Abstract:
A solid state imaging device includes an imaging area where a plurality of first pixels and a plurality of second pixels are respectively arranged in the form of a matrix, each of the first pixels and the second pixels having a photoelectric conversion portion and outputting a signal in accordance with brightness of incident light when selected; a plurality of first memories that respectively store signals of selected first pixels out of the plurality of first pixels; and a plurality of second memories that are respectively connected in parallel to the first memories and respectively store signals of selected second pixels out of the plurality of second pixels. The signals stored in the first memories and in the second memories are successively read to a horizontal signal line.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims priority under 35 U.S.C. §119 on Patent Application No. 2005-333322 filed in Japan on Nov. 17, 2005, the entire contents of which are hereby incorporated by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     The present invention relates to a solid state imaging device, a method for driving the same, and a camera, and more particularly, it relates to a solid state imaging device for use in a high-definition camera or the like, a method for driving the same, and a camera using the same.  
         [0003]      FIG. 7  shows an exemplified conventional solid state imaging device including MOS transistors. As shown in  FIG. 7 , the solid state imaging device has an imaging area  120  where a plurality of amplifying unit pixels are two-dimensionally arranged. Each amplifying unit pixel includes a photodiode (PD) portion  111 ; a floating diffusion portion (FD)  117  connected to the PD portion  111  through a read transistor  112  for storing charge read from the PD portion  111 ; a reset transistor  113  for initializing the state of the FD portion  117 ; and a detection transistor  114  connected to the FD portion  117  for controlling the signal output of the pixel.  
         [0004]     Each row of the amplifying unit pixels is selected by a vertical shift register  141  operated in accordance with a drive timing pulse sent from a timing generator circuit  140 . Signals of the amplifying unit pixels of the selected row are stored in row memories  123 . Thereafter, a horizontal shift register  142  is driven by a drive timing pulse sent from the timing generator circuit  140 , so that the pixel signals stored in the row memories  123  can be successively output as device signals from an output amplifier  127  through a horizontal signal line  126 .  
         [0005]      FIG. 8  is a timing chart in a horizontal drive period besides a vertical blanking period of the conventional solid state imaging device. A horizontal drive period is composed of a horizontal blanking period and a horizontal active period. The horizontal blanking period starts at timing T 1 , a reset pulse is applied, at timing T 2 , to a reset pulse line  132  on an nth row (wherein n is a positive integer) with a voltage of a V DD  power supply  116  set to a high (H) level, so as to simultaneously reset the FD portion  117  and select the detection transistor  114  on the nth row. Thereafter, a read pulse is applied to a read pulse line  131  at timing T 3 , so as to read the charge of the PD portion  111  to the FD portion  117 . A signal corresponding to the read charge is stored in the row memory  123  through the detection transistor  114 . Then, a reset pulse is applied, at timing T 5 , to the reset pulse line  132  on the nth row with the voltage of the V DD  power supply  116  set to a low (L) level, so as to set the potential of the FD portion  117  to a low level and place the detection transistor  114  on the nth row in an unselected state. The signals stored in the row memories  123  are successively output from the solid state imaging device by operating the horizontal shift register  142  during the horizontal active period.  
         [0006]     In this manner, in the solid state imaging device having one row memory for one row of pixels correspondingly to each horizontal signal line  126 , images are generally drawn by reading signals from pixels and storing them in memories in a horizontal blanking period included in a horizontal drive period besides a vertical blanking period and outputting the signals from the row memories in a horizontal active period included in the horizontal drive period besides the vertical blanking period (see, for example, Japanese Laid-Open Patent Publication Nos. 9-163234 and 4-877).  
         [0007]     In the conventional solid state imaging device, if signals are read from pixels and the read signals are stored in row memories in the horizontal active period included in the horizontal drive period besides the vertical blanking period, signals of pixels on an (n+1)th row are overwritten on signals of pixels on the nth row remaining in the row memories  123 , and therefore, an accurate image cannot be obtained and the image is disadvantageously degraded.  
         [0008]     Although the horizontal drive period besides the vertical blanking period is described above, since an image is basically not drawn in the vertical blanking period, pixel signals may be read and the read signals may be stored in row memories in the horizontal active period included in the horizontal drive period as an exception.  
