JPH02312485A - Color image pickup device - Google Patents

Abstract

PURPOSE:To suppress abnormal coloring of a high brightness part and unnatural coloring due to a false color signal by retarding a luminance signal separated by a separation means for 2 horizontal scanning periods, adding and averaging the signal with a luminance signal without delay from the separation means to generate a color difference signal suppressing signal. CONSTITUTION:A color difference signal suppressing signal is formed by adding and averaging a luminance signal YOH not delayed and a luminance signal Y2H delayed for 2 horizontal scanning periods by a delay means 3. On the other hand, A position where a false color signal of a simultaneous processing color difference signal obtained by applying simultaneous processing to a line sequential color difference signal appears is a position where it appears in the line sequential color difference signal and a position apart by one horizontal scanning period and 2 horizontal scanning periods. Since the appearance position of the false color signal in the simultaneous processing color difference signal is included during the production period of the color difference signal suppressing signal, no false color signal is included in the simultaneous processing color difference signal suppressed in response to the color difference signal suppressing signal. Then all false color signals included in the simultaneous processing color difference signal are eliminated with a high brightness part abnormal coloring signal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a color imaging device, and more particularly to a color imaging device using a field storage type color difference line sequential method.

[Prior Art] Many of the color imaging devices currently in use, such as color video cameras, have a large number of color separation filters arranged in a lattice pattern on the image receiving surface of a solid-state imaging device such as a CCD (charge-coupled device). By arranging an optical filter, a so-called color filter array, color information of the subject is obtained from the solid-state image sensor. Among them, in the field accumulation type color difference line sequential color imaging device, which is a typical color image pickup device, the charge is accumulated and output to the CCD every one field time, and the color signal indicating the color information of the subject is divided into two different color difference. The signals are obtained alternately for each scanning line. In this way, the color arrangement of the color filter array arranged on the solid-state image sensor is limited to one type, so that two different color information is output alternately from the solid-state image sensor in the form of color difference signals. Not done.

Here, the color filter array is magenta, cyan, and green.

An example of a case where the image is composed of four complementary colors of yellow and yellow will be explained.

Figure 3 shows a field storage type linear color difference sequential CCD.
FIG. 1 is a partial schematic block diagram of a conventional color video camera using a conventional color video camera. Hereinafter, with reference to FIG. 3, the steps from the video signal obtained by the CCD to the creation of a composite video signal, which is the output of the color video camera, will be explained.

A field storage linear color difference sequential type CCDI converts a subject image captured as an optical image by an optical system (not shown) into an electrical signal, that is, a video signal P, according to its color and brightness.

FIG. 4 is a partial arrangement diagram showing an example of the arrangement of color separation filters provided for each pixel on the image receiving surface of the CCDI.

Referring to FIG. 4, each pixel constituting the CCDI has four complementary colors (magenta, Mg
, green G, cyan Cy, and yellow Ye). therefore,
On the CCD 1, there is a color filter row in which color separation filters of two complementary colors (magenta Mg, green G) are arranged alternately, and color separation filters of other two complementary colors (cyan Cy, yellow Ye) are arranged alternately. The color filter rows are arranged alternately. These two types of color filter rows are arranged such that the color filter rows in which the Cy and YeO color separation filters are arranged are arranged so that the same color separation filters are not arranged above and below them.
The color filter rows in which the g and G color separation filters are arranged are arranged so that the same color separation filters are arranged above and below. In CCDI, the charge accumulated in each pixel is 1
It is read out every horizontal scanning period IH.

At this time, charges accumulated in two adjacent pixel columns constituting one scanning line are read out simultaneously.

Note that the combination of pixel columns constituting one scanning line is shifted by one column between odd-numbered fields and even-numbered fields.

The video signal P obtained by reading out the accumulated charge from the CCDI in this way is processed by a luminance/chrominance signal separation circuit (hereinafter referred to as
It is abbreviated as Y/C separation circuit. )2, the color difference signal component C
and a luminance signal component Y. The luminance signal component Y is further converted into a narrowband luminance signal YL having a bandwidth as narrow as that of the wideband luminance signal YO and the color difference signal component C in the normal band.

Here, the video signal P from the CCDI is an output signal from a pixel column in which Mg and G color separation filters are arranged, and c
Output signals from pixel columns in which Y and Ye color separation filters are arranged are alternately repeated. 4th again
Referring to the figure, the arrangement of color separation filters between pixel columns constituting one scanning line is M g / Cy (G / Y
e) (in the figure, refer to the Nth scanning line (N is an integer of 1 or more)), the modulation component of the signal obtained from these pixel columns by the color separation filter is (Mg + Cy) - (G
+Ye). In this formula, Mg, Ye
, G and Cy are complementary colors magenta and yellow, respectively.

