JPS61161090A - Color solid-state image pick-up device - Google Patents

Abstract

PURPOSE:To simplify a signal processing circuit for color separation with high resolution by producing chrominance difference signals on the basis of brightness signals from filter means, the first prime color signals from computing means and the second prime color signals from changeover means. CONSTITUTION:By delaying the output of a BPF53 by 1H with a 1H delaying circuit 54, a 2R-2B signal and a -2B signal are produced and introduced into a subtractive circuit 55 to produce a red modulated signal 2R. A blue modulated signal -2B is produced at every 1H period at the outputs of the circuit 54 and the BPF53 alternately so that it is obtained as continuous signal by a changeover switch 55 inverted at every 1H period. The separated red and blue modulated signals are demodulated at demodulating circuits 57, 58 and supplied to processing circuits 60, 61. The brightness signal Y is obtained as R+2G+B signal by passing through a LPF52. After passing through the processing circuit 59, the signal Y is supplied together with the red and blue signals to a color matrix circuit 62. The output from the circuit 62, that is, the signal Y and the chrominance difference signals R-Y, B-Y are supplied to an encoder 63.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a color solid-state imaging device, and particularly to a so-called color solid-state imaging device that obtains a color signal by disposing a color filter on a single solid-state Ifi element such as a COD. The present invention relates to a single-chip color solid-state imaging device.

[Prior art] Recently, solid-state m such as COD and MOS have been used for video cameras.
A single-plate color solid-state Ila image element using one image element is being actively developed. In such a single-chip color solid-state image sensor, a pixel of an image sensor such as a CCD has a ratio of 1:
A mosaic color filter array corresponding to 1 is provided.

FIG. 4 is a diagram showing an example of a color filter array used in a conventional single-chip color solid-state image sensor.

In addition, in FIG. 4, only a part of the color filter array is depicted for convenience of explanation. In the figure, R represents a red light transmission filter, B represents a blue light transmission filter, and G represents a green light transmission filter, and each square corresponds to one pixel of the solid-state image sensor. Note that in this color filter array, two identical color filters are lined up in the vertical direction, and this is because the solid-state image sensor performs a 2=1 interlaced operation. That is, in the first field, n)-1°( shown in Figure 4)
n + 1)H, (n + 2)H lines are scanned in order,
In the second field, nH-, (n+1)H-.

(n+2) H- lines are scanned in order.

FIG. 5 is a schematic block diagram showing an example of a conventional color solid-state imaging device using a color filter array as shown in FIG. The configuration and operation of the color solid-state imaging device shown in FIG. 5 will be described below. A color filter array as shown in FIG. 4 is arranged on the light receiving surface of the solid-state image sensor 21. As shown in FIG. The output signal of this solid-state image sensor 21 is considered in the first field (n) (R, G, R, G, . . . in lines)
It becomes a repeating signal of G, B, G on the (n+1)H line.
.

The (n+2)H line becomes a repetitive signal of <R, G, R, G, . . . , which is the same as the nH line. Therefore, a red signal (hereinafter referred to as R signal), a green signal (hereinafter referred to as G signal), and a blue signal (hereinafter referred to as B signal) can be easily separated by sampling and holding each pixel. In the device shown in Figure 5,
The sample and hold circuit 22 is a circuit that samples only the G signal, and the sample and hold circuits 23 and 25 sample the R signal.
This is a circuit that samples only the signal, and the sample and hold circuits 24 and 26 are circuits that sample only the B signal. Here, the R signal and B signal are transmitted during one horizontal scanning period (
Since they can only be obtained alternately every 1H period (hereinafter referred to as 1H period), they cannot be obtained simultaneously from the same scanning line. Therefore, the R signal or B signal separated by the sample and hold circuits 25 and 26 from the signal delayed by 1H period using the delay circuit 27 is interpolated as the R signal or B signal of the scanning line. Switches 28 and 29 are interlocking switches for performing this interpolation operation, and are inverted every 1H period. In this way, the synchronized R signal, G signal,
The B signals are applied to a color matrix circuit 33 via process circuits 30, 31, and 32, respectively, and the luminance signal Y and color difference are converted into signals RY and BY. The output of the color matrix circuit 33 is given to an encoder 34 and converted into a video signal.

