JPH0955888A - Solid-state image pickup element and image pickup device using this element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To extend the dynamic range of the output signal quantity to incident light quantity. SOLUTION: For example, two load capacities 18 and 19 are provided for one vertical signal line 13, and signals outputted from picture elements in plural rows different by storage times are read out through vertical signal lines 13 by MOS transistors 16 and 17 as operation switched and are stored in load capacities 18 and 19. Meanwhile, signals stored in load capacities 18 and 19 are led out from output terminals 25 and 26 through horizontal signal lines 22 and 23 by MOS transistors 20 and 21.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state image pickup device and an image pickup apparatus using the same, and more particularly, it is possible to read pixel information obtained by photoelectric conversion in pixel units.
The present invention relates to a Y-address type solid-state imaging device and an imaging device using the same.

[0002]

2. Description of the Related Art In an amplification type solid-state image sensor, which is a type of XY address type solid-state image sensor, an active element (MOS transistor) having a MOS structure or the like is used to form a pixel so that the pixel itself has an amplification function. I am configuring. A conventional example of this amplification type solid-state imaging device is shown in FIG. In FIG. 8, a large number of pixel transistors 81 are arranged in a matrix, and the gate electrodes of the respective pixel transistors 81 are arranged in rows in units of vertical selection lines 82.
, Each source electrode is connected to the vertical signal line 83 in column units, and the power supply voltage VD is applied to each drain electrode. Each vertical selection line 82 has a vertical scanner 84.
Connected to the output end of the

Each vertical signal line 83 is connected to the drain electrode of an NchMOS transistor 85 which is an operation switch. The source electrode of the MOS transistor 85 is connected to one end of the load capacitance 86 and also to the drain electrode of the NchMOS transistor 87 which is a horizontal switch, and its gate electrode has an operation pulse φO.
P is applied. The other end of the load capacitance 86 is grounded. The source electrode of the MOS transistor 87 is connected to the horizontal signal line 88, and the gate electrode thereof is connected to the output terminal of the horizontal scanning circuit 89. One end of the horizontal signal line 88 is connected to the output terminal 90.

In the amplification type solid-state image pickup device having the above structure,
The incident light is photoelectrically converted by the pixel transistor 81 into a signal charge having a charge amount corresponding to the light amount. Pixel transistor 8
A signal corresponding to the amount of incident light from 1 is held in the load capacitance 86 via the vertical signal line 83 and the MOS transistor 85 which is an operation switch. The held signal is output to the horizontal signal line 88 via the MOS transistor 87, which is a horizontal switch controlled by the horizontal scanning circuit 89, and the output terminal 90 is further passed through the horizontal signal line 88.
From the outside.

In such an amplification type solid-state image pickup device, an output signal which is almost linear with respect to the signal charge accumulated in the unit pixel is obtained by photoelectric conversion, and the dynamic range of the image pickup device depends on the amount of signal charge that can be accumulated in the unit pixel. Will be decided. FIG. 9 is an input / output characteristic diagram showing the relationship between the amount of incident light and the amount of output signal of the image sensor. As is clear from this input / output characteristic diagram, the dynamic range of the image sensor is
It is determined by the saturation signal amount and noise level of the pixel.

[0006]

As described above, in the conventional amplification type solid-state image pickup device, the amount of signal charge that can be stored in a unit pixel is limited according to the size of the unit pixel, so that the brightness is low. If the aperture of the camera lens is adjusted to the subject, the signal of the high-luminance subject will be saturated, and if the aperture of the camera lens is adjusted to the high-luminance subject, the signal of the low-luminance subject will be buried in the noise. We could not obtain the dynamic range required for recognition.

The present invention has been made in view of the above problems, and an object thereof is to provide a solid-state image pickup device capable of dramatically expanding the dynamic range of the incident light amount to the output signal amount and the solid-state image pickup device. An object is to provide an imaging device used.

[0008]

In the solid-state image pickup device according to the present invention, a plurality of storage means are provided for each vertical signal line to which pixels in the same column are commonly connected, and pixels from a plurality of rows with different storage times are provided. The output signals are read out by the plurality of first switch means through the vertical signal lines and stored in the plurality of storage means, while the signals stored in these storage means are read out by the plurality of second switch means and are stored in the plurality of storage means. It is configured to output through a horizontal signal line.

