JPS6188688A - Color image pickup device - Google Patents

Abstract

PURPOSE:To minimize the reduction in saturation of a high brightness part by using a luminance signal and a chrominance signal obtained through gamma correction to apply gamma correction to a chrominance carrier signal from the carrier while being modulated by the chrominance signal. CONSTITUTION:A color difference signal of a detection circuit 24 and an output of a low-pass filter 30 are inputted to a white balance circuit 25 to adjust the white balance of a picture. An output of the white balance circuit 25 is reproduced by using a 1H delay circuit 26 and a 1H switching circuit 27 so as to be synchronized with two color difference signals. The color difference signal is modulated by a chrominance subcarrier at a balanced modulation circuit 28 and becomes a chrominance carrier signal. gamma correction is conducted by using an output of a luminance signal gamma correction circuit 51 to apply gain control to the chrominance carrier signal at a chrominance signal gamma correction circuit 52. The output of the chrominance signal gamma correction 52 is mixed with an output of the luminance signal gamma correction circuit 51 by a mixing circuit 29, and synchronizing signal is added to obtain a decoded color signal.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a color imaging device capable of performing gamma correction.

(Conventional configuration and its problems) As is well known, color image transmission/reception systems use NTSC
The PAL system, the SECAM system, and other systems have been adopted in various countries. In any of these systems, it is prescribed that the camera on the image sending side is equipped with a gamma (hereinafter abbreviated as γ) correction circuit for correcting the nonlinearity of the signal voltage versus light emission output characteristic of the color picture tube.

In the following description, the NTSC system will be used.

FIG. 1 is a diagram for explaining the configuration of a typical color video camera that uses three primary colors: red (hereinafter abbreviated as R), green (hereinafter abbreviated as G), and blue (hereinafter abbreviated as B). 1, 2.
3 is an imaging device for R, G, and B, respectively, 4, 5.6
are R and G, respectively.

A signal processing circuit including a γ correction circuit for B, 7 and 8° 9 are a luminance signal, 1 color difference signal (hereinafter abbreviated as ■ signal), Q
Matrix circuits 10 and 11 for synthesizing color difference signals (hereinafter abbreviated as Q signals) are respectively balanced modulation circuits 12 that modulate the double signal Q signal with a color subcarrier and obtain ■ and Q carrier color signals. is a mixing circuit that synthesizes a luminance signal, (2) and Q carrier color signals, a synchronization signal, etc.

In a color camera having the configuration shown in Fig. 1, 1, 2,
γ correction can be applied to the R2O and B signals obtained from each imaging device shown in 3 independently in each signal processing circuit shown in 4 and 5.6.

However, the configuration shown in Figure 1 corresponds to a three-tube color video camera for commercial use, etc., and in order to realize a compact video camera for home use, for example, the configuration, weight, adjustment, and ease of handling are required. , there are many difficulties in terms of price, etc.

Currently, the mainstream of simple color video cameras for home use is a method that multiplexes and extracts luminance information and color information from a single imaging device.

For example, if a color filter as described in JP-A-59-137909 is applied to a solid-state image sensor, which is a type of imaging device, to configure a color camera, an ultra-small color video camera can be created with a simple circuit configuration. It can be realized.

FIG. 2 shows an example of a signal processing circuit for a color video camera using a solid-state imaging device (hereinafter abbreviated as color imaging device) equipped with a color filter as described in Japanese Patent Laid-Open No. 59-137909. The output signal A of the color image sensor 20 passes through a low-pass filter 21 and a process circuit 22, and is led to a mixing circuit 29 as a luminance signal.

