JPS5875394A - Single plate type color image pickup device - Google Patents

Abstract

PURPOSE:To obtain high horizontal/vertical image resolution, by obtaining high band luminance signals from the output of a single image pickup element and at the same time obtaining the low band luminance signals and color signals from the residual branch output to combine these signals. CONSTITUTION:The low band luminance signal YL22 and color signals R23 and B24 are obtained at one time by a solid-state image pickup element 1. These signals can be obtained just by obtaining the sum or difference of two element which are horizontally adjacent to each other or adjacent with every second element. This the vertical image resolution of the luminance signal is parallel to that of the color signal in the black/white photograhing mode. While the high band luminance signal YH is obtained by obtaining the sum of the two elements which are vertically adjacent to each other with every second element. With combination of these signals, the color video signals are obtained with the horizontal/vertical image resolution of a high level as that obtained in the case of the black/white photography.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a solid-state imaging device having a color separation function, and more particularly to a single-chip color imaging device using photoelectric conversion elements of different types with different sensitive spectral bands.

A single-chip color imaging device that uses seven two-dimensional solid-state imaging devices to obtain color video signals must have a color separation function for at least three colors, and usually a color filter is placed on the imaging device to separate the subject image. A method is adopted in which spatial sampling is performed for each color component.

In this case, it is desirable to effectively use limited pixels to increase sampling efficiency, and various methods have been proposed for arranging color filters.

For example, while brightness signals require high resolution, color signals can achieve their purpose even with a relatively low resolution. The method of arranging only the G filter in both the horizontal and vertical directions in a checkerboard pattern, and arranging the 6 red (R) filters and the blue (B) filters in a repeating pattern between them is highly efficient; bayer array,
This is known as an interline array. However, even with such arrangement arrangement, the horizontal resolution of the luminance signal is lower than in the case of monochrome imaging in which all pixels are used for the luminance signal, and the response becomes O at the Nyquist limit.

Furthermore, in JP-A No. 6.5-425, the following color filters are used: an extra color (W) transmission filter, a yellow (Ye) transmission filter, a green (G) transmission filter, and a cyan color (Cy) transmission filter. A one-dimensional filter is configured by a repeating array using this as a unit, and each color signal is obtained by calculation within the group of elements. A technique is described in which the summation in the vertical direction within a set is performed on an element-by-element basis in the horizontal direction. According to this, the horizontal resolution of the luminance signal can be obtained to the same level as in the case of monochrome imaging. However, video signals are usually interlaced. Therefore, in order to obtain the luminance signal using a series of signals, the group of elements must be constructed within one field unless a field memory is used. In other words, the vertical elements in the group of elements are spaced apart on the pixel, so the vertical resolution of the luminance signal is extremely reduced, and even at % of the Nyquist limit, the response is θ. Become.

The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to provide a single-chip color imaging device that can obtain high horizontal and vertical resolution.

To summarize the present invention, photoelectric conversion elements of different types with different sensitive spectral bands are arranged in the horizontal and vertical directions as a set, and in the case of repetition in the horizontal direction, the first photoelectric conversion element is The characteristic that is the sum of the sensitive spectral characteristic and that of the second photoelectric conversion element has a finite response over the entire visible region, and the characteristic that is the sum of the sensitive spectral characteristic of the third photoelectric conversion element and that of the third photoelectric conversion element. indicates a similar shape to the additive characteristic of the sensitive spectrum characteristics of the first and second photoelectric conversion elements, and even on the same vertical column between one horizontal column separated by 94t and the third photoelectric conversion element or the second photoelectric conversion element, The third and third photoelectric conversion elements are arranged in a mating manner. In the secondary mode, each color signal and low-range luminance signal are obtained from calculations within a set of 7 rows and columns of elements in one horizontal column, so there is no deterioration in vertical resolution for either the color signal or the luminance signal, and one field Since the high-band luminance signal is created by adding signals between vertically adjacent elements within the frame and passed through a high-pass filter, it is possible to increase the horizontal resolution without degrading the vertical resolution. It is possible to obtain horizontal and vertical resolution comparable to that of The present invention will be explained in detail below using the drawings.

FIG. 1 is a diagram showing an embodiment of the present invention in which a W filter, a G filter, a Ye filter, and a σcy filter are used as color filters. That is, the W filter is used as a G filter, and the Ye filter is used as a cy filter. Each pair forms a pair and is adjacent to each other in the horizontal direction, and the pair of both (G, W) and (ye, cy)
are arranged alternately and repeatedly in the horizontal direction, and when comparing between horizontal rows separated by horizontal rows, two on the same vertical row
The elements are also a combination of (W, G) or we, cy).

Here, the low-frequency components of the luminance signal are horizontally adjacent (W,
G) or between Ye and Cy), it is obtained for each pixel in the horizontal direction, and does not require pixel signal processing in the vertical direction. That is, the vertical resolution maintains the value at the time of monochrome imaging. In this case, the horizontal resolution can be obtained up to % of the naive strike limit in one field.

