KR20170083872A - Camera focusing method - Google Patents

Abstract

An embodiment of the present invention discloses a focus adjustment method of a camera.
A method of adjusting a focus of a camera according to an embodiment of the present invention includes moving a lens by a first step number in a first direction and a second direction opposite to the first direction and detecting a first focus position having a maximum focus value ; Comparing the focus values at a forward position and a backward position shifted by a second number of steps from the current position and the current position with the first focus position as a current position; If the focus value at the current position is the maximum, the difference between the first focus position, the step number, the focus value difference between the first focus position and the forward position, and the focus value difference between the current position and the rear position Estimating a focal point position as a basis; And moving the current position to the forward position or the backward position where the focus value is maximum, if the focus value of the forward position or the backward position is the maximum as a result of the comparison.

Description

[0002] Camera focusing method [0003]

Embodiments of the present invention relate to a focus adjustment apparatus and method.

The auto focus function adjusts the position of the lens forward / backward so as to make the blurred image blurred to the clear image, so that the image of the subject can be most clearly formed on the image sensor.

In the case of surveillance cameras, a method for quickly and accurately finding the point having the greatest focus value is required for rapid monitoring.

Korean Patent No. 10-0850461

Embodiments of the present invention relate to a method of adjusting focus in a camera capable of automatically and quickly adjusting an object accurately and quickly.

A method of adjusting a focus of a camera according to an embodiment of the present invention includes moving a lens by a first step number in a first direction and a second direction opposite to the first direction and detecting a first focus position having a maximum focus value ; Comparing the focus values at a forward position and a backward position shifted by a second number of steps from the current position and the current position with the first focus position as a current position; If the focus value at the current position is the maximum, the difference between the first focus position, the step number, the focus value difference between the first focus position and the forward position, and the focus value difference between the current position and the rear position Estimating a focal point position as a basis; And moving the current position to the forward position or the backward position where the focus value is maximum, if the focus value of the forward position or the backward position is the maximum as a result of the comparison.

Changing the current position to the estimated focal position and decreasing the second step number if the estimated position is different from the forward position or the backward position; And determining the estimated focal position as a final focal position of the lens if the second step number is a minimum value.

Changing the current position to the estimated focal position and maintaining the second number of steps if the estimated focal position is the forward position or the back position and is not a previous position of the lens; Changing the current position to the estimated focal position and decreasing the second number of steps if the estimated focal position is the forward position or the back position and the previous position of the lens; And determining an intermediate position between a previous position and a current position of the lens as a final focus position if the second step number is the minimum value.

The method further includes changing the current position to the forward position or the backward position if the forward position or the backward position with the maximum focus value is not the previous position of the lens, ; Changing the current position to the forward position or the backward position and reducing the second step number if the forward position or the backward position with the maximum focus value is the previous position of the lens; And determining an intermediate position between a previous position and a current position of the lens as a final focus position if the second step number is the minimum value.

에 따라 초점 위치를 추정하는 단계; 및 상기 제1 초점 위치와 상기 후방 위치의 초점 값 차이가 상기 현재 위치와 상기 전방 위치의 초점 값 차이보다 크면,

에 따라 초점 위치를 추정하는 단계;를 포함할 수 있다. 여기서, Ex는 초점 위치, Ax는 현재 위치, Sw는 제2 스텝 수, L은 현재 위치와 제2 스텝 수의 절반의 합 또는 차이다. Wherein the focal position estimating step includes a step of, when the difference between the focus values of the first focus position and the forward position is greater than the focus value difference of the current position and the backward position,

Estimating a focal position according to the focal position; And if the difference in focus value between the first focus position and the backward position is greater than the difference in focus value between the current position and the forward position,

And estimating a focal position according to the position information. Here, Ex is the focus position, Ax is the current position, Sw is the second step number, and L is the sum or difference of half the current position and the second step number.

The method comprising: comparing focus values at the first focus position, at a forward position and at a back position shifted by a third number of steps at the first focus position; And if the focus value at the first focal point position is not the maximum, the lens is moved by the fourth step number larger than the third step number in the direction in which the focus value increases, And correcting the previous position of the first focus position to the first focus position.

Embodiments of the present invention enable fast and accurate focusing on a subject, thereby improving performance and optimizing auto focus.

