KR101082048B1 - Estimation method of auto focus search range of camera module - Google Patents

Abstract

PURPOSE: An estimation method of an auto focus search range of a camera module is provided to drive a lens module only within an auto focus search range. CONSTITUTION: An initial current is applied to a lens driving unit. An initial video image is captured(S303). The initial focus value of the initial image is calculated(S304). The applied current is increased by the fixed step unit(S305). The focus value of the captured image is calculated(S308). An auto focusing search range is established(S310).

Description

{Estimation method of auto focus search range of camera module}

The present invention relates to a method for setting an auto focusing search range of a camera module.

The camera module photoelectrically converts image light formed by an optical system including a lens into an electrical signal by a photoelectric conversion element such as a charge coupled device (CCD) or a complementary metal-oxide semiconductor (CMOS). And an apparatus for performing a predetermined image processing on a photoelectrically converted video signal and outputting a still image or a moving picture.

In general, the camera module has an auto focus (AF) function that measures a distance to a subject and automatically moves the focus lens to take a focused picture.

The camera module uses an actuator to autofocus to focus by moving the lens to the desired position. The actuator is a lens driver that moves the lens in proportion to the intensity of the input current or voltage, and the range of the current or voltage applied to the actuator differs for each camera module.

For example, if the range of current that can be applied to the actuator of the camera module is 0-1024, the effective search range of the actuator for the actual auto focusing is 60-70 of the entire search range corresponding to the range of current 0-1024. About%.

Therefore, conventionally, the auto focusing function is performed by searching all the auto focusing search ranges initially set beyond the effective search range of 60 to 70% of the actuator. As a result, there is a problem in that auto focusing is delayed by searching for an unnecessary 30 to 40% dead zone area.

The present invention provides a method for setting an auto focusing search range of a camera module that can improve an auto focusing speed by setting a valid auto focusing search range for each camera module.

According to one aspect of the present invention, there is provided a method for setting an auto focusing search range of a camera module including a lens driver for driving a lens by an applied current. The method includes (a) applying an initial current to the lens driver to capture an initial image image, (b) calculating an initial focus value of the initial image image, and (c) measuring the current applied to the lens driver. Capturing a video image in increments of a set staff, calculating a focus value of the captured video image, and (d) setting the autofocusing search range using the initial focus value and the focus value of the video image It includes.

According to another feature of the present invention, a method for setting an auto focusing search range of a camera module including a lens driver for driving a lens by an applied current is provided. The method comprises: (a) applying an initial current to the lens driver to capture an initial image image, (b) calculating an initial focus value of the initial image image, and (c) a current to be applied to the lens driver. Capturing the video image of the first group while increasing the number of units by a set staff, and calculating the captured image data of the first group as the focus value of the first group, respectively (d) of the focus values of the first group. Setting a first focus value as a starting point of the autofocusing search range when a first focus value and the initial focus value satisfy a set first reference value, and (e) determining a maximum focus value among the plurality of focus values And (f) capturing the second group of image images while applying the maximum current value corresponding to the maximum focus value in a predetermined step unit while applying the lens driver to the lens driver. And calculating the captured image of the second group as the focus value of the second group, respectively, (g) a second reference value in which a second focus value and the maximum focus value are set among the focus values of the second group. If it is satisfied, and setting the second focus value to the end point of the auto focus search range.

According to an exemplary embodiment of the present invention, a time for searching for a dead zone area unnecessary for auto focusing is determined by determining an effective search range (auto focusing search range) necessary for auto focusing and driving the lens unit only within the auto focusing search range. In short, the auto focusing speed can be improved.

