KR20140108015A - Camera module - Google Patents

Abstract

A camera module is provided. The camera module includes: a lens unit including a focus lens; a lens driving unit which drives the lens unit; an imaging unit which images light passing through the lens unit and generates an image signal; a frequency information detection unit which detects image frequency information from the image signal generated at each position of the focus lens; a lens position detection unit which detects the position of the focus lens; and a control unit which calculates an auto focus evaluation value by integrating the image frequency information detected according to a movement of the position of the focus lens, calculates a depth of field by using a distance from the position of the focus lens to a subject, detects a change in the auto focus evaluation value according to the movement of the focus lens, calculates a threshold value of the auto focus evaluation value by using the auto focus evaluation value and the depth of field, and moves the focus lens to an in-focus position at which the focus lens is in focus.

Description

Camera module {CAMERA MODULE}

The present invention relates to a camera module.

In recent years, the camera supports Auto Focusing (AF), a function that automatically adjusts the focus.

Among the autofocus operation systems, the contrast detection system detects and integrates the high frequency components of the image signal generated by the image pickup device to obtain the autofocus evaluation value, and moves the focus lens to the in-focus position where the focus of the focus lens is aligned .

The in-focus operation in the autofocus is performed by moving the focus lens to obtain the autofocus evaluation value, and when the autofocus evaluation value is less than the threshold value set after the focus lens passes the position at which the maximum autofocus evaluation value is detected, Move the focus lens again.

When the depth of field is taken into consideration, the amount of blur increases according to the depth of field, which increases the operation time of the autofocus sum or decreases the amount of variation of the autofocus evaluation value.

Korean Patent Publication No. 10-1997-7005290

In order to solve the above problems, the present invention provides a camera module that quickly and accurately implements autofocusing operation by reflecting lens position, depth of field, and auto focusing evaluation value.

The objects of the present invention are not limited to the above-mentioned objects, and other objects not mentioned can be clearly understood from the following description.

According to an aspect of the present invention, there is provided a camera module including: a lens unit including a focus lens; A lens driving unit for driving the lens unit; An imaging unit for imaging the light passing through the lens unit to generate an image signal; A frequency information detector for detecting image frequency information from an image signal generated for each position of the focus lens; A lens position detector for detecting a position of the focus lens; And calculating the autofocus evaluation value by integrating the image frequency information detected in accordance with the positional shift of the focus lens, calculating the depth of field using the distance from the position of the focus lens to the subject, And a control unit for calculating the autofocus evaluation value threshold value using the autofocus evaluation value and the depth of field to move the focus lens to a focus position where the focus lens is focused .

BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features and advantages of the present invention will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which: FIG.

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. It is provided to fully inform the owner of the scope of the invention.

The camera module according to the embodiment of the present invention can reduce the amount of blurring caused by passing through the in-focus position to a minimum while performing auto focusing, and can shorten the time of the auto focusing operation.

The camera module according to an exemplary embodiment of the present invention may compare the amount of blur obtained by the amount of actual blurring caused by passing through the in-focus position because the image frequency information obtained by performing auto-focusing according to the noise and brightness variations may be inaccurate If the difference is large, the autofocusing can be resumed and the autofocusing can be performed at a high level.

1 is a block diagram illustrating a camera module according to an exemplary embodiment of the present invention.
2 is a graph exemplarily showing the relationship between the position of the lens and the distance from the lens to the subject.
3 is a graph exemplarily showing the relationship between the autofocus evaluation value and the distance to the subject.

While the present invention has been described in connection with certain exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and similarities.

It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

In order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

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

1 is a block diagram illustrating a camera module according to an exemplary embodiment of the present invention.

1, a camera module 100 according to an exemplary embodiment of the present invention includes a lens unit 110, a lens driving unit 120, an imaging unit 130, a frequency information detection unit 140, a lens position detection unit 150 A storage unit 160, and a control unit 170.

