KR100961121B1 - Method and apparatus for auto focusing - Google Patents

Abstract

According to an aspect of the present invention, a first scanning step of scanning a focus value at a first predetermined interval by moving a lens along an optical axis in a first scan area from macro to infinity with respect to a first imaging area And a second scan step of scanning a focus value at a second predetermined interval in a second scan area including a lens position at an optimum focus value among the focus values scanned in the first scan step, and the second scan. Positioning the lens at an optimal lens position having an optimal focus value in the step, and after the imaging region is moved from the first imaging region to the second imaging region, a focus value for the second imaging region at the optimal lens position Determining whether a variation value, which is a difference between an optimal focus value in the second scanning step, falls within a preset threshold range, and according to the variation value determined in the determination step. It is possible to provide an auto focusing method including a third scanning step of moving a lens.

Auto focusing, scan

Description

AUTO FOCUSING METHOD AND APPARATUS {METHOD AND APPARATUS FOR AUTO FOCUSING}

The present invention relates to an auto focusing method and apparatus used in an imaging apparatus, and more particularly, to a method and apparatus for performing auto focusing by moving a lens as the imaging region is changed.

Recently, the rapid development of the information society is required to develop not only a mobile communication terminal that merely delivers voice but also a complex mobile communication terminal with various functions. Accordingly, in accordance with the multimedia era, a portable composite mobile communication terminal having both a video transmission and reception function and a voice transmission / reception function are implemented. As such a composite mobile communication terminal, a digital camera function is provided in a mobile communication terminal that a user normally carries. There is this added camera phone.

In general, an autofocus camera module processes an image obtained through a CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor) sensor with an ISP, and then passes an edge passed through a high pass filter (HPF). The extracted focus value is extracted in every picture unit and transferred to the CPU, and the CPU moves the distance and distance of the focus lens based on the calculated focus value. In response to the command, the actuator driver is commanded, and the actuator is driven to automatically focus as the lens moves.

In recent years, mobile communication terminals including not only a digital camera function but also a camcorder function for capturing a video have been released. In order to perform the camcorder function, research on a continuous auto focusing method continues as the imaging area is changed. have. In auto focusing of such continuous image capturing area, auto focusing time and power consumption may be important variables.

SUMMARY OF THE INVENTION In order to solve the above problems, an object of the present invention is to provide an auto focusing method and apparatus for performing auto focusing by determining whether a range of a focus value that changes when an imaging area is changed is within a predetermined threshold range.

According to an aspect of the present invention, a first scanning step of scanning a focus value at a first predetermined interval by moving a lens along an optical axis in a first scan area from macro to infinity with respect to a first imaging area And a second scan area including a lens position at an optimum focus value among the focus values scanned in the first scanning step, and a second scan area scanning the focus value at a second predetermined interval in the second scan area. Scanning, positioning the lens at an optimal lens position having an optimal focus value in the second scanning step, and after the imaging region is moved from the first imaging region to the second imaging region, the lens at the optimal lens position Determining whether a variation value, which is a difference between a focus value for a second imaging area and an optimum focus value in the second scanning step, falls within a preset threshold range, and the determining step In accordance with the change value determination stand it can provide a method for auto focusing a third scanning step of moving the lens.

The second scan area may be between lens positions having a focus value within a predetermined range with respect to an optimum focus value among the focus values scanned in the first scanning step.

The second interval may be denser than the first interval.

In the third scanning step, when the variation value is within the threshold range, the second scanning step may be performed on the second imaging area.

In the third scanning step, when the variation value is out of the threshold range, the first scanning step may be performed on the second imaging area.

The auto focusing method may further include determining a direction in which the lens moves before proceeding with the first scanning step.

According to another aspect of the present invention, there is provided an autofocusing apparatus for focusing an imaging device when an imaging area is changed from a first imaging area to a second imaging area, the lens unit for receiving an optical signal with respect to the imaging area, the received light An image sensor for converting a signal into an electric video signal, a calculator for generating focus value data, etc. for the video signal, a storage for storing the data generated by the calculator and a predetermined threshold value, A controller for generating a lens control signal according to a value; And a driving unit which moves the lens according to a lens control signal applied from the control unit, wherein the calculating unit includes a focus value of the second imaging area at the optimal lens position with respect to the first imaging area and the first imaging area. It may be determined whether the variation value, which is a difference between the optimal focus values for, corresponds to a range of the threshold stored in the storage unit.

