharpness value of the image formed by the imaging plate when the image acquisition device is located at a preset coordinate and a wide-angle position;

Determine whether the back focus of the image acquisition device is shifted according to the preset sharpness value and the current sharpness value; wherein, the preset sharpness value is the image acquisition device located at a preset coordinate and a wide-angle position, and the The peak value of the sharpness value of the image formed by the imaging plate;

When the back focus of the image capture device is shifted, the position of the imaging plate is adjusted to calibrate the focus.

In a second aspect, an embodiment of the present invention further provides a focal length calibration device for an image acquisition device, including:

a detection unit, used for detecting the current clear value of the image on the imaging plate every preset period;

Wherein, the current sharpness value is the sharpness value of the image formed by the imaging plate when the image acquisition device is located at a preset coordinate and a wide-angle position;

a judgment unit, configured to judge whether the back focus of the image capture device is shifted according to the preset sharpness value and the current sharpness value; wherein, the preset sharpness value is the image capture device located at preset coordinates, wide-angle In the position, the peak value of the clear value of the image formed by the imaging plate;

An adjustment unit, configured to adjust the position of the imaging plate to calibrate the focal length if the back focus of the image acquisition device is deviated.

The focal length calibration method and device for an image acquisition device provided by the embodiments of the present invention have the following advantages: the current sharpness value of the image on the imaging plate is detected every preset period; Whether the back focus of the image acquisition device is shifted; when the back focus of the image acquisition device is shifted, adjust the position of the imaging plate to calibrate the focal length, automatically detect, judge and adjust, reducing the burden of manual adjustment and maintenance It reduces the burden on personnel, improves maintenance efficiency, and ensures the clarity of images.

In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below, and are described in detail as follows in conjunction with the accompanying drawings.

Description of drawings

In order to illustrate the technical solutions of the embodiments of the present invention more clearly, the following briefly introduces the accompanying drawings used in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and therefore do not It should be regarded as a limitation of the scope, and for those of ordinary skill in the art, other related drawings can also be obtained according to these drawings without any creative effort.

FIG. 1 shows a schematic diagram of an application environment of a focal length calibration method of an image acquisition device provided by an embodiment of the present invention;

FIG. 2 shows a schematic flowchart of a focal length calibration method of an image acquisition device provided by a first embodiment of the present invention;

FIG. 3 shows a schematic flowchart of sub-steps of step S102 of the focal length calibration method of the image acquisition device provided by the first embodiment of the present invention;

FIG. 4 shows a schematic flowchart of sub-steps of step S103 of the focal length calibration method of the image acquisition device provided by the first embodiment of the present invention;

FIG. 5 shows a schematic flowchart of a focal length calibration method of an image acquisition device provided by a second embodiment of the present invention;

6 shows a schematic flowchart of a focal length calibration method for an image acquisition device provided by a third embodiment of the present invention;

FIG. 7 shows a functional unit diagram of a focal length calibration device of an image acquisition device provided by an embodiment of the present invention.

Icons: 10-first driving device; 20-second driving device; 30-third driving device; 40-image information processor; 50-controller; 60-memory; 70-peripheral interface; 200-image acquisition device 201-detection unit; 202-judgment unit; 203-adjustment unit.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. The components of the embodiments of the invention generally described and illustrated in the drawings herein may be arranged and designed in a variety of different configurations.

Thus, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but is merely representative of selected embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present invention.

It should be noted that relational terms such as the terms "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any relationship between these entities or operations. any such actual relationship or sequence exists. Moreover, the terms "comprising", "comprising" or any other variation thereof are intended to encompass a non-exclusive inclusion such that a process, method, article or device that includes a list of elements includes not only those elements, but also includes not explicitly listed or other elements inherent to such a process, method, article or apparatus. Without further limitation, an element qualified by the phrase "comprising a..." does not preclude the presence of additional identical elements in a process, method, article or apparatus that includes the element.

A preferred embodiment of the present invention provides a focal length calibration method for an image acquisition device, which is applied to the controller 50 . The image acquisition device can be, but is not limited to, a video camera or a camera, and the image acquisition device includes an imaging plate and a focusing lens group. As shown in FIG. 1 , the controller 50 is electrically connected to the first driving device 10 , the second driving device 20 , the third driving device 30 , the image information processor 40 , the memory 60 and the peripheral interface 70 , respectively.

