KR100822474B1 - Auto focus method for using luminunce data ? ?? data and apparatus thereof - Google Patents

Abstract

Provided are an autofocus method using luminance data and a photographing apparatus using the same. According to the present autofocus method, when the spot (SPOT) exists in the photographed subject based on the signal-processed output data, and the spot exists in the photographed subject, the luminance data and the AF (Auto Focus) are determined. Performing AF using the data. As a result, by performing auto focus (AF) using the luminance data and AF data calculated while moving the focus lens, the spot is weak or there are several spots, and the spot is at the edge of the subject. In addition, AF can be appropriately performed.

AF, AF data, spot, luminance data

Description

Autofocus method using luminance data and AF data and photographing apparatus using the same {Auto focus method for using luminunce data & AF data and apparatus

1 is a block diagram of a photographing apparatus to which the present invention is applicable;

2 is a flowchart provided to explain an autofocus method using luminance data and AF data when an image of a subject having a spot is to be photographed according to an embodiment of the present invention;

3 is a diagram illustrating magnitudes of luminance data and AF data calculated in FIG. 2 according to a change in position of a focus lens.

Explanation of symbols on the main parts of the drawings

110: lens unit 120: lens driving unit

150: DSP 170: control unit

180: memory

The present invention relates to an autofocus method and a photographing apparatus using the same, and more particularly, to an autofocus method using luminance data and AF data and a photographing apparatus to which the same is applied.

The photographing apparatus refers to an apparatus for recording an image signal generated by photographing a subject on a recording medium after predetermined signal processing. The imaging of the subject is performed by an imaging device provided in the photographing apparatus.

In order to capture the subject more clearly, the subject optical image formed on the image pickup device must be in focus. To this end, the photographing apparatus is provided with a focus lens for focusing on the subject optical image.

The photographing apparatus automatically adjusts the position of the focus lens to provide a function of automatically focusing on the object optical, which is called auto focus (AF). Specifically, AF is a function of focusing by generating contrast data by imaging the contrast of the captured image and positioning the focus lens at the position where the AF data is largest. When the subject is in focus, the shape of the subject is clear and the contrast is clear. Therefore, the AF data is increased.

On the other hand, when photographing a subject including a headlight, that is, a subject including a spot, distortion of AF data occurs.

Thus, when shooting a subject including a spot, clip data may be used in performing AF.

However, if the spot present in the subject is weak, there are multiple spots, or the spot is at the edge of the subject, the clip data value does not occur.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide an autofocus method using luminance data and AF data and an image photographing apparatus using the same in order to achieve an optimal focus even in a subject having a spot. In providing.

In accordance with an aspect of the present invention, an autofocus method includes: determining whether a spot exists in a photographed subject based on data processed by signal processing; And if it is determined that a spot exists in the photographed subject, performing AF using luminance data and AF (Auto Focus) data.

The AF performing step may include performing AF by moving the focus lens such that luminance data is less than or equal to a predetermined value and AF data is greater than or equal to a predetermined value.

The AF performing step may include moving the focus lens to a position having the maximum value of the AF data near the position having the lowest value of the luminance data.

The data processed and output by the signal may include at least one of luminance data, clip data, and auto gain control (AGC) data.

On the other hand, according to the present invention, the photographing apparatus includes: a digital signal processor (DSP) for generating data from an image signal generated by capturing an optical image of a subject incident through a focus lens; And determining whether a spot exists in the photographed subject based on the data output from the DSP, and if it is determined that the spot exists, performing AF using the luminance data and the AF (Auto Focus) data received from the DSP. It includes a control unit.

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

1 is a block diagram of a photographing apparatus to which the present invention is applicable. Referring to FIG. 1, the photographing apparatus 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, and a controller. 170, and a memory 180.

The lens unit 110 allows the optical image of the subject to be formed on the CCD 130. The lens unit 110 is provided with a focus lens (not shown) that is movable in the optical axis direction to focus the optical image formed on the zoom lens (not shown) and the CCD 130.

