JP2003244557A - Imaging device, imaging system and driving method of the imaging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a photograph output which is corrected using photographic conditions. <P>SOLUTION: An image pickup device having an area sensor 20, containing a plurality of photoelectric conversion elements which are arranged two- dimensionally has a frame memory 50 for storing the photograph output at exposure from a gain adjusting circuit 21 connected to the sensors 20, a condition memory circuit 40 for storing photographic conditions at photographic exposure, an AE controller 30 for acquiring correction conditions by using the stored photographic conditions, and an operation processing circuit 60 for correcting the photograph output by using the correction output from the circuit 21 controlled by the controller 30. <P>COPYRIGHT: (C)2003,JPO

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, an image pickup system, and a driving method of the image pickup device, and more particularly to an image pickup device using radiation represented by visible light or X-rays, such as a still camera or a radiation image pickup device. An image pickup device preferably used for a one-dimensional or two-dimensional image pickup device,
The present invention relates to an imaging system and a driving method of an imaging device.

[0002]

2. Description of the Related Art Conventionally, most of the photographs are silver halide photographs using an optical camera and a silver halide film. Although semiconductor technology has advanced, imaging devices such as video camcorders capable of capturing moving images using a solid-state imaging device using a Si single crystal sensor represented by a CCD type sensor and a MOS type sensor have been developed. The image does not match the silver halide photograph in terms of the number of pixels and the SN ratio, and it was usual to use the silver halide photograph for imprinting a still image.

On the other hand, in recent years, there has been an increasing demand for image processing by a computer, storage by an electronic file, and transmission of an image by electronic mail, and an electronic image pickup apparatus which outputs a digital signal comparable to a silver halide photographic image is desired.
This can be said not only in general photography but also in the fields of inspection and medical care.

[0004] For example, X-ray photography is generally used in the medical field as a silver halide photography technique. This is to irradiate an affected part of a human body with X-rays emitted from an X-ray source and judge the presence or absence of, for example, a bone fracture or a tumor based on the information of its transmission, and has been widely used for a long time in medical diagnosis. Usually, the X-rays that have passed through the affected area are once made incident on the phosphor, converted into visible light, and exposed to a silver salt film. However, although the silver salt film has the advantages of high sensitivity and high resolution, it has the disadvantages that it takes time to develop, it takes time to store and manage, and it cannot be sent to a remote place immediately. As described above, there is a demand for an electronic X-ray imaging device that outputs a digital signal that is not inferior to a silver salt photographic image. Of course, this applies to nondestructive inspection of specimens such as structures regardless of the medical field.

In response to this demand, an image pickup apparatus using a large sensor in which image pickup elements using photoelectric conversion elements of hydrogenated amorphous silicon (hereinafter referred to as a-Si) are arranged two-dimensionally has been developed. This type of image pickup device uses, for example, a sputtering device, a chemical vapor deposition device (CVD device) or the like on an insulating substrate having a side of approximately 30 to 50 cm to form a metal layer or a
Depositing a Si layer etc., for example about 2000 × 200
It is possible to form zero semiconductor diodes, apply a reverse bias electric field to them, and simultaneously detect the electric charges that flow in the reverse direction of these individual diodes by the thin film transistors (hereinafter, referred to as TFTs) that are simultaneously formed. It was done. It is widely known that when a reverse electric field is applied to a semiconductor diode, a photocurrent flows according to the amount of light incident on the semiconductor layer, and this is utilized. However, even when no light is applied, a so-called dark current flows, and this causes shot noise, which is a factor that reduces the detection capability of the entire device, that is, the sensitivity called SN ratio. This may adversely affect medical diagnosis and examination decisions. Needless to say, it is a problem if a lesion or defective portion is missed due to this noise. Therefore, how to reduce this dark current is important.

It is also known that if a bias is constantly applied to a semiconductor diode or other photoelectric conversion element, the current flowing may increase defects in the semiconductor and gradually deteriorate the performance. This appears as a phenomenon in which the dark current increases or the current due to light, that is, the photocurrent decreases. Further, if the electric field is continuously applied, not only the number of defects increases, but also the migration of ions and the electrolysis cause the threshold value of the TFT to move and the metal used for wiring to corrode, leading to a decrease in the reliability of the entire device. Sometimes. Poor reliability in commercializing medical devices and testing devices can cause problems. For example, a failure should not occur during urgent diagnosis / treatment or inspection. Up to now, the sensitivity and reliability have been described by taking a semiconductor diode as an example, but the present invention is not limited to this, and is applicable to various types of photoelectric conversion elements, and is not a problem limited to a diode.

FIG. 1 shows an example of a schematic block diagram of an X-ray imaging apparatus. In FIG. 1, reference numeral 1 denotes a sensor unit in which a large number of photoelectric conversion elements and TFTs are formed on an insulating substrate, and an IC or the like for controlling them is mounted. The sensor part is roughly composed of a bias applying terminal (Bias) for applying an electric field to the photoelectric conversion element and a start terminal (START) for giving a read or initialization start signal, and each photoelectric conversion element arranged two-dimensionally. There are three terminal portions of an output terminal (OUT) that outputs the output of the above as a serial signal. An X-ray source 2 emits pulsed X-rays under the control of the control circuit 5. The X-rays pass through the examination part of the specimen such as the affected part of the patient, and the transmitted X-rays containing the information are directed to the sensor part 1. Although not shown, there is a phosphor between the sensor unit 1 and the sample, and the transmitted X-rays are converted into visible light. The converted visible light enters the photoelectric conversion element in the sensor unit. Reference numeral 3 denotes a power source for applying an electric field to the photoelectric conversion element, and a control switch (S
W) or controlled by the control circuit 5.

[0008]

However, the above-mentioned device has the following points that can be improved.

FIG. 2 shows an example of the operation of the X-ray imaging apparatus shown in FIG. 2A to 2D are schematic timing charts showing the operation in the image pickup apparatus.
FIG. 2A shows the operation of the image pickup apparatus. Figure 2 (B)
Is the X-ray emission timing of the X-ray source 2. FIG. 2C shows the timing of the bias applied to the photoelectric conversion element. Figure 2
(D) shows the current flowing through the photoelectric conversion element. Figure 3
Is a flow chart showing the flow of operation.

As shown in FIG. 2C, no bias is applied to the photoelectric conversion element up to the arrow (SW ON) in FIG. 2A (Bias OFF). Here, as shown in FIG. 3, <SW ON? > 301 is detected, and if the control switch (SW) is turned on, [Bi
as ON] 302. This is also shown in FIG. 2 (C). At the same time, Int. , The charge of each photoelectric conversion element in the sensor unit 1 is initialized as indicated by [Initialize Sensors] 303 in FIG. When the initialization is completed, the control circuit 5 controls the X-ray source 2 to emit X-rays. As a result, the image pickup device is exposed (Exp. In FIG. 2B and [E in FIG.
xpose] 304). After this, the Rea of FIG.
d, as indicated by [Read Sensors] 305 in FIG. 3, the charge including the optical information flowing in each photoelectric conversion element is read by the operation of the internal TFT and IC. After that, as shown in FIG. 2C or [Bi of FIG.
as OFF], the electric field of the photoelectric conversion element is set to 0.
Turn it off. Then, it waits until the next control switch is turned on.

However, in the above operation, the current of the photoelectric conversion element before and after the exposure is large as shown in FIG. A semiconductor, especially an amorphous semiconductor such as a-Si, has a large dark current immediately after a bias is applied, and a current flows though light is not incident for a while. This indicates that a good X-ray image may not be reproduced in some cases due to the influence of shot noise as described above. In this case, proper diagnosis and inspection may not be possible. It is explained that the cause of this dark current is that there is a place where the Fermi level in the forbidden band moves relatively due to the change of the electric field in the semiconductor, which causes the movement of electrons and holes in the trap near the center of the forbidden band. This trap is caused by a defect in the semiconductor or a discontinuity in the crystal structure at the semiconductor-insulator interface, and this increase in dark current occurs in any material and photoelectric conversion element of any structure. Also,
Immediately after the electric field is applied, one of the causes is that an electric current such as ions moves and an unstable current flows until they are stabilized.

