Image pickup apparatus, image pickup system and driving method of image pickup apparatus

An image pickup apparatus of an embodiment includes pixel units each including a photoelectric conversion unit and an amplification transistor that outputs a signal based on an electric carrier generated by the photoelectric conversion unit, a first output line to which signals from first and other pixel units are output, and a second output line to which signals from second and other pixel units are output. A connection unit is arranged to control an electric connection between input nodes of the amplification transistors of the first and second pixel units is arranged. A control unit is arranged to selectively output a signal from at least one of the first and second pixel units to the first output line out of the first and second output lines when the connection unit mutually connects the input nodes of the first and second pixel units.

BACKGROUND OF THE INVENTION

1. Field of the Invention

One disclosed aspect of the embodiments relates to an image pickup apparatus, an image pickup system and a driving method of the image pickup apparatus.

2. Description of the Related Art

There is suggested an image pickup apparatus that has a connection unit for mutual connection or non-connection of input nodes of amplification transistors of a plurality of pixels. FIG. 8 of Japanese Patent Laid-Open No. 2010-103437 describes an image pickup apparatus that has a connection transistor for connection or non-connection of a plurality of floating diffusion regions. FIG. 9 of Japanese Patent Laid-Open No. 2009-016972 describes an image pickup apparatus that has a reset switch for common connection of floating diffusions of a plurality of pixels in the identical pixel block. The image pickup apparatuses described in these patent literatures are configured such that signals of a plurality of pixels are output to different output lines, in a case where the connection transistor or the reset switch is turned off, that is, in a case where a plurality of floating diffusions is not mutually connected.

SUMMARY OF THE INVENTION

An image pickup apparatus corresponding to an embodiment according to one aspect of the embodiments includes: a plurality of pixel units each including a photoelectric conversion unit and an amplification transistor that outputs a signal based on an electric carrier generated by the photoelectric conversion unit; a first output line to which a signal from two or more pixel units, including a first pixel unit, among the plurality of pixel units is output; a second output line to which a signal from two or more pixel units, including a second pixel unit, among the plurality of pixel units is output; a connection unit configured to control an electric connection between an input node of the amplification transistor included in the first pixel unit and an input node of the amplification transistor included in the second pixel unit; and a control unit configured to selectively output a signal from at least one of the first pixel unit and the second pixel unit to the first output line out of the first output line and the second output line, in a case where the connection unit mutually connects the input node of the first pixel unit and the input node of the second pixel unit.

A driving method of an image pickup apparatus corresponding to an embodiment according to another aspect of the embodiments, in which the image pickup apparatus includes: a plurality of pixel units each including a photoelectric conversion unit and an amplification transistor that outputs a signal based on an electric carrier generated by the photoelectric conversion unit; a first output line to which a signal from two or more pixel units, including a first pixel unit, among the plurality of pixel units is output; a second output line to which a signal from two or more pixel units, including a second pixel unit, among the plurality of pixel units is output; and a connection unit configured to control an electric connection between an input node of the amplification transistor included in the first pixel unit and an input node of the amplification transistor included in the second pixel; and the driving method includes: a first output step of selectively outputting a signal from at least one of the first pixel unit and the second pixel unit to the first output line out of the first output line and the second output line, in a case where the connection unit mutually and electrically connects the plurality of input nodes; and a second output step of outputting a signal from the first pixel unit to the first output line and outputting a signal from the second pixel unit to the second output line, in a case where the connection unit blocks the electric connection of the plurality of input nodes.

DESCRIPTION OF THE EMBODIMENTS

According to some embodiments, it is possible to read out signals at high speed or reduce the power consumption. Alternatively, according to some embodiments, it is possible to achieve both the speed-up of the reading of signals and the low power consumption. One disclosed feature of the embodiments may be described as a process which is usually depicted as a timing diagram. A timing diagram may illustrate the timing relationships of several entities, such as signals, events, etc. Although a timing diagram may describe the operations as a sequential process, some operations may be performed in parallel or concurrently. In addition, unless specifically stated, the order of the operations or timing instants may be re-arranged. Furthermore, the timing or temporal distances may not be scaled or depict the timing relationships in exact proportions.

In an image pickup apparatus, it is requested to read out signals from pixels at higher speed. In an image pickup apparatus known to the inventor, when the floating diffusions of a plurality of pixels are mutually connected, the same signal is output to a plurality of output lines. The present inventor found that it was possible to perform the reading of signals from pixels in a shorter time in such an image pickup apparatus.

Moreover, the image pickup apparatus is requested to have low power consumption. The present inventor found that it is possible to reduce the power consumption in an image pickup apparatus known to the inventor.

In view of such challenges, some embodiments enable the reading of signals at high speed, the reduction of power consumption, or both the speed-up of the reading of signals and the low power consumption in an image pickup apparatus that has a connection unit for mutual connection or non-connection of input nodes of amplification transistors of a plurality of pixels.