Further, in the image pickup device according to the present invention, a solid-state image pickup device for obtaining a plurality of output signals based on a plurality of rows of pixels having different accumulation times is used, and a plurality of output signals output from the solid-state image pickup device are processed by a signal processing circuit. It is configured so that they are synchronized with each other and added to output them as a video signal.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a configuration diagram showing an embodiment of a solid-state image sensor according to the present invention. FIG.
, A pixel transistor (in this example, NchMOS
A large number of (indicated by transistors) 11 are arranged in a matrix, the gate electrode of each pixel transistor 11 is connected to a vertical selection line 12 in a row unit, each source electrode is connected to a vertical signal line 13 in a column unit, and each drain is further connected. Power supply voltage V for electrodes
D is applied. Each vertical selection line 12 is connected to the output terminals of the vertical scanning circuit 14 and the electronic shutter scanning circuit 15.

The vertical scanning circuit 14 is composed of a shift register or the like, and in order to sequentially read pixel information for each line while performing vertical scanning, a vertical selection pulse φV (..., φVm, , ΦVp, ...) is given. The electronic shutter scanning circuit 15 is also composed of a shift register or the like, and is for controlling the pixel accumulation time for each line.

Each vertical signal line 13 has an operation switch (first
Of the NchMOS transistors 16 and 17, which are the switching means of the above). These MOS transistors 16 and 17 are formed to have the same size, and the operation pulse φ is applied to each gate electrode thereof.
OP1 and φOP2 are applied. MOS transistor 1
Each of the source electrodes 6 and 17 is connected to one end of each of two load capacitors 18 and 19 which are storage means, and two NchMOs which are horizontal switches (second switch means).
The drain electrodes of the S transistors 20 and 21 are connected. The other ends of the load capacitors 18 and 19 are both grounded.

The source electrodes of the MOS transistors 20 and 21 are connected to the horizontal signal lines 22 and 23, respectively, and the gate electrodes are commonly connected to the output terminal of the horizontal scanning circuit 24. The horizontal scanning circuit 24 is composed of a shift register or the like, makes the MOS transistors 20 and 21 conductive, and connects one end of each of the load capacitors 18 and 19 to the horizontal signal lines 22 and 2.
3, the horizontal scanning pulse φH (..., φV) is applied to each gate electrode of the MOS transistors 20 and 21.
n, φVn + 1, ...) Is given. Horizontal signal lines 22, 23
One end of each is connected to the output terminals 25 and 26, respectively. The amplification type solid-state imaging device 10 is configured as described above.

Next, the amplification type solid-state image pickup device 10 having the above structure.
The operation of will be described. First, the pixel transistor 11 of the vertical selection line 12 of the φVm row, which has been accumulated for a time almost close to the vertical scanning period, is switched from the vertical signal line 13 to a MOS transistor 1 which is an operation switch during a certain horizontal blanking period.
It is read out via 6 and held as a signal voltage in the load capacitance 18. Then, with respect to the pixel transistor 11 of the vertical selection line 12 of the φVm row which has been read, the signal charge accumulated in the pixel transistor 11 is reset.
The electronic shutter scanning circuit 15 controls the pixel accumulation time.

Next, in the same horizontal blanking period, φ read once and reset, for example, 1/1000 second before.
The signal of the pixel transistor 11 of the Vp row vertical selection line 12 is read from the vertical selection line 12 to the load capacitance 19 via the MOS transistor 17 and held as a signal voltage.
Regarding the pixel transistor 11 of the vertical selection line 12 of the φVp row for which reading has been completed,
The signal charge accumulated in is reset. Then, assuming that the vertical scanning period is 1/60 second, the load capacitance 1
Signals with storage times of (1 / 60-1 / 1000) seconds and 1/1000 seconds are stored in 8 and 19, respectively. These signals will be referred to as L signal and S signal, respectively.

