JPS5975774A - Solid-state image pickup device - Google Patents

Abstract

PURPOSE:To perform optical AGC operation with a sufficient function by providing every photosensitive picture element with a circuit which detects the amount of charge of every photosensitive picture element and generates a voltage corresponding to the amount of charge, and connecting its circuit output to an MOS transistor (TR) for every picture element. CONSTITUTION:When photosensitive picture elements 2a-2n are irradiated with light, signal charges are generated corresponding to the intensity of the light and the amounts of charge are detected by potential detection parts 21a-21n to generate corresponding voltages. Those voltages are applied to MOS TRs 22a-22n at source electrodes and an external reference voltage VREF is aplied to gate electrodes to generte a potential barrier thereunder; when the amount of charge of some photosensitive picture element increases until the voltage detected by the potential detection part becomes below the potential barrier, a current flows to the drain of the MOS TR. A transfer gate 3 is opened by the driving pulse to move signal charges generated by the photosensitive picture elements 2a-2n to a CCD register 4, thus achives the optical AGC function.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to the configuration of a solid-state imaging device.

[Technical background of the invention]

In solid-state imaging devices, when used as image sensors such as video cameras, charge-coupled devices (Oh, arge ComplexDeVic) are used to ensure proper output even when the brightness of the subject changes greatly.
The so-called optical automatic gain control (Automatic Ga
1n Control (hereinafter referred to as AdC) function is required.

As a solid-state imaging device having such an optical AGO function, a structure as shown in FIG. 1 is well known.

The photosensitive pixel 2a generates a signal pixel according to the intensity of the irradiated light on a semi-cotton substrate/soil made of, for example, P-type silicon.
. This transfer gate 3 transfers the charge of the photosensitive pixel to the above 0
' This is a gate to control the transfer to the OD register, and the COD register is the output section for the signal charge! The information is sequentially transferred to 10,000 people. The original diode 6 generates a reference output for determining the Rinsuke time, and at the end of -1000, the original diode 2 of C generates /? : Output gate 7 that performs control for extracting charges, a floating diffusion region that stores signal charges flowing in under the control of this output gate, and a floating diffusion region g that discharges the charges stored in this floating diffusion region g to reset it. A reset gate is provided, and a reset drain 10 is provided for discharging the charge led by the reset gate. A source follower circuit ii for detecting the floating diffusion region J'0) potential is connected to the floating diffusion region ♂. This source follower circuit /l consists of a MOS transistor /l and a resistor /3 which are constructed on the same substrate, and has a gate electrode /l.
YuG is connected to the input, the source electrode /28 is connected to a suitable DC voltage, and the drain electrode 12D is connected to the output and also to ground through the resistor 13. This output is input to an operation signal generator provided outside the substrate, which has the function of driving the transfer gate 3 and operating the reset gater.

The operation of the solid-state imaging device having such a configuration is as follows.

Photocurrents generated in the photosensitive pixels 2a to 2n according to the light intensity pattern are accumulated as signal charges. The photosensitive pixels of Kosai 1 and others are arranged in the main row at 2a-, 2n [? The transfer gate 3 operates (opens and closes in response to the same pulse output from the No. B generator) and transfers the accumulated signal charge to the COD register. By driving this CCD and the register, The signal charge is transferred to the output section rL, where it is converted into a voltage corresponding to the amount of charge and taken out as a time series signal.On the other hand, the original diode 6 is transferred to the sensor f,
The entire photodiode 6 is placed in parallel near the J elements λa~ and 2n, so in the vicinity of the 7L pixel, it outputs an output for approximately the same light intensity as the pixel. Then, the average value of the original illumination applied to the entire pixel is output from the floating diffusion region ♂. Appropriate DC voltages va and vb are applied to the output door and reset drain 10 provided at the end of the original diode B, and since a deep potential well is formed under the reset drain 10, the reset electrode Excess charge can be discharged by applying a pulse again. What is extracted from the floating diffusion region g'7j and detected by the source follower is the average value of the charge 471 generated and stored in each pixel, and is shown in Figure 2, tb+. At time t as shown in the waveform diagram.

After the reset, the output level gradually decreases. This output is input to the motion coefficient generator/Il
−, the reference voltage ■R9, which is the standard for this,
2(a) in which the transfer gate 3 and the reset gate are opened when the time t1 exceeds 1.
Outputs the synchronization pulse shown in In this way, when the intensity of the light irradiated to the photodiode B is high, the voltage value detected by the source follower B quickly reaches the reference voltage for use, so the transfer gate 3 is opened quickly, and the photosensitive Since the integration interval in the linear element λ!L-, 2n becomes short, the voltage value output from the transfer field output part j does not increase due to the COD register ≠, and conversely, when the irradiation light intensity is small, Since the opening of the transfer gate 3 is delayed, the output voltage from the output section j (tIJ, &s addition!) is not small, and as a result, the AGO function is achieved.