According to the present invention, the auto focusing time can be shortened by varying the auto focusing process according to the variation range of the imaging area, and the power consumption can be reduced.

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

1 is a flowchart of an auto focusing method according to an embodiment of the present invention.

Referring to FIG. 1, in the auto focusing method 100 according to the present embodiment, a first scan step 110, a second scan step 120, and a lens are moved to an optimal lens position for a first imaging area. 130, determining whether the variation value is within a threshold range after the imaging region is changed to the second imaging region, and a third scanning step 150 for moving the lens according to the variation value. Can be.

The first scanning step 110 may scan a focus value at a first predetermined interval by moving a lens along an optical axis in a first scan area from macro to infinity with respect to the first imaging area. have.

The lens has a predetermined moving range and may be moved along the moving axis. A driving device for moving the lens may be connected, and the driving device may be operated by a driving signal generated by an auto focusing algorithm.

In the first scanning step 110, the moving range of the lens is equally divided at the first interval and the lens is moved to the image at the equalized position with respect to the first imaging area while moving the lens from macro to infinity. Can be used to measure the focus value. The focus value may be a sharpness of an image.

The second scan step 120 may scan a focus value at a second predetermined interval in a second scan area including a lens position at an optimum focus value among the focus values scanned in the first scan step. . The optimal focus value may be a maximum value of the scanned focus values.

The second scan area may be between lens positions having a focus value within a predetermined range with respect to an optimum focus value among the focus values scanned in the first scanning step. The range of the focus value for determining the second scan area may be determined by an experiment. Here, the focus values at the positions of the lenses corresponding to the upper limit and the lower limit of the second scan area may be the same.

In the present embodiment, the focus value for the image at the equalized position can be measured while dividing the second scan zone at equal intervals and moving the lens in the second scan zone. The second interval may be denser than the first interval in the first scanning step.

In the step 130 of moving the lens to an optimal lens position, the lens may be positioned at an optimal lens position having an optimal focus value in the second scanning step.

The optimal focus value in the second scan step may be the maximum value of the scanned focus values. When the lens is positioned at the optimal lens position, optimal focusing may be completed for the first imaging area.

In step 140, if the fluctuation value falls within a preset threshold range, the image capturing region is changed from the first image capturing region to the second image capturing region, and then, in the second scanning step, the second image capturing at the optimal lens position. It may be determined whether a variation value, which is a difference between the focus value for the region and the optimum focus value in the second scan step, falls within a preset threshold range. The threshold can be determined by experiment. The threshold may be a range in which an optimal focus value for the second imaging area may be located within the second scanning range without changing the second scanning range for the first imaging area.

When the image capturing region is changed from the first image capturing region to the second image capturing region, a focus value for the second image capturing region at an optimal lens position that is an optimal focusing position with respect to the first image capturing region is obtained for the first image capturing region. It will be different from the optimal focus value.

In this step, the difference between the focus value for the second image capturing region and the optimal focus value at the optimal lens position representing the optimal focus value for the first image capturing region may be defined as a variation value. In this step, it may be determined whether the variation value falls within a preset threshold range. That is, it is a step of determining whether the absolute value for the value obtained by subtracting the optimum focus value from the focus value for the second imaging area at the optimum lens position measured in the second step is smaller than a preset threshold.

In the third scanning step 150, the lens may be moved according to the variation value determined in the determining step 140.

In the determination step 140, when the change value falls within the threshold range, the third scan step 150 may proceed to the second scan step. In this step, the focus value for the second imaging area may be scanned by moving the lens in a second scan section determined during the scanning process for the first imaging area. The lens may be moved to an optimal lens position determined through the second scanning process.

In the determination step 140, when the change value is out of the threshold range, the third scan step may proceed to the first scan step. That is, the focus value for the second imaging area may be scanned while the lens is moved from macro to infinity. After the first scan step is performed, the second scan step may proceed, and the lens may be moved to an optimal lens position determined through the second scan step. In the present embodiment, the step 160 of determining the scan direction before the first scan step may be further included. That is, it may be determined in which direction the first scan step is performed by moving the lens from the current lens position with respect to the second imaging area.

As described above, in the present embodiment, if the difference between the first imaging area and the second imaging area is not large, the time required for scanning can be reduced by immediately proceeding the second scanning step without proceeding with the first scanning step. In addition, the power to move the lens for scanning can be reduced.

2 is a graph showing focus values according to lens positions.