1 is a block diagram schematically illustrating a focusing device according to an embodiment of the present invention.
2 is a flowchart illustrating a focus adjustment method of a focus adjustment unit according to an embodiment of the present invention.
3 is a graph for explaining a first focus position detection method according to an embodiment of the present invention.
4 is a flowchart illustrating a focus adjustment method during a secondary search of a focus adjusting unit according to an exemplary embodiment of the present invention.
5A to 5C are enlarged views of the vicinity of the first focus position in the graph shown in FIG.
6 is a flowchart illustrating a method of correcting a first focus position detected by a first search according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. In the present specification and drawings, the same reference numerals are used for constituent elements having substantially the same configuration, and redundant description is omitted.

1 is a block diagram schematically illustrating a focusing device according to an embodiment of the present invention.

1, the focus adjusting apparatus 1 according to the present embodiment includes an optical unit 10, an image sensor 20, a signal processing unit 30, a focusing unit 40, a memory 50, 60). The focus adjusting device 1 may be incorporated in the camera module.

The optical section 10 optically processes light from a subject and may include a plurality of lenses such as a zoom lens and a focus lens.

The image sensor 30 may be implemented with a complementary metal oxide semiconductor (CMOS) or a charge coupled device (CCD), and converts an optical signal input through the optical unit 10 into an electrical image signal.

The signal processing unit 30 can perform signal processing such as color processing and sharpness processing of an electrical image signal output from the image sensor 30. [

The focus adjusting unit 40 analyzes a video signal of a photographed subject while moving the focus lens between a near distance and a long distance (infinity) in a predetermined number of steps, and calculates a focus value for the position of the focus lens. The focus adjustment unit 40 can detect the first focus position by the first search which is a rough search and the second focus position which is the final focus position by the second search which is the detailed search.

The focus adjusting unit 40 can detect the first focus position having the maximum focus value by moving the focus lens in the basic step number (first step number) during the primary search.

The focus adjusting unit 40 moves the focus lens forward and backward by a second number of steps from the first focus position of the focus lens during the second search and repeats the process of comparing the focus values a predetermined number of times to obtain a second focus position Can be detected. Here, the forward direction is a short distance direction, and the rear direction is a short distance direction. The second number of steps may have a value smaller than the first number of steps. The second number of steps may be varied to maintain or decrease as the comparison process is repeated during the secondary search. The second number of steps has a minimum value and a maximum value, and can be set to a predetermined number of steps within a range of a minimum value and a maximum value. For example, the second step number may have a first value which is a maximum value in the first step, a second value between the maximum value and the minimum value in the second step, and a third value which is the minimum value in the third step. The minimum value and the maximum value of the second step number can be determined in consideration of at least one of optical characteristics, zoom magnification, ISP characteristic, and the like.

The focus adjustment unit 40 may store the focus value for the focus lens position in the memory 50. [ The focus adjusting unit 40 outputs a control signal so that the focus lens is located at the detected second focus position. The focus position detection of the focus adjusting unit 40 will be described later in detail.

The memory 50 may be a magnetic disk, an optical disk, a ROM, a RAM, a flash memory, or the like, which is built in or mountable in the focus adjusting device 1.

The driving unit 60 may include a zoom motor for moving the zoom lens and the focus lens, a focus motor, and a motor driver for driving the zoom motor and the focus motor. The driving unit 60 controls the motor speed in accordance with the control signal output by performing the AF operation of the focus adjusting unit 40 and moves the focus lens to the focus position. The amount of one-time movement of the focus lens, that is, the number of steps can be varied.

2 is a flowchart illustrating a focus adjustment method of a focus adjustment unit according to an embodiment of the present invention. 3 is a graph for explaining a first focus position detection method according to an embodiment of the present invention.

And the focus lens is moved to the start position by driving the driver 60. [ The starting position of the focus lens may be a position closest to the image sensor 20 (near) or a farthest position (remote).

The focus adjusting unit 40 may determine the direction in which the focus lens should be moved during the primary search, move the first step number in the determined direction, and detect the first focus position (S20). The focus value calculated for each position of the focus lens may be stored in the memory 50 in correspondence with the time and / or the focus lens position.