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 changes the position of the focus lens on the optical axis by moving the focus lens provided in the lens unit 110 in the 'Near' direction or the 'Far' direction, under the control of the controller 170 to be described later. You can.

The CCD 130 (Charge Coupled Device) 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 imaging device may be implemented as the photographing apparatus. The CDS / AGC / ADC 140 removes noise from the output signal of the CCD 130 by using a correlated double sampling circuit, and uses an auto gain control circuit. Gain is adjusted so that the level of the signal is kept constant, and converted into a digital video signal using an analog to digital conveter (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 applies it to the recording / reproducing unit 160. The recording / reproducing unit 160 reproduces the signal processed image signal on a display device (not shown) such as an LCD (Liquid Crystal Display) or compresses it to a predetermined format and records the image signal on a recording medium (not shown).

In addition, the DSP 150 generates AF (Auto Focus) data, luminance data, AGC data, and clip data from the image signal in the signal processing process and applies them to the controller 170.

The controller 170 determines whether a spot exists in a subject to be photographed using at least one of luminance data, AGC data, and clip data generated by the DSP 150, and if it is determined that the spot exists, the luminance data. And autofocus using AF data. The autofocus method will be described later.

Luminance data and AF data output from the DSP 150 are stored in the memory 180. In addition, the memory 180 stores data necessary for performing autofocus.

Hereinafter, a method of autofocusing using luminance data and AF data will be described. 2 is a flowchart provided to explain an autofocus method using luminance data and AF data when a subject having a spot is to be photographed according to an exemplary embodiment of the present invention, and FIG. 3 is calculated from FIG. The magnitudes of the luminance data and the AF data are shown in accordance with the change in the position of the focus lens.

First, the controller 170 determines whether the photographing mode in which the subject is to be captured is taken (S305).

If it is determined in the shooting mode (S305-Y), the control unit 170 receives the luminance data, AGC data, and clip data generated in the DSP 150 (S310). Specifically, the DSP 150 generates luminance data, clip data, and AGC data based on the image signal output from the CDS / AGC / ADC 140, and controls the generated luminance data, clip data, and AGC data. Is applied.

The controller 170 determines whether a spot exists in the photographed subject by using at least one of luminance data, clip data, and AGC data applied from the DSP 150 (S315). Specifically, when the luminance data value and the clip data value are low or the AGC data value is high, the controller 170 determines that a spot exists in the photographed subject.

If it is determined that there is a spot (S315-Y), the controller 170 receives luminance data from the DSP 150 while moving the focus lens (S320). In detail, the controller 170 controls the lens driver 120 to move the focus lens, and the DSP 150 generates luminance data from the image signal photographed according to the moving region of the focus lens, and outputs the luminance data to the controller 170. do.

The controller 170 determines whether the luminance data value is minimum (S325).

The determination of whether the luminance data value is minimum is determined based on whether the luminance data value decreases or increases based on the plurality of luminance data values received by the controller 170.

For example, it is assumed that the focus lens moves from 'Near' to 'Far' as shown in FIG. 3. While the focus lens moves from the 'Near' to the 'P1' position, the luminance data value decreases. On the other hand, while the focus lens moves from the 'P1' position to 'Far', the luminance data value increases. Accordingly, the controller 170 determines that the luminance data value is minimum when the focus lens is at the 'P1' position.

If it is determined that the luminance data value is not the minimum (S325-N), the controller 170 moves the focus lens by controlling the lens driver 120 in a direction in which the luminance data value decreases (S330). The controller 170 moves the focus lens in a direction in which the luminance data value decreases, and then receives the luminance data from the DSP 150 again to determine whether the luminance data value is minimum (S320 and S325). That is, the controller 170 moves the focus lens in the direction of the 'P1' position from the position where the current focus lens is located, and then receives the luminance data to determine whether the luminance data value is minimum.