FIG. 4 shows an example of another operation of the X-ray imaging apparatus. The block diagram of the entire apparatus is almost the same as that in FIG. In FIG. 4, operations and expressions equivalent to those in FIG. 2 are indicated by the same symbols. Most of the operation is shown in FIG.
The operation is the same as the above operation, but the difference is that the electric field is continuously applied to the photoelectric conversion element as shown in FIG. That is, as can be seen from FIG. 5, in the series of operations of the exposure operation, the Bias can be set without performing [Bias ON / OFF].
The ON state is maintained. As a result, the dark current is reduced as shown in FIG. 4D as compared with the operation shown in FIG. 2, and it seems that a good image can be obtained. However, in reality, there is a hidden problem, and this operation cannot be adopted as a product. The reason for this is that in this operation, the hospital constantly applies an electric field to the photoelectric conversion element during a time when the hospital may be used, such as during consultation time. In the operation of FIG. 2, for example, 100 a day
While it is applied to the photoelectric conversion element for a total of 300 seconds assuming that the imaging operation is performed once per time in 3 seconds, in the operation of FIG. 4, assuming that the usable time such as the consultation time is 8 hours, it is about 30,000. This is an operating condition for operating for about 100 times as long as a second. This means that the electric field is applied to the photoelectric conversion element even when the user is not actually operating to take an image (that is, when there is no operation). This leads to a decrease in reliability as described above, and is not suitable for practical use in consideration of maintenance costs.

(Object of the Invention) An object of the present invention is to solve this problem and to provide an image pickup apparatus having high sensitivity, high reliability, and good usability, and a method for driving the image pickup apparatus.

It is another object of the present invention to provide an image pickup device and a driving method thereof which can obtain information with a small noise and a high SN ratio.

A further object of the present invention is to provide an image pickup apparatus which can obtain image information at a desired timing, and which can prevent unnecessary irradiation of radiation such as X-rays, and a driving method thereof.

In addition, the present invention does not use a silver salt film,
An object of the present invention is to provide an imaging device and a driving method thereof that can obtain image information with high immediacy and can obtain image information that can be inspected at a remote place.

[0017]

According to the present invention, in an image pickup apparatus having an image pickup means including a plurality of photoelectric conversion elements arranged two-dimensionally, a means for storing a photographing output at the time of photographing exposure, and a photographing at the time of the photographing exposure. An image pickup apparatus comprising: a condition storing unit; a unit that obtains a correction output by using the stored shooting condition; and a unit that corrects the shooting output by using the correction output. Is.

Further, according to the present invention, the light source, the area sensor, and at least the photographing condition for the light source are controlled A
An E controller, a condition storage unit that stores the setting value of the AE controller, a frame memory that stores a shooting output at the time of shooting, and a setting value stored in the condition storage unit. The present invention provides an imaging system including an arithmetic processing circuit that corrects a photographing output stored in the frame memory using the corrected output, and a system control unit that controls each unit.

Further, the present invention is obtained by using a step of storing a photographing output at the time of photographing exposure, a step of storing a photographing condition at the time of photographing exposure, and a step of storing the photographing condition after the photographing exposure. And a step of correcting the photographing output with a correction output.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION An image pickup apparatus, an image pickup system and a driving method of the image pickup apparatus according to the present invention will be described below. The configuration of the photographing apparatus of the present invention is best shown by the configuration of FIG.

In the present invention, by using the photoelectric conversion element in a stabilized state, more accurate and reliable information reading can be performed.

Further, according to the present invention, since the photoelectric conversion element is not always in the standby state, the life of the element can be extended, the reliability of the apparatus main body can be improved, and the maintenance fee can be reduced. it can.

FIG. 6 shows an operation example of the X-ray imaging apparatus of the present invention. The block diagram of the entire apparatus is almost the same as that in FIG. In FIG. 6, operations and expressions equivalent to those in FIG. 2 are indicated by the same symbols. Most of the operation is shown in FIG.
6 is the same as that of FIG. 6 (A) and FIG. 7, but a [Wait] 701 operation is added between the [Bias ON] 302 and the initialization of the sensor section [Initialize Sensors] 303. . This [Wa
it] 701 is sufficient to wait, for example, 3 to 5 seconds, and as a result, the effect of the dark current is as shown in FIG.
It can be greatly improved compared to (D).

This waiting operation (Wait 701) may be activated for a desired time after the photographing switch is turned on by the timer means, or may be turned on again by the photographer.

As described above, the waiting time is about 3 to 5 seconds, and in practice, the problem of rising of the device can be solved. In addition, the waiting time can be appropriately adjusted as necessary.

In the case of an apparatus that automatically takes a picture after a predetermined time if the switch (shutter) is turned on once by a timer means or the like, it is desirable that the object or sample is immovable. This is because the photographer can always photograph the intended state.

[0027] For example, when the image is automatically taken after the switch is turned on by the timer means or the like, [SW ON] 3
01, that is, a sample such as a patient must not move for 3 to 5 seconds after the control switch (so-called shutter button) is turned on. Usually, a doctor (technologist) poses a patient, which is a sample, so that the affected part can be seen well, or arranges the sample, and in some cases, stops breathing and the operation of the sample and turns on the control switch. On the other hand, it is too long to wait for 3 to 5 seconds until the exposure is started, and the patient may not be able to put up with it for a short period especially when the breathing is stopped. Actually [Wai
t] 701, the image does not blur even if it moves during the time t] 701, but the patient does not know when the exposure starts, and as a result, between a and b,
In other words, it cannot move until the exposure is completed after turning on the control switch. Further, even if the doctor turns on the control switch at a shutter chance when he / she wants to take an image with another sensor or the like, the specimen such as the stomach, intestine or machine may move within 3 to 5 seconds.

Therefore, in addition to (1) high sensitivity, (2) high reliability, and (3) usability, that is, an image pickup apparatus capable of photographing at an arbitrary timing will be described. Further, the image pickup device generally includes a device that captures image information, but it is particularly preferable to use an X-ray image pickup device.

Another embodiment of the present invention will be described below with reference to the drawings.

FIG. 8 is a schematic system block diagram of an image pickup apparatus according to another embodiment of the present invention. In this embodiment, a radiation imaging apparatus for the purpose of X-ray inspection (for example, X-ray diagnosis) is configured. In FIG. 8, the same reference numerals are given to corresponding portions with respect to the respective units similar to those in FIG.

In FIG. 8, reference numeral 1 denotes a sensor section in which, for example, a large number of photoelectric conversion elements (photoelectric conversion means) and TFTs are formed on an insulating substrate, and an IC for controlling these is mounted. The sensor unit 1 roughly includes a bias application terminal (Bias) for applying an electric field to the photoelectric conversion element and a start terminal (STA) for giving a read or initialization start signal.
RT) and an output terminal (OUT) for outputting the output from each photoelectric conversion element arranged two-dimensionally as a serial signal. An X-ray source 2 emits pulsed X-rays under the control of the control circuit 4. This X
The X-rays pass through the affected part or the inspection part of the sample such as a patient or an object, and the transmitted X-rays containing information are directed to the sensor part 1. Although not shown in the figure between the sensor unit 1 and the patient, there is usually a wavelength converter such as a phosphor, and the transmitted X-rays are converted into wavelengths that can be detected by the sensor unit 1, for example, visible light. Incident on the photoelectric conversion element. Reference numeral 3 is a power supply for applying an electric field to the photoelectric conversion element, which is controlled by SW1 which functions as a first switch means. The control circuit 4 is connected to SW1 and SW2 which functions as a second switch means, and controls start signals of various operations given to the sensor unit 1 based on these two pieces of information and other information. At the same time, the X-ray source 2 is given timing for emitting X-rays.