One embodiment is directed to an image pickup apparatus that has a plurality of pixel units. One pixel unit includes at least one photoelectric conversion unit and an amplification transistor corresponding thereto. A plurality of pixel units includes a first pixel unit and a second pixel unit. A signal from the first pixel unit is output to at least a first output line. A signal from the second pixel unit is output to at least a second output line. The signals from the pixel units denote signals including at least elements based on electric carriers generated by the photoelectric conversion units included in the pixels.

The image pickup apparatus according to some embodiments has a connection unit that controls electric connection between an input node of the amplification transistor of the first pixel unit and an input node of the amplification transistor of the second pixel unit. In a case where the connection unit mutually connects the input nodes of the amplification transistors of two pixel units, signals of two pixel units may be added. In this case, the addition signal of two signals may be output from an amplification transistor. A signal averaging a plurality of signals is one specific example of the addition signal. The addition signal is one specific example of the signal from at least one of two pixel units. This is because the addition signal varies on the basis of an electric carrier generated by either one of the photoelectric conversion units.

Here, even when the connection unit mutually connects the input nodes of the amplification transistors of two pixel units, by transferring only the electric carrier of the photoelectric conversion unit of one pixel unit to the input node of the amplification transistor, it is possible to output only the signal from the pixel unit. By mutually connecting a plurality of input nodes, it is possible to increase the capacity of the input nodes. Therefore, by reading out only the electric carrier of the photoelectric conversion unit of one pixel unit, for example, in a case where the amount of electric carriers generated by the photoelectric conversion unit is large because of the incidence of very strong light, it is possible to reduce the possibility that the signal is saturated in a subsequent circuit.

The image pickup apparatus according to some embodiments has a control unit that selectively outputs a signal to either one of a first output line and a second output line, in a case where a connection unit mutually connects a plurality of input nodes. For example, when the connection unit mutually connects the input nodes of the first and second pixel units, the control unit outputs a signal from at least one of the first and second pixel units to the first output line and blocks the output of signals from the first and second pixel units to the second output line. In this case, the voltage or current of the first output line, that is, the signal value varies according to the voltage or current of the input node of the amplification transistor included in the first pixel unit. Meanwhile, the signal value of the second output line may be decided on the basis of the output of a transistor different from the amplification transistors included in the first and second pixel units or the output of a circuit different from the first and second pixel units. Simply, the second output line may be an electric floating.

To be more specific, in some embodiments, switches are arranged in series in an electric path from a power source to the first output line through the transistor of the first pixel unit and an electric path from the power source to the second output line through the transistor of the second pixel unit. In such embodiments, signals are output by turning on the switches. The signals are blocked by turning off the switches.

In some embodiments, a connection unit mutually connects a plurality of input nodes, and, after the connection is terminated, a control unit selectively outputs a signal to one output line. This driving may be performed in the embodiments formed such that the switches in series with the above-mentioned amplification transistors are not installed and the signal output is controlled by the bias of the amplification transistors. In such embodiments, for example, after the connection unit terminates the connection, the control unit supplies a voltage to cause one amplification transistor to be in an inactive state, to the input node of the amplification transistor. Alternatively, after the connection unit terminates the connection, the control unit supplies a voltage to cause one amplification transistor to be in an inactive state, to a main node of the amplification transistor. Thus, the bias states of the amplification transistors of two pixel units are independently controlled.

Here, in some embodiments, there is a parasitic capacity between an input node of an amplification transistor and an output line. In such a case, even when the output of a signal to the second output line is blocked, the signal value of the second output line varies according to the voltage or current of the input node of the amplification transistor included in the first or second pixel unit, through coupling capacitance. Thus, in the blocking of the output of a signal to the second output line, the correlation between an input node and an output node does not have to be necessarily adjusted to 0, and both of them may have correlation with each other.

In an embodiment, in a case where a connection unit mutually connects a plurality of input nodes, a signal is selectively output to a part of a plurality of output lines. According to such a configuration, it is possible to output another signal to the remaining output lines in parallel. Therefore, it is possible to speed up the reading of signals. Alternatively, according to such a configuration, it is possible to reduce the power consumption since a signal is not output to the remaining output lines.

In the following, the embodiments are described in detail with reference to the drawings. The disclosure is not limited to only the embodiments described in the following. A variation, in which a configuration of the embodiments described in the following is partially modified within a range not exceeding the spirit of the disclosure, is also an embodiment of the disclosure. Moreover, an example in which the configuration of one of the following embodiments is partially added to another embodiment or an example in which the configuration is partially replaced with that of another embodiment is also an embodiment of the disclosure.

