JP4334788B2 - Imaging apparatus and television camera using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image pickup apparatus and a television camera using the same, and more particularly to a technique effective when applied to a single-plate color image pickup device using a Bayer color filter array.
[0002]
[Prior art]
As a conventional technique, there is a color difference line sequential method using a color filter array as a single plate type color imaging method for obtaining a color signal (pixel data) from one CCD that performs interlace scanning. This is a method in which color signals are obtained in a line-sequential manner in the form of color difference signals.
[0003]
An example is shown in FIG. A color filter array formed by repeating this process is used with 2 columns and 4 rows as a basic unit.
First, in the odd field, the odd-numbered pixels in the vertical direction and the even-numbered pixels are added and read. In the next even field, the combination method is changed and the even-numbered pixel and the odd-numbered pixel are added. Then, Ye + G, Cy + Mg, Ye + G, Cy + Mg,... Signals are obtained from the odd-numbered scanning lines, and Ye + Mg, Cy + G, Ye + Mg, Cy + G,.
[0004]
At this time, since Mg = R + B, Cy = B + G, and Ye = R + G, Ye + G + Cy + Mg = 2R + 3G + 2B, and a luminance signal can be obtained by adding two pixels in the horizontal direction.
[0005]
Further, by taking the difference between the two pixels in the horizontal direction, (Cy + Mg) − (Ye + G) = 2B−G from the odd-numbered scanning line.
From the even-numbered scanning lines, (Ye + Mg) − (Cy + G) = 2R−G, and a color difference signal can be obtained.
[0006]
Another single-plate color imaging method using a color filter array is an RGB vertical stripe method. This is a system in which RGB color filters are arranged in the vertical direction, and color signals are obtained dot-sequentially in the form of primary color signals.
[0007]
Another single-plate color imaging method using a color filter array is a Bayer method. In this example, G, which is a main component of a luminance signal that requires high resolution, is arranged in a checkered pattern, and two color components R and B that may have a relatively low resolution are arranged in a checkered pattern in the remaining part.
[0008]
[Problems to be solved by the invention]
As a result of examining the prior art, the present inventor has found the following problems.
The conventional color difference line sequential method has the feature that the resolution of the luminance signal can be increased. However, the resolution of the color difference signal cannot be increased, and an operation is required for color separation, and the characteristics of the color filter are different. In other words, when the signal is saturated in a high-luminance part, the color reproduction is inferior.
[0009]
The RGB vertical stripe method has a simple circuit configuration and excellent color reproducibility, but has a drawback that the horizontal resolution of the luminance signal is as low as 2/3 of the color difference sequential method.
[0010]
In addition, the Bayer method has a feature of obtaining signals with high color reproducibility by reading out all pixels and sequentially scanning, but a normal television camera adds two pixels in the vertical direction for interlaced scanning. There was a disadvantage that was not good.
[0011]
An object of the present invention is to obtain a luminance signal and a color signal with higher resolution in a single-plate color camera.
The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.
[0012]
[Means for Solving the Problems]
Of the inventions disclosed in this application, the outline of typical ones will be briefly described as follows.
[0013]
(1) For conversion elements arranged in a row direction and a column direction Placement of Bayer color filter array In the imaging device The Bayer color filter array has a green color filter arranged in a checkered pattern, and a blue color filter and a red color filter arranged in a checkered pattern in the remaining part, Each of the conversion elements color Signal charge Interlaced scanning 1 field period In between Reading means for reading; and Means for converting the color signal charge read by the reading means into a digital color signal, a frame memory for storing the color signal converted into digital by the means for conversion, and a color signal stored in the frame memory In the odd field of interlaced scanning, for the green signal corresponding to the green color filter, a checkered green signal for two vertical rows is alternately read out for each pixel in the horizontal direction, and the blue color filter is used. For the corresponding blue signal, the blue signal of the checkered blue signal and red signal for two rows in the vertical direction is repeatedly read out twice for each pixel in the horizontal direction, and the red signal corresponding to the red color filter is read. Reads out the red signal of the checkered blue signal and red signal for two rows in the vertical direction twice for each pixel in the horizontal direction, In the next even field, for the green signal corresponding to the green color filter, checkered green signals for two vertical lines shifted by one line from the two vertical lines are alternately displayed for each pixel in the horizontal direction. Read out the blue signal corresponding to the blue color filter by repeatedly reading out the blue signal of the checkered blue signal and red signal for two vertical rows shifted by one row from the two vertical rows twice For the red signal corresponding to the red color filter, the red signal of the checkered blue signal and the red signal for two vertical lines shifted by one line from the two vertical lines is converted into one pixel in the horizontal direction. Read twice every time, Output means for outputting at the timing of interlaced scanning; , With Ru .