Further, a color difference signal is obtained by using an output signal of the color image sensor 20 using a bandpass filter 23 and a detection circuit 24. In order to adjust the white balance of the image, the output of the detection circuit 24 and the output of the low-pass filter 30 are input to a white balance circuit 25. As it is, the output of the white balance circuit 25 will repeat two types of color difference signals every horizontal period (hereinafter abbreviated as IH), so the IH delay circuit 26 and each IH switching circuit 27 are used to simultaneously output two color difference signals Convert and regenerate. The color difference signal thus obtained is modulated by a color subcarrier in a balanced modulation circuit 28 to become a carrier color signal. Furthermore, mixing circuit 2
At step 9, the signal is mixed with the previous luminance signal and a synchronization signal etc. are added to obtain a composite color signal.

The example signal processing circuit shown in FIG. 2 does not include a γ correction circuit.

FIG. 3 shows an example of a circuit configuration in which a γ correction circuit is added to the circuit configuration of FIG. 2. Components 20 to 30 in FIG. 3 are the same as those with the same reference numerals in FIG.

Two types of color difference signal output from the IH switching circuit 27 and a luminance signal from the process circuit 22 are led to a decoder 31 and separated into three primary color components (R, G, B). The separated R2O and B signals are sent to γ correction circuits 4, 5, . After that, the matrix circuit 32 combines the luminance signal and two types of color difference signals again. In this case, the two types of color difference signals are determined by the IH switching circuit 2.
It is not necessary that the primary color components are the same as those of the two types of color difference signals outputted from 7, and for example, I and Q signals may be combined.

Furthermore, the luminance signal does not need to have the same primary color components as the luminance signal output from the process circuit 22, and the primary color components of the luminance signal may be corrected. Out of the outputs of the matrix circuit 32, two types of color difference signals are modulated by color subcarriers in a balanced modulation circuit 28 to become a carrier color signal, which is mixed with a luminance signal which is an output of the matrix circuit 22 in a mixing circuit 29, and a synchronization signal etc. A composite color signal is obtained.

When the signal processing circuit shown in FIG. 3 is used, it is possible to perform γ correction on each of R, G, and B similarly to the signal processing circuit shown in FIG. As a result, it is possible to obtain an accurately gamma-corrected composite color signal, but three independent circuits for R, G, and B are required as gamma correction circuits, and decoders and matrix circuits are also required before and after the gamma correction circuits. The mutual adjustment of each circuit becomes complicated, which goes against the characteristics of a simple color video camera for home use: small size, low price, easy adjustment, and ease of handling.

FIG. 4 is a diagram for explaining the gamma correction method described in Japanese Patent Application No. 52-143300. Components 20 to 30 in FIG. 4 are the same as those with the same reference numerals in FIG.

The signal flow in FIG. 4 is the same as that in FIG. 2, and the output from the mixing circuit 29 is passed through the γ correction circuit 41 to obtain a composite color signal.

The γ correction circuit shown in FIG. 4 is simple and suitable for use in a simple color video camera, but it also has problems such as a decrease in color saturation in high-brightness areas.

(Effects of the Invention) The present invention has a simple configuration, performs γ correction on a luminance signal and a carrier color signal, and realizes a color imaging device that is small, inexpensive, and easy to adjust and handle.

(Structure of the Invention) In order to achieve this object, the color imaging device of the present invention uses a corrected luminance signal and a corrected color signal obtained by γ correction, and a carrier wave is modulated by the color signal. It consists of performing γ correction on the obtained carrier color signal.

(Description of Embodiment) FIG. 5 shows the configuration of a color solid-state imaging device according to an embodiment of the present invention. Items 20 to 30 in FIG. 5 are the same as those with the same symbols in FIG. 51 is a luminance signal γ correction circuit, and 52 is a color signal γ correction circuit.

