KR101558982B1 - Method for auto focusing of camera - Google Patents

Abstract

Disclosed is an auto focusing method. The auto focusing method of an auto focusing apparatus of a camera including a temperature sensing part, a compensation value calculation part, a compensation control part and a lens driving part includes: a step in which the temperature sensing part acquires a temperature value by sensing the temperature of a lens of the camera; a step in which the compensation value calculation part calculates lens movement value from a predetermined initial position, corresponding to a temperature value, wherein the compensation value calculation part acquires and stores in advance: a unit compensation amount, which is a number of minimum step for a change in edge value to exceed a predetermined first reference value; the direction of the lens moving; and the change in edge by temperature; a step in which the compensation control part calculates direction and number of steps for the lens to move to a position corresponding to the movement of the lens from the current position of the lens; and a step in which the compensation control part adjusts the position of the lens to the calculated direction and number of steps by controlling the lens driving part.

Description

METHOD FOR AUTO FOCUSING OF CAMERA [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention [0002] The present invention relates to a method of adjusting an auto-focus of a camera, and more particularly to a method of automatically adjusting an auto-focus of an infrared camera.

Any object with a temperature above 0 K will emit radiant energy. An infrared camera is a device that senses heat energy emitted by an object and converts the sensed heat energy into an electric signal to acquire an image. Since the infrared camera can acquire a thermal image, it can easily acquire an image of an object to be photographed at night and can clearly distinguish a background and an object, and is used in various fields for military use or civilian use. Infrared cameras used for military purposes are often used for portable surveillance and reconnaissance purposes, and infrared cameras used in civilian areas are used for security surveillance CCTV, industrial and medical use.

Since the optical lens of the infrared camera needs to be able to transmit heat energy easily, a lens which is realized with germanium or silicon material is used unlike a general camera. However, lenses implemented with materials with good thermal transmittance, such as germanium or silicon, show a large change in refractive index with respect to temperature change compared to a camera lens that shoots a general visible light region. Therefore, when the temperature of the lens changes due to the use time of the camera or the surrounding environment, the focus is blurred. If the focus of the camera is blurred, the boundary between the object and the background in the acquired image is not clear, so that the object to be monitored can not be accurately discriminated.

1 shows an example of a focus change according to a temperature change of an infrared camera.

1 (a) to 1 (c) show images obtained by photographing a test target when the temperature of the infrared camera 10 is -10 ° C, 26 ° C, and 50 ° C, respectively. As shown in FIG. 1, it can be seen that when the temperature of the infrared camera is optimized in the state where the focus of the infrared camera is lowered at 26 ° C, or when the temperature is increased, the focus is blurred.

In order to compensate for the temperature change depending on the environment in which the camera is used, the infrared camera drives a motor that adjusts the position of the lens in the camera along the optical axis, thereby changing the focal position to prevent the focal point from being blurred. In this case, edge detection algorithm is mainly used to obtain an optimal focus position. Here, an edge is a feature indicating the boundary of each region in the acquired image, which means a discontinuity point of a pixel, and the outline of an object is usually expressed by an edge in the image. In other words, the edge is mainly used to distinguish the object from the background by using the difference in brightness between the boundary between the object and the background in the image. Although there are various methods for detecting the edge, it is typical to detect a discontinuous point of a pixel value or a differential value of a pixel value between adjacent pixels in an image.

Conventionally, the focal position adjustment method using the edge detection algorithm first detects an edge value in the acquired image, and changes the focal position by moving the camera lens in a direction in which the edge value detected in the image decreases, that is, in a direction in which the image is blurred . Then, the edge position detected in the previously acquired image is compared with the edge value detected in the changed image, while changing the focus position in the direction in which the edge value increases (direction in which the boundary is sharpened in the image). Then, the focus position was repeatedly changed until it was determined that the edge value comparison result was the maximum, and the focus was adjusted by driving the motor so as to stop the movement of the lens at the focus position determined as the maximum edge value. However, such a focus adjustment method has a problem in that it is difficult to adjust the focus fast because of a large amount of calculation because the extraction and comparison of the edge values of the previous image and the current image are continuously performed. Further, if the edge value obtained from the image is not accurate, there is a problem that the focus can be adjusted based on a position other than the object to be shot.

Korean Patent No. 10-1025911 (registered on Mar. 23, 2011) discloses a method for shortening the focus adjustment time by storing previously acquired focus position in a memory and utilizing it for next focus position adjustment .