[0014]
(2) In a television camera having an imaging device in which Bayer color filter arrays are arranged in conversion elements arranged in a row direction and a column direction, the Bayer color filter array has green color filters arranged in a checkered pattern. The blue color filter and the red color filter are respectively arranged in a checkered pattern in the remaining part, and the imaging apparatus Read means for reading out the color signal charge of each conversion element in one field period of interlaced scanning, means for converting the color signal charge read by the read means into a digital color signal, and means for converting In the frame memory storing the color signal converted into digital and the color signal stored in the frame memory, in the odd field of the interlaced scanning, the green signal corresponding to the green color filter is equivalent to two lines in the vertical direction. The checkered green signal is alternately read for each pixel in the horizontal direction, and the blue signal corresponding to the blue color filter is the blue signal of the checkered blue signal and the red signal for the two vertical rows. Is read twice for each pixel in the horizontal direction, and the red signal corresponding to the red color filter is a checkered blue signal for two rows in the vertical direction. The red signal is read out twice for each pixel in the horizontal direction, and in the even field next to the odd field, the green signal corresponding to the green color filter is 1 to 2 in the vertical direction. The checkered green signals for two vertical lines shifted by lines are alternately read for each pixel in the horizontal direction, and the blue signal corresponding to the blue color filter is shifted by one line from the two vertical lines. The blue signal of the checkered blue signal and red signal for two lines in the vertical direction is repeatedly read out twice, and the red signal corresponding to the red color filter is shifted by one line from the two lines in the vertical direction. Output means for repeatedly reading out the red signal of the checkered blue signal and red signal for two rows in the vertical direction twice for each pixel in the horizontal direction and outputting them at the timing of interlaced scanning , Comprising a.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings together with embodiments (examples) of the invention.
Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiment of the invention, and the repetitive description thereof is omitted.
[0017]
(Embodiment 1)
FIG. 1 is a diagram for explaining a schematic configuration of an imaging apparatus according to Embodiment 1 of the present invention. In FIG. 1, 101 is a single-plate CCD element using a Bayer-type (Bayer array) primary color filter, 102 is an ADC, 103 is a frame memory, 104 is a DAC, 105 is an interlace monitor, 106 is a sequential scanning drive circuit, and 107 is 2 shows an interlace scan timing generation circuit.
[0018]
As shown in FIG. 1, the image pickup apparatus of Embodiment 1 includes a single-plate CCD element 101 using a well-known Bayer method (Bayer array) primary color filter, and a known sequential scanning method (non-scanning method). From a sequential scanning drive circuit 106 driven by an interlace method, a well-known ADC (analog-digital converter) 102 for converting a stored charge signal output by sequential scanning from the single-plate CCD element 101 into a digital signal, and the ADC 102 A well-known frame memory 103 that stores the output digital signal, an interlace scanning timing generation circuit 107 that controls reading of signals for each color stored in the frame memory 103 at the timing of the interlaced scanning signal, and a frame memory For each color of interlace timing output from 103 It is composed of a known DAC (digital / analog converter) 104 that converts a digital signal into an analog signal. The color signal output from the image pickup apparatus according to the first embodiment is converted into an interlace color signal and output. Therefore, it is possible to output a color signal with good color reproducibility, which is a feature of a single-plate CCD element using a Bayer-type (Bayer array) primary color filter. Therefore, the interlace timing color signal output from the DAC 104 can be displayed on the conventional interlace monitor 105.
[0019]
That is, in the image pickup apparatus of the first embodiment, the single-plate CCD element 101 is driven by a sequential scanning method, so that the accumulated charge signal from each pixel is read out from all the pixels without mixing the pixels. The read signal is temporarily stored on the frame memory 103, and a color signal (pixel data) is output from the frame memory 103 at the timing of the interlace signal for each color signal.
[0020]
FIG. 2 is a diagram illustrating an example of an array of Bayer-type primary color filter arrays used in the imaging apparatus according to the first embodiment. However, in the imaging apparatus of Embodiment 1, a Bayer system in which color filters are arranged in a checkered pattern is used as a color filter array in the single-plate color imaging system. However, in FIG. 2, m, n, and n ′ are arbitrary odd numbers.
[0021]
As is apparent from FIG. 2, in the imaging apparatus of Embodiment 1, green filters indicated by G, which are main components of a luminance signal that requires high resolution, are arranged in a checkered pattern and indicated by B, which is another color. The blue filter and the red filter indicated by R are arranged in a checkered pattern in the remaining portions. However, the arrangement of the B and R filters is such that filters of the same color are arranged in the horizontal and vertical directions, such as G and B or G and R, respectively.
[0022]
FIG. 3 is a diagram for explaining a color signal reading operation from the frame memory. However, FIG. 3A is a diagram showing the pixel arrangement on the two-dimensional memory (frame memory 103), and FIG. 3B is a diagram for explaining the read position of the green signal in the scan line of the odd field. FIG. 3C is a diagram for explaining the reading position of the green signal in the even-line scanning line, and FIG. 3D is the blue signal in the odd-field scanning line. FIG. 3E is a diagram for explaining a read position, FIG. 3E is a diagram for explaining a blue signal read position in the even-line scan line, and FIG. 3F is a scan of the odd field. FIG. 3G is a diagram for explaining the read position of the red signal for the even-numbered field scan line. However, m, n, and n ′ shown in FIG. 3 are the same as m, n, and n ′ of the CCD element shown in FIG. Further, in the following description, in order to simplify the description, among the pixels controlled in the horizontal direction and the vertical direction, in a region where four pixels are arranged in the horizontal direction and five pixels are arranged in the vertical direction. Although the case of pixels will be described, the same applies to all the other pixels and the color filter array of the single-plate CCD element 101.
[0023]
Hereinafter, the reading operation of the green signal, the blue signal, and the red signal will be described based on FIG. 3A to FIG.
