JP4129338B2 - Color imaging device and imaging apparatus - Google Patents

Description

[0001]
BACKGROUND 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]
[Prior art]
2. Description of the Related Art In recent years, an electronic camera that captures a subject image with a CCD image sensor and stores the obtained image data in a flash memory such as a compact flash (CF) or smart media (SSFDC) has been put into practical use. This electronic camera is small and lightweight, and it is possible to rewrite image data.
[0003]
By the way, in order to pick up a color image with a CCD image pickup device, it is necessary to arrange a color filter in each pixel of the image pickup device and obtain signals corresponding to the three primary colors of RGB. There are two types of color filters of the CCD color image pickup device: an RGB filter which is a primary color system and a CMY filter which is a complementary color system. Any color filter may be used, but it is important to optimally set the sensitivity of the image sensor.
[0004]
[Problems to be solved by the invention]
As described above, it is important to appropriately set the sensitivity of a color imaging device. Generally, when the sensitivity is high, the dynamic range is reduced, and it is difficult to perform good imaging on an object that is too bright. On the other hand, if the sensitivity is low, it is difficult to capture a dark subject.
[0005]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a color imaging device capable of obtaining a relatively high sensitivity and widening the dynamic range, and an imaging apparatus using the same. There is to do.
[0006]
[Means for Solving the Problems]
(Constitution)
In order to solve the above problems, the present invention adopts the following configuration.
[0007]
That is, the present invention performs a periodic color coding sequence IMAGING plane, a color image sensor having a different sensitivity for each the unit sequence (block), the periodic color coding sequences is composed of RGB primaries A high-sensitivity block and a low-sensitivity block are arranged in a checkered pattern that does not share a side with each other .
[0008]
According to another aspect of the present invention, there is provided an image pickup apparatus using the color image pickup device having the above-described configuration, an image signal generating unit that generates a predetermined image signal based on an output of the image pickup device, and the signal generation process by the image signal generating unit. An addition means for adding the signal output from the sensitive block and the signal output from the low sensitivity block is provided.
[0009]
According to another aspect of the present invention, there is provided an image pickup apparatus using the color image pickup device having the above-described configuration, an image signal generating unit that generates a predetermined image signal based on an output of the image pickup device, and the signal generation process by the image signal generating unit. It is characterized by comprising selection means for selecting either a signal output from a sensitive block or a signal output from a low-sensitive block.
[0010]
Further, the present invention provides an image signal generation means for generating a predetermined image signal based on the output of the image sensor, and predetermined automatic control based on the output of the image sensor, in the image pickup apparatus using the color image sensor having the above configuration. Automatic control means for performing processing, subject brightness determination means for determining the brightness of the subject, and signals used in automatic control processing in the automatic control means based on the output of the subject brightness determination means from the high-sensitivity block And a selecting means for selecting from the signal output from the low-sensitivity block.
[0011]
Here, preferred embodiments of the present invention include the following.
(1) The automatic control means adjusts the exposure and focus based on the output of the subject brightness determination means.
(2) One pixel signal is generated from a 4 × 4 square, and the square is shifted by two pixel pitches to obtain a two-dimensional pixel signal.
[0012]
(Function)
According to the present invention, a periodic color coding arrangement is applied to the imaging surface, and different unit arrays (blocks) have different sensitivities, so that pixel values are selectively or added according to the respective outputs. As a result, the sensitivity characteristics of the image sensor can be optimized. Specifically, high-sensitivity pixels are used for low-luminance subjects, and low-sensitivity pixels are used for high-luminance subjects, so that the dynamic range is sufficiently large while being relatively high-sensitivity. It becomes possible to do.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
The details of the present invention will be described below with reference to the illustrated embodiments.
[0014]
FIG. 1 is a block diagram showing a circuit configuration of an imaging apparatus according to an embodiment of the present invention.
[0015]
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 imaging device incorporating a color filter, 106 is a CCD driver, and 107 is A / D conversion. 108 is a digital process unit for performing color signal generation processing, matrix conversion processing, and other various digital processing, 109 is a card interface, 110 is a memory card such as CF, and 111 is an LCD image display System 112 is a system controller (CPU), 113 is an operation switch system, 114 is an operation display system, 115 is a lens driver, and 116 is an exposure control driver.
[0016]
The above basic configuration is the same as that of a conventional general apparatus, but the difference of the present embodiment is the configuration of the CCD color image sensor 105 and the processing by the digital process unit 108 associated therewith. The imaging device of the present embodiment performs periodic color coding arrangement on the imaging surface, and has different sensitivities for each unit arrangement (block).
[0017]
The color filter array in the color image sensor is an RGB Bayer array as shown in FIG. A high-sensitivity block 21 in which a high transmittance filter is arranged for each 2 × 2 cell and a low-sensitivity block 22 in which a low transmittance filter is arranged are arranged in a checkered pattern that does not share sides.
[0018]
An image signal generation process (color signal generation process) in the case of using the above color image sensor will be described. A 4 × 4 square surrounded by a broken line in FIG. 2 is a basic grid for generating a color signal, and a pixel signal is generated by adding signals of each pixel in the square. That is, by adding two R, two B, and four G in the high-sensitivity block 21 in the square and two R, two B, and four G in the low-sensitivity block 22, one pixel is equivalent. Are generated. Then, a two-dimensional pixel signal is obtained by shifting the above-mentioned square by two pixel pitches.
[0019]
FIG. 3 is a diagram showing sensitivity characteristics in the image sensor of the present embodiment. The horizontal axis represents the amount of incident light (logarithm), and the vertical axis represents the CCD output (logarithm). 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.
[0020]
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 finally obtained sensitivity is as indicated by C in the figure. . That is, it has sensitivity from the time when the amount of incident light is low, and does not reach the saturation level until the amount of incident light is large. That is, a sufficiently large dynamic range can be obtained with relatively high sensitivity.
[0021]
FIG. 4 is a flowchart for explaining the operation in the present embodiment. First, at the start of processing (1st release), the absolute luminance level in the subject is measured (S1). In this measurement, the luminance in the direction of the subject may be measured by a sensor, or the output of the CCD image sensor can be used.
[0022]
Next, it is determined whether or not the measured luminance is greater than or equal to a predetermined value (S2). If it is greater than or equal to the predetermined value, 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).
[0023]
Next, by the 2nd release (S5), a subject image is picked up by a color image pickup device in which RGB color filters are arranged in a Bayer pattern and high transmittance filters and low transmittance filters are arranged in a checkered lattice pattern. The signal from the photoelectric conversion element (each pixel) is amplified. Then, after A / D conversion of the amplified signal, each Bayer data is stored (S6).
[0024]
Next, the output of the high sensitivity pixel and the low sensitivity pixel is added to perform image signal generation processing (S7). The generation of the image signal is as described with reference to FIGS. 2 and 3, and the color signal corresponding to one pixel is obtained by adding the outputs of the high-sensitivity pixel and the low-sensitivity pixel in the 4 × 4 cell. And the square is shifted by 2 pixel pitches to generate a two-dimensional image signal.
[0025]
Next, white balance is adjusted, and further matrix processing is performed (S8). In matrix processing, spectral sensitivity is corrected by well-known matrix conversion to reduce color reproduction errors.
[0026]
Next, the obtained RGB signal is subjected to γ conversion processing and Y / C separation processing, and then JPEG compression processing is performed, and the compressed image data is recorded on a memory card or the like (S9).
[0027]
As described above, according to the present embodiment, by adding the signals of the high sensitivity pixel and the low sensitivity pixel, the dynamic range can be expanded while maintaining a relatively high sensitivity. If one Bayer array of RGB is assumed to be 1 unit, the pixel is added by 4 units, so that the resolution is reduced to ½ compared to the conventional case. However, when the number of pixels of the image sensor becomes sufficiently large due to future increase in the number of pixels, the reduction in resolution due to the selective use of pixels can be ignored, and the effect of the above-described embodiment becomes more effective.
[0028]
In the present 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 to adjust the AE and AF due to the subject being too bright. Defects can be prevented in advance. On the contrary, when the luminance of the subject is smaller than the predetermined value, that is, when the subject is dark, the AE and AF adjustment using the high-sensitivity pixel is performed, and thus the AE and AF are poorly adjusted due to the subject being dark. Can be prevented in advance.
[0029]
In addition, this invention is not limited to embodiment mentioned above. In the embodiment, the signals of the high-sensitivity pixel and the low-sensitivity pixel are added. Instead, in the image signal generation process, a selection unit that selects either the high-sensitivity pixel or the low-sensitivity pixel according to the brightness of the subject. If the subject is bright, only the low-sensitivity pixel signal may be used, and if the subject is dark, only the high-sensitivity pixel signal may be used.
[0030]
Also, the RGB arrangement is not necessarily limited to the Bayer arrangement, and various arrangements are possible. Furthermore, the configuration of the imaging apparatus is not limited to that shown in FIG. 1 and can be changed as appropriate according to the specifications. In addition, various modifications can be made without departing from the scope of the present invention.
[0031]
【The invention's effect】
As described above in detail, according to the present invention, a periodic color coding array is applied to the imaging surface, and each unit array (block) has different sensitivities. By using the pixel value, it is possible to realize a color imaging device having high sensitivity and high dynamic range. By using this, it is possible to realize an imaging apparatus that can perform good imaging from a dark scene to a bright scene.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a circuit configuration of an imaging apparatus according to an embodiment of the present invention.
FIG. 2 is a diagram showing an arrangement of color filters in the color image sensor used in the embodiment.
FIG. 3 is a diagram showing sensitivity characteristics in the color image sensor used in the embodiment.
FIG. 4 is a flowchart for explaining the operation of the embodiment.
[Explanation of symbols]
DESCRIPTION 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 ... Pre-process 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 (4)