FIG. 9A shows the appearance of SW1 and SW2. SW1 and SW2 are mounted in a single grip-like case so that the operator can easily handle them.
Make up one. Two switches and springs are mounted on the respective switches in the case, and both the switches SW1 and SW2 are turned off when the hands are released. In addition, SW2 is locked, and normally it is unlocked and movable only when SW1 is turned on when SW1 is turned on.
W2 is mechanically prohibited so that it is not turned on. In the present embodiment, this prohibition is performed mechanically, but this prohibition is performed electrically. For example, even if SW2 is pressed by mistake when SW1 is off, it is electrically invalidated and SW2 is turned off.
Does not have to be turned on. FIG. 9 (A) shows a state in which the hand is released and the switch lever 7 interlocked with SW1.
The switch lever 74 interlocked with 3 and SW2 is released, and both SW1 and SW2 are off. When handling the switch box 71, the operator grasps the grip portion 72 and puts his thumb on the SW1 switch lever 73.
I only touch it. From this state, if you press it with your thumb lightly, it will be in the state shown in FIG. This is because the spring force of the switch lever 73 is weaker than the pressing force required to press the elastic member such as the spring of the switch lever 74. In this state, SW1 is on, SW2
Is off. When pushed harder,
The state (C) is entered, and both SW1 and SW2 are turned on. In this way, the switch box 71 is configured so as to have three states.
It is configured such that SW1 and SW2 are never turned on in a state where is not touched, that is, when there is no operation. Also,
The force of the elastic member such as the spring of the switch lever 73 is appropriately adjusted, and it is configured so that an ordinary person cannot press the switch lever 73 for a long time, for example, for one minute or longer. This prohibits the state in which SW1 and SW2 are inadvertently kept pressed for a long time. That is, it can be regarded as no operation when the state is not changed for one minute.

SW1 and SW2 are not limited to the above mechanical switch structure. SW1 and SW2 may be provided independently so as to achieve the above-mentioned action as an electric circuit. Also, SW1 and SW2 are not mechanical switches,
It may be composed of an electric switch (for example, a transistor). For example, one mechanical switch (SW0) and one electrical switch can be used to configure SW1 and SW2. In this case, for example, if SW0 is pressed once, SW1
After turning on and releasing SW0, SW2 is turned on when SW0 is pressed again, and SW1 and SW2 are turned off when SW0 is released after that. It is sufficient to identify whether or not the button is pressed once by displaying, for example, LEDs of different emission colors.

An example of the operation of the image pickup apparatus of this embodiment shown in FIG. 8 will be described with reference to FIG. FIG. 10 (A)
10D is a timing chart showing the operation in the image pickup apparatus, and FIG. 11 is a flowchart showing the flow of the operation. FIG. 10A shows the operation of the imaging device. FIG. 10B shows the X-ray emission timing of the X-ray source 2. FIG. 10C shows the timing of the bias applied to the photoelectric conversion element. FIG. 10D shows a current flowing through a certain photoelectric conversion element. As shown in FIG. 10C, no electric field, that is, a bias is applied to the photoelectric conversion element up to the arrow shown by (SW1 ON) in FIG. 10A (Bias OFF). This is because the control circuit 4 recognizes no operation and controls the power supply 3 in the sleep mode (Stop MODE). In the present embodiment, no operation means that SW1 is off, and the control circuit 4 judges this by the fact that SW1 is off.
The broken line shows the state where no bias is applied.
Here, as shown in FIG. 11, <SW1 ON? > 901 is determined, and if the control switch (SW1) is turned on, [Bias ON] 902 is performed. This is
Also shown in (C). In this state, the sensor unit 1 is shown in FIG.
0 (A) or Wait or [Wait] 903 in FIG.
It becomes a standby state as indicated by. This state is called a standby mode (Stand-by MODE).
During this standby state, the dark current of the photoelectric conversion element decreases as shown in FIG. At this time, the control circuit 4 prohibits the operator from turning on SW2 for a certain period of time until the dark current decreases. Whether or not the dark current has decreased may be detected directly, or the time required until the dark current decreases may be grasped in advance and prohibited during that time.
The method of prohibiting may be mechanically or electrically. Alternatively, a display such as a lamp indicating prohibition may be shown to the operator. Further, even if SW2 is pressed, the control circuit does not have to start the photographing operation. The operator may prepare for photographing a sample such as a patient or an object during the prohibition. After the prohibition is lifted, if necessary, give instructions such as "hold your breath" or start moving the object,
Turn on SW2 at the timing you want to obtain an image (SW2 O
N) 904. When SW2 is turned on, the exposure mode (Exp
(OSUREMODE) starts, and FIG. 10 (A) or FIG.
Int. Or [Initialize Sensor
s] 905, the charges of the individual photoelectric conversion elements in the sensor unit 1 are initialized. When the initialization is completed, the control circuit 4 controls the X-ray source 2 to emit X-rays. This is shown in FIG. 10 (B) and FIG. Or [Expo
exposure] 906 is performed. When the exposure is completed, the imaging of the sample is completed, and the sample may move freely at this point. That is, it does not have to move between a and b shown in FIG. Usually, the initialization of the sensor unit 1 is completed in 30 to 300 ms, and the pulse width of the X-ray is 50 to 200 ms. Therefore, it is sufficient that the sensor unit 1 is stationary for about 0.5 seconds. Imager after exposure
(A) or Read or [Read Sens of FIG.
ors] 907, the charge including the optical information flowing in each photoelectric conversion element is read by the operation of the internal TFT and IC. After that, <SW1 ON in FIG. 11? >
At 908, the state of SW1 is detected, and if SW1 is off, as shown in FIG. 10C or [B of FIG.
ias OFF] 909, the electric field of the photoelectric conversion element is set to zero. Then, it waits until the next control switch is turned on. When SW1 is turned on for continuous shooting or the like, as shown in FIG. 11, SW2 is changed so that the shooting direction of the sample is changed or the sample of the next patient or the like can be immediately taken.
Wait for ON detection. If you do this, 2 for continuous shooting
For the second time, Wait, [Wai] of FIG.
t] 903, which is efficient because there is no need to wait as indicated by 903. Further, when it is desired to interrupt the work while SW1 is turned on during the work, SW1 is turned off when the switch lever of SW1 is released, as shown in FIG.
s OFF] 909.

As described above, in the present embodiment, no electric field is applied to the photoelectric conversion element during no operation, and the dark current is reduced during exposure, and furthermore, the patient does not receive an instant. Therefore, the imaging device is provided with high reliability, high sensitivity, and good usability only by remaining stationary for a while.

It is needless to say that the electric field of the photoelectric conversion element does not have to be zero when no operation is performed, and it is effective to suppress the electric field as compared with various operations.

12A to 12D and FIG.
FIG. 6 is a timing chart and a flowchart showing the operation of still another embodiment of the present invention. The system configuration is omitted since it is almost the same as that of the above-described embodiment.
The difference from the above-described embodiment is the configuration of the control circuit. Here, FIGS. 10A to 10D and FIG. 1 are described with reference to FIGS.
The description will focus on the parts different from 1.