L held in the load capacitors 18 and 19
The S signal is the MOS transistor 2 which is a horizontal switch.
0, 21 to the horizontal signal lines 22, 23, and output signals OUT1, O through output terminals 25, 26.
Each is derived to the outside as UT2. Here, FIG. 4 illustrates the relationship between the signal amounts of the output signals OUT1 and OUT2 with respect to the incident light amount. That is, the output signal OUT1 is saturated with the incident light amount R1 equivalent to that in the conventional example, while the other output signal OUT2 is used.
Does not saturate until the incident light amount R2.

In this way, for example, two load capacitors 18 and 19 are provided for one vertical signal line 13, and signals output from pixels in a plurality of rows with different storage times are supplied to the vertical signal line 13 through MOS transistors. The signals stored in the load capacitors 18 and 19 are read out by the 16 and 17 and stored in the load capacitors 18 and 19.
The output signals OUT1 and OUT2 having different accumulation times can be simultaneously obtained from the single solid-state image pickup device 10 by outputting the signals through the horizontal signal lines 22 and 23 by 0 and 21. Therefore, in the conventional solid-state imaging device, a pixel is saturated and a video signal for which contrast is not obtained is output from the other terminal, and a signal with contrast for a very wide range of incident light quantity from a separate terminal. Is obtained.

In the present embodiment, the two load capacitors 18 and 19 are provided for one vertical signal line 13, but the number is not limited to two and three or more may be provided. is there. In this case, it is necessary to provide the same number of operation switches and horizontal switches.

Further, in the solid-state image pickup device 10 having the configuration of FIG. 1, since signals from pixels in different rows are simultaneously derived as the output signals OUT1 and OUT2,
It is not convenient for displaying and image processing. The image pickup apparatus according to the present invention can cope with this.

FIG. 3 is a block diagram showing an embodiment of the image pickup apparatus according to the present invention. In FIG. 3, a pixel signal (an output signal OUT1 in the description of FIG. 1) output from the solid-state image sensor 10 in a row to be scanned later is output to the FIFO (Fir)
By passing the line memory 31 for N rows (st In First Out), the time is adjusted (simultaneous) to the output signal OUT2 which is output in the same row as the output signal OUT1 and later than the output signal OUT1. The signal processing circuit 30 configured to add the synchronized output signals OUT1 and OUT2 by the adder 32 is used.

Here, in the case of the configuration of FIG. 1, the capacity of the line memory 22 may be (mp) rows. This means that, as described with reference to FIG. 1, if the φVp row with a short storage time is set to be scanned before the φVm row with a long storage time, the memory capacity can be reduced. Means Because φV
Since the accumulation time of the p row is represented by the product of the row difference from the φVm row and the horizontal scanning time, the row difference between the φVp row and the φVm row will be small if the accumulation time of the φVp row that is scanned first is set short. This is because the capacity of the memory is reduced as a result.

In this way, the line memory 22 stores the L signal (output signal OUT1) which is the pixel signal of the row to be scanned later.
When the pixel signal of the same row is output as the S signal (output signal OUT2) again, the L signal and the S signal are added and output as a video signal, so that the incident light amount vs. output as shown in FIG. A signal quantity relationship is obtained. As a result, as is clear from the input / output characteristic diagram of FIG. 4, although the sensitivity changes at the boundary of the incident light amount R1, the relationship becomes non-linear.
The dynamic range of incident light is dramatically expanded.

By the way, in any solid-state image pickup device, since the saturation signal amount of the pixel varies, if the output signal OUT1 and the output signal OUT2 are simply added, in the range of the light amounts R1 and R2 in FIG. The variation of the saturation signal amount of the pixel appears in the image as it is. That is, in the range of the light amounts R1 and R2, the output signal OUT1 has variations in the saturation signal amount of the pixel, and therefore the addition signal (OUT1 +
OUT2) becomes a signal with a very poor SN ratio in which the variation of the saturation signal amount of the output signal OUT1 is caused, that is, the output signal OUT2 is superimposed on the fixed pattern noise.

