JP6704975B2 - Imaging device, imaging system, and imaging method - Google Patents

Description

The present invention relates to an image pickup apparatus using an image pickup element, and more particularly to improving the image quality of a picked-up image.

In the image pickup apparatus, a CCD or CMOS image sensor is used as a sensor for detecting radiation. The characteristics of the sensor are affected by the temperature change of the sensor array itself in which the sensor is arranged or the peripheral circuit for operating the sensor. Then, since the dark current of the sensor changes due to the temperature change, a difference between the image and the offset value due to the dark current occurs, which deteriorates the image quality of the radiation image.

Patent Document 1 discloses a method of arranging a plurality of temperature sensors in a plurality of sub-arrays of a sensor array (CMOS image sensor), and changing and correcting a dark current correction value according to the value of the temperature sensor. ..

JP, 2006-33036, A

However, in the imaging device disclosed in Patent Document 1, it is complicated to associate the data of the plurality of sub-arrays with the data of the plurality of temperature sensors, and the data processing for the correction described above may be complicated. there were.

Therefore, it is an object of the present invention to facilitate correspondence between sub-array data and temperature sensor data in an imaging device having a plurality of temperature sensors and a plurality of sub-arrays.

Therefore, in order to solve the above-mentioned problems, the imaging device of the present invention includes a plurality of sensors each having a conversion element for converting radiation into an electric charge and outputting a signal corresponding to the electric charge . A sensor array having a sub-array, and a plurality of temperature sensors that output a signal according to the temperature of the sensor array, and the radiation is used as the conversion element included in one sub-array of the plurality of sub-arrays. A sensor including a photoelectric conversion element that performs photoelectric conversion that converts light converted by a scintillator that converts light into electric charge, and outputs a signal according to the temperature of the sensor array and the forward voltage when a forward voltage is supplied. A signal output from the one sub-array and a signal of the one temperature sensor via a wiring commonly connected to one temperature sensor of the plurality of temperature sensors including at least one or a plurality of diodes. And are read out.

According to the present invention, in an imaging device having a plurality of temperature sensors and a plurality of sub-arrays, it is possible to facilitate correspondence between sub-array data and temperature sensor data.

It is a block diagram which shows the radiation imaging system in a 1st Example. It is a figure which shows the sensor in 1st Example. It is a figure which shows the temperature sensor in a 1st Example. It is a figure which shows the subarray in a 1st Example. 4 is a timing chart showing the timing of reading a signal from the sensor array in the first embodiment. 6 is a timing chart showing the timing of reading a signal from a plurality of sub-arrays by one AD conversion unit in the first embodiment. It is a figure which shows arrangement|positioning of the temperature sensor of the imaging device in a 2nd Example. It is a figure which shows the temperature sensor in a 3rd Example. It is a figure which shows the timing which reads the signal of the imaging device in a 3rd Example.

(Example 1)
FIG. 1 is a diagram showing an example of a block diagram of a radiation imaging system in the first exemplary embodiment of the present invention.

First, the overall configuration of the radiation imaging system will be described with reference to FIG. FIG. 1 is an example of a block diagram of a radiation imaging system according to the present exemplary embodiment.

The radiation imaging system 1 includes a radiation imaging apparatus 100, a processing unit 101 that performs image processing and system control, a display unit 102 including a display, a radiation control unit 103, and a radiation source 104 that generates radiation. When performing radiation imaging, the processing unit 101 can control the radiation imaging apparatus 100 and the radiation control unit 103 in synchronization. Radiation (X-rays, α-rays, β-rays, γ-rays, etc.) that has passed through the subject is detected by the radiation imaging apparatus 100 and subjected to predetermined processing by the processing unit 101 and the like, and then image data of the subject is generated. .. The image data is displayed on the display unit 102 as a radiation image. The radiation imaging system 1 in this embodiment corresponds to the imaging system in the present invention.

Next, the overall configuration of the radiation imaging apparatus 100 will be described. The radiation imaging apparatus 100 in this embodiment includes a sensor array 105 and a plurality of temperature sensors 127. The sensor array 105 has a plurality of sub-arrays 120. In each sub-array 120, a plurality of sensors that output a signal according to radiation or light are arranged. The temperature sensor 127 outputs a signal according to the temperature of the sensor array 105. A signal output from one sub-array 120 of the plurality of sub-arrays 120 and a signal from the temperature sensor 127 arranged in the one sub-array 120 are read out via a common wiring. The radiation imaging apparatus 100 in this embodiment corresponds to the imaging apparatus in the present invention. Hereinafter, each part will be described in detail.

