JP3728075B2 - Imaging method and imaging apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vertical pixel shift imaging method using a plurality of all-pixel sequential readout CCDs and an imaging apparatus using this method.
[0002]
[Prior art]
In recent years, progress in semiconductor technology has been remarkable, and high-density and inexpensive elements have been produced. CCDs used in video cameras and the like are also becoming smaller and more pixels.
[0003]
As for broadcasting systems, next-generation ones such as EDTVII and HDTV are beginning to spread, and CCDs corresponding to the next generation are also being developed. Among them, an all-pixel sequential readout CCD (hereinafter referred to as “all-pixel CCD”) that can be output non-interlaced without adding two pixels vertically is one of promising elements.
[0004]
Under such circumstances, there is a pixel shift imaging method as a technique for making a video camera that is inexpensive, has high resolution, and has good color reproduction. In particular, with regard to vertical pixel shifting, it is possible to obtain an HDTV signal using, for example, an EDTVII all-pixel CCD, which is considered to greatly contribute to the improvement of the vertical resolution by the appearance of the all-pixel CCD. This is particularly useful for providing a video camera at low cost for consumer use.
[0005]
Here, a conventional vertical pixel shift imaging method using three all-pixel CCDs will be described.
[0006]
FIG. 6 shows a signal processing circuit for processing signals obtained by using three all-pixel CCDs, GCCD 101, BCCD 102, and RCCD 103, which are shifted by half a pixel in the vertical direction in the RGB imaging system. These three all-pixel CCDs are respectively covered with G, B, and R monochromatic filters. As shown in FIG. 2, the pixel positions of the BCCD 102 and RCCD 103 covered with the B and R filters are covered with the G filter. It is installed so as to be shifted in the vertical direction by 1/2 pixel with respect to the pixel position of the GCCD 101.
[0007]
Hereinafter, description will be given along the flow of signals.
[0008]
The optical image of the subject input to the imaging device is divided by a prism (not shown), travels in three different optical paths, and forms an image on each of the GCCD 101, the BCCD 102, and the RCCD 103. Each CCD converts the formed optical image into an electrical signal and outputs it. The output signal from each CCD is processed by the CDS circuit 104 and AGC circuit 105, respectively, and then converted into a digital signal by the A / D converter 106.
[0009]
The processing line for the G signal processing is switched with the 1H delay circuit 107 in the field period in order to obtain a luminance signal by performing vertical addition with the B and R signals by a combination of different lines in the even field and odd field. A line changeover switch 108 is inserted. This can also be realized by switching the readout line between the even field and odd field by a timing generator (TG) (not shown) for the CCD. The combination of the lines will be described later with reference to FIG.
[0010]
Bands of these G, B, and R signals are limited by LPFs 109, 110, and 111 in the horizontal and vertical directions, respectively. The G (GL) signal filtered by the LPF 109 is directly input to a matrix conversion circuit (YC-MAT) 113 that performs matrix conversion processing to obtain a low-frequency luminance signal and a color difference signal. The B (BL) signal and the R (RL) signal are input to the YC-MAT circuit 113 after the white balance circuit 112 adjusts the white balance. The YC-MAT circuit 113 generates a low-frequency luminance signal YL and color difference signals Pb and Pr from the input GL signal, BL signal, and RL signal.
[0011]
The G, B, and R signals A / D converted by the A / D conversion circuit 106 are subjected to matrix conversion processing (Y′-MAT) for performing a matrix conversion process for obtaining a luminance signal Y ′ that is achromatic and has no aliasing. ) Input to 614. In the Y′-MAT circuit 614, by using the G signal selected for each field by the line changeover switch circuit 108, different combinations of the even field and odd field as shown in FIG. 3 are adjacent in the vertical direction. The luminance signal Y ′ is generated using the data of the two pixels. In the example shown in FIG. 3, in the even field, the switch circuit 108 selects a signal input via the 1H delay circuit 107, and in the odd field, selects a signal input directly from the A / D circuit 106.
[0012]
Using the G, B, and R signals input in this way,
[Expression 1]
Y '= 0.5G + 0.25B + 0.25R
Then, the high frequency region is extracted by the horizontal and vertical HPF 115 to generate the high frequency signal Y′H.
[0013]
By adding this high-frequency signal Y′H to the low-frequency luminance signal YL, it is possible to obtain a wide-band Y signal that is not folded back in the vertical high frequency region.
[0014]
In the signal obtained in this way, the resolution of the luminance in the vertical direction is improved by the vertical pixel shift arrangement of the CCD, and there is no aliasing when achromatic.
[0015]
At this time, in the vertical direction, the graph old. The frequency characteristic indicated by dat is obtained. This is a graph std. Of the same figure obtained by arranging three CCDs having the number of pixels twice as large as that of the CCD in the vertical direction without shifting the pixels. It is inferior compared with the frequency characteristic indicated by dat.
