KR20220014605A - apparatus and method for calculating backlash of lens gear - Google Patents

Abstract

The present invention relates to a lens gear backlash calculation method for a surveillance camera with a lens gear, which includes the following steps of: positioning the lens gear at an end in a first direction; extracting a first high-frequency component of a first surveillance image captured in a state where the lens gear is positioned at the end in the first direction; moving the lens gear by a unit step in a second direction; extracting a second high-frequency component of a second surveillance image captured in a state where the lens gear is moved by the unit step in the second direction; comparing the first and second high-frequency components; determining whether the surveillance image data is changed by comparing the first and second high-frequency components; and calculating the backlash of the lens gear by analyzing the number of unit steps corresponding to the time point at which the surveillance image data has changed.

Description

Apparatus and method for calculating backlash of lens gear

An embodiment of the present invention relates to a surveillance camera, and more particularly, to an apparatus and method for calculating a lens gear backlash of a surveillance camera having a lens gear in which a lens driving unit is implemented in a gear shape.

In general, a surveillance camera may be equipped with a zoom lens, a variable focus lens, and a fixed focus lens depending on the intended use. A zoom lens is mainly used for a camera that frequently zooms in/out, but it is expensive and the control operation is complicated. On the other hand, fixed focus lenses have a fixed focal length and are mainly used in low-cost cameras that do not require lens control. On the other hand, a variable focus lens is a lens that can change the focal length according to the purpose of installation. It is relatively cheaper than a zoom lens and has the advantage of easy control of the lens by using a method of focusing the lens while manually moving the focal length. have.

However, in a surveillance camera to which a variable focus lens is applied, the user can use a zoom lens to move the focal length according to the installation environment and purpose, and then focus using the focusing lens so that the subject is in focus. distortion may occur. In order to correct the deviation of the focus, a process of mechanically adjusting the focus of the lens is required.

In general, the focus adjustment of a lens for a surveillance camera to which the variable focus lens is applied is performed in a special environment such as a collimator, and the position of the PI (Photo Interrupter) sensor is compared with the actual measured value of the lens. It can be implemented by performing correction of the error and the degree of deviation of the locus curve.

However, in the case of a surveillance camera having a lens gear that is not provided with a PI sensor and a lens driving unit is implemented in the form of a gear, lens gears that mesh with each other, for example, backlash when the driven gear and the driving gear are meshed, that is, There is a certain space between the gears.

Although the design value of the backlash is provided corresponding to the lens gear, the actual backlash of the lens gear may be different from the design value because there is a different deviation for each mechanism, and accordingly, an error caused by the backlash when the lens gear is moved This may cause a problem that the lens does not move to the exact position desired by the user.

An embodiment of the present invention relates to an apparatus and method for calculating a lens gear backlash of a surveillance camera having a lens gear in which a lens driving unit is implemented in the form of a gear, after moving the lens gear to the end in the first direction, the lens gear is installed unit step by unit. By calculating the backlash value of the lens gear by analyzing the high-frequency data of the image taken by moving it in the second direction, it is possible to remove the error caused by the backlash, and through this, the lens gear that can perform more accurate lens focus adjustment An apparatus and method for calculating backlash are provided.

In order to achieve the above object, there is provided a method for calculating backlash of a lens gear according to an embodiment of the present invention, the method comprising: locating the lens gear at an end in a first direction; extracting a first high-frequency component of a first monitoring image captured in a state where a lens gear is positioned at an end of the first direction; moving the lens gear in unit steps in a second direction; extracting a second high frequency component of a second monitoring image captured in a state in which the lens gear is moved by unit steps in the second direction; comparing the first and second high-frequency components; determining whether the monitoring image data has changed by comparing the first and second high-frequency components; and calculating the backlash of the lens gear by analyzing the number of unit steps corresponding to the point in time when the change in the monitoring image data occurs.

