KR20080024637A - Auto focus control method and photographing apparatus having auto focus function - Google Patents

Abstract

A method for controlling an autofocus function and a photographing apparatus adopting the method are provided to detect peak data sections usable commonly in general photographing and spotlight photographing, thereby obtaining a clear image regardless of objects and environments. It is determined whether a rising section of AF(AutoFocus) data is matched to a rising section of processed data, which are obtained by processing the AF data(S220). It is determined whether a falling section of the AF data is matched to a falling section of the processed data(S240). An AF operation is performed by using peak data sections where the rising section of the AF data is matched to the rising section of the processed data or the falling section of the AF data is matched to the falling section of the processed data.

Description

Auto focus control method and photographing apparatus to which the method is applied {Auto focus control method and photographing apparatus having auto focus function}

1 is a flowchart illustrating an autofocus method of a conventional photographing apparatus;

2 is a view showing the size of AF data according to a change in position of a focus lens in a conventional photographing apparatus;

3 is a block diagram showing a schematic configuration of a photographing apparatus according to an embodiment of the present invention;

4A and 4B are diagrams illustrating the size of AF data according to a change in position of a focus lens in a photographing apparatus according to an exemplary embodiment of the present invention.

5 is a flowchart illustrating an autofocus control method of a photographing apparatus according to an exemplary embodiment.

Explanation of symbols on the main parts of the drawings

100: recording device 110: lens unit

120: lens driver 130: CCD

140: CDS / AGC / ADC 150: DSP

160: recording / playback unit 170: control unit

180: memory

The present invention relates to an autofocus control method and a photographing apparatus to which the method is applied. More particularly, the present invention relates to an autofocus control method and a photographing apparatus to which the method is applied, irrespective of a subject and environment to be a subject.

In general, a photographing apparatus such as a camcorder and a camera photoelectrically converts an optical signal incident through a lens into an electrical signal, and then performs a predetermined image processing on the photoelectrically converted image signal to perform a photographing operation. In the use of such a photographing apparatus, an Auto Focus (AF) function for clear photographing is provided. An autofocus function enables a general user, not an expert, to easily operate a photographing apparatus to obtain a clear image.

The user may take a spot light when the illuminance distribution is extreme, particularly when a bright light exists at a predetermined ratio or more in a night environment. In this case, when spotlight photography is performed using the conventional autofocus control method, the focus may not be accurately performed, and the shape of the subject may be blurred and the distinction of contrast may become unclear. In order to solve this problem, the method shown in FIGS. 1 and 2 is conventionally used.

1 is a flowchart illustrating an autofocus method of a conventional photographing apparatus. 2 is a diagram illustrating the size of AF data according to a change in position of a focus lens in a conventional photographing apparatus.

According to FIG. 1, first, the photographing apparatus detects AF data through a filtering process on input luminance data (S10). That is, after extracting only luminance components of a specific frequency, the luminance data is passed through two high pass filters having different frequencies to detect the first AF data and the second AF data shown in FIG.

At this time, when it is determined that the illuminance is in the dark state and the bright part is present in a predetermined amount or more, and spotlighting is performed (S30), spot AF data is generated (S50). That is, the ratio of the first AF data and the second AF data is calculated to generate spot AF data used for spotlight shooting. Then, the AF operation is performed using the spot AF data (S70).

In the case where the spotlight shooting is not performed in step S30, the AF operation is performed using the first AF data or the second AF data.

However, when using the conventional autofocus method as described above, when the object and the environment to be the subject change, the focus is not performed correctly, the shape of the subject is blurred, and the contrast of the contrast becomes unclear. For example, when a bright light existing in the night environment moves or a relatively dark pedestrian moves with respect to the light, using the same spot AF data, the focus may not be performed correctly.

Accordingly, an object of the present invention is to control the autofocus by detecting the peak data section that can be commonly used for general shooting and spotlight shooting in order to obtain a clear image regardless of the object and environment of the subject. A method and a photographing apparatus to which the method is applied are provided.

In accordance with another aspect of the present invention, an autofocus control method of an imaging apparatus includes determining whether an ascending section of an auto focus (AF) data and a processed data processed by the AF data match, the AF data and the processed data. Determining whether the falling section of the data coincides, and performing autofocus using the peak data section in which the rising section and the falling section coincide.

