JP2014014190A - Solid-state imaging device and imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid-state imaging device and an imaging apparatus that are advantageous for accelerating speed of an electronic shutter operation.SOLUTION: An electronic shutter unit 16 supplies a reset signal RST set in a valid state and transfer signals Txn, ..., set in a valid state to each pixel in row units to reset all of each pixel. In this case, reset of each pixel by the electronic shutter unit 16 is simultaneously executed on all of each pixel. After resetting each pixel, the electronic shutter unit 16 supplies the transfer signals Txn, ..., set in an invalid state to each pixel in row units to release the reset of each pixel, and starts accumulation of signal charge in each pixel. In this case, release of the reset of each pixel by the electronic shutter unit 16 is executed sequentially on each pixel in row units.

Description

  The present invention relates to various solid-state imaging devices such as CMOS image sensors and imaging devices using the same, and more particularly to a solid-state imaging device and imaging device that enable high-speed electronic shutter control.

Solid-state imaging devices typified by CMOS image sensors are used in various camera devices and mobile phones.
The CMOS image sensor includes a pixel region portion in which a plurality of pixels having a photoelectric conversion portion made of a photodiode are arranged in a two-dimensional direction on the same semiconductor substrate, and a peripheral circuit region formed outside the pixel region portion. (See Patent Document 1).

By the way, the CMOS image sensor resets the signal charge accumulated in the photoelectric conversion unit, and after a predetermined time has elapsed, the signal charge accumulated in the photoelectric conversion unit is read by reading the signal charge accumulated in the photoelectric conversion unit. It has an electronic shutter function to control the accumulation period.
In other words, by resetting the signal charges accumulated in the photoelectric conversion unit before the predetermined accumulation period with respect to the read timing, only the signal charges of the light incident during the predetermined accumulation period are accumulated and output.

A conventional CMOS image sensor having an electronic shutter function will be described with reference to FIGS.
As shown in FIG. 8, the pixel area unit 2, the vertical scanning circuit 3, the column CDS circuit 4, the horizontal scanning circuit 5, the output circuit 6, and the timing generation circuit 7 are included.
The pixel area unit 2 is a plurality of pixels each having a photoelectric conversion unit arranged in a two-dimensional direction. In addition, the pixel region unit 2 receives color component light corresponding to the spectral characteristics of the color filter disposed on the top thereof, and generates a pixel signal corresponding to the amount of light.
The vertical scanning circuit 3 scans the pixel region portion 2 in the vertical direction (in the column direction) in units of rows.
The column CDS circuit 4 takes in each pixel signal of the pixel region unit 2 in units of columns and performs CDS processing and other signal processing.
The horizontal scanning circuit 5 scans the column CDS circuit 4 in the horizontal direction.
The output circuit 6 performs necessary signal processing on the image signal transferred from the column CDS circuit 4 and outputs it as an image signal.
The timing generation circuit 7 synchronizes the operation timings of the vertical scanning circuit 3, the column CDS circuit 4, and the horizontal scanning circuit 5.

The CMOS image sensor of this example shows a case where a reset transistor, an amplification transistor, and a selection transistor are shared by two pixels adjacent in the vertical direction.
Here, the photoelectric conversion units of two adjacent pixels are 201A and 201B.
Corresponding sources of transfer transistors 202A and 202B are connected to the photoelectric conversion units 201A and 201B, respectively.
Transfer lines 203A and 203B are connected to the gates of the transfer transistors 202A and 202B.
The drains of the transfer transistors 202A and 202B are connected in common and connected to one reset transistor 204.
The floating diffusion FD between the drains of the transfer transistors 202 A and 202 B and the source of the reset transistor 204 is connected to the gate of one amplification transistor 205.
The drain of the reset transistor 204 and the drain of the amplification transistor 205 are connected to the power supply line 206.
The gate of the reset transistor 204 is connected to the reset line 207.
The source of the amplification transistor 205 is connected to the drain of the selection transistor 208.
The gate of the selection transistor 208 is connected to the selection line 209, and the source of the selection transistor 208 is connected to the vertical signal line 210.

