Driving method for an image pickup apparatus, image pickup apparatus, and image pickup system

The present invention provides a driving method for an image pickup apparatus that appropriately performs both readout of a signal of a reference pixel and mixing of mutual signals output by a plurality of effective pixels, and the present invention also provides an image pickup apparatus and an image pickup system.

BACKGROUND

Technical Field

The present disclosure relates to a driving method for an image pickup apparatus, an image pickup apparatus, and an image pickup system.

Description of the Related Art

An image pickup apparatus in which pixels are arranged in a matrix comprising rows and columns has been proposed. An image pickup apparatus described in Japanese Patent Laid-Open No. 2011-097646 has a configuration in which signals output from pixels in a plurality of columns which are electrically connected to a single signal line are mixed with one another on the signal line.

SUMMARY

An aspect of the present invention relates to a driving method for an image pickup apparatus that includes a plurality of pixels arranged in rows and columns, and a plurality of signal lines each being arranged corresponding to one of the columns of the plurality of pixels, the plurality of pixels including a plurality of effective pixels arranged in the rows and the columns, and a plurality of reference pixels arranged in at least one row and the columns corresponding to the columns in which the plurality of effective pixels are arranged and outputting only a signal of a noise level, each of the plurality of effective pixels including a photoelectric conversion unit to perform a photoelectric conversion of incident light and an amplification transistor having an input node for inputting charges generated by the photoelectric conversion unit, and each of the plurality of reference pixels including an amplification transistor having an input node, the driving method including: a first operation of overlapping a first period with a second period during which a signal generated based on the charges generated by the photoelectric conversion unit in each of the plurality of effective pixels is output to one of the signal lines by connecting a plurality of amplification transistors in a first number of the plurality of effective pixels, to the one of the signal lines, without electrically connecting the input node of the amplification transistor in each of the plurality of effective pixels, and a second operation of: individually outputting the signal of the noise level to the single signal line by the amplification transistor in each of the plurality of reference pixels, or overlapping a third period with a fourth period when a signal generated based on a potential at the input node of each of the plurality of reference pixels is output to the one of signal lines by connecting a plurality of amplification transistors in a second number of the plurality of reference pixels, to the one of the signal lines, without electrically connecting the input node of the amplification transistor in each of the plurality of reference pixels to the other of the plurality of reference pixels, the second number being fewer than the first number.

In addition, another aspect of the present invention relates to a driving method for an image pickup apparatus that includes a plurality of pixels arranged in rows and columns, and a plurality of signal lines each being arranged correspond to one of the columns of the plurality of pixels, the plurality of pixels including a plurality of effective pixels arranged in the rows and the columns, and reference pixels arranged in at least one row and the columns corresponding to the columns in which the plurality of effective pixels are arranged, each of the plurality of effective pixels including a photoelectric conversion unit to perform a photoelectric conversion of incident light and an amplification transistor having an input node for inputting charges generated by the photoelectric conversion unit, and each of the plurality of reference pixels including a light-shielded photoelectric conversion unit and an amplification transistor having an input node, the driving method including: a first operation of overlapping a first period with a second period during which a signal generated based on the charges generated by the photoelectric conversion unit in each of the plurality of effective pixels is output to one of the signal lines by connecting a plurality of amplification transistors in a first number of the plurality of effective pixels, to the one of the signal lines, without electrically connecting the input node of the amplification transistor in each of the plurality of effective pixels, and a second operation of: individually outputting the signal of the noise level to the single signal line by the amplification transistor in each of the plurality of reference pixels, or overlapping a third period with a fourth period when a signal generated based on a potential at the input node of each of the plurality of reference pixels is output to the one of signal lines by connecting a plurality of amplification transistors in a second number of the plurality of reference pixels, to the one of the signal lines, without electrically connecting the input node of the amplification transistor in each of the plurality of reference pixels to the other of the plurality of reference pixels, the second number being fewer than the first number.

In addition, another aspect of the present invention relates to an image pickup apparatus including: a plurality of pixels arranged in rows and columns; a plurality of signal lines each being arranged to correspond to one of the columns of the plurality of pixels; and a control unit that causes the plurality of pixels to perform both a first operation and a second operation, the plurality of pixels including a plurality of effective pixels arranged in the rows and the columns, and a plurality of reference pixels that are arranged in at least one row and the columns corresponding to the columns in which the plurality of effective pixels are arranged and output only a signal of a noise level, each of the plurality of effective pixels including a photoelectric conversion unit to perform a photoelectric conversion of incident light and an amplification transistor having an input node to which charges generated by the photoelectric conversion unit are input, and each of the plurality of reference pixels including an amplification transistor having an input node, a first operation of overlapping a first period with a second period during which a signal generated based on the charges generated by the photoelectric conversion unit in each of the plurality of effective pixels is output to one of the signal lines by connecting a plurality of amplification transistors in a first number of the plurality of effective pixels, to the one of the signal lines, without electrically connecting the input node of the amplification transistor in each of the plurality of effective pixels, and a second operation of: individually outputting the signal of the noise level to the single signal line by the amplification transistor in each of the plurality of reference pixels, or overlapping a third period with a fourth period when a signal generated based on a potential at the input node of each of the plurality of reference pixels is output to the one of signal lines by connecting a plurality of amplification transistors in a second number of the plurality of reference pixels, to the one of the signal lines, without electrically connecting the input node of the amplification transistor in each of the plurality of reference pixels to the other of the plurality of reference pixels, the second number being fewer than the first number.

DESCRIPTION OF THE EMBODIMENTS

However, according to the technology described in Japanese Patent Laid-Open No. 2011-097646, review for appropriately performing both readout of a signal of a reference pixel that only outputs a signal different from a signal of an effective pixel such as a noise level and mixing of mutual signals output from a plurality of effective pixels has not been conducted. Hereinafter, a technology for addressing this problem will be described.

First Exemplary Embodiment

FIG. 1Aillustrates a configuration of an image pickup apparatus according to the present exemplary embodiment.

A pixel array100is provided with an effective pixel area101ain which effective pixels102aare arranged in a matrix comprising rows and columns, and an OB pixel area101bin which optical black pixels (hereinafter, will be referred to as OB pixels)102bare arranged in a matrix. The OB pixel102bis an example of a reference pixel that only outputs a signal of a noise level according to the present exemplary embodiment. The OB pixel area101bis adjacent to the effective pixel area101a. The effective pixel102aoutputs both a noise signal corresponding to the signal of the noise level and a signal based on charges generated by a photoelectric conversion of incident light (hereinafter, will be referred to as photoelectric conversion signal) to a signal line109. The OB pixel102boutputs the noise signal corresponding to the signal of the noise level to the signal line109. Hereinafter, the noise signal output by the effective pixel102awill be referred to as effective noise signal, and the noise signal output by the OB pixel102bwill be referred to as OB noise signal. It is noted that the effective pixels102a, the OB pixels102b, and the signal line109are illustrated only in one column inFIG. 1A, but in actuality, the effective pixels102a, the OB pixels102b, and the signal lines109are provided across several thousands of columns. Hereinafter, pixels collectively represented by including the effective pixels102aand the OB pixels102bare referred to as pixels102.

