JPH022294A - Solid-state image pickup element - Google Patents

Abstract

PURPOSE:To simplify structure considerably and to eliminate the need for an iris mechanism of mechanical structure and an electronic shutter or the like in an electronic camera or the like adopting a solid-state image pickup element by obtaining a function signal corresponding to a correction signal charge obtained a photodetection element and using the signal so as to control the pickup signal charge. CONSTITUTION:The signal charge of the photodetection element 1 is fed to a source (1st output terminal) of a MOS transistor(TR) being a function control circuit 5 for the image signal charge. The signal charge of the photodetection element 2 is a correction signal charge and in the case of exposure suppression, the control circuit 3 is controlled to an open circuit and fed to a function circuit 4. The function circuit 4 supplies a control signal B of the opposite polarity to the change in the correction signal charge to the gate of the MOS TR 1 being the function control circuit 5 while being superimposed on the bias voltage Vb. As a result, the output signal given to the source of the TR Q1 decreases it level when the exposure is changed for a prescribed value or over and the exposure is suppressed. On the other hand, in case no exposure suppression is applied, the control circuit 3 is controlled to be a closed circuit to interrupt the correction signal charge to the function circuit 4.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a solid-state image sensor, and is particularly suitable for use in electronic cameras, VTR cameras, and the like.

(Prior Art) Conventionally, an image pickup tube has been frequently used as an image pickup element in the electronic camera or VTR camera. However, in recent years,
They are being replaced by small and lightweight solid-state image sensors.

The solid-state image element is a CCD
There are two types of MOS, both of which have hundreds of thousands of light-receiving elements (photodiodes) lined up like eyes on the board.The light-receiving elements perform photoelectric conversion and sequentially read out signal charges to capture images. It is something.

When suppressing exposure in the electronic camera and the like, the exposure time is controlled by providing a mechanical aperture mechanism or an electronic shutter.

(Problems to be Solved by the Invention) In electronic cameras and the like, since the exposure suppression function is an essential requirement, the actual situation is that an aperture JMBN and an electronic shutter are provided separately from the solid-state image sensor. Therefore, what about the mechanical structure and circuit configuration of electronic cameras, etc.? 'Ji became cumbersome, which was an obstacle to making it smaller and lighter.

The above-mentioned problem would be solved if the solid-state image sensor itself had an exposure suppression function, but currently no solid-state image sensor having an exposure suppression function has been developed.

The present invention solves the above-mentioned problems, and its purpose is to provide a solid-state image sensor that can suppress exposure.

(Means and Effects for Solving the Problems) The object of the present invention is to arrange a plurality of light receiving elements in a matrix, and transfer the imaging signal charge obtained from each light receiving element to the first output of the function control circuit. At the same time, a part of the signal charge at the back of the light receiving element is supplied to the function circuit as a correction signal charge, and a function signal corresponding to the correction signal charge obtained from the function circuit is sent to the function control circuit. This is achieved by supplying the imaging signal charge to the first control terminal of the function control circuit and controlling the imaging signal charge using the function control circuit.

That is, the function circuit is configured to generate, for example, a function signal of opposite polarity in response to the correction signal charge.

Then, when the imaging signal charge is supplied to the first output terminal of the function control circuit and the function signal is supplied to the first control terminal, the signal charge amount of the imaging signal charge is controlled by the function signal of the opposite polarity. Ru. Therefore, the output signal of the function control circuit is
The exposure amount of the light-receiving element is controlled by controlling the supply and cutoff of the function signal to the first control terminal and the function change of the function signal, each time the function signal changes in response to the function signal. The same effect can be obtained if

(Embodiment) Next, the present invention will be described in detail with reference to the drawings.

In explaining the embodiments, the basic concept of the present invention will be explained with reference to FIGS. 1 and 2, and then specific examples will be explained. Note that FIG. 1 is a signal charge and output signal characteristic diagram for explaining the basic concept of the present invention, and FIG. 2 is a circuit diagram schematically showing the circuit configuration of a solid-state image sensor.