FIG. 1is a view illustrating an equivalent circuit of an image pickup apparatus of some embodiments. An image pickup apparatus1has a plurality of pixel units100arranged in an image pickup region. The plurality of pixel units100is arranged so as to form a matrix including a plurality of rows and a plurality of columns. One row includes the plurality of pixel units100in which signals are read out in parallel. One column includes the plurality of pixel units100connected to a same output line105.FIG. 1illustrates 16 pixel units100. In the image pickup apparatus1of some embodiments, more pixel units may be arranged. Here, in other embodiments, the plurality of pixel units100is arranged at random.

In a case where there is a notation of two-digit figures following a hyphen such as “pixel unit100-11,” it is assumed that the figures following the hyphen show the addresses of the row and the column. For example, in the case of a pixel unit100-12, it denotes a pixel unit arranged in the second row of the first column. A photoelectric conversion unit10-12denotes a photoelectric conversion unit included in the pixel unit100-12. Moreover, in a case where there is a notation of a single-digit figure following a hyphen, it is assumed that the figure following the hyphen shows the address of the row or column. For example, in the case of a first selection control signal PSELA103-2, it shows a first selection control signal corresponding to the pixel unit100of the second row, and, in the case of an output line105-3, it shows an output line electrically connected to the pixel unit100included in the third column.

A pixel unit100includes at least a photoelectric conversion unit10and an amplification transistor13. The photoelectric conversion unit10is, for example, a photodiode. The amplification transistor13is electrically connected to the output line105. Subsequently, the amplification transistor13outputs a signal based on an electric carrier generated by the photoelectric conversion unit10to the output line105. The amplification transistor13and a current source, which is electrically connected to the output line105and is not illustrated, form a source follower circuit. In other embodiments, the amplification transistor13may form a differential amplification amplifier and a source-grounded amplification circuit. The amplification transistor13may include an MOS transistor and a JFET. A signal output to the output line105is transmitted to a subsequent column circuit which is not illustrated. In the column circuit, signal processing such as amplification, noise reduction and AD conversion is performed.

In some embodiments, a transfer transistor11is arranged between the photoelectric conversion unit10and an input node12of the amplification transistor13. The transfer transistor11transfers an electric carrier generated by the photoelectric conversion unit10to the input node12of the amplification transistor13. In this case, for example, the input node12of the amplification transistor13may be a node configured to include a floating diffusion region, for example. In some embodiments, the transfer transistor11is not arranged. In this case, the photoelectric conversion unit10is directly connected to the input node12of the amplification transistor13. That is, the input node12of the amplification transistor13is configured to include a semiconductor region forming the photoelectric conversion unit10.

The input node12of the amplification transistor is electrically connected to the input node12of another amplification transistor13through a connection transistor14. By turning on the connection transistor14, the two input nodes12become conductive. By turning off the connection transistor14, the two input nodes12become non-conductive. That is, the connection transistor14is included in a connection unit that controls electric connection between the input nodes12of the amplification transistors13included in the plurality of pixel units100. Also, in some embodiments, by connecting the plurality of input nodes12by the connection unit, signals of a plurality of pixel units are added or averaged.

The connection unit mutually and electrically connects the input nodes12of the amplification transistors13of the plurality of pixel units100connected with respective output lines105. For example, in an embodiment illustrated inFIG. 1, the connection unit may mutually connect the plurality of input nodes12in the combination of pixel units having two rows and two columns enclosed with a dotted line200. In some of other embodiments, the connection unit mutually connects the plurality of input nodes12in the combination of pixel units having one row and two columns. Besides this, various combinations such as combination of two rows and three columns and combination of three rows and three columns are possible. Moreover, in an embodiment in which the plurality of pixel units100is not arranged in a matrix manner, combination that cannot be expressed by a row and column is also possible.

Moreover, in the embodiment illustrated inFIG. 1, the connection transistor14is arranged in each of the plurality of pixel units100. In some of other embodiments, n−1 (n represents a natural number) items of connection transistors14are arranged in n pixel units100. In this case, since it is possible to reduce the number of transistors, the area of the photoelectric conversion unit can be enlarged.

The input node12of the amplification transistor13is electrically connected to one of two main nodes of a reset transistor15through the corresponding connection transistor14. The other of the two main nodes of the reset transistor15is electrically connected to a wiring that supplies a voltage to reset the voltage of the input node12. With such a configuration, it is possible to supply the voltage for reset from the wiring that supplies the voltage, to each of the input nodes12through the reset transistor15and the connection transistor14.

In the embodiment illustrated inFIG. 1, each of the input nodes12is electrically connected to the reset transistor15through the connection transistor14. According to such a configuration, it is possible to set the capacity of the input nodes12to mutually close values or an equal value. As a result, it is possible to reduce the fixed-pattern noise in these embodiments. In some of other embodiments, the reset transistor15may be directly connected to one of the input nodes12.