The sensor array 105 is configured by tiling (two-dimensional array) a plurality of sub-arrays 120 on a plate-shaped base. With such a configuration, a large sensor array 105 can be formed. A plurality of sensors are arranged for each sub array 120. Further, here, the configuration in which the semiconductor substrate is tiled so that the sub-array 120 forms 7 columns×2 rows is illustrated, but the configuration is not limited to this. In the present embodiment, the sub-array 120 is one of the areas obtained by dividing the area of the sensor array 105 where the plurality of sensors are arranged into a plurality of areas. Further, the plurality of divided regions are arranged adjacent to each other. Therefore, one sub-array 120 may be defined in each tiled semiconductor substrate, or a plurality of sub-arrays 120 may be defined in the semiconductor substrate. Hereinafter, the sub-array 120 will be described as a region separated for each semiconductor substrate of the sensor panel 105.

A scintillator (not shown) that converts radiation into light may be provided on the sub-array 120, for example. A plurality of photoelectric conversion elements (sensors) are arranged on the side opposite to the radiation incident side of the scintillator. A conversion element that performs photoelectric conversion, such as a MIS type or a PIN type, is used for each sensor. Thereby, an electric signal based on the applied radiation dose is obtained. That is, in the present embodiment, each sensor and the scintillator corresponding thereto can form a conversion element that generates an electric charge according to radiation. The conversion element may directly convert radiation into electric charges.

The driving unit 210 includes a row scanning circuit 203 and a column scanning circuit 204 described later.

The signal reading unit 20 includes at least a signal amplification unit 107 including a differential amplifier and the like, and an AD conversion unit 108 that performs analog-digital conversion (AD conversion). The signal reading unit 20 can read the signals of the sensors selected by the row scanning circuit 203 and the column scanning circuit 204 described later. A plurality of electrodes for inputting/outputting signals or supplying power is arranged on the upper side and the lower side of the sensor array 105. The electrodes are connected to an external circuit, and for example, a flying lead type printed wiring board (not shown) is used for the connection. Then, the signal from the sub-array 120 is read by the signal reading unit 20 via the electrode. The control signal from the control unit 109 is input to the sub array 120 via the electrodes.

The control unit 109 communicates control commands with the processing unit 101, communicates synchronization signals, and outputs image data to the processing unit 101. In addition, the control unit 109 controls the sub-array 120 or each unit, and performs drive control of each sensor and temperature sensor and operation mode control. Further, the control unit 109 combines the image data (digital data) of each sub-array 120 AD-converted by the AD conversion unit 108 of the signal reading unit 20 into one frame data and outputs the frame data to the processing unit 101. Further, the control unit 109 can perform control such that the temperature data is read from the temperature sensor 127 frame by frame during a period in which a signal is read from the sensor 202 to be read for one frame in the sub-array 120. The control unit 109 can calculate the temperature of the sensor array 105 or the amount of change in the temperature of the sensor array 105 from the acquired data of the temperature sensor 127.

The processing unit 101 can perform the offset correction by subtracting the frame data for offset from the acquired one frame data. Dark current is generated in the sub-array 120 even during the period when the radiation for imaging is not applied. Therefore, the sub array 120 has an offset value in the image data. The processing unit 101 has image data acquired in a state where no radiation is applied for a predetermined period as frame data for offset of the sub-array 120. Then, the processing unit 101 can perform offset correction by subtracting the frame data for offset from the image data acquired in a period different from the predetermined period. Further, the processing unit 101 can prepare the offset correction data of the sensor array 120 corresponding to the temperature data. Furthermore, in the case of having a plurality of sensor arrays 120, each sensor array 120 may have offset correction data. The processing unit 101 can also select offset correction data based on the temperature data and perform offset correction. In this way, the image data can be offset-corrected according to the temperature of the sensor array 120.

