JP2006043293A - Radiation imaging apparatus and method of controlling the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radiation imaging apparatus capable of taking animated images highly sensitively while securing the high resolution at the time of simple radiography, and a method of controlling the same. <P>SOLUTION: Signals are read on the whole from a plurality of pixels while making the pitch of the pixels appropriate for a static image at the time of taking animated images, and the pixels are added. The frame rate can be increased while obtaining a high sensitivity by the reading and addition of pixels in this way. However, if the relation of the number of added pixels to the number of vertical scanning and to the number of horizonal scanning is not appropriately adjusted, the image quality and the effective area are reduced, and therefore, the number of vertical scanning and the number of horizontal scanning are integral numbers of times of the number of added pixels. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a radiation imaging apparatus suitable for use in medical diagnosis, industrial nondestructive inspection, and the like, and a control method thereof. In the present invention, electromagnetic waves such as X-rays and γ rays, α rays, and β rays are also included in the radiation.

  2. Description of the Related Art In recent years, digital X-ray imaging devices using a photoelectric conversion device that converts light into an electrical signal have been put into practical use due to advances in semiconductor technology.

  Digital X-ray imaging devices have better sensitivity and image quality than conventional film types, and digital X-ray imaging devices store images with digital data, so various image processing is performed after shooting Thus, there are advantages such that the image can be processed more easily and the image management is easy. In addition, taking advantage of these advantages, it is possible to perform imaging at a lower dose, new medical services such as remote diagnosis that transfers image data using a network, and more patient-friendly diagnosis.

  By using a digital X-ray imaging device having these advantages, it is possible to provide higher quality medical services compared to conventional X-ray imaging devices, such as improved diagnostic accuracy, more efficient diagnosis, and deployment to new medical services. .

  In such a digital X-ray imaging apparatus, a two-dimensional sensor in which pixels having photoelectric conversion elements and switching elements are arranged in an array is used. A TFT (Thin Film Transistor) is mainly used as the switching element, and a MIS (Metal Insulator Semiconductor) type photoelectric conversion element or a PIN type photoelectric conversion element is used as the photoelectric conversion element.

  These TFT, MIS type photoelectric conversion element and PIN type photoelectric conversion element are manufactured by an amorphous silicon process. The amorphous silicon process is used because active elements such as TFTs and photoelectric conversion elements can be formed uniformly over a large area. For example, Patent Document 1 (Japanese Patent Laid-Open No. 2003-78124), Patent Document 2 (Japanese Patent Laid-Open No. 9-293850) and Patent Document 3 (Japanese Patent Laid-Open No. No. 288184).

  In these inventions, X-rays transmitted through the human body are converted into electric signals by a phosphor that converts radiation into visible light and a MIS photoelectric conversion element that converts the converted visible light into electric signals.

  Further, in the digital X-ray imaging apparatus, in addition to still image shooting, moving image shooting such as fluoroscopic imaging and CT imaging can be performed by increasing the readout operation and increasing the sensitivity. Moving images can be taken with an image intifier (I / I) or an imaging device using a CCD and a reduction optical system, but with an X-ray imaging device using I / I or a CCD, as a still image, Since it is not possible to obtain an image that can withstand the diagnosis, if it is desired to take a still image during moving image shooting, shooting is performed using a device that switches to a film shooting device during moving image shooting. That is, a plurality of X-ray imaging apparatuses are necessary for each application. Therefore, such an X-ray imaging apparatus is not only large and expensive, but also has a delay until switching from I / I or CCD to film, so it cannot be said that it is easy to use.

  On the other hand, when it is possible to perform moving image shooting such as fluoroscopic imaging and still image shooting with a single digital X-ray imaging apparatus, it is possible to improve workability and save space. In other words, if a digital X-ray imaging device can shoot a moving image, a single device can shoot a still image and a moving image, and in the case of taking a still image during moving image shooting, the shooting can be performed very efficiently. Can do. In addition, the digital X-ray imaging apparatus is advantageous in that the image quality and field of view of moving images can be improved because image distortion is smaller and the field of view is superior compared to I / I and CCD. Furthermore, it is possible to perform various imaging such as fluoroscopy and tomographic imaging with a single device, and it is possible to improve the efficiency of the medical field. Therefore, the practical application of a moving image photographing digital X-ray imaging apparatus is desired.

  However, in order to realize a digital X-ray imaging apparatus from still image shooting (simple shooting) to moving image shooting (fluoroscopic imaging and CT imaging), resolution required for simple imaging and CT imaging and fluoroscopy are required. It must be compatible with the opposite characteristics of sensitivity required for shooting.

  In the digital X-ray imaging apparatus, the resolving power depends on the composition and thickness of the phosphor, the layer configuration between the phosphor and the photoelectric conversion element, and the pixel pitch. In particular, the pixel pitch is generally required to be about 100 to 200 μm in order to realize the resolving power required for simple photographing (still image).