However, when an infrared camera is used for surveillance and reconnaissance on a remote object, it is common to set the target distance for detecting the target to infinity and to set the focusing area to the entire screen. If the focus area is set to the entire screen, the edge value of the entire screen is calculated and compared with the edge value of the previous image. Therefore, there is a problem that the calculation amount is still large and the focus adjustment speed is slowed down. In particular, an infrared camera mounted on a moving means capable of sudden altitude change such as an aircraft may cause a large temperature change within a short time, but the focus adjustment speed may not correspond to the temperature change.

In addition, even if the last acquired focal position is stored and used again, there is a limit in that detection and comparison of edge values must be repeatedly performed in order to obtain an optimal focal position in accordance with changes in the surrounding environment such as temperature.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an automatic focus adjustment method of a camera capable of shortening the focus adjustment in response to a change in temperature,

According to an aspect of the present invention, there is provided a method of automatically adjusting a focus of a camera including a temperature sensor, a compensation value calculator, a compensation controller, and a lens driver, Sensing the temperature of the camera lens to obtain a temperature value; Wherein the compensation value calculation unit stores a unit compensation amount as a minimum number of steps in which a change in an edge value is equal to or greater than a predetermined first reference value and an edge change amount according to a moving direction of the lens and a temperature, Calculating a lens movement amount corresponding to a temperature value; Calculating the number of steps and the direction at which the compensation control unit should move the lens from a current position of the lens to a position corresponding to the lens movement amount; And adjusting the position of the lens in the number of steps and the direction calculated by controlling the lens driving unit by the compensation control unit; .

Wherein the unit compensation amount is obtained by analyzing an image obtained by moving the lens position of the camera at a room unit, which is a minimum moving unit of the lens movable from the initial position, at room temperature, Is calculated by calculating the number of minimum steps appearing to be equal to or larger than the first reference value with respect to the edge value at the edge.

The edge change amount is obtained by calculating the percentage change of the edge value by comparing the edge value of the image obtained at each temperature with the edge value at the initial position by varying the temperature while maintaining the position of the lens at the initial position state And a change of the edge value calculated by the value of the percentage with respect to temperature is acquired in the form of a function formula for temperature by a trend line acquisition technique.

The lens shift amount is calculated in units of steps using an edge value compensation rate and a unit compensation rate obtained by subtracting the value of the edge change amount obtained by substituting the current temperature value into the function expression at the edge change amount at the initial position .

The automatic focus adjustment method of the camera may further include an edge detection unit that detects an edge value in an image in a predetermined manner by the automatic focus adjustment apparatus, and when the compensation control unit is at a predetermined cycle or when a user command is applied, The lens position is corrected so that an edge value applied by the edge detection unit is a maximum value, and the corrected lens position is updated to the current position of the lens ; And further comprising:

Therefore, the automatic focus adjustment method of a camera according to the present invention can obtain an edge change rate according to a temperature change of a camera as an approximate function, store it in an infrared camera, and then use an approximate function as an edge change rate according to the temperature of the lens, The amount of computation for adjusting the focus position can be drastically reduced. Therefore, it is possible to quickly adjust the focus position even in a sudden temperature change, and the same approximate function can be applied to a plurality of infrared cameras manufactured in the same manner, so that it can be easily applied to a mass-produced infrared camera. Also, it is possible to apply a periodic or aperiodic method of adjusting the focal position using an existing edge detection algorithm to compensate for errors caused by using an approximate function, thereby ensuring reliability.

1 shows an example of a focus change according to a temperature change of an infrared camera.
Fig. 2 shows an example of a test system for an auto-focusing device of an infrared camera of the present invention.
FIG. 3 is a graph showing the amount of change of the edge value for each temperature of the infrared camera.
4 shows an automatic focusing device of an infrared camera according to an embodiment of the present invention.
5 illustrates a method of adjusting an auto focus of an infrared camera according to an embodiment of the present invention.
FIG. 6 is a detailed view of the compensation value-based auto focus adjustment step of FIG.

In order to fully understand the present invention, operational advantages of the present invention, and objects achieved by the practice of the present invention, reference should be made to the accompanying drawings and the accompanying drawings which illustrate preferred embodiments of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to the preferred embodiments of the present invention with reference to the accompanying drawings. However, the present invention can be implemented in various different forms, and is not limited to the embodiments described. In order to clearly describe the present invention, parts that are not related to the description are omitted, and the same reference numerals in the drawings denote the same members.

Throughout the specification, when an element is referred to as "including" an element, it does not exclude other elements unless specifically stated to the contrary. The terms "part", "unit", "module", "block", and the like described in the specification mean units for processing at least one function or operation, And a combination of software.

