JPH0197088A - Chroma signal processor for veneer color camera - Google Patents

Abstract

PURPOSE:To simplify a chroma signal processing circuit by mixing luminace signals into chroma signals obtained from the outputs of subtraction circuit in two horizontal scanning periods at an arbitrary ratio in the separation circuit separating the output signals of an image pickup element and in the subtraction circuit subtracting the separated picture element signals at the arbitrary ratio, and directly obtaining color difference signals. CONSTITUTION:When the gain of addition signals S1 is set to '1', the gain a1 of addition signal Sa becomes smaller than '1'. Consequently, the output signals of separation circuits 121 and 122 are added to amplifiers 131 and 132, for example, and the gain of the amplifier 131 is set to 1+a1 and that of the amplifier 132 to 1-a1. The output signals of the amplifiers 131 and 132 are added to the subtraction circuit 141 and the obtained signals are band-restricted in a low pass filter 151, whereby they are delayed in a 1H delay circuit 161 for one horizontal scanning period. When the output signals of the low pass filter 151 and the 1H delay circuit 161 are added in an addition circuit 181, the color difference signals CB can be obtained. Thus, the color difference signals can be obtained by gain-adjusting the amplifiers 131 and 133, or the amplifiers 132 and 134.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a single-chip color camera, and in particular, it simplifies the signal processing circuit even when demodulating a chroma signal using signals obtained during two horizontal scanning periods. This invention relates to a chroma signal processing bag for a single-panel color camera.

[Conventional technology]

Are recent home video cameras solid-state cameras? By using i-devices, we have achieved smaller size, lighter weight, higher reliability, and higher productivity. In particular, a single-chip color camera that uses only one image sensor combined with a mosaic color filter is an effective configuration for reducing costs.

Single-chip color cameras must obtain brightness and chroma signals simultaneously from one image sensor, so image quality, especially resolution and single-color reproducibility, tends to deteriorate. Various color filters or signal processing methods have been proposed to obtain this.

An example of a conventional single-chip color camera is JP-A-58-1989.
It has been proposed in 79. The color filter and signal processing circuit of the single-chip color camera proposed in JP-A-58-198979 are shown in Figures 2 and 3, respectively.The operation of the conventional single-chip color camera shown in Fig. -198979, but will be briefly explained below.

The color filters shown in Figure 2 are Ye (yellow transmission) and Cy
A horizontal pixel row Qx in which (cyan transmission) is repeated;
Horizontal pixel rows Q2 in which G (green transparent) and W (gold transparent) are repeated are arranged alternately every other column, and horizontal pixel rows fl in which Ye and W are repeated between them.
at jla is located. Here, when the image sensor corresponding to the color filter mixes and reads out the pixel signals of two adjacent columns, in the n-th horizontal scanning period, Y
Pixel signals of pixel column Q1 where e and cy are repeated and Y
The pixel signals of the pixel column Q3 in which e and W are repeated are mixed and extracted. Similarly, in the (n+1)th horizontal scanning period, the pixel signals of the pixel column a2 in which G and W are repeated,
The pixel signals of the pixel column Q4 in which Ye and W are repeated are mixed and extracted.

As a result, the signal SngSn''l obtained in the n-th and n+1-th horizontal scanning periods is expressed by the following equation.

5n=2・Ye+Cy+W+・(2・Ye−Cy−W
)CO3ωt=2・Ye+Cy+W+K・(R-2B)
・cosωt −(1)S, +1=Ye+2
・W+G+K・(G+Ye-2W)cosωt=Ye+
2・W10G−K・(R+2B)・cO8ωt...(2
) However, K is the modulation component M from the constant 5nySn+1, (=to-(R-2B)
−coSωt) e Mn+t (=K・(R+ 2
B).cos ωt) and performs addition and subtraction, the addition signal A n+1 g subtraction signal D11+1 is expressed by the following equation, so B and H chroma signals can be obtained.

