JP2000316163A - Color image pickup element and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a sufficiently large dynamic range while maintaining high sensitivity as a color image pickup element. SOLUTION: In a color image pickup element in which RGB system filters are Beyer arrayed, high-sensitive blocks and low-sensitive blocks are checkerwise arranged so that their sides are not shared, and signals from the high-sensitive blocks and signals from the low-sensitive blocks are selected according to the brightness of a subject. That is, periodic color coding arrangement is applied to an image pickup face, and each unit array (block) has different sensitivity so that the signals can be selected or added according to each output to obtain pixel values. Thus, the color image pickup element having high sensitivity and a dynamic range can be realized. Then, the image pickup device for operating satisfactory image pickup from a dark scene to a bright scene can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup device used for an electronic camera (digital still camera), a video camera, and the like, and more particularly to a color image pickup device with improved sensitivity characteristics and an image pickup apparatus using the same. .

[0002]

2. Description of the Related Art In recent years, an electronic camera has been put into practical use in which a subject image is picked up by a CCD image pickup device or the like and the obtained image data is stored in a flash memory such as a compact flash (CF) or a smart media (SSFDC). .
This electronic camera is small and lightweight, and is capable of rewriting image data.

In order to capture a color image using a CCD image sensor, it is necessary to arrange color filters in each pixel of the image sensor to obtain signals corresponding to the three primary colors of RGB.
The color filters of the CCD color image sensor include two filters, an RGB filter which is a primary color system and a CMY filter which is a complementary color system.
There are types. Although any color filter may be used, it is important to set the sensitivity of the image sensor optimally.

[0004]

As described above, it is important to appropriately set the sensitivity of a color image sensor. Generally, a high sensitivity reduces a dynamic range, and is suitable for an object that is too bright. Difficult imaging becomes difficult. Conversely, if the sensitivity is low, it becomes difficult to image a dark subject.

The present invention has been made in consideration of the above circumstances, and has as its object to provide a color image sensor capable of obtaining a relatively high sensitivity and having a wide dynamic range, and an image pickup device using the same. It is to provide a device.

[0006]

(Structure) In order to solve the above problem, the present invention employs the following structure.

That is, the present invention relates to a color image pickup device,
It is characterized in that a periodic color coding arrangement is applied to the imaging surface, and each unit arrangement (block) has a different sensitivity.

According to the present invention, there is provided an image pickup apparatus using a color image pickup device having the above-mentioned configuration, wherein an image signal generation means for generating a predetermined image signal based on an output of the image pickup device, and a signal generation step by the image signal generation means And an adding means for adding a signal output from the high-sensitivity block and a signal output from the low-sensitivity block.

Further, according to the present invention, in an image pickup apparatus using the color image pickup device having the above-mentioned configuration, an image signal generation means for generating a predetermined image signal based on an output of the image pickup device, and a signal generation step by the image signal generation means And a selecting means for selecting one of the signal output from the high-sensitivity block and the signal output from the low-sensitivity block.

According to the present invention, there is provided an image pickup apparatus using the color image pickup device having the above configuration, wherein an image signal generating means for generating a predetermined image signal based on an output of the image pickup device, and a predetermined signal based on an output of the image pickup device. An automatic control means for performing automatic control processing of the object, a subject brightness determination means for determining the brightness of the subject, and a signal used in the automatic control processing in the automatic control means based on an output of the subject brightness determination means. And selecting means for selecting from a signal output from a low-sensitivity block and a signal output from a low-sensitivity block.

Here, preferred embodiments of the present invention include the following. (1) The periodic color coding array is a Bayer array composed of RGB primaries, and high-sensitivity blocks and low-sensitivity blocks are arranged in a checkered pattern without sharing sides. (2) The automatic control means adjusts the exposure and focus based on the output of the subject luminance judgment means. (3) One pixel signal is generated from 4 × 4 cells, and two-dimensional pixel signals are obtained by shifting the cells by two pixel pitches.

(Operation) According to the present invention, a periodic color coding arrangement is applied to an image pickup surface, and a unit arrangement (block) thereof is provided.
Since different sensitivities are provided for each output, the sensitivity characteristics of the image sensor can be optimized by selectively or adding pixel values in accordance with the respective outputs. Specifically, by using high-sensitivity pixels for low-luminance subjects and using low-sensitivity pixels for high-luminance subjects, the dynamic range is relatively large while having relatively high sensitivity. It is possible to do.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the illustrated embodiments.

