KR101900429B1 - Method and apparatus for determining lens focus - Google Patents

Abstract

A method of determining a focus of a lens according to an embodiment of the present invention includes the steps of measuring a distance between a subject and a lens through a distance measuring sensor, AOI (Area Of Interest), instructing to change the moving direction of the lens, extracting the contrast of the AOI in the frame photographed corresponding to the focus in accordance with the movement direction of the lens, Stopping the movement of the lens and determining a focal point corresponding to the position of the stopped lens as the focal point, wherein when the contrast for the frame photographed through the lens is reduced, There is provided a method and an apparatus for determining a focus of a lens that does not repeat blurring and sharpening of a focus by stopping movement of the lens That there is an effect.

Description

TECHNICAL FIELD [0001] The present invention relates to a method and an apparatus for determining a focus of a lens,

Field of the Invention [0002] The present invention relates to a method and apparatus for determining a focus of a lens, and more particularly, to a method and apparatus for determining a focus of a lens based on a distance between the subject and a lens and a contrast of a frame to be photographed by the lens.

With the development of electronic devices that perform various functions, the number of devices with built-in cameras is increasing. For example, a camera is incorporated in a processing terminal such as a notebook or a smart phone, a portable expander, and a broadcasting photographing robot.

The camera typically extracts the contrast for a plurality of images taken through the lens while moving the lens from min to max when determining the focus. At this time, the camera determines the focus by extracting the position having the largest contrast and fixing the lens to the corresponding position. That is, as the lens is moved globally to extract the contrast for all images, the focus is blurred and repeated. Accordingly, the user can confirm that the focus blurring and sharpening are repeated when the camera is used.

 Not only unnecessarily inaccurate focus is provided to the user by repeating the blurring and sharpening of the focus, but also it may take a long time to determine the focus because the contrast of the entire movement of the lens is extracted. Thus, there is a need for a method that can determine the focus faster, without providing the user with an inaccurate focus.

[Related Technical Literature]

A method and apparatus for changing a focus of a camera (Patent Document 10-2016-046037)

SUMMARY OF THE INVENTION The present invention provides a method and apparatus for determining a focus of a lens that does not repeat blurring and sharpening of a focus by stopping movement of the lens by detecting a moment when the contrast of a frame photographed through the lens is reduced will be.

Another problem to be solved by the present invention is to provide a method and apparatus for determining a focus of a lens which can reduce a calculation amount required for determining a focus by extracting only a contrast for a limited range by limiting a range to be determined for determining a focus will be.

The problems of the present invention are not limited to the above-mentioned problems, and other problems not mentioned can be clearly understood by those skilled in the art from the following description.

According to an aspect of the present invention, there is provided a method for determining a focus of a lens, comprising: measuring a distance between a subject and a lens through a distance measuring sensor; measuring at least one Area Of Interest (AOI) ), Instructing to change the moving direction of the lens, extracting the contrast of the AOI in the frame photographed corresponding to the focus in accordance with the movement direction of the lens, detecting the contrast reduction from the contrast point Stopping the movement of the lens, and determining the focus corresponding to the position of the stopped lens as the focus point.

According to another feature of the invention, the method further comprises the step of, after the step of measuring the distance, sensing a change in the predetermined distance and the measured distance, the step of instructing to change the direction of movement of the lens, And determining a moving direction of the lens in accordance with the distance and the change in the measured distance.

According to another aspect of the present invention, the predetermined distance may be an initial distance value between the subject and the lens or a distance measured immediately before.

According to another aspect of the present invention, the step of determining the sensing may include sensing a change based on a predetermined distance and a distance measured through the distance measuring sensor.

According to still another aspect of the present invention, the step of detecting the change may be a step of detecting a change based on a contrast between a frame photographed at a predetermined distance and a frame photographed at a measured distance.

According to another aspect of the present invention, the step of setting the AOI may be a step of setting the AOI to one range when the distance is larger than the predetermined distance.

According to still another aspect of the present invention, the step of setting to one range may include the step of setting one range to the center of the frame.

According to another aspect of the present invention, the step of setting the AOI may further comprise setting the AOI to two ranges when the distance is smaller than the predetermined distance.

