KR20100067711A - Auto-focusing method - Google Patents

Abstract

PURPOSE: An automatic focusing method for embodying sequence of shots about each automatic focus domain as the focusing optimization is provided to implement best successive focusing by following plural tracking areas. CONSTITUTION: An auto-tracking function is activated is determined(S10). If the auto tracking function is activated, a plurality of auto focusing areas of the next frame is tracked(S20). The information is updated about each auto focusing area(S40). If the input of user is not detected(S50), the auto focusing area information is transmitted to a lens activation controller(S60).

Description

Auto Focusing Method {AUTO-FOCUSING METHOD}

The present invention relates to an auto focusing method for a plurality of objects or regions of interest in a camera device, wherein the focusing optimization for each of the auto focus regions is used to generate a sequence of shots for each auto focus region. It is related with the autofocus method which makes it possible.

In general, the compact camera module (CCM) is a compact and is applied to various IT devices such as a camera camera, a portable mobile communication device such as a PDA, a smart phone, and a toy camera. Increasingly, devices equipped with small camera modules are gradually being released to meet various consumer tastes.

Such a camera module is manufactured using an image sensor such as a CCD or a CMOS as a main component, and collects an image of an object through the image sensor and stores it as data in a memory in the device, and the stored data is stored in the LCD or PC in the device. The image is displayed through a display medium such as a monitor.

In recent years, auto focusing technology has been widely used to detect a subject using a luminance signal of a subject captured by a camera lens and to automatically focus the optical system according to the detected subject.

In this type of auto focusing, the entire subject within the photographing range of the camera is not targeted for auto focusing, but only the subject in the range of interest of a part of the photographing range. In contrast-based auto focusing, an image signal of a range targeted for auto focusing is extracted from an image signal received by the entire imaging area of the image sensor, and the focus is controlled so that the contrast of the extracted image signal is the highest. As a result, the subject of autofocus is limited to a subject in a partial range.

However, currently used DSC cameras only provide the function of following the movement of the subject to a "one" tracking area.

In addition, in the case of auto focusing according to a technology currently used, when a subject moves within a predetermined image and leaves the image area (for example, when the subject moves out of the image and disappears), information about an existing following subject A problem arises in that a loss cannot be made so that the subject can no longer be followed.

In addition, the conventional contrast auto-focusing method may unfocus an image while the lens position is changed, for example, to find an optimal lens position for generating a focused image, in which case the moving object is in a range of interest. Is very likely to fail to follow.

On the other hand, in actual shooting, not only one subject is always the target of auto focusing, but it is sometimes necessary to change the auto focusing target to another subject at the discretion of the user. There is a problem in terms of the rapid following response of the moving object in the setting of the range of interest.

In addition, in the case of the currently used DSC camera, it provides the tracking capability of the moving object, but in the case of a small device such as a mobile phone, due to hardware constraints such as memory, a separate algorithm for mobile phone application is required. to be.

The auto focusing algorithm according to the present invention was devised to solve the problems related to the auto focusing method in the related art as described above. It is an object of the present invention to provide a plurality of auto focusing methods for enabling an arbitrary shot.

In addition, the auto focusing algorithm according to the present invention can stably follow a subject without losing information on an existing subject even when the subject moves within a predetermined image and leaves the image area. It is an object of the present invention to provide an auto focusing method.

In addition, the auto focusing algorithm according to the present invention is not only at the time of changing the lens position for generating the focused image, but also at the change of the zoom factor and the camera view position such as zoom in, zoom out, and the like. It is an object of the present invention to provide an auto focusing method capable of steadily following a moving object even when the image contrast changes due to a change in lighting conditions.

In addition, an object of the present invention is to provide an auto focusing method capable of quickly processing a target change of a moving object and optimally applicable to a small device such as a mobile phone in hardware.

On the other hand, the auto focusing algorithm according to the present invention was created with the above main objectives in mind, but is not necessarily limited thereto, and a new object that can be created or predicted from the configuration of the present invention described below will be described. It is to be noted that and effects are not excluded.

In order to achieve this problem, in the auto focusing method for a plurality of selected areas, by an input of a user through a touch pad for auto tracking for a moving object in a predetermined image. A plurality of center points selected; A plurality of auto focusing regions configured to surround each of the plurality of center points; And a plurality of tracking sub-areas set around each of the plurality of auto-focusing regions, wherein the plurality of center points, the plurality of auto-focusing regions, and the plurality of tracking sub-regions follow the movable body and the movable body The position of each of the auto focusing regions is changed and the positions of each of the tracking sub-regions are updated according to the movement of, so that the shots can follow the movement of the subject to a plurality of tracking regions to enable continuous shots with optimal focusing for each. It is characterized by.