Represents green and cyan signal components. Similarly,
If the signal components of red and blue, which are primary color lights, are represented by R and B, respectively, Mg = B + R, Cy = B + G
, Y e = R+G, so the above equation can be transformed as follows.

(Mg+Cy)-(G+Ye)=28-G...■ Next, the arrangement of color separation filters between the pixel columns that make up one scanning line is Mg -Ye (G/CY
) (see the N+1st scanning line in the figure), the modulation component of the signals obtained from these pixel columns by the color separation filter is expressed as (Mg+Ye)-(G+Cy).

Transforming this in the same way as before, the following formula % formula % As can be seen from the above formulas ■ and ■, from the video signal P,
A line sequential signal is obtained in which signals 2B-G and 2R-G appear alternately every horizontal scanning period IH. Signal 2R-G
and 28IG are equivalently regarded as color=6-difference signal component C, and are applied to the white balance circuit 4.

In addition, a wideband luminance signal YOH and a narrowband luminance signal YL
is created by removing the modulated color signal from the video signal P from the CCDI. By removing the modulated color signal from the video signal P, the signal component obtained from the scanning line corresponding to the Nth scanning line in FIG.
Cy) + (G + Ye), the signal component obtained from the scanning line corresponding to the N+1st scanning line is (Mg + Ye)
It becomes ten (G+cy). When these are transformed, both are 2R
It becomes +3G+2B. Therefore, these are equivalently regarded as a luminance signal component Y, and are converted into a wideband luminance signal YOH and a narrowband luminance signal Y.

The broadband luminance signal YOH is given to the enhancement circuit 3,
The narrowband luminance signal Y is applied to a white balance circuit 4.

In order to accurately reproduce the actual color of the object in the reproduced image, the white balance circuit 4 uses the Y/C separation circuit 2 based on the level of the color difference signal component obtained by imaging an achromatic object. The level of the color difference signal component C is controlled from. Specifically, when capturing an image of an achromatic subject, (2B-G)-kx (2R+3G+2B)=0
and (2R-G)-to' X (2R+3G+2B)
Perform the operation C-k (or ni') x YL while controlling the value of constant and ni' so that =O holds true (C=
2B-G or 2R-G, YL=2R+3G+2B).

The color difference signal components subjected to white balance adjustment in this manner are supplied to the line sequential synchronization circuit 9 as line sequential color difference signals in which color difference signals R-Y and B-Y appear alternately for each scanning line.

The line sequential synchronization circuit 9 converts the input signal into one horizontal scanning period IH.
delay circuits 7a and 7b that delay the input signal by 1, an averaging circuit 7c that adds and averages the two input signals, and a switching circuit that switches the two input signals every horizontal scanning period IH and outputs them alternately to the two signal lines. 8. Line sequential synchronization circuit 9
The line sequential color difference signals applied to delay circuits 7a and 7b
The signal is delayed by one horizontal scanning period IH and delayed by two horizontal scanning periods 2H, and is also provided to the averaging circuit 7C. On the other hand, the line sequential color difference signal C delayed by 2H for two horizontal scanning periods by the delay circuits 7a and 7b is also applied to the averaging circuit 7C. The averaging circuit 7C has these two
The two line sequential color difference signals, that is, the line sequential color difference signal without time delay and the line sequential color difference signal delayed by 2H during two horizontal scanning periods are averaged and applied to the switching circuit 8. On the other hand, the switching circuit 8 is also given a line-sequential color difference signal delayed by one horizontal scanning period IH by the delay circuit 7a. Therefore, the switching circuit 8 outputs a signal obtained by adding and averaging the line sequential color difference signal delayed by 1 horizontal scanning period IH, the line sequential color difference signal without time delay, and the line sequential color difference signal delayed by 2H by 2 horizontal scanning periods. are output alternately every horizontal scanning period IH. By the way, in the line sequential color difference signal given from the white balance circuit 4 to the line sequential synchronization circuit 9, the color difference signal R
-Y and B-Y appear alternately every horizontal scanning period IH. Therefore, by averaging the line sequential color difference signal delayed by 2H for 2 horizontal scanning periods and the line sequential color difference signal without time delay, a signal is obtained by adding and averaging the temporally adjacent color difference signals RY. and a signal obtained by adding and averaging temporally adjacent color difference signals B-Y are arranged alternately. Therefore, the color difference signal R-Y in the line-sequential color-difference signal delayed by IH for one horizontal scanning period is the B-Y signal in the line-sequential color-difference signal that has been averaged, and the line-sequential color-difference signal delayed by IH for one horizontal scanning period. The color difference signal B-Y at
are located in the same time period as the RY signal in the line-sequential color difference signal that has been averaged. Therefore, the switching circuit 8 can alternately apply the averaged line sequential color difference signal and the line sequential color difference signal delayed by one horizontal scanning period IH to the two signal lines every one horizontal scanning period IH. , means that the line-sequential color difference signal is separated into the color difference signal B-Y and the color difference signal RY while maintaining the temporal arrangement relationship. That is, the color difference signal RY is applied to one signal line, and the color difference signal B-Y is applied to the other signal line. Therefore, the color difference signals R-Y and t3-, which are sent temporally shifted from each other as line-sequential color difference signals,
Y is converted so that it is sent in parallel in time, that is, it is synchronized. The color difference signals R-Y and B-Y synchronized as described above are balanced-modulated by a balanced modulation circuit 10 to become a chroma signal in order to be added to a chroma signal in a mixing circuit 5, which will be described later. Chroma signal is signal line 2
The signal is applied to the chroma signal gain control circuit 11 via the chroma signal gain control circuit 11.