In another embodiment of the image pickup apparatus according to the present invention, it is constructed so as to be able to cope with this. FIG. 5 is a block diagram showing the structure thereof. In the figure, the same parts as those in FIG. 3 are designated by the same reference numerals. In the signal processing circuit 30 according to this embodiment, a clipping circuit 33 is further provided between the output terminal of the output signal OUT1 of the solid-state imaging device 10 and the line memory 31 in order to remove the above-described variation in the saturation signal amount of the pixel. The clip circuit 34 is inserted between the output terminal of the output signal OUT2 and the adder 32.

Here, the clipping circuits 33 and 34 are circuits for replacing a signal of a certain level or more with the certain value, and the certain certain value is smaller than the smallest value of the saturated signal amounts of pixels having variations. Also set to take small. The clipping circuit 3 is also provided on the output signal OUT2 side.
4 is inserted, but as is clear from the input / output characteristics of FIG. 4, the output signal OUT2 does not reach the saturation level up to the incident light amount R2. It is also possible to omit the circuit 34.

FIG. 6 shows the input / output characteristics of the clip circuits 33 and 34. Clip circuit 3 having such input / output characteristics
By inserting 3, 34, even if the output signal OUT1 reaches the saturation level of the pixel, the output signal OUT1 is clipped at the clip level set to be smaller than the saturation signal amount of the pixel. It is possible to obtain a video signal with a high SN ratio without being affected by fixed pattern noise.

Further, in place of the linear input / output characteristic shown in FIG. 6, the non-linear input / output characteristic shown in FIG.
In addition to the above, it is possible to eliminate the unnatural step characteristic at the incident light amount R1 in the input / output characteristic of FIG. 4 and smooth the input / output characteristic. As a result, a video signal having a natural gradation can be obtained.

[0028]

As described above, according to the solid-state image pickup device of the present invention, a plurality of storage means are provided for one vertical signal line, and signals output from pixels in a plurality of rows having different storage times are stored. While the signals are stored in the plurality of storage means through the vertical signal lines and the signals stored in these storage means are output through the plurality of horizontal signal lines, a pixel signal is saturated and a video signal with no contrast is obtained. In addition, since it is possible to obtain a video signal having a contrast with respect to a very wide range of incident light quantity, it is possible to dramatically expand the dynamic range of the incident light quantity to the output signal quantity.

Further, according to the image pickup device of the present invention, a solid-state image pickup device which obtains a plurality of output signals based on a plurality of rows of pixels having different accumulation times is used, and a plurality of output signals outputted from the solid-state image pickup device are simultaneously detected. The signals from pixels in different rows are not output at the same time because of the addition of these signals and the addition of these signals to output as a video signal.Therefore, there is a problem in displaying or image processing. It is possible to obtain a perfect video signal and expand the dynamic range of the amount of incident light versus the amount of output signal.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a solid-state image sensor according to the present invention.

FIG. 2 is an input / output characteristic diagram of the solid-state image sensor according to the present invention.

FIG. 3 is a configuration diagram showing an embodiment of an imaging device according to the present invention.

FIG. 4 is an input / output characteristic diagram of the image pickup apparatus according to the present invention.

FIG. 5 is a configuration diagram showing another embodiment of the imaging device according to the present invention.

FIG. 6 is an input / output characteristic diagram of an example of a clip circuit.

FIG. 7 is an input / output characteristic diagram of another example of the clip circuit.

FIG. 8 is a configuration diagram showing a conventional example.

FIG. 9 is an input / output characteristic diagram of a conventional example.

[Explanation of symbols]

 10 Solid-state image sensor 11 Pixel transistor 12 Vertical selection line 13 Vertical signal line 14 Vertical scanning circuit 15 Electronic shutter scanning circuit 16,17 MOS transistor (operation switch) 18,19 Load capacity 20,21 MOS transistor (horizontal switch) 22,23 Horizontal signal line 24 Horizontal scanning circuit 25, 26 Output terminal 30 Signal processing circuit 31 Line memory 32 Adder 33, 34 Clamp circuit

[Procedure amendment]

[Submission date] May 10, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction contents]