1 is a schematic configuration diagram of a camera module according to an embodiment of the present invention.
2 is a schematic diagram of a device equipped with a camera module according to an embodiment of the present invention.
3 is a diagram illustrating a method of determining, by the controller of FIG. 2, a starting point of an autofocusing search range.
FIG. 4 is a graph illustrating a change in focus value according to a current applied to a lens driver in the method of FIG. 3.
5 is a diagram illustrating a method of determining, by the controller of FIG. 2, an end point of an auto focusing search range.
FIG. 6 is a graph illustrating a change in focus value according to a current applied to a lens driver in the method of FIG. 5.

As the inventive concept allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

Terms including ordinal numbers such as first and second may be used to describe various components, but the components are not limited by the terms. The terms are used only for the purpose of distinguishing one component from another.

For example, without departing from the scope of the present invention, the second component may be referred to as the first component, and similarly, the first component may also be referred to as the second component.

When a component is said to be "connected" or "connected" to another component, it may be directly connected to or connected to that other component, but it may be understood that another component may exist in between. Should be. On the other hand, when a component is said to be "directly connected" or "directly connected" to another component, it should be understood that there is no other component in between.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In the present application, the terms "comprises", "having", and the like are used to specify that a feature, a number, a step, an operation, an element, a component, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

Now, a method for setting an auto focusing search range of a camera module according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. The description may be omitted.

1 is a schematic configuration diagram of a camera module according to an embodiment of the present invention, Figure 2 is a schematic configuration diagram of a device equipped with a camera module according to an embodiment of the present invention.

As shown in FIG. 1, the camera module includes a lens unit 10, an image sensor 20, a current applying unit 30, and a lens driver 40.

The lens unit 10 includes a plurality of lenses and moves up and down in the optical axis direction according to the control signal of the lens driving unit 40, and enters the light energy of the subject to pass through the image sensor 20.

The image sensor 20 is positioned at the rear end of the lens unit 10 and converts light energy passing through the lens unit 10 into an electrical signal to output an image image.

In the current applying unit 30 of the present invention, the "auto focusing search range" of the lens driving unit 40 is stored, and the current applying unit 30 moves to the lens driving unit 40 by a current range corresponding to the auto focusing search range. Apply a current. In this case, the current applying unit 30 may further include a separate memory unit for storing the auto focusing search range.

The auto focusing search range is determined according to the focus value of the video image input through the image sensor 20. That is, the auto focusing search range is a focus value (FV) of an image image according to the position of the lens unit 10 while moving the position of the lens unit 10 while photographing a specific chart 1 positioned at a predetermined interval (10 cm). , focus value). The lens unit 10 is moved by the lens driver 40, and the lens driver 40 moves the lens unit 10 according to the current applied from the current applying unit 30, so that the auto focusing search range is applied to the current. The focus value FV that changes according to the current applied from the unit 30 is within a range that satisfies the set reference value.

The auto focusing search range stored in the current applying unit 30 is determined by the controller 210 of the apparatus 200 employing the camera module 100 shown in FIG. 2.

Although the apparatus of FIG. 2 illustrates the mobile communication terminal 200 employing the camera module 100 of the present embodiment as an example, it will be obvious to those skilled in the art that the apparatus of FIG. 2 is also applied to various devices in which the camera module 100 may be employed.

In the mobile communication terminal 200 according to the present embodiment, the camera module 100 illustrated in FIG. 1 is employed and includes a controller 210. The mobile communication terminal 200 is provided with various components for performing communication and various functions, but since it is a well-known configuration, detailed description thereof will be omitted.

The controller 30 is connected to the rear end of the image sensor 20 to process and output an image image input through the image sensor 20, and according to a focus value of the image image input through the image sensor 20. The auto focusing search range of the driver 40 is set and output to the current applying unit 30.

Hereinafter, a method of determining the auto focusing search range by the controller of the present invention will be described in more detail with reference to FIGS. 3 to 6.

3 is a diagram illustrating a method of determining, by the controller of FIG. 2, a starting point of an autofocusing search range.

While the controller 210 determines the auto focusing search range, the camera module 100 generates a specific chart (shown in FIG. 1 as an AF chart 1) located at a predetermined distance (shown as 10 cm in FIG. 1). Shooting is a prerequisite.