Between the control unit 109 and the processing unit 101, control commands or control signals and image data are exchanged via various interfaces. The processing unit 101 outputs setting information such as an operation mode and various parameters or shooting information to the control unit 109 via the control interface 110. In addition, the control unit 109 outputs device information such as an operation state of the radiation imaging apparatus 100 to the processing unit 101 via the control interface 110. The control unit 109 also outputs the image data obtained by the radiation imaging apparatus 100 to the processing unit 101 via the image data interface 111. Further, the control unit 109 uses the READY signal 112 to notify the processing unit 101 that the radiation imaging apparatus 100 is ready for imaging. Further, the processing unit 101 uses the external synchronization signal 113 to notify the control unit 109 of the timing of radiation irradiation start (exposure) in response to the READY signal 112 from the control unit 109. Further, the control unit 109 outputs a control signal to the radiation control unit 103 to start radiation irradiation while the exposure permission signal 114 is enabled.

The temperature sensor 127 is arranged in each sub-array 120 to acquire the temperature of the sensor array 105. The temperature sensor 127 and the sub-array 120 are connected by a common wiring. Note that the position of the temperature sensor 127 is at the end of the surface, but is not limited to this. It can be arranged at any position on the surface of the sub-array 120 as long as radiation or light does not enter. At least the sub-array 120 and the temperature sensor 127 are arranged on a common semiconductor substrate. Further, the temperature sensor 127 may be arranged in a region different from the sub array 120 on the semiconductor substrate. In addition, the configuration in which the sub-array 120 and the temperature sensor 137 are formed on the common semiconductor substrate is also included in the configuration arranged on the common semiconductor substrate.

The cooling panel 133 has a function of cooling the sensor array 105. It is possible to reduce the temperature change of the sensor array 105 and suppress the fluctuation of the characteristics of the sensor array. The cooling panel 133 is made of a material having a high thermal conductivity so that the entire surface of the sensor array 105 has a uniform temperature.

The cooling device 131 has a function of controlling the temperature of the cooling panel 133 to be constant. The cooling hose 132 is connected to the cooling device 131 and the cooling panel and has a function as a path for circulating the cooling liquid. The cooling device 131 can maintain the temperature at 27° C., for example, by circulating the temperature-controlled cooling liquid.

Next, an example of the sensor will be described with reference to FIG. FIG. 2 is an equivalent circuit diagram showing an example of the circuit configuration of each sensor 202 forming the sub-array 120.

As shown in FIG. 2, each of the plurality of sensors may include, for example, a first portion ps1, a second portion ps2, and a third portion ps3. Note that the control unit 109 can control whether or not the transistors M1 to M13, which are transistors included in the respective portions, can be conducted.

The first portion ps1 may include a photodiode PD, transistors M1 to M3, a floating diffusion capacitance CFD (hereinafter, FD capacitance CFD), and a sensitivity switching capacitance CFD1. The photodiode PD is a photoelectric conversion element and can generate electric charges according to radiation or light. The photodiode PD converts the light generated by the scintillator described above into an electric signal according to the applied radiation. The photodiode PD may be one that can directly detect radiation and generate an electric charge. Then, an amount of charge corresponding to the radiation or light is generated in the photodiode PD, and a voltage of the FD capacitor CFD according to the amount of generated charge is output to the second portion ps2. The sensitivity switching capacitor CFD1 is used to switch the sensitivity of the sensor 202 to radiation, and is connected to the photodiode PD via the transistor M1 (switch element). When the control unit 109 activates the WIDE signal, the transistor M1 becomes conductive, and the voltage of the combined capacitance of the FD capacitance CFD and the capacitance CFD1 is output to the second portion ps2. As described above, in the sensor 202, the sensitivity to radiation is changed depending on whether or not the capacitance CFD1 is used. Further, the transistor M2 initializes the electric charge of the photodiode PD by activating the PRES signal, and resets the voltage output to the second portion ps2. If the sensitivity switching function is not included, M1 and CFD1 are not included in ps1.

