JPH033497A - Signal processing system for video camera - Google Patents

Abstract

PURPOSE:To obtain proper white balance to a color temperature over a wide range from indoor color temperature to outdoor color temperature by detecting color temperature and varying a matrix constant of a color demodulation matrix in response to the detected color temperature. CONSTITUTION:An automatic white balance circuit 9 generates a DC control signal CD controlling the gain of a red and blue AGC circuit in a process circuit 8 so that a level ratio of color difference signals (R-YL), (B-YL) from a circuit such as the process circuit 8 is a prescribed value, that is, the white balance is taken. The DC control signal CD is fed to a matrix correction circuit 11, from which a control signal CM controlling a color demodulation matrix circuit 3 is formed so as to have a prescribed matrix constant in response to the color temperature. Thus, excellent white balance is obtained over a wide range of color temperature by having only to add a circuit with simple constitution to obtain excellent color reproducibility even at the image pickup at indoor or outdoor.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a signal processing method for a video camera for improving color reproducibility.

[Conventional technology]

For video cameras using Moss Solid Surface Elements, we place emphasis on color reproducibility and have been certified by the Televisier Society d'101.5.
4. No. 11 (NOV'12)pp, 1001~
As described in 1009, there are four color multiplexing methods: W (white), G (green), Cy (cyan), and Yel (yellow).
It uses a color filter method in which a color filter is placed on the light-receiving surface of the solid-state image sensor.

According to such a video camera, for each horizontal stroke, W +
Signals W + g 10 , *7e from the pixel through the G + Cy tye color filter are all output from the solid-state image sensor. In the color demodulation matrix, the following additions and subtractions are performed on these to create three primary color signals r, g, b and a luminance signal Y.

(w-o, ) + (y, -g) = 2 r
tx)(stomach-y,)+(o-g)=2b
(2) 7, + Q, -W + 5 g 34 g
t81w + OF + 76 + B
(4) The luminance signal Y obtained in this way is similarly divided into a predetermined band (for example, 4.5MH2
), the signal is band-limited by the LPF, and then supplied to a process circuit where processing such as r correction is performed.

In addition, red signal r, green signal g, and green signal are each 700kHz.
The signal is supplied to an LPF of about 2, band-limited, and then supplied to a process circuit. In the process circuit, the red signal r and the green signal are AGC which performs gain control to maintain white balance.
After each is supplied to the circuit and the respective level is adjusted, γ
Processing such as correction is performed. On the other hand, after the green signal g has undergone γ correction, it is added to the Y matrix, which forms the low-frequency luminance signal, together with the γ-corrected red signal r and green signal.

A color difference signal (R-Y,
(B-Y, ) is formed, and a chroma signal is formed in the encoder circuit and mixed with the luminance signal Y to form a composite color signal.

[Problem to be solved by the invention]

By the way, in this method, sensitivity is emphasized and W is used.

Complementary color filters of Y, C, and 7 are used, but the color reproducibility is inferior to that of primary color filters. In particular, it is extremely difficult to obtain the required spectral characteristics of the five primary colors over a wide range of color temperatures from indoors to outdoors.

Therefore, in the past, methods such as determining the constants of the color demodulation matrix (IJ) were adopted with emphasis on indoor color reproducibility9.
I'm trying to reduce the chance of turning green with a fluorescent knife. For this reason, when taking pictures outside, the white balance is a little LMg (
Magenta) There was a problem that it became blurry.

SUMMARY OF THE INVENTION An object of the present invention is to provide a video camera (C) (signal processing method) that solves these problems and allows an appropriate white balance to be obtained over a wide range of color temperatures from indoors to outdoors.

[Means to solve the problem]

In order to achieve the above object, the present invention includes means for detecting color temperature and means for changing a matrix constant of a color demodulation matrix in accordance with the detection output of the means.

[Effect]

In the color demodulation matrix, a matrix constant is determined to obtain an appropriate white balance for each color temperature, and by selecting a matrix constant that corresponds to the detected color temperature, the color temperature changes. However, you can always get the correct white balance.

〔Example〕

Below, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a signal processing system for a video camera according to the present invention, in which 1 indicates a solid-state image element;
2 is preamplifier, 3 is color demodulation matrix, 4 to 7 are LP
F, 8 is a process circuit, 9 is an auto white balance circuit, 10 is an encoder, and 11 is a matrix correction circuit.