In this embodiment, as can be seen from FIG. 12 (A) or FIG. 13, the initialization of the sensor unit is started immediately after a certain waiting time in the standby mode. Or [Initialize
Sensors] 1002 is about to start. Further, even after one initialization is completed, the initialization is started immediately, and the initialization is performed periodically, that is, the continuous internal charge reset is continued. As a result, it is possible to prevent the electric charge in the sensor unit from accumulating due to dark current due to the standby state becoming longer than necessary. This periodic charge reset is actually the same as the charge reading operation after exposure and the storage time may be slightly different, but the operation sequence is almost the same, and the obtained signal is not used as information. is there. Although the periodic charge resetting operation in the sensor section (photoelectric conversion element) is not shown, the circuit in the control circuit 4 in FIG. 8 detects and determines the states of SW1 and SW2 as shown in FIG. While being repeated periodically. When the SW2 is turned on in this state, the exposure mode is started after the initialization (charge reset operation) at the time when this is detected is completed. Further, in the present embodiment, the charge read [Read Sensors] 907 including the optical information in the exposure mode is followed by the Get FPN, [G] of FIG.
et FPN Data] 1003, data reading for correction of fixed pattern noise (FPN), and then Get GN of FIG. 12 (A) or FIG.
As indicated by [Get GAIN Data] 1004, the data for gain variation correction is read.
However, these operations also read charges including optical information [R
The operation of the sensor is the same as that of the ead Sensors 907, and only reads the charge in the dark state (that is, the state in which the X-ray is not irradiated) and reads the charge of the reference light information irradiated by some method. The reference light information can be obtained by irradiating and reading a light source such as an X-ray in the absence of the sample.

That is, the feature of the image pickup apparatus in the present embodiment is that the sensor section always repeats the same operation until the exposure mode ends after the standby [Wait] 903 in the standby mode ends. The fact that the movements of the sensor unit periodically make the same movements of the respective units inside the sensor unit are in equilibrium state, and there is no strange transient response, etc., and a very stable SN ratio is good. Image information is obtained. Further, it is also a great effect that the control method is simplified and the circuit can be simplified. Further wait [Wait] 903
Even during the process, the reading operation of charge after exposure is actually performed [Rea
d Sensors] 907.

Further, initialization is performed after SW2 is turned on [I
Since the initialize Sensors 1002 is not started, the time until the exposure [Exposure] 906 is shortened, and 1/2 of the time required for initialization is shortened on average. As a result, the time during which the specimen such as the patient must be stationary (between a and b or a'-
(b), the initialization of the sensor unit usually ends in 30 to 300 ms, and assuming that the pulse width of the X-ray is 50 to 200 ms, it should be stationary for about 0.3 seconds on average. become. This is a major feature of the present embodiment because the charge reset operation, that is, the initialization operation, is periodically performed during the standby mode and the transition to the exposure mode is facilitated.

Further, in the present embodiment, as shown in FIG. 13, a timer is provided in the control circuit, and even if the exposure mode is finished, SW1 is turned off for a predetermined time (5 minutes in the present embodiment). Even so, [Bias OFF], that is, the sleep mode is not set. As a result, even if the shooting is not continuous, it does not enter the sleep mode if it is within a certain period of time, and waits for the next shooting [Wait] 903.
You don't have to. Further, even if the switch box 71 has a structure as illustrated in FIGS. 9A to 9C, the sleep mode does not occur even if the finger is released for a short time. That is, in the present embodiment, the control circuit interprets that the SW1 is off for a short period of time (for example, within 5 minutes) as still working, and determines that it is not in the non-operation state. As a result, even if the shooting is not completely continuous, if it continues for a while, the sleep mode will not be entered, and the next shooting will be in a standby state [Wai
t] 903. Further, the control circuit automatically enters the [Bias OFF] 909, that is, the sleep mode when the SW1 is off for a certain time (for example, 5 minutes or more). This improves efficiency while maintaining high reliability and improves usability. In addition, in this embodiment, [READY lamp ON / OFF] indicating that the preparation is OK 1
001 and 1007 are controlled to improve usability.

Still another embodiment will be described with reference to FIGS. 14 to 20.

FIG. 14 is an overall system block diagram of an image pickup apparatus according to still another embodiment of the present invention. In this embodiment, a radiation imaging apparatus that can be used for medical X-ray diagnosis and nondestructive inspection is configured. In FIG. 14, 10 is X
An X-ray source capable of emitting a line 13 in a pulse shape,
The X-ray pulse is turned on and off and the tube voltage of the tube in the X-ray source is controlled by the AE controller 30 that functions as an imaging condition control unit
The tube current is controlled. The X-rays 13 emitted from the X-ray source 10 pass through a subject (specimen) 11 which is a patient or an object to be diagnosed or examined, and CsI and Gd which convert the X-rays into visible light.
_The light enters the phosphor 12 made of ₂ O ₂ S or the like. At this time, the X-ray transmitted through the subject 11 has a different transmission amount depending on the size and shape of the bones and internal organs inside the subject 11, the presence or absence of lesions, the difference in the material of the constituent members, and the like, and includes such image information. The X-rays 13 are converted into visible light by the phosphor 12 and enter the two-dimensional area sensor 20 serving as image information light as image information light 14. The two-dimensional area sensor 20 has a plurality of photoelectric conversion elements arranged two-dimensionally and a drive circuit for driving them, and converts the image information light 14 into an electric signal containing two-dimensional information and outputs it. The two-dimensional area sensor 20 is controlled by the AE controller 30 in terms of signal storage time and drive speed. The output of the two-dimensional area sensor 20 is input to the gain adjustment circuit 21 and also to the AE controller 30 as information for controlling the shooting conditions.

The outputs of the control panel 32, the temperature sensor 33 and the photo timer 31 are also input to the AE controller 30 in order to control the photographing conditions. Control panel 3
2 is a condition in which the doctor or the technician inputs the conditions by the panel operation so that the optimum photographing output can be obtained at each photographing exposure in consideration of the patient's symptom, physique, age, size and thickness of the object, and desired information. Is converted into an electric signal and input to the AE controller 30. The temperature sensor 33 detects the temperature of a room or tube during photographing exposure, the temperature of components such as the two-dimensional area sensor 20 whose characteristics change depending on the temperature and the optimum operating conditions change, and inputs them to the AE controller 30. To do. It is preferable that these detected temperatures are the temperatures at the time when the exposure is performed. The photo timer 31 is located at an arbitrary position between the subject 11 and the two-dimensional area sensor 20, for example, and detects the amount of X-rays that pass through a reference portion (eg, alveolar part) of the subject 11 during photographing exposure to detect the amount of X-rays. It is input to 30. Since the X-ray absorption by the photo timer 31 is very small, it has almost no adverse effect on the photographic exposure. The AE controller 30 determines the X-ray pulse width of the X-ray source 10 and the two-dimensional area sensor 2 based on the values of these inputs immediately before or during the photographing exposure.
Zero accumulation time, drive speed and gain adjustment circuit 21
The amplification factor of is automatically controlled and set. With these controls, the output of the gain adjusting circuit 21 can be set to an appropriate shooting output.

Further, at this time, the conditions controlled and set by the AE controller 30 at the time of photographing exposure can be stored as condition values in the condition memory circuit 40 serving as condition storing means. The condition memory circuit 40 can store the condition and at the same time, store the condition value stored in the opposite direction in the AE controller 3
It is also possible to enter 0. At this time, the AE controller 30 can control / set and operate the X-ray source 10, the two-dimensional area sensor 20, and the gain adjusting circuit 21 based on the condition value input from the condition memory circuit 40. In other words, it is possible to perform the photographing exposure again under the same control / setting as the past photographing exposure conditions. At this time, by making some conditions or control / settings different, correction exposure can be performed and the output of the gain adjustment circuit 21 can be used as a correction output. In other words, if the system is operated in the same manner as in the previous photographing exposure without emitting the X-ray pulse, the correction output of the dark output of the two-dimensional area sensor 20 can be obtained.

In FIG. 14, a portion within a broken line 80 is a correction circuit, and the photographing output obtained at the time of photographing exposure can be stored once in the frame memory 50 which is the photographing output storing means through the switch 51, and the correction output obtained at the time of compensation exposure. B and the shooting output A stored in the frame memory 50, the arithmetic processing circuit 6
It is possible to obtain the image information output P which has been processed with 0 to eliminate the error at the time of photographing. This image information output P is transmitted to an image processing system or the like.