According to another aspect of the present invention, the step of setting the two ranges may comprise setting the two ranges to the top and bottom of the frame or to the left and right of the frame.

According to still another aspect of the present invention, the step of extracting the contrast of the AOI may be a step of continuously extracting the contrast of the AOI in the current frame and the AOI in the immediately preceding frame.

According to an aspect of the present invention, there is provided a lens focus determination apparatus including a lens for photographing a subject, a distance measurement sensor configured to measure a distance between the lens and the subject, and at least one AOI Wherein the processor instructs to change the direction of movement of the lens, extracts the contrast of the intra-frame AOI photographed in focus with respect to the direction of movement of the lens, Stopping the movement of the lens and determining the focus corresponding to the position of the stopped lens as the photographing focus when it is detected that the contrast is reduced from the point.

According to another aspect of the present invention, a processor is configured to detect a change in a predetermined distance and a measured distance, and to determine a direction of movement of the lens in accordance with a predetermined distance and a change in the measured distance.

According to another aspect of the present invention, the processor is configured to set the AOI to one range if the distance is greater than a predetermined distance.

According to another aspect of the present invention, the processor may be configured to set the AOI to two ranges if the distance is less than a predetermined distance.

According to another aspect of the present invention, the processor can be configured to successively extract the contrast of the AOI in the currently captured frame and the AOI in the immediately preceding frame.

The details of other embodiments are included in the detailed description and drawings.

The object of the present invention is to provide a method and an apparatus for determining a focus of a lens that does not repeat blurring and sharpening of focus by stopping the movement of the lens by detecting a moment when the contrast for a frame photographed through the lens is reduced, .

The present invention has the effect of providing a method and apparatus for determining a focus of a lens that can reduce the amount of calculation required to determine the focus by limiting the range to be determined for determining the focus and extracting only the contrast for the limited range.

The effects according to the present invention are not limited by the contents exemplified above, and more various effects are included in the specification.

1 is a block diagram showing a schematic configuration of a lens focus determination apparatus according to an embodiment of the present invention.
FIG. 2 illustrates a procedure for determining a focus of a lens according to a method for determining a focus of a lens according to an embodiment of the present invention.
3A to 3D are schematic views showing a graph of contrast according to a lens position and a screen of a subject according to focus according to an embodiment of the present invention.
4A to 4E are schematic views showing a screen for setting an AOI according to a distance between a subject and a lens according to an embodiment of the present invention.
5 is a block diagram showing a schematic configuration of a terminal in which a lens focus determining apparatus according to another embodiment of the present invention is implemented.
FIGS. 6A to 6D are graphs showing contrasts according to lens positions of a terminal according to an embodiment of the present invention, and schematic views illustrating a screen for a subject according to focus. FIG.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention, and the manner of achieving them, will be apparent from and elucidated with reference to the embodiments described hereinafter in conjunction with the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Is provided to fully convey the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims.

The shapes, sizes, ratios, angles, numbers, and the like disclosed in the drawings for describing the embodiments of the present invention are illustrative, and thus the present invention is not limited thereto. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail. Where the terms 'comprises', 'having', 'done', and the like are used herein, other parts may be added as long as '~ only' is not used. Unless the context clearly dictates otherwise, including the plural unless the context clearly dictates otherwise.

In interpreting the constituent elements, it is construed to include the error range even if there is no separate description.

Although the first, second, etc. are used to describe various components, these components are not limited by these terms. These terms are used only to distinguish one component from another. Therefore, the first component mentioned below may be the second component within the technical spirit of the present invention.

Like reference numerals refer to like elements throughout the specification unless otherwise specified.

It is to be understood that each of the features of the various embodiments of the present invention may be combined or combined with each other partially or entirely and technically various interlocking and driving is possible as will be appreciated by those skilled in the art, It may be possible to cooperate with each other in association.

1 is a block diagram showing a schematic configuration of a lens focus determination apparatus according to an embodiment of the present invention.