[Problems with background technology]

However, in a de-body imaging device with such a configuration, the AGO is
It operates based on the average value of the ft and intensity that hit each photosensitive pixel, so for example, if there is a locally strong source, the average value will be As the integral becomes smaller, Ado does not function, and a large amount of charge is generated from the pixel of the neck J-suke where this strong FF was recovered and flows into the surrounding pixels. However, there are intersections that significantly degrade the output signal. When a stiff condition occurs, the image and image will be removed.When a strong light erupts, the so-called pluming phenomenon will occur, in which the size of the emitting area apparently increases.
This seriously impairs its function as an image sensor.

[Purpose of the invention]

In order to solve the above problems, the present invention ("optical A" that can perform a sufficient function even when there are local variations in light intensity) has been developed.
An object of the present invention is to provide a solid-state imaging device that can perform GO operation.

[Summary of the invention]

In order to achieve the above object, in the solid-state imaging device according to the present invention, a circuit is provided for each pixel to detect the amount of charge of each photosensitive pixel and generate a voltage corresponding to the amount of charge, and the output of this circuit is connected to the drain. By connecting the electrode and gate electrode to the source electrode of the MOS transistor for each pixel, which is commonly connected, the signal charge is output from the pixel with the largest amount.
By performing the QAGO function, the maximum output can always be kept constant even if the IC is locally exposed to strong light.

[Embodiments of the invention]

Some embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 is a connection diagram showing the structure and connections of the solid-state imaging device according to the present invention, in which a photosensitive pixel array 21L-2n including a charge storage section is provided on a substrate 1, and a transfer gate is provided on one side of the photosensitive pixel array 21L-2n. 3. ODD register ≠ is arranged in parallel, and this CCD
This is similar to the conventional example in that an output section j is provided at one end of the register≠. On the other side of the photosensitive pixel rows 2a and 2n, there is a potential detection section connected to each photosensitive pixel section, which non-destructively detects the signal charge and generates it as a potential output;
n-channel MO8) transistor n whose source electrode is connected to each potential detection section, 2/a-yu/n
Each gate electrode of this MOS transistor U a -42H is connected to the base layer and a reference voltage REF is applied to it, and each drain electrode is commonly connected to detect the current. It is input to the department force. This current machine part J generates an output when a predetermined θ1 current flows, and the output is inputted to the operation coefficient generating part /2' which is disguised on the board/outside. The output of the motion coefficient generator/U' is input to the transfer gate 3.

The operation of the charge transfer device having such a configuration is as follows.

When light is irradiated onto the photosensitive pixels 2a-,zn, a signal charge is generated according to the light intensity, and this amount of charge is detected by the potential detection unit 2.
/ I! L-:L/n is detected and a corresponding voltage is generated. In other words, when there is no charge, the potential is high (H), and as the charge increases, the potential drops and becomes low (L).
The voltage is such that it is at the same level. This voltage is MO
'S') is input to the source electrodes of transistors 2.2a to 2.2rl, and the external reference voltage V is input to the gate electrode.
Since a potential barrier is formed at the VQ end of the curvature when Y is applied, the amount of charge generated in any photosensitive pixel increases, and when the voltage detected by the potential detection section becomes smaller than the potential barrier, that MOS ) TIR flows through the drain of the transistor. Since this current is detected by the current detector force and input to the operation signal generator 7.2', a driving pulse is sent from the operation signal generator 7.2' to the transfer gate 3. This pulse opens and causes the signal charges generated in the photosensitive pixels 2a-, 2n to move toward the COD register μ. This drive pulse interval becomes shorter as the light intensity at any of the photosensitive pixels 2a-n increases and the amount of signal charge generated increases.
Since this pulse interval becomes the integration time, the configuration on the male side has an optical A G 0 function.

FIG. μ is a block diagram showing a part of one pixel of the embodiment of FIG. 3, and particularly shows the structure of the potential detecting section 2/ in detail. This 'i''L is a potential detection point.
s, 2/ is MOS) U/gate electrode (Gl
is the input, the drain electrode (CD) is the output, an appropriate DC voltage is applied to the source electrode (S), and the train electrode (D
) consists of a source follower circuit connected to a load by MOS) Ranjisme, and the gate electrode (
G) has a photosensitive pixel! Since the charges generated at the drain electrode (Dl) are added one after another, the potential of the output at the drain electrode (Dl) gradually decreases, and it is possible to detect the potential corresponding to the amount of generated charges.

FIG. 5 is a block diagram showing a part of one pixel of the embodiment shown in FIG.
0/ and a storage electrode 202, and the output from the storage electrode 202 is input to a potential detection section 27'. The potential detection section 27' consists of a source follower circuit consisting of a MOS transistor and two MOS transistors 2.7 and 2g whose gate electrodes and drain electrodes are connected in common, respectively, and the source of the M08 transistor. The electrode is connected to the storage electrode and to the gate electrode of a MOS transistor 27 which is the input of the source follower circuit. Note that a driving pulse P similar to that applied to the transfer gate 3 is applied to the MOS) ranlameta 26 gate electrode, and an external voltage Vc is applied to the common drain electrode.
ing.