On the other hand, the wideband luminance signal YOH is subjected to contour compensation by the enhancer circuit 3 to emphasize the contours of the image. Generally, the enhancer circuit 3 includes two delay circuits that delay an input signal by 1H for one horizontal scanning period.

Contains an addition circuit and a subtraction circuit. The enhancer circuit 3 generates a signal obtained by delaying the applied broadband luminance signal YOH by one horizontal scanning period IH by one delay circuit, and a signal obtained by delaying the applied broadband luminance signal YOH by 2 horizontal scanning periods 2H by two delay circuits. That is, the luminance signal YIH delayed by one horizontal scanning period IH and the luminance signal Y delayed by two horizontal scanning periods
2H and the original luminance signal YOH without time delay,
A vertical contour signal representing the contour portion of the image is created using an addition circuit and a subtraction circuit. Furthermore, enhancer circuit 3
adds this vertical contour signal to the luminance signal YIH delayed by 18 IH in the horizontal scanning period (=1), and supplies it to the mixing circuit 5 via the signal line 1.

Furthermore, the broadband luminance signal YOH from the Y/C separation circuit 2
is not only given to the enhancer circuit 3, but also given to the chroma signal gain control circuit 11 via the process circuit 6.

The chroma signal gain control circuit]] adjusts the chroma signal from the balanced modulation circuit [0] according to the level of the luminance signal (hereinafter referred to as the high luminance color suppression signal) applied via the process circuit 6. It is attenuated with a gain and applied to the mixing circuit 5. Here, the role of the chroma signal gain control circuit 11 will be explained. As explained earlier, the color difference signals R-Y and B are set so that the level of the line-sequential color difference signal is always 0 when an achromatic object is imaged in the white balance circuit 4.
-Y is created. Specifically, when capturing an achromatic subject, (2B-G) -kX (2R+3G+2B
) -〇 and (2R-G)-'(2R+3G+2B
) = 0 using k and ′ to calculate (2B−
G)-kx (2R+3G+2B) and (2R-G)
-' x (2R+3G+2B) is performed. Therefore, as the luminance of the achromatic object being imaged increases, the level of the luminance signal component 2R+3G+2B and the level of the color difference signal components 2B-G and 2R-G increase at the same rate, and the result of the above calculation becomes 0. It should be.

However, when the subject is an achromatic color (white) with very high luminance, a phenomenon occurs in which the color difference signal component becomes saturated before the luminance signal component. This occurs because the dynamic ranges of the color difference signal component and the luminance signal component are different, and the brightness of the subject exceeds the dynamic range of the color difference signal component but is within a range that would not exceed the dynamic range of the luminance signal component. occurs in

In such a case, the calculation results in the white balance circuit 4, that is, the levels of the color difference signals RY and BY do not become O. Therefore, when a composite video signal is created from a chroma signal created from such color difference signals,
Although the object is achromatic, the object is not white but colored in the reproduced image obtained from the composite video signal.

The chroma signal gain control circuit 11 is provided to suppress such abnormal coloring phenomena in high brightness areas.