Referring to FIG. 3, the focus adjusting unit 40 moves the focus lens by a first step number in a short distance from the near side and tracks the change of the focus value. The focus value tends to increase when the focus lens moves in the first step number unit from the start position to the far distance direction, but the focus value tends to decrease after the focus position Ex. If the focus value tends to decrease, the focus adjusting unit 40 moves the focus lens again in the first step unit in the reverse direction (far to near direction) and detects the first focus position Px having the maximum focus value .

The focus adjustment unit 40 moves the focus lens forward and backward by a second number of steps at the current position with the first focus position Px as the start position during the second search and compares the focus values The second focus position, which is the final focus position, can be detected a plurality of times (S40). The secondary search of the focus adjusting section 40 will be described later with reference to FIG.

The focus adjusting unit 40 moves the focus lens to the second focus position and focuses it (S60).

4 is a flowchart illustrating a focus adjustment method during a secondary search of a focus adjusting unit according to an exemplary embodiment of the present invention. 5A to 5C are enlarged views of the vicinity of the first focus position in the graph shown in FIG. 4 and 5 together.

The focus adjustment unit 40 starts the secondary search when the first focus position Px is detected.

The focus adjusting unit 40 can determine the second step number (S41). The focus adjusting unit 40 can determine the second step number through optical characteristics of the lens, zoom information, image processing processor (ISP) characteristics, and the like. The focus adjusting unit 40 may increase or decrease the second step number stepwise between the maximum value and the minimum value. The step of the second number of steps can be set in advance and can be changed according to the focus time and accuracy. The minimum value may be determined by reflecting the noise characteristic of the focus value, the ISP characteristic, and the like.

Table 1 is an example in which the second step number is set to the first to third steps according to the depth of focus corresponding to the zoom magnification. For example, the focus adjusting unit 40 may set the maximum value and the minimum value of the second step number differently according to the depth of focus. The focus adjusting unit 40 can increase the maximum value and the minimum value of the second step number from a low magnification (focus depth 1) to a high magnification (focus depth 3). At depth of focus 1, the number of second steps can be changed from 6 steps -> 4 steps -> 2 steps. At the depth of focus 2, the number of second steps can be changed from 7 steps -> 5 steps -> 3 steps. At the depth of focus 2, the number of second steps can be changed from 8 steps -> 6 steps -> 4 steps.

Stage 1 Step 2 Step 3 Depth of focus 1 6 4 2 Depth of focus 2 7 5 3 Depth of focus 3 8 6 4

The focus adjusting unit 40 sets the first focus position Px to the start position of the secondary search.

The focus adjusting unit 40 can move the focus lens forward and backward by the second step number at the current position Ax (S42). The current position Ax is a reference position for moving the focus lens forward and backward, and is a position at which the focus lens is currently fixed. When the secondary search is started, the current position Ax becomes the first focus position Px. The current position Ax may be changed each time the process of comparing the focus values by moving the focus lens forward and backward during the secondary search is repeated.

The focus adjustment unit 40 adjusts the focal length Fx in the current position Ax, the forward position Cx in which the focus lens has moved forward by the second step number, and the backward position Bx in the backward position in the second step, (S43).

As a result of the comparison at step 43, if the focus value of the current position Ax is the maximum, the focus adjusting unit 40 can estimate the focus position Ex (S44).

The difference ABy between the focus value Ay of the current position Ax and the focus value By of the back position Bx is equal to the focus value Ay of the current position Ax, (Ax + Sw) at which the half of the second step number Sw is added at the current position Ax and at the present position, if the focus position Ex is larger than the difference ACy between the focus position Cy of the front position Cx / 2). ≪ / RTI >

The focus adjusting unit 40 can estimate the focus position Ex by using the proportional relationship of the following equation (1) when ABy> ACy. Where L is the difference between the focus position Ex and the position Ax + Sw / 2.

...(1)

...(One)

The difference ACy between the focus value Ay of the current position Ax and the focus value Cy of the forward position Cx is smaller than the focus value Ay of the current position Ax The focus position Ex is greater than the difference Axy between the current position Ax and the position where the half of the second step number Sw is subtracted from the current position Ax- ≪ / RTI > Sw / 2).

The focus adjusting section 40 can estimate the focus position Ex by using the proportional relation of the following equation (2) when ABy <ACy.

...(2)

...(2)

On the other hand, when the focus adjusting unit 40 has a relation of ABy = ACy, the focus adjusting unit 40 can estimate the current position Ax as the focus position Ex. This can be confirmed by equations (1) and (2). If ABy = ACy in the equations (1) and (2), L = Sw / 2 becomes Ex = Ax.