  On the other hand, in fluoroscopic imaging, CT imaging, and the like, it is desirable that the sensitivity of the digital X-ray imaging apparatus and the frame rate of moving images be high. In fluoroscopic imaging and CT imaging, X-ray irradiation per unit time is limited to about 1/10 to 1/100 of simple imaging because the patient has to be irradiated with X-rays for a long time. Therefore, since the X-ray dose reaching the imaging device is 1/10 to 1/100 that of simple imaging, in order to realize a signal-to-noise ratio (S / N ratio) necessary for diagnosis in fluoroscopic imaging and CT imaging. It is desired that the photoelectric conversion element has high sensitivity. On the other hand, the resolution does not need to be as fine as simple shooting. In particular, in CT imaging, since a computer performs an operation on image data and converts it into a tomographic image of a human body, a resolution of 100 μm to 200 μm is not required. In fluoroscopic imaging, the necessary resolution varies depending on the part to be imaged and the imaging purpose, but high resolution is not required for imaging such as a preview for still image shooting.

  In general, in order to improve the sensitivity of an optical sensor using a photoelectric conversion element, it is a simple method to increase the pixel (increase the pixel pitch). However, enlarging the pixels leads to a decrease in resolving power, making it impossible to obtain the resolution required for simple shooting.

JP 2003-78124 A Japanese Patent Laid-Open No. 9-293850 JP-A-9-288184

  SUMMARY OF THE INVENTION An object of the present invention is to provide a radiation imaging apparatus and a control method therefor capable of capturing a moving image with high sensitivity while ensuring high resolution during simple imaging.

  In a digital X-ray imaging device with a pixel pitch suitable for simple imaging, when CT imaging or fluoroscopy imaging is performed, readout is performed from a plurality of pixels, and pixel addition is performed to add pixel outputs, which is apparently large. It can be treated as a pixel.

By using this method, it is possible to solve the trade-off between the resolution required for simple imaging and the sensitivity required for CT imaging or fluoroscopic imaging. At this time, the sensitivity improved by pixel addition is approximately n ^1/2 times the sensitivity when no pixel addition is performed (n is the number of pixel additions). By such pixel addition, a large sensitivity can be obtained during fluoroscopic imaging or CT imaging, and a necessary resolution can be obtained by reading out in units of pixels during simple imaging. Further, by performing reading together during fluoroscopic imaging and CT imaging, the time until reading from all the pixels in the sensor can be shortened, and the frame rate can be improved.

  However, when pixel addition is performed by the digital X-ray imaging apparatus, there is a problem that the number of pixel addition may be limited depending on the number of horizontal scanning and vertical scanning of the two-dimensional sensor. That is, when the number of vertical scans × the number of horizontal scans is not divisible by the required number of added pixels, lines or remainder lines less than the desired number of added pixels are generated. For example, when 15 pixel addition is performed using a two-dimensional sensor with 2800 × 2800 vertical scans × horizontal scans, 15 pixels are not added at the end of scanning, and a line or a surplus line less than 15 pixels is generated. To do.

  In such a case, if pixel addition is performed for only the surplus line, the signal-noise ratio is different at the portion where the number of pixel additions is different, so that a discontinuous portion of the shadow is generated in the image as it is. And this part is difficult to correct because the signal-to-noise ratio is different.

  On the other hand, when the extra line is not used as an image, the field of view is narrowed by the extra line. For this reason, the field of view differs between a still image and a moving image, and usability is reduced.

  As described above, the number of pixel additions in which a surplus line is generated is not desirable in terms of image quality and usability, and it is preferable to set the number of rows and the number of columns of the two-dimensional sensor so that the restriction on the number of pixel additions does not occur. And in order to implement | achieve this, what is necessary is just to set the number of rows and the number of columns of a two-dimensional sensor so that it may become the integral multiple of the pixel addition number in the pixel addition to perform.

  In addition, in order to enable a wider variety of pixel addition numbers and to cope with various moving image applications and shooting situations, the value of the vertical scanning number × horizontal scanning number of the two-dimensional sensor is set to a common multiple of the necessary pixel addition number. Is desirable. Furthermore, if the number of rows and columns of the two-dimensional sensor is set to a multiple of a large number such as 12, the number of pixel addition numbers can be increased.

  The inventors of the present application have come up with the following aspects of the invention based on these new findings.

  A radiation imaging apparatus according to the present invention includes a photoelectric conversion unit in which a plurality of pixels including photoelectric conversion elements are arranged in an array on a substrate, and a reading unit that simultaneously reads signals from two or more pixels included in the plurality of pixels. And adding means for electrically adding the simultaneously read signals, and the number of pixels from which the reading means simultaneously read signals is a fixed number, and is disposed in the photoelectric conversion means. The number of rows and columns of the pixels is an integral multiple of the predetermined number.

  A radiation imaging system according to the present invention includes the above-described radiation imaging apparatus and radiation generation means for generating radiation via a subject toward the photoelectric conversion means.

  A method for controlling a radiation imaging apparatus according to the present invention is a method for controlling an operation of a radiation imaging apparatus having photoelectric conversion means in which a plurality of pixels including photoelectric conversion elements are arranged in an array on a substrate. A readout step of simultaneously reading out signals from two or more pixels included in the pixel and an addition step of electrically adding the signals read out simultaneously, and the signals are simultaneously read out in the readout step The number of pixels is a fixed number included in the divisor of the number of rows and columns of the pixels arranged in the photoelectric conversion means.

  A program according to the present invention is a program for causing a computer to perform an operation of a radiation imaging apparatus having photoelectric conversion means in which a plurality of pixels including photoelectric conversion elements are arranged in an array on a substrate. A target for reading out signals simultaneously in the readout procedure by executing a readout procedure for simultaneously reading signals from two or more pixels included in the plurality of pixels and an addition procedure for electrically adding the simultaneously read signals. The number of pixels is a constant number included in the divisor of the number of rows and the number of columns of the pixels arranged in the photoelectric conversion means.

  According to the present invention, it is possible to perform moving image shooting with high sensitivity while ensuring high resolution during simple shooting. That is, when performing pixel addition at the time of moving image shooting, the number of columns and rows of pixels are appropriately defined, so that shooting with high sensitivity can be performed. Accordingly, since it is not necessary to increase the size of the pixel, the resolution at the time of simple photographing is not reduced. In addition, a high frame rate can be obtained during moving image shooting.

  Furthermore, when the number of pixels and the number of columns are adjusted to enable a plurality of types of pixel additions, it is possible to select an appropriate number of pixel additions according to the part and application. Therefore, since various imaging | photography is possible using one radiation imaging device, efficiency improvement of a medical field is attained.

  Further, even if compared with a conventional digital X-ray imaging device for simple imaging, no special device or technology such as an IC is required, so that an increase in cost can be suppressed. Therefore, if it is cheaper than moving image capturing apparatuses such as conventional CT imaging apparatuses and fluoroscopic imaging apparatuses, it becomes easier to introduce the radiation imaging apparatus according to the present invention to the medical field, and dramatically improve medical services. Is planned.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings.

(First embodiment)
First, a first embodiment of the present invention will be described. FIG. 1 is a schematic diagram showing the structure of a digital X-ray imaging apparatus.

In the digital X-ray imaging apparatus, the X-ray 120 emitted from the X-ray source 119 and transmitted through the human body 121 is converted into visible light 102 by the phosphor 101, and the visible light 102 is further formed on a glass substrate using an amorphous silicon process. The two-dimensional sensor 103 formed in this way is converted into an electrical signal. The composition of the phosphor 101 is not particularly limited. For example, a phosphor containing Gd ₂ O ₂ S, Gd ₂ O ₃ or CsI as a main component can be used.

  The two-dimensional sensor 103 is a switching circuit driven by a photoelectric conversion element (see FIG. 2) that converts and accumulates visible light 102 carrying information on the human body 121 emitted from the phosphor 101 into an electrical signal, and a vertical drive circuit 105. Pixels composed of elements (see FIG. 2) are two-dimensionally arranged. The electric signal output from the switching element is amplified by a signal amplifier circuit (see FIG. 2) included in the readout circuit 104, and then sent to the control board 124 via the relay board 123. The A / D converter 106 Converted to digital signal.

  The control board 124 further includes a control computer 108 that sends a control signal for driving the two-dimensional sensor 103 to the readout circuit 104 and the vertical drive circuit 105, and the two-dimensional sensor 103, the vertical drive circuit 105, and a signal amplification circuit. A regulator 107 that generates a necessary voltage is provided. The regulator 107 is supplied with a power supply voltage from the power supply 114. An FPD (flat panel detector) 112 is configured by the phosphor 101, the two-dimensional sensor 103, the control board 124, and the like.

  The image data converted into a digital signal by the A / D converter 106 is sent to the image processing device 109, processed into an image suitable for diagnosis, and then displayed on the monitor 118. The image can also be output to the printer 116 by an operator's operation.

  Further, the image data is appropriately stored in a recording device 122 in the control PC (personal computer) 111, an external recording device 117, or a recording device on the hospital network 126.

  Such control of the X-ray imaging apparatus is all performed by the control PC 111, and synchronization with the X-ray source 119, image storage, image printing, connection to a hospital network, and operation indicator lamp 125 on / off. Etc. can also be performed by the control PC 111. The control PC 111 can communicate with the X-ray control console 115 using the internal program / control board 110 to control X-rays.

  The control console 113 is used when inputting patient ID registration, imaging part information input, X-ray source setting, image processing method of the captured image, and the like, and transmits the information to the control PC 111.

  FIG. 2 is a block diagram illustrating an imaging unit of the digital X-ray imaging apparatus according to the first embodiment of the present invention. The imaging unit includes a two-dimensional sensor 103 in which pixels using a TFT as a signal transfer unit and a MIS type photoelectric conversion element (to be described later) as a photoelectric conversion unit are two-dimensionally arranged, and a vertical drive that controls ON / OFF of the TFT. The circuit 105, the signal amplification circuit 201 that amplifies the electric signal output from the TFT, the sample hold circuit 203 that holds the signal until the signal from the signal amplification circuit 201 is transferred, and the electric signal held in the sample hold circuit 203 A time-series multiplexer circuit 204, an A / D converter 106 that converts an analog signal output from the multiplexer circuit 204 into a digital signal, a sensor power supply 205 that supplies a voltage necessary for photoelectric conversion to the photoelectric conversion element, and a TFT. Power supply (Vcom) 207 for turning on and TFT for turning off Source (Vss) 208 is provided. The signal amplification circuit 201 is provided with an amplifier 202 and the like. Although not shown in FIG. 2, as described above, the phosphor 101 is provided on the X-ray incident side of the imaging unit as a wavelength converter that converts radiation into visible light. A protective sheet for protecting 101 from humidity and external impact is attached.

  The sensor power supply 205 that supplies a voltage necessary for photoelectric conversion is, for example, disclosed in Japanese Patent Laid-Open No. 9-288184. Since the MIS type photoelectric conversion element requires refresh, And a voltage source for photoelectric conversion voltage.

  In the present embodiment, the imaging unit shares the signal line with the upper and lower pixels and shares the gate line with the left and right pixels. Further, the sensor bias line is shared by all pixels. Further, the two image pickup units are substantially combined in the vertical direction, and can be driven independently in the vertical direction. Furthermore, the vertical drive circuit 105 does not need to be at both ends of the gate line, and may be provided on only one side if the wiring resistance of the gate line is sufficiently small.

  FIG. 3 is a cross-sectional view showing the structure of the pixel in this embodiment. In the present embodiment, the pixel uses a TFT 319 as a signal transfer unit and a MIS photoelectric conversion element 320 as a photoelectric conversion element.

The TFT 319 includes at least a gate electrode 302 formed using aluminum or an aluminum alloy on an insulating substrate 301 such as glass, and an amorphous nitride film that is an insulating semiconductor thin film formed on the gate electrode 302. An insulating layer 303, a channel layer 304 made of hydrogenated amorphous silicon (a-Si: H), a source electrode 306 and a drain electrode 307 formed using aluminum or an aluminum alloy, and a channel layer 304 and a drain electrode 307. And an N ⁺ amorphous silicon layer 305 having negative conductivity that makes ohmic contact between the channel layer 304 and the source electrode 306.

On the other hand, the MIS photoelectric conversion element 320 includes a sensor lower electrode layer 309 formed using aluminum or an aluminum alloy on the same substrate 301 substrate as the TFT 319, and an insulating semiconductor formed on the sensor lower electrode layer 309. An insulating layer 310 made of an amorphous nitride film that is a thin film, a photoelectric conversion layer 311 formed using a-Si: H that absorbs visible light and generates charges, and holes from the sensor bias line 314 to the photoelectric conversion layer 311 An N ⁺ amorphous silicon layer 312 having a negative conductivity that prevents injection of silicon, a transparent electrode 313 formed using ITO or the like that functions as an electrode when a voltage necessary for photoelectric conversion is applied to the photoelectric conversion element, and A sensor bias line 314 formed using aluminum or an aluminum alloy for supplying a voltage from the sensor power supply. It has been kicked. Further, a protective layer 315, an adhesive layer 316, a phosphor layer 101, a phosphor protective layer 318, and the like are provided above them.

  As described above, in this embodiment, the layer configurations of the TFT 319 and the MIS type photoelectric conversion element 320 are almost the same, so forming them in parallel simplifies the process, improves the yield, and increases the sensor manufacturing cost. Can be reduced. However, the TFT 319 and the sensor may be formed separately. In this case, the manufacturing process is more complicated than the case of forming in parallel, but it becomes easy to set each film thickness to the one suitable for the purpose. Obtainable.

  Note that the size of one pixel is preferably adjusted so as to satisfy the sensitivity and resolution in simple photographing. Moreover, it is preferable to select a manufacturing method and manufacturing conditions for the MIS photoelectric conversion element 320 and the TFT 319 that are suitable in view of yield and performance. Further, the thickness of each thin film is preferably selected so that desired characteristics and yield can be obtained.

  In the present embodiment, the above-described circuit configuration is used to configure an imaging unit having a horizontal scanning number (pixel column number) of 2880 and a vertical scanning number (pixel row number) of 2880. Since the value 2880 is a divisor such as 2, 4, 5, 6, 10, 12, 16, 18, 20, 24... There is an advantage that there are many variations. The greater the variation in the number of added pixels, the more the digital X-ray imaging apparatus can be used for various imaging applications. The number of scans and the number of pixels are not limited to those described above, but it is preferable that the number of divisors is large.

  Next, the pixel addition operation will be described. FIG. 4 is a block diagram showing a configuration of the vertical drive circuit 105. The vertical drive circuit 105 is provided with a shift register 402 that is a sequential logic circuit and a gate output circuit 401 that determines a voltage supplied to the gate line of the TFT.

  The gate output circuit 401 includes a voltage (Vcom) for turning on the TFT, a voltage (Vss) for turning off the TFT, a control signal OE for switching the voltage output to the gate line, and outputs Q1 to Q1 of the shift register 402. Qn is input. The outputs Q1 to Qn of the shift register correspond to the control of the gate lines g1 to gn on a one-to-one basis. The gate output circuit 401 outputs the Vcom voltage when the output Q of the shift register 402 is Hi and the control signal OE is Hi, and outputs the Vss voltage in other states.

  Shift data DIO and vertical shift clock CPV are input to the shift register 402, and the ON / OFF timing of the TFT can be controlled by these two signals.

  Here, the operation of the vertical drive circuit 105 will be described with reference to FIG. For convenience, the description will be made assuming that the components (each stage) of the shift register 402 are D flip-flops. However, the components of the shift register 402 are not limited to D flip-flops, and other flip-flops (for example, JK flip-flops). Or the like).

  First, as shown in FIG. 5, signals OE, CPV and DIO are given. When the first CPV clock rises, the output Q1 of the shift register 402 becomes Hi. Furthermore, since the signal DIO is Hi when the next CPV clock rises, the output Q1 remains Hi. At this time, since the output Q1 of Hi is input to the stage that outputs the output Q2, the output Q2 also becomes Hi.

  When the control signal OE becomes Hi in this state, the Vcom voltage is supplied from the gate output circuit 401 to the gate lines g1 and g2 (arrow a).

  Next, after the control signal OE is set to Lo, when the CPV clock is input while the signal DIO is Lo, the output Q1 becomes Lo. At this time, the output Q3 becomes Hi because the output Q2 is Hi. Similarly, when the CPV clock is input, the output Q2 becomes Lo and the output Q4 becomes Hi because the output Q3 is Hi.

  When the control signal OE becomes Hi in this state, the Vcom voltage is supplied from the gate output circuit 401 to the gate lines g3 and g4 (arrow b).

  The timing of switching the voltage supplied to the gate line can be controlled by the timing as described above.

  In FIG. 5, the area between the arrows C corresponds to two-line simultaneous reading in the two-dimensional sensor. That is, FIG. 5 shows the driving of the vertical driving circuit 105 in the two-pixel addition. Therefore, when pixel addition is performed, first, CPV clocks corresponding to the number of pixel additions are input while the signal DIO is Hi, and the control signal OE is set to Hi. After that, by keeping the signal DIO at Lo and inputting the CPV clocks corresponding to the number of pixel additions between the two consecutive control signals OE, the Vcom voltage is sequentially supplied to the gate lines at the same time. The TFTs can be turned on simultaneously.

  As an example, FIG. 6 shows drive timings when 8-pixel addition reading is performed. When reading an electrical signal carrying human body information accumulated in the photoelectric conversion element, first, in order to initialize the potential of the signal amplifier circuit 201 and the signal line connected thereto, the signal RC is set to Hi, The capacitor attached to the amplifier 202 in the amplifier circuit 201 is reset, and the output of the signal amplifier circuit 201 and the potential of the signal line are reset. This reset operation eliminates signals unrelated to human body information, reduces noise, and improves image quality.

  During the reset operation period of the amplifier 202, desired pulses are given as the control signals CPV and DIO to operate the shift register 402. Then, necessary pulses are supplied to the control signals DIO and CPV, and after a sufficient reset operation, the control signal OE is set to Hi to turn on the TFT.

  In FIG. 6, since the signal CPV is input for 8 clocks while the signal DIO is Hi, the 8-line TFTs are turned on all at once, and signals of 8 pixels are simultaneously transmitted per signal line. All of these signals are added and accumulated in a capacitor associated with the amplifier 202 of the signal amplification circuit 201, and the sum from the refresh is obtained. The output of the amplifier 202 at this time is held by the sample hold circuit 203 by setting the control signal SH to Hi.

  The signal held in the sample hold circuit 203 is read out in time series by the multiplexer circuit 204 and sent to the A / D converter 106 when the next line is read out. In order to read out all the pixels in the imaging unit, the operation in the section B shown in FIG. 6 may be repeated.

  The digital X-ray imaging apparatus according to the present embodiment can perform readout for each pixel in addition to pixel addition readout. In this case, as shown in FIG. 7, the driving is performed at such a timing that one pulse of CPV is input while the signal DIO is Hi.

  In this way, it is possible to switch whether or not to add pixels by switching the drive timing. That is, in moving image shooting such as CT shooting or fluoroscopic shooting, pixel addition is performed to improve sensitivity, and when simple shooting (still image shooting) becomes necessary, the timing is immediately switched and pixels are read out one by one. It can be switched to driving. Therefore, according to the present embodiment, it is possible to perform high-sensitivity moving image shooting and high-definition still image shooting with a single device.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. The second embodiment is different from the first embodiment mainly on the structure and operation of the multiplexer circuit. FIG. 8 is a block diagram showing a multiplexer circuit, a signal amplifier circuit, and a sample hold circuit of a digital X-ray imaging apparatus according to the second embodiment of the present invention.

  A signal amplifier circuit 801 in FIG. 8 corresponds to the signal amplifier circuit 201 in FIG. 2, and its circuit configuration is the same as that of the signal amplifier circuit 201. A sample hold circuit 802 in FIG. 8 corresponds to the sample hold circuit 203 in FIG. 2, and its circuit configuration is the same as that of the sample hold circuit 203.

Here, the structure and operation of the multiplexer circuit 803 will be described. The sample and hold circuit 802 is provided with a sample and hold capacitor C _SH that holds the signal of the signal amplification circuit 801, and a switch SW1 for taking out a signal from the sample and hold capacitors C _{SH1 to} C _SHn in the multiplexer circuit 803. To SWn. The switches SW1 to _SWn are connected to sample and hold capacitors C _{SH1 to} C _SHn , respectively. The outputs of the switches SW1 to SWn are commonly connected to the buffer amplifier BAmp. The capacitors associated with the buffer amplifier BAmp and the sample hold capacitors C _{SH1 to} C _SHn are set to have the same capacitance, and the voltage held in one sample hold capacitor C _SH is inverted by the buffer amplifier BAmp, etc. The output is doubled. Further, the multiplexer circuit 803 is provided with a register unit 804 that outputs control signals MUX1 to MUXn for controlling the switches SW1 to SWn. That is, ON (conducting) / OFF (non-conducting) control of the switches SW1 to SWn is performed by the control signals MUX1 to MUXn output from the register unit 804. For example, two pixels can be added by simultaneously turning on two switches SW.

  FIG. 9 is a diagram illustrating the circuit configuration and operation of the register unit 804. As shown in FIG. 9A, the register 804 is provided with, for example, a shift register 901 having the same number (n) of D flip-flops as the number of signal lines and n AND circuits. To the register unit 804, a signal CLK that is a shift signal, a signal IO that is a shift clock, and a signal MUX_OE that controls ON / OFF of the output of the control signal MUX are input as control signals.

  FIG. 9B shows the operation when performing two-pixel addition. As shown in FIG. 9B, when the signals IO and CLK are input, the output Q1 of the shift register 901 becomes Hi (arrow a1), and when the CLK pulse is input while the output Q1 is Hi, the output is output. Q2 becomes Hi. In this state, when the signal MUX_OE becomes Hi, the control signals MUX1 and MUX2 become Hi. Further, when two pulses of CLK are input, the output Q1 becomes Lo and the output Q2 becomes Lo, while the outputs Q3 and Q4 become Hi.

By repeating such an operation, the switches SW1 to SWn can be turned ON / OFF for each two lines. At this time, switch between the amplifier Amp1~Ampn and the sample hold capacitor C _SH in the signal amplifying circuit 801 is off.

FIG. 10 is a timing chart showing an operation when the charge held in the sample hold circuit 802 is read by adding two pixels. First, reset the output and the associated capacitor charge of the buffer amplifier BAMP, to a state suitable for reading out the charge held in the sample hold capacitor C _SH, and the control signal RC2 to Hi, the buffer amplifier BAMP The switch associated with is turned on.

Then, after resetting the buffer amplifier BAmp, the control signal RC2 is set to Lo to turn off the switch. Next, as described above, two pulses of CLK are input while the control signal IO remains Hi, so that two pixels can be added. In this state, signal when MUX_OE Hi signal as a control signal MUX1 and MUX2 to the Hi is output, the switch SW1 and SW2 are turned, the sample hold capacitor C _SH1 and voltage buffer amplifier held in C _SH2 Input to BAmp. As a result, the sum of the voltages held in the sample hold capacitors C _SH1 and C _SH2 is inverted and output as the output of the buffer amplifier BAmp. In order to read all the signals held in the sample hold circuit 802, the operation in the section B shown in FIG. 10 may be repeated.

  Thus, in this embodiment, since the circuit configuration is such that pixel addition can be performed in the multiplexer circuit 803, pixel addition in the horizontal direction can be performed.

  Note that an amplifier and / or a filter circuit for noise removal may be provided between the signal amplifier circuit 801 and the sample hold circuit 802 as necessary.

Further, the multiplexer circuit 803 may be provided with a plurality of buffer amplifiers BAmp so as to share the reading from the sample hold capacitors C _{SH1 to} C _SHn . In this case, for example, a configuration as shown in FIG. 11 can be adopted. However, when such a configuration is adopted, since the outputs of the buffer amplifiers BAmp are shared, it is necessary to set the pattern of the signal MUX_OE so that the outputs do not overlap. The number of the sample-hold capacitor C _SH allotted to one buffer amplifier BAmp is maximum pixel number addition. For example, in the 2880 × 2880 line two-dimensional sensor shown in FIG. 2, when the maximum number of added pixels is 120 pixels, the number of sample and hold capacitors C _SH handled by one buffer amplifier BAmp needs to be 120. In addition, the required number of buffer amplifiers, sample and hold circuits, and signal amplifier circuits are 24 sets.

  In any of the first and second embodiments, it is preferable to use a signal amplifier circuit, a sample hold circuit, and a multiplexer circuit manufactured by a semiconductor IC process using crystalline silicon. In general, in an IC process, the smaller the IC chip, the lower the manufacturing cost. Therefore, if one IC is used to read all the lines of the two-dimensional sensor, the chip size increases, which is not preferable in manufacturing. Therefore, it is practical to mount a plurality of IC chips each including a signal amplification circuit, a sample hold circuit, and a multiplexer circuit in a two-dimensional sensor. In this case, as described above, the number of lines handled by one IC chip needs to be larger than the maximum number of pixel additions and an integral multiple of the number of pixel additions.

  Further, the photoelectric conversion element of the two-dimensional sensor is not limited to the MIS type photoelectric conversion element, and for example, a PIN type photoelectric conversion element can also be used. FIG. 12 is a cross-sectional view illustrating the structure of a pixel using a PIN photoelectric conversion element.

In the example shown in FIG. 12, a gate electrode 1202 made of chromium, aluminum, or an aluminum alloy, an insulating film 1203 made of an amorphous silicon nitride film, and hydrogenated amorphous silicon (a-Si: H) are used for the TFT 1219 on a glass substrate 1201. Channel layer 1204 formed using a metal such as aluminum or an aluminum alloy, and negative conductivity having an ohmic contact between the channel layer 1204 and the metal electrode. An N ⁺ amorphous silicon layer 1205 is provided.

On the other hand, in the PIN photoelectric conversion element 1220, the sensor lower electrode layer 1209 formed using aluminum or an aluminum alloy on the glass substrate 1201 and the injection of holes from the sensor lower electrode layer 1209 to the photoelectric conversion layer 1211 are blocked. N ⁺ amorphous silicon layer 1210 having negative conductivity, photoelectric conversion layer 1211 made of hydrogenated amorphous silicon that converts visible light emitted from the phosphor into an electric signal, photoelectric conversion layer 1211 from sensor bias line 1214 and transparent electrode 1213 P ⁺ amorphous silicon layer 1212 having positive conductivity for preventing injection of electrons into the electrode, sensor bias line 1214 made of aluminum or aluminum alloy for supplying voltage, and a transparent electrode material such as ITO A transparent electrode 1213 is provided. Further, a protective layer 1215, an adhesive layer 1216, a phosphor layer 1217, a phosphor protective layer 1218, and the like are provided above them.

  The digital X-ray imaging apparatus according to the present invention can also be applied to, for example, an X-ray diagnostic system. FIG. 13 is a schematic diagram showing an X-ray diagnostic system to which the present invention is applied.

  In the X-ray room (imaging room), the X-ray 6060 generated by the X-ray tube (X-ray generator) 6050 passes through the chest 6062 of the patient or subject 6061 and enters the image sensor 6040. This incident X-ray includes information inside the patient 6061. The scintillator (phosphor) emits light in response to the incidence of X-rays, and this is photoelectrically converted by the photoelectric conversion element of the sensor panel to obtain electrical information. The image sensor 6040 outputs this information to the image processor 6070 as an electrical signal (digital signal). An image processor 6070 serving as an image processing unit performs image processing on the received signal and outputs the processed signal to a display 6080 serving as a display unit in a control room (operation room). The user can obtain information inside the patient 6061 by observing the image displayed on the display 6080. Note that the image processor 6070 also has a function of a control unit, and can switch a shooting mode of a moving image / still image or control the X-ray tube 6050.

  Further, the image processor 6070 transfers the electric signal output from the image sensor 6040 to a remote place via a transmission processing unit such as a telephone line 6090, and displays it on a display unit (display) 6081 in another place such as a doctor room. It can also be displayed. It is also possible to store the electrical signal output from the image sensor 6040 in a recording means such as an optical disk and make a diagnosis by a remote doctor using this recording means. Moreover, it can also record on the film 6110 by the film processor 6100 used as a recording means.

  The embodiment of the present invention can be realized by, for example, a computer executing a program. Also, means for supplying a program to a computer, for example, a computer-readable recording medium such as a CD-ROM recording such a program, or a transmission medium such as the Internet for transmitting such a program is also applied as an embodiment of the present invention. Can do. The above program can also be applied as an embodiment of the present invention. The above program, recording medium, transmission medium, and program product are included in the scope of the present invention.

