JPH01114287A - Chroma signal processor of veneer color camera - Google Patents

Abstract

PURPOSE:To prevent the mixture of other chrominance components and the occurrence of line crawl by obtaining the R, G and B signals of straight polarity in chroma signal demodulation circuits of same constitution. CONSTITUTION:Subtraction circuits 141 and 142 which obtain the difference signals between the output signals of separation circuits 121-128 which execute separation for respective picture element signals and the output signals of amplifier circuits 131-138, delay circuits 161-163 which delay the outputs for one horizontal scan period, and addition circuits 191-193 which add the output signals of the subtraction circuits and those of the delay circuits are provided. One chroma signal demodulation circuit is constituted by a pulse generation circuit 18 generating a pulse signal for controlling the separation circuits 121-128 in such a way that the objective picture element signal is added to the input side of the subtraction signals of the subtraction circuits 141 and 142 and the input side of signals to be subtracted, and the chroma signal decodemodulation circuits are provided for the number of the chroma signals to be demodulated. Thus, other chrominance components are impervious to be mixed and the occurrence of line crawl can be prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a single-chip color camera, and in particular has a simple circuit.
The present invention relates to a signal processing device for a single-chip color camera that can obtain a good ROMA signal even when using an image sensor whose pixel's effective aperture ratio differs depending on the type of color filter.

[Conventional technology]

In recent years, home video cameras have achieved smaller size, lighter weight, higher reliability, and higher productivity by using solid-state image sensors. 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.

Since a single-chip color camera must simultaneously obtain a luminance signal and a chroma signal from one image sensor, image quality, particularly resolution and color reproducibility, tends to deteriorate. Various color filters or signal processing methods have been proposed to obtain high-quality color video signals with single-chip color cameras.

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 the conventional example are shown in FIGS. 2 and 3, respectively. The operation of the conventional single-chip color camera shown in the figure is described in detail in Japanese Patent Laid-Open No. 198979/1982, but will be briefly explained below.

The color filters shown in Figure 2 are ye (yellow transmission) and cy
A horizontal pixel row Ql in which (cyan transmission) is repeated;
Horizontal pixel rows Q2 in which G (green transmission) and W (all color transmission) are repeated are arranged alternately every other row, and horizontal pixel rows Q2 in which Ye and W are repeated between them,
s, Q4 are placed. Here, when the image sensor corresponding to the color filter mixes and reads out the pixel signals of two adjacent columns, in the Nth horizontal scanning period, Ya
and the pixel signal of repeated pixel column gz of Cy and Ye
The pixel signals of the pixel column Q8 in which the pixel rows Q8 and W are repeated are mixed and extracted. Similarly, during the (n+1)th horizontal scanning period, the pixel signals of the pixel column Q2, in which G and W are repeated, and the Y
The pixel signals of the pixel column Q4 in which e and W are repeated are mixed and extracted. As a result, the signal S n HS n''1 obtained in the n-th and n+1-th horizontal scanning periods is expressed by the following equation.

S n = 2 ・Ye+Cy+W+K”(2・Ye
Cy W) CO3ωt=2-Ye+Cy+W+K・(
R-2B)-CO5ωt-C1)Sn+z=Ye
+2・W+G+K(G+Ye 2W)CO5c,+t
=Ye+2'W 10G K(R+2B)・COS ωt
, +++ (2) However, K is a constant Sn, and from Sn+1, the modulation component Mn (=K・(R-2B)
・C08c, +t).

Mn”1.(=-K ・(R+2B) ・CO8ω
t) and performs addition and subtraction, the addition signal An+t and the subtraction signal D n + 1 are expressed by the following equations, so B and H chroma signals can be obtained.

A n+ s ”” M n + M n+ 1=-4
B -K-CO3ωt...(3)D n
+1 == M n -M n+1=2・R- to -CO
3ωt (4) That is, in the signal processing circuit shown in FIG. In addition, modulation component Mn or Mn+t is extracted. The extracted modulation component Mn or Mn+1 is delayed by one horizontal scanning period by the H delay circuit 5. Two modulation components Mn and M n + obtained simultaneously from the bandpass filter 4 and the IH delay circuit 5
1 to the adder 6 and the subtractor 7, respectively, to obtain an addition signal A n '' + and a subtraction signal D n+1.The addition signal An+1 and the subtraction signal D n '' thus obtained are
Demodulate 1! In addition to 81.82, by converting to a low frequency signal, a B signal and an R signal can be obtained.

On the other hand, the brightness signal is a signal Sn obtained from an image sensor.