The focus adjustment unit 40 can determine whether the estimated focal position Ex is the forward position Cx or the backward position Bx (S45).

If it is determined in step 45 that the estimated focus position Ex is not the forward position Cx or the backward position Bx, the focus adjustment unit 40 determines whether or not the second step number used in step 42 is the minimum value (S46). The current position Ax is changed to the estimated focal position Ex.

If it is determined in step 46 that the second step number is the minimum value, the focus adjusting unit 40 may determine the estimated focal position Ex as the second focal position (S47).

If it is determined in step 46 that the second step number is not the minimum value, the focus adjusting unit 40 returns to step 41 and can determine the second step number again. At this time, the focus adjusting unit 40 can reduce the number of the second steps and decrease the number of the second steps. The focus adjustment unit 40 may repeat the steps after step 42. [ That is, the focus adjusting unit 40 moves the focus lens to the forward position Cx and the backward position Bx by the second step number reduced by the estimated focal position Ex and the estimated focal position Ex, Values can be compared.

As a result of the comparison at step 43, if the focus value of the forward position Cx or the focus position of the rear position Bx is the maximum, the focus adjustment unit 40 sets the focus position to the front position Cx or the back position Bx, The focus lens can be moved (S48). The current position Ax is changed to the moved forward position Cx or the backward position Bx.

The focus adjusting unit 40 may determine whether the front position Cx or the back position Bx of the focus lens moved in step 48 is the previous position of the focus lens S49. In step S49, the focus adjusting unit 40 can determine whether the estimated focus position Ex is the front position Cx or the back position Bx in step 45 and is the previous position of the focus lens. Here, the previous position of the focus lens may be either the position of the focus lens immediately before the current position Ax or the position of the focus lens before the current position Ax.

If it is determined in step 49 that the focus lens is not returned to the previous position, the focus adjustment unit 40 maintains the second step number and repeats the steps after step 42 in the changed current position Ax can do.

If it is determined in step 49 that the focus lens has returned to the previous position, the focus adjustment unit 40 may determine whether the second step number used in step 42 is the minimum value (S50).

If it is determined in step 50 that the second step number is not the minimum value, the focus adjusting unit 40 may return to step 41 to determine the second step number again. At this time, the focus adjusting unit 40 may lower the number of the second steps and decrease the number of the second steps. The focus adjustment unit 40 may repeat the steps after step 42. [

If it is determined in step 50 that the second step number is the minimum value, the focus adjusting unit 40 can determine the intermediate position between the current position Ax of the focus lens and the previous position as the second focus position (S51). In the embodiment of the present invention, when the focus lens returns to the previous position, that is, as shown in FIG. 5C, when the current position Ax repeats positions (Ax1, Ax2) Or Ax2) and the current position Ax2 or Ax1 as the second focus position.

This can be confirmed from the fact that L is 0 when ACy is 0 in equation (1) and L is 0 when ABy is 0 in equation (2).

The focus adjustment unit 40 can perform the steps after step 42 once more by checking the second step number of the minimum value even if the second step number is the minimum value to check once again whether or not to return to the previous position.

6 is a flowchart illustrating a method of correcting a first focus position detected by a first search according to an embodiment of the present invention.

Referring to FIG. 6, the focus adjusting unit 40 may correct the first focus position Px detected by the first search.

The focus adjusting unit 40 can determine the third step number of the focus lens (S31). The third step number may be smaller than the first step number.

The focus adjustment unit 40 sets the focus position at the front position in which the first focus position Px is the current position Ax and the focus lens is moved forward by the third step number determined at the current position Ax, The focus value at the rear position in which the focus lens is moved backward by three steps can be calculated (S32).

The focus adjustment unit 40 may compare the focus values at the current position Ax, the forward position, and the backward position (S33).

As a result of the comparison in step 33, if the focus value of the current position Ax is the maximum, the focus adjustment unit 40 can maintain the first focus position Px without correction (S34).

As a result of the comparison in step 33, if the focus value of the current position Ax is not the maximum, the focus adjusting unit 40 can determine the moving direction of the focus lens (S35). The focus adjusting unit 40 can determine a direction in which the focus value is larger than the current position Ax as the movement direction.