On the other hand, if it is determined that the luminance data value is the minimum (S325-Y), the control unit 170 receives AF data from the DSP 150 while moving the focus lens near the position having the minimum value of the luminance data (S335). .

That is, as shown in FIG. 3, the case where the luminance data is minimized is when the focus lens is located at the point 'P1' existing in the 'B area'. Accordingly, the controller 170 receives the AF data generated according to the movement of the focus lens from the DSP 150 while moving the focus lens in the 'B area' near 'P1'.

The controller 170 determines whether the authorized AF data value is the maximum (S340).

The determination of whether the AF data value is maximum is determined based on whether the control unit 170 increases or decreases the value of the AF data based on the plurality of received AF data values.

For example, as shown in FIG. 3, it is assumed that the focus lens moves in the 'B area' which is near the position where the luminance data value is minimum. The AF data value increases while the focus lens moves from the 'near' of 'a' to the 'P2' point. On the other hand, while the focus lens moves from the point 'P2' to the 'far of area c', the AF data value decreases. Accordingly, the controller 170 determines the point 'P2' as the position where the AF data value is maximized.

If it is determined that the AF data value is not the maximum (S340-N), the controller 170 controls the lens driver 120 to move the focus lens in the direction in which the AF data increases (S345). The controller 170 moves the focus lens in a direction in which the AF data value increases, and then receives AF data from the DSP 150 again to determine whether the AF data value is the maximum (S320, S325), that is, the controller 170. ) Moves the focus lens in the direction of the 'P2' position from the current position of the focus lens, and then receives AF data to determine whether the AF data value is the maximum.

However, if it is determined that the AF data value is the maximum (S340-Y), the control unit 170 determines the position of the focus lens when the AF data value becomes the maximum, the position where the subject is in focus, and the AF data value is determined. The focus lens is stopped at the maximum position (S350). That is, the controller 170 moves the focus lens to the 'P2' point and stops it. As a result, the controller 170 completes the AF operation.

On the other hand, when it is determined that no spot exists in the subject, the controller 170 receives the AF data generated by the DSP 150 while moving the focus lens. At this time, since no spot exists in the subject, luminance data is not necessary in performing AF. AF is determined by determining a position where the AF data value is maximum based on the received AF data, and moving the focus lens to a position where the AF data value is maximum to stop.

As described above, according to the present invention, even when it is desired to photograph the subject in which the spot exists, the optimum focus can be achieved by using the luminance data and the AF data.

In addition, although the preferred embodiment of the present invention has been shown and described above, the present invention is not limited to the specific embodiments described above, but the technical field to which the invention belongs without departing from the spirit of the invention claimed in the claims. Of course, various modifications can be made by those skilled in the art, and these modifications should not be individually understood from the technical spirit or the prospect of the present invention.

Claims (5)

In the autofocus method of the photographing apparatus, Determining whether a spot exists in the photographed subject based on the data processed and output; And If it is determined that a spot exists in the photographed subject, performing AF by moving a focus lens by using luminance data and AF (Auto Focus) data; The AF performing step, And performing AF by moving the focus lens so that the luminance data is equal to or less than the predetermined value and the AF data becomes equal to or greater than the predetermined value. delete The method of claim 1, The AF performing step, Moving the focus lens to a position having a maximum value of the AF data near a position having a minimum value of the luminance data. The method of claim 1, The signal processed and output data is, And at least one of luminance data, clip data, and auto gain control (AGC) data. A digital signal processor (DSP) for generating data from an image signal generated by capturing an optical image of a subject incident through a focus lens; And The controller determines whether a spot exists in the photographed subject based on the data output from the DSP, and if it is determined that the spot exists, the control unit performs AF using the luminance data and the AF (Auto Focus) data received from the DSP. Including; The control unit, And focusing by moving the focus lens so that the luminance data is less than or equal to the predetermined value and the AF data is greater than or equal to the predetermined value.

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