An output node of the amplification transistor13is electrically connected to the output line105through a selection transistor16. By turning on the selection transistor16, it outputs a signal from the corresponding amplification transistor13to the output line105. Moreover, by turning off the selection transistor16, it blocks the output of a signal from the corresponding amplification transistor13to the output line105. Therefore, by combination of turning on and off a plurality of selection transistors16, from the plurality of amplification transistors13, the one to output a signal is selected. That is, in some embodiments, the plurality of selection transistors16forms the control unit. Here, the selection transistor16may be arranged in series in an electric path between a power source node and the amplification transistor13.

The control node of each transistor is electrically connected to a control line. Here, a description is given using four pixel units100-11,100-12,100-21and100-22enclosed with a dotted line200-11as an example. First, connection transistors14-11and14-21are electrically connected to a connection control line101-1. Connection transistors14-12and14-22are electrically connected to a connection control line101-2. Next, a selection transistor16-21is electrically connected to a first selection control line102-1. The selection transistor16-11is electrically connected to a second selection control line103-1. Subsequently, the selection transistor16-12and the selection transistor16-22are electrically connected to a third selection control line103-2. A reset transistor15-11is electrically connected to a reset control line201-1. The control node of the transistor of another pixel unit100is connected to the corresponding control line as illustrated inFIG. 1. In some embodiments, a scanning circuit which is not illustrated supplies a driving signal to the control line. In other embodiments, the drive signal may be supplied from the outside of the image pickup apparatus.

In the embodiment illustrated inFIG. 1, a control node of the selection transistor16-11and a control node of the selection transistor16-21are connected to different control lines. That is, the selection transistor16-11and the selection transistor16-21are controlled independently from each other. In another respect, two selection control lines are arranged to the selection transistors included in two pixel units arranged in the same row. With such a configuration, when the connection unit connects the input node12-11of the amplification transistor13-11and the input node12-21of the amplification transistor13-21, the control unit selectively outputs a signal from at least one of the pixel unit100-11and the pixel unit100-21to either one of the output line105-1and the output line105-2.

To be more specific, when the connection unit connects four input nodes12-11,12-21,12-12and12-22, the selection transistor16-11is turned on and the selection transistors16-21,16-12and16-22are turned off. By this means, a signal from one of four pixel units100-11,100-21,100-12and100-22or their addition signal is output to the output line105-1. Meanwhile, the output of signals from the pixel unit100-21(or100-11,100-12or100-22) to the output line105-2is blocked. Alternatively, the selection transistor16-21may be turned on and the selection transistors16-11,16-12and16-22may be turned off. By this means, the signal from one of four pixel units100-11,100-21,100-12and100-22or their addition signal is output to the output line105-2. Meanwhile, the output of signals to the output line105-1is blocked.

It is possible to output a signal from a pixel unit, which is different from four pixel units100-11,100-21,100-12and100-22, to one of the output line105-1and the output line105-2, that is, the output line105in which the output of signals is blocked. Therefore, it is possible to output signals to two output lines105-1and105-2in parallel. As a result, it is possible to read out signals at high speed in these embodiments.

For example, in a case where the output of signals from four pixel units100-11,100-21,100-12and100-22to the output line105-2is blocked, a signal from the pixel unit100-23is output to the output line105-2by turning on the selection transistor16-23. In some embodiments, the selection transistors16-13and16-23respectively corresponding to pixel units100-13and100-23are controlled independently from each other. Therefore, when the connection unit connects the input node12-13and the input node12-23, a signal from at least one of the pixel unit100-13and the pixel unit100-23may be selectively output to the output line105-2out of the output line105-1and the output lines105-2. According to such a configuration, an addition signal from four pixel units100-11,100-21,100-12and100-22enclosed with the dotted line200-11and an addition signal from four pixel units100-13,100-23,100-14and100-24enclosed with a dotted line200-12can be read out in parallel. As a result, it is possible to read out signals at high speed in these embodiments.

Here, in a case where the connection unit makes the input nodes12-11,12-12,12-21and12-22non-conductive, by turning on both of the selection transistors16-11and16-21, signals are respectively output from the pixel units100-11and100-21to the output lines105-1and105-2in parallel. According to the embodiment of such a configuration, it is possible to acquire images of high-resolution.

Moreover, in the embodiment illustrated inFIG. 1, a selection transistor16-2corresponding to the pixel unit of the second row is electrically connected to the common third selection control line103-2. Since it is possible to reduce the number of wirings using such a configuration, the aperture of the photoelectric conversion unit can be enlarged.

By contrast with this, in some other embodiments, the selection transistor16-12corresponding to the pixel unit100-12and the selection transistor16-22corresponding to the pixel unit100-22can be controlled independently from each other. That is, the selection transistor16-12and the selection transistor16-22may be connected to different control lines. In such embodiments, when the connection unit mutually connects the input nodes of the amplification transistors13included in the pixel units100of the second row, a signal may be selectively output to one of the plurality of output lines105-1and105-2. As a result, it is possible to read out signals at high speed in these embodiments. Alternatively, it may be possible to uniform the size of wiring apertures in the plurality of pixel units100by increasing the number of control lines.