A vertical scanning circuit112sequentially scans the effective pixels102aand the OB pixels102bfor each row. The effective pixel102alocated in a row selected by the vertical scanning circuit112outputs both the effective noise signal and the photoelectric conversion signal to the signal line109. The OB pixel102blocated in the row selected by the vertical scanning circuit112outputs the OB noise signal to the signal line109. The vertical scanning circuit112is an example of a control unit.

A signal processing circuit103is provided with a current supply unit104, an amplification unit105, a signal holding unit106, and a horizontal scanning circuit107. Although the current supply unit104is illustrated as a single block, a plurality of current supply units104each provided while corresponding to the signal line109in each of the columns are collectively illustrated as a single block. In addition, the same applies to the amplification unit105and the signal holding unit106. A plurality of amplification units105and a plurality of the signal holding units106each provided while corresponding to the signal line109in each of the columns are respectively illustrated as single blocks.

The horizontal scanning circuit107sequentially scans the signal holding units106in the respective columns. Accordingly, the signals held by the signal holding units106in the respective columns are sequentially transferred from the signal holding units106in the respective columns to an output amplifier108. The output amplifier108outputs signals obtained by amplifying the signals output from the signal holding units106in the respective columns to an external part of the image pickup apparatus.

A timing generator110(hereinafter, will be referred to as TG110) controls operations of the current supply unit104, the amplification unit105, the signal holding unit106, the horizontal scanning circuit107, and the vertical scanning circuit112.

The vertical scanning circuit112can change the number of rows of the pixels selected at the same time on the basis of the control from the TG110.

FIG. 1Billustrates respective circuit configurations of the effective pixel102aand the OB pixel102baccording to the present exemplary embodiment. InFIG. 1B, reference symbols are assigned to elements provided in the OB pixel102b. The effective pixel102aand the OB pixel102bhave the same configuration except that light is shielded in a photoelectric conversion unit201in the OB pixel102b.

The photoelectric conversion unit201generates charges based on incident light. A transistor202is provided on an electric path between the photoelectric conversion unit201and a floating diffusion unit (hereinafter, will be referred to as FD unit corresponding to initial letters of floating diffusion)203. The transistor202is a transfer transistor that controls ON and OFF of charge transfer from the photoelectric conversion unit201to the FD unit203. One main node of a transistor204is electrically connected to the FD unit203, and the other main node is supplied with a power supply voltage VDD. The transistor204is a reset transistor that controls ON and OFF of potential reset of the FD unit203. An input node of a transistor205is electrically connected to the FD unit203, one main node is supplied with the power supply voltage VDD, and the other main node is electrically connected to one main node of a transistor206. The transistor205is an amplification transistor that outputs a signal based on the potential of the FD unit203. The other main node of the transistor206is electrically connected to the signal line109. The transistor206is a selection transistor that switches a conductive state and a non-conductive state between the transistor205functioning as the amplification transistor and the signal line109. Control nodes of the transistor202, the transistor204, the transistor206are respectively supplied with a signal ptx, a signal pres, and a signal psel in the stated order from the vertical scanning circuit112.

The transistor205in the pixel102performs a source follower operation by using the current supplied from the current supply unit104and the power supply voltage VDD.

Pulses for driving the OB pixels102bon an n-th row are set as pres[n], ptx[n], and psel[n], and pulses for driving the effective pixels102aon an m-th row are set as pres[m], ptx[m], and psel[m].

FIG. 2is a circuit diagram for one column of the signal processing circuit103illustrated inFIG. 1A.

The current source corresponding to the current supply unit104supplies the current to the transistor205in the pixel102via the signal line109.

The amplification unit105includes a feedback capacitance309, an input capacitance310, a switch311, and a differential amplifier312. An inverting node of the differential amplifier312is electrically connected to one node of the input capacitance310, one node of the feedback capacitance309, and one node of the switch311. A reference voltage Vref is input to a non-inverting node of the differential amplifier312. An output node of the differential amplifier312is electrically connected to the other node of the feedback capacitance309, the other node of the switch311, and the signal holding unit106.

The signal holding unit106is constituted by a switch301, a switch302, an N-signal holding capacitance303, an S-signal holding capacitance304, a switch305, and a switch306. The switch301and the switch302are both a CMOS switch. ON and OFF of the switch301are controlled by a signal pn output from the TG110and a signal pn_b corresponding to an inverted signal of the signal pn. ON and OFF of the switch302are controlled by a signal ps output from the TG110and a signal ps_b corresponding to an inverted signal of the signal ps.

The horizontal scanning circuit107controls ON and OFF of the switch305and ON and OFF of the switch306. When the switch305is turned ON, the signal held by the N-signal holding capacitance303is output to the output amplifier108. When the switch306is turned ON, the signal held by the S-signal holding capacitance304is output to the output amplifier108. The output amplifier108outputs a signal obtained by amplifying the signal held by the N-signal holding capacitance303and the signal held by the S-signal holding capacitance304.

FIG. 3is a driving timing chart of the image pickup apparatus illustrated inFIG. 1A.

The image pickup apparatus mixes the signals of the effective pixels102ain X rows (X is a number higher than or equal to 2) with one another on the single signal line109. The image pickup apparatus also mixes the signals of the OB pixels102bin Y rows that are fewer than the X rows with one another on the single signal line109. A case where X=2 and Y=1 are set in the image pickup apparatus according to the present exemplary embodiment will be described.

In the operation illustrated inFIG. 3, each of the FD units203in the effective pixels102ain a plurality of rows holds the charges generated by the photoelectric conversion unit201in each of the effective pixels102a. Subsequently, the vertical scanning circuit112selects the effective pixels102ain the plurality of rows at the same time. That is, a period for outputting the signal based on the charges generated by each of the photoelectric conversion units201by each of the transistors205in the plurality of effective pixels102ais overlapped with one another. Accordingly, the signal output from each of the effective pixels102ain the plurality of rows is mixed with one another on the signal line109. Each of the FD units203in the OB pixels102bin a plurality of rows holds charges based on a dark current component generated by the photoelectric conversion unit201in each of the OB pixels102b. Subsequently, the vertical scanning circuit112individually selects the OB pixels102bon the respective rows. Accordingly, the signal is output from the OB pixel102bfor one row each to the signal line109without being mixed with the other signals.

InFIG. 3, the operation related to the OB pixel102bis performed during a period from a time t1to a time t10. The operation related to the effective pixel102ais performed during a period from a time t11to a time t14.

The respective signals illustrated inFIG. 3correspond to the respective signals illustrated inFIG. 1BandFIG. 2.

The signal ptx, the signal pres, and the signal psel illustrated inFIG. 3are signals for respectively controlling the transistor202, the transistor204, and the transistor206in the stated order.

