Abstract:
A solid-state imaging element includes: a plurality of light receiving elements provided within an imaging region on a semiconductor substrate; a color filter with a plurality of colors provided on the plurality of light receiving elements for filtering with a predetermined color; a vertical shift register disposed adjacent to the light receiving elements for transferring a charge from the light receiving elements; and a first horizontal shift register and a second shift register disposed interposing the imaging region therebetween for transferring a charge transferred from the vertical shift register and outputting a signal in accordance with the charge, respectively; wherein a respective charge of the light receiving elements accumulated therein in accordance with a light transmitted through filters of the same color in the color filter is transferred exclusively via either one of the first horizontal shift register or the second horizontal shift register to be outputted as the signal.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS  
       [0001]     The present application claims the benefit of priority to Japanese Patent Application JP 2005-281847 filed in the Japanese Patent Office on Sep. 28, 2005, which is incorporated herein to the extent permitted by law.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a solid-state imaging element and a solid-state imaging apparatus, and, in particular, it relates to a Charge-Coupled Device (CCD) type solid-state imaging element and a solid-state imaging apparatus provided with at least two or more charge transfer horizontal shift registers.  
         [0004]     2. Related Art  
         [0005]     A conventional CCD type solid-state imaging element is generally composed of a plurality of light receiving elements which are arrayed in vertical and horizontal directions on a semiconductor substrate, a plurality of charge transfer vertical shift registers which are arranged adjacent to each of these light receiving elements, and charge transfer horizontal shift registers which are juxtaposed to one end of each of these charge transfer vertical shift registers, and whereby a charge accumulated in each light receiving element in accordance with an incident light is transferred via the vertical shift registers and the horizontal shift registers.  
         [0006]     An output amplification circuit is provided at one end of each of the charge transfer horizontal shift registers. The output amplification circuit, which is operable to output a voltage corresponding to a quantity of charge transferred, outputs information of a quantity of charge accumulated in each light receiving element as a voltage signal.  
         [0007]     As there is a need for further improvements in functions and operability of a solid-state imaging apparatus provided with such a solid-state imaging element as described above, demands for higher mega-pixels and higher frame rates are increasing for this solid-state imaging element for use in the solid-state imaging apparatus.  
         [0008]     In particular, in the case where the solid-state imaging element is made to have enhanced mega-pixels, its frame rate decreases due to an increased number of light receiving elements formed on a semiconductor substrate, thereby impairing the ease of use and operability of the solid-state imaging apparatus since it becomes difficult to shorten imaging intervals, and an upper limit of continuous imaging is suppressed and so on.  
         [0009]     Therefore, nowadays, in order to enhance pixel-multiplication of the solid-state imaging elements and at the same time to improve the frame rate, there are attempted for the solid-state element to increase its drive frequency and/or to pluralize output channels of signals to be outputted from the horizontal shift register.  
         [0010]     In the case of pluralizing the output channels, charge transfer horizontal shift registers may be provided in a plurality of numbers. More specifically, as shown in  FIG. 10 , it is practiced that a first horizontal shift register  300   a  and a second horizontal shift register  300   b  are disposed facing each other, and interposing therebetween an imaging region  200  in which a plurality of light receiving elements  100  are arrayed in a grid. Refer, for example, to a Japanese Patent Application Publication No. 1996-125158.  
         [0011]     A charge transfer vertical shift register which is disposed adjacent to the light receiving elements  100  for transferring a charge accumulated in a light receiving element  100  to a first horizontal shift register  300   a  or to a second horizontal shift register  300   b  is provided as many numbers as required within an imaging region  200 . And, in particular, in the solid-state imaging element shown in  FIG. 10 , a first vertical shift register  400   a  for transferring a charge to the first horizontal shift register  300   a  and a second vertical shift register  300   b  for transferring a charge to a second horizontal shift register  300   b  are disposed alternately.  
         [0012]     By arranging as described above so that a signal is enabled to be output from the first horizontal shift register  300   a  and the second horizontal shift register  300   b,  the frame rate can be improved. In  FIG. 10, 500   a  denotes a first output amplification circuit provided at one end of the first horizontal shift register  300   a,  and  500   b  denotes a second output amplification circuit provided at one end of the second horizontal shift register  300   b.    
