JP3515585B2 - Two-chip imaging device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-plate type image pickup device, and more particularly to improvement of color resolution of an image.

[0002]

The human eye is less sensitive to color than it is to luminance. Therefore, NTSC (National T
In the standards such as the Elevision System Committee), the color resolution is set lower than the luminance resolution.
In the plate type image pickup device, the G and R / B methods are mainly used. That is, in this image pickup device, as shown in FIG. 12, for example, a filter F1 that transmits green light in all pixels transmits red (red) light onto one CCD (solid-state image sensor). A filter F2 in which the pixels to be turned on and the pixels to transmit blue light are alternately arranged is provided on another CCD. These CC
The output signal of D is superimposed on the corresponding pixels in the video processing circuit. That is, the brightness is represented by a signal of 1 dot, but the color is represented by a signal of 2 dots (a pixel signal including an R signal corresponding to red and a pixel signal including a B signal corresponding to blue).

[0003]

As described above, the conventional device is constructed so that the color signal is generated from the information of two pixels, and the information amount of the color signal is insufficient as compared with the luminance signal. , I can't get good image quality. When an image signal having such a low color resolution is input to a computer and image processing is performed on a pixel-by-pixel basis, deterioration of the image quality is often noticeable. To deal with this, it is possible to obtain a RGB signal by adopting a so-called three-plate type image pickup device in which three CCDs are provided and each CCD is provided with a filter for transmitting red, green and blue respectively. Such a configuration causes a problem that the scale of the device becomes large and the circuit configuration becomes complicated.

The present invention provides a two-plate type image pickup device capable of increasing the color resolution without complicating the circuit structure and generating an image signal whose image quality does not deteriorate even when image processing is performed by a computer or the like. The purpose is to do.

[0005]

In a two-plate type image pickup device according to a first aspect of the present invention, a filter array is repeated in units of a total of four pixels each having two pixels arranged in the horizontal direction and four pixels in the vertical direction. Among them, two pixels on one diagonal line are both green (G) filters, and two pixels on the other diagonal line are each provided with a first complementary color filter that is a cyan (Cy) filter and a yellow (Ye) filter. A first image sensor and a second complementary color filter having the same filter arrangement as that of the first complementary color filter; and a second image capturing the same optical image as the optical image captured by the first image sensor. Image sensor and two pixels adjacent to the first image sensor
The signal detected by the
Two adjacent pixels of the second image sensor at the same position
R, G, and B signals based on the signal detected by the RGB signal extraction means, and the filter array of the second complementary color filter has a filter array of the first complementary color filter for the optical image. The filter array is offset by one pixel pitch in the horizontal or vertical direction .
Pair the optical image of two adjacent pixels of the image sensor
Next to the second image sensor at the same optical position
From 4 pixels including 2 pixels in contact with each other,
A Cy signal for one pixel and a Ye signal for one pixel are obtained, and R
In the GB signal extracting means, the B signal is the G signal and the Cy signal.
And the R signal is extracted from the G signal and the Ye signal.
It is characterized in that that. Further, a two-plate type image pickup device according to claim 3 of the present invention has first and second array units each of which has a total of four pixels arranged in two lines in the first and second directions. Includes a first complementary color filter in which first and second array units are alternately and repeatedly arranged, and only one of the first and second array units is repeatedly arrayed in the second direction. A first image sensor and a second complementary color filter having the same filter arrangement as the first complementary color filter,
A second image sensor for capturing an optical image and the same optical image captured in the first image sensor, a first i
The signals detected by the two adjacent pixels of the image sensor and 2
A second image that is optically in the same position with respect to the optical image of the pixel.
Signals and based on that detected by the two adjacent pixels you of Mejisensa
And Zui, RGB to extract R, G and B signals
And a signal extraction means, and four pixels are composed of a green (G) filter, a magenta (Mg) filter, a yellow (Ye) filter, and a cyan (Cy) filter, and the green filter and the magenta filter are in the first or second direction. Adjacent to each other, the arrangement of the green filters and magenta filters in the second arrangement unit is opposite to the arrangement of the green filters and magenta filters in the first arrangement unit, and the filter arrangement of the second complementary color filter is Is shifted by one pixel pitch in the first or second direction with respect to the filter arrangement of the first complementary color filter for the optical image, and is adjacent to the first image sensor.
2 pixels and the optical image of 2 pixels at the same optical position
4 screens including 2 adjacent pixels of a certain second image sensor
From the element, Mg signal, G signal, Ye signal, Cy signal
One pixel each is obtained, and the RGB signal is extracted by the RGB signal extraction means.
No., G signal, B signal are Mg signal, G signal, Ye signal, C
It is characterized in that it is extracted based on the y signal .

[0006]

The present invention will be described below with reference to illustrated embodiments. FIG. 1 is a block diagram of a still video camera which is an embodiment of the present invention.