Referring to FIG. 1, the lens focus determining apparatus 100 is a device for determining a focus of a lens in contrast to a subject 200 photographed through a lens, and photographing the subject 200 according to a determined focus. At this time, the lens focus determining apparatus 100 includes a power supply unit 110, a subject accommodating unit 120, a distance measuring sensor 130, a lens 140 and a processor 150.

The power supply unit 110 of the lens focus determination apparatus 100 applies a voltage so that the lens focus determination apparatus 100 can operate. Specifically, the power supply unit 110 applies a voltage to the distance measuring sensor 130, the lens 140, and the processor 150.

The object accommodating portion 120 of the lens focus determining apparatus 100 has a configuration configured to accommodate an object 200 to be imaged. Accordingly, the object accommodating portion 120 is disposed to face the lens 140 so that the lens 140 can photograph the object 200. [ At this time, for example, the subject 200 may be a book.

The distance measuring sensor 130 of the lens focus determining apparatus 100 is configured to measure the distance d between the lens 140 and the subject 200. [ For example, the distance measuring sensor 130 is an infrared sensor, and includes a light receiving unit and a light emitting unit. The light emitting unit emits infrared rays to the subject 200 and the light receiving unit receives the infrared rays reflected from the subject 200 to measure the distance d between the lens 140 and the subject 200. Accordingly, the distance measuring sensor 130 may be disposed at the same height as the lens 140. [

The lens 140 of the lens focus determining apparatus 100 photographs the subject 200. For example, the lens 140 may be composed of a convex lens and a concave lens. When the distance d between the subject 200 and the lens 140 is longer than the predetermined distance, the convex lens can take the image of the subject 200. [ In addition, when the distance d between the subject 200 and the lens 140 is shorter than a predetermined distance, the concave lens can photograph the subject 200. [ At this time, the subject 200 photographed through the lens 140 can be displayed through the display unit 310 of the terminal 300.

The processor 150 of the lens focus determining apparatus 100 performs arithmetic processing for determining the photographing focus of the lens 140. [ Specifically, the processor 150 sets an Area Of Interest (AOI), which is a range for extracting contrast in a frame photographed through the lens 140. The processor 150 also detects a change in the distance between the predetermined subject 200 and the lens 140 and the distance d between the measured subject 200 and the lens, . At this time, the processor 150 instructs to change the focus according to the moving direction of the lens. Accordingly, the processor 150 extracts the contrast of a plurality of intra-frame AOIs photographed corresponding to the focus. If it is detected that the contrast is decreased from the predicted contrast point, the processor 150 stops the movement of the lens and determines the focus corresponding to the predicted contrast point as the photographing focus. Here, the predicted contrast point means a point that is predicted to have the maximum contrast value when the contrast of AOIs in a plurality of frames is extracted and compared. The predicted contrast point can be extracted if the contrast increases and then decreases.

In FIG. 1, for convenience of explanation, the lens focus determination apparatus 100 is shown as being implemented in a portable magnifier, but it is not limited thereto and can be implemented in various electronic apparatuses.

Hereinafter, FIG. 2 will be referred to for a detailed description of the lens focus determination method in the lens focus determination apparatus 100. FIG.

FIG. 2 illustrates a procedure for determining a focus of a lens according to a method for determining a focus of a lens according to an embodiment of the present invention. For convenience of explanation, the components will be described with reference to FIG. 1 and reference numerals.

The processor 150 of the lens focus determining apparatus 100 measures the distance between the subject 200 and the lens 140 through the distance measuring sensor 130 at step S210.

For example, the processor 150 measures the distance d between the subject 200 and the lens 140 via the distance measuring sensor 130. [

In some embodiments, after measuring the distance d between the subject 200 and the lens 140, the processor 150 calculates the distance d 'between the predetermined subject 200 and the lens 140, You can detect changes. That is, the processor 150 can detect that the distance between the subject 200 and the lens 140 measured at the predetermined distance d 'has changed to d. Here, the predetermined distance d 'may be an initial distance value between the subject 200 and the lens 140 or a distance between the subject 200 and the lens 140 measured immediately before.