       SUMMARY OF THE INVENTION  
       [0013]     Over the solid-state imaging element described above, in most cases, a color filter is mounted. The color filter is composed by arranging a monochrome filter of respective colors on each light receiving element. In the case of a so-called RGB primary color, consisting of three colors of red (R), green (G) and blue (B), a monochrome filter having either one of these three colors is disposed thereon.  
         [0014]     In  FIG. 10 , the color of a filter arrayed on each light receiving element is denoted by “R”, “G” and “B”, wherein “R” denotes that its portion is a red filter, “G” denotes its portion is a green filter, and “B” denotes its portion is a blue filter. By way of example, the color filter of  FIG. 10  show a color filter configuration of a Bayer array (checkered pattern arrangement) which is widely used in conventional RGB primary color filters.  
         [0015]     The color filter is composed by arranging in repetition a basic unit having respective color filters disposed in a predetermined pattern. In particular, in a color filter of the Bayer array, the basic unit for a repeat pattern is composed of four filters arrayed in 2 by 2 rows and columns; two green color filters disposed diagonally on one way, one red color filter and one blue color filter disposed diagonally on the other way. In the case where the first vertical shift register and the second vertical shift register are disposed alternately as described above, when considering respective quantities of charges at the two green color filters, a charge which was accumulated in one of the light receiving elements thereof and a charge which was accumulated in the other one of the light receiving elements thereof are arranged to be transferred via the first horizontal shift register and the second horizontal shift registers, respectively, so as to be converted to respective signals and outputted separately.  
         [0016]     Therefore, there was a problem that an uncertain output characteristic difference resulted in between a signal outputted from the first horizontal shift register and a signal outputted from the second horizontal shift register due to additions of respective influences of a process variation in the first output amplification circuit provided at the first horizontal shift register and the influence of a process variation in the second output amplification circuit provided at the second horizontal shift register. As to this output characteristic, there may be contained an output characteristic of the amplification circuits, linearity of output, any noise superimposed on the output and the like. In this characteristic, respective characteristics of the vertical shift register, the horizontal shift register and the output circuit are superimposed.  
         [0017]     It is possible for signals differing in filter colors from each other to compensate for the output characteristic difference by an output characteristic compensation processing per color in a separate circuit at the time of generating an image data signal using these signals. However, in the case of the same color as the green color filters, because the same colors are compared simultaneously and visually, there was a problem that an output characteristic difference becomes more conspicuous thereby degrading image quality.  
         [0018]     Therefore, a solid-state imaging element contemplated according to an embodiment of the present invention includes a plurality of light receiving elements mounted within an imaging region on a semiconductor substrate; a color filter with a plurality of colors provided on the plurality of light receiving elements for filtering with a predetermined color; charge transfer vertical shift registers disposed adjacent to each of the plurality of the light receiving elements for transferring charges from the light receiving elements; and a first charge transfer horizontal shift register and a second charge transfer horizontal shift register, disposed so as to sandwich the imaging area, for transferring respective charges transferred from respective vertical shift registers, and outputting signals based on these charges, respectively, wherein respective charges in respective light receiving elements accumulated therein in accordance with light transmitted through filters of the same color in the color filter are allowed to be transferred exclusively via either one of the first horizontal shift register or the second horizontal shift register, and outputted as respective signals.  
         [0019]     Further, the color filter has a configuration where it is constructed by arranging a basic unit in repetition in which respective monochromic color filters are disposed in a predetermined pattern, and also that two or more filters of the same color are arranged in the basic unit. Here, the basic unit has a Bayer array, and the color referred to as the same color is green.  