As shown in FIGS. 3B and 3C, in the interlaced odd field in the green signal readout, the odd-numbered (m, m + 2, m + 4) pixels and the even-numbered (m + 1, m + 3) pixels in the vertical direction. Are alternately read for each pixel in the horizontal direction. Thus, the signals of G1, G2, G3, G4,... From the nth scanning line in the odd field, and G5, G6, G7, G8,. A signal is obtained.
[0024]
In the next even field, the odd-numbered (m + 2, m + 4) pixels and the even-numbered (m + 1, m + 3) pixels in the vertical direction are alternately read out for each pixel in the horizontal direction. As a result, G5, G2, G7, and G4 signals are obtained from the n'th scanning line in the even field, and G9, G6, G11, and G8 signals are obtained from the next n + 1'th scanning line.
[0025]
Therefore, in the output of the color signal (G signal) in the interlaced odd field, as shown in FIG. 3B, in the case of the nth scanning line in the odd field, the green color of the pixels in the m or m + 1th row. Signals G1, G2, G3, and G4 are output. Similarly, in the case of the (n + 1) th scanning line in the odd field, the green signals G5, G6, G7, and G8 of the pixels in the m + 2 or m + 3 row are output.
[0026]
Further, in the output of the color signal in each scanning line in the even field, as shown in FIG. 3C, in the case of the n′th scanning line in the even field, the pixel of the m + 1 or m + 2 row is displayed. Green signals G5, G2, G7, and G4 are output. Similarly, in the case of the n ′ + 1th scanning line in the even field, the green signals G9, G6, G11, and G8 of the pixels in the m + 3 or m + 4th row are output.
[0027]
At this time, in the imaging device of Embodiment 1, the resolution of the obtained green signal is equal to the pixel pitch in the horizontal direction and equal to the pitch of the vertical two-pixel mixture by interlacing in the vertical direction, so that the resolution is high. A color signal can be obtained.
[0028]
As shown in (d) and (e) of FIG. 3, in the interlaced odd field in the blue signal readout, the even-numbered (m + 1, m + 3) pixels in the vertical direction are repeatedly read out twice for each pixel in the horizontal direction. . As a result, B1, B1, B2, and B2 signals are obtained from the nth scan line in the odd field, and B3, B3, B4, and B4 signals are obtained from the next (n + 1) th scan line.
[0029]
In the next even field, the even-numbered (m + 1, m + 3) pixels in the vertical direction are repeatedly read twice for each pixel in the horizontal direction. As a result, B1, B1, B2, and B2 signals are obtained from the n'th scanning line in the even field, and B3, B3, B4, and B4 signals are obtained from the next n + 1'th scanning line.
[0030]
Accordingly, in the output of the color signal (B signal) in the interlaced odd field, as shown in FIG. 3D, in the case of the nth scanning line in the odd field, the blue signal of the pixel in the (m + 1) th row is used. Certain B1 and B2 signals are output. Similarly, in the case of the (n + 1) th scanning line in the odd field, the blue and blue signals B3 and B4 of the pixels in the (m + 3) th row are output.
[0031]
Further, in the output of the color signal on each scanning line in the even field, as shown in FIG. 3E, in the case of the n′th scanning line in the even field, the blue signal of the pixel in the m + 1th row. B1 and B2 signals are respectively output. Similarly, in the case of the n ′ + 1th scanning line in the even field, the blue and blue signals B3 and B4 of the pixels in the (m + 3) th row are respectively output.
[0032]
At this time, in the image pickup apparatus of Embodiment 1, the resolution of the obtained blue signal is equal to two columns of pixel pitches in the horizontal direction, and equal to the pitch of two vertical pixel mixtures by interlacing in the vertical direction. A color signal with high resolution can be obtained.
[0033]
As shown in (f) and (g) of FIG. 3, in the interlaced odd field in red signal readout, the odd-numbered (m, m + 2) pixels in the vertical direction are repeatedly read out twice for each pixel in the horizontal direction. . As a result, R1, R1, R2, and R2 signals are obtained from the nth scanning line in the odd field, and R3, R3, R4, and R4 signals are obtained from the next (n + 1) th scanning line.
[0034]
In the next even field, odd-numbered (m + 2, m + 4) pixels in the vertical direction are repeatedly read out twice for each pixel in the horizontal direction. As a result, R3, R3, R4, and R4 signals are obtained from the n'th scanning line in the even field, and R5, R5, R6, and R6 signals are obtained from the next n + 1'th scanning line.
[0035]
Accordingly, in the output of the color signal (R signal) in the interlaced odd field, as shown in FIG. 3F, in the case of the nth scanning line in the odd field, the red signal of the pixel in the mth row is used. Certain R1 and R2 signals are output. Similarly, in the case of the (n + 1) th scanning line in the odd field, the red and red signals R3 and R4 of the pixels in the (m + 2) th row are output.
[0036]
Further, in the output of the color signal in each scanning line in the even field, as shown in FIG. 3G, in the case of the n′th scanning line in the even field, the red signal of the pixel in the (m + 2) th row. R3 and R4 signals are respectively output. Similarly, in the case of the n ′ + 1th scanning line in the even field, signals R5 and R6 that are red signals of the pixels in the (m + 4) th row are output.