It is a schematic diagram which shows the structure of a digital X-ray imaging device. It is a block diagram which shows the imaging part of the digital X-ray imaging device which concerns on the 1st Embodiment of this invention. It is sectional drawing which shows the structure of the pixel in 1st Embodiment. 2 is a block diagram showing a configuration of a vertical drive circuit 105. FIG. 3 is a timing chart showing the operation of the vertical drive circuit 105. It is a timing chart which shows the drive timing in the case of performing 8 pixel addition reading. It is a timing chart which shows the operation | movement which reads out one pixel at a time. It is a block diagram which shows the multiplexer circuit of the digital X-ray imaging device which concerns on the 2nd Embodiment of this invention, a signal amplifier circuit, and a sample hold circuit. 6 is a diagram showing a circuit configuration and operation of a register unit 804. FIG. 10 is a timing chart showing an operation in the case where the charge held in the sample hold circuit 802 is read by adding two pixels. 5 is a block diagram showing a configuration in which a plurality of buffer amplifiers BAmp are provided in a multiplexer circuit 803. FIG. It is sectional drawing which shows the structure of the pixel using a PIN type photoelectric conversion element. It is a schematic diagram which shows the X-ray diagnostic system to which this invention is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101: Phosphor 102: Visible light 103: Two-dimensional sensor 104: Reading circuit 105: Vertical drive circuit 106: A / D converter 107: Regulator 108: Computer for control 119: X-ray source 120: X-ray 201, 801: Signal Processing circuit 202: Amplifier 203, 802: Sample hold circuit 204, 803: Multiplexer circuit 6040: Image sensor 6050: X-ray tube 6060: X-ray 6061: Subject 6070: Image processor 6080: Display 6081: Display 6100: Film processor 6110: the film

Claims (12)

Photoelectric conversion means in which a plurality of pixels including photoelectric conversion elements are arranged in an array on a substrate;
Reading means for simultaneously reading signals from two or more pixels included in the plurality of pixels;
Adding means for electrically adding the simultaneously read signals;
Have
The number of pixels to be read simultaneously by the reading means is a fixed number,
A radiation imaging apparatus, wherein the number of rows and columns of pixels arranged in the photoelectric conversion means is an integral multiple of the predetermined number.   2. The radiographic imaging according to claim 1, wherein the two or more pixels for which the reading unit simultaneously reads signals are arranged in at least one of the vertical scanning direction and the horizontal scanning direction. apparatus.   3. The radiation imaging apparatus according to claim 1, wherein at least one of the number of rows and the number of columns is a multiple of 12. 4.   The radiation imaging apparatus according to any one of claims 1 to 3, further comprising a wavelength converter that converts a wavelength of the irradiated radiation. 5. The radiation imaging apparatus according to claim 4, wherein the wavelength converter includes, as a main component, one type selected from the group consisting of Gd ₂ O ₂ S, Gd ₂ O _3, and CsI. The photoelectric conversion element is
A metal thin film layer formed on the substrate;
An insulating layer formed on the metal thin film layer and blocking passage of electrons and holes;
A photoelectric conversion layer formed on the insulating layer;
An N-type injection blocking layer formed on the photoelectric conversion layer and blocking the passage of holes;
A conductive layer formed on the injection blocking layer;
The radiation imaging apparatus according to claim 1, wherein the radiation imaging apparatus is a MIS type photoelectric conversion element having the following characteristics. The photoelectric conversion element is
A metal thin film layer formed on the substrate;
An N-type semiconductor layer formed on the metal thin film layer and blocking the passage of holes;
A photoelectric conversion layer formed on the N-type semiconductor layer;
A P-type semiconductor layer formed on the photoelectric conversion layer and blocking the passage of electrons;
A conductive layer formed on the P-type semiconductor layer;
6. The radiation imaging apparatus according to claim 1, wherein the radiation imaging apparatus is a PIN photoelectric conversion element including   The photoelectric conversion element contains one kind of compound selected from the group consisting of amorphous selenium, gallium arsenide, lead iodide, mercury iodide, and cadmium telluride. The radiation imaging apparatus according to item 1.   The radiation imaging apparatus according to claim 1, wherein the pixel includes a thin film transistor as a switching element connected to the photoelectric conversion element. The radiation imaging apparatus according to any one of claims 1 to 9,
Radiation generating means for generating radiation through the subject toward the photoelectric conversion means;
A radiation imaging system comprising: A method for controlling the operation of a radiation imaging apparatus having photoelectric conversion means in which a plurality of pixels including photoelectric conversion elements are arranged in an array on a substrate,
A readout step of simultaneously reading signals from two or more pixels included in the plurality of pixels;
An adding step of electrically adding the simultaneously read signals;
Have
The number of pixels for which signals are simultaneously read in the reading step is a fixed number included in the divisor of the number of rows and the number of columns of the pixels arranged in the photoelectric conversion means. Control method of imaging apparatus. A program for causing a computer to perform an operation of a radiation imaging apparatus having photoelectric conversion means in which a plurality of pixels including photoelectric conversion elements are arranged in an array on a substrate,
On the computer,
A readout procedure for simultaneously reading signals from two or more pixels included in the plurality of pixels;
An addition procedure for electrically adding the simultaneously read signals;
And execute
The number of pixels for which signals are simultaneously read in the reading procedure is a fixed number included in the divisor of the number of rows and the number of columns of the pixels arranged in the photoelectric conversion means. .

Images