The first and second monitoring images may be image data obtained by photographing the same subject in the same first environment, and the first environment may be an environment photographed in the collimator.

A first high frequency component of the first examination image and a second high frequency component of the second examination image may correspond to image data of an edge region of the subject among the monitoring image data.

The extracted first high-frequency component is implemented as an average value of first high-frequency components extracted a plurality of times with respect to the captured first monitoring image, and the extracted second high-frequency component is extracted a plurality of times for the captured second monitoring image. It may be implemented as an average value of the second high-frequency components.

The unit step may be set to a length of 1/n (n is a positive integer) of the backlash design value of the lens gear.

In the comparing of the first and second high-frequency components, a data value corresponding to the extracted first high-frequency component is compared with a data value corresponding to the extracted second high-frequency component, and the difference exceeds a preset reference value. It may include a step of determining whether or not to do so.

The step of moving the lens gear in unit steps in the second direction may be repeated until the difference between the first and second high-frequency components exceeds the reference value.

A lens gear backlash calculation apparatus according to an embodiment of the present invention includes: a lens gear moving unit for initially controlling the lens gear to be positioned at an end in a first direction, and then moving the lens gear in unit steps in a second direction; Extracting a first high frequency component of a first monitoring image photographed in a state where the lens gear is positioned at the end of the first direction, and second monitoring photographed in a state in which the lens gear is moved by unit steps in the second direction a high-frequency component extracting unit for extracting a second high-frequency component of the image; Comparing the first and second high-frequency components to determine whether the monitoring image data has changed, and analyzing the number of unit steps corresponding to the point in time when the change of the monitoring image data occurs to calculate the backlash of the lens gear It includes a backlash calculator.

The first and second monitoring images may be image data obtained by photographing the same subject in the same first environment.

A first high frequency component of the first examination image and a second high frequency component of the second examination image may correspond to image data of an edge region of the subject among the monitoring image data.

The extracted first high-frequency component is implemented as an average value of first high-frequency components extracted a plurality of times with respect to the captured first monitoring image, and the extracted second high-frequency component is extracted a plurality of times for the captured second monitoring image. It may be implemented as an average value of the second high-frequency components.

The unit step may be set to a length of 1/n (n is a positive integer) of the backlash design value of the lens gear.

The backlash calculator may compare a data value corresponding to the extracted first high frequency component with a data value corresponding to the extracted second high frequency component to determine whether the difference exceeds a preset reference value.

According to this embodiment of the present invention, in the apparatus and method for calculating the lens gear backlash of a surveillance camera having a lens gear in which the lens driving unit is implemented in the form of a gear, the lens gear is moved to the end in the first direction and then the unit step By moving the lens gear in the second direction and analyzing the high-frequency data of the captured image to calculate the backlash value of the lens gear, it is possible to remove the error caused by the backlash, and through this, more accurate lens focus adjustment can be performed. can

1 is a block diagram schematically showing the configuration of a surveillance camera according to an embodiment of the present invention.
FIG. 2 is a view showing an example of a lens gear of the lens driving unit shown in FIG. 1 .
FIG. 3 is a block diagram showing an internal configuration of the backlash correction unit shown in FIG. 1 ;
4 is a flowchart illustrating a method of calculating lens gear backlash according to an embodiment of the present invention.

The contents described in the technical field of the background of the present invention are only for helping the understanding of the background of the technical idea of the present invention, and therefore it can be understood as content corresponding to the prior art known to those skilled in the art of the present invention. none.

In the following description, for purposes of explanation, numerous specific details are set forth to aid in understanding various embodiments. It will be evident, however, that various embodiments may be practiced without these specific details or in one or more equivalent manners. In other instances, well-known structures and devices are shown in block diagram form in order to avoid unnecessarily obscuring the various embodiments.

Each block of the accompanying block diagram may be executed by computer program instructions (execution engine), which may be loaded on the processor of a general-purpose computer, special-purpose computer, or other programmable data processing equipment, so that the computer or The instructions, executed by the processor of the other programmable data processing equipment, will create means for performing the functions described in each block of the block diagram.