[0037]
At this time, in the imaging apparatus of Embodiment 1, the resolution of the obtained red signal is equal to two columns of pixel pitches in the horizontal direction, and equal to the pitch of two vertical pixel mixtures by interlacing in the vertical direction. A color signal with high resolution can be obtained.
[0038]
By performing the above operation, for the green signal, a color signal is output for every two pixels in the horizontal direction in the CCD element 101, and for the blue signal and the red signal, two pixels in the horizontal direction in the imaging device and two pixels in the vertical direction. A color signal is output every time. Therefore, when converting to an interlace signal and outputting it, color information can be separated for each line in the vertical direction. In the horizontal direction, the color information can be separated for each pixel of the green signal, and the color information can be separated for every two pixels of the blue and red signals.
[0039]
Further, consider the luminance signal. When the luminance signal Y is synthesized from each color signal, it can be calculated according to the equation Y = R + 2G + B.
For example, in an interlaced odd field, luminance signals Y1, Y2, Y3, and Y4 calculated by the following equation 1 are obtained from the nth scanning line, respectively.
[0040]
[Expression 1]
Y1 = R1 + 2 × G1 + B1
Y2 = R1 + 2 × G2 + B1
Y3 = R2 + 2 × G3 + B2
Y4 = R2 + 2 × G4 + B2
[0041]
At this time, the luminance signals Y1 and Y2 and Y3 and Y4 of two horizontally adjacent pixels use the same blue and red signals, but use the same green signals. Since the contribution of each color signal to the luminance signal is green, the resolution of the luminance signal is higher than that of the single channel of the blue signal and the red signal even in the horizontal direction. Therefore, a luminance signal with high resolution can be obtained.
[0042]
As described above, in the imaging apparatus according to the first embodiment, the sequential scanning drive circuit 106 functioning as a reading unit is configured to operate all pixels (all conversion elements) of the CCD element 101 based on the timing output from the interlace scanning timing generation circuit 107. ) Is read out in one field period, the read signal charge is converted into a digital signal by the ADC 102 and stored in the frame memory 103, and the digital signal stored in the frame memory 103 is stored. Issue When reading, a signal corresponding to the color of the color filter at the interlaced scanning timing based on the control signal from the interlace scanning timing generation circuit 107. Issue Read, this read signal Issue Even if it is a Bayer type imaging device in which color filters are arranged in a checkered pattern in the conversion elements arranged in the row direction and the column direction, the conversion elements are converted into analog signals by the DAC 104 and output. The signal charges are read for each conversion element without adding the signal charges. By signal processing, Since output can be performed by interlaced scanning, a high-resolution color signal and luminance signal can be obtained with good color reproduction.
[0043]
(Embodiment 2)
FIG. 4 is a diagram for explaining a schematic configuration of the imaging apparatus according to the second embodiment of the present invention.
However, the imaging apparatus according to the second embodiment is different from the imaging apparatus according to the first embodiment except that only the configuration of the frame memory 401 and the correction processing unit 402 is different. 401 and the correction processing unit 402 will be described in detail.
[0044]
As shown in FIG. 4, a frame memory 401 for storing the digital signal output from the ADC 102 of the second embodiment, and an averaging process or interpolation process set in advance for the digital signal read from the frame memory 401 are performed. The correction processing means 402 is configured to perform.
[0045]
That is, in the imaging apparatus according to the second embodiment, the correction processing unit 402 performs either the averaging process or the interpolation process according to the color signal read from the frame memory 401 under the control of the interlace scan timing generation circuit 107. It is the structure which selects and performs the selected process. However, as will be described later, in the imaging apparatus according to the second embodiment, in order to prevent generation of a false signal when, for example, a striped pattern image having a period equal to the pixel pitch of the single-plate CCD element 101 is input, Averaging processing is performed on the signal. Also, interpolation processing for improving resolution is performed on blue and red, which have a smaller number of allocated pixels than green.
[0046]
Note that the output timings of the color signal directly output from the frame memory 401 via the correction processing unit 402 and the corrected color signal from the correction processing unit 402 are scanning timings controlled by the interlace scanning timing generation circuit 107. Thus, it goes without saying that it is controlled by a known technique.
[0047]
FIG. 5 is a diagram for explaining a green signal reading operation from the frame memory in the imaging apparatus according to the second embodiment. However, FIG. 5A is a diagram for explaining the read position of the green signal in the odd-line scanning line, and FIG. 5B is the green signal averaging process in the odd-field scanning line. It is a figure for demonstrating the subsequent reading position. FIG. 5C is a diagram for explaining the read position of the green signal in the even-line scanning line, and FIG. 5D is the green signal averaging process in the even-field scanning line. It is a figure for demonstrating the subsequent reading position. However, m, n, and n ′ shown in FIG. 5 are the same as m, n, and n ′ of the single-plate CCD element 101 shown in FIG.
[0048]
Hereinafter, the averaging process by the correction processing unit 402 for the green signal will be described with reference to FIGS.
As shown in FIGS. 5A and 5B, when a green signal is read from the frame memory 401, an averaging process using color signals located in the left-right direction on the two-dimensional memory is performed.