That is, the chroma signal gain control circuit 11 attenuates the chroma signal from the balanced modulation circuit 10 at an attenuation rate proportional to the level of the luminance signal YOH applied via the process circuit 6, thereby preventing abnormal coloring in high luminance areas. to suppress.

The process circuit 6 is a circuit for converting the luminance signal YOH into a signal that can directly control the gain of the chroma signal gain control circuit 1 and inputting it to the chroma signal gain control circuit 11.

Finally, the mixing circuit 5 combines the luminance signal whose contour has been compensated by the enhancer circuit 3 and the chroma signal whose abnormal coloring in the high luminance area has been suppressed by the chroma signal gain control circuit 11, and further combines the luminance signal whose contour has been compensated by the enhancer circuit 3 and the chroma signal whose abnormal coloring in the high luminance part has been suppressed by the chroma signal gain control circuit 11. A reference signal is added and output as a final composite video signal.

[Problems to be Solved by the Invention] In conventional color imaging devices, in the process of creating the final chroma signal given to the mixing circuit, a signal (
A luminance signal without time delay was used as the high-luminance discoloration suppression signal). However, such a method still has problems as described below. FIG. 5 is a plan view showing an example of a captured image that makes the problem particularly noticeable.

The black part 21a and the black part 2 as shown in FIG.
1. Assume that an achromatic image 21 composed of a rectangular white portion 21b located within a is captured by a conventional color imaging device using a field storage type color difference line sequential method.

First, this image 21 is formed on a CCD as an optical image. At that time, the black part 21a and the white part 21b with constant brightness
Suppose that the vertical boundaries between the two are formed on the CCD at positions corresponding to the n and n+mth (n and m are positive integers) scanning lines. FIG. 6 shows a CCD corresponding to a part of image 2 (portion with minute width d in FIG. 5).
Image 2 showing the arrangement of color separation filters by enlarging the image receiving surface of
FIG. 1 is a plan view showing the correspondence relationship with FIG. Figures 5 and 6
Referring to the figure, as described above, each scanning line includes two pixel columns in which two different types of color separation filters are arranged alternately, and from each scanning line, color difference signal components 2B-G and Either one of 2R−G and the luminance signal component 2R+
3G+2B is obtained. Now, the black part 21 of image 21
Among the vertical boundaries between a and the white portion 21b, the upper boundary coincides with the n-th scanning line, and the lower boundary coincides with the n10m-th scanning line. Therefore, this means that the upper boundary is formed at any position within the width of the nth scan line, and the lower boundary is formed at any position within the width of the n+mth scan line.

In the following explanation, for the sake of simplicity, the upper boundary is located between two pixel columns constituting the n-th scanning line, and the lower boundary is located midway between two pixel columns constituting the n10m-th scanning line. shall be located in each.

FIG. 7 shows the n-3rd to n0m + shown in FIG.
FIG. 7 is a diagram showing a luminance signal component Y and a color difference signal component C obtained from each of the third scanning lines in a tabular format with respect to a minute width d. In the figure, the number in parentheses is the number of the corresponding scanning line, indicating from which scanning line the luminance signal component Y and color difference signal component C are obtained.

With reference to FIG. 6 and FIG. 7, from n-3rd to n-1
Scan lines up to the scan line and n+m+1 to n+m+3
Since the first scanning line belongs to the black portion 21a of the image 21, both the luminance signal component and the color difference signal component obtained from these scanning lines are 0. On the other hand, n+
Since the 1st to n0m-1th scanning lines belong to the white part 21b of constant luminance in the image 21, the luminance signal components obtained from these scanning lines Y (n+1) to Y
((n +m) -1,) are all 2R+3G+2
It is the same non-zero value represented by B.

Furthermore, the color difference signal component C(n
+1) ~C((n+m)-1,) is represented by 2B-G (≠0) and 2R-G for each scanning line -17=
(≠0). The color difference signal components represented by 2B-G and the color difference signal components represented by 2R-G are the same. However, n
Both the n+m-th scanning line belong to different regions, the black portion 21a and the white portion 21b. Therefore, the signal obtained from one scan line contains color and luminance information of two different regions. First, the n-th scanning line is composed of a pixel column belonging to the black portion 21a and a pixel column adjacent to this below and belonging to the white portion 21b. Therefore, the output of the upper pixel column, that is, Mg
and the signal component of G becomes 0. Therefore, the luminance signal component Y given by (Mg+Ye)+(Ye+Cy) is expressed as Ye+Cy, and (Mg+Ye)-(G
The color difference signal component C represented by +Cy) is represented by Ye-Cy. On the other hand, the n0mth scanning line is the black part 21
The pixel column belonging to a and the white part 21 adjacent to the above
pixel column belonging to b. Therefore, the output of the lower pixel column, that is, the Ye and Cy signal components become O. Therefore, the luminance signal component Y (narrowband luminance signal YL, wideband luminance signal YOH) is represented by Mg+G, and the color difference signal component C is represented by Mg-G.