In addition, prior art documents related to the above-mentioned color solid-state Wi image device include Toshiko, JP-A-57-37989, JP-A-57-39684, JP-A-57-136885.
It should be pointed out that there are publications such as Japanese Patent Application Laid-Open No. 58-210780.

[Problems to be Solved by the Invention] In a conventional color solid-state MS device using a color filter array as shown in FIG. , the light utilization rate is low, and the G filters that transmit G light, which is the main component of the luminance signal, are arranged only in a checkerboard pattern, resulting in low resolution in diagonal directions and color separation. In addition, this pixel readout method requires a large number of sample and hold circuits, which makes the signal processing circuit complicated.Also, in this pixel readout method, the first field, second field, etc. in interlaced scanning are Corresponding pixels are independent, and pixel readout takes one frame time (1/3
0sec) period. Therefore, when a moving subject is imaged, a field afterimage occurs and the image quality deteriorates.

This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and it provides a color solid-state imaging device with high light utilization, high resolution, simple signal processing circuit for color separation, and low afterimage. is intended to provide.

[Means for Solving the Problems] The present invention has unit color mosaic filters arranged in four rows in the vertical direction and two columns in the horizontal direction, which are arranged periodically in the horizontal and vertical directions. A color mosaic filter composed of a color mosaic filter, a solid-state image sensor having pixels provided at positions corresponding to each filter element of this color mosaic filter, and a luminance signal and a color difference signal from pixel signals output from this solid-state W4 image element. and a signal processing circuit for creating the. The solid-state image sensor is 2
Two rows of pixels adjacent to each other in the vertical direction are scanned horizontally at the same time.
It is configured to add and output read signals from pixels. Further, in the color mosaic filter, the color arrangement of each unit color mosaic filter is selected in a predetermined relationship. In other words, when capturing an image of a uniform white screen,
From the solid-state image sensor, the red signal component and the blue signal component are modulated at the same repetition period and at a phase different by 1800 degrees from each other on the first horizontal scanning line (either the odd-numbered horizontal scanning line or the even-numbered horizontal scanning line). pixel signals are output, and in the second horizontal scanning line (the other of the odd-numbered horizontal scanning line and the even-numbered horizontal scanning line), only one of the red signal component and the blue signal component is the same as that of the first horizontal scanning line. The color arrangement is selected such that a pixel signal is output that is modulated with the same period and phase as the first horizontal scanning line and has the same low frequency component as that of the first horizontal scanning line. Further, the signal processing circuit includes a first filter means,
It includes a second filter means, a 1Hil extension means, a calculation means, a switching means, and a color difference signal creation means. 1st
The filter means is solid 11! ! ! The second filter means extracts the low frequency component of the pixel signal output from the element and outputs it as a luminance signal, the second filter means extracts and outputs the modulation component of the pixel signal output from the solid-state image sensor, and the 1H delay means The output of the second filter means is delayed by one horizontal movement MwJ, the calculation means calculates the output of the second filter means and the output of the 1H delay means to create a first primary color signal, and the switching means 1
The output of the filtering means and the output of the 18il spreading means are switched every horizontal scanning period to create a second primary color signal different from the first primary color signal, and the color difference signal creating means receives the signal from the first filtering means. A color difference signal is created based on the first primary color signal from the luminance signal calculation means and the second primary color signal from the switching means.

[Operations] In this invention, by using a color mosaic filter selected in a predetermined color arrangement, processing of the output signal of the solid-state image sensor is facilitated, and the configuration of the interstage signal processing circuit is simplified.

[Embodiment] The first factor is a diagram showing an example of a color mosaic filter used in a color solid-state Wa image device according to an embodiment of the present invention. In addition, in this FIG. 1, like FIG. 4, only a part of the color mosaic filter is depicted for convenience of explanation. In the figure, W is a transparent filter for red light (R light) and green light (G light).

