JP2714320B2 - Solid-state imaging device and driving method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state imaging device in which pixels are arranged two-dimensionally.

In recent years, when the temperature of the surface of the earth, an object, or a human body is known in a non-contact manner in the field of industry or medical treatment, there is a method of detecting infrared rays emitted from an object or the like by an infrared sensor. Is increasing.

For this reason, it is necessary to improve the noise resistance and performance.

[0004]

2. Description of the Related Art FIG. 7 shows a configuration diagram of a conventional solid-state imaging device. FIG. 7A illustrates an interline solid-state imaging device, and FIG. 7B illustrates a line address solid-state imaging device.

[0005] The solid-state imaging device 11 in FIG.
A predetermined number of pixels 12 (three pixels in the figure) each including a photodiode 12a, an accumulation gate 12b, and a transfer gate 12c are provided in the vertical readout CCD 13 in the vertical direction. A vertical reading CCD provided with the pixels 12
13 is a predetermined number (three in the figure), CCD 14 for horizontal reading
Are provided in the horizontal direction. That is, the pixels 12 are arranged in a matrix. The CCD 14 for horizontal reading
It is output via the amplifier 15.

In the solid-state imaging device 11, the CCDs 13 and 14 perform vertical signal reading and horizontal signal reading.

That is, when the photodiode 12a of any pixel 12 receives light, the charge is accumulated in the accumulation gate 12b, and is transferred to the vertical reading CCD 13 via the transfer gate 12c. Thereafter, the horizontal readout CCDs 14 are sequentially read from the vertical readout CCDs 13 for each row.
And the signal is sequentially extracted from the amplifier 15 to the outside.

Further, the solid-state imaging device 1 shown in FIG.
Reference numeral 6 denotes photodiodes 17a and switching elements (for example, MOSFETs) 17b constituting the pixels 17, each of which is arranged in a matrix (3 × 3 pixels in the figure).
Of these, the shift register 18 vertically shifts each pixel 17.
Is scanned, and the charges from the photodiodes 17a due to light reception are temporarily stored in the parallel storage units 19 for each column. Then, the data is transferred from each parallel storage unit 19 to the horizontal reading unit 20 and output via the amplifier 21.

The solid-state imaging device 16 accesses only one row and outputs a signal to the outside, and thereafter reads the next one row in the same manner.

That is, charges are read from the pixels 17 in one row by the shift register 18 to the predetermined parallel accumulation section 19 at a time, one column at a time, and thereafter, the horizontal reading section 20 performs horizontal reading to perform amplification. A signal is output to the outside via the line 21. When the reading of the signal for one row is completed, the signal from the pixel 17 of another row is read out to the outside in the same manner, and the accumulation and the reading are sequentially performed row by row. .

[0011]

However, the interline solid-state imaging device 11 shown in FIG.
Since the storage gate 12b is provided for each pixel, when the area of the pixel (cell) is reduced, the area of the storage gate is also reduced and the maximum amount of stored charges is reduced.
There is a problem that the N ratio decreases.

On the other hand, the line address type solid-state imaging device 16 shown in FIG. 7B has a storage section 19 for each column, so that the influence of the reduction in cell area is small. But,
As the number of pixels in the column direction increases, the access time for one row decreases. That is, when the frame period is T _F and the pixels are N rows, the longest integration time is T _F / N, and the access time is reduced. This reduces the maximum stored charge,
There is a problem that the SN ratio decreases.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has as its object to provide a solid-state imaging device capable of preventing a decrease in the maximum accumulated charge amount due to an increase in the number of pixels and improving an SN ratio.

[0014]

SUMMARY OF THE INVENTION The object of the present invention is to provide a first switching element for reading out charges generated in a light receiving element, a storage area for storing charges read out by the first switching element, and the storage area. And a first vertical unit that drives the first switching element of each pixel of the pixel unit in the row direction in a row direction. A scanning unit, a second vertical scanning unit that drives the second switching element of each pixel of the pixel unit in a row direction, and accumulates the electric charge transferred by the second switching element in a column direction. This problem can be solved by a configuration including a predetermined number of storage units and a horizontal scanning unit that reads out the charges of the storage units and outputs a signal.

In the driving method, the electric charges generated in the light receiving elements in the two-dimensionally arranged pixels and the electric charges generated in the light receiving elements are read out in a row direction on the pixel arrangement and accumulated in the accumulation region, The electric charge accumulated in the accumulation region and the electric charge generated in the light receiving element are transferred in the row direction on the pixel array , the electric charge is accumulated in the accumulation unit for each column, and the electric charge accumulated in each accumulation unit the reading in the column direction on the sequence of the pixel to the signal output.

