JPS62108694A - Color solid-state image pickup device - Google Patents

Abstract

PURPOSE:To reduce a color moire setting a spatial frequency in which a moire is generated as a high frequency by raising a sampling frequency equivalently by obtaining a green color signal with the operation of a complementary color signal obtained from several kinds of correction filters. CONSTITUTION:Signals W, Ye, Cy, and G photoelectric-converted and obtained at a sensor 1 are amplified at an amplifier 2, and are inputted to a matrix circuit 3. At the matrix circuit 3, operations shown in equations I-IV are performed, and a luminance signal (y), a red signal (r), a green signal (g), and a blue signal (b) are obtained. Next, at a process encoder 4, the signals (r), (g), and (b), after they are synthesized to a color difference signal, are changed to an NTSC signal with signal (y). At such a time, so that four picture elements G, Ye, Cy, and W are used to obtain the signal (g) as shown in equation III, a spurious chrominance signal generated at each picture element is canceled mutually and is no more generated, and therefore, the color moire included in the green signal is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a color solid-state imaging device that reduces false color signals.

[Background of the invention]

As an example of a conventional solid-state imaging device,
Previsi Soun Gakuyo Technical Report Volume 5 Ugly 29 No. 6 announced on the 6th
Pages 1 to 66, by Kajino et al. [Narrow channel COD single-panel color camera].

In this example, the solid-state image sensor is red (R) and green (G).

A cyan (Cy,) signal is obtained. After this solid-state imaging device obtains a blue (/?) signal from Cy-G calculation, R2O,
Gamma correction is performed on the three colors E, and the signals are input into the encoder in the form of color difference signals of R-C and B-G, and R+G+
Signal processing is performed using the luminance (r) signal obtained from Cy.
It outputs a TSC signal.

In this example, since the R and G signals are directly obtained from the solid-state image sensor, an image quality with good color S/N can be obtained.

Now, from the viewpoint of sensitivity, Cy is better than using primary color filters such as R and G with a solid-state image sensor.

It is preferable to use a complementary color filter such as yellow (?
) This is because the complementary color filter transmits two colors at the same time, whereas the complementary color filter transmits two colors at the same time, increasing the amount of light that is photoelectrically converted and improving the spectral sensitivity.

As solid-state imaging devices using complementary color filters, the devices shown in FIGS. 4 and 5 can be considered.

Figure 4 shows picture element i of a solid-state image sensor using a complementary color filter.
The picture elements are transparent (F') and G.

Seisha from cy,, y-. Also, FIG. 5 shows a system configuration diagram of an imaging device made in the same year. In FIG. 5, 14 indicates a solid-state image sensor having the pixel arrangement shown in FIG.
5 is a preamplifier, 16 is a matrix circuit 17 is a process encoder circuit, and 18 is an NTSC output terminal.

Next, the operation of the solid-state imaging device using this complementary color filter will be explained.

The W, Ya, Cy, and Ga signals output from the solid-state image sensor 14 using a complementary color filter are transmitted to the preamplifier 1.
5) After each amplitude is applied to the IJ circuit 16
1, signal, r signal, b reconnaissance 1g signal are calculated.

(Here, lowercase letters are used to indicate that signal processing has been performed.) The y+r and "b'+"9 signals are obtained by the calculation of the following equation.

y mouth W+Yg+Cy+G (11r-W +
Ya −Cy −G (21b, =W−Y
g +Cy-G (31 dar
G(4) The signal y+r+lx, .M obtained in this way is processed by the encoder circuit 17 in exactly the same way as in the previous example, and then outputted from the NTSC output terminal 18 to the NTSC signal.
Output as a signal.

By the way, when an object with a thin pattern is imaged by a solid-state imaging device using a complementary color filter as shown in FIG. 5, the image becomes glaring and has moiré.

Moiré occurs when a high frequency signal folds back into a low frequency signal due to signal sampling1,3.

This phenomenon is particularly noticeable in solid-state imaging devices. Hereinafter, this moiré will be briefly explained using FIG. 6.