At this time, the processor 150 measures a distance d 'between the predetermined object 200 and the lens 140 through the distance measuring sensor 130, and detects a change d' between the object 200 and the lens 140 Can be detected. In addition, the processor 150 may sense the change based on the contrast of the frame photographed at a predetermined distance d 'and the frame photographed at the measured distance d. That is, the processor 150 may calculate the contrast of each frame to detect a change in distance.

The processor 150 of the lens focus determining apparatus 100 then sets at least one AOI based on the distance between the subject 200 and the lens 140 (S220).

Specifically, when the distance d between the subject 200 and the lens 140 is larger than the predetermined distance, the processor 150 can set the AOI range to one range. Here, the predetermined distance may be a reference distance for determining the AOI range, for example, 5 cm. When the AOI range is set to one range, the processor 150 can set one range to the center of the frame. By setting one range to the center of the frame, the processor 150 can obtain overall focus for the frame.

In addition, when the distance d between the subject 200 and the lens 140 is smaller than the predetermined distance, the processor 150 can set the AOI range to two ranges. At this time, the processor 150 can set the two ranges to the upper and lower sides of the frame or to the left and right sides of the frame. That is, in the case of affixation, the processor 150 sets the AOI to the upper and lower sides of the frame or the left and right sides of the frame in two ranges, so that the focus is uniform in the center, upper, lower, left, and right sides of the frame. Accordingly, when the subject 200 photographed by the lens 140 is a character, the problem that the thickness of characters is different at the time of conversion into a binary image can be solved.

Subsequently, the processor 150 of the lens focus determining apparatus 100 instructs to change the moving direction of the lens 140 (S230).

First, the processor 150 may determine the direction of movement of the lens 140 according to the sensed distance d 'and the measured distance d. Specifically, when the measured distance d is larger than the predetermined distance d ', the processor 150 can determine the moving direction of the lens 140 as a first direction, for example, a forward direction. Further, when the measured distance d is smaller than the predetermined distance d ', the processor 150 can determine the moving direction of the lens 140 as a second direction, for example, a rearward direction. Accordingly, the processor 150 instructs to change the moving direction of the lens 140 in accordance with the moving direction of the lens 140 determined to be the front or rear direction.

Then, the processor 150 of the lens focus determining apparatus 100 extracts the contrast of AOI in the frame photographed corresponding to the focus in accordance with the moving direction of the lens 140 (S240).

The focus is changed in accordance with the moving direction of the lens 140. [ Accordingly, the processor 140 extracts the contrast of a plurality of intra-frame AOIs photographed corresponding to the respective focuses changed in accordance with the moving direction of the lens 140. [ That is, the processor 140 can continuously extract the contrast between the AOI in the current frame and the AOI in the immediately preceding frame. At this time, when the distance between the subject 200 and the lens 140 is larger than the predetermined distance, the processor 150 extracts the contrast of the AOI determined as one range in the center of the frame. Further, when the distance between the subject 200 and the lens 140 is smaller than the predetermined distance, the processor 150 extracts the contrast of the AOI determined on the upper and lower sides of the frame or on the left and right sides of the frame in two ranges .

Then, the processor 150 of the lens focus determining apparatus 100 stops the movement of the lens 140 when it detects that the contrast is reduced from the predicted contrast point (S250).

Here, the predicted contrast point refers to a point that is predicted to have a maximum contrast value when the contrast of AOIs in a plurality of frames is extracted and compared. The predicted contrast point can be extracted if the contrast increases and then decreases. That is, when the processor 150 senses that the consecutively extracted contrast is increased or decreased, the processor 150 stops the movement of the lens 140.

Subsequently, the processor 150 of the lens focus determining apparatus 100 determines the focus corresponding to the position of the stopped lens as the focus point (S260).

That is, the processor 150 determines the focal point corresponding to the position of the lens 140 at the moment when it senses that the contrast is reduced. When the subject is photographed through the lens 140 with the determined photographing focus, the user can recognize the subject 200 most clearly.

