JPS60157386A - Color solid-state image pickup device - Google Patents

Abstract

PURPOSE:To remove an interfering signal without deteriorating vertical resolution by removing the interfering signal in a luminance signal zone when there is the level difference of luminance signal in each horizontal scanning period and there is no change of horizontal amplitude. CONSTITUTION:A horizontal end part detecting circuit 41 detects a signal corresponding to amplitude change (edge part) in the direction of horizontal scanning line of a luminance signal and supplies to a full-wave rectifier circuit 42. The full-wave rectifier circuit 42 converts horizontal edge signals in positive and negative directions into one directional signals and supplies them to a switch circuit 43. Vertical relative error signals of luminance signals and color difference signals are supplied to the switch circuit 43. When a horizontal edge signal is present, above-mentioned vertical relative error signals are cut off, and when there is no horizontal edge signal, this is conducted and supplied to a horizontal aperture compensating circuit 27 as controlling signals. Thus, interfering signals in a luminance signal zone generated by vertical relative error are removed.

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, in color solid-state imaging devices using solid-state imaging elements and color filters, the horizontal resolution is limited by the repetition period of the color filters in the horizontal direction. Therefore, as a method to widen the luminance signal band using an image sensor with a small number of pixels, as shown in Figure 1, photodiodes (constituting one pixel) are arranged so as to be shifted by half a pitch every horizontal line. It has been proposed to widen the band of the luminance signal by simultaneously reading out signals from a plurality of lines and then adding these signals to obtain a luminance signal.

In FIG. 1, the rectangle indicated by the dotted line indicates the photodiode 2, (2a, 2b, 2cm==)e, and in correspondence with this photodiode 2, a cyan Cy filter 12, a yellow Ye filter 13, a magenta M filter 1
4 are arranged in sequence.

With such an array configuration of the photodiode 2 and the color filter, in the n-th (c) horizontal scan, the photodiodes (2a, 2a') are connected from the output terminal a to the photodiodes (2a, 2a').

2a″...) output signals, namely Cy, M, Ye
A spatially modulated signal is obtained by the filter, and photodiodes (2b, 2b') are output from the output terminal of b.

2b''...) output signals, namely Ye, Cy, M
A spatially modulated signal is obtained from the filter.

When operating a solid-state image sensor having the configuration of photodiodes and color filters shown in Fig. 1, horizontal lines a,
The signal charges of the photodiodes b are transferred by separate horizontal transfer circuits, and the two transfer circuits are operated with a phase difference. In other words, the output signal of the horizontal transfer circuit appears at the output terminal point-sequentially, but the output signal of the horizontal transfer circuit A (
When the pulses applied to the horizontal transfer circuit are operated with different phases so that the output signal group of the horizontal transfer circuit B (not shown) has a phase of 1800 with the output signal group of the horizontal transfer circuit B (not shown). FIG. 2 shows the relative phases and spectral characteristics of the output signals of the horizontal transfer circuits A and B.

In FIG. 2, 4 indicates the output signal of the horizontal transfer circuit A, that is, the photodiodes 2a, 2a', 2a''..., and (B) indicates the output signal of the horizontal transfer circuit B, that is, the photodiodes 2b, 2b', 2b'... This figure schematically shows the output signals of .

In FIG. 2, the time interval between the signals is 1/f (f: horizontal transfer lock frequency), and by the method described above, there is a phase difference of 180° between the respective signals of west, Φ).

Also, if the red signal is R1, the green signal is G, and the green signal is B, then Cy=(G+B), Ye=(G+R), M=(B+R)
Therefore, the spectral characteristics of the output signal from each photodiode are as shown in FIG.

FIGS. 3(5) and 3(B) are diagrams showing the spectral distributions of the signal sequences shown in FIGS. 2(2) and (B). The frequency f' is the horizontal transfer lock frequency, and the color carrier due to the modulated color signal is generated near the frequency of 3Af. The phase of the color carrier at this time is shown in Figure 4.

As shown in (2), there is a 180° difference.

Therefore, by adding the output signals of the horizontal transfer circuits A and B, the color carriers existing near the frequency of 3Af described above are canceled out. Further addition results in a signal as shown in Figure 6, in other words, the number of horizontal photodiodes is doubled under the same constraint, which is essentially equivalent to doubling the horizontal sampling frequency. Become. FIG. 6 shows the spectral distribution of the signal shown in FIG.

As is clear from FIGS. 5 and 6, horizontal transfer circuit A
If the output signals of The band of the luminance signal is limited to Kf due to the color carrier. however,
Conventional luminance signal band! The horizontal resolution is significantly improved compared to if.

The above explanation is based on the nth (F'Il)th in FIG.
.

