JPH0787513A - Method and device for video signal processing - Google Patents

Abstract

PURPOSE:To rationallize the processing of a signal expressing color information like a color difference signal of a video signal used in an image pickup part of a video camera or the like. CONSTITUTION:A suppression level setting means 1 obtains a suppression level HL, by which the color component of a color component signal CR should be suppressed, from a white balance gain WG which adjusts color components of the video signal by multiplying to adjust the white balance. A color component suppressing means 2 suppresses the color component of the color component signal CR in accordance with the suppression level HL to obtain a processed signal CS.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal processing device and a video signal processing method, and more particularly, it processes a signal representing a color component such as a color difference signal of a video signal used in an image pickup unit such as a video camera. Apparatus and processing method.

[0002]

2. Description of the Related Art Generally, a color CCD (Charge Coupled Device) used as an image pickup section of a video camera or the like.
A color filter for detecting a color is attached to the light receiving section of. For example, a two-color filter (Ye [yellow], Cy
[Cyan]) and a color filter obtained by superimposing them (G (green) in the case of Ye and Cy) for a total of three colors are used to detect the color (FIG. 5). The color detection sensitivities of the three color filters are not uniform, and the transmittance of the two G filters that are stacked is the lowest, so that the color detection sensitivity is also the lowest.

By the way, in recent years, a CCD camera using a conventional analog system is being changed to a CCD camera using a digital system which can be easily adjusted. In the following, a color signal when using such a color CCD will be described. The video signal processing in the digital system will be described. First, white balance will be described. The white balance is to make the levels of R, G, and B signals detected through the Ye, Cy, and G filters uniform when the CCD is irradiated with white light. The subject is represented as white, and an image with normal color is obtained. Therefore, in order to realize this white balance, it is necessary to perform processing for applying an appropriate gain to the output level of each color component.

A specific example is shown below. The graph of FIG. 6 shows CCs corresponding to filters of three colors of Ye, G, and Cy.
7 is a graph showing the level of the output voltage obtained from D.
Note that SL in FIG. 6 indicates a saturation value of the output level of the CCD [hereinafter referred to as CCD saturation level], and even if the light corresponding to the illuminance higher than this is irradiated, the CCD output level can be higher than this. It is a limit value that there is no. In addition, since Ye = R + G and Cy is Cy = B + G,
R and B can be obtained by R = Ye-GB and B = Cy-G, respectively.

It is assumed that the output level of the CCD when a white subject is imaged at a certain color temperature is as shown in FIG. R component included in the signal corresponding to the Ye filter,
If the ratio of the G component of the signal corresponding to the G filter and the B component included in the signal corresponding to the Cy filter is R: G: B = 2: 4: 1, these components should be the same. To do this, multiply the R component by 2, multiply the G component by 1, and multiply the B component by 4. Therefore, the gain R to be applied to each component
The ratio of g, Gg and Bg is Rg: Gg: Bg = 2: 1: 4. Hereinafter, these Rg, Gg, and Bg are referred to as a white balance gain (WG).

The phenomenon of high brightness pseudo signal, so-called highlight green, which occurs when the white balance of the video signal is lost when a high brightness subject is imaged, will be described below. C when irradiated with white light at a certain color temperature
The output level of the CD is as shown in FIG. 7, the ratio of the R component, the G component and the B component is R: G: B = 2: 4: 1, and the ratio of the white balance gain is Rg: Gg. : Bg = 2: 1: 4 (FIG. 7). FIG. 8 shows a state in which only the illuminance is doubled in this state. Ye in this state
Assuming that the output level of 1 has just reached the CCD saturation level (SL), the other output levels have not yet reached the CCD saturation level (SL), so the ratio of the R component, G component, and B component is R: G: B = 2: 4: 1 is maintained, and an output signal representing white is obtained by applying a white balance gain having a ratio of Rg: Gg: Bg = 2: 1: 4. However, if only the illuminance is tripled in the state of FIG. 7 and, as shown in FIG. 9, the CCD saturation level (SL) is exceeded for all the filters, it is represented by (Ye-G) and (Cy-G). R component
The B component is not output at all, and only the G component signal is output. As a result, a phenomenon occurs in which white light is colored green when the brightness is increased on the image display. This is called highlight green. As a method for suppressing such highlight green, YL = (Ye + G + Cy) / 3 [hereinafter, referred to as a low-frequency luminance signal], which is an average value of each signal of Ye, G, and Cy, is detected, and this low A method is adopted in which the color component is cut when the band luminance signal (YL) exceeds a certain level (hereinafter, this level is referred to as a suppression level (HL ')).

[0007]

However, according to the video signal processing method according to the conventional example, the suppression level is dealt with by setting the suppression level to a low constant value.
0, all color components have CCD saturation level (S
L) has not been reached, and the low-frequency luminance signal (YL) is at the suppression level (H
If it exceeds L '), the color component is cut off.
For this reason, even the color that should have been originally expressed is cut, the color information is not effectively utilized, and there is a problem that the color display on the screen is not effective.