The second portion ps2 may include transistors M3 to M7, a clamp capacitor CCL, and a constant current source. The transistor M3, the transistor M4, and the constant current source (for example, a transistor having a current mirror configuration) are connected in series so as to form a current path. When the control unit 109 activates the enable signal EN input to the gate of the transistor M3, the transistor M4 receiving the voltage from the first portion ps1 is activated. In this way, the source follower circuit is formed, and the voltage corresponding to the voltage from the first portion ps1 is output. In the subsequent stage, a clamp circuit composed of transistors M5 to M7 and a clamp capacitor CCL is provided. Specifically, one terminal n1 of the clamp capacitor CCL is connected to the node between the transistor M3 and the transistor M4 of the first portion ps1, and the other terminal n2 is connected to the transistor M5 that functions as a clamp switch. It is connected. Further, the transistor M6, the transistor M7, and the constant current source are directly connected so as to form a current path, and the other terminal n2 is connected to the gate of the transistor M7. With this configuration, the influence of kTC noise (so-called reset noise) generated in the photodiode PD of the first portion ps1 can be reduced. Specifically, the voltage corresponding to the voltage from the first portion ps1 at the time of resetting is input to the terminal n1 of the clamp capacitor CCL. In addition, the activation of the clamp signal PCL brings the transistor M5 into a conductive state, and the clamp voltage VCL is input to the terminal n2 of the clamp capacitor CCL. In this way, the potential of the terminal n2 is clamped as a noise component, and the change in voltage due to the subsequent generation and accumulation of charges in the photodiode PD is output as a signal component. The enable signal EN is also input to the gate of the transistor M6, and the enable signal EN is activated to activate the transistor M7. In this way, the source follower circuit is formed, and the voltage corresponding to the gate voltage of the transistor M7 is output to the third portion ps3.

The third portion ps3 may include transistors M8, M10, M11, M13, analog switches SW9, SW12, and capacitors CS and CN. The third portion ps3 corresponds to the holding portion in the present invention. The holding unit has a signal holding unit and a reference signal unit. The signal holding portion has a function of holding a signal according to the amount of charge generated in the photoelectric conversion element. Specifically, it has M8, M10, SW9, and a capacity CS. The reference signal unit has a function of holding a reference signal that serves as a reference for the amount of generated charges. Specifically, it has M9, M11, SW12, and a capacitor CN.

The transistor M8 and the capacitor CS form a sample hold circuit, which functions as a signal holding unit that holds the output value from the second portion ps2. First, the operation of holding a signal in the signal holding unit will be described. Specifically, the control unit 109 switches the state (conducting state or non-conducting state) of the transistor M8 using the control signal TS1 so that the signal (the signal according to the optical component) obtained from the second portion ps2 is capacitively coupled. Hold in CS, ie, sample. Further, the transistor M10 functions as an amplifier by its source follower operation, and the signal is amplified thereby. The amplified signal is output from the terminal S by turning on the analog switch SW9 using the control signal VSR. Next, the operation of holding the reference signal by the reference holding unit will be described. Similarly, the reference signals can be held in the transistors M11 and M13, the analog switch SW12, and the capacitor CN.

Next, the configuration of the temperature sensor in the first embodiment will be described in detail with reference to FIG. FIG. 3 is a diagram showing an example of the configuration of the temperature sensor in the first embodiment.

First, the overall configuration of the temperature sensor will be described. The temperature sensor 127 in FIG. 3 includes at least one or a plurality of diodes. Furthermore, it has a signal amplification part which amplifies the signal of the diode, and a signal holding part which holds the signal output from the signal amplification part. Further, the temperature sensor 127 has a reference holding unit that holds a reference signal that serves as a reference for the temperature of the sub-array 120. The temperature sensor 127 further includes a second signal amplification unit that amplifies a reference signal that serves as a temperature reference of the sub-array 120, and a reference holding unit that holds the signal output from the second signal amplification unit. is doing. Hereinafter, each configuration will be specifically described.

First, the diode of the temperature sensor 127 will be described. D1 to D4 are diodes having a PN junction. The material of the diode is a silicon semiconductor. The forward voltage and temperature characteristics below will be described for the case of using a PN junction type diode made of a silicon semiconductor. The relationship between the current I flowing in the PN junction diode and the applied voltage V is represented by the mathematical expression (1).
I=Io(exp(qV/nkT)-1)) (1)
Here, q is a unit charge, n is an ideal factor, k is a Boltzmann constant, T is temperature, and Io is a saturation current. As an example of the characteristic based on Expression (1), the PN junction diode functions as a temperature sensor having a forward voltage characteristic of about 0.6 V at room temperature and a temperature characteristic of a forward voltage of about −2.5 mV/° C. In this embodiment, four diodes are connected in series to provide a forward voltage of about 2.4 V and an output characteristic of about −10 mV/° C. at room temperature. Since the output of the temperature sensor can be kept within the output range equivalent to that of the sensor shown in FIG. 2, it can be read using the signal reading unit 20 shown in FIG. .

