JP2001069517A - Color image pickup device and digital still camera using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a color image pickup device that can enhance resolution for each primary color light. SOLUTION: Mg(magenta) and G(green) are arranged repeatedly in a horizontal direction in a 1st arrangement 31 of a CCD of a complementary color filter 30 in the color image pickup device. Cy (cyan) and Ye(yellow) are arranged repeatedly in the horizontal direction in a 2nd arrangement 32. The Mg and the G are arranged repeatedly in the horizontal direction in a 3rd arrangement 33, similarly to the case with the 1st arrangement, while the color arrangement is shifted by one pixel with respect to the 1st arrangement 31. The same arrangement as that of the 2nd arrangement 32 is adopted for a 4th arrangement 34. The 1st arrangement 31, the 2nd arrangement 32, the 3rd arrangement 33 and the 4th arrangement 34 are arranged repeatedly in a vertical direction. Arranging the complementary color filters in this way can uniformly arrange pixels receiving R(red) and B(blue) lights without impartiality, to enhance resolution each color.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a color image pickup apparatus and a digital still camera using the same.

[0002]

2. Description of the Related Art Conventionally, an image pickup device including a solid-state image pickup device such as a CCD has been used as an image pickup device for a video camera and a digital still camera. 2. Description of the Related Art A solid-state imaging device of an imaging device such as a CCD converts light from a subject into an electric signal by a current output according to the amount of light. A solid-state imaging device converts the amount of electric charge accumulated within a predetermined time according to the intensity of light into an electric signal. Can not shoot. Therefore, for example, as shown in FIG. 4, a plurality of color filters 222 are provided on the light receiving surface 221a side of a photodiode 221 as a solid-state image sensor, and light incident on each color of the color filters 222 is converted into an electric signal. A color image is generated by combining the electrical signals converted for each color.

The color filters 222 include a primary color filter 70 composed of red (R), blue (B), and green (G) as shown in FIG. 5, and a cyan (Cy) and magenta (Mg) as shown in FIG. ) And a complementary color filter 80 made of yellow (Ye). The primary color filter 70 has an advantage that color reproducibility is high because the incident light is decomposed into three colors that are components of the three primary colors of light. However, the primary color filter 70 is 1
Since only one color of light is transmitted by one filter, there is a problem that the amount of light input to the solid-state imaging device is small and the sensitivity is low.

On the other hand, although the complementary color filter 80 is inferior to the primary color filter 70 in color reproducibility, Cy = G + B, Mg =
Since light of two color bands is transmitted by a filter of one color such as B + R and Ye = G + R, the amount of light input to the solid-state imaging device is larger than that of the primary color filter 70, and the sensitivity is higher.
In particular, in recent years, an imaging device used for a digital still camera or the like has a tendency that the light receiving area per solid-state imaging device is reduced because the number of pixels is increased without changing its physical size. Therefore, in order to secure necessary sensitivity, it is more advantageous to use an image sensor using a complementary color filter as a color filter of a video camera (including a digital video camera) or an imaging device of a digital still camera.

[0005] In the complementary color filter, it is necessary to obtain more green (G) information, which is most sensitive to vision, in order to approximate the sensitivity characteristic of the image pickup device to the sensitivity characteristic of human vision. Therefore, a four-color filter in which a G filter is added to a complementary color filter of Mg, Cy, and Ye is used.

[0006]

The light transmitted through the filter is converted into an electric signal corresponding to the color of the transmitted light, and "luminance" Y is calculated based on the converted electric signal.
A color difference consisting of “redness” Cr and “blueness” Cb is calculated. The image data of the subject is formed from the luminance Y and the color differences Cr and Cb. The luminance Y is obtained by the following equation, and the color differences Cr and Cb are obtained by the following equations, respectively.