In such a configuration, when a drive pulse φ is applied to the common gate electrode of the MOS transistor at the same timing as the transfer gate, the MOS transistor is reset and placed in a floating state with no external input. As charges accumulate in the charge storage section 20.2, the potential of the source electrode of the MOS transistor decreases, so the amount of charge accumulation 8 can be detected by the amount of change in potential. This potential is MO'S) transistor n and u, ? It is detected in the same way as in the case of Fig. 1 by the source follower circuit configured by the MOS for comparison
The signal is sent to the transistor 22.

FIGS. 6 to 6 show specific examples of the current detection section. FIG. 6 shows an increase in the voltage drop in a blood flow resistance whose one end is connected to a DC voltage VD, and in FIGS. Then, an external voltage vDD is applied to the drain/electrode, a pulse with the same timing as the driving pulse P of the transfer gate 3 is applied to the gate electrode, and in FIG. Take out one output,
In Fig. g, there is a follower path 3 from the source electrode. The voltage drop output is taken out through the .

It should be noted that the potential detecting section and the 2/O % flow detecting section are not limited to those in the above embodiment, and any type of one can be used.

〔Effect of the invention〕

In the solid-state imaging device according to the present invention as described above, it is possible to detect the maximum of the electric currents and fleas generated in each pixel and output the US motion nollus to the transfer gate. Even if a light pattern with uneven light intensity is imaged, the integration time can be determined using the pixel where the brightest blob 0 hits as a reference, so signal defects such as blooming (13. Stable AG
C! ir = be able to do it.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the configuration and connections of a conventional solid-state imaging device, Figure 2 is a time chart showing its operation, and Figure 3 is a diagram showing the configuration and connections of a conventional solid-state imaging device.
The figure shows the structure of one example of the solid-state imaging device according to the present invention, and the attached drawings show the structure and details of the solid-state imaging device according to the present invention. /... Substrate 1.2 a, -2n... Photosensitive pixel, 3
...transfer electrode, ≠...charge transfer device, /ko, 72'
...Operation (iT number generator, U/a-Y/n...electronic image mountain part, engineering a~2un...MOS transistor, J
...Current detection unit, 2 Hiroshi, Yu 6. ,? ,7,30・
・・11os,）rangister, 29・・Taru Postal Co., Ltd.
3/...Inverter, 3 pieces...Source follower circuit, 20λ...W8 electrode. Figure 1 Figure 2 Figure 3 Figure 1 Figure 4

Claims (1)

[Scope of Claims] /, a photosensitive pixel row consisting of a plurality of photosensitive pixels that generate signal charges according to the intensity of irradiated light, a charge transfer device arranged in parallel thereto to transfer the signal charges, and this charge transfer device. a transfer electrode that is located between the transfer device and the photosensitive pixel row and controls the movement of signal charges generated in each of the photosensitive pixels toward the charge transfer device; and a transfer electrode that detects the integration status of the charges in the photosensitive pixels. In a solid-state imaging device having a detection section on a substrate for causing an external operation signal generation section to output a signal for controlling the transfer electrode, the pixel non-destructively outputs the accumulated signal charge amount from each photosensitive pixel. A plurality of potential detection sections are provided for each potential detection section, and the voltage output obtained by this potential detection section is input to each source electrode, a common external reference voltage is applied to each gate electrode, and each drain electrode is connected to a common connection. A plurality of MOS transistors provided for each pixel are connected to the commonly connected drain electrodes, and a predetermined current flows through them.
A solid-state imaging device characterized in that the detection section includes a current detection section that generates a signal when the current detection section is activated. ! The solid-state imaging device according to claim 1, wherein the potential detection section is a source follower circuit connected to the photosensitive pixel. 3. A source electrode is connected to a storage electrode for each pixel in which a potential detection section is provided in the photosensitive pixel, a drain electrode is connected in common and is given a constant potential, and a gate electrode controls the transfer electrode. 2. The solid-state imaging device according to claim 1, comprising a MOS l-transistor provided for each pixel to which a signal is applied, and a source follower circuit connected to the source electrode. 4. The solid-state imaging device according to claim 1, wherein the long current detection section is a DC resistance. ! , a MOS transistor whose current detecting section inputs the source electrode, applies a set voltage to the drain electrode, and inputs the control signal for the transfer electrode to the gate electrode;
S) Claims 1 to 3 constituted by an inverter connected to the source electrode of the transistor.
The solid-state imaging device described in . g, 11f, the current detection part is read by a MOS transistor whose source electrode is input, a set voltage is input to the drain electrode, and a control signal for the phase shift electrode is input to the gate electrode, and the source electrode of this MOS transistor. Claim 1 consisting of a source follower circuit
A solid-state imaging device according to items 1 to 3.