The lens unit 110 collects the light reflecting the subject 50, and causes the image pickup unit 130 to form an image. For this purpose, the lens unit 110 may include an optical system including a plurality of lenses, and the lenses may form an optical group for each function. Here, the lens unit 110 may include a focus lens 115 that performs focus adjustment.

The focus lens 115 is adjusted in position to adjust the focus on the subject 50. Here, the focus lens 115 can be adjusted in position by the lens driving unit 120.

The image sensing unit 130 senses light passing through the lens unit 110 and generates an image signal for the image of the subject 50. Here, the image sensing unit 130 may include an image sensing element for sensing the image of the subject 50. The image pickup device may be implemented by charge coupled devices (CCD) or complementary metal oxide semiconductor (CMOS). The image pickup unit 130 can detect the luminance data for each pixel of the image pickup device and generate an image signal. The image pickup unit 130 may provide the generated image signal to the frequency information detector 140 or the controller 170.

The frequency information detector 140 detects frequency information of an image signal. Here, the frequency information detector 140 may include a filter for detecting a frequency component of an image signal. For example, the frequency information detector 140 may detect a high frequency component using a band pass filter. The frequency information detector 140 detects a frequency component of the image signal and converts the complexity of the image into a numerical value.

The lens position detection unit 150 senses the position of the focus lens 115. In addition, the lens position detector 150 may generate lens position information for the position of the detected focus lens 115. The lens position detection unit 150 can provide the lens position information to the control unit 170. [

The storage unit 160 stores the detected image frequency information corresponding to the focal length of the lens unit 110. In addition, the storage unit 160 may store the autofocus evaluation value calculated by the control unit 170. [ In addition, the storage unit 160 may store a reference value for determining a misfit period.

The control unit 170 controls the lens driving unit 120 to perform autofocusing. Here, the controller 170 may control the lens driver 120 to move the focus lens 115 to adjust the focal distance.

The control unit 170 controls the lens driving unit 120 to move the focus lens 115 from the minimum focal distance to the maximum focal distance. For example, the control unit 170 can control the lens driving unit 120 by setting the moving direction of the initial lens so that the focus lens 115 moves from a long distance to a short distance.

The controller 170 performs autofocusing using a contrast detection method. The contrast detection method detects an evaluation value (hereinafter referred to as an autofocus evaluation value) by detecting and integrating a high frequency component of an image signal, shifts the focus lens 115 in a direction in which the autofocus evaluation value increases, And moves the lens 115 (hereinafter referred to as an in-focus method).

When the auto focus evaluation value decreases after the focus lens passes the position at which the maximum auto focus evaluation value is detected, the control unit 170 determines the position where the maximum auto focus evaluation value is detected As shown in FIG.

 The control unit 170 includes an autofocus evaluation value calculation unit 172 and a depth of field calculation unit 174 for performing auto focusing.

The autofocus evaluation value computing unit 172 computes an autofocus evaluation value to determine the direction in which the focus lens 115 is moved when the autofocus operation starts. At this time, the autofocus evaluation value computing section 172 can integrate the high frequency components detected in accordance with the movement of the focus lens 115 in the area for judging the autofocus operation among the entire imaging areas. Further, the auto focus evaluation value computing section 172 can use the accumulated data as the auto focus evaluation value.

The depth of field calculation unit 174 calculates the depth of field using the distance from the position of the focus lens 115 to the subject 50. [ The depth-of-field calculating unit 174 may provide the depth-of-field calculation information to the autofocus controller 170. [

2 and 3, the autofocusing of the control unit 170 will be described in more detail.

2 is a graph exemplarily showing the relationship between the position of the lens and the distance from the lens to the subject.

3 is a graph exemplarily showing the relationship between the autofocus evaluation value and the distance to the subject.

The depth of field calculation unit 174 of the control unit 170 may calculate the front depth of field and the rear depth of field. Here, the front depth of field is a range in which the focus lens 115 is focused from the position of the subject 50 to the near side. The rear depth of field is a range in which the focus lens 115 is focused from the position of the subject 50 to the infinite distance inf side.