Accordingly, the lens-focus determining apparatus 100 can extract the contrast of the AOI in the frame photographed corresponding to the focus changed according to the moving direction of the lens, . Accordingly, as compared with the conventional method in which the contrast is increased and then decreased repeatedly, that is, the focal point is blurred and sharpened repeatedly to determine the focus point, the lens focus determination apparatus 100 determines that the contrast increases, The blurring becomes sharp and becomes blurred, the movement of the lens is stopped, so that the contrast extraction amount is relatively small, so that the photographing focus can be determined more quickly.

3A to 3D are schematic views showing a graph of contrast according to a lens position and a screen of a subject according to focus according to an embodiment of the present invention.

Referring to FIG. 3A, the first contrast graph 410 shows contrast according to the first lens position 411. When the lens 140 of the lens focus determination apparatus 100 moves in accordance with the determined moving direction, the contrast is changed according to the movement of the lens. For example, when the lens 140 moves to the first lens position 411, the contrast may increase. At this time, the first lens position 411 is a position corresponding to one-third of the distance that the lens 140 can move to the maximum.

Referring to FIG. 3B, the display unit 310 of the terminal 300 displays a contrast screen displayed on the first contrast graph 410 and a screen for a subject according to the first lens position 411. Specifically, the display unit 310 displays a screen for a photographed subject at a focus corresponding to the lens position when the contrast is the middle between the minimum and maximum. At this time, the focus is blurred and the subject is also blurred.

Referring to FIG. 3C, the second contrast graph 420 shows a contrast according to the second lens position 421. For example, when the lens 140 is moved to the second lens position 421, which is the middle distance of the maximum movable distance, the contrast 422 may increase and then decrease to the maximum value. At this time, the lens 140 stops moving and can move to the third lens position 424 corresponding to the maximum contrast 423.

Referring to FIG. 3D, the display unit 310 of the terminal 300 displays the contrast of the second contrast graph 420 and the screen of the subject according to the third lens position 424. Specifically, the display unit 310 displays a screen for a subject photographed with a focus corresponding to the third lens position 424 of which contrast is the maximum value. The subject photographed with the focus corresponding to the third lens position 424 is clearly displayed. Therefore, the focus corresponding to the third lens position 424 is determined as the photographing focus. That is, the photographing focus is the focus corresponding to the lens position when the contrast decreases from the maximum value.

Accordingly, the lens-focus determining apparatus 100 can quickly determine the photographing focus by stopping the movement of the lens 140 at a moment when the focus becomes sharp and again tends to be blurred.

4A to 4E are schematic views showing a screen for setting an AOI according to a distance between a subject and a lens according to an embodiment of the present invention.

Referring to FIG. 4A, the object accommodating unit 120 of the lens focus determining apparatus 100 can receive the subject 200 as a book. At this time, the distance between the lens 140 and the subject 200 may be 13 cm.

Referring to FIG. 4B, the lens focus determination apparatus 100 sets the AOI 311 based on the distance between the subject 200 and the lens 140. Accordingly, the AOI 311 can be set in a part of the frame for the subject 200 displayed on the display unit 310 of the terminal 300. [ For example, when the reference distance for setting the AOI 311 is 10 cm and the distance between the subject 200 and the lens 140 is 10 cm or more, the lens focus determination apparatus 100 sets the AOI 311 in one range Can be set at the center of the frame. Therefore, the lens-focus determining apparatus 100 extracts only the contrast of the AOI 311 set at the center of the frame, rather than extracting the contrast for the entire range of the frame.

Referring to FIG. 4C, the distance between the lens 140 of the lens focus determination apparatus 100 and the subject 200 may be 5 cm.

4D, when the distance between the lens 140 of the lens focus determination apparatus 100 and the subject 200 is less than 10 cm, the lens focus determination apparatus 100 determines that the first AOI 312 and the second AOI 312 (313), that is, two ranges. In this case, the arrangement of the first AOI 312 and the second AOI 313 may vary depending on the arrangement of the display unit 310 of the terminal 300. [ For example, when the display unit 310 of the terminal 300 is arranged vertically, the first AOI 312 may be set on the upper side of the frame. Also, the second AOI 313 may be set to the lower side of the frame.

