JPS59108493A - Color solid-state image pickup device - Google Patents

Abstract

PURPOSE:To obtain an excellent color television signal by eliminating a pseudo color signal generated in a color edge section less in the vertical correlation of a color signal when the vertical correlation of the chroma signal of an object image is less. CONSTITUTION:A color carrier signal separated by band pass filters 27, 28 is synchronizingly detected by synchronizing detectors 29, 30, the signal is subtracted by a subtractor 31 and full-wave-recified by a full-wave rectifier circuit 32. An output of the full-wave rectifier circuit 32 represents the degree of vertical correlation of a chroma signal of the object and this output is given to a suppressing circuit 34 as a control signal via a comparator 33. This suppressing circuit 34 suppresses the color carrier signal only when the vertical correlation is less to eliminate the pseudo color signal disturbance so as to avoid the color carrier signal from being supplied to the synchronizing detectors 22, 23.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a color solid-state imaging device using a color filter and a solid-state imaging device.

Conventional Structures and Problems As is well known, solid-state image sensors are of the C0D (charge non-pulled device) type or BB type of charge transfer element.
There are D (bucket prigade device) type and x-Y address element MOS type, of which MO8
type solid-state image sensor reads out signals by sequentially switching MO9 type transistors using vertical and horizontal shift registers, so spike noise occurs especially due to switching pulses caused by horizontal scanning.Moreover, as the number of pixels increases, the signal becomes smaller. In contrast, this spike noise increases and limits the SN ratio of image quality.

However, since X-Y addressing type solid-state image sensors address and read out signal charges from pixels, there is no crosstalk between adjacent signal charges in the vertical direction, and a mosaic color filter as shown in Figure 1 is used. It is suitable for color one-sided methods that use vertical correlation to obtain color signals. In Figure 1, the part indicated by the dotted line is the photodiode of the light receiving section, and the solid line indicates the color filter element.0 Also, due to the internal structure of the COD, the signal charge of the light receiving section is transferred to the storage section for each frame. The frame transformer 77 method transfers at high speed and sequentially reads out from this storage section through a horizontal transfer stage, and the signal charge of the photodiode is read out to an independent vertical transfer line for each vertical line, and this signal charge is horizontally transferred every horizontal scanning period. There is an interline method in which the signal is transferred to a horizontal transfer stage and sequentially taken out as a serial signal from the horizontal transfer stage, but in the case of the former frame transfer method, channel stoppers exist only in the vertical direction, so signal charges are transferred in the adjacent vertical direction. Since the color one-way method that uses vertical correlation to separate color signals is not possible, a striped color filter for R, G, and B as shown in It is necessary to use a one-color system that does not cause color mixing even if there is a color difference. However, this method has the disadvantage that a wide band of luminance signals cannot be obtained because the color filters are repeated every three.

In addition, in the case of the interline method, the photodiodes that are the light receiving sections must be arranged separately, so it is possible to use the mosaic color filter shown in Figure 1, but the transfer efficiency of the vertical transfer stage is was not 100%, color mixing occurred due to components left behind.

By solving the above problems, we have eliminated the influence of non-transfer efficiency on image quality in the vertical transfer stage of solid-state image sensors, and achieved a high light utilization rate without causing a decrease in horizontal resolution due to the repetition of horizontal color filters. Color solid-state imaging devices are being considered.

Below, we will provide an overview of Kazuko's color solid-state imaging device.

FIG. 3 shows the structure of a priming water transfer type solid-state imaging device, which is one of the components of the color solid-state imaging device.
In the figure, 1 is a solid-state image sensor, 5. 2, (2a, 2b, 2c, . . . ) are photodiodes that are light receiving sections. Normally, this photodiode 2
is formed of a PN junction, and the centers of the photodiodes 2 are arranged in a staggered manner so as to be interleaved with respect to the adjacent vertical direction.

3, (3a, 3b, 3c...) are vertical signal lines, and the connection relationship between the photodiode 2 and this vertical signal line 3 is as shown in FIG. The vertical signal lines 3 are connected to alternate vertical signal lines 3. That is, the photodiode 2a of the first horizontal line in FIG. 3 is connected to the vertical signal line 3alC.

The photodiode 2b of the second horizontal line is connected to the vertical signal line 3b, and so on.
S-FET4. (4a, 4b, 4c...)
connected via.