Fig. 2 shows an example of a test system for an auto-focusing device of an infrared camera of the present invention.

The test system for the auto-focusing device of the infrared camera shown in FIG. 2 includes an infrared camera 10 to be tested, a temperature chamber 20 in which an internal temperature can be adjusted and an infrared camera 10 is disposed, Controls the chamber 20 to adjust the internal temperature of the temperature chamber 20, controls the infrared camera 10 to change the focus position of the infrared camera 10 to acquire a video signal, A control terminal 30 for analyzing the infrared light emitted from the temperature chamber 20 and an infrared camera 10 disposed in the temperature chamber 20 to form an optical collimated light beam so as to obtain an image of a test target disposed outside the temperature chamber 20, a collimator 40 and a work table 50 on which a test target for measuring a change in focus according to a temperature change of the infrared camera 10 is disposed.

The infrared camera 10 disposed in the temperature chamber 20 captures the test target provided on the work table outside the temperature chamber through the collimator 40 under the control of the control terminal 30 and outputs the captured image as a video signal To the control terminal 50. Also, the infrared camera 10 is provided with a contact type temperature sensor (not shown) on the lens barrel to sense the temperature of the camera and transmit a temperature signal to the control terminal 50.

The temperature chamber 20 varies the temperature within a predetermined temperature control range (for example, -20 ° C to 60 ° C) under the control of the control terminal 30, thereby controlling the ambient temperature of the infrared camera 20 disposed therein .

The control terminal 30 receives the temperature signal from the infrared camera 10 and detects the temperature of the infrared camera 10, particularly the temperature of the lens, and controls the temperature chamber 20 so that the temperature of the infrared camera 10 can be varied. do. Then, the infrared camera 10 is controlled at each variable temperature to capture an image of the test target, and the captured image is received and analyzed to determine an optimal focal position for each temperature.

The control terminal 30 first controls the infrared camera 10 in a room temperature environment (for example, 25 DEG C) in which the temperature of the temperature chamber 20 is not adjusted, And moves the position to the predetermined initial position. When the lens position of the infrared camera 10 is moved to the initial position, an edge value is discriminated and stored in an image signal obtained by photographing a test target using an edge detection algorithm. In the present invention, the edge value determined from the image signal obtained at the room temperature and the lens position is the initial position is referred to as an initial edge value. Thereafter, the control terminal 30 confirms the change of the edge value while moving the position of the lens to a preset minimum movement unit (hereinafter referred to as a step). The control terminal 30 determines, on a step-by-step basis, the position of the lens whose change in the edge value according to the positional change of the lens with respect to the edge value obtained at the initial position changes to be equal to or larger than the first reference value (0.5% in this example). Then, the step amount until the change of the edge value changes beyond the first reference value is designated as the unit compensation amount (m _step ). That is, the unit compensation amount (m _step ) means the minimum number of steps in which the change in the edge value at room temperature is equal to or greater than the first reference value.

When the unit compensation amount (m _step ) is obtained, the control terminal 30 moves the lens position of the infrared camera 10 to the initial position, and adjusts the internal temperature of the temperature chamber 20 to the lowest temperature (-20 < 0 > C). When the internal temperature of the temperature chamber 20 is stabilized to the adjusted temperature and the temperature signal is outputted from the infrared camera 10 at the adjusted temperature, the control terminal 30 receives the video signal from the infrared camera 10, Calculate the value. Then, the obtained edge value is compared with the initial edge value, and the edge value variation obtained by obtaining the difference between the two edge values as a percentage is stored. The control terminal 30 moves the position of the lens in the first direction (for example, the forward direction (+) of the lens or the second direction (for example, the backward direction (-) of the lens) And determines the lens moving direction for compensating for the temperature change. The moving direction of the lens can be determined using the above-described edge detection algorithm. That is, the direction in which the edge value increases can be determined to be the lens moving direction.

Thereafter, the control terminal 30 sequentially raises the internal temperature of the temperature chamber 20 to a maximum temperature (60 ° C) within a temperature control range at a predetermined temperature unit (for example, 5 ° C) The difference between the two edge values is calculated as an edge value change amount, and the lens movement direction is determined and stored.

As a result, the control terminal 30 obtains the initial edge value and the unit compensation amount when the lens position is the initial position in the room temperature environment, and then changes the temperature in units of a predetermined temperature, The amount of change and the lens movement direction are calculated and stored.