Next, the operation of the electronic shutter of the CMOS image sensor will be described.
Here, the operation of a so-called rolling electronic shutter that resets the signal charge of each pixel while sequentially scanning each pixel in the vertical direction (column direction) in units of rows will be described.
In FIG. 8, the symbols n, n + 1... And the subscripts n, n + 1... Attached to the transfer signal Tx indicate row addresses in the vertical direction.
The subscripts m, m + 1,... Attached to the reset signal RET are added to distinguish the reset signal RET supplied in units of two pixels.
In the row of address n (hereinafter referred to as n line), as shown in FIG. 9A, the reset signal RETm output from the vertical scanning circuit 3 is applied to the reset line 207 in the state of “H”, and The transfer signal Txn is applied from the vertical scanning circuit 3 to the transfer line 203A as a positive logic pulse.
Then, the transfer transistor 202A and the reset transistor 204 are turned on, and a reset operation for removing unnecessary charges accumulated in the n-line photoelectric conversion unit 201A and the floating diffusion FD is performed.
Then, when the transfer transistor 202A is turned off when the transfer signal Txn falls to “L”, accumulation of photocharges in the photoelectric conversion unit 201A is started from that point. In other words, the accumulation period is started.
The same operation as described above is performed for the n + 1 line, the n + 2 line, the n + 3 line,. That is, the shutter target addresses are sequentially selected and the electronic shutter operation is performed.

JP 2008-236634 A

In such a rolling electronic shutter operation, each pixel is reset while scanning each row in the vertical direction (in the column direction), so that the start time of the signal charge accumulation period in each pixel gradually shifts in the vertical direction. . In other words, the point at which the shutter opens is gradually delayed.
As described above, it is known that when the start time of the accumulation period in each row is shifted, for example, distortion occurs in an image obtained by imaging a moving subject.
The distortion of the image becomes more prominent as the shift of the starting point of the accumulation period in each row increases.
Therefore, it is preferable to speed up the electronic shutter operation in order to ensure the quality of the captured image.
When attempting to realize a high-speed shutter operation in the CMOS image sensor as described above, as shown in FIG. 9 (B), it is sufficient to shorten the pulse width of the transfer signal Tx.
However, since the lower limit value of the pulse width of the transfer signal Tx is limited by the wiring resistance and stray capacitance of each transfer line 203A, 203B, there is a limit to speeding up the electronic shutter operation.
The present invention has been made in view of such circumstances, and an object thereof is to provide a solid-state imaging device and an imaging device that are advantageous in increasing the speed of an electronic shutter operation.

A solid-state imaging device according to the present invention includes a pixel area unit in which a plurality of pixels each having a photoelectric conversion unit in which signal charges are accumulated are arranged along a horizontal direction and a vertical direction, and each pixel in the pixel area unit is arranged in units of rows. A vertical scanning unit that selects and reads the signal charges from each pixel in units of rows, and supplies a reset signal that is in an enabled state and a transfer signal that is in an enabled state to each pixel in units of rows. An electronic shutter unit that cancels reset of each pixel by supplying a transfer signal in an invalid state to each pixel in a row unit after resetting all, and starts accumulation of the signal charge in each pixel; Prepare.
An imaging device of the present invention includes an imaging unit using a solid-state imaging device, a control unit that controls the imaging unit, and an operation unit that operates the imaging unit, and the solid-state imaging device stores signal charges. A plurality of pixels each having a photoelectric conversion unit arranged in a horizontal direction and a vertical direction; and each pixel in the pixel region unit is selected in units of rows, and the signals are output from the pixels in units of rows. A vertical scanning unit for reading out charges, and a transfer signal in an invalid state after resetting all the pixels by supplying a reset signal in an effective state and a transfer signal in an effective state to each pixel in a row unit Is provided to each pixel in a row unit to release the reset of each pixel, and to start accumulation of the signal charge in each pixel.

According to the present invention, since each pixel can be reset by switching the transfer signal from the valid state to the invalid state, the lower limit value of the pulse width of the transfer signal due to the wiring resistance or stray capacitance of each transfer line as in the prior art. There is no need to consider constraints.
Therefore, it is possible to reduce the deviation of the starting point of the accumulation period in each row, which is advantageous for speeding up the electronic shutter operation, and suppressing the occurrence of distortion in the image obtained by imaging the moving subject. This is advantageous in ensuring the quality of the captured image.

It is a block diagram which shows the structure of the solid-state imaging device 10 in embodiment. 3 is a circuit diagram showing a configuration of a memory block 36. FIG. 4 is an explanatory diagram showing a relationship between an input signal and an output signal of a latch 42. FIG. It is a signal waveform diagram which shows the rolling electronic shutter operation | movement of the solid-state imaging device 10 in embodiment. It is a signal waveform diagram explaining the case where speeding-up of rolling electronic shutter operation | movement of the solid-state imaging device 10 in embodiment is aimed at. It is a signal waveform diagram explaining the global electronic shutter operation | movement of the solid-state imaging device 10 in embodiment. It is a block diagram which shows the structure of the imaging device 400 using the solid-state imaging device 10 in this Embodiment. It is a block diagram which shows the structure of the CMOS image sensor in a prior art example. (A) is a signal diagram for explaining an electronic shutter operation in a conventional CMOS image sensor, and (B) is a signal waveform diagram for explaining a case of speeding up the electronic shutter operation.