6 is a vertical shift register, and this vertical shift register receives vertical scanning pulses φsP and clock pulses φv1. φ
■It has two input terminals, and the output terminal of each stage of the vertical shift register 5 is connected to the MOS-
Q, which is commonly connected to the gate I of one horizontal line of FET4. Also, one end of the vertical signal line 3 is connected to the transfer MO8-FET7,
(7a, 7b, 7cm...=, 7a', 7b', 7c
'...) is connected to the source. This M.O.
The gates of the S-FETs 7 are connected in common and serve as a transfer pulse input line (φTG). At the drain part of the transfer MO8-FET7, transfer capacitive elements 8, (8
a, sb, Bc・----, 8a', 8b'.

8d...) are connected. Here, the capacitance of the transfer capacitive element 8 is sufficiently smaller than the capacitance of the vertical signal line 3. A transfer gate 9 is adjacent to the transfer capacitive element 8 . (9
a, 9b, 9c・river=, 9a', 9b', 9a'...
) is connected. By the way, the transfer capacitive element 8
The capacitance of the vertical signal line 3 is sufficiently smaller than that of the vertical signal line 3. Transfer gates 9° (9a, 9
b, 9 c---, 9a', 9b', 9c'---
---.) are provided, and their gates are commonly connected to form a transfer gate input line (φTB). Adjacent to this transfer gate 9 is a charge-coupled horizontal shift register (
(hereinafter abbreviated as horizontal COD) 10, (10a.

10a') is arranged, and one end of the horizontal direction is connected to the signal output section 11. (11a, connected to 111().

For details of the priming water transfer type solid-state image sensor, please refer to the patent application filed in 1973
Since it is described in No. 135690, a brief explanation will be given here.

Signal charges are accumulated in the photodiode 2 by the incident light from the subject during one vertical period. The vertical scanning pulse generated from the vertical shift register 5 is sent to the vertical switch MO.
In addition to the gate of the 8-FET 4, the signal charges accumulated in the photodiode 2 are transferred onto the vertical signal line 3. Next φT
A voltage is applied to G and φTC to transfer the signal charge transferred to the vertical signal line 3 to the transfer capacitor 8.0 The signal charge transferred to the transfer capacitor 8 is applied to the transfer gate 9. This transfers it to the horizontal C0D1o.

Then, the signal charges transferred to the horizontal CCD 1o are transferred to the signal output unit 1 during one horizontal scanning period by an appropriate transfer lock.
1 (Ji is read out. The clock frequency of this horizontal transfer is determined by the number of photodiodes 2 arranged in one horizontal line, and in the case of 384 photodiodes 2, it is approximately 7.2
MHz.

The solid-state image sensing device, which is one of the components of this device, is based on the above-mentioned principle of operation, and is further characterized in that signals of a plurality of horizontal lines are simultaneously read out during one horizontal scanning period.

That is, in the nH-th horizontal scan of the first field, the signals of the two horizontal lines a and b shown in FIG.
In the (n+1)H-th horizontal scan of the first field, the signals of two horizontal lines C and d are read out, and the second
In the nHth horizontal scan of the field, 2 of b and C
The signals of two horizontal lines are transferred to the (n +
1') In the H-th horizontal scan, the signals of d and the next horizontal line (not shown) are read out simultaneously.

FIG. 4 is a diagram showing a color filter, which is one of the components of this device.

In Figure 4, the rectangle indicated by the dotted line is 9 in Figure 3.
・The photodiode shown 2. (2a, 2b, 2c...
) is schematically shown, and corresponding to this photodiode 2, a cyan (Cy) filter 12 and a yellow (Ye) filter 12 are installed.
) filter 13 and magenta (M) filter 14 are repeatedly arranged in sequence.

With such an array configuration of the photodiode 2 and the color filter, in the nH-th horizontal scan, the horizontal CGD 11
From the output terminal of a, photodiodes (2a, 2a',
2a''-...) output signal, that is, Cy,
A spatially modulated signal is obtained by the M and Ye filters, and from the output terminal of the horizontal CCD 11a', the output signals of the photodiodes (2b, 213, 2b''...), that is, by the Ye, Cy, and M filters are obtained. A spatially modulated signal is obtained.