Characteristic A shown in FIG. 1 shows the exposure amount versus output (signal charge) characteristic of the light receiving element 1.2. The signal charge of the light-receiving element 1 is used as the signal charge for imaging to the source (first
output terminal). The signal charge of the light-receiving element 2 becomes a correction signal charge, and when suppressing exposure, the control circuit 3 is controlled to open circuit and is supplied to the function circuit 4.

The function circuit 4 obtains a control signal B having a polarity opposite to the change in the correction signal charge, and the function signal B is applied to the gate (first control terminal) of the MO3I transistor Q1, which is the function control circuit 5. It is supplied superimposed on the bias voltage vb.

As a result, the output signal appearing at the source of transistor Q1 (MO3) has output characteristic C, which is controlled by characteristic B (combined in this case), and when the exposure amount changes beyond a predetermined value, the level decreases and the exposure The amount will be suppressed.

On the other hand, when the exposure suppression is not performed, the control circuit 3 is controlled to be a closed circuit, and the transmission of the correction signal charge to the function circuit 4 is interrupted. As a result, the gate of the transistor Q1 is fixed to the bias voltage vb, and the output signal corresponds to the signal charge for imaging. Therefore, similarly to characteristic A, the level change of the output signal changes in accordance with the exposure amount.

Next, specific examples of the solid-state image sensor will be described with reference to FIGS. 3 to 8.

The light receiving element 1.2 is a MOS F on the same semiconductor substrate.
The capacitor C1, which is configured with an ET structure and stores signal charges, is also configured with a junction capacitance.

When suppressing exposure, do not supply the reset pulse ■1 to the gate of the MOS transistor Q2 which becomes the control circuit 3,
Also, without supplying reset bias ■2 to the source, l-
Turn off transistor Q2.

As a result, the correction signal charge is
OS A current is supplied to data 1 of transistor Q3 and flows from capacitor C2 to transistor Q3 in accordance with the amount of charge! control d.

At this time, since the gate voltage V3 and bias voltage 4 of the P-channel MOS transistor Q4 are cut off, the current 1d becomes a discharge current using the charge stored in the capacitor C2 as a power source, and the amount of current is The amount of correction signal charge, in other words, is proportional to the amount of exposure of the light receiving element 2.

Figure 4 shows the amount of signal charge for correction and the electric charge 'd+i I d
As the exposure amount increases and the correction signal charge amount increases (approaches 0 point), the current 1d increases. The change in current 1d is determined as shown in FIG.

On the other hand, the function control circuit 5 is composed of an N-channel depletion transistor Q1, and its gate voltage Vp (function signal) changes in function according to the current 1d.

As shown in FIG. 4, the current 1d increases in the negative direction as the exposure amount increases, so the current Id of the transistor Q1
becomes a dog in proportion to the amount of exposure, as shown in FIG.

Electric? Ai is applied to the capacitor CI,
The terminal voltage of the capacitor C1 during photographing changes as shown in FIG.

That is, the capacitor CI maintains a constant voltage Vv due to the video bias voltage Vv applied to the differential amplifier 6, which will be described later.
is being charged.

Then, when the light-receiving element 1 is exposed to light at the start of photography, electric charges are discharged in accordance with the amount of exposure. For convenience of explanation, assuming here that charging with the current i is not performed, the terminal voltage decreases as shown by characteristic a due to discharge corresponding to the exposure amount of the light-receiving element l-1.

However, in this embodiment, since the light-receiving element 1 discharges and at the same time charges with the current i, the terminal voltage does not drop suddenly as in characteristic a, but as in characteristic become. The difference between a and b corresponds to the exposure control amount, and this exposure suppression amount is controlled by the current i, in other words, by the function signal Vp.

When shooting, ↑ MO to read out the darkest signal charge in the Y direction
Both the 3I-transistor Q5 and the MOS transistor Q6 for reading in the X direction are controlled to be in the on state.

As a result, the terminal voltage of the bias resistor R1, in other words, the terminal voltage of the non-inverting input terminal ->- of the differential amplifier 6 changes in level as shown in the above characteristics. Therefore, the output signal Vout of the differential amplifier 6 provided as a preamplifier
The characteristics also change in the same way as the characteristics described above, and an output signal similar to that obtained when exposure is suppressed is obtained.

Next, the device structure of the solid-state image sensor will be explained with reference to FIG. 1.2 in the figure corresponds to the light receiving element, and a transistor Q
P′ becomes the source of transistor Q3 and the drain of transistor Q3.
layers are formed.

A transistor Q1 is formed between the light receiving element 1 and the light receiving element 2, and a transistor Q1 is formed between the light receiving element 1 and the light receiving element 1.
A transistor Q3 is formed between the two layers.

On the other hand, the vertical shift register 12 shown as VSR is
The vertical selection lines 13 for one field are selected by a switch signal, and the horizontal shift register 14 indicated as IISR selects the horizontal readout line 15.

Now, if the upper vertical selection line 13 (corresponding to the transistor Q6) in FIG. The signal will be supplied to the differential amplifier 6 via.

Note that if exposure suppression is not to be performed, the transistor Q2 is controlled to be turned on, and the transmission of the correction signal charge to the function circuit 4 is cut off. Further, the transistor Q4 is controlled to be turned on, and the capacitor C2 is charged to a predetermined voltage by the voltage v4, thereby fixing the gate voltage of the transistor Ql. That is, in this case, no function signal is supplied. Therefore, the function control operation by the transistor Q1 is not performed, and the imaging signal charge is supplied to the differential amplifier 6 as it is.

Regarding the arrangement of the light receiving elements 1.2, the number of light receiving elements 2 does not need to be the same as the number of light receiving elements I-1 (as shown in FIG. It is sufficient to arrange one or more.

Although the present invention has been described in detail above, the present invention is not limited thereto, and various modifications are possible.

For example, by selecting the capacitance value of the capacitor C2 and the characteristics of the transistor Q3, the above-mentioned characteristics can be arbitrarily varied. For example, the saturation point .

Further, in the above embodiment, the case where a MOSFET is used as the function circuit has been described, but the present invention is not limited to this. Various output characteristics can be obtained by combining these.

Furthermore, the present invention can also be used to suppress blooming by providing a circuit with negative characteristics.

(Effects of the Invention) As described above, the present invention obtains a function signal corresponding to the correction signal charge obtained from the light receiving element, and controls the imaging signal charge obtained from the light receiving element using the function signal. . Therefore, by selecting the function change of the function signal, the characteristics of the imaging signal charge can be varied, and by this variation, it is possible to obtain the same output characteristics as when the exposure of the solid-state image sensor is suppressed. can.

Therefore, in electronic cameras etc. that use solid-state image sensors,
There is no need to provide a mechanical aperture mechanism, an electronic shutter, etc., and the structure can be greatly simplified.

[Brief explanation of the drawing]

FIG. 1 is a signal charge vs. output characteristic diagram explaining the basic concept of the present invention, FIG. 2 is a schematic circuit diagram explaining the basic concept of the present invention, FIG. 3 is a circuit diagram showing a specific example, and FIG. Figures 4 and 5
Figure 6 is a current characteristic diagram showing the generation of a function signal, Figure 6 is a characteristic diagram showing control of imaging signal charge by a function signal, Figure 7 is a partially cutaway plan view showing the device structure of a solid-state image sensor, FIG. 8 is a plan view of the main parts showing the arrangement of the light receiving elements. Reference numerals in the figure 1.2... Light receiving element, 3... Control circuit, 4.
...Function circuit, 5...Function control circuit, 6...
Differential amplifiers, Ql, Q6...M that make up Inharc
Os transistor, A, B, C, a, b...characteristics. Figure 1 Figure 2 Figure 2 Figure 2

Claims (1)

[Claims] 1) A plurality of light receiving elements arranged in a matrix, a first switching circuit that reads signal charges generated from the light receiving elements in the Y direction in response to a clock signal, and reading by the first switching circuit. A solid-state image sensor comprising: a second switching circuit that reads out signal charges in the X direction in response to a clock signal;
A desired number of the plurality of light-receiving elements that obtain signal charges for at least one field are set as correction light-receiving elements, and transmission and interruption of correction signal charges generated from the correction light-receiving elements is arbitrarily controlled. a control circuit; a function circuit that obtains a function signal corresponding to the amount of transmission of the correction signal charge when transmitting the correction signal charge; A solid-state imaging device including a function control circuit that controls imaging signal charges.