The system control circuit 10 is a microcomputer, and controls the entire still video camera.

The image pickup optical system 11 includes a lens 12 and a diaphragm 13. The lens 12 is driven by the zoom drive circuit 14 during the zooming operation, and is driven by the focus drive circuit 15 during the focusing operation. The aperture of the diaphragm 13 is adjusted by the iris drive circuit 16 during exposure control.
The zoom drive circuit 14, the focus drive circuit 15, and the iris drive circuit 16 are controlled by the system control circuit 10.

The light beam passing through the image pickup optical system 11 is guided to the first and second CCDs (image sensors) 22 and 23 through the prism 21, and the same subject image is formed on these CCDs 22 and 23. It Further, this light beam is guided to the finder optical system 25 via the prism 21 and the mirrors 24 and 29. First and second CCDs 22, 2
3 are provided with filters 51 and 52, respectively. The CCDs 22 and 23 are driven by the CCD driver 26, and thereby, the image signals corresponding to the subject images formed on the CCDs 22 and 23 are supplied to the correlated double sampling (CDS) circuits 31 and 32. The CCD driver 26 operates by the pulse signal output from the synchronization signal generation circuit 27 controlled by the system control circuit 10.

The image signals input to the CDS circuits 31 and 32 are subjected to predetermined processing such as gamma correction in the preprocessing circuits 33 and 34 after the reset noise is removed. Then, this image signal is converted into a digital signal in the A / D converters 35 and 36, and the image memories 41 to 44.
Stored in. Image memory 41 to which image signals are stored
The address of 44 is controlled by the system control circuit 10 via the address control circuit 45.

The video processing circuit 46 includes image memories 41-4.
The image signal stored in 4 is subjected to the processing described later, whereby the R signal, the G signal, and the B signal are output together with the luminance signal. These signals are output to the computer or display device via the interface circuit.

The manual switch 47 connected to the system control circuit 10 is provided for operating the present still video camera, and the display element 48 is provided for displaying the contents of the operation by the manual switch 47 and the like.

The prism 21 has first and second light separating surfaces 21a and 21b.
By the action of a and 21b, the first and second CCD2
The amount of light guided to 2, 23 and the finder optical system 25 is separated into a ratio of 4: 4: 2, for example, and light of the same intensity is guided to each CCD 22, 23. That is, a part of the light rays that have entered the prism 21 from the imaging optical system 11 are reflected by the first light splitting surface 21a and guided to the second CCD 23, and the other light rays pass through the first light splitting surface 21a. The light is transmitted and guided to the second light separation surface 21b. At the second light separation surface 21b, a part of the light rays is reflected and guided to the first CCD 22, and the other light rays, that is, the first and second light separation surfaces 21a and 21b.
The light beam that has passed through is emitted to the outside of the prism 21.
This light beam is reflected by the mirrors 24 and 29 and guided to the finder optical system 25. The mirrors 24 and 29 are members for shifting the optical axis of the finder optical system 25 from the optical axis of the photographing optical system 11, and can be omitted.

The amounts of light guided to the first and second CCDs 22 and 23 do not necessarily have to be the same, and when the amounts of light are different, the magnitudes of these output signals are adjusted by adjusting the gains of the outputs of the CCDs 22 and 23. The same can be done.

FIG. 2 shows the first and second CCDs 22, 2
3 shows an array of color filters 51, 52 provided on the light receiving surface of No. 3. These color filters 51,
Reference numeral 52 is a complementary color checkered color filter having the same configuration. In these color filters 51 and 52, filter elements that transmit magenta (Mg), yellow (Ye), cyan (Ce), and green (G) are alternately arranged. That is, in addition to green (G), magenta (Mg), yellow (Ye), and cyan (Ce) having different spectral characteristics of complementary colors are included in a total of 4 pixels in which two pixels are arranged in each of the horizontal direction and the vertical direction. Three pixels are provided.

The positional relationship between the second color filter 52 and the CCD 23 is shown by the CCD of the first color filter 51.
Compared with the positional relationship with respect to 22, the second color filter 52 is provided so as to be shifted by one pixel with respect to the CCD 23 in the horizontal direction (left direction in FIG. 2). For example, paying attention to the pixel P at the upper left corner of the screen, the first color filter 51 is magenta, but the second color filter 52 is green.

As described above, the pixel spectral characteristics of the CCDs 22 and 23 are regularly changed and are of the complementary color difference line sequential type. Further, the pixel spectral characteristic of the second CCD 23 is horizontally displaced from the pixel spectral characteristic of the first CCD 22 by one pixel.

The output signal of the first CCD 22 and the second CC
The output signal of D23 is converted into a digital signal by the image memory 4
1 to 44 are temporarily stored, they are read from these memories and processed in the video signal processing circuit 46. That is, the corresponding pixels are superimposed on each other, and the R signal, the G signal, and the B signal corresponding to each pixel are extracted from the superimposed signals to obtain a video signal.