[0008]

The present invention has been made in view of the above-mentioned drawbacks of the related art, and a white balance gain (W) for adjusting the white balance by multiplying each color component of a video signal.
G), the suppression level (HL) is set, and the color component of the color component signal (CR) is suppressed according to the suppression level (HL), thereby making the color component of the color component signal (CR) effective. The present invention provides a video signal processing device and a video signal processing method that can effectively utilize the color display of a screen.

[0009]

[Operation] According to the video signal processing device of the present invention, as shown in FIG. 1, it comprises a suppression level setting means (1) and a color component suppressing means (2). For example, the white balance gain (W
G), the suppression level (HL) for suppressing the color component of the color component signal (CR) is set, and the suppression level (HL)
Based on the above, the processed signal (CS) in which the color component of the color component signal (CR) is suppressed is output by the color component suppression means (2). Therefore, regardless of the value of the white balance, a change is made based on the white balance gain (WG) as compared with the conventional case in which the suppression level (HL ′) is set to a lower fixed value with a margin. It is possible to set the suppression level (HL) while performing the above.

Further, according to the video signal processing method of the present invention, the suppression level (H) for suppressing the color component of the color component signal (CR) based on the white balance gain (WG).
L) is set, and the color component of the color component signal (CR) is suppressed based on the suppression level (HL). Therefore, the suppression level can be optimally set according to the state of the color component signal (CR) while maintaining the white balance, so that, for example, all the color components are at the CCD saturation level (S
It is possible to set the suppression level (HL) so that it is not necessary to cut the color component based on the white balance gain (WG) when it is in a state where L) is not reached and accurate color can be expressed. Thus, it is possible to effectively utilize the color information and validate the color display on the screen.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A video signal processing apparatus and a video signal processing method according to embodiments of the present invention will be described below with reference to the drawings. The video signal processing device according to the embodiment of the present invention is a partial circuit of a color signal processing circuit as shown in FIG. 2, and processes color components of a video signal output from a CCD via a CDS, It is a device that suppresses highlight green while maintaining white balance. The video signal processing device described below essentially requires one for each of the three colors of R, G, and B (or two colors of R and B), but in the present embodiment, the R system circuit is used. Only the configuration will be described, and the other systems have the same configuration and operation, and the description will be omitted.

As shown in FIG. 2, the circuit comprises a gain setting circuit (11), a clipping circuit (12) and a color component suppressing circuit (13), and a color difference signal (YL) is generated based on the low-frequency luminance signal (YL). This is a circuit that cuts the color components when highlight green appears while maintaining the white balance of the chroma signal (CR) indicating the color components such as RY). The gain setting circuit (11) and the clipping circuit (12) constitute an embodiment of the suppression level setting means (1), and the color component suppressing circuit (13) is equivalent to the color component suppressing means (2). This is an example.

The gain setting circuit (11) adjusts the white balance of the color components of the video signal, based on the white balance gain (WG) which is the gain to be applied to the color signals of each primary color system. ) Is generated and output to the clip circuit (12). The white balance gain (WG) is generated so that the integrated value of the color difference signals (RY) in one screen unit approaches a predetermined value. The clipping circuit (12) clips the low-frequency luminance signal (YL) based on the reference gain (SC), sets a suppression level (HL) that is a level for suppressing the color component, and sets the color component suppression circuit (1).
It is a circuit for outputting to 3). Color component suppression circuit (13)
Is based on the suppression level (HL), the chroma signal (C
R) is a differential amplifier circuit that cuts the color component. In addition,
The chroma signal (CR) is an example of the color component signal (CR).

According to the video signal processing apparatus in the embodiment of the present invention, as shown in FIG. 2, the suppression level (the suppression level for suppressing the color component of the color component signal (CR) based on the white balance gain (WG). Suppression level setting means (1) for setting HL) and color component suppression means (2) for outputting a processed signal (CS) in which the color component of the color component signal (CR) is suppressed based on the suppression level (HL). It has and. Therefore, the white balance gain (W
The suppression level (H
L) is set to a lower constant value than in the conventional case, the suppression level (H) is a level for suppressing the color component based on the white balance gain (WG).
It becomes possible to set while changing L).

The video signal processing method according to the embodiment of the present invention will be described below, supplementing the operation of the apparatus.
First, the suppression level (HL) based on the white balance gain (WG) obtained based on the color difference signal (CY).
To set. At this time, first, the gain setting circuit (11)
The white balance gain (WG) previously obtained on the basis of the color difference signal (CY) is input to, and the gain of the gain setting circuit (11) is set by this, and at the same time, the gain setting circuit (11) The DC voltage of a constant value input to this white balance gain (WG)
Is applied to the clip circuit (12) as a reference gain (SC) while going up and down corresponding to. Next, the clip circuit (1
2) Low gain signal (YL) with reference gain (SC)
Is entered. The clip circuit (12) compares the reference gain (SC) with the low-frequency luminance signal (YL), and the low-frequency luminance signal (YL) equal to or lower than the reference gain (SC) is clipped, as shown in FIG. Suppression level (HL)
Is set. Next, the color component of the chroma signal (CR) is cut based on the suppression level (HL). At this time, the chroma signal (CR) and the suppression level (HL) are input to the color component suppression circuit (13), and the color component of the chroma signal (CR) is suppressed based on the suppression level (HL). The higher the suppression level (HL), the greater the degree of suppression of color components, and the maximum suppression level (HL) is 10
The 0% color component is cut and the output signal (CS) becomes 0. At the minimum value of the suppression level (HL), the color component is not cut at all and the chroma signal (CR) is output as the output signal (CS).
Will be output as is.

