JPH0530433A - Image pickup device - Google Patents

Abstract

PURPOSE:To take sufficient gradation of a bright part and to widen the dynamic range by forming a video signal by one field period from a signal read or integrated or added for one field period. CONSTITUTION:A signal charge generated in a light receiving section of a photoelectric conversion section 1 is stored to a storage capacitor for a prescribed period in response to an external incident luminous quantity and the signal charge stored for each picture element is read sequentially by a read out scanning section 3 to generate a time series electric signal corresponding to the spatial distribution of the incident luminous quantity. In this case, at least part of the signal charge stored in the storage capacitor is read to the outside of the storage capacitor for twice or over within one field period of the video output signal and the signal read for one field period is integrated or added to generate the video signal for one field period. Thus, the deterioration in the effective sensitivity is suppressed and even when the incident luminous quantity is increased, the luminous quantity dependency of the output signal is not weaken. Thus, the gradation of the bright part is taken sufficiently to widen the dynamic range.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup device, and more particularly to a storage operation type image pickup device which generates an electric signal corresponding to a spatial distribution of an incident amount of light.

[0002]

2. Description of the Related Art A signal charge generated according to the amount of incident light is accumulated for a predetermined period, the signal charges accumulated for each pixel are sequentially read out, and a time series electric signal corresponding to a spatial distribution of the incident light amount is generated. As the image pickup apparatus, that is, the storage type image pickup apparatus, for example, a photoconductive type image pickup tube, a solid-state image pickup element, or the like is known. The operation principle of the photoconductive type image pickup tube is described in, for example, Japanese Patent Laid-Open No. 58-1194231, and regarding the solid-state image pickup element, for example, Japanese Patent Publication No.
No. 9-26154 (Patent No. 1291858).

In the storage type image pickup device, for example, a photoconductor to which a voltage is applied in a state in which carrier injection from an external circuit is blocked, a reverse biased photodiode, or the like is provided in a light receiving portion which generates a signal charge by incident light. Is used. In addition, the generated signal charge is generally stored in the storage capacity of the photoconductor or the photodiode itself.
Further, the readout of the accumulated signal charges to the external circuit is performed by electron beam scanning, scanning of a selected pixel by turning on / off a switching transistor, or the like.

In the operation of the storage type image pickup device, signal storage and readout are periodically repeated in each pixel. Figure 8
Shows a schematic operation principle of one pixel portion of the storage-type image pickup device. (A) is a reading process, (b) is a reading process.
Indicates the accumulation process. Here, a case where a photoconductor is used as the light receiving portion will be described. In FIG. 8, the photoconductor 801 is shown in a schematic band diagram,
Reference numeral 802 represents a conduction band edge, and 803 represents a valence band edge. The direction of the voltage applied to the photoconductor 801 is positive in the downward direction.

Immediately after the signal is read out, that is, at the stage when the signal starts to be accumulated, a predetermined voltage V ₀ is applied to the photoconductor 801 by the power source 804. During the accumulation period,
Electrons 806 and holes 8 generated by incident light 805
07 is separated by the electric field and travels to move the photoconductor 801.
Is accumulated in the storage capacity of. At this time, as shown in FIG. 8B, in the circuit formed by the photoconductor 801 and the power source 804, the switch 808 is in the open state, so that the photoconductor 801 is caused by the reverse voltage formed by the accumulated charges. The voltage applied to is decreasing as indicated by arrow B in FIG. Q is the amount of charge generated by the incident light during the accumulation period
_s , and the capacitance of the photoconductor 801 is C _p , the voltage applied to the photoconductor 801 at the end of the accumulation period, that is, at the start of reading is V ₀ −V _s = V ₀ −Q _s / C _p Has become.

At the time of reading, as shown in FIG. 8A, the switch 808 is closed, and an electric signal corresponding to the signal charge amount Q _s (or signal voltage V _s ) is output to the signal detection unit 809.
Through the output terminal 810. At the same time, the voltage applied to the photoconductor 801 is reset as shown by the arrow A in FIG. 8A, and the power supply voltage V ₀ is applied to the photoconductor 801 again.

