JPS63198495A - Video camera - Google Patents

Abstract

PURPOSE:To prevent deterioration in color reproducibility caused by gamma-correction by executing the primary conversion of a linear sequential color signal demodulated from a modulated signal, generating three primary color signals from thus obtained color difference signal and a narrow band luminance signal, and executing the gamma-correction. CONSTITUTION:A frequency multiplex signal from a solid-state image pickup element 1 is subjected to an AGC circuit 2, LPFs 3, 4, and a BPF 5, and comes to be luminance signal Y, a narrowband luminance signal YL, and a modulated signal. The signal Y and the signal YL are inputted respectively to a signal processing circuit 13 and a matrix circuit 12. On the other hand, the modulated signal undergoes a synchronizing detector 6, an LPF 8, a switching circuit 10, and a one-H delay line 9, so that color difference signals 2R-G, 2B-G are inputted to the circuit 12, and thus color signals R, G, B are generated. A signal G is gamma-corrected in a gamma-correction circuit 16, while R and B are in gamma-correction circuits 17, 18. From-corrected color signals R', B', and luminance signal YL', a color difference matrik circuit 19 generates color difference signals, which are supplied to an encoder 20 along with a luminance signal Y' from the circuit 13, and thus a color video signal is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a video camera using a color difference line sequential type solid-state image sensor, and particularly to processing of an output signal of the solid-state image sensor.

[Conventional technology]

Solid-state image sensors include MOS and CCD types, but currently, CCD-type solid-state image sensors are becoming more popular due to their smaller size and higher sensitivity, and in particular, solid-state image sensors with color difference line sequential method is becoming mainstream.

Here, a color difference line sequential type CCDC solid-state image sensor will be briefly described.

On the light-receiving surface of the solid-state image sensor, one of four complementary color filters, Mg (magenta), G (green), Ye (yellow), and Cy (cyan), is provided on each pixel. The arrangement relationship of these complementary color filters is shown in FIG. In the figure, arrow A is in the horizontal scanning direction;
If arrow B is the vertical scanning direction, the adjacent 2
Two pixel columns are scanned simultaneously. In other words, as indicated at the right end of Figure 6, the pixel of the Mg filter starts at the (n-1)th line (the line is a horizontal scanning line, and hereinafter the i-th line is referred to as the i-line). pixel row and c
When the pixel row starting from the pixel of the y filter is simultaneously scanned horizontally, in the next n lines, the next two pixel rows, the pixel row starting from the pixel of the G filter and the pixel row starting from the pixel of the cy filter, are simultaneously scanned horizontally. scan.

Furthermore, in the odd and even fields, as indicated at the left and right ends of FIG. 6, the two pixel columns that are simultaneously scanned horizontally are shifted by one from each other.

From these pixels, color pixel signals (hereinafter referred to as Mg pixel signal, G pixel signal, Ye pixel signal, and cy pixel signal, respectively) according to the complementary color filters provided therein are obtained.
The simultaneously read color pixel signals of two pixel columns that are simultaneously horizontally scanned are added together and output. Therefore, in FIG. 6, regarding the (n-1) line of the odd field, the sum signal of the Mg pixel signal and the cy pixel signal (
It is called the (Mg+Cy) signal. The same applies hereafter) and (Q+Ye
) signals are obtained alternately and repeatedly, and on the n line, (G
+Cy) signal and (Mg+Ye) signal are obtained alternately and repeatedly. These repetitive signals are obtained alternately for each line, and are obtained by frequency multiplexing a baseband signal and a modulation signal centered at the pixel repetition frequency (clock frequency) fc.

Here, since the baseband signal is an average signal, (
n-1) line, (Mg+Cy)+ (G+Ye) --...-(1
), and on the n line, (G+Cy) + (Mg+Ye) - (2), but if the red signal is R1 and the green signal is B, then Ye=G+R, M
Since g-R+B and Cy=G+B, formula (1),
Both (2) are 3G + 2R + 2B ・
...(3). Further, equation (3) approximates a luminance signal, and this is used as the luminance signal Y. Also, since the modulation signal is expressed as the average difference between the maximum value and the minimum value of the waveform that changes with the clock frequency fc, (n-1)
For the line, (Mg+Cy)-(G+Ye)=28-G-(4) For the n line, (Mg+Ye) (G+Cy)=2R-c----
...(5) However, the G signal is approximated to the luminance signal Y, and as a result, equations (4) and (5) each represent different color difference signals.

Therefore, in the odd field, the luminance signal Y shown in equation (3) is used as a baseband signal, and the carrier wave of clock frequency fc is used as the baseband signal as shown in equation (4).

A signal (FIGS. 7(a) and 7(b)) obtained by frequency multiplexing the modulated signal modulated by the color difference signal expressed by (5) is obtained line-sequentially.