It is obtained by applying Sn"1 to a low-pass filter 9 to remove modulation components. Also, after adding the signal obtained from the image sensor to a low-pass filter 10 and converting it into a low-frequency signal without modulation components. , subtraction circuit] 1, and by subtracting the B signal and R signal obtained by the demodulation circuits s1 and 82, the G signal can be obtained.

As described above, when the color filters shown in FIG. 2 are combined and the signal processing circuit shown in FIG. 3 is used, the luminance signal, R signal, B signal, etc. can be obtained simultaneously.

These are added to the encoder circuit 17 to obtain a color video signal.

[Problem that the invention seeks to solve]

By the way, it is known that in an on-chip device in which a color filter piece is formed directly on each pixel of an image sensor, a light condensing effect occurs because the color filter piece has a thin convex lens shape at the periphery. In a pixel corresponding to a color filter piece formed in the shape of a convex lens, the effective aperture area increases due to the light condensing effect.

Here, for example, change the G filter to Y. Assuming that this is realized by overlapping the filter and the Cy filter, and the Y,3 filter is formed in the shape of a convex lens, the effective aperture ratio of the pixel corresponding to the Ye filter and the G filter is Cy
It becomes larger than the effective aperture ratio of the pixel corresponding to the filter and the W filter. As a result, the output signals Sn and S0+1 of the image sensor expressed by equations (1) and (2) are as follows.

S'n=2'Ye+Cy+W+2・α・Ye1K・(
R-28) CO3ωt+K・2α(G+R)CO3ω
t=S n +2 α・(G+R)+K・2 α(G+
R) CO3c, +t −(5)...(6) where O〈α〈1 As a result, the signal A' obtained by adding and subtracting the modulation components
H + t D'n"l is expressed as the following formula.

A'. +ヱ= -4・B -K-CO3ωtD'
n + x = K-R・(2+ a-door CO5(, +
t - (8) As is clear from equations (7) and (8), A'. The first problem occurs in that other color signal components are mixed into the B signal demodulated from +1 by the demodulation circuit.

In addition, since the type of color filter is switched every horizontal scanning period, the signal applied to the subtraction input side of the subtractor 7 and the signal applied to the subtracted input side are obtained in the n+2th horizontal scanning period. Subtraction signal D'. +2 becomes the following formula.

D' n+x=- to -R・(2+ α)・CO3ωt
-(9) This has a polarity inverted from that of the subtraction signal D'□10 obtained in the (n+1)th horizontal scanning period shown in equation (8). Therefore, in order to obtain the R signal, it is necessary to invert the polarity of the signal converted to a low frequency by the demodulation circuit 82 every horizontal scanning period, and in general, care must be taken to suppress changes in the DC component in such an operation. Therefore, a second problem arises in that the R signal demodulated by the conventional signal processing method is likely to cause line crawl due to changes in the DC component for each horizontal scanning period.

Further, the G signal is a signal obtained by band-limiting the output signal of the image sensor with the low-pass filter ]-0 as described above, and a signal obtained by band-limiting the output signal of the image sensor with the band filter 4 and the normal demodulation circuit 81. It is obtained by subtracting the signal obtained by band-limiting with a low-pass filter included in 82. Generally, it is difficult to match the frequency characteristics of a low-pass filter with the frequency characteristics when converting into a low-pass signal through a bandpass filter. As a result, especially at the boundary of the object, the R of the output signal of the image sensor obtained from the low-pass filter 10 is
A third problem occurs in that the G signal and the B component cannot be completely removed by the signals obtained by the demodulation circuits 81 and 82, and other color signal components are likely to be mixed into the G signal at the boundary.

As described above, according to conventional signal processing circuits, when a difference occurs in the effective aperture ratio of pixels due to the light-condensing effect of color filter pieces, other color signal components are added to the demodulated R and B signals. The disadvantage is that line crawl is likely to occur in the R signal, and if the frequency characteristics of the signal obtained by the low-pass filter and the signal obtained by the bandpass filter are different, the subject boundary may occur. There is a drawback that other color signal components are likely to be mixed into the G signal of the area.

The purpose of the present invention is to prevent other color signal components from being mixed into the B and R signals even when a difference occurs in the effective aperture ratio of pixels, and to prevent other color signal components from being mixed into the G signal at the object boundary. It is an object of the present invention to provide a signal processing device that is difficult to control and does not cause line crawl.