At the time t1, pres[n] turns to a Low level (hereinafter, will be referred to as Lo) to turn the transistor204OFF. Accordingly, reset of the FD unit203is cancelled. The vertical scanning circuit112sets the signal psel[n] on the selected row to a High level (hereinafter, will be referred to as Hi). Accordingly, the transistor206in the OB pixel102bon the n-th row is turned ON. Accordingly, the transistor205in the OB pixel102bon the n-th row is connected to the signal line109via the transistor206.

At the time t2, the TG110sets the signal pc for controlling the switch311to Hi. Subsequently, the TG110sets the pulse pc to Lo at the time t3. Accordingly, a potential at the signal line109based on a potential at the reset FD unit203is clamped by the input capacitance310. The output of the amplification unit105at the time t3corresponds to a reference potential Vref.

At the time t4, the TG110sets the signal ptn to Hi. Accordingly, the switch301is turned ON. Subsequently, at the time t5, the TG110sets the signal ptn to Lo. As a result, the N-signal holding capacitance303holds a signal output by the amplification unit105at the time t5(hereinafter, will be referred to as N-signal). The N-signal is a signal having an offset variation for each column of the amplification unit105as a main component.

At the time t6, the vertical scanning circuit112sets the signal ptx[n] to Hi.

Subsequently, at the time t7, the vertical scanning circuit112sets the signal ptx[n] to Lo. Accordingly, the FD unit203holds the charges based on the dark current component generated by the photoelectric conversion unit201in the OB pixel102b. The transistor205outputs the signal based on this potential at the FD unit203to the signal line109via the transistor206.

A signal corresponding to a difference between the potential clamped by the input capacitance310at the time t3and the signal line109at the time t6is input to an inverting input node of the differential amplifier312.

The amplification unit105outputs a signal obtained by amplifying the signal input to the inverting input node to the signal holding unit106.

This amplification factor of the differential amplifier312is determined on the basis of a ratio of capacitance values between the input capacitance310and the feedback capacitance309. This output signal obtained by amplifying the signal based on the charges generated by the photoelectric conversion unit201by the amplification unit105is referred to as S-signal.

At the time t8, the TG110sets the signal pts to Hi. Accordingly, the switch302is turned ON. Thereafter, at the time t9, the TG110sets the signal pts to Lo. As a result, the S-signal holding capacitance304holds the S-signal output by the amplification unit105.

In addition, at the time t9, the vertical scanning circuit112sets the signal psel[n] to Lo.

Subsequently, the horizontal scanning circuit107scans the signal holding units106in the respective columns. That is, the switches305and the switches306in the respective columns are sequentially turned ON. Accordingly, each of the S-signal and the N-signal held by the signal holding units106in the respective columns is output to the output amplifier108.

Next, the operation related to the effective pixel102awill be described. A difference from the previously described operation related to the OB pixel102bwill be mainly described hereinafter.

At the time t11, the vertical scanning circuit112sets both the signal psel[m] and the signal psel[m+1] to Hi. Accordingly, the transistors206in the effective pixels102aon the m-th row and the (m+1)-th row are turned ON at the same time. In addition, at the time t11, the vertical scanning circuit112sets both the signal pres[m] and the signal pres[m+1] to Lo. Accordingly, the transistor205in the effective pixel102aon the m-th row outputs the signal based on the potential at the reset FD unit203to the signal line109. Similarly, the transistor205in the effective pixel102aon the (m+1)-th row outputs the signal based on the potential at the reset FD unit203to the signal line109. Accordingly, the signal output by the transistor205in the effective pixel102aon the m-th row is mixed with the signal output by the transistor205in the effective pixel102aon the (m+1)-th row on the signal line109.

Thereafter, the TG110sets the signal pc to Hi, and then the signal pc is set to Lo. Thereafter, the TG110sets the signal ptn to Hi, and then the signal ptn is set to Lo. Accordingly, the N-signal holding capacitance303holds the N-signal.

At the time t12, the vertical scanning circuit112sets both the signal ptx[m] and the signal ptx[m+1] to Hi. Subsequently, at the time t13, the vertical scanning circuit112sets both the signal ptx[m] and the signal ptx[m+1] to Lo. Accordingly, the transistor205in the effective pixel102aon the m-th row outputs the signal based on the charges generated while the photoelectric conversion unit201performs the photoelectric conversion of the incident light to the signal line109. Similarly, the transistor205in the effective pixel102aon the (m+1)-th row outputs the signal based on the charges generated while the photoelectric conversion unit201performs the photoelectric conversion of the incident light to the signal line109. Accordingly, the signal output by the transistor205in the effective pixel102aon the m-th row is mixed with the signal output by the transistor205in the effective pixel102aon the (m+1)-th row on the signal line109.

Thereafter, the TG110sets the signal pts to Hi, and then the signal pts is set to Lo. Accordingly, the S-signal holding capacitance304holds the S-signal.

Subsequently, the horizontal scanning circuit107scans the signal holding units106in the respective columns. That is, the switches305and the switches306in the respective columns are sequentially turned ON. Accordingly, each of the S-signal and the N-signal held by the signal holding units106in the respective columns is output to the output amplifier108.

The image pickup apparatus according to the present exemplary embodiment mixes the signals output by the effective pixels102ain the plurality of rows with one another on the single signal line109. On the other hand, the image pickup apparatus according to the present exemplary embodiment independently reads out the signal output by the OB pixel102bfor one row each.

With regard to the OB pixels102btoo, descriptions will be given of a case where the signals output by the OB pixels102bin the plurality of rows are mixed with one another on the signal line109similarly as in the effective pixels102a. In this case, to obtain the ten S-signals of the OB pixels102bin the respective columns, the OB pixels102bon 20 rows are provided in a case where the signals output by the OB pixels102bin two rows are mixed with one another.

On the other hand, since the image pickup apparatus according to the present exemplary embodiment individually reads out the OB pixels102bfor each row, the OB pixels102bin ten rows may be provided. Therefore, the image pickup apparatus according to the present exemplary embodiment can reduce the area of the OB pixel area101bby a size corresponding to the OB pixels102bin ten rows.

Therefore, in the OB pixel area101btoo, the image pickup apparatus according to the present exemplary embodiment has the effect of reducing the area of the pixel array as compared with the case where the signals output by the OB pixels102bin the plurality of rows are mixed with one another on the signal line109.

By electrically connecting the FD units203in the plurality of effective pixels102aarranged in the X rows to one another, a combined capacitance (hereinafter, will be referred to as combined capacitance A) may be generated, and the charges of the plurality of photoelectric conversion units201may be mixed with one another by the combined capacitance A in some cases. That is, this case corresponds to a case where the input nodes of the transistors205in the plurality of effective pixels102aarranged in the X rows are electrically connected to one another. Hereinafter, descriptions will be given of a situation where the FD unit203in the OB pixel102bis not electrically connected to the other OB pixel102bin this case. The single FD unit203holds the charges of the photoelectric conversion unit201in the OB pixel102bin this case. Thus, the charges of the photoelectric conversion unit201in the OB pixel102bis held by a capacitance value of the FD unit203which is lower than a capacitance value of the combined capacitance A. Therefore, a noise component included in the signal output by the transistor205in the OB pixel102btends to have a larger amplitude than a noise component included in the signal output by the transistor205which is based on the charges mixed by the combined capacitance A. Accordingly, even when the signal output by the image pickup apparatus which is based on the charges of the OB pixel102bis subtracted from the signal output by the transistor205which is based on the charges mixed by the combined capacitance A, the noise component is not accurately reduced. Therefore, the quality of the image generated on the basis of the signal output by the image pickup apparatus is decreased.