The obtained narrowband luminance signal YL and color difference signal component C are
The signals are converted into color difference signals R, -Y and BY while being white balanced adjusted by a white balance circuit.

Therefore, the color difference created from the color difference signal component and the luminance signal component obtained from the part corresponding to the minute width d of the scanning line from the n+1st to (n 10m) -1th belonging to the achromatic white part 2]b Signal R-Y or B-Y both become 0. However, the luminance signal components obtained from the n-th and n10m-th scanning lines include a signal obtained by imaging an object with a luminance of 0, that is, an achromatic black, and a signal obtained by imaging an object whose luminance is not O, that is, nothing. This includes signals obtained by imaging colored white. On the other hand, white balance adjustment is performed by performing calculations on the luminance signal component and color difference signal component when creating the color difference signal under conditions such that the calculation result is 0 when an achromatic white subject is imaged. It will be done. Therefore, the color difference signals RY and BY obtained from the n and n+mth scanning lines are both not O.

FIG. 8 is a simplified waveform diagram showing the process from which the color difference signal components obtained from each scanning line are converted into the final chrominance signal. The waveform of the output luminance signal YOH is shown. As described above, the luminance signal component Y is at a constant level, which is not 0, in all the portions corresponding to the portions included in the white portion 21b among the (n+1)th to n+m−1th scanning lines. but,
Black portion 21a of the n and n10mth scanning lines
In the portion corresponding to the boundary between the white portion 21b and the white portion 21b, the level is lower than that. Therefore, the luminance signal YOH has a waveform as shown in FIG. 8(A).

With reference to FIG. 8(B) and FIG. 5, from nth to n+
Of the scanning lines up to the m-th, the white part -20=21, from the part corresponding to b, the color difference signal component 2R-
G and 28-G are obtained alternately. Hereinafter, the scanning line from which the color difference signal component 2R-G is obtained is referred to as the R line, and the color difference signal component 2
The scanning line from which BG is obtained is called a B line. As described above, in the n+1st to n10m-1th scanning lines, the color difference signal components obtained from the R line and the color difference signal components obtained from the B line are the same.

However, the levels of the color difference signal components 2R-G obtained from the n and n10m-th scanning lines corresponding to the boundary between the black part 21.2 and the white part 21b are from the n+1st to (n0m)
- lower than that obtained from the R line among the first scan lines. Further, all color difference signal components obtained from the scanning lines belonging to the black portion 21a, that is, scanning lines other than those mentioned above, are zero.

Next, referring to FIG. 8(C), when the color difference signal components shown in FIG. 8(B) are converted into line-sequential color difference signals, the n and n+mth scanning lines are The color difference signals created in the part corresponding to -21= are all 0, but the color difference signals obtained from the part corresponding to the white part 21b among the n and n+mth scanning lines are 0 and 5. z, signal q,
and (12 (hereinafter referred to as a false color signal)) appear.

Next, with reference to FIGS. 8(D) to (H), FIG.
) is delayed by one horizontal scanning period in the line-sequential synchronization circuit (see Fig. 8 (
D)) is further delayed by one horizontal scanning period IH (eighth
Figure (E)). Next, in this way, two horizontal scanning periods 2H
The delayed line sequential color difference signal (FIG. 8(E)) and the original line sequential color difference signal without time delay (FIG. 8(C)) are averaged and are shown in FIG. 8(F). (hereinafter referred to as an averaged color difference signal).

Next, the line sequential color difference signal (
Figure 8 (D)) and averaged color difference signal (Figure 8 (F))
are alternately outputted to two signal lines every 1H horizontal scanning difference period to obtain synchronized color difference signals B-Y (Fig. 8 (G)) and R-Y (Fig. 8 (H)). . Figure 8 (G)
As can be seen from (H), the false color signals q and q2 appearing on the R line also appear on the scanning line one scanning line and two scanning lines later, respectively, in the synchronized color signal RY.