Next, an embodiment of the present invention will be described with reference to FIGS.
Below, the case where the solid-state imaging device 10 of this invention is comprised by the CMOS image sensor is demonstrated.
As shown in FIG. 1, the solid-state imaging device 10 includes a pixel area unit 12, a vertical scanning unit (column scanning unit) 14, an electronic shutter unit 16, a column CDS circuit 18, and a horizontal scanning unit (row scanning unit). 20, an output circuit 22, and a timing generation circuit 24.

The pixel region portion 12 is a portion where a plurality of pixels having a photoelectric conversion portion made of a photodiode are arranged along the horizontal direction and the vertical direction.
In this embodiment, a case where two pixels adjacent in the vertical direction individually have a photoelectric conversion unit and a transfer transistor, and a reset transistor, an amplification transistor, and a selection transistor are shared is shown.
Of the two pixels adjacent in the vertical direction, one pixel is denoted by reference numeral 26A, and the other pixel is denoted by reference numeral 26B.
One pixel 26A includes a photoelectric conversion unit 201A, a transfer transistor 202A, a reset transistor 204, an amplification transistor 205, and a selection transistor 208.
The other pixel 26B includes a photoelectric conversion unit 201B, a transfer transistor 202B, the reset transistor 204, the amplification transistor 205, and the selection transistor 208.
Hereinafter, the transfer transistors 202A and 202B, the reset transistor 204, the amplification transistor 205, and the selection transistor 208 are collectively referred to as a pixel transistor.
In the present embodiment, as described above, a case where two adjacent pixels share each transistor except the transfer transistor will be described. However, the present invention can be applied even when independent transistors are used for each pixel, or when three or more pixels share each transistor except the transfer transistor.

The transfer transistors 202A and 202B read out the signal charges of the photoelectric conversion units 201A and 201B to the floating diffusion FD.
The reset transistor 204 resets the floating diffusion FD.
The amplification transistor 205 generates a pixel signal corresponding to the potential of the floating diffusion FD.
The selection transistor 208 selects a pixel that outputs a pixel signal.

The sources of the corresponding transfer transistors 202A and 202B are connected to the output terminals (cathodes) of the photoelectric conversion units 201A and 201B, respectively.
Transfer lines 203A and 203B are connected to the gates of the transfer transistors 202A and 202B, respectively.
The drains of the transfer transistors 202A and 202B are connected in common and connected to the reset transistor 204.
The floating diffusion FD between the drains of the transfer transistors 202 A and 202 B and the source of the reset transistor 204 is connected to the gate of the amplification transistor 205.
The drain of the reset transistor 204 and the drain of the amplification transistor 205 are connected to the power supply line 206.
The gate of the reset transistor 204 is connected to the reset line 207.
The source of the amplification transistor 205 is connected to the drain of the selection transistor 208.
The gate of the selection transistor 208 is connected to the selection line 209, and the source of the selection transistor 208 is connected to the vertical signal line 210.

The column CDS circuit 18 takes in each pixel signal of the pixel region section 12 in units of columns and performs CDS processing and other signal processing.
The horizontal scanning unit 20 scans the column CDS circuit 18 in the horizontal direction. In other words, the horizontal scanning unit 20 performs signal processing in units of columns on the pixel signals read out in units of rows by the vertical scanning unit 14.
The output circuit 22 performs necessary signal processing on the image signal transferred from the column CDS circuit 18 and outputs it as an image signal.
The timing generation circuit 24 synchronizes operation timings of the vertical scanning unit 14, the electronic shutter unit 16, the column CDS circuit 18, and the horizontal scanning unit 20.

The vertical scanning unit 14 selects each pixel of the pixel region unit 12 in units of rows and reads out signal charges from the pixels in units of rows. In other words, each pixel in the pixel region 12 is selected in units of rows and each pixel is controlled.
The vertical scanning unit 14 includes a timing control block 28, an address decoder 30, a timing generation circuit 32, a level shifter 34, a memory block 36, and a driver 38.
The timing control block 28 generates various pulse signals for generating a reset signal RET, a transfer signal Tx, and a selection signal SEL, which will be described later, and supplies them to the timing generation circuit 32.
The timing control block 28 generates various pulse signals for generating the sequential shutter control signal I_txn, the set signal Sn, and the reset signal Rn shown in FIG.
The timing control block 28 supplies address data for specifying a row in the pixel area 12 to the address decoder 30.
The address decoder 30 decodes the address data supplied from the timing control block 28 and identifies a row in the pixel area unit 12.