A n ” 1 = M n + M n+1 = -48
−to −cosωt −(3) DIl+l:
Mn-Mn+i = 2 ・RyuK 11cogωt −(
4) That is, in the signal processing circuit shown in FIG. 3, the signal S obtained alternately from the image sensor 2 every horizontal scanning period
After amplifying n # S n + x with the amplifier 3, it is added to the bandpass filter 4 to extract the modulation component MII or Main, and the extracted modulation component Mll or M n
+1 is delayed by one horizontal scanning period by the IH delay circuit 5. The two modulation components MR and M n + 1 obtained simultaneously from the bandpass filter 4 and the IH delay circuit 5 are added to the adder 6 and the subtracter 7, respectively, and the sum signal A n +
1 and a subtracted signal Da"l are obtained.The added signal An+x and subtracted signal DM+1 thus obtained are added to the demodulation circuits 81 and 82 and converted into low-frequency signals to obtain the B signal and the R signal.

On the other hand, the luminance signals are the signals SR and Sn obtained from the imaging probe.
The signal obtained from the imaging probe is added to the low-pass filter 10 to convert it into a low-pass signal free of modulation components. B obtained by demodulation circuits 81 and 82 in addition to calculation circuit 11
The G signal can be obtained by subtracting the R signal.

The R, G, and B signals obtained as described above are applied to the encoder circuit 17. FIG. 4 shows a general configuration of the encoder circuit 17 used here.

(For example, Fig. 2 of JP-A-56-122283, JP-A-58
-3386 in Fig. 2), and in the engoder circuit in Fig. 4, G
.

The B and R signals are added to a Y signal synthesis circuit 23 to obtain a Y signal used as a color difference signal. The obtained Y signal is added to subtraction circuits 143 and 144 together with the B signal and R signal, and two color difference signals B-Y are obtained from the respective outputs.

Obtain RY. Modulate the obtained color difference signal! 11
%11°192, and after being modulated by subcarriers, it is applied to the adder circuit 20 together with the luminance signal to obtain a color video signal.

[Problem that the invention seeks to solve]

In the conventional example described above, since the Rv (3G B 4:3 signal) is demodulated and the color difference signal is synthesized, a G signal demodulation circuit or a color difference signal synthesis circuit is required in addition to the R signal and B signal demodulation circuits. This not only increases the circuit scale, but also requires gain adjustment when performing subtraction in the G signal demodulation circuit or color difference signal synthesis circuit, leading to an increase in manufacturing costs.

The purpose of the present invention is to apply a color filter that demodulates a chroma signal using signals from two horizontal scanning periods.
The object of the present invention is to simplify the signal processing circuit by directly obtaining color difference signals.

[Means for solving problems]

The above object is to provide a separation circuit that separates an output signal obtained from an image sensor into each pixel signal, and a subtraction circuit that can subtract the output signals of each separation circuit at an arbitrary ratio.

A delay circuit that delays the output signal of the subtraction circuit by one horizontal scanning period, an addition circuit that adds the output signal of the subtraction circuit and the output signal of the delay circuit, and a modulation circuit that modulates the output signal of the addition circuit with a subcarrier are provided. This is achieved by

[Effect]

In the present invention, a portion l# for separating the output signal of the image sensor
A subtraction circuit that subtracts the pixel signal separated from the ii circuit at an arbitrary ratio operates to mix a luminance signal at an arbitrary ratio into the chroma signal obtained from the output of the subtraction circuit in two horizontal scanning periods. As a result, a color difference signal can be directly obtained by adding the output signals of the subtraction circuits obtained during two horizontal scanning periods, and the chroma signal processing circuit can be simplified.

(Example) Hereinafter, an example of the present invention will be explained using FIG. 1.
In the figure, the color filter shown in FIG. 2 is combined with the image sensor 2, as in the conventional example.

It is assumed that an operation is performed in which pixel signals of two adjacent columns are mixed and read out.

At this time, in the n-th horizontal scanning period, the signal of pixel column Q1 and the signal of pixel column Q3 are mixed and read out, so the signal obtained from image sensor 2 is as shown in FIG. 5(a).
e+Ye) and (cy+w) are repeated alternately. Also, in the n + 1st horizontal scanning period, the pixel column Qx
Since the signal from the pixel column Q4 and the signal from the pixel column Q4 are mixed and read out, the signal obtained from the image sensor 2 is a signal in which (G+Ye) and (W+W) are alternately repeated, as shown in FIG. 5(b).

Therefore, the signal obtained from the image sensor 2 is amplified by the amplifier 3 and then added to the one-separation circuits 121 to 124.