The above-described accumulation and readout processes are periodically repeated in each pixel, and the signal accumulated in each pixel is sequentially read out in the image pickup apparatus as a whole.
A time series electric signal reflecting the spatial distribution of the incident light is output.

In the storage type image pickup device whose basic operation principle has been described above, the charge generated by the incident light is stored for a predetermined period and then read out, so that the sensitivity is higher than that of the non-storage type image pickup device. There is an advantage that a high SN ratio can be obtained.

In the storage type image pickup device, higher sensitivity can be obtained by using a system in which the signal charges generated by the incident light are multiplied in the photoconductor. As a specific example of such an image pickup device, a photoconductive film mainly composed of amorphous selenium is used as a target to cause avalanche multiplication of electric charges in the photoconductive film to achieve high sensitivity (for example, an image pickup tube). JP-A-63-304551).

FIG. 9 is a logarithmic plot with respect to the target voltage applied to the photoconductive film of the signal current at the time of blue light irradiation of an avalanche multiplication type image pickup tube using amorphous selenium having a film thickness of 10 μm as the photoconductive target. It was done. As the target voltage is applied, the photocurrent once shows a saturation tendency from around 250V. In this saturation region, the generation efficiency of electron-hole pairs per incident photon is almost 1. When the voltage is further increased, a sharp increase in the signal current is seen at a voltage of about 700 V or higher. This is because avalanche multiplication of charges occurs in amorphous selenium, and it is possible to obtain very high sensitivity by operating by applying such a high electric field with dark current injection blocked. it can.

The fact that such a high sensitivity can be obtained with an avalanche multiplication type image pickup tube is described in, for example, page 17 of the proceedings of the National Conference of the Television Society of 1989, and the film thickness is 6 μm. It is disclosed that the amorphous selenium-based thin film of (1) is used as a photoconductive target to obtain a sensitivity 80 times higher than the conventional one.

[0012]

In the course of operation of the storage type image pickup device, as described above, the voltage applied to the light receiving portion such as the photoconductor or the photodiode is reduced by the charges generated by the incident light. To go. On the other hand, the magnitude of the photocurrent generated in the light receiving section generally depends on the amount of light and the applied voltage. For this reason, it is known that even if the amount of incident light is constant, the efficiency of photo-charge conversion decreases as the voltage decreases during the accumulation period, and the effective sensitivity decreases.
Journal of Applied Physics 28, (1989
Pp. 178-186 (Japanese Journal of Applied Phys
ics, 28 (1989) pp178-186).
The magnitude of this effect depends on the amount of accumulated signal charges, and in the region where the amount of accumulated signal charges is small and the accompanying decrease in photocurrent can be ignored, the photo-charge conversion efficiency during the accumulation period is constant, so the output signal is It is proportional to the amount of incident light. That is, when the dependence of the output signal current I _{s on} the incident light amount P is written as logI _s ∝γ · logP, the γ value is almost 1. As the amount of incident light increases, the sensitivity decreases gradually during the accumulation period, so that the output signal is not proportional to the amount of incident light, and the γ value becomes smaller than 1. In particular, when the accumulated signal charge amount reaches CV ₀ , no voltage is applied to the photoconductive film, so that the output signal is saturated at a light amount larger than that.

The effect as described above is obtained by the dependence of the photocurrent on the voltage as in the case of using the avalanche multiplication type image pickup tube whose photocurrent-voltage characteristics are shown in FIG. Is particularly significant when is large. FIG. 10 is a plot of the output signal in the case of irradiating blue light to an avalanche multiplication type image pickup tube in which amorphous selenium having a film thickness of 10 μm is used as a photoconductive target is plotted against the number of incident photons.
The target voltage is selected so that the avalanche multiplication factor for blue light is about 100 when there is no sensitivity reduction due to accumulated charge. What is indicated by a chain line in the figure is the light amount dependency when γ = 1. As is clear from the figure, the signal current is proportional to the amount of incident light at low illuminance, but in the region where the incident photon density is large, the γ value is smaller than 1 due to the above effect.

As described above, in the storage type image pickup device, when the incident light amount increases, the effective sensitivity decreases and the light amount dependency of the output signal becomes weak. Therefore, there is a problem that the gradation of the bright part cannot be sufficiently obtained and the dynamic range is narrow.