         [0020]     Still further, a solid-state imaging apparatus according to one embodiment of the present invention, provided with a solid-state imaging element which includes a plurality of light receiving elements mounted within an imaging region on a semiconductor substrate; a color filter with a plurality of colors mounted on the plurality of the light receiving elements for filtering with a predetermined color; charge transfer vertical shift registers disposed adjacent to each of the light receiving elements for transferring charges from the light receiving elements; and a first charge transfer horizontal shift register and a second charge transfer horizontal shift register disposed so as to sandwich the imaging region, for transferring charges transferred from the vertical shift registers, respectively, and outputting respective signals based on these charges, wherein a solid-state imaging element thereof transfers respective charges of the plurality of light receiving elements accumulated therein in accordance with respective light transmitted through filters of the same color in the color filter exclusively via either one of the first horizontal shift register or the second horizontal shift register and outputs as respective signals.  
         [0021]     According to the present invention, it is enabled for respective charges accumulated in respective light receiving elements in accordance with the light transmitted through filters of the same color to be transferred exclusively via either one of the first horizontal shift register or the second horizontal shift register to be outputted as respective signals, thereby ensuring for respective charges in respective light receiving elements accumulated therein in accordance with the light transmitted through the filters of the same color to be transferred via the same horizontal shift register, so that the occurrence of an output characteristic difference can be prevented in the signals with the same color.  
         [0022]     In a solid-state imaging element and a solid-state imaging apparatus provided with this solid-state imaging element according to the present invention, the solid-state imaging element is constructed by forming a plurality of light receiving elements, charge transfer vertical shift registers and charge transfer horizontal shift registers, respectively, in a predetermined position on a semiconductor substrate, and also by forming a color filter including a plurality of filters of a plurality of colors thereon, wherein, in particular, as the horizontal shift registers, a first horizontal shift register and a second horizontal shift register are formed in a manner to interpose a light receiving region in which the plurality of light receiving elements are formed.  
         [0023]     Then, in the solid-state imaging element, respective charges in the plurality of light receiving elements accumulated therein in accordance with respective light transmitted through filters of the same color in the color filter are allowed to be transferred exclusively via either one of the first horizontal shift register or the second horizontal shift register and to be outputted as a signal.  
         [0024]     By the arrangement described above so that respective charges accumulated in respective light receiving elements in accordance with the light passed through the filters of the same color in the color filter are allowed to be transferred via the same horizontal shift register and outputted as a signal, it becomes possible to prevent, in principle, the influence of an output characteristic difference to occur between an output amplification circuit of the first horizontal shift register and an output amplification circuit of the second horizontal shift register at least in the signals of the same color.  
         [0025]     In the description hereinafter, for the sake of simplicity, “a charge in the plurality of light receiving elements accumulated respectively in accordance with the light passed through the filters of the same color in the color filter” will be referred to as “a signal charge”.  
         [0026]     According to an embodiment of the invention, by successful elimination of the influence due to the output characteristic difference in signals of the same color, when generating a predetermined image data signal from these signals, it is able to compensate for an output characteristic difference between the output amplification circuit of the first horizontal shift register and the output amplification circuit of the second horizontal shift register, simply by a gain control processing such as a white balance or the like, thereby preventing a noise occurrence in the image data signal.  
         [0027]     In addition, as it becomes possible to eliminate a compensation signal processing for correcting the output characteristic difference, which was conventionally required, production efficiency of the solid-state imaging element and the solid-state imaging apparatus can be improved. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0028]     Other features and advantages of the present invention will be apparent from the following description taken in connection with accompanying drawings wherein:  
         [0029]      FIG. 1  is a schematic block diagram of a solid-state imaging apparatus according to an embodiment of the invention;  
         [0030]      FIGS. 2A and 2B  are schematic diagrams showing a solid-state imaging element according to the embodiment of the invention, in which  FIG. 2A  shows a readout condition in a first field, while  FIG. 2B  shows a readout condition in a second field;  
         [0031]      FIGS. 3A and 3B  are schematic diagrams showing a solid-state imaging element according to the embodiment of the invention more in detail, in which  FIG. 3A  shows a readout condition in the first field while  FIG. 3B  shows a readout condition in the second field;  
         [0032]      FIGS. 4A and 4B  are schematic diagrams showing a method of forming respective electrodes for vertical charge transfer;  
         [0033]      FIG. 5  is a schematic diagram showing a modified version of the solid-state imaging element according to the embodiment of the invention;  
         [0034]      FIG. 6  is a schematic diagram showing another modified version of the solid-state imaging element according to the embodiment of the invention;  
         [0035]      FIGS. 7A and 7B  are schematic diagrams showing an example of a 2 by 4 complementary color filter;  
         [0036]      FIGS. 8A and 8B  are schematic diagrams showing another example of the 2 by 4 complementary color filter;  
         [0037]      FIGS. 9A and 9B  are schematic diagrams showing an example of a 2 by 8 complementary color filter; and  
         [0038]      FIG. 10  is a schematic diagram showing a conventional solid-state imaging element. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0039]     By referring to the accompanying drawings, preferred embodiments of the present invention will be described in detail in the following.  FIG. 1  is a schematic block diagram showing a solid-state imaging apparatus A according to an embodiment of the present invention. The solid-state imaging apparatus A is a digital still camera or what is called a digital camera. However, it is not limited to the digital still camera, and may include a digital video camera, a camera unit built in a portable telephone and the like.  