Meanwhile, the image pickup apparatus according to the present exemplary embodiment mixes the signals output by the plurality of transistors205in the effective pixel area101awith one another on the signal line109. Accordingly, an amplitude difference between the noise component included in the signal based on the charges of the plurality of effective pixels102aand the noise component included in the signal based on the charges of the OB pixel102bhardly occurs. Therefore, the image pickup apparatus according to the present exemplary embodiment has the effect with which the area of the pixel array can be reduced while the decrease in the image quality is suppressed.

A signal corresponding to a difference between the signal based on the output of the OB pixel102band the signal based on the output of the effective pixel102ais generated in an external part of the image pickup apparatus. Accordingly, it is possible to generate a signal in which the dark current component is reduced from the signal based on the output of the effective pixel102a. Accordingly, an influence of a fluctuation by a temperature of a reference for the black color of the image generated on the basis of the signal output by the image pickup apparatus can be reduced. Accordingly, it is possible to improve the quality of the image generated on the basis of the signal output by the image pickup apparatus according to the present exemplary embodiment.

According to the present exemplary embodiment, the example in which the reference pixel that only outputs the signal of the noise level is the OB pixel102bhas been described. As another example, the reference pixel may be a dummy pixel in which the photoelectric conversion unit201provided in the OB pixel102bis omitted.

According to the present exemplary embodiment, the configuration in which each of the pixels102switches the conductive state and the non-conductive state of the electric path between the transistor205and the signal line109by ON and OFF of the transistor206has been described. As another example, a configuration in which each of the pixels102does not include the transistor206may also be adopted. In this case, the power supply voltage VDD supplied to the transistor204is set as a first voltage, and a voltage having a voltage value different from the first voltage is set as a second voltage. When the transistor204is turned ON in a case where the first voltage is supplied, the FD unit203is set to have a potential at which the transistor205does not output the signal to the signal line109. On the other hand, when the transistor204is turned ON in a case where the second voltage is supplied, the FD unit203is set to have a potential at which the transistor205outputs the signal to the signal line109. Accordingly, the transistor205in which the FD unit203is set to have the potential based on the second voltage outputs the signal to the signal line109. Therefore, by switching the voltage supplied to the transistor204between the first voltage and the second voltage, it is possible to select the pixel102that outputs the signal to the signal line109. In the image pickup apparatus according to the present exemplary embodiment, in a case where the signals of the pixels102in a plurality of rows are mixed with one another on the signal line109, the voltage supplied to the transistor204in the pixels102in the plurality of rows is set as the second voltage. Accordingly, the image pickup apparatus according to the present exemplary embodiment can mix the signal output by each of the plurality of pixels102with one another on the signal line109.

According to the present exemplary embodiment, in a state in which all the transistors206in the plurality of effective pixels102aare ON, a current flowing through the transistor205of each of the plurality of effective pixels102afluctuates in accordance with the potential at the FD unit203in each of the plurality of effective pixels102a. Even in a case where the current flowing through the transistor205fluctuates as described above, according to the present exemplary embodiment, the operation for the transistor205to output the signal based on the potential at the FD unit203to the signal line109is dealt with as the source follower operation. This also applies to the subsequent exemplary embodiments.

According to the present exemplary embodiment, the example in which the OB pixels102bcorresponding to the example of the reference pixel are arranged in the plurality of rows has been described, but it suffices if the OB pixel102bon at least one row may be provided in the image pickup apparatus according to the present exemplary embodiment.

Second Exemplary Embodiment

With regard to the image pickup apparatus according to the present exemplary embodiment, a difference from the first exemplary embodiment will be mainly described.

The image pickup apparatus mixes the signals of the effective pixel102ain X rows (X is a number higher than or equal to 2) with one another on the single signal line109. The image pickup apparatus also mixes the signals of the OB pixels102bin Y rows that are fewer than the X rows on the single signal line109with one another. A case where X=3 and Y=2 are set in the image pickup apparatus according to the present exemplary embodiment will be described.

The configuration of the image pickup apparatus according to the present exemplary embodiment is the same as that inFIG. 1Adescribed in the first exemplary embodiment. The configuration of the pixel102according to the present exemplary embodiment is the same as that inFIG. 1Bdescribed in the first exemplary embodiment. In addition, the configurations of the amplification unit105and the signal holding unit106according to the present exemplary embodiment are the same as those inFIG. 2described in the first exemplary embodiment.

FIG. 4is a timing chart illustrating the operation of the image pickup apparatus according to the present exemplary embodiment. The operation of mixing the signals of the OB pixels102bin the Y rows with one another on the single signal line109is performed during a period from a time t101to a time t104. The operation of mixing the signals of the effective pixels102ain the X rows with one another on the single signal line109is performed during a period from a time t105to a time t108.

At the time t101, the vertical scanning circuit112sets both the signal pres[n] and the signal pres[n+1] to Lo. Accordingly, reset of the FD unit203in the OB pixel102bis cancelled.

In addition, at the time t101, the vertical scanning circuit112sets both the signal psel[n] and the signal psel[n+1] to Hi. Accordingly, the transistors206in the OB pixels102bin the n-th row and the (n+1)-th row are turned ON. Accordingly, the signal output by the transistor205in the OB pixel102bin the n-th row and the signal output by the transistor205in the OB pixel102bin the (n+1)-th row are mixed with one another on the signal line109.

Thereafter, the TG110sets the signal pc to Hi, and then the signal pc is set to Lo. Accordingly, the potential at the signal line109when the TG110sets the signal pc to Lo is clamped by the input capacitance310.

Thereafter, the TG110sets the signal pn to Hi, and then the signal pn is set to Lo. Accordingly, the N-signal holding capacitance303holds the signal output by the amplification unit105.

Thereafter, the vertical scanning circuit112selects the effective pixels102ain three rows at the same time. The other operation is the same as the operation of mixing the signal output by each of the effective pixels102ain the plurality of rows with one another which has been described in the first exemplary embodiment.

According to the present exemplary embodiment, the signal output by each of the effective pixels102ain the three rows is mixed with one another, and the signal output by each of the OB pixels102bin the two rows is mixed with one another. Meanwhile, descriptions will be given of a case where the signal output by each of the OB pixels102bin the same three rows is mixed with one another as the case where the signal output by each of the effective pixels102ain the three rows is mixed with one another. In this case, when ten S-signals output from the OB pixel area101bare to be used, the OB pixels102bin 30 rows are to be provided. However, like the present exemplary embodiment, by mixing the signals output by the OB pixel102bin the two rows with one another, it suffices if the OB pixels102bin 20 rows are provided. Therefore, as compared with the case where the signal output from each of the OB pixels102bin the three rows is mixed with one another, the area of the OB pixel area101bcan be reduced by a size corresponding to the OB pixels102bin ten rows.