Y = {(Mg + Cy) + (G + Ye)} / 4 = (2R + 3G + 2B) / 4 Cr = (Mg + Cy) − (G + Ye) = 2B−G Cb = (Mg + Ye) − (G + Cy) = 2R−G

Conventionally, as shown in FIG. 6A, an image pickup device provided with a complementary color filter 80 has been used as an image pickup device dedicated to a digital still camera. FIG.
In the case of an imaging apparatus in which the complementary color filters 80 are arranged as shown in FIG. 6A, when light transmitted through the complementary color filters 80 is decomposed into primary color components, the results are as shown in FIGS. 6B to 6D.
As shown in FIG. 6B, the light receiving elements corresponding to the primary red R are arranged in a staggered manner, and as shown in FIG. 6C, the light receiving elements corresponding to the primary green G are sufficiently arranged. .

However, as shown in FIG. 6D, the light receiving element corresponding to the primary color blue B has extremely poor horizontal resolution. In the case of R and G, even at a position where there is no light receiving element that receives the corresponding color, it is possible to interpolate light amount information at a position where there is no light receiving element from light amount information received by surrounding light receiving elements. However, in the case of B, for example, FIG.
In (d), even-numbered columns such as the second and fourth columns from the left have no light-receiving element for interpolating light amount information in the vertical direction, and therefore have a problem that the resolution in the horizontal direction is particularly low.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a color imaging device capable of increasing the resolution of each color of primary color light and a digital still camera using the same.

[0011]

According to a first aspect of the present invention, there is provided a color image pickup apparatus including a first pixel having a first filter transmitting red light and blue light, and a second filter transmitting green light. A second pixel, a third pixel having a third filter that transmits green light and blue light, and a fourth pixel having a fourth filter that transmits red light and green light. A first arrangement section in which first and second pixels are alternately and repeatedly arranged in a first direction; a second arrangement section in which third and fourth pixels are alternately arranged in a first direction; A third arrangement unit in which the arrangement unit is arranged so as to be shifted by one pixel, and a fourth arrangement unit in which the arrangement unit of the pixels is the same as the second arrangement unit is a first arrangement unit, a second arrangement unit, and a third arrangement unit ,
A plurality of rows are repeatedly arranged in the second direction in the order of the fourth arrangement section. Accordingly, the light receiving elements that receive the light of each color of the primary color components can be arranged substantially evenly on a predetermined plane, and the resolution of each color of the primary color light can be increased.

According to the color image pickup apparatus of the second aspect of the present invention, since the charge accumulation type optical sensor is used as the solid-state image pickup device, the subject can be photographed in a short time, for example. According to the digital still camera of the third aspect of the present invention, since the digital still camera of the first or second aspect is provided, it is possible to capture a high-quality image with high resolution for each color of the primary color light.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment showing an embodiment of the present invention will be described with reference to the drawings. FIG. 2 is a digital still camera according to one embodiment of the present invention. As shown in FIG. 2, the digital still camera 1 includes a control unit 10, a condenser lens 11, a CCD 20 as a color imaging device, an A / D converter 12, and a RAM (Rand) capable of temporarily storing image data.
om Access Memory) 13, a flash memory 14 for recording image data, a liquid crystal display (LCD) 15 capable of displaying an image based on the image data, and a VRAM (Video RA) for storing display image data of an image displayed on the LCD 15.
M) 16, an interface 17 for outputting image data recorded in the flash memory 14 to an external device, and the like.

The control unit 10 includes a CPU (Central
A processing unit), a ROM (not shown) in which programs for performing various controls of the digital still camera 1 are recorded, and input means (not shown).
As the input means, there are a shutter button for inputting a photographing execution instruction from a user, and a plurality of input buttons for inputting operations of various functions of the digital still camera 1. The condenser lens 11 is provided with a stop (not shown) for adjusting the amount of light incident on the condenser lens 11.

As the RAM 13, a DRAM (Dynamic RAM) having a self-refresh function is used. The flash memory 14 is a rewritable recording medium capable of holding recorded contents without energization,
It is built in the digital still camera 1 or is detachably attached to the digital still camera 1. By using a memory card such as a PCMCIA-compliant memory card or a compact flash memory that can be attached to a PCMCIA card adapter as the flash memory 14, the personal computer having a PCMCIA card slot can directly read and write the contents of the flash memory 14. Can be.

Next, the CCD 20 will be described in detail. As shown in FIG. 3, a CCD including a plurality of solid-state imaging devices is used as the CCD 20. As the solid-state imaging device, a charge storage type optical sensor such as a photodiode is used. As shown in FIG. 3, the CCD 20 is composed of a plurality of pixels 22 arranged in a matrix in the horizontal and vertical directions. As shown in FIG. 4, the pixel 22 is composed of one photodiode 221 and the light receiving surface of the photodiode 221. And one color filter 222 attached to the side 221a.

As the color filter 222, Cy, M
A complementary color filter 30 composed of g, Ye, and G is used. Complementary color filter 30 of CCD 20 according to the present embodiment
Are arranged as shown in FIG.

As shown in FIG. 1A, the first
In the arrangement section 31, Mg pixels and G pixels are repeatedly arranged in the horizontal direction as the first direction in FIG.
In the second array section 32 of the CCD 20, Cy pixels and Ye pixels are repeatedly arranged in the horizontal direction. CCD20
In the third arrangement section 33, similarly to the first arrangement section, Mg pixels and G pixels are repeatedly arranged in the horizontal direction, and are displaced horizontally by one pixel with respect to the first arrangement section 31. It is arranged in. The fourth array unit 34 of the CCD 20
As in the arrangement unit 32, Cy pixels and Ye pixels are repeatedly arranged in the horizontal direction. The first array section 31,
Second array section 32, third array section 33, and fourth array section 3
4 are repeatedly arranged in a vertical direction as a second direction perpendicular to the first direction.

In the case of the CCD 20 in which the pixels 22 are arranged as shown in FIG. 1A, when light passing through the complementary color filter 30 is decomposed into primary color components, as shown in FIGS. 1B to 1D. Become. As described above, the components of light passing through Cy, Mg, Ye, and G are Cy = G + B, Mg = B + R,
Ye = G + R, G = G.

As shown in FIG. 1A, the complementary color filter 30
Is arranged, as shown in FIGS. 1B to 1D, R
And the pixels that receive B and B can be evenly arranged without bias. For example, as shown in FIG. 6, when compared with a CCD generally used in a conventional digital still camera in which a complementary color filter 80 is arranged, it can be seen that the B light receiving elements are evenly arranged.

Next, the digital still camera 1 of the present embodiment
The operation of will be described. When the power switch of the digital still camera 1 (not shown) is set to “ON”, the digital still camera 1 enters a standby state in which shooting is possible. At this time, in the CCD 20, the light condensed by the condensing lens 11 is converted into an electric signal every several tenths to several hundredths of a second. The converted electrical signal is
The signal is converted into a digital signal by the A / D converter 12. When the user uses the LCD 15 as a finder, image data converted into a digital signal is transferred to the VRAM 16 and a shooting target is displayed on the LCD 15 as a moving image.

When the user enters a “half-pressed” state in which a shutter button (not shown) is pressed halfway through the operation range, exposure and focus are set and fixed. The exposure at the time of photographing can be changed by the control unit controlling the aperture and the shutter speed of the condenser lens 11, that is, the charge accumulation time of the CCD 20, based on data output from the CCD 20. As the shutter of the digital still camera 1, one or both of a mechanical shutter that physically blocks light and an electronic shutter that controls the charge accumulation time of the CCD 20 can be used.

When the user enters the “fully pressed” state in which the shutter button is pressed to the limit of the operation range,
The following processing is performed. First, accurate photometry and focusing are performed on the subject. When the photometry and the focusing are completed, all the electric charges accumulated in the CCD 20 are discharged once, and then the light from the subject is condensed by the condenser lens 11 and is incident on the CCD 20, and the CCD 20 responds to the amount of the incident light. An electric signal is output based on the amount of charge.

The electric signal output from the CCD 20 is converted into a digital signal by the A / D converter 12. The digital signal converted from the electric signal is D
The address is directly designated in the RAM 13 by a direct memory access (MA) without a control unit, and is temporarily stored.