In the embodiment illustrated inFIG. 1, the connection transistor14is controlled at every row. In such an embodiment, it is possible to perform a reset operation in each row. Alternatively, in such an embodiment, it is possible to select combination of pixels to be added, from combination of two rows and two columns and combination of one row and two columns.

Next, an embodiment of a driving method of the image pickup apparatus is described below.FIGS. 2 and 3are views schematically illustrating a timing chart of drive signals. The drive signals illustrated inFIG. 2orFIG. 3are supplied to control lines to which the same reference numerals are assigned in the image pickup apparatus of the embodiment illustrated inFIG. 1. For example, drive signal PSELA is supplied to the first selection control line102-1. Drive signal PSELB is supplied to the second selection control line103-1and the third selection control line103-2. Drive signal PRESA is supplied to the connection control lines101-1and101-2. Further, drive signal PRESB is supplied to the reset control line201-1. Moreover, although it is not illustrated inFIG. 1, the transfer transistor11is electrically connected to the transfer control line in each row. Further, drive signals PTX104-1to PTX104-4inFIGS. 2 and 3are supplied to a transfer control line that is not illustrated. When a drive signal is “High,” a relevant transistor is turned on. When a drive signal is “Low,” a relevant transistor is turned off. Moreover, a scanning circuit that is not illustrated supplies these drive signals.

The timing chart illustrated inFIG. 2corresponds to the operation of a first reading mode. First, drive signal PSELA102-1and drive signal PSELB103-1are set to “High” in a reading period of the pixel unit100included in the first line. By this means, the selection transistors16-11and16-21corresponding to the pixel unit100of the first row are turned on.

Next, drive signal PRESA101-1is set from “High” to “Low” and drive signal PRESB201-1is set from “High” to “Low.” By this means, the connection transistors14-11and14-21and the reset transistor15-11are turned off. Since electric connection between wiring VRES that supplies a power source voltage for reset and the input node12of the amplification transistor13included in the pixel unit100of the first row is disconnected, the input node12is released from the reset state.

In some embodiments, drive signal PRESA101may be set to “Low” before drive signal PRESB201. By this means, it is possible to suppress the influence of the difference in the timings at which the selection transistor16-11and the selection transistor16-21become non-conductive, which may be caused by wiring delay or threshold variation of the transistors.

Next, by setting drive signal PTX104-1to “High,” an electric carrier of the photoelectric conversion unit10included in the pixel unit100of the first row is transferred to the input node12. Since the selection transistor16-11is turned on, the amplification transistor13-11outputs a signal based on an electric carriers generated by a photoelectric conversion unit10-11to the output line105-1. Moreover, since the selection transistor16-21is turned on, the amplification transistor13-21outputs a signal based on an electric carrier generated by a photoelectric conversion unit10-21to the output line105-2. By setting drive signal PRESA101-1and drive signal PRESB201-1to “High” after the signal of the output line105is transmitted to a subsequent column circuit, the voltage of the input node12of the pixel unit100of the first row is reset.

Drive signal PSELB103-2is set to be “High” in a reading period of the pixel unit100included in the second row. By this means, the selection transistor16corresponding to the pixel unit100of the second row gets in a conductive state. The reset state of a reading node12of the second row is cancelled by setting PRESA101-2and PRESB201-1to “Low” in order, and the electric carrier of the photoelectric conversion unit10of the second row is transferred to the reading node12by setting PTX104-2to “High.” Afterwards, similar to the first row, after the signal of the pixel unit100of the second row is output to the output line105, drive signal PRESA101-2and drive signal PRESB201-1are set to be “High” to reset the voltage of the input node12.

After that, the similar operation is performed in the pixel units100included the third and subsequent rows. Moreover, in the above-mentioned description, although a description has been given using the operation of the pixel units100of the first and second columns as an example, the similar operation is performed in the pixel units100of odd-numbered columns and even-numbered columns.

By the above operation, it is possible to realize the first reading mode to output signals of a plurality of pixel units in parallel at every row. To be more specific, when the connection unit blocks the electric connection of the plurality of input nodes12, a signal from the first pixel unit100-11is output to the first output line105-1and a signal from the second pixel unit100-21is output to the second output line105-2.

The timing chart illustrated inFIG. 3corresponds to the operation of the second reading mode. In the second reading mode, when the connection unit mutually connects the input nodes12of the plurality of pixel units100enclosed with one dotted line200, a signal is selectively output to part of the plurality of output lines105. In the second reading mode, an electric carrier transferred by the transfer transistor11is added in the input node12. That is, an addition signal acquired by adding signals of the plurality of pixel units100is output.