Here, when the moving object for auto tracking is deviated from the edge portion of the image, the edge portion of the tracking sub-region remains in agreement with the edge portion of the image and at the same time only the auto focusing region inside the tracking sub-region Move toward the edge of the image to follow the moving object within a tracking sub-area, and the moving object for auto-tracking is completely out of the edge of the image, so that only the auto focusing area is moved by the movement in the tracking sub-area. Even when the edge portion of the image is reached, the auto focusing region and the tracking sub region are both configured to be maintained at the edge portion of the image.

Advantageously, following the moving body comprises: a) cutting a sub image around the tracking sub-region; b) smoothing the sub-images in the before and after frames by convolving with a Gaussian function; c) calculating the gradient of the front and back sub-images by convolving with a Gaussian derivative; And d) iterating to find the location of the new center point.

Here, the following of the moving object stops the following process when the center point moves only by one pixel, or when the repetition step exceeds a preset limit, or when the center point is located outside the boundary. Characterized in that.

Meanwhile, an auto focusing method for a plurality of selected areas according to the present invention includes: a) determining whether a default auto focusing area setting value is input to an auto focusing area controller and an auto tracking function is activated; b) when the auto tracking function is activated, tracking each of the plurality of auto focusing regions in the next frame and then updating information for each region; c) transmitting information regarding the updated plurality of auto focusing regions to a lens activation controller; d) determining whether a sequence shot function is activated; And e) when the continuous shot function is activated, transmitting a next auto focusing area (next AF area) to the lens controller for each next shot in the shot sequence.

In this case, if there is no area to be followed according to the determination of the following area, the user selects the auto focusing area, and then the area selected by the user is inputted to the auto focusing area controller again. It is characterized by performing the step repeatedly.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention.

Auto focusing system for multiple selected areas

As shown in FIG. 1, an auto focusing system for a plurality of selected areas according to the present invention includes a lens unit 100, a tracking unit 200, an auto focusing area selection unit 300, and an auto focusing controller 400. It is composed of

First, the auto focusing area selection unit 300 is a means for receiving an input for a region of interest from a user. The present invention is configured to allow continuous shots by selecting a plurality of regions of interest and focusing on each of them, so that the user inputs the regions of interest by a "touch pad method".

The plurality of ROIs input from the auto focusing area selection unit 300 are input to the auto focusing controller 400. The auto focusing controller 400 may be selected by a user input for auto tracking of a moving object 20 in a predetermined image 10 as shown in FIG. 3. Surround a center of interest 11, a plurality of auto focusing areas 13 set to surround each of the center points 11, and each of the auto focusing areas 13. A plurality of tracking sub-windows 12 are set around.

The tracking unit 200 corresponds to an apparatus for tracking a subject and automatically shifting positions of the plurality of auto focusing regions while following a movement of a subject in a plurality of regions of interest designated by a user on the screen. The tracking unit 200 sets and updates the auto focusing area in the image processing unit 202 with the image received from the image input unit 201. This auto tracking function is determined by the tracking activation means 203.

The lens unit 100 enables continuous shooting with an image focused on each of the plurality of ROIs followed by the tracking unit 200. The continuous shot activating means 101 determines whether such continuous shooting is operated. When continuous shooting is activated by the continuous shot activating means 101, each tracked auto focusing area is sequentially input to the auto focusing input unit 103 (see 102), and the auto focusing processing unit 104 performs auto Data for focusing is calculated. Based on this, the lens activation controller 105 sets and controls the position of the lens unit (not shown) for each focusing.

2 is a flowchart illustrating an operation performed by the auto focusing system for the plurality of ROIs described above.

As shown in FIG. 2, first, a default auto focusing area setting value is input to the auto focusing area controller 400 and it is determined whether the auto tracking function is activated (S10).

If auto tracking is activated, the plurality of auto focusing areas are tracked in the next frame (s20), and information is updated for each area (s40).

Thereafter, when the user's input is not detected (s50), the plurality of pieces of autofocusing regions are transmitted to the lens activation controller 105 (s60).

Next, after determining whether the continuous shot function is activated (S70), the next auto focusing area is transmitted to the lens controller for each next shot in the shot sequence (S80).

On the other hand, if there is no area to be followed according to the determination of the following area (s30), the user selects the auto focusing area and then the area selected by the user is input to the auto focusing area controller 400 again. The described steps s10 to s80 are repeatedly performed.

Algorithm for each of the plurality of focusing regions

As shown in Fig. 3, auto focusing according to the present invention is largely performed by three areas.

These three regions may include one area of interest central point selected by a user input for auto tracking of a moving object 20 within a given image 10; 11), an auto fucusing area 13 set to surround the center point 11, and a tracking sub-window 12 set around the auto focusing area 13. It consists of.

One center point 11 is an area selected by the user for tracking the moving object 20.