         [0009]     In driving a solid state imaging device for a high quality high-definition image, however, all of the horizontal blanking period, the horizontal active period and the horizontal drive period as a sum of the horizontal blanking period and the horizontal active period are much shorter than in conventional technique. Therefore, it is necessary to rapidly perform an operation for reading signals from pixels and storing the read signals in row memories and an operation for outputting the signals from the row memories in a solid state imaging device for a high-definition image. Accordingly, signals stored in row memories exhibit unstable values, and hence, there arises a problem that the quality of an image created in accordance with the signals read from the row memories is largely degraded.  
       SUMMARY OF THE INVENTION  
       [0010]     The present invention was devised to overcome the aforementioned conventional problems, and an object of the invention is realizing a high quality solid state imaging device capable of stably storing signals in row memories and reading the signals from the row memories.  
         [0011]     In order to achieve the object, the solid state imaging device of the invention includes two row memories provided in parallel.  
         [0012]     Specifically, the solid state imaging device of this invention includes an imaging area where a plurality of first pixels and a plurality of second pixels are respectively arranged in the form of a matrix, each of the first pixels and the second pixels having a photoelectric conversion portion and outputting a signal in accordance with brightness of incident light when selected; a plurality of first memories that respectively store signals of selected first pixels out of the plurality of first pixels; a plurality of second memories that are respectively connected in parallel to the first memories and respectively store signals of selected second pixels out of the plurality of second pixels; a horizontal signal line to which the signals stored in the first memories and in the second memories are read; and an output amplifier connected to the horizontal signal line, and an operation for reading the signals stored in the first memories to the horizontal signal line and an operation for outputting the signals from the output amplifier are performed at least partly in parallel with an operation for storing the signals of the selected second pixels out of the plurality of second pixels in the second memories, and an operation for reading the signals stored in the second memories to the horizontal signal line and an operation for outputting the signals from the output amplifier are performed at least partly in parallel with an operation for storing the signals of the selected first pixels out of the plurality of first pixels in the first memories.  
         [0013]     The solid state imaging device of this invention includes the plural first memories for storing the signals of the selected first pixels out of the plural first pixels and the plural second memories respectively connected to the first memories in parallel for storing the signals of the selected second pixels out of the plural second pixels. Therefore, the operation for reading signals from pixels and storing them in memories and the operation for outputting the signals stored in the memories can be performed in parallel. Accordingly, there is no need to complete the operation for reading the signals from the pixels and storing them in the memories within a horizontal blanking period included in a horizontal drive period besides a vertical blanking period, and hence, time for storing the signals in the memories can be sufficiently secured. As a result, the signals can be stably stored in the memories and can be stably read from the memories in the present solid state imaging device.  
         [0014]     Preferably, in the solid state imaging device of the invention, the plurality of first pixels are disposed on odd rows in the imaging area, the plurality of second pixels are disposed on even rows in the imaging area, the plurality of first memories and the plurality of second memories are disposed correspondingly to respective columns of the imaging area, first pixels disposed on one odd row out of the plurality of first pixels are simultaneously selected, second pixels disposed on one even row out of the plurality of second pixels are simultaneously selected, and the operation for reading the signals stored in the first memories to the horizontal signal line and the operation for outputting the signals from the output amplifier are performed alternately with the operation for reading the signals stored in the second memories to the horizontal signal line and the operation for outputting the signals from the output amplifier.  
         [0015]     The solid state imaging device of the invention may further include a plurality of drive pulse lines for driving the plurality of first pixels and the plurality of second pixels, and at least one of the operation for reading the signals stored in the first memories to the horizontal signal line and the operation for outputting the signals from the output amplifier or at least one of the operation for reading the signals stored in the second memories to the horizontal signal line and the operation for outputting the signals from the output amplifier is preferably stopped while a drive pulse is being applied to at least one of the plurality of drive pulse lines. Thus, it is possible to suppress degradation in picture quality caused when noise derived from the drive pulse is superposed on a signal output from a memory.  
         [0016]     Alternatively, at least one of the operation for reading the signals stored in the first memories to the horizontal signal line and the operation for outputting the signals from the output amplifier or at least one of the operation for reading the signals stored in the second memories to the horizontal signal line and the operation for outputting the signals from the output amplifier is preferably stopped at a rise and a fall of a drive pulse applied to at least one of the plurality of first pixels and the plurality of second pixels. Thus, noise derived from the drive pulse can be prevented from being superposed on a signal output from a memory and increase in time required for outputting signals from memories can be suppressed.  