Here, the depth-of-field computing unit 174 may calculate the front depth of field using the following equation (1) and calculate the backward depth of field using the following equation (2).

[Equation 1]

Df = (? XFxLxL) / (fxf +? XFxL)

&Quot; (2) "

Db = (? X F x L x L) / (f x f -? X F x L)

In the equations (1) and (2), Df is front depth of field, Db is rear depth of field, δ is diameter of allowable confusion circle, F is aperture value of focus lens, and L is distance to subject.

When the focus lens 115 is moved from the first lens position ls_a to the third lens position ls_c in accordance with the third subject point c1 at the first subject point a1 and the in-focus position is found, When the focus lens 115 is moved to the second lens position ls_b, the first subject point a1 is found at the first lens position ls_a, which is the position of the previous focus lens 115, To obtain the first rear depth of field Db1 at the first subject point a1.

The controller 170 obtains the third subject position c1 from the third lens position ls_c which is the position of the focus lens 115 at the next time and calculates the third subject position c1 at the third subject position c1 3 Front depth of field (Df3) can be obtained.

The autofocus evaluation value at the first lens position ls_a, which is the position of the previous focus lens 115 when the subject 50 is located at the second subject point b1, is calculated from the first rear field depth Db1 Can be reduced corresponding to the distance.

3, the distance from the first object point a1 to the second object point b1 is a first distance P1 and the distance from the second object point b1 to the third object point c1 is a second distance (BL_a) at the first subject point (a1) and the third blurring degree (BL_a) at the third subject point (c1) when the second subject point (b1) (BL_c) can be approximated by the following equations (3) and (4).

&Quot; (3) "

BL_a = P1 / Db1

&Quot; (4) "

BL_c = P2 / Df3

The control unit 170 can predict the autofocus evaluation value at the position of the focus lens 115 next after the focus lens 115 passes the in-focus position.

The autofocus evaluation value Fval_a and the second autofocus evaluation value Fval_b are set at the first subject point a1 and the second subject point b1 respectively and the autofocus evaluation value Fval_a and the second autofocus evaluation value Fval_b are set at the third lens position ls_c When the predicted autofocus evaluation value is set to the third autofocus evaluation value Fval_c when the focus lens 115 is moved, the controller 170 uses the first blur degree BL_a and the third blur degree BL_c , The third autofocus evaluation value (Fval_c) can be expressed by the following equation (5).

&Quot; (5) "

(Fval_b - Fval_c) / (Fval_b - Fval_a) = BL_c / BL_a

Fval_c = Fval_b - (BL_c / BL_a) x (Fval_b - Fval_a)

Also, the controller 170 can estimate the third autofocus evaluation value Fval_c at the third lens position ls_c using Equation (5).

When the third autofocus evaluation value Fval_c is smaller than the second autofocus evaluation value Fval_b, the control unit 170 sets the third autofocus evaluation value Fval_c to an autofocus evaluation value threshold value .

Next, when the focus lens 115 is moved to an infinite distance side, the control unit 170 calculates the autofocus evaluation value threshold value using the backward depth of field according to the previous position of the focus lens and the front depth of field according to the position of the secondary focus lens Value can be calculated.

When the focus lens 115 is moved to the near side, the controller 170 calculates the auto focus evaluation value threshold value using the front depth of field according to the previous position of the focus lens and the backward depth of field according to the position of the next focus lens. Can be calculated.

Here, the focus lens 115 may be set to a previous stage at a previous time as the focus lens 115 is moved step by step. Further, the next time may be set to a later stage than the present time as the focus lens 115 moves stepwise in the set interval.

When the focus lens 115 moves in correspondence with the first object point a1 at the third object point c1 and the third object point c1 and the second object point b1 move, The autofocus evaluation value Fval_c and the second autofocus evaluation value Fval_b are respectively set as the focus evaluation value and the autofocus evaluation value predicted when the focus lens 115 is moved to the first lens position ls_a 1 auto focus evaluation value (Fval_a). At this time, the controller 170 may express the first autofocus evaluation value Fval_a using the first degree of blur (BL_a) and the third degree of blur (BL_c) according to Equation (6) below.