FIG. 3 shows this superposed state. As understood from this figure, the magenta (Mg) of the filter 51 of the first CCD 22 and the green (G) of the filter 52 of the second CCD 23 are the same as the green (G) of the filter 51 and the magenta (Mg) of the filter 52. ), Yellow (Ye) of the filter 51 and cyan (Cy) of the filter 52 correspond to the same pixel, and cyan (Cy) of the filter 51 and yellow (Ye) of the filter 52 correspond to the same pixel, respectively. In FIG. 3, Px is a horizontal pixel interval (1 pitch), and Py is a vertical pixel interval (1 pitch).
Pitch) respectively.

First, the extraction of the R signal will be described. The R signal included in magenta (Mg) is R _Mg , the B signal is B _Mg ,
The R signal included in yellow (Ye) is R _Ye and the G signal is G
_When G signal included in _Ye and cyan (Cy) is G _Cy and B signal is B _Cy , Mg = R _Mg + B _Mg , Ye = R _Ye + G _Ye , Cy = G _Cy + B
It can be represented as _Cy .

The R signal is a magenta (M
g) and yellow (Ye), and the four pixels of green (G) and cyan (Cy) (pixels shaded in FIG. 3) superimposed on them are obtained by the following formula. R _S = (Mg + Ye) -α (G + Cy) = R _Mg + B _Mg + R _Ye + G _Ye −αG-αG _Cy −αB _Cy = R _Mg + R _Ye + G _Ye −α (G + G _Cy ) + B _Mg −αB _Cy = R _Mg + R _Ye (1) However, in order for this expression (1) to hold, the condition is that α = G _Ye / (G + G _Cy ) = B _Mg / B _Cy .

The B signal is similarly obtained by the following equation. B _S = (Mg + Cy) -β (G + Ye) = R _Mg + B _Mg + G _Cy + B _Cy -βG-βR _Ye -βG _Ye = B _Mg + B _Cy + G _Cy -β (G + G _Ye ) + R _Mg -βR _Ye = B _Mg + B _Cy (2) However, in order for this equation (2) to hold, it is a condition that β = G _Cy / (G + G _Ye ) = R _Mg / R _Ye holds.

Regarding the G signal, a luminance signal (Y) and
It is obtained from R _S and B _S obtained by the equations (1) and (2). That is, G _S = Y−R _S −B _S = (Mg + Cy + G + Ye) −R _S −B _S = G + G _Ye + G _Cy (3)

Next, the spectra of the RGB signal and the luminance signal Y thus obtained will be considered.

First, the spectrum of the luminance signal Y will be described.
Let S _O (x, y) = Σ _m Σ _n δ (x−2mP _x , y−4 nP _y ), where δ is a delta function, x is a horizontal coordinate, and y is a vertical direction. Coordinates, m and n are integers). And M
The optical image distributions for the g, G, Ye, and Cy pixels are I _A1Mg (x, y) and I _A1G (x, respectively) for the first CCD 22.
y), I _A1Ye (x, y), I _A1Cy (x, y), and the second C
For CD23, I _A2Mg (x, y) and I _A2G (x, y, respectively)
y), I _A2Ye (x, y), and I _A2Cy (x, y), and spectra are obtained for a combination of 4 pixels which are connected by a line L in FIG.

Here, the first and second CCDs 22, 2
Assuming that the output of each pixel of 3 is equal, I _AMg (x, y) = I _A1Mg (x, y) = I _A2Mg (x, y) I _AG (x, y) = I _A1G (x, y ) = I _A2G (x, y) I _AYe (x, y) = I _A1Ye (x, y) = I _A2Ye (x, y) I _ACy (x, y) = I _A1Cy (x, y) = I _A2Cy Let (x, y). Then, the spectra of the luminance signal components of the first and second fields are _expressed as I _Y1 (u, v) = I _AMg (u, v) exp (-jP _y v) + I _AG (u, v) exp (-jP _y v) + I _AYe (u, v) + I _ACy (u, v) I _Y2 (u, v) = I _AMg (u, v) + I _AG (u, v) + I _AYe (u, v) exp (-jP _y v) + I _ACy (u, v) exp (-jP _y v) (where u is a horizontal angular spatial frequency, v is a vertical angular spatial frequency, and j is an imaginary number), the first and second
The luminance signal spectrum of the field is Y ₁ (u, v) = I _Y1 (u, v) * {S _O (u, v) (1 + exp (-jP _x u)) (1 + exp (-j2P _y v))} = I _Y1 (u, v) * {S _O (u, v) 4exp (-jP _x u / 2) exp (-jP _y v) ・ cos (P _x u / 2) cos (P _y v)} ( 4) Y ₂ (u, v) = I _Y2 (u, v) * {S _O (u, v) exp (-jP _y v) (1 + exp (-jP _x u)) ・ (1 + exp (-j2P _y v ))} = I _Y2 (u, v) * {S _O (u, v) 4exp (-jP _x u / 2) exp (-j2P _y v) ・ cos (P _x u / 2) cos (P _y v )} (5) Where S _O (u, v) is the basic sampling sequence S
_In the spectrum of _O (x, y), S _O (u, v) = (1 / 8P _x P _y ) Σ _m Σ _n δ (u −2πm / 2p _x , v −2πn / 4P _y ). The * symbol represents convolution integral.