Reference numeral 70 denotes a system control circuit, which is shown in FIG.
Through detection of pressing of SW1 and SW2 in the switch box 71 as shown in FIG. 9C, the X-ray source 10 and the two-dimensional area sensor 20 via the AE controller 30 are detected though not shown. , The gain adjustment circuit 21 is controlled to perform photographing exposure and correction exposure, and the switch 51, the frame memory 50 and the arithmetic processing circuit 60 are controlled to operate as the correction circuit 80.

FIG. 15 is a schematic overall circuit diagram showing an example of the structure of the two-dimensional area sensor 20, FIG. 16 (A) and FIG.
(B) is a schematic plan view and a schematic cross-sectional view of each constituent element corresponding to one pixel in the two-dimensional area sensor 20.
The parts having the same functions as those in FIG. 14 are designated by the same reference numerals. In FIG. 15, S11 to S33 are photoelectric conversion elements, and the lower electrode side is indicated by G and the upper electrode side is indicated by D. C11
To C33 are storage capacitors, and T11 to T33 are transfer TFTs. Vs is a reading power supply, and Vg is a refreshing power supply, which are connected to the G electrodes of all the photoelectric conversion elements S11 to S33 via switches SWs and SWg, respectively. The switch SWs is connected via an inverter to the refresh control circuit RF, and the switch SWg is controlled so that SWg is on during the refresh period and SWs is on during the other periods. One pixel is composed of one photoelectric conversion element, a capacitor, and a TFT,
The signal output is detected by the signal wiring SIG by the detection integrated circuit I.
It is connected to C. The two-dimensional area sensor of the present embodiment divides a total of nine pixels into three blocks, transfers the outputs of three pixels per block at the same time, and the output signals are sequentially converted into outputs by the detection integrated circuit through the signal wiring.
Further, the three pixels in one block are arranged in the horizontal direction, and the three blocks are arranged vertically in order to arrange the respective pixels two-dimensionally.

The portion surrounded by the broken line in the figure can be formed on the same large-sized insulating substrate, and a schematic plan view of the portion corresponding to the first pixel is shown in FIG. 16 (A). S
11 is a photoelectric conversion element, T11 is a switching element TF
T (thin film transistor), C11 are capacitors that are charge storage elements, and SIG is signal wiring. In the present embodiment, the capacitor C11 and the photoelectric conversion element S11
In particular, the elements are not separated and the capacitor C11 is formed by increasing the area of the electrode of the photoelectric conversion element S11. This is possible because the photoelectric conversion element and the capacitor of the present embodiment have the same layer structure, which is also a feature of the present embodiment. Further, FIG. 16B shows a schematic cross-sectional view of a portion indicated by a broken line AB in the drawing. A silicon nitride film SiN108 for passivation and CsI, Gd ₂ O is formed on the pixel.
A phosphor 12 such as ₂ S is formed. When an X-ray 13 containing image information is incident from above, the phosphor 12 converts the X-ray into image information light 14, and this light is incident on a photoelectric conversion element.

Here, an example of a method for forming each element having the structure shown in FIGS. 16A and 16B will be described in order.

First, about 500 angstroms of Cr is deposited as the lower metal layer 102 on the glass substrate 101, which is an insulating material, by sputtering or the like, and then patterning is performed by photolithography to etch unnecessary areas.
As a result, the lower electrode of the photoelectric conversion element S11, the TFT T
The gate electrode of 11 and the lower electrode of the capacitor C11 are formed.

Next, the SiN layer (107) / i-type semiconductor layer (104) / n-type semiconductor layer (105) is respectively grown to about 2000 angstroms / 5 in the same vacuum by CVD.
000 Å / 500 Å is deposited. These layers serve as an insulating layer / photoelectric conversion semiconductor layer / hole injection blocking layer of the photoelectric conversion element S11, a gate insulating film / semiconductor layer / ohmic contact layer of the TFT T11, and an intermediate layer of the capacitor C11. It can also be used as a cross portion insulating layer of signal wiring. The thickness of each layer is not limited to this, and may be optimally designed according to the voltage, current, charge, incident light amount, etc. used as a two-dimensional area sensor.
At least SiN cannot pass electrons and holes, and
It has a thickness that can function as the gate insulating film of the TFT.
Generally, 500 angstrom or more is required.

After each layer is deposited, A is formed as the upper metal layer 106.
1 is deposited by sputtering or the like at a thickness of about 10,000 angstroms. Further, by patterning by photolithography and etching unnecessary areas, the upper electrode of the photoelectric conversion element S11,
A source electrode and a drain electrode which are main electrodes of the TFT T11, an upper electrode of the capacitor C11, and a signal wiring SIG are formed.

Further, the n layer only in the channel portion of the TFT T11 is RIE method (reactive ion etching method).
Then, the SiN layer (10
7) / i-type semiconductor layer (104) / n-type semiconductor layer (10
5) is etched to separate each element. With this, the photoelectric conversion element S11, the TFT T11 and the capacitor C11
Is completed. Although the first pixel has been described above, it goes without saying that other pixels are formed at the same time.

Further, in order to improve durability, the upper part of each element is usually covered with a passivation film 108 such as SiN,
Further, a phosphor 12 such as CsI or Gd ₂ O ₂ S is formed.

As described above, in this embodiment, the common lower metal layer 102, the SiN layer (107) / i-type semiconductor layer (104) in which the photoelectric conversion element, the TFT, the capacitor, and the signal wiring SIG are simultaneously deposited. It can be formed only by etching the / n-type semiconductor layer (105) and the upper metal layer 106 and each layer. In addition, the photoelectric conversion element S
There is only one injection element layer in 11 and they can be formed in the same vacuum. Further, since the interface between the gate insulating film and the i layer, which is important for the characteristics of the TFT, can be formed in the same vacuum, desired performance can be easily obtained. Furthermore, since the intermediate layer of the capacitor C11 includes an insulating layer which is less likely to leak due to heat, a capacitor having good characteristics is formed.

The operation of the photoelectric conversion elements S11 to S33 used in this embodiment will be described here. FIG. 17
17A and 17B are schematic energy band diagrams of the photoelectric conversion element showing the operations of the refresh mode (initialization mode) and the photoelectric conversion mode of this embodiment, respectively.
FIG. 16B shows a state in the thickness direction of each layer in FIG. 1
02 is a lower electrode made of Cr (hereinafter referred to as G electrode)
Is. 107 is Si that blocks passage of both electrons and holes
It is an insulating layer formed of N, and its thickness is such that electrons and holes cannot move due to the tunnel effect.
It is set to 00 angstrom or more. 104 is a photoelectric conversion semiconductor layer formed of an intrinsic semiconductor i layer of hydrogenated amorphous silicon (a-Si), 105 is an n-type a-Si injection blocking layer that blocks hole injection into the photoelectric conversion semiconductor layer 104, Reference numeral 106 denotes an upper electrode (hereinafter referred to as a D electrode) formed of Al. In the present embodiment, the D electrode does not completely cover the n layer, but since electrons can freely move between the D electrode and the n layer, the potentials of the D electrode and the n layer are always the same, and The explanation assumes that. This photoelectric conversion element has two kinds of operations, a refresh mode and a photoelectric conversion mode, depending on how the voltages of the D electrode and the G electrode are applied.

In the refresh mode shown in FIG. 17A, the D electrode is given a negative potential with respect to the G electrode, and the holes indicated by black circles in the i layer 104 are guided to the D electrode by the electric field. . At the same time, the electrons indicated by white circles are injected into the i layer 104. At this time, some holes and electrons are n
It recombines and disappears in the layers 105 and i-layer 104. If this state continues for a sufficiently long time, the holes in the i layer 104 are swept out from the i layer 104.