&Quot; (6) "

(Fval_b - Fval_c) / (Fval_b - Fval_a) = BL_c / BL_a

Fval_a = Fval_b- (BL_a / BL_c) x (Fval_b - Fval_c)

Also, the controller 170 can estimate the first autofocus evaluation value Fval_a at the first lens position ls_a using Equation (6).

When the focus lens 115 moves from the third lens position ls_c to the first lens position ls_a and the first autofocus evaluation value Fval_a is smaller than the second autofocus evaluation value Fval_b, 170 can set the third autofocus evaluation value Fval_c to the autofocus evaluation value threshold value for detecting the in-focus position.

If the difference between the autofocus evaluation value threshold and the autofocus evaluation value is greater than a preset reference value, the control unit 170 determines that the autofocus is not correct and reattempts autofocusing.

The control unit 170 can set the autofocus threshold to which the depth of field is applied corresponding to the moving direction of the focus lens 115, thereby reducing the number of moving steps of the focus lens to find the in-focus position. In addition, the control unit 170 can shorten the time required for the speeding-up and blurring of the in-focus operation. In addition, when the difference between the predicted autofocus evaluation value and the actual autofocus evaluation value is large, the controller 170 determines the similar in-focus position according to the noise and brightness variation to prevent the autofocus miscellaneous seconds and improve the stability of auto focusing have.

The camera module according to the embodiment of the present invention can reduce the amount of blurring caused by passing through the in-focus position to a minimum while performing auto focusing, and can shorten the time of the auto focusing operation.

The camera module according to an exemplary embodiment of the present invention may compare the amount of blur obtained by the amount of actual blurring caused by passing through the in-focus position because the image frequency information obtained by performing auto-focusing according to the noise and brightness variations may be inaccurate If the difference is large, the autofocusing can be resumed and the autofocusing can be performed at a high level.

The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics 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.

The scope of protection of the present invention should be construed according to the following claims, and all technical ideas falling within the scope of the same shall be construed as falling within the scope of the present invention.

Claims (5)

A camera module for performing autofocusing,
A lens unit including a focus lens;
A lens driving unit for driving the lens unit;
An imaging unit for imaging the light passing through the lens unit to generate an image signal;
A frequency information detector for detecting image frequency information from an image signal generated for each position of the focus lens;
A lens position detector for detecting a position of the focus lens; And
Calculating an autofocus evaluation value by integrating the image frequency information detected in accordance with the positional shift of the focus lens, calculating a depth of field using a distance from the position of the focus lens to a subject, And a control unit for detecting a change in the autofocus evaluation value and calculating an autofocus evaluation value threshold value using the autofocus evaluation value and the depth of field to move the focus lens to a in-focus position at which the focus lens is focused Camera module.
The method according to claim 1,
The control unit
An autofocus evaluation value calculation unit for calculating the auto focus evaluation value by integrating the image frequency information; And
And a depth of field calculation unit for calculating the depth of field.
3. The method of claim 2,
Wherein the controller calculates the autofocus evaluation value threshold value by calculating a front depth of field and a rear depth of field corresponding to the in-focus position through the depth of field calculation unit.
The method of claim 3,
Wherein the control unit calculates the autofocus evaluation value threshold value using the depth of backward depth according to the previous position of the focus lens and the depth of the front depth according to the position of the focus lens when the focus lens moves to the infinite distance side, And calculates the autofocus evaluation value threshold value using the front depth of field according to the previous position of the focus lens and the backward depth of field according to the position of the next focus lens when the focus lens moves toward the near side. module. 3. The method of claim 2,
Wherein the controller determines that the difference between the autofocus evaluation value and the autofocus evaluation value is greater than a preset reference value and re-executes autofocusing.

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