[0049]
In the reading of the green signal for the nth scanning line in the interlaced odd field, as in the first embodiment, the mth and m + 1th pixels G1, G2, G3, G4 in the vertical direction to be read from the frame memory 401 are read. ,... Are alternately read out and input to the correction processing means 402. Similarly, when the green signal is read for the n + 1th scanning line in the odd field, the green signals of the m + 2 and m + 3 pixels G5, G6, G7, G8,. Read out and input to the correction processing means 402.
[0050]
Here, as shown in FIG. 5B, the correction processing unit 402 is configured to obtain a color signal for a pixel to be read from color signals for three pixels in the horizontal direction. That is, the correction processing unit 402 obtains a color signal for the pixel to be read by averaging processing that weights the color signal of the pixel to be read and the color signal of the pixel to be read before and after this pixel. It has a configuration.
[0051]
For example, when the pixel to be read is G2, the correction processing unit 402 performs G1: for the color signals of G1 and G3 that are pixels before and after G2, with respect to the color signal of G2 to be read. After the weighting of G2: G3 = 1: 2: 1, the averaging process is performed. Accordingly, when the color signal after the averaging process corresponding to G2 to be read is g2, g2 is expressed by the following formula 1.
[0052]
[Expression 2]
g2 = (G1 + 2 × G2 + G3) / 4 (Formula 1)
In addition, when the pixel to be read is G3, g3 is expressed by the following equation 2 when the color signal after the averaging process corresponding to G3 to be read is g3.
[0053]
[Equation 3]
g3 = (G2 + 2 × G3 + G4) / 4 (Formula 2)
Similarly, when the pixels to be read are G6 and G7 in the reading of the green signal for the n + 1th scanning line of the interlaced odd field, after the averaging process corresponding to G6 and G7 to be read If the color signals are g6 and g7, respectively, g6 and g7 are represented by the following equations 3 and 4, respectively.
[0054]
[Expression 4]
g6 = (G5 + 2 × G6 + G7) / 4 (formula 3)
g7 = (G6 + 2 × G7 + G8) / 4 (formula 4)
At this time, the color signals at the start of reading and at the end of reading for each of the n, n + 1th scanning lines are the color signals of the pixels (G1, G4 and G5, G6) to be read.
[0055]
Also, as shown in FIGS. 5C and 5D, in the green signal readout for the n′th scanning line of the interlaced even field, the m + 1 and m + 2 pixels G5 in the vertical direction to be read out. , G 2, G 7, G 4,... Are alternately read out and input to the correction processing means 402. Similarly, when the green signal is read for the n ′ + 1th scanning line in the even field, the green signals of the m + 3 and m + 4 pixels G9, G6, G11, G8,. The data are alternately read and input to the correction processing unit 402.
[0056]
Accordingly, when the pixel to be read is G2, the correction processing unit 402 performs G5 on the color signals of G5 and G7 that are pixels before and after G2, with respect to the color signal of G2 to be read. After the weighting of G2: G7 = 1: 2: 1, the averaging process is performed. Therefore, when the color signal after the averaging process corresponding to G2 to be read is g′2, g′2 is expressed by the following formula 5.
[0057]
[Equation 5]
g′2 = (G5 + 2 × G2 + G7) / 4 (Formula 5)
Further, when the pixel to be read is G7, if the color signal after the averaging process corresponding to G7 to be read is g′3, g′3 is expressed by the following Expression 6.
[0058]
[Formula 6]
g′3 = (G2 + 2 × G7 + G4) / 4 (formula 6)
Similarly, when the pixels to be read are G6 and G11 in the reading of the green signal for the n ′ + 1th scanning line of the interlaced even field, the averaging processing corresponding to G6 and G11 to be read is performed. If the subsequent color signals are g′6 and g′7, respectively, g′6 and g′7 are expressed by the following equations 7 and 8, respectively.
[0059]
[Expression 7]
g′6 = (G9 + 2 × G6 + G11) / 4 (Expression 7)
g′7 = (G6 + 2 × G11 + G8) / 4 (formula 8)
At this time, the color signals at the start of reading and at the end of reading for each of the n ′, n ′ + 1th scanning lines are the color signals of the pixels (G5, G4 and G9, G8) to be read.
As described above, the averaging process by the correction processing unit 402 is the same as the digital low-pass filter process performed in the horizontal direction of the pixels of the CCD element 101.
[0060]
As described above, in the correction processing unit 402, the spatial sample position is raised and lowered every other pixel that causes a problem when reading out a green signal from the CCD element 101 that employs a Bayer array as an on-chip color filter. The phenomenon is corrected by averaging the color signal of the pixel to be read and the color signal of the pixel to be read before and after this pixel. As a result, even when an image having a period equal to the pixel pitch in the vertical direction, that is, a horizontal stripe pattern having a vertical Nyquist frequency, is input to the CCD element 101, a monochrome signal is output for each pixel in the horizontal direction. It is possible to prevent the phenomenon that the horizontal stripes become false signals that are folded back into vertical stripes.
[0061]
FIG. 6 is a diagram for explaining a blue signal readout operation from the frame memory in the imaging apparatus according to the second embodiment. However, FIG. 6A is a diagram for explaining the read position of the green signal in the odd-line scanning line, and FIG. 6B is the diagram after the blue signal interpolation processing in the odd-field scanning line. It is a figure for demonstrating the read-out position. FIG. 6C is a diagram for explaining a blue signal readout position in the even-line scanning line, and FIG. 6D is a diagram after blue signal interpolation processing in the even-field scanning line. It is a figure for demonstrating the read-out position.