[Means for solving problems]

The above purpose is to provide a separation circuit that separates the output signal obtained from the image sensor into each pixel signal, an amplifier circuit that amplifies the output signal of each separation circuit, a subtraction circuit that obtains a difference signal between the output signals of each amplifier circuit, and a subtraction circuit that obtains a difference signal between the output signals of each amplifier circuit. A delay circuit that delays the output of the 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 target pixel signal on the subtraction signal input side and subtracted signal input side of the subtraction circuit. This is achieved by constructing one chroma signal demodulation circuit with a pulse generation circuit that generates a pulse signal for controlling the separation circuit so that chroma signals are added, and providing as many chroma signal demodulation circuits as there are chroma signals to be demodulated.

[Effect]

In the present invention, since the amplifier circuit that amplifies the output signal of the separation circuit operates to equalize the effective aperture ratio of each pixel, it is possible to reduce other color signal components mixed into the R signal and the B signal. Furthermore, since the G signal is demodulated by a chroma signal demodulation circuit having the same configuration as the B and R signals, the frequency characteristics of the G signal can be made equal to those of the B and R signals. This can prevent false coloration at the subject boundary. The pulses generated by the Matahals generation circuit control the input separation circuit so that the output signal of the subtraction circuit in the chroma signal demodulation circuit always has positive polarity. As a result, by switching the output polarity every horizontal scanning period, it is possible to prevent line crawling, which is likely to occur.

〔Example〕

Embodiments of the present invention will be described below with reference to FIG. 1st
In the figure, as in the conventional example, the color filter shown in FIG. 2 is combined with the image sensor 2, and the pixel signals of two adjacent columns are mixed and read out. Further, in the color filter shown in FIG. 2, it is assumed that the effective aperture ratio of the Ye and G pixels is (1-10α) times that of the other pixels.

At this time, during the n-th horizontal scanning period, the signals of the pixel column Ω and the signals of the pixel column Ω8 are mixed and read out, so the signal obtained from the image sensor 2 is as shown in FIG. 4(a).
e+Ye) and (Cy+W) are repeated alternately. Also, during the (n+1)th horizontal scanning period, the signal of pixel column Q2 and the signal of pixel column Q4 are mixed and read out, so the signal obtained from image sensor 2 is (G + Y) as shown in FIG. 4(b). e) and (W+W) are repeated alternately. Therefore, after the signal obtained from the image sensor 2 is amplified by the amplifier 3, it is applied to the separation circuits 121 to 12B. A sampling pulse of the phase shown in FIG. 4(C) obtained from the pulse generating circuit 18 is added to the separation circuit 12z, and a pixel signal of (Ye+Ye) is applied to the n-th horizontal scanning period, and a pixel signal of (Ye+Ye) is applied to the n+1-th horizontal scanning period. separates (G+Ye) pixel signals. - direction separation circuit 122 is shown in FIG.
), and in the n-th horizontal scanning period, the pixel signal of (W + Cy) is added to the pixel signal of n+1
During the th horizontal scanning period, (W+W) pixel signals are separated.

Here, the output signals of the separation circuits 12g122 are applied to the amplifier circuits 131 and 132, respectively, and the amplification factor of the amplifier circuit 131 is set to □ times, and the amplification factor of the amplifier circuit 132 is set to 11 times, so that the effective pixel Correct the difference in aperture ratio. Furthermore, the output signals of the amplifier circuits 131 and 132 are respectively added to the subtraction signal input side and the subtracted signal input side of the subtraction circuit 141, and the resulting output signal of the subtraction circuit 14 is band-limited by a low-pass filter 151. IH delay circuit 1
6z to delay one horizontal scanning period. As a result, the signal S1 obtained by adding the output signal of the low-pass filter 1-51 and the output signal of the IH delay circuit 16z to the adder circuit 19 is as follows, and the signal S1 obtained by adding the output signal of the low-pass filter 1-51 and the output signal of the IH delay circuit 16z is as follows. I get a signal.

=4・B...(10
) Also, a sampling pulse with the phase shown in FIG. 4(e) is applied to the separation circuit 128, and in the n-th horizontal scanning period (
The pixel signals of Y e + Y e ) are separated, and the pixel signals of (W+W) are separated in the n+1-th horizontal scanning period. On the other hand, the sampling pulse shown in FIG. 4(f) is applied to the separation circuit 1.24, and (Cy + W
), the pixel signal of (G
10 Y e) pixel signals are separated.