As shown in FIG. 3, the controller 210 controls the camera module 100 to capture a specific chart 1 in a state in which the current value of the current applying unit 30 is set to zero (S301). ). Then, a zero current value (initial current value) is applied to the lens driver 40, and the lens unit 10 captures the specific chart 1 in an initialized state according to zero driving of the lens driver 40 ( S302).

The controller 210 captures an initial image image captured by the image sensor 20 (S303), squares a difference between adjacent green pixels among the Bayer patterns of the initial image image, adds the square roots, and then adds the square root values. An initial focus value FV0 is calculated by (square root) (S304).

The method for obtaining the focus value from the controller 30 is as shown in Equation 1 below.

Here, G12, G11, G13 ... represent the pixel value (brightness value) of the green pixel among the via pattern of the image sensor included in the said camera module.

Next, the control unit 210 increases the current value of the current applying unit 30 by the set step (S305).

Then, the current of the current value + the step is applied to the lens driving unit 40, the lens unit 10 moves by a distance corresponding to the current value of the lens driving unit 40 to take a specific chart (1) (S306) .

The controller 210 captures the first image captured by the lens unit 10 by a distance corresponding to the current value (S307) and calculates a first focus value FV1 of the first image image (S308). ).

The controller 210 determines whether the initial focus value FV0 and the first focus value FV1 satisfy the following Equation 2 (S309).

Here, the first reference value is a value in which the focus value is higher than the initial image image so that the image image is focused for the first time, and thus the focus value is in a normal range. The first reference value may be variously set according to the type of the camera module 100. In the present invention, it can be set to 0.03 (± 0.01).

When the initial focus value FV0 and the first focus value FV1 satisfy Equation 2, a current value corresponding to the first focus value FV1 is set as a start point of the “auto focusing search range” (S310). .

However, when the initial focus value FV0 and the first focus value FV1 do not satisfy Equation 2, the controller 210 repeatedly performs step S309 in step S305 to satisfy Equation 2. A current value corresponding to the first focus value FV1 is set as the start point of the auto focusing search range (S310).

4 is a graph illustrating a change in focus value according to a current applied to the lens driver in the method of FIG. 3, wherein the X axis of FIG. 4 is a current value of the current applying unit 30, and the Y axis is a focus value.

As shown in FIG. 4, the control unit 210 of the present invention captures an image image while increasing a current value in units of steps set from an initial current value, and focus value FV0 and a first value of the initially captured initial image image. When the first focus value FV1 of the captured image image at the current value satisfies the set reference value, the first current value at that time is set as the start current value of the auto focusing search range. In FIG. 4, the first current value is illustrated as 256.

5 is a diagram illustrating a method of determining, by the controller of FIG. 2, an end point of an auto focusing search range.

As shown in FIG. 5, the controller 210 controls the camera module 100 to capture a specific chart 1 in a state in which the current value of the current applying unit 30 is set to zero (S501). ). Then, an initial current value is applied to the lens driver 40, and the lens unit 10 captures the specific chart 1 in an initialized state according to the initial driving of the lens driver 40 (S502).

The controller 210 captures an initial image image captured by the image sensor 20 (S503), squares a value obtained by adding squared differences between adjacent green pixels among the via patterns of the initial image image, and initializing a focus value. (FV0) is calculated (S504). In this case, an equation for calculating the focus value is the same as that of Equation 1 above.

Next, the control unit 210 increases the current value of the current applying unit 30 by the set step (S505).

Then, the current of the current value + the step is applied to the lens driving unit 40, the lens unit 10 moves by a distance corresponding to the current value of the lens driving unit 40 to take a specific chart (1) (S506) .

The controller 210 captures the first image captured by the lens unit 10 by a distance corresponding to the current value (S507), and calculates a first focus value FV1 of the first image image (S508). ).