These computer program instructions may also be stored in a computer-usable or computer-readable memory that may direct a computer or other programmable data processing equipment to implement a function in a particular manner, and thus the computer-usable or computer-readable memory. It is also possible to produce an article of manufacture containing instruction means for performing the functions described in each block of the block diagram, the instructions stored in the block diagram.

And, since the computer program instructions may be mounted on a computer or other programmable data processing equipment, a series of operating steps are performed on the computer or other programmable data processing equipment to create a computer-executed process to create a computer or other program It is also possible that instructions for performing the possible data processing equipment provide functionality for performing the functions described in each block of the block diagram.

In addition, each block may represent a module, segment, or portion of code that includes one or more executable instructions for executing specified logical functions, and in some alternative embodiments, the functions recited in the blocks or steps are ordered It is also possible to occur outside of

That is, the two illustrated blocks may be substantially simultaneously performed, and the blocks may also be performed in the reverse order of their corresponding functions, if necessary.

The terminology used herein is for the purpose of describing particular embodiments and not for the purpose of limitation. Throughout the specification, when a part "includes" a certain component, it means that other components may be further included, rather than excluding other components, unless otherwise stated. Unless otherwise defined, terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

Hereinafter, embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

1 is a block diagram schematically showing the configuration of a surveillance camera according to an embodiment of the present invention, and FIG. 2 is a diagram showing an example of a lens gear of the lens driving unit shown in FIG. 1 .

Referring to FIG. 1 , a surveillance camera 100 includes a lens unit 110 , a driving unit 120 , an imaging device 130 , an image processing module 140 , and a backlash correcting unit 150 .

The lens unit 110 may include a variable focus lens 112 , and the variable focus lens 112 may include, for example, a zoom lens and a focus lens. In addition, the lens unit 110 is configured to include an aperture 116 for adjusting the amount of light incident on the lens (112).

The driving unit 120 may perform an operation of driving the lens unit 100 according to a predetermined control signal. In the case of the embodiment of the present invention, the driving unit 120 may include an aperture driving unit 126 and a lens driving unit 122 . In this case, the aperture driver 126 and the lens driver 122 may include a driving element such as a motor, and an external control signal, for example, from the image processing module 140 and/or the backlash correction unit 150 . It operates according to the output control signal to control the operation of the lens 112 or the diaphragm 116 .

For example, the opening amount of the diaphragm 116 may be automatically adjusted to adjust the amount of incident light including the subject, and the diaphragm driver 126 may automatically adjust the opening amount of the diaphragm 116 according to an input diaphragm control signal. can be adjusted. The opening amount of the diaphragm 116 is adjusted by the operation of the diaphragm driver 126, so that when the periphery is bright, such as in daylight, the opening amount of the diaphragm 116 is reduced to reduce the amount of incident light, and when the periphery is dark, such as at night. In this case, the amount of opening of the diaphragm 116 is increased to increase the amount of incident light, so that a bright image can be taken.

In addition, the position of the lens 112 is controlled by the lens driving unit 122 . For example, when the lens is a zoom lens, when a wide angle-zoom (zoom-out) signal is generated, the focal length of the zoom lens is shortened and the angle of view is widened, and the telephoto-zoom When the (zoom-in) signal is generated, the focal length of the zoom lens 112 may be increased, and thus the angle of view may be narrowed.

In the case of the embodiment of the present invention, the lens driving unit 122 is characterized in that it is provided with a lens gear implemented in the form of a gear.

Referring to FIG. 2 , the lens driving unit 122 may include lens gears 210 and 220 meshing with each other, for example, a driven gear 210 and a driving gear 220 , and the lens gears 210 . , 220 ) operates according to a control signal output from the image processing module 140 and/or the backlash corrector 150 as described above, so that the lens movement operation may be controlled.

