JPH04120993A - Color image pickup device - Google Patents

Abstract

PURPOSE:To prevent a color signal from being suppressed by a color signal suppression circuit even when a false color signal at a vertical edge is not caused by using a color temperature detection circuit so as to discriminate whether or not a color temperature of an object is a color temperature at which the false color signal is caused. CONSTITUTION:A color temperature detection circuit 16 discriminates whether or not a color temperature of an object is a color temperature at which no false color signal is caused, and when the color temperature is a color temperature at which no false color signal is caused, the suppression of a color signal by a color signal suppression circuit 19 is limited by using a vertical edge detection signal obtained by a vertical contour correction circuit 10 and an adder circuit 9. Thus, complete disregard of color information by suppressing the color signal even when no false color signal is in existence, can be prevented and the color reproducibility is enhanced.

Description

[Detailed description of the invention] The present invention will be described in the following order.

A. Industrial field of application B0 Overview of the invention C9 Background art [Figs. 2 and 3] D0 Problems to be solved by the invention E8 Means for solving the problems F1 Effects G. Examples [First Figure 1 H1 Effects of the Invention (A, Industrial Application Field) The present invention is a color imaging device, in particular, a color imaging device that is controlled by a vertical edge detection circuit that detects vertical edges, and a vertical edge detection signal that is the output of the vertical edge detection circuit. The present invention relates to a color imaging device having a color signal suppression circuit that suppresses color signals.

(B. Summary of the Invention) The present invention provides the above-mentioned color imaging device, in order to prevent the color signal from being suppressed by the color signal suppression circuit even when the color temperature is such that color false signals at vertical edges do not occur. A color temperature detection circuit determines whether or not the color temperature of the subject is a color temperature that causes a color false signal, and if the color temperature does not cause a color false signal, the color signal suppression circuit restricts suppression of the color signal. This is how it happens.

(C, Background Art) [Figures 2 and 3] Many color imaging devices, such as color solid-state imaging devices, are equipped with a color signal suppression circuit to prevent the generation of color false signals at vertical edges. FIG. 2 is a circuit diagram showing an example of such a color solid-state imaging device.

1 is a solid-state image sensor, for example a CCD, 2 is a preamplifier, 3
4 is a CDS circuit (correlated double sampling circuit); 4 is an auto gain controller; 5a and 5b are sample and hold circuits that extract specific color signals S1 and s2 from the signals; 6.
7.8 is the output signal S of the sample and hold circuits 5a and 5b.
1. By adding or subtracting S2, color signals C, , C2 and luminance signals Y0 . This is an addition or subtraction circuit for calculating.

11 to 13 are delay circuits for one water year period. Generally, in order to extract the primary color signals R1G and B by providing a color filter as shown in FIG. 3 on the surface of a single-plate solid-state image sensor, for example,
The premise is to add one color signal to another,
Or you need to subtract. For example, in the case of color coding as shown in Figure 3, Yo
, , obtain C0,C.

Y o + = Y e + Cy 1 M g + G
Co = (Ye+Mg)-(C,y+G)C,=-(
(Ye+Mg)-(Cy+Mg)) and each of the above signals Y. 1, C, , C, are processed in the primary color separation circuit 14 using, for example, the following arithmetic expression to obtain primary color signals R, G, and B.

G=Y,,-C,-C R=co-α(Yo+-C1) B=C,+β(y,,-c,) By the way, the signals Co, c input to the primary color separation circuit 14
When performing addition and subtraction operations to create ,,yo,, the addend,
The summand, the subtrahend, and the minuend are not simultaneously supplied as signals from the solid-state imaging device. Therefore, by taking advantage of line correlation, the signal from one horizontal period ago and the current signal can be
It is necessary to perform simultaneous addition or subtraction using an H delay circuit, and the one-horizontal period delay circuits 11 to 13 play the role of adding or subtracting the signal before the -horizontal period.

15 is a white balance circuit, and 16 is a color temperature detection circuit. The color temperature detection circuit 16 inputs the primary color signals R, G, and B which are the outputs of the primary color separation circuit 14, determines the color signal of the object, and controls the white balance circuit 15 based on the determination result. Specifically, white balance is achieved by controlling the gains of two primary color signal systems, red R and blue B.

A color difference matrix 17 obtains color difference signals R-Y and B-Y from the primary color signals R, G and B. 18 is a color difference signal R-Y;
This is a modulator that modulates and superimposes B-Y.