In addition, the color signal is calculated by the calculation within the above group of elements, that is, the R (red) signal is calculated by (Y e - G) and [w - cy), and the ear (blue) signal is calculated by (c y - a plus (W - Y
e), which also does not require vertical pixel signal amount processing, has a high vertical resolution of color signals, and can generate large deviation color signals for optical images with large luminance changes in the vertical direction. do not have. The timing of the above signal processing is shown in Figure 1.

On the other hand, in Fig. 1, between adjacent horizontal columns in one field, two elements on the same vertical column are always (W, G).
, or Ye, Cy), a luminance signal of one pixel period can be obtained by taking the addition signal for each pixel between the -horizontal column. The obtained luminance signal has a low vertical resolution, but a high horizontal resolution equivalent to that during monochrome imaging.

Since it is mainly the low frequency components that are involved in vertical resolution,
By passing this signal through a high-pass filter to remove low-frequency components and combining it with the low-frequency luminance signal with high vertical resolution, it is possible to obtain a luminance signal with high resolution in both the vertical and vertical directions. Note that the appropriate frequency for dividing the two is a percentage of the naive strike limit. The response of this combined luminance signal to the incident light image in the horizontal and vertical directions is shown in FIGS. 3(a) and 3(b).

The wp diagram is a diagram showing the resolvable spatial frequency region of the above-mentioned combined luminance signal, where the white part P is a low frequency component with high vertical resolution, and the shaded part Q is a high frequency component with high horizontal resolution. Each component corresponds to the other.

In the case of the gJ1 diagram, the pair (W, G) in the horizontal direction and (Ye
'J Cy) set boundaries are displaced between fields/elements in the horizontal direction. As shown in Figure 5(,), in an arrangement in which the above-mentioned sets of elements are arranged in the same vertical column, this is close to the naive strike limit (h> of the naive strike limit in the case of all pixels alone). In-phase state on the right (In-
Out-phase
The response difference in e) is maximum at 17', and a strong moiré false signal is generated, whereas when the checkerboard arrangement as shown in FIG. 5(b) is used, the In-p
This is because the difference between the hase and 0out-phase responses can be reduced to %, and moiré false signals are significantly reduced. The reason for this is that the horizontal naive strike limit is increased in FIG. 5(b) compared to FIG. 5(,).

Figure 5 is a diagram showing an embodiment of the present invention in which a magenta (Ma) transmission filter, an R transmission filter, a G transmission filter, and a cy transmission filter are used as color filters.

This is the same as the case where W→Ma, Ye-+R is set as shown in Figure 1, and the sensitive spectral characteristics of the luminance signal are
) to CB 10G + R) and the timing of color signal extraction changes, the discussion in FIG. 1 can be applied as is. Also, instead of the combination of color filters in Figure 1, (G, Ma, B, Ye) or R.

The present invention is also applicable to a combination of Cy, B, Ye) and can be discussed in the same way.

FIG. 7 is a circuit block diagram for implementing the present invention in the case of the color filter arrangement of FIG. 1. The output from the solid-state image sensor l equipped with the color filter array shown in FIG. Each is led to an adder circuit 2. The output from the adder circuit 2 is a sum signal between adjacent horizontal columns in the field, which is passed through a high-pass filter 12 to produce a high-band luminance signal (Y
H)-l is output. On the other hand, the remaining branch outputs from the solid-state image sensor l are supplied to the sample and hold circuits J, 4', ! and t, and only the G signal, W signal, cy signal, and Ye-fold signal are extracted, respectively. Above sample hold circuit J'
The outputs from , u, , 6 and g are each branched, and each l output of the former is added to the adder circuit! (G +
/ component of the luminance signal is formed by w), and each l of the latter
The outputs are added in an adder circuit to form another component of the luminance signal by (Cy + Y e). The outputs from the adder circuits r and 2 are switched by the switching circuit /g with a duty of /2/, respectively, and the outputs from the above (G 1 W)
The signal and (,Cy+Ye) signal are output alternately. The signal from the switching circuit /41 is further passed through a low-pass filter /g- to remove high-frequency components and output as a low-frequency luminance signal (YL) J-. Above sample hold circuit! , 41. ．． Among the branch outputs from 5 and 2, the /output from circuit G and the /output from circuit j are led to a subtraction circuit /θ that subtracts the latter from the former, and the /component of the R signal is formed by (w - c y). , the /output from circuit 3 and the /output from circuit g are a subtraction circuit that subtracts the former from the latter //
The signal from the subtraction circuit 10 and // is switched by the switching circuit /j at the duty ratio /:/, and the other /component of the R signal is formed by (Ye-). Cy) signal and (Ye-G) signal are output alternately.The signal from the switching circuit 7.5 is further passed through a low pass filter 1 to remove high frequency components, and the R signal 3. is output.