This was done for the horizontal line b, but the n+1(E()
The same holds true for the horizontal lines of eyes c and d. Furthermore, the same holds true for the n-th (H)th, ie, c, horizontal line in the next field.

In the color imaging device as described above, the color carrier signal generated at 3Af is canceled out by vertical correlation (adding signals for two lines read simultaneously).

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

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

FIG. 7 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 having no vertical correlation is imaged.

Between the a line b, which constitutes the horizontal scanning line of n@, and the line e and f, which constitute the horizontal scanning line of n+2@
The subject image changes vertically between the lines. That is, the area above the a line is a red subject image, the area between the b line and the e line is a white subject image, and the area below the f line is a black subject image. n pass when capturing such a subject image,
The output signal in horizontal scanning of n+2fi is equal to %
The carrier signal of the frequency component of f remains without being canceled out. That is, in the nth (H) horizontal scanning line, a color carrier of %f of the signal corresponding to red is generated in the output of the a line, and since the output of the b line is white and no color carrier is generated, even if they are added, , the color carrier corresponding to the red signal is not canceled out.

-For achromatic objects, the spectral characteristics of each color filter are generally designed so that color carriers do not occur.However, as the color temperature of the object changes, the relative energy of the light to the wavelength changes significantly, so as mentioned above, As such, it is practically impossible to eliminate the generation of color carriers in achromatic subjects. Unfortunately, even on the n+2 (F()-th) horizontal scanning line, the level of the color carrier of the signal corresponding to white on the e line is not equal to the level of the color carrier of the signal corresponding to black on the quantity line, so %f color carriers do not cancel out.

The color carriers generated when there is no correlation in the vertical direction are within the luminance signal band and significantly degrade the image quality. Therefore, the vertical correlation error of the image is detected using the luminance signal and the color signal, and this error is detected. In the horizontal scanning line where the signal is detected, it has already been proposed to remove the interference of the luminance signal caused by the color carrier signal occurring at -3Af.

The signals of multiple horizontal lines are simultaneously read out in one horizontal scanning line, and the vertical correlation of the signals is used to cancel the color carrier, and when there is no vertical correlation, the vertical correlation error signal is detected and the band of the luminance signal is An electric signal processing circuit of a color solid-state imaging device configured to remove interference signals generated within the image sensor will be described with reference to FIG. In FIG. 8, numeral 15 is a solid-state image sensor, to which a color filter as shown in FIG. 1 is glued. Reference numeral 16 denotes a synchronizing signal generator, and it is convenient that the original oscillation frequency is four times that for 3.58. A drive circuit 17 generates a drive pulse for the solid-state image sensor 15 using the output pulse of the synchronization signal generator 16,
It is supplied to the solid-state image sensor 15. The two output signals of the solid-state image sensor 15 are supplied to an adder circuit 18 and added together, and the output signal of the adder circuit 18 is supplied to a low-pass filter 19 with a pole frequency of 9Af to remove unnecessary high-frequency components. The signal is supplied to two horizontal avertia compensation circuits, and then supplied to an encoder 2° as a luminance signal subjected to horizontal spacing compensation.

On the other hand, for the color signal, the output signal of the adder circuit 18 is supplied to the output signal filter 21 with a center frequency of %f,
Extract the color carrier signal. The obtained color carrier signal is synchronously detected by the synchronous detection circuit 22 and 23 using the reference signal for synchronous detection with a phase difference of 900 degrees, unnecessary high-frequency components are removed by the Rono Sfil filter 24 and 25, and then the color temperature is determined. The correction circuit 32133 adds the low-frequency luminance signals separated by the rotary filter 28,
Or by subtracting, white balance is achieved when the color temperature of the subject changes. The white balanced color signal is supplied to the encoder 2o to obtain a color television signal. Here, the frequency of the reference signal supplied to the synchronous detection circuits 22 and 23 is % times the horizontal transfer lock frequency, and is in a synchronous relationship with the horizontal transfer gate. 26 is a reference signal for synchronous detection obtained from the synchronous signal generator 16.
This is a phase shift circuit for shifting the phase by 0 degrees and giving a phase difference of 90 degrees to the reference signals supplied to the synchronous detection circuits 22 and 23.

If the output signal of the bandpass filter shown in FIG. 8 is Sa, as is clear from FIG. 6, 1 (Cy-2) sin ωt + 2 T
(Ye −M )CO3ωt.

CO52yr --ft and 5ln2 π
If high-frequency components are removed by synchronous detection with a -5ft reference signal, the output signal of the low-pass filter 24 is 1 (Cy-2), and the output signal of the low-pass filter 26 is 2. 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.