From the expressions (4) and (5), in the luminance signal spectrum, the 1 / 2Px, 1 / 4Py, and 3 / 4Py components disappear, and at the 0, 1 / Px, and 1 / Py ( I _Y1
(u, v) + I _Y2 (u, v)) The spectrum is convoluted (convolution integral), and at (1 / 2Py) (I
It can be seen that the _Y1 (u, v) -I _Y2 (u, v)) spectrum is combo rooted. Therefore, the luminance signal spectrum is as shown in FIG. In FIG. 5, the horizontal axis is the spatial frequency in the horizontal direction, and the vertical axis is the spatial frequency in the vertical direction.

As shown in this figure, in the horizontal direction, (I _Y1 (u, v) + I _Y2 (u,
v)) signal sideband components appear, and (I _Y1 (u, v) −I _Y2 (u,
The sideband component of the v)) signal appears. In addition, this 1/2
The amplitude of the sideband component at Py is small, and the image distribution I
_{As A} (x, y) is flat (uniform), v = 2πm / P
In case of frequency of y (m is an integer), Mg + G and Ye + C
When the values of y are equal, I _Y1 = I _Y2 , so this sideband component disappears.

The spectrum of the R signal is also obtained in the same manner as the case of the luminance signal. That is, the first and second C
Assuming that the output of each pixel of CD22 and CD23 is equal,
And the spectrum of the R signal component of the second field, I _R1 (u, v) = I _AMg (u, v) exp (-jP _y v) -α I _AG (u, v) exp (-jP _y v) + I _AYe (u, v) -αI _ACy (u, v) I _R2 (u, v) = I _AMg (u, v) -αI _AG (u, v) + I _AYe (u, v) exp (-jP _y v ) −αI _ACy (u, v) exp (-jP _y v), the spectrum of the R signal in the first and second fields is R ₁ (u, v) = I _R1 (u, v) * { _{S O (u, v) (} 1 + exp (-jP x u)) (1 + exp (-j2P y v))} = I R1 (u, v) * {S O (u, v) 4exp (-jP x u / 2) exp (-jP _y v) ・ cos (P _x u / 2) cos (P _y v)} (6) R ₂ (u, v) = I _R2 (u, v) * {S _O (u, _{v) exp (-jP y v)} (1 + exp (-jP x u)) · (1 + exp (-j2P y v))} = I R2 (u, v) * {S O (u, v) 4exp (-jP _x u / 2) exp (-j2P _y v) -cos (P _x u / 2) cos (P _y v)} (7)

As understood from the equations (6) and (7), the spectrum of the R signal appears at the same place as the luminance signal (FIG. 6 (a)). Further, when the image distribution I _A (x, y) has a frequency of v = 2πm / Py (m is an integer) such as flat, or when the values of Mg−αG and Ye−αCy are equal,
Since I _R1 = I _R2 , the 1/2 Py component disappears due to the interlacing as well as the luminance signal.

The spectrum of the B signal is also obtained in the same manner as in the case of the luminance signal. That is, the first and second C
Assuming that the output of each pixel of CD22 and CD23 is equal,
And the spectrum of the B signal component of the second field, I _B1 (u, v) = I _AMg (u, v) exp (-jP _y v) -β I _AG (u, v) exp (-jP _y v)- βI _AYe (u, v) + I _ACy (u, v) I _B2 (u, v) = I _AMg (u, v) −βI _AG (u, v) −βI _AYe (u, v) exp (-jP _y v) + I _ACy (u, v) exp (-jP _y v), the spectrum of the B signal in the first and second fields is B ₁ (u, v) = I _B1 (u, v) * { S _O (u, v) (1 + exp (-jP _x u)) (1 + exp (-j2P _y v))} = I _B1 (u, v) * {S _O (u, v) 4exp (-jP _x u / 2) exp (-jP _y v) ・ cos (P _x u / 2) cos (P _y v)} (8) B ₂ (u, v) = I _B2 (u, v) * {S _O (u, v) exp (-jP _y v) (1 + exp (-jP _x u)) ・ (1 + exp (-j2P _y v))} = I _B2 (u, v) * {S _O (u, v) 4exp (-jP _x u / 2) exp (-j2P _y v) · cos (P _x u / 2) cos (P _y v)} (9).

