JPS59156091A - Color image pickup device - Google Patents

Abstract

PURPOSE:To reduce generation of false signals at the time of chrominance demodulating from output of an image pickup element and suppress generation of moire by providing a deciding device that decides whether a conditional expression is satisfied or not, and outputs only a false signal when not satisfied and a device that output chrominance signal in which the false signal is suppressed. CONSTITUTION:When output of W (white), Cy (cyan) and Ye (yellow) are inputted in a matrix circuit 5, the matrix circuit 5 outputs a signal of W-(Cy+ Ye), i.e. output 1, to a slicing circuit 6. The silicing circuit 6 outputs a false signal that does not satisfy W<=Cy+Ye, i.e. a signal 2. The false signal detected by the slicing circuit 6 enters matrix circuits 7, 8. The matrix circuit 7 subtracts Cy output and false signal from W output. Accordingly, an R signal 9 in which the false signal is suppressed is outputted from the matrix circuit 7. Similarly, a B signal 10 in which the false signal is suppressed is outputted from the matrix circuit 8.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application] The present invention relates to an image pickup device having a color separation filter, and more particularly to a color image pickup device designed to reduce false signals.

[Prior art]

Generally, when photographing using a color image sensor having nine color separation filters, a false signal is generated due to the pitch of one color separation filter and the beat of the image formed on the imaging surface. This beat component is called moiré, and causes significant deterioration of color image quality, especially when the frequency is within the color band.

When a complementary color filter is used as a color separation filter, color demodulation is performed by calculation as will be described later, which causes a characteristic moiré.

As a conventional technique to suppress these moire.

A method is used that uses a crystal filter to suppress the spatial frequencies that cause beats. The response function R(fl) of this crystal filter is shown in the following equation.

Here, f is the spatial frequency and jo is the trap frequency.

As is clear from equation (1), the spatial frequency response of the crystal filter falls with a cosine function. For this reason, there was a drawback that the resolution deteriorated.

Since the method of suppressing moire using a crystal filter has such drawbacks, it is desired to suppress moire at the signal processing stage without using a crystal filter or the like. However, at present, this method is not effective because it is difficult to distinguish between the original color signal and moiré.

〔the purpose〕

An object of the present invention is to reduce the generation of pseudo signals and suppress the generation of moire when color demodulating the output of an image sensor having a single color separation filter.

〔overview〕

The characteristics of the present invention are white (r), yellow (Ye)
1 conditional expression V/≦Ye+C'y in an imaging device having at least six color separation filters that transmit each color of cyan (C1/) and magenta (M, q'I).

A determination means for determining whether at least one conditional expression among #7sYe×Mg and W≦C"'I+M!I is satisfied, and outputting only a pseudo signal if not satisfied; and determining means for determining the Ye from the W output. , C'y and big
The present invention further includes means for removing one of the outputs and the pseudo signal to output a color signal in which the pseudo signal is suppressed.

〔Example〕

First, let's look at the principle behind the occurrence of moiré when demodulating one color.

This will be explained using an example of crack occurrence.

FIG. 1 shows an example of a striped color separation filter.

This filter is white (W) and yellow.

A filter that transmits three colors: (Ye) and cyan ((,'y).

It consists of W, Ye, Cy are red (R) and green (G')
It is connected to blue (B) using the following formula.

W = R+ G 10B f21Ye =
R+G f31Cy = G + B
(41 Therefore, the demodulation of R and H is given by the following equation.

R= W −C'y (slB=
W -Ye (61) Next, an example of the occurrence of moiré will be explained.

When a repeating pattern of black and white as shown in Fig. 1 (bl) is imaged using the striped color separation filter shown in Fig. 1 (α), R
and the large magenta color of the B component.

The reason for this coloring is that the W filter section is white and the output signal is large, whereas the Cy and Yt filter sections are black and the signals are small, so that pseudo signals are generated.

If it is shown by equations (5) and (6).