Referring to FIG. 4E, when the display unit 310 of the terminal 300 is disposed horizontally, the first AOI 312 may be set to the left of the frame. Also, the second AOI 313 may be set to the right of the frame. At this time, since the distance between the lens 140 of the lens focus determining apparatus 100 and the subject 200 is 5 cm, which is smaller than the reference distance, the AOI is set to two ranges.

Accordingly, the lens-focus determining apparatus 100 can extract the contrast for the set AOI, not the contrast for the entire frame area, to determine the focus point, so that the calculation amount for contrast extraction is reduced and the subject can be picked up clearly.

5 is a block diagram illustrating a schematic configuration of a terminal in which a lens focus determination apparatus according to another embodiment of the present invention is implemented.

Referring to FIG. 5, a lens focus determination apparatus may be implemented in the terminal 300. Accordingly, the terminal 300 can determine the focal point of the lens through contrast with the subject 200 photographed through the lens, and photograph the subject 200 according to the determined focal point. The terminal 300 includes a display unit 310, a distance measurement sensor 320, a lens 330, and a processor 340.

The display unit 310 of the terminal 300 can display the subject 200 photographed through the lens 330. [ At this time, the display unit 310 can display the subject 200 to be photographed with the focus corresponding to the position of the lens 330. [

The distance measuring sensor 320, the lens 330, and the processor 340 of the terminal 300 are the same as those described with reference to FIG. 1, and thus description thereof is omitted.

Accordingly, the terminal 300 includes the lens focus determination device to quickly determine the focus, thereby allowing the user to take a clear picture in a short time when photographing a subject such as an object, a background, or a portrait.

FIGS. 6A to 6D are graphs showing contrasts according to lens positions of a terminal according to an embodiment of the present invention, and schematic views illustrating a screen for a subject according to focus. FIG.

Referring to FIG. 6A, the third contrast graph 510 shows the contrast according to the fourth lens position 511. When the lens 330 of the terminal 300 moves according to the determined moving direction, the contrast is changed according to the movement of the lens. For example, when the lens 140 moves to the fourth lens position 511, the contrast may increase. At this time, the fourth lens position 511 is a position corresponding to one-third of the distance that the lens 330 can move to the maximum.

Referring to FIG. 6B, the display unit 310 of the terminal 300 displays a screen for a subject according to the contrast displayed on the third contrast graph 510 and the fourth lens position 511. Specifically, the display unit 310 displays a screen for a photographed subject at a focus corresponding to the lens position when the contrast is the middle between the minimum and maximum. At this time, the focus is blurred and the subject is also blurred.

Referring to FIG. 6C, the fourth contrast graph 520 shows the contrast according to the fifth lens position 521. For example, when the lens 330 is moved to the fifth lens position 521 which is the middle distance of the maximum movable distance, the contrast may increase to a maximum value and then decrease. At this time, the lens 330 can stop moving.

6D, the display unit 310 of the terminal 300 displays a screen for a subject in accordance with the contrast displayed on the fourth contrast graph 520 and the fifth lens position 521. Specifically, when the contrast decreases from the maximum value, the display unit 310 displays a screen for a photographed subject with a focus corresponding to the fifth lens position 521. [ The subject photographed with the focus corresponding to the fifth lens position 521 is clearly displayed. Therefore, the focus corresponding to the fifth lens position 521 is determined as the photographing focus. That is, the photographing focus is the focus corresponding to the lens position when the contrast decreases from the maximum value.

Accordingly, the terminal 300 stops the movement of the lens 330 at a moment when the focal point becomes clear and again tends to be blurred, so that the photographing can be quickly determined and the subject can be photographed clearly.

In this specification, each block or each step may represent a part of a module, segment or code that includes one or more executable instructions for executing the specified logical function (s). It should also be noted that in some alternative embodiments, the functions mentioned in the blocks or steps may occur out of order. For example, two blocks or steps shown in succession may in fact be performed substantially concurrently, or the blocks or steps may sometimes be performed in reverse order according to the corresponding function.

The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. The software module may reside in a RAM memory, a flash memory, a ROM memory, an EPROM memory, an EEPROM memory, a register, a hard disk, a removable disk, a CD-ROM or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor, which is capable of reading information from, and writing information to, the storage medium. Alternatively, the storage medium may be integral with the processor. The processor and the storage medium may reside within an application specific integrated circuit (ASIC). The ASIC may reside within the user terminal. Alternatively, the processor and the storage medium may reside as discrete components in a user terminal.