Next, the signal amplification section will be described. The signal amplification unit includes at least one transistor (M23). M23 is a transistor that operates as a source follower, and has a function of amplifying a signal corresponding to the forward voltage VF of the diode output from the temperature sensor as the temperature signal S.

Next, the second signal amplification section will be described. M29 as the second signal amplifying unit is a transistor that operates as a source follower, and has a function of amplifying the reference signal VCL output from the N terminal of the temperature sensor as the reference signal N.

Next, the signal holding unit will be described. The signal holding unit includes at least M24 and CS and constitutes a sample hold circuit for the temperature sensor signal. M24 is a sample hold transistor (sample hold switch S). CS is a temperature sensor signal holding capacitor. Further, it may have a transistor M26 for signal amplification. M26 operates as a source follower, and functions as a transistor for amplifying the temperature sensor signal.

Next, the reference holding unit will be described. The reference holding unit includes at least M30 and CN, and constitutes a sample hold circuit for accumulating a reference signal. M30 is a sample hold transistor (sample hold switch N). CN is a reference signal hold capacitor. Further, it may have a transistor M32 for signal amplification. The M32 operates as a source follower and functions as a transistor for amplifying the reference signal.

Next, the transfer switch will be described. M25 is a transfer switch S for outputting the temperature sensor signal amplified in M26 to the S signal output line. M31 is a transfer switch N for outputting the reference signal amplified by M32 to the N signal output line.

Next, each signal related to the control of the temperature sensor 127 and the operation based on the signal will be described. Each signal described below is input from the control unit 109.

First, the EN signal will be described. The EN signal is input from the control unit 109 and has a function of controlling the operating state of each transistor. The EN signal is connected to the gates of the diode constant current selection switch (M21), the diode signal amplifier constant current selection switch (M22), and the reference voltage amplifier constant current selection switch (M28). When the EN signal is at high level, these selection switches M21, M22, M28 are turned on. When the EN signal is at a high level, a constant current flows through the diodes D1 to D4 connected in series, and a signal corresponding to the forward voltage VF of the diode is output as a signal output of the temperature sensor from the transistor M23 in the operating state.

The PCL signal is a signal for controlling the reference voltage selection switch M27. When the EN signal is at a high level and the PCL signal is at a high level, the reference voltage selection switch M27 is turned on, and the reference signal VCL is amplified and output from the activated transistor M29.

The TS signal is a sample hold control signal of the signal output of the temperature sensor, and the forward voltage VF of the diode is applied to the capacitor CS through M23 by setting the TS signal to high level and turning M24 on. Next, the signal TS is set to low level and M24 is turned on, whereby the holding of the temperature sensor signal in the sample hold circuit is completed.

The TN signal is a sample hold control signal of the reference signal VCL, and the reference signal VCL amplified via M29 is applied to the capacitor CN by setting the TN signal to a high level and turning M30 on. Next, the signal TN is set to low level and M30 is turned off, whereby the holding of the reference signal VCL in the sample hold circuit is completed.

After the sample holding of the capacitors CS and CN, M26 and M32 are turned on, and the held signals can be read nondestructively until the samples are held again.

The TSEL signal is a temperature sensor selection signal and controls the on/off state of the transfer switch S (M25) and the transfer switch N (M31). Then, the signal S of the temperature sensor signal holding capacitor (CS) and the signal N of the reference voltage VCL holding capacitor (CN) are output.

In the temperature sensor 127 of the present embodiment, as will be described later, the diode of the temperature sensor is not energized at all times but discretely energized as shown in FIG.

The sub-array 120 in the first embodiment will be described with reference to FIG. FIG. 4 is a diagram showing a configuration example of the sub-array 120. As shown in FIG. 4, in the sub-array 120, a plurality of sensors 202 are arranged in the vertical direction that is the long side and in the lateral direction that is the short side. The sub-array 120 has a plurality of sensors arranged in a matrix. In this embodiment, one of the column signal lines 206 and 207 is commonly used by the temperature sensor 127 and the sub-array.

The signals of the sub-array 120 and the temperature sensor 127 are read by the signal reading unit 20 via a common wiring. The present embodiment further includes a row scanning circuit that scans a plurality of sensors of the sub-array 120 on a row-by-row basis, and the row scanning circuit commonly scans a predetermined row of sensors and temperature sensors.

The driving unit 210 has a row scanning circuit 203 for driving each sensor 202 and a column scanning circuit 204 for reading a signal from each sensor 202.

The row scanning circuit 203 and the column scanning circuit 204 are composed of shift registers, for example, and operate based on a control signal from the control unit 109. The row scanning circuit 203 inputs a control signal to each sensor 202 via the row signal line 205, and drives each sensor 202 in a row unit based on the control signal. For example, the row scanning circuit 203 functions as a row selection unit, and selects the sensor 202 for which signal reading is to be performed for a plurality of sensors at a predetermined selection cycle for each row. Further, the column scanning circuit 204 functions as a column selection unit, selects each sensor 202 for each column based on the control signal, and sequentially outputs the signals from each sensor 202 at a predetermined read cycle. When the row selection signal V0 is enabled, the temperature sensor 127 outputs the output of the temperature sensor 127 to the reference signal output terminal N and the signal output terminal S. Regarding V0, it is a row dedicated to the temperature sensor.

The sub-array 120 further has VST, HST, CLKV, and CLKH as input terminals. The input terminal VST is a terminal to which the row scan start signal VST is input. The input terminal CLKV is a terminal to which the row scanning clock signal CLKV is input. The input terminal CLKH is a terminal to which the column scanning clock signal CLKH is input. The input terminal HST is a terminal to which the column scan start signal HST is input.

The row scanning circuit 203 selects a plurality of sensors for each row and sequentially scans the sensors in the row direction, which is the sub-scanning direction, in synchronization with the row scanning clock CLKV. The column scanning circuit 204 sequentially selects the column signal line of the sensor in the row selected by the row scanning circuit 203 for each sensor in synchronization with the column scanning clock signal CLKH. When the row signal line 205, which is the output line of the row scanning circuit 203, is enabled, signals and reference signals are output via the column signal lines 206 and 207. The column scanning circuit 204 sequentially selects the signals output to the column signal lines 206 and 207, whereby the signals of the respective sensors are sequentially output to the analog voltage output lines 208 and 209.

Further, the sub-array 120 has a chip select terminal CS, a signal output terminal S, and a reference signal output terminal N. The chip select terminal CS is a terminal for making a signal readable from the sub-array 120. The signal output terminal SIG is a terminal for reading the signal held in the capacitance CS of each sensor 202, and the reference signal output terminal N is held in the capacitance CN.

As an example of the operation mode, a driving method of the sensor 202 and the temperature sensor in the moving image shooting mode will be described with reference to FIG. Although the case where the sensor 202 is driven will be described below, the temperature sensor can also be read by the same driving method. In the following driving method, the same signal names in FIGS. 2 and 3 are driven at the same timing.

First, as shown in FIG. 5, the operation mode setting and the shooting start setting are performed at time t1. After that, at time t2, driving for photographing is started, and reset driving RD and sampling driving SD are alternately repeated. Further, after the sampling drive SD and before the next reset drive RD, a read operation RO for reading a signal from the sub-array 120 is performed.

The reset drive RD performs a reset operation and an operation of clamping an output component at the time of reset as a noise component. Specifically, as shown in FIG. 5, at time t2, the enable signal EN is set to the high level to bring the transistors M3 and M6 into the conductive state. As a result, the transistors M4 and M7 are brought into a state capable of performing the source follower operation.

At time t3, the signals PRES and WIDE (not shown) are set to a high level to bring the transistor M1 for sensitivity switching into a conductive state and the transistor M2 for resetting into a conductive state. As a result, the photodiode PD is connected to the reference voltage VRES, the photodiode PD is reset, and the voltages of the capacitors CFD1 and CFD are also reset. In addition, a voltage corresponding to the gate voltage of the transistor M4 immediately after the reset is input to one terminal n1 (terminal on the transistor M4 side) of the clamp capacitor CCL.

At time t4, the signal PCL is set to the high level, and the transistor M5 for performing the above-described clamping is turned on. As a result, the clamp voltage VCL is input to the other terminal n2 (terminal on the transistor M7 side) of the clamp capacitor CCL. Further, at time t4, the signals TS and TN are set to the high level, and the transistor M8 for performing the above-described sampling is made conductive. As a result, the capacitors CS and CN are both in the initial state (the voltage of the output value of the second portion ps2 when the gate voltage of the transistor M7 is the reference voltage VCL).

At time t5, the signals PRES and WIDE (not shown) are set to the low level to bring the transistors M1 and M2 into the non-conducting state. As a result, the capacitance CFD1 and the capacitance CFD are fixed to the voltage immediately after the reset because the transistor M1 is in a non-conducting state, and the terminal n1 of the clamp capacitance CCL has a voltage corresponding to the gate voltage of the transistor M4 immediately after the reset. Is set to.

At time t6, the signal PCL is set to low level to turn off the transistor M5. As a result, charges corresponding to the potential difference between the terminals n1 and n2 (potential difference between the voltage according to the reference voltage VRES and the reference voltage VCL) are held in the clamp capacitor CCL, and the above-described kTC noise clamping is completed. Further, at time t6, the signals TS and TN are set to low level, and the transistors M8 and M11 are made non-conductive. As a result, the voltages of the capacitors CS and CN are fixed. At time t6, the exposure permission signal 114 described above is set to a high level (permission state). After that, charges are generated and accumulated in the photodiode PD.

At time t7, the enable signal EN is set to low level to turn off the transistors M3 and M6. This renders the transistors M4 and M7 inoperative.

As described above, the series of operations of the reset drive RD is completed. That is, in the reset drive RD, the photodiode PD is reset, the voltage corresponding to the kTC noise caused by the photodiode PD of the first portion ps1 is held in the clamp capacitor CCL, and the capacitors CS and CN are initialized. It

The reset drive RD can be performed collectively for all the sensors, and the reset drive RD performed thereafter (for example, at times t31 to t32) can also be performed at the same timing as described above. Further, by preventing the shift of the control timing, the continuity of data can be maintained between the adjacent sensors.

Next, in the sampling drive SD, the sensor 202 is driven and an operation of holding the obtained signal in the capacitor CS is performed. Specifically, at time t11, the enable signal EN is set to the high level to render the transistors M3 and M6 conductive, and the transistors M4 and M7 enter the source follower operation. The gate voltage of the transistor M4 (that is, the voltage of the FD capacitor CFD) changes according to the amount of charge generated and accumulated in the photodiode PD, and the voltage corresponding to the changed gate voltage is one of the clamp capacitors CCL. Is input to the terminal n1 and the potential of the terminal n1 changes. The potential change of the other terminal n2 of the clamp capacitor CCL follows the potential change of the terminal n1. Here, as described above, since the voltage corresponding to the kTC noise is held in the clamp capacitor CCL, the amount of this potential change is output to the third portion ps3 as a signal component.

From time t12 to t14, the signal of the sensor 202 is held in the capacitor CS. At time t12, the signal TS is set to the high level to make the transistor M8 conductive, and sampling of the output value of the second portion ps2 is started. Specifically, the capacitance CS becomes the voltage of the output value of the second portion ps2 (the voltage corresponding to the gate voltage of the transistor M7) according to the driving at the time t11. Next, at time t13, since the sampling is started at time t12, the exposure permission signal 114 is set to the low level (prohibited state). After that, at time t14, the signal TS is set to the low level to make the transistor M8 non-conductive, that is, the output value of the second portion ps2 is held. Specifically, the voltage of the capacitor CS is fixed at the output value of the second portion ps2.

Next, at time t15, the signal PRES is set to the Hi level, and the resetting transistor M2 is turned on. As a result, the voltages of the FD capacitor CFD and the capacitor CFD1 are reset to the reference voltage VRES, and the voltage of the terminal n1 is also reset to the same state as at time t3.

At time t16, the signal PCL is set to Hi level to make the transistor M5 conductive, and the clamp voltage VCL is input to the other terminal n2 (terminal on the transistor M7 side) of the clamp capacitor CCL. At time t17, the signal PRES is set to the low level to turn off the transistors M1 and M2. As a result, the capacitance CFD1 and the capacitance CFD are fixed at the voltage immediately after the reset, and the terminal n1 of the clamp capacitance CCL is set to the voltage corresponding to the gate voltage of the transistor M4 immediately after the reset.