To switch from this state to the photoelectric conversion mode shown in FIG. 17B, the D electrode gives a positive potential to the G electrode. Then, the electrons in the i layer 104 are instantly guided to the D electrode. However, holes are not guided to the i layer 104 because the n layer 105 functions as an injection blocking layer. When light enters the i-layer 104 in this state, the light is absorbed and electrons and
A pair of holes is generated. The electrons are guided to the D electrode by the electric field, and the holes move in the i layer 104 and reach the interface between the i layer 104 and the insulating layer 107. However, since it cannot move into the insulating layer 107, it remains inside the i layer 104.
At this time, the electrons move to the D electrode and the holes move to the interface of the insulating layer 107 in the i layer 104, so that a current flows from the G electrode to maintain the electrical neutrality in the element. This current corresponds to the electron-hole pair generated by light and is therefore proportional to the incident light. After maintaining the photoelectric conversion mode of FIG. 17B for a certain period and then returning to the refresh mode of FIG. 17A, the holes remaining in the i layer 104 are guided to the D electrode as described above, At the same time, a current corresponding to this hole flows. The amount of the holes corresponds to the total amount of light incident during the photoelectric conversion mode period. At this time, a current corresponding to the amount of electrons injected into the i layer 104 also flows, but since this amount is approximately constant, it may be detected by subtracting it. That is, the photoelectric conversion elements S11 to S33 in the present embodiment.
Outputs the amount of incident light in real time,
It is also possible to output the total amount of light incident during a certain period.
This can be said to be a major feature of the photoelectric conversion element of this embodiment.

However, if the period of the photoelectric conversion mode is long for some reason or the illuminance of the incident light is strong, the current may not flow although the light is incident as in D. This is as shown in FIG.
This is because a large number of holes remain in the i layer 104, the electric field in the i layer 104 becomes small due to the holes, and the generated electrons are not guided to the D electrode and are recombined with the holes in the i layer 104. When the light incident state changes in this state, the current may flow unstablely, but when the refresh mode is set again, the holes in the i layer 104 are swept out, and in the next photoelectric conversion mode, it is proportional to the light again. Electric current is obtained.

Further, in the above description, when sweeping out the holes in the i layer 104 in the refresh mode, it is ideal to sweep out all the holes, but sweeping out only some of the holes is effective, and is equal to the above. The current is obtained and there is no problem. That is, it is sufficient if the state of FIG. 17C is not obtained at the next detection opportunity in the photoelectric conversion mode, the potential of the D electrode with respect to the G electrode in the refresh mode, the period of the refresh mode, and the injection blocking layer of the n layer 105. The characteristics of should be decided. Further, in the refresh mode, injection of electrons into the i layer 104 is not a necessary condition, and the potential of the D electrode with respect to the G electrode is not limited to be negative. This is because when a large number of holes remain in the i layer 104, the electric field in the i layer is applied in the direction of guiding the holes to the D electrode even if the potential of the D electrode with respect to the G electrode is positive. Similarly, the characteristics of the injection blocking layer of the n-layer 105 are not required to be able to inject electrons into the i-layer 104.

Next, FIGS. 14, 15 and 18 to 20.
An example of the operation of the radiation imaging apparatus of this embodiment will be described using. As described above, the photoelectric conversion element in this embodiment operates as an optical sensor that outputs a photocurrent proportional to the incident light in the photoelectric conversion mode if refreshed periodically. FIG. 18 is a timing chart showing an operation of reading optical information and an operation of reading FPN correction data in the exposure mode of this embodiment. First, the operation [Exposure] for reading optical information will be described.

First, the system control circuit 70 causes the two-dimensional area sensor 20 to perform a refresh operation represented by R at the top in FIG. Here, the refresh operation will be described. First, Hi is applied to the control wirings g1 to g3 and s1 to s3 by the shift registers SR1 and SR2 shown in FIG. Then, the transfer TFTs T11 to T33 and the switches M1 to M3 turn on and become conductive, and all the photoelectric conversion elements S1
The D electrodes of 1 to S33 have the GND potential (integral detector A
(The input terminal of mp is designed to be the GND potential here). At the same time, the refresh control circuit RF outputs Hi, the switch SWg is turned on, and all the photoelectric conversion elements S11 to S3.
The G electrode 3 has a positive potential by the refreshing power source Vg. Then, all the photoelectric conversion elements S11 to S33 enter the refresh mode and are refreshed. Next, the refresh control circuit RF outputs Lo, the switch SWs is turned on, and the G electrodes of all the photoelectric conversion elements S11 to S33 are set to a negative potential by the reading power supply Vs. Then, all photoelectric conversion elements S1
1 to S33 are in the photoelectric conversion mode and at the same time the capacitor C
11 to C33 are initialized. In this state, the control wirings g1 to g3, s1 are controlled by the shift registers SR1 and SR2.
Lo is applied to s3. Then transfer TFT T1
1 to T33 and the switches M1 to M3 are turned off, and the D electrodes of all the photoelectric conversion elements S11 to S33 are open in terms of DC, but the potentials are held by the capacitors C11 to C13. However, since X-rays are not incident at this time, no light is incident on all the photoelectric conversion elements S11 to S33 and no photocurrent flows. This completes the refresh operation (R).

Next, the two-dimensional area sensor 20 performs a dummy read operation represented by D in the upper part of FIG. This is because the photoelectric conversion element S11 has the same reason as the dark current when the bias application is turned on in the photoelectric conversion element described in the previous example.
This is because a dark current still flows due to the change of the G electrode in S33. However, this current can be made smaller than the current flowing when the bias is applied from the electric field 0 to some extent depending on the potential and direction of the refresh power supply Vg and the pulse width of the RF Hi. However, since it does not completely become 0, the dark current is reduced by the small Wait effect if dummy reading is performed.
This operation is the same as the charge reading of optical information described later. Control wiring g by shift register SR1
A Hi control pulse is applied to the shift register SR
By applying control pulses to the two control wirings s1 to s3, v1 to v3 are sequentially output through the transfer TFTs T11 to T13 and the switches M1 to M3. Similarly, charges of other photoelectric conversion elements are sequentially output up to v9 by the control of the shift registers SR1 and SR2 (OUT). However, these outputs v1 to v9 are not used. This output is not used in this dummy read operation. This dummy reading has a role of resetting charges due to a dark current due to a change in the G electrode of the photoelectric conversion elements S11 to S33 described above, and this dark current is attenuated as shown in FIG.
It has the same effect as Wait shown in (A). Therefore, increasing the number of dummy readings reduces the adverse effect of dark current. In this embodiment, the dummy reading is performed twice in consideration of usability.

After that, X which is expressed as E in FIG.
Line pulse irradiation is performed (X13). At this time, the two-dimensional area sensor 20 has transfer TFTs T11 to T33 of of
f. In this state, the X-ray source 10 emits an X-ray pulse 13. Then, a photocurrent flowing by a certain amount of light is accumulated in each of the capacitors C11 to C33 as an electric charge and is retained even after the end of the X-ray incidence.

Further, after that, charge reading including optical information represented by O1 to 9 is performed (OUT). The operation of the two-dimensional area sensor 20 is the same as that of the dummy reading, but the output thereof includes optical information, that is, two-dimensional information of the internal structure of the sample such as a human body, which is designated as O1-9. As described above, the exposure operation [Exposure] of the two-dimensional area sensor 20 according to the present embodiment is seen in detail, initialization-dummy reading-dummy reading-exposure-reading (RD-D).
-EO)) combined operation.

On the other hand, in the exposure mode Exposu
The FPN correction data reading operation indicated by [Get FPN Data] in re MODE is the same as the operation of reading optical information [Exposure] and the operation of the two-dimensional area sensor 20. However, X-rays are not emitted as indicated by F of X13. The operation at this time is F, and the next F
The operation of outputting the outputs FO1 to 9 including the PN information is F
It is expressed as O. In other words, [Get FPN Dat
The FPN correction data reading operation indicated by a] is a combination operation of initialization-dummy reading-dummy reading-non-exposure state-reading (R-D-D-F-FO).