Blue light (B light) is transmitted through, ye is a yellow filter that transmits R light and G light, and Gy is a cyan filter that transmits G light.
Transmits light and B light. The color mosaic filter shown in Figure 1 consists of 4 rows and 2 columns of color mosaic filters.
The unit color mosaic filters are arranged periodically in the horizontal and vertical directions. Unit color mosaic filter vertically yellow,
A first row of filter elements is a repeat of yellow, green, yellow, and a second row is a repeat of cyan, cyan, transparent, cyan.
It consists of a filter element sequence.

By the way, in this embodiment, two rows of pixels are simultaneously scanned horizontally and signals from two vertically adjacent pixels are added.
In the two fields in which (mixed) readout and increment scanning are performed, a solid-state image sensor is used that changes the combination of lines to be mixed. In Figure 1, the first field (2n+1)H, (2n+2)H, (2n+2)H,
horizontal scanning lines of n+3)H and (2n+4)H, and (2n+1)H' and (2n+2)H- of the second field.

It shows the combination of pixels to be mixed in each horizontal scanning line of (2n+3)H-.

FIGS. 2A and 2B show the signals obtained when uniform white light is incident on the color solid-state image sensor equipped with the color mosaic filter shown in FIG. .

(2n + 3) H line) and even line ((2n + 2
)H, (2n + 4)H line) shows the tweet.

Similarly, FIGS. 2C and 2d illustrate the second field. In these FIGS. 2A to 2D, the vertical axis corresponds to the signal amount, and the vertical axis corresponds to the horizontal direction. for example,
At the left end of the odd numbered line in the first field, Ye
and Ye are mixed and output, so the signal amount at the corresponding position in Figure 2A is Ye +Ye -28+2G
At the adjacent position, Gy and Cy are mixed and output, so the amount of signal obtained is Cy+Cy-2B
+2G.

FIG. 3 is a schematic block diagram showing a color solid-state imaging device according to an embodiment of the present invention using a color mosaic filter as shown in FIG. In the figure, a solid-state image sensor 51
A color mosaic filter as shown in FIG. 1 is arranged on the light-receiving surface of.

As mentioned above, this solid-state I#l imaging device @51 has two systems that simultaneously horizontally scan two rows of pixels and add and read out signals from two vertically adjacent pixels to perform incremental scanning. The field is configured to change the combination of lines to be mixed.

The output of the solid-state image sensor 51 is applied to a low-pass filter 52 and a bandpass filter 53. The output of low pass filter 52 is applied to color matrix 62 via process circuit 59. The output of the bandpass filter 53 is one input of the subtraction circuit 55,
IH delay circuit 54. These signals are applied to one terminal of the switch 56, respectively. The output of the 1Hil extension circuit 54 is sent to the subtraction circuit 55.
and the other terminal of the switch 56. The output of the subtraction circuit 55 is sent to the demodulation circuit 57
, are provided to color matrix 62 via process circuitry 60. The switching contact of the switch 56 is connected to the demodulation circuit 58. It is connected to a color matrix 62 via a process circuit 61 . The color matrix 62 is a circuit that creates a luminance signal Y and color difference signals RY and BY based on the signals from the process circuits 59 to 61, and its output is given to an encoder 63. The encoder 63 creates and outputs a color video signal from the luminance signal and color difference signal.

Next, the operation of the color solid-state imaging device shown in FIG. 3 will be explained. First, as is clear from FIGS. 2A and 2B, in the odd rows of the first field, (Ye +Ye) −
(Cy +Cy)-2R+2G-(2B+2G)-2
The R-2B color difference signal is modulated, and in even rows (
Ye +G)-(W+CV)-(R+2G)-(R+
A primary color signal of 2G+2B)--2B is modulated.