The sampling pulse with the phase shown in FIG. During the scanning period, (G+Ye) pixel signals are separated. On the other hand, the separation circuit 122 is
A sampling pulse with a phase shown in d) is applied to separate a (W+Cy) pixel signal in the n-th horizontal scanning period, and a (W+W) pixel signal in the n+1-th horizontal scanning period.

Furthermore, a sampling pulse with the phase shown in FIG. 5(e) is applied to the separation circuit 123, and in the n-th horizontal scanning period
+Ye) pixel signal and (W+W) pixel signal in the n+1st horizontal scanning period.

do. Similarly, the sampling pulse shown in FIG. 5(f) is applied to the separation circuit 124, and in the nth horizontal scanning period (C
y+W) pixel signals are separated, and (G+Ye) pixel signals are separated in the n+1-th horizontal scanning period.

Here, when W, Cy, and Me are decomposed into R, G, and B, the following equations are obtained.

W=R+G+'B...(5
)cy=a+B...(6
)Ye=R+G...(
7) Therefore, the sum signal S1 of the difference signal between the output signal obtained from the layer separation circuit 121 and the output signal obtained from the separation circuit 122, and a signal obtained by delaying this difference signal by one horizontal scanning period is as follows. Yes, B signal is obtained.

Sx=((W+Cy)+(W+W))−((Ye
+Ye)+(G+Ya))-(8)=4・B On the other hand, the addition signal S of the output signals of the separation circuits 121 and 122
a is as shown in the following formula.

5a=(W+Cy)+(W+W)+(Ya+Ye)+(
G+Ya)=8・G+6・R+4・B
...(9) From equation (9), S & is the luminance signal ((Ye+Ye
)+(Cy+W)) or ((G+Ye)+(W+
It can be seen that the component composition is the same as that of W)) (4・G+3・R+2・B).

Therefore, the B-Y color difference signal CB is synthesized using the B signal obtained from the addition signal S1 and the luminance signal obtained from the addition signal Sa. At this time 81. The gain is adjusted so that the output of St is equal to that of the monochrome subject, but (8),
As is clear from the comparison of equation (9), when the gain of the addition signal S1 is 1, the gain a1 of the addition signal Sa is smaller than 1. Therefore, the color difference signal CB is as shown in the following equation.

Ca=Slax ・Sa = ((w+cy)+(w+w))((Ye+Ya)+(
G-+Ye))-a x's ((W+Cy)+(W+W)
)+ ((Y e +Y e )+ (G+Y e )
)=(1-ax)((W+Cy)+(W+W))(1
+az) ((Ye+Ye)+(G+Ye))
...(lO)(8
) and (10), the color difference signal Ca has a gain of the output signal of the separation circuit 122 that is smaller than that at the time of B signal demodulation by al, and a gain of the output signal of the separation circuit 121 of 81.
All you have to do is make it larger and then perform the subtraction.

That is, in the signal processing circuit of the embodiment shown in FIG.
2, the gain of the amplifier 131 is set to (1+al), and the gain of the amplifier 132 is set to (1-ax). The output signals of the amplifiers 131 and 132 are added to the subtraction circuit 141, and the resulting signal is band-limited by the reduction filter 151, and then the IH
The delay circuit 161 delays the signal by one horizontal scanning period. Output signal of low-pass filter 151 and IH delay circuit 16
1 output signal in addition circuit 181, a color difference signal C is obtained.If this is added to modulation circuit 191 and modulated with a subcarrier, a B-Y modulation signal is obtained.

Similarly, the output signals of the separation circuits 123 and 124 are transferred to the amplifier circuit 1.
33 and 134 and is amplified and then added to the subtraction circuit 142. At this time, the gain of the amplifier circuits 133 and 134 is made to correspond to the ratio az when matching the magnitude of S2 and the above-mentioned addition signal Sa for a monochrome subject, which is determined by the following equation, and (
1-ax)s(1+az).