For example, when the lens is a zoom lens, when the lens gear is moved in the first direction in response to the wide angle-zoom (zoom-out) signal, the focal length of the zoom lens is short the angle of view is widened, and when the lens gear is moved in a second direction opposite to the first direction in response to the telephoto-zoom (zoom-in) signal, the focal length of the zoom lens is gradually increased and the angle of view is increased. This can be narrow.

However, this is an embodiment, and the lens gear is moved in the second direction in response to the wide angle-zoom (zoom-out) signal, and the telephoto-zoom (zoom-in) signal is Correspondingly, the lens gear may be moved in the first direction.

At this time, as shown in FIG. 2 , when the driven gear 210 and the driving gear 220 are meshed with each other, there is backlash, that is, a predetermined space between the gears.

In this case, the design value of the backlash is provided corresponding to the lens gears 210 and 220, but since there is a different deviation for each mechanism, the actual backlash of the lens gears 210 and 220 may be different from the design value, and accordingly When the lens gear moves, a problem may occur that the lens does not move to an exact position desired by the user due to an error caused by the backlash.

The embodiment of the present invention is characterized in that it further includes a backlash correction unit 150 in order to remove the effect of errors caused by such backlash, and the backlash correction unit 150 is the lens gears (210, 220). An operation of calculating the backlash value of the lens gear by moving to the end in the first direction and then moving unit step by unit in the second direction to analyze the high-frequency data of the captured image may be performed.

In the embodiment shown in FIG. 1 , the backlash correction unit 150 is described as being included in the monitoring camera 100 , but the embodiment of the present invention is not limited thereto. That is, the backlash correction unit 150 may be located outside the monitoring camera 100 to perform an operation of calculating the backlash of the lens gear provided in the monitoring camera.

The optical signal incident on the lens unit 110 of the surveillance camera 100 passes through the lens 112 and then reaches the light receiving surface of the imaging device 130 to form an image of the subject. An image formed on the light receiving surface of the imaging device 130 is converted into an electrical image signal by a photoelectric conversion process.

As the imaging device 130 , a charge coupled device (CCD) or a complementary metal oxide semiconductor image sensor (CMOS) that converts an optical signal into an electrical signal may be used. The image pickup device 130 as CMOS has a great advantage in maintaining the power of the monitoring camera 00 due to low power consumption required for shooting, and has a relatively low manufacturing cost, which is advantageous for making the area of the image pickup device large, and mass production is easy. do. On the other hand, the image pickup device 130 as a CCD has advantages in that it generates much less noise and has a very fast image information transmission speed compared to CMOS, so that the storage speed during continuous shooting is fast and the image quality is excellent.

Thereafter, the image signal output from the imaging device 130 is input to the image processing module 140 to perform various image processing. The video signal subjected to such processing may be temporarily stored in the surveillance camera 100 and then transmitted to a digital video recorder or a network video recorder. For example, the image processing module 140 is configured to convert image data according to a person's vision, such as Auto White Balance, Auto Exposure (AE), Auto Focus (AF), Gamma Correction ( By performing signal processing such as Gamma Correction, image quality may be improved, and an image signal of improved image quality may be output. In this case, in performing the Auto Focus (AF) operation, the image processing module 140 divides one frame into a plurality of window regions without utilizing the entire input image signal, and among them, AF may be performed using only an image signal corresponding to the window area by selecting a specific window. The selected specific window may be implemented as one single window or a plurality of multiple windows.

In addition, the image processing module 140 may include a digital signal processing unit (not shown), through which color filter array interpolation, color matrix, color correction, Image processing such as color enhancement may be performed.

In the case of a surveillance camera equipped with a variable focus lens, the focus data determined during the design of the lens module may have an error with the initially designed value after the surveillance camera to which the lens module is applied is assembled. For this purpose, it is possible to perform focus adjustment on a device or space that provides a special environment such as a collimator for a surveillance camera.

