JP2010034663A - Imaging device - Google Patents

Abstract

An object of the present invention is to provide an imaging apparatus capable of reducing image quality degradation due to noise to an amplifier.
A controller has a function of take-out operation control, and the take-out operation control function resets an amplifier in the charge-voltage conversion amplifier for a take-out operation of taking out a voltage value held by a sample hold of the charge-voltage conversion amplifier. Since the control is performed so that it is performed during the reset of the amplifier, the reset is performed even when noise caused by driving the switching element that performs the extraction operation is mixed, so that the image quality deterioration due to the noise to the amplifier can be reduced. At this time, preferably, if control is performed so that A / D conversion is also performed while the amplifier is reset, the noise is reset even if noise due to driving of the A / D converter is mixed, and image quality deterioration due to noise to the amplifier is further reduced. It can be further reduced.
[Selection] Figure 4

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. 8, this circuit is composed of a plurality of gate lines G and data lines D arranged two-dimensionally, and turns on a capacitor Ca that accumulates 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. 8, 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 in a state of being converted into a voltage by a charge-voltage conversion 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 charge voltage conversion amplifier and the A / D converter are mounted on the circuit board 102 as shown in FIG.

  As shown in FIG. 9B, the reading interval, which is the time interval for reading one carrier on the gate line G, is the time for resetting the amplifier, the time for turning on the gate of the thin film transistor, and the amplifier output hold (sample hold is ON). ) Time, A / D conversion time, and the like. If the readout time for each frame rate is a “readout period”, as shown in FIG. 9A, the readout interval is 10 (10 lines from the gate lines G1 to G10). The frame rate is also a time interval between frame synchronization signals, and the timing of outputting a frame representing an image unit (that is, reading a frame) is controlled in synchronization with the frame synchronization signal. That is, carrier reading is started after a fixed time from the synchronization signal (fixed time “0” in FIG. 9) with respect to the frame synchronization signal having a fixed period (see, for example, Patent Document 1). In FIG. 9, the above-described readout interval corresponds to a charge-voltage conversion period by the charge-voltage conversion amplifier. Further, when a period from the end of reading to the start of the next reading is a “blank period”, X-ray irradiation is performed during the blank period, and X-rays are incident on the X-ray conversion layer. Note that the period from the end of X-ray irradiation (incident) to the next frame synchronization signal is a as shown in FIG.

The timing chart shown in FIG. 9 shows a case where the operation is performed at high speed. At the same time as the charge-voltage conversion, an operation for taking out from the sample hold (see hatching in the upper right oblique line in FIG. 9) and A / D conversion (in FIG. 9). (See hatching in the upper left diagonal line). Usually, as shown in the timing chart of FIG. 10, after performing charge-voltage conversion by the charge-voltage conversion amplifier (including holding (accumulation) by sample-hold), an operation for taking out from the sample-hold (upper right diagonal line in FIG. 10) ) And A / D conversion (see the hatching in the upper left diagonal line in FIG. 10). Therefore, in FIG. 10, the read interval is a time obtained by adding the charge-voltage conversion period, the extraction operation, and A / D conversion. On the other hand, in FIG. 9, by performing the extraction operation and the A / D conversion simultaneously with the charge voltage conversion, as described above, the read interval can be shortened to the charge voltage conversion period. The time required for the D conversion can be saved.
Japanese Patent Laying-Open No. 2006-30421 (page 7-9, FIG. 4)

  However, in the method of performing charge-voltage conversion by the charge-voltage conversion amplifier as shown in FIG. 10 and accumulating in the sample hold and then performing the extraction operation from the sample hold and A / D conversion, the flat panel type shown in FIG. In a multi-channel imaging device such as an imaging device (flat panel imaging device) equipped with a detector, when collecting image data at a high speed, the number of integrated circuits (ICs) of the A / D converter is set. It is necessary to increase it, which is not good in terms of cost, power consumption and heat generation. Further, in the method of performing the extraction operation and the A / D conversion simultaneously with the charge voltage conversion as shown in FIG. 9, in the period from the end of reset to the sample hold in the amplifier portion, the circuit after the sample hold (the stage after the sample hold) There is a problem that image quality is deteriorated due to noise generated by driving a switching element or an A / D converter.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an imaging apparatus capable of reducing deterioration in image quality due to noise to an amplifier.

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. A circuit, a charge-voltage conversion circuit that converts and holds charge information read by the storage / read-out circuit into voltage information, and an imaging device that obtains an image based on the voltage information held by the charge-voltage conversion circuit And an extraction operation control means for controlling the extraction operation for extracting the voltage information held in the charge-voltage conversion circuit to be performed during an amplifier reset for resetting the amplifier in the charge-voltage conversion circuit. To do.

  [Operation / Effect] According to the first aspect of the present invention, the take-out operation control means is provided, and the take-out operation control means performs the take-out operation for taking out the voltage information held in the charge-voltage conversion circuit. Control to be done during amplifier reset to reset the amplifier inside. Since the extraction operation is performed during unpreset, even if noise due to driving the element that performs the extraction operation is mixed, it is reset and image quality degradation due to noise to the amplifier can be reduced. In the case where the operation is performed at a high speed as shown in FIG. 9, it is possible to perform the extraction operation during the amplifier reset by making the reset time of the amplifier reset longer than the conventional one. Further, by lengthening the reset time, power consumption of the amplifier in the charge-voltage conversion circuit can be suppressed, and power consumption and heat generation can be reduced.

  A normal imaging device includes an analog / digital conversion circuit that converts an analog value of voltage information held and taken out by a charge-voltage conversion circuit from a digital value to a digital value. Not only noise caused by driving an element that performs an extraction operation, but also noise caused by driving an analog / digital conversion circuit at the subsequent stage of the element is likely to be mixed into the amplifier. Therefore, it is preferable that the take-out operation control means performs control so that the take-out operation and the conversion operation in the analog / digital conversion circuit are performed during amplifier reset (the invention according to claim 2). Since the extraction operation and the conversion operation in the analog / digital conversion circuit are performed during the unpreset, not only the noise caused by driving the element performing the extraction operation but also the driving of the analog / digital conversion circuit in the subsequent stage of the element Even if noise is mixed, it is reset, and image quality deterioration due to noise to the amplifier can be further reduced.

  According to the imaging apparatus of the present invention, the take-out operation control unit controls the take-out operation to take out the voltage information held in the charge-voltage converter circuit during the amplifier reset that resets the amplifier in the charge-voltage converter circuit. Therefore, even if noise due to driving the element that performs the extraction operation is mixed, it is reset and image quality deterioration due to noise to the amplifier 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 the X-ray imaging apparatus according to the 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 a charge of the X-ray imaging apparatus. It is a peripheral circuit diagram of a voltage conversion amplifier and an A / D converter. 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 that detects X-rays, a charge-voltage conversion amplifier 3 that amplifies the carrier read out by the detection element circuit 2 into a voltage, and the charge-voltage conversion amplifier 3 An A / D converter 4 for converting a voltage analog value into a digital value, and an image processing unit 5 for obtaining an image by performing signal processing on the voltage value converted into a digital value by the A / D converter 4; The controller 6 that controls the circuits 1 and 2, the charge / voltage conversion amplifier 3, the A / D converter 4, the image processing unit 5, the memory unit 7 and the monitor 9 described later, and the processed image are stored. Memory unit 7 and input An input unit 8 which performs a constant, and a monitor 9 for displaying the processed images. 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 charge-voltage conversion amplifier 3 corresponds to the charge-voltage conversion circuit in the present invention. The A / D converter 4 corresponds to the analog / digital conversion circuit in the present invention.

  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 charge-voltage conversion amplifier 3 is electrically connected to each data line D (D1 to D10 in FIG. 3) and electrically connected to each data line D. Amplifier capacitor 32, amplifier 31 for each data line D, sample hold 33 electrically connected in parallel to amplifier capacitor 32, and switching element 34 electrically connected to sample hold 33 for each data line D And. The amplifier 31 and the end of the data line D of the detection element circuit 2 are electrically connected to each data line D via the switching element SW. The carrier read to the data line D is sent to the amplifier 31 and the amplifier capacitor 32 of the charge-voltage conversion amplifier 3 with the switching element SW turned ON. The supplied carrier is amplified with the amplifier 31 and the amplifier capacitor 32 converted into a voltage, and the sample hold 33 temporarily accumulates the amplified voltage value for a predetermined time. The voltage value once accumulated is sent to the A / D converter 4 with the switching element 34 turned ON, and the A / D converter 4 converts the analog value of the sent voltage into a digital value.

  The charge-voltage conversion amplifier 3 includes the sample hold 33 so that the voltage value is held (accumulated) by the sample hold 33. In addition, the switching element 34 is turned on to take out the voltage value held by the sample hold 33 of the charge-voltage conversion amplifier 3, and then the analog value of the voltage sent to the A / D converter 4 is obtained. The A / D converter 4 performs A / D conversion that converts the digital value into a digital value. In the present embodiment, the above-described extraction operation and the conversion operation (that is, A / D conversion) in the A / D converter 4 are performed during amplifier reset.

  Returning to the description of FIG. 2, the image processing unit 5 performs various signal processing on the voltage value converted into a digital value by the A / D converter 4 to obtain an image. The controller 6 comprehensively controls the circuits 1 and 2, the charge / voltage conversion amplifier 3, the A / D converter 4, the image processing unit 5, the memory unit 7 and the monitor 9 described later, etc. It also has a function of controlling the conversion operation (that is, A / D conversion) in the A / D converter 4 to be performed during amplifier reset (a function of extraction operation control). The image processing unit 5 and the controller 6 are composed of a central processing unit (CPU) and the like. The controller 6 corresponds to the take-out operation control means in this invention.

  The memory unit 7 writes and stores image information and the like, and the image information and the like are read from the memory unit 7 in response to a read command from the controller 6. The memory unit 7 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 6 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, a program relating to a control sequence for controlling the take-out operation and the conversion operation in the A / D converter 4 to be performed during amplifier reset is stored in the memory unit 7, and the control sequence is read out by the controller 6 by reading the program. To run.

  The input unit 8 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 input is set in the input unit 8, input setting data is sent to the controller 6, and based on the input setting data, the circuits 1, 2, the charge / voltage conversion amplifier 3, the A / D converter 4, the image processing unit 5 and the memory unit 7 And the monitor 9 are controlled.

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 of the charge-voltage conversion amplifier 3 connected to the data line D is reset and the thin film transistor Tr is turned on (that is, the gate is turned on), carriers are read to the data line D. Then, it is amplified in a state of being converted into a voltage by the amplifier 31 and the amplifier capacitor 32 of the charge-voltage conversion amplifier 3.

  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 in a state of being converted into a voltage by an amplifier 31 and an amplifier capacitor 32, temporarily stored in a sample hold 33, and converted from an analog value to a digital value by an A / D converter 4. Is done. Based on the voltage value converted into the digital value, the image processing unit 5 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 7 via the controller 6 and are read from the memory unit 7 via the controller 6 as necessary. Further, the image information is displayed on the monitor 9 via the controller 6.

  Next, the control of the take-out operation performed during amplifier reset and the conversion operation (that is, A / D conversion) in the A / D converter 4 will be described with reference to FIG. FIG. 4A is a timing chart of the reading interval, and FIG. 4B is a timing chart obtained by subdividing the reading interval.

  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.

  Specifically, as shown in FIG. 4B, after the amplifier reset is completed, 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. After the amplifier output stabilization waiting time, which is the time to start, elapses, the sample hold 33 indicating the amplifier output hold is turned ON. After the sample hold 33 is turned off and the switching element 34 is turned on, the A / D converter 4 is turned on to convert the analog value into a digital value.

  As described above, when the switching element 34 is turned ON, the voltage value held by the sample hold 33 of the charge-voltage conversion amplifier 3 is extracted (see hatching in the upper right diagonal line in FIG. 4), and then A conversion operation in the A / D converter 4 that converts the analog value of the voltage sent to the A / D converter 4 into a digital value in the A / D converter 4 (upper left diagonal line in FIG. 4) (See the hatching section). In the conventional FIG. 9, the amplifier reset has already been completed when the take-out operation (see hatching in the upper right oblique line in FIG. 9) is performed. Of course, the conversion by the A / D converter 4 after the take-out operation is performed. The amplifier is not reset even when the operation (ie, A / D conversion) (see the hatching in the upper left diagonal line in FIG. 9) is performed. Therefore, in the period from the end of reset to the sample and hold in the amplifier part, the image quality deteriorates due to noise caused by driving the circuit after the sample and hold (in this embodiment, the switching element 34 and the A / D converter 4). Let

  On the other hand, in FIG. 4 of the present embodiment, the reset operation time of the amplifier reset is made longer than before (see the arrow at the time of amplifier reset in FIG. 4), so that the extraction operation and the A / D conversion are being reset. To do. The A / D conversion time of all amplifier outputs depends on the number and speed of the A / D converters 4, but in a flat panel photographing apparatus having a large number of pixels, in general, the A / D conversion is longer than the amplifier reset time. Make the time longer. Therefore, by increasing the reset time in accordance with the A / D conversion time including the time required for the extraction operation, the power consumption of the amplifier can be suppressed although the charge-voltage conversion period and the read interval become longer.

  According to the above-described X-ray imaging apparatus according to the present embodiment, the controller 6 has a function of controlling the extraction operation, and the function of the extraction operation control uses the voltage value held by the sample hold 33 of the charge-voltage conversion amplifier 3. The take-out operation to be taken out is controlled to be performed during the amplifier reset for resetting the amplifier 31 of the charge-voltage conversion amplifier 3. Since the extraction operation is performed during unpreset, even if noise due to driving of the element (in this case, the switching element 34) that performs the extraction operation is mixed, it is reset, and image quality degradation due to noise to the amplifier can be reduced. . In the case where the operation is performed at a high speed as shown in FIG. 9, it is possible to perform the extraction operation during the amplifier reset by making the reset time of the amplifier reset longer than the conventional one. Further, by lengthening the reset time, the power consumption of the amplifier in the charge-voltage conversion circuit (here, the charge-voltage conversion amplifier 3) can be suppressed, and power consumption and heat generation can be reduced.

  An ordinary imaging apparatus (here, an X-ray imaging apparatus) is an analog / digital conversion circuit that converts an analog value of a voltage value held and taken out by a charge-voltage conversion circuit (here, a charge-voltage conversion amplifier 3) into a digital value. (Here, A / D converter 4). Not only the noise caused by driving the element that performs the extraction operation (the switching element 34 in this case) but also the noise caused by driving the A / D converter 4 at the subsequent stage of the element is likely to be mixed into the amplifier. Therefore, in this embodiment, the function of the take-out operation control is preferably controlled so that the take-out operation and the conversion operation (that is, A / D conversion) in the A / D converter 4 are performed during amplifier reset. . Since the extraction operation and A / D conversion are performed during unpreset, not only the noise caused by driving the element (in this case, the switching element 34) that performs the extraction operation, but also the A / D converter 4 subsequent to the element is driven. Even if noise due to the mixing is mixed, it is reset, and image quality degradation due to noise to the amplifier can be further reduced.

  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 embodiment, the take-out operation and the conversion operation (that is, A / D conversion) in the A / D converter 4 are controlled to be performed during the amplifier reset, but the A / D converter 4 is driven. If the noise caused by the operation is so small that it can be ignored, for example, as shown in FIG. 5, control is performed so that only the take-out operation (see hatching in the upper right diagonal line in FIG. 5) is performed during amplifier reset, and the amplifier reset ends. At the same time, control for performing A / D conversion or control for performing A / D conversion in the middle of amplifier reset and terminating amplifier reset in the middle of A / D conversion may be performed.

  (6) In the above-described embodiment, the A / D converter is described as a single configuration. However, the charge / voltage conversion amplifiers are divided into a plurality of groups, and an A / D converter is provided for each group, thereby converting the conversion speed. May be raised. For example, as shown in FIG. 6, the charge-voltage conversion amplifier 3 is divided into two groups, and an A / D converter 4 is provided for each group (that is, two A / D converters 4 are provided). The conversion speed may be doubled and a control sequence (timing chart) as shown in FIG. 7 may be used.

  (7) When image acquisition is performed at high speed, the control sequence (timing chart) shown in FIG. 4, FIG. 5 or FIG. 7 is used. The timing chart may be used. 4, FIG. 5, and FIG. 7 and the reading interval of FIG. 10 are illustrated so as not to have a large difference on the drawing, but here, the reading interval of FIG. 4, FIG. 5, and FIG. It should be noted that the description is made on the assumption that the interval is considerably shorter than the readout interval of FIG.

  (8) In the above-described embodiment, the charge voltage conversion amplifier 3 and the A / D converter 4 are separately provided, but the charge voltage conversion amplifier 3 may include the A / D converter 4.

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. 2 is a peripheral circuit diagram of a charge-voltage conversion amplifier and an A / D converter of an X-ray imaging apparatus. FIG. (A) is the timing chart of the read interval which concerns on an Example, (b) is a timing chart which subdivided the read interval. (A) is the timing chart of the read interval which concerns on a modification, (b) is a timing chart which subdivided the read interval. It is a peripheral circuit diagram of the charge voltage conversion amplifier and the A / D converter of the X-ray imaging apparatus when the charge voltage conversion amplifier is divided into two groups. (A) is a timing chart of the reading interval when the charge-voltage conversion amplifier is divided into two groups, and (b) is a timing chart in which the reading interval is subdivided. It is a schematic block diagram of the conventional X-ray imaging apparatus. (A) is a timing chart of the conventional reading interval, and (b) is a timing chart obtained by subdividing the reading interval. 9A is a timing chart of a conventional read interval, and FIG. 9B is a timing chart obtained by subdividing the read interval.

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 ... Detection element circuit 23 ... X-ray conversion layer 3 ... Charge voltage conversion amplifier 34 ... Switching element 4 ... A / D converter 6 ... Controller

Claims (2)

  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 A charge-voltage conversion circuit that converts the stored charge information into voltage information and holds it, and an imaging device that obtains an image based on the voltage information held by the charge-voltage conversion circuit, which is held by the charge-voltage conversion circuit An image pickup apparatus comprising: a take-out operation control unit configured to control a take-out operation to take out the voltage information during an amplifier reset for resetting an amplifier in the charge-voltage conversion circuit.   2. The imaging apparatus according to claim 1, further comprising an analog / digital conversion circuit that converts an analog value of voltage information held and extracted by the charge-voltage conversion circuit from a digital value into a digital value, wherein the extraction operation control means includes the extraction operation control unit. An image pickup apparatus that controls an operation and a conversion operation in the analog / digital conversion circuit to be performed during the amplifier reset.

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