Table 1 shows an example of the amount of change in the edge value per temperature acquired by the control terminal 30 and the lens moving direction.

FIG. 3 is a graph showing the amount of change of the edge value for each temperature of the infrared camera.

The control terminal 30 generates a graph as shown in FIG. 2 for the change amount of the stored edge value per temperature as shown in Table 1, and obtains a trend line of the created graph to calculate the change amount of the edge value And calculates a function expression. In Fig. 3, each of a plurality of points represents an edge change amount obtained at each of the variable temperatures, and a solid line represents a trend line corresponding to the edge change amount.

The technique of obtaining the trend line of the graph is a well-known technique, which will not be described in detail here. In FIG. 3, for example, a function formula corresponding to a trend line is obtained as a quadratic function formula as shown in Equation (1).

In Equation (1), x represents a temperature and y represents an amount of edge change.

The function formula of Equation (1) represents a function formula for the variation of the edge value of each infrared ray camera of FIG. 3, and the function formula may be different according to the infrared camera. Since the edge change amount y with respect to the temperature x is expressed by a function formula as in Equation 1, when the infrared camera 10 is actually used, the temperature x of the infrared camera 10 is substituted into the obtained equation It is possible to calculate the edge change amount y of the image which is focussed by the temperature at the initial position. In other words, when the actual infrared camera is used, it is possible to calculate the change amount y of the edge simply by using the obtained equation without using the edge detection algorithm. Therefore, it is possible to omit repetitive calculation of the edge value unlike the conventional method, and the computation amount can be drastically reduced.

For example, the unit compensation amount (m _step ) can be obtained as shown in Equation (2), in which the infrared camera obtains the optimum focal position according to the temperature.

That is, the number of minimum steps in which the change in the edge value at room temperature is equal to or larger than the first reference value (0.5% in this example), for example, can be obtained in 30 steps.

Assuming that the temperature of the current infrared camera is 40 ° C, the edge value change amount according to the temperature change is obtained as shown in Equation (1), so that the edge value change amount y is 87.496 %.

The edge value compensation ratio C can be calculated as shown in Equation (3).

Where 100 represents the amount of edge change at the initial position.

According to Equation (3), the edge value compensation ratio C is calculated to be approximately 12.5%.

Since the unit compensation amount (m _step ) for compensating the edge value variation amount of 0.5% is obtained as shown in Equation (2), the movement amount of the lens for obtaining the optimum focus at the current temperature (40 ° C) .

That is, the lens of the infrared camera 10 must move by 750 steps in order to obtain an optimal focus at the current temperature (40 ° C). The direction of movement of the lens should be shifted in the (-) direction according to Table 1. As a result, if only the temperature value is obtained, the movement position of the lens for performing the temperature compensation of the infrared camera 10 can be obtained.

This value can be equally applied to all infrared cameras manufactured using the same manufacturing method. Therefore, the unit compensation amount (m _step ) is calculated in the above-described manner for a certain number (for example, up to 10) of infrared cameras selected as the samples without the need for each of the plurality of infrared cameras to individually perform the temperature compensation through the edge detection algorithm. And the temperature compensation for the remaining camera can be performed using the function formula for the obtained unit compensation amount (m _step ) and the change amount of the edge value.

However, in order to increase the accuracy of the temperature compensation, it is possible to separately acquire and store the function formula for the unit compensation amount (m _step ) and the variation amount of the edge value at the time of manufacture for each individual camera. Even when the function formula for the unit compensation amount (m _step ) and the variation amount of the edge value is obtained individually for each of the plurality of infrared cameras, there is no change in the calculation amount to be calculated by the actual infrared camera, And the memory capacity can be reduced.

4 shows an automatic focusing device of an infrared camera according to an embodiment of the present invention.

4 includes a temperature sensing unit 110, a compensation value calculation unit 120, a compensation control unit 130, a lens driving unit 140, And an edge detection unit 150.

First, the temperature sensing unit 110 is implemented as a contact type temperature sensor on the lens barrel of the infrared camera 10 to sense the lens temperature and output the temperature value to the compensation value calculation unit 120. The compensation value calculation unit 120 stores in advance a function formula for the unit compensation amount (m _step ) and the variation amount of the edge value acquired in the test system of FIG. 2. When the temperature value is applied in the temperature sensing unit 110, (D) of the lens with respect to the value according to Equations (2) to (4) and transmits the calculation result to the compensation controller 130. At this time, the movement amount d of the lens represents the movement amount from the initial position of the lens.