An object of the present invention is to solve such a problem and to provide an image pickup apparatus capable of maintaining the proportional relationship between the incident light quantity and the output signal over a wide range of the incident light quantity.

[0016]

The above-mentioned problem is that at least a part of the signal charges accumulated in the storage capacitor is read out twice or more within one field period of the video output signal and is read out during one field period. This can be solved by forming a video signal for one field period from the signal obtained by integrating or adding the signals.

That is, the image pickup device of the present invention has a light receiving section for generating a signal charge by the incidence of light, and stores the signal charge generated in the light receiving section in the storage capacitor for a predetermined period according to the amount of incident light from the outside. At least one of the signal charges stored in the storage capacitor is stored in the storage-type imaging device that stores and sequentially reads out the signal charges stored in each pixel to generate a time-series electric signal corresponding to the spatial distribution of the incident light amount. Part
A video signal for one field period is formed by reading the video output signal to the outside of the storage capacitor more than once within one field period and integrating or adding the signals read during the one field period. It is characterized by

Further, in addition to the storage capacitance, each pixel is provided with a second charge storage means having an electrostatic capacitance larger than the storage capacitance, and at least a part of the signal charge stored in the storage capacitance is imaged. Within one field period of the output signal, the charge is transferred to and accumulated in the second charge accumulating means more than once.
The signal charge stored in the charge storage means and the storage capacitor is read out to the outside of the pixel every one field period.

Further, the signal charge is transferred from the storage capacitor to the second charge storage means in synchronization with the operation of the horizontal switching transistor for reading out a signal from each pixel. .

Further, the number of times the signal charges are read out of the storage capacitor is variable within one field period of the video output signal.

Further, the charge generated by the incident light is multiplied in the photoconductor.

Further, the photoconductor is amorphous Se.

[0023]

The operation principle of the image pickup apparatus according to the present invention will be described with reference to FIGS. FIG. 1 is a configuration diagram showing an example of a basic configuration of an image pickup apparatus according to the present invention. In FIG. 1, reference numeral 1 denotes a photoelectric conversion unit that has a light receiving unit that generates a photocarrier by incident light 2 and that stores the generated signal charge.
Reference numeral 3 denotes a reading scanning unit for reading out the accumulated signal to an external circuit and at the same time resetting the photoelectric conversion unit 1 to return the voltage applied to the light receiving unit of the photoelectric conversion unit 1 to a predetermined voltage.
4 is an integrator for integrating the read signals, 5 is an integrator 4
A video signal generator for processing the signal from the output terminal to output a video signal of a predetermined system from the output terminal 6, and 7 for controlling the operations of the read scanning unit 3, the integrator 4, and the video signal generator 5. Is a synchronizing signal generator.

The read scanning unit 3 performs read scanning twice or more during one field period τ of the video signal. As a result, the signals read out one after another are transferred to the integrator 4 at time τ
The video signal is generated by the video signal generator 5 for one field period.

FIG. 2 shows the time change of the photocurrent i _p generated in the photoconductor of the photoelectric conversion unit for a unit pixel when the amount of incident light is constant. In the case of the image pickup device of FIG. 3, (b) is the case of the storage image pickup device of the present invention. The photocurrent decreases with time from the value i _p (V ₀ ) at the start of accumulation due to the effect that the applied voltage of the light receiving unit decreases during the accumulation period τ as described above, and the applied voltage is reset by reading the signal. Once again i _p (V ₀₎
Becomes In the case of (a), since the signal is read with the period of one field period τ as a cycle, the signal charge amount Q _s for one field period is

[0026]

[Equation 1]

Can be written, and becomes smaller than the value i _p (V ₀ ) × τ when there is no voltage drop as shown by the shaded area in the figure. On the other hand, in the image pickup apparatus according to the present invention, n times (n ≧ 2, 8 times in FIG. 2B) during one field period τ.
(1) reading scanning is performed, and these signals are added to obtain a signal for one field period. Therefore, the signal charge amount for one field period is

[0028]

[Equation 2]

Therefore, it is possible to suppress the reduction of the effective sensitivity as shown by the shaded area in FIG.