         [0017]     In this case, the solid state imaging device preferably further includes a horizontal shift register for controlling read of the signals stored in the first memories and the signals stored in the second memories to the horizontal signal line, and an operation of at least one of the horizontal shift register and the output amplifier is preferably stopped when the operation for reading the signals stored in the first memories or the second memories to the horizontal signal line is stopped.  
         [0018]     Furthermore, the solid state imaging device preferably further includes a plurality of vertical signal lines each for connecting each column of the plurality of first pixels and the plurality of second pixels to each pair of a first memory and a second memory disposed correspondingly to each column of the plurality of first pixels and the plurality of second pixels, at least a part of the plurality of first pixels and at least a part of the plurality of second pixels preferably includes a floating diffusion portion for reading charge of the photoelectric conversion portion; a read transistor connected between the photoelectric conversion portion and the floating diffusion portion; a reset transistor for initializing a state of the floating diffusion portion; and a detection transistor connected between the floating diffusion portion and the vertical signal line, and the plurality of drive pulse lines include a plurality of read pulse lines connected to gates of the read transistors disposed in the respective rows of the imaging area, a plurality of reset pulse lines connected to gates of the reset transistors and power lines respectively connected to the reset transistors and the detection transistors.  
         [0019]     In the solid state imaging device of the invention, the operation for storing the signals of the selected first pixels out of the plurality of first pixels in the first memories and the operation for storing the signals of the selected second pixels out of the plurality of second pixels in the second memories are preferably performed over a horizontal blanking period and a horizontal active period that is included neither in a vertical blanking period nor in a horizontal blanking period. Thus, even when the horizontal blanking period is short, time spent on the operation for reading the signals from the pixels can be sufficiently secured, so as to largely improve the picture quality.  
         [0020]     In the solid state imaging device of the invention, at least a part of the operation for reading the signals stored in the first memories to the horizontal signal and the operation for outputting the signals from the output amplifier is preferably performed in parallel with at least a part of the operation for storing the signals of the selected second pixels out of the plurality of second pixels in the second memories in one horizontal blanking period, and at least a part of the operation for reading the signals stored in the second memories to the horizontal signal and the operation for outputting the signals from the output amplifier is preferably performed in parallel with at least a part of the operation for storing the signals of the selected first pixels out of the plurality of first pixels in the first memories in another horizontal blanking period. Thus, even when the horizontal drive period is short, the time spent on the operation for reading the signals from the pixels can be sufficiently secured, so as to largely improve the picture quality.  
         [0021]     The solid state imaging device of the invention preferably further includes an analog/digital conversion portion for converting signals sent from the first memories and the second memories into digital signals.  
         [0022]     The camera of this invention includes the solid state imaging device of the invention.  
         [0023]     The method of this invention for driving a solid state imaging device including a plurality of pixels respectively having photoelectric conversion portions and arranged in the form of a matrix; and a plurality of first memories and a plurality of second memories each receiving signals of pixels of a corresponding column, includes the steps of (a) selecting pixels disposed on one row and storing signals of the pixels disposed on the one row in the first memories; (b) successively reading and outputting the signals stored in the first memories; (c) selecting pixels disposed on another row different from the one row and storing signals of the pixels disposed on the different row in the second memories; and (d) successively reading and outputting the signals stored in the second memories, and the step (b) and the step (c) are carried out in parallel at least partly, and the step (d) and the step (a) are carried out in parallel at least partly.  
         [0024]     In the method for driving a solid state imaging device of this invention, an operation for reading signals from pixels and storing them in memories and an operation for outputting signals stored in the memories can be performed in parallel. Accordingly, there is no need to complete the operation for reading the signals from the pixels and storing them in the memories within a horizontal blanking period included in a horizontal drive period besides a vertical blanking period, and hence, time for storing the signals in the memories can be sufficiently secured.  
         [0025]     Preferably, in the method for driving a solid state imaging device of the invention, a drive pulse is applied to the pixels disposed on the one row in the step (a), the signals are stopped to be read and output in the step (d) when the drive pulse rises in the step (a), a drive pulse is applied to the pixels disposed on the different row in the step (c), and the signals are stopped to be read and output in the step (b) when the drive pulse rises in the step (c).  
         [0026]     In the method for driving a solid state imaging device of the invention, the step (a) and the step (b) are preferably carried out in a horizontal blanking period and in a horizontal active period besides a vertical blanking period and the horizontal blanking period.  