The image pickup apparatus according to the present exemplary embodiment mixes the signal output by each of the effective pixels102ain the X rows with one another on the single signal line109. Subsequently, the signal output by each of the OB pixels102bin the Y rows that are fewer than X rows with one another on the single signal line109. Accordingly, as compared with the case where the signals output by the OB pixels102bin the same three rows are mixed with one another as the case where the signal output by the effective pixels102ain the three rows are mixed with one another, it is possible to reduce the area of the OB pixel area101b. Thus, the image pickup apparatus according to the present exemplary embodiment can reduce the area of the pixel array.

By electrically connecting the FD units203in the plurality of effective pixels102aarranged in the X rows to one another, a combined capacitance (hereinafter, will be referred to as combined capacitance A) may be generated, and the charges of the plurality of photoelectric conversion units201may be mixed with one another in the combined capacitance A in some cases. Hereinafter, descriptions will be given of a situation in which the FD units203in the plurality of OB pixels102barranged in the Y rows that are fewer than the X rows are electrically connected to each other in this case. By electrically connecting the FD units203in the OB pixels102bin the Y rows with one another, a combined capacitance (hereinafter, will be referred to as combined capacitance B) is generated, and the charges of the plurality of photoelectric conversion units201are mixed with one another in the combined capacitance B in this case. Thus, a capacitance value of the combined capacitance B is a value lower than the capacitance value of the combined capacitance A. Therefore, a noise component included in the signal output by the transistor205which is based on the charges mixed by the combined capacitance B tends to have a larger amplitude than a noise component included in the signal output by the transistor205which is based on the charges mixed by the combined capacitance A. Accordingly, even when the signal output by the image pickup apparatus which is based on the charges mixed by the combined capacitance B is subtracted from the signal output by the image pickup apparatus which is based on the charges mixed by the combined capacitance A, the noise component is not accurately reduced. Therefore, the quality of the image generated on the basis of the signal output by the image pickup apparatus is decreased.

Meanwhile, the image pickup apparatus according to the present exemplary embodiment mixes the signals output by the plurality of transistors205with one another on the signal line109in each of the effective pixel area101aand the OB pixel area101b. Accordingly, an amplitude difference between the noise component included in the signal based on the charges of the plurality of effective pixels102aand the noise component included in the signal based on the charges of the plurality of OB pixels102bhardly occurs. Therefore, the image pickup apparatus according to the present exemplary embodiment has the effect with which the area of the pixel array can be reduced while the decrease in the image quality is suppressed.

Third Exemplary Embodiment

With regard to the image pickup apparatus according to the present exemplary embodiment, a difference from the first exemplary embodiment will be mainly described. The image pickup apparatus according to the present exemplary embodiment sets a voltage difference of control voltages for controlling ON and OFF of the transistor204in the reference pixel to be smaller than a voltage difference of control voltages for controlling ON and OFF of the transistor204in the effective pixel102a. The control voltage for controlling ON and OFF of the transistor204is equivalent to the signal pres output by the vertical scanning circuit112.

The configuration of the image pickup apparatus according to the present exemplary embodiment is the same as the configuration illustrated inFIG. 1A,FIG. 1B, andFIG. 2described in the first exemplary embodiment.

In the image pickup apparatus according to the first exemplary embodiment, the signal of the OB pixel102bis output from the single transistor205to the signal line109. On the other hand, the signal of the effective pixel102ais output from the two transistors205to the signal line109. Herein, a period from when the signal of the OB pixel102bat the same signal level starts to be output to the signal line109until the signal becomes statically determinate at the signal level is compared with a period from when the mixed signal of the effective pixel102astarts to be output to the signal line109until the signal becomes statically determinate at the signal level. The number of transistors205in the OB pixel102bwhich output the signal to the signal line109at the same time is lower than that in the effective pixel102a. Thus, the period from when the signal of the OB pixel102bis output to the signal line109until the potential at the signal line109becomes statically determinate at the relevant signal level is longer as compared with the case of the signal of the effective pixel102a. Thus, a case occurs where the TG110sets the signal ps from Hi to Lo before the potential at the signal line109becomes statically determinate at the signal level of the signal output by the OB pixel102b. In this case, the S-signal holding capacitance304holds a signal obtained by amplifying a signal, which has an amplification smaller than that of the signal output by the OB pixel102b, by the amplification unit105. Therefore, even when the signal based on the output of the OB pixel102bis subtracted from the signal based on the output of the effective pixel102a, the dark current component may not accurately be subtracted in some cases.

In view of the above, in the image pickup apparatus according to the present exemplary embodiment, the vertical scanning circuit112sets a Lo potential of the signal pres to be higher in the one frame period during which the mixing of the mutual signals of the pixels102in the plurality of rows is performed on the signal line109as compared with the other one frame during which the above-described mixing is not performed. While the vertical scanning circuit112sets the Lo potential of the signal pres to be higher, the potential at the FD unit203is increased via a parasitic capacitance between a control node of the transistor204and the FD unit203. Accordingly, as compared with the case where the number of rows in which the signal output from each of the pixels102is mixed with one another is relatively high, it is possible to shorten the period from when the signal of the pixel102is output to the signal line109until the potential at the signal line109becomes statically determinate in the case where the number of rows is relatively low. In a case where a parasitic capacitance exists between a line for supplying the signal pres to the pixels102in the respective rows and the FD unit203, the potential at the FD unit203is facilitated to be increased by increasing the Lo potential of the signal pres.

FIG. 5illustrates an operation of the image pickup apparatus according to the present exemplary embodiment.

The operation illustrated inFIG. 5is the same as the operation illustrated inFIG. 3except for the potential of the signal pres[n], the potential of the signal pres[m], and the potential of the signal pres[m+1].

InFIG. 5, the potentials of the signal pres[n], the signal pres[m], and the signal pres[m+1] in a case where the signals output by the effective pixels102ain the plurality of rows are mixed with one another on the single signal line109in the one frame are indicated by broken lines. On the other hand, inFIG. 5, the potentials of the signal pres[n], the signal pres[m], and the signal pres[m+1] in a case where the signals output by the effective pixels102ain the plurality of rows are not mixed with one another on the single signal line109in the one frame are indicated by solid lines.

The potential at the signal line109is indicated by vline illustrated inFIG. 5.

Hereinafter, the operation of setting the potentials of the signal pres[n], the signal pres[m], and the signal pres[m+1] to be the potentials indicated by the broken line will be described.

At the time t202, the vertical scanning circuit112sets the signal pres[n] to Lo. Accordingly, the signal pres[n] is set to have the potential indicated by the broken line.

The parasitic capacitance exists between the control node of the transistor204and the FD unit203. With this parasitic capacitance, the potential at the FD unit203fluctuates depending on the potential at the control node of the transistor204. As illustrated inFIG. 5, the potential at the FD unit203after the signal pres[n] turns to Lo is decreased with respect to the potential at the FD unit203when the signal pres[n] is at Hi.

