JPS623587A - Color solid-state image pickup device - Google Patents

Abstract

PURPOSE:To reduce the occurrence of a false chrominance component and to simplify the constitution of a demodulation circuit for a modulated component by applying a polarity inversion on an output signal by every color filter synchronizing with the repeating period of a color filter array arrangement and next, by separating the modulated component by passing the polarity-inverted output signal through a low-pass filter. CONSTITUTION:The output signal of a solid-state image pickup element 13 is supplied to a demodulation circuit 14 for the separation of the modulated component. The demodulation circuit 14 consists of a polarity inversion circuit 15 which inverts the polarity of the output signal of the solid-state image pickup element 13 synchronizing with the repeating period of a color filter array, a driving circuit 16 and a lowp-pass filter 17. A sum signal of blue and red, B+R signal, and a difference signal of them, B-R signal, the high frequency components of which are eliminated by the low-pass filter 17 obtained by every scanning line from the demodulation circuit 14 in line sequentially, are delayed at a 1H delay line 18 and are added and subtracted with an original signal which are not delayed. A B signal is obtained separately with erasing an R component that is an antiphase component with each other in the B+R signal and the B-R signal, and in the same manner, and R signal is obtained by subtraction.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a color imaging device using a solid-state imaging device, and in particular eliminates the need for a bandpass filter for color separation and suppresses the generation of false color signals. The present invention relates to a color solid-state imaging device equipped with a color signal demodulation circuit.

(Prior Art) A single-chip color solid-state imaging device that obtains a color television signal using a single solid-state imaging device such as a charge-coupled device (hereinafter abbreviated as COD) extracts luminance information from the output signal of the solid-state imaging device. and a plurality of signals representing color information. As an example, the vertical correlation frequency separation method is well known. FIG. 6 shows the configuration of this type of single-chip color solid-state imaging device. In the solid-state image sensor 1, a color filter array, which is constructed by overlapping two types of color filters, transparent and yellow, and transparent and cyan, is placed at a position where a real image of a subject is formed. Red light and blue light are spatially modulated by this color filter array, frequency-multiplexed with a low-frequency luminance signal component as a carrier wave component (hereinafter abbreviated as modulation component) determined by the frequency of spatial modulation, and output from the image sensor 1. be done.

The output signal of the image sensor 1 is separated into a low-pass component and a modulation component by a low-pass filter 2 and a bandpass filter 3, and the separated modulation component and this are divided into one horizontal scanning period (hereinafter abbreviated as IH).

) with the delayed component in the delay line 4, and the added and subtracted signals are demodulated in demodulators 5 and 6, and then passed through a low-pass filter 7.8 to extract the red and blue signals. There is. Using these two primary color signals and the low frequency component, a color television signal is formed by a conventional processing circuit 9, 10, 11 and a color encoder 12.

(Problems to be Solved by the Invention) In the prior art shown in FIG.
odujation Tranafer F'unct
ion ) is high, and an output signal is obtained with a very large amplitude change between two horizontally adjacent pixels of the solid-state image sensor at the horizontal contour of the subject. Due to this large amplitude change, the bandpass filter 3 separates the modulated components.
Ringing occurs, which becomes a false color signal and degrades image quality.

