KR100319863B1 - A method of determining a monochromatic subject, a method of adjusting a white balance using the same, and a suitable device - Google Patents

Abstract

The present invention relates to a white balance of a video camera. More particularly, the present invention relates to a monochromatic subject judging method, a white balance adjusting method, and a device suitable for the method.

A white balance adjustment method of the present invention is a method of adjusting a white balance of a video camera, comprising the steps of: determining whether a monochromatic subject exists; If the result of the determination is a monochromatic subject, selecting one of the prepared adjustments according to the lighting condition to adjust the white balance; And a step of extracting a white region when the determination result is not a monochromatic subject and adjusting white balance of the extracted white region.

The white balance adjustment method according to the present invention has an effect of preventing erroneous white balance adjustment from being performed by selecting one of the white balance adjustment values set in accordance with the illumination condition in the case of a monochrome subject.

Description

A method of determining a monochromatic subject, a method of adjusting a white balance using the same, and a suitable device

The present invention relates to a white balance of a video camera, and more particularly, to a method and apparatus for determining a monochromatic subject that interferes with white balance adjustment, and a white balance adjustment method using the same.

In a video camera, the color of a photographed subject differs depending on lighting conditions. This is because the energy distribution of each wavelength of R, G, and B varies depending on the lighting condition, and is expressed as a color temperature.

1 is a graph showing the energy distribution of each wavelength of RGB according to the color temperature. 1 shows a color temperature of about 3000.K, a thick solid line shows a color temperature of about 5600.K, and a thin solid line shows a color temperature of about 7000.K.

The color temperature of 3000.K corresponds to the lighting condition of the incandescent bulb of the room, the color temperature of 5600.K corresponds to the lighting condition of the outdoor sunlight, and the color temperature of 7000.K corresponds to the lighting condition of the fluorescent lamp.

When a subject is photographed with a video camera, the energy distribution of each wavelength of RGB incident from the subject varies depending on lighting conditions even if the subject is the same, so that the color of the subject changes depending on lighting conditions.

To resolve this, white balance adjustment is necessary. The white balance adjustment is to adjust the gain of RGB according to the lighting condition based on the white produced by the RGB synthesis so that the same subject can be expressed with the same color.

White is represented by 0.3R + 0.6G + 0.1B. Therefore, since the RGB signals obtained by picking up a white subject have different energy levels according to the lighting conditions, it is the white balance adjustment that the gain of these signals is adjusted so as to become the normal white obtained by the combination of these signals.

It is preferable to perform the white balance every time the illumination condition is changed. When white balance is adjusted, a white region is detected in a state of photographing a subject including white, and white balance adjustment is performed based on the detected white region.

In order to discriminate the white region, the video camera selects a portion having a relatively high luminance. However, in practice, a portion having a single color is often recognized as a white region, resulting in a problem that an incorrect adjustment value is generated.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for discriminating a monochromatic subject.

Another object of the present invention is to provide an apparatus suitable for the monochromatic subject discriminating method.

It is still another object of the present invention to provide an improved white balance method for preventing monochromatic overtracking.

1 is a graph showing the energy distribution of each wavelength of RGB according to the color temperature.

2 is a flowchart illustrating a method of discriminating monochromatic colors according to the present invention.

Figs. 3A to 3B are shown for illustrating an example of a subject area in the flowchart shown in Fig.

FIG. 4 is a schematic view showing a method of extracting a region excluding a peripheral portion of a screen.

5 is a flowchart illustrating an example of determining whether a monochromatic subject exists in the region shown in FIG.

6 is a block diagram showing the configuration of an apparatus for performing the method shown in FIG.

7 is a flowchart illustrating a white balance adjustment method according to the present invention.

FIG. 8 is a block diagram showing a configuration of a video camera that performs a white balance adjustment method according to the present invention.

According to another aspect of the present invention, there is provided a method for determining a monochromatic subject, comprising the steps of: calculating a scattering degree of a luminance signal on a screen of an object; Comparing the scatter value with a predetermined threshold value; And determining that the object is a monochromatic subject if the scattering result as a result of the comparing process is smaller than a predetermined threshold value.

According to another aspect of the present invention, there is provided a monochromatic subject determination apparatus, comprising: a block divider for storing a luminance signal of a frame unit and block-outputting the luminance signal; A block average value calculation unit for calculating an average value of luminance signals for each block output from the block divider; An average value calculator for receiving the output of the block average value calculator and calculating an average value thereof; A scatter calculator operable to receive the output of the average value calculator for each block and to calculate the dispersion of the outputs; And a comparison unit for determining whether a monochrome subject is present according to the average value output from the average value calculation unit and the magnitude of the scattered output from the scatter calculator.

According to another aspect of the present invention, there is provided a white balance adjustment method for a video camera, including the steps of: determining whether a monochromatic subject exists; If the result of the determination is a monochromatic subject, selecting one of the prepared adjustments according to the lighting condition to adjust the white balance; And a step of extracting a white region when the determination result is not a monochromatic subject and adjusting white balance of the extracted white region.

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

2 is a flowchart illustrating a method of discriminating monochromatic colors according to the present invention. In the monochromatic discriminating method according to the present invention, the scattering degree of the luminance signal is obtained in the subject area, and whether or not a monochromatic subject exists is determined based on the magnitude of the obtained scattering degree. Specifically, if the scattering degree of the luminance signal is smaller than the predetermined threshold, it is discriminated as a monochromatic subject. Here, an average value of the luminance signal in the subject area is used as the threshold value.

Shadows L Is calculated by means of meadn deviation and standard deviation.

Average deviation M _d And standard deviation S _d Lt; RTI ID = 0.0 > Y _i , And the average value of the luminance signal in the subject area is K If you say

,

Standard Deviation S _d The

Respectively.

Here, n is the number of pixels in the subject area.

In the method shown in Fig. 2, first, an average value of luminance signals in the subject area is obtained (S200). Here, the subject area refers to an area occupied by the subject, but may also be an area including the subject. The subject area is determined by contour extraction. The method of using the area including the subject is simple and the area except the peripheral part is used on the screen. In most cases, since the subject is located near the center of the screen, the area including the subject can be approximated only by removing the peripheral portion.

First, an average value of luminance signals is obtained in the subject area (S200)

And obtains a scattering degree of the luminance signal in the subject area (S210)

The average value of the luminance signal obtained in S200 is compared with the dispersion of the luminance signal obtained in S210 (S220)

If the scattering degree of the luminance signal is smaller than the predetermined threshold value, for example, the average value of the luminance signal, it is determined as a monochromatic subject (S230)

Figs. 3A to 3B are shown for illustrating an example of a subject area in the flowchart shown in Fig. 3A shows an example of a region (shaded portion) 300 occupied by a subject and FIG. 3B shows an example of a region (shaded portion) 310 that includes a subject 320. FIG. The example shown in Fig. 3A is set by extracting the outline of the subject and extracting the area included in the outline. The example shown in FIG. 3B is set by extracting an area excluding the periphery of the screen.

FIG. 4 is a schematic view showing a method of extracting a region excluding a peripheral portion of a screen. As shown in FIG. 4, the full screen 200 is divided into 64 sub-screens A _0.0 ~ A _7.7 ), And an area excluding the sub-screens of the peripheral part among the divided sub-screens A _1,1 ~ A _6.6 .

5 is a flowchart illustrating an example of determining whether a monochromatic subject exists in the region shown in FIG.

First, A _1,1 ~ A _6.6 The average value of the luminance signal K (S500)

A _1,1 ~ A _6.6 Of the luminance signal D (S510) Here, it is possible to exclude a block having a value that deviates from a predetermined range in calculation of the dispersion.

The average value of the luminance signals obtained in S500 K And the scattering of the luminance signal obtained in S510 D (S520)

D end K Is determined to be a monochromatic subject (S530)

6 is a block diagram showing the configuration of an apparatus for performing the method shown in FIG. The apparatus shown in Fig. 6 includes a block divider 60, an average value calculator 62, an average value calculator 64, a scatter calculator 66, and a comparator 68.

The block divider 60 divides an input video signal into blocks and outputs the blocks. This block divider 60 may be implemented by a frame memory and an address generator. The frame memory stores the input video signal in frame units. The address generator divides the video signal stored in the frame memory according to the block segment, and sequentially outputs the divided sub-blocks. At this time, the subblocks in the peripheral part are not outputted.

The block-by-block average value calculator 62 calculates the average value of the luminance signals of the sub-blocks sequentially output from the block divider 60.

The average value calculator 64 and the scatter calculator 66 calculate an average value and a scatter value on a screen basis from the average values of the luminance signals for each block output from the average value calculator 62 for each block.

The comparator 68 compares the average value provided by the average value calculator 64 and the scatter value provided by the scatter calculator 66. The comparison result of the comparison unit 68 indicates whether or not a monochromatic subject exists. That is, if the scattering degree is smaller than the average value, the comparator 68 outputs a " high " signal indicating that it is a monochromatic subject.

7 is a flowchart illustrating a white balance adjustment method according to the present invention. The method shown in FIG. 7 selects one of the prepared adjustments according to the illumination condition according to whether a monochromatic subject exists or not, thereby adjusting white balance or performing normal white balance adjustment.

First, it is determined whether or not the subject is a monochromatic subject. (S700) Whether or not a monochromatic subject is present is determined by the method shown in Fig. 2 and the apparatus shown in Fig. That is, if the scattering degree of the luminance signal of the subject is smaller than the predetermined threshold value, it is determined that the subject is a monochromatic subject. The concept of such a monochromatic subject also includes a white subject.

If it is determined in step S700 that the object is not a monochrome subject, a normal white balance operation is performed (S710). That is, a white area is extracted from the screen and a gain of the RGB signal is adjusted referring to the extracted white area.

If it is determined that the subject is a monochromatic subject in S700, the lighting condition is determined (S720)

Select one of the prepared adjustments according to the lighting conditions to adjust the white balance. The lighting conditions are determined by the degree of opening of the camera iris. The aperture of the camera is closed as the illumination becomes brighter, and as the illumination becomes darker, the aperture is opened, so that the illumination state can be determined by determining the degree of opening of the aperture.

That is, when the degree of opening of the diaphragm is equal to or greater than a predetermined threshold value, it is determined as an outdoor sunlight condition and adjusted to a white balance adjustment value corresponding to a color temperature of 5600K (S730). If the aperture value is less than the threshold value, And adjusts to the white balance adjustment value corresponding to 3000.K color temperature (S740).

The degree of opening of the diaphragm is detected by the Hall element attached to the lens. The Hall element detects magnetic force as the diaphragm opens and closes, outputs it as a voltage value, and is commonly used in video cameras. In the outdoor condition, since it is brighter than the room, the aperture is closed and the hole value is lowered.

According to the monochromatic subject discrimination method of the present invention, a white subject is also determined as a monochromatic subject. In the case of a white subject, it is correct to perform normal white balance adjustment on the subject, but since the prepared white balance adjustments are set in the state of picking up a white subject, approximate values can also be obtained by the white balance adjustment method of the present invention.

FIG. 8 is a block diagram showing a configuration of a video camera that performs a white balance adjustment method according to the present invention. 8 includes a lens unit 80, a solid-state image pickup device 82, a double correlation sampling unit 84, an A / D conversion unit 86, a signal processing unit 88, An automatic gain control section 92, a shutter control section 94, a timing generator 96, a diaphragm driving section 98, a diaphragm control section 100, and a Hall detector 102.

Here, the shutter control section 94 controls the shutter timing by soft operation. Specifically, the timing of the shutter is controlled by adjusting the readout timing of the solid-state image sensor 82 through the timing generator 96.

The white balance operation is performed through the signal processing unit 88, the microprocessor 90, the automatic gain control unit 92, and the hall detector 102.

In carrying out the white balance operation according to the present invention, the signal processing unit 88 calculates an average luminance value and a scattering degree of an area including a subject on the screen. The microprocessor 90 compares the average brightness value provided by the signal processing unit 88 with the scatter and determines whether or not a monochromatic subject exists.

In the case where the object is not a monochrome subject, that is, when the scattering degree is equal to or larger than the average luminance value, a normal white balance operation is performed. In performing a normal white balance operation, the signal processing unit 88 extracts a white region from the screen and calculates the ratio of R / G / B or R-Y / B-Y to the extracted region. The microprocessor 90 controls the gain of R / G / B through the automatic gain control unit 92 so that the ratio of R / G / B or RY / BY output from the signal processing unit 88 satisfies a predetermined condition do.

In the case of a monochromatic subject, that is, when the scattering degree is smaller than the average luminance value, one of the stored white balance adjustment values is selected and output. Here, the pre-stored white balance adjustment values are RGB gain adjustment values obtained by taking white balance on a white subject in typical lighting conditions. Typical lighting conditions can be 5600.k for outdoor sunlight and 3000.k for indoor incandescent bulb lighting.

The selection criterion for the gain adjustment is the open state of the aperture. The iris is closed as the amount of incident light increases. That is, it is more open in the outdoor sunlight condition than in the incandescent bulb lighting condition of the room. The boundary values of these two conditions are experimentally determined and indoor and outdoor conditions are determined by the obtained experimental values. In the example of the present invention, the value detected by the hall detector 102 is " 8 " which is the middle value of the detection range. However, this reference value may vary depending on the apparatus.

If the value detected by the hall detector 102 is equal to or larger than "8", it is determined that the condition is the outdoor sunlight illumination condition, and the gain adjustment values corresponding thereto are applied to the automatic gain control unit 92.

When the value detected by the hall detector 102 is smaller than "8", it is determined that the condition is the incandescent bulb lighting condition of the room, and the gain adjustment values corresponding thereto are applied to the automatic gain control unit 92.

Through such operation, the apparatus shown in FIG. 6 outputs gain adjustment values for each illumination condition prepared in advance, without performing a normal white balance operation when it is determined that the object is a monochrome subject. In this manner, the normal white balance operation is not performed on the monochromatic subject, thereby preventing the off-tracking from occurring.

As described above, the white balance adjustment method according to the present invention has an effect of preventing erroneous white balance adjustment from being performed by selecting one of the white balance adjustment values set in accordance with the lighting condition in the case of a monochrome subject.

Claims (15)

Calculating a scattering degree of a luminance signal on a screen of a subject; Comparing the scatter value with a threshold value; And determining the monochromatic subject as a result of the comparison if the scattering degree is less than a predetermined threshold value. The monochromatic subject determination method according to claim 1, wherein the calculation of the scatter factor is performed on the luminance signal of the area occupied by the subject. The method according to claim 1, wherein the calculation of the scatter factor is performed on a luminance signal of a region including a subject and excluding a peripheral portion of a screen. 2. The method according to claim 1, wherein the threshold value is an average value of luminance signals in a region considered in the calculation of the dispersion. A block divider that stores a luminance signal of a frame unit, blocks the luminance signal, and outputs the block signal; A block average value calculation unit for calculating an average value of luminance signals for each block output from the block divider; An average value calculator for receiving the output of the block average value calculator and calculating an average value thereof; A scatter calculator operable to receive the output of the average value calculator for each block and to calculate the dispersion of the outputs; And And a comparison unit for determining whether a monochromatic subject exists based on the average value output from the average value calculation unit and the magnitude of the scattered image output from the scatter calculator. 6. The apparatus according to claim 5, wherein the block dividing unit performs blocking on an area excluding the peripheral part in the frame picture. 6. The apparatus according to claim 5, wherein the block average value calculation unit performs an average calculation on blocks excluding blocks located in the periphery of a screen among the blocks output from the block divider. A method of adjusting a white balance of a video camera, Determining whether a monochromatic subject exists; If the result of the determination is a monochromatic subject, selecting one of the prepared adjustments according to the lighting condition to adjust the white balance; And Extracting a white region when the determination result is not a monochrome subject, and adjusting a white balance based on the extracted white region. 9. The method according to claim 8, wherein the monochromatic subject determination step Calculating a scattering degree of a luminance signal on a screen of a subject; Comparing the scatter value with a threshold value; And determining that the subject is a monochromatic subject if the scattering degree is less than a predetermined threshold value. 10. The white balance adjustment method according to claim 9, wherein the calculation of the scatter factor is performed on the luminance signal of the area occupied by the subject. 10. The white balance adjustment method according to claim 9, wherein the calculation of the scatter factor is performed on a luminance signal of a region including a subject and excluding a peripheral portion of the screen. 10. The white balance adjustment method according to claim 9, wherein the threshold value is an average value of luminance signals in a region considered in the calculation of the dispersion. 9. The method of claim 8, wherein the step of selecting one of the prepared adjustments according to the illumination condition and adjusting the white balance Detecting a degree of opening of the camera iris; Comparing the calculated aperture value with a reference value for determining an illumination condition; And And adjusting white balance by selecting one of the prepared adjustments according to indoor and outdoor conditions according to a result of the comparing process. 14. The white balance adjustment method according to claim 13, wherein the prepared adjustments are obtained by performing white balance adjustment in a state in which a white subject is imaged under a predetermined lighting condition. 15. The white balance adjustment method according to claim 13 or 14, wherein the lighting conditions are outdoor solar light and incandescent bulb conditions.