Drive signal PSELA102-1inFIG. 3is supplied to the selection transistor16of the pixel unit100arranged in the even-numbered columns of the first row. Meanwhile, drive signal PSELA102-3is supplied to the selection transistor16of the pixel unit100arranged in the odd-numbered columns of the first row.

Drive signal PSELA102-1and drive signal PSELA102-3are set to “High.” By this means, the selection transistors16-21and16-13are turned on. At this time, drive signal PSELB103-1and drive signal PSELB103-1are “Low.” Therefore, the selection transistors16-11,16-12,16-22,16-23,16-14and16-24are turned off.

Next, drive signal PRESB201-1and drive signal PRESB201-2are set to “Low.” By this means, reset transistors15-11and15-12are turned off. Since the electric connection between wiring VRES that supplies a power source voltage for reset and the input node12is disconnected, the input node12is released from the reset state.

Next, an electric carrier of the photoelectric conversion unit10is transferred by setting drive signals PTX104-1, PTX104-2, PTX104-3and PTX104-4to “High.” At this time, sine the connection transistor14is turned on, the transferred electric carrier is added.

Among four selection transistors16corresponding to four pixel units100enclosed with the dotted line200-11, the selection transistor16-21is turned on and the other selection transistors16are turned off. Therefore, signals from four pixel units100enclosed with the dotted line200-11are output to the output line105-2. The output of the signals from these pixel units100to the output line105-1is blocked.

Among four selection transistors16corresponding to four pixel units100enclosed with the dotted line200-12, the selection transistor16-13is turned on and the other selection transistors16are turned off. Therefore, signals from four pixel units100enclosed with the dotted line200-12are output to the output line105-1. The output of the signals from these pixel units100to the output line105-2is blocked.

After a signal of the output line105is transmitted to a subsequent column circuit, the voltage of the input node12is reset similar to the first mode. Afterwards, a signal from the pixel unit of the next row is read out. Moreover, in the above description, although a description has been given using the operation of the pixel units100of the first and second rows, the similar operation is performed in the pixel units100of the odd-numbered rows and the even-numbered columns.

By the above operation, it is possible to realize the second reading mode to selectively output a signal acquired by adding signals of a plurality of pixel units to part of a plurality of output lines. To be more specific, when the connection unit mutually and electrically connects the plurality of input nodes12, signals from four pixel units100enclosed with the dotted line200-11are output to the output line105-2and the output of the signals to the output line105-1is blocked.

Moreover, at this time, a signal from the pixel unit100different from four pixel units100enclosed with the dotted line200-11is output to the output line105-1. That is, in a case where signals are added in the combination of two rows and two columns, two addition signals are read out in parallel.

As described above, in some embodiments, when the connection unit mutually connects the plurality of input nodes12, the control unit selectively outputs a signal to one of the first output line105-1and the second output line105-2. Thus, according to such embodiments, since it is possible to read out signals in parallel, signals can be read out at high speed. Alternatively, according to such a configuration, it is possible to reduce the power consumption since a signal is not output to the remaining output lines.

Another embodiment is described below. The difference from Embodiment 1 is that a pixel unit includes two photoelectric conversion units. That is, the pixel unit includes two pixels. Therefore, only the difference from Embodiment 1 is described, and description of the similar parts to Embodiment 1 will not be repeated.

FIG. 4Ais a view illustrating an equivalent circuit of an image pickup apparatus of some embodiments. The same reference numerals are assigned to the components same asFIG. 1and the detailed description will not be repeated.

A first pixel unit300-1includes the photoelectric conversion unit10-11, the photoelectric conversion unit10-12and the amplification transistor13-11. The first pixel unit includes transfer transistors11- and11-12respectively corresponding to the photoelectric conversion units10-11and10-12. The photoelectric conversion unit10-11is electrically connected to the input node12-11of the amplification transistor13-11through the transfer transistor11-11. The photoelectric conversion unit10-12is electrically connected to the input node12-11of the amplification transistor13-11through the transfer transistor11-12. An electric carrier generated by the photoelectric conversion unit10-11and an electric carrier generated by the photoelectric conversion unit10-12may be added in the input node12-11at the timing at which two transfer transistors11-11and11-12are turned on.

An output node of the amplification transistor13-11is electrically connected to the output line105-1through the selection transistor16-11. By turning on the selection transistor16-11, it outputs a signal from the corresponding amplification transistor13-11to the output line105-1. Moreover, by turning off the selection transistor16-11, it blocks the output of signals from the corresponding amplification transistor13-11to the output line105-1.

