JP2000244931A - Digital still camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve deficiencies the geometrical array of red(R), green(G) and blue(B) phosphors and R, G, and B filters by making the positions of R, G and B filters in a color filter array approximately coincide with the positions of R, G and B phosphors in a shadow mask type color cathode ray-tube(CRT). SOLUTION: A solid state image pickup element 1 is constituted as a total pixel reading IT-CCD image pickup device, has photodiodes 3 and vertical transfer CCDs 4 respectively corresponding to plural regularly arranged pixels and includes also plural horizontal transfer CCDs 5 and an output circuit 6. In the digital still camera, an image of a subject formed on a photodiode 3 of the element 1 at the time of picking up the image is photoelectrically converted into a picture signal, the picture signal is transferred in the vertical direction by the CCDs 4 and outputted from the circuit 6 to the external through the CCDs 5 arranged on the lowermost step of the element 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical system for forming an image of a subject to be imaged through a color filter array, a photodiode corresponding to each of a plurality of regularly arranged pixels, and a charge coupled device. The present invention relates to a digital still camera, comprising: a solid-state imaging device having an element and generating an image signal by photoelectrically converting an image formed on the photodiode by the optical system.

[0002]

2. Description of the Related Art Recently, an image of a subject is taken as a still image, for example, by an imaging device such as a digital still camera, and the obtained image is displayed on a color cathode ray tube (CRT) of a personal computer (hereinafter referred to as a personal computer). There are a growing number of imaging-display systems. In such an imaging-display system, it is important to match the conditions for capturing and reproducing (displaying) an image as much as possible in order to improve display image quality.

For example, in an image pickup and display system as shown in FIG. 3, when an image 52 of a subject is picked up by a conventional digital still camera 51, the image 52 is sensitized (photodiode) of an image pickup element 54 by an optical system (lens) 53. ) Is converted into an image signal. This image signal is transferred by a charge-coupled device (CCD) of the imaging device 54, and a still image is obtained by the image signal for one frame period. At that time, on the front of the image sensor 54,
For example, as schematically shown in FIG. 4, filters 6 corresponding to red (red; hereinafter, referred to as R), green (green; hereinafter, referred to as G), and blue (blue; hereinafter, referred to as B).
Since the color filter array 55 in which 1R, 61G and 61B are regularly arranged is arranged, the image 52
Are converted into R, G, B image signals 56.

[0004] The R, G, B image signals 56 generated as described above are input to a color CRT 58 of a personal computer 57. In the case of a shadow mask type color CRT as shown in the drawing, R, G, B
Of phosphors 59R, 59G, and 59B are arranged in a regular triangular shape, so that R, G, and
The phosphors 59R, 59G, and 59B irradiated with the R, G, and B electron beams generated according to the B image signal 56 emit light.
As a result, the image 60 is displayed as a still image on the display surface of the color CRT 58.

[0005]

In the conventional imaging-display system as described above, an R, G, B filter for converting a captured image into an R, G, B image signal on the imaging side. Is different from the geometrical arrangement of the R, G, B phosphors for performing the reconstruction process from the R, G, B image signals to the display image on the display side. As a result, when an image captured by a digital still camera is displayed on the color CRT side, a problem occurs that geometrical positional distortion occurs. This inconvenience appears as a lightning-like distortion when displaying a straight line in an oblique direction, for example, and causes deterioration in the display quality of the displayed still image.

The present invention has been made in view of the above-mentioned problems, and the geometric arrangement of the R, G, and B phosphors of a shadow mask type color cathode ray tube used for image display is different from that of a digital still camera. It is an object of the present invention to eliminate the above-mentioned problem by faithfully reproducing the G and B filters.

[0007]

According to the first aspect of the present invention, there is provided an optical system for forming an image of an object to be imaged through a color filter array, the optical system being arranged regularly. A solid-state imaging device having a photodiode and a charge-coupled device corresponding to each of the plurality of pixels to be generated, and generating an image signal by photoelectrically converting an image formed on the photodiode by the optical system. In the digital still camera, the plurality of pixels are arranged in the solid-state imaging device such that each of pixels in odd rows adjacent to each of pixels in even rows is shifted by half a horizontal pixel pitch, and the color filter In the array, filters corresponding to each pixel in the horizontal direction are repeatedly arranged in the order of red filter, green filter, blue filter, and A filter corresponding to three pixels consisting of two pixels horizontally adjacent and one pixel vertically adjacent to the two pixels is arranged so as to be composed of a red filter, a green filter and a blue filter, and the red filter of the color filter array , The position of the green filter and the position of the blue filter substantially coincide with the positions of the red phosphor, the green phosphor, and the blue phosphor of the shadow mask type color cathode ray tube, respectively.