The source electrodes of the MOS transistors 20 and 21 are connected to the horizontal signal lines 22 and 23, respectively, and the gate electrodes are commonly connected to the output terminal of the horizontal scanning circuit 24. The horizontal scanning circuit 24 is composed of a shift register or the like, makes the MOS transistors 20 and 21 conductive, and connects one end of each of the load capacitors 18 and 19 to the horizontal signal lines 22 and 2.
3, the horizontal scanning pulse φH (..., φH) is applied to each gate electrode of the MOS transistors 20 and 21.
n, φHn + 1, ...) Is given. Horizontal signal lines 22, 23
One end of each is connected to the output terminals 25 and 26, respectively. The amplification type solid-state imaging device 10 is configured as described above.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction contents]

Next, the amplification type solid-state image pickup device 10 having the above structure.
The operation will be described based on the timing chart of FIG. First, the pixel transistor 1 of the vertical selection line 12 of the φVm row accumulated for a time almost close to the vertical scanning period.
1 from a vertical signal line 13 to a MOS transistor 1 which is an operation switch during a certain horizontal blanking period (HBLK).
It is read out via 6 and held as a signal voltage in the load capacitance 18. Then, with respect to the pixel transistor 11 of the vertical selection line 12 of the φVm row which has been read, the signal charge accumulated in the pixel transistor 11 is reset.
Note that the resetting of the pixels is performed by applying the substrate pulse φSUB to the substrate. The electronic shutter scanning circuit 15 controls the pixel accumulation time.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0015

[Correction method] Change

[Correction contents]

Next, in the same horizontal blanking period, φ read once and reset, for example, 1/1000 second before.
The signal of the pixel transistor 11 of the vertical selection line 12 of the Vp row is read from the vertical signal line 13 to the load capacitance 19 via the MOS transistor 17 and held as a signal voltage.
Regarding the pixel transistor 11 of the vertical selection line 12 of the φVp row for which reading has been completed,
The signal charge accumulated in is reset. Then, assuming that the vertical scanning period is 1/60 second, the load capacitance 1
Signals with storage times of (1 / 60-1 / 1000) seconds and 1/1000 seconds are stored in 8 and 19, respectively. These signals will be referred to as L signal and S signal, respectively.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0022

[Correction method] Change

[Correction contents]

In this way, the L signal (output signal OUT1) which is the pixel signal of the row to be scanned later as the video signal is stored in the line memory 22, and the pixel signal of the same row is again the S signal (output signal OUT2). Then, the L signal and the S signal are added and output as a video signal, whereby the relationship between the incident light amount and the output signal amount as shown in FIG. 4 is obtained. As a result, as is clear from the input / output characteristic diagram of FIG. 4, the sensitivity changes at the incident light amount R1 and becomes a non-linear relationship, but the dynamic range of the incident light is dramatically expanded.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Name of item to be corrected] Fig. 10

[Correction method] Added

[Correction contents]

FIG. 10 is a timing chart for explaining the operation of the present invention.

[Procedure correction 6]

[Document name to be amended] Drawing

[Name of item to be corrected] Fig. 10

[Correction method] Added

[Correction contents]

[Figure 10]

Claims (5)

[Claims] 1. A large number of pixels arranged in a matrix and outputting a signal according to the amount of incident light, and a plurality of storage means provided for each of the vertical signal lines commonly connecting the pixels in the same column. A plurality of first switch means for reading signals output from pixels of a plurality of rows having different accumulation times through vertical signal lines and storing the signals in the plurality of storage means; and a plurality of signals stored in the plurality of storage means. And a plurality of second switch means for outputting through the horizontal signal line. 2. The solid-state image pickup device according to claim 1, wherein an accumulation time of pixels is controlled by using an electronic shutter. 3. The pixel of the row scanned first as a video signal among the pixels of the plurality of rows is set to have a shorter accumulation time than the pixel of the row scanned last. The solid-state image sensor according to claim 1. 4. A solid-state image sensor for obtaining a plurality of output signals based on pixels of a plurality of rows having different accumulation times, and a plurality of output signals from the solid-state image sensor are synchronized and added to output as a video signal. An image pickup apparatus comprising: a signal processing circuit. 5. The image pickup apparatus according to claim 4, wherein the signal processing circuit adds the synchronized output signals after passing through a circuit having a linear or nonlinear input / output characteristic.