The first driving device 10 is used for receiving the instruction of the controller 50 to drive the imaging plate to move. The first driving device 10 may use a stepping motor.

The second driving device 20 is used for receiving an instruction from the controller 50 to drive the focusing lens group to zoom. The second driving device 20 may use a DC motor.

The third driving device 30 is used for receiving an instruction from the controller 50 to drive the focusing lens group to focus. The third driving device 30 may use a DC motor.

The image information processor 40 is used to collect the image on the imaging plate and convert it into a sharpness value of the image, that is, the sharpness value, and transmit the sharpness value to the controller 50 .

The memory 60 may be used to store software programs and modules, such as program instructions/modules corresponding to the image processing apparatus and method in the embodiments of the present invention, and the focal length calibration apparatus 200 of the image acquisition apparatus. The controller 50 executes various functional applications and data processing by running the software programs and modules stored in the memory 60, such as the focal length calibration method of the image acquisition device provided by the embodiment of the present invention. The memory 60 may also be used to store other data transmitted by the controller 50 .

The focal length calibration device 200 of the image capturing device includes at least one software function module that can be stored in the memory 60 or fixed in an operating system (OS) of the controller 50 in the form of software or firmware.

The peripheral interface 70 is used to connect an external input device, and the user can adjust and modify the focal length calibration device 200 of the image capturing device through the external input device.

The focal length calibration method of the image acquisition device provided by the first embodiment of the present invention is applied to the controller 50, and the specific steps are shown in FIG. 2:

Step S101: Detect the current sharpness value, the front sharpness value and the rear sharpness value of the image on the imaging plate every preset period.

The front clear value is the clear value of the image formed after the imaging plate is moved from the current position by a preset distance in a direction close to the focusing lens group; The sharpness value of the image formed after the direction of the focus lens group is moved by a preset distance; the current sharpness value is the sharpness value of the image formed by the imaging plate when the image acquisition device is located at the preset coordinates and at the wide-angle position; The current position is the position of the imaging plate when the image on the imaging plate corresponds to the current sharpness value.

The preset period can be preset as 12 hours, 48 hours, 78 hours, etc., which is not limited herein.

Every preset period of time, the controller 50 controls the second driving device 20 to drive the focusing lens group to zoom to the wide-angle position. At this time, the image information processor 40 collects the image on the imaging plate and converts it into a sharpness value of the image, which is the current sharpness value. The image information processor 40 transmits the current sharpness value to the controller 50 .

After receiving the current sharpness value transmitted by the image information processor 40, the controller 50 controls the first driving device 10 to drive the imaging plate to move a preset distance from the current position in a direction close to the focusing lens group. At this time, the image information processor 40 collects the image on the imaging plate and converts it into a sharpness value of the image, which is the former sharpness value. The image information processor 40 transmits the front sharpness value to the controller 50 .

Similarly, the post-sharpness value of the image on the imaging plate is detected.

The preset distance can be modified adaptively according to different image capturing devices.

Step S102: According to the preset sharpness value, the current sharpness value, the front sharpness value and the rear sharpness value, determine whether the back focus of the image capturing device is shifted? If yes, go to step S103; if not, go to step S101.

Wherein, the preset sharpness value is the peak value of the sharpness value of the image formed by the imaging plate when the image acquisition device is located at a preset coordinate and a wide-angle position. The preset coordinates are preset by the staff when the image acquisition device is installed, and are used to control the angle and direction of the image acquisition device. Images are different.

Specifically, as shown in FIG. 3, the sub-steps of step S102 include:

Step S1021: Determine whether the product of the preset sharpness value and the preset first threshold value is greater than the current sharpness value? If yes, go to step S1022; if not, go to step S101.

Specifically, the value range of the preset first threshold is 80%-85%. The product of the preset sharpness value and the preset first threshold value is the lowest value within the allowable error range with guaranteed sharpness, and when the product of the preset sharpness value and the preset first threshold value is greater than the When the current sharpness value is present, it means that the sharpness value of the image at this time has exceeded the allowable error range. In order to further determine whether the back focus of the image acquisition device is shifted, step S1022 is performed.