On the other hand, vertical correlation errors are detected as follows. The correlation error in an achromatic subject is determined by Ronox filter 2.
8 is used, and is supplied to a delay circuit 29 for one horizontal scanning period, and a signal delayed by one horizontal scanning period and a signal that is not delayed are supplied to a subtraction circuit 3o. The subtraction circuit 3° outputs the signal error during two horizontal scanning periods and supplies it to the double-wave rectifier circuit 31. The double-wave rectifier circuit 31 converts the error signals in both the positive and negative directions into a unidirectional signal and supplies it to the adder circuit 40 . Correlation errors for chromatic objects are determined by using two white-balanced color difference signals: a signal in which the color difference signal is delayed by one horizontal scanning period in a one horizontal scanning period delay circuit 34, and a signal without the delay. are supplied to the subtraction circuits 36 and 37. The subtraction circuits 34.35 detect errors in the color difference signals during two horizontal scanning periods, and supply the detected errors to the double wave detection rectification circuits 38.39. The double-wave rectifier circuit converts the error signals in both the positive and negative directions into one direction, and supplies the converted signal to the adder circuit 4°. The adder circuit 40 adds the vertical correlation error signal detected from the luminance signal and the vertical correlation error signal detected from the color difference signal, and then adds the vertical correlation error signal detected from the luminance signal to the horizontal avertia compensation circuit 27 for the luminance signal.
The amount of Abacha compensation is controlled. In other words, by taking advantage of the fact that the frequency of the color carrier generated at %f and the peak of the compensation frequency in the horizontal abutment compensation circuit almost match, horizontal abutment compensation is not performed for a signal with a vertical correlation error signal. This makes interference by color carriers of %f less noticeable isometrically compared to normal signals.

When detecting such a signal with no vertical correlation and controlling the compensation amount in the horizontal avertia compensation circuit, if the vertical correlation error signal does not change in the horizontal scanning line (the seventh
(If the change in the subject is parallel to the horizontal line as shown in the figure)
However, as shown in Figure 9, when the frequency component in the horizontal scanning direction included in the vertical correlation error signal changes diagonally with respect to the horizontal scanning line, the frequency component in the horizontal scanning direction included in the luminance signal It is converted into a side wave of the frequency in the scanning direction and causes disturbance to the luminance signal. This is shown in Figure 10,
When controlling the compensation amount of the horizontal avertia compensation signal using the vertical correlation error signal fe, the multiplication characteristics of the control circuit cause the amount of compensation on the luminance signal f8 to be controlled by the vertical correlation error signal fe.

This is due to reasons such as conversion to a lower value wave signal or frequency conversion of low frequency noise included in the vertical correlation error signal. In any case, in the case of a subject whose image does not change parallel to the horizontal scanning line, an interference signal is generated in the luminance signal, resulting in a significant deterioration of image quality.

OBJECTS OF THE INVENTION The present invention provides a color solid-state imaging device that simultaneously reads signals of a plurality of vertically adjacent lines of a solid-state imaging device and obtains a luminance signal by adding the signals of the read plural lines. The purpose is to remove interference signals generated within a luminance signal band when the vertical correlation is slightly low without deteriorating the resolution in the vertical direction, and to obtain good image quality.

Structure of the Invention The present invention detects the level difference for each horizontal scanning period of a luminance signal and a color signal obtained by adding signals of a plurality of lines read out simultaneously, and detects the amplitude change of the luminance signal in the horizontal direction. The color solid-state imaging device is configured to detect and remove a frequency that becomes an interfering signal within a luminance signal band only when the difference signal exists and there is no amplitude change in the horizontal scanning direction of the luminance signal. , it is possible to obtain a good television video signal.

DESCRIPTION OF EMBODIMENTS Below, in a color solid-state imaging device according to the present invention, an embodiment of a luminance signal vertical correlation error correction circuit used to remove interference signals generated within the luminance signal band when there is no vertical correlation in the subject image. will be explained using FIG.

In FIG. 11, numeral 27 denotes a horizontal averthir compensation circuit configured to be able to control the amount of compensation of the horizontal averthir compensation signal, and is supplied with the signal output from the low-pass filter as in the conventional example of FIG. After being horizontally compensated, it is input to the encoder.

The luminance signal is also supplied to a horizontal edge detection circuit 41, which detects a signal corresponding to the amplitude change (edge portion) of the luminance signal in the horizontal scanning line direction and supplies it to a double-wave rectifier circuit 42. The double-wave rectifier circuit 42 converts the horizontal edge signals in both positive and negative directions into a unidirectional signal and supplies it to the switch circuit 43 . The switch circuit 43 is also supplied with a vertical correlation error signal of the luminance signal and color difference signal detected in the same manner as in the conventional example shown in FIG. The correlated error signal is cut off, and when there is no horizontal edge signal, the vertical correlated error signal is made conductive and supplied as a control signal to the horizontal avertia compensation circuit. In the horizontal avertia compensation circuit, based on the control signal, when the level of the control signal, that is, the level of the vertical correlation error signal, is large, the horizontal avertia compensation amount is reduced to reduce the brightness generated by the vertical correlation error isometrically. Remove interfering signals within the signal band. Furthermore, as in this embodiment, the control circuit detects the edge portion of the luminance signal in the horizontal scanning direction and stops the control of the horizontal avertia compensation circuit when the edge signal exists. It is possible to remove the interference of the luminance signal due to the multiplication characteristic of .