As described above, in the image pickup device according to the present invention, the accumulated charge is read out in a cycle shorter than one field period of the video output signal, thereby preventing the decrease of the photocurrent due to the reverse electric field formed by the accumulated charge. . Since the signal read out within one field period is integrated into a signal for one field period, reduction in effective sensitivity can be suppressed even when the amount of incident light is large, and the video output signal itself is in the field. The period is unchanged, and no change is required in the signal output destination.

In the image pickup apparatus according to the present invention, in order to integrate a plurality of signals read within one field period, in addition to using an integrator, for example, a frame memory is used to add signals that have been once stored. Alternatively, a second charge storage unit may be provided for each pixel. In the latter case, the signal charge accumulated in the capacitance of the light receiving unit is read out in a cycle shorter than one field period of the video output signal to obtain the second signal charge.
Alternatively, the charge may be stored in the charge storage means and read out every one field period.

In the image pickup apparatus according to the present invention, the number n of read scans performed within one field period of the video output signal is also n.
May be variable. In this case, when the illuminance is low, the normal operation is performed with n = 1, and when the illuminance is high, n ≧ 2 and γ is set.
It is possible to prevent the value from decreasing. Furthermore, n may be automatically switched according to the signal charge amount.

[0033]

Embodiment 1 FIG. 3 is a partial circuit configuration diagram of a photoelectric conversion unit in a first embodiment of an image pickup device according to the present invention.

Reference numeral 301 is a photodiode, 302 is a transparent electrode, 303 is a power source, 304 is a storage switching transistor, 305 is a vertical switching transistor, and 30.
6 is a horizontal switching transistor, 307 is a horizontal signal line, 308 is a horizontal selection switching transistor, 30
9 is a vertical signal line, 310 is an output amplifier, 311 is an output terminal, 312 is a capacitor, 313 is a vertical switch gate, 31
4 is a vertical selection means, 315 is a horizontal switch gate, 31
6 is a horizontal selection means, 317 is a storage switch gate, 31
Reference numeral 8 is a storage switch control means.

One end of the photodiode 301 is connected to a power source 303 via a transparent electrode 302 common to each pixel, and the other end is horizontally connected via a storage switching transistor 304, a vertical switching transistor 305, and a horizontal switching transistor 306. It is connected to the signal line 307. Further, the horizontal signal line 307 is connected to the vertical signal line 309 via the horizontal selection switching transistor 308, and one end of the vertical signal line 309 is connected to the output terminal 311 via the output amplifier 310. The connection between the storage switching transistor 304 and the vertical switching transistor 305 is connected to the capacitor 312, and the other end of the capacitor 312 is at the ground potential. The vertical switching transistor 305 and the horizontal selection switching transistor 308 are controlled by the vertical selection means 314 via the vertical switch gate 313, and the horizontal switching transistor 306 is controlled by the horizontal selection means 316 via the horizontal switch gate 315. In addition, the storage switching transistor 304
Is controlled by the storage switch control means 318 via the storage switch gate 317.