As described above, the one center point 11 is preferably input by the user by a touch pad method, unlike in the related art, and can quickly cope with object selection and change of a moving object by the touch pad method. It becomes a more suitable object selection means for a small device such as.

The auto focusing area 13 corresponds to an area for performing a focusing process based on the selected center point.

In the present invention, one of the technical features of the present invention further includes a tracking sub-region 12 which is an area surrounding the auto-focusing region 13. Since image processing is performed only within this tracking sub-area 12, the effect of reducing memory usage and calculation amount is generated, and it is not only a configuration adopted to be more suitably used for a small device such as a mobile phone, but also retains the data described below. In terms of configuration is essential. Because it typically processes 30 frames per second, the region of interest is not shifted by a large distance between the frames, and if the maximum shift between the two frames is 20% of the image, then the amount of computation can be reduced by up to 20 times. Memory can be reduced by five times.

As can be seen in FIG. 4A, the center point 11, the auto focusing region 13 and the tracking sub-region 12 described above together track the movable body 20 within a predetermined overall image 10, and the movable body ( According to the movement of 20, the position of the auto focusing region 13 is changed and the position of the tracking sub-region 12 is updated.

In the movement of the movable body 20, when the movable body 20 for auto tracking is deviated from the right edge portion of the predetermined whole image 10 as shown in FIG. 4B, the edge portion of the tracking sub-region 12 is an image ( The auto focusing region 13 inside the tracking sub-region 12 is kept in alignment with the edge of 10, so that the moving object 20 continues to follow in the tracking sub-region 12. It is moved to the right toward the edge portion.

As shown in FIG. 4C, if the moving object 20 for auto tracking is completely deviated to the right from the edge of the image 10 (eg, when the moving object disappears from the screen), only the auto focusing area 13 is the tracking sub area 12. Even when the edge of the entire image 10 is reached by the movement within), both the auto focusing region 13 and the tracking sub-region 12 are configured to remain at the edge portion of the image 10. .

That is, in the conventional art, when a subject moves within a predetermined image and leaves a predetermined image area (for example, when the subject moves out of the image and disappears), information on an existing following subject is lost, In the present invention, even in this case, both the auto focusing area 13 and the tracking sub area 12 are configured to be maintained at the edge of the image, so that the tracking data for the moving object can be continuously maintained to stably follow the subject. Make sure

The following describes a processing step for following a moving object according to the present invention which reliably follows the moving object in any environment.

First, a sub image is cut around the tracking sub area 12.

Next, the sub-images in the frames before and after the cut time (n, n + 1) are smoothed by convolving with a Gaussian function represented by Equation 1 below.

For smoothing the initial image, σ = 0.1 is used. And for sub-image downscale, σ = 0.9.

For example, a sample Gaussian matrix for σ = 0.8 is shown below.

The gradient of the front and back sub-images is then calculated by convolving with a Gaussian derivative.

Here, Gaussian derivatives are real valued functions.

In one dimension, as in Equation 2 below, the derivative of Gaussian has the same characteristics as the result of polynomial and Gaussian.

8 is a diagram illustrating a Gaussian derivative constituting two derivatives, a Gaussian function on the x-axis and a Gaussian function on the y-axis.

In each area, as shown in Figure 8, these functions change very small in part with increasing (white) and decreasing (black) in certain parts of the trend.

Finally, iteration takes place to find the location of the new center point.

The sequence of iterations has the following characteristics:

1. On average, 5 repetitions are sufficient and recommended.

2. At the first iteration (k = 1), the initial estimate is set by predicting the motion based on tracking the preceding frames.

3. The image structure is obtained to obtain an image display calculation method that does not change for rotation, noise, zoom factor, and defocusing by Gaussian function and Gaussian derivative filters.

4. Each iteration minimizes the display picture for each level (use 2 levels with 4 elements of downscale). Downscale the level for big image shift detection and downscale the initial size for accurate shift detection.

On the other hand, the calculation regarding the following of the moving object stops when the center point moves only by one pixel, or when the repetition step exceeds a preset limit, or when the center point is located outside the boundary. It is preferable.

By the above-described setting of the tracking sub-region and the moving object tracking processing, the present invention creates the following effects, which will be described with reference to FIGS. 5 to 7 (although in FIGS. 5 to 7 one focusing). Although shown as an example for the selection area, the same effect can be expected by the continuous shot).

First, FIG. 5 shows the tracking performance according to the present invention when the image focusing is continuously changed.

That is, even when the position of the lens is changed to generate a focused image and the image is defocused as shown in FIGS. 5B to 5D, one center point 11 selected by the user with respect to the moving object 20 is selected. The auto focusing region 13 and the tracking sub-region 12 can stably follow the moving object of interest.

6 also shows the tracking performance according to the present invention upon change in zoom factor and camera view position.