A second pixel unit300-2includes the photoelectric conversion unit10-21, a photoelectric conversion unit10-22and an amplification transistor13-22. The second pixel unit includes transfer transistors11-21and11-22respectively corresponding to the photoelectric conversion units10-21and10-22. The photoelectric conversion unit10-21is electrically connected to the input node12-21of the amplification transistor13-22through the transfer transistor11-21. The photoelectric conversion unit10-22is electrically connected to the input node12-21of the amplification transistor13-22through the transfer transistor11-22. An electric carrier generated by the photoelectric conversion unit10-21and an electric carrier generated by the photoelectric conversion unit10-22may be added in the input node12-21at the timing at which two transfer transistors11-21and11-22are turned on.

An output node of the amplification transistor13-22is electrically connected to the output line105-2through the selection transistor16-22. By turning on the selection transistor16-22, it outputs a signal from the corresponding amplification transistor13-22to the output line105-2. Moreover, by turning off the selection transistor16-22, it blocks the output of signals from the corresponding amplification transistor13-22to the output line105-2.

The connection transistor14-11is arranged corresponding to the first pixel unit300-1. The connection transistor14-21is arranged corresponding to the second pixel unit300-2. The electric connection between the input node12-11of the amplification transistor13-11included in the first pixel unit300-1and the input node12-21of the amplification transistor13-22included in the second pixel unit300-2is controlled by these connection transistors14-11and14-21. The connection transistor14is included in a connection unit. InFIG. 4A, a dotted line400shows the combination of a plurality of pixel units300that are mutually connected by the connection unit.

In the embodiment illustrated inFIG. 4A, a control node of the selection transistor16-11and a control node of the selection transistor16-22are connected to different control lines. That is, the selection transistor16-11and the selection transistor16-22are controlled independently from each other. With such a configuration, when the connection unit connects the input node12-11of the amplification transistor13-11and the input node12-21of the amplification transistor13-22, the control unit selectively outputs a signal to either one of the output line105-1and the output line105-2.

In these embodiments, two photoelectric conversion units10share one amplification transistor13. Therefore, it is possible to reduce the number of transistors arranged per one pixel. As a result, it is possible to enlarge the apertures of the photoelectric conversion units10in these embodiments.

Also,FIG. 4Billustrates an equivalent circuit of an embodiment in which a pixel unit300having the equivalent circuit illustrated inFIG. 4Ais arranged in a 2-row, 4-column matrix. In these embodiments, a signal from another pixel unit can be output to the output line105in which the output of signals is blocked. As a result, it is possible to read out signals at high speed in these embodiments. InFIG. 4B, the dotted line400shows the combination of the plurality of pixel units300that are mutually connected by the connection unit.

An embodiment of a driving method of the image pickup apparatus is described below.FIGS. 5 and 6are views schematically illustrating a timing chart of drive signals. The drive signals illustrated inFIG. 5orFIG. 6are supplied to control lines to which the same reference numerals are assigned in the image pickup apparatus of the embodiment illustrated inFIG. 4. Drive signal PTX104-1is supplied to a control line connected to transfer transistors11-11,11-21,11-31and11-41. Drive signal PTX104-2is supplied to a control line connected to transfer transistors11-12,11-22,11-32and11-42. Drive signal PTX104-3is supplied to a control line connected to transfer transistors11-13,11-23,11-33and11-43. Drive signal PTX104-4is supplied to a control line connected to transfer transistors11-14,11-24,11-34and11-44. When a drive signal is “High,” a relevant transistor is turned on. When a drive signal is “Low,” a relevant transistor is turned off. Moreover, a scanning circuit that is not illustrated may supply these drive signals.

The timing chart illustrated inFIG. 5corresponds to the operation of the first reading mode. The selection transistors16-11,16-22,16-31and16-42are turned on by setting drive signal PSELA102-1and drive signal PSELB-2to “High.”

Next, drive signal PRESA101-1and drive signal PRESB201-1are set to “Low” in order. By this means, the connection transistors14-12and14-22and the reset transistor15-11are turned off. Further, input nodes12-11,12-22,12-31and12-42are released by the reset state.

Next, drive signal PTX104-1supplied to a control line connected to the transfer transistor11is set to “High.” By this means, an electric carrier of the photoelectric conversion unit10of the first row is transferred to the corresponding input node12. The photoelectric conversion unit of the first row denotes, for example, the photoelectric conversion unit10-11out of two photoelectric conversion units10-11and10-21included in the pixel unit300-1.

Amplification transistors13-11,13-22,13-13and13-42output signals based on the transferred electric carriers to the corresponding output line105. After the signals are transmitted to a subsequent column circuit, drive signal PRESA101-1and drive signal PRESB201-1are set to “High.” By this means, the voltage of the input node12is reset.

Subsequently, by setting drive signal PRESA101-1and drive signal PRESB201-1to “Low” in order, the input nodes12-11,12-22,12-31and12-42are released from the reset state. Next, by setting drive signal PTX104-2to “High,” an electric carrier of the photoelectric conversion unit10of the second row is transferred to the input node12. The photoelectric conversion unit of the second row refers to, for example, the photoelectric conversion unit10-12out of two photoelectric conversion units10-11and10-12included in a pixel unit300-11.