[0016]
[Problems to be solved by the invention]
As described above, in the conventional vertical pixel shifting imaging method, since the high frequency luminance signal Y ′ is generated by adding two pixels in the vertical direction, Y ′ in the high frequency obtained by the vertical pixel shifting arrangement is obtained. The response of the image sensor drops, and the effect of shifting the vertical pixels is reduced.
[0017]
The present invention has been made in view of the above problems, and an object of the present invention is to provide an imaging method for generating a high-frequency luminance signal with high response by using outputs from a plurality of CCDs arranged in a vertically shifted manner. It is providing the imaging device using.
[0018]
[Means for Solving the Problems]
According to the present invention, using three all pixels sequentially reading image sensor, compares each of the CCD monochromatic R, G, is covered by a B filter, a CCD covered with G filters and other CCD An imaging method in a vertical pixel shift arrangement in which pixels are shifted by half a pixel in the vertical direction, and a signal obtained from a CCD in which the half pixel placement position is shifted and a signal obtained from another CCD. A high luminance signal is generated by alternately using each field.
[0019]
Further, according to the present invention, all the pixels are sequentially read out and three image sensors are used, and each CCD is covered with a single color R, G, B filter, and the CCD covered with the G filter is compared with other CCDs. An image pickup apparatus having a vertical pixel shift arrangement in which pixels are shifted by half a pixel in the vertical direction, and a signal obtained from a CCD in which the half pixel placement position is shifted, and a signal obtained from another CCD. Are used alternately for each field to have a high-frequency luminance signal generating means for generating a high-frequency luminance signal.
[0020]
According to the above configuration, the resolution and response of the brightness when the image is picked up by using all the three pixel CCDs by the vertical pixel shifting arrangement are improved, and the performance close to that of a three-plate CCD having the number of pixels for the scanning line is realized. An imaging method and an imaging apparatus that can be provided can be provided at a lower cost.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
[0022]
FIG. 1 shows a signal processing circuit for processing signals obtained using three all-pixel CCDs, GCCD 101, BCCD 102, and RCCD 103 arranged by shifting by half a pixel in the vertical direction in the RGB imaging system. These three all-pixel CCDs are covered with G, B, and R monochromatic filters, respectively, and as shown in FIG. It is shifted and arranged.
[0023]
Hereinafter, description will be given along the flow of signals.
[0024]
The optical image of the subject input to the imaging device is divided by a prism (not shown), travels in three different optical paths, and forms an image on each of the GCCD 101, the BCCD 102, and the RCCD 103. Each CCD converts the formed optical image into an electrical signal and outputs it. The output signal from each CCD is processed by the CDS circuit 104 and AGC circuit 105, respectively, and then converted into a digital signal by the A / D converter 106.
[0025]
Bands of these G, B, and R signals are limited by LPFs 109, 110, and 111 in the horizontal and vertical directions, respectively. The G (GL) signal filtered by the LPF 109 is directly input to a matrix conversion circuit (YC-MAT) 113 that performs matrix conversion processing to obtain a low-frequency luminance signal and a color difference signal. The B (BL) signal and the R (RL) signal are input to the YC-MAT circuit 113 after the white balance circuit 112 adjusts the white balance. The YC-MAT circuit 113 generates a luminance signal YL and color difference signals Pb and Pr from the input GL signal, BL signal, and RL signal.
[0026]
The G, B, and R signals A / D converted by the A / D conversion circuit 106 are subjected to matrix conversion processing (Y′-MAT) for performing a matrix conversion process for obtaining a luminance signal Y ′ that is achromatic and has no aliasing. ) 114. In the present embodiment, two types of luminance signals Y1 ′ and Y2 ′ are generated using the G, B, and R signals input by the following equation.
[0027]
[Expression 2]
Y1 '= G
Y2 '= 0.5B + 0.5R
In the Y′-MAT circuit 114, a line cycle switch 114-1 having a field period is inserted, and switching is performed so that Y1 ′ and Y2 ′ are alternately output as the luminance signal Y ′ for each field. In the example shown in FIG. 4, the line selector switch 114-1 is switched so that Y1 'is selected in the even field and Y2' is selected in the odd field. The luminance signal Y ′ selected and output by the line changeover switch 114-1 extracts a high frequency region by the horizontal and vertical HPF 115 to generate a high frequency signal Y′H.
[0028]
This high-frequency luminance signal Y′H is added to the low-frequency luminance signal YL to obtain a high-band luminance signal Y that is not folded back in the vertical high frequency range.
[0029]
Further, by inserting an optical crystal LPF having a vertical sampling frequency as a null point, a folding signal at a high frequency can be removed in advance.
[0030]
The signal thus obtained is the graph new. As shown in dat, the conventional old. Compared with dat, vertical pixel resolution improves the resolution and response of the luminance in the vertical direction, and it is possible to obtain a non-returned one when achromatic.