The timing generation circuit 32 generates a reset signal RET, a transfer signal Tx, a selection signal SEL, a shutter control signal I_txn, a latch set signal Sn, and a latch reset signal Rn based on the various pulse signals supplied from the timing control block 28. To do. These signals are supplied to the row specified by the address decoder 30.
The level shifter 34 increases the voltages of the reset signal RET, the transfer signal Tx, and the selection signal SEL supplied from the timing generation circuit 32 to a voltage sufficient to drive the memory block 36 or the driver 38 in the subsequent stage.
The memory block 36 constitutes a part of the electronic shutter unit 16, and generates the transfer signal Txn based on the shutter control signal I_txn, the latch set signal Sn, and the latch reset signal Rn.
The memory block 36 will be described in detail later.
The driver 38 supplies the reset signal RET, the transfer signal Tx, and the selection signal SEL supplied from the level shifter 34 via the memory block 36 to each pixel transistor, and drives these transistors.

The electronic shutter unit 16 resets all of the pixels by supplying the reset signal RST in the valid state and the transfer signal Txn in the valid state to each pixel in units of rows. Then, after resetting all of the pixels, the transfer signal Txn in an invalid state is supplied to each pixel in units of rows, thereby releasing the reset of each pixel and starting the accumulation of signal charges in each pixel. .
The electronic shutter unit 16 includes a timing control block 28, an address decoder 30, a timing generation circuit 32, a level shifter 34, a memory block 36, and a driver 38.

Next, the memory block 36 constituting a part of the electronic shutter unit 16 will be described in detail.
As shown in FIG. 2, the memory block 36 includes a plurality of transfer signal generation units 40 provided in units of transfer lines 203A (203B), in other words, in units of rows.
In the present embodiment, the transfer signal generation unit 40 is configured to include a latch 42, a first OR gate 44, and a second OR gate 46.

In the present embodiment, the latch 42 has a positive logic set input terminal 42A, a positive logic reset input terminal 42B, and a negative logic output terminal 42C.
FIG. 3 is an explanatory diagram showing the relationship between the set signal S input to the set input terminal 42A, the reset signal R input to the reset input terminal 42B, and the output signal Q bar of the output terminal 42C.
As shown in FIG. 3, the latch 42 holds the output signal Q bar at “0” when the set signal S becomes “1”, and sets the output signal Q bar at “1” when the reset signal R becomes “1”. ”.
In other words, the latch 42 holds the output signal Q bar at “L” when the set signal S is supplied, and holds the output signal Q bar at “H” when the reset signal R is supplied.
Such a latch 42 corresponds to a memory that holds 1-bit data.

As shown in FIG. 2, the first OR gate 44 receives the positive logic shutter control signal I_txn supplied from the timing generation circuit 32 and the positive logic latch set signal Sn supplied from the timing generation circuit 32. The
The output terminal of the first OR gate 44 is connected to the set input terminal 42A of the latch 42.
Therefore, the logical sum of the shutter control signal I_txn and the latch set signal Sn is supplied to the set input terminal 42A of the latch 42.
The second OR gate 46 receives the shutter control signal I_txn and the output signal Q bar of the output terminal 42C of the latch 42. Hereinafter, for convenience of explanation, the output signal Q bar is referred to as a latch output signal M_txn.
The second OR gate 46 outputs a logical sum of the shutter control signal I_txn and the latch output signal M_txn as the transfer signal Txn.
Therefore, each transfer signal generator 40 has a latch 42 that is set by the logical sum of the shutter control signal I_txn and the latch set signal Sn and is reset by the latch reset signal Rn. Based on this, a transfer signal Txn is generated.
Further, the transfer signal Txn is configured by a logical sum of the shutter control signal I_txn and the latch output signal M_txn.

Next, the rolling electronic shutter operation of the solid-state imaging device 10 of the present embodiment will be described with reference to FIG. In the following description, the signal level is described by positive logic, and therefore “L” corresponds to “0” and “H” corresponds to “1”.
In advance, the timing generation circuit 32 fixes the reset signal RST to “H” as shown in FIG.
As shown in FIGS. 4A to 4C, the electronic shutter unit 16 fixes the latch set signal Sn to “L” and sets the shutter control signals I_txn,... To “L”. The latch reset signal Rn is simultaneously supplied to each transfer signal generator 40 as a positive logic pulse signal.
Then, as shown in FIG. 4 (D), the transfer signal generating unit 40 of the latch output signal M_txn, ...... simultaneously "H", therefore, as shown in FIG. 4 (F), each transfer signal Txn, ... also becomes “H” at the same time.
As a result, all the pixels in each row are simultaneously reset, in other words, a shutter period in which the electronic shutter is applied is started.
That is, the electronic shutter unit 16 resets all of the pixels by supplying the reset signal RST in the valid state and the transfer signal Txn in the valid state to each pixel in units of rows.
In this case, the resetting of each pixel by the electronic shutter unit 16 is performed simultaneously on all the pixels.