Step S1022: Determine whether the product of the current sharpness value and the preset second threshold value is greater than the maximum value of the former sharpness value and the rear sharpness value? If yes, go to step S101; if not, go to step S103.

Specifically, the value range of the preset second threshold is 80%-85%.

If the product of the current sharpness value and the preset second threshold value is less than or equal to the maximum value of the front sharpness value and the rear sharpness value, it means that the current sharpness value is not within the allowable error range, thus indicating that , the back focus of the image acquisition device is shifted. Through two judgments and double verifications in steps S1021 and S1022, the problem of misjudgment caused by environmental influence factors, such as rain and fog, can be solved, and the accuracy of the detection results can be improved.

Step S103: Adjust the position of the imaging plate to calibrate the focal length.

Specifically, the sub-steps of step S103 shown in FIG. 4 include:

Step S1031 : controlling the first driving device 10 to drive the imaging plate to move to a first position in a wide-angle position, so that the image on the imaging plate is in a first clearest state.

Specifically, the controller 50 controls the first driving device 10 to drive the imaging plate to move step by step.

The controller 50 receives and records the sharpness value of the image on the imaging plate transmitted by the image information processor 40 every time the controller 50 moves, and records the position of the imaging plate corresponding to the sharpness value.

The peak value of the clear value is calculated according to the hill-climbing algorithm, and the first position associated with the peak value is queried according to the peak value of the clear value. Because when the imaging plate moves from the allowed position farthest from the focusing lens group to the position closest to the focusing lens group, the arrangement of sharpness values of the image on the imaging plate presents a peak shape.

The first driving device 10 is controlled to drive the imaging plate to move to the first position. Therefore, it is ensured that the image on the imaging plate is in the first position in the first clearest state.

Step S1032: Controlling the second driving device 20 to drive the focusing lens group to zoom to the longest focal position.

Specifically, keeping the imaging plate at the first position, the controller 50 controls the second driving device 20 to drive the focusing lens group to zoom to the longest focal position.

Step S1033: Control the third driving device 30 to drive the focusing lens group in the longest focal position to focus to a second position where the image on the imaging plate is in the second clearest state.

Specifically, the controller 50 controls the third driving device 30 to drive the focusing lens group to move.

The controller 50 receives and records the sharpness value of the image on the imaging plate transmitted by the image information processor 40, and records the position of the focusing lens group corresponding to the sharpness value.

The peak value of the clear value is calculated according to the hill-climbing algorithm, and the second position associated with the peak value is queried according to the peak value of the clear value. Because when the focusing lens group moves, the arrangement of the sharpness values of the image on the imaging plate also presents a peak shape. The sharpness of the image on the imaging plate is highest when the focusing lens group is located at the second position associated with the peak.

The controller 50 controls the third driving device 30 to drive the focusing lens group to focus on the second position.

Therefore, the first position is the position of the imaging plate when the image on the imaging plate is the clearest when the focusing lens group is focused to the second position and zoomed to the longest focal position. .

Step 1034 : Keep the focusing lens group focused on the second position, and control the second driving device 20 to drive the focusing lens group to re-zoom to the wide-angle position.

Step 1035: Control the first driving device 10 to drive the imaging plate to move to a third position in the wide-angle position, so that the image on the imaging plate is in the third clearest state.

Similar to step S1031, the third position is when the focusing lens group is focused to the second position and zoomed to the wide-angle position, when the image on the imaging plate is the clearest, the imaging plate the position it is in.

Step 1036: Determine whether the distance between the third position and the first position is less than a preset third threshold? If yes, go to step S1037; if not, go to step S1038.

Specifically, when the distance value between the third position and the first position is smaller than a preset third threshold, it means that the focusing lens group is located at the wide-angle position or the longest focal position, and the imaging plate The position corresponding to the clearest state of the image on the imaging plate is very close, and within the allowable error range, it means that when the imaging plate is in the third position, the focusing lens group is zoomed to the wide-angle position or The ideal sharpness of the image can be obtained by zooming to the maximum focal position.