In FIG. 2, (I) represents a focus value for the first imaging area, and (II) represents a focus value for the second imaging area. (III) shows a focus value for another second imaging area.

When the first scanning area is scanned in the first scanning step 110 of FIG. 1, a focus graph I of the first imaging area may be obtained. Here, the lens may move from macro to infinity along the optical axis. In this embodiment, the lens has a macro position of 450 and an infinity of 850.

According to this embodiment, the movement range of the lens is divided into eight, and the focus value can be scanned at the indicated lens positions 450, 500, 550, 600, 650, 700, 750, 800, and 850, respectively. In the present embodiment, it may have the maximum focus value A at the point where the lens position is 600.

In the first scanning step, a lens position having a focus value within a predetermined range based on the optimum focus value may be determined as the second scan region. In this embodiment, a fine scan focus value FVf having a predetermined range is determined with respect to the optimum focus value FVb, and the lens position 550 (a) in which the fine scan focus value FVf appears. And 650 (a ') may be the lower limit and the upper limit of the second scan zone, respectively.

In the second scanning step, the lens may be moved in the second scan zones 550 ˜ 650, and the focus value may be scanned at each position by dividing the second scan zone at equal intervals. That is, a scan may be performed on the a-a 'interval in the graph. The second interval may be more densely determined than the first interval in the first scanning step. Therefore, a detailed scan of the second scan area is possible to find an optimal lens position.

In the second step, the position of the lens in which the optimum focus value determined by the scan appears is called an optimal lens position. Once the optimal lens position is determined, the lens can be moved to the optimal position. In the present embodiment, the point A where the lens position is 600 may be the optimal lens position.

If the imaging area is changed from the first imaging area to the second imaging area by moving the imaging device, a third scanning step must be performed to focus on the second imaging area.

In the present embodiment, (II) is a graph showing the focus value according to the lens position with respect to the second imaging area.

When the imaging area is changed from the first imaging area to the second imaging area, the focus value A 'for the second imaging area and the first imaging at the optimum lens position 600 measured in the second scanning step are performed. It is determined whether the change value corresponding to the difference of the optimum focus value A for the region falls within a preset threshold range.

The threshold can be predetermined by experiment. The threshold may be set to, for example, 10% of an optimal focus value determined in the second scan step.

In the present embodiment (II), the variation value may fall within a threshold range. In this case, the third scan step may proceed to the second scan step. That is, the scan of the second imaging area may be performed in the second scan area which is the scan range of the camera determined through the first scanning step with respect to the first imaging area. In the present Example (II), all the focus values according to the camera positions are shown for the second imaging area. However, in the auto focusing method according to the embodiment of the present invention, the scanning process is performed only for the bb 'section within the second scanning area. Can proceed.

The scan step may proceed in the same manner as the second scan step described above, except that the subject of the imaging is changed from the first imaging area to the second imaging area.

In the present embodiment, the position having the optimum focus value B among the scanned values by performing the second scan on the second scan zone b-b 'is determined as the optimal lens position, and the lens is optimally determined. Can be moved to the lens position. In this embodiment, about 630 points may be an optimal lens position B with respect to the second imaging area.

In the present embodiment, (III) is a graph showing the focus value according to the lens position with respect to the second imaging area different from the above (II).

In the present embodiment (III), the variation value may be outside the threshold range. In this case, the third scan step may proceed to the first scan step. That is, in the present embodiment (III), both the first scanning step and the second scanning step may be performed on the second imaging area as the first scanning step and the second scanning step are both performed on the first imaging area. .

That is, the first scan step of moving the lens from the macro to infinity to measure the focus value at a first predetermined interval, and includes a first focus step including the optimum focus value measured in the first scan step. A second scan step may proceed for the two scan zones. In this embodiment, the position C having the optimum focus value FVb and the second scan region c-c 'are determined by the first scanning step, and the second scan range c-c' is determined. The second scan step may proceed. The optimal lens position may be determined by the second scanning step. Here, the position of 750 may be an optimal lens position with respect to the second imaging area.

As described above, in the present embodiment, if the difference between the first imaging area and the second imaging area is not large, the time required for scanning can be reduced by immediately proceeding the second scanning step without proceeding with the first scanning step. In addition, the power to move the lens for scanning can be reduced.

3 is a configuration diagram of an auto focusing device according to another embodiment of the present invention.