In the same figure, α is the signal, β is the sampling point, and γ is the signal after sampling.Also, (α) shows the case when a DC signal is sampled, and (b) shows the sampling frequency and stop. 〈This shows the case when high-frequency signals with the same frequency are sampled.'' In (α) and (b), the frequency is different from the DC signal and the high-frequency signal at the time of input, but the output signal after sampling is the same. It turns out that it becomes a thing. Note that the folding of the high frequency signal into the low frequency signal occurs around a frequency that is 1/2 of the sampling frequency.

□ Therefore, it can be seen that by increasing the sampling frequency and increasing the folding frequency of a high frequency signal into a low frequency signal, moiré can be eliminated.

However, increasing the sampling frequency requires high-speed operation of two circuits that increase the number of picture elements of the solid-state image sensor, and the sampling frequency in the vertical direction of the video screen depends on the interlaced scanning of the television receiver. Therefore, it is extremely difficult to increase the sampling frequency.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a color solid-state imaging device that reduces false color signals (color moiré) contained in green signals and obtains high-quality reproduced images.

[Summary of the invention] ゛The main point of the present invention is to obtain a green signal by calculating complementary color signals obtained from several types of complementary color filters, thereby increasing the sampling frequency isometrically, making the spatial frequency where moiré occurs higher, and The goal is to reduce color moiré contained in the signal.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 1 shows the pixel arrangement of the color solid-state imaging device of this embodiment, and FIG. 2 shows a block diagram of the color solid-state imaging device of this embodiment.

In FIG. 2, 1 indicates a color solid-state image sensor (sensor) having the pixel arrangement shown in FIG. 1, 2 is a preamplifier, 3 is a matrix circuit, 4 is a process encoder circuit,
5 is an NTSC signal output terminal.

W + , Y a r obtained by photoelectric conversion in sensor 1
C'/.

The G signal is amplified by the preamplifier 2 and sent to the matrix circuit 3.
is input. In the matrix circuit, ytG+Yt+C
y+W −2CR+20+B) (5) r −W −
Cy + Ya -G -2R, (61 q = 3 + Y, a + Cy -F74G
(71h=cy G+TF'
)'#-2B,,+81 and the calculations shown in equations (5) to (8) are performed to obtain a luminance (y) signal.

Obtain a red (r) signal, a green (,9) signal, and a blue (h) signal.

Next, in the process encoder circuit 4, as in the prior art example, the τ, , q, and b signals are combined into a color difference signal and then converted into an NTSC signal together with the l signal.1. The signal is output from the NTSC signal output terminal 5. By the way, the Y signal is Y-0,3r
,+0.59. q + 0.11 b (
Usually represented by 91. In formula (1), the b signal is excessive, but solid-state image sensors have low blue sensitivity and can be replaced by formula (1).

The advantages of using the calculation of equation (3) to obtain the l signal will be explained below. The right hemisphere of FIG. 1 shows a signal in which the amount of light increases and decreases in the vertical direction. The period of this Iki number is exactly equal to two X pictures, but if an l signal is created using only the G picture elements for this incident light, the l signal becomes +Δ, which turns into a low frequency and becomes a false color signal. Such high frequency signals cannot be reproduced as video signals, so they can be removed. In this example,
Since the g signal is generated from the four picture elements G, Ya, Cy, and FF', +Δ or -Δ generated in each picture element cancels each other out, and the l signal becomes 0, so that no K color signal is generated. On the other hand, the false color signal in the horizontal direction is the same as the conventional one. According to this embodiment, q −50+Yg in the matrix circuit
By setting +Cy-W, color moiré included in the green signal can be reduced.

By the way, in this example, 7 reads two lines at the same time.

By applying the present invention to an MO5 type color solid-state imaging device, flicker can also be suppressed. First, a signal reading method of the MO5 type color solid-state imaging device which reads two lines simultaneously will be explained with reference to FIG. FIG. 3 shows a part of the solid-state image sensor, in which 6 is a horizontal shift register, 7 is a vertical shift register 8a to 8c are vertical MO transistor switches,
9α to 9c are horizontal MO5) transistor switches, 10α
~10c is a photoelectric conversion element, 11αb is an interlace changeover switch, and 12α is a vertical MO5) Coupling capacitance C between the gate line α of the transistor and the photoelectric conversion element 10α, .
13α represents the coupling capacitance C2a between the gate line of the vertical MO transistor 5) and the photoelectric conversion element 10α. 12h, 1
3b, 12c, and 13c similarly indicate the coupling capacitance between each photoelectric conversion element and the gate line. Further, 2 indicates a preamplifier circuit. In this solid-state imaging device, a pulse is applied from the vertical shift register 7 to one vertical gate line once per field to select a certain row. Next, columns are sequentially selected by the horizontal shift register 6, and the signal charges stored in the light source conversion elements are transferred to
.