[0016]

As described above, the accumulation of charges in the accumulation region of each pixel in the column direction is performed by the first vertical scanning unit, and the transfer of charges from the accumulation region to the accumulation unit is performed by the second scanning unit. . Then, the horizontal scanning unit reads out the charges in the storage unit and outputs a signal.

As a result, it is possible to lengthen the charge storage time in the storage section. Even if the storage area of each pixel becomes smaller as the number of pixels increases, a reduction in the maximum stored charge amount is prevented, and the SN ratio is reduced. Can be improved.

[0018]

FIG. 1 shows a configuration diagram of a first embodiment of the present invention. The solid-state imaging device 31 _A in FIG. 1, first and second
First and second shift registers 3 as vertical scanning units
2, 33, the pixel unit 34 _A, storage unit 35 _A1 to 35 _A4, horizontal reading unit 36 is a horizontal scanning unit, and a by the amplifier 37.

The pixel unit 34 _A, the pixel 41, such as those which are arranged in a two-dimensional 4 rows × 4 columns. Pixel 41 is
Electric charges generated by the photodiode 42 as a light receiving element are accumulated in the accumulation region 44 via the first switching element (for example, MOSFET) 43, and the electric charge in the accumulation region 44 is transferred by the second switching element (for example, MOSFET) 45. Is done.

The first switching element 43 of each pixel 41 has the same address line 46 _{1 to} 46 in the row direction.
Is driven by _4, it is driven by the same address lines 47 ₁ to 47 ₄ in the second switching element 44 in the row direction. The charge transferred by the second switching element 45 is:
Via data lines 48 ₁ to 48 _4, respectively sent to the storage unit 35 _A1 to 35 _A4 provided in each column.

The horizontal read section 36 includes storage sections 35 _{A1 to} 35 A
_It reads out the charge stored in _A4 , and outputs an image signal via the amplifier 37.

The area of each of the storage units 35 _{A1 to} 35 _A4 is
It is formed to be larger than the area of the accumulation region 44 in each pixel 41.

FIG. 2 shows an operation time chart of FIG. Note that the pixels in FIG. 1 are positioned in 4 rows × 4 columns and are displayed in a matrix. The drive signals of the first shift register 32 are φ21 to φ24, and the drive signals of the second shift register 33 are φ11 to φ14.

[0024] In this case, the drive signal φ11~φ14 output from the second shift register 33 is a pulse for sequentially reading out the vertical pixel 41 of the pixel section 34 _A, a plurality are turned on at the same time Never. On the other hand, the driving signal φ21 output from the first shift register 32
.About..phi.24 are pulses for determining the time for reading charges from the photodiode 42, and a plurality of pulses may be in the ON state at the same time.

Now, when the first switching element 43 is turned on by the drive signal φ21 of the first shift register 32, the pixels (1, 1), (2, 1), (3, 1),
The reading of the charges generated in the photodiodes (4, 1) is started. At this time, the drive signal φ11 from the second shift register 33 is still in the off state, and thus the electric charge read from each photodiode 42 is
It is stored in each storage area 44.

Therefore, in this state, the second shift register
33, the drive signal φ11 is turned on,
The electric charge accumulated in the accumulation region 41 is stored in the accumulation unit for each column.
35 _A1~ 35_A4Are transferred to each other and accumulated. this
In this case, all the charges accumulated in the accumulation region 44 are transferred.
In this case, the drive signal φ21 remains on, and the
The charge from the ion 42 is directly stored in the storage section 35._A1~ 35_A4
Is transferred to That is, both the drive signals φ11 and φ21 are
In the on state, the accumulation region 44 serves as a channel.
Will work.

[0027] Then, the drive signal .phi.21, .phi.11 is turned off, charges stored in the storage unit 35 _A1 to 35 _A4, the
The image data is read out by the horizontal reading unit 36, transferred, and sequentially output to the outside via the amplifier 37 as an image signal.

During the accumulation of the accumulation units 35 _{A1 to} 35 _A4 , the drive signal φ22 is turned on by the first shift register 32, and the pixels (1, 2), (2, 2),
The electric charge is read out from each of the accumulation regions 44 of (3, 2) and (4, 2). Then, similarly, an image signal is output from the horizontal reading unit 36.

These operations are sequentially and repeatedly performed up to the drive signals φ24 and φ14 of the first and second shift registers 32 and 33.

It should be noted that the pixel (1, 1) is read by the horizontal read unit 36.
During the horizontal readout of the charges of the photodiode 42 in (4) and (4), the pixels (1, 2) to (4)
The charge of the photodiode 42 of 2) is stored in the storage units _{35A1 to} 35A3.
5 _A4 may be supplied to the pixel (1,3)-
The charge of the photodiode in (4, 3) may be read.

As described above, the effective area of the accumulation region is:
From becoming area of the storage unit 35 _A1 to 35 _A4, it is possible to set a large storage area. The effective integration time is determined by the output pulse (φ2
1 to φ24), and a value larger than the above-mentioned T _F / N can be obtained.

That is, by taking advantage of the storage time in the interline type and the storage area in the line address type, it is possible to prevent a decrease in the maximum stored charge amount.
Therefore, even if the number of pixels is increased and the accumulation region 44 of the pixel 41 is reduced, the maximum accumulated charge amount does not decrease, and the SN ratio can be improved.

Next, FIG. 3 shows a configuration diagram of a second embodiment of the present invention. The solid-state imaging device 31 _B in FIG. 3, the pixel portion 34 _B is one obtained by sharing provided a single storage area 51 into two pixels 41 adjacent in the column direction.

In this case, the drive signal φ21 of the first shift register 32 drives the pixels 41 in the first and second rows,
The drive signal φ22 drives the pixels 41 on the third and fourth rows. The drive signals φ21 and φ22 are supplied to each pixel 41 via a gate (for example, MOSFET) 52 provided in each row, and the gates 52 in the first and third rows are controlled by a first interlace signal φf1, Gate 5 on the second and fourth rows
2 is controlled by the second interlace signal φf2.

The drive signals φ11 and φ12 of the second shift register 33 drive one second switching element 45 corresponding to each storage area 51. That is, the second switching element 45 of one of the pixels 41 can be omitted from the two pixels 41 sharing the accumulation region 51.

The other structure is the same as that of FIG.

FIG. 4 shows the operation time chart of FIG.
Show The solid-state imaging device 31 of FIG. _BRead out the charge of
The principle is the same as FIG. 1 (FIG. 2), and the driving order is different.
Just do it. That is, the first shift register 32
Charge readout from the photodiode 42 by the
Every other row by field switching signals φf1 and φf2
To read in column-wise interlaced
It is.

As shown in FIG. 4, the first and third odd-numbered rows are driven while the first field switching signal φf1 is on, and two rows are driven while the second field switching signal φf2 is on. It drives the even-numbered rows of the fourth and fourth rows.

Therefore, two pixels adjacent to each other in the column direction of the pixel 41 can share the storage area 51.

Next, FIG. 5 shows a configuration diagram of a third embodiment of the present invention. The solid-state imaging device 31 _C in FIG. 5, is obtained by sharing provided a single storage area 61 into two pixels 41 on which the pixel portion 34 _C are adjacent in the row direction.

In this case, each of the drive signals φ21 to φ24 from the first shift register 32 is supplied to the first switching element 43 of the pixel 41 in the odd-numbered column of each row via the gate (for example, MOSFET) 62a. At the same time, the first switching element 43 of the pixel 41 in the even-numbered column of each row is supplied via a gate (for example, a MOSFET) 62b.

The gate 62b is controlled by the first field switching signal φf1, and the gate 62a is controlled by the second field switching signal φf2.

The drive signals φ11 to φ14 of the second shift register 33 drive one second switching element 45 corresponding to each storage area 61. In other words, the second switching element 45 of any one of the two pixels 41 sharing the accumulation region 61 can be omitted.

In this case, the data is stored in the storage area 61 of each column.
Since it is intended to be sent from, two data lines 63 _1, 63 ₂ via the two storage portions 35 _B1, 35 _B2 in charge is accumulated.

The other structure is the same as that of FIG.

FIG. 6 shows an operation time chart of FIG. FIG. 3 shows a case in which signal charges are read out by interlacing in the column direction, and FIG. 5 shows a case in which signal charges are read out by interlacing in the row direction.

That is, the charge readout from the photodiode 42 by the first shift register 32 is performed every other column by the field switching signals φf1 and φf2. The signal output by the horizontal readout unit 36 is shown in FIGS. Same as 3.

As shown in FIG. 6, while the first field switching signal φf1 is on, the first and third odd-numbered columns are driven, and while the second field switching signal φf2 is on, The second and fourth even-numbered columns are driven.

As described above, two pixels adjacent to each other in the row direction of the pixel 41 can be shared by the storage area 61.

The first to third embodiments correspond to the pixel 41
Are arranged in two dimensions of 4 rows × 4 columns,
The number is not limited.

[0051]

As described above, according to the present invention, the accumulation of electric charges in the accumulation area of the pixel is performed by the first vertical scanning section, and the transfer of the electric charge from the accumulation area to the accumulation section is performed by the second vertical scanning section. By using the scanning unit, it is possible to prevent a decrease in the maximum accumulated charge amount due to an increase in the number of pixels, and to improve the SN ratio.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a first embodiment of the present invention.

FIG. 2 is an operation time chart of FIG.

FIG. 3 is a configuration diagram of a second embodiment of the present invention.

FIG. 4 is an operation time chart of FIG. 3;

FIG. 5 is a configuration diagram of a third embodiment of the present invention.

FIG. 6 is an operation time chart of FIG. 5;

FIG. 7 is a configuration diagram of a conventional solid-state imaging device.

[Explanation of symbols]

31 _{A to} 31 _C solid-state imaging device 32 First shift register 33 Second shift register 34 _{A to} 34 _C Pixel section 35 _{A1 to} 35 _A4 , 35 _B1 , 35 _B2 accumulation section 36 Horizontal reading section 37 Amplifier 41 Pixel 42 Photo Diode 43 First switching element 44, 51, 61 Storage area 45 Second switching element

Claims (6)

(57) [Claims] 1. A first switching element (43) for reading out charges generated in a light receiving element (42), and a storage area (44, 51) for storing charges read out by the first switching element (43). , 61) and the storage area (4
The second pixel section in which pixels (41) is formed are arranged two-dimensionally with the switching element (45) for transferring the charge of 4,51,61) and (34 _A to 34C _c), the pixel portion (34 the first vertical scanning unit that drives _a to 34C _C) said first switching element of each of pixels (41) to (43) in the row direction (32), the pixel portion of (34 _a to 34C _C) A second vertical scanning section (33) for driving the second switching element (45) of each pixel (41) in a row direction, and a column for transferring the charges transferred by the second switching element (45). A predetermined number of storage units (35 _{A1 to} 3
5 _A4 , 35 _B1 , 35 _B2 ) and a horizontal scanning unit (36) for reading out the electric charges of the respective storage units (35 _{A1 to} 35 _A4 , 35 _B1 , 35 _B2 ) and outputting a signal. Solid-state imaging device. 2. The pixel (4) of the pixel section (34 _B ).
1), the storage region (51) of two pixels adjacent in the column direction is shared, and the second region of any one of the two pixels is used.
The solid-state imaging device according to claim 1, wherein the switching element (45) is omitted. 3. The pixel (4) of the pixel section (34 _C ).
In 1), the accumulation region (61) of two pixels adjacent in the row direction is shared, and the second region of any one of the two pixels is used.
The solid-state imaging device according to claim 1, wherein the switching element (45) is omitted. 4. A sequence of pixel charges generated by the light receiving element in pixels arranged in a two-dimensional (41) (42) (41)
Readout in the upper row direction and storage area (44, 51, 61)
The charge accumulated in the accumulation region (44, 51, 61) and the charge generated in the light receiving element (42) are stored in the pixel (41).
Is transferred to the row direction on the array, the storage unit of each column of said charge _{(35 A1 ~35 A4, 35 B1} , 35 B2) a step of storing, the respective storage unit _{(35 A1 ~35 A4, 35 B1} , the driving method of the solid-state imaging device which comprises 35 _B2) a step of the accumulated charge is to read out <br/> the column direction on the sequence signal output of the pixel (41) in the. 5. The two pixels (4) adjacent in the column direction.
The storage region (51) of (1) is shared, and the charge generated in the light receiving element (42) is stored in the storage region (51) every other row of the pixels (41). ) in claim 4 further comprising a be accumulated in the accumulation unit by transferring by every one line (35 _A1 to 35 _A4) of the pixel charges produced by the accumulated charge and the light receiving element (42) (41) Driving method of a solid-state imaging device. 6. The two pixels (4) adjacent in the row direction.
The storage region (61) of (1) is shared, and the charge generated in the light receiving element (42) is stored in the storage region (61) every other column of the pixels (41) , and the storage region (61) ) storage unit by transferring by every one column of the pixels generated charges accumulated charge and the light receiving element (42) (41) in (35 _B1, 35 _B2) according to claim 4 further comprising a be accumulated in Driving method of a solid-state imaging device.