However, if the error caused by the backlash deviation of the lens gear is not corrected, the correct focus adjustment of the lens by the collimator may not be performed.

Accordingly, the backlash correction unit 150 according to the embodiment of the present invention performs an operation of calculating the actual backlash value of the lens gear in order to remove the error caused by the backlash, and through this, a more accurate lens focus adjustment is performed. be able to

A detailed internal configuration and operation of the backlash correction unit 150 according to an embodiment of the present invention will be described in more detail below with reference to FIGS. 3 and 4 .

FIG. 3 is a block diagram illustrating an internal configuration of the backlash correcting unit shown in FIG. 1 , and FIG. 4 is a flowchart illustrating a method of calculating lens gear backlash according to an embodiment of the present invention.

First, referring to FIG. 3 , the backlash correcting unit 150 may include a lens gear moving unit 310 , a high frequency voice part extracting unit 320 , and a backlash calculating unit 330 . Here, the backlash correction unit 150 may be implemented as a processor, and the processor may be configured to process instructions of a computer program by performing basic arithmetic, logic, and input/output operations. The command may be provided to the processor by a memory or a communication module. For example, the processor may be configured to execute a received command according to a program code stored in the memory.

At this time, the components in the backlash correcting unit 150 as the processor, that is, the lens gear moving unit 310 , the high frequency voice part extracting unit 320 , and the backlash calculating unit 330 are stored in the backlash correcting unit 150 . It may be understood that different functions performed by the processor according to the control command provided by the program code are expressed separately.

The backlash correction unit 150 according to the embodiment of the present invention moves the lens gear to the end in the first direction and then moves the lens gear in the second direction by unit steps to analyze the high-frequency data of the photographed image to analyze the lens gear. It is possible to perform an operation of calculating a backlash value of .

More specifically, referring to FIGS. 1 to 4 , first, the lens gear moving unit 310 moves the lens gears 210 and 220 toward the ends in the first direction (ST 410 ). The lens gear moving unit 310 may receive a control signal output from the image processing module 140 to control the operation of the lens driving unit 122 .

In the case of an embodiment of the present invention, the lens driving unit 122 is characterized in that it is provided with a lens gear implemented in the form of a gear, and thus the lens driving unit 122 is meshed with lens gears 210 and 220, for example. It may include a driven gear 210 and a driving gear 220 .

For example, when the lens is a zoom lens, the lens gear moving unit 310 may move the lens gear in response to a wide angle-zoom (zoom-out) signal that is a control signal of the image processing module 140 . may be moved toward the end in the first direction, and thus the focal length of the zoom lens may be shortened to the maximum.

Conversely, in response to the telephoto-zoom (zoom-in) signal, which is a control signal of the image processing module 140 , the lens gear moving unit 310 moves the lens gear moving unit 310 to move the lens gear. It can be moved to the end in the second direction, so that the focal length of the zoom lens can be maximized.

That is, the lens gear moving unit 310 initializes the zoom lens to a wide-angle mode or a telephoto mode by moving the lens gear toward the end in the first direction or the second direction.

Thereafter, an examination image is photographed using a zoom lens of a wide-angle mode as an example of the initialized mode, and the high-frequency component extractor 320 extracts a first high-frequency component of the examination image by analyzing the photographed image data. (ST 420).

The photographing of the examination image may be performed in a device or space providing a special environment such as the aforementioned collimator, and the high-frequency component of the examination image is, for example, edge data of an edge region of the subject. ) can be implemented.

In addition, since the photographed inspection image data may have distortion due to noise, the high-frequency component extracting unit 320 extracts the first high-frequency component on the inspection image multiple times, and A combination of the results of the first high frequency component extraction, for example, an average value thereof may be used as the first high frequency component extraction value.