The output signals of the separation circuits 128, 1.24 thus obtained are added to the amplifier circuits 13a, i3a and amplified. Here G, Y
When the effective aperture ratio increases only in the e pixel (J7), other color signal components will not be mixed into the R signal from equation (8), so the amplification factors of the amplifier circuits 138 and 134 are both 1x is fine. The output signals of the amplifier circuits 138 and 134 are applied to the subtracted signal input side and the subtracted signal input side of the subtraction circuit 142, respectively. After the output signal of the subtraction circuit 142 is band-limited by a low-pass filter 152, it is delayed by one horizontal scanning period by a 1H delay circuit 162. Low pass filter 1
52 and the output signal of the IH delay circuit 162 to an adder circuit 192, a signal S2. is as shown in the following equation, and a positive R signal can always be obtained.

52=((1,+ α)(Ye+Ye)) (Cy+
W) ((1+α)(G+Ye))+(W+W)=(2
+α)・R...(IJ) On the other hand, the addition signal S of pixel signals obtained during two horizontal scanning periods
a contains R, G, and B components in the following proportions.

5a=((1+α)(Ye+Ye))+(cy+w)ten((1+α)(G+'Ye))+(W+W)=(8
+4・α)・G+(6+3・α)・Ri・B...
(]2) From the relationship of equations (10), (11), and (12), 2
The G signal can be obtained by amplifying and subtracting the output signal S1182 of the adder circuits 19x and 192 by a factor of 1 or 3 from the addition signal Sa of pixel signals obtained during the horizontal scanning period. This relationship can be separated into pixel signals and summarized as follows.

5s=Sa S knee 3・S2 (13) Therefore, the sampling pulse shown in FIG. 4(g) is added to the separation circuit 125, and (Y e +
Separate the pixel signals of Y e ). This is added to the subtraction signal input side of the amplification addition/subtraction circuit]7. Similarly, separation circuit 1
(Cy+W), (G+Ye) were separated by applying the sampling pulses shown in FIG.
), (W+W) pixel signals respectively]-38
In addition to ~13δ, the output signal of 3 times 1, 36.1.37 is added to the subtracted signal input side of the addition/subtraction circuit 20, and the output signal of the amplifier circuit 138 is applied to the subtraction signal input side of the addition/subtraction circuit 20. Further, the output signal of the adder/subtracter circuit 20 is band-limited by a low-pass filter 153 and then delayed by an IH delay circuit 63. The output signal of the 1H delay circuit 168 obtained in this way and the output signal of the low-pass filter 153 are added to an adder circuit 19.
8, the equation (]3) is satisfied and a G signal can be obtained.

Further, from a comparison with FIGS. 4(C), (g), and 4), the output signal of the separation circuit 121 is a sum signal of the output signal of the separation circuit 12B and the output signal of the separation circuit 127. Similarly, the output signal of the separation circuit 122 is the sum of the output signal of the separation circuit 126 and the output signal of the separation circuit 128, and the output signal of the separation circuit 123 is the sum of the output signal of the separation circuit 125 and the output signal of the separation circuit 128. The addition signal and the output signal of the separation circuit 124 are the output signal of the separation circuit 126, the output signal of the separation circuit 127, and the addition signal. Therefore, the separation circuit 125
Another embodiment shown in FIG. 5 in which the separation circuits 121 to 24 are omitted by combining the output signals of the circuits 121 to 128 with adder circuits 211 to 214 can also provide the same effect as the embodiment shown in FIG. It will be done.

Furthermore, the embodiment shown in FIG. 1 has been explained by taking as an example the signal processing in which the R, G, and B signals are demodulated and then added to the concoder circuit 17, but a simple signal processing method using a luminance signal instead of demodulating the G signal Processing is possible. The embodiment in this case, as shown in FIG. After adding it to the bandpass filter 153, the IH delay circuit 163 and addition circuit 198 may be used to obtain a luminance signal in the same band as the R signal and the B signal.

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+
The present invention is similarly applicable to the case where two other types of signals Sc and Sb are obtained in the first horizontal scanning period and two types of chroma signals Ca and Cb are obtained according to the following relationship.

Ca=(Sa Sb) 10(Sc+5d)Cb=(Sa
Sb) + (Sd-8c) This can be done, for example, by using the color filter shown in FIG.
This corresponds to the case where an operation is performed to read out only the signal of the pixel column.

〔Effect of the invention〕

As described above, according to the present invention, R, G, and B signals of positive polarity can always be obtained with a demodulation circuit having the same configuration, so that a chroma signal without any other color signal components mixed in can be obtained.