The controller 210 compares the N th calculated focus value with the N-1 th calculated focus value (S509).

If the Nth calculated focus value is smaller than the N-1th calculated focus value, the N-1th focus value is set to the maximum focus value MAX (S510).

If the N th calculated focus value is larger than the N-1 th calculated focus value, the control unit 210 repeatedly performs step S509 in step S505 to set the maximum focus value MAX.

As such, when the maximum focus value MAX is set, the controller 210 increases the current value (maximum current value) corresponding to the maximum focus value MAX by the set step (S511).

Then, the maximum current value + the current of the step is applied to the lens driver 40, the lens unit 10 moves by a distance corresponding to the current value of the lens driver 40 to photograph the specific chart 1 (S512). ).

The controller 210 captures the captured second image image by moving the lens unit 10 by a distance corresponding to the current value (S513), and calculates a second focus value FV2 of the second image image (S514). ).

In addition, the controller 210 determines whether the maximum focus value MAX and the second focus value FV2 satisfy the following Equation 3 (S515).

Here, the second reference value is a value in which the focus value is out of the normal range because the second focus value FV2 is lower than the maximum focus value MAX so that the focus value is out of the normal range, and the second reference value is a type of the camera module 100. It can be set in various ways, in the present invention was set to 0.25 (± 0.05).

When the maximum focus value MAX and the second focus value FV2 satisfy the above Equation 3, a current value corresponding to the second focus value FV2 is set as an end point of the autofocusing search range (S516).

However, if the maximum focus value MAX and the second focus value FV2 do not satisfy the above Equation 3, the control unit 210 repeats the step 515 in step S511 to satisfy Equation 3 A current value corresponding to the second focus value FV2 is set as an end point of the auto focusing search range (S516).

 FIG. 6 is a graph illustrating a change in focus value according to a current applied to a lens driver in the method of FIG. 5, wherein the X axis of FIG. 6 is a current value of the current applying unit 30, and the Y axis is a focus value.

As shown in FIG. 6, the control unit 210 of the present invention captures an image image while increasing a current value in units of steps set from an initial current value, and the maximum focus value MAX at which the focus value of the image image is maximized. The second focus value FV2 corresponding to the second current value is calculated while increasing the current value in the set step unit from the maximum current value corresponding to the maximum focus value MAX, and the maximum focus value MAX When the second focus value FV2 satisfies the set reference value, the second current value corresponding to the second focus value at that time is set as the end current value of the autofocusing search range. In FIG. 6, the second current value is 720.

Through the above method, the controller 210 of the present invention can set the start point and the end point of the auto focusing search range, and the start point and the end point of the set auto focusing search range are stored in the current applying unit 30.

When the camera module 100 intends to photograph the subject, the current applying unit 30 applies a current corresponding to the stored auto focusing search range to the lens driver 40. Then, the lens driver 40 drives the lens unit 10 by a distance corresponding to the current applied from the current applying unit 30.

As described above, in the present invention, by setting the effective search range required for auto focusing, the controller 210 may reduce the time for searching to a dead zone area that is unnecessary for auto focusing, thereby improving the auto focusing speed. .

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

10: lens unit
20: image sensor
30: current applying unit
40: lens driving unit
100: camera module
200: mobile communication terminal
210: control unit

Claims (15)

In the auto focusing search range setting method of the camera module including a lens driving unit for driving the lens by the applied current,
(a) capturing an initial image by applying an initial current to the lens driver;
(b) calculating an initial focus value of the initial video image;
(c) capturing a video image while increasing a current applied to the lens driver by a set step, and calculating a focus value of the captured video image, and
and (d) setting the auto focusing search range using the initial focus value and the focus value of the video image. The method of claim 1,
(e) the lens driving unit driving the lens within a range corresponding to the auto focusing search range and photographing a subject. The method of claim 1,
And the camera module captures a specific chart located at a distance of a first interval, and captures the specific chart while moving a lens according to a current applied to the lens driver. The method of claim 1,
The focus value FV is an autofocusing search range setting method of a camera module calculated by the following equation.