If the distance between the third position and the first position is greater than or equal to a preset third threshold, it means that when the imaging plate is at the third position, it is not satisfied that the focusing lens group is zoomed to Image conditions with ideal sharpness can be obtained from the wide-angle position or zooming to the longest focal position.

Step S1037: Calibrate the focal length according to the third position.

Step S1038: Cover the first position with the third position, generate a new first position, and delete the existing second position and the third position.

Specifically, for example, the recorded first position is S, the second position is M, and the third position is N. The third position covers the first position, that is, the new first position is N. The second position and the third position are deleted.

The focal length calibration method of the image acquisition device provided by the second embodiment of the present invention is applied to the controller 50, and the specific steps are shown in FIG. 5:

Step S201: Detect the current sharpness value of the image on the imaging plate every preset period.

Step S202: Determine whether the product of the preset sharpness value and the preset first threshold value is greater than the current sharpness value? If yes, go to step S203; if not, go to step S201.

Step S203: Detect the front sharpness value and the rear sharpness value of the image on the imaging plate.

Step S204: Determine whether the product of the current sharpness value and the preset second threshold value is greater than the maximum value of the former sharpness value and the rear sharpness value? If yes, go to step S201; if no, go to step S205.

Step S205: Adjust the position of the imaging plate to calibrate the focal length.

Step-by-step detection and judgment, when the inspection result of step S202 is no, the remaining steps do not need to be performed, which reduces the operating burden of the image acquisition device, thereby improving the operating efficiency of the equipment

The focal length calibration method of the image acquisition device provided by the third embodiment of the present invention is applied to the controller 50, and the specific steps are shown in FIG. 6 :

Step S301: Detect the current sharpness value of the image on the imaging plate every preset period.

Step S302: According to the preset sharpness value and the current sharpness value, determine whether the back focus of the image capture device is shifted? If yes, go to step S303; if not, go to step S301.

Specifically, it is judged whether the product of the preset sharpness value and the preset first threshold value is less than or equal to the current sharpness value, if so, the back focus of the image acquisition device is not shifted; if not, then The back focus of the image capture device is shifted.

Step S303: Adjust the position of the imaging plate to calibrate the focal length.

Please refer to 7, FIG. 5 is a focal length calibration device 200 of an image acquisition device according to a preferred embodiment of the present invention. It should be noted that the basic principle and the technical effect of the focal length calibration device 200 of the image acquisition device provided in this embodiment are the same as those of the above-mentioned embodiments. For brief description, the parts not mentioned in this embodiment can be referred to. The corresponding contents in the above-mentioned embodiments.

The focal length calibration device 200 of the image acquisition device is applied to the controller 50, and the focal length calibration device 200 of the image acquisition device includes:

The detection unit 201 is configured to detect the current sharpness value of the image on the imaging plate every preset period. Specifically, the detection unit 201 may perform step S301.

Wherein, the current sharpness value is the sharpness value of the image formed by the imaging plate when the image acquisition device is located at a preset coordinate and a wide-angle position.

The detection unit 201 is further configured to detect the front sharpness value and the rear sharpness value of the image on the imaging plate every preset period. Therefore, the detection unit 201 may perform steps S101, S201 and S203.

Wherein, the front clear value is the clear value of the image formed after the imaging plate moves from the current position by a preset distance in a direction close to the focusing lens group; the rear clear value is the image plate from the current position along the The sharpness value of the image formed after moving away from the focusing lens group by a preset distance; the current position is the position where the imaging plate corresponds to the current sharpness value.

Judging unit 202, configured to judge the image capture according to the preset sharpness value and the current sharpness value, or according to the preset sharpness value, the current sharpness value, the former sharpness value and the back sharpness value Whether the back focus of the unit is shifted. Specifically, the judging unit 202 may execute steps S102 and S302.

Wherein, the preset sharpness value is the peak value of the sharpness value of the image formed by the imaging plate when the image acquisition device is located at a preset coordinate and at a wide-angle position.

The judging unit 202 is specifically configured to judge whether the product of the preset sharpness value and the preset first threshold value is less than or equal to the current sharpness value, and if not, the back focus of the image capturing device is shifted.