It is taken out to the outside. The interlace changeover switch 11αb is used to perform pseudo inclace scanning within the solid-state image sensor in accordance with the interlace scanning of the television receiver. In the A field, the vertical gate line is paired with the vertical gate line α. Become. In the next B field, the interlace changeover switch is changed so that the vertical gate line C becomes bare with the vertical gate line C. By repeating this pseudo-interlaced scanning, the number of T pixels equal to the number of vertical picture elements is
A limiting resolution of V lines is obtained.

The cause of flicker that occurs in this MO5 type solid-state imaging device that reads two lines simultaneously is the coupling capacitance between the photoelectric conversion element and the vertical gate line. The flicker phenomenon and its suppression method will be explained below.

Of the coupling capacitance between the photoelectric conversion element and the vertical gate line,
15α and 13h are involved in flicker.

13c, which is a coupling capacitance between a photoelectric conversion element and a vertical gate line unrelated to the photoelectric conversion element.

When vertical gate lines α and h form a pair, the coupling capacitance is 1
A charge of Q = c + 5h - Vh is stored in 5A. However, Vh is the high level of the vertical shift register,
This is the difference between the potential after the photoelectric conversion element reads out the signal charge. On the other hand, when the vertical gate lines S and C become bare, the potential of the vertical gate line C changes after reading out the signal charge.
Coupling capacitance 13 as it drops from high level to low level
At A, on the contrary, the charge Q decreases. As described above, since the charge read from the photoelectric conversion element differs by 2Q from field to field, it appears as flicker on the screen of the television device. This flicker occurs for the reasons explained above and has the following characteristics.

(1) Photoelectric conversion elements in the same row have flickers of the same phase.

(2) The photoelectric conversion elements in adjacent rows have the same amount and opposite phase.

Therefore, flicker is suppressed by adding the signal charges of the photoelectric conversion elements in adjacent rows by the same number of elements. This is the condition for flicker suppression.

In this embodiment, the Y signal, r4W, ! Both the signal and the b signal satisfy the above conditions, and flicker is suppressed.

As described above, this embodiment has the effect of reducing color moiré contained in green signals and suppressing 7-bit color in the MO5O5 type solid-state camera 2 that reads two lines at the same time.

〔Effect of the invention〕

According to the present invention, the color moiré contained in the green signal can be reduced while maintaining the conventional circuit scale, so that in a color solid-state imaging device, the image quality of the video signal can be improved while reducing the cost.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing a pixel arrangement of a solid-state image sensor according to an embodiment of the present invention, FIG. 2 is a block diagram showing a color solid-state image sensor according to an embodiment of the present invention, and FIG.
The system configuration diagram of the type 5 color solid-state imaging device, Figure 6, is as follows:
Sample, 11. FIG. 3 is a waveform diagram showing changes in input/output signals due to switching. 1... Color solid-state image sensor 3...
・・・・・・・・・Matrix circuit 5・・・・・・・
...NTSC signal output terminal・12・Figure 1 Lead 2 Figure 3 Figure 4 Gray

Claims (1)

[Claims] 1. Transparent (W), yellow (Ye), cyan (Cy), green (
a photoelectric conversion section that outputs a signal of color G); a Y signal generation circuit that generates a luminance (Y) signal from the output of the photoelectric conversion section; )
In a color solid-state imaging device that has a Y signal generation circuit that generates a signal, a b signal generation circuit that generates a blue (b) signal, and a signal generation circuit that generates a green (g) signal, the g signal is generated. A color solid-state imaging device characterized in that it is obtained by an arithmetic circuit that roughly follows the following arithmetic formula. g=-W+Ye+Cy+3G 2. The photoelectric conversion section includes a pixel array consisting of a photoelectric conversion element and a switch element; a horizontal and vertical scanning circuit that sequentially selects the pixel array; and transmits the signal charge of the pixel to the outside. 2. The solid-state imaging device according to claim 1, wherein the circuit comprises a signal line.