Sz=((Ye+Ye)+(W+W))−
((C'I +W)+(G+Y a));2・R...
(11) After the output signal of the subtraction circuit 142 is band-limited by the reduction filter m152, it is delayed by one horizontal scanning period by the IH delay circuit 162. If the output signal of the reduction filter 152 and the output signal of the IH delay circuit 162 are added in the adder circuit 182, R-
A Y color difference signal cR is obtained. This is added to the modulation circuit 192 and modulated with a subcarrier, and then added to the addition circuit 20 together with the output signal of the modulation circuit 191 and the output signal of the low-pass filter 9 to obtain a color video signal. In the conventional example shown in FIG. While the demodulation circuits 81 and 82 for obtaining B and R signals and the subtraction circuits 143 and 144 for obtaining color difference signals require adjustment, in the embodiment of the present invention shown in FIG.
1 (or 132) and the amplifier circuit 133 (or 13
A color difference signal can be obtained by simply performing the gain adjustment in step 4).

In the embodiment shown in FIG. 1, the IH delay circuit 161.1
After synchronizing and adding the signals of two horizontal scanning periods at 62,
It is assumed that modulation is performed by modulation circuits 191 and 192. On the other hand, in another embodiment shown in FIG.
. This allows IH
Since only one delay circuit is required, it is possible to further downsize the signal processing circuit.

It is clear from the linearity of the signal that the embodiment of FIG. 6 provides the same effect as the embodiment of FIG. 1.

Note that in the color video signal of the NTSC system, the phase of the modulation signal in consecutive horizontal scanning periods is shifted by 180 degrees, but in this case, if the adder circuit 183 is replaced with a subtracter circuit,
An addition signal can be obtained during the horizontal scanning period.

Further, in the conventional example and the embodiment of the present invention, the image sensor 2 has a second
An example has been described in which the color filters shown in the figure are combined and signals from two pixel columns are mixed and read out. However, as is clear from the description of the embodiment, two types of signals Sa and St are obtained in the n-th horizontal scanning period, and n+1
The present invention is similarly applicable to the case where two other types of signals Sc and Sb are obtained in the second horizontal scanning period, and two types of chroma signals Ca and Cb are obtained due to the relationship between the lines.

Ca” (St Sb)+ (Sc Sa)Cb=
(Sa-8J + (Sa-8c)) This corresponds to, for example, the case where the color filter shown in FIG. 7 is used and the image sensor performs an operation of reading out only the signal of one pixel column in each horizontal scanning period.

〔Effect of the invention〕

According to the present invention, even when obtaining a color video signal using pixel signals of two horizontal scanning periods, color difference signals can be synthesized with a simple configuration, so that the number of adjustment points can be reduced or the processing circuit can be simplified.

[Brief explanation of the drawing]

1 and 6 are block diagrams showing an embodiment of a signal processing device for a single-chip color camera according to the present invention, and FIGS. 2 and 7 are block diagrams showing a color filter for a single-chip color camera to which the present invention can be applied. A plan view showing an example, FIG. 3 is a block diagram showing the configuration of a signal processing device for a single-chip color camera shown in the conventional example, and FIG. 4 shows a signal processing device for a single-chip color camera shown in FIG. FIG. 5 is a block diagram showing an example of the configuration of the encoder circuit used. FIG. 5 is a diagram showing the phase relationship between a pixel signal obtained from an image sensor and a sampling pulse used for signal separation in the embodiment. 2... Image pickup element, 12... Separation circuit, 13... Amplification circuit, 14... Subtraction circuit, 16... IH delay circuit, 18... Addition circuit, 18... Modulation circuit. 2nd mouth 3rd captivity ≠ figure 7゛ blue 2! 1 me 7 mouth

Claims (1)