The determining unit 202 may also be specifically configured to determine whether the product of the preset sharpness value and the preset first threshold value is greater than the current sharpness value. Specifically, the determination unit 202 may perform steps S1021 and S202.

When the product of the preset sharpness value and the first threshold value is greater than the current sharpness value, the determining unit 202 may also be specifically configured to determine whether the product of the current sharpness value and the preset second threshold value is greater than the predetermined sharpness value. The maximum value of the preceding sharpness value and the preceding sharpness value. Specifically, the determination unit 202 may perform steps S1022 and S204.

If the product of the preset sharpness value and the first threshold value is greater than the current sharpness value, the product of the current sharpness value and the second threshold value is less than or equal to the former sharpness value and the rear sharpness value is the maximum value, the back focus of the image acquisition device is shifted.

The adjusting unit 203 is configured to adjust the position of the imaging plate to calibrate the focal length if the back focus of the image acquisition device is shifted. Specifically, the adjustment unit 203 may execute step S103, step S203 and step S303.

Specifically, the adjustment unit 203 includes:

The first control module is configured to control the first driving device 10 to drive the imaging plate to move to a first position in a wide-angle position, so that the image on the imaging plate is in a first clearest state. Specifically, the first control module may execute step S1031.

The second control module is configured to control the second driving device 20 to drive the focusing lens group to zoom to the longest focal position. Specifically, the second control module may execute step S1032.

The third control module is configured to control the third driving device 30 to drive the focusing lens group in the longest focal position to focus to a second position where the image on the imaging plate is in the second clearest state. Specifically, the third control module may execute step S1033.

The second control module is further configured to keep the focusing lens group focused on the second position, and control the second driving device 20 to drive the focusing lens group to zoom to a wide-angle position. Specifically, the second control module may execute step S1034.

The first control module is further configured to control the first driving device 10 to drive the imaging plate to move to a third position in the wide-angle position, so that the image on the imaging plate is in the third clearest state. Specifically, the first control module may execute step S1035.

The determining unit 202 is further configured to determine whether the distance between the third position and the first position is smaller than a preset third threshold. Specifically, the determination unit 202 may execute step S1036.

The execution module is configured to calibrate the focus according to the third position if the distance value between the third position and the first position is smaller than a preset third threshold. Specifically, the execution module may execute step S1037.

A reset module, configured to cover the first position with the third position to generate a new first position if the distance between the third position and the first position is greater than or equal to a preset third threshold position, and delete the existing second position and the third position. Specifically, the reset module may execute step S1038.

To sum up, in the focal length calibration method and device of the image acquisition device provided by the preferred embodiment of the present invention: first, the current sharpness value of the image on the imaging plate is detected every preset period, or the current sharpness value, previous sharpness value and post sharpness value; according to said preset sharpness value and said current sharpness value, or according to said preset sharpness value, said current sharpness value, said previous sharpness value and said back sharpness value The clear value is used to determine whether the back focus of the image acquisition device is shifted; when the back focus of the image acquisition device is shifted, the position of the imaging plate is adjusted to calibrate the focal length, and the controller automatically detects, judges, and adjusts. Reduce the burden of manual adjustment, reduce the burden of maintenance personnel, improve maintenance efficiency, and ensure the clarity of the image; secondly, according to whether the product of the preset clear value and the preset first threshold value is greater than the current clear value, the Whether the product of the current sharpness value and the preset second threshold value is greater than the maximum value of the front sharpness value and the rear sharpness value, it is judged that the back focus of the image acquisition device is shifted, and double verification can solve the problem of environmental problems. Influencing factors, such as misjudgment problems caused by rain and fog, improve the accuracy of the detection results; then, if the distance between the third position and the first position is less than the preset third threshold, then The focal length is calibrated according to the third position, so as to ensure the clarity of the image on the imaging plate during the process of zooming the focusing lens group from the wide-angle position to the longest focal position when the imaging plate is in the third position; finally, step by step detection It is judged that when the inspection result of step S202 is negative, the remaining steps are not performed, thereby reducing the operating burden of the image capturing device, thereby improving the operating efficiency of the device.