When the configuration of the photodiode and color filter shown in FIG. 4 is applied to the solid-state image sensor shown in FIG. is the horizontal CC via the priming transfer stage.
D 10a and 10a' are simultaneously transferred, but 2
The two horizontal CODs are operated with a phase difference of 107, -. In other words, the output signal of the horizontal COD appears point-sequentially at the output terminal, but the output signal of the horizontal CCD
The 111 force signal group of 10a' is connected to the horizontal CCD 10
Horizontal CC when the water i1'7 COD is operated by changing the phase of the transfer pulse applied to the horizontal COD so that the output signal of a has a phase of 11 and 18CP.
The relative phase and spectral characteristics of the output signals of D 1'Oa and 10a' are shown in FIG. 6.

In FIG. 6, A is the output signal of the horizontal CCD 10a, that is, the photodiodes 2a, 2a', 2a'', etc., and B is the output signal of the horizontal CCD 1ob, that is, the photodiode 2b.
, 2b', 2b'', . . . output signals are schematically shown.

In Figure 6, the time between the signal and the bow is 1/f (f
: horizontal transfer lock frequency), and by the method described above, there is a phase difference of 1800 between the A and B signals. If Sunda Red Shingetsu is R1, green light is G, and green light is B, then Cy=(G+B), M=(R+B), Ye=(R+G)
Therefore, the 11 spectral characteristics of the output signal from each photodiode are as shown in FIGS. 5A and 5H.

6A and 6B are diagrams showing the spectral distribution of the signal sequences shown in FIGS. 5A and 5B. The frequency f is the horizontal transfer lock frequency, and the color carrier by the modulated color signal is 3Af.
Occurs near the frequency of The phase of the color carrier at this time is shown in FIG. 7A.

As shown in B, there is a difference of 180°.

Therefore, by adding the output signals of the horizontal CCDs 1oa and 10a', the color carriers existing near the frequency of %f are canceled out. By further adding the signal shown in Figure 8, the number of horizontal photodiodes is doubled on the same side, so the horizontal sampling frequency is essentially doubled. is equal to FIG. 9 shows the spectral distribution of the signal train shown in FIG.

As is clear from FIGS. 8 and 9, the horizontal CCD 10
When the output signals of a and 10a' are added, the color carrier near %f of the horizontal transfer lock frequency is canceled out, and the color carrier of the modulated color signal is generated near %f of the horizontal transfer lock frequency, so the actual of the luminance signal ('I'
r I'Q 翰', E f for said color carrier
i is limited to However, this value of %f is equivalent to twice the conventional luminance signal band %f, and the horizontal resolution is greatly improved.
We explained about the horizontal line of (n+1)H
The same holds true for the horizontal lines of eyes c and d. Furthermore, the same holds true for the nH-th horizontal line of the second field, that is, the c horizontal line.

Next, the electrical signal processing circuit of the color solid-state imaging device is
This will be explained using a diagram. In FIG. 10, reference numeral 15 denotes a solid-state image sensor, which has the structure described above and has a color filter bonded to it. Reference numeral 16 denotes a synchronization signal generator, which conveniently uses a frequency four times as high as 3.5 sMHz as the original oscillation frequency. This synchronizing signal generator 16 generates a pulse φ
sP, φv1. Drive signals for the solid-state image sensor 16 such as φV21φTG, φTC, and φTB are generated by a drive circuit 17 and supplied to the solid-state image sensor 13. The two output signals of the solid-state image sensor 150 are supplied to an adder 18 and added together, and the output signal of the adder is supplied to a low-pass filter 19 with a pole frequency supplied to

On the other hand, regarding the color signal, the output signal of the adder 18 is supplied to a bandpass filter 21 with a center frequency of %f, and a color carrier signal is extracted. Synchronous detection is performed using different reference signals for synchronous detection, unnecessary high-frequency components are removed by low-pass filters 24 and 25, and then supplied to an encoder 2° to obtain a color television signal.
Here, the frequency of the reference signal supplied to the synchronous detectors 22 and 23 is '3< times the horizontal transfer lock frequency f, and is in a synchronous relationship with the horizontal transfer lock. The phase shifter shifts the phase of the reference signal for synchronous detection obtained from the synchronous signal generator by 900, and shifts the phase by 900 to the reference signal supplied to the synchronous counter 22.23.
This is a phase shifter to provide a phase difference of .

Sc
Then, as is clear from Fig. 8, 1<1. 2〈
1 W equals 2π・100 f.

If this signal is synchronously detected using reference signals of (:0δ2π·100 ft and sin 2π·100 ft and the high-frequency components are removed, the output signal of the low-pass filter 24 becomes 1(C-,).