Meanwhile, the case where the Lo potential of the signal pres[n] is set as the potential indicated by the solid line will be described. In that case, with respect to the case where the Lo potential of the signal pres[n] is the potential indicated by the broken line, the period from when the signal pres[n] turns to Lo until the potential at the FD unit203is statically determinate is lengthened. Thus, as indicated by vline inFIG. 5, as compared with the case where the Lo potential of the signal pres[n] is the potential indicated by the broken line, the period from when the signal pres[n] turns to Lo until the potential at the signal line109is statically determinate is lengthened in a case where the Lo potential of the signal pres[n] is the potential indicated by the solid line. When the TG110sets the signal ptn from Hi to Lo before the potential at the signal line109is statically determinate, the potential of the N-signal held by the N-signal holding capacitance303is different from the potential of the N-signal held in a case where the potential at the FD unit203becomes statically determinate.

On the other hand, in the operation illustrated inFIG. 5, the Lo potential of the signal pres[n] is set as the potential indicated by the broken line. Accordingly, it is possible to shorten the period until the potential at the signal line109becomes statically determinate. Thus, the N-signal holding capacitance303can hold the N-signal in a state in which the potential at the signal line109is statically determinate.

Similarly, the S-signal holding capacitance304can also hold the S-signal in which the potential at the signal line109is statically determinate.

Accordingly, the image pickup apparatus according to the present exemplary embodiment can hold the S-signal and the N-signal of the OB pixel102bafter the potential at the signal line109becomes statically determinate. As a result, it is possible to improve the accuracy of the signal of the OB pixel102b. Accordingly, the signal from which the dark current component is accurately subtracted can be obtained by subtracting the signal based on the output of the OB pixel102bfrom the signal based on the output of the effective pixel102a. Furthermore, the Lo potential of the signal pres of the effective pixel102awhere the mixing of the mutual signals in the plurality of rows is performed on the signal line109is set as the same as that of the OB pixel102b. With this configuration, the image pickup apparatus according to the present exemplary embodiment can obtain the signal from which the dark current component is further accurately subtracted can be obtained.

It is noted that, according to the present exemplary embodiment, the vertical scanning circuit112sets the Lo potential of the signal pres to be higher in the one frame period during which the mixing of the mutual signals of the pixels102in the plurality of rows is performed on the signal line109than that in the other one frame period during which the above-described mixing is not performed. As another example, in the same frame period, the Lo potential of the signal pres may be set to be higher in the OB pixel102bwhere the mixing of the mutual signals output from the pixels in the plurality of rows is not performed than that in the effective pixel102awhere the mixing of the mutual signals output from the pixels in the plurality of rows is performed. In this case too, each of the N-signal holding capacitance303and the S-signal holding capacitance304can obtain the N-signal and the S-signal based on the output of the OB pixel102bafter the potential at the signal line109becomes statically determinate. Accordingly, the image pickup apparatus can accurately obtain the S-signal and the N-signal based on the output of the OB pixel102b. It is noted that the other one frame period during which the above-described mixing is not performed may be a period during which the operation of individually reading out the signals of the effective pixels102ais performed. Alternatively, the other one frame period during which the above-described mixing is not performed may be a period during which, by electrically connecting the FD units203of the mutual effective pixels102ato one another, charges averaged over the plurality of effective pixels102aare generated, and the operation of reading out the signal based on the averaged charge is performed.

In addition, according to the present exemplary embodiment, the vertical scanning circuit112sets the Lo potential of the signal pres to be higher in a case where the mixing of the signals of the pixels102in the plurality of rows on the signal line109is performed than that in a case where the above-described mixing is not performed. As another example, the vertical scanning circuit112may set a Hi potential of the signal pres to be lower in a case where the mixing of the signals of the pixels102in the plurality of rows on the signal line109is performed than that in a case where the above-described mixing is not performed. Since the Hi potential of the signal pres is set to be lower, the potential at which the FD unit203is reset is decreased. While the potential at which the FD unit203is reset is decreased, it is possible to decrease a potential difference between the potential at which the FD unit203becomes statically determinate after the transition of the signal ptx from Hi to Lo and the potential in a state in which the FD unit203is reset. Accordingly, after the transition of the signal ptx from Hi to Lo, it is possible to shorten the period until the potential at the FD unit203becomes statically determinate since the Hi potential of the signal pres is decreased. Thus, the image pickup apparatus in this example can obtain the S-signal and the N-signal based on the output of the OB pixel102bwhere the signals of the pixels in the plurality of rows are not mixed with one another on the signal line109in a state in which the signal line109is statically determinate. It is noted that the vertical scanning circuit112may set the Hi potential of the signal pres to be lower in the one frame period during which the mixing of the mutual signals of the pixels102in the plurality of rows is performed on the signal line109than that in the other one frame period during which the above-described mixing is not performed. In addition, in the same frame period, the Hi potential of the signal pres in the OB pixel102bwhere the mixing of the mutual signals output from the pixels in the plurality of rows is not performed may be set to be lower than that in the effective pixel102awhere the mixing of the mutual signals output from the pixels in the plurality of rows is performed.

It is noted thatFIG. 5illustrates that the potential vline at the time t202and he potential vline at the time t208are the same potential. However, in a case where the current amount supplied to the signal line109at the time t202is the same as that at the time t208, the potential vline at the time t208tends to the potential having a larger amplitude than that of the potential vline at the time t202. In the above-described case too, the image pickup apparatus according to the present exemplary embodiment can attain the above-described effect.

Fourth Exemplary Embodiment

With regard to the image pickup apparatus according to the present exemplary embodiment, a difference from the third exemplary embodiment will be mainly described.

The image pickup apparatus according to the present exemplary embodiment sets the voltage difference of the control voltage between ON and OFF of the transistor202in the optical black pixel102bto be lower than the voltage difference of the control voltage between ON and OFF of the transistor202in the effective pixel102a. The control voltage for controlling ON and OFF of the transistor202is equivalent to the signal ptx output by the vertical scanning circuit112.

FIG. 6illustrates the operation of the image pickup apparatus according to the present exemplary embodiment.

In the image pickup apparatus according to the present exemplary embodiment, the vertical scanning circuit112sets the Hi potential of the signal ptx to be lower in the one frame period during which the mixing of the mutual signals of the pixels102in the plurality of rows is performed on the signal line109than that in the other one frame period during which the above-described mixing is not performed. Accordingly, an upward swing width of the potential at the FD unit203when the signal ptx is set to Hi is decreased. Accordingly, it is possible to shorten the period until the potential at the signal line109becomes statically determinate after the transition of the signal ptx from Hi to Lo. Accordingly, the S-signal holding capacitance304can hold the S-signal based on the output of the OB pixel102bwhere the mixing of the mutual signals of the pixels in the plurality of rows on the signal line109is not performed after the potential at the signal line109becomes statically determinate. Thus, by subtracting the signal based on the output of the OB pixel102bfrom the signal based on the output of the effective pixel102a, the signal from which the dark current component is accurately subtracted can be obtained. Furthermore, the Hi potential of the signal ptx of the effective pixel102awhere the mixing of the mutual signals in the plurality of rows is performed on the signal line109is set to be the same as that of the OB pixel102b. With this configuration, the image pickup apparatus according to the present exemplary embodiment can obtain the signal from which the dark current component is further accurately subtracted can be obtained.