In the several embodiments provided in this application, it should be understood that the disclosed apparatus and method may also be implemented in other manners. The apparatus embodiments described above are merely illustrative, for example, the flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality and possible implementations of apparatuses, methods and computer program products according to various embodiments of the present invention. operate. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code that contains one or more functions for implementing the specified logical function(s) executable instructions. It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It is also noted that each block of the block diagrams and/or flowchart illustrations, and combinations of blocks in the block diagrams and/or flowchart illustrations, can be implemented in dedicated hardware-based systems that perform the specified functions or actions , or can be implemented in a combination of dedicated hardware and computer instructions.

In addition, each functional module in each embodiment of the present invention may be integrated to form an independent part, or each module may exist independently, or two or more modules may be integrated to form an independent part.

If the functions are implemented in the form of software function modules and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention can be embodied in the form of a software product in essence, or the part that contributes to the prior art or the part of the technical solution. The computer software product is stored in a storage medium, including Several instructions are used to cause a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, Read-Only Memory (ROM, Read-Only Memory), Random Access Memory (RAM, Random Access Memory), magnetic disk or optical disk and other media that can store program codes .

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. A focal length calibration method of an image acquisition device is characterized by comprising the following steps:

detecting the current clear value of the image on the imaging plate every other preset period;

the current definition value is the definition value of an image formed by the imaging plate when the image acquisition device is located at a preset coordinate and a wide-angle position;

judging whether the back focus of the image acquisition device deviates or not according to a preset clear value and the current clear value; the preset definition value is the peak value of the definition value of the image formed by the imaging plate when the image acquisition device is positioned at a preset coordinate and a wide-angle position;

and when the back focus of the image acquisition device deviates, adjusting the position of the imaging plate to calibrate the focal length.

2. The method for calibrating the focal length of an image capturing device according to claim 1, wherein the step of determining whether the back focus of the image capturing device is shifted according to the preset sharpness value and the current sharpness value comprises:

and judging whether the product of the preset definition value and a preset first threshold value is less than or equal to the current definition value or not, if not, shifting the back focus of the image acquisition device.

3. The focus calibration method of an image capturing apparatus according to claim 1, wherein the step of the focus calibration method of an image capturing apparatus further comprises:

detecting a front clear value and a rear clear value of an image on the imaging plate every other preset period;

the front clear value is the clear value of an image formed after the imaging plate moves a preset distance from the current position along the direction close to the focusing lens group; the rear clear value is the clear value of an image formed after the imaging plate moves a preset distance from the current position along the direction far away from the focusing lens group; the current position is the position of the imaging plate when the image on the imaging plate corresponds to the current definition value;

the step of judging whether the back focus of the image acquisition device deviates or not according to a preset clear value and the current clear value comprises the following steps:

and judging whether the back focus of the image acquisition device deviates or not according to the preset definition value, the current definition value, the front definition value and the back definition value.

4. The method for calibrating the focal length of an image capturing device according to claim 3, wherein the step of determining whether the back focus of the image capturing device is shifted according to the preset sharpness value, the current sharpness value, the front sharpness value, and the back sharpness value comprises:

judging whether the product of the preset clear value and a preset first threshold value is larger than the current clear value or not;

if the product of the preset definition value and a preset first threshold value is larger than the current definition value, judging whether the product of the current definition value and a preset second threshold value is larger than the maximum value of the front definition value and the rear definition value;

and if the product of the current clear value and a preset second threshold value is less than or equal to the maximum value of the front clear value and the rear clear value, the rear focus of the image acquisition device is deviated.

5. The focus calibration method of an image capture device according to claim 1, wherein said step of adjusting said imaging plate position to calibrate the focus comprises:

controlling a first driving device to drive the imaging plate to move to a first position at a wide-angle position so that an image on the imaging plate is in a first clearest state;

controlling a second driving device to drive the focusing lens group to zoom to the longest focus position, and controlling a third driving device to drive the focusing lens group at the longest focus position to focus to a second position at which an image on the imaging plate is in a second clearest state;

keeping the focusing lens group focused at the second position, and controlling the second driving device to drive the focusing lens group to zoom again to a wide-angle position; controlling the first driving device to drive the imaging plate to move to a third position at the wide-angle position so that the image on the imaging plate is in a third clearest state;

and if the distance value between the third position and the first position is smaller than a preset third threshold, calibrating the focal length according to the third position.