As mentioned above, when the lens gear, that is, the driven gear 210 and the driving gear 220 are meshed with each other, there is a predetermined space backlash between the gears, and the backlash is generally a deviation for each mechanism. has a different value from the design value. Accordingly, when the lens gear is moved, there may be a problem in that the lens does not move to an exact position desired by the user due to an error caused by the backlash.

The embodiment of the present invention is characterized in that the actual backlash value is calculated and utilized when adjusting the lens focus in order to remove the effect of error due to such backlash.

To this end, the lens gear moving unit 310 moves the lens gears 210 and 220 moved to the ends of the first direction (or second direction) in the second direction (or first direction) by unit steps. An operation is performed (ST 430).

In this case, the unit step is characterized in that it is set smaller than the design value of the backlash. More specifically, the unit step may be set to a length of 1/n (n is a positive integer) of the design value of the backlash. For example, the unit step may be set to 1/5 of the backlash design value.

Assuming that the backlash of the actual lens gear coincides with the design value, the lens gear, that is, the driven gear 210 and the driving gear 220 may not mesh until 5 unit step movements are performed. However, as mentioned above, the backlash generally has a value different from the design value due to the deviation of each mechanism.

Accordingly, when the first lens gear located at the end of the first direction moves by a unit step in the second direction, an inspection image is again photographed while moving by the unit step, and the captured image data is analyzed to analyze the high frequency The component extractor 320 extracts a second high-frequency component of the examination image (ST 440).

The photographing of the examination image may be performed in a device or space providing a special environment such as the aforementioned collimator, and the high-frequency component of the examination image is, for example, edge data of an edge region of the subject. ) can be implemented.

In addition, since the photographed inspection image data may have distortion due to noise, the high-frequency component extraction unit 320 extracts the second high-frequency component on the inspection image a plurality of times, and A combination of the results of the second high frequency component extraction, for example, an average value thereof may be used as the second high frequency component extraction value.

Thereafter, the backlash calculator 330 compares the first high frequency component and the second high frequency component of the inspection image (ST 450).

For example, the backlash calculator 330 compares a data value corresponding to the extracted first high frequency component with a data value corresponding to the extracted second high frequency component to determine whether the difference exceeds a preset reference value. can judge In this case, the preset reference value may be stored in the backlash calculator 330, which may be changed or updated by the user.

The backlash calculator 330 may determine whether there is a change in the captured surveillance image data based on whether the difference between the first and second high frequency components of the inspection image exceeds the reference value (ST 460).

In general, the edge data of the edge of the subject in the captured image data includes high-frequency components, and these high-frequency components show a sensitive difference even to minute changes in image data compared to the low-frequency components of the image data. , it is possible to detect a change in the image data by recognizing that the high-frequency component is changed.

For example, as mentioned above, a first high-frequency component of the surveillance image captured in a state located at the end of the first direction is compared with a second high-frequency component of the surveillance image captured after moving unit steps in the second direction. Therefore, if there is no difference, the first unit step moves in the second direction once again to capture a surveillance image, and compares the second high-frequency component of the re-captured monitoring image with the first high-frequency component again. This operation may be repeated until the data change, that is, the difference between the first and second high-frequency components exceeds the reference value.

Finally, when it is determined that there is a data change because the difference between the first and second high-frequency components exceeds the reference value, the backlash calculator analyzes the number of unit steps corresponding to the time when the data change occurs to analyze the lens gear can calculate the actual backlash of (ST 470).

By using the calculated actual backlash degree of the lens gear, it is possible to remove an error caused by the backlash, and through this, more accurate lens focus adjustment can be performed.

Therefore, according to the apparatus and method for calculating the lens gear backlash of a surveillance camera according to an embodiment of the present invention, the image captured by moving the lens gear to the end in the first direction and then moving the lens gear in the second direction by unit steps By calculating the backlash value of the lens gear by analyzing the high-frequency data of

As described above, in the present invention, specific matters such as specific components, etc., and limited embodiments and drawings have been described, but these are only provided to help a more general understanding of the present invention, and the present invention is not limited to the above embodiments. , various modifications and variations are possible from these descriptions by those of ordinary skill in the art to which the present invention pertains.

