JP2019121988A - Radiation image pickup device and control method of the same - Google Patents

Abstract

To suppress effectively an image horizontal stripe in a radiation image caused by disturbance.SOLUTION: A control device of a radiation image pickup device, comprises: a disturbance source specification part 12a specifying a kind of a disturbance source to be handled; a frequency measurement part 12b measuring a frequency of disturbance generated by the disturbance source; a first adjustment part 13a controlling the disturbance source so as to correspond a period of the disturbance generated by the disturbance source to a prescribed period in accordance with a timing for reading out an electric charge from each photoelectric conversion element of a sensor array; and a second adjustment part 13b controlling a start timing of a reading flow of the electric charge in a mine image acquisition mode or a dark image acquisition mode so as to correspond the reading interval in the same pixel region of a main image and a dark image to the period of the disturbance generated by the disturbance source. The first adjustment part 13a and the second adjustment part 13b are selectively executed on the basis of the kind of the disturbance source.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to a radiation imaging apparatus and a control method of the radiation imaging apparatus.

  There is known a radiation imaging apparatus using a flat panel type image sensor.

  In recent years, in this type of radiation imaging apparatus, horizontal stripe pattern or vertical stripe pattern noise (hereinafter referred to as “image horizontal stripe”) in a radiation image due to an electromagnetic wave arriving at an image sensor for further improvement in image quality There is a request to curb

  Image horizontal stripes generated in the radiation image are mainly in the fluctuating magnetic field (hereinafter abbreviated as “fluctuating magnetic field”) of the electromagnetic wave acting on the wiring part (for example, signal line, gate line or bias line) of the image sensor It occurs due to.

  More specifically, the image sensor generally has a configuration in which pixels formed of photoelectric conversion elements for converting radiation into signal charges and switch elements (for example, TFTs) for transferring the signal charges to the outside are two-dimensionally arranged. It has become. The radiation image is generated by matrix-driving the switch elements of the sensor array and sequentially transferring the signal charges generated by the photoelectric conversion elements to the reading device.

  The readout of signal charges from the sensor array is usually performed in units of one row. At this time, when a varying magnetic field acts on the wiring portion of the sensor array, an electromotive current is generated in the wiring portion. Then, such electromotive current is superimposed on the signal charge generated by each photoelectric conversion element in the image sensor, and appears as pattern noise in the form of horizontal stripes in the radiation image.

  From such a background, for example, Patent Document 1 detects the disturbance frequency of the disturbance source affecting the image sensor as a method of suppressing such image horizontal stripes, and matrix-drives the image sensor according to the disturbance frequency. It has been described to change the scanning cycle at that time.

JP, 2015-111767, A

  By the way, the image sensor of such a radiation imaging apparatus is usually exposed to electromagnetic waves from various disturbance sources (hereinafter also referred to as “variable magnetic field”). As a disturbance source for emitting an electromagnetic wave to the environment, typically, a large power flows, and a commercial power supply (for example, a single-phase AC power supply of 60 Hz), a switching power supply in a radiation imaging apparatus, A drive motor (for example, a motorized bed) installed adjacent to the radiation imaging device may be mentioned.

  In this respect, in the prior art according to Patent Document 1, since the scanning cycle (which represents the cycle for reading out the signal charges for one row in the image sensor; the same applies hereinafter) is changed to the cycle according to the disturbance frequency. Measures can be taken to suppress image horizontal stripes only for one disturbance source. Therefore, in the prior art according to Patent Document 1, for example, in the case where a plurality of switching power supplies having different switching frequencies are present as disturbance sources, it is not possible to take measures to suppress image horizontal stripes.

  Also, in the prior art according to Patent Document 1, the countermeasure for suppressing the image horizontal stripes is performed only for the disturbance source in the high frequency band compared to the scanning period (corresponding to several kHz in frequency conversion). In general, low-frequency disturbance sources such as commercial power supplies can not be dealt with to suppress image horizontal stripes.

  On the other hand, since the frequency of the disturbance source (for example, the commercial frequency of the commercial power supply or the switching frequency of the switching power supply) fluctuates in time, in order to suppress image horizontal stripes in real time according to the frequency of the disturbance source There is a need for technology to deal with

  The present disclosure has been made in view of the above problems, and is capable of more effectively suppressing image horizontal stripes in a radiation image caused by disturbance, and control of the radiation image imaging apparatus. Intended to provide a method.

The main present disclosure to solve the above-mentioned problems is
A radiation imaging apparatus that performs initialization, charge accumulation and readout of accumulated charges on a sensor array composed of a plurality of photoelectric conversion elements to generate a radiation image,
A main image acquisition mode for generating a radiation image according to a main image by performing radiation irradiation during the charge storage, and generating the radiation image according to a dark image without performing radiation irradiation during the charge storage A driving unit that executes a dark image acquisition mode and generates a difference between the main image and the dark image as a normal image;
A disturbance source identification unit that identifies the type of disturbance source to be dealt with based on a predetermined sensor signal;
A frequency measurement unit that measures the frequency of the disturbance generated by the disturbance source;
A first adjustment unit configured to control the disturbance source such that the frequency of the disturbance generated by the disturbance source corresponds to a predetermined cycle related to the timing of reading out electric charge from each photoelectric conversion element of the sensor array;
The start timing of the charge readout flow in the main image acquisition mode or the dark image acquisition mode is controlled so that the readout interval in the same pixel area of the main image and the dark image corresponds to the period of the disturbance generated by the disturbance source. A second adjustment unit to
Equipped with
It is a radiographic imaging apparatus which selectively performs the control processing by a said 1st adjustment part or the control processing by a said 2nd adjustment part based on the classification of the said disturbance source.

And in other aspects,
A radiation imaging apparatus that performs initialization, charge accumulation and readout of accumulated charges on a sensor array composed of a plurality of photoelectric conversion elements to generate a radiation image,
A main image acquisition mode for generating a radiation image according to a main image by performing radiation irradiation during the charge storage, and generating the radiation image according to a dark image without performing radiation irradiation during the charge storage A driving unit that executes a dark image acquisition mode and generates a difference between the main image and the dark image as a normal image;
A frequency measurement unit that measures the frequency of the disturbance generated by the disturbance source;
A first adjustment unit configured to control the disturbance source such that the frequency of the disturbance generated by the disturbance source corresponds to a predetermined cycle related to the timing of reading out electric charge from each photoelectric conversion element of the sensor array;
It is a radiographic imaging apparatus provided with these.

And in other aspects,
A radiation imaging apparatus that performs initialization, charge accumulation and readout of accumulated charges on a sensor array composed of a plurality of photoelectric conversion elements to generate a radiation image,
A main image acquisition mode for generating a radiation image according to a main image by performing radiation irradiation during the charge storage, and generating the radiation image according to a dark image without performing radiation irradiation during the charge storage A driving unit that executes a dark image acquisition mode and generates a difference between the main image and the dark image as a normal image;
A frequency measurement unit that measures the frequency of the disturbance generated by the disturbance source;
The start timing of the charge readout flow in the main image acquisition mode or the dark image acquisition mode is controlled so that the readout interval in the same pixel area of the main image and the dark image corresponds to the frequency of the disturbance generated by the disturbance source. A second adjustment unit to
It is a radiographic imaging apparatus provided with these.

And in other aspects,
A control method of a radiation image capturing apparatus, which generates a radiation image by executing initialization, charge accumulation and readout of accumulated charges on a sensor array including a plurality of photoelectric conversion elements,
A main image acquisition mode for generating a radiation image according to a main image by performing radiation irradiation during the charge storage, and generating the radiation image according to a dark image without performing radiation irradiation during the charge storage Executing a dark image acquisition mode, generating a difference between the main image and the dark image as a normal image;
Identify the type of disturbance source to be dealt with based on a predetermined sensor signal,
Measuring the frequency of the disturbance generated by the disturbance source;
The disturbance source is controlled such that the frequency of the disturbance generated by the disturbance source corresponds to a predetermined period related to the timing of reading out the charge from each photoelectric conversion element of the sensor array,
The start timing of the charge readout flow in the main image acquisition mode or the dark image acquisition mode is controlled so that the readout interval in the same pixel area of the main image and the dark image corresponds to the period of the disturbance generated by the disturbance source. And
It is a control method which makes control processing by the 1st adjustment part or control processing by the 2nd adjustment part selectively perform based on classification of the disturbance source.

  According to the radiation imaging device according to the present disclosure, it is possible to more effectively suppress the image horizontal stripes in the radiation image caused by the disturbance.

A figure showing an example of composition of an imaging device concerning an embodiment The figure which shows typically the use condition of the imaging device which concerns on embodiment A diagram schematically showing an appearance of an imaging device according to an embodiment Schematic of the circuit structure of the TFT panel which concerns on embodiment The figure which shows an example of the read-out circuit of read-out IC concerning embodiment A figure showing an example of composition of a switching power supply concerning an embodiment Diagram for explaining the operation of the drive unit according to the embodiment A diagram showing an example of a disturbance source causing a fluctuating magnetic field to act on a TFT panel The figure which shows the relationship of the electric charge acquisition timing of read-out IC which concerns on embodiment, and the disturbance which a switching power supply generate | occur | produces Graphic representation of equation (2) A figure explaining operation of this dark difference interval adjustment part concerning an embodiment The flowchart which shows one example of operation of the control control equipment of the image pickup device which relates to the execution form In the flow of FIG. 12 which concerns on embodiment, when the classification of a disturbance source is a switching power supply, it is a figure which shows transfer of the signal of a control apparatus and each part In the flow of FIG. 12 which concerns on embodiment, when the classification of a disturbance source is a commercial power source, it is a figure which shows transfer of the signal of a control apparatus and each part in Graphic representation of equation (4) A figure showing an example of operation of an imaging device concerning modification 2

  Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the present specification and the drawings, components having substantially the same functions will be assigned the same reference numerals and redundant description will be omitted.

[Overall configuration of radiation imaging apparatus]
Hereinafter, with reference to FIGS. 1 to 6, an example of the entire configuration of a radiation imaging device 1 (hereinafter, abbreviated as “imaging device 1”) according to the present embodiment will be described.

  FIG. 1 is a diagram showing an example of the configuration of an imaging device 1 according to the present embodiment. FIG. 2 is a view schematically showing a use state of the imaging device 1 according to the present embodiment. FIG. 3 is a view schematically showing the appearance of the imaging device 1 according to the present embodiment.

  The imaging device 1 according to the present embodiment includes a control device 10, a TFT panel 20, a readout IC 30, a gate drive IC 40, a switching power supply 50, a disturbance sensor 60, and a clock generation unit 70.

  The imaging apparatus 1 according to the present embodiment is, for example, an X-ray imaging apparatus, and as illustrated in FIG. 2, receives an X-ray emitted from a radiation generation apparatus 200 (for example, an X-ray generation apparatus) and transmitted through an object. By doing this, a radiation image relating to the subject is acquired.

  In addition, as shown in FIG. 3, the imaging device 1 according to the present embodiment accommodates each part in the case K1. A power switch K2, a changeover switch K3, an indicator K4, a connector K5, and the like are provided on one side of the housing K1. In addition, a plate-like scintillator K6 is disposed in the case K1 so as to cover the TFT panel 20, and when receiving radiation, the electromagnetic wave having a wavelength longer than that of radiation such as visible light is directed toward the TFT panel 20. It is supposed to emit.

  The control device 10 is communicably connected to the readout IC 30, the gate drive IC 40, the switching power supply 50, the disturbance sensor 60, and the clock generation unit 70, and centrally controls the respective units of the imaging device 1.

  The control device 10 identifies the type of the disturbance source to be dealt with based on the drive signal 11 that controls the execution of the imaging process and the sensor signal from the disturbance sensor 60, and identifies the disturbance frequency of the disturbance source. 12, an adjustment unit 13 that executes image horizontal fringe suppression processing that copes with disturbances. Then, according to the configuration of the control device 10, control for suppressing the image horizontal stripes generated in the above-described radiation image is performed (details will be described later).

  The control device 10 is also realized by, for example, an FPGA, a CPU, a dedicated hardware circuit, or a combination thereof.

  The disturbance sensor 60 has a magnetic intensity and frequency (hereinafter referred to as “the magnetic field”) generated by a disturbance source (for example, a switching power supply 50, a commercial power supply facility, an external drive motor, etc. described later with reference to FIG. 8). , Also referred to as “disturbance intensity and disturbance frequency”. Then, the disturbance sensor 60 sends information related to the detected disturbance intensity and disturbance frequency to the control device 10.

  As the disturbance sensor 60, typically, a Hall element (hereinafter, also referred to as "Hall element 60") is used. The disturbance sensor 60 is disposed at a position close to the disturbance source candidate or a position close to the TFT panel 20. For example, a position at which the switching frequency of the switching power supply 50 can be detected (see FIG. 6) It is arrange | positioned in the position (refer FIG. 8) which can detect the frequency of the electric power which the commercial power source applicable to a source candidate supplies.

  Note that as the disturbance sensor 60, a sensor that detects only either the disturbance intensity or the disturbance frequency may be used. As the disturbance sensor 60, for example, a voltage sensor that detects a switching signal from the switching terminal of the switching power supply 50 may be used. Further, as the disturbance sensor 60, for example, a current sensor may be used which detects an electromotive current flowing to a signal line or a bias line of the sensor array of the TFT panel 20 by a fluctuating magnetic field generated by a disturbance source.

  The clock generation unit 70 generates a clock signal, and inputs the clock signal to the control device 10. The control device 10 executes an operation based on the clock signal, and performs, for example, measurement of the switching frequency of the switching power supply 50 described later with reference to the clock signal.

  FIG. 4 is a schematic view of a circuit configuration of the TFT panel 20 according to the present embodiment.

  The TFT panel 20 is a known TFT panel, in which pixels formed of photoelectric conversion elements 21 for converting radiation into signal charges and switch elements 22 for transferring the signal charges to the outside are arranged in a two-dimensional matrix. It consists of a sensor array. In the following, for convenience of explanation, the sensor array of the TFT panel 20 is also referred to simply as a "sensor array".

  Each photoelectric conversion element 21 is provided in each of a plurality of regions (pixels) partitioned by a plurality of scanning lines 24 and a plurality of signal lines 23.

  The photoelectric conversion element 21 generates an electric signal (electric current, electric charge) according to the dose of the radiation (or the light amount of the electromagnetic wave converted by the scintillator K6) irradiated to the photoelectric conversion element 21, for example, a photodiode And phototransistors.

  As the photoelectric conversion element 21 constituting the TFT panel 20, one that directly detects the irradiation amount of X-rays may be used, or one that detects visible light converted by a phosphor may be used. Good.

  Each photoelectric conversion element 21 is provided in each of a plurality of regions (pixels) partitioned by a plurality of scanning lines 24 and a plurality of signal lines 23.

  The switch element 22 is for holding an electric charge in the photoelectric conversion element section (equivalent capacitance of the photoelectric conversion element 21 and a capacity connected in parallel with the photoelectric conversion element 21), and like the photoelectric conversion element 21, a plurality of regions Are provided respectively. Each switch element 22 is connected to the scanning line 24 in which the gate electrode is close, to the signal line 23 in which the source electrode is close, and to the photoelectric conversion element 21 in the same region. Therefore, the photoelectric conversion element 21 is indirectly connected to the scanning line 24 and the signal line 23.

  The plurality of bias lines 25 are provided between each signal line 23 and the signal line 23 so as to be parallel to the signal line 23 and not to be conductive with the intersecting scan line 24. The connection 26 is provided to extend in parallel with the scanning line 24 at the edge of the substrate. A plurality of bias lines 25 are connected to the connection 26. When the power supply switch K2 is turned on, a bias voltage is applied to each photoelectric conversion element 21 from a power supply circuit (not shown) via the bias line 25.

  The gate drive IC 40 is connected to each scanning line 24 so as to sequentially switch the voltage applied to each scanning line 24 between the on voltage and the off voltage.

  The readout IC 30 is connected to each signal line 23, and reads out the signal charge released from each photoelectric conversion element 21 to each signal line 23.

  That is, the gate drive IC 40 controls each switch element in the TFT panel 20, and the readout IC 30 reads out the signal charge from each photoelectric conversion element 21 in the TFT panel 20. The read IC 30 and the gate drive IC 40 are controlled, for example, by the control signal from the control device 10 to set the conditions for reading out the signal charges from the photoelectric conversion elements or to start and end the read processing.

  FIG. 5 is a view showing an example of the read circuit of the read IC 30 according to the present embodiment. Note that FIG. 5 shows only the circuit configuration when reading out the signal charge generated by one photoelectric conversion element 21 for the convenience of description.

  The readout IC 30 according to the present embodiment has a correlated double sampling (hereinafter, "CDS") function. In the CDS function, as shown in FIG. 5, the reset voltage is sampled and held by one sample and hold circuit (CDS1 in FIG. 5), and the signal voltage is sampled and held in the other sample and hold circuit (CDS2 in FIG. 5) This is a method of obtaining a voltage difference between the signal voltage and the reset voltage. By this, it is possible to remove reset noise generated in the charge amplifier 31 and the like at the time of reset.

  The photoelectric conversion element 21 is connected to the CDS circuit 32 (represents the sample hold circuit of the CDS 1 and the sample hold circuit of the CDS 2 through the switch element 22 for taking out the accumulated signal charge and the charge amplifier 31. The same applies to the following). It is done. A subtraction circuit 33 is connected to the subsequent stage of the CDS circuit 32. The subtraction circuit 33 calculates the difference voltage of the reset voltage held by the CDS 2 from the signal voltage held by the CDS 1.

  First, in the state where the switch element 22 is turned off and the connection of the photoelectric conversion element 21 is disconnected, the read out IC 30 acquires charges (that is, reset voltage) in the CDS 1 (hereinafter referred to as “N read”). After the N reading, the gate driving IC turns on the switch element 22, and the read IC 30 acquires a signal charge (that is, a signal voltage) from the photoelectric conversion element 21 in the CDS 2 (hereinafter referred to as "S reading") ). After the S reading, a subtraction circuit 33 calculates a value obtained by subtracting the reset voltage indicated by CDS2 from the signal voltage indicated by CDS1. The readout IC 30 stores the difference value between the signal voltage and the reset voltage obtained in this manner in the frame memory as a normal signal charge amount in one pixel area.

  The readout IC 30 alternately executes N reading and S reading execution in units of one row of the sensor array of the TFT panel 20 to acquire signal charges of all pixels of the sensor array.

  FIG. 6 is a diagram showing an example of the configuration of the switching power supply 50 according to the present embodiment.

  The switching power supply 50 generates DC power of a desired voltage to operate each part, and supplies the power to each part. The switching power supply 50 is, for example, a DC / DC converter, receives DC power from the battery 52, converts it into a desired voltage, and outputs it to each part.

  The imaging device 1 according to the present embodiment includes a plurality of switching power supplies 50 (each of 50a, 50b, and 50c in FIG. 6 corresponds to the switching power supply 50). Note that the imaging device 1 according to the present embodiment is provided with a plurality of switching power supplies 50 in this manner, so that desired voltages (Va, Vb, and Vc in FIG. 6 differ from each other according to the characteristics of various load devices). Or the switching power supply 50 is disposed in the vicinity of the installation position of the load device.

  The plurality of switching power supplies 50a, 50b, and 50c are, for example, DC / DC converters that operate independently. The plurality of switching power supplies 50a, 50b, and 50c operate on the basis of a switching signal generated by an oscillation circuit incorporated therein, a clock signal IC, and the like.

  The switching power supplies 50a, 50b, and 50c according to the present embodiment use a DC / DC converter of a PWM (Pulse Width Modulation) driving method from the viewpoint of operating at a desired switching frequency. And the voltage which the switching power supply 50 outputs is adjusted to a target voltage by controlling the duty ratio at the time of turning on / off a switch element by feedback control.

  Each of the switching power supplies 50a, 50b, and 50c according to the present embodiment is configured to vary the switching frequency of the switching signal by the control signal from the control device 10. The switching frequency of each of the switching power supplies 50a, 50b, and 50c according to the present embodiment is connected to an oscillation circuit built in each of the switching power supplies 50a, 50b, and 50c by, for example, a control signal from the control device 10 (frequency adjustment unit 13a). It is set by changing the resistance values of the variable resistance elements 51a, 51b, 51c. However, the configuration for setting the switching frequency is arbitrary, and a configuration for changing the value set in the register of the clock generation IC may be used.

  Also, the switching frequency (disturbance frequency) and disturbance intensity of each of the switching power supplies 50a, 50b, 50c are detected by the disturbance sensors 60a, 60b, 60c, and the controller 10 based on the sensor signals of the disturbance sensors 60a, 60b, 60c. (Disturbance detection unit 12) is monitoring. The switching frequency of each of the switching power supplies 50a, 50b, and 50c according to the present embodiment may be feedback-controlled separately by the control device 10 (frequency adjustment unit 13a) by sensor signals or the like of the disturbance sensors 60a, 60b, and 60c. It has become.

  As the disturbance sensors 60a, 60b, 60c for detecting the switching frequency (disturbance frequency) and the disturbance intensity of the switching power supplies 50a, 50b, 50c, for example, holes disposed adjacent to the switching power supplies 50a, 50b, 50c respectively A voltage sensor etc. which detect a switching signal from a switching terminal of element or switching power supply 50a, 50b, 50c are used. A plurality of sensors 60a, 60b, 60c may be prepared as described above, or may be one.

  The control device 10 (frequency measurement unit 12b, frequency adjustment unit 13a) measures the switching frequency of each of the switching power supplies 50a, 50b, and 50c by performing, for example, FFT analysis of a sensor signal of a Hall element. The switching frequency is adjusted to be a desired frequency (details will be described later with reference to FIG. 9).

  Next, each configuration of the control device 10 according to the present embodiment will be described with reference to FIGS. 7 to 11.

[Drive part]
The driving unit 11 controls the reading IC 30 and the gate driving IC 40 to execute an imaging process.

  Such imaging processing itself is similar to known processing. Specifically, the drive unit 11 receives an X-ray that has been emitted from the radiation generation apparatus 200 and transmitted through the subject by the TFT panel 20. At this time, the drive unit 11 controls the readout IC 30 and the gate drive IC 40 to obtain signal charges from the photoelectric conversion elements 21 of the pixels of the TFT panel 20, and performs imaging based on the signal charges of the pixels. .

  Note that the timing of charge accumulation of the imaging device 1 and the timing of radiation emission of the radiation generation device 200 may be synchronized, for example, by detecting radiation with a radiation detection unit provided in the imaging device 1, or imaging Synchronization may be achieved by communication between the device 1 and the radiation generating device 200.

  The drive unit 11 performs a radiation exposure during charge storage to generate a radiation image (hereinafter referred to as a “main image”) (main image acquisition unit 11a), and a charge storage when radiation is stored. The dark image acquisition mode (dark image acquisition unit 11b) for generating a radiation image (hereinafter referred to as "dark image") without irradiation is continuously executed to generate the difference between the main image and the dark image as a normal image. Do.

  Here, “continuously” typically means performing the dark image acquisition mode, for example, within 10 seconds after the execution of the present image acquisition mode.

  Thus, the drive unit 11 according to the present embodiment cancels out the noise component caused by the dark current of the photoelectric conversion element of each pixel, and performs long-period disturbance caused by the fluctuating magnetic field of the disturbance source outside the imaging device 1. Offset (to be described later with reference to FIG. 12).

  FIG. 7 is a diagram for explaining the operation of the drive unit 11 according to the present embodiment. FIG. 7A is a time chart showing the operation of the drive unit 11 according to the present embodiment. FIG. 7B is a view for explaining the correction process of the drive unit 11 according to the present embodiment.

  As shown in FIG. 7A, the drive unit 11 obtains a dark image after obtaining the main image, and subtracts the dark image from the main image to generate a regular image. The acquisition process of the present image and the acquisition process of the dark image consist of initialization, accumulation, and readout. Each operation is performed under the control of the drive unit 11.

  In the initialization step (S1), the readout IC 30 sweeps out the dark current accumulated in the sensor array before photographing, and after adjusting the photoelectric conversion to be performed correctly, all the TFTs of the sensor array are turned off. Do.

  In the storage step (S2), the radiation generating apparatus 200 irradiates radiation to the photoelectric conversion elements 21 of each pixel of the TFT panel 20 through the subject. As a result, the density information of the radiation transmitted through the subject is converted into electric charge in each pixel on the sensor array and accumulated in each pixel.

  In the reading step (S3), the gate driving IC 40 turns on the TFTs in the first row of the sensor array, and sequentially acquires the signal charges transferred to the respective column signal lines from the photoelectric conversion elements 21 arranged in the pixel region of the first row. Do. Furthermore, the gate drive IC 40 acquires digital data of the entire sensor array by sequentially scanning the rows of TFTs that are turned on.

  In the standby step (S4), the drive unit 11 waits for the time of the main dark difference interval set by the adjustment unit 13 before starting acquisition of a dark image (details will be described later).

  After the waiting step (S4), the drive unit 11 executes an initialization step (S5), an accumulation step (S6), and a reading step (S7) in order to obtain a dark image. At this time, the initialization step (S5), the storage step (S6) and the readout step (S7) are the initialization steps except that the radiation generator 200 turns off the radiation irradiation in the storage step (S6). S1) The same as the storage step (S2) and the reading step (S3).

  After the above-described steps S1 to S7, the drive unit 11 generates a dark image stored in the dark image frame memory from the image data of the main image stored in the frame memory for the main image as shown in FIG. 7B. The subtractive image data is subtracted to generate a normal radiation image to be displayed on a display device (not shown).

[Disturbance detector]
The disturbance detection unit 12 includes a disturbance source identification unit 12a and a frequency measurement unit 12b.

  The disturbance source identification unit 12 a identifies the type of disturbance source to be dealt with among the plurality of disturbance source candidates based on the sensor signal acquired from the disturbance sensor 60. Here, the type of the disturbance source to be dealt with by the disturbance source identifying unit 12a is the switching power source 50 or the like inside the imaging device 1 when dealing with the disturbance source In other words, according to whether it is a type to which a frequency change command can be made, or whether the disturbance source is a commercial power supply outside the imaging apparatus 1 (in other words, a type to which a frequency change command can not be made). This is to execute a different coping method in the adjustment unit 13 described later.

  When the type of the disturbance source to be dealt with in the disturbance source identifying unit 12a is identified as the switching power supply 50 or the like inside the imaging device 1, the countermeasure against the disturbance source is performed by the frequency adjusting unit 13a described later. It will be. On the other hand, when the type of the disturbance source is specified as a commercial power supply or the like outside the imaging device 1, the countermeasure against the disturbance source is performed by the main dark difference interval adjustment unit 13b described later.

  The frequency measurement unit 12 b specifies the disturbance frequency of the disturbance source to be dealt with based on the sensor signal acquired from the disturbance sensor 60. Here, the purpose of specifying the disturbance frequency of the disturbance source to be dealt with by the frequency measurement unit 12b is to cope with the disturbance of the disturbance source not to appear as image horizontal stripes in the radiation image in the adjustment unit 13 described later. It is.

  FIG. 8 is a view showing an example of a disturbance source that applies a fluctuating magnetic field to the TFT panel 20. As shown in FIG. FIG. 8A shows an aspect in which the switching power supply 50 mounted in the imaging device 1 is a disturbance source. Moreover, FIG. 8B has shown the aspect as which the commercial power supply installation M1 arrange | positioned in the proximity of the imaging device 1 is a disturbance source. Further, FIG. 8C shows an aspect in which the drive motor M2 of the external device is a disturbance source.

  Since all of switching power supply 50, commercial power supply equipment M1, and drive motor M2 shown in FIG. 8 handle high power, the intensity of the fluctuating magnetic field generated by the disturbance source is also large, and when capturing a radiation image, the TFT It is easy to generate an electromotive current in the signal lines and the bias lines of the panel 20. On the other hand, switching power supply 50 generally generates high frequency disturbances of 1000 kHz or higher, whereas commercial power supply equipment generally generates low frequency disturbances of 1 kHz or lower. From these characteristics as well, it is desirable to change the measures to suppress the image horizontal stripes.

  Since the strength of the fluctuating magnetic field generated by the switching power supply 50, the commercial power supply equipment M1, the drive motor M2, etc. changes with the current level depending on the current level, it may be a disturbance source to be dealt with Change. In addition, since the frequency of the fluctuating magnetic field generated by these also generally changes with time, it also changes as to whether or not it corresponds to a disturbance source to be dealt with. The degree to which the fluctuating magnetic field generated by these acts on the TFT panel 20 also depends on the use environment of the imaging device 1 (for example, the arrangement position of the imaging device 1) and the use mode of the imaging device 1 (for example, the imaging device 1). Of the switching power supply 50) and the like.

  The disturbance detection unit 12 (disturbance source identification unit 12a) includes a plurality of disturbance source candidates preset in the ROM of the control device 10, such as the switching power supply 50, the commercial power supply equipment M1, and the drive motor M2 shown in FIG. Identify the disturbance source to be dealt with from within.

  Note that information on “disturbance source candidate” (hereinafter referred to as “disturbance source candidate information”) is, for example, type information on “disturbance source candidate” (for example, switching power supply 50, commercial power supply facility M1, or drive motor M2) Identification information of "disturbance source candidate" (for example, switching power supply 50a, switching power supply 50b, or switching power supply 50c) according to the same type, and determination criteria information (for example, disturbance strength) And the outliers from the reference of the disturbance frequency).

  The disturbance detection unit 12 (disturbance source identification unit 12a) is, for example, a disturbance sensor 60 (60a, 60b, 60c, 60d in FIG. 8) provided to identify the type of disturbance source from among a plurality of disturbance source candidates. , 60e) to detect disturbance intensity or disturbance frequency. Then, the disturbance detection unit 12 determines whether or not image horizontal stripes can be generated in the radiation image for each of a plurality of disturbance source candidates based on, for example, a sensor signal of the disturbance sensor 60 (for example, the hall element 60). And set (that is, identify) the disturbance source candidate that exceeds the determination criteria (for example, the threshold of the disturbance intensity) set in the disturbance source candidate information as the “classification of the disturbance source to be dealt with”.

  The disturbance detection unit 12 (frequency measurement unit 12b) measures the disturbance frequency of the disturbance source based on, for example, a sensor signal of the disturbance sensor 60 (for example, the Hall element 60). The disturbance detection unit 12 can measure the disturbance intensity and the disturbance frequency of the disturbance source, for example, by performing frequency analysis (for example, FFT operation) on the sensor signal acquired from the Hall element 60.

  The disturbance detection unit 12 (disturbance source identification unit 12a), for example, analyzes the frequency of the measurement data to identify the peak frequency. Then, the disturbance detection unit 12 stores, in advance, the reference frequency of the inside of the imaging device 1 (the switching power supply 50) in order to exclude the disturbance frequency of the inside of the imaging device 1 (the switching power supply 50). If the signal value of the removed frequency is greater than or equal to the threshold value, it is determined that there is a disturbance outside the imaging device 1.

  On the other hand, the disturbance detection unit 12 (frequency measurement unit 12b) may use, for example, a voltage sensor that acquires a switching signal from the switching terminal of each of the switching power supplies 50a, 50b, and 50c as the disturbance sensor 60. In this case, for example, the disturbance detection unit 12 can detect the switching frequency by counting the switching signals of the switching power supplies 50a, 50b, and 50c with the clock signal.

  On the other hand, the disturbance detection unit 12 (frequency measurement unit 12b) is, for example, as the disturbance sensor 60, a current flowing through a signal line or a bias line in the TFT panel 20 (any within the effective pixel area or outside the effective pixel area). A current sensor that detects a time change may be used. In this case, the readout IC 30 can function as the disturbance sensor 60.

  More preferably, when the disturbance detection unit 12 (frequency measurement unit 12b) performs frequency measurement, processing is performed at a predetermined frequency based on time or imaging operation when the imaging device 1 is activated. Is set to The execution timing of the disturbance detection unit 12 is typically set as the degree of one radiographic image capturing operation or every predetermined time interval. By this, it becomes possible to follow in real time the fluctuation of the disturbance frequency of the disturbance source (or a disturbance source candidate).

  Note that the timing at which the disturbance detection unit 12 (frequency measurement unit 12b) executes the frequency measurement may be as long as the specification of the disturbance frequency is completed before the start of reading the dark image, and during imaging preparation, during main image storage, During readout of the main image, any timing during reset of the main dark space and storage of the dark image may be used.

[Adjustment department]
The adjustment unit 13 performs adjustment to suppress image horizontal stripes in accordance with the type of disturbance source specified by the disturbance detection unit 12.

  The adjustment unit 13 includes a frequency adjustment unit 13a (corresponding to a first adjustment unit of the present invention) and a main dark difference interval adjustment unit 13b (corresponding to a second adjustment unit of the present invention).

  The frequency adjustment unit 13a is executed when the disturbance source to be dealt with is an object (here, the switching power supply 50) capable of changing the frequency in the imaging device 1 and the frequency of the disturbance source (here, the switching power supply Control of the switching frequency of 50) suppresses the appearance of disturbance as image horizontal stripes in the radiation image.

  Specifically, the frequency adjustment unit 13a has a predetermined period related to the timing of reading out the charge from each photoelectric conversion element of the TFT panel 20 corresponds to a period corresponding to the disturbance frequency of the disturbance source (hereinafter, “period of disturbance source” Feedback control is performed on the disturbance frequency of the disturbance source so as to be an integral multiple of approximately Here, “to be approximately integral multiples” means to include a range of tolerance due to the control limit of the control device 10, etc., in addition to the aspect in which the integral multiples are completely matched the same).

  As a result, the timing for reading out the charge from each photoelectric conversion element of the TFT panel 20 and the disturbance of the disturbance source become synchronized, and the generation of the image horizontal stripes is suppressed.

  The dark difference interval adjustment unit 13b is executed when the disturbance source to be dealt with is a target (here, a commercial power source) that can not issue a frequency change command outside the imaging device 1, and the disturbance frequency of the disturbance source (here Then, by controlling the main dark difference interval in the drive unit 11 in accordance with the frequency of the commercial power supply, it is possible to suppress the appearance of disturbance as an image horizontal stripe in the radiation image.

  Specifically, the main dark difference interval adjustment unit 13b sets the interval between the start timing of the charge readout flow in the main image acquisition mode and the start timing of the charge readout flow in the dark image acquisition mode (hereinafter referred to as “main dark The main dark difference interval is controlled such that the difference interval is referred to as “a difference interval” is an integral multiple of the period of the disturbance source (details will be described later).

  As a result, the timing for reading out the charge from the same pixel area of the main image and the dark image is synchronized with the disturbance of the disturbance source, and the generation of the image horizontal stripes is suppressed.

  It should be noted that while switching power supply 50 generally generates high frequency disturbances of 1000 kHz or higher, commercial power supply equipment M1 and drive motor M2 generally generate low frequency disturbances of 1 kHz or lower. Even in the above, it is necessary to change the measures for suppressing the image horizontal stripes.

  In the following, an aspect in which the frequency adjustment unit 13a copes with the switching power supply 50 which is a typical disturbance source inside the imaging device 1 and a typical dark difference interval adjustment unit 13b is outside the imaging device 1 The aspect which copes with the commercial power source which is a disturbance source is demonstrated.

  First, the frequency adjustment unit 13a will be described in detail.

  FIG. 9 is a diagram showing the relationship between the charge acquisition timing of the read out IC 30 (see FIG. 5) according to this embodiment and the disturbance N1 generated by the switching power supply 50. As shown in FIG. FIG. 9A shows a state in which the cycle of the interval between charge acquisition timing of CDS 1 and charge acquisition timing of CDS 2 (hereinafter referred to as “CDS interval”) is not equal to an integral multiple of the cycle of disturbance N 1. The period of the CDS interval represents a state in which the period is equal to an integral multiple of the period of the disturbance N1.

  9A and 9B, the horizontal axis represents a time axis, and the lower column of the time axis indicates the contents of the read operation of the read IC 30 at the corresponding timing. The arrow position of “CDS1” indicates the charge acquisition timing (sample hold timing) of CDS1, and the arrow position of “CDS2” indicates the charge acquisition timing (sample hold timing) of CDS2 for the same pixel as the CDS1. ing. The “scanning cycle” is expressed as a cycle for reading the switch elements 22 for one row (here, N reading time + S reading time).

  9A and 9B, the vertical axis represents the input voltage to the CDS (CDS1 or CDS2) of the read circuit of the read IC 30. Here, for convenience of explanation, an aspect is shown in which only disturbance (for example, about 2000 kHz) generated by the switching power supply 50 is input to the CDS circuit input voltage.

  The readout IC 30 sequentially drives the switch elements 22 of each column for each row of the TFT panel 20, and sequentially acquires signal charges from the photoelectric conversion elements 21 arranged in the corresponding pixel region. At this time, the reading IC 30 performs N reading and S reading in this order for each row, and determines a value obtained by subtracting the reset voltage of the CDS 1 from the signal voltage of the CDS 2 as the normal signal charge of the photoelectric conversion element 21. Go.

  At this time, as shown in FIG. 9A, when the phase of the disturbance N1 at the charge acquisition timing of the CDS1 is different from the phase of the disturbance N1 at the charge acquisition timing of the CDS2, a voltage difference caused by the disturbance N1 occurs between the CDS1 and the CDS2. It will be. As a result, in the radiation image, image horizontal stripes due to the disturbance N1 are generated.

  In this respect, as shown in FIG. 9B, if the phase of the disturbance N1 at the charge acquisition timing of the CDS1 matches the phase of the disturbance N1 at the charge acquisition timing of the CDS2, the read IC 30 generates the signal voltage of the CDS1 to the reset voltage of the CDS2. When subtracting N1, the disturbance N1 is also canceled out and the disturbance N1 is eliminated from the signal charge. In other words, if the period corresponding to the switching frequency is an integral multiple of the CDS interval, the read out IC 30 can obtain the signal charge from which the disturbance is eliminated. At this time, since the CDS interval is the same in each pixel area, the readout IC 30 can acquire the signal charge from which the disturbance is eliminated in each pixel area.

From this point of view, the frequency adjustment unit 13a more preferably makes the period corresponding to the switching frequency of the switching power supply 50 be an integral multiple of the period related to the CDS interval (see equation (1)), ie, switching The switching power supply 50 is controlled so that the frequency becomes a frequency whose phase is aligned with the cycle related to the CDS interval.

The amplification factor of disturbance in the CDS circuit 32 (hereinafter referred to as "CDS gain") is the signal value of the disturbance N1 acquired at the charge acquisition timing of the CDS1 and the signal value of the disturbance N1 acquired at the charge acquisition timing of the CDS2. It is a difference and can be expressed as the following equation (2).

  FIG. 10 is a graph of the equation (2). The horizontal axis of FIG. 10 represents the frequency of the disturbance, and the vertical axis represents the CDS gain when the disturbance is acquired by the CDS circuit 32.

  As shown in FIG. 10, the CDS gain is 0 times depending on the relationship between the disturbance frequency and the CDS interval. FIG. 10 shows, as an example, a graph in the case where the CDS interval is 100 us, and in this case, the frequency at which the CDS gain is 0 is a frequency of an integral multiple of 10 kHz having the same cycle as 100 us. That is, by setting the frequency of the disturbance near a frequency that is an integral multiple of 10 kHz, it is possible to suppress the influence of the disturbance.

  For example, the frequency adjustment unit 13a stores in advance the target frequency of the switching power supply 50 in which the CDS interval and the CDS gain become low in association with each other in the ROM etc., and switches the respective switching power supplies 50 to become the target frequency. Feedback control of frequency.

  For each of the plurality of switching power supplies 50, the frequency adjustment unit 13a typically determines the CDS gain to reduce the image horizontal stripes to a desired size (for example, 0.16 times or less), and the switching frequency is determined. Control feedback. The switching frequency is typically set to 1000 kHz or more. At this time, different switching frequencies may be set in each of the plurality of switching power supplies 50. Note that FIG. 10 shows an example in which the target frequency of the switching frequency is set to the frequency range of 2000 ± 0.25 kHz when the target CDS gain is 0.16 or less.

  As the target frequency of the switching frequency, more preferably, in addition to the condition relating to the CDS gain, a frequency at which jitter does not occur is selected. When jitter occurs in the switching signal, there is a problem that a current change lower in frequency and frequency than the switching frequency occurs. The occurrence of jitter may depend on the input voltage of the switching power supply and the switching frequency. In such a case, a plurality of target frequencies may be provided, and the input voltage measurement means of the switching power supply may be provided to select a frequency at which jitter does not occur depending on the input voltage. Alternatively, the frequency measuring means may determine whether the frequency is stable and select a frequency at which jitter does not occur.

  The method of feedback control of the switching frequency of the switching power supply 50 by the frequency adjustment unit 13a is as described above with reference to FIG.

  Specifically, frequency measurement of the switching frequency of each of the plurality of switching power supplies 50a, 50b, and 50c (or one of the switching power supplies 50 identified by the disturbance source identifying unit 12a) is performed by the function of the frequency measuring unit 12b. Then, the frequency adjustment unit 13a adjusts the switching frequency of the switching power supplies 50a, 50b, and 50c, for example, by changing the resistance value of the variable resistors 51a, 51b, and 51c based on the measured switching frequency. Then, the frequency adjustment unit 13a repeatedly performs measurement of the switching frequency and adjustment of the switching frequency to perform feedback control of the switching frequency.

  As described above, by controlling the switching frequency of each of the plurality of switching power supplies 50 so that the CDS gain becomes smaller, the frequency adjustment unit 13a can suppress generation of image horizontal stripes caused by each of the plurality of switching power supplies 50. .

  Next, the main dark difference interval adjustment unit 13b will be described.

The main dark difference interval adjustment unit 13 b sets the readout interval of the main image of the drive unit 11 and the dark image in the same pixel area to an integral multiple of the period corresponding to the disturbance frequency of the disturbance source ( Main dark difference interval in drive unit 11 (refers to the time interval between the read start timing when acquiring the main image and the read start timing when acquiring the dark image, and in FIG. 7A, the processing of S3, S4, S5 and S6) Adjust the total time). In other words, the timing of acquiring an image signal from the same pixel of the main image and the dark image is aligned with the timing of the same phase of disturbance such as a commercial power source.

  FIG. 11 is a diagram for explaining the operation of the main dark difference interval adjustment unit 13b.

  FIG. 11 shows an aspect in which the image horizontal stripe N2 generated in the main image and the image horizontal stripe N2 generated in the dark image are mutually offset when generating a normal image.

  The main dark difference interval adjustment unit 13b starts the charge reading flow in the main image acquisition mode (the start timing of S3 in FIG. 7) when the disturbance detection unit 12 identifies the commercial power source or the like as a disturbance source to be dealt with. A process of adjusting the interval (main dark difference interval) of the charge read flow in the dark image acquisition mode (the start timing of S7 in FIG. 7) is executed.

  The main dark difference interval adjustment unit 13 b first acquires the disturbance frequency of the disturbance source to be dealt with, which is measured by the disturbance detection unit 12. Next, the main dark difference interval adjustment unit 13b causes the readout interval in the same pixel area of the main image and the dark image of the drive unit 11 to be an integral multiple of the period corresponding to the disturbance frequency of the disturbance source. The adjustment of the time width of the waiting step (S4) or the adjustment of the time width of the accumulation step (S6) or both of them is performed to adjust the main dark difference interval.

  As a result, as shown in FIG. 11, when generating a normal radiation image by subtracting a dark image from the main image, it is possible to cancel long-period disturbance such as a commercial power source.

  Note that the main dark difference interval adjustment unit 13b can also perform the read operation without driving the TFT during dark image storage, and adjust the accumulation time from the cycle of the signal value. For example, the period of disturbance is determined by FFT operation, and the accumulation time of the dark image is varied so that the phase of the main image readout and the phase of the dark image readout substantially coincide with each other. Also, the period of the peak may be measured from the signal value subjected to the LPF calculation focusing on the noise of the low frequency component to determine the period of the disturbance. Also, the accuracy may be improved by carrying out during the main image storage.

[Operation flow of control device]
FIG. 12 is a flowchart showing an example of the operation of the control device 10 of the imaging device 1 according to the present embodiment. The flowchart illustrated in FIG. 12 is, for example, an operation that the control device 10 executes according to a computer program. This process is performed, for example, each time the imaging process of the imaging device 1 is performed.

  FIG. 13 is a diagram showing exchange of signals between the control device 10 and each part when the type of the disturbance source is the switching power supply 50 in the flow of FIG. FIG. 14 is a diagram showing exchange of signals between the control device 10 and each part when the type of the disturbance source is a commercial power supply in the flow of FIG.

  Here, as a typical example, the Hall element 60 is provided in the vicinity of each of the switching power supply device 50 and the commercial power source M1, and the disturbance detection unit 12 is a disturbance indicated by a sensor signal of each Hall element 60. The aspect which identifies which kind of disturbance source of the switching power supply 50 and the commercial power supply M1 is specified based on intensity | strength is shown.

  In step S11, the control device 10 (disturbance source identification unit 12a) first performs disturbance of a disturbance intensity having a magnitude that causes image horizontal stripes to be generated based on a sensor signal from the disturbance sensor 60 (for example, a Hall element). It is determined whether or not exists. At this time, when it is determined that such a disturbance does not exist (S11: NO), the control device 10 (disturbance detection unit 12) ends the series of flows. On the other hand, when it is determined that such a disturbance is present (S11: YES), the process proceeds to the subsequent S12.

  In step S12, control device 10 (disturbance source identification unit 12a) selects the type of disturbance source to be dealt with from among a plurality of disturbance source candidates based on the sensor signal from disturbance sensor 60 (for example, a Hall element). Identify In step S12, when the disturbance source to be dealt with is the inside of the imaging device 1 (here, the switching power supply 50) (step S12: YES), the control device 10 (disturbance source identification unit 12a) performs processing in step S13. If the disturbance source to be coped with is not inside the imaging device 1 (here, a commercial power source) (S12: NO), the control device 10 (S12: NO) advances the process to step S14. .

  In step S13, control device 10 (frequency adjustment unit 13a) refers to the currently set CDS interval to reduce the CDS gain of the disturbance (that is, the cycle related to the CDS interval is equal to that of switching power supply 50). The target frequency of the switching frequency of the switching power supply 50 is determined so as to be approximately an integral multiple of the period corresponding to the switching frequency of

  In step S13, the control device 10 (frequency adjustment unit 13a, frequency measurement unit 12b) performs feedback control of the switching power supply 50 so that the switching frequency becomes the target frequency while performing frequency measurement of the switching frequency of the switching signal. Do.

  In step S14, after the controller 10 (the main dark difference interval adjustment unit 13b and the frequency measurement unit 12b) measures the frequency of the disturbance frequency of the commercial power supply M1, the control apparatus 10 performs the main darkening based on the disturbance frequency of the commercial power supply M1. Adjustment of the time width of the waiting step (S4) in FIG. 7A so that the difference interval (interval for reading out the charge in the same pixel area of the main image and the dark image) becomes an integral multiple of the period corresponding to the disturbance frequency of the disturbance source. Alternatively, the time width of the accumulation step (S6) is set.

  In this manner, the control device 10 (adjustment unit 13) can appropriately cope with a plurality of disturbance sources that cause the fluctuating magnetic field to act on the TFT panel 20 so that the image horizontal stripes do not occur.

[effect]
As described above, in the radiation imaging device 1 according to the present embodiment, a plurality of disturbance source candidates and means for coping with the disturbance source candidates are set in advance. Then, in the radiation image capturing apparatus 1 according to the present embodiment, the disturbance detection unit 12 specifies the type of disturbance source to be dealt with from the plurality of disturbance source candidates based on the sensor signal from the disturbance sensor 60 And identify the disturbance frequency of the disturbance source. Then, based on the type of the disturbance source and the disturbance frequency of the disturbance source, the adjustment unit 13 (frequency adjustment unit 13a and main dark difference interval adjustment unit 13b) executes predetermined disturbance countermeasure processing.

  In the radiation image capturing apparatus 1 according to the present embodiment, thereby, a state in which a plurality of disturbance sources can induce image horizontal stripes in the TFT panel 20 (for example, the disturbance intensity of the disturbance sources is increased, or Even when the disturbance frequency of (1) is changed, generation of image horizontal stripes can be suppressed for each of the plurality of disturbance sources.

  More specifically, according to the radiation imaging device 1 according to the present embodiment, for example, one or more of the plurality of switching power supplies 50a, 50b, 50c existing in the imaging device 1 become disturbance sources. Also, the occurrence of image horizontal stripes can be suppressed by feedback control on the switching power supplies 50a, 50b, and 50c by the frequency adjustment unit 13a.

  Further, according to the radiation imaging device 1 according to the present embodiment, for example, even when there is a disturbance source such as a commercial power source that can not be frequency controlled, the main dark difference interval by the main dark difference interval adjustment unit 13b By the adjustment of, it is possible to suppress the generation of image horizontal stripes. Moreover, according to the radiation imaging device 1 according to the present embodiment, it is possible to cope with low frequency disturbances by the adjustment of the main dark difference interval by the main dark difference interval adjustment unit 13b.

  Further, according to the radiation image capturing apparatus 1 according to the present embodiment, even when the disturbance frequency of the disturbance source changes, the generation of the image horizontal stripes is suppressed by the frequency adjustment unit 13a and the main dark difference interval adjustment unit 13b. So you can deal with in real time.

(Modification 1)
In the above embodiment, the frequency adjustment unit 13a shows the aspect of determining the target frequency of the switching frequency of the switching power supply 50 on the basis of the cycle related to the CDS interval of the read IC 30.

  However, instead of the cycle related to the CDS interval, the target frequency of the switching frequency (disturbance frequency) of the switching power supply 50 is based on the scan cycle of the readout IC 30, the folding cycle in the scan cycle, or the cycle related to the sampling frequency. It may be determined.

  In this case, the frequency adjustment unit 13a performs switching so that the cycle related to the switching frequency of the switching power supply 50 is the scanning cycle of the readout IC 30, the aliasing frequency in the scanning cycle, or an integral multiple of the cycle related to the sampling frequency. Determine the target frequency of the frequency.

  In this case, the target frequency of the switching frequency is determined, for example, as a frequency near an integral multiple of 5 kHz since the scanning frequency is 5 kHz if the scanning cycle is 200 us.

  Also, the target frequency of the switching frequency is in the vicinity of an odd multiple of the folding frequency (half of the scanning frequency). For example, when the scanning cycle is 200 us, the scanning frequency is 5 kHz and the folding frequency is 2.5 kHz so the reference frequency is 2.5 kHz. The frequency is determined to be in the vicinity of the odd multiple thereof.

  In the imaging device 1 according to the first modification, the disturbance remains in a state of being superimposed on the signal charge, but the component of the disturbance is uniformly superimposed in the radiation image or a predetermined frequency Will be adjusted to overlap. Therefore, the component of the disturbance is removed by the filtering process performed by the control device 10 before displaying the image on the display device (not shown).

It is known that the relationship between the frequency of the image horizontal stripes, the scanning period, and the disturbance frequency can be simply expressed as the following equation (4).

  FIG. 15 is a graph of the equation (4). The horizontal axis of FIG. 15 represents the frequency of the disturbance, and the vertical axis represents the frequency of the image horizontal stripes caused by the disturbance. As shown in FIG. 15, when the period corresponding to the disturbance frequency is an integral multiple of the scanning period, the frequency of the image horizontal stripes is zero, and the disturbance is uniformly superimposed. When the period corresponding to the disturbance frequency is in the vicinity of an odd multiple of the aliasing frequency, the frequency of the image horizontal stripes becomes high, so that image processing can be performed to reduce the visibility and reduce high frequency components.

  When the target frequency of the switching frequency is set to a frequency near an integral multiple of the scanning frequency, the offset may be shifted although a partial horizontal stripe is not generated. Although the offset deviation is a negligible level and can be ignored, for example, readout of only the offset component (not including the image signal) is performed before image reading starts, during image reading, or after image reading. Correction may be performed to remove the offset by taking the difference.

  As described above, the imaging device 1 according to the first modification is preferable in that generation of image horizontal stripes can be suppressed even when the read IC 30 does not have the CDS function.

(Modification 2)
FIG. 16 is a diagram illustrating an example of the operation of the imaging device 1 according to the second modification.

  In the imaging device 1 according to the second modification, the main dark difference interval adjustment unit 13 b further causes the read interval in the same pixel area of the main image and the dark image to correspond to the cycle of the switching frequency of the switching power supply 50. This embodiment differs from the above embodiment in that the dark difference interval can be adjusted.

  That is, the main dark difference interval adjustment unit 13b according to the second modification controls the main dark difference interval such that the main dark difference interval is substantially an integral multiple of the period of the switching frequency of the switching power supply 50.

  The imaging apparatus 1 according to the second modification is preferable in that generation of image horizontal stripes can be suppressed even when there is a switching power supply 50 that can not perform frequency control.

(Other embodiments)
The present invention is not limited to the above embodiment, and various modifications can be considered.

  In the above embodiment, as an example of the disturbance detection unit 12, after the disturbance source identification unit 12a specifies the disturbance source, the frequency measurement unit 12b performs the frequency measurement of the disturbance source.

  However, the disturbance detection unit 12 may measure the frequency with one Hall element 60 installed near the TFT panel 20, and specify the type of the disturbance source based on the frequency band. In this aspect, the disturbance source identification unit 12a sets the reference frequency for each of the plurality of disturbance source candidates, and the disturbance source candidate is selected when the disturbance frequency of the disturbance source candidate deviates from the reference frequency by the threshold or more. Measure the disturbance frequency of Disturbance Source Specifying Unit 12a For example, when the disturbance intensity around the fundamental frequency 60 Hz of the commercial power supply is large, it is identified as a commercial power supply outside the apparatus as the type of the disturbance source.

  Also, the disturbance detection unit 12 may be configured to execute the countermeasure processing by the adjustment unit 13 at predetermined intervals or sequentially instead of the mode in which the processing by the adjustment unit 13 is performed when the disturbance intensity increases. Good.

  In the above embodiment, the dark image acquisition mode is performed after the main image acquisition mode is executed as an example of the drive unit 11. However, after the dark image acquisition mode is performed in the reverse order. The image acquisition mode may be executed. In addition, the drive unit 11 may adjust the main dark difference interval only by adjusting the accumulation time without providing the standby time (S4).

  Further, in the above embodiment, as an example of the adjustment unit 13, the aspect in which the CDS interval and the scanning cycle are fixed is shown. However, the adjustment unit 13 may further adjust the CDS interval or the scanning cycle. Also in this aspect, since the control device 10 operates based on one clock signal, frequency measurement and control of the CDS interval can be performed, thereby suppressing deterioration in the accuracy of lateral streak reduction caused by a gap between clocks. can do.

  In addition, when determining the target frequency of the switching frequency, the adjustment unit 13 holds the signal value only with the sample-and-hold circuit and performs digital conversion with the ADC, or in a configuration with direct conversion of the charge amplifier output with the ADC. The interval from when the charge amplifier is reset and integration starts to when it is sampled and held, or the interval from when the ADC starts conversion as the reference frequency, are determined as frequencies near that integer multiple It is also good.

  Further, in the above embodiment, as an example of the adjustment unit 13, a mode is shown in which frequency control can not be performed for the drive motor M2 external to the imaging device 1 and the external switching power supply. The external switching power supply may be configured to be frequency controllable. In that case, the adjustment unit 13 can cope with disturbances such as the drive motor M2 and an external switching power supply by the frequency adjustment unit 13a.

  Also, the means for measuring the frequency by the frequency measurement unit 12b monitors the voltage of the switching terminal of the switching power supply and inputs it as a digital signal of H / L to the digital operation circuit and counts the number of clocks until signal change. Good. In order to increase the accuracy of counting, the number of clocks in a period in which switching is performed multiple times may be counted. An f / V conversion circuit may be used to convert to a voltage and measure with an ADC. A change in wiring current may be measured. It is also possible to measure the voltage change across the resistors arranged in series on the wiring. The magnetic flux change of the wiring may be measured, for example, using a Hall element.

  Further, as a means for controlling the frequency by the frequency adjustment unit 13a, there is a switching power supply IC which can set the operating frequency by a resistance value, and a variable resistance may be used for this resistance to switch and control the resistance value. The variable resistor may be a component capable of setting the resistance value digitally or a circuit configured in an analog manner. Some switching power supply ICs can control the operating frequency with an external clock signal, and may be controlled from the outside.