In this case, the AF data is any one of data obtained by extracting a component having a luminance lower than a specific frequency and then passing at least two high pass filters having different frequencies. do.

The processed data may be obtained by calculating a ratio between two data among the data obtained by passing the at least two high pass filters.

On the other hand, the photographing apparatus of the present invention is a focus lens that can be moved in the optical axis direction, a signal processing unit for detecting AF (Auto Focus) data by using the electrical luminance data of the optical image incident through the focus lens photoelectric conversion; And after detecting a peak data section by using the AF data detected by the signal processor and the processed data of the AF data, outputting a control signal for controlling the focus lens for performing autofocus. It includes a control unit.

The control unit may detect, as a peak data section of the focus lens, a point where the rising section and the falling section of the AF data and the processed data coincide.

Hereinafter, with reference to the accompanying drawings will be described in detail an embodiment of the present invention. However, in describing the present invention, when it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be abbreviated or omitted.

3 is a block diagram showing a schematic configuration of a photographing apparatus according to an embodiment of the present invention.

Referring to FIG. 3, the photographing apparatus 100 includes a lens unit 110, a lens driving unit 120, a CCD 130, a CDS / AGC / ADC 140, a DSP 150, a recording / reproducing unit 160. ), A controller 170, and a memory 180.

Although the configuration of the lens unit 110 is not shown in detail, the lens unit 110 includes a fixed lens, a zoom lens, an aperture, and a focus lens. Among these, the focus lens is provided to be movable in the optical axis direction to focus the optical image.

The lens driver 120 moves the zoom lens and the focus lens provided in the lens unit 110 in the optical axis direction. In particular, the lens driver 120 may change the position of the focus lens on the optical axis by moving the focus lens in the 'NEAR' direction or the 'FAR' direction under the control of the controller 170.

The CCD (Charge Coupled Device) 130 is an imaging device that converts and outputs an optical image of a subject into an electrical signal. In addition to the CCD 130, the MOS (Metal Oxide Semiconductor) type image pickup device may be used to make the spherical yarn of the photographing apparatus 100.

The CDS / AGC / ADC 140 removes noise from an electrical signal output from the CCD 130 by using a correlated double circuit, and uses an auto gain control circuit. After the gain is adjusted so that the level of the signal is kept constant, it is converted into a digital video signal using an analog-to-digital converter (ADC).

The digital signal processor (DSP) 150 performs signal processing such as AWB (Auto White Balance) on the image signal output from the CDS / AGC / ADC 140 and transmits the signal to the recording / reproducing unit 160. The image signal transmitted to the recording / reproducing unit 160 is reproduced in a display device such as an LCD or compressed in a predetermined format and recorded on a recording medium.

In addition, the DSP 150 generates AF (Auto Focus) data by using luminance data included in the image signal. That is, the DSP 150 extracts components below a specific frequency from the luminance data, and then passes two high pass filters having different frequencies, thereby providing two types of AF data (first AF data and second AF). Data). Here, the number of high pass filters may be two or more, and in this case, the AF data may also be two or more.

For example, the DSP 150 extracts only a frequency component of 2 MHz or less from the luminance data, passes a low pass filter that passes a relatively low frequency (150, 200, or 250 KHz), and detects the first AF data, and then relatively high frequency. The second AF data is detected by passing through a low pass filter that passes a frequency (750, 800, or 850 KHz).

The controller 170 calculates the processed data through the ratio (first AF data / first AF data) of the first AF data and the second AF data. Here, the controller 170 may calculate the processed data through not only the first AF data and the second AF data, but also data necessary for performing the autofocus operation.

The controller 170 detects a peak data section for performing autofocusing during spotlighting by using any one of the first AF data and the second AF data. That is, the controller 170 detects a section in which the rising section and the falling section of the AF data and the processing data coincide as the peak data section of the focus lens. In this case, it is more advantageous for the peak data section detection to use the second AF data detected through the low pass filter passing the relatively high frequency (750, 800, or 850 KHz).

The memory 180 stores data necessary for performing autofocus, and in particular, the detected peak data section is stored for use in autofocusing.

4A and 4B are diagrams illustrating the size of AF data according to a change in position of a focus lens in the photographing apparatus according to an exemplary embodiment.