Next, as shown in FIG. 4C, the electronic shutter unit 16 sequentially outputs each shutter control signal I_txn, I_txn + 1,... To each transfer signal generation unit 40 as a positive logic pulse signal.
Here, the pulse width ΔX of each shutter control signal I_txn,... Is the same, and the time when the preceding shutter control signal falls coincides with the time when the next shutter control signal rises. .
As shown in FIG. 4D, each latch output signal M_txn,... Sequentially transitions from “H” to “L” in response to each shutter control signal I_txn,. .
Therefore, as shown in FIG. 4F, each transfer signal Txn,... Falls with a delay of the pulse width ΔX from the falling time of each latch output signal M_txn,.
In FIG. 4F, the shutter period A indicates a shutter period determined at the falling edge of each latch output signal M_txn,..., And the shutter period B is an actual value obtained by adding a pulse width ΔX to the shutter period A. The shutter period is shown.
Thereby, reset of each pixel is sequentially released in units of rows, and accumulation of signal charges in the photoelectric conversion units 201A and 201B of each pixel is started. In other words, the accumulation period starts.
That is, after resetting each pixel, the electronic shutter unit 16 releases the reset of each pixel by supplying the transfer signal Txn,. Start accumulation.
In this case, the reset release of each pixel by the electronic shutter unit 16 is sequentially executed for each pixel in units of rows.
Therefore, as shown in FIG. 4, it can be seen that the shutter period B in each row of the pixel region portion 12 is shifted (delayed) by the pulse width ΔX.
That is, if the number of rows in the pixel region portion 12 is N, the shift amount of the shutter period B between the first row and the last row is ΔX × (N−1).

Next, the case of speeding up the electronic shutter operation will be described with reference to FIG.
That is, in order to increase the speed of the electronic shutter operation, the pulse width ΔX of each shutter control signal I_txn, I_txn + 1,... May be shortened as indicated by a broken line in FIG.
Here, the lower limit value of the pulse width ΔX of each shutter control signal I_txn, I_txn + 1,... Only needs to be a time sufficient for the transfer signal generation unit 40 to operate normally.
That is, conventionally, the lower limit value of the pulse width of the transfer signal Tx is limited by the wiring resistance and stray capacitance of each transfer line 203A, 203B.
In contrast, in the present embodiment, the pulse of the shutter control signal sufficient to operate the transfer signal generation unit 40, in other words, the gate circuit including the latch 42, the first OR gate 44, and the second OR gate 46. It is sufficient to secure the width ΔX.
When expressed in units of one clock of the clock signal for operating the vertical scanning unit 14, conventionally, about 10 clocks were required as the pulse width of the transfer signal Tx. In the present embodiment, the shutter control signal For example, two clocks are sufficient for the pulse width ΔX.
Therefore, the shift amount of the shutter period B can be shortened to about 1/5, which is extremely advantageous for speeding up the electronic shutter operation.

Next, the global electronic shutter operation will be described with reference to FIG.
The global electronic shutter operation refers to an electronic shutter operation in which the shutter period for all the pixels in the pixel region unit 12 is the same. In other words, the shift of the shutter period is zero, and therefore the accumulation period is started at the same timing.

In advance, the timing generation circuit 32 fixes the reset signal RST to “H” as shown in FIG.
As shown in FIGS. 6A to 6C, the electronic shutter unit 16 temporarily sets the latch set signal Sn to “L”. Then, with the shutter control signals I_txn,... Fixed to “L”, the latch reset signal Rn is simultaneously output to each transfer signal generator 40 as a positive logic pulse signal.
Then, as shown in FIG. 6 (D), the latch output signals M_txn, M_txn + 1,... Of each transfer signal generation unit 40 become “H” at the same time, and therefore, as shown in FIG. Txn, Txn + 1,... Simultaneously become “H”.
As a result, all the pixels in each row are simultaneously reset, in other words, a shutter period in which the electronic shutter is applied is started.
That is, the electronic shutter unit 16 resets all of the pixels by supplying the reset signal RST in the valid state and the transfer signal Txn in the valid state to each pixel in units of rows.
In this case, the resetting of each pixel by the electronic shutter unit 16 is performed simultaneously on all the pixels.