Subsequently, the simultaneous color difference signals R-Y and B-Y as shown in FIGS. 8(G) and (H) are balanced-modulated by a balanced modulation circuit, thereby producing the signals shown in FIG. 8(1). You can get a Roma signal like this. As can be seen from FIG. 8(I), false color signals in the simultaneous color difference signal appear in the same portion of the chroma signal. This chroma signal is attenuated in the chroma signal gain control circuit at an attenuation rate proportional to the level of the luminance signal YOH (FIG. 8(A)) with no time delay, which is simultaneously applied thereto. Therefore, the chroma signal after passing through the chroma signal gain control circuit corresponds to the part where the level of the luminance signal YOH (Fig. 8 (A)) is not 0 in the original chroma signal (Fig. 8 (I)). The signal of the portion (portion corresponding to the n-th to n+m-th scanning line) is attenuated (FIG. 8(J)). Therefore, among the false color signals included in the original chroma signal, those corresponding to the portion where the level of the luminance signal YOH is 0 (
The false color signals appearing on the n+m+1 and n+m+2 scan lines are not attenuated and appear as they are in the chroma signal after passing through the chroma signal gain control circuit. As a result, the portions corresponding to the n+m+1 and n0m+2-th scanning lines in the reproduced image, that is, the white portions 21 that should originally be black.
A phenomenon occurs in which the lower part of a is colored unnaturally.

Incidentally, the chroma signal gain control circuit is originally intended to suppress abnormal coloring in high brightness areas.

Therefore, assume that the brightness of the white portion 21b is extremely high and exceeds the dynamic range of the color difference signal component, that is, there is a need to suppress abnormal coloring. In such a case, the line-sequential color difference signal obtained from the scanning line corresponding to the high-luminance portion 21b does not become O. This high brightness portion 21b
A non-zero line-sequential color difference signal (hereinafter referred to as a high-brightness abnormal coloring signal) obtained from the scanning line corresponding to the chroma signal also appears in the chroma signal, so the chroma signal obtained in such a case is The result will be as shown in Figure 8 (K). In this case, the brightness of the white portion 21b is higher than in the case where only the false color signal appears, so the level of the chroma signal is higher than that shown in FIG. 8(I). Next, a portion of this chroma signal corresponding to a portion where the level of the luminance signal YOH is not 0 is attenuated by a chroma signal gain control circuit. Therefore, when the ROMA signal as shown in FIG. 8(K) passes through the chroma signal gain control circuit, the signal becomes as shown in FIG. 8(L). As can be seen from FIGS. 8(K) and 8(L), because the brightness of the white portion 21b is too high, a high brightness abnormal coloring signal (n+3) is newly generated in the chroma signal in addition to the false color signal.
The signals appearing in the n0m-1th scanning line from the white part 21. The false color signal appearing in the part corresponding to the lower part of b still remains as it is (of course, in this case, the level of the brightness signal YOH used for the high brightness color suppression signal that controls the gain of the chroma signal gain control circuit) is higher than that in the case where only false color signals appear). Therefore, in the reproduced image, although no abnormal coloring occurs in the white portion 21b, the lower part of the white portion 21b is still unnaturally colored. Note that this problem commonly occurs in color imaging devices using the field storage type color difference line sequential method, and under conditions other than the various conditions in this example, that is, when the boundary between the white part and the black part is 1 This problem also occurs when the image corresponds to a position shifted from the center of the pixel rows constituting the scanning line, and when the color arrangement of the color filter example is other than that shown in FIG.

As described above, according to the conventional imaging device, the abnormal coloring phenomenon in the high-brightness part of the subject can be avoided, but there is a clear boundary in the vertical direction, as typified by the captured image shown in Fig. 5. The coloring phenomenon caused by false color signals that occurs when an image is captured cannot be avoided. Therefore, when an object whose color has no vertical correlation with the color of the background is imaged, the color of the lower part of the object in the reproduced image becomes unnatural and different from the actual color due to the false color signal.

SUMMARY OF THE INVENTION An object of the present invention is to provide a color imaging device that can solve the above-mentioned problems and simultaneously suppress abnormal coloring phenomena in high-brightness areas and unnatural coloring phenomena caused by false color signals in reproduced images. It is.

[Means for Solving the Problems] In order to achieve the above object, a color imaging device according to the present invention captures an image of a subject and captures colors derived line-sequentially in the form of a luminance signal and a color difference signal. an imaging means for deriving a video signal consisting of a signal, a means for separating the video signal from the imaging means into a luminance signal and a line-sequential color difference signal, and a means for delaying the luminance signal separated by the separation means for two horizontal scanning periods. , means for creating a color difference signal suppression signal by adding and averaging the undelayed luminance signal from the separation means and the delayed luminance signal delayed by the delay means; and means for simultaneously generating the line-sequential color difference signals separated by the separation means. and means for suppressing the synchronized color difference signal from the synchronized color difference signal creation means in response to the color difference signal suppression signal from the color difference signal suppression signal creation means. Ta.