In the even field, since it is indicated at the right end in FIG. 6, the (Cy+G) signal and (Ye+M
g) signals are obtained alternately, and (C
y+Mg) and (Ye+G) signals are obtained alternately. Therefore, the baseband signal is n lines, (n + 1
) Both lines are Cy + G + Y e + M
g, which is similar to equation (3) and represents the luminance signal Y, and the modulation signal is n lines, (Ye+Mg)
(Cy+G)=2R-G, which is similar to the color difference signal in equation (5), and on the (n+1) line, (Cy+Mg)-(Ye+G)=2B-G, which becomes equation (5).
This is similar to the color difference signal in 4).

Therefore, even in the even field, a signal is obtained in which the luminance signal Y is used as a baseband signal and a modulation signal of a line-sequential color difference signal is frequency multiplexed thereon.

The above has been a description of the operation of the solid-state image sensor. In a video camera, the output signal of the solid-state image sensor is subjected to predetermined processing, and a standard color video signal is generated and output. An example of this processing method is described in, for example, TV Technology March 1986, pp. 45-52.

According to this, first, the output signal of the solid-state image sensor is converted into a narrowband luminance signal YH1 having the same band as the wideband luminance YH1 color difference signal.
The modulated signal C is synchronously detected to obtain a line-sequential color difference signal 2R-G/2B-G. Broadband luminance signal Y1. I is the same as the previous luminance signal Y, and is simply referred to as the luminance signal Y. These luminance signal Y and narrowband luminance signal Y are supplied to the processor as they are, but the line sequential color difference signal 2R-G/2B-G is added to the narrowband luminance signal Yt to become the line sequential color signal R/B. After white balance adjustment, the image is supplied to the processor.

In the processor, wideband luminance signal Y, narrowband luminance signal YL
Then, the line sequential color signal R/B is gamma-corrected, and then the line sequential color difference signal RY/B-Y is formed from the narrowband luminance signal YL and the line sequential color signal R/B.

This line-sequential color difference signal R-Y/B-Y is supplied to a synchronization circuit consisting of an IH delay line and a switch, and a color difference signal B-Y is formed in the same manner as the continuous color difference signal R-Y. These color difference signals R'-Y and B-Y are supplied to a modulation circuit to form a carrier color signal.

[Problem that the invention seeks to solve]

In a television receiver, three primary color signals are formed from the received color video signal and these signals are supplied to a color cathode ray tube. At this time, since the color cathode ray tube has a γ characteristic (γ=2.2) for each primary color, the video camera processor performs γ correction of 1/γ as described above.

By the way, in a television receiver, the luminance signal of the received color video signal is YA, and the color signal is G', R.
', B', the luminance signal YA is: YA = 0.59G '+0.3OR' +0.11
Three primary color signals are generated as B' (6). In this case, the color signals R', B' are reproduced from the carrier color signal, while the color signal G' is formed according to equation (6).

On the other hand, in the color video signal output from the video camera, as is clear from the above description, the luminance signal Y corresponds to the luminance signal YA, and the color signals R and B correspond to the color signal R'
, B', which are γ-corrected to become a luminance signal YA and a color signal R', respectively.

B' is expressed as follows.

YA = Y'7 R' = RIA, B'-BI
/lr...-(8; Therefore, from these signals, the formula (
The color signal G' obtained by 7) is YA=y17=y
', then 0.59, Y' = 0.59G', 4+0.3OR'
, 4+0.11B'l, then equation (9) can be expressed as follows.

0.59 0.59. Furthermore, these color signals G', R', and B' are supplied to a color cathode ray tube, and due to their γ characteristics, the three primary color outputs E c, EM, and E a of the color cathode ray tube are as follows.

E* = (R')1 (R', +) γ=RE, = (
B') γ = (R1/γ) γ = B This causes a problem in that green reproduction errors occur in the reproduced image of the color cathode ray tube, and red and high-saturation colors in the front direction tend to change in hue toward the edges. was there.

SUMMARY OF THE INVENTION An object of the present invention is to provide a video camera that can solve these problems and prevent deterioration in color reproducibility caused by γ correction.

[Means for solving problems]

In order to achieve the above object, the present invention provides a processing means for forming a carrier color signal of a standard color video signal from a modulation signal in an output signal of a color difference line sequential image sensor. A means for sequentially and simultaneously converting a line-sequential color signal obtained by demodulating the signal, and a means for generating three primary color signals from two continuous color difference signals and a narrowband luminance signal obtained by the means are arranged. do.