Next, as shown in FIGS. 6A, 6 </ b> B, and 6 </ b> E, the electronic shutter unit 16 performs latching in a state where the reset signal RST is supplied to each pixel in units of rows selected by the vertical scanning unit. Reset signal Rn is disabled. In this state, the latch set signal Sn is simultaneously supplied to each transfer signal generator 40 as a positive logic pulse signal.
The latch output signals M_txn, M_txn + 1,... Simultaneously fall to “L” when the latch set signal Sn rises from “L” to “H”.
Here, since the shutter control signals I_txn, I_txn + 1,... Are fixed to “L”, the transfer signals Txn, Txn + 1,. ”To“ L ”.
As a result, all the resets of each pixel are released simultaneously.
That is, after resetting each pixel, the electronic shutter unit 16 releases the reset of each pixel by supplying the transfer signal Txn,. Start accumulation.
In this case, the reset release of each pixel by the electronic shutter unit 16 is performed simultaneously on all the pixels.
Accordingly, all the shutter periods (global shutter periods) of each pixel are the same, and the signal charge accumulation period is started at the same timing.
In this case, since the shift of the shutter period between the rows becomes zero, it is possible to prevent distortion from occurring in the image obtained by capturing the moving subject, and to ensure the quality of the captured image. This is advantageous.
In order to realize the global electronic shutter operation, it is only necessary to supply a transfer signal to all of the pixels simultaneously. Conventionally, in order to generate such a transfer signal, a global electronic shutter operation is performed. It was necessary to provide a dedicated gate circuit.
For this reason, there is a disadvantage in reducing the size and cost of the solid-state imaging device 10.
In contrast, in the present embodiment, a global electronic shutter operation can be realized with a simple configuration in which the transfer signal generation unit 40 is provided in units of rows, and the solid-state imaging device 10 can be reduced in size and cost. It is extremely advantageous to plan.

According to the present embodiment, the electronic shutter unit 16 resets all the pixels by supplying the reset signal in the valid state and the transfer signal in the valid state to each pixel in units of rows. After that, the reset signal of each pixel is released by supplying the invalidated transfer signal to each pixel in units of rows. Thereby, accumulation of signal charges in each pixel is started.
Therefore, since each pixel can be reset by switching the transfer signal from the valid state to the invalid state, the lower limit value of the pulse width of the transfer signal Tx due to the wiring resistance or stray capacitance of each transfer line 203A, 203B as in the past. There is no need to consider constraints.
Therefore, it is possible to reduce the shift of the start time of the accumulation period in each row. In other words, it is possible to reduce the shift of the shutter period that occurs in units of rows.
Therefore, it is advantageous for speeding up the electronic shutter operation, and it is possible to suppress the occurrence of distortion in an image obtained by imaging a moving subject, which is advantageous for ensuring the quality of the captured image.

Further, in the present embodiment, the electronic shutter unit 16 is provided with the transfer signal generation unit 40 having the latch 42 for each row.
The latch 42 is set by the logical sum of the shutter control signal I_txn and the latch set signal Sn, and is reset by the latch reset signal Rn.
The transfer signal generation unit 40 generates the transfer signal Txn by the logical sum of the shutter control signal I_txn and the latch output signal M_txn.
Therefore, in order to transition to the invalid state of the transfer signal Txn from the effective state, the shutter of the degree of short pulse width sufficient to transfer signal generation unit 40 including a latch 42 operates a control signal I_txn rolling transmission Gosei each row formed What is necessary is just to supply to the part 40 sequentially.
Therefore, it is possible to reduce the deviation of the start point of the accumulation period in each row, in other words, it is possible to reduce the deviation of the shutter period that occurs in units of rows.
Here, the pulse width of the shutter control signal I_txn may be short enough to operate the transfer signal generation unit 40. For this reason, it is possible to reduce the shift at the start time of the accumulation period in each row. In other words, it is possible to reduce the shift in the shutter period that occurs in units of rows.
Therefore, it is possible to increase the speed of the electronic shutter operation with a simple configuration in which the transfer signal generation unit 40 is provided in the electronic shutter unit 16, which is advantageous in ensuring the quality of the captured image while reducing the cost. .

Further, according to the present embodiment, the global electronic shutter operation can be easily realized as described above.
However, when the global electronic shutter operation is performed, as shown in FIGS. 6A, 6D, and 6F, when the pulse signal of the latch set signal Sn rises, each latch output signal, each transfer signal, Will fall at the same time, resulting in an instantaneous increase in power consumption.
Therefore, it is necessary to consider such an increase in current consumption when designing the peripheral circuit constituting the solid-state imaging device 10, and there is a concern that the design cost may increase.
On the other hand, if the speed of the rolling electronic shutter operation is increased, it is possible to obtain an effect close to that in the case of performing the global electronic shutter operation, and it is not necessary to consider the increase in current consumption as described above. This is advantageous in reducing the design cost.