As can be understood from the equations (8) and (9), the spectrum of the B signal appears at the same place as that of the luminance signal like the R signal (FIG. 6B). Also the image distribution I
_{When A} (x, y) has a frequency of v = 2πm / Py (m is an integer) such as flat, Mg−βG and −βYe + Cy
When the values are the same, I _B1 = I _B2 , so that the 1/2 Py component disappears due to the interlacing as well as the luminance signal.

The spectrum of the G signal can also be obtained in the same manner as described above. That is, the first and second CCDs
Assuming that the output of each pixel of 22 and 23 is equal, the spectrum of the B signal component of the first and second fields is calculated as I _G1 (u, v) = I _Y1 (u, v) -I _R1 (u, v ) −I _B1 (u, v) = −I _AMg (u, v) exp (-jP _y v) + (1-α−β) I _AG (u, v) exp (-jP _y v) + (2 −β) I _AYe (u, v) + (2-α) I _ACy (u, v) I _G2 (u, v) = I _Y2 (u, v) −I _R2 (u, v) −I _B2 ( u, v) = -I _AMg (u, v)-(1-α-β) I _AG (u, v) + (2-β) I _AYe (u, v) ・ exp (-jP _y v) + If (2−α) I _ACy (u, v) exp (-jP _y v) is set, G ₁ (u, v) = I _G1 (u, v) * {S _O (u, v) (1 + exp ( -jP _x u)) (1 + exp (-j2P _y v))} = I _G1 (u, v) * {S _O (u, v) 4exp (-jP _x u / 2) exp (-jP _y v ) ・ Cos (P _x u / 2) cos (P _y v)} (10) G ₂ (u, v) = I _G2 (u, v) * {S _O (u, v) exp (-jP _y v ) (1 + exp (-jP _x u)) ・ (1 + exp (-j2P _y v))} = I _G2 (u, v) * {S _O (u, v) 4exp (-jP _x u / 2) exp (- _{j2P y v) · cos (P} x u / 2) cos (P y v)} and made (11).

As can be understood from the equations (10) and (11), the G signal also has a spectrum at the same position as the luminance signal, like the R and B signals (FIG. 6C). Also, the image distribution I _A (x, y) is v = 2πm such as flat.
In the case of the frequency of / Py (m is an integer), -Mg + (1-
If the values of α-β) G and (2-α) Cy are equal, I
_{Since G1} = I _G2 , the 1/2 Py component disappears due to the interlacing as well as the luminance signal.

Next, the spectra of the respective color signals according to the present embodiment shown in FIGS. 6A to 6C are compared with the spectra when a G, R / B system filter as shown in FIG. 12 is used. Compare.

FIG. 7 shows the result of analyzing the spectrum in the case of using the G, R / B type filter by the same method as described above. As shown in this figure, in the R signal and the B signal, the sideband component is (1 / 2Px, 1 / 4P
y). Therefore, according to Nyquist's theorem, the cut-off frequency of the low-pass filter provided to cut the sideband wave component to obtain the fundamental wave component of the color signal is 1 / 4Px in the horizontal direction and 1 / 8Py in the vertical direction. Limited to.

On the other hand, according to the structure using the complementary color checkered color filter as in the present embodiment, as shown in FIG. 6, the sideband components are (1 / Px, 0) and (1 / 2Py, 0). Therefore, the cutoff frequency of the low-pass filter provided to obtain the fundamental wave component of the color signal is 1/2 in the horizontal direction.
Px may be lower than 1/4 Py in the vertical direction. That is, according to the present embodiment, the cutoff frequency of the low-pass filter can be increased by a factor of two as compared with the comparative example of FIG. It has been enlarged and the resolution has improved.

Regarding the G signal, in this embodiment, (0, 1
/ 2Py), a sideband component appears at the position where the sideband component does not appear at this position in the comparative example, but the sideband component in the vertical direction disappears due to interlacing as described above. It doesn't really matter.

FIG. 8 shows the reproducible spectrum range in this example and the comparative example. In the comparative example, the spectral range of the color signal is ¼ Px as indicated by a broken line B1.
However, in this embodiment, it is enlarged to 1/2 Px as shown by the broken line B2. The spectral range of the luminance signal is shown by the solid lines S1 and S in the comparative example and the present example.
It is the same as indicated by 2.