         [0027]     In the method for driving a solid state imaging device of the invention, at least part of the step (b) and the step (c) is carried out in parallel in one horizontal blanking period, and at least part of the step (d) and the step (a) is carried out in parallel in another horizontal blanking period. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0028]      FIG. 1  is a circuit diagram of a solid state imaging device according to Embodiment 1 of the invention;  
         [0029]      FIG. 2  is a timing chart in a horizontal drive period besides a vertical blanking period of the solid state imaging device of Embodiment 1;  
         [0030]      FIG. 3  is a timing chart for showing a driving state of a solid state imaging device according to Modification 1 of Embodiment 1;  
         [0031]      FIG. 4  is a timing chart for showing a driving state of a solid state imaging device according to Modification 2 of Embodiment 1;  
         [0032]      FIG. 5  is a timing chart for showing a driving state of a solid state imaging device according to Modification 3 of Embodiment 1;  
         [0033]      FIG. 6  is a circuit diagram of a solid state imaging device according to Modification 4 of Embodiment 1;  
         [0034]      FIG. 7  is a circuit diagram of a conventional solid state imaging device; and  
         [0035]      FIG. 8  is a timing chart for showing a driving state of the conventional solid state imaging device. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0000]     Embodiment 1  
         [0036]     Embodiment 1 of the invention will now be described with reference to the accompanying drawings.  FIG. 1  shows the circuit configuration of a solid state imaging device according to Embodiment 1 of the invention. As shown in  FIG. 1 , the solid state imaging device of this embodiment has an imaging area  10  where a plurality of amplifying unit pixels  21  are arranged in the form of a matrix. Although the imaging area  10  shown in  FIG. 1  has a matrix of two rows by three columns, the numbers of rows and columns can be arbitrarily set.  
         [0037]     Each pixel  21  includes a photoelectric conversion portion (PD portion)  11  of a photodiode formed on a semiconductor substrate and a floating diffusion (FD) portion  17  connected to the PD portion  11  through a read transistor  12  for storing charge of the PD portion  11 . The FD portion  17  is connected to a V DD  power supply  16  through a reset transistor  13  and to a vertical signal line  15  through a detection transistor  14 .  
         [0038]     The gate of the read transistor  12  is connected to a read pulse line  31 , and the gate of the reset transistor  13  is connected to a reset pulse line  32 . The read pulse line  31  and the reset pulse line  32  are provided correspondingly to each row of pixels, and the vertical signal line  15  is provided correspondingly to each column of the pixels.  
         [0039]     A first memory  23  and a second memory  24  working as row memories for storing signals of pixels of a corresponding one row are connected to each vertical signal line  15 , and the first memory  23  and the second memory  24  are connected to each other in parallel. The output terminals of the first memory  23  and the second memory  24  are both connected to a horizontal signal line  26  through a horizontal control transistor  25 , and the horizontal signal line  26  is connected to an output amplifier  27 .  
         [0040]     The read transistor  12  and the reset transistor  13  are driven by a vertical shift register  41 , and the horizontal control transistor  25  is driven by a horizontal shift register  42 . The vertical shift register  41  and the horizontal shift register  42  are driven by a timing generator  40 .  
         [0041]     Now, the operation of the solid state imaging device of this embodiment will be described.  FIG. 2  is a timing chart in a horizontal drive period besides a vertical blanking period of the solid state imaging device of this embodiment. Although timing for driving a (n+1)th row (wherein n is a positive integer) is shown in  FIG. 2 , the timing for driving an nth row is substantially the same as that shown in  FIG. 2  except that a memory for storing signals and a memory for outputting signals are reversed.  
         [0042]     A horizontal drive period is composed of a horizontal blanking period and a horizontal active period. The horizontal blanking period starts at timing T 1 , and an operation for reading signals from respective pixels  21 B disposed on the (n+1)th row and storing them in the second memories  24  is started. The operation for reading the pixel signals of the (n+1)th row includes a series of operations including an operation for selecting each pixel  21 B of the (n+1)th row, an operation for resetting the corresponding FD portion  17 , an operation for reading charge of the corresponding PD portion  11 , an operation for amplifying the charge of the PD portion  11  and an operation for unselecting each pixel  21 B of the (n+1)th row.  
         [0043]     At timing T 2 , with a voltage at a high (H) level applied to the V DD  power supply  16 , a reset pulse is applied to the reset pulse line  32 . Thus, the reset transistor  13  is turned on so as to reset the FD portion  17  and select the detection transistor  14  at the same time.  