(G12, G11, G13 ... means the pixel value of the green pixel of the buyer pattern of the image sensor included in the camera module) The method of claim 1,
In step (d),
(f) setting a first current value corresponding to a first focus value as a start point of the auto focusing search range when the initial focus value and the first focus value of the first video image satisfy a set first reference value; And
(g) when the maximum focus value among the focus values and the second focus value of the second video image satisfy a set second reference value, set a second current value corresponding to the second focus value as an end point of the auto focusing search range; Auto focusing search range setting method of the camera module further comprising the step of. The method of claim 5,
The starting point of the auto focusing search range in the step (f) is the first current value corresponding to the first focus value that satisfies the following equation.

Here, FV0 is an initial focus value, FV1 is a first focus value of a first video image, and a first reference value is a value at which a focus image is focused for the first time due to a higher focus value than an initial video image. Can be set differently depending on The method of claim 5,
And the end point of the auto focusing search range in step (g) is the second current value corresponding to the second focus value satisfying the following equation.

Here, MAX is the maximum focus value, FV2 is the second focus value of the second video image, and the second reference value is a value that causes the focus of the video image to be blurred by lowering the second focus value compared to the maximum focus value. Can be set differently) The method of claim 5,
In step (g), the maximum focus value is set to the auto focusing search range of the camera module determined as the N-1 th calculated focus value if the N th calculated focus value is smaller than the N-1 th calculated focus value. Way. In the auto focusing search range setting method of the camera module including a lens driving unit for driving the lens by the applied current,
(a) capturing an initial image by applying an initial current to the lens driver;
(b) calculating an initial focus value of the initial video image;
(c) capturing an image of the first group by increasing the current applied to the lens driver in a set step unit, and calculating the captured image of the first group as a focus value of the first group, respectively;
(d) setting the first focus value as a start point of the autofocusing search range when the first focus value and the initial focus value satisfy the set first reference value among the focus values of the first group;
(e) determining a maximum focus value among the plurality of focus values,
(f) capturing the second group of image images while applying the maximum current value corresponding to the maximum focus value by the set step unit while applying the lens driver to the second group; Calculating with the focus value of,
(g) setting the second focus value as an end point of the autofocusing search range when the second focus value and the maximum focus value among the focus values of the second group satisfy the set second reference value. How to set auto focusing search range of module. 10. The method of claim 9,
and (h) the lens driving unit driving the lens according to a current applied from the start point to the end point to photograph the subject. 10. The method of claim 9,
And the camera module captures a specific chart located at a distance of a first interval, and captures the specific chart while moving a lens according to a current applied to the lens driver. 10. The method of claim 9,
The focus value FV is an autofocusing search range setting method of a camera module calculated by the following equation.

(G12, G11, G13 ... means the pixel value of the green pixel of the buyer pattern of the image sensor included in the camera module) 10. The method of claim 9,
The starting point of the auto focusing search range in the step (d) is the first current value corresponding to the first focus value that satisfies the following equation.

Here, FV0 is an initial focus value, FV1 is a first focus value of a first video image, and a first reference value is a value at which a focus image is focused for the first time due to a higher focus value than an initial video image. Can be set differently depending on 10. The method of claim 9,
And the end point of the auto focusing search range in step (g) is the second current value corresponding to the second focus value satisfying the following equation.

Here, MAX is the maximum focus value, FV2 is the second focus value of the second video image, and the second reference value is a value that causes the focus of the video image to be blurred by lowering the second focus value compared to the maximum focus value. Can be set differently) 10. The method of claim 9,
In the step (e), the maximum focus value is set to the auto focusing search range of the camera module determined as the N-1 th calculated focus value if the N th calculated focus value is smaller than the N-1 th calculated focus value. Way.

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