It is noted that the Hi potential of the signal ptx may be set to be lower in the OB pixel102bwhere the mixing of the mutual signals output from the pixels in the plurality of rows is not performed than that in the effective pixel102awhere the mixing of the mutual signals output from the pixels in the plurality of rows is performed in the same frame period.

In addition, the vertical scanning circuit112may set the Lo potential of the signal ptx to be higher in the one frame period during which the mixing of the mutual signals of the pixels102in the plurality of rows is performed on the signal line109than that in the other one frame period during which the above-described mixing is not performed. Accordingly, with the parasitic capacitance between the control node of the transistor202and the FD unit203, the potential at the time of the reset of the FD unit203is set to be increased. In addition, the amplitude between Hi and Lo of the signal ptx is also decreased. Accordingly, the upward swing of the potential at the FD unit203which occurs at the time of the transition of the signal ptx from Lo to Hi is suppressed by increasing the Lo potential of the signal ptx. Accordingly, after the transition of the signal ptx from Hi to Lo, the period until the potential at the signal line109becomes statically determinate is shortened by increasing the Lo potential of the signal ptx. Therefore, also in a case where the Lo potential of the signal ptx is increased, the same effect as the case where the Hi potential of the signal ptx is decreased can be attained. It is noted that the Lo potential of the signal ptx may be set to be higher in the OB pixel102bwhere the mixing of the mutual signals output from the pixels in the plurality of rows is not performed than that in the effective pixel102awhere the mixing of the mutual signals output from the pixels in the plurality of rows is performed in the same frame period.

The image pickup apparatus according to the present exemplary embodiment may be operated in combination with the operation described in the third exemplary embodiment.

The image pickup apparatus according to the first to fourth exemplary embodiments may adopt a configuration of further including a dummy pixel in which the photoelectric conversion unit201provided in the OB pixel102bis omitted. In this case, the current supplied to the dummy pixel by the current supply unit104and the respective signals supplied to the dummy pixel by the vertical scanning circuit112can be the same as those in the OB pixel102b.

It is noted thatFIG. 6illustrates that the potential vline at the time t202and he potential vline at the time t208are the same potential. However, in a case where the current amount supplied to the signal line109at the time t202is the same as that at the time t208, the potential vline at the time t208tends to the potential having a larger amplitude than that of the potential vline at the time t202. In the above-described case too, the image pickup apparatus according to the present exemplary embodiment can attain the above-described effect.

Fifth Exemplary Embodiment

With regard to the image pickup apparatus according to the present exemplary embodiment, a difference from the first exemplary embodiment will be mainly described.

In the image pickup apparatus according to the first exemplary embodiment, the period from the signal is output to the signal line109until the potential at the signal line109becomes statically determinate at the relevant signal level is longer for the signal of the OB pixel102bthan that for the effective pixel102a. The image pickup apparatus according to the present exemplary embodiment sets a current amount of the current supplied to the transistor205in the pixel102where the mixing of the mutual signals of the pixels in the plurality of rows on the signal line109is not performed to be higher than a current amount of the current supplied to the transistor205in the pixel102where the above-described mixing is performed.

Hereinafter, the current amount of the current supplied to the transistor205by the current supply unit104will be described.

A transconductance gm of the transistor205is represented by Expression (1) below.
gm=√{(2 μCox)(W/L)Id}(1)

μ denotes a carrier mobility, Cox denotes a gate capacitance of the transistor205per unit area, W denotes a channel length of the transistor205, L denotes a channel width of the transistor205, and Id denotes a drain current supplied to the transistor205. As gm is increased, a driving force of the transistor205is increased. Therefore, as gm is increased, the period from the transition of the signal ptx from Hi to Lo until the signal line109becomes statically determinate is shortened. As described in the first exemplary embodiment and the second exemplary embodiment, in the same frame, the image pickup apparatus mixes the signals output by the pixels102in X rows (X is a number higher than or equal to 2) with one another and mixes the signals output by the pixels102in Y rows that are fewer than the X rows with one another.

A current value of the current supplied to the pixels102where the signals output by the pixels102in the X rows are mixed with one another is set as Idm, and a current value of the current supplied to the pixels102where the signals output by the pixels102in the Y rows are mixed with one another is set as Idn. The current supply unit104sets values of the current value Idm and the current value Idn such that Expression (2) below is established.
Idm=Idn×Y/X(2)

FIG. 7illustrates a configuration of the current supply unit104according to the present exemplary embodiment.

A transistor401constitutes a cascode circuit together with a transistor400so that the transistor400stably supplies a current. A transistor402is a switch for switching ON and OFF of current supply to the signal line109. A voltage supply that is not illustrated in the drawing supplies a predetermined voltage to an input node of the transistor400. Accordingly, the transistor400supplies a current having a current value based on the voltage supplied to the input node of the transistor400to the signal line109. The voltage supply that is not illustrated in the drawing supplies a predetermined voltage to an input node of the transistor401. Accordingly, a drain potential at the transistor400is kept constant. Hereinafter, descriptions will be given while the transistor400, the transistor401, and the transistor402are all an N-type MOS transistor.

In order that the current supply unit104changes the current value of the current supplied to the signal line109, one or both of the voltages values of the voltage supplied to the input node of the transistor400and the voltage supplied to the input node of the transistor401may be changed.

The current supply unit104supplies both the current having the current value Idm and the current having the current value Idn that is higher than the current value Idm to the signal line109in the same frame period. In a case where the current supply unit104supplies the current having the current value Idn, as compared with the case where the current having the current value Idm is supplied, one or both of the voltage supplied to the input node of the transistor400and the voltage supplied to the input node of the transistor401may be increased. Accordingly, in the mixing of the mutual signals of the pixels102in the Y rows that are fewer than the X rows, as compared with the case where the current having the current value Idm is supplied, it is possible to shorten the period from the transition of the signal ptx from Hi to Lo until the signal line109becomes statically determinate.

A case exists where the signals of the effective pixels102ain the plurality of rows are mixed with one another on the signal line109, and the signals of the OB pixels102bare individually read out. In this case, when the signals of the effective pixel102aare read out, the current supply unit104supplies the current having the current value Idm to the signal line109. Meanwhile, when the signals of the OB pixels102bare read out, the current supply unit104supplies the current having the current value Idn to the signal line109. Accordingly, the N-signal holding capacitance303can hold the N-signal based on the output of the OB pixel102bin the state in which the potential at the signal line109is statically determinate. Similarly, the S-signal holding capacitance304can hold the S-signal based on the output of the OB pixel102bin the state in which the potential at the signal line109is statically determinate. Accordingly, the same effect as the effect described in the third exemplary embodiment can be attained.

It is noted that the current value of the current supplied by the current supply unit104may be set to be higher in the one frame period during which the mixing of the signals of the pixels102in the plurality of rows on the signal line109is not performed than that in the other one frame period during which the above-described mixing is performed.