[Function] As described above, in the color imaging device according to the present invention, the color difference signal suppression signal is created by adding and averaging the undelayed luminance signal and the luminance signal delayed by two horizontal scanning periods by the delay means, unlike the conventional one. be done. On the other hand, when a false color signal is included in the line sequential color difference signal, the position where the false color signal appears in the synchronized color difference signal obtained by synchronizing the line sequential color difference signals is determined by the position where it appears in the line sequential color difference signal and the position where the false color signal appears in the line sequential color difference signal. This is a position shifted by one horizontal scanning period and two horizontal scanning periods from there. Therefore, the appearance position of the false color signal in the simultaneous color difference signal is included within the generation period of the color difference signal suppression signal. Therefore, the synchronized color difference signal suppressed in response to the color difference signal suppression signal does not include a false color signal.

[Embodiment] FIG. 1 is a partially schematic block diagram of a color video camera showing an embodiment of the present invention. Referring to the figure -28=, this color video camera uses a field accumulation type color difference line sequential type CC, similar to the conventional color video camera.
DI, a Y/C separation circuit 2, an enhancer circuit 3 having two one-horizontal scanning period delay circuits for contour compensation as in the conventional case, a white balance circuit 4, a mixing circuit 5,
A line sequential synchronization circuit 9 having the same internal configuration as the conventional one,
It includes a balanced modulation circuit 10 and a chroma signal gain control circuit 11. The basic function and operation of each of all these functional units is the same as that of the conventional color video camera shown in FIG. However, unlike the prior art, the signal applied to the chroma signal gain control circuit 1 to control its gain is not the luminance signal YOH without time delay.

This color video camera further includes an averaging circuit 12a and a process circuit 12b, which were not provided in the past.
The color difference signal suppression signal generation circuit 12 includes a color difference signal suppression signal generation circuit 12 including the following. The color difference signal suppression signal generation circuit 12 receives the wideband luminance signal YOH from the Y/C separation circuit 2 and the luminance signal Y2H delayed by 2 horizontal scanning periods 2H, which is created inside the enhancer circuit 3 when creating the vertical contour signal. is given. Brightness signal YOH
and the luminance signal Y2H delayed by two horizontal scanning periods are averaged by the averaging circuit 12a. The resulting signal is given to the chroma signal gain control circuit 11 as a color difference signal suppression signal via the process circuit 12b.

The role of the process circuit 12b is similar to that of the process circuit 6 in the conventional color video camera shown in FIG. Therefore, unlike the conventional case, the chroma signal gain control circuit 11 operates at an attenuation rate proportional to the level of the signal obtained by averaging the luminance signal Y2H delayed by 2H for two horizontal scanning periods and the luminance signal YOH without time delay. The mixing circuit 5 attenuates the chroma signal from the balanced modulation circuit 10.
give to

Here, assume that an image 21 as shown in FIG. 5 is captured. In the following explanation, the correspondence between the image 21 and the scanning lines and pixel columns on the CCDI is the same as in the explanation of the conventional problems (see FIG. 6). FIG. 2 is a simplified waveform diagram showing the process until the final ROM signal is created when an image as shown in FIG. 5 is captured, similar to FIG. 8. Refer to FIG. 2 for the following explanation.

The process before passing through the chroma signal gain control circuit 11 from the color difference signal component and luminance signal component obtained from each scanning line, that is, until the chroma signal applied to the signal line 2 is created, is the same as the conventional process ( (See FIGS. 2(A)-(H)). Therefore, in this case, in the chroma signal output from the balanced modulation circuit 10 as in the conventional case, the false color signal is generated at the n and n+mth scanning lines corresponding to the vertical boundary between the black portion 21a and the white portion 21b. and appear in the scanning lines one scanning line and two scanning lines after each of these (FIG. 2(H)). Also, the white part 21 of image 21
If the luminance of b is very high and exceeds the dynamic range of the color difference signal component, the chroma signal containing the high luminance abnormally colored signal (Fig. 2 (I)) is also generated for the same reason as before.
is output from the balanced modulation circuit]0.