Next, the actual method of extracting the RGB signals will be described with reference to FIG. In the pixel arrangement of this figure,
The first and second CCDs 22 and 23 are represented by parameters A and B, respectively, the horizontal direction is represented by a parameter i, and the vertical direction is represented by a parameter j. In this figure, among the pixels shown in an overlapping manner, the one located above is the first C
Corresponding to the CD22, the one below is the second CCD
23. The signal from each pixel is
For the CCD 22 of, VA, i, j = Mg, VA, i + 1, j = G VA, i, j + 1 = Ye, VA, i + 1, j + 1 = Cy VA, i, j + 2 = G, VA, i + 1, j + 2 = Mg VA, i, j + 3 = Ye, VA, i + 1, j + 3 = Cy, and for the second CCD 23, VB , i, j = G, VB, i + 1, j = Mg VB, i, j + 1 = Cy, VB, i + 1, j + 1 = Ye VB, i, j + 2 = Mg, VB, i The arrangement is such that + 1, j + 2 = G VB, i, j + 3 = Cy and VB, i + 1, j + 3 = Ye. Where i = 1,3,5, ...; j = 1,5,
It shall take the values of 9, ...

In the first scan, the signal of the first field, that is, VA, i, j = Mg, VA, i + 1, j = G VA, i, j + 2 = G, VA, i + 1, j + 2 = Mg VB, i, j = G, VB, i + 1, j = Mg VB, i, j + 2 = Mg, VB, i + 1, j + 2 = G are extracted, and in the second scan Signal of the second field, that is, VA, i, j + 1 = Ye, VA, i + 1, j + 1 = Cy VA, i, j + 3 = Ye, VA, i + 1, j + 3 = Cy VB , i, j + 1 = Cy, VB, i + 1, j + 1 = Ye VB, i, j + 3 = Cy, VB, i + 1, j + 3 = Ye are extracted.

The above all pixel signals are the image memories 41 to 44.
Memorized in. These pixel signals are sent to the video processing circuit 46.
Is read out, and Ri, k = (VA, i, j + VA, i, j + 1) -α (VB, i, j + VB, i, j + 1) = (Mg + Ye) -α (G + Cy) (12) Ri, k + 1 = (VB, i, j + 2 + VA, i, j + 3) -α (VA, i, j + 2 + VB, i, j + 3) = (Mg + Ye) −α (G + Cy) (13) Bi, k = (VA, i, j + VB, i, j + 1) −β (VB, i, j + VA, i, j + 1) = (Mg + Cy) -β (G + Ye) (14) Bi, k + 1 = (VB, i, j + 2 + VB, i, j + 3) -β (VA, i, j +2 + VA, i, j + 3) = (Mg + Cy) -β (G + Ye) (15) Gi, k = (VA, i, j + VA, i, j + 1 + VB, i, j + VB, i, j + 1) -pRk-qBk = (Mg + Ye + G + Cy) -pRk-qBk (16) Gi, k + 1 = (VB, i, j + 2 + VA, i, j + 3 + VA, i, j + 2 + VB, i, j +3) -pRk + 1-qBk + 1 = (Mg + Ye + G + Cy) -pRk + 1-qBk + 1 (17) RGB signals are obtained.

Similarly, Ri + 1, k = (VB, i + 1, j + VB, i + 1, j + 1)-. Alpha. (VA , i + 1, j + VA, i + 1, j + 1) = (Mg + Ye) -α (G + Cy) (18) Ri + 1, k + 1 = (VA, i + 1, j + 2 + VB, i + 1, j + 3) -α (VB, i + 1, j + 2 + VA, i + 1, j + 3) = (Mg + Ye) -α (G + Cy) (19) Bi + 1, k = (VB, i + 1, j + VA, i + 1, j + 1) -β (VA, i + 1, j + VB, i + 1, j + 1) = (Mg + Cy) -β (G + Ye) (20) Bi + 1, k + 1 = (VA, i + 1, j + 2 + VA, i + 1, j + 3) -β (VB, i + 1, j + 2 + VB, i + 1, j + 3) = (Mg + Cy) -Β (G + Ye) (21) Gi + 1, k = (VB, i + 1, j + VB, i + 1, j + 1 + VA, i + 1, j + VA, i + 1, j + 1) -pRi + 1, k-qBi + 1, k = (Mg + Ye + G + Cy) -pRi + 1, k-qBi + 1, k (22) Gi + 1, k + 1 = (VA, i + 1, j + 2 + VB, i + 1, j + 3 + VB, i + 1, j + 2 + VA, i + 1, j + 3) -pRi + 1, k + 1 -qBi + 1, k + 1 = (M + Ye + G + Cy) - pRi + 1, k + 1 - qBi + 1, k + RGB signals 1 (23) is obtained. Here, p and q may be 1 by referring to the expression (3), but it is preferable that they can be appropriately adjusted according to the value of the Y component.

The constants α, β, p and q are determined by adjusting the parameters of software executed in the system control circuit 10.

For the even field, the j + 1 th and j
By combining the + 2nd pixel, the above (1
RGB signals are obtained by the same equations as in equations (2) to (23). Note that the above equation is a linear calculation method without gamma correction, and if the gamma-corrected signals are stored in the image memories 41 to 44, after linear conversion, those calculations are performed. After the calculation, the normal gamma correction is performed.