[0062]
Hereinafter, based on (a) to (d) of FIG. 6, interpolation processing by the correction processing unit 402 for the blue signal will be described.
As shown in FIG. 6A, in the blue signal readout for the n-th scanning line in the interlaced odd field, as in the first embodiment, the vertical m + 1th target to be read out from the frame memory 401 is the same. The blue signals of the pixels B1, B2, B13,... Are read out twice and input to the correction processing means 402 as B1, B1, B2, B2,. Similarly, in the blue signal readout for the (n + 1) th scanning line in the odd field, the blue signals of the m + 3th pixels B3, B4, B23,. It is input to the correction processing means 402 as B3, B3, B4, B4,.
[0063]
Here, as shown in FIG. 6B, the correction processing unit 402 is configured to output the blue signal read out first time as it is to the subsequent DAC 104 out of the blue signals read out twice. It has become. On the other hand, for the blue signal read out second time, a value interpolated from the first blue signal read out next time is output as a blue signal.
[0064]
That is, in the blue signal interpolation process for the nth scanning line in the odd field, first, the correction processing unit 402 outputs the blue signal of the (m + 1) th pixel B1 in the vertical direction. Next, a value b1 interpolated from the blue signal of the pixel B1 and the blue signal of the pixel B2 that is adjacent in the horizontal direction is output. Next, the correction processing unit 402 outputs a blue signal of B2 as the next pixel, and thereafter outputs a value b2 interpolated from the blue signal of B2 and the blue signal of a pixel (not shown) adjacent to B2. The correction processing unit 402 outputs the blue signal for the nth scanning line of the odd field to the next-stage DAC 104 by sequentially performing the interpolation processing described above.
[0065]
Similarly, in the blue signal interpolation processing for the (n + 1) th scanning line in the odd field, B3, interpolated values b3, B4, interpolated value b4,... Are sequentially calculated and output to the DAC 104 in the next stage. To do.
[0066]
Further, in the blue signal interpolation process for the n′th scanning line of the even field, B1, interpolated values b′1, B2, interpolated value b′2,. It is calculated and output to the DAC 104 at the next stage. Also in the blue signal interpolation processing for the n ′ + 1-th scanning line of the even field, B3, interpolated values b′3, B4, interpolated value b′4,. And output to the DAC 104 in the next stage.
[0067]
However, as the interpolation processing for the blue signal, for example, among the blue signals input from the frame memory 401 twice, the blue signal input for the second time and the blue signal input as the signal for the next pixel are 1 Is obtained as values b1, b2,. For example, the value of the pixel b1 obtained by the interpolation processing is 1/2 of the blue signal of the left pixel B1 of the pixel (b1) and 1/2 of the blue signal of the right pixel B2 of the pixel (b1). Are added to generate a blue signal for the pixel b1. Therefore, the values b1, b2,... Obtained by the interpolation processing are expressed by the following equations 9 to 16.
[0068]
[Equation 8]
b1 = (B1 + B2) / 2 (formula 9)
b2 = (B2 + (B13)) / 2 (Equation 10)
b3 = (B3 + B4) / 2 (Formula 11)
b4 = (B4 + (B23)) / 2 (Expression 12)
b′1 = (B1 + B2) / 2 (Formula 13)
b′2 = (B2 + (B13)) / 2 (Expression 14)
b′3 = (B3 + B4) / 2 (Equation 15)
b′4 = (B4 + (B23)) / 2 (Expression 16)
[0069]
The signals b1, b2,... Obtained by the interpolation in this way are output instead of the second signal read out twice from the frame memory 401, and the horizontal resolution of the blue signal is reduced. Since the pixel pitch can be made equal, a blue signal with higher resolution can be obtained. For example, the signal b1 obtained by the interpolation is obtained by spatially interpolating a pixel signal between B1 and B2 (horizontal direction) actually measured by the CCD element 101. It is possible to improve the resolution.
[0070]
FIG. 7 is a diagram for explaining the read operation of the red signal from the frame memory in the imaging apparatus according to the second embodiment. However, FIG. 7A is a diagram for explaining the read position of the red signal in the odd-line scanning line, and FIG. 7B is a diagram after the red signal interpolation processing in the odd-field scanning line. It is a figure for demonstrating the read-out position. FIG. 7C is a diagram for explaining the read position of the red signal in the even-line scanning line, and FIG. 7D is a diagram showing the red signal after the interpolation process in the even-field scanning line. It is a figure for demonstrating the read-out position.
[0071]
Hereinafter, the interpolation processing by the correction processing means 402 for the red signal will be described with reference to FIGS.
As shown in FIG. 7A, in the red signal readout for the nth scanning line of the interlaced odd-numbered field, the mth of the vertical direction to be read from the frame memory 401 is the same as in the first embodiment. The red signals of the pixels R1, R2, R13,... Are read out twice and input to the correction processing means 402 as R1, R1, R2, R2,. Similarly, in the red signal readout for the (n + 1) th scanning line in the odd field, the red signals of the m + 2 pixels R3, R4, R23,. R3, R3, R4, R4,... Are input to the correction processing means 402.