The output signal of the 0-pass filter 26 is 2·H(Y
e −M) color difference signals are obtained. By modulating these two color difference signals with a color subcarrier and adding the luminance signal, a standard composite color television signal can be obtained.

In this color separation method, two types of color difference signals are obtained by synchronously detecting a color carrier signal generated at %f.

Therefore, when an object without vertical correlation is imaged, some kind of interference may occur in the color signal.

Next, a description will be given of color signals when an object without vertical correlation is imaged.

FIG. 11 is a schematic diagram showing a combination of a subject image, a photodiode of an image sensor, and a color filter when a part of the subject without vertical correlation is imaged.

Between the a line and the b line that make up the same horizontal scanning line, the e line and f line that make up the n+2 (H) horizontal line
The subject image changes vertically between the lines. That is, the area above the a line is a white subject image, the area between the b line and the e line is a red subject image, and the area below the f line is a green subject image. When such a subject image is captured, n(H
), n+2 (Hl), schematic diagrams of the output signal of the adder 18 during horizontal scanning of Hl are shown in FIGS. 12(A) and (B), respectively.As is clear from FIG. The R, G, and H signal components obtained from the repetition of six color filters in the horizontal line are R:G:B=4:2:2, and the color signal in the n(H) horizontal line is the red signal. is obtained.

Next, the color signal on the n+2 (H) horizontal line is the 12th
As is clear from Figure B, 6 of the horizontal line n+2 (c)
R2G, BO obtained from repetition of color filters
Since the signal components are R:G:E=2:2:O, n+2
The color signal on the horizontal line (b) is a yellow signal.

In this case, even though the color of the subject changes from red to green, yellow appears at the boundary between the colors of the subject on the television screen, which causes deterioration in image quality.

As explained above, if there is little vertical correlation of color signals in the vertical direction of the subject, false color signals will occur at the vertical color edges (color errors with little vertical correlation of color signals), resulting in poor image quality. lead to deterioration.

In order to prevent the generation of the above-mentioned interference signal, a birefringent crystal plate is installed in front of the image sensor to suppress the vertical frequency components included in the subject image incident on the image sensor to less than % of the number of vertical pixels. This is possible with vj <, but the vertical resolution will be less than % of the original resolution, resulting in an extremely blurry image
Installation of birefringent crystal plates must be avoided at all costs.

17.

OBJECTS OF THE INVENTION The present invention provides a color solid-state imaging device that simultaneously reads signals of a plurality of lines in the vertical direction of a solid-state imaging device and obtains a color signal from a signal obtained by adding the signals of the read plural lines. To obtain good image quality by removing a false color signal generated at a color edge part where the vertical correlation of color signals is small without deteriorating the resolution in the vertical direction when the vertical correlation of the signals is small.

Structure of the Invention In the present invention, a difference in the waveforms of color difference signals for each of multiple lines read out simultaneously is detected, and only when the difference signal exists at a predetermined level or higher, the output of the multiple lines read out simultaneously is detected. To obtain a good television video signal by removing a color signal component obtained from a signal.

DESCRIPTION OF EMBODIMENTS Hereinafter, in the color solid-state imaging device according to the present invention, when there is little vertical correlation of color signals in a subject image, the pseudo 18, -7 color signals that occur at color edge portions where there is little vertical correlation of color signals will be removed. An example will be explained using FIG. 13.

In FIG. 13, numbers 16 to 26 are the same as those explained in FIG. 10, and therefore their explanation will be omitted. 27.
28 is a band pass filter with a center frequency of 3af;
29 and 30 are synchronous detectors, 31 is a subtracter 32, a double-wave rectifier N path 532 is a comparator, and 34 is a color carrier suppression circuit.

The two lines of output signals simultaneously read out from the solid-state image sensor 15 are filtered through a bandpass filter 27 with a center frequency of +4 f.
．． 28, respectively, and the color carrier signals are separated. The separated color carrier signal is supplied to the synchronous detectors 29 and 30 to be used as a reference signal for synchronous detection.
synchronous detection. The synchronously detected signal is sent to the subtracter 31.
: is subtracted and double-wave rectified by a double-wave rectifier circuit. Here, it is necessary to insert a band-limiting low-pass filter between the synchronous detector and the subtracter, but it is omitted in the drawing.