         [0040]      FIG. 1  shows a solid-state imaging element  10  for use of imaging in a solid-state imaging apparatus A, and a timing generator  20  for generating a drive signal for driving this solid-state imaging element  10  at a predetermined timing. In addition, in the solid-state imaging apparatus A, there are provided a power source such as a battery, a memory for storing image data signals, a controller for controlling the solid-state imaging apparatus A and the like. Although a circuitry configuring the above-mentioned components is given in a separate circuit (as a chip other than the solid-state imaging element  10 ) in  FIG. 1 , it may be incorporated on the same chip, or may be provided separately on plural chips. By way of example, the solid-state imaging element  10  according to the embodiment of the present invention will be described as a CCD solid-state imaging apparatus of the interlace method.  
         [0041]     The solid-state imaging element  10  is composed of a semiconductor substrate, on this semiconductor substrate, there are provided a plurality of light receiving elements  11  consisting of photo diodes arrayed vertically and horizontally at a predetermined distance, a first horizontal shift register  13   a  and a second horizontal shift register  13   b  disposed in a manner to interpose an imaging region  12  in which a plurality of light receiving elements  11  are arrayed, a first vertical shift register  14   a  disposed along one side of a row of light receiving elements  11  disposed in vertical directions, and a second vertical shift register  14   b  disposed along the other side of the row of light receiving elements  11 .  
         [0042]     Further, over the semiconductor substrate, a color filter is provided. According to the embodiment of the present invention, the color filter is composed of a so-called 2 by 2 primary color filter having a Bayer array, in which green color filters are arranged in a checkered pattern. For convenience of description, respective colors of filters mounted on each of the light receiving elements  11  are denoted by “R”, “G” and “B”, where “R” denotes that a red color filter is provided, “G” denotes that a green color filter is provided, and “B” denotes that a blue color filter is provided.  
         [0043]     As to the horizontal transfer, in this embodiment of the present invention, the horizontal transfer therein uses a well-known two phase drive method. Two phases of a drive signal are denoted by a first horizontal drive signal Hφ 1  and a second horizontal drive signal Hφ 2 , respectively, which are supplied to both of the first horizontal shift register  13   a  and the second horizontal shift register  13   b,  for application to enable charge transfer.  
         [0044]     In particular, the first horizontal shift register  13   a  and the second horizontal shift register  13   b  are disposed opposite to each other so as to interpose the imaging region  12  in which a plurality of light receiving elements  11  are mounted, then in response to a first horizontal drive signal Hφ 1  and a second horizontal drive signal Hφ 2  supplied from a timing generator  20 , the first horizontal shift register  13   a  transfers a signal charge in a direction from the left-hand side to the right-hand side in  FIG. 1 , while the second horizontal shift register  13   b  transfers a signal charge in a direction from the right-hand side to the left-hand side in  FIG. 1 .  