The compensation control unit 130 calculates the difference between the current position of the lens and the movement amount d of the applied lens when the movement amount d of the lens is applied from the compensation value calculation unit 120 and controls the lens driving unit 140 And moves the lens by the calculated difference. Here, the compensation control unit 130 calculates the difference between the current position of the lens and the movement amount d of the applied lens because the movement amount d of the lens indicates the amount of movement from the initial position of the lens.

Meanwhile, the compensation control unit 130 may perform a correction operation in response to a predetermined period or a user command. When the focus position of the lens is moved using the movement amount d of the lens calculated by the compensation value calculation unit 120, a small error as shown in Equation (3) can be generated, and a change in the edge value using the trend line Is also a function formula obtained by approximate processing, and therefore includes an error. The change in refractive index, or focus, of an infrared camera is most affected by temperature, but is also influenced by other factors such as changes in air pressure. Accordingly, the compensation controller 130 can correct the error in response to a predetermined period or a user command, thereby maintaining the optimal focal position.

The compensation control unit 130 controls the lens driving unit 140 to move the position of the lens while transmitting the edge detection signal to the edge detection unit 150 to obtain the edge value, And corrects the error of the lens position. That is, the focal position of the lens is corrected by using the focal position adjustment method using the existing edge detection algorithm. The compensation control unit 130 updates the current position to recognize the corrected focal position as the current position of the lens.

The lens driving unit 140 changes the position of the lens according to the control of the compensation control unit 130. [ At this time, the lens driving unit 140 moves the lens in units of steps which is a predetermined minimum moving unit.

The edge detector 150 receives and analyzes the image acquired by the infrared camera 10 under the control of the compensation controller 130, acquires the edge value, and transmits the edge value to the compensation controller 130.

Although the edge detector 150 is shown in FIG. 4 to improve the reliability of the automatic focus controller of the infrared camera, the edge detector 150 may not be included in the auto focus controller of the infrared camera of the present invention .

5 illustrates a method of adjusting an auto focus of an infrared camera according to an embodiment of the present invention.

Referring to FIG. 4, the autofocus method of the infrared camera of FIG. 5 will be described. First, the compensation controller 130 determines whether to perform a correction operation (S10). The compensation controller 130 may determine that the compensation operation is performed when a predetermined period or a user command is applied.

If it is determined that the correction operation is not performed, the automatic focus adjustment method using the compensation value obtained in the test system of FIG. 2, i.e., the unit compensation amount (m _step ) and the variation amount of the edge value, (S20). However, if it is determined that the correction operation is to be performed, the focus position of the lens is corrected using the conventional focal position adjustment method using the edge detection algorithm (S30). Then, the corrected focal position is updated to the current lens position (S40). For example, assuming that the initial position of the focus lens at room temperature is K = 4500 step points, and the lens position before the correction operation is 3550 step points, the position corrected by the focus position adjustment method using the edge detection algorithm is 3560 steps Point, the current focus position has an optimum focus position and an error of 10 steps. Accordingly, the position of the lens after the correction operation is shifted to the position of 3560 steps. However, the compensation control unit 130 moves the position of the moved 3560 step to the previous lens position To be recognized as the position of 3550 steps. That is, when adjusting the auto focus position, the focus position adjustment operation for temperature compensation is performed in a state where the error of 10 steps is corrected.

FIG. 6 is a detailed view of the compensation value-based auto focus adjustment step of FIG.

As described above, in the compensation value-based auto focus adjustment step, the functional formulas for the unit compensation amount (m _step ) and the variation amount of the edge value are obtained using the test system of FIG. 2 and stored in the infrared camera.

The temperature sensing unit 110 of the infrared camera acquires the temperature value and transmits it to the compensation value calculation unit 120 (S21). The compensation value calculation unit 120 determines whether the applied temperature value is equal to the previous temperature value (S22). If it is determined that the previous temperature value is the same as the current temperature value, it is not necessary to compensate for the temperature, and the temperature sensing unit 110 again obtains the temperature value and transmits it to the compensation value calculation unit 120 (S21).

However, if the applied temperature value differs from the previous temperature value, the compensation value calculation unit 120 calculates the edge change amount y according to the temperature value by substituting the temperature value x into the function formula for the change amount of the edge value ( S23). The compensation value calculation unit 120 then calculates the edge value compensation rate C as shown in Equation 3 using the calculated edge variation quantity y and then calculates the edge value compensation rate C and the unit compensation amount m _step (4) to obtain the lens shift amount (d). Also, the lens moving direction is acquired according to Table 1 and transmitted to the compensation control unit 130 (S24). The compensation controller 130 controls the lens driver 140 according to the obtained lens movement amount d and the lens movement direction to move the lens to perform an auto focus adjustment operation according to the temperature change.