6. The focus calibration method of an image capturing device according to claim 5, wherein the step of controlling the first driving device to drive the imaging plate to move to the first position at the wide angle position so that the image on the imaging plate is in the first clearest state comprises:

controlling the first driving device to drive the imaging plate to move step by step;

recording the clear value of the image on the imaging plate and the position of the imaging plate corresponding to the clear value in each moving step;

calculating a peak value of the clear value according to a hill climbing algorithm, and inquiring a first position associated with the peak value according to the peak value of the clear value;

and controlling the first driving device to drive the imaging plate to move to the first position.

7. The method for calibrating the focal length of an image capturing device according to claim 5, wherein the step of controlling the third driving device to drive the group of focusing lenses at the longest focal position to focus at the second position, which makes the image on the imaging plate at the second sharpest state, comprises:

controlling the third driving device to drive the focusing lens group to move;

recording a clear value of an image on the imaging plate and a position of the focusing lens group corresponding to the clear value;

calculating a peak value of the clear value according to a hill climbing algorithm, and inquiring a second position associated with the peak value according to the peak value of the clear value;

and controlling the third driving device to drive the focusing lens group to move to the second position.

8. A focus calibration apparatus for an image pickup apparatus, comprising:

the detection unit is used for detecting the current clear value of the image on the imaging plate every other preset period;

the current definition value is the definition value of an image formed by the imaging plate when the image acquisition device is located at a preset coordinate and a wide-angle position;

the judging unit is used for judging whether the back focus of the image acquisition device deviates or not according to a preset clear value and the current clear value; the preset definition value is the peak value of the definition value of the image formed by the imaging plate when the image acquisition device is positioned at a preset coordinate and a wide-angle position;

and the adjusting unit is used for adjusting the position of the imaging plate to calibrate the focal length if the back focus of the image acquisition device deviates.

9. The focus calibration apparatus of an image capturing apparatus according to claim 8,

the detection unit is also used for detecting the front clear value and the rear clear value of the image on the imaging plate every other preset period;

the front clear value is the clear value of an image formed after the imaging plate moves a preset distance from the current position along the direction close to the focusing lens group; the rear clear value is the clear value of an image formed after the imaging plate moves a preset distance from the current position along the direction far away from the focusing lens group; the current position is the position of the imaging plate when the image on the imaging plate corresponds to the current definition value;

the judging unit is specifically configured to judge whether a product of the preset clear value and a preset first threshold is greater than the current clear value;

if the product of the preset clear value and a preset first threshold is greater than the current clear value, the judging unit is further configured to judge whether the product of the current clear value and a preset second threshold is greater than the maximum value of the front clear value and the rear clear value;

and if the product of the current clear value and a preset second threshold value is less than or equal to the maximum value of the front clear value and the rear clear value, the rear focus of the image acquisition device is deviated.

10. The focal length calibration apparatus of an image capturing device according to claim 8, wherein the adjusting unit includes:

the first control module is used for controlling the first driving device to drive the imaging plate to move to the first position under the wide-angle position so that the image on the imaging plate is in the first clearest state;

the second control module is used for controlling the second driving device to drive the focusing lens group to zoom to the longest focus position;

the third control module is used for controlling a third driving device to drive the focusing lens group in the longest focus position to focus to a second position which enables the image on the imaging plate to be in a second clearest state;

the second control module is further configured to keep the focusing lens group focused at the second position, and control the second driving device to drive the focusing lens group to zoom to a wide-angle position;

the first control module is further used for controlling the first driving device to drive the imaging plate to move to a third position in the wide-angle position, so that the image on the imaging plate is in a third clearest state;

the judging unit is further configured to judge whether a distance value between the third position and the first position is smaller than a preset third threshold;

and the execution module is used for calibrating the focal length according to the third position if the distance value between the third position and the first position is smaller than a preset third threshold value.

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