As described above, according to the video signal processing method of the embodiment of the present invention, the suppression level (HL), which is the level at which the color component of the video signal should be cut based on the white balance gain (WG). Is variable. Therefore, unlike the conventional method in which the suppression level (HL) is fixed and set to a low value, while maintaining the white balance,
In addition, the suppression level (H
Since L) can be optimally set, the color information of the chroma signal (CR) can be effectively used.

An example thereof is shown in FIG. FIG. 4 is a graph showing the difference in suppression level set by the method of the conventional example and the method of the present embodiment. As shown in FIG. 4, Ye, G, Cy
Although the average value of each of the signals becomes high, if none of them has reached the CCD saturation level (SL) (that is, if highlight green does not occur), the conventional method uses Ye, G, YL, which is the average value of each Cy signal,
Since the low band luminance signal (YL) represented by the formula (Ye + G + Cy) / 3 exceeds the suppression level (HL ') set to a low constant value, the color component was cut off.
However, according to the processing method of the present embodiment, the suppression level (HL) is variably set according to the state of the chroma signal (CR) while maintaining the white balance, and therefore, as shown in FIG. A suppression level (HL) having a higher value than the conventional suppression level (HL ') is set. Therefore, it is possible to prevent the color components from being cut, and it is possible to make effective use of the color components that have been cut in the past, and to perform more accurate color expression.

According to this embodiment, the suppression level (H
The white balance gain (WG) to be used as a reference for determining L) is obtained based on the color difference signal (CY), but the present invention is not limited to this, and for example, an image is obtained using a color temperature sensor. The same effect can be obtained by directly detecting the color temperature of the signal and obtaining the white balance gain (WG) based on the detection result.

[0019]

As described above, according to the video signal processing device of the present invention, the suppression level (HL) is set to a lower fixed value with a margin regardless of the white balance value. Compared to the conventional
It is possible to set the suppression level (HL) while changing it based on the white balance gain (WG).

Further, according to the video signal processing method of the present invention, the color component of the color component signal (CR) is calculated based on the white balance gain (WG) which is a gain applied to each color component for white balance. A suppression level (HL) to be suppressed is set, and the color component of the color component signal (CR) is suppressed based on the suppression level (HL). For this reason,
For example, when all the color components have not reached the CCD saturation level (SL) and accurate colors can be expressed, the suppression level (so that the color components do not have to be cut based on the white balance gain (WG)). HL) can be set, and the color display of the screen can be enabled by effectively utilizing the color data.

[Brief description of drawings]

FIG. 1 is a principle diagram of a video signal processing device according to the present invention.

FIG. 2 is a configuration diagram of a video signal processing device according to an embodiment of the present invention.

FIG. 3 is a timing diagram illustrating an operation of the video signal processing device according to the embodiment of the present invention.

FIG. 4 is a graph illustrating an operation effect of the video signal processing method according to the embodiment of the present invention.

FIG. 5 is a cross-sectional view illustrating a color filter related to a general CCD.

FIG. 6 is a first diagram for explaining a video signal processing method according to a conventional example.
FIG.

FIG. 7 is a first graph illustrating highlight green.

FIG. 8 is a second graph illustrating highlight green.

FIG. 9 is a second graph illustrating highlight green.

FIG. 10 is a second diagram illustrating a video signal processing method according to a conventional example.

[Explanation of symbols]

 (1) Suppression level setting means (2) Color component suppression means (11) Gain setting circuit (12) Clip circuit (13) Color component suppression circuit (CR) Chroma signal [color component signal] (CS) Processed signal (HL) Suppression level (SC) Reference gain (WG) White balance gain

Claims (4)

[Claims] 1. A suppression level setting means (1) for setting a suppression level (HL) based on a white balance gain (WG) for multiplying each color component of a video signal to adjust a white balance, and the suppression level (HL). Depending on the color component signal (CR)
And a color component suppressing means (2) for suppressing the color components of the above to obtain a processed signal (CS). 2. A suppression level (HL) is set based on a white balance gain (WG) that adjusts white balance by multiplying each color component of a video signal, and the suppression level (H) is set.
A video signal processing method characterized by suppressing the color component of a color component signal (CR) according to L). 3. A white balance gain (WG) for adjusting white balance by multiplying each color component of the video signal based on a color difference signal indicating color information of the video signal, and suppressing based on the white balance gain (WG). Level (H
L) is set and the color component of the color component signal (CR) is suppressed according to the suppression level (HL). 4. A white balance gain (WG) for adjusting white balance by multiplying each color component of a video signal based on a color temperature of a subject video, and a suppression level (HL) based on the white balance gain (WG). ) Is set, and the color component signal (CR) is set according to the suppression level (HL).
A video signal processing method, characterized in that the color components of