For example, assuming that the current temperature (T) is 40 ° C, the initial position of the focus lens at room temperature is K = 4500 step points, and the present temperature (T) 40 ° C is substituted into the function formula for the variation of the edge value is 87.5 %, Respectively. This indicates that the position of 87.5% of the optimal edge value is the focal position when the edge value at room temperature 25 ° C is 100%. Therefore, the infrared camera must perform the focus position compensation by 100 - 87.5 = 12.5% in order to compensate the temperature change.

If the number of minimum steps in which the change of the edge value at room temperature is equal to or greater than the first reference value (0.5% in this example, for example) is obtained in 30 steps, then (12.5 / 0.5) * The temperature compensation can be performed by moving the lens in the compensation direction by 30 = 750 steps.

If the current position of the lens is 4500 steps which is the initial position, as shown in Table 1, when the current temperature is higher than the room temperature, the lens compensation direction is (-) direction, 750 = 3750 steps, and the compensation control unit 130 controls the lens driving unit 140 to move the lens position to the position of 3750 steps. Since the final lens position for temperature compensation is 3750 step positions, if the current lens position is not the initial position, the calculated compensation lens position? As the current lens position, the moving direction and distance of the lens can be calculated. For example, if the current lens position is 2000 steps, the compensation lens position is 3750 steps, so it is moved by 3750 - 2000 = 1750 steps.

As a result, in the present invention, the edge change rate according to the temperature change of the infrared camera is obtained as an approximate function using the test system, and the result is stored in the infrared camera. The edge change rate according to the temperature of the lens, The amount of computation for adjusting the focus position can be drastically reduced.

Although the above description has been made with reference to an infrared camera having a large change in refractive index according to temperature, the concept of the present invention is not limited to an infrared camera but can be applied to a general optical camera.

The method according to the present invention can be implemented as a computer-readable code on a computer-readable recording medium. A computer-readable recording medium includes all kinds of recording apparatuses in which data that can be read by a computer system is stored. Examples of the recording medium include a ROM, a RAM, a CD-ROM, a magnetic tape, a floppy disk, an optical data storage device, and the like, and a carrier wave (for example, transmission via the Internet). The computer-readable recording medium may also be distributed over a networked computer system so that computer readable code can be stored and executed in a distributed manner.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art.

Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

Claims (5)

A method for adjusting an auto-focus of an automatic focusing device of a camera including a temperature sensor, a compensation value calculator, a compensation controller, and a lens driver,
Sensing the temperature of the lens of the camera to obtain a temperature value;
Wherein the compensation value calculation unit stores a unit compensation amount as a minimum number of steps in which a change in an edge value is equal to or greater than a predetermined first reference value and an edge change amount according to a moving direction of the lens and a temperature, Calculating a lens movement amount corresponding to a temperature value;
Calculating the number of steps and the direction at which the compensation control unit should move the lens from a current position of the lens to a position corresponding to the lens movement amount; And
Adjusting the position of the lens in the number of steps and direction calculated by controlling the lens driving unit by the compensation control unit; Lt; / RTI >
The unit compensation amount
The lens position of the camera moves at a step unit which is a minimum moving unit of the lens movable from the initial position at room temperature, and analyzes the acquired image to determine whether the change in the edge value in the image is greater than an edge value Calculating a number of minimum steps appearing above the first reference value,
The edge change amount
The edge value of the image obtained at each temperature is varied with the edge value at the initial position by varying the temperature while maintaining the position of the lens at the initial position, and the change of the edge value is calculated as a percentage, The change of the edge value calculated by the value of the percentage is obtained in the form of a function formula for temperature by a trend line acquisition technique,
The lens movement amount
Is calculated in units of steps using an edge value compensation rate and a unit compensation rate obtained by subtracting the value of the edge change amount obtained by substituting the current temperature value in the function expression at an edge change amount at an initial position. Adjustment method. delete delete delete 2. The method of claim 1,
Further comprising an edge detecting unit for detecting an edge value in an image in a predetermined manner,
Wherein the compensation control unit controls the lens driving unit to apply an image obtained by varying the lens position to the edge detection unit at a predetermined cycle or when a user command is applied and to set the edge value applied from the edge detection unit to a maximum value Correcting the lens position and updating the corrected lens position to the current position of the lens; The method of claim 1, further comprising:

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