In addition, it is conceivable that the solid-state imaging device 10 is used in an imaging device such as a digital still camera and the subject image captured by the solid-state imaging device 10 is displayed on a display in the form of a moving image.
In this case, since there is a limit to the transfer speed at which an image signal is read from the solid-state imaging device 10, it is necessary to read out all the pixels of the solid-state imaging device 10 by thinning out in units of rows.
Specifically, a row from which the image signal is not read is set for each predetermined row.
However, since the charge is accumulated and saturated in the pixels in the row where reading is not performed, it is necessary to control the pixels in the row where reading is not performed to a state where the shutter is applied (reset state).
Therefore, it is necessary to provide a gate circuit for performing such dedicated control in units of rows, resulting in inconveniences that complicate the configuration, increase the size of the solid-state imaging device 10, and increase the cost.
However, in this embodiment, only the control latch set signal Sn supplied, the shutter control signal I_txn to the transfer signal generating unit 40 can control the reset state of the pixel in the row. Therefore, the configuration can be simplified, which is advantageous in reducing the size and cost of the solid-state imaging device 10.
Further, the electronic shutter operation can be changed variously only by changing the latch set signal Sn and the shutter control signal I_txn supplied to each transfer signal generation unit 40.
Therefore, it is not necessary to provide a number of dedicated gate circuits corresponding to the type of electronic shutter operation, so that various electronic shutter operations can be easily realized while simplifying the configuration, reducing the size, and reducing the cost. It will be advantageous.

Moreover, when using the solid-state imaging device 10 for imaging devices, such as a digital still camera, combining the electronic shutter function of the solid-state imaging device 10 and a focal plane shutter is considered.
The focal plane shutter moves the light shielding plate provided in front of the solid-state imaging device 10 in parallel with the vertical direction (column direction) of the solid-state imaging device 10.
Since the focal plane shutter is mechanically driven, the moving speed of the light shielding plate is not constant and increases with time. That is, the moving speed of the light shielding plate is low at the start of movement, increases as the movement progresses, and becomes the highest at the end of movement.
On the other hand, when the above-described rolling electronic shutter operation is performed, a shift in the start timing of the accumulation period of each pixel in a row unit that occurs in the vertical direction increases linearly.
Therefore, when the rolling electronic shutter operation and the focal plane shutter are used in combination, there is a concern that a change in the moving speed of the light shielding plate may affect the captured image.
In view of this, it is conceivable to control the shift of the start timing of the accumulation period of each pixel in the vertical direction so as to suppress the influence of the change in the moving speed of the light shielding plate on the image. In other words, it is conceivable to perform control so that the shift in the start timing of the accumulation period of each pixel in units of rows increases nonlinearly.
In order to make the shift of the start timing of the accumulation period of each pixel in units of rows nonlinear, the pulse width ΔX of the shutter control signal I_txn may be made nonlinear.
In this case as well, since it is not necessary to provide a dedicated gate circuit in order to make the shift of the start timing of the accumulation period of each pixel in a row non-linear, it is possible to simplify the configuration, reduce the size, and reduce the cost. Is advantageous.

Next, with reference to FIG. 7 will be described the case where the solid-state imaging device 10 according to the present invention is applied to an image pickup apparatus such as a digital still camera.
As shown in FIG. 7 , the imaging apparatus 400 includes an imaging optical system 300, an imaging unit 310, a system control unit 320, a drive control unit 330, a memory medium 340, an operation panel unit 350, a display 360, and the like.

The imaging optical system 300 includes a zoom lens 301, a diaphragm mechanism 302, and the like disposed in a lens barrel, and forms a subject image on a light receiving unit of an image sensor.
The imaging optical system 300 is mechanically driven by the control of the drive control unit 330 based on an instruction from the system control unit 320 to perform control such as autofocus.

The imaging unit 310 performs imaging of a subject using the solid-state imaging device 10 illustrated in FIG. 1, and outputs an imaging signal (image signal) to the system control unit 320 mounted on the main board.
That is, the imaging unit 310 performs processing such as AGC (automatic gain control), OB (optical black) clamping, CDS (correlated double sampling), and A / D conversion on the output signal of the image sensor described above, and performs digital imaging. Generate and output a signal.