Next, the operation of the image pickup apparatus of this embodiment will be described. When the storage switching transistor 304, the vertical switching transistor 305, and the horizontal switching transistor 306 are all turned on, the power supply voltage V ₀ is applied to the photodiode 301 and the capacitance 3
There is no charge on both ends of 12. This state will be called the initial state. When light is incident on the photodiode 301 after the storage switching transistor 304, the vertical switching transistor 305, and the horizontal switching transistor 306 are all turned off, a signal charge is generated, and a charge corresponding to the polarity of the power supply voltage is generated in the photodiode 3.
01 and the source of the storage switching transistor 304 are stored. At this time, the accumulated signal charge amount is set to Q
_s , and the storage capacitance of the photodiode 301 is C _p ,
The applied voltage to the photodiode 301 is V ₀ -Q _s / C _p . Here, when the storage switching transistor 304 is turned on, the signal charge is distributed to the photodiode 301 and the capacitor 312. When the electrostatic capacity of the capacitor 312 is C, an electric charge of CQ _s / (C _p + C) is accumulated in the capacitor 312, and the applied voltage of the photodiode 301 is V
₀ −Q _s / (C _p + C). At this time, if C is made sufficiently larger than C _p, most of the signal charges are accumulated in the capacitor 312, and the voltage applied to the photodiode 301 is restored to the power supply voltage V ₀ . In this way, when the storage switching transistor 304 is turned off, new signal charge is stored in the photodiode 301, and when the storage switching transistor 304 is turned on, the signal charge is stored in the capacitor 3.
Then, the voltage applied to the photodiode 301 is restored and the voltage applied to the photodiode 301 is recovered. In this embodiment, by repeating the above process within one field period, the decrease in sensitivity due to the decrease in the voltage applied to the photodiode 301 is suppressed. When one field period has elapsed, the vertical switching means 314 and the horizontal selecting means 316 again cause the storage switching transistor 304, the vertical switching transistor 305,
Then, all the horizontal switching transistors 306 are turned on, and the signal charges accumulated in the photodiode 301 and the capacitor 312 are read out to the output amplifier 310 through the horizontal signal line 307 and the vertical signal line 309. At the same time, the photodiode 301 and the capacitor 312 return to the initial state. The one-field period refers to the cycle of the vertical synchronizing signal in the video output signal.

In the image pickup apparatus of this embodiment, the storage switching transistor 304 is turned on / off 100 times within one field period.
When it was turned off and operated, good characteristics were obtained in which the signal current was proportional to the incident light amount over a wide range of the incident light amount. Further, in the case of the present embodiment, since the signal charge integrating means is provided for each pixel of the solid-state image pickup element, it is not necessary to increase the charge transfer rate in the horizontal signal line 307 and the vertical signal line 309, and It has the feature that it is not necessary to provide a memory or an integrator outside the solid-state image sensor.

In the present embodiment, the gate of the storage switching transistor 304 is connected to the dedicated storage switch gate 317, and the on / off timing is controlled by the storage switch control means 318.
For example, the gate of the storage switching transistor 304 may be connected to the horizontal switch gate 307 so that charge is transferred to the capacitor 312 each time a signal is read from a pixel on the same vertical line. It will be easy.

Embodiment 2 FIG. 4 is a sectional view showing a part of a pixel portion of a photoelectric conversion portion in a second embodiment of the image pickup device according to the present invention. In this embodiment, a solid-state image pickup device in which a photoconductive film mainly composed of amorphous silicon containing hydrogen is laminated on a scanning substrate is used for a photoelectric conversion part.

401 is a p-type Si substrate, 402 is a drain, 403 is a source, 404 is a switching transistor, 405 is a signal line, 406 is a pixel electrode, 407 is an insulating layer, 408 is a photoconductive film, and 409 is an electron injection blocking layer. , 41
0 is a transparent electrode.

A switching transistor 404 composed of a drain 402 and a source 403 is provided on one surface of a p-type Si substrate 401. A signal line 405 is connected to the drain 402, and a pixel electrode 406 made of Al is connected to the source 403. A photoconductive film 408 mainly composed of amorphous silicon containing hydrogen is stacked on the upper end of the pixel electrode 406 above the insulating layer 407, and an electron injection blocking layer made of SiO ₂ is formed on the photoconductive film 408. Four
09 and a transparent electrode 410 mainly composed of tin oxide are covered.

The solid-state image pickup device having the above-described pixel structure was used as the photoelectric conversion section to obtain the image pickup apparatus of this embodiment having the structure shown in FIG.

Reference numeral 501 is a synchronizing signal generator, 502 is a pixel selection circuit, 503 is a scanning substrate section of a solid-state image pickup device, 504 is a light receiving section, 505 is an amplifier, 506 is a frame memory, 5
Reference numeral 07 is a digital arithmetic circuit, 508 is a video signal generator, 5
Reference numeral 09 is an output terminal.