Also, what is the frequency of the reference signal supplied to the synchronous detectors 29 and 30? Af and is in a synchronous relationship with the horizontal transfer lock 2
The reference signals supplied to the two synchronous detectors are the same signal. The subtraction signal of the color difference signal that has been double-wave rectified by the double-wave rectifier 32 is supplied to a comparator 33, where the voltage is compared with an arbitrary reference potential, and when the subtraction signal of the color difference signal is higher than the reference potential, it is controlled from the output terminal of the comparator 33. Output as a signal. The suppression circuit 34 is controlled by a control signal, and when supplied with the control signal, suppresses the color carrier signal, prevents the color carrier from being supplied to the synchronous detector, and eliminates the above-mentioned false color signal interference.

Next, as shown in FIG. 11, the operation will be described when an object image with no vertical correlation of color signal components is captured. 1st
Figure 1: e when scanning the horizontal line of n+2(f(),
If the color carriers obtained from the output signals from each line of f are synchronously detected using a reference signal of sin 2π・%・ft, each color difference signal Se, Sf becomes ivf + Y e and Se−, respectively. 1(C-2)-1 to 1M+Yesf=K1(C-, knee)=2 to 10 levels of color difference signals are obtained. A control signal is obtained by subtracting the color difference signals obtained above, rectifying both waves, and passing them through a comparator. Here, by arbitrarily changing the reference voltage of the comparator 1f, it is possible to arbitrarily determine from which level or higher the vertical correlation is to be corrected.

In this embodiment, 31 is a subtraction circuit for convenience of explanation, but the color carrier of the solid-state image sensor output signal is 2.
Since there is a difference of 1800 between the two lines, it is actually used as an adder.

Effects of the Invention As described above, according to the present invention, signals of a plurality of vertical lines of a solid-state image sensor are simultaneously read out, and a modulated color signal is obtained from a signal obtained by adding the signals. When the vertical correlation of the color signals of the atmospheric image is low, it is possible to remove the false color signals generated at the color edge portions where the vertical correlation of the color signals is low, so that it is possible to obtain a good color television signal.

Furthermore, since the vertical frequency component of the subject image is not suppressed to less than % of the number of vertical pixels using a birefringent crystal plate, the vertical resolution does not deteriorate.

[Brief explanation of drawings]

1 and 2 are front views for explaining color filters in a conventional color solid-state imaging device, respectively. FIG. 3 is a circuit diagram of a solid-state imaging device configured to simultaneously read out signals from multiple horizontal lines. The figure is a front view showing the relationship between the color filter and photodiode used in the device, and FIGS. 5A and 5B are a in FIG. 6. A schematic diagram showing the output signal obtained by horizontal scanning of the line b, Figures 6A and B are spectrum diagrams of each signal in Figure 5,
7A and 7B are vector diagrams showing the phase of the color carrier of each signal in FIG. 5, FIG. 8 is a schematic diagram showing a signal obtained by adding each signal in FIG. The spectrum diagram of the signal, Fig. 10 is 22. 16...Solid-state image sensor, 16...Synchronization signal generation! , 18...7Jng device, 19...
...Pulse filter, 20...Engineer/coder, 21.24.25...0-pass filter, 2
2, 23... Synchronous detector, 27゜28...
...Band pass filter, 29.30...Synchronous detector, 31...Subtractor, 32...-Double wave rectifier circuit, 33...Comparator, 34... ...
...Suppression circuit. Name of agent: Patent attorney Toshio Nakao and one other person Σ
A To ω Saddle mark LD Betsuya Tomo1a Hasumi Shiri Kurado or Δ Nito Seri h9 Monk

Claims (1)

[Claims] A first color filter element having a first spectral characteristic, a second color filter element having a second spectral characteristic, and a third color filter element having a third spectral characteristic are arranged horizontally. Each vertical signal is a signal obtained from color filters that are arranged sequentially in the direction and the color components spatially modulated by the color filter elements are reversed by 180 degrees for each horizontal line, and a light receiving section corresponding to the color filter element. It has a solid-state image sensor that can obtain the same color signal in the line and reads out the signals of the light receiving elements of the adjacent horizontal lines simultaneously in multiple signal lines, and by adding the signals read out simultaneously, the color signal can be obtained. and extracting and comparing each color difference signal component from the output signals of the plurality of lines read simultaneously, and suppressing the color signal if the absolute value of the obtained signal is larger than a predetermined value. 24. A color solid-state imaging device characterized by: