JP2002344809A - Image pick up unit, its drive method, radiographic device and radiographic system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem that the corelation of images is eliminated in the connection part of imaging elements in the case of using an amplifying imaging element such as a CMOS imaging element. SOLUTION: Sample-and-hold circuits are provided in pixel for an optical signal and a noise signal. The optical signal and the noise signal are preserved independent of exposure and simultaneously outputted from the sample-and-hold circuits (two-line output in each string) in structure. Thus, batch exposure (an electronic shutter function) is realized between the imaging elements and between the pixels and also noise is surely corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an imaging apparatus, a driving method thereof, a radiation imaging apparatus, and a radiation imaging apparatus system using the same, and more particularly, to a large-sized image reading apparatus using high-energy radiation such as X-rays and gamma rays. The present invention relates to a radiation imaging apparatus having a large area and a system using the same.

[0002]

2. Description of the Related Art In recent years, digitalization has been advanced in various fields of medical treatment. In the field of X-ray diagnostics as well, a two-dimensional X-ray imaging apparatus that converts incident X-rays into visible light with a scintillator (phosphor) and digitizes the visible light image with an image sensor for digitizing images. Are being developed.

[0003] As a two-dimensional X-ray imaging apparatus, for example, a small CCD type imaging element has been put to practical use for dentistry. For mammography and chest imaging, amorphous silicon (a-Si) of a maximum of 43 cm □ is used. The used large-area still image pickup device has been put to practical use. An imaging element using an amorphous silicon semiconductor on a glass substrate can be easily manufactured in a large area, and there is an imaging element in which a large area X-ray imaging apparatus is realized by attaching four panels to each other as tiles. An example of this type of technology is described in US Pat. No. 5,315,101.

[0004] Proposals have been made to construct a large-area X-ray imaging apparatus using a plurality of single-crystal imaging elements (such as silicon imaging elements). Examples of this type of technology are described in US Pat. No. 4,323,925 and US Pat. No. 6,0059,911. Examples of the single crystal image sensor include a CCD image sensor using silicon, a MOS image sensor, and a CMOS image sensor. As described above, in the field of medical X-ray diagnostics that are being digitized, next-generation moving image capturing apparatuses (such as fluoroscopy) are expected as still image capturing apparatuses.

The technical problems here include (1) high sensitivity and high-speed reading technology, (2) enlargement, and (3) cost reduction. With respect to the issues of (1) high sensitivity and (2) high-speed reading, a moving image is required to have 10 times or more higher sensitivity and reading speed than an imaging device using amorphous silicon. To capture a moving image, humans are continuously irradiated with X-rays. However, taking into account the effects of X-ray irradiation, the dose of X-rays is reduced from several tens to one hundredth.
The reading speed is required to be 60 to 90 frames / sec. To perform this reading, several tens times higher sensitivity and several tens times higher speed are required.

[0006] Amorphous silicon does not have sufficient semiconductor characteristics for high-speed operation, and it is more difficult to finely process a semiconductor on a glass substrate with a large-area imaging device using the same than a single-crystal silicon semiconductor substrate. As a result, the capacity of the output signal line increases. This capacitance causes the largest noise (kTC noise). The manufacturing process of the amorphous silicon type large plate imaging device is a CCD type imaging device or CM
This is advantageous in that a large-area one can be obtained as compared with the OS-type imaging device. However, the photoelectric conversion unit is not a complete depletion type, and a drive circuit and an amplifier for the image sensor are required outside (see FIG. 52 of JP-A-8-116004). Since it is necessary to perform the operation later, the image pickup device itself is relatively low in price, but the cost has finally increased. As described above, it is difficult to fulfill the above-mentioned requirements.

Further, the CCD type image pickup device is a fully depleted type and has high sensitivity, but is not suitable for a large area image pickup device. Since the CCD type image pickup device is a charge transfer type, it has a large area and the number of transfer stages increases (the number of pixels increases).
The transfer becomes more problematic. In other words, the drive voltage differs between the drive end and the center, and complete transfer becomes difficult. The power consumption is represented by CVf ² (C is the capacitance between the substrate and the well, V is the pulse amplitude, and f is the pulse frequency). The larger the area, the larger the C and V, and the lower the power consumption. 10 times or more larger than that of the image sensor. As a result, the peripheral drive circuit becomes a heat source and a noise source, and is not high S / N. Thus, the CCD type imaging device has a surface that is not suitable for a large-sized imaging device.

Further, in the configuration of a simple large-area imaging device using a large number of single-crystal imaging devices, dead space is always created in a joint portion of each imaging device (peripheral circuits such as shift registers and amplifiers, external signals and power supplies). (A region for providing an external terminal and a protection circuit for the exchange is always required separately from the region.) This portion becomes a line defect, and the image quality is deteriorated. For this reason, a configuration is adopted in which light from the scintillator is guided to the image sensor while avoiding a dead space by using a tapered FOP (fiber optic plate), but an extra FOP is required and the manufacturing cost is increased. In particular, tapered FOPs are very costly. Furthermore, tapered FO
In P, the light from the scintillator is FO according to the taper angle.
There is a problem that it becomes difficult for the light to enter the P, the output light quantity is reduced, and the sensitivity of the image pickup device is offset, and the sensitivity of the entire apparatus is deteriorated.

In order to compensate for the above-mentioned drawbacks of the amorphous silicon image sensor and the CCD type image sensor, a large area CM is used.
A configuration in which an OS type image sensor is tiled has been proposed (Japanese Patent Application Laid-Open No. 2000-184282).

[0010]

However, the conventional amplification type image pickup device such as a CMOS type image pickup device has the following inconveniences. (A) In a general driving method of an amplification type image pickup device, stored charges of one horizontal scanning line are sequentially read in units of horizontal scanning lines in the same row. While reading out the stored charges from a certain horizontal scanning line, the charges are stored in the remaining horizontal scanning lines. In this case, the charge accumulation time differs for each horizontal scanning line. If this charge is read out and reproduced as an image, the image will be different in timing for each scanning period. This difference in storage time rarely causes a problem in still image shooting, but causes a problem in moving image shooting because images flow. In particular, in an imaging apparatus in which a plurality of imaging elements (an imaging element panel in which a plurality of pixels are formed) are tiled, discontinuity occurs in images between the imaging elements as described later, which is a serious problem. In addition, in X-ray moving image shooting, during the reading time of a certain horizontal scanning line, it is the exposure time of another horizontal scanning line, and it is necessary to irradiate partially unnecessary X-rays. The application of this method is difficult in the field. (B) In order to prevent a charge accumulation period from being different between a horizontal scanning line to be read first and a horizontal scan to read later, a mechanical shutter is provided to accumulate charges in each horizontal scanning line. There is a method for keeping the period constant, but this method has a disadvantage that the apparatus becomes large.

[0011] Such a large area CMOS type image pickup device is
The following is a description of the problem (a) in particular when a high-speed moving image is shot using an imaging device with tiles attached. FIG. 14 is a plan view of an imaging device in which four imaging elements are tiled. Imaging area (imaging element panel) A1, A
2, B1, and B2 are configured by arranging a plurality of pixel units in the horizontal and vertical directions. In the imaging region, Hn indicates a column scanned by the column scanning circuit, and Vn indicates a row scanned by the row scanning circuit. Further, a column scanning circuit, a row scanning circuit, a memory circuit, and an output amplifier are provided for each imaging region.

FIG. 15 shows a schematic configuration of one pixel unit and a signal readout circuit of each image sensor. FIG. 15 employs a method of scanning and reading out each row. In addition, in the conventional circuit of FIG.
It is a double sampling circuit. In FIG.
SR is a row scanning circuit, and HSR is a column scanning circuit. Also,
PD is a photodiode, TR1 is a transfer switch, TR
2 is a reset switch, TR3 is a row selection switch, TR
4 is an amplifying transistor, TR5 is a switch for resetting a signal line, TR6 and 7 are sample switches, TR8 and T
R9 is a read switch. TR1 to TR9 are MO
It is an S transistor. _CTS is an optical signal holding capacity,
C _TN is a reset signal holding capacity.

The details of the conventional circuit shown in FIG. 15 will be described later.
Resets the reset signal (noise component, dark current component)
Signal holding capacity C_TNAnd the optical signal (optical signal component,
Noise component and dark current component)_TSKeep in
You. Then, each storage capacity C _TN, C_TSFaith held in
Signal, and differentially detected by a differential circuit (not shown).
As a result, an optical signal from which noise components have been removed is output.
You. An imaging device in which such a plurality of imaging elements are bonded.
When capturing a moving subject,
"Connecting" becomes important.

FIG. 16 shows an image synthesis in a case where four image sensors are stuck together. When the four image sensors are separately and independently driven in the scanning direction indicated by the arrows in FIG. 16, a connection portion of the four screens (a connection portion between the imaging regions A1 and B2, a connection portion between the imaging regions B1 and A2). Connection part between the imaging areas A1 and B1,
The image is no longer correlated at the connection between the imaging areas B2 and A2). For example, a scanning period in the row direction is adjacent to the row of the imaging area A1 (the row where scanning ends) and the row of the imaging area B2 (the row where scanning starts) adjacent to the vicinity of the connection between the imaging areas A1 and B2. Since a time shift of minutes occurs, the correlation of the images is lost. At this time, the “connection” of the moving images is concerned about basically, the imaging regions A1 and B1, the imaging regions A1 and B2, and the imaging regions B2 and A2 to which the images are connected.
2. These are the imaging areas B1 and A2. Like this
In a configuration in which an image pickup device using an amplification type image pickup device such as an OS type image pickup device is bonded, there is a problem that image correlation is lost at a joint between the image pickup devices and image quality is deteriorated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and has as its object to provide an imaging apparatus capable of obtaining a seamless image with high speed and high sensitivity even when a plurality of imaging elements are bonded. An object of the present invention is to provide a driving method of an imaging apparatus, a radiation imaging apparatus, and a radiation imaging system using the same.

[0016]

According to the present invention, there is provided an imaging apparatus comprising:
Including an image sensor having a plurality of pixels arranged in a dimension,
The pixel includes a photoelectric conversion unit that performs photoelectric conversion, an optical signal storage unit that stores an optical signal generated by the photoelectric conversion unit, and a noise signal storage unit that stores a noise signal.

Further, the image pickup apparatus of the present invention includes a plurality of image pickup devices having a plurality of pixels arranged two-dimensionally, photoelectric conversion means for performing photoelectric conversion for each pixel, and light generated by the photoelectric conversion means. Having optical signal storage means for storing a signal,
A unit that collectively transfers the optical signals of the pixels of the plurality of imaging elements to the optical signal storage unit; and a unit that sequentially outputs the optical signals stored in the optical signal storage unit to an output line for each pixel. , Is characterized by having.

Further, a radiation imaging apparatus according to the present invention comprises: an imaging apparatus according to any one of claims 1 to 14;
A scintillator and an equal-magnification optical transmission unit are provided.

Further, a radiation imaging system according to the present invention is a radiation imaging apparatus according to any one of claims 15 to 16, a signal processing means for processing a signal from the radiation imaging apparatus, and the signal processing means. A recording unit for recording a signal from the signal processing unit; a display unit for displaying a signal from the signal processing unit; a transmission processing unit for transmitting a signal from the signal processing unit; and generating the radiation. And a radiation source.

Further, the driving method of the image pickup apparatus according to the present invention is as follows.
An imaging apparatus having a plurality of imaging elements having a plurality of pixels arranged in a dimension, the pixels having photoelectric conversion means for performing photoelectric conversion, and optical signal accumulation means for accumulating optical signals generated by the photoelectric conversion means Wherein the plurality of imaging devices are collectively reset at the same timing, the plurality of imaging devices are collectively exposed at the same timing, and a signal after exposure is stored in the optical signal storage unit. Features.

In the present invention, a sample and hold circuit for an optical signal and a noise signal is provided in a pixel.
The exposure dose can be adjusted appropriately by performing the batch exposure and irradiating the pulsed radiation exposure at this timing. Further, even when high-speed shooting is performed using a plurality of image pickup devices, no seam or flow of images occurs. Further, F
PN correction can be performed for each pixel.

[0022]

Embodiments of the present invention will be described below in detail with reference to the drawings.

(First Embodiment) FIG. 1 is a circuit diagram showing a first embodiment of an imaging apparatus according to the present invention. FIG.
It is a circuit diagram of a pixel. In the present embodiment, a high-speed, high-sensitivity moving image with no temporal and spatial seamlessness is realized by bonding image sensors. In addition, the charge accumulated at a common time from all the elements using a CMOS image sensor can be read at a high signal-to-noise ratio (S / N). It should be noted that the image sensor described in the specification of the present application refers to an image sensor panel in which a plurality of pixels are two-dimensionally arranged. This imaging element panel has a pixel area on the entire surface, and realizes a large-area imaging device by bonding a plurality of imaging element panels on a base (see FIG. 4).

In FIG. 1, PD is a photodiode for performing photoelectric conversion, C _PD is a junction capacitance of the photodiode (indicated by a broken line), and C _FD is a capacitance of a floating diffusion (floating diffusion region) for accumulating electric charges (indicated by a broken line). ),
M1 is a transfer MOS transistor (transfer switch) for transferring the charge generated by the photodiode PD to the floating diffusion, M2 is a reset MOS transistor (reset switch) for discharging the charge accumulated in the floating diffusion, and M3 is a photoelectric conversion. A selection MOS transistor (selection switch) for selecting a section, and M4 is an amplification MOS transistor (pixel amplifier 1) functioning as a source follower.

M8 is a MOS transistor as a sample switch constituting a sample and hold circuit for storing an optical signal, which is a feature of the present embodiment, and CH1 is a hold capacitor for an optical signal. M11 is a MOS transistor as a sample switch constituting a sample and hold circuit for storing a noise signal, and CH2 is a noise signal hold capacitor. M10 is an amplification transistor (pixel amplifier 2) as a source follower for amplifying the output from the optical signal sample hold and outputting the amplified signal to the signal line. M
Reference numeral 13 denotes an amplification transistor (pixel amplifier 3) as a source follower for amplifying an output from the noise signal sample hold and outputting the amplified signal to a signal line. Further, M
Reference numerals 9 and M12 denote MOS transistors as selection switches for the pixel amplifiers 2 and 3.

In this embodiment, these optical signals and noise signal sample-and-hold circuits are used in order to perform batch reset and batch exposure of each image sensor at the same timing. Further, since the image signal can be stored in the sample and hold circuit independently of the exposure, the optical signal and the noise signal can be read out many times during the exposure period without destruction. Using this function, signal reading for automatic exposure can be performed while performing exposure.

Next, noise will be described. In general,
In an amplification type imaging device such as a CMOS type imaging device, amplifying means (in-pixel amplifier) is provided inside to improve a signal gain in order to improve a signal-to-noise ratio (S / N) at the time of reading. MOS generally used as this amplification means
The threshold value Vth of the MOS transistor tends to vary at the source follower of the transistor. This variation is peculiar to the design and manufacture of the device and is bad in that it varies for each pixel and each device. In particular, an imaging element for an X-ray imaging apparatus is large and tends to have large variations within the element. When using a plurality of image sensors,
The variation between elements is large. This variation is a fixed output variation, so-called fixed pattern noise (FP).
N), appears as a non-uniform background image.

Further, 1 / f noise (flicker noise) and thermal noise are liable to occur in the MOS transistor. Since this noise is random noise, a random background image is generated. Assuming that the channel length of the MOS transistor is L and the channel width is W in device design, thermal noise is proportional to (L / W) ・, and 1 / f noise is inversely proportional to L · W. In order to reduce the noise of the transistor, the channel length L should be minimized and the channel width W should be set large. In particular, if the channel width W of the source follower as an amplifier serving as a large noise source is set large, the gate-to-drain This is difficult to implement because the parasitic capacitance of the device becomes large, the gain is reduced, and the sensitivity is reduced.

In this embodiment, a PMOS transistor having essentially small 1 / f noise is used as at least a source follower. Thereby, the size can be reduced to about 1/10 of that of the NMOS transistor. Further, even if X-rays passing through the scintillator directly hit the transistor, the PMOS transistor has higher X-ray durability than the NMOS transistor (increase in leakage current, threshold V
th variation is small).

In general, it is known to use a double sampling circuit to reduce low-frequency noise components such as 1 / f noise and fixed pattern noise (FPN) due to variations in threshold and noise from a power supply. FIG. 15 shows a conventional one-pixel circuit and a double sampling circuit in a signal readout circuit as described above.

In this circuit, first, the reset signal ΦRE
The reset switch Tr2 is closed by S, and then the photodiode PD is reset. Next, the row selection MOS transistor Tr3 is closed, and the dark signal appears on the output signal line through the amplification MOS transistor Tr4. At this time, by closing the sample switch Tr6, the reset signal (noise component and dark current component) is transferred to the reset signal holding capacitor C.
After holding at _TN , the sample switch Tr6 is opened. Next, the reset switch Tr2 is opened, and the optical signal charges accumulated in the photodiode PD are transferred to the amplification MOS transistor Tr4 by opening the transfer MOS transistor Tr1. At the same time, the row selection MOS transistor Tr3 is closed,
The optical signal appears on the output signal line through the amplification MOS transistor Tr4. At this time, by closing the sampling switch Tr7, the optical signal after holding (optical signal component, the noise component, the dark current component) to the optical signal holding capacitor C _TS, opening the sampling switch Tr7.

Next, the read switches Tr8, Tr9
At the same time, read the reset signal held in the reset signal holding capacitor _CTN and the optical signal held in the optical signal holding capacitor _CTS into a differential circuit (not shown), and subtract the optical signal from the reset signal. As a result, an optical signal from which noise has been removed is output. Next, in order to read all rows, each column line is selectively sampled, and then the next row is selected, and the same operation is repeated again.

Here, the thermal noise (kTC) in the photoelectric conversion unit
Noise) does not occur if complete depletion transfer is performed by the pixel switch. The reset noise (kTC noise) in the floating diffusion is removed by the correlated double sampling circuit together with the 1 / f noise and the FPN due to the variation in the threshold Vth. However, although the two source followers and the capacity for the correlated double sampling circuit for each column are roughly the same, they are not completely the same, causing variations in the threshold Vth and the capacity, etc. A linear fixed pattern is generated (for each column).

Further, since the threshold value Vth changes exponentially with temperature, even if each source follower has a temperature difference of 1 ° C. or less, it appears as a fluctuation in output, and as shown in X-ray fluoroscopy, a low irradiation dose. In the case of photographing, even a slight change affects the image quality. For this reason, the two source followers of the sample-and-hold circuit must have an arrangement structure in which the variation of the threshold value Vth is as small as possible, as described later, and a mechanism that does not cause a temperature difference during operation. If the read timing of the optical signal and the noise signal from the sample hold is different as in the related art, the time difference causes a temperature change.

Therefore, in this embodiment, as described above, the sample and hold circuits for the optical signal and the noise signal are provided in the pixel, and the optical signal and the noise signal are stored independently of the exposure. Are output at the same time (two lines per column). For batch exposure, it is necessary to provide a memory in the pixel, and this sample and hold circuit first functions as a memory in the pixel. Furthermore, it has a function of removing noise. Since the optical signal and the noise signal are taken into the sample hold circuit from the pixel amplifier 1 with a very fast time difference, a large 1
/ F noise can be ignored.

Further, the thermal noise, 1 / f noise, and FPN in the pixel amplifier are removed by using this circuit. The variation between the two sample-and-hold circuit elements is determined by reducing the variation of the threshold Vth as much as possible by arranging a capacitor as close to the pixel as possible and using the output source follower as a cross arrangement used in a normal MOS circuit layout. By doing so, it is reduced as much as possible. As described above, the sample and hold circuit functions as a storage unit for each pixel for batch exposure, and also functions as a unit for removing noise.

FIG. 2 is a schematic diagram of an entire circuit for 3 × 3 pixels for simplicity. Details of one pixel circuit portion are as shown in FIG. The gate of the transfer switch M1 is ΦTX from a vertical shift register VSR which is a kind of vertical scanning circuit.
And the gate of the reset switch M2 is connected to ΦRES from the vertical scanning circuit. The gate of the selection switch M3 is connected to ΦSEL from the vertical scanning circuit. For simplicity, only three control lines are shown. An optical signal and a noise signal from each pixel are output to a differential amplifier A1 via two signal output lines via a column scanning circuit (horizontal shift register, multiplexer). Column selection M
The OS transistor M20 is operated by a signal from the horizontal shift register HSR, and is a switch for selecting a signal line in a column direction.

FIG. 3 is a timing chart showing the operation timing of the pixel section in this embodiment. Hereinafter, FIG.
The circuit operation will be described based on FIG. First, photoelectric conversion is performed by the photodiode PD. Exposure is batch exposure, and is performed at the same timing and period for all pixels of each image sensor. Therefore, there is no time lag between images between the imaging elements and between the scanning lines. During the photocharge accumulation period, the transfer switch M1 is in the off state, and the generated photocharge is transferred to the junction capacitance C _PD.
Is accumulated in The floating diffusion C _FD, which is formed in the gate of the source follower constituting the pixel amplifier 1 (M4), this while light charges are not transferred.

When the accumulation of the photodiode PD is completed, as shown in FIG. 3C, the signal ΦTX from the vertical shift register VSR is set to the high level for all the pixels at once, and the transfer switch M1 is turned on to store the photodiode PD. completely transferring stored charge in the floating diffusion C _FD formed in the gate of the source follower M4 constituting the pixel amplifier 1. Thereafter, the signal ΦTX is set to the low level for all the pixels at once, the transfer switch M1 is turned off, and the signal ΦSEL1 from the vertical shift register VSR is set to the high level for all the pixels as shown in FIG. As a result, the selection switch M3 is turned on, and the source follower circuit including the load current source I and the pixel amplifier 1 is brought into an operating state.

At the same time, as shown in FIG. 3 (f), the signal .phi.SH1 from the vertical shift register VSR is set to the high level, and the sample switch M8 is turned on, whereby the signal from the photodiode PD is transferred to the capacitor through the pixel amplifier 1 (M4). Batch transfer to CH1. At the same time, as shown in FIG. 3C, by setting the signal ΦTX to the low level for all the pixels at once, the photodiode PD is ready for exposure in the next frame. At the same time, as shown in FIG. 3D, the signal ΦSH1 is set to the low level at once for all the pixels, and the sample switch M8 is turned off, thereby completing the operation of holding the optical signal charges in the sample and hold circuit.

Next, a signal ΦRES from the vertical shift register VSR in all pixels as shown in FIG. 3 (b) to a high level, the floating diffusion C _FD is reset by turning on the reset switch M2.
Immediately, as shown in FIG. 3 (g), the signal ΦSH2 from the vertical shift register VSR is set to the high level at once for all the pixels, and the reset signal is transferred to the capacitor CH2 by turning on the sample switch M11. Next, the signal ΦSH2 is set to low level for all pixels at once, and the sample switch M11
Is turned off, the transfer and holding of the optical signal and the noise signal to the sample and hold circuit are completed.

Also, as shown in FIG. 3 (e), the signal ΦSEL2
To a high level for each row, and select switches M9 and M12
Is turned on, the load current source and the pixel amplifiers 2 and 3 (M1
(0, M13) is activated. Thereby, the hold capacities CH1, CH2
The optical signal and the noise signal held in the pixel amplifiers 2 and 3
At the same time to the noise signal output line and the optical signal output line. The signals transferred to the noise signal output line and the optical signal output line are subjected to (signal-noise) subtraction processing by a subtraction output amplifier (not shown) connected to the noise signal output line and the optical signal output line. , Thermal noise, 1 / f noise, and a signal from which FPN has been removed. Note that the subtraction output amplifier corresponds to the differential amplifier in FIG.

In the above operation, the charge from the photodiode PD is transferred to the floating diffusion C _FD
, No kTC noise is generated. However, when the size of the pixel is as large as 160 μm square, complete transfer becomes difficult. In this case, kTC noise is generated, and in the above readout, the reset noise (kTC noise) in the floating diffusion included in the optical signal and the noise signal has no correlation and is output as random noise. However, at the time of shooting a moving image, fixed pattern noise has a greater effect on image quality than random noise. Therefore, in the present embodiment, sufficiently high image quality can be obtained even when complete transfer is difficult. An example of further removing the reset noise will be described later.

After performing the batch reset of the photodiode PD in this manner, the batch exposure is performed, and the optical signal and the noise signal are stored in the sample and hold circuit in the pixel, so that the exposure of the next frame and the signal of these signals are performed. Reading can be performed independently. As a result, exposure can be performed while performing high-speed reading, so that a multi-pixel drive under a low irradiation dose as in a large-area X-ray imaging apparatus, the accumulation time can be as long as possible even in high-speed operation, and the optical signal intensity can be increased. It is possible to further reduce the noise and improve the signal-to-noise ratio (S / N).

Further, since a plurality of image pickup devices can be driven by a common drive pulse, peripheral drive pulse generation circuits can be simplified. In addition, it can be seen that the common drive enables the common use of the imaging element drive circuit, and is excellent in mounting.

FIG. 4 shows a 408 mm square image sensor having nine pixels of 136 mm square having the pixels of FIG.
An example in the case of configuring the large-area radiation moving image capturing apparatus of FIG. Nine imaging elements 100 are bonded on a base, and a large-screen imaging device is configured as a whole.

FIG. 5 is a sectional view taken along line AA of FIG. The scintillator 101 is made of Gd ₂ O ₂ S, CsI, or the like using europium, terbium, or the like as an activator, and is a FOP (Fiber Optic Platform).
e) installed on 102; The FOP 102 is an equal-magnification optical transmission unit for guiding the light generated by the scintillator 101 to the image sensor at equal magnification. The FOP 102 serves to absorb X-rays not absorbed by the scintillator 101 and protect the image sensor from X-ray damage.

X-rays strike the scintillator 101 and are converted into visible light, which is transmitted by the FOP 102 and detected by the image sensor. Preferably, the scintillator is selected such that its emission wavelength matches the sensitivity of the imaging device.
The external processing substrate 103 is a substrate having a circuit for supplying a power source, a clock, and the like of the image sensor, and extracting and processing signals from the image sensor. The flexible substrate 104 includes a TAB (Tape Auto) between each image sensor and the external processing substrate.
This is a wiring board for performing an electrical connection by using a “bonded bonding”. Although X-rays are used as radiation, α-rays, β-rays, γ-rays, and the like can be used.

The nine image sensors 100 are adhered on the base 105 so that substantially no gap is formed between the image sensors. The fact that there is substantially no gap means that the nine image sensors are formed by the nine image sensors. That is, there is no lack of an image between image sensors. The input of the clock and the like of the image sensor, the input of the power supply, and the output of the signal from the image sensor are performed through the flexible substrate 104 connected to the electrode pad at the end of the image sensor, and the external processing board 10 disposed on the back side of the image sensor.
Perform between 3. Even if the thickness of the TAB flexible substrate 104 is sufficiently small with respect to the size and passes through the gap between the imaging elements, no defect on the image occurs.

FIG. 6 shows an example in which one image pickup element is taken out from the currently mainstream 8-inch wafer 301. CMOS
A single 136 mm square CMOS imaging device substrate is formed by a process. In a medical X-ray imaging apparatus, the size of a pixel may be as large as about 100 μm to 200 μm. In the present embodiment, the pixel size is 160 μm □. As shown in FIG. 6, a vertical shift register and a horizontal shift register are formed in the image sensor, and an external terminal (electrode pad) is provided at an element end near the horizontal shift register. This electrode pad is used for connection with the flexible substrate as described above.

FIG. 7 shows a state in which a unit block (a unit for selecting and driving one row) of the vertical shift register is arranged together with one pixel circuit in one area (one cell). One pixel circuit is as shown in FIG. The area of the unit block and the pixel circuit do not reflect the actual element layout because of the schematic diagram. The vertical shift register is a simple circuit composed of a static shift register and a transfer gate for generating the transfer signal ΦTX, the reset signal ΦRES, and the selection signal ΦSEL. These are driven by signals from a clock signal line (not shown). The circuit configuration of the shift register is not limited to this, and an arbitrary circuit configuration can be adopted by various driving methods such as addition and thinning-out reading.
However, as in the present embodiment, it is assumed that the functional blocks are arranged together with the pixel circuits in one cell, the shift register is provided in the effective area, and the image sensor in the entire effective area is realized.

Also, instead of a shift register, an n-to- ²ⁿ decoder can be used as the scanning circuit. In this case, by connecting the output of the counter that sequentially increments to the input of the decoder, sequential scanning can be performed in the same manner as the shift register. On the other hand, by inputting the address of the area where the image is desired to be obtained to the input of the decoder, An image of an arbitrary area can be obtained by scanning. The common processing circuit arranged in each area (cell) in the effective area means a circuit that collectively processes a plurality of components such as a final signal output amplifier, a serial / parallel conversion multiplexer, a buffer, and various gate circuits. .

FIG. 8 shows a layout of one area (cell) in which the shift register is arranged. A light receiving area is arranged in the center, and a scanning circuit (shift register or the like) area, a pixel amplifier, a wiring area, a signal / noise S / H circuit area are provided around the light receiving area.

Cell size: 160 μm □ S / H circuit area: 15 μm × 320 μm Pixel light receiving area: 130 μm □ Pixel amplifier, wiring area: 15 μm × 320 μm Shift register block: 15 μm × 160 μm Therefore, the aperture ratio is 66%. The layout of one area where the shift register is not arranged is the one shown in FIG. 8 from which the shift register block is deleted, and at least the light receiving area of the one area where the shift register is not arranged is one where the shift register is arranged. It is the same as the light receiving area of the area (cell).

FIG. 9 shows the configuration (plan view) of the image pickup device of this embodiment. In the present embodiment, a vertical shift register and a horizontal shift register are arranged in an effective area of the image sensor, and a plurality of pixels are arranged two-dimensionally in the vertical and horizontal directions in the image sensor. Further, one block of the shift register for processing one line is arranged so as to fit within one pitch, and these blocks are arranged to form a series of vertical shift register blocks to form a horizontal shift register block. These blocks extend linearly in the vertical and horizontal directions.

Further, at least the light receiving region has the same area for all the pixels. In FIG. 9, the area of one pixel circuit and the area of a light receiving region in one pixel circuit are equal between cells. In addition, it is preferable that the area of the light receiving region is equal between all the cells. However, the area of the light receiving region in a cell in one line at the end of the image sensor is set to be equal to the internal cell in order to take a margin for slicing. May be different from the area of the light receiving region.
Also, in FIG. 9, bumps are provided on the external terminals,
A protection resistor and a protection diode for protecting the internal circuit from static electricity are connected to these bumps.

In this embodiment, the light receiving areas are uniformly sized and the centers of gravity are arranged at equal pitches in each image pickup element and between the image pickup elements. Since there is no variation in sensitivity between the elements or within the imaging element and no variation in the center of gravity of the light receiving region, a substantially seamless image can be obtained even with a tiled configuration. Further, since no dead space is generated around the image sensor, the entire area of the image sensor becomes an effective area.

By arranging these image pickup devices in a tile shape with substantially no gap, an image pickup device having a large area can be formed. Further, by adopting the circuit configuration as described above, it is possible to obtain a large-area image which is substantially seamless in time and space. Here, in a medical X-ray imaging apparatus, the size of a pixel may be as large as about 100 μm □ to 200 μm □. Therefore, even if a shift register is arranged in an effective pixel area, a circuit such as a sample hold circuit is provided in a pixel. However, since a sufficiently large aperture ratio can be realized even if the above is arranged, there is no problem.

In this embodiment, since the shift register is arranged in the effective area, the X-rays passing through the scintillator directly hit the shift register. However, the use of a static shift register as the shift register causes the influence of the X-rays. I try not to. The shift register circuit is used to sequentially transfer pulse signals. That is,
In principle, the static type is relatively insensitive to X-rays, so that it can be used in a place where X-rays directly hit as in this embodiment. Therefore, the use of the static shift register makes it possible to realize an imaging device with reduced X-ray damage and errors and improved reliability.

Further, in this embodiment, a CM is used as an image pickup device.
Since the OS type image sensor is used, power consumption is low,
This is suitable for forming a large-area imaging device. In addition,
The reason why the multiplexer is formed in the image sensor is to speed up the operation of the image sensor. In addition, a signal is taken out from the image sensor through an electrode pad, and there is a large stray capacitance around the electrode pad. Therefore, the signal transmission characteristics can be compensated for by providing an amplifier before the electrode pad.

In this embodiment, FO is used as the unity optical transmission means.
Although P is used, an equal-magnification lens optical system such as a Selfoc lens may be used. Although the use efficiency of light is lower in the lens optical system than in the FOP, there is an advantage that the manufacturing cost of the imaging device can be significantly reduced.

(Second Embodiment) Next, a second embodiment of the present invention will be described. The imaging apparatus according to the second embodiment has the same basic configuration as that of the first embodiment, but differs from the first embodiment in the circuit configuration of one pixel. FIG. 10 shows a one-pixel circuit according to the second embodiment of the present invention. In the present embodiment, the still image shooting and the high-speed moving image shooting are realized by mode switching by performing the kTC correction in the photoelectric conversion unit in the pixel and further providing the sensitivity switching unit in the pixel.

Here, the specific conditions required for the photoelectric conversion unit in the X-ray imaging device for both still image shooting and moving image shooting will be described. The irradiation X-ray dose at the time of shooting a moving image is about 1/100 of that at the time of shooting a still image, and the amount of at most several X-ray photons per pixel (actually incident on the pixel is the visible light converted from this X-ray). Therefore, the maximum sensitivity is required for the image sensor. However, there is no problem with the dynamic range. Further, a reading speed of 60 to 90 frames / second is required. The pixel resolution may be as coarse as 200 μm □ to 400 μm □. On the other hand, when photographing a still image, a dynamic range close to 80 dB is required. Pixel resolution is 100
μm □ to 200 μm □ is required. There has been no imaging device that satisfies these specifications at the same time.

Therefore, in the present embodiment, an image sensor satisfying these specifications is realized by adopting a pixel circuit configuration as shown in FIG. 10 in the CMOS image sensor.
In FIG. 10, PD is the same buried photodiode as that used in a CCD or the like as a photoelectric conversion unit. The buried photodiode suppresses dark current generated on the SiO ₂ surface by providing a p ⁺ layer having a high impurity concentration on the surface. Further, the capacitance C _{PD of the} photodiode PD is designed to be minimum in order to obtain the maximum sensitivity at the time of capturing a moving image. As will be described later, reducing the capacitance of the photodiode PD reduces the dynamic range. Irradiation X dose is 10 compared to video
Since the dynamic range is insufficient at the time of shooting a still image of 0 times or more, a capacitor C1 for expanding the dynamic range is provided in parallel with the photodiode PD.

M14 is a switch for switching between a still image mode (high dynamic range) and a moving image mode (high sensitivity mode). The floating diffusion (floating diffusion region) capacitance C _FD (not shown) for accumulating electric charges is also designed to have the minimum capacitance so that the sensitivity becomes maximum during moving images. Floating diffusion (floating diffusion region) is amplified M
It is formed so as to be connected to the gate of the OS transistor M4. M2 is a reset MOS transistor (reset switch) for discharging electric charges accumulated in the floating diffusion, M3 is a selection MOS transistor (selection switch) for selecting the pixel amplifier 1, and M
Reference numeral 4 denotes an amplification MOS transistor (pixel amplifier 1) functioning as a source follower.

A clamp circuit, which is a feature of the present embodiment, is provided at a stage subsequent to the pixel amplifier 1. This clamp circuit removes kTC noise generated in the photoelectric conversion unit. C _CL is a clamp capacitance, and M5 is a clamp switch. A sample and hold circuit is provided after the clamp circuit as in the first embodiment. M6 is a selection MOS transistor (selection switch) for selecting the pixel amplifier 2, and M7 is an amplification MO functioning as a source follower.
This is an S transistor (pixel amplifier 2). M8 is a sample MO constituting a sample-and-hold circuit for storing an optical signal.
The S transistor switch and CH1 are hold capacitors.

M9 is a selection MOS transistor (selection switch) for selecting the pixel amplifier 3, and M10 is an amplification MOS transistor (pixel amplifier 3) functioning as a source follower. M11 is a sample MOS transistor switch constituting a sample and hold circuit for storing a noise signal, and CH2 is a hold capacitor. M12 is a selection MO for selecting the pixel amplifier 3.
The S transistor (selection switch) and M13 are amplification MOS transistors (pixel amplifiers 3) that function as source followers.

In the present embodiment, as in the first embodiment, these optical signals and a sample-and-hold circuit in a pixel for noise are used to perform batch reset and batch exposure of each image pickup device at the same timing. Further, since an image signal can be stored in this portion independently of exposure, an optical signal and a noise signal can be read out many times during the exposure period without destruction. Using this function, signal reading for automatic exposure can be performed while performing exposure.

Next, the configuration of the pixel section will be described. In a conventional pixel unit, signal charges generated in a photodiode are transferred to a floating diffusion by a transfer switch, and charges accumulated in the floating diffusion are converted into charges / voltages, and the amplified MOS transistors (pixel amplifiers) function as source followers. It is output as a voltage. In the case of a photodiode having a small area, a signal charge can be completely transferred to the floating diffusion by applying a sufficiently large voltage to the gate of the transfer transistor, and the photodiode can be completely depleted. In this case, no kTC noise occurs due to complete transfer. However, as described above, there is a specific condition required for the photoelectric conversion unit in the X-ray imaging device for both still image shooting and moving image shooting. To satisfy this condition,
In the present embodiment, the configuration is as described below.

First, in a photodiode having a pn junction, when the photo-generated carriers Q _P are stored in the capacitance C _{PD of the} photodiode portion and converted into a voltage, the optical signal voltage V _P due to the photo-generated carriers is V _P = Q _P / C _PD (1) There is a reset noise generated each time the photodiode is reset. This appears as random noise. The reset noise V _N is as follows: V _N = √ (kTC _PD ) (2) k: Boltzmann's constant, T: temperature (K).

[0071] In addition, S / N _{ratio, V P / V N = Q} P · √ (1 / (kTC PD)) ... is (3). In order to increase the light utilization factor, it is better to increase the area of the photodiode. However, when the area of the photodiode is increased, the capacitance _CPD also increases. In order to obtain the highest sensitivity (S / N ratio) at the time of capturing a moving image, it is desirable to reduce the capacitance C _PD of the photodiode as much as possible. Further, the magnitude ΔV of the output of the pixel amplifier having the floating diffusion amplifier structure is expressed as follows.

ΔV = G · Q _P / C _FD (4) G is the gain of the source follower, C _FD is the capacitance of the floating diffusion, and Q _P is the signal charge stored in the capacitance C _FD .

As is apparent from the equation (4), as ΔV increases with respect to the same signal charge Q _P , the charge / voltage conversion gain increases, which is advantageous from the viewpoint of the S / N surface and the like. In order to increase ΔV with respect to the same signal charge Q, the gain G of the source follower usually hardly changes to about 0.7 to 0.9, so it is necessary to minimize the capacitance C _FD as in the photodiode. is there.

[0074] larger and the pixel is 160 .mu.m □ in the present embodiment, in order to reduce the capacitance C _PD at a moderate aperture ratio (area of the photodiode) is limited. The capacitance _CPD can be reduced by reducing the electrode area while keeping the area of the photodiode unchanged. However, in this method, the charge collection efficiency of the electrode is reduced, and the signal charge is completely transferred to the floating diffusion by the transfer switch. It becomes difficult. In the present embodiment, complete transfer is not performed, no transfer switch is provided, and a photodiode and a floating diffusion are directly connected to form a photoelectric conversion unit. Further, the capacitance C _{PD of the} photodiode and the capacitance C _{FD of the} floating diffusion are designed to be minimized so that the sensitivity becomes maximum when capturing a moving image.

In the present embodiment, since the transfer is not complete, kTC noise is generated at the time of resetting the photoelectric conversion unit. However, removing this kTC noise (reset noise) in a circuit requires high S / N of the photoelectric conversion device. This is an important point of N-Nation. For this reason, the present embodiment has a configuration in which a clamp circuit is provided for each pixel. It is known to use a clamp circuit for removing kTC noise. If the pixel size is relatively small, 50 to 100 μm square, and complete transfer is possible, this is not the case because kTC noise does not occur in the photoelectric conversion unit.

As in the first embodiment, when shooting a moving image, kT
The case where the FPN is more important than the C noise is not limited to this. However, in order to obtain an image sensor that can be used in both the still image mode and the moving image mode, even in the still image mode, k
It is necessary to remove TC noise, and it is essential to provide a clamp circuit in the pixel. In the present embodiment, a clamp circuit is provided before the sample exposure circuit for batch exposure so that kTC noise can be removed even in the moving image mode of batch exposure.

[0077] In order to increase the dynamic range of the photodiode for still image shooting better large capacitance C _PD is defined, but then the signal voltages will be lowered, resulting in lowered S / N. In order to widen the dynamic range at the time of still image shooting while maintaining the highest sensitivity at the time of moving image shooting, a sensitivity (dynamic range) switching circuit is provided, and a capacitor and a switch are provided for each pixel in the present embodiment. S / S
N becomes worse, but in order to improve S / N,
In particular, a clamp circuit for removing kTC noise is required.

FIG. 11 is a timing chart showing the operation timing of the pixel section in this embodiment. Hereinafter, the circuit operation will be described with reference to FIG. First, photoelectric conversion is performed by the photodiode PD. Exposure is collective exposure, and is performed at the same timing and period for all pixels of each image sensor. Therefore, there is no time lag between images between the imaging elements and between the scanning lines. In the present embodiment, the structure is such that the charge of the photodiode PD is not completely transferred to the floating diffusion, and there is no transfer switch. The photocharge generated by the photodiode PD is represented by capacitances C _PD and C _FD
Is accumulated in This photocharge includes reset noise (kTC noise) at the end of the previous frame. The operation from this state will be described. In the movie mode, the signal Φ
SC is set to low level.

[0079] First, a signal ΦSEL1 from the vertical shift register VSR in all pixels as shown in FIG. 11 (c) to a high level, stored in the capacitance C _PD and C _FD by turning on the selection switch M3, M6 The electric charge is converted into a voltage by a source follower constituting the pixel amplifier 1 (M4) and is stored in the clamp capacitor _CCL . The clamp capacitor C _CL is clamped to a reset level including reset noise of the photoelectric conversion unit at the time of reset of the previous frame, and by holding the photoelectric charge including reset noise here, reset noise is _generated from the clamp capacitor C _CL. Is output.

As shown in FIG. 11F, the signal ΦSEL1 from the vertical shift register VSR and the signal ΦSEL simultaneously
By setting SH1 to the high level and turning on the sample switch M8, this optical signal is collectively transferred to the capacitor CH1 through the pixel amplifier 2 (M7). Next, the signal Φ
By setting SH1 to low level and turning off the sample switch M8, the holding of the optical signal charge in the sample and hold circuit is completed. Immediately, as shown in FIG. 11B, the signal ΦRE from the vertical shift register
By setting S to the high level and turning on the reset switch M2, the floating diffusion _CFD is reset.

[0081] Simultaneously, the signal ΦCL from the vertical shift register VSR as shown in FIG. 11 (e) to a high level, and sets the reference voltage clamp capacitor C _CL by turning on the clamp switch M5. At the same time, FIG.
As shown in (g), the vertical shift register V
When the signal ΦSH2 from the SR is set to the high level and the sample switch M11 is turned on, the noise signal when set to the reference voltage is transferred to the capacitor CH2. Next, the signal ΦSH2 is set to the low level for all the pixels at once, and the transfer and holding of the optical signal and the noise signal to the sample and hold circuit are completed.

Next, as shown in FIG. 11D, a signal .PHI.SEL2
To a high level for each row, and select switches M9 and M12
Is turned on, the load current source and the pixel amplifiers 3 and 4 (M1
(0, M13) is activated. Thereby, the hold capacities CH1, CH2
The optical signal and the noise signal held in the pixel amplifiers 3 and 4
At the same time to the noise signal output line and the optical signal output line.

The signals transferred to the noise signal output line and the optical signal output line are subtracted output amplifiers (not shown) connected to the noise signal output line and the optical signal output line.
Is performed. At this time, since the optical signal and the noise signal are taken into the sample hold circuit from the pixel amplifier 2 with a very fast time difference, 1 / f noise having a large value at a low frequency can be removed, and a high frequency component can be ignored. Further, there is no variation in the threshold value Vth due to the temperature difference between the output stage source followers in this time difference. The output charge stored in the hold capacitor is obtained from the output of one pixel amplifier at the time of both resetting and inputting the signal charge continuously in time. By taking the difference, the thermal noise, 1 / f noise,
FPN due to temperature difference and process variation can be removed.

As described above, the collective exposure of the photodiode PD is performed after the collective reset of the photodiode PD, and the optical signal and the noise signal are accumulated in the sample and hold circuit in the pixel, thereby exposing the next frame and exposing these signals. Reading can be performed independently. As a result, since exposure can be performed while performing high-speed reading, multi-pixel driving under a low irradiation dose as in a large-area X-ray imaging device, the accumulation time can be as long as possible even in high-speed operation, and the optical signal intensity can be increased. Furthermore, noise reduction can be performed to improve the signal-to-noise ratio (S / N).

On the other hand, in the still image mode, the same operation as described above is performed when the signal ΦSC is set to the high level and the capacitor C1 is connected in parallel with the photodiode PD. in this case,
Since the capacitor C1 has a capacity _almost ten times as large as the capacity _CFD , a wide dynamic range can be realized. Further, the kTC noise of the photoelectric conversion unit can be removed for each pixel by the clamp circuit. Further, by providing a sample-and-hold circuit for storing an optical signal and storing a noise signal in a pixel, it is possible to remove FPN caused by thermal noise, 1 / f noise, temperature difference, and process variation in the pixel amplifier. Accordingly, in the moving image mode, high-speed, high-sensitivity moving image shooting with no temporal or spatial connection can be realized with nine image sensors.
On the other hand, in the still image mode, high-sensitivity, high-dynamic-range still image shooting can be realized.

(Third Embodiment) FIG. 12 is a view similar to FIG.
FIG. 2 is a block diagram illustrating an overall configuration when an imaging device is configured using an imaging element including 0 pixels. In FIG. 12, an X-ray source 11 is attached to a subject (eg, a human chest) 110.
Radiation is irradiated from 1 and the radiation transmitted through the subject 110 enters the image sensor unit 112. The imaging element unit is configured by tiling the nine imaging elements of the first or second embodiment, further comprising a scintillator for converting X-rays into visible light, an X-ray shielding member, a peripheral driving circuit, and the like. The pixels of the image sensor have the configuration of the first or second embodiment. Further, a radiation imaging apparatus can be configured by combining scintillators.

The 4 × 8 system signals (signals output from the 9 image sensors via the 9 × 2 output lines) from the image sensor unit 112 are output from the signal A / D converter 113 and the FPN A
The analog signal is converted into a digital signal by the / D converter 114. The image sensor driving unit 115 is an image sensor unit 1
12 and is mounted adjacent to the T.12. The A / D-converted signal is sent to the image processing circuit 116, and the image processing circuit 116 and the memory 117 perform synthesis of image signals of the nine imaging devices, correction of defect noise, and the like. The processed signal is sent to the recording unit 118
Or displayed on a display unit (monitor) 119 and printed as necessary. The overall control of these circuits and devices is performed by the controller 120, and the controller 120 controls the timing of the X-ray source 111 and the image sensor.

The memory signals stored in the temporary storage memory 117 are subjected to image processing (γ processing, interpolation processing, etc.) for synthesizing each image sensor signal as one image (image processing circuit 116), and the output is It is stored in a large image memory, and the memory output is displayed on the display unit 119 and the like. The image processing ends when the photographing ends. The data captured by the imaging device is transferred to a personal computer or the like, where software processing or the like for analyzing the subject is performed.

Note that such an image processing method can be performed based on a program stored in a computer such as a personal computer. The present invention also includes an information recording medium such as a CDROM in which such a program is recorded. Then, by reading a program recorded in a CD ROM or the like, the image processing method according to the present invention can be executed.

(Fourth Embodiment) FIG. 13 is a diagram showing an example in which an X-ray imaging system is configured using the radiation imaging apparatus of the present invention. In FIG. 13, the X-ray tube 60
X-ray 6060 generated at 50 is a patient or subject 60
61 through the chest 6062, scintillator, FOP,
Radiation imaging apparatus 604 including an image sensor, an external processing substrate, and the like
Incident at 0. The incident X-ray contains information on the inside of the body of the patient 6061, and the scintillator emits light in response to the incidence of the X-ray, and this is photoelectrically converted by the imaging device, thereby obtaining electrical information. This information is converted into a digital signal, image-processed by an image processor 6070, and can be observed on a display 6080 in the control room.

This information can be transferred to a remote place by a transmission means such as a telephone line 6090, and can be displayed on a display 6081 such as a doctor's room at another place or stored in a storage means such as an optical disk. It is also possible for a doctor to make a diagnosis. Further, it can be recorded on a film 6110 by a film processor 6100.

[0092]

As described above, the present invention can provide the following effects. (1) Since the sample and hold circuits for the optical signal and the noise signal are provided in the pixel, the simultaneous exposure makes it possible to make the image pickup exposure time of the image pickup regions of the respective image pickup devices attached at the same time, thereby achieving noise correction. A circuit can be provided for each pixel, and high-speed high-speed moving image shooting can be performed. (2) Since a plurality of image pickup devices can be constituted by the same type of image pickup device, the steps up to the manufacture of the image pickup device unit can be simplified, and the production becomes easy, so that the cost can be reduced. (3) Since a plurality of image sensors can be driven by a common drive pulse, the number of peripheral drive circuits is small, and mounting is simple.
Further, low power consumption, low noise, and low cost can be achieved. (4) A radiation imaging device can be configured with a high-sensitivity imaging device, and the exposure dose can be adjusted appropriately by irradiating radiation exposure at the timing of batch exposure, so that the radiation exposure dose can be considerably reduced and a human-friendly device is realized. it can.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a pixel circuit of a first embodiment of an imaging device according to the present invention.

FIG. 2 is a diagram illustrating an entire circuit of the image sensor according to the embodiment of FIG. 1;

FIG. 3 is a timing chart for explaining an operation of the pixel circuit according to the embodiment of FIG. 1;

FIG. 4 is a diagram showing a layout of the image sensor of the embodiment of FIG. 1;

FIG. 5 is a sectional view taken along line AA of FIG.

FIG. 6 is a diagram illustrating an example in which one image sensor is manufactured from one piece of wear.

FIG. 7 is a diagram showing a state where unit blocks of the vertical shift register of the embodiment of FIG. 1 are arranged together with one pixel circuit in one area (cell).

FIG. 8 is a diagram showing a layout of one area (cell) including the shift register of the embodiment of FIG. 1;

FIG. 9 is a diagram showing a state in which pixels of the embodiment of FIG. 1 are arranged.

FIG. 10 is a circuit diagram showing a pixel circuit according to a second embodiment of the present invention.

FIG. 11 is a timing chart showing operation timings of the embodiment of FIG.

FIG. 12 is a block diagram illustrating an embodiment of the radiation imaging apparatus according to the present invention.

FIG. 13 is a diagram showing one embodiment of the radiation imaging system of the present invention.

FIG. 14 is a plan view showing a conventional imaging device.

FIG. 15 is a circuit diagram showing a pixel circuit of a conventional imaging device.

FIG. 16 is a diagram for explaining image composition of the imaging device in FIG. 14;

[Explanation of symbols]

M1 transfer switch M2 reset switch M3 selection switch M4 amplification MOS transistor M5 clamp switch M6 selection switch M7 amplification MOS transistor M8, M11 sample switch M9, M12 selection switch M10, M13 amplification transistor M14 mode switching switch PD photodiode CH1 optical signal hold Capacitance CH2 Noise signal hold capacitance _CPD Photodiode junction capacitance _CFD floating diffusion capacitance 100 Image sensor 101 Scintillator 102 FOP 103 External processing substrate 104 Flexible substrate 105 Base 110 Subject 111 X-ray source 112 Image sensor unit 113, 114 A / D converter 115 Image sensor driving circuit 116 Image processing circuit 117 Memory 118 Recording unit 11 9 Display unit 120 Controller 6040 Radiation imaging device 6050 X-ray tube 6060 X-ray 6070 Image processor 6081 Display 6090 Telephone line 6100 Film processor 6110 Film

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) H01L 27/146 H01L 31/00 A 31/09 27/14 A H04N 5/32 K (72) Inventor Noriyuki Kaibe Tokyo 3-30-2 Shimomaruko, Ota-ku F-term (reference) in Canon Inc. BX02 CX03 DX04 GX03 GY35 GZ01 HX02 JX00 5F088 AA01 AB05 BA03 BB07 EA04 JA14 JA17 KA08 KA10 LA07 LA08

Claims (18)

[Claims] 1. An image pickup device having a plurality of pixels arranged two-dimensionally, said pixels comprising: a photoelectric conversion unit for performing photoelectric conversion; and an optical signal storage unit for storing an optical signal generated by said photoelectric conversion unit. An image pickup apparatus comprising: a noise signal storage unit configured to store a noise signal. 2. The imaging device according to claim 1, further comprising a plurality of said imaging elements. 3. The image pickup device according to claim 2, wherein the optical signals of the pixels of the plurality of image sensors are respectively transferred to the corresponding optical signal storage means at a time, and the pixels of the plurality of image sensors are collectively transferred. An image pickup apparatus, comprising: means for collectively transferring noise signals to the corresponding noise signal storage means. 4. A photoelectric conversion unit that includes a plurality of image sensors having a plurality of pixels arranged two-dimensionally and performs photoelectric conversion for each pixel, and an optical signal storage that stores an optical signal generated by the photoelectric conversion unit. Means for transferring the optical signals of the pixels of the plurality of imaging elements to the optical signal storage means at once, and sequentially outputting the optical signals stored in the optical signal storage means for each pixel. And an output unit for outputting the image to the imaging device. 5. The imaging device according to claim 1, wherein the pixel is configured to amplify a signal from the photoelectric conversion unit and output the amplified signal, and an input of the amplification unit. An imaging apparatus comprising: reset means for resetting a unit; optical signal storage means for storing a signal from the amplification means; and noise signal storage means. 6. The imaging device according to claim 1, wherein the pixel amplifies a signal from the photoelectric conversion unit and outputs the amplified signal. Reset means for resetting an input section of the first amplifying means, signal clamping means for clamping a signal from the first amplifying means, and second amplifying means for amplifying and outputting a signal from the signal clamping means. An image pickup apparatus comprising: an optical signal storage unit for storing a signal from the second amplification unit; and a noise signal storage unit. 7. The imaging apparatus according to claim 1, wherein said optical signal storage means and said noise signal storage means have a sample hold circuit. 8. The imaging device according to claim 6, wherein the pixel further has a sensitivity switching unit connected to the photoelectric conversion unit. 9. The imaging device according to claim 8, wherein the sensitivity switching unit is disposed between the photoelectric conversion unit and the charge storage unit, the charge storage unit being connected in parallel to the photoelectric conversion unit. An imaging device comprising: a sensitivity changeover switch. 10. The imaging device according to claim 6, wherein the pixel amplifies a signal from the optical signal accumulating unit and outputs the amplified signal. An imaging device comprising: a fourth amplification unit that amplifies and outputs a noise signal from the noise signal accumulation unit. 11. The imaging apparatus according to claim 10, wherein the third amplification unit and the fourth amplification unit are arranged in a cross. 12. The method according to claim 1, wherein
13. The imaging device according to claim 1, wherein the optical signal storage unit and the noise signal storage unit are arranged in adjacent regions in a pixel. 13. The method according to claim 1, wherein
In the imaging device described in the paragraph, the amplification means is a P-type MO.
An imaging device comprising an S transistor. 14. The method according to claim 1, wherein
The imaging device according to claim 1, wherein the photoelectric conversion unit is of a completely depleted transfer type. 15. The method according to claim 1, wherein:
A radiation imaging apparatus comprising: the imaging apparatus according to any one of the preceding items, a scintillator, and an equal-magnification optical transmission unit. 16. The radiation imaging apparatus according to claim 15, wherein the equal-magnification optical transmission means is a fiber optic plate. 17. The radiation imaging apparatus according to claim 15, a signal processing unit that processes a signal from the radiation imaging apparatus, and a signal from the signal processing unit. Recording means for displaying, a display means for displaying a signal from the signal processing means, a transmission processing means for transmitting a signal from the signal processing means, and a radiation source for generating the radiation. A radiation imaging system, comprising: 18. An image pickup device having a plurality of pixels arranged in a two-dimensional manner, wherein each of the pixels has a photoelectric conversion unit for performing photoelectric conversion, and an optical signal storage for storing an optical signal generated by the photoelectric conversion unit. Means for simultaneously resetting the plurality of image sensors at the same timing, simultaneously exposing the plurality of image sensors at the same timing, and storing the exposed signals in the optical signal storage. A method of driving an imaging device, wherein the driving method is stored in a unit.