FIG. 10 shows an example of the arithmetic circuit configuration for carrying out the extraction of the RGB signals described above, and this circuit is provided inside the video signal processing circuit 46. In this figure, the output signal from the first CCD 22 is the switch 5
1 is input to one of the image memories 41 and 42, and the output signal from the second CCD 23 is input to one of the image memories 43 and 44 via the switch 52. Switch 5
1, 52 are switched under the control of the system control circuit 10, and when the image signal of the first field is input, one terminal 51a, 52a side, and when the image signal of the second field is input, the other Terminals 51b, 5
2b side is connected respectively. That is, the image memory 4
The image signals of the first field are stored in 1 and 43, and the image signals of the second field are stored in the image memories 42 and 44.

The signals read from the image memories 41 to 44 are subjected to a predetermined operation in any of the adders 61 to 65, the subtractors 66 to 69 and the level shift circuits 71 to 76, and the G signal and R signal are outputted. The signal and the B signal are sought.
The G signal is directly output from the G terminal 81, but the R signal and the B signal are output via the switches 53 and 54 to the R terminal 82.
Alternatively, it is output from the B terminal 83. The arithmetic operation by the arithmetic circuit of FIG. 10 is in accordance with the expressions (12) to (23), and the operation of this circuit will be described by taking the expression (12) as an example.

First, the switches 51 and 52 are switched to one of the terminals 51a and 52a, respectively, and the image memory 41 stores the magenta signal (VA, i,
j) is stored, and the green signal (VB, i, j) of the first field is stored in the image memory 43. Then, the switches 51 and 52 are switched to the other terminals 51b and 52b, the yellow signal (VA, i, j + 1) of the second field is stored in the image memory 42, and the second field is stored in the image memory 44. The cyan signal (VB, i, j + 1) of is stored.

The magenta signal of the first field (VA, i,
j) and the yellow signal (VA, i, j + 1) of the second field is
It is added in the adder 61. The green signal (VB, i, j) of the first field and the cyan signal (VB, i, j + 1) of the second field are added by the adder 63.
The output signal of the adder 61 is multiplied by the coefficient 1 in the level shift circuit 74, and the output signal of the adder 63 is multiplied by the coefficient α in the level shift circuit 73. Subtractor 6
In 7, the output signal of the level shift circuit 73 is subtracted from the output signal of the level shift circuit 74, and (1
The expression 2) is executed. At this time, the switch 53 is switched to the R output terminal side, and the R signal is output from the R terminal 82.

The level shift amounts in the level shift circuits 71 to 76 are controlled by the system control circuit 10 according to the contents of the calculation. That is, the level shift circuits 71 to 74 are set to one of α, β and 1, and the level shift circuits 75 and 76 are set to one of p and q. The switches 53 and 54 are i
When calculating the th pixel, switch to the upper side of the figure
When the first pixel is calculated, it is switched to the lower side of the figure.

FIG. 11 shows another embodiment of the complementary color filter. This filter consists of cyan (Cy), yellow (Ye) and green (G) and has no magenta. In the case of this filter, the B signal, the R signal, and the G signal are obtained from the signals of the four pixels surrounded by the broken line in the figure by the following formulas. B = Cy ₁ − (G ₁ + G ₂ ) / 2 R = Ye ₂ − (G ₁ + G ₂ ) / 2 G = (G ₁ + G ₂ ) / 2 where the subscript 1 is the upper pixel signal in FIG. 11. , Subscript 2
Indicates the lower pixel signal.

The filter shown in FIG. 11 can also achieve the same effect as when the complementary color checkered color filter is used, but since the arithmetic expression is particularly simple, the circuit structure can be further simplified.

As described above, according to this embodiment, the resolution of the color signal can be increased to the same level as that of the luminance signal. Therefore, when such an image signal is input to the computer and image processing is performed in pixel units. Even if there is, there is no problem that the image quality is noticeably deteriorated. Further, in this embodiment, since the filters 51 and 52 of the two-plate type and having the same structure are used,
The resolution of the color signal can be improved without increasing the scale of the device and with a simple and inexpensive circuit configuration.

[0054]

As described above, according to the present invention, it is possible to increase the color resolution with a simple circuit configuration, and it is possible to obtain the effect that the image quality does not deteriorate even when image processing is performed by a computer or the like.

[Brief description of drawings]

FIG. 1 is a block diagram showing a circuit configuration of a still video camera to which an embodiment of the present invention is applied.

FIG. 2 is a diagram showing an array of color filters provided on the light receiving surfaces of the first and second CCDs.

FIG. 3 is a diagram showing a state in which corresponding pixels are overlapped with each other regarding output signals of the first and second CCDs.

FIG. 4 is a diagram for explaining a method of extracting color signals in first and second fields.

FIG. 5 is a diagram showing a spectral distribution of a luminance signal in the example.

FIG. 6 is a diagram showing a spectral distribution of color signals in the example.

FIG. 7 is a diagram showing a spectral distribution of color signals in a comparative example.

FIG. 8 is a diagram showing a reproducible spectrum range in a comparative example and an example.

FIG. 9 is a diagram for explaining a color signal extraction method according to the embodiment.

FIG. 10 is a circuit diagram showing a configuration example of a video signal processing circuit.

FIG. 11 is a diagram showing another example of complementary color filters.

FIG. 12 is a diagram showing a color filter provided in a conventional two-plate image pickup device.

[Explanation of symbols]

51,52 Filter

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields investigated (Int.Cl. ⁷ , DB name) H04N ^9/ 04-9/11

Claims (4)

(57) [Claims] 1. A filter array is repeated in units of a total of 4 pixels each having 2 pixels arranged in the horizontal direction and 2 pixels in the vertical direction, and two pixels on one diagonal line of the four pixels are green (G) filters. In addition, a first image sensor having a first complementary color filter in which two pixels on the other diagonal are a cyan (Cy) filter and a yellow (Ye) filter, respectively, and the same first complementary color filter as the first image sensor A second image sensor that includes a second complementary color filter having a filter array and captures an optical image that is the same as the optical image captured by the first image sensor; and a second image sensor that is adjacent to the first image sensor. Detected in pixels
Signal that is optically the same as the optical image of the two pixels.
Two adjacent pixels of the second image sensor
R signal, G signal and B signal based on the detected signal
RGB signal extraction means for extracting a signal, wherein the filter arrangement of the second complementary color filter is one pixel in the horizontal or vertical direction with respect to the filter arrangement of the first complementary color filter for the optical image. It is shifted by the pitch and is adjacent to the first image sensor.
Optically the same position for two pixels and the optical image of the two pixels
The two adjacent pixels of the second image sensor in
From 4 pixels, G signal for 2 pixels and Cy signal for 1 pixel
Signal and a Ye signal for one pixel are obtained, and the RGB signal is extracted.
In the means, the B signal is the G signal and the Cy signal.
And the R signal is extracted from the G signal and the Ye signal.
A two-plate type imaging device characterized by being extracted from 2. The method for the first image sensor
Arrangement of a first complementary color filter and the second image
An arrangement of the second complementary color filter with respect to the sensor;
Are the same, and the deviation for the one pixel pitch is
Arrangement of the first and second image sensors with respect to the academic image
Relative to the horizontal or vertical direction by one pixel pitch
2 according to claim 1, characterized in that it is carried out by Las
Plate type image pickup device. 3. A first and second array unit comprising a total of four pixels, each arrayed with two pixels in the first and second directions, and having the first and second arrays in the first direction. A first image sensor having a first complementary color filter, in which units are alternately and repeatedly arranged and only one of the first or second array units is repeatedly arranged in the second direction; A second image sensor including a second complementary color filter having the same filter arrangement as the first complementary color filter, and capturing an optical image identical to the optical image captured by the first image sensor; Detected by two adjacent pixels of the first image sensor
Signal that is optically the same as the optical image of the two pixels.
Two adjacent pixels of the second image sensor
R signal, G signal and B signal based on the detected signal
RGB signal extraction means for extracting signals, wherein the four pixels are green (G) filters and magenta (M)
g) filter, yellow (Ye) filter, cyan (C
y) a filter, wherein the green filter and the magenta filter are adjacent to each other in the first or second direction, and the green filter and the magenta filter in the first array unit are arranged with respect to the first array unit. The arrangement of the green filters and the magenta filters in the second arrangement unit is opposite, and the filter arrangement of the second complementary color filter is the same as the filter arrangement of the first complementary color filter for the optical image. It is shifted by one pixel pitch in the first or second direction and is adjacent to the first image sensor.
2 pixels and the optical image of the 2 pixels are optically the same.
Two adjacent pixels of the second image sensor
From 4 pixels including, Mg signal, G signal, Ye signal, Cy
A signal is obtained for each pixel, and the RGB signal extraction means
Where the R signal, the G signal, and the B signal are the Mg signals,
A two-plate type imaging device, which is extracted based on a G signal, a Ye signal, and a Cy signal . 4. The first image sensor for the first image sensor
Arrangement of a first complementary color filter and the second image
An arrangement of the second complementary color filter with respect to the sensor;
Are the same, and the deviation for the one pixel pitch is
Arrangement of the first and second image sensors with respect to the academic image
Relative to the first or second direction by one pixel pitch
The method according to claim 3, wherein the shift is performed by shifting.
Two-plate type imaging device.