[0031]
Further, the luminance signal Y ′ causes flicker in a single color and low frequency image portion, but this problem does not occur because the low luminance signal is generated by a normal luminance expression.
[0032]
At this time, the new. The frequency characteristics of dat are shown in FIG. It can be seen that the frequency response of dat is comparable to that of a three-plate CCD having the number of pixels corresponding to the scanning line, and at the same time, the high frequency response is higher than the conventional one as described above.
[0033]
[Other Embodiments]
Note that the present invention can be applied to an imaging apparatus (for example, a video camera) including a single device even if the present invention is applied to an imaging system including a plurality of devices (for example, a host computer, an interface device, a camera head, etc.). May be.
[0034]
【The invention's effect】
As described above in the embodiment, the resolution and response of luminance when the image is picked up by using all the three pixel CCDs are improved by the vertical pixel shift arrangement, and the three-plate CCD having the number of pixels for the scanning line is improved. An imaging method and an imaging apparatus capable of realizing close performance can be provided at a lower cost.
[0035]
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of a camera signal processing circuit according to an embodiment of the present invention.
FIG. 2 is a diagram for explaining a vertical pixel shift arrangement;
FIG. 3 is a diagram illustrating a conventional luminance signal generation method.
FIG. 4 is a diagram illustrating a luminance signal generation method according to an embodiment.
FIG. 5 is a comparison diagram of frequency characteristics.
FIG. 6 is a block diagram illustrating a configuration of a conventional camera signal processing circuit.
[Explanation of symbols]
101 GCCD
102 BCCD
103 RCCD
104 CDS circuit 105 AGC circuit 106 A / D converter 107, 114-1 1H delay circuit 108 Line changeover switch 109, 110, 111 LPF
112 White balance circuit 113, 114, 614 Matrix conversion circuit 115 HPF115

Claims (12)

All three pixels are sequentially read out and three image sensors are used. Each CCD is covered with a single color R, G, B filter, and the CCD covered with the G filter is half a pixel in the vertical direction compared to other CCDs. In the imaging method in the vertical pixel shift arrangement in which the divided pixels are shifted, the signal obtained from the CCD with the shifted half pixel position and the signal obtained from the other CCD are alternately used for each field. An imaging method characterized by generating a high-frequency luminance signal. When a signal obtained from a CCD covered with a G filter is used, Y ′ = G, where G is the signal and Y ′ is a signal for obtaining a high-frequency luminance signal. Item 2. The imaging method according to Item 1 . When a signal obtained from a CCD covered with R and B filters is used, R is a signal obtained from a CCD covered with an R filter, B is a signal obtained from a CCD covered with a B filter, and Y ′ when a signal for obtaining a high-frequency luminance signal, Y '= 0.5R + imaging method according to claim 1 or 2, characterized in that it is 0.5B. The imaging method according to claim 2 or 3, wherein the determination of the high-frequency luminance signal by extracting the high frequency of the signal Y '. Generates a low-frequency luminance signal in the vertical direction, to the low-frequency luminance signal, imaging according to any one of claims 1 to 3, wherein generating a luminance signal by adding the high-frequency luminance signal Method. All three pixels are sequentially read out and three image sensors are used. Each CCD is covered with a single color R, G, B filter, and the CCD covered with the G filter is half a pixel in the vertical direction compared to other CCDs. In the imaging device in the vertical pixel shift arrangement in which the minute pixels are shifted,
High-frequency luminance signal generating means for generating a high-frequency luminance signal by alternately using a signal obtained from a CCD whose half-pixel arrangement position is shifted and a signal obtained from another CCD for each field; An imaging apparatus characterized by the above. When a signal obtained from a CCD covered with a G filter is used, Y ′ = G, where G is the signal and Y ′ is a signal for obtaining a high-frequency luminance signal. Item 7. The imaging device according to Item 6 . When a signal obtained from a CCD covered with R and B filters is used, R is a signal obtained from a CCD covered with an R filter, B is a signal obtained from a CCD covered with a B filter, and Y ′ The imaging apparatus according to claim 6 or 7 , wherein when a signal for obtaining a high-frequency luminance signal is used, Y '= 0.5R + 0.5B. The imaging apparatus according to claim 7 or 8 , wherein the high-frequency luminance signal generation unit obtains a high-frequency luminance signal by extracting a high frequency of the signal Y '. Generates a low-frequency luminance signal in the vertical direction, to the low-frequency luminance signal, to claim 6, characterized by further comprising a luminance signal generation means for generating a luminance signal by adding the high-frequency luminance signal 8 The imaging device according to any one of the above. Imaging device according to any one of claims 6 to 10 in the vertical direction sampling frequency, characterized by further comprising a low-pass filter configured as a null point. The imaging apparatus according to claim 11 , wherein the low-pass filter is an optical crystal low-pass filter.

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