−31= Next, in the above case, the color difference signal suppression signal generation circuit 1
The color difference signal suppression signal created in step 2 will be explained. In the above case, the level of the luminance signal YOH output from the Y/C separation circuit 2 is the same as in the conventional case.
The boundary between 1a and the white part 21b becomes O in all parts other than the part included in the white part 21b (FIG. 2 (J)). Therefore, the luminance signal Y2H generated in the enhancer circuit 3 and delayed by 2H for 2 horizontal scanning periods
becomes as shown in Fig. 2 (K). These two luminance signals ((J) and (K) in FIG. 2) are sent to the averaging circuit 1.2 in the color difference signal suppression signal generation circuit 12.
It is averaged by a.

Therefore, the signal output from the averaging circuit 12a is as shown in FIG. 2(L). In this color video camera, this averaging signal is given to a chroma signal gain control circuit as a color difference signal suppression signal. Therefore, the chroma signal that has passed through the chroma signal gain control circuit 11 is the averaged luminance signal (second
It is obtained by attenuating the signal in the portion where the level is not 0 in FIG. On the other hand, a portion where the level of the averaged luminance signal is not 0 is the same as a portion where a false color signal and a high brightness abnormal coloring signal appear in the original chroma signal. Therefore, the chroma signal gain control circuit 11 removes all the false color signals and high brightness abnormally colored signal parts included in the original chroma signal (FIG. 2 (H) or (I)), and the chroma signal gain Control circuit 1
As shown in FIG. 2(M), the chroma signal outputted from No. 1 contains neither a false color signal nor a high-luminance abnormally colored signal. Therefore, in the reproduced image based on the composite video signal output from the mixing circuit 5, the lower part of the white part 21b is not colored unnaturally as in the conventional case, and the abnormality in the high brightness part that occurs when the brightness of the white part 21b is high. Coloring phenomena are also suppressed as before.

Note that the boundary between the black part 21a and the white part 21b = 33
- The same applies when the field corresponds to a position shifted from the middle of the pixel rows constituting one scanning line, and when the color arrangement of the color filter example arranged on the image sensor is different from that in this example. Effects can be obtained.

Note that the signal processing order and the arrangement of each circuit in the color imaging device according to the present invention are not limited to this embodiment.

[Effects of the Invention] As described above, according to the color imaging device according to the present invention,
All false color signals included in the simultaneous color difference signal are removed together with the high brightness abnormal coloring signal.

Therefore, when an object whose color has no vertical correlation with the color of the background is imaged, the lower part of the object will not be colored unnaturally by false color signals in the resulting reproduced image. Therefore, the quality of the reproduced image is improved as a result, and the function as a color imaging device is improved.

[Brief explanation of drawings]

FIG. 1 is a partial schematic block diagram of a color video camera showing an embodiment of the present invention, FIG. FIG. 3 is a partial schematic block diagram of a conventional field storage type color difference line sequential method color video camera, FIG. 4 is a plan view showing the arrangement of color filters on the image receiving surface of a CCD in the conventional example and the embodiment, and FIG. 6 is an example of a captured image for explaining the conventional example and the embodiment, FIG. 6 is a diagram showing the correspondence relationship between the image shown in FIG. Figure 6 is a diagram showing the luminance signal component and color difference signal component obtained from each of the scanning lines shown in a table format, and Figure 8 is a waveform diagram showing the process until the final ROM signal is created in the conventional example. It is. In the figure, 1 is a CCD, 2 is a Y/C separation circuit, 3 is an enhancer circuit, 4 is a white balance circuit, 5 is a mixing circuit, 6 and 12b are process circuits, 7a and 7b are delay circuits, 7C and 12a are addition 8 is a switching circuit, 9 is a line-sequential synchronization circuit, ] 0 is a balanced modulation circuit, 1
1 is a chroma signal gain control circuit, and 12 is a color difference signal suppression signal generation circuit. In addition, in the figures, the same reference numerals indicate the same or corresponding parts. = 36 ~ 10,000, 8 figures

Claims (1)

[Scope of Claims] An image capturing means for capturing an image of a subject and deriving a video signal consisting of a luminance signal and a color signal, the image capturing means linearly deriving the color signal in the form of a color difference signal, means for separating the video signal from the imaging means into a luminance signal and a line-sequential color difference signal; means for delaying the luminance signal separated by the separation means by two horizontal scanning periods; and a non-delayed luminance signal from the separation means. and means for adding and averaging the delayed luminance signal delayed by the delay means to create a color difference signal suppression signal; and means for suppressing the synchronized color difference signal from the synchronized color difference signal creation means in response to the color difference signal suppression signal from the color difference signal suppression signal creation means.