Similarly, as is clear from FIGS. 2C and 2D,
In the odd rows of the second field, (Ye +G) - (Cy
A primary color signal of +w>-12B is modulated, and in even rows (Ye +'v'e) -(Cy +Cy)
A color difference signal of -2R-2B is modulated. The fundamental frequency of these modulation signals is r
[Hz], it becomes "/2 [H2]" which is half of that. Therefore, the center frequency of the bandpass filter 53 is f
/2 [Hz] allows the modulation components of each line to be extracted. Since the modulation component is used as a color signal as described later, the band of the bandpass filter 53 is ±0.5MH1.
It is enough.

As a result of the above, in the first field, 2
A modulated signal is obtained by repeating R-28, -2B, and the second
12B for every odd and even row in the field, 2R-2B
A modulated signal is obtained by repeating.

Therefore, the output of the bandpass filter 53 is 1Hil! If delayed by 1H by the delay circuit 54, the 2R-2B signal and -2B signal
Signals can be obtained simultaneously. These signals are input to the subtraction circuit 55, and a red modulation signal of 2R is calculated. On the other hand, the -2B blue modulation signal is transmitted to the 1H delay circuit 5.
4 and the output of the bandpass filter 53 alternately every 1H period, so they can be obtained as a continuous signal by the changeover switch 56 which is inverted every 1H period. The thus separated red and blue modulated signals are demodulated by demodulation circuits 57 and 58, respectively, and processed by process circuits 60 and 61.
given to.

On the other hand, the luminance signal Y can be obtained as an R+2G+8 signal by using a low-pass filter 52 with a cutoff frequency r/2[H21. After passing through the process circuit 59, this luminance signal Y is added to the color matrix circuit 62 together with the red and blue signals mentioned above, and the color difference signal R-Y
form.

The output of the color matrix circuit 62, that is, the luminance signal Y and the color difference signals @R-Y and B-Y, are supplied to an encoder 63 and converted into, for example, an NTSC video signal.

Note that the frequency f mentioned above is, for example, 400 degrees horizontally and 5 degrees vertically.
Approximately 7.16MHz when using a llil element image of 00 pixels
It is.

In the above embodiment, the color difference signal of 2R-28 and the primary color signal of 12B are modulated for each scanning line.
Various modifications are possible. Other embodiments are shown in FIGS. 6-8. The variable a signal and luminance signal in these Examples are summarized in Table 1 below. In short, in this invention,
When imaging uniform white light, solid! In the first horizontal scanning line (one of the odd-numbered horizontal scanning lines and the even-numbered horizontal scanning line) from the fi image element, the red signal component and the blue signal component are modulated with the same repetition period and with phases 180° different from each other. pixel signals are output, and in the second horizontal scanning line (the other of the odd horizontal scanning lines and the even horizontal scanning lines), only one signal component of the red signal or the blue signal is output from the first horizontal scanning line. The color arrangement of the unit color mosaic filter with 4 rows and 2 columns is selected such that a pixel signal is output that is modulated with the same period and the same phase as that of the first horizontal scanning line and has the same low frequency component as that of the first horizontal scanning line. It is fine as long as it is. In addition, the above figures 6 to 8
It goes without saying that signal processing using a color mosaic filter as shown in the figure can also be realized using the same concept as the embodiment shown in FIG.

(Margin below) According to this invention, color mosaic element is a complementary color frame with high light utilization. High-sensitivity color solid-state photography It also contributes significantly to the luminance signal. included in the output from all pixels. will not deteriorate. Also, color It can be easily done by filtering method, and conventional example. Need to provide multiple pull-hold circuits In the invention, two rows of pixels are simultaneously Since solid-state mechanical elements are used, all Yield (read at 1/60sec> One of the major features of body image sensors is This characteristic can be utilized during the autumnal equinox.