         [0045]     At one ends of the first horizontal shift register  13   a  and the second horizontal shift register  13   b,  there are provided a first output amplification circuit  15   a  and a second output amplification circuit  15   b,  respectively. By means of the first output amplification circuit  15   a  and the second output amplification circuit  15   b,  and in response to a signal charge transferred thereto, a predetermined voltage signal is generated and outputted therefrom, respectively.  
         [0046]     In the following description of the embodiment of the present invention, the first horizontal shift register  13   a  is inclusive of the first output amplification circuit  15   a,  and the second horizontal shift register  13   b  is inclusive of the second output amplification circuit  15   b.    
         [0047]     The first vertical shift register  14   a  is provided on one side of a column of light receiving elements  11  disposed in vertical directions in  FIG. 1 , and the second vertical shift register  14   b  is provided on the other side thereof. The first vertical shift register  14   a  and the second vertical shift register  14   b  are disposed alternately in the imaging region  12  interposing each column of light receiving elements  11 .  
         [0048]     The first vertical shift register  14   a  and the second vertical shift register  14   b  are arranged to be driven in response to a first vertical drive signal Vφ 1 , a second vertical drive signal Vφ 2 , a third vertical drive signal Vφ 3 , and a fourth vertical drive signal Vφ 4  supplied from a timing generator  20 . The first vertical shift register  14   a  is operable to transfer a signal charge from the bottom to the upper direction in  FIG. 1  for enabling the signal charge to be read out by the first horizontal shift register  13   a,  and the second vertical shift register  14   b  is operable to transfer a signal charge from the upper to the bottom direction in  FIG. 1  for enabling the signal charge to be read out by the second horizontal shift register  13   b.    
         [0049]     When reading out image data imaged in the solid-state imaging element  10  constructed as described above, as a first field, signal charges are read out and transferred from light receiving elements  11  in odd-numbered columns in the imaging region  12  shown in  FIG. 1 , subsequently, as a second field, signal charges are read out and transferred from light receiving elements  11  in even-numbered columns in the imaging region  12 .  
         [0050]     Here, according to the embodiment of the present invention, as shown in  FIG. 2A , when reading signal charges in the first field from light receiving elements  11  in odd numbered columns, a signal charge from a light receiving element  11  provided with a green color filter is read out to the first vertical shift register  14   a,  and a signal charge from a light receiving element  11  provided with a red color filter is read out to the second vertical shift register  14   b.    
         [0051]     The signal charge read out by the first vertical shift register  14   a  is transferred to the first horizontal shift register  13   a,  to be output from the first horizontal shift register  13   a  as a first green color signal. Further, the signal charge read out by the second vertical shift register  14   b  is transferred to the second horizontal shift register  13   b  to be output therefrom as a red color signal.  
         [0052]     Subsequently, when reading out signal charges in the second field from light-receiving elements  11  in even-numbered columns in the imaging region  12 , a signal charge from a light receiving element  11  provided with a green color filter is read out by a first vertical shift register  14   a,  and a signal charge from a light receiving element  11  provided with a blue color filter is read out by a second vertical shift register  14   b.    
         [0053]     The signal charge read out by the first vertical shift register  14   a  is transferred to the first horizontal shift register  13   a  to be output therefrom as a second green color signal. Further, the signal charge read out by the second vertical shift register  14   b  is transferred to the second horizontal shift register  13   b  to be output therefrom as a blue color signal.  
         [0054]     As described hereinabove, the first green color signal read out in the first field and the second green color signal read out in the second field are transferred exclusively via first vertical shift registers, respectively, to be output from the first horizontal shift register  13   a,  thereby enabling to eliminate an output characteristic difference between the first green color signal and the second green color signal, and produce a high quality image data signal.  
         [0055]     As described above, because that in the first field, signal charges of the light receiving elements  11  provided with the green filter are read out to the first vertical shift register  14   a  while signal charges of the light receiving element  11  provided with the red filter are read out to the second vertical shift register  14   b,  and also that in the second field, signal charges of the light receiving elements  11  provided with the green filter are read out to the first vertical shift register  14   a  while signal charges of the light receiving elements  11  provided with the blue filter are read out to the second vertical shift register  14   b,  as shown in  FIGS. 3A and 3B , respective light receiving elements  11  are adjusted with respect to the directions of readout of signal charges.  
         [0056]     For the light receiving elements  11  provided with a green filter, a channel stop  16  is provided on the side of the second vertical shift register  14   b  opposite to the first vertical shift register  14   a,  while for the light receiving elements  11  provided with the red filter and the blue filter, a channel stop  16  is provided on the side of each of the first vertical shift registers  14   a  opposite to the second vertical shift register  14   b,  so that the directions of transfer of the signal charges are controlled by this channel stop  16  to ensure for the signal charges to be read either by a predetermined first vertical shift register  14   a  or a predetermined second vertical shift register  14   b.    
         [0057]     As shown in  FIGS. 3A and 3B , a channel stop  16  provided in a staggered pattern on both sides of the vertical shift register is connected not to be isolated electrically between a predetermined pixel while it is arranged in the staggered pattern, thereby ensuring to perform the function of a conventional channel stop. That is, for the channel stop  16 , it is ensured not to impair the functions thereof to suppress a difference of potentials between an edge portion and a center portion on the surface of the substrate in the imaging region by applying a preset potential (presently, a ground potential is widely used), and suppress a noise by disposing holes generated in the light receiving elements or in the vertical registers to a preset potential.  
         [0058]     With reference to  FIGS. 3A and 3B , “ 1 ”, “ 2 ”, “ 3 ” and “4” shown in the columns of the first vertical register  14   a  and the second vertical shift register  14   b,  denote respective registers to which a bias of a first vertical drive signal Vφ 1 , a second vertical drive signal Vφ 2 , a third vertical drive signal Vφ 3 , and a fourth vertical drive signal Vφ 4  is applied, respectively. In the first field, a readout potential is formed by applying a readout voltage to the electrode of “1” register portion, so as to read out a signal charge from a light receiving element  11  provided with a green filter to a first vertical shift register  14   a,  at the same time to read out a signal charge from a light receiving element  11  provided with a red filter to a second vertical shift register  14   b.  In the second field, a readout potential is formed by applying a readout voltage to the electrode of a “3” register portion, so as to read out a signal charge from a light receiving element  11  provided with a green filter to a first vertical shift register  14   a,  and at the same time to read out a signal charge from a light receiving element  11  provided with a blue filter to a second vertical shift register  14   b.    
         [0059]     Respective electrodes to which each of the first vertical drive signal Vφ 1 , the second vertical drive signal Vφ 2 , the third vertical drive signal Vφ 3  and the fourth vertical drive signal Vφ 4  is applied are formed in such a manner as will be described in the following.  
         [0060]     With reference to  FIG. 4A , first of all, on a semiconductor substrate, a second electrode  22  is formed to cover a portion “ 2 ” of a vertical register, and also a fourth electrode  24  is formed to cover a portion “ 4 ” of the vertical register. In particular, the second electrode  22  and the fourth electrode  24  are formed in a continuous linear pattern extending in the horizontal directions as shown in  FIG. 4A  so as to be able to apply a vertical drive signal applied from a bus line provided outside the pixel region, which is not shown, in the horizontal directions in  FIG. 4A .  
         [0061]     Then, as shown in  FIG. 4B , on the second electrode  22 , a first electrode  21  is formed linearly likewise the second electrode  22 , and also, on the fourth electrode  24 , a third electrode  23  is formed linearly likewise the fourth electrode  24 .  
         [0062]     In particular, the first electrode  21  is formed narrower than the second electrode  22  and to have protrusions projecting in orthogonal directions so as to cover each portion “ 1 ” of the vertical register. The third electrode  23  is formed narrower than the fourth electrode  24  and to have protrusions projecting in orthogonal directions so as to cover each portion “ 3 ” of the vertical register.  
         [0063]     Then, on the first electrode  21 , second electrode  22 , third electrode  23  and fourth electrode  24 , a semiconductor layer to serve as a first vertical shift register  14   a  and a second vertical shift register  14   b  is formed.  
         [0064]     In the above description of the embodiment of the present invention, although it is described that the directions of transfer of signal charges in the first horizontal shift register  13   a  and the second horizontal shift register  13   b  are opposite to each other, however, it is not limited thereto, and it may be arranged as shown in  FIG. 5  so that the first horizontal shift register  13   a  and the second horizontal shift register  13   b  transfer their signal charges in the same direction.  
         [0065]     Further, in the above description of the embodiment of the present invention, although the first horizontal shift register  13   a  and the second horizontal shift register  13   b  are provided parallel to the horizontal directions as shown in  FIG. 1 , and the first vertical shift register  14   a  and the second vertical shift register  14   b  are provided parallel to the vertical directions as shown in  FIG. 1 , it is not limited thereto, and it may be arranged to the same effect so that a first horizontal shift register  13   a′  and a second horizontal shift register  13   b′  are provided parallel to the longitudinal directions with an imaging region  12  interposed therebetween as shown in  FIG. 6 , as well as a first vertical shift register  14   a′  and a second vertical shift register  14   b′  are provided parallel to the horizontal directions as shown in  FIG. 6 .  
         [0066]     The term “horizontal” in the first horizontal shift register  13   a,    13   a′  and the second horizontal shift register  13   b,    13   b′  as well as the term “vertical” in the first vertical shift register  14   a,    14   a′  and the second vertical shift register  14   b,    14   b′  are used simply to discriminate between the first horizontal shift register  13   a,    13   a′  and the second horizontal shift register  13   b,    13   b′  as well as between the first vertical shift register  14   a,    14   a′  and the second vertical shift register  14   b,    14   b′,  thereby not limiting the directions thereof.  
         [0067]     Further, the first horizontal shift register  13   a,    13   a′  and the second horizontal shift register  13   b,    13   b′  are not limited to two, and any number thereof more than two may be provided as required.  
         [0068]     Still further, in the embodiment of the present invention described above, the color filter is described to be a 2 by 2 primary color filter, however, it is not limited to the 2 by 2 primary color filter. In addition to the primary color filter, a complementary color filter using cyan (Cy), yellow (Ye), magenta (Mg) and green (G) may be used as well. Further, the arrangement of the filters is not limited to the 2 by 2, and it may be 2 by 4.  
         [0069]     With reference to  FIGS. 7A and 7B , when a 2 by 4 complementary color filter is used, readout directions of signal charges to a first vertical shift register  14   a  and a second vertical shift register  14   b  are shown by void arrows, respectively, where  FIG. 7A  shows a readout condition in a first field while  FIG. 7B  shows a readout condition in a second field. In the first field, a readout signal is applied to a first electrode  21 , and in the second field, a readout signal is applied to a third electrode  23  for reading out a signal charge from a predetermined light receiving element  11 .  
         [0070]     With reference to  FIGS. 8A and 8B , in the case of a modified version of the 2 by 4 complementary color filter of  FIGS. 7A and 7B , readout directions of signal charges to a first vertical shift register  14   a  and a second vertical shift register  14   b  are shown by void arrows, where  FIG. 8A  shows a readout condition in the first field, while  FIG. 8B  shows a readout condition in the second field.  
         [0071]     In the 2 by 4 complementary color filter shown in  FIGS. 8A and 8B , arrangements of cyan (Cy) and yellow (Ye) are replaced in part from those in  FIGS. 7A and 7B .  
         [0072]     With reference to  FIGS. 9A and 9B , in the case where a 2 by 8 complementary color filter is used, readout directions of signal charges to a first vertical shift register  14   a  and a second vertical shift register  14   b  are shown by void arrows, where  FIG. 9A  shows a readout condition in the first field while  FIG. 9B  shows a readout condition in the second field. In the first field, a readout signal is applied to a first electrode  21 , and in the second field, a readout signal is applied to a third electrode  23 , respectively, to read out a signal charge from a predetermined light receiving element  11 .  
         [0073]     The present invention contains subject mater related to Japanese Patent Application No. JP2005-281847 filed in the Japanese Patent Office on Sep. 28, 2005, the entire contents of which being incorporated herein by reference.  
         [0074]     It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof.