JP4434067B2 - Imaging device - Google Patents

Description

  The present invention relates to an imaging apparatus used in the medical field, the industrial field, the nuclear field, and the like.

  An imaging device that obtains an image based on charge information will be described taking an example in which X-rays are incident and converted into charge information. The imaging apparatus includes an X-ray sensitive X-ray conversion layer, and the X-ray conversion layer converts into carriers (charge information) by the incidence of X-rays. An amorphous amorphous selenium (a-Se) film is used as the X-ray conversion layer.

  In addition, the imaging device includes a circuit that accumulates and reads out carriers converted by the X-ray conversion layer. As shown in FIG. 6, this circuit is composed of a plurality of gate lines G and data lines D arranged two-dimensionally, and also turns on a capacitor Ca for accumulating carriers and a carrier accumulated in the capacitor Ca. Thin film transistors (TFTs) Tr that are read out by switching between / OFF are arranged in a two-dimensional manner. The gate line G controls ON / OFF switching of each thin film transistor Tr and is electrically connected to the gate of each thin film transistor Tr. The data line D is electrically connected to the reading side of the thin film transistor Tr.

  For example, as shown in FIG. 6, the control sequence when the gate line G is composed of 10 gate lines G1 to G10 and the data line D is composed of 10 data lines D1 to D10 is as follows. First, carriers are generated by the incidence of X-rays, and the carriers are accumulated in the capacitor Ca as carriers. The gate line G1 is selected from the gate drive circuit 101, and each thin film transistor Tr connected to the selected gate line G1 is selected and designated. The accumulated carriers are read out from the capacitors Ca connected to the selected thin film transistors Tr, and are read out in the order of the data lines D1 to D10. Next, the gate line G2 is selected from the gate driving circuit 101, and the stored carriers are read out from the capacitor Ca connected to the selected gate line G1 and each thin film transistor Tr in the same procedure, and the data Read in the order of lines D1 to D10. Similarly, the remaining gate lines G are sequentially selected to read out a two-dimensional carrier. Each read carrier is amplified by an amplifier and converted from an analog value to a digital value by an A / D converter. A two-dimensional image is obtained based on the carrier converted into the digital value. The amplifier and the A / D converter are mounted on the circuit board 102 as shown in FIG. Incidentally, the amplifier and the A / D converter may be configured by a plurality (two in FIG. 7) of circuit boards 102 as shown in FIG.

  However, when the circuit board 102 includes a plurality of circuit boards 102 as shown in FIG. 7, there may be a difference in carrier signal level (luminance) between the circuit boards 102. Even if a signal level difference does not occur in each circuit board 102 in a certain shooting mode indicating a shooting mode, a signal level difference may occur in each circuit board 102 in another shooting mode. This is because by dividing the circuit board into multiple parts, the high-frequency characteristics (response characteristics against instantaneous current) of the power supply (not shown) supplied to the amplifier and A / D converter differ from circuit board to circuit board. This is because even if converted to, the value becomes different.

  The present invention has been made in view of such circumstances, and an object thereof is to provide an imaging device capable of reducing a signal level difference.

In order to achieve such an object, the present invention has the following configuration.
That is, the invention described in claim 1 is a conversion layer that converts light or radiation information into charge information by the incidence of light or radiation, and storage / readout that stores and reads out charge information converted by the conversion layer. Circuit, and an amplification / analog / digital conversion circuit that amplifies the charge information read by the storage / readout circuit and converts the analog value into a digital value, and the amplification / analog / digital conversion circuit includes a plurality of circuits. An imaging device that is configured with a substrate and obtains an image based on charge information converted into a digital value. The readout / amplification time, which is the time from the start of reading of charge information to amplification, and the charge information generated on each circuit board Time change means for associating the signal level difference with each other and changing the setting to the optimum readout / amplification time that reduces the signal level difference. And it is characterized in and.

  [Operation / Effect] According to the invention described in claim 1, when the amplification / analog / digital conversion circuit is composed of a plurality of circuit boards, the signal level difference of the charge information generated in each circuit board is changed in time. Reduce by means. That is, the time changing means associates the readout / amplification time, which is the time from the start of readout of charge information to the amplification, with the signal level difference described above, and sets the optimum readout / amplification time to reduce the signal level difference. change. As a result, even if the circuit board characteristics differ from each other, the amount of signal level can be controlled for each circuit board by manipulating the readout and amplification time, and the optimum readout and amplification time that reduces the signal level difference By changing the setting to, the signal level difference can be reduced.

  An example of the above-described invention is to configure the time changing means so that the setting of the readout / amplification time can be changed for each shooting mode indicating the shooting mode (the invention according to claim 2). With this configuration, even if the circuit board has the same circuit board and the characteristics of the circuit board differ for each shooting mode, the amount of signal level can be controlled for each shooting mode by manipulating the readout and amplification times. The signal level difference can be reduced by changing the setting to the optimum read / amplification time that reduces the signal level difference.

  Another example of the invention described above is that the time changing means is configured so that the read / amplification time can be changed for each circuit board (the invention according to claim 3). By configuring in this way, even if the circuit board characteristics are different from each other, it is possible to control the amount of signal level for each circuit board by manipulating the read / amplification time, and the optimal signal level difference is reduced. The signal level difference can be reduced by changing the setting to the readout / amplification time.

  Note that the invention according to claim 3 is dependent on claim 2, that is, the readout / amplification time may be configured to change the setting for each imaging board and the imaging mode indicating the imaging mode and each circuit board. Good.

  In these inventions described above, the read / amplification time is preferably in the range of 13 μsec or more and 17 μsec or less. The readout / amplification time described above is conventionally about 18 μsec, but it has been found that a signal level difference occurs at this time. Therefore, as a result of associating the read / amplification time with the signal level difference, it was found that the preferable read / amplification time is in the range of 13 μsec or more and 17 μsec or less.

  According to the imaging apparatus of the present invention, when the amplification / analog / digital conversion circuit is constituted by a plurality of circuit boards, the time changing means is the readout / amplification that is the time from the start of readout of the charge information to the amplification. The time and the signal level difference described above are associated with each other, and the setting is changed to the optimum read / amplification time that reduces the signal level difference. As a result, the amount of signal level can be controlled for each circuit board by manipulating the readout / amplification time, and the signal level difference can be reduced by changing the setting to the optimum readout / amplification time that reduces the signal level difference. Can be reduced.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic block diagram of an X-ray imaging apparatus according to an embodiment, FIG. 2 is a schematic cross-sectional view around the X-ray conversion layer of the X-ray imaging apparatus, and FIG. 3 is an amplifier of the X-ray imaging apparatus. FIG. 4 is a schematic block diagram schematically illustrating the flow of data in the A / D conversion circuit. In the present embodiment, X-rays will be described as an example of incident radiation, and an X-ray imaging apparatus will be described as an example of an imaging apparatus.

  The X-ray imaging apparatus according to the present embodiment performs imaging by irradiating a subject with X-rays. Specifically, an X-ray image transmitted through the subject is projected onto an X-ray conversion layer (in this embodiment, an amorphous selenium film), and carriers (charge information) proportional to the density of the image are generated in the layer. Is converted into a carrier.

  As shown in FIG. 1, the X-ray imaging apparatus accumulates and reads out carriers converted by a gate drive circuit 1 that selects a gate line G, which will be described later, and an X-ray conversion layer 23 (see FIG. 2). A detection element circuit 2 for detecting X-rays, an amplifier / A / D conversion circuit 3 for amplifying the carrier read by the detection element circuit 2 and converting the analog value into a digital value, and an amplifier / A / An image processing unit 4 that obtains an image by performing signal processing on the carrier converted into a digital value by the D conversion circuit 3, these circuits 1 to 3, the image processing unit 4, a memory unit 6 and a monitor 8, which will be described later, and the like. A controller 5 that performs overall control, a memory unit 6 that stores processed images, an input unit 7 that performs input settings, and a monitor 8 that displays processed images and the like. In this specification, information such as a carrier and an image is image information related to the image. The X-ray conversion layer 23 corresponds to the conversion layer in the present invention, the detection element circuit 2 corresponds to the storage / readout circuit in the present invention, and the amplifier / A / D conversion circuit 3 corresponds to the amplification / analog in the present invention. / Corresponds to a digital conversion circuit.

  The gate drive circuit 1 is electrically connected to a plurality of gate lines G. By applying a voltage from the gate driving circuit 1 to each gate line G, a thin film transistor (TFT) Tr described later is turned on to release reading of carriers accumulated in a capacitor Ca described later, and the voltage applied to each gate line G Is stopped (the voltage is set to −10 V), and the thin film transistor Tr is turned off to block carrier reading. Note that the thin film transistor Tr is turned off by applying a voltage to each gate line G to cut off carrier reading and stopping the voltage to each gate line G to turn on and release carrier reading. It may be configured.

  The detection element circuit 2 includes a plurality of gate lines G and data lines D arranged in a two-dimensional manner, and switches the capacitor Ca that accumulates carriers and the carriers accumulated in the capacitor Ca to ON / OFF. The thin film transistors Tr to be read out are arranged in a two-dimensional manner. The gate line G controls ON / OFF switching of each thin film transistor Tr and is electrically connected to the gate of each thin film transistor Tr. The data line D is electrically connected to the reading side of the thin film transistor Tr.

  For convenience of explanation, in this embodiment, it is assumed that 10 × 10 thin film transistors Tr and capacitors Ca are formed in a vertical and horizontal two-dimensional matrix arrangement. That is, the gate line G is composed of ten gate lines G1 to G10, and the data line D is composed of ten data lines D1 to D10. The gate lines G1 to G10 are respectively connected to the gates of ten thin film transistors Tr arranged in parallel in the X direction in FIG. 1, and the data lines D1 to D10 are arranged in parallel in the Y direction in FIG. Each of the ten thin film transistors Tr is connected to the reading side. A capacitor Ca is electrically connected to the side opposite to the reading side of the thin film transistor Tr, and the number of the thin film transistor Tr and the capacitor Ca corresponds one to one.

  In the detection element circuit 2, as shown in FIG. 2, the detection elements DU are patterned on the insulating substrate 21 in a two-dimensional matrix arrangement. That is, the gate lines G1 to G10 and the data lines D1 to D10 described above are wired on the surface of the insulating substrate 21 by using a thin film forming technique by various vacuum deposition methods and a pattern technique by a photolithography method. Ca, the carrier collection electrode 22, the X-ray conversion layer 23, and the voltage application electrode 24 are laminated in order.

  The X-ray conversion layer 23 is formed of an X-ray sensitive semiconductor thick film. In this embodiment, the X-ray conversion layer 23 is formed of an amorphous amorphous selenium (a-Se) film. The X-ray conversion layer 23 converts X-ray information into carriers as charge information by the incidence of X-rays. The X-ray conversion layer 23 is not limited to amorphous selenium as long as it is an X-ray sensitive material in which carriers are generated by the incidence of X radiation. In addition, when imaging is performed by injecting radiation other than X-rays (such as γ-rays), a radiation-sensitive material that generates carriers by the incidence of radiation may be used instead of the X-ray conversion layer 23. Good. Further, when imaging is performed with light incident, instead of the X-ray conversion layer 23, a photosensitive material that generates carriers by the incidence of light may be used.

  The carrier collection electrode 22 is electrically connected to the capacitor Ca, collects the carrier converted by the X-ray conversion layer 23 and accumulates it in the capacitor Ca. Similarly to the thin film transistor Tr and the capacitor Ca, a large number (10 × 10 in this embodiment) of the carrier collection electrodes 22 are formed in a vertical / horizontal two-dimensional matrix arrangement. The carrier collecting electrode 22, the capacitor Ca, and the thin film transistor Tr are separately formed as each detecting element DU. Further, the voltage application electrode 24 is formed over the entire surface as a common electrode of all the detection elements DU.

  As shown in FIG. 3, the amplifier / A / D conversion circuit 3 includes an amplifier 31 that amplifies the carrier, a sample hold 32 that temporarily accumulates the amplified carrier for a predetermined time, and an amplification read by the sample hold 32. And an A / D converter 33 for converting the state carrier from an analog value to a digital value. In this embodiment, the amplifier / A / D conversion circuit 3 is composed of a plurality (two in FIG. 1) of circuit boards.

  The image processing unit 4 performs various signal processing on the carrier converted into a digital value by the A / D converter 33 of the amplifier / A / D conversion circuit 3 to obtain an image. The controller 5 controls the circuits 1 to 3, the image processing unit 4, the memory unit 6, the monitor 8, and the like, and has a function of changing the setting to the optimum reading / amplifying time in this embodiment. The image processing unit 4 and the controller 5 are composed of a central processing unit (CPU) and the like. The controller 5 corresponds to the time changing means in this invention.

  The memory unit 6 writes and stores image information and the like, and the image information and the like are read from the memory unit 6 in response to a read command from the controller 5. The memory unit 6 includes a storage medium represented by ROM (Read-only Memory), RAM (Random-Access Memory), and the like. Note that a RAM is used for writing image information. For example, when the controller 5 executes the control sequence by reading a program related to the control sequence, a ROM is used exclusively for reading the program related to the control sequence. In this embodiment, when an imaging mode to be described later and the model of the amplifier / A / D conversion circuit 3 are recognized, an optimum amplifier output stabilization waiting time at which a difference in signal level registered in the table is reduced is recognized. A program related to a control sequence that reads out according to the model of the amplifier / A / D conversion circuit 3 and reads out the carrier with the read amplifier output stabilization waiting time is stored in the memory unit 6 and controlled by reading the program. The sequence is executed by the controller 5. Specific contents of the above-described table will be described later.

  The input unit 7 includes a pointing device represented by a mouse, a keyboard, a joystick, a trackball, a touch panel, or the like, or an input means such as a button, a switch, or a lever. When the input setting is made in the input unit 7, the input setting data is sent to the controller 5, and the circuits 1 to 3, the image processing unit 4, the memory unit 6, the monitor 8, and the like are controlled based on the input setting data.

Subsequently, a control sequence of the X-ray imaging apparatus of the present embodiment will be described. While applying a bias voltage V _A of the high voltage to the voltage application electrode 24 (for example, several 100V~ number about 10 kV), thereby applying X-rays to be detected.

  Carriers are generated in the X-ray conversion layer 23 by the incidence of X-rays, and the carriers are accumulated in the capacitor Ca through the carrier collection electrode 22 as charge information. A target gate line G is selected by a scanning signal (that is, a gate driving signal) for reading a signal (here, carrier) of the gate driving circuit 1. In the present embodiment, description will be made assuming that gate lines G1, G2, G3,..., G9, G10 are selected one by one in order. The scanning signal for reading signals from the gate driving circuit 1 is a signal for applying a voltage (for example, about 15 V) to the gate line G.

  A target gate line G is selected from the gate drive circuit 1, and each thin film transistor Tr connected to the selected gate line G is selected and designated. A voltage is applied to the gate of the thin film transistor Tr selected and designated by this selection designation to turn on. Carriers accumulated from the capacitors Ca connected to the selected and designated thin film transistors Tr are read out to the data line D via the thin film transistors Tr that have been designated and designated to be turned on. That is, the detection element DU related to the selected gate line G is selected and designated, and carriers accumulated in the capacitor Ca of the selected and designated detection element DU are read out to the data line D.

  On the other hand, the order of reading from the detection elements DU for the same gate line G selected and designated will be described as being selected and read one by one in the order of the data lines D1 to D10. That is, when the amplifier 31 connected to the data line D is reset and the thin film transistor Tr further shifts to the ON state (that is, the gate is ON), the carrier is read to the data line D and amplified by the amplifier 31. Is done.

  That is, the address (address) designation of each detection element DU is performed based on the scanning signal for signal reading from the gate drive circuit 1 and the selection of the amplifier 31 connected to the data line D.

  First, the gate line G1 is selected from the gate driving circuit 1, the detection element DU related to the selected gate line G1 is selected and specified, and the carrier accumulated in the capacitor Ca of the selected and specified detection element DU is the data Read in the order of lines D1 to D10. Next, the gate line G2 is selected from the gate drive circuit 1, and the detection element DU related to the selected gate line G2 is selected and specified in the same procedure, and is stored in the capacitor Ca of the selected detection element DU. The read carriers are read in the order of the data lines D1 to D10. Similarly, the remaining gate lines G are sequentially selected to read out a two-dimensional carrier.

  Each read carrier is amplified by an amplifier 31, temporarily stored by a sample hold 32, and converted from an analog value to a digital value by an A / D converter 33. Based on the carrier converted into the digital value, the image processing unit 4 performs various signal processing to obtain a two-dimensional image. The obtained two-dimensional image and image information represented by a carrier are written and stored in the memory unit 6 via the controller 5 and are read from the memory unit 6 via the controller 5 as necessary. The image information is displayed on the monitor 8 via the controller 5.

  As shown in FIG. 1, when the amplifier / A / D conversion circuit 3 is configured by a plurality of (two in FIG. 1) circuit boards, carrier signals are transmitted by each amplifier / A / D conversion circuit 3. There may be a level (luminance) difference. Further, even if there is no signal level difference in each amplifier / A / D conversion circuit 3 in a certain shooting mode indicating the mode of shooting, the signal level difference is different in each amplifier / A / D conversion circuit 3 in another shooting mode. May occur. This is because the amplifier / A / D conversion circuit 3 is divided into a plurality of circuit boards, whereby the high frequency characteristics of the power supply (not shown) supplied to the amplifier 31 and the A / D converter 33 of the amplifier / A / D conversion circuit 3 are obtained. This is because (the response characteristic with respect to the instantaneous current) differs for each amplifier / A / D conversion circuit 3, and even if the carrier is converted into a digital value, the value becomes different.

  Therefore, in this embodiment, as shown in FIG. 4, the read / amplification time, which is the time from the start of reading of the carrier to the amplification, is changed. In this embodiment, the setting of the readout / amplification time is changed for each imaging mode, and the setting is changed for each amplifier / A / D conversion circuit 3. FIG. 4A is a timing chart of the reading interval in each photographing mode, and FIG. 4B is a timing chart obtained by subdividing the reading interval.

  Note that the shooting mode indicating the shooting mode includes a high-speed shooting mode indicating a shooting mode with a short frame rate and a low-speed shooting mode indicating a shooting mode with a long frame rate. The high-speed shooting mode includes a partial reading mode that is a mode in which only a predetermined area is partially read and shooting is performed, and a mode in which shooting is performed by simultaneously selecting two or more gate lines G. In addition, the low-speed shooting mode includes an entire reading mode in which the entire area is switched and selected for each gate line G to perform shooting. In the present embodiment, as shown in FIG. 4A, the partial readout mode will be described as an example as the high-speed shooting mode, and the entire readout mode will be described as an example as the low-speed shooting mode.

  In FIG. 4A, in the partial read mode, it is assumed that only the upper half of the screen, that is, only five lines from the gate lines G1 to G5 are read. Then, while reading to the gate line G5 in the entire reading mode, reading of the frame is completed at the time of reading on the gate line G5 in the partial reading mode. Therefore, in the partial reading mode, reading of the gate line in the next frame starts from the reading on the gate line G5 in the entire reading mode until the reading of the frame corresponding to the reading on the gate line G10 is completed.

  In both modes, frame readout starts in synchronization with the frame synchronization signal. Therefore, when the frame synchronization signal is set to the start of frame readout in the partial readout mode, each frame synchronization signal and partial readout mode There is a one-to-one correspondence with the start of frame reading, and two frame synchronization signals correspond to the start of frame reading in the overall reading mode. Therefore, in FIG. 4A, the frame rate in the partial read mode is half of the frame rate in the full read mode.

  The read interval is a time interval for reading one carrier of the gate line G. In this specification, the readout interval is subdivided into timing charts as shown in FIG. 4B, and the gate line selected next from the start of the amplifier reset in the amplifier 31 in the gate line G to be selected. The interval until the amplifier reset start in the amplifier 31 in G is shown. Further, the read / amplification time, which is the time from the start of carrier read to amplification, indicates the time from when the gate of the thin film transistor Tr shifts to the ON state until the amplifier output hold is turned ON.

  Specifically, as shown in FIG. 4B, simultaneously with the completion of the amplifier reset, the gate line G is selected and the gate of the thin film transistor Tr shifts to the ON state. By this transition, the carrier is read from each detection element DU regarding the gate line G. After the gate of the thin film transistor Tr shifts to the OFF state, the time from the start of amplifier reset until the output of the amplifier 31 stabilizes, more precisely, the output of the amplifier 31 stabilizes after the gate of the thin film transistor Tr shifts to the OFF state. The amplifier output hold is turned ON after the amplifier output stabilization waiting time, which is the time to start, elapses. After the amplifier output hold is turned off, the A / D converter 33 is turned on to convert the analog value into a digital value.

  In this embodiment, the amplifier reset time (start / end), gate ON time (ON / OFF), amplifier output hold time (ON / OFF) and A / D conversion time shown in FIG. The (ON / OFF) timing is configured so that the controller 5 can change the timing, the gate drive circuit 1, the detection element circuit 2, the amplifier / A / D conversion circuit 3, and the controller 5. In the present embodiment, as described above, in order to change the readout / amplification time for each shooting mode and each amplifier / A / D conversion circuit 3, the above-described amplifier output stabilization wait time is set to the shooting mode and each amplifier / A. Change for each / D conversion circuit 3.

  More specifically, a table is stored in the memory unit 6, and the table is created by associating the amplifier output stabilization waiting time with the signal level difference generated in each amplifier / A / D conversion circuit 3. The optimum amplifier output stabilization waiting time in which the signal level difference is reduced based on the rule and the experimental data obtained in advance is registered in the table for each imaging mode and each amplifier / A / D conversion circuit 3. The “optimum amplifier output stabilization wait time that reduces the signal level difference” is not necessarily the amplifier output stabilization at the minimum signal level difference among multiple candidates that associate the amplifier output stabilization wait time with the signal level difference. There is no need for the waiting time. If the signal level difference is within the allowable range even if it is not the minimum, the amplifier output stabilization waiting time for the signal level difference is selected in advance by the operator, and the amplifier output stabilization waiting time is selected. May be registered in the table. Moreover, if the signal level difference is set within the allowable range from 0 to a predetermined value, and if the signal level difference falls within the range, one amplifier output stability is stabilized from the amplifier output stabilization waiting time at each signal level difference. The waiting time may be selected at random, and the amplifier output stabilization waiting time may be registered in the table. The amplifier output stabilization wait time is preferably set so that the read / amplification time is within the range of 13 μsec to 17 μsec.

  When the photographing mode and the model of the amplifier / A / D converter circuit 3 are recognized, the optimum amplifier output stabilization waiting time at which the difference in signal level registered in the table is reduced is determined as the recognized photographing mode and amplifier / A / D. The controller 5 executes the control sequence by reading out from the memory unit 6 a program related to the control sequence that reads out according to the model of the conversion circuit 3 and reads out the carrier with the read amplifier output stabilization waiting time.

  When the amplifier output stabilization waiting time is changed as shown in FIG. 4B, the time during which the amplifier output hold is turned on is also changed. As a result, after the gate of the thin film transistor Tr is turned on, The time until the amplifier output hold is turned on, that is, the readout / amplification time is also changed.

  According to the X-ray imaging apparatus according to this embodiment described above, when the amplifier / A / D conversion circuit 3 is composed of a plurality of (two in FIG. 1) circuit boards, each amplifier / A / D conversion is performed. The controller 5 reduces the signal level difference of carriers (charge information) generated in the circuit 3. That is, the controller 5 associates the readout / amplification time, which is the time from the start of carrier readout to amplification, with the signal level difference described above, and changes the setting to the optimum readout / amplification time at which the signal level difference is reduced. . As a result, even if the characteristics of each amplifier / A / D conversion circuit 3 are different from each other, the amount of signal level can be controlled for each amplifier / A / D conversion circuit 3 by manipulating the readout / amplification time. The signal level difference can be reduced by changing the setting to the optimum read / amplification time that reduces the signal level difference.

  In this embodiment, the controller 5 is configured so that the setting can be changed for each shooting mode (partial reading mode and whole reading mode in this embodiment) in which the readout / amplification time indicates the mode of shooting. With this configuration, even when the amplifier / A / D conversion circuit 3 is on the same circuit board and the characteristics of the amplifier / A / D conversion circuit 3 are different for each photographing mode, the read / amplification time can be manipulated. Thus, the amount of signal level can be controlled for each shooting mode, and the signal level difference can be reduced by changing the setting to the optimum readout / amplification time that reduces the signal level difference.

  In this embodiment, the controller 5 is configured so that the read / amplification time can be changed for each amplifier / A / D conversion circuit 3. With this configuration, even if the characteristics of the amplifier / A / D conversion circuit 3 are different from each other, the amount of signal level is controlled for each amplifier / A / D conversion circuit 3 by manipulating the readout / amplification time. The signal level difference can be reduced by changing the setting to the optimum read / amplification time that reduces the signal level difference.

  The read / amplification time is conventionally about 18 μsec, but it has been found that a signal level difference occurs at this time. Therefore, as a result of associating the read / amplification time with the signal level difference, it was found that the preferable read / amplification time is in the range of 13 μsec or more and 17 μsec or less.

  The present invention is not limited to the above-described embodiment, and can be modified as follows.

  (1) In the above-described embodiment, the X-ray imaging apparatus as shown in FIG. 1 has been described as an example. However, the present invention is also applicable to an X-ray fluoroscopic imaging apparatus disposed on a C-type arm, for example. May be. The present invention may also be applied to an X-ray CT apparatus.

  (2) In the embodiment described above, the present invention provides a “direct conversion type” detection element circuit in which radiation represented by incident X-rays is directly converted into charge information by an X-ray conversion layer (conversion layer). Although applied, an indirect conversion type detection element circuit that converts incident radiation into light by a conversion layer such as a scintillator and converts the light into charge information by a conversion layer formed of a photosensitive material The present invention may be applied.

  (3) In the above-described embodiment, the detection element circuit for detecting X-rays has been described as an example. However, the present invention uses a radioisotope (RI) as in an ECT (Emission Computed Tomography) apparatus. The detection element circuit is not particularly limited as long as it is a detection element circuit for detecting radiation, as exemplified by a detection element circuit for detecting γ-rays emitted from an administered subject. Similarly, the present invention is not particularly limited as long as it is an apparatus that performs imaging by incidence of radiation, as exemplified by the above-described ECT apparatus.

  (4) In the above-described embodiments, radiation imaging represented by X-rays and the like has been described as an example, but the present invention can also be applied to an apparatus that performs imaging by incidence of light.

  (5) In the above-described embodiments, the shooting modes are the high-speed shooting mode and the low-speed shooting mode, but the present invention can also be applied to other shooting modes. In addition, the partial readout mode has been described as an example of the high-speed shooting mode and the entire readout mode has been described as an example of the low-speed shooting mode. However, the mode is not limited to the mode of the embodiment. For example, as a high-speed shooting mode, there is a mode in which shooting is performed by simultaneously selecting two or more gate lines G, but this is also applied to a mode in which shooting is performed by simultaneously selecting two or more gate lines G. can do.

  (6) In the above-described embodiment, when the photographing mode and the model of the amplifier / A / D conversion circuit 3 are recognized, the optimum amplifier output stabilization waiting time in which the signal level difference registered in the table is reduced is recognized. A program related to the control sequence for reading out the carrier according to the mode and the model of the amplifier / A / D conversion circuit 3 and reading the carrier with the read amplifier output stabilization waiting time is stored in the memory unit 6 and the program is read. By having the controller 5 execute the control sequence according to the above, the controller 5 has a function of changing the setting to the optimum readout / amplification time. For example, an optimum amplifier output stabilization wait time is input and set in the input unit 7 (see FIG. 1), and input setting data relating to the optimum amplifier output stabilization wait time is sent to the controller 5, so A function of changing the setting for the amplification time may be provided.

  (7) In the above-described embodiment, the readout / amplification time setting is changed for each shooting mode and the amplifier / A / D conversion circuit 3. However, depending on the shooting mode, each amplifier / A / D conversion circuit 3 has a signal level. If there is no difference, the read / amplification time may be set and changed for each amplifier / A / D conversion circuit 3. If there is no signal level difference in each amplifier / A / D conversion circuit 3 in a certain shooting mode, the readout / amplification time is not changed for each amplifier / A / D conversion circuit 3 in that shooting mode. The reading and amplification time can be unified and changed.

  (8) In the above-described embodiment, the optimum readout / amplification time is set in the range of 13 μsec or more and 17 μsec or less, but is not limited to this range. When the readout / amplification time is changed according to the type of circuit, the optimum readout / amplification time may be appropriately changed accordingly.

  (9) In the above-described embodiment, the read / amplification time is changed by changing the amplifier output stabilization wait time (see FIG. 4). It is not limited to changing the waiting time. For example, when changing the timing of the timing chart of FIG. 4 other than the amplifier output stabilization waiting time, the gate ON time (ON / OFF) is changed as shown in FIG. The read / amplification time may be changed by shifting the time until the amplifier output hold is turned on. Further, the read / amplification time may be changed by changing both the amplifier output stabilization waiting time and the gate ON time.

1 is a schematic block diagram of an X-ray imaging apparatus according to an embodiment. 1 is a schematic cross-sectional view around an X-ray conversion layer of an X-ray imaging apparatus. FIG. 2 is a schematic block diagram schematically illustrating the flow of data in an amplifier / A / D conversion circuit of an X-ray imaging apparatus. (A) is a timing chart of the reading interval in each photographing mode according to the embodiment, and (b) is a timing chart obtained by subdividing the reading interval. It is a timing chart which subdivided the read-out interval concerning a modification. It is a schematic block diagram of the conventional X-ray imaging apparatus. It is a schematic block diagram of the conventional X-ray imaging apparatus.

Explanation of symbols

2 ... Detection element circuit 23 ... X-ray conversion layer 3 ... Amplifier / A / D conversion circuit 5 ... Controller

Claims (4)

  A conversion layer that converts light or radiation information into charge information by the incidence of light or radiation, a storage / read circuit that stores and reads out charge information converted by the conversion layer, and a read / write circuit that reads the charge information Amplification / analog / digital conversion circuit that amplifies the converted charge information and converts the analog value into a digital value, and the amplification / analog / digital conversion circuit is composed of a plurality of circuit boards and converted into digital values. An imaging device that obtains an image based on charge information, and correlates a read / amplification time, which is a time from the start of reading of charge information to amplification, and a signal level difference of charge information generated in each circuit board. An image pickup apparatus, comprising: time changing means for changing the setting to the optimum readout / amplification time in which a signal level difference is reduced.   The imaging apparatus according to claim 1, wherein the time changing unit is configured so that the readout / amplification time can be set and changed for each imaging mode indicating a mode of imaging.   3. The imaging apparatus according to claim 1, wherein the time changing means is configured so that the setting of the readout / amplification time can be changed for each of the circuit boards. 4. The imaging apparatus according to claim 1, wherein the readout / amplification time is in a range of 13 μsec to 17 μsec. 5.

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