FIG. 16 shows an example of the initialization operation [Initialize Sensors] in the standby mode. The operation is performed during the exposure operation of FIG. 15 [Exposure
e], but there is no X-ray pulse irradiation period E.
Also, no output is used. [Initialize Sen
The initialization operation indicated by "sors" is a combined operation of the operations of R-D-D-D '. If this initialization operation is repeated not only once but a plurality of times, unnecessary charges due to dark current flowing in the photoelectric conversion element can be reset, and a good state can be created in the next exposure operation. . Therefore, during the standby mode, this initialization operation may be periodically performed to perform a periodic charge reset operation of the photoelectric conversion element.

Here, an example of the operation of the entire system of this embodiment is shown in FIGS. 14 and 15 and FIGS. 20 (A) to 20 (C).
Described in. The operation of the two-dimensional area sensor 20 is typically considered to be three as shown in FIGS. 20 (A), 20 (B) and 20 (C). First, the operation will be described with reference to FIG. 20 (A). When there is no operation, the two-dimensional area sensor 20 is in the rest mode and no electric field is applied to the photoelectric conversion element. First, a doctor or a technician places a specimen to be inspected, that is, the subject 11 between the X-ray source 10 and the two-dimensional area sensor 20, and poses or positions the subject so that the region to be inspected can be observed. When the pose or the arrangement is completed, turn on SW1 in the switch box 71.
Set to N. Then, the two-dimensional area sensor 20 shifts to the standby mode. At the same time, the conditions are input to the control panel 32 in consideration of the patient's symptom, physique, age, composition of the object, size, and desired information of the sample obtained in advance by an interview. This signal is an electric signal and is transmitted to the AE controller 30. At the same time, the condition memory circuit 4
These conditions are stored in 0.

In this state, "READ" in the control panel 32 is displayed.
When the doctor or the technician presses SW2 in the switch box 71 after confirming that "Y lamp" is lit, the initialization operation [Initiali] performed at that time
After waiting for the end of [ze Sensors], the mode is shifted to the exposure mode and the exposure operation [Exposure] is started.
At this point, the temperature sensor 33 detects the temperature of the room, the temperature of the tube, the two-dimensional area sensor 20, etc. at the time of photographing exposure.
The temperature of a component whose characteristics change with temperature and the optimum operating condition changes is detected and input to the AE controller 30.
These detected temperatures are just the temperatures just before the photographing exposure. At the same time, these temperatures are stored in the condition memory circuit 40 as conditions.

Here, the AE controller 30 determines the initial condition during the exposure operation based on the information from the control panel 32 and the information from the temperature sensor 33. At the same time, these initial conditions are stored in the condition memory circuit 40. The contents of the initial conditions are the voltage, current and maximum pulse width of the bulb of the X-ray source 10 and the driving speed of the two-dimensional area sensor 20. For example,
If the chest or the thick part of the object is set on the control panel 32, the tube voltage of the X-ray source 10 is set high, and if the abdomen or the thin part of the object is set low. Also,
If the control panel 32 indicates a child, a pregnant woman, or a component that may be affected by X-rays, the termination condition by the photo timer 31 is set to be short, and the maximum pulse width is also set to be short. Two-dimensional area sensor 20
When the temperature is high, the dark current of the photoelectric conversion element is high, but TF
Since the capacity of T is high, the driving speed is increased to set the optimum conditions to suppress the accumulation of dark current and prevent the decrease of S / N. Conversely, when the temperature is low, the capacity of the TFT is low but the dark current of the photoelectric conversion element is also low. Therefore, the driving speed is lowered and the distortion of the image due to the reduction of the charge transfer of the TFT is suppressed.

Under these initial conditions, FIGS.
When the X-ray is emitted at the timing E of (C) and passes through the subject 11 and enters the phosphor 12, it is converted into light, and the light enters the photoelectric conversion elements S11 to S33. At the same time, the light also enters a photo timer 31 placed between the subject 11 and the two-dimensional area sensor 20. These lights include information on the internal structure of the human body and the like. The output of the photo timer 31 is input to the AE controller 30 at any time, and when the integration of this value exceeds a certain value determined by the initial condition, the AE controller 30 stops the X-ray. As a result, an optimum exposure amount can be obtained in the exposure operation. Further, if the maximum pulse width determined by the initial condition is reached, the AE controller 30 stops the X-ray regardless of the photo sensor 31. At this time, the condition memory circuit 40 stores these actually emitted pulse widths as the exposure time.

The outputs O1 to 9 containing the optical information at this time are input to the gain adjusting circuit 21 and also to the AE controller 30. The AE controller 30 determines the gains for making these outputs appropriate values at any time, stores the values in the condition memory circuit 40, and at the same time, instructs the gain adjustment circuit 21. As a result, the gain adjustment circuit 2
The output of 1 is the optimum shooting output for processing them later. This shooting output is once stored in the frame memory 50, which is a shooting output storage means, via the switch 51 controlled by the system control circuit 70.

As described above, the AE controller 3
0 is a control panel 32, a temperature sensor 33, a photo timer 3
X depending on the setting and output of the 1 and 2D area sensor 20
The radiation source 10, the two-dimensional area sensor 20, and the gain adjustment circuit 2
1 can be automatically controlled almost in real time, and as a result, the photographing output can be obtained under various conditions close to the optimum. This completes the exposure operation.

Next, the system control circuit 70 starts the FPN correction data reading operation, and the two-dimensional area sensor 20 again.
Refresh operation, dummy read. At the same time, the system control circuit 70 controls the condition memory circuit 40 during the exposure operation.
The various conditions stored in are called to the AE controller 30. Then, except for the X-ray source 10, it is operated under exactly the same conditions as during the exposure operation. That is, the outputs of the temperature sensor 33 and the photo timer 31 are not used, and the operation is performed based on the value stored in the condition memory circuit 40. The X-ray source 10 does not operate in the correction mode and does not emit X-rays. However, even if the X-ray source 10 is not moved, the two-dimensional area sensor 20 performs the reading operation after waiting a time corresponding to the exposure time in the photographing mode. The drive speed and the gain of the gain adjusting circuit 21 are operated under the same conditions as in the photographing mode to obtain outputs FO1-9 including FPN information. The output of the gain adjusting circuit 21 at this time is used as a correction output. That is, the X-ray source 10, the two-dimensional area sensor 20, and the gain adjusting circuit 21 can be set and controlled to the values stored in the condition memory circuit 40 to obtain the correction output.

This correction output is the current of each pixel when dark (non-irradiation), fixed pattern noise at the time of transfer, the amplifier inside the two-dimensional area sensor 20 and the gain adjusting circuit 21.
This output reflects the offset voltage of the. Since this correction output has the same accumulation time as during the exposure operation, the amount of influence due to the accumulation of current during dark is also the same. Further, since the correction output has the same driving speed, the amount of influence of the fixed pattern due to the influence of clock leak is also the same. Further, since the gain is the same, the influence amount of the offset voltage is also the same. That is, since the condition memory circuit 40 operates in exactly the same manner in the photographing mode and the correction mode except for the X-ray source, not only the influence amount described above but also the influence amounts not preferable for photographing other than X-ray emission and non-emission are the same. become. Therefore, the correction output includes the same amount of only the undesired error in the photographing output.

Therefore, the photographing output stored in the frame memory 50 is set to A, the correction output obtained in the correction mode is set to B, and the subtraction process is performed by the arithmetic processing circuit 60 to obtain P = AB.
Then, it is possible to obtain a good image information output P by removing an error such as a fixed pattern of the shooting output obtained in the shooting mode. Here, a simple expression (P
= AB). Note that the correction method is not limited to this, and can be changed as appropriate.