Sixth Exemplary Embodiment

With regard to the image pickup apparatus according to the present exemplary embodiment, a difference from the fifth exemplary embodiment will be mainly described.

The image pickup apparatus according to the present exemplary embodiment outputs both an image signal for generating an image and a focus detection signal used for a focus detection of an image plane phase difference AF system.

In the image pickup apparatus according to the present exemplary embodiment, a focus detection pixel where light is shielded in a part of the photoelectric conversion unit201is arranged in the effective pixel area101a. A signal based on an output of the focus detection pixel where light is shielded in the part of the photoelectric conversion unit201corresponds to the focus detection signal.

It is noted that the signal output by the effective pixel102ais an image pickup signal corresponding to a signal for generating an image. Hereinafter, the effective pixel102awill be referred to as image pickup pixel.

FIG. 8Aillustrates an arrangement of the pixel102of the image pickup apparatus according to the present exemplary embodiment. The image pickup apparatus according to the present exemplary embodiment includes a dummy pixel row601in which the dummy pixel is arranged and an OB pixel row602in which the OB pixel is arranged. Furthermore, the image pickup apparatus according to the present exemplary embodiment includes an image pickup row603in which the image pickup pixel is arranged and a focus detection row604in which the focus detection pixel and the image pickup pixel are arranged. The OB pixel arranged in the OB pixel row602has the same configuration as the OB pixel102bdescribed in the first exemplary embodiment. The image pickup pixel has the same configuration as the effective pixel102adescribed in the first exemplary embodiment. The dummy pixel arranged in the dummy pixel row601has the configuration in which the photoelectric conversion unit201provided in the OB pixel102bis omitted. The configuration of the current supply unit104according to the present exemplary embodiment has the same configuration as the current supply unit104described in the fifth exemplary embodiment.

Each of the current supply units104in the respective columns has a configuration in which the current having either the current value Idm or the current value Idn can be switched for each column to be supplied.

The configuration of the signal processing circuit103according to the present exemplary embodiment has the same configuration as the configuration of the signal processing circuit103described in the first exemplary embodiment.

FIG. 8Billustrates an order of the signals output by the image pickup apparatus illustrated inFIG. 8Aand current values supplied by the current supply unit104. The vertical scanning circuit112sequentially scans the dummy pixel row601and the OB pixel row602. Thereafter, the vertical scanning circuit112scans the image pickup row603and the focus detection row604. It is noted that, in the image pickup apparatus according to the present exemplary embodiment, with regard to the image pickup row603, the signals of the image pickup pixels in a plurality of rows are mixed with one another on the signal line109. On the other hand, with regard to the other pixels including the dummy pixel, the OB pixel, and the focus detection pixel, the image pickup apparatus according to the present exemplary embodiment individually reads out for one row each. In a period during which the vertical scanning circuit112scans the image pickup row603, the current supply unit104supplies the current having the current value Idm to the signal line109. On the other hand, in a period during which the vertical scanning circuit112scans the other pixel row, the current supply unit104supplies the current having the current value Idn to the signal line109. Accordingly, the image pickup apparatus according to the present exemplary embodiment has the same effect as the image pickup apparatus according to the fifth exemplary embodiment. Furthermore, with regard to the signals of the focus detection pixel and the dummy pixel too, the image pickup apparatus according to the present exemplary embodiment can obtain the N-signal and the S-signal in a state in which the potential at the signal line109is statically determinate. Since the image pickup apparatus outputs the focus detection signal having the improved accuracy, it is possible to improve the accuracy of the focus detection.

Seventh Exemplary Embodiment

The image pickup apparatus described in the first exemplary embodiment to the sixth exemplary embodiment can be applied to various image pickup systems. Examples of the image pickup systems include a digital still camera, a digital camcorder, a monitoring camera, and the like.FIG. 9is a schematic diagram of an image pickup system where the image pickup apparatus according to any one of the first exemplary embodiment to the sixth exemplary embodiment of the present invention is applied to the digital still camera as the example of the image pickup system.

The image pickup system exemplified inFIG. 9includes an image pickup apparatus154, a barrier151for protecting a lens, a lens152that focuses an optical image of a subject on the image pickup apparatus154, and a diaphragm153for varying a quantity of light that passes through the lens152. The lens152and the diaphragm153constitute an optical system that focuses light on the image pickup apparatus154. The image pickup system exemplified inFIG. 9also includes an output signal processing unit155that performs processing on an output signal that is output from the image pickup apparatus154.

The output signal processing unit155performs AD conversion for converting an analog signal output by the image pickup apparatus154into a digital signal. In addition to this, the output signal processing unit155also performs an operation of outputting image data by appropriately performing various corrections and compression. The image pickup system exemplified inFIG. 9further includes a buffer memory unit156that temporarily stores the image data and an external interface unit (external I/F unit)157used to communicate with an external computer or the like. The image pickup system further includes a recording medium159such as a semiconductor memory that performs recording or readout of the image pickup data and a recording medium control interface unit (recording medium control I/F unit)158that performs recording or readout with respect to the recording medium159. It is noted that the recording medium159may be built in the image pickup system or may be detachably attached to the image pickup system.

The image pickup system further includes an overall control/calculation unit1510that controls various calculations and the entire digital still camera and a timing generation unit1511that outputs various timing signals to the image pickup apparatus154and the output signal processing unit155. Herein, the timing signals and the like may be input from an external part, and it suffices when the image pickup system includes at least the image pickup apparatus154and the output signal processing unit155that processes the output signal that is output from the image pickup apparatus154. As described above, the image pickup system according to the present exemplary embodiment can perform the image pickup apparatus while the image pickup apparatus154is applied to the image pickup system.

In the case of the image pickup apparatus that performs the image plane phase difference AF according to the sixth exemplary embodiment, the image pickup apparatus154outputs the focus detection signal based on the signal output by the focus detection pixel and the image pickup signal to the output signal processing unit155. The output signal processing unit155detects whether or not a focused state is established by using the focus detection signal. The output signal processing unit155also generates the image by using the image pickup signal. In a case where the output signal processing unit155detects that the focused state is not established, the overall control/calculation unit1510drives the optical system in a direction to establish the focus state. The output signal processing unit155detects again whether or not the focused state is established by using the focus detection signal output from the image pickup apparatus154. Hereinafter, the image pickup apparatus154, the output signal processing unit155, and the overall control/calculation unit1510repeat this operation until the focused state is established.

It is noted that the above-described exemplary embodiments are all merely specific examples for carrying out the present invention, and the technical scope of the present invention should not be construed to a limited extent by these examples. That is, the present invention can be carried out in various modes without departing from the technical spirit or the main characteristics. In addition, the respective exemplary embodiments described above may be combined with each other to carry out the present invention.

Accordingly, it is possible to more appropriately perform both the readout of the signal of the reference pixel and the mixing of the mutual signals output by the plurality of effective pixels.

This application claims the benefit of Japanese Patent Application No. 2014-095493, filed May 2, 2014, which is hereby incorporated by reference herein in its entirety.