In the figure, the output from the solid-state camera device 1 is 9 W *
The 7*#Cylg signal is amplified by a preamplifier 2 to a level suitable for signal processing, and then supplied to a color demodulation matrix 3 to generate three primary color signals r, g, b and a luminance signal Y. Among these, the primary color signal r.

g and b are each LPF with a passband of about 700kHz
Band-limited at 4,5.6, luminance signal Y44.5MH2
After being band-limited by the LPF 7 with a pass band of , the signals are respectively supplied to the process circuit 8 . In the process circuit 8, color difference signals (R-YL), (B-
Similarly, the luminance signal Y is also subjected to signal processing such as γ correction, white clipping, black clipping, etc. These color difference signals (R-Yt,)-(B-Y,) are supplied to the auto white balance circuit 9 and the encoder circuit 10, and
A luminance signal Y is also supplied to the encoder circuit 10 to generate a composite color video signal S.

The auto white balance circuit 9 adjusts the level ratio of the color difference signals (R-Y, ) and (B-Y,) from the process circuit 8 to a predetermined value, that is, the white balance is maintained. A DC control signal CD is generated to control the gains of the red and back AGC circuits in the process circuit 8, as shown in FIG. This DC control signal CI is also supplied to the matrix correction circuit 11 to form a control signal CM that controls the color demodulation matrix circuit 3 so that a predetermined matrix constant is achieved according to the color temperature.

Next, referring to FIG. 2, a specific example of the color demodulation matrix 3 and matrix correction circuit 11 in FIG. 1 will be described.

In the figure, the level of the DC control signal C8 from the auto white balance circuit 9 (FIG. 1) decreases when the color temperature becomes high, and the level of the DC control signal C8 from the auto white balance circuit 9 (FIG. 1) decreases when the color temperature becomes high.
A group corresponding to a predetermined color temperature is supplied to the negative terminal of the comparator 15 of No. 1, and is supplied to the positive terminal of this comparator 15! The level is compared with the S voltage E. Therefore, when a DC control signal C is supplied due to the detection of a high color temperature exceeding this predetermined color temperature, the control signal C, output from the matrix correction circuit 11 becomes l Hl (
high level).

In the color demodulation matrix 5, when the color temperature is lower than the predetermined color temperature set in the matrix correction circuit 11 and the control signal CIII is IIL'', the resistors R1 to R4, the comparator 12, and the Therefore g j Cy
The above equation (1) is calculated for the l ``!@ l '' color signal, and the primary color signal R is generated. At the same time, the resistors R5 to R8 and the comparator 15 perform the calculation of the above equation (2) to generate the primary color signal port, and the resistors R2 to R12 and the comparator 14 perform the calculation of the above equation (8). The primary color signal G is generated.

When the color temperature is υ higher than the predetermined color temperature set in the matrix correction circuit 11 and the control signal CM becomes IH'', the switch S1.32 is turned on, and the resistor Rx is connected to the resistor R2, and the resistor RY is connected to the resistor R1. They are connected in parallel, respectively.Thereby, the matrix constant is changed so that the calculation constant of the above equation (1) is changed.

Here, as mentioned above, the solid-state image sensor 1 (FIG. 1) uses a complementary color filter, and the primary color signal R is formed from the signal obtained from the complementary color filter.
As shown in c, in a high color temperature state, a non-negligible lift υ occurs in the short wavelength region corresponding to the primary color signal R, and therefore K
However, in this embodiment, the resistors R1# and RF are connected to the resistors R2e and RF as a whole.
When connected in parallel to R5, the lift in the short wavelength region becomes particularly small, as shown in FIG. 5(b).

This means that the 91-color reproduction (Mg) is less blurry than K, and the color reproduction is more or less blurred, and the color reproducibility is improved in terms of visual field even when shooting outdoors where the color temperature is high.

Note that in this embodiment, the solid-state image sensor 1 is
It may be Moa reduction or 000 plates.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to obtain good white balance over a wide range of one color temperature by simply adding a circuit with a simple configuration, and the color reproduction is excellent even in outdoor and indoor imaging. You can get sex.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a signal heating system for a video camera according to the present invention, FIG. 2 is a block diagram showing a specific example of the color demodulation matrix and matrix correction circuit in FIG. 1, and FIG. (a) is a diagram showing the spectral characteristics of the primary color signal H under high color temperature in the conventional technology, and (b) is a diagram showing the spectral characteristics of the primary color signal H under high color temperature in the conventional technology.
It is a figure showing the same spectral characteristics in the example shown in the figure. Explanation of symbols 1... Solid-state image sensor, 5... Color demodulation matrix, 8... Process circuit, 9... Auto white balance circuit, 10... Encoder, 11... Matrix correction circuit. 1 Figure 5 (Q) (b)

Claims (1)

[Claims] 1. In a video camera that uses a solid-state image sensor and processes a plurality of output signals of the solid-state image sensor with a color demodulation matrix to generate a primary color signal, a color temperature is detected, and a color temperature is detected according to the detected color temperature. A signal processing method for a video camera, characterized in that a matrix constant of the color demodulation matrix is changed.