[Effect]

3 from the above modulation signal output by the color difference line sequential image sensor
It is possible to generate two primary color signals, and γ correction is applied to each of these primary color signals. Two color difference signals are formed using these primary color signals, but the narrowband luminance signal that forms these color difference signals is different from the wideband luminance signal, and in a television receiver, these color difference signals and the wideband luminance signal are If three primary color signals are formed from , the same error will be included in each primary color signal, and no hue error will appear.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a video camera according to the present invention, in which 1 is a solid-state image sensor, 2 is an AGC (automatic gain control) circuit, 3 and 4 are LPFs (low-pass filters), and 5 is a BPF. (bandpass filter), 6 is a synchronous detector, 7 is an input terminal, 8 is an LPF, 9 is an IH (1 horizontal period) delay line, 10 is a switching circuit, 11 is an input terminal, 12 is a matrix circuit, 13 is a signal processing circuit, 14.
15 is a white balance circuit, 16 to 18 are gamma correction circuits, 19 is a color difference matrix circuit, and 20 is an encoder.

In the figure, a solid-state image sensor 1 is a solid-state image sensor of the color difference line sequential method described in FIG. 6, and outputs a frequency multiplexed signal as described in FIG.

This frequency multiplexed signal becomes a constant level signal in the AGC circuit 2, and is supplied to the LPF 3.4 and the BPF 5. L
In the PF3, the baseband luminance signal Y in the frequency multiplexed signal is separated and supplied to the signal processing circuit 13.

The LPF 4 extracts a reduction component of the luminance signal Y in the frequency multiplexed signal in a band approximately equal to the color signal, and supplies it to the matrix circuit 12 as a narrowband luminance signal YL.

The BPF 5 separates the modulated signal in the frequency multiplexed signal. This modulation signal is synchronously detected by the synchronous detector 6 using the clock of the pixel repetition frequency fc in the solid-state image sensor 1 from the input terminal 7, and the harmonic components are removed by the LPF 8, resulting in a line-sequential color difference signal 2R-G/2B-G. is obtained. This line-sequential color difference signal 2R-G/2B-G is directly supplied to the switching circuit 10, and also delayed by the IH delay line 9 and supplied to the switching circuit 10. This switching circuit 10 is controlled by a switching signal of frequency fN/2 (where f is the horizontal synchronization frequency) from an input terminal 11, and continuous color difference signals 2R-G and continuous color difference signals 2B-G are simultaneously obtained. It will be done. These color difference signals 2R-0, 2B=G are supplied to the matrix circuit 12.

The matrix circuit 12 performs the following arithmetic processing using the narrowband luminance signal YL and color difference signals 2R-G and 2B-G to generate color signals G, R, and B. However, narrowband luminance signal YL
is YLW3G+2R+2B according to equation (3).

G= (Yt-(2R-G) (28-G))R
= −(YL+4(2R-G)−(2B-G))B=
-(YL-(2R-G)+4(2B-G)) The color signal G obtained by the matrix circuit 12 is subjected to γ correction by the γ correction circuit 16, and is supplied to the color difference matrix circuit 19. Also,
The color signals R and B obtained by the matrix circuit 12 are respectively
After the white balance is adjusted by the white balance adjustment circuit 14.15, the signal is subjected to γ correction by the γ correction circuit 17.18, and then supplied to the color difference matrix circuit. The color difference matrix circuit 19 receives the γ-corrected color signals G' and R'.

From B', YL' = 0.59G'+0.3OR' +0.
11B' (However, G' = Cl7. R' = R
≠, B'=Bμ), and from this and the color signals R' and B', two color difference signals R'
-YL J,B/-YL L is formed.

On the other hand, in the signal processing circuit 13, the luminance signal Y is subjected to processing such as γ correction, horizontal and vertical contour compensation. This luminance signal Y' is the color difference signal R' from the color difference matrix circuit 19.
-Yt' and B'YL' are supplied to the encoder 20 to form a standard color video signal.

Therefore, when a television receiver receives such a color video signal, it separates the luminance signal Y' and two color difference signals R'YL', B'-YL', and converts the three primary colors as described above. Signal R,,B,,
Generate co. Therefore, these are expressed as follows.

Ro = (R'Yt') + Y' = R1++ (Y'
YL') Bo = (B', YL') + Y' = 13
! A+(Y'Yt')0.59 0.59 =G'+(Y'-YL')=GI/r+(Y
'-YL') Therefore, the primary color outputs E R, E s of the color cathode ray tube.

E is expressed as follows.

ER=ROr=(RI/Ir+(Y'-YL'
))'E s = Boγ= [B'%r+(Y'
-YL'))'Ec=Go7 = (G'A+(Y
'-YL'))' As described above, the three primary color outputs of the color cathode ray tube all contain the same error (Y'-YL'), and although the saturation changes, the hue does not. The error (Y'YL') becomes large only at high saturation, and the reproduced image changes linearly in the direction of saturation, so the color reproducibility error is hardly noticeable.