【The invention's effect】

According to the first invention, an image of a subject to be imaged is formed on a photodiode of a solid-state imaging device via a color filter array by an optical system of a digital still camera, and this image is photoelectrically converted. When generating an image signal, the plurality of pixels are arranged in the solid-state imaging device such that each of the odd-numbered pixels adjacent to each of the even-numbered pixels is shifted by half the horizontal pixel pitch. The color filter array has a filter corresponding to each pixel in the horizontal direction, which is repeatedly arranged in the order of a red filter, a green filter, and a blue filter, and two pixels adjacent in the horizontal direction and the two pixels vertically. A filter corresponding to three pixels consisting of one pixel adjacent in the direction comprises a red filter, a green filter, and a blue filter. , The positions of the red, green, and blue filters of the color filter array substantially match the positions of the red, green, and blue phosphors of the shadow mask type color cathode ray tube, respectively. become. As a result, geometrical positional distortion between the R, G, B phosphors of the shadow mask type color cathode ray tube and the R, G, B filters of the digital still camera is removed, and the display quality is improved.

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a plan view schematically showing a configuration of a solid-state imaging device used in a digital still camera according to a first embodiment of the present invention, and FIG. 2 is a color filter disposed on the solid-state imaging device of the first embodiment. It is a figure which shows the structure of an array typically. Note that the digital still camera according to the present embodiment targets still images.

The solid-state imaging device 1 according to the present embodiment is configured as an all-pixel read-out IT-CCD imaging device.
As shown in FIG. 1, a photodiode 3 and a vertical transfer C corresponding to each of a plurality of pixels 2 arranged regularly.
It has a CD 4 and a horizontal transfer CCD 5 and an output circuit 6.

The photodiode 3 functions as a photosensitive portion when an image of a subject (not shown) to be imaged is formed via a color filter array described later, and photoelectrically converts the formed image. Thus, an image signal is generated. The vertical transfer CCD 4 has a function of transferring the generated image signal in the vertical direction (up and down direction in the figure), and the image signal transferred by the vertical transfer CCD 4 is transferred to the horizontal transfer CCD 5 arranged at the lowermost stage. After that, it is output from the output circuit 6 to the outside.

In this embodiment, the pixel arrangement pattern is changed with respect to the conventional all-pixel read-out IT-CCD image pickup device. That is, in the conventional all-pixel reading IT-CCD imaging device, pixels having the same structure are arranged at the same pixel pitch in the horizontal direction and the vertical direction, respectively. A plurality of pixels 2 to be arranged within
Are arranged such that each of the odd-numbered pixels 2 adjacent to each of the even-numbered pixels 2 is shifted by half the horizontal pixel pitch.

In this embodiment, the filter arrangement pattern of the color filter array is also changed in response to the change of the pixel arrangement pattern. That is, the color filter array 7 of the present embodiment is a primary color filter corresponding to all-pixel independent reading, and a filter corresponding to each pixel in the horizontal direction is a red (R) filter 8R, a green (G) filter 8G, and a blue filter. (B) Filter 8
The filters corresponding to three pixels, which are repeatedly arranged in the order of B and are composed of two pixels horizontally adjacent to each other and one pixel vertically adjacent to the two pixels, must be a red filter 8R and a green filter. The filter is arranged so as to include the filter 8G and the blue filter 8B. By using this filter arrangement pattern, the positions of the red filter 8R, the green filter 8G, and the blue filter 8B of the color filter array 7 are respectively changed to the red phosphor, the green phosphor, and the blue phosphor of the shadow mask type color cathode ray tube (CRT). It will almost coincide with the body position.

Next, the operation of the digital still camera according to the present embodiment will be described. In the digital still camera according to the present embodiment, the image of the subject formed on the photodiode 3 of the solid-state imaging device 1 at the time of imaging is photoelectrically converted into an image signal, and then transferred in the vertical direction by the vertical transfer CCD 4. Thereafter, the signal is output from the output circuit 6 to the outside via the horizontal transfer CCD 5 arranged at the lowermost stage of the solid-state imaging device 1. At this time, the image of the subject is converted into R, G, and B image signals by the color filter array 7 arranged in front of each photodiode 3 as shown in FIG. The R, G, and B image signals are read out from all the pixels in order from the upper left pixel during one frame period, for example, and the obtained R, G, and B image signals for one frame period are obtained. Becomes a still image.