In this embodiment, the synchronization signal generator 501 is
With the horizontal and vertical sync signals corresponding to one field period, an external switch can be used to generate sync signals with frequencies of 2 to 50 times each. As a result, the pixel selection circuit 502 is driven to selectively control the horizontal and vertical switching transistors of the scanning substrate unit 503 of the solid-state imaging device to perform scanning 2 to 50 times within one field period, and the accumulated light is stored in the light receiving unit 504. Read out the signal charge. The signal obtained by each scan is amplified by the amplifier 505 and stored in the frame memory 506, and then the signal for one field period is integrated by the digital arithmetic circuit 507. The integrated signal becomes a video output signal through the video signal generation unit 508 and is output from the output terminal 509.

In the image pickup apparatus of the present embodiment, in addition to the effect that the γ value is kept at 1 in a wide range of incident light quantity, the number of scans within one field period can be switched according to the usage conditions such as illuminance. There are features.

Third Embodiment FIG. 6 is a block diagram of the third embodiment of the image pickup apparatus according to the present invention. In this embodiment, an avalanche multiplication type image pickup tube using a photoconductive film mainly composed of amorphous selenium as a target is used for the photoelectric conversion section.

Reference numeral 601 is a glass substrate, 602 is a transparent conductive film, 603 is a hole injection blocking layer, 604 is an amorphous semiconductor layer, 605 is an Sb ₂ S ₃ layer, 606 is an electron gun housing, and 607.
Is a sync signal generator, 608 is an electron beam, 609 is a scanning system, 610 is an amplifier, 611 is an integrator, 612 is a video signal processing unit, 613 is a load resistor, 614 is a DC power supply, and 61
Reference numeral 5 is an output terminal.

First, a method of manufacturing the image pickup tube will be described. A transparent conductive film 602 mainly composed of indium oxide is formed on a glass substrate 601, and a hole injection blocking layer 60 made of CeO ₂ having a film thickness of 15 nm is further formed on the transparent conductive film 602.
3, and an amorphous semiconductor layer 604 mainly containing selenium and having a film thickness of 10 μm is formed as a photoconductive film by a vacuum evaporation method. On the amorphous semiconductor layer 604, an Sb ₂ S ₃ layer 605 as an electron injection blocking layer is vapor-deposited to a thickness of 100 nm in an inert gas atmosphere of 2 × 10 to ¹ Torr to form an electron gun housing 606. The image pickup tube of the present embodiment is obtained by connecting and vacuum-sealing.

In this embodiment, the sync signal generator 607 generates horizontal and vertical sync signals corresponding to 1 field period of 1/60 second and 525 scanning lines, as well as sync signals of 20 times the respective frequencies. Scanning system 6 of electron beam 608
09 receives a synchronizing signal of 20 times frequency and performs 20 scans within one field period. The signal obtained by each scan is amplified by the amplifier 610 and sent to the integrator 611,
The signals for 20 times are integrated. The integrated signal becomes a video output signal through the video signal processing unit 612, and the output terminal 6
It is output from 15.

FIG. 7 shows about 10 in the image pickup apparatus of this embodiment.
This is a plot of the amount of signal current when blue light is radiated, which is measured by operating the device under the condition that the avalanche multiplication factor is about 100 by applying a target voltage of 50V.

A solid line 701 shows the result of this embodiment when the number of scans n in one field period is 20, and a broken line 702 shows the measurement result in the case of the conventional method (n = 1). The alternate long and short dash line 703 shows the ideal characteristic of γ = 1. As is clear from the figure, in the case of the imaging device according to the present invention,
Despite the use of the avalanche multiplication type imaging tube in which the photocurrent has a strong voltage dependency, the light amount dependency of the signal current is significantly improved.

Although the present invention has been specifically described based on the above embodiment, the present invention is not limited to the above embodiment and can be variously modified without departing from the scope of the invention. is there. For example, in the above-described embodiment, visible light was mainly imaged, but it goes without saying that the image pickup apparatus according to the present invention is also applicable to an image pickup apparatus for electromagnetic waves other than visible light, such as ultraviolet rays and X-rays. Yes.

[0053]

As described above, according to the image pickup device of the present invention, it is possible to suppress the decrease in the effective sensitivity due to the decrease in the voltage applied to the photoconductor due to the charge generated by the incident light. it can. Therefore, when the amount of incident light is large, the dependency of the output signal on the amount of light is weakened, and the problem that the gradation of the bright part cannot be obtained sufficiently can be solved, and an imaging device with a wide dynamic range can be provided.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an example of a basic configuration of an image pickup apparatus according to the present invention.