The system control unit 320 is provided with a CPU 321, a ROM 322, a RAM 323, a DSP 324, an external interface 325, and the like.
The CPU 321 uses the ROM 322 and the RAM 323 to send an instruction to each unit of the imaging apparatus and controls the entire system.
The DSP 324 performs various kinds of signal processing on the imaging signal from the imaging unit 310, thereby generating a still image or moving image video signal (for example, a YUV signal) in a predetermined format.
The external interface 325 is provided with various encoders and D / A converters, and with external elements (in this example, the display 360, the memory medium 340, and the operation panel unit 350) connected to the system control unit 320. Various control signals and data are exchanged.

The memory medium 340 can appropriately store images taken on various memory cards, for example, and the memory medium can be exchanged with the memory medium controller 341, for example. As the memory medium 340, in addition to various memory cards, a disk medium using magnetism or light can be used.
The operation panel unit 350 is provided with input keys for a user to give various instructions when performing a shooting operation with the imaging apparatus. The CPU 321 monitors an input signal from the operation panel unit 350, Various operation controls are executed based on the input contents.
The display 360 is a small display such as a liquid crystal panel incorporated in the imaging apparatus, and displays a captured image.

  If the solid-state imaging device 10 of the present invention is applied to such an imaging device 400, the speed of the electronic shutter operation can be increased, so that the distortion of the image displayed on the display 360 can be suppressed, and the captured image can be suppressed. This is advantageous in ensuring the quality of the product.

  DESCRIPTION OF SYMBOLS 10 ... Solid-state imaging device, 12 ... Pixel area part, 14 ... Vertical scanning part, 16 ... Electronic shutter part, 20 ... Horizontal scanning part, 26A, 26B ... Pixel, 40 ... Transfer signal generation part, 42 ... Latch, 201A, 201B ... Photoelectric conversion unit, RETn ... Reset signal, Txn ... Transfer signal, I_txn ... Shutter control signal, Sn ... Latch set signal, Rn ... Latch reset signal.

Claims (6)

A pixel region portion in which a plurality of pixels having a photoelectric conversion portion in which signal charges are accumulated are arranged along the horizontal direction and the vertical direction;
A vertical scanning unit that selects each pixel of the pixel region unit in units of rows and reads the signal charges from the pixels in units of rows;
After resetting all the pixels by supplying the reset signal in the valid state and the transfer signal in the valid state to each pixel in units of rows, the transfer signal in the invalid state is supplied to each pixel in units of rows. An electronic shutter unit that releases reset of each pixel by supplying and starts accumulation of the signal charge in each pixel; and
The electronic shutter unit has a transfer signal generation unit provided in a row unit, and a global electronic shutter operation is possible in which the shutter period for all the pixels in the pixel region unit is the same,
The transfer signal generator has a latch,
The electronic shutter unit generates a shutter control signal, a latch set signal, and a latch reset signal,
The latch is set by a logical sum of the shutter control signal and the set signal for latch, and is reset by the reset signal for latch,
The transfer signal generation unit generates the transfer signal by a logical sum of the shutter control signal and the output signal of the latch.
Solid-state imaging device. The resetting of the pixels by the electronic shutter unit is performed simultaneously on all of the pixels.
The solid-state imaging device according to claim 1. Release of the reset of each pixel by the electronic shutter unit is sequentially executed on a row basis for each pixel.
The solid-state imaging device according to claim 1. The speed of the electronic shutter operation by the electronic shutter unit is determined by the pulse width of the shutter control signal.
The solid-state imaging device according to any one of claims 1 to 3. The lower limit value of the pulse width of the shutter control signal is a time sufficient for the transfer signal generation unit to operate normally.
The solid-state imaging device according to claim 4. An imaging unit using a solid-state imaging device, a control unit that controls the imaging unit, and an operation unit that operates the imaging unit,
The solid-state imaging device
A pixel region portion in which a plurality of pixels having a photoelectric conversion portion in which signal charges are accumulated are arranged along the horizontal direction and the vertical direction;
A vertical scanning unit that selects each pixel of the pixel region unit in units of rows and reads the signal charges from the pixels in units of rows;
After resetting all the pixels by supplying the reset signal in the valid state and the transfer signal in the valid state to each pixel in units of rows, the transfer signal in the invalid state is supplied to each pixel in units of rows. An electronic shutter unit that releases reset of each pixel by supplying and starts accumulation of the signal charge in each pixel; and
The electronic shutter unit has a transfer signal generation unit provided in a row unit, and a global electronic shutter operation is possible in which the shutter period for all the pixels in the pixel region unit is the same,
The transfer signal generator has a latch,
The electronic shutter unit generates a shutter control signal, a latch set signal, and a latch reset signal,
The latch is set by a logical sum of the shutter control signal and the set signal for latch, and is reset by the reset signal for latch,
The transfer signal generation unit generates the transfer signal by a logical sum of the shutter control signal and the output signal of the latch.
Imaging device.

Images