Similarly, among the branch outputs from the sample and hold circuits 3, 41, j and
The / output from is led to a subtraction circuit /- which subtracts the latter from the former, and (W Ye) forms the / component of the B signal,
The /output from circuit 3 and the /output from circuit j are led to a subtraction circuit /3 which subtracts the former from the latter, and the other /component of the B signal is formed by (Cy-G). The above subtraction circuit 7.
The signals from 2 and /3 are switched at the duty /:/ by the switching circuit /l and the above (w - y e)
The signal and the (cy-G) signal are output alternately. The signal from the switching circuit /l is further passed through a low-pass filter θ to remove high-frequency components, and a B signal θ is output. Note that the switching circuits are not used in circuits /j and /2, and averaging circuits are used instead, and the R signal is 7.
(W+Ye-cy-G), B signal is (W+Cy+Ye
-G). Even when the color filter arrangement is as shown in Fig. 4, YH, Y
It is possible to separate and extract L, R, and B signals. However, in this case, YH and YL are composed of (R+G+B).

As explained above, according to the present invention, although the luminance signal l component and the color signal co component are obtained simultaneously by a single image sensor, the reduced luminance signal and the color signal are adjacent to each other in the horizontal direction. Since the vertical resolution of luminance and color signals can be obtained by simply calculating the sum or difference between adjacent elements in the element, the vertical resolution of luminance and color signals is equivalent to that of black and white imaging. A high-band luminance signal is obtained by taking the signals, and a color video signal having horizontal and vertical resolution as high as that of monochrome imaging can be obtained by the above combination.

Incidentally, as an example of the present invention, the case where the color ailter arrangement on the image sensor is as shown in FIGS. 1 to 4 has been described.
The arrangement is not limited to these arrangements, and the unit of horizontal arrangement is a set of elements in which color filters of different types with different spectral characteristics are adjacent in the horizontal direction, and the spectral characteristics are determined in each of the first half element and the second half element. As long as the sum of the spectral characteristics between elements in the vertical direction is always constant and transmits the entire visible region,
The present invention is applicable to any color filter arrangement. In addition, although we have explained the case where the color filter is arranged on a solid-state image sensor, the invention is not limited to this, and when each photoelectric conversion element itself has different spectral characteristics. It is clear that these are also included in the scope of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a color filter arrangement diagram in an embodiment of the present invention, FIG. 1 is a diagram showing the timing of separating and extracting a luminance signal and a color signal in the case of the color filter arrangement of FIG. 1, and FIG. 3(a) , (b) is a diagram of the rectangular wave response obtained by the present invention, (,) shows the response in the horizontal direction, and (b) shows the response in the vertical direction. *Figure 5 is a diagram showing the range of spatial frequencies that can be responded to in the present invention, Figure 5 is an example of a combination of pixels to obtain a low-frequency luminance signal according to the present invention, and (b) is (, ). 7 shows a circuit block diagram for implementing the present invention in the color filter arrangement of FIG. 1. /: Single-chip color image sensor 1.2: /l (delay line, 3,
G, s, l: Sample and hold circuit, 2,! , ri: addition circuit, 10. //, /ko, /3: subtraction circuit, /4I switch circuit, is, /l switch circuit or averaging circuit, /7: high-pass filter, /♂, /ri, ko θ: low-pass filter. Agent Patent Attorney Fukushi Aihiko-Q' U↑ odd 3rd figure'”-phasell-F-O-〆! Sweat criminal J Hand Benke Nao Push Figure 2 Self-4ttr

Claims (1)

[Claims] 1. An imaging device consisting of a group of light receiving elements arranged horizontally and vertically, in which different types of photoelectric conversion elements each sensitive to a different spectral band are adjacent to each other in the horizontal direction. In a color imaging device in which a pair of photoelectric conversion elements is arranged in a horizontal direction, and a set of photoelectric conversion elements is arranged repeatedly in the horizontal direction, the sensitive spectral characteristics of the first photoelectric conversion element and the sensitive spectral characteristics of the second photoelectric conversion element are The added characteristic has a finite response over the entire visible region, occupies the position of the first half of the above group of elements, and has the sensitive spectral characteristics of the third photoelectric conversion element and the sensitive spectral characteristics of the third photoelectric conversion element. The added characteristic is similar to the added characteristic of the sensitive spectrum characteristics of the first photoelectric conversion element and each of the first photoelectric conversion elements, and occupies the position of the remaining one element of the group of elements, / A first photoelectric conversion element and a second photoelectric conversion element on the same vertical column between the water columns separated by a horizontal column,
A single-chip color imaging device characterized in that it is a combination of a third photoelectric conversion element and a gJ da photoelectric conversion element. 2. There is a boundary where a horizontally adjacent set of the first photoelectric conversion element and the second photoelectric conversion element replaces a horizontally adjacent set of the third photoelectric conversion element and the third photoelectric conversion element. ,
2. The single-chip color imaging device according to claim 1, wherein the single-chip color imaging device is arranged so that the elements are displaced in the horizontal direction between vertically adjacent horizontal rows. 3. A patent characterized in that the signal added between one pixel existing on the same vertical column between one horizontal column separated by the above/horizontal column passes through a high-pass transmission filter and becomes a high-luminance signal component. A single-chip color imaging device according to claims 1 to 1.