Reference numeral 19 denotes a color signal suppression circuit for suppressing the color signal output from the modulator 18, which is comprised of an amplifier whose gain can be controlled, and suppresses the color signal using a vertical edge detection signal. The vertical edge detection signal is generated by adding the output of the CDS circuit 3 to the output of the vertical contour correction circuit 10 by an adder circuit 9. That is, since the vertical contour correction circuit 10 emphasizes contours in the vertical direction, its output signal is used to detect vertical edges and suppress color signals. 20 is a delay circuit for adding an IH delay signal, 21 is a low-pass filter, 22 is an adder circuit,
23 is a band pass filter; 24 is an addition circuit that adds the color signal, luminance signal, and synchronization signal; 25 is a correction circuit that performs gamma correction in the luminance signal system; 26 is a delay circuit for creating the lH delay signal; low pass filter, 2
8 is an adder circuit, 29 is a horizontal contour correction circuit, and 30 is an adder circuit, which generates a luminance signal, and a circuit 31 that performs white clipping, synchronization signal addition, etc.;
Send to 4. The output of this adder circuit 24 becomes an NTSC color video signal.

As described above, this color imaging device uses the output signal of the adder circuit 9 as a vertical edge detection signal to control the color signal suppression circuit 19, so that the color signal is always suppressed when a vertical edge is reached. The reason why the color signal is suppressed in this way is as follows.

As mentioned above, in order to create the primary color signals R, G, and B, color signals are added and subtracted, but since the signals to be added or subtracted are not simultaneously supplied from the image sensor side, one horizontal period delay circuits 11 to 13 are used. A signal that was output one horizontal period ago is created, and this signal is added or subtracted from the signal that is currently output from the image sensor side. In other words, addition and subtraction are performed simultaneously.

However, this technique is based on the premise that there is line correlation. Therefore, for vertical edges without line correlation, color artifacts may occur and the image may become very unsightly.

Therefore, the color signal is suppressed at the vertical edge to prevent color from occurring.

This color signal suppression is performed by lowering the gain of the gain control amplifier 19.

(D. Problem that the invention attempts to solve) By the way, the second
The conventional color imaging device shown in the figure has a problem in that whenever there is a vertical edge, color signals are suppressed and color information is ignored.

However, according to the findings of the inventors of the present invention, color false signals do not always occur at vertical edges, and color false signals may or may not occur at vertical edges depending on the color temperature of the subject. In the case of the above color coding (see Figure 3), when the signal intensities of magenta Mg and green G are relatively similar, and when the signal intensities of yellow Ye and cyan cy are relatively similar, vertical Few color false signals occur at the edges. In other words, when the intensity ratio of the primary color signals R and B is close to 1:1, there are fewer color artifacts.

However, in the past, color signals were suppressed at all vertical edges. This is not preferable from the viewpoint of color image reproducibility.

SUMMARY OF THE INVENTION Therefore, it is an object of the present invention to prevent color signals from being suppressed by a color signal suppression circuit even when no color false signals occur at vertical edges.

(E. Means for Solving the Problems) In order to solve the above problems, the color imaging device of the present invention uses a color temperature detection circuit to determine whether or not the color temperature of the subject is a color temperature that causes false color signals. However, when the color temperature is such that no false color signal occurs, the suppression of the color signal by the color signal suppression circuit is restricted.

(F. Effect) According to the color imaging device of the present invention, the color temperature detection circuit determines whether or not the color temperature of the subject is a color temperature that does not cause color false signals, and the color temperature that does not cause color false signals is determined by the color temperature detection circuit. In some cases, the suppression of the color signal by the color signal suppression circuit controlled by the vertical edge detection signal is restricted, so that even when no color false signal is generated, the color signal is suppressed and color information is prevented from being ignored. I can do it. Therefore, color reproducibility can be improved.

(G. Embodiment) [FIG. 1] Hereinafter, the color imaging device of the present invention will be described in detail according to the illustrated embodiment.

FIG. 1 is a circuit diagram showing one embodiment of the color imaging device of the present invention.

This color imaging device differs from the conventional color imaging device shown in Fig. 2 in that the suppression of color signals by the color signal suppression circuit is prohibited in certain cases, but in other respects. Since they are common, and the common features have already been explained, the common parts will be illustrated in FIG. 1 using the same reference numerals as used in FIG. 2, and only the different parts will be explained. Note that the color coding is also as shown in FIG.

33 is a color signal suppression restriction circuit inserted in the path of the vertical edge detection signal outputted from the adder circuit 9 and controlling the color signal suppression circuit 19.