Although the embodiments of the present invention have been described in detail with reference to the accompanying drawings, it is to be understood that the present invention is not limited to those embodiments and various changes and modifications may be made without departing from the scope of the present invention. . Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. Therefore, it should be understood that the above-described embodiments are illustrative in all aspects and not restrictive. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

100: lens focus determination device
110: Power supply
120:
130: Distance measuring sensor
140: lens
150: Processor
200: Subject
300:
310:
311: AOI
312: 1st AOI
313: 2nd AOI
320: Distance measuring sensor
330: lens
340: Processor
410: First contrast graph
411: First lens position
420: second contrast graph
421: second lens position
422: Contrast
423: maximum contrast
424: Third lens position
510: Third contrast graph
511: fourth lens position
520: Fourth contrast graph
521: fifth lens position

Claims (15)

A method of determining a focus of a lens in which an operation is implemented by a processor,
Measuring a distance between the subject and the lens through the distance measuring sensor;
Setting at least one Area Of Interest (AOI) within a frame photographed by the lens based on the distance;
Directing the lens to change the moving direction of the lens;
Extracting a contrast of the AOI in a frame photographed corresponding to a focus according to a moving direction of the lens;
Stopping the movement of the lens when it is sensed that the contrast is reduced from a predicted contrast point; And
And determining the focus corresponding to the position of the stopped lens as the focus point. The method according to claim 1,
After the step of measuring the distance,
Further comprising sensing a change in a predetermined distance and the measured distance,
The step of instructing to change the moving direction of the lens comprises:
Further comprising determining a direction of movement of the lens in accordance with the predetermined distance and the change in the measured distance. 3. The method of claim 2,
The predetermined distance may be,
The initial distance value between the subject and the lens or the measured distance immediately before the subject. 3. The method of claim 2,
The method of claim 1,
And sensing the change based on the predetermined distance and the measured distance through the distance measurement sensor. 3. The method of claim 2,
Wherein the step of sensing the change comprises:
And detecting the change based on a contrast of a frame photographed at the predetermined distance and a frame photographed at the measured distance. The method according to claim 1,
The step of setting the AOI comprises:
If the distance is greater than the predetermined distance,
And setting the AOI to one range. The method according to claim 6,
Wherein the setting of the one range includes:
And setting the one range to the center of the frame. The method according to claim 1,
The step of setting the AOI comprises:
If the distance is smaller than the predetermined distance,
And setting the AOI to two ranges. 9. The method of claim 8,
Wherein setting the two ranges comprises:
And setting the two ranges to the upper and lower sides of the frame or to the left and right sides of the frame. The method according to claim 1,
The step of extracting the contrast of the AOI comprises:
And continuously extracting the contrast of the AOI in the immediately preceding frame and the AOI in the frame currently being photographed. A lens for photographing a subject;
A distance measuring sensor configured to measure a distance between the lens and the subject; And
And a processor configured to set at least one Area Of Interest (AOI) within a frame photographed by the lens based on the distance,
The processor comprising:
Wherein the control unit instructs to change the moving direction of the lens and extracts a contrast of the AOI in a frame photographed corresponding to the moving direction of the lens and when it is sensed that the contrast is reduced from the predicted contrast point, And to determine the focal point corresponding to the position of the stopped lens as the photographing focal point. 12. The method of claim 11,
The processor comprising:
Detecting a predetermined distance and a change to the measured distance,
And to determine a moving direction of the lens in accordance with the predetermined distance and the change in the measured distance. 12. The method of claim 11,
The processor comprising:
If the distance is greater than the predetermined distance,
And to set the AOI to one range. 12. The method of claim 11,
The processor comprising:
If the distance is smaller than the predetermined distance,
And to set the AOI to two ranges. 12. The method of claim 11,
The processor comprising:
And to continuously extract the contrast of the AOI in the immediately preceding frame and the AOI in the currently photographed frame.

Images