That is, while preparing to shoot, the user can change the image zoom factor such as zoom in or zoom out and also change the view position of the camera. According to the present invention, even in this situation, as shown in FIGS. 6A to 6C, one center point 11 and the auto focusing region 13 and the tracking sub-region 12 selected by the user with respect to the movable body 20 are provided. It can be seen that follows well the moving object of interest.

In addition, Figure 7 also shows the tracking performance according to the present invention when the image contrast (image contrast) changes with the change in the lighting (lighting) conditions.

In other words, image contrast may change while adjusting the camera to suit the current lighting conditions. According to the present invention, even in such a situation, as shown in FIGS. 7A and 7B, one center point 11 and the auto focusing region 13 and the tracking sub-region 12 selected by the user with respect to the movable body 20 are provided. It can be seen that steadily follows the moving object of interest.

Since the contents described above are provided in the form of preferred embodiments of the present invention, those skilled in the art should understand that various modifications and equivalent other embodiments are possible therefrom. Accordingly, the scope of the present invention is not limited to the disclosed embodiments, but various modifications and improvements of those skilled in the art using the basic concept of the present invention as defined in the following claims also belong to the scope of the present invention.

1 is a block diagram of an auto focusing system for a plurality of selected regions in accordance with the present invention;

2 is an operational flow diagram of the system according to FIG.

3 is a diagram illustrating one center point, an auto focusing area, and a tracking sub area used in an auto focusing method according to the present invention;

4 is a diagram illustrating an operation of one center point and an auto focusing region and a tracking sub-region used in the auto focusing method according to the present invention.

5 is a diagram showing tracking performance according to the present invention when image focusing is continuously changed.

6 shows tracking performance in accordance with the present invention upon change in zoom factor and camera view position.

7 is a diagram showing tracking performance according to the present invention when a change in image contrast according to a change in lighting conditions.

8 is a diagram illustrating a Gaussian derivative constituting two derivatives, a Gaussian function on the x-axis and a Gaussian function on the y-axis.

* Description of the main symbols in the drawings *

10: image 11: center point

12: Tracking sub area 13: Auto focus area

20: moving object

100: lens unit 200: tracking unit

300: auto focusing area selection unit 400: auto focusing controller

Claims (6)

In the auto focusing method for a plurality of selected areas, A plurality of center points selected by a user's input through a touch pad for auto tracking of moving objects in a given image; A plurality of auto focusing regions configured to surround each of the plurality of center points; And A plurality of tracking sub-areas set around each of the plurality of auto focusing regions Including, The plurality of center points, the plurality of auto focusing regions and the plurality of tracking sub-regions together follow the movable body, change positions of each of the auto focusing regions and update positions of each of the tracking sub-regions in accordance with the movement of the movable body. And follow the movement of the subject in the plurality of tracking areas to enable continuous shots with optimal focusing for each of the plurality of selected areas. The method of claim 1, When the moving object for the auto tracking is out of the edge portion of the image, the edge portion of the tracking sub-region remains in agreement with the edge portion of the image and at the same time, only the auto focusing region inside the tracking sub-region is in the tracking sub-region. Move toward the edge of the image to follow the moving object within an area, wherein the moving object for auto tracking is completely out of the edge of the image and only the auto focusing area is moved by the movement within the tracking sub-area. Even when the edge portion is reached, both the auto focusing region and the tracking sub region are configured to be held at the edge portion of the image. The method of claim 2, Following the moving body, a) cutting a sub image around the tracking sub-region; b) smoothing the sub-images in the before and after frames by convolving into a Gaussian function according to the following equation:

; c) calculating the gradient of the front and back sub-images by convolving with a Gaussian derivative; And d) iterating to find the location of the new center point; Auto focusing method for a plurality of selected areas comprising a. The method of claim 3, The calculation for the following of the mobile body, The center point moves by only one pixel, or The repeating step exceeds a preset threshold, or The center point is located outside the boundary. An autofocus method for a plurality of selected areas, characterized by stopping at. In the auto focusing method for a plurality of selected areas, a) determining whether a default auto focusing area setting value is input to an auto focusing area controller and the auto tracking function is activated; b) if the auto tracking function is activated, tracking each of the plurality of auto focusing regions in the next frame and then updating information for each region; c) transmitting information regarding the updated plurality of auto focusing regions to a lens activation controller; d) determining whether a sequence shot function is activated; And e) if a subsequent shot function is activated, transferring the next autofocus area to the lens controller for each next shot in the shot sequence; Auto focusing method for a plurality of selected areas comprising a. The method of claim 5, If there is no area to be followed according to the determination of the following area, the user selects the auto focusing area, and then the area selected by the user is inputted to the auto focusing area controller again. Auto focusing for a plurality of selected areas, characterized in that it is performed repeatedly.

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