[0072]
Here, as shown in FIG. 7B, the correction processing unit 402 outputs the red signal read out first time as it is to the subsequent DAC 104 as it is. It has a configuration. On the other hand, for the red signal read for the second time, a value interpolated from the first red signal read for the next time is output as a red signal.
[0073]
That is, in the interpolation process of the red signal for the nth scanning line in the odd field, first, the correction processing unit 402 outputs the red signal of the mth pixel R1 in the vertical direction. Next, a value r1 interpolated from the red signal of the pixel R1 and the red signal of the pixel R2 that is adjacent in the horizontal direction is output. Next, the correction processing unit 402 outputs a red signal of R2 as the next pixel, and thereafter outputs a value r2 interpolated from the red signal of R2 and a red signal of a pixel R13 (not shown) adjacent to R2. The correction processing unit 402 outputs the red signal for the nth scanning line in the odd field to the DAC 104 in the next stage by sequentially performing the interpolation processing described above.
[0074]
Similarly, in the red signal interpolation process for the n + 1th scanning line in the odd field, R3, interpolated values r3, R4, interpolated value r4,... Output to.
[0075]
Similarly, in the red signal interpolation processing for the n′-th scanning line in the even field, R3, interpolated values r′3, R4, interpolated value r′4,. Are sequentially calculated and output to the DAC 104 at the next stage. Also, in the red signal interpolation processing for the n ′ + 1-th scanning line in the even field, R3, interpolated values r′3, R4, interpolated value r′4,. It is sequentially calculated and output to the DAC 104 at the next stage.
[0076]
However, as the interpolation process for the red signal, for example, the red signal inputted for the second time among the red signals inputted twice from the frame memory 401 and the signal of the next pixel, like the blue signal described above. Are obtained as values r1, r2,... Weighted by 1: 1 with the input red signal. For example, the value of the pixel r1 obtained by the interpolation process is 1/2 of the red signal of the left pixel R1 of the pixel (r1) and 1/2 of the red signal of the right pixel R2 of the pixel (r1). Are added to generate a red signal of the pixel r1. Therefore, as values obtained by the interpolation processing, for example, r1 to r4 and r′3 to r′6 are expressed by the following equations 17 to 24.
[0077]
[Equation 9]
r1 = (R1 + R2) / 2 (Equation 17)
r2 = (R2 + (R13)) / 2 (Equation 18)
r3 = (R3 + R4) / 2 (Equation 19)
r4 = (R4 + (R23)) / 2 (Formula 20)
r′3 = (R3 + R4) / 2 (Formula 21)
r′4 = (R4 + (R23)) / 2 (Formula 22)
r′5 = (R5 + R6) / 2 (Equation 23)
r′6 = (R6 + (R71)) / 2 (Equation 24)
[0078]
The signals r1, r2,... Obtained by the interpolation in this way are output instead of the second signal read out twice from the frame memory 401, and the horizontal resolution of the red signal is reduced. Since it can be made equal to the pixel pitch, a red signal with higher resolution can be obtained. For example, the signal r1 obtained by the interpolation is obtained by spatially interpolating the pixel signal between R1 and R2 (horizontal direction) actually measured by the CCD element 101, so that the horizontal direction of the red signal It is possible to improve the resolution.
[0079]
In the second embodiment, it goes without saying that the averaging process and the interpolation process may be performed in the frame memory 401 using pixel data located in the left, right, up, down, or both directions on the two-dimensional memory.
[0080]
In the second embodiment, an averaging process is performed by weighting the color signal of the pixel to be read and the color signal of one or two pixels read before and after this pixel, and the pixel to be read is processed. Although the configuration for obtaining the corresponding color signal is not limited to this, the configuration for obtaining the color signal corresponding to the pixel to be read out by interpolation processing from the color signals of any two or more pixels on the top, bottom, left and right But it goes without saying.
Furthermore, it goes without saying that the weighting ratio may be an arbitrary ratio.
[0081]
The invention made by the present inventor has been specifically described based on the embodiment of the invention, but the invention is not limited to the embodiment of the invention and does not depart from the gist of the invention. Of course, various changes can be made.
[0082]
【The invention's effect】
The effects obtained by the representative ones of the inventions disclosed in the present application will be briefly described as follows.
(1) Even in a Bayer-type imaging device in which color filters are arranged in a checkered pattern on conversion elements arranged in the row direction and the column direction, reading is performed for each conversion element without adding the signal charge of each conversion element, By performing signal processing on the read signal charges, high-resolution color signals and luminance signals can be obtained with good color reproduction.
[0083]
(2) The color of the pixel to be read out is a phenomenon in which the spatial sample position rises and falls every other pixel, which is a problem when reading a green signal from a CCD element that employs a Bayer array as an on-chip color filter. Since the correction is made by averaging the signal and the color signal of the pixel to be read before and after this pixel, for example, a horizontal stripe pattern having a period equal to the pixel pitch in the vertical direction, that is, a vertical Nyquist frequency Even when an image such as the above is input to the CCD element, it is possible to prevent a phenomenon in which a black and white signal is output for each pixel in the horizontal direction, resulting in a false signal in which horizontal stripes are folded back into vertical stripes. .
[0084]
(3) The blue signal and / or red signal obtained by the interpolation is output instead of the second signal read out from the frame memory twice, and the horizontal direction of the blue signal and / or red signal is output. Since the resolution can be made equal to the pixel pitch, a blue signal and / or a red signal with higher resolution can be obtained.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining a schematic configuration of an imaging apparatus according to a first embodiment of the present invention.