Furthermore, the output signal of the solid-state image sensor 1 is a pulse amplitude modulation signal (hereinafter abbreviated as a PAM signal) obtained in synchronization with the clock pulse that drives the solid-state image sensor 1, and in addition to the video signal component, there is clock noise. Contains ingredients. Therefore, the bandpass filter 3 that separates the modulation components is a PAM with
The amount of attenuation outside the passband must be large enough to sufficiently remove clock noise components from the signal. Therefore, in the conventional method shown in FIG. 6, the configuration of the bandpass filter becomes complicated. Also, if the attenuation outside the passband is insufficient,
The above-mentioned PAM signal is first added to a low-pass filter that removes the clock noise component, and then the modulation component is separated by a bandpass filter, or the PAM signal is sampled and held, only the video signal component is separated, and then the bandpass filter is applied. This requires a means to remove the clock noise component, such as a configuration that separates the modulation component with a filter, making the configuration complicated. As described above, the conventional color solid-state imaging device of the type shown in FIG. 6 has the problem that a false color signal is generated due to the bandpass filter 3 that separates the modulation component, and the demodulation circuit for the modulation component is complicated. There was a point.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a color solid-state imaging device that eliminates the above-mentioned drawbacks, generates fewer false color signals, and has a simple configuration of a modulation component demodulation circuit.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention provides a means in which a color filter array in which color filters are arranged horizontally and vertically at a predetermined repetition period is combined. , a color sensor comprising a solid-state image sensor configured to frequency-multiplex a signal representing luminance information with a plurality of signals representing color information as a modulation component having a period equal to the repetition period in the horizontal direction of the color filter array. A solid-state imaging device,
The polarity of the output signal of the solid-state image sensor is alternately inverted for each pixel in synchronization with the horizontal repetition period of the color filter array, and the color information is expressed as the average value of the polarity-inverted signals. It is characterized in that it is obtained by separating and demodulating modulated components.

(Function) In order to solve the above-mentioned conventional problems, the present invention separates the modulation components without using a bandpass filter. Since the output corresponds to each color filter in time series according to the array of It is configured to separate modulation components by passing them through a bandpass filter. According to the above-mentioned means, by reversing the polarity of each different color filter, the output signal components corresponding to the color light components that can commonly pass through each color filter are canceled out and eliminated, and the output signal components that are different from each other are eliminated. It is possible to separate and obtain only the modulation component.

Therefore, the bandpass filter conventionally used to separate modulation components is no longer necessary, and the above-mentioned conventional drawbacks are solved.

(Embodiment 1) FIG. 1 is a block diagram showing a first embodiment of the present invention. In the figure, the solid-state image sensing device 13 is combined with a color filter array arranged as shown in FIG. 2 as an example. The color filter array shown in Fig. 2 is a frame storage type arrangement, and is a repeating arrangement in units of 4 pixels in the vertical direction and 2 pixels in the horizontal direction, and in the A field, the odd-numbered columns,
In the B field, each even numbered column is read out and interlaced. In each color filter, transparent-green (W-G) is arranged on the nth scanning line, and cyan-yellow (CY-Ya) is arranged on the n+1th scanning line. In this example of the color filter array, red light is arranged. Transparent W
The and Ye filters are arranged in a checkered pattern with opposite phases for each scanning line, and the W and CY filters that can transmit blue light are arranged vertically with the same phase for each scanning line, so the output signal of each scanning line The included modulation components are a blue and red sum signal (B+R) on the n-th scanning line, and a difference signal (B-R) on the n+1-th scanning line.

In the configuration diagram of FIG. 1, the output signal of the solid-state image pickup device 13 combined with the color filter array is supplied to a demodulation circuit 14 for separating modulation components.

The demodulation circuit 14 includes a polarity inversion circuit 15 that inverts the polarity of the output signal of the solid-state image sensor 13 in synchronization with the repetition period of the color filter play, that is, the repetition period of the modulation component, a drive circuit 16, and a low-pass filter 17. ing. In the example of the color filter array shown in FIG. 2, the color filters are arranged horizontally in units of two pixels, so the repetition period of the modulation component is equal to the horizontal clock pulse period that drives the solid-state image sensor 13. It has doubled. Drive circuit 1
6 drives the solid-state image sensor 13 and supplies the polarity inversion circuit 15 with a clock pulse having a period twice that of the horizontal clock pulse.

FIGS. 3(a) to 3(d) are waveform diagrams illustrating the operation of the demodulation circuit 14. FIG. 2A shows an output signal of the solid-state image sensor 13. The figure shows waveforms when the solid-state image sensor 13 is a CCD. In Figure (a), as is well known, period T1 is a reset period, T1 is a feed-through period, and T is an output period. 4 is a horizontal clock pulse period, and the signal of each pixel is outputted every period of T4. The output signal shown in Figure (a) shows the case of the n-th scanning line in Figure 2, and is a repetition of the W signal corresponding to the W filter and the G signal corresponding to the G filter for each pixel. .