Because Ye2U, C'y'::0 becomes R2W/, fl-W.

Despite the black and white pattern, the R and B outputs on the screen are sharp, giving a magenta color tone.

This pseudo signal is generated when color demodulation is performed by calculation from a signal of an image sensor having a one-color separation filter.

Next, the basic concept of the present invention for reducing moire will be explained in detail.

As mentioned above, W, Cy, Yt and R, G, B are (
The relationships expressed by equations 2) to (4) exist. therefore.

There is usually the following relationship between W and "'/r Y tO.

W≦Cy+Ye (Ha However, if the striped color separation filter shown in Fig. 1 (α) is used to image a black and white pattern as shown in Fig. 1 (, 61), even though the output of W is large, Regardless, C″
The output of y, 'kj is /J easy W, C'y,
.

The relationship of Ye is as shown in equation (8).

f > Cy + Yt (slAt this time, R and B determined by equations (5) and (6) contain many pseudo signal components. This is because when demodulating R and B from equations (5) and (6), Even if the difference between the outputs of W, Cy, and Pg is a difference in brightness as shown in Figure 1, it will be demodulated into a color, so the excess of the W component shown in equation (8) is demodulated into R and B.The present invention includes:
This excess is detected and removed from R and B to reduce the above-mentioned false signal.

Next, a specific method for reducing the pseudo signal will be explained. The first method is to detect the excess and subtract it from R and B.

FIG. 2 shows a waveform diagram during signal processing using this method.

Detection of the excess component, that is, the component that does not satisfy Equation (C), is performed by extracting the positive part of the output (1) obtained by subtracting the sum of W, C'y, and Ye using a slice circuit, etc. (As can be seen from Equation (C) As shown in Figure 2 (1), the output (1) is negative in the original color signal and there should be no positive part.
The reason there is a positive part like this is because a pseudo signal is generated. Signal (2) is obtained by extracting only the positive part of output (1), and this signal (2) is subtracted from color signal (6) to suppress the pseudo signal l mixed in one color signal (5). do. Signal (4) is a signal with suppressed pseudo signals.

The second method is to perform gain control using signal (2) shown in FIG. That is, signal (2)
When this is detected, the gain of the gain control circuit to which one color signal is input/output is lowered to suppress the false signal.

Below, the above 1. A detailed explanation of the present invention according to the second method will now be given.

FIG. 6 shows a first embodiment of the present invention based on the first method. In the figure, 5 is a matrix circuit that subtracts the sum of C'y output and Yt ratio output from W output, and 6 is a matrix circuit that subtracts the sum of C'y output and Yt ratio output from W output.
) A slice circuit extracts the pseudo signal that does not satisfy the formula, 7
8 is a matrix circuit that subtracts the output from the C''yy output Rice circuit 6 from the W output, and 8 is a matrix circuit that subtracts the output from !86 from the W output at the Ye small output slice time.

In the circuit configured as above, when the IF, Cy, and Ye outputs are input to the matrix circuit 5, the matrix circuit 5 outputs the signal '(C'y+''lt), that is, the output shown in FIG. (1) is output to slice circuit B.

The slice circuit 6 outputs a pseudo signal that does not satisfy the above formula (C), that is, signal (2) in FIG. 2. The pseudo signal detected by the slice circuit 6 enters the matrix circuit 7.8.

The matrix circuit 7 subtracts the cy ratio output and the pseudo signal from the W output. Therefore, the matrix circuit 7 outputs the R signal 9 in which the pseudo signal is suppressed. Similarly, the matrix circuit 8 outputs the B signal 1o in which the pseudo signals are suppressed.

That is, according to this embodiment, color signals 9 and 1o in which pseudo signals such as signal (4) in FIG. 2 are suppressed can be obtained.

Next, a second embodiment of the present invention is shown in FIG.

This embodiment is a wick for the second method.