[Brief explanation of the drawing]

FIGS. 1, 5, and 6 are block diagrams showing an embodiment of a single-plate color lamella signal processing device according to the present invention, and FIGS. 2 and 7 show a single-plate color camera to which the present invention can be applied. Fig. 3 is a block diagram of a signal processing device for a single-chip color camera shown in a conventional example, and Fig. 4 shows a pixel signal obtained from an image sensor and signal separation in an embodiment. FIG. 3 is a diagram showing the phase relationship of sampling pulses used in FIG. 2...Image sensor, 12...Separation circuit, 13...Amplification circuit, ], 4...Subtraction circuit, 6...IH delay circuit, ]8...Pulse generation circuit, 19 ...addition circuit, 20...addition/subtraction circuit.

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. and one color filter group located between the first horizontal pixel column among the plurality of pixel groups.
Corresponding to a third pixel group on a second horizontal pixel column consisting of a column or two adjacent columns, the transmitted light is smaller by an arbitrarily determined first color component than the first color filter group, and A third color filter group having an arbitrarily determined second color component larger than the second color filter group, and a fourth color filter group located between the third pixel group on the second horizontal pixel column. corresponding to the pixel group, the transmitted light is transmitted from the first color filter group to the second color filter group.
a fourth color filter group that has fewer color components than the second color filter group and has more color components than the second color filter group, an output signal of the first horizontal pixel column, and the second horizontal pixel column. using an image sensor equipped with a drive circuit that alternately takes out output signals of the first pixel group and the output signals of the third pixel group at every horizontal scanning period, a first subtraction circuit that obtains a difference signal between the output signal of the group and the output signal of the fourth pixel group; a first delay circuit that delays the output signal of the first subtraction circuit by one horizontal scanning period; a first addition circuit that adds an output signal of the first subtraction circuit and an output signal of the first delay circuit; an output signal of the first pixel group and an output signal of the fourth pixel group; a second subtraction circuit that obtains a difference signal between the output signal of the second pixel group and the output signal of the third pixel group; and a second subtraction circuit that delays the output signal of the second subtraction circuit by one horizontal scanning period. Chroma signal processing for a single-chip color camera, characterized in that it comprises a delay circuit, and a second addition circuit that adds the output signal of the second subtraction circuit and the output signal of the second delay circuit. Device. 2. The first subtraction circuit amplifies the output signal of the first separation circuit that extracts the output signal of the first pixel group and the output signal of the third pixel group, and the first separation circuit. First thing to do
an amplifier circuit, an output signal of the second pixel group, and the fourth pixel group.
a second separation circuit that extracts the output signal of the pixel group; a second amplification circuit that amplifies the output signal of the second separation circuit; and an output signal of the first amplification circuit and the second amplification circuit. The second subtraction circuit is configured with a first subtraction circuit that subtracts the output signal of the circuit, and the second subtraction circuit 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; 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 separation circuit, a fourth amplifier circuit that amplifies the output signal of the fourth separation circuit, and a second amplifier circuit that subtracts the output signal of the third amplifier circuit and the output signal of the fourth amplifier circuit. 2. A chroma signal processing device for a single-chip color camera according to claim 1, characterized in that it is constituted by a subtraction circuit. 3. The first subtraction circuit and the second subtraction circuit are
a fifth separation circuit that extracts the output signal of the first pixel group; a sixth separation circuit that extracts the output signal of the second pixel group; and a sixth separation circuit that extracts the output signal of the third pixel group. a seventh separation circuit; an eighth separation circuit that extracts the output signal of the fourth pixel group; a fifth amplification circuit that amplifies the output signal of the fifth separation circuit; a sixth amplifier circuit that amplifies the output signal of the circuit; a seventh amplifier circuit that amplifies the output signal of the seventh separation circuit; and an eighth amplifier circuit that amplifies the output signal of the eighth separation circuit. and a third addition circuit that adds the output signal of the fifth amplifier circuit and the output signal of the seventh amplifier circuit, and the output signal of the sixth amplifier circuit and the output of the eighth amplifier circuit. a fourth addition circuit that adds the signals; a third subtraction circuit that subtracts the output signal of the third addition circuit and the output signal of the fourth addition circuit; and the fifth amplifier circuit. a fifth addition circuit for adding the output signal of the eighth amplifier circuit and the output signal of the eighth amplifier circuit;
a sixth addition circuit that adds the output signal of the amplifier circuit and the output signal of the seventh amplifier circuit; and subtracts the output signal of the fifth addition circuit and the output signal of the sixth addition circuit. 2. A chroma signal processing device for a single-chip color camera according to claim 1, further comprising a fourth subtraction circuit.