Next, in FIG. 2(b), the polarity inversion circuit 15
shows the clock pulses supplied to the The above-mentioned period T is twice the horizontal clock pulse period T4. The polarity inversion circuit 15 inverts the polarity of the output signal of the solid-state image sensor 13 by W signal for each pixel in accordance with this clock pulse, thereby obtaining the output signal shown in FIG.

As shown in the figure, this output signal has a W signal of positive polarity and a G signal of negative polarity. As a result, R included in the W signal,
G.

Among the signal components corresponding to all three primary color lights of B, the signal components corresponding to G cancel each other out with the negative polarity G signal, and the average value of the output signal shown in Figure (C) is shown by W-G. will be the value. This average value is equal to the modulation component B-1-H described above. Therefore, if the output signal of the polarity inversion circuit 15 is supplied to the low-pass filter 17 and the high frequency components are removed,
) is obtained as a demodulated modulation component B+R signal.

Next, the modulated component BR signal can be demodulated and obtained from the (n+1)th scanning line in exactly the same manner.

B-1 obtained line-sequentially for each scanning line from the demodulation circuit 14
The -R and BR signals are then delayed by IH delay line 18. The delayed signal is then added to and subtracted from the original, undelayed signal. By this addition, the B+R signal and the B-R
The R components of the signals that are out of phase with each other are eliminated to obtain a separated B signal, and similarly, the B components that are in phase with each other are eliminated by subtraction to obtain a separated R signal. Note that it is necessary to use a delay line that can delay the low frequency signal of the IH delay line 18U.

The R and B signals separated by addition and subtraction are used together with the luminance signal obtained by passing the output signal of the solid-state image sensor 13 through the low-pass filter 2 to form a color television signal. It should be noted that the components indicated by reference numerals 2 and 9 to 2 in FIG. 1 are the same as the components described in the conventional example shown in FIG. 6, such as a low-pass filter, a process circuit, and a color encoder. omitted.

(Embodiment 2) FIG. 4 is a configuration diagram showing a second embodiment of the present invention. This embodiment uses a color filter array in which the modulation components obtained from the solid-state image sensor become two different types of color difference signals. This method includes, for example, Kune et al., Technical Report of the Television Society, March 1981, VUL 6.
．． A4517) In a paper published on pages 23 to 28 entitled "Color image evaluation of field readout method COD," two color difference signals represented by 2R-G and 2B-G are line-sequentially processed for each scanning line. A color imaging device is shown in which the images are taken out, delayed by IH, and then synchronized.

FIG. 5 shows the arrangement of the color filter array of this method. This color filter array is a field accumulation type arrangement, and as shown in the figure, the odd-numbered columns are Y and C.
Y filters are arranged horizontally alternately for each pixel, and maze/re(My) and G filters are arranged horizontally alternately for each pixel in the even-numbered columns, and in the second and fourth columns. KMJI and G are arranged 180 degrees interchanged.

In the configuration diagram of FIG. 4, the solid-state image sensor 19 combined with the color filter array of FIG. 5 outputs the signals of two vertical pixels added together inside the solid-state image sensor. That is, in the nth scanning line of the A field, Ye+M,→
C! The signals corresponding to each color filter are added and output in the order of 10G-+Ys + MIF→..., and in the same way, on the n+1st scanning line, Y6+Ys+MIF→...
An output signal is obtained in which signals corresponding to each color filter are added in the order of 9→Ye+G→.... In the B field, output signals are obtained in the same combination order as in the A field. The output signal of each of the above-mentioned scanning lines includes a modulation component with a repetition period of 2 pixels in the horizontal direction, and this modulation component is (Yθ + Mg) in the n-th scanning line.
-(C,-1-G) = 2 RG,, at the n+1st scanning line, (Yθ+G)-(Cy+My)=()-
It is 2B.