Similar to the operation in the first row, the amplification transistors13-11,13-22,13-13and13-42output signals based on the transferred electric carriers to the corresponding output line105. After the signals are transmitted to a subsequent column circuit, drive signal PRESA101-1and drive signal PRESB201-1are set to be “High.” By this means, the voltage of the input node12is reset.

By the above operation, it is possible to realize the first reading mode to output signals of a plurality of pixel units in parallel at every row. To be more specific, when the connection unit blocks the electric connection of the plurality of input nodes12, a signal from the first pixel unit300-11is output to the first output line105-1and a signal from the second pixel unit300-21is output to the second output line105-2.

Here, the electric carriers transferred by the transfer transistor11may be added in the input node12. That is, the electric carriers of the plurality of photoelectric conversion units included in a pixel unit300may be added.

The timing chart illustrated inFIG. 6corresponds to the operation of the second reading mode. In the second reading mode, when the connection unit mutually connects the input nodes12of a plurality of pixel units300enclosed with a dotted line400, a signal is selectively output to either one of the plurality of output lines105-1and105-2.

The electric carriers transferred by the transfer transistor11may be added in the input nodes12. That is, a signal acquired by adding the signals of the plurality of pixel units100may be output. For example, by setting drive signal PRESA101to “High,” the electric carriers read from the photoelectric conversion unit10through the transfer transistor11are added in pixel units enclosed with a dotted line400-11. Further, by setting either one of drive signal PSELA102-1and drive signal PSELB103-2to “High,” a signal is selectively output to the corresponding output line105.

Thus, it is possible to realize the second reading mode in which a signal acquired by adding signals of a plurality of pixel units is selectively output to part of a plurality of output lines.

As described above, in some embodiments, when the connection unit mutually connects the plurality of input nodes12, the control unit selectively outputs a signal to one of the first output line105-1and the second output line105-2. According to such embodiments, since it is possible to read out signals in parallel, signals can be read out at high speed. Alternatively, according to such a configuration, it is possible to reduce the power consumption since a signal is not output to the remaining output lines.

Moreover, in some embodiments, two photoelectric conversion units share an amplification transistor in a pixel unit. With such a configuration, it is possible to reduce the number of transistors. As a result, in these embodiments, it is possible to enlarge the apertures of the photoelectric conversion units.

An embodiment of an image pickup system is described below. Examples of the image pickup system include a digital still camera, a digital camcorder, a copier, a fax, a mobile phone, a car-mounted camera and an observation satellite.FIG. 7illustrates a block diagram of a digital still camera as an example of the image pickup system.

As illustrated inFIG. 7, a reference numeral “1001” represents a barrier for lens protection, a reference numeral “1002” represents a lens that forms an optical image of an object in an image pickup apparatus1004, and a reference numeral “1003” represents a diaphragm to change the amount of light passing through the lens1002. The reference numeral “1004” represents an image pickup apparatus that is described in the above-mentioned embodiments and that converts the optical image formed by the lens1002into image data. Here, it is assumed that an AD conversion unit is formed in a semiconductor substrate of the image pickup apparatus1004. A reference numeral “1007” represents a signal processing unit that compresses various kinds of correction or data in image pickup data output from the image pickup apparatus1004. Moreover, inFIG. 7, a reference numeral “1008” represents a timing generation unit that outputs various kinds of timing signals to the image pickup apparatus1004and the signal processing unit1007, and a reference numeral “1009” represents an entire control unit that controls the entire digital still camera. A reference numeral “1010” represents a frame memory unit to temporarily store image data, a reference numeral “1011” represents an interface unit to perform recording or reading in a recording medium, and a reference numeral “1012” represents a detachably-mounted recording medium, such as a semiconductor memory, to record or read out image pickup data. A reference numeral “1013” represents an interface unit to perform communication with an external computer or the like. Here, a timing signal or the like may be input from the outside of the image pickup apparatus The image pickup system only has to have at least the image pickup apparatus1004and the signal processing unit1007that processes an image pickup signal output from the image pickup apparatus1004.

In this embodiment, a configuration has been described in which the image pickup apparatus1004and the AD conversion unit are formed in the same semiconductor substrate. However, the image pickup apparatus1004and the AD conversion unit may be installed in different semiconductor substrates. Moreover, the image pickup apparatus1004and the signal processing unit1007may be formed in the same semiconductor substrate.

In the embodiment of the image pickup system, the image pickup apparatus of Embodiment 1 or Embodiment 2 is used for the image pickup apparatus1004. Thus, it is possible to read out signals at high speed by applying the embodiment in the image pickup system.

This application claims the benefit of Japanese Patent Application No. 2013-001081, filed Jan. 8, 2013, which is hereby incorporated by reference herein in its entirety.