As for the operation of switching the SW2 from the standby mode to the exposure mode, the operation method shown in FIGS. 20B and 20C is also preferable. Figure 20
In (B), an example is shown in which the initialization operation is forcibly stopped when the SW2 is turned on (*), and the exposure operation is started again. In FIG. 20C, if the second dummy reading of the initialization operation is not completed when the SW2 is turned on, X-rays are emitted after the dummy two times are completed and this is used as an exposure operation. When a sample such as a patient needs to be stationary, the time (between a and b) in FIG. 20 (B) is shorter than that in FIG. 20 (A), and that in FIG. 20 (C) is shorter than that in FIG. 20 (B). Is possible. However, in FIG. 20 (B) than in FIG. 20 (C), and in FIG. 20 (A) than in FIG. 20 (B), the transition is performed at the expected timing regardless of the timing of turning on the SW2. Therefore, it is easy to optimize with other operations and improve performance. That is, in FIG. 20A, the initial operation and the exposure operation of the entire system are continuous, there is no strange transient response, there is a time margin in the X-ray control, and the number of controls can be increased. In FIG. 20B, there is a time margin in the X-ray control, the number of controls can be increased, and the time required to stop the specimen such as the patient is short. Figure 20
In (C), in the panel operation, both the initial operation and the exposure operation are continuous, there is no strange transient response, and the time required to stop the specimen such as the patient is very short.

In the two-dimensional area sensor of this embodiment, for simplification of description, it is assumed that nine pixels are two-dimensionally arranged in a 3 × 3 array, and three pixels are simultaneously transferred and output in three divisions. However, the present invention is not limited to this. For example, if 2000 × 2000 pixels are arranged two-dimensionally with a pixel size of 5 × 5 pixels per 1 mm in the vertical and horizontal directions, a two-dimensional area sensor of 40 cm × 40 cm can be obtained. A radiation imaging apparatus for the purpose of diagnosis and high precision nondestructive inspection can be configured. Then, unlike the film, the output can be instantly displayed on the CRT, and the output can be converted into digital and processed by a computer to be converted into an output suitable for the purpose. It can also be stored in a storage means such as an optical disk or a magneto-optical disk, so that past images can be retrieved instantly. Also, the sensitivity is better than that of the film, and a clear image can be obtained with a weak X-ray dose that has little influence on the human body and environment.

Although the embodiments of the present invention have been described above, the present invention is not limited to these. For example,
As an image information injection device, strobe, subject and lens,
By mounting two switches on the shutter button, it becomes a still camera with AE function. Further, natural light, an object, and a lens may be used without a strobe. In this case, an exposure operation may be performed by providing a mechanical shutter in front of the photoelectric conversion element and opening the mechanical shutter. Further, a so-called electronic shutter in which the accumulation time is changed by electrical control to perform the AE operation may be used.

Further, it is obvious that the sensor as the image pickup means may be arranged in one dimension even if it is not arranged in two dimensions, that is, a one-dimensional line sensor may be used to obtain the same effect.

In the rest mode, the electric field is not applied to the photoelectric conversion element, but the effect can be obtained by suppressing the electric field as compared with the other modes. In this case, the dark current is small and the SN ratio is high, and the standby state [Wait] can be set short as compared with the case where the electric field is not applied immediately after the start of the standby mode.

[0083]

As described above, according to the present invention,
By turning on the switch means, a voltage or current is applied to the photoelectric conversion means, and after the dark current is reduced, the switch means is turned on again to start exposure immediately.

That is, it is not necessary to always apply an electric field or the like to the photoelectric conversion means, and it is possible to use highly reliable photocurrent after the dark current is reduced and obtain image information with a high SN ratio without shot noise. The exposure can be started immediately after the desired image, and an easy-to-use imaging device can be provided.

When combined with an X-ray source, it is possible to provide an X-ray imaging apparatus for medical diagnosis or non-destructive inspection which can obtain a digital signal having excellent reliability, sensitivity and usability, instead of a silver salt film, and can be used in a remote area. You can get appropriate diagnosis from doctors and technicians.

[Brief description of drawings]

FIG. 1 is a schematic system block diagram having a photoelectric conversion device.

FIGS. 2A to 2D are schematic timing charts for explaining driving and output examples of the photoelectric conversion device.

FIG. 3 is a flowchart illustrating an example of driving the photoelectric conversion device.

4A to 4D are schematic timing charts for explaining examples of driving and output of the photoelectric conversion device.

FIG. 5 is a flowchart illustrating an example of driving the photoelectric conversion device.

6A to 6D are schematic timing charts for explaining driving and output examples of the photoelectric conversion device.

FIG. 7 is a flowchart illustrating an example of driving the photoelectric conversion device.

FIG. 8 is a schematic system block diagram for explaining a preferred example including a photoelectric conversion device.

FIG. 9A to FIG. 9C are schematic perspective views for explaining a preferable example of a switch.

10A to 10D are schematic timing charts for explaining an example of driving and output of a photoelectric conversion device.

FIG. 11 is a flowchart illustrating an example of driving the photoelectric conversion device.

12A to 12D are schematic timing charts for explaining driving and output examples of the photoelectric conversion device.

FIG. 13 is a flowchart illustrating an example of driving the photoelectric conversion device.

FIG. 14 is a schematic system block diagram for explaining an example of an imaging device having a photoelectric conversion device.

FIG. 15 is a schematic overall circuit diagram for explaining an example of a photoelectric conversion unit.

16A is a schematic plan view for explaining an example of one pixel of a photoelectric conversion section, and FIG. 16B is a schematic cross-sectional view for explaining an example of one pixel of a photoelectric conversion section.

17 (A) to (C) are schematic energy band diagrams of photoelectric conversion elements, respectively.

FIG. 18 is a schematic timing chart for explaining driving and output examples of the photoelectric conversion device.

FIG. 19 is a schematic timing chart for explaining an example of driving and output of the photoelectric conversion device.

20A to 20C are schematic operation explanatory diagrams for explaining an example of the operation of the entire system.

[Explanation of symbols]

1 sensor 2 X-ray source 3 power supplies 4 control circuit 5 control circuit

Continued front page    F-term (reference) 4M118 AA01 AA05 AB01 CA03 CB11                       CB14 DB09 DD12 FB09 FB13                       FB16 GA10                 5C022 AA08 AB01 AB15 AB37 AC42                       AC69                 5C024 AX02 AX12 AX17 CX33 GX02                       HX18 HX55

Claims (10)

[Claims] 1. An imaging apparatus having an imaging means including a plurality of photoelectric conversion elements arranged two-dimensionally, means for storing a shooting output at the shooting exposure, and means for storing shooting conditions at the shooting exposure. An image pickup apparatus comprising: a unit that obtains a correction output using the stored shooting conditions; and a unit that corrects the shooting output using the correction output. 2. The correction output means obtains the correction output by operating in a state where no light is incident on the photoelectric conversion element, using the stored photographing condition. Item 1. The imaging device according to item 1. 3. The means for obtaining the correction output obtains the correction output by making reference light in the absence of a subject incident on the photoelectric conversion element to operate by using the stored photographing condition. The image pickup apparatus according to claim 1, wherein: 4. The image pickup apparatus according to claim 1, wherein the means for obtaining the correction output has a means for controlling a driving condition of the image pickup means according to the photographing condition. 5. The image pickup device according to claim 1, further comprising a phosphor that converts X-rays into visible light. 6. A light source, an area sensor, an AE controller that controls at least a shooting condition regarding the light source, a condition storage unit that stores a setting value of the AE controller, and a frame memory that stores a shooting output at the time of shooting. An arithmetic processing circuit that corrects the shooting output stored in the frame memory using a correction output obtained by controlling the light source using the set value stored in the condition storage means. . 7. The image pickup system according to claim 6, further comprising a gain adjusting circuit, wherein the gain can be automatically and set controlled by the AE controller. 8. The imaging system according to claim 6, wherein the AE controller controls a storage time and a driving speed of the area sensor. 9. The imaging system according to claim 6, further comprising a phosphor that converts X-rays into visible light. 10. A step of storing a photographing output at the time of photographing exposure, a step of storing a photographing condition at the time of photographing exposure, and a step of storing a photographing output at the time of photographing exposure by a correction output obtained by using the stored photographing condition after the photographing exposure. A method of driving an image pickup apparatus, comprising: a step of correcting a shooting output.