Therefore, the spirit of the present invention should not be limited to the described embodiments, and not only the claims described below, but also all of the claims and all equivalents or equivalent modifications to the claims will be said to belong to the scope of the spirit of the present invention. .

Claims (14)

A method for calculating lens gear backlash of a surveillance camera having a lens gear, the method comprising:
positioning the lens gear at an end in the first direction;
extracting a first high-frequency component of a first surveillance image captured in a state where the lens gear is positioned at the end of the first direction;
moving the lens gear in unit steps in a second direction;
extracting a second high frequency component of a second monitoring image captured while the lens gear is moved by unit steps in the second direction;
comparing the first and second high-frequency components;
determining whether the monitoring image data has changed by comparing the first and second high-frequency components; and
and calculating the backlash of the lens gear by analyzing the number of unit steps corresponding to the point in time when the change in the monitoring image data occurs. According to claim 1,
The first and second monitoring images are image data obtained by photographing the same subject in the same first environment. 3. The method of claim 2,
The first environment is an environment photographed in the collimator. 3. The method of claim 2,
The first high frequency component of the first examination image and the second high frequency component of the second examination image correspond to image data of an edge region of the subject among the monitoring image data. According to claim 1,
The extracted first high-frequency component is implemented as an average value of the first high-frequency components extracted a plurality of times with respect to the captured first monitoring image,
The extracted second high-frequency component is a lens gear backlash calculation method implemented as an average value of the second high-frequency components extracted a plurality of times with respect to the captured second monitoring image. According to claim 1,
The lens gear backlash calculation method in which the unit step is set to a length of 1/n (n is a positive integer) of the backlash design value of the lens gear. According to claim 1,
In the comparing of the first and second high-frequency components, a data value corresponding to the extracted first high-frequency component is compared with a data value corresponding to the extracted second high-frequency component, and the difference exceeds a preset reference value. Lens gear backlash calculation method comprising the step of determining whether or not. 8. The method of claim 7,
A method of calculating lens gear backlash in which the step of moving the lens gear in unit steps in the second direction is repeated until the difference between the first and second high-frequency components exceeds the reference value. In the lens gear backlash calculation device of a surveillance camera having a lens gear,
a lens gear moving unit for initially controlling the lens gear to be positioned at the end of the first direction, and then moving the lens gear in a second direction unit step at a time;
Extracting a first high frequency component of a first monitoring image photographed in a state where the lens gear is positioned at the end of the first direction, and second monitoring photographed in a state in which the lens gear is moved by unit steps in the second direction a high-frequency component extracting unit for extracting a second high-frequency component of the image;
Comparing the first and second high-frequency components to determine whether the monitoring image data has changed, and analyzing the number of unit steps corresponding to the time when the change of the monitoring image data occurs to calculate the backlash of the lens gear A lens gear backlash calculation device including a backlash calculation unit. 10. The method of claim 9,
The first and second monitoring images are image data obtained by photographing the same subject in the same first environment. 11. The method of claim 10,
A first high frequency component of the first examination image and a second high frequency component of the second examination image correspond to image data of an edge region of the subject among the monitoring image data. 10. The method of claim 9,
The extracted first high-frequency component is implemented as an average value of the first high-frequency components extracted a plurality of times with respect to the captured first monitoring image,
The extracted second high-frequency component is a lens gear backlash calculation device implemented as an average value of the second high-frequency components extracted a plurality of times with respect to the captured second monitoring image. 10. The method of claim 9,
The unit step is set to a length of 1/n (n is a positive integer) of the backlash design value of the lens gear. 10. The method of claim 9,
The backlash calculator is configured to compare a data value corresponding to the extracted first high frequency component with a data value corresponding to the extracted second high frequency component to determine whether the difference exceeds a preset reference value. Device.

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