The digital data stored in the RAM 13 is used for white balance adjustment, color information interpolation processing,
After various types of image correction such as color correction are performed, an appropriate color image is generated. And the flash memory 14
In order to increase the number of recordings to
Int Photographic Experts Group) is compressed into image data in a file format, and is generated as image data having a small data size. JPEG file is about 1670
This is a commonly used image compression method that can handle images of all colors, and the image quality can be adjusted by changing the compression ratio. The image format of the JPEG file uses the above-described image signals of luminance Y, redness Cr, and blueness Cb to create an image. Therefore, the human eye accurately reproduces the information of the more sensitive luminance Y, so that the image quality can be maintained even if the color difference information of the redness Cr and the blueness Cb is compressed, and the high image quality and the data size can be maintained. It is possible to create small image data.

The creation of the JPEG image data is performed by the control unit 10 by a predetermined algorithm using software, and a dedicated circuit can be provided for speeding up. When the compression of the image data is completed, the image data
M13 is copied to the flash memory 14 and recorded.

As described above, according to the color image pickup apparatus and the digital still camera using the same according to the embodiment of the present invention, the arrangement of the complementary color filters is changed to correspond to the primary color light passing through the complementary color filters. The light receiving elements are more uniformly distributed as compared with the related art. Therefore, R,
The resolution of each of the G and B primary color components can be improved.

Although the embodiment using the CCD as the image sensor has been described above, it is needless to say that the present invention can be applied to other area type optical sensors such as a CMOS sensor.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating an arrangement of filters of a color imaging device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a digital still camera according to one embodiment of the present invention.

FIG. 3 is a schematic diagram illustrating a state where light receiving elements of the color imaging device are arranged.

FIG. 4 is a schematic diagram illustrating a positional relationship between a solid-state imaging device and a filter.

FIG. 5 is a schematic diagram illustrating an arrangement state of primary color filters used in a conventional color imaging device.

FIG. 6 is a schematic diagram showing an arrangement of complementary color filters used in a conventional color imaging device of a digital still camera.

[Explanation of symbols]

 Reference Signs List 1 digital camera 20 CCD (imaging device) 22 pixel 30 complementary color filter 31 first arrangement portion 32 second arrangement portion 33 third arrangement portion 34 fourth arrangement portion 221 photodiode (solid-state image sensor) 221a light receiving surface 222 color filter

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 27/14 H01L 27/14 D 27/148 B F-term (Reference) 2H054 AA01 2H083 AA02 AA26 AA31 AA54 4M118 AA10 AB01 BA10 CA02 FA06 GC09 GC14 5B047 AB04 BB01 BC07 5C065 AA01 AA03 BB48 CC01 DD02 DD17 EE05 EE08 EE11 GG18 GG29 GG30 GG32

Claims (3)

[Claims] 1. A pixel having a color filter and a solid-state imaging device for converting light transmitted through the color filter into an electric signal, wherein the pixels are arranged in a plurality of rows in a first direction and a plurality of pixels in a first direction perpendicular to the first direction. A color image pickup device arranged in a matrix of two or more columns in two directions, comprising: a first pixel having a first filter that transmits red light and blue light; and a second pixel having a second filter that transmits green light.
A pixel, a third pixel having a third filter that transmits green light and blue light, and a fourth pixel that transmits red light and green light.
A first array portion in which the first pixel and the second pixel are alternately and repeatedly arranged in the first direction; and the third pixel and the fourth pixel are the first pixel. A second array portion alternately and alternately arranged in the first direction, a third array portion in which the first array portion is arranged so as to be shifted by one pixel in the first direction, and a second array portion identical to the second array portion. A color imaging apparatus, wherein four arrangement units are repeatedly arranged in the second direction in the second direction in the order of the first arrangement unit, the second arrangement unit, the third arrangement unit, and the fourth arrangement unit. 2. The color imaging device according to claim 1, wherein the solid-state imaging device is a charge storage type photosensor. 3. A digital still camera comprising the color imaging device according to claim 1.