[Claims] 1. A first horizontal pixel consisting of a plurality of two-dimensionally arranged pixel groups having a photoelectric conversion function, and one column or two adjacent columns among the plurality of pixel groups. a first color filter group corresponding to the first pixel group on the column; and a second color filter group corresponding to the second pixel group located between the first pixel group on the first horizontal pixel column. a color filter group, and a third pixel on a second horizontal pixel column consisting of one column or two adjacent columns located between the first horizontal pixel column among the plurality of pixel groups. a third color whose transmitted light corresponds to the group and whose transmitted light is less by an arbitrarily determined first color component than the first color filter group and greater by an arbitrarily determined second color component than the second color filter group; Corresponding to a fourth pixel group located between the filter group and the third pixel group on the second horizontal pixel column, the transmitted light is transmitted from the first color filter group to the second color component. a fourth color filter group that is smaller than the second color filter group and has more of the first color component than the second color filter group, an output signal of the first horizontal pixel column, and an output of the second horizontal pixel column. a first separation circuit that extracts an output signal of the first pixel group and an output signal of the third pixel group using an image sensor equipped with a drive circuit that alternately extracts signals every horizontal scanning period; a first amplification circuit that amplifies the output signal of the first separation circuit; a second separation circuit that extracts the output signal of the second pixel group and the output signal of the fourth pixel group; a second amplification circuit that amplifies the output signal of the second separation circuit; and a second amplification circuit that amplifies the output signal of the second separation circuit;
a first subtraction circuit that subtracts the output signal of the amplifier circuit;
a third separation circuit that extracts the output signal of the first pixel group and the output signal of the fourth pixel group; a third amplification circuit that amplifies the output signal of the third separation circuit; a fourth separation circuit that extracts the output signal of the second pixel group and the output signal of the third pixel group; a fourth amplification circuit that amplifies the output signal of the fourth separation circuit; a second subtracting the output signal of the amplifier circuit and the output signal of the fourth amplifier circuit;
a subtraction circuit, a first delay circuit that delays the output signal of the first subtraction circuit by one horizontal scanning period, and an output signal of the first subtraction circuit and an output signal of the first delay circuit are added together. a first addition circuit; a second delay circuit that delays the output signal of the second subtraction circuit by one horizontal scanning period; an output signal of the second subtraction circuit; and an output signal of the second delay circuit. a second modulation circuit that modulates the output signal of the first addition circuit; a second modulation circuit that modulates the output signal of the second addition circuit; 1. A chroma signal processing device for a single-chip color camera, comprising a third addition circuit that adds the output signal of the first modulation circuit and the output signal of the second modulation circuit. 2. A plurality of pixel groups having a photoelectric conversion function arranged in a two-dimensional manner, and a first pixel on a first horizontal pixel column consisting of one column or two adjacent columns among the plurality of pixel groups. a first color filter group corresponding to a pixel group; a second color filter group corresponding to a second pixel group located between the first pixel group on the first horizontal pixel column; Among the plurality of pixel groups, transmitted light corresponds to a third pixel group on a second horizontal pixel column, which is composed of one column located between the first horizontal pixel columns or two adjacent columns. a third color filter group that is smaller than the first color filter group by an arbitrarily determined first color component and larger than the second color filter group by an arbitrarily determined second color component; Corresponding to a fourth pixel group located between the third pixel group on the second horizontal pixel column, the transmitted light is less by the second color component than the first color filter group. From the color filter group, the first
a fourth color filter group that has as many color components as , and a drive circuit that alternately extracts the output signal of the first horizontal pixel column and the output signal of the second horizontal pixel column every horizontal scanning period. a first separation circuit that extracts an output signal of the first pixel group and an output signal of the third pixel group using an image sensor;
a first amplification circuit that amplifies the output signal of the first separation circuit; a second separation circuit that extracts the output signal of the second pixel group and the output signal of the fourth pixel group; a second amplification circuit that amplifies the output signal of the second separation circuit; a first subtraction circuit that subtracts the output signal of the first amplification circuit and the output signal of the second amplification circuit; a third pixel group for extracting the output signal of the first pixel group and the output signal of the fourth pixel group;
a separation circuit, a third amplification circuit that amplifies the output signal of the third separation circuit, and a fourth separation circuit that extracts the output signal of the second pixel group and the output signal of the third pixel group. a fourth amplification circuit that amplifies the output signal of the fourth separation circuit; and a second subtraction that subtracts the output signal of the third amplification circuit and the output signal of the fourth amplification circuit. a first modulation circuit that modulates the output signal of the first subtraction circuit, a second modulation circuit that modulates the output signal of the second subtraction circuit, and an output signal of the first modulation circuit. and a first addition circuit that adds the output signal of the second modulation circuit; and a first addition circuit that delays the output signal of the first addition circuit by one horizontal scanning period.
1. A chroma signal processing device for a single-chip color camera, comprising: a delay circuit; and a second addition circuit that adds the output signal of the first addition circuit and the output signal of the first delay circuit.