A color imaging device that performs periodic color coding arrangement on the imaging surface and has different sensitivity for each unit arrangement (block),
Said periodic color coding sequences are Bayer array composed of RGB primaries, sensitive block and the low-sensitivity block features and to Luke error image sensor that is arranged side in a checkerboard pattern that do not share with each other . The color image pickup device according to claim 1 , an image signal generation unit that generates a predetermined image signal based on an output of the image pickup device, and a signal from the high-sensitivity block in a signal generation process by the image signal generation unit imaging apparatus characterized by comprising comprises an adding means for adding the signals output from the output low-sensitivity block. The color image pickup device according to claim 1 , an image signal generation unit that generates a predetermined image signal based on an output of the image pickup device, and a signal from the high-sensitivity block in a signal generation process by the image signal generation unit imaging apparatus characterized by comprising comprises a selecting means for selecting one of the output and the signal output from the low-sensitivity block. 2. The color image pickup device according to claim 1 , an image signal generation unit that generates a predetermined image signal based on an output of the image pickup device, and an automatic control unit that performs a predetermined automatic control process based on an output of the image pickup device. When the subject brightness determination means for determining brightness of an object, a signal used in automatic control process in the automatic control means on the basis of an output of the object brightness determination unit, low the signal output from the high-sensitive block An imaging apparatus comprising: selection means for selecting a signal output from a sensitive block.

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