2 is a diagram illustrating an example of an array of Bayer-type primary color filter arrays used in the imaging apparatus according to Embodiment 1. FIG.
3 is a diagram for explaining a color signal reading operation from a frame memory in the imaging apparatus according to Embodiment 1. FIG.
FIG. 4 is a diagram for illustrating a schematic configuration of an imaging apparatus according to a second embodiment of the present invention.
5 is a diagram for explaining a green signal readout operation from a frame memory in the imaging apparatus according to Embodiment 2. FIG.
6 is a diagram for explaining a blue signal reading operation from a frame memory in the imaging apparatus according to Embodiment 2. FIG.
7 is a diagram for explaining a read operation of a red signal from a frame memory in the imaging apparatus according to Embodiment 2. FIG.
FIG. 8 is a diagram for explaining an arrangement of color filter arrays in a conventional single-chip CCD element of a color difference line sequential method.
[Explanation of symbols]
101 ... Single-plate CCD element 102 ... ADC
103: Frame memory 104 ... DAC
105 ... Interlace monitor 106 ... Sequential scan drive circuit
107: Interlace scanning timing generation circuit
401: Frame memory 402: Correction processing means

Claims (4)

In an imaging device in which a Bayer color filter array is arranged in conversion elements arranged in a row direction and a column direction,
The Bayer color filter array has a green color filter arranged in a checkered pattern, and a blue color filter and a red color filter arranged in a checkered pattern in the remaining part,
Reading means for reading in one field period of the interlaced scanning said color signal charges of the conversion elements,
Means for converting the color signal charge read by the reading means into a digital color signal;
A frame memory for storing the color signal digitally converted by the means for converting;
The color signal stored in the frame memory is
In the odd field of interlaced scanning,
For the green signal corresponding to the green color filter, a checkered green signal for two vertical rows is alternately read for each pixel in the horizontal direction,
For the blue signal corresponding to the blue color filter, the blue signal of the checkered blue signal and red signal for two rows in the vertical direction is repeatedly read out twice for each pixel in the horizontal direction,
For the red signal corresponding to the red color filter, the red signal of the checkered blue signal and red signal for the two rows in the vertical direction is read out twice for each pixel in the horizontal direction,
In the even field next to the odd field,
For the green signal corresponding to the green color filter, the checkered green signal for two vertical lines shifted by one line from the two vertical lines is alternately read for each pixel in the horizontal direction,
For the blue signal corresponding to the blue color filter, the blue signal of the checkered blue signal and the red signal for two vertical rows shifted by one row from the two vertical rows is repeatedly read twice.
Regarding the red signal corresponding to the red color filter, the red signal of the checkered blue signal and the red signal for two vertical lines shifted by one line from the two vertical lines for each pixel in the horizontal direction. Repeatedly read twice
Output means for outputting at the timing of interlaced scanning ;
An imaging apparatus comprising: The imaging device according to claim 1 ,
The image pickup apparatus characterized in that the output means outputs the color signal after averaging or interpolating the pixels located on the left, right, top and bottom or both . The imaging device according to claim 1 or 2 ,
The output means combines the luminance signal Y according to Y = R + 2G + B when the red signal is R, the green signal is G, and the blue signal is B, and the luminance signals of two pixels adjacent in the horizontal direction are , green for blue signal using the blue signal corresponding to the same blue color filters, the red signal using the red signal corresponding to the same red color filter, corresponding to different green color filter for the green signal imaging apparatus characterized by using the signals. In a television camera having an imaging device in which a Bayer color filter array is arranged in conversion elements arranged in a row direction and a column direction,
The Bayer color filter array has a green color filter arranged in a checkered pattern, and a blue color filter and a red color filter arranged in a checkered pattern in the remaining part,
The imaging device
Read means for reading out the color signal charge of each conversion element in one field period of interlace scanning,
Means for converting the color signal charge read by the reading means into a digital color signal;
A frame memory for storing the color signal digitally converted by the means for converting;
The color signal stored in the frame memory is
In the odd field of interlaced scanning,
For the green signal corresponding to the green color filter, a checkered green signal for two vertical rows is alternately read for each pixel in the horizontal direction,
For the blue signal corresponding to the blue color filter, the blue signal of the checkered blue signal and red signal for two rows in the vertical direction is repeatedly read out twice for each pixel in the horizontal direction,
For the red signal corresponding to the red color filter, the red signal of the checkered blue signal and red signal for the two rows in the vertical direction is read out twice for each pixel in the horizontal direction,
In the even field next to the odd field,
For the green signal corresponding to the green color filter, the checkered green signal for two vertical lines shifted by one line from the two vertical lines is alternately read for each pixel in the horizontal direction,
For the blue signal corresponding to the blue color filter, the blue signal of the checkered blue signal and the red signal for two vertical rows shifted by one row from the two vertical rows is repeatedly read twice.
Regarding the red signal corresponding to the red color filter, the red signal of the checkered blue signal and the red signal for two vertical lines shifted by one line from the two vertical lines for each pixel in the horizontal direction. Repeatedly read twice
Output means for outputting at the timing of interlaced scanning;
A TV camera characterized by comprising:

Images