The color signal suppression restriction circuit 33 is controlled by the output signal of the color temperature detection circuit 16. The color temperature detection circuit 16 detects the color temperature of the subject based on the primary color signals R, G, and B obtained by the primary color separation circuit 14, and controls the white balance circuit 15 based on this detection result. It is determined whether the color temperature is such that a color false signal occurs at a vertical edge, and if the color temperature is such that a color false signal does not occur, a color signal suppression prohibition signal is sent to the color signal suppression restriction circuit 33. .

Whether or not the color temperature of the subject is such that a color false signal occurs at the vertical edge is determined by the intensity ratio of red signal R and blue signal B of 1 = 1 (in this case, the color temperature is about 5000). It is judged based on whether or not it deviates from a preset allowable range centered around No output.

In this way, the color temperature detection circuit 16 in FIG. 1 is similar to the color temperature detection circuit 16 shown in FIG. This is different from the color temperature detection circuit 16 of the conventional color imaging device shown in FIG.

According to the color imaging device shown in FIG. 1, a color false signal is generated to suppress the color signal in the color signal suppression circuit 19 based on the vertical edge detection signal obtained by the vertical edge correction circuit lO and the addition circuit 9. It is permitted only when the color error occurs, and prohibited when color false signals do not occur. Therefore, even though the color temperature is such that color false signals do not occur, color signal suppression can be performed to prevent color false signals from occurring, thereby preventing color reproducibility at vertical edges from being unnecessarily impaired.

Incidentally, in this embodiment, the color temperature detection circuit 16 was designed to detect the color temperature using the primary color signals R, G, and B.
However, the present invention is not necessarily limited to this. (However, it is possible to provide a color temperature detection element that optically directly detects color temperature on the front of the color imaging device, and to process the output signal of the element to generate a color signal suppression prohibition signal.) Alternatively, a white balance control signal may be generated.

Furthermore, in this embodiment, suppression of color signals at vertical edges is allowed or completely prohibited depending on the color temperature.
Instead of completely prohibiting the suppression, the suppression of color signals may be restricted depending on the color temperature. In other words, the degree of restriction on suppression is changed depending on the color temperature. Specifically, when the color false signal is strong (when it occurs, color signal suppression is completely allowed), but when the color false signal is weak (when it occurs, the color signal suppression is partially suppressed, and no color false signal occurs) If not, the suppression of the color signal may be completely prohibited.In other words, the amount of suppression of the color signal may be continuously changed depending on the color signal.

Note that the present invention can be applied to general color imaging devices in which output signals of an imaging device having a color filter formed on its surface are synchronized using a delay circuit and then processed to obtain primary color signals.

(H, Effect of the Invention) As described above, the color imaging device of the present invention includes a vertical edge detection circuit that detects vertical edges, and a vertical edge detection signal that is the output of the vertical edge detection circuit. In a color imaging device having a color signal suppression circuit that suppresses a signal, a color temperature detection circuit is provided that determines whether the color temperature of a subject is a color temperature at which a color false signal occurs, and an output of the color temperature detection circuit is provided. The present invention is characterized in that the signal restricts the suppression of the color signal by the color signal suppression circuit when the color temperature is not a color temperature at which a color false signal occurs.

Therefore, according to the color imaging device of the present invention, the color temperature detection circuit determines whether or not the color temperature of the subject is a color temperature that does not cause color false signals, and when the color temperature is such that color false signals do not occur, the vertical Since the suppression of the color signal by the color signal suppression circuit controlled by the edge detection signal is restricted, it is possible to prevent the color signal from being suppressed and the color information to be ignored even when no color false signal is generated. Therefore, color reproducibility can be improved.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing one embodiment of the color imaging device of the present invention, FIG. 2 is a circuit diagram showing a conventional example, and FIG. 3 is a coding diagram showing an example of color coding. Explanation of symbols 9.10... Vertical edge detection circuit, 1G... Color temperature detection circuit, 19... Color signal suppression circuit, 33... Color signal suppression restriction circuit.

Claims (1)

[Claims] (1) In a color imaging device that has a vertical edge detection circuit that detects a vertical edge and a color signal suppression circuit that suppresses a color signal under the control of a vertical edge detection signal that is the output of the vertical edge detection circuit, A color temperature detection circuit is provided for determining whether the temperature is a color temperature at which a color false signal occurs, and an output signal of the color temperature detection circuit determines whether the color temperature is a color temperature at which a color false signal occurs or not. A color imaging device characterized in that the suppression of color signals by a color signal suppression circuit is restricted.