In the figure, 11 and 12 are matrix circuits, 16 and 14 are gain control circuits, 15 is an R signal with suppressed pseudo signals, and 16 is a B signal with suppressed pseudo signals; everything else is the same as in Figure 3. show something

In this embodiment, the process until the pseudo signal (2) in FIG. 2 is detected from the slice circuit 6 is the same as in the first embodiment. The matrix circuit 11 subtracts the Cy output from the W output. Therefore, from the matrix circuit 11, the second
An R signal including a pseudo signal l such as signal (3) in the figure is output. The R signal including this pseudo signal A is transmitted to the gain control circuit 1.
Enter 6. The gain control circuit 15 lowers the gain of the pseudo signal A portion of the signal input from the matrix circuit 11 in response to the signal from the slice @ path 6.

Remove spurious signals. Therefore, the R signal 15 becomes a signal in which pseudo signals are suppressed.

Similarly, from the matrix circuit 12, the signal (6
) is used as a signal B including a pseudo signal A such as The B signal containing the pseudo signal A is input to the gain control port @14.

The gain control circuit 14 uses the signal from the slice circuit 6 to reduce the gain of the pseudo signal A portion of the signal input from the matrix circuit 12, thereby removing the pseudo signal. therefore.

The B signal 16 becomes a signal with suppressed pseudo signals.

Although the above embodiment has been described using a striped color separation filter, a dotted color separation filter, an example of which is shown in FIG. 5, may also be used.

When the color OI tone is calculated by calculating the outputs of a plurality of color separation filters, the effect is exactly the same as that of the embodiment described above. Also, the filter is white W.

Although the explanation was given using yellow Ye and cyan Cy,
It can also be applied when macenta My is used, M than W! 7
The positive part of subtracting the sum of and Ye, or MI and C from W
Pseudo signals can be suppressed using the positive part obtained by subtracting the sum of y.

〔effect〕

According to the first aspect of the present invention, it is possible to reduce the possibility that a change in luminance becomes a color pseudo signal, that is, color moire due to sampling by a color separation filter.

The effect is profound.

[Brief explanation of drawings]

Figure 1 (α) is an explanatory diagram of a stripe filter;
bj is a diagram showing an example of a black and white pattern that causes moiré,
FIG. 2 is a signal forming diagram for suppressing moiré showing the principle of the present invention, and FIG. 3 is a block diagram of the first embodiment of the present invention.
FIG. 4 is a block diagram of a second embodiment of the present invention, and FIG. 5 is an explanatory diagram of a dot-shaped color separation filter. 5, 7, '8.11, 12...matrix circuit,
6... Slice circuit, +3.44... Gain control circuit. Representative Patent Attorney Akira Takahashi 4;

Claims (4)

[Claims] (1) White (W), yellow (Ye), cyan (Cy). and macenter (Ml).
Conditional expressions W≦Ye+Cy, W≦Yt+Mg. and determining means for determining whether at least one conditional expression among W≦Cy+Mg is satisfied, and outputting only a pseudo signal if not satisfied; A color imaging device characterized by comprising means for removing the pseudo signal and outputting a color signal in which the pseudo signal is suppressed. (2) The determining means determines that W output, Ye, C'y and M! A color imaging device according to the patent, characterized in that it is comprised of a matrix circuit that receives any two small outputs as inputs, and a slice circuit. (3) The means for outputting the suppressed color signal of the pseudo signal receives the W output, any one of the Yt, Cy, and M1 outputs, and the pseudo signal detected by the determining means. , and a matrix that subtracts the sum of any one of the Ye, Cy, and M1 outputs and the pseudo signal from the W output} I
The color imaging device according to claim 1, characterized in that it is a Jx circuit. (4) The means for outputting the color signal in which the pseudo signal is suppressed is a W output. A matrix circuit that reduces the output of any one of Ye, Cy, and My ratio outputs. The color imaging device according to claim 1, further comprising a gain control circuit that controls the gain of the output of the matrix circuit using the pseudo signal.