FIG. 1 is a block diagram showing a circuit configuration of an image pickup apparatus according to one embodiment of the present invention.

In the figure, 101 is a lens system, 102 is a lens driving mechanism, 103 is an exposure control mechanism, 104 is a filter system such as an LPF, 105 is a CCD color image pickup device having a built-in color filter, 106 is a CCD driver, and 107 is A A digital processor for performing color signal generation processing, matrix conversion processing, and other various digital processing; 109, a card interface; 110, a memory card such as a CF;
Denotes an LCD image display system, 112 denotes a system controller (CPU), 113 denotes an operation switch system, 114 denotes an operation display system, 115 denotes a lens driver, and 116 denotes an exposure control driver.

Although the above basic configuration is the same as that of a conventional general device, the present embodiment is different from the conventional device in the configuration of the CCD color image sensor 105 and the processing by the digital processing unit 108 accompanying the configuration. . The image sensor of the present embodiment applies a periodic color coding arrangement to the imaging surface, and has a different sensitivity for each unit arrangement (block).

The arrangement of the color filters in the color image sensor is an RGB Bayer arrangement as shown in FIG. A high-sensitivity block 21 in which a high transmittance filter is arranged for every 2 × 2 cells and a low-sensitivity block 22 in which a low transmittance filter is arranged are arranged in a checkered pattern without sharing sides.

An image signal generation process (color signal generation process) using the above color image pickup device will be described. A 4 × 4 square surrounded by a broken line in FIG. 2 is a basic lattice for generating a color signal, and a pixel signal is generated by adding signals of respective pixels in the square. That is, two Rs, two Bs, four Gs in the high-sensitivity block 21 in the cell,
By adding two Rs, two Bs, and four Gs in the low-sensitivity block 22, a pixel signal corresponding to one pixel is generated. Then, a two-dimensional pixel signal is obtained by shifting the above-mentioned cells by two pixel pitches.

FIG. 3 is a diagram showing sensitivity characteristics of the image sensor according to the present embodiment. The horizontal axis is the amount of incident light (log), and the vertical axis is the CCD output (log). The sensitivity in the high-sensitivity block 21 is high as indicated by A in the figure, and the sensitivity in the low-sensitivity block 22 is low as indicated by B in the figure.

As in this embodiment, by adding the pixel signals of the high-sensitivity block 21 and the low-sensitivity block 22 within a 4 × 4 cell, the sensitivity finally obtained is indicated by C in the figure. Become like That is, it has sensitivity from the time when the amount of incident light is low, and does not reach the saturation level up to a point where the amount of incident light is large. That is, a sufficiently large dynamic range can be obtained while having relatively high sensitivity.

FIG. 4 is a flowchart for explaining the operation in the present embodiment. First, at the start of the processing (1st release), the absolute luminance level of the subject is measured (S1). In this measurement, the luminance in the subject direction may be measured by a sensor, or the output of a CCD image sensor may be used.

Next, it is determined whether or not the measured luminance is equal to or more than a predetermined value (S2). If the measured brightness is equal to or more than the predetermined value, the exposure and focus are automatically adjusted using the output of the low-sensitivity pixel (S3). . If the measured luminance is smaller than the predetermined value, the exposure and focus are automatically adjusted using the output of the high-sensitivity pixel (S4).

Next, by the second release (S5),
An image of a subject is captured by a color image sensor in which RGB color filters are arranged in a Bayer array and a high transmittance filter and a low transmittance filter are arranged in a checkered lattice pattern. Amplify the signal. Then, after A / D conversion of the amplified signal, each Bayer data is stored (S6).

Next, the output of the high-sensitivity pixel and the output of the low-sensitivity pixel are added to perform an image signal generation process (S7). This image signal generation is as described with reference to FIGS. 2 and 3 above. The output of the high-sensitivity pixel and the output of the low-sensitivity pixel in the 4 × 4 cell are added and a color signal corresponding to one pixel is added. Is generated, and a two-dimensional image signal is generated by shifting the cells by two pixel pitches.

Next, the white balance is adjusted.
Further, matrix processing is performed (S8). In the matrix processing, the spectral sensitivity is corrected by a well-known matrix conversion in order to reduce a color reproduction error.

Next, γ is calculated for the obtained RGB signals.
After performing the conversion processing and the Y / C separation processing, JPEG compression processing is performed, and the compressed image data is recorded on a memory card or the like (S9).