4A is a diagram illustrating the size of AF data according to the change of the position of the focus lens when the object to be the subject is distinct, such as a day environment. Referring to the drawing, the peak data section coincides with the rising and falling sections of the second AF data and the processed data as the focus lens proceeds from 'NEAR' to 'FAR' direction, or 'FAR' to 'NEAR' direction. It is detected in the section F to be.

4B is a diagram illustrating the size of AF data according to a change in position of a focus lens when spotlight photography is performed in a night environment. Referring to the drawings, the section 1 is a section in which the second AF data and the processed data rise equally. And section (2) is a section in which the second AF data falls, and a section in which the processed data rises. That is, since the rising section and the falling section do not coincide, they are not detected as the peak data section.

Similarly, the sections 3 and 4 are not detected as the peak data section because the rising section and the falling section do not coincide. However, referring to the drawing, it can be seen that the section F detected as the peak data section coincides with the rising section and the falling section of the processed data.

5 is a flowchart illustrating an autofocus control method of a photographing apparatus according to an exemplary embodiment.

Referring to FIG. 5, first, the DSP 150 detects AF data (S200). That is, the DSP 150 extracts components below a specific frequency from the luminance data, and then passes two high pass filters having different frequencies to obtain two types of AF data (first AF data and second AF data).

Then, the lens driver 120 moves the focus lens until the rising section (S210). In other words, the controller 170 moves the focus lens in the 'NEAR' to 'FAR' direction or the 'FAR' to 'NEAR' direction until a rising section in which the second AF data detected from the luminance data increases. The driving unit 120 is controlled.

At this time, the control unit 170 determines whether the rising section of the second AF data and the rising section of the processed data match (S220). That is, the controller 170 calculates the processed data through the ratio (first AF data / first AF data) of the first AF data and the second AF data detected by the DSP 150, so that the processed data is stored during the rising period of the second AF data. Determine if it rises.

If it is determined that the rising section of the second AF data coincides with the rising section of the processed data, the lens driving unit 120 moves the focus lens until the falling section comes out (S230). That is, the controller 170 controls the lens driver 120 to move the focus lens in the same direction as in step S210 until a falling section in which the second AF data detected from the luminance data increases.

At this time, the controller 170 determines whether the falling section of the second AF data and the falling section of the processed data match (S240). That is, the controller 170 calculates the processed data through the ratio (first AF data / first AF data) of the first AF data and the second AF data detected by the DSP 150, so that the processed data is stored during the falling section of the second AF data. Determine if you are descending.

The controller 170 detects the peak data section (S250) and performs an AF operation (S250). In other words, the controller 170 detects a section in which the rising section and the falling section of the second AF data coincide with the rising section and the falling section of the processed data as the peak data section. The controller 170 controls autofocusing during normal shooting and spotlight shooting by using the detected peak data section.

As described above, according to the present invention, the peak data section in which the ascending and descending sections of the AF data and the AF data processed are detected and used for autofocus control, thereby irrespective of the subject and environment of the subject. A clear image can be obtained.

In addition, although the preferred embodiment of the present invention has been shown and described above, the present invention is not limited to the above-described specific embodiment, the technical field to which the invention belongs without departing from the spirit of the invention claimed in the claims. Anyone of ordinary skill in the art that various modifications can be made, as well as such changes are within the scope of the claims.

Claims (5)

Determining whether the ascending intervals of the AF data and the processed data processed the AF data match; Determining whether the falling section of the AF data and the processed data match; And And performing an auto focus using a peak data section in which the rising section and the falling section coincide with each other. The method of claim 1, The AF data may be any one of data obtained by extracting a luminance data of components below a specific frequency and then passing at least two high pass filters having different frequencies. Focus control method. The method of claim 2, And said processed data is obtained by calculating a ratio between two data among data obtained by passing said at least two high pass filters. A focus lens capable of moving in the optical axis direction; A signal processor which detects AF data by using electrical luminance data in which the optical image incident through the focus lens is photoelectrically converted; And After detecting the peak data section by using the AF data detected by the signal processing unit and the processed data processed the AF data, and outputs a control signal for controlling the focus lens for performing autofocus. And a control unit. The method of claim 4, wherein The control unit, And a point at which the rising section and the falling section of the AF data and the processed data coincide as the peak data section of the focus lens.

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