FIG. 2 is a block diagram showing another embodiment of the video camera according to the present invention, in which 21 and 22 are comb filters, and parts corresponding to those in FIG. do.

This embodiment includes a color difference matrix circuit 19 and an encoder 2.
Comb filters 21 and 22 are provided between the two color difference signals R'-YL' outputted by the color difference matrix circuit 19.
, B'-YL' are supplied to the encoder 20 via comb filters 21 and 22, respectively.

FIG. 3 is a block diagram showing still another embodiment of the video camera according to the present invention, in which 23 is a balanced modulator, 24 is a comb filter, 25 is an adder, and the parts corresponding to those in FIG. The same reference numerals are used to omit duplicate explanations.

In this embodiment, a comb filter 24 is provided in the encoder 20, and two color difference signals R'-YL' and B'YL' from a color difference matrix circuit 19 are modulated by a balanced modulator 23 to form a carrier color signal. After this carrier color signal is passed through a comb filter 24, it is added to the luminance signal Y' from the signal processing circuit 13 in an adder 25.

Next, the functions and effects of providing the comb filters of the embodiments shown in FIGS. 2 and 3 will be explained.

In a solid-state image sensor using a color difference line sequential method, the vertical resolution of color signals is degraded. Now, for example, Fig. 4(a)
Assume that you have captured an image of an object whose color changes diagonally from red to white, as shown in . The R signal component is the output color difference signal 2R-G, 2
Since it is included only in the color difference signals 2R-G of B-G, it is obtained every other line as shown in FIG. 4(b). As described above, the IH delay line 9 and the switching circuit 10 cause the (K+1) line without the color difference signal 2R-G, (
Since the K+3) line complements the color difference signal 2R-G of the (K+2) line, it becomes an R signal component as shown in FIG. 4(d), and as a result, as shown in FIG. 4(C),
The contours of the red and white areas become discontinuous. Therefore, if an IH rough feed forward type filter shown in FIG. 5 is used as an example of the comb filters 21, 22, 24,
+1) line is (K+ (K+1))/2 is (K+2
) line is ((K+1)+ (K+2))/2 is (K
+3) Since the lines ((K+2) + (K+3)) /2 are obtained, the discontinuities in the outlines of the red and white areas become finer, as shown in Figure 4 (e) and (f). The discontinuity will be compensated for.

At the same time, the S/N ratio can also be improved by inserting a comb filter.

Since the center of gravity of the comb filter shifts downward by zH, in the embodiment shown in FIG. This will generate a signal. In Figure 2, two comb filters are required because the comb filter is inserted in the baseband color difference signal path, but by targeting the baseband color difference signal, the comb filter can be used. A narrow band IH delay line can be used as the constituting IH delay line. Since the embodiment shown in FIG. 3 is intended for a carrier color signal obtained by balanced modulation, only one comb filter is required.

〔Effect of the invention〕

As explained above, according to the present invention, the same error is included in the three primary color signals in the television receiver, and the hue error of the reproduced image can be suppressed, thereby improving the color reproducibility. An excellent effect of a significant improvement can be obtained.

[Brief explanation of the drawing]

1, 2, and 3 are block diagrams showing embodiments of the video camera according to the present invention, and FIG. 4 is an explanatory diagram showing the operation and effect of the embodiment shown in FIGS. 2 and 3. ,・
Fig. 5 is a block diagram showing a specific example of the comb-shaped filter in Figs. FIG. 3 is a signal spectrum diagram showing an output signal of an image sensor. 1...Color difference line sequential type solid-state image sensor, 3, 4...
...Low pass filter, 5...Band pass filter, 6...Synchronous detector, 9...
・IH delay line, 10...Switching circuit, 1
2... Matrix circuit, 13... Signal processing circuit, 16-18... γ correction circuit, 19.
...Color difference matrix circuit, 20...Encoder, 21, 22.24...Comb filter. Figure 1 Figure 2 Figure 4

Claims (1)

[Claims] 1. An imaging device that outputs a frequency multiplexed signal of a luminance signal and a modulation signal modulated with a line-sequential color difference signal, and a first device that separates a wideband luminance signal, a narrowband luminance signal, and the modulation signal from the frequency multiplexed signal. means, second means for demodulating the modulated signal to generate the line sequential color difference signal, third means for generating two continuous color difference signals from the line sequential color difference signal, and the two color difference signals. fourth means for generating three primary color signals from and the narrowband luminance signal;
a fifth means for correcting;
a sixth means for generating two continuous color difference signals;
A video camera characterized in that it has a seventh means for encoding the color difference signal outputted from the means and the broadband luminance signal.