As described above, according to the present embodiment, by adding the signals of the high-sensitivity pixel and the low-sensitivity pixel, it is possible to expand the dynamic range while maintaining relatively high sensitivity. Note that one RGB Bayer array is 1
In terms of units, by adding pixels in units of four, the resolution is reduced by half compared to the conventional case. However, if the number of pixels of the image sensor becomes sufficiently large due to the future high pixel count,
The reduction in resolution due to the selective use of pixels can be ignored, and the effects of the present embodiment described above become more effective.

In this embodiment, when the brightness of the subject is equal to or higher than a predetermined value, that is, when the subject is bright, the AE and AF are adjusted by using the low-sensitivity pixels, so that the AE and AF due to the subject being too bright are adjusted. Incorrect AF adjustment can be prevented beforehand. Conversely, when the luminance of the subject is smaller than a predetermined value, that is, when the subject is dark, the AE and AF are adjusted by using the high-sensitivity pixels, so that the AE and AF are not properly adjusted due to the dark subject. Can be prevented beforehand.

The present invention is not limited to the above embodiment. In the embodiment, the signal of the high-sensitivity pixel and the signal of the low-sensitivity pixel are added. Instead, in the image signal generation processing, a selection unit that selects either the high-sensitivity pixel or the low-sensitivity pixel according to the brightness of the subject May be used, and when the subject is bright, only the signal of the low-sensitivity pixel is used, and when the subject is dark, only the signal of the high-sensitivity pixel may be used.

Further, the arrangement of RGB is not necessarily limited to the Bayer arrangement, and various arrangements are possible. Further, the configuration of the imaging device is not limited to that of FIG. 1 at all, and can be appropriately changed according to specifications. In addition, various modifications can be made without departing from the scope of the present invention.

[0031]

As described above in detail, according to the present invention, a periodic color coding arrangement is applied to the imaging surface, and different sensitivity is provided for each unit arrangement (block). By selectively or adding pixel values, a color imaging device having high sensitivity and high dynamic range can be realized. And
By using this, it is possible to realize an imaging apparatus capable of performing good imaging from a dark scene to a bright scene.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a circuit configuration of an imaging device according to an embodiment of the present invention.

FIG. 2 is a diagram showing an arrangement of color filters in a color imaging device used in the embodiment.

FIG. 3 is a diagram illustrating sensitivity characteristics of the color imaging device used in the embodiment.

FIG. 4 is a flowchart for explaining the operation of the embodiment.

[Explanation of symbols]

 21 high sensitivity block 22 low sensitivity block 101 lens system 102 lens drive mechanism 103 exposure control mechanism 104 filter system 105 CCD image sensor 106 CCD driver 107 preprocess 108 digital process 109 card interface 110 ... Memory card 111 LCD image display system 112 System controller 113 Operation switch system 114 Operation display system 115 Lens driver 116 Exposure control driver

Claims (5)

[Claims] 1. A color image pickup device wherein a periodic color coding arrangement is applied to an image pickup surface, and each unit arrangement (block) has a different sensitivity. 2. The method according to claim 1, wherein said periodic color coding arrangement is RGB.
2. The color image pickup device according to claim 1, wherein a high-sensitivity block and a low-sensitivity block are arranged in a checkerboard pattern that does not share sides with each other in a Bayer array composed of primary colors. 3. A color image sensor according to claim 2, image signal generating means for generating a predetermined image signal based on an output of said image sensor, and said high sensitivity in a signal generating step by said image signal generating means. An image pickup apparatus comprising: an adding unit that adds a signal output from a low-sensitivity block to a signal output from a low-sensitivity block. 4. A color image pickup device according to claim 2, image signal generation means for generating a predetermined image signal based on an output of said image pickup device, and said high sensitivity in a signal generation step by said image signal generation means. An image pickup apparatus comprising: a selection unit that selects one of a signal output from a low-sensitivity block and a signal output from a low-sensitivity block. 5. A color image sensor according to claim 2, an image signal generating means for generating a predetermined image signal based on an output of said image sensor, and a predetermined automatic control process based on an output of said image sensor. Automatic control means for performing the control, a subject brightness determination means for determining the brightness of the subject, and a signal used in the automatic control processing in the automatic control means based on the output of the subject brightness determination means, An imaging apparatus comprising: a selection unit that selects from a signal output and a signal output from a low-sensitivity block.