The focus adjusting unit 40 can move the focus lens in the determined moving direction by the predetermined number of steps (? Step larger than the third step number?) (Third step number +?) (S36) Can be determined by parameters of the camera.

The focus adjusting unit 40 can determine whether the focus value is decreased at the position of the moved focus lens (S37).

As a result of the determination in step 37, if the focus value decreases, the focus adjusting unit 40 can correct the position of the focus lens before movement to the first focus position (S38).

As a result of the determination in step 37, if the focus value increases, the focus adjustment unit 40 can repeat the steps after step 36 again.

The focus adjustment method according to an embodiment of the present invention performs a method of moving the focus lens to a position where the focus value is maximum and a method of estimating the focus position using a proportional relation. Accordingly, the focus adjustment method according to the embodiment of the present invention can detect the focus position more quickly and accurately than the focus adjustment method that moves only to the position having the maximum focus value.

Also, the focus adjustment method according to an embodiment of the present invention can detect an accurate focus position by detecting a focus position roughly by a primary search and detecting an accurate focus position by a secondary search. At this time, in the secondary search, the process of comparing the focus value between the current position, the forward position and the backward position is changed (decreased) and the repetition is performed, thereby shortening the time for detecting the focus position and detecting the accurate focus position have. By limiting the number of iterations, the focus position detection time can be further shortened. Also, when the predicted focus position is repeatedly predicted at the same position, the focus position is taken as an average of the previous position and the current position, thereby reducing the number of repetitions of the focus position detection.

The focus adjustment method according to an embodiment of 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 computer-readable recording medium include ROM, RAM, CD-ROM, magnetic tape, floppy disk, optical data storage, and the like. In addition, the computer-readable recording medium may be distributed over network-connected computer systems so that computer readable codes can be stored and executed in a distributed manner. In addition, functional programs, codes, and code segments for implementing the present invention can be easily inferred by programmers of the technical field to which the present invention belongs.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, You will understand the point. Accordingly, the true scope of protection of the present invention should be determined only by the appended claims.

Claims (6)

Moving a lens by a first number of steps in a first direction and in a second direction opposite to the first direction and detecting a first focus position having a maximum focus value;
Comparing the focus values at a forward position and a backward position shifted by a second number of steps from the current position and the current position with the first focus position as a current position;
If the focus value at the current position is the maximum, the difference between the first focus position, the step number, the focus value difference between the first focus position and the forward position, and the focus value difference between the current position and the rear position Estimating a focal point position as a basis; And
And moving the current position to the forward position or the backward position where the focus value is the maximum if the focus value of the forward position or the backward position is the maximum as a result of the comparison. The method according to claim 1,
Changing the current position to the estimated focal position and decreasing the second step number if the estimated position is different from the forward position or the backward position; And
And determining the estimated focal position as a final focal position of the lens if the second step number is a minimum value. The method according to claim 1,
Changing the current position to the estimated focal position and maintaining the second number of steps if the estimated focal position is the forward position or the back position and is not the previous position of the lens;
Changing the current position to the estimated focal position and decreasing the second number of steps if the estimated focal position is the forward position or the back position and the previous position of the lens; And
And determining an intermediate position between a previous position of the lens and the current position as a final focus position if the second step number is the minimum value. The method according to claim 1,
Changing the current position to the forward position or the backward position and maintaining the second step number if the forward position or the back position where the focus value is the maximum is not the previous position of the lens;
Changing the current position to the forward position or the backward position and reducing the second step number if the forward position or the backward position with the maximum focus value is the previous position of the lens; And
And determining an intermediate position between a previous position of the lens and the current position as a final focus position if the second step number is the minimum value. 2. The method of claim 1,
If the difference in focus value between the first focus position and the forward position is greater than the difference in focus value between the current position and the back position,

Estimating a focal position according to the focal position; And
If the difference between the focus values of the first focus position and the backward position is greater than the focus value difference of the current position and the forward position,

And estimating a focal position according to the focal position,
Where Ex is the focus position, Ax is the current position, Sw is the second step number, and L is the sum or difference of half of the current position and the second step number. The method according to claim 1,
Comparing the focus values at the first focus position, the forward position and the back position shifted by the third step number from the first focus position; And
If the focus value at the first focus position is not the maximum, the lens is moved by the fourth step number larger than the third step number in the direction of increasing the focus value, And correcting the previous position to the first focus position.

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