The output signal obtained from the solid-state imaging probe 19 is sent to the demodulation circuit 20.
As in the case of the first embodiment, the polarity is inverted for each pixel in accordance with a clock pulse having a repetition period equal to the modulation component supplied from the drive circuit 22 in the polarity inversion circuit 21, and then the polarity is inverted for each pixel. High frequency components are removed by a pass filter 23, and the two color difference signals represented by 2R-G and G-2B are obtained by line-sequentially demodulating each scanning line.

The obtained color difference signal is added or subtracted by a predetermined amount from the low-band luminance signal obtained by passing the output signal of the solid-state image sensor 19 through the low-pass filter 25 in the white balance circuit 24, so that when an achromatic object is imaged, the color difference signal is The white balance is adjusted so that it becomes zero. The color difference signal after white balance adjustment is sent to the next KIH
Synchronization circuit 26 consisting of a delay line and a changeover switch
Then, two color difference signals are simultaneously obtained from the line sequential signals obtained for each scanning line.

Using the obtained two color difference signals and the luminance signal obtained by the low-pass filter 2 and the process circuit 11, a color encoder 27 forms a color television. The components are the same as those of the conventional example shown in FIG.

(Effects of the Invention) The present invention has been described above with reference to two embodiments, but as clarified by the explanation, the present invention is capable of repeating a modulation component when separating and demodulating a modulation component included in an output signal of a solid-state image sensor. The polarity of the output signal is alternately inverted pixel by pixel in synchronization with the cycle, and the signal components commonly included in two horizontally adjacent pixels are canceled to obtain a modulation component.

Therefore, according to the present invention, it is possible to eliminate the bandpass filter that was conventionally required to separate modulation components, compared to the conventional example whose configuration was complicated due to the need to remove the clock noise component. It is possible to realize a color solid-state imaging device whose configuration can be greatly simplified and which can obtain clear color images in which the generation of false color signals caused by bandpass filters has been eliminated.

In the description of the embodiment, the repetition period of the modulation component was about 2 pixels, but the same holds true even if the repetition unit is 4 pixels, 6 pixels, or more.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a first embodiment of the present invention, FIG. 2 is a schematic diagram showing the arrangement of a color filter array used in that embodiment, and FIGS. 4 is a configuration diagram showing a second embodiment of the present invention; FIG. 5 is a schematic diagram showing the arrangement of a color filter array used in the second embodiment; FIG. FIG. 6 is a configuration diagram showing a conventional color solid-four-wood imaging device. In the figure, 1. 131 19 is a solid-state image sensor, 2 is a low-pass filter, 3 is a bandpass filter, 4 is an IH delay line, 5,
6 is a demodulator, 7 and 8 are low-pass filters, 9.10.11 is a process circuit, 12 is a color encoder, 14e20 is a demodulation circuit, 15.21 is a polarity inversion circuit, 16.22 is a drive circuit, 17.23 is a low-pass filter, 18. 24 is a white balance circuit, 25 is a low-pass filter, 26 is a synchronization circuit, and 27 is a color encoder. Agent Patent Attorney Shinsuke Honjo Figure 2 Figure 5 B 4-Fult TIT2T3 T4 N O J4+Is Meni 3a4- Mataya 1ω BA Duty

Claims (1)

[Claims] A color filter array in which color filters are arranged at a predetermined repetition period in the horizontal and vertical directions is combined, and a signal representing luminance information and a plurality of signals representing color information are arranged at a repetition period in the horizontal direction of the color filter array. In a color solid-state imaging device including a solid-state imaging device configured to be obtained by frequency multiplexing as a modulation component, the polarity of the output signal of the solid-state imaging device is determined by the horizontal repetition period of the color filter array. 1. A color solid-state imaging device characterized in that a plurality of modulation components representing the color information are obtained by separating and demodulating a plurality of modulation components representing the color information as an average value of the polarity-inverted signals.