  In the above embodiment, as one example of the control device 10, each function of the drive unit 11, the disturbance detection unit 12, and the adjustment unit 13 is described as being realized by one control device, but a part of each function is described. Of course, all may be realized by being distributed to a plurality of control devices.

  Although the specific examples of the present invention have been described above in detail, these are merely examples and do not limit the scope of the claims. The art set forth in the claims includes various variations and modifications of the specific examples illustrated above.

  According to the control device of the radiation imaging device according to the present disclosure, it is possible to more effectively suppress the image horizontal stripes in the radiation image caused by the disturbance.

DESCRIPTION OF SYMBOLS 1 radiation image imaging apparatus 10 control apparatus 11 drive part 11a this image acquisition part 11b dark image acquisition part 12 disturbance detection part 12a disturbance source identification part 12b frequency measurement part 13 adjustment part 13a frequency adjustment part 13b this dark difference space | interval adjustment part 20 TFT Panel 30 readout IC
40 gate drive IC
50 switching power supply 60 disturbance sensor 70 clock generator

Claims (17)

A radiation imaging apparatus that performs initialization, charge accumulation and readout of accumulated charges on a sensor array composed of a plurality of photoelectric conversion elements to generate a radiation image,
A main image acquisition mode for generating a radiation image according to a main image by performing radiation irradiation during the charge storage, and generating the radiation image according to a dark image without performing radiation irradiation during the charge storage A driving unit that executes a dark image acquisition mode and generates a difference between the main image and the dark image as a normal image;
A disturbance source identification unit that identifies the type of disturbance source to be dealt with based on a predetermined sensor signal;
A frequency measurement unit that measures the frequency of the disturbance generated by the disturbance source;
A first adjustment unit configured to control the disturbance source such that the frequency of the disturbance generated by the disturbance source corresponds to a predetermined cycle related to the timing of reading out electric charge from each photoelectric conversion element of the sensor array;
The start timing of the charge readout flow in the main image acquisition mode or the dark image acquisition mode is controlled so that the readout interval in the same pixel area of the main image and the dark image corresponds to the period of the disturbance generated by the disturbance source. A second adjustment unit to
Equipped with
The radiographic imaging device which selectively performs the control processing by a said 1st adjustment part or the control processing by a said 2nd adjustment part based on the classification of the said disturbance source. A radiation imaging apparatus that performs initialization, charge accumulation and readout of accumulated charges on a sensor array composed of a plurality of photoelectric conversion elements to generate a radiation image,
A main image acquisition mode for generating a radiation image according to a main image by performing radiation irradiation during the charge storage, and generating the radiation image according to a dark image without performing radiation irradiation during the charge storage A driving unit that executes a dark image acquisition mode and generates a difference between the main image and the dark image as a normal image;
A frequency measurement unit that measures the frequency of the disturbance generated by the disturbance source;
A first adjustment unit configured to control the disturbance source such that the frequency of the disturbance generated by the disturbance source corresponds to a predetermined cycle related to the timing of reading out electric charge from each photoelectric conversion element of the sensor array;
A radiation imaging apparatus comprising: A radiation imaging apparatus that performs initialization, charge accumulation and readout of accumulated charges on a sensor array composed of a plurality of photoelectric conversion elements to generate a radiation image,
A main image acquisition mode for generating a radiation image according to a main image by performing radiation irradiation during the charge storage, and generating the radiation image according to a dark image without performing radiation irradiation during the charge storage A driving unit that executes a dark image acquisition mode and generates a difference between the main image and the dark image as a normal image;
A frequency measurement unit that measures the frequency of the disturbance generated by the disturbance source;
The start timing of the charge readout flow in the main image acquisition mode or the dark image acquisition mode is controlled so that the readout interval in the same pixel area of the main image and the dark image corresponds to the frequency of the disturbance generated by the disturbance source. A second adjustment unit to
A radiation imaging apparatus comprising: The type of the disturbance source includes a first disturbance source type capable of a frequency change command and a second disturbance source type not capable of a frequency change command.
The control process by the first adjustment unit is executed to cope with the first disturbance source type,
The control process by the second adjusting unit is executed to cope with the second disturbance source type.
The radiation imaging device according to claim 1. The type of the disturbance source includes a third type of disturbance source inside the radiation imaging device and a fourth type of disturbance source outside the radiation imaging device.
The control process by the first adjustment unit is executed to cope with the third disturbance source type;
The control process by the second adjusting unit is executed to cope with the fourth disturbance source type.
The radiation imaging device according to claim 1. The first adjustment unit is configured to set the disturbance source such that a predetermined period relating to the timing of reading out the charge from each photoelectric conversion element of the sensor array is approximately an integral multiple of the period of the disturbance generated by the disturbance source. The radiographic imaging apparatus of Claim 1 or 2 which controls. The second adjustment unit may perform the main image acquisition mode or the dark image such that a read interval in the same pixel area of the main image and the dark image is approximately an integral multiple of a period of the disturbance generated by the disturbance source. The radiation imaging device according to claim 1, wherein the start timing of the charge readout flow in the acquisition mode is controlled. If there are multiple said disturbance sources to be dealt with,
The control process according to the first adjustment unit or the control process according to the second adjustment unit is selectively performed based on the type of the disturbance source for each disturbance source. Radiation imaging device. The type of the disturbance source includes a switching power supply mounted in the radiation imaging apparatus, and when the switching power supply is identified as the type of the disturbance source, the control process by the first adjustment unit is performed.
The radiation imaging device according to claim 1. The first adjustment unit determines a target frequency of the switching frequency of the switching power supply based on a predetermined cycle related to the timing of reading out the charge from each photoelectric conversion element of the sensor array, and performs feedback control to the switching power supply. The radiation imaging device according to claim 9. The radiation imaging device according to claim 9, wherein the switching power supply is a PWM drive DC / DC converter. The disturbance source includes a plurality of the switching power supplies,
The radiographic imaging device according to any one of claims 9 to 11, wherein the first adjustment unit is configured to be capable of frequency control for each of the plurality of switching power supplies. The predetermined period relating to the timing for reading out the charge from each photoelectric conversion element of the sensor array is a period relating to the interval for reading out the reset charge and the signal charge from the same pixel area in correlated double sampling. The radiographic imaging device of description. The radiographic imaging device according to claim 13, wherein the first adjustment unit controls the disturbance source such that a gain of the disturbance caused by the disturbance source becomes equal to or less than a predetermined value in the correlated double sampling. The type of the disturbance source includes a commercial power supply facility or a drive motor disposed outside the radiation image pickup apparatus, and when the commercial power supply facility or the drive motor is specified as the classification of the disturbance source, the second type Execute control processing by the adjustment unit of
The radiation imaging device according to claim 1. The frequency measuring unit executes processing at a predetermined frequency based on time or imaging operation when the radiation image capturing apparatus is activated, and detects fluctuations in the frequency of disturbance generated by the disturbance source, The radiation imaging device according to claim 1, wherein the first adjustment unit or the second adjustment unit is configured to execute processing based on the changed frequency. A control method of a radiation image capturing apparatus, which generates a radiation image by executing initialization, charge accumulation and readout of accumulated charges on a sensor array including a plurality of photoelectric conversion elements,
A main image acquisition mode for generating a radiation image according to a main image by performing radiation irradiation during the charge storage, and generating the radiation image according to a dark image without performing radiation irradiation during the charge storage Executing a dark image acquisition mode, generating a difference between the main image and the dark image as a normal image;
Identify the type of disturbance source to be dealt with based on a predetermined sensor signal,
Measuring the frequency of the disturbance generated by the disturbance source;
The disturbance source is controlled such that the frequency of the disturbance generated by the disturbance source corresponds to a predetermined period related to the timing of reading out the charge from each photoelectric conversion element of the sensor array,
The start timing of the charge readout flow in the main image acquisition mode or the dark image acquisition mode is controlled so that the readout interval in the same pixel area of the main image and the dark image corresponds to the period of the disturbance generated by the disturbance source. And
A control method for selectively executing control processing by the first adjustment unit or control processing by the second adjustment unit based on the type of the disturbance source.

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