FIG. 3 is a diagram showing a color filter used in an embodiment of the invention described in a car. FIG. 2A is a diagram showing an output signal of a mechanical element of the color mosaic filter of FIG. 1, and particularly shows an output signal when uniform white light is imaged. FIG. 3 is a schematic block diagram showing a color solid-state Wi image device according to an embodiment of the present invention. FIG. 4 is a diagram showing an example of a color filter array used in a conventional color solid-state imaging device. FIG. 5 is a schematic block diagram showing an example of a conventional color solid-state LFI image device. 6 to 8 are diagrams showing color mosaic filters used in other embodiments of the present invention.

In the figure, 51 is a solid-state 1liI image element, 52 is a low-pass filter, 53 is a bandpass filter, 54 is a 1H delay circuit, 5
5 is a subtraction circuit, 56 is a switch, 57 and 58 are 11
1 circuit, 59 to 61 are process circuits, 62 is a color matrix circuit, and 63 is an encoder.

Claims (5)

[Claims] (1) A color mosaic filter configured by periodically arranging unit color mosaic filters in the horizontal and vertical directions, which are configured by arranging color filters in four rows in the vertical direction and two columns in the horizontal direction; A color mosaic filter comprising: a solid-state image sensor having pixels provided at positions corresponding to each filter element of a color mosaic filter; and a signal processing circuit that creates a luminance signal and a color difference signal from a pixel signal output from the solid-state image sensor. The solid-state imaging device is configured to horizontally scan two rows of pixels simultaneously, add read signals from two vertically adjacent pixels, and output the result, and the solid-state imaging device In the mosaic filter, the color arrangement of each unit mosaic filter is selected to have a predetermined relationship, and the predetermined relationship means that when an image of a uniform white screen is captured,
From the solid-state image pickup device, a red signal component and a blue signal component have the same repetition period and are 180° different in phase from each other on the first horizontal scanning line (either an odd-numbered horizontal scanning line or an even-numbered horizontal scanning line). The modulated pixel signal is output, and in the second horizontal scanning line (the other of the odd-numbered horizontal scanning line and the even-numbered horizontal scanning line), only one of the red signal component and the blue signal component is transmitted to the first horizontal scanning line. The relationship is such that a pixel signal is output that is modulated with the same period and the same phase as that of the first horizontal scanning line and has the same low frequency component as that of the first horizontal scanning line, and the signal processing circuit is configured to: a first filter means for extracting a low frequency component of a pixel signal output from the image sensor and output as a luminance signal; a second filter means for extracting a modulation component of the pixel signal output from the solid-state image sensor; , 1H delay means for delaying the output of the second filter means by one horizontal scanning period, and a first primary color signal by processing the output of the second filter means and the output of the 1H delay means. and a switching means that switches between the output of the first filter means and the output of the 1H delay means every horizontal scanning period to create a second primary color signal different from the first primary color signal. and color difference signal creation means for creating a color difference signal based on the luminance signal from the first filter means, the first primary color signal from the calculation means, and the second primary color signal from the switching means. and a color solid-state imaging device. (2) The unit color mosaic filter of 4 rows and 2 columns is:
Claim 1, characterized in that the color arrangement in the first column is selected as yellow, yellow, green, yellow, and the color arrangement in the second column is selected as cyan, cyan, transparent, cyan. The color solid-state imaging device according to item 1. (3) The unit color mosaic filter of 4 rows and 2 columns is:
The color array in the first column is selected as cyan, cyan, green, cyan, and the color array in the second column is yellow, yellow,
The color solid-state imaging device according to claim 1, characterized in that transparent and yellow are selected. (4) The unit color mosaic filter of 4 rows and 2 columns is:
Claim 1, characterized in that the color arrangement in the first column is selected as transparent, yellow, cyan, yellow, and the color arrangement in the second column is selected as cyan, cyan, transparent, cyan. The color solid-state imaging device according to item 1. (5) The unit color mosaic filter of 4 rows and 2 columns is:
Claim 1, characterized in that the color arrangement in the first column is selected as transparent, cyan, yellow, cyan, and the color arrangement in the second column is selected as yellow, yellow, transparent, yellow. The color solid-state imaging device according to item 1.