         [0044]     Next, at timing T 3 , a read pulse is applied to the read pulse line  31 , so as to turn on the read transistor  12 . Thus, the charge of the PD portion  11  is read to the FD portion  17 , and a signal corresponding to the charge read from the PD portion  11  is output to the corresponding vertical line  15  through the detection transistor  14 . The signal output to the vertical signal line  15  is stored in the corresponding second memory  24 .  
         [0045]     Then, after terminating the horizontal blanking period at timing T 4 , the voltage of the V DD  power supply  16  is set to a low (L) level, and a reset pulse is applied again to the reset pulse line  32  at timing T 5 . Thus, the potential of the FD portion  17  is set to L level, and hence, the detection transistor  14  is placed in an unselected state. Thereafter, the voltage of the V DD  power supply  16  is set to H level at timing T 7 , and thus, the operation for reading the signals from the respective pixels  21 B of the (n+1)th row and storing them in the second memories  24  is completed.  
         [0046]     On the other hand, after terminating the horizontal blanking period at timing T 4 , an operation for reading signals of respective pixels  21 A of the nth row having been stored in the first memories  23  to the horizontal signal line  26  is started, and the signals read to the horizontal signal line  26  are successively output from the output amplifier  27 . In this manner, a part of the operation for reading the signals from the pixels  21 B of the (n+1)th row and storing them in the second memories  24  and the operation for outputting the signals of the pixels  21 A of the nth row having been stored in the first memories  23  are performed in parallel in the horizontal active period following the horizontal blanking period.  
         [0047]     In a conventional solid state imaging device, an operation for reading signals from pixels and storing them in memories and an operation for reading signals from the memories should be separately performed, and therefore, it is necessary to complete the operation for reading the signals from the pixels and storing them in the memories within the horizontal blanking period. In a solid state imaging device for a high quality high-definition image, however, the horizontal blanking period is 4 μsec. or less, and therefore, it is difficult to complete, within this short horizontal blanking period, the operation for reading the signals from the pixels and storing them in the memories.  
         [0048]     On the other hand, in the solid state imaging device of this embodiment, the operation for reading the signals from the pixels and storing them in the memories and the operation for reading the signals from the memories can be performed in parallel. Therefore, a part of the operation for reading the signals from the pixels and storing them in the memories can be performed in the horizontal active period besides the horizontal blanking period. Accordingly, since the operation for reading the signals from the pixels and storing them in the memories is allowed to have a time margin, the signals can be stably stored in the memories, and as a result, the picture quality of the solid state imaging device can be largely improved.  
         [0049]     Although the signals of the pixels  21 A of the nth row are stored in the first memories  23  and the signals of the pixels  21 B of the (n+1)th row are stored in the second memories  24  in this embodiment, the signals of the pixels  21 A of the nth row may be stored in the second memories  24  and the signals of the pixels  21 B of the (n+1)th row may be stored in the first memories  23  as far as the signals are stored in the respective memories alternately.  
         [0050]      FIG. 1  shows the case where each pixel includes the reset transistor and the reset pulse line is provided in each row, but the same effects is obtainable even when pixels arranged in plural rows share the reset transistor and the reset pulse line is provided in every plural rows.  
         [0000]     Modification 1 of Embodiment 1  
         [0051]      FIG. 3  is a timing chart in a horizontal drive period besides a vertical blanking period of a solid state imaging device according to Modification 1 of Embodiment 1. The solid state imaging device of this modification has the same circuit configuration as the solid state imaging device of Embodiment 1. In the solid state imaging device of this modification, while a reset pulse is being applied to the reset pulse line  32 , the operation of the horizontal shift register  42  and the operation of the output amplifier  27  for outputting signals are stopped.  
         [0052]     In the case where the operation for reading the signals from the respective pixels  21 B of the (n+1)th row and storing them in the second memories  24  and the operation for outputting the signals of the respective pixels  21 A of the nth row from the first memories  23  are performed in parallel, it is apprehended that when a reset pulse is applied from the reset pulse line  32  to the respective pixels  21 B of the (n+1)th row, a crosstalk signal of the reset pulse is superposed as noise on the signals of the pixels  21 A of the nth row. When the noise is thus caused, signals ultimately output from the output amplifier include noise, and hence, an image created in accordance with the output signals is largely degraded in the picture quality.  
         [0053]     In the solid state imaging device of this modification, while a drive pulse is being applied to the reset pulse line  32 , the operation of the horizontal shift register  42  is stopped so as to stop the operation for reading the signals of the pixels  21 A of the nth row having been stored in the first memories  23  to the horizontal signal line  26  and the operation for outputting the signals read to the horizontal signal line  26  from the output amplifier  27 . Therefore, the signals output from the output amplifier  27  can be free from noise derived from the reset pulse, and hence, an image with high picture quality can be obtained.  