FIG. 2 is a diagram showing the time dependence of photocurrent for explaining the principle of the present invention.

FIG. 3 is a circuit configuration diagram of a part of a light receiving section of the first embodiment of the image pickup apparatus according to the present invention.

FIG. 4 is a diagram showing a part of a light receiving portion of a second embodiment of the image pickup device according to the present invention.

FIG. 5 is a configuration diagram of a second embodiment of the image pickup apparatus according to the present invention.

FIG. 6 is a configuration diagram of a third embodiment of the image pickup apparatus according to the present invention.

FIG. 7 is a diagram showing the relationship between the signal current and the number of incident photons in the third embodiment of the image pickup device according to the present invention.

FIG. 8 is a diagram showing an operation principle in one pixel portion of the storage type image pickup device.

FIG. 9 is a diagram showing an example of a relationship between a signal current and a target voltage in an avalanche multiplication type image pickup tube.

FIG. 10 is a diagram showing an example of a relationship between a signal current and the number of incident photons in a conventional storage-type imaging device.

[Explanation of symbols]

1 ... Photoelectric conversion part, 2 ... Incident light, 3 ... Read-out scanning part, 4
... integrator, 5 ... video signal generating section, 6 ... output terminal, 7 ... synchronization signal generating section, 301 ... photodiode, 304 ... storage switching transistor, 312 ... capacitance, 317 ...
Storage switch gate, 318 ... Storage switch control means,
501 ... Sync signal generator, 502 ... Frame memory, 5
07 ... Digital arithmetic circuit, 607 ... Synchronous signal generator, 6
11 ... integrator.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Tetsuya Oshima             1-280, Higashi Koikekubo, Kokubunji, Tokyo             Central Research Laboratory, Hitachi, Ltd. (72) Inventor Tadaaki Hirai             1-280, Higashi Koikekubo, Kokubunji, Tokyo             Central Research Laboratory, Hitachi, Ltd. (72) Inventor Setsu Kubota             1-10-11 Kinuta, Setagaya-ku, Tokyo, Japan             Broadcasting Association Broadcast Technology Institute (72) Inventor Kenkichi Tanioka             1-10-11 Kinuta, Setagaya-ku, Tokyo, Japan             Broadcasting Association Broadcast Technology Institute (72) Inventor Keiichi Shitara             1-10-11 Kinuta, Setagaya-ku, Tokyo, Japan             Broadcasting Association Broadcast Technology Institute

Claims (6)

[Claims] 1. A light-receiving unit that generates a signal charge upon incidence of light, and stores the signal charge generated in the light-receiving unit in a storage capacitor for a predetermined period in accordance with the amount of incident light from the outside. In a storage-type imaging device that sequentially reads the accumulated signal charges and generates a time-series electric signal corresponding to the spatial distribution of the incident light amount, at least a part of the signal charges accumulated in the storage capacitor is A video signal for one field period is formed by reading out to the outside of the storage capacitor twice or more within one field period and integrating or adding signals read in the one field period. Image pickup device. 2. Each pixel is provided with a second charge storage means having an electrostatic capacity larger than the storage capacity separately from the storage capacity, and at least a part of the signal charge stored in the storage capacity is imaged. The signal charge transferred to and accumulated in the second charge accumulating means more than once in one field period of the output signal and accumulated in the second charge accumulating means and the accumulating capacitor is stored in the pixel every one field period. The image pickup apparatus according to claim 1, wherein the image is read out to the outside. 3. The transfer of signal charge from the storage capacitor to the second charge storage means is performed in synchronization with the operation of a horizontal switching transistor for reading out a signal from each pixel. The image pickup apparatus according to claim 2. 4. The image pickup apparatus according to claim 1, 2 or 3, wherein the number of times the signal charges are read out of the storage capacitor is variable within one field period of the video output signal. 5. The image pickup device according to claim 1, wherein charges generated by incident light are multiplied in the photoconductor. 6. The image pickup device according to claim 1, wherein the photoconductor is amorphous Se.