The R, G, B image signals for one frame period generated in this manner are used as shadow mask type color CRs.
When T is input to a personal computer using as a display device, R, G, B phosphors arranged in an equilateral triangle on the display surface of a shadow mask type color CRT are converted into R, G, B image signals 56 which are input. In response, the image of the subject is displayed as a still image on the display surface of the shadow mask type color CRT.

In the still image displayed on the shadow mask type color CRT, the R, G, B phosphors of the shadow mask type color CRT and the R, G, B phosphors of the digital still camera when a conventional digital still camera is used.
Since the “geometric positional distortion between the G and B filters” has been removed, the image quality does not deteriorate due to the positional distortion, and the display image quality improves. The improvement in the display image quality is apparent from the fact that "pixel shifting in a three-chip CCD digital still camera improves the horizontal resolution".

Further, as described above, "geometric positional distortion between R, G, B phosphors of a shadow mask type color CRT and R, G, B filters of a digital still camera".
Is removed, in particular, the jagged distortion around the contour of the object in the display image is improved.

By the way, in human visual perception, it is not usually possible to detect that a line is inclined when the angle of inclination of a straight line is within 1 °. Is about 30 times as sensitive to the visual acuity of the image, and if the straight line is distorted like a lightning bolt, the image quality is greatly deteriorated. Therefore, when the jagged distortion is improved as described above, it significantly contributes to the improvement of the display image quality.

Further, in this embodiment, it is apparent that the digital still camera has 1 / γ characteristics in correspondence with the display surface of the shadow mask type color CRT having γ characteristics. . Therefore, accurate gamma correction can be performed on the display image of the shadow mask type color CRT in consideration of the CCD image pickup device side based on a software method.
, A faithful reproduction of a still image can be realized.

Further, the digital still camera according to the present embodiment is limited to the case of displaying on a shadow mask type color CRT. However, the digital still camera can capture a high quality image for displaying a high quality image on the shadow mask type color CRT. Therefore, it can be used as a “high-quality image capturing device”. Further, by combining the digital still camera of the present embodiment with a personal computer using a shadow mask type color CRT, a “high quality image capturing / reproducing system” can be constructed.

[Brief description of the drawings]

FIG. 1 is a plan view schematically showing a configuration of a solid-state imaging device used in a digital still camera according to a first embodiment of the present invention.

FIG. 2 is a diagram schematically illustrating a configuration of a color filter array arranged on the solid-state imaging device according to the first embodiment.

FIG. 3 is a diagram illustrating an example of an imaging-display system that displays an image captured by a conventional digital still camera on a color cathode ray tube.

FIG. 4 is a diagram schematically showing a configuration of a color filter array of a conventional digital still camera.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Solid-state image sensor 2 Pixel 3 Photodiode 4 Vertical transfer CCD 5 Horizontal transfer CCD 6 Output circuit 7 Color filter array 8R Red filter 8G Green filter 8B Blue filter

Claims (1)

[Claims] 1. An optical system for forming an image of a subject to be imaged through a color filter array, and a photodiode and a charge-coupled device corresponding to each of a plurality of regularly arranged pixels, A digital still camera, comprising: a solid-state imaging device that generates an image signal by photoelectrically converting an image formed on the photodiode by an optical system; wherein the plurality of pixels are adjacent to each of pixels in an even-numbered row. The odd-numbered rows of pixels are arranged in the solid-state imaging device so as to be shifted by half the horizontal pixel pitch, and the color filter array is configured such that a filter corresponding to each pixel in the horizontal direction has a red filter, a green filter, and a blue filter. The two pixels that are repeatedly arranged in the order of the filters, and that are horizontally adjacent to each other, and that are vertically adjacent to the two pixels. A filter corresponding to three pixels consisting of one pixel is arranged so as to be composed of a red filter, a green filter, and a blue filter, and positions of the red filter, the green filter, and the blue filter of the color filter array are respectively located in a shadow mask type color cathode ray tube. Wherein the positions of the red phosphor, the green phosphor and the blue phosphor are substantially matched with each other.