IMAGING DEVICE, IMAGING SYSTEM, METHOD FOR CONTROLLING THE DEVICE AND THE SYSTEM, AND PROGRAM

Abstract

Imaging system with: an imaging device (100) having a detector in which a plurality of image elements, each comprising a conversion element (201, 601) configured to convert radiation or light into an electric charge, are arranged in a matrix form, and which is configured to perform an image pickup operation to output image data corresponding to emitted radiation or emitted light, and a control unit (106) configured to control operations including the image pickup operation of the detector; and a control computer (108) configured to control the imaging device, wherein the image capturing operation comprises a first image capturing operation and a second image capturing operation, wherein the first image capturing operation comprises a first accumulation operation in which the conversion element is configured to generate the electrical charge for a first accumulation time, and a first output operation in which the detector is configured to scan in a first scanning area corresponding to a portion of the plurality of image elements to output image data in the first scanning area, wherein the second image capturing operation comprises a second accumulation operation in which the conversion element is configured to generate the electrical charge for a second accumulation time, and a second output operation in which the detector is configured to scan in a second scanning area that is larger than the first scanning area to output image data in the second scanning area, characterized in that the control computer (108), when a change from the first scanning area to the second scanning area is instructed, is configured to perform arithmetic processing for determining the second accumulation time of the second accumulation operation based on information about a total amount of the first accumulation times in the first image pickup operation before a change of the scanning area such that an image artifact caused by a level difference between a dark time output of the first image pickup operation and a dark time output of the second image pickup operation is less than a predetermined allowable value, wherein the dark time output of the first or second image pickup operation is an electrical signal corresponding to the electrical charge for the first or second accumulation time in a dark state in which no radiation or light is present,and supply a control signal to the control unit based on the determined second accumulation time of the second accumulation operation, and , the control unit (106) is configured to control the operation of the detector such that the detector is configured to perform the second accumulation operation with the determined second accumulation time of the second accumulation operation.

Description

Technical area

[0001] The present invention relates to an imaging device, a radiation imaging device, an imaging system, a method for controlling the devices and the system, and a program. More specifically, the present invention relates to an imaging device used in a radiation imaging system, an imaging system, a method for controlling the device and the system, and a program, which are preferably used in capturing still images such as photography and recording films such as fluoroscopy in medical diagnostics.In embodiments of the present invention, the radiation includes not only alpha radiation, beta radiation, and gamma radiation, which are rays consisting of particles (including photons) emitted as a result of radiation damage, but also rays such as X-rays, particle radiation, and cosmic rays having an energy at least the same level as that of the alpha radiation, beta radiation, and gamma radiation. Background technology

[0002] In recent years, radiation imaging devices using flat-panel detectors (hereinafter referred to as FPDs) made of semiconductor materials have come into practical use as image pickup devices used in medical imaging diagnostics and non-destructive testing using X-rays. Such radiation imaging devices are used, for example, as digital imaging devices for capturing still images, such as photography, and recording films, such as fluoroscopy, in medical imaging diagnostics.

[0003] In such a radiation imaging device, arbitrary switching of the areas (field sizes) in which readout is performed by the FPDs is discussed, as disclosed in Japanese Patent Laid-Open Nos. 11-128213 and 11-318877.

[0004] However, when the ranges are expanded as a result of the switchover, the areas where FPD sampling is performed differ in pixel sensitivity and / or dark time outputs from the areas where FPD sampling is not performed. Accordingly, a ghost image (a level difference) may appear in a captured image, which is influenced by the readout (sampling) range, causing a deterioration in image quality.

[0005] During scanning in radiation imaging devices, image artifacts can be induced in generated images, and there are various approaches to reduce or avoid such induced image artifacts.Among other things, the document DE 10 2006 013 475 A1 discloses a method for synchronizing an image acquisition device with a first, older image data set, wherein the acquisition of image data is synchronized with a phase of the heart muscle in successive recordings, the document US 2007 / 0 297 562 A1 discloses an X-ray CT scanner in which image artifacts caused by the afterglow of the detector in successive recordings are eliminated, the document US 2004 / 0 218 729 A1 discloses a method for processing fluoroscopic images in which a model is generated to predict the afterglow of the detector and is used to correct image artifacts caused by the afterglow, and the document US 6 701 000 B1 discloses a method for reducing image artifacts due to residual signals in the detector in successive recordings. Summary of the invention

[0006] The present invention provides an imaging technique capable of reducing the level difference that may occur in a captured image and is affected by the scanning range, thereby preventing a significant reduction in image quality.

[0007] According to a first aspect of the present invention, there is provided an imaging system as defined in claim 1.

[0008] Further developments and modifications of the imaging system according to the first aspect of the present invention are defined in claims 2 to 6.

[0009] According to a second aspect of the present invention, there is provided an imaging apparatus as defined in claim 7.

[0010] According to a third aspect of the present invention, there is provided a method of controlling an imaging device as defined in claim 8.

[0011] According to a fourth aspect of the present invention, there is provided a program for causing a computer to control an imaging apparatus as defined in claim 9.

[0012] According to the present invention, the driving operation of the FPD unit enables a ghost image (a level difference) that may occur in a captured image and is influenced by the scanning range to be reduced, thereby preventing a significant reduction in image quality. Short description of the drawings Fig. 1 is a conceptual block diagram illustrating an imaging system including an imaging apparatus according to a first embodiment of the present invention. Fig. 2 is a conceptual equivalent circuit diagram of the imaging apparatus according to the first embodiment of the present invention. Fig. 3 is a flowchart showing an example of the operation of the imaging apparatus and the imaging system according to embodiments of the present invention. Fig. 4A is a timing chart illustrating the overall operation of the imaging apparatus and the imaging system according to the first embodiment of the present invention. Fig. 4B is a timing chart illustrating an operation of the imaging apparatus and the imaging system according to the first embodiment of the present invention. Fig. 4C is a timing chart illustrating further operation of the imaging apparatus and the imaging system according to the first embodiment of the present invention. Fig. 4D is a timing chart illustrating further operation of the imaging apparatus and the imaging system according to the first embodiment of the present invention. Fig. 5A schematically illustrates an example of the configuration of a control computer according to an embodiment of the present invention. Fig. 5B is a characteristic diagram of the integration amount of accumulation times and a dark time output, illustrating the concept and advantages according to embodiments of the present invention. Fig. 5C is another characteristic diagram of the integration amount of accumulation times and the dark time output, illustrating the concept and advantages according to embodiments of the present invention. Fig. 6A is a conceptual equivalent circuit diagram of an imaging apparatus according to a second embodiment of the present invention. Fig. 6B is another conceptual equivalent circuit diagram of the imaging apparatus according to the second embodiment of the present invention, Fig. 7A is a timing chart illustrating the overall operation of the imaging apparatus and an imaging system according to the second embodiment of the present invention. Fig. 7B is a timing chart illustrating an operation of the imaging apparatus and the imaging system according to the second embodiment of the present invention. Fig. 7C is a timing chart illustrating another operation of the imaging apparatus and the imaging system according to the second embodiment of the present invention. Fig. 7D is a timing chart illustrating another operation of the imaging apparatus and the imaging system according to the second embodiment of the present invention. Fig. 8A is a timing chart illustrating an operation according to the second embodiment of the present invention. Fig. 8B is a timing chart illustrating another operation according to the second embodiment of the present invention. Fig. 8C is a timing chart illustrating another operation according to the second embodiment of the present invention. Description of implementation examples

[0013] Herein, embodiments of the present invention will be described in detail with reference to the accompanying drawings. First embodiment

[0014] Fig. 1 is a conceptual block diagram illustrating a radiation imaging system including an imaging apparatus according to a first embodiment of the present invention. Referring to Fig. 1, the radiation imaging system includes an imaging device 100, a control computer 108, a radiation control device 109, a radiation generating device 110, a display device 113, and a console or operating unit 114. The imaging device 100 includes an FPD 104, which includes a detection unit 101, a drive circuit 102, and a readout circuit 103. The detection unit 101 includes a plurality of pixels, each of which converts radiation or light into an electrical signal. The drive circuit 102 drives the detection unit 101. The readout circuit 103 outputs the electrical signal supplied by the controlled detection unit 101 as image data.The imaging device 100 further includes a signal processing unit 105 that processes the image data supplied from the FPD 104 to output the processed image data, a control unit 106 that supplies a control signal to each component to control the operation of the FPD 104, and a power supply unit 107 that supplies a bias voltage to each component. The signal processing unit 105 receives a control signal from the control computer 108 described below to supply the received control signal to the control unit 106. The control unit 106 controls the drive circuit 102 so that switching is performed between at least two scanning areas in response to a control signal received from the control computer 108 described below.The drive circuit 102 is configured to be capable of switching between the scanning areas in response to the control signal received from the control unit 106. According to the first embodiment, the control unit 106 has a function of switching between a first scanning area A and a second scanning area B. In the first scanning area A according to the first embodiment, a part of the plurality of pixels is scanned by the drive circuit 102. For example, when the sum of the number of pixels is equal to approximately 2800 rows by approximately 2800 columns, pixels of approximately 1000 rows by approximately 2800 columns are scanned by the drive circuit. In the second scanning area B according to the first embodiment, pixels are scanned in an amount larger than that of the first scanning area A, for example, all pixels.The power supply unit 107 includes a power supply circuit, such as a regulator, that receives a voltage from an external power supply or a built-in battery (not shown) to supply a voltage required in the detection unit 101, the drive circuit 102, and the readout circuit 103.

[0015] The control computer 108 performs synchronization between the radiation generating device 110 and the imaging device 100, transmits control signals for determining the state of the imaging device 100, and performs image processing for correcting, storing, and / or displaying the image data from the imaging device 100. Additionally, the control computer 108 transmits a control signal for determining radiation irradiation conditions based on information from the console 114 to the radiation control device 109.

[0016] The radiation control device 109 controls an operation for radiating radiation from a radiation source 111 included in the radiation generating device 110 and the operation of a radiation field limiting mechanism 112 in the radiation generating device 110 in response to the control signal received from the control computer 108. The radiation field limiting mechanism 112 has a function of changing a specific radiation field irradiated with the radiation or the light corresponding to the radiation, which is located in the detection unit 101 in the FPD 104. The console 114 is used by an operator to input information about a test subject and image acquisition conditions, which are used as parameters in various controls in the control computer 108, and transmits the information and image acquisition conditions to the control computer 108.The display device 113 displays the image data that has been subjected to image processing in the control computer 108.

[0017] Fig. 2 is a conceptual equivalent circuit diagram of the imaging device according to the first embodiment of the present invention. Fig. 2, the same reference numerals are used to identify the same components used in Fig. 1. A detailed description of such components is omitted herein. The imaging device according to Fig. 2 includes the FPD unit, which, for simplicity, includes pixels of n rows by m columns, where both n and m are integers equal to or greater than two. The imaging device practically includes pixels of a number greater than n rows by m columns. For example, a 17-inch imaging device includes pixels of approximately 2800 rows by approximately 2800 columns.

[0018] The detection unit 101 includes a plurality of pixels arranged in a matrix pattern. Each pixel has a conversion element 201 that converts the radiation or light into an electric charge, and a switching element 202 that outputs an electric signal corresponding to the electric charge. In the first embodiment, a PIN photodiode arranged on an insulating substrate, such as a glass substrate, and composed primarily of amorphous silicon material is used as the photoelectric transducer that converts the light irradiated to the conversion element into the electric charge.As the conversion element 201, it is preferable to use an indirect conversion element equipped with a wavelength converter on the incident side of the radiation of the aforementioned photoelectric transducer, or a direct conversion element that directly converts the radiation into electric charge. The wavelength converter converts radiation into light within a waveband that can be detected by the photoelectric transducer. As the switching element 202, it is preferable to use a transistor having one control terminal and two main terminals. In the first embodiment, a thin-film transistor (TFT) is used as the switching element 202. One electrode of the conversion element 201 is electrically connected to one of the two main terminals of the switching element 202, and the other electrode of the conversion element 201 is electrically connected to a bias power supply 107a via a common bias line Bs.The control terminals of the plurality of switching elements in the row direction, for example, the switching elements T11 to T1m, are commonly electrically connected to a drive line G1 of the first row. A drive signal for controlling the conductive state of the switching element is supplied from the drive circuit 102 via the drive line to each switching element in each row. The drive circuit 102 controls the conductive state and the non-conductive state of the switching element 202 for each row to scan the picture elements for each row. In the embodiments of the present invention, the scanning area means an area where the drive circuit 102 scans the picture elements for each row, as described above. Although the picture elements are arranged from n rows to m columns in . Fig. 2 for convenience, the picture elements of approximately 1000 rows by approximately 2800 columns are practically scanned as the first scanning area A by the drive circuit 102 when the sum of the number of picture elements is, for example, equal to approximately 2800 rows by approximately 2800 columns. The remaining main terminal of each of the plurality of switching elements in the column direction, for example, the switching elements T11 to Tn1, is electrically connected to a signal line Sig1 of the first column. The electrical signal corresponding to the electric charge of the conversion element is supplied to the readout circuit 103 through the signal line while the switching element is in the conductive state. The electrical signals output from the plurality of picture elements are transmitted in parallel to the readout circuit 103 through the plurality of signal lines Sig1 to Sigm arranged in the column direction.

[0019] The readout circuit 103 includes an amplifier circuit 207 for each signal line. The amplifier circuit 207 amplifies each of the electrical signals output in parallel from the detection unit 101. The amplifier circuit 207 includes an integrating amplifier 203 that amplifies the output electrical signal, a variable amplifier 204 that amplifies the electrical signal from the integrating amplifier 203, a sample and hold circuit 205 that samples and holds the amplified electrical signal, and a buffer amplifier 206. The integrating amplifier 203 includes an operational amplifier that amplifies the readout electrical signal and outputs the amplified electrical signal, an integrating capacitor, and a reset switch. The integrating amplifier 203 is capable of varying the value of the integrating capacitor to change the gain.The output electrical signal is input to an inverting input terminal of the operational amplifier, a reference voltage Vref is supplied from a reference power supply 107b to a non-inverting input terminal of the operational amplifier, and the amplified electrical signal is output from an output terminal of the operational amplifier. The integration capacitor is connected between the inverting input terminal and the output terminal of the operational amplifier. The sample and hold circuit 205 is provided for each amplifier circuit and includes a sampling switch and a sampling capacitor.The readout circuit 103 includes a multiplexer 208 that sequentially outputs the electrical signals read out in parallel by the amplifier circuit 207 as a serial image signal, and a buffer amplifier 209 that performs impedance conversion on the image signal to output the impedance-converted image signal. An image signal Vout, which is an analog electrical signal output from the buffer amplifier 209, is converted into digital image data in an analog-to-digital (A / D) converter 210, and the digital image data is supplied to the signal processing unit 105. The data processed in the signal processing unit 105 as shown in FIG. Fig. 1 processed image data are transmitted to the control computer 108.

[0020] The drive circuit 102 provides a drive signal comprising a conducting voltage Vcom that sets the switching element in the conducting state and a non-conducting voltage Vss that sets the switching element in the non-conducting state, in response to the control signal (D-CLK, OE or DIO) that is output by the control unit 106 according to Fig. 1 to each drive line. The drive circuit 102 controls the conducting state and the non-conducting state of the switching element with the control signal to drive the detection unit 101.

[0021] The power supply unit 107 according to Fig. 1 comprises the bias power supply 107a and the reference power supply 107b for the Fig. 2. Bias power supply 107a supplies a bias voltage Vs through bias line Bs to the other electrode of each conversion element. Reference power supply 107b supplies the reference voltage Vref to the non-inverting input terminal of each operational amplifier.

[0022] The control unit 106 according to Fig. 1 receives the control signals from the control computer 108, etc., located external to the imaging device via the signal processing unit 105 and supplies the control signals to the drive circuit 102, the power supply unit 107, and the readout circuit 103 to control the operation of the FPD 104. The control unit 106 supplies the control signal D-CLK, the control signal OE, and the control signal DIO to the drive circuit 102 to control the operation of the drive circuit 102. The control signal D-CLK is a shift clock for a shift register used as the drive circuit, the control signal DIO is a pulse signal transmitted through the shift register, and the control signal OE is used to control the output side of the shift register. The control unit 106 is capable of controlling the drive circuit 102 with these control signals to switch between the first scanning area A and the second scanning area B.Additionally, the control unit 106 provides a control signal RC, a control signal SH, and a control signal CLK to the readout circuit 103 to control the operation of each component in the readout circuit 103. The control signal RC is used to control the operation of the reset switch in the integrating amplifier 203, the control signal SH is used to control the operation of the sample and hold circuit 205, and the control signal CLK is used to control the operation of the multiplexer 208.

[0023] It will now be discussed with reference to Fig. 1 to 3, with particular reference to Fig. 3, an example of the operation of the imaging device and the entire imaging system according to an embodiment of the present invention is described. After the irradiation conditions are determined by the control computer 108 in response to an operator's operation with the console 114, image acquisition begins. An object is irradiated with the desired radiation emitted by the radiation generating device 110 controlled by the radiation control device 109 under the determined irradiation conditions. The imaging device 100 outputs image data corresponding to the radiation transmitted through the object. The output image data is subjected to image processing in the control computer 108 and displayed on the display device 113.

[0024] The control computer 108 asks the operator whether to continue image acquisition. If an instruction (NO) not to continue image acquisition is received from the operator, the image acquisition is terminated. If an instruction (YES) to continue image acquisition is received from the operator, the control computer 108 asks the operator whether to change or switch the scanning area. If an instruction (NO) not to change or switch the scanning area is received from the operator, the control computer 108 controls the radiation control device 109 and the radiation generation device 110 under the image acquisition conditions that have been determined to irradiate the object with radiation again under the same conditions. If an instruction (YES) to change or switch the scanning area is received from the operator, the control computer 108 determines the scanning area to change or switch to.The control computer 108 then performs arithmetic processing to determine an accumulation operating time, which is described below. The control computer then supplies the control signal to the imaging device 100 based on the determined scanning area and accumulation operating time, so that the next image acquisition is performed in the determined scanning area at the determined accumulation operating time.

[0025] Now, with reference to Fig. 4A to Fig. 4D Examples of operations of the imaging system according to the first embodiment of the present invention are described. Referring to Fig. 4A, the imaging device 100, upon supplying the bias voltage Vs to the conversion element 201, performs an idle operation during an idle period. In the idle operation, at least one initialization operation K1 is repeated several times to stabilize the fluctuation in characteristics of the FPD 104 caused by the start of the supply of the bias voltage Vs. The initialization operation is an operation for applying an initial bias voltage to the conversion element before the accumulation operation in order to initialize the conversion element. In the example according to Fig. 4A, as the idle operation, an accumulation operation W1 and the initialization operation K1 are repeated in pairs several times.

[0026] Fig. Fig. 4B is a timing chart showing an example of the operation of the imaging device during a period AA' according to Fig. 4A. Referring to Fig. 4B, in the accumulation mode W1, the non-conductive voltage Vss is applied to the switching element 202, while the bias voltage Vs is applied to the conversion element 201 to place the switching elements in all pixels in the non-conductive state. In the initialization mode K1, the integration capacitor in the integrating amplifier 203 and the signal line are reset by the reset switch, and the conductive voltage Vcom is applied from the drive circuit 102 to the drive line G1 to place the switching elements T11 to T1m in the first row in the conductive state. Placing the switching elements in the conductive state causes the conversion elements to be initialized.In the first embodiment, although the electric charge of each conversion element is output from the corresponding switching element as the electric signal in this state, no data corresponding to the electric signal is output from the readout circuit 103 because the sample-and-hold circuit and the subsequent circuits are not operated. The integration capacitor and the signal line are reset again later to process the output electric signal. However, when the data is to be used for correction, etc., the sample-and-hold circuit and the subsequent circuits can be operated in a manner similar to that of an image output operation or a dark image output operation, which will be described below.Repeating the control of the conduction state of the switching element and the reset from the first line to the nth line causes the detection unit 101 to be initialized. In the initialization operation, the reset switch may be kept in the conduction state to continue the reset at least during a time when the switching element is in the conduction state. The time when the switching element is in the conduction state in the initialization operation may be shorter than the time when the switching element is in the conduction state in the image output operation described below. Additionally, in the initialization operation, the switching elements in multiple rows may be conducting simultaneously. In such a case, it is possible to reduce the time required for the entire initialization operation to quickly stabilize the fluctuation in characteristics of the FPD 104.The initialization operation K1 in the first embodiment is performed in the same period as the image output operation included in the fluoroscopy operation following the idle operation.

[0027] Fig. Fig. 4C is a timing chart showing an example of the operation of the imaging device during a period BB' according to Fig. 4A. After the idle operation is performed to place the acquisition unit 101 in a state where image acquisition can be performed, the imaging device 100, in response to the control signal from the control computer 108, performs the fluoroscopy operation by scanning the FPD 104 in the first scanning area A. The fluoroscopy operation corresponds to a first image acquisition operation. In the first image acquisition operation, image data corresponding to the first scanning area is output from the FPD 104 scanned in the first scanning area. The period during which the imaging device 100 performs the fluoroscopy operation is called a fluoroscopy period.During the fluoroscopy period, the imaging device 100 performs the accumulation operation W1, which is performed during a period corresponding to the time period at which the radiation is irradiated, to cause the conversion element 201 to generate the electric charge in response to the irradiated radiation, and performs an image output operation X1 in which image data is output based on the electric charge generated in the accumulation operation W1. As shown in FIG. Fig. 4C, in the image output mode X1, the control unit 106 supplies the control signal D-CLK corresponding to the number of lines corresponding to the second scanning area to the drive circuit 102, with the control signal OE and the control signal DIO in a low state (Lo). Accordingly, the control voltage Vcom is not supplied from the drive circuit 102 to the drive lines G1 and G2, and the first and second lines corresponding to the second scanning area are therefore not scanned. Then, the integration capacitor and the signal line are reset, and the control voltage Vcom is applied from the drive circuit 102 to the drive line G3 to turn the switching elements T31 to T3m in the third line on. As a result, the electrical signal based on the electrical charge generated in the conversion elements S31 to S3m in the third line is supplied to each signal line.Each of the electrical signals output in parallel through the respective signal lines is amplified in the integrating amplifier 203 and the variable gain amplifier 204 in each amplifier circuit 207. The amplified electrical signals are held in parallel in the sample-and-hold circuits 205 in the respective amplifier circuits 207. The sample-and-hold circuits 205 operate in response to the control signal SH. After the electrical signals are held, the integrating capacitors and the signal lines are reset. After the reset, the conduction voltage Vcom, as in the third row, is applied to the drive line G4 in the fourth row to turn the switching elements T41 to T4m in the fourth row on.During the period in which the switching elements T41 to T4m in the fourth line are turned on, the multiplexer 208 sequentially outputs the electrical signals held in the sample-and-hold circuits 205. As a result, the electrical signals read out in parallel from the picture elements in the first line are converted into a serial image signal, and the serial image signal is output. The A / D converter 210 converts the image signal into image data corresponding to one line and outputs the converted image data. Performing the above operation for each line from the third line to the nth line causes image data corresponding to one frame to be output from the imaging device 100.In addition, in the first embodiment, the imaging device 100 performs the accumulation operation W1, which is performed in the same period as the above-described accumulation operation W1, to cause the conversion element 201 to generate the electric charge in a dark state in which radiation emission is not performed, and performs a dark image output operation F1 in which dark image data is output based on the electric charge generated in the accumulation operation W1. In the dark image output operation F1, an operation similar to the image output operation X1 is performed in the imaging device 100.The time resulting from adding the time at which the accumulation operation is performed to the time resulting from subtracting the time at which each switching element is in the conductive state from the time at which the image output operation is performed is called the accumulation time. The time at which each switching element is in the conductive state is called the sampling time. The time at which a set of image sensing operations including the accumulation operation, the image output operation, the accumulation operation, and the dark image output operation is performed is called the frame time, and an inverse of the frame time is called the frame speed. The accumulation operation W1 in the first embodiment corresponds to a first accumulation operation, and the image output operation X1 or the dark image output operation F1 in the first embodiment corresponds to a first output operation.Although the picture elements in the first and second lines are not scanned in the first embodiment, the present invention is not limited to this scanning mode. For example, all the second picture elements corresponding to the picture elements in the first and second lines may be scanned simultaneously, or the second picture elements may be scanned in a scanning period shorter than that of the first picture elements in the first scanning area. In other words, the scanning may be performed so that the normal image sensing operation is not performed on the second picture elements during the first image sensing operation. Although the picture elements in the second scanning area are scanned in the initialization operation K1 according to FIG. Fig. 4B are sequentially scanned, the present invention is not limited to this scanning mode, and the scanning may be performed in a manner similar to that of the image output mode X1.

[0028] Upon receiving the instruction to change or switch the scanning range from the console 114, the control computer 108 performs the arithmetic processing to determine the accumulation time in response to the instruction. The period in which the arithmetic processing is performed is referred to as the calculation period. The arithmetic processing is described with reference to Fig. 5A to 5C are described in detail.

[0029] Fig. Fig. 4D is a timing chart showing an example of the operation of the imaging device during a period CC' according to Fig. 4A. After the arithmetic processing, the control computer 108 supplies the control signal corresponding to the accumulation time determined in the arithmetic processing to the imaging device 100. The imaging device 100 performs the photography operation (capturing still images) by scanning the FPD 104 in the second scanning area B, which is larger than the first scanning area A, in response to the control signal supplied from the control computer 108. The photography operation corresponds to a second image pickup operation. In the second image pickup operation, the image data corresponding to the second scanning area is output from the FPD 104 scanned in the second scanning area. The period in which the imaging device 100 performs the photography operation is referred to as a photography period.During the photography period, the imaging device 100 performs an accumulation operation W2, which is performed in an accumulation operation time Tw determined in the arithmetic processing, to cause the conversion element to generate the electric charge in response to the irradiated radiation, and performs an image output operation X2 in which image data is output based on the electric charge generated in the accumulation operation W2. As shown in FIG. Fig. As shown in Fig. 4D, although the accumulation operation W2 in the first embodiment is similar to the accumulation operation W1, the accumulation operation W2 differs from the accumulation operation W1 because the period of the accumulation operation W2 is different from that of the accumulation operation W1. In contrast, although the image output operation X2 is similar to the image output operation X1 except that the first and second lines are scanned in the same manner as the third and subsequent lines, the image output operation X2 differs from the image output operation X1 because the period of the image output operation X2 is longer than that of the image output operation X1.However, the accumulation operation W2 may be performed in the same period as that of the accumulation operation W1, and the image output operation X2 may be performed in the same period as that of the image output operation X1, depending on the result of the arithmetic processing. In addition, in the first embodiment, the imaging device 100 performs the accumulation operation W2, which is performed in the same period as the above-described accumulation operation W2, to cause the conversion element to generate the electric charge in the dark state in which radiation is not emitted, and performs a dark image output operation F2 in which dark image data is output based on the electric charge generated in the accumulation operation W2. In the dark output operation F2, an operation similar to the image output operation X2 is performed in the imaging device 100.In addition, the imaging device 100 in the first embodiment performs an initialization operation K2 before each accumulation operation W2. Although the initialization operation K2 is similar to the above-described initialization operation K1, the initialization operation K2 differs from the initialization operation K1 because the period of the initialization operation K2 is different from that of the initialization operation K1. However, as in the accumulation operation W2, the initialization operation K2 may be performed in the same period as that of the initialization operation K1, depending on the result of the arithmetic processing. The accumulation operation W2 in the first embodiment corresponds to a second accumulation operation, and the image output operation X2 or the dark image output operation F2 in the first embodiment corresponds to a second output operation.

[0030] Now, with reference to Fig. 5A to 5C describe the arithmetic processing performed by the control computer. Referring to Fig. 5B and Fig. In FIG. 5C, the horizontal axis represents the integration or total amount of accumulation times in the FPD 104, and the vertical axis represents pixel output data acquired in the dark state as the dark time output.

[0031] It will now be discussed with reference to Fig. 5B and Fig. 5C describes how the level difference occurs on which the arithmetic processing according to the embodiments of the present invention is based. As is the case according to Fig. As shown in Figure 5B, the inventors found that the dark time output from the flat panel detector depends on the scanning history of the pixels, more specifically, on the integration or total amount of accumulation times since the bias voltage was applied to the conversion element in the flat panel detector. In the first image pickup operation in the first embodiment, the image pickup operation is performed in the first scanning area. Accordingly, the image pickup operation is performed on the pixels included in the first scanning area A a plurality of times, and the dark time output components accumulated during the accumulation operation are not completely output in each output operation and remain in the pixels. The components remaining in the pixels are used as the scanning history of the pixels.In contrast, in the first image pickup operation, the normal image pickup operation is not performed on the pixels included in the second scanning area B. This is because, for example, the accumulation operation is continuously performed, the entire second scanning area B is scanned at one time, or the output operation of the pixels in the second scanning area B is performed in a scanning period shorter than that of the pixels in the first scanning area A. In such a case, the accumulation time in the first scanning area A is different from that in the second scanning area B.For example, when the output operation of the pixels in the second scanning area B is performed in a scanning period shorter than that of the pixels in the first scanning area A, the integration amount of the accumulation times during the first image pickup operation for the pixels included in the first scanning area A becomes smaller than that for the pixels in the second scanning area B. As a result, the dark time output of the pixels included in the first scanning area A is . Fig. 5B is designated A, and the dark time output of the picture elements included in the second scanning area B is in Fig. 5B denoted by B or C. The dark time output of the pixels included in the second scanning area B depends on the integration amount of the accumulation times, which depends on the length of the period of fluoroscopy operation, and is shown in Fig. 5B, denoted by B or C. Accordingly, a difference occurs between the dark time output A of the first scanning area and the dark time output C of the second scanning area, and the difference in the dark time output is displayed as the level difference. Specifically, the difference in the dark time output between the first scanning area and the second scanning area increases with the length of the fluoroscopy operation period, and therefore, the level difference becomes more pronounced. As described above, the dark time output of the flat panel detector depends on the integration amount of the accumulation times, which represents the scanning history of the pixels.Accordingly, the inventors have found that a difference in the dark time output occurs between the areas subjected to scanning in the flat panel detector during image acquisition and the areas not subjected to scanning in the flat panel detector during image acquisition, causing the level difference which is an image artifact caused by the scanning area.

[0032] As it is in Fig. As shown in Fig. 5C, the dark time output of the flat panel detector depends on the accumulation operation time Tw in the conversion element. Accordingly, the inventors found that the level difference representing an image artifact caused by the scanning area depends on the integration amount of the accumulation times before the scanning area is switched and the accumulation operation time Tw in the conversion element in the image pickup operation after the scanning area is switched. The inventors also found that if the level difference is smaller than a predetermined allowable value, the level difference caused by the output difference in the image is not recognized, and the image picked up by the imaging device can be used.The predetermined allowable value is a value specific to the flat panel detector and can be acquired and set in advance, for example, during pre-shipment testing. Since the level difference smaller than the random noise of the flat panel detector is generally hidden in the random noise and cannot be detected or perceived, the allowable value is particularly preferably smaller than the output level of the random noise.

[0033] As described above, the control computer 108 performs arithmetic processing for determining the accumulation operation time in the image pickup operation after the scanning range is switched, based on the information on the integration amount of the accumulation times in the image pickup operation before the scanning range is switched. The arithmetic processing is performed so that the image artifact caused by the scanning range is less than the predetermined allowable value. As a result, the upper limit of the accumulation operation time is equal to the time at which the level difference is equal to the predetermined allowable value. However, it is necessary for the radiation generating device 110 to generate the radiation in which the dose necessary for image pickup is ensured within a period of time that is within the accumulation operation time.If the accumulation operation time is too short, a case may occur where the dose necessary for image acquisition can only be ensured in a short period exceeding the limit of the radiation generating device, or can only be ensured at a high intensity. In other words, the time at which the radiation generating device 110 can radiate the radiation necessary for image acquisition corresponds to the lower limit of the accumulation operation time. Accordingly, the control computer 108 determines the accumulation operation time so that the level difference within a time interval in which the radiation generating device 110 can radiate the radiation necessary for image acquisition after the scanning area is switched becomes smaller than the predetermined allowable value.However, if the arithmetic processing results in a short time exceeding the limit of the radiation generating device, the lower limit of the accumulation operation time is equal to a shortest radiation time, which is a limit time during which the radiation generating device can emit radiation. In such a case, the control computer 108 controls the radiation generating device so that the intensity of the emitted radiation is increased to ensure the dose necessary for image acquisition. Specifically, the control computer 108 controls the tube current of the radiation source in the radiation generating device to adjust the intensity of the radiation.

[0034] The control computer 108 supplies the control signal based on the determined accumulation operation time to the control unit in the imaging device. The control unit controls the drive circuit so that the accumulation operation in the FPD unit is performed within the determined accumulation time. In addition, the control computer 108 supplies the control signal based on the determined accumulation operation time to the radiation control device to control the radiation generation device in accordance with the determined accumulation operation time so that the radiation generation device emits the radiation necessary for image acquisition after the scanning area is changed or switched.

[0035] With reference to Fig. 5A, an example of the configuration in which the arithmetic processing according to an embodiment of the present invention is performed, and an example of the arithmetic processing is described. Referring to Fig. 5A, the control computer 108 includes an image data processor 501, a sensor 502, an accumulation operation time determination part 503, and a characteristic data storage part 504. The characteristic data storage part 504 stores the integration amount of the accumulation times in the first image pickup operation, the accumulation operation time in the second image pickup operation, and data regarding the dark time output, which indicates the characteristics of the FPD unit. A lookup table including such data is preferably used in the characteristic data storage part 504. The characteristic data storage part 504 also stores information regarding the shortest irradiation time and a maximum output intensity of the radiation generating device. In the embodiments of the present invention, the accumulation operation time determination part 503 and the characteristic data storage part 504 are collectively referred to as an arithmetic processing unit 505.

[0036] The image data transmitted from the imaging device 100 is subjected to image processing in the image data processor 501 and transmitted to the display device 113. The control unit 106 in the imaging device 100 transmits information about the scanning areas in the first image sensing operation, information about the frame speed in the first image sensing operation, and information about the time of the first image sensing operation to the sensor 502. The sensor 502 determines the accumulation times in units of frames for each scanning area based on the received information and totals the determined accumulation times. Then, the sensor 502 adds the totalized accumulation times in units of frames for each frame to acquire information about the integration amount of the accumulation times in each scanning area in the image sensing operation, and supplies the information to the accumulation operation time determination part 503.Instead of the information from the control unit 106, information transmitted from a photo timer (not shown) provided in the imaging device separately from the FPD may be used. Alternatively, instead of the information from the control unit 106, information input in advance using the console 114 may be used. When the information from the console 114 is used, it is not necessary to add the accumulation times in units of frames, and the information about the entire first image pickup operation can be acquired from the console 114. The sensor 502 can supply the information directly to the accumulation operation time determination part 503 without processing. In this case, the look-up table in the characteristic data storage part 504 is preferably used.The scanning range, frame speed and scanning time in the first image sensing mode, the accumulation operation time in the second image sensing mode and the data concerning the dark time output are stored in the lookup table.

[0037] Upon receiving an operator input for instructing a change of the radiation field, the console 114 transmits information regarding the dose of radiation necessary for image acquisition after the scanning area is changed or switched to the accumulation operation time determining part 503. In response to the control signal from the console 114, the accumulation operation time determining part 503 determines the accumulation operation time Tw based on the information on the integration amount of the accumulation times in each scanning area, the information on the dose of radiation required, and the data stored in the characteristic data storing part 504.

[0038] The determined accumulation operation time Tw is transmitted from the accumulation operation time determining part 503 to the control unit 106 in the imaging device 100. The control unit 106 controls the drive circuit so that the accumulation operation in the FPD unit is performed within the inputted accumulation operation time Tw. The accumulation operation time Tw and the information on the required radiation dose are transmitted from the accumulation operation time determining part 503 to the radiation control device 109 to control the radiation generating device 110 according to the accumulation operation time Tw so that the radiation generating device 110 emits the radiation necessary for image acquisition.

[0039] As described above, performing the image pickup operation after the scanning range is switched in accordance with the time based on the integration amount of the accumulation times in the image pickup operation before the scanning range is switched allows the level difference affected by the scanning range to be reduced without complicated image processing, thereby preventing a significant deterioration in image quality. Although the accumulation operation time Tw is determined in the first embodiment, the present invention is not limited to the determination of the accumulation operation time Tw.For example, both the accumulation operation time Tw and the time of the initialization operation K2 immediately before the accumulation operation time Tw may be calculated and determined, and control may be performed such that the image output operation X2 or the like is performed in combination with the initialization operation K2. Although the control computer 108 performs the arithmetic processing in the first embodiment, the present invention is not limited to this. The control unit 106 in the imaging device 100 may perform the arithmetic processing in response to the control signal from the control computer 108. The second image pickup operation may be performed without the first image pickup operation and the switching of the scanning areas.In such a case, arithmetic processing may be performed assuming that the integration amount of the accumulation times in the first image sensing operation is zero to determine the accumulation operation time in the second image sensing operation. The accumulation operation time in the second image sensing operation is increased in this case compared to the case where the first image sensing operation and the switching of the scanning areas are performed. Second embodiment

[0040] It will now be discussed with reference to Fig. 6A and Fig. 6B, an imaging device according to a second embodiment of the present invention is described. In the second embodiment, the same reference numerals are used to identify the same components as in the first embodiment. A detailed description of such components is omitted herein. Although the imaging device with the FPO unit comprising pixels of n rows by m columns is shown in Fig. 6A is shown for simplicity, as is the case with Fig. 2 is the case, the imaging device practically comprises the picture elements of a number greater than n rows by m columns.

[0041] Although the PIN photodiode is used in the conversion element 201 in the detection unit 101 in the first embodiment, a photoelectric transducer having a metal-insulator-semiconductor (MIS) structure is used as an MIS-type conversion element in a conversion element 601 in a detection unit 101' in the second embodiment. Although an output switching element is provided for one pixel, a refresh switching element 603 for one pixel is provided in the second embodiment in addition to an output switching element 602. One of the main terminals of the refresh switching element 603 is electrically connected to a first electrode 604 of the conversion element 601 and to one of the two main terminals of the output switching element 602.The other of the main terminals of the refresh switching element 603 is electrically connected via a common line to a refresh power supply 107c included in the power supply unit 107. The control terminals of a plurality of refresh switching elements 603 in the row direction are electrically connected in common to a refresh drive line Gr. Drive signals are applied from a refresh drive circuit 102r to the refresh switching elements 603 in each row via the refresh drive line Gr.

[0042] As it is in Fig. As shown in Fig. 6B, in the conversion element 601, a semiconductor layer 606 is provided between the first electrode 604 and a second electrode 608, an insulating layer 605 is provided between the first electrode 604 and the semiconductor layer 606, and an impurity semiconductor layer 607 is provided between the semiconductor layer 606 and the second electrode 608. The second electrode 608 is electrically connected to a bias power supply 107a' via the bias line Bs. The bias voltage Vs is supplied from the bias power supply 107a' to the second electrode 608 in the conversion element 601, and the reference voltage Vref is supplied via the output switching element 602 to the first electrode 604 in the conversion element 601 to perform the accumulation operation in the conversion element 601, as is the case with the conversion element 201.In the fluoroscopy mode and the photography mode, a refresh voltage Vt is supplied to the first electrode 604 via the refresh switching element 603, and the conversion element 601 is refreshed with a bias voltage |Vs-Vt|.

[0043] With reference to Fig. 7A to 7D, examples of the operations of the imaging apparatus and the imaging system according to the second embodiment of the present invention are described. In the second embodiment, as shown in Fig. 7A, an initialization operation K1', an image output operation X1' and a dark image output operation F1' instead of the initialization operation K1, the image output operation X1 and the dark image output operation F1 in the Fig. 4A. In addition, an image output operation X2' and a dark image output operation F2' are performed instead of the image output operation X2 and the dark image output operation F2 in the embodiment shown in Fig. 4A. In addition, the imaging device 100 in the second embodiment performs a switching operation, described in detail below, during the calculation period. The remaining operations are similar to those in the first embodiment. A detailed description of such operations is omitted herein. The operations that are different from those in the first embodiment will now be described with reference to Fig. 7B to 7D.

[0044] The detection unit 101' according to the second embodiment comprises, for one pixel, in addition to the output switching element 602, the refresh switching element 603. Accordingly, the initialization operation K1' differs from the idle operation in the second embodiment, which is shown in Fig. 7B, the initialization operation K1 in which a conversion element 201 operates for one pixel. In the initialization operation K1', the control voltage Vcom is supplied from the drive circuit 102 to the drive line G to turn the output switching element 602 on, and the electric charge in the conversion element 601 is output from the output switching element 602 as an electric signal, as in the first embodiment. Then, the control voltage Vcom is supplied from the refresh drive circuit 102r to the refresh drive line Gr to turn the refresh switching element 603 on. At this time, the refresh voltage Vt is supplied from the refresh power supply 107c.As a result, the bias voltage |Vs-Vt| is applied to the conversion element 601 to remove the electric charge remaining in the conversion element 601, thereby refreshing the conversion element 601. Then, the integration capacitor and the signal line are reset, the output switching element 602 is again turned on, and an original bias voltage |Vs-Vrefl is applied to the conversion element 601 to initialize the conversion element 601. Sequentially performing the above operation in units of rows realizes the initialization operation K1'. As described above, since the remaining operations are similar to those in the first embodiment, a detailed description of such operations is omitted herein.

[0045] The difference between the image output operation X1' in the fluoroscopy operation in the second embodiment shown in Fig. 7C, and the image output mode X1, as well as the difference between the dark image output mode F1' in the fluoroscopy mode in the second embodiment shown in Fig. 7C and the dark image output operation F1 are similar to those between the initialization operation K1' and the initialization operation K1 described above. Since the remaining operations are similar to those in the first embodiment, a detailed description of such operations is omitted herein.

[0046] In the image output mode X2' and the dark image output mode F2' in the photography mode in the second embodiment, which are shown in Fig. 7D, the control voltage Vcom is supplied from the drive circuit 102 to the drive line G to turn the output switching element 602 on, as in the first embodiment. As a result, the electric charge in the conversion element 601 is output from the output switching element 602 as an electric signal in units of lines, and image data is output from the imaging device via the readout circuit 103. Then, the control voltage Vcom is supplied from the refresh drive circuit 102r to the refresh drive line Gr to turn the refresh switching element 603 on. At this time, the refresh voltage Vt is supplied from the refresh power supply 107c.As a result, the bias voltage |Vs-Vt| is applied to the conversion element 601 to remove the remaining electric charge in the conversion element 601, thereby refreshing the conversion element 601. Then, the integration capacitor and the signal line are reset, the output switching element 602 is again turned on, and the original bias voltage |Vs-Vref| is applied to the conversion element 601 to initialize the conversion element 601. Sequentially performing the above operation in units of lines realizes the image output operation X2' or the dark image output operation F2'. Although the image output operation X2' differs from the image output operation X1' because the period of the image output operation X2' is different from that of the image output operation X1', the image output operation X2' can be performed in the same period as the image output operation X1'.

[0047] Now, with reference to Fig. 8A to 8C, the switching operation according to the second embodiment of the present invention is described.

[0048] In the Fig. In the switching operation shown in FIG. 8A, the FPD 104 performs the initialization operation K2', which is similar to the initialization operation K1, once or a plurality of times during the period having the same length as that of the period of the image output operation X2' and the dark image output operation F2' in the photography operation. In other words, the FPD 104 performs the initialization operation K2', which corresponds to the image output operation X2' or the dark image output operation F2' in the photography operation, which is performed after the scanning area is switched, once or a plurality of times. In the initialization operation K2', the switching operation is performed by the initialization operation corresponding to the image pickup operation performed after switching, and better image data having a small amount of image artifact can be acquired.Since the accumulation operation is not performed, it is possible to quickly stabilize the characteristics of the conversion element. Specifically, as the switching operation including the plurality of initialization operations, the initialization operation corresponding to the image capturing operation performed after a switching operation is preferably performed at least once immediately before the image capturing operation performed after the switching operation.

[0049] In the Fig. 8B, the FPD 104 performs a refresh operation R described below at least once. Then, the FPD 104 performs the initialization operation K2', which corresponds to the image output operation X2' or the dark image output operation F2' in the photography mode, once or repeatedly. With this switching operation, in addition to the advantages of the Fig. 8A, it is possible to further reduce the level difference because the electric charge remaining in the conversion element is eliminated in the refresh operation R. The refresh operation will now be described with reference to Fig. 8C. In the Fig.In the refresh operation shown in FIG. 8C, the drive circuit 102 does not apply the conducting voltage Vcom to the output switching element 602, and the output switching element 602 is maintained in the non-conductive state. In this state, the refresh drive circuit 102r applies the conducting voltage Vcom to the refresh switching element 603 in units of rows to place the refresh switching element 603 in the conductive state. As a result, the bias voltage |Vs-Vt| is applied to the conversion element 601 to remove the electric charge remaining in the conversion element 601, thereby refreshing the conversion element 601. Sequentially performing the above operation in units of rows realizes the refresh operation R.

[0050] After the refresh operation R, the integration capacitor and the signal line are reset, the conducting voltage Vcom is applied from the drive circuit 102 to the drive line G to turn the output switching element 602 on, and the electric charge in the conversion element 601 is output from the output switching element 602 as an electric signal. Then, the conducting voltage Vcom is applied from the refresh drive circuit 102r to the refresh drive line Gr to turn the refresh switching element 603 on. At this time, the refresh voltage Vt is applied from the refresh power supply 107c. As a result, the bias voltage |Vs-Vt| is applied to the conversion element 601 to remove the electric charge remaining in the conversion element 601, thereby refreshing the conversion element 601 again.Then, the integration capacitor and the signal line are reset, the output switching element 602 is again turned on, and the original bias voltage |Vs-Vref| is applied to the conversion element 601 to initialize the conversion element 601. Sequentially performing the above operation in units of rows realizes the initialization operation K2'.

[0051] Also in the second embodiment, the second image pickup operation may include the initialization operation as is the case in the first embodiment.

[0052] In the second embodiment, the imaging device 100 performs the switching operation during the calculation period, in addition to performing the image pickup operation after the radiation field is switched in the accumulation time based on the integral dose of radiation in the image pickup operation before the radiation field is switched. Accordingly, in addition to the advantages of the first embodiment, it is possible to reduce the amount of level difference included in the image data output from the imaging device 100 to further reduce the level difference.

[0053] The embodiments of the present invention can be realized, for example, by a program executed by a computer included in the control unit 106. A unit for supplying the program to the computer, for example, a computer-readable recording medium such as a compact disc read-only memory (CD-ROM) that has recorded the program, or a communication medium such as the Internet over which the program is transmitted, is also applicable as an embodiment of the present invention. In addition, the program is also applicable as an embodiment of the present invention. The program, the recording medium, the communication medium, and the program product are within the scope of the present invention. A combination simply adopted from the first or second embodiment is also within the scope of the present invention.

[0054] While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation to encompass all such modifications and equivalent structures and functions. List of reference symbols 100 imaging device 101 Recording unit 102 Control circuit 103 Readout circuit 104 flat screen detector 105 Signal processing unit 106 Control unit 107 Power supply unit 108 control computers 109 Radiation control device 110 Radiation generating device 111 Radiation source 112 Radiation field limitation mechanism 113 Display device

Claims

[1] Imaging system with: an imaging device (100) having a detector in which a plurality of image elements, each comprising a conversion element (201, 601) configured to convert radiation or light into an electric charge, are arranged in a matrix form, and which is configured to perform an image pickup operation to output image data corresponding to emitted radiation or emitted light, and a control unit (106) configured to control operations including the image pickup operation of the detector; and a control computer (108) configured to control the imaging device, wherein the image capturing operation comprises a first image capturing operation and a second image capturing operation, wherein the first image capturing operation comprises a first accumulation operation in which the conversion element is configured to generate the electrical charge for a first accumulation time, and a first output operation in which the detector is configured to scan in a first scanning area corresponding to a portion of the plurality of image elements to output image data in the first scanning area, wherein the second image capturing operation comprises a second accumulation operation in which the conversion element is configured to generate the electrical charge for a second accumulation time, and a second output operation in which the detector is configured to scan in a second scanning area that is larger than the first scanning area to output image data in the second scanning area, characterized by , that the control computer (108), when a change from the first scanning area to the second scanning area is instructed, is configured to perform arithmetic processing for determining the second accumulation time of the second accumulation operation based on information about a total amount of the first accumulation times in the first image pickup operation before a change of the scanning area such that an image artifact caused by a level difference between a dark time output of the first image pickup operation and a dark time output of the second image pickup operation is less than a predetermined allowable value, wherein the dark time output of the first or second image pickup operation is an electrical signal corresponding to the electrical charge for the first or second accumulation time in a dark state in which no radiation or light is present,and supply a control signal to the control unit based on the determined second accumulation time of the second accumulation operation, and, the control unit (106) is configured to control the operation of the detector such that the detector is configured to perform the second accumulation operation with the determined second accumulation time of the second accumulation operation. [2] Imaging system according to claim 1, wherein the control computer (108) comprises a characteristic data storage part (504), a sensor (502) and an accumulation operation time determination part (503), the characteristic data storage part (504) is configured to store the total amount of the first accumulation times in the first image recording operation, the determined second accumulation time of the second accumulation operation, data concerning a dark time output, which is an electrical signal corresponding to the electrical charge for the first accumulation time in a dark state in which no radiation or light is present, and information about a shortest radiation time, which represents a lower limit time of radiation or light emission by a radiation generating device (110), and a maximum output strength, which represents an upper limit strength of radiation or light emission by the radiation generating device (110), which indicate characteristics of the detector, the sensor (502) is configured to supply the information about the total amount of the first accumulation times in the first image pickup operation to the accumulation operation time determination part (503), and the accumulation operation time determining part (503) is configured to determine the second accumulation time of the second accumulation operation based on the information on the total amount of the first accumulation times in the first image sensing operation and the data and the information stored in the characteristic data storing part. [3] Imaging system according to claim 2, additionally comprising: a console (114) configured to provide information about the dose of radiation or light necessary for the second image acquisition operation to the control computer (108), wherein the accumulation operation time determining part (503) is configured to determine the second accumulation time of the second accumulation operation further based on the information on the dose of the radiation or the light necessary for the second image pickup operation. [4] The imaging system according to claim 2 or 3, wherein the control computer (108) is configured to perform the arithmetic processing for determining the second accumulation time of the second accumulation operation such that the second accumulation time of the second accumulation operation is greater than or equal to the shortest irradiation time of the radiation generating device (110). [5] Imaging system according to one of claims 1 to 4, wherein each of the picture elements additionally comprises a switching element (202, 602) configured to output the electrical signal corresponding to the electrical charge for the first accumulation time in the first accumulation mode or the electrical signal corresponding to the electrical charge for the second accumulation time in the second accumulation mode, the detector comprises: a detection unit (101) in which the picture elements are arranged in a matrix form, a drive circuit (102) configured to control a conductive state of the switching element for driving the detection unit, and a readout circuit (103) configured to output the electrical signal supplied by the detection unit as image data through a signal line connected to the switching element, the readout circuit (103) comprises a reset switch configured to reset the signal line, and the control unit (106) is configured to control the drive circuit (102) and the reset switch in connection with the change from the first scanning range to the second scanning range such that the detector is configured to perform an initialization operation for initializing the conversion element during a period between the first image recording operation and the second image recording operation. [6] Imaging system according to claim 5, additionally comprising: a power supply unit (107) comprising: a reference power supply configured to apply a reference voltage to one electrode of the conversion element (601) via the switching element (602), a refresh power supply configured to apply a refresh voltage to the one electrode of the conversion element (601) via the switching element (602), and a bias power supply configured to apply a bias voltage to the other electrode of the conversion element (601), wherein the conversion element (601) is a metal-insulator-semiconductor (MIS) type conversion element, the detector is configured to perform a refresh operation in which the switching element is set to a non-conductive state, another switching element (603) is set to the conductive state, the bias voltage is applied to the other electrode, and the refresh voltage is applied to the other electrode via the other switching element to refresh the conversion element, and the control unit (106) is configured to cause the detector to perform the refresh operation and the initialization operation after the refresh operation during the period between the first image pickup operation and the second image pickup operation. [7] Imaging device (100), comprising: a detector in which a plurality of image elements, each comprising a conversion element (201, 601) configured to convert radiation or light into an electric charge, are arranged in a matrix form, and which is configured to perform an image pickup operation to output image data corresponding to emitted radiation or emitted light; and a control unit (106) configured to control operations including the image acquisition operation of the detector, wherein the image capturing operation comprises a first image capturing operation and a second image capturing operation, wherein the first image capturing operation comprises a first accumulation operation in which the conversion element is configured to generate the electrical charge for a first accumulation time, and a first output operation in which the detector is configured to scan in a first scanning area corresponding to a portion of the plurality of image elements to output image data in the first scanning area, wherein the second image capturing operation comprises a second accumulation operation in which the conversion element is configured to generate the electrical charge for a second accumulation time, and a second output operation in which the detector is configured to scan in a second scanning area that is larger than the first scanning area to output image data in the second scanning area, characterized by , that the control unit (106), when a change from the first scanning area to the second scanning area is instructed, is configured to control the operation of the detector such that the detector is configured to perform the second accumulation operation with a second accumulation time of the second accumulation operation determined by arithmetic processing based on information about a total amount of first accumulation times in the first image pickup operation before a change of the scanning area such that an image artifact caused by a level difference between a dark time output of the first image pickup operation and a dark time output of the second image pickup operation is less than a predetermined allowable value, wherein the dark time output of the first or second image pickup operation is an electrical signal corresponding to the electrical charge for the first or second accumulation time in a dark state,in which there is no radiation or light. [8] A method for controlling an imaging device (100) comprising a detector in which a plurality of image elements, each comprising a conversion element (201, 601) configured to convert radiation or light into an electric charge, are arranged in a matrix form, and which is configured to perform an image pickup operation to output image data corresponding to emitted radiation or emitted light, and controls the operations including the image pickup operation of the detector, the method comprising the step of: Performing a second image capturing operation after a first image capturing operation, wherein the first image capturing operation comprises a first accumulation operation in which the conversion element generates the electrical charge for a first accumulation time, and a first output operation in which the detector is scanned in a first scanning area corresponding to a part of the plurality of pixels to output image data in the first scanning area, wherein the second image capturing operation comprises a second accumulation operation in which the conversion element generates the electrical charge for a second accumulation time, and which is performed in a second accumulation time of the second accumulation operation, and a second output operation in which the detector is scanned in a second scanning area that is larger than the first scanning area to output image data in the second scanning area, characterized by , that the second accumulation time of the second accumulation operation, when a change from the first scanning area to the second scanning area is instructed, is determined in arithmetic processing based on information on a total amount of first accumulation times in the first image sensing operation before a change of the scanning area such that an image artifact caused by a level difference between a dark time output of the first image sensing operation and a dark time output of the second image sensing operation is less than a predetermined allowable value, wherein the dark time output of the first or second image sensing operation is an electric signal corresponding to the electric charge for the first or second accumulation time in a dark state in which no radiation or light is present. [9] A program that causes a computer to control an imaging device (100) comprising a detector in which a plurality of image elements, each comprising a conversion element (201, 601) configured to convert radiation or light into an electric charge, are arranged in a matrix form, and which is configured to perform an image pickup operation to output image data corresponding to emitted radiation or light, and controls the operations including the image pickup operation of the detector, the program causing the computer to perform: a second image pickup operation after a first image pickup operation, wherein the first image pickup operation comprises a first accumulation operation in which the conversion element generates the electrical charge for a first accumulation time, and a first output operation in which the detector is scanned in a first scanning area corresponding to a part of the plurality of pixels to output image data in the first scanning area, wherein the second image pickup operation comprises a second accumulation operation in which the conversion element generates the electrical charge for a second accumulation time, and which is performed in a second accumulation time of the second accumulation operation, and a second output operation in which the detector is scanned in a second scanning area that is larger than the first scanning area to output image data in the second scanning area, characterized by , that the second accumulation time of the second accumulation operation, when a change from the first scanning area to the second scanning area is instructed, is determined in arithmetic processing based on information on a total amount of first accumulation times in the first image sensing operation before a change of the scanning area such that an image artifact caused by a level difference between a dark time output of the first image sensing operation and a dark time output of the second image sensing operation is less than a predetermined allowable value, wherein the dark time output of the first or second image sensing operation is an electric signal corresponding to the electric charge for the first or second accumulation time in a dark state in which no radiation or light is present.

Images