         [0054]     Although the operation for reading the signals of the pixels  21 A of the nth row from the first memories  23  is described in this modification, the operation of the horizontal shift register  42  is similarly stopped while reading the signals of the pixels  21 B of the (n+1)th row from the second memories  24 .  
         [0055]     Furthermore, in the case where the solid state imaging device includes, apart from the reset pulse line, another drive pulse line to which a dive pulse is applied in the horizontal active period, the operation of the horizontal shift register may be stopped while the drive pulse is being applied to this drive pulse line.  
         [0056]     Although the signal output operation is stopped by stopping the horizontal shift register in this modification, it may be stopped by stopping the operation of the output amplifier instead.  
         [0000]     Modification 2 of Embodiment 1  
         [0057]      FIG. 4  is a timing chart in a horizontal drive period besides a vertical blanking period of a solid state imaging device according to Modification 2 of Embodiment 1. The solid state imaging device of this modification has the same circuit configuration as the solid state imaging device of Embodiment 1. In the solid state imaging device of this modification, the operation of the horizontal shift register  42  and the operation of the output amplifier  27  for outputting signals are stopped at a rise and a fall of a drive pulse applied to a drive pulse line such as the reset pulse line  32 .  
         [0058]     Noise derived from a drive pulse is easily caused at a rise and a fall of the drive pulse. Therefore, when the operation for reading a signal from a memory is stopped at a rise and a fall of a drive pulse, a signal substantially free from noise derived from the drive pulse can be obtained and time for stopping the output operation can be short.  
         [0059]     As a result, the operation for reading signals having been stored in memories to the horizontal signal line can be performed with a time margin, and hence an image can be accurately output so as to attain a high picture quality. Also, the horizontal active period can be shortened by reducing the time spent on the read operation, so as to shorten time necessary for reading signals of one row of pixels. Thus, the number of frames output in unit time can be increased, and therefore, an image can be rapidly output.  
         [0060]     In this modification, the output is stopped not only at a rise and a fall on the reset pulse line  32  but also at a rise of the V DD  power supply  16 , and therefore, the occurrence of noise derived from the V DD  power supply  16  can be also suppressed.  
         [0000]     Modification 3 of Embodiment 1  
         [0061]      FIG. 5  is a timing chart in the horizontal drive period besides the vertical blanking period of a solid state imaging device of Modification 3 of Embodiment 1. The solid state imaging device of this modification has the same circuit configuration as the solid state imaging device of Embodiment 1. In the solid state imaging device of this modification, the operation for outputting the signals of the pixels  21 A of the nth row having been stored in the first memories  23  is performed in parallel to the operation for reading the signals of the pixels  21 B of the (n+1)th row and storing them in the second memories  24  in the horizontal blanking period.  
         [0062]     Therefore, also in a high-definition camera in which a horizontal drive period composed of a horizontal blanking period and a horizontal active period is short, time for reading the signals from the memories can be sufficiently secured, and hence, the signals can be easily read from the memories. As a result, the picture quality can be largely improved.  
         [0000]     Modification 4 of Embodiment 1  
         [0063]      FIG. 6  is a circuit diagram of a solid state imaging device of Modification 4 of Embodiment 1. In  FIG. 6 , like reference numerals are used to refer to like elements shown in  FIG. 1  so as to omit the description. As shown in  FIG. 6 , the solid state imaging device of this modification includes an AD (analog/digital) conversion portion  28  connected to the output of the horizontal control transistor  25 . Thus, a signal read from each pixel is converted into a digital signal, so as to be output as each bit through the horizontal signal line  26  and the output amplifier  27 .  
         [0064]     Also in such a digital-output solid state imaging device, fast drive can be performed by providing two row memories in parallel. The drive timing may be any of those described in Embodiment 1 and Modifications 1 through 3.  
         [0065]     Since the solid state imaging device described in each of Embodiment 1 and Modifications 1 through 3 can be rapidly driven, a camera using such a solid state imaging device can attain a high picture quality and a rapid operation.  
         [0066]     As described so far, the solid state imaging device of this invention can stably perform signal storage in row memories and signal read from the row memories and can attain a high picture quality, and therefore, the invention is useful for a solid state imaging device for use in a high-definition camera, a method for driving the same, and a camera using the same.