FIGS. 12 and 13 show specific configuration examples of the embodiment shown in FIG. 11. In FIG. 12, the horizontal avertia compensation circuit 27 is composed of a delay line 44, a subtraction circuit 45, a gain control circuit 46, and an addition circuit 47. The gain control circuit 46 controls the horizontal avertia compensation signal amount. are doing.

The horizontal edge portion detection circuit 41 of the luminance signal includes a delay line 48,
It consists of a subtraction circuit 49, and the delay time of the delay line 48 is made shorter than the delay time of the delay line 44, and the frequency peak of the horizontal etch detection signal is made higher than that of the horizontal avertia compensation signal, thereby reducing detection errors. That's what I do.

FIG. 13 shows an embodiment in which the two delay lines in FIG. 12 are combined into one, and the intermediate tap of the delay line is used to obtain a horizontal avertia compensation signal and a horizontal edge signal. .

In the embodiment, the method of detecting the vertical correlation error signal is similar to the conventional example shown in FIG. 8, in which the correlation error is obtained using the luminance signal and color signal obtained by adding together multiple line signals read out simultaneously. Although described above, it goes without saying that the present invention can be applied to other methods, for example, to obtain vertical correlation error signals of luminance signals and chrominance signals using a plurality of line signals read out simultaneously.

Effects of the Invention As described above, according to the present invention, in a color solid-state imaging device that obtains a luminance signal by simultaneously reading out signals from a plurality of vertical lines of a solid-state image sensor and adding the signals, a subject image can be obtained. This is a good method because it can eliminate the interference signal that occurs in the luminance signal band when the vertical correlation of You can get a color television signal.

[Brief explanation of the drawing]

Figure 1 is a front view showing the relationship between color filters and photodiodes in a conventional color solid-state imaging device, and Figure 2 (A)
, (B) are schematic diagrams showing output signals obtained by horizontal scanning of lines a and b in Figure 1, Figures 3 (A) and (B) are spectrum diagrams of each signal in Figure 2, Figure 4 (A), (B)
is a spectrum diagram showing the phase of the color carrier of each signal in Figure 2, Figure 5 is a schematic diagram showing a signal obtained by adding each signal in Figure 2, Figure 6 is a spectrum diagram of the signal in Figure 5, Fig. 7 is a front view showing the relationship between a subject and color filters that have no vertical correlation, Fig. 8 is an overall electrical circuit diagram of the device, and Fig. 9 is a front view showing the relationship between a subject and color filters that have no vertical correlation. Fig. 10 is a spectrum diagram of the signal in the subject of Fig. 9;
FIG. 11 is a block diagram showing an embodiment of the vertical correlation error correction circuit used in the solid-state imaging device of the present invention;
Figures (A) and (B) are block diagrams showing a specific configuration of the vertical correlation error correction circuit in the same embodiment, and FIG. 13 is a block diagram showing another specific configuration. 15... Solid-state image sensor, 18... Addition circuit,
27...Horizontal aperture compensation circuit, 41...
・Horizontal edge detection circuit, 43...Switch circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person 2nd
Figure 3 Figure 9 Figure 10 Figure 11 q Figure 12 Figure 7 Procedural amendment (blade side March 6, 1985 Patent Application No. 189092 2 Name of the invention Color solid-state imaging device 3 Correction Relationship with the case involving the person who filed the patent application Person name 1006 Kadoma, Kadoma City, Osaka Prefecture Name (
582) Matsushita Electric Industrial Co., Ltd. Representative Toshihiko Yamashita 4 Agent 571 Address 7, Matsushita Electric Industrial Co., Ltd., 1006 Oaza Kadoma, Kadoma City, Osaka Prefecture ""Figure 12 (8) and (B) are in the same embodiment" is replaced with "Figure 12 is in the same embodiment"
We will correct it.

Claims (1)

[Claims] The vertical correlation error of the luminance signal and the chrominance signal is detected, and the vertical correlation error signal is used to control the horizontal avertia compensation signal of the luminance signal. At the same time, the amplitude change of the luminance signal in the horizontal direction is detected, and this amplitude change portion is A color solid-state imaging device characterized in that the vertical correlation error signal is cut off and the horizontal avertia compensation signal is not controlled in a portion where the amplitude of the luminance signal changes in the horizontal direction.