The auto focusing apparatus 300 according to the present embodiment may include a lens unit 301, an image sensor 302, an operation unit 303, a storage unit 304, a control unit 305, and a driver 306. have.

The lens unit 301 may be moved along the optical axis within the moving range to focus on the imaging area.

The image sensor 302 may convert an optical signal of a subject into an electrical signal and output the electrical signal. As the image sensor, a Charge Coupled Device (CCD) or a Complementary Metal Oxide Semiconductor (CMOS) sensor may be used.

The calculator 303 may perform signal processing such as auto white balance (AWB) or auto exposure (AE) on the image signal output from the image sensor and provide the same to the storage unit 304. The image signal transmitted to the storage unit 304 may be reproduced in a display device or compressed in a predetermined format and recorded on a recording medium.

The storage unit 304 stores a threshold value, a focus value, lens driver position data, etc. necessary for performing the auto focusing, and may be used to control the calculation and the lens driver.

The controller 305 may perform auto focusing by determining whether a focus is on a photographed subject by using a focus value that is auto focus data generated by the calculator 303. The controller may apply a lens control signal to the lens driver 306.

The lens driver 306 may move the lens along the optical axis. This may move the focal point of the lens by moving the lens unit 301 in a short or long distance.

Here, the operation unit 303 is configured to store a variation value which is a difference between a focus value for the second imaging area and an optimal focus value for the first imaging area at the optimum lens position for the first imaging area. It may be determined whether it falls within the range of the threshold.

It is intended that the invention not be limited by the foregoing embodiments and the accompanying drawings, but rather by the claims appended hereto. It will be apparent to those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. something to do.

1 is a flowchart of an auto focusing method according to an embodiment of the present invention.

2 is a graph showing a focus value for the first imaging area, the second imaging area, and another second imaging area according to the position of the lens in the auto focusing method according to the embodiment of the present invention.

3 is a configuration diagram of an auto focusing apparatus in which an auto focusing method according to an embodiment of the present invention can be used.

<Code Description of Main Parts of Drawing>

110: first scan step 120: second scan step

130: positioning the lens in the optimum lens position

140: determination step 150: third scanning step

Claims (7)

A first scanning step of scanning a focus value at a first predetermined interval by moving a lens along an optical axis in a first scan area that is a whole section that can be moved for auto focusing with respect to the first imaging area; A second scan step of setting a second scan area including a lens position at an optimal focus value among the focus values scanned in the first scan step, and scanning the focus value at a second interval preset in the second scan area ; Positioning a lens at an optimal lens position having an optimal focus value in the second scanning step; After the imaging area is moved to a second imaging area different from the first imaging area, a variation that is a difference between a focus value for the second imaging area at the optimal lens position and an optimal focus value in the second scanning step Determining whether a value falls within a preset threshold range; And If the variation value is within the threshold range, the second scanning step is performed on the second imaging area, and when the variation value is out of the threshold range, the first scanning step is performed on the second imaging area. Third scan step Auto focusing method comprising a. The method of claim 1, The second scan zone, And among lens positions having a focus value within a predetermined range with respect to an optimum focus value among the focus values scanned in the first scanning step. The method of claim 1, The second interval is, And denser than said first interval. delete delete The method of claim 1, Before proceeding with the first scanning step, Determining the direction in which the lens moves Auto focusing method comprising a further. An auto focusing apparatus for focusing an imaging device when the imaging area is changed from the first imaging area to the second imaging area, A lens unit which receives an optical signal with respect to the imaging area; An image sensor unit converting the received optical signal into an electrical image signal; A calculator configured to generate focus value data and the like for the video signal; A storage unit for storing the data generated by the operation unit and a predetermined threshold value; A controller for generating a lens control signal according to the value calculated by the calculator; And A driving unit for moving the lens unit in accordance with the lens control signal applied from the control unit Including; The calculation unit may include a variation value that is a difference between a focus value for the second imaging area and an optimal focus value for the first imaging area at an optimal lens position for the first imaging area, and corresponds to a range of the threshold stored in the storage unit. Judge whether When the variation value is out of the threshold range, the lens unit is moved and scanned along the optical axis in a first scan area in which the lens unit is movable with respect to the second imaging area, and the variation value is within the threshold range. The rear side scans the lens unit by moving the lens unit along an optical axis in a second scan area narrower than the first scan area with respect to the second imaging area. And the second scan zone is set to include a lens position at an optimal focus value among the focus values scanned in the first scan zone with respect to the first imaging area.

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