The output signal obtained from the color image sensor 20 passes through a low-pass filter 21 and a process circuit 22, undergoes γ correction in a luminance signal γ correction circuit 51, and then is guided to a mixing circuit 29. Further, a color difference signal is obtained by using an output signal of the color image sensor 20 using a bandpass filter 23 and a detection circuit 24. In order to adjust the white balance of the image, the output of the detection circuit 24 and the output of the low-pass filter 30 are input to a white balance circuit 25. If the output of the white balance circuit 25 is left as it is, two types of color difference signals will be repeated for each IH, so the IH delay circuit 2
6. Using the IH switching circuit 27, the two color difference signals are simultaneously generated and reproduced. The color difference signal thus obtained is modulated by the color subcarrier in the balanced modulation circuit 28 to become a carrier color signal. This carrier color signal is sent to the color signal γ correction circuit 52.
Gain control is performed using the output of the luminance signal γ correction circuit 51 to perform γ correction. The output of the color signal γ correction circuit 52 is mixed with the output of the luminance signal γ correction circuit 51 in a mixing circuit 29, and a synchronization signal and the like are further added to obtain a composite color signal.

FIG. 6 shows an example of the luminance signal γ correction input/output characteristic 61, input waveform 60, and output waveform 62 of the luminance signal γ correction circuit 51. In FIG. 6, the luminance signal γ correction input/output characteristic 61
is not a so-called 2,2-square characteristic, but is approximated by a polygonal line at two points. When the input waveform 60 passes through the luminance signal γ correction circuit 51, an output waveform 62 is obtained.

FIG. 7 shows an example of gain control of the color signal γ correction circuit 52. In FIG. 7, a carrier color signal 72 is input to a variable gain control circuit 73, whose gain is controlled by a gain control signal 71, and a gain control output signal 74 is obtained. The gain control characteristic of the variable gain control circuit 72 does not have to be linear as shown in FIG. 8(a), but is shown in FIG. 8(b).

It may be non-linear as shown in (c).

In FIG. 5, the gain control signal input to the color signal γ correction circuit 52 is not only the output of the luminance signal γ correction circuit 51, but also the output of the process circuit 22 before γ correction, and the output of the IH switching circuit 27. Further, a signal obtained by detecting a carrier color signal before color signal γ correction, or a signal obtained by appropriately processing a combination thereof may be used.

Although the above-mentioned embodiments have been explained using a solid-state image sensor, the present invention can also be applied to a color video camera using an image pickup tube such as a vidicon.

(Effects of the Invention) In the present invention, in order to apply γ correction to the two systems of the luminance signal and the color signal separately, the saturation of the high brightness area is reduced by controlling the control signal input to the color signal γ correction circuit. can be kept to a minimum. Furthermore, since the γ correction circuits for the luminance signal and the chrominance signal are each independent, there is no need to delicately adjust each other, and the adjustment can be simplified.

As a result, it is useful for making color video cameras smaller, lighter, and less expensive, and it is also possible to improve playback image quality.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a color video camera that uses the three primary colors of red, green, and blue, Fig. 2 is a block diagram of a single-chip color video camera that uses a solid-state image sensor, and Fig. 3 is a block diagram of a color video camera that uses the three primary colors of red, green, and blue.
Fig. 4 is a block diagram of a single-chip color video camera that performs gamma correction on a composite color signal, and Fig. 5 shows a single-chip color video camera that performs gamma correction according to the present invention. A configuration diagram showing an embodiment of the camera, FIG. 6 is a diagram explaining γ correction of a luminance signal, FIG. 7 is a diagram explaining γ correction of a color difference signal, and FIG. 8 is a diagram explaining gain control characteristics. . Patent applicant: Matsushita Electronics Co., Ltd. Figure 6

Claims (2)

[Claims] (1) An imaging means for obtaining a luminance signal and a color signal, a means for obtaining a carrier color signal by modulating a carrier wave with the color signal, and an addition means for adding the luminance signal and the carrier color signal to obtain a color video signal. and the luminance signal is gamma-corrected by a predetermined amount in advance, and the corrected luminance signal or;
A color imaging device characterized in that gamma correction is performed on the carrier color signal using the color signal. (2) The color imaging device according to claim (1), wherein gamma correction is performed on the carrier color signal using the carrier color signal.