From time t18 to t19, the voltage corresponding to fixed pattern noise such as thermal noise, 1/f noise, temperature difference, and process variation depending on the circuit configuration of the second portion ps2 is held in the capacitor CN. At time t18, the signal TN is set to the high level to turn on the transistor M11. As a result, the capacitor CN is charged and becomes the voltage of the output value of the second portion ps2 when the gate voltage of the transistor M7 is the reference voltage VCL. At time t19, the signal TN is set to low level to turn off the transistor M11. As a result, the voltage of the capacitor CN is fixed. Finally, at time t20, the signal PCL is set to low level to make the transistor M5 non-conductive, and at time t21, the enable signal EN is set to low level to make the transistors M3 and M6 non-conductive (transistors M4 and M7 are non-conductive). To

As described above, the series of operations of the sampling drive SD is completed. It should be noted that the sampling drive SD can be performed collectively for all the sensors in order to prevent deviation of the control timing of each sub-array 120, similarly to the reset drive RD described above. The polarities of the high level and the low level of each signal level are examples, and the signal level may be inverted depending on the system.

Next, a read operation for reading each data of the temperature sensor 127 and the sub-array 120 by one signal reading unit 20 when the three sub-arrays 120 are combined will be described with reference to FIG. By the read operation, the signal can be read from the temperature sensor 127 while the signal is read from the sensor of the sub-array 120 for one frame to be read.

In the sensor array 105, three tiled sub-arrays 120 are set as one block, and the one block is used as a conversion region of one AD converter of the AD conversion unit 108 to perform AD conversion.

First, each signal in the figure will be described. CLKH is a synchronization signal for reading the sensor signal, and the sensor signal output of the sub-array 120 is sequentially switched in synchronization with CLKH. CLKAD is an AD clock signal that controls the timing of AD conversion. CS0 to CS2 are signals for selecting the operated sub-array 120, and CS0 to CS2 are assigned to the three sub-arrays 120. Output from the sensor 202 and temperature sensor 127 of each selected sub-array 120 is enabled. ADIN is an output signal from the sub-array 120, which is a signal input to the AD conversion unit 108. ADOUT is a 16-bit output signal after AD conversion by the AD conversion unit 108. VST, CLKV, HST, and CLKH are signals similar to those in FIG.

First, the control unit 109 reads a signal from the temperature sensor 127 before reading a signal from the sub array 120. When acquiring the data from the temperature sensor 127, the control unit 109 enables the row selection signal V0 in FIG.

First, the chip select CS0 is enabled, and the output ADIN(T0) of the temperature sensor of the sub-array 120 selected by CS0 is input to the AD converter, AD-converted by the CLKAD pulse and output as ADOUT(T0). Then, similarly, each sub-array 120 is selected by CS1 and CS2. Then, the signals are AD-converted in synchronization with the CLKAD pulse and output as ADOUT(T1) and ADOUT(T2). This completes the reading of signals from the plurality of temperature sensors. Next, reading from the sub array 120 is performed.

When the row scanning clock CLKV rises while the row scanning start signal VST is high, the row signal line V1 of the row scanning circuit 203 is enabled inside the sub-array 120. When the row signal line V1 is enabled, the outputs of the sensor rows P0(1,1) to P2(n,1) shown in FIG. 7 selected by the row signal line V1 are valid.

First, a read operation for one row of the sub-array 120 which is activated in CS0 will be described. First, the chip select CS0 is enabled and the output of the sub-array 120 is validated. Inside the sub-array 120, when the column scanning clock CLKH rises while the column scanning start signal HST is high, the column selection row signal H1 of the column scanning circuit 204 is enabled. In synchronization with the rising edge of CLKH, the column selection row signal of the column scanning circuit 204 switches to H2,... Hn. In synchronization with the switching of the signals, the signals P0(1,1), P0(2,1),... P0(n,1) are sequentially output to ADIN. The sensor signal output to ADIN is AD-converted in synchronization with the CLKAD pulse. Then, the signal of each sensor is output as ADOUT(P0(1,1)) ADOUT(P0(2,1)),... ADOUT(P0(n,1)). When the column scan from P0(1,1) to P0(n,1) of the sub-array 120 is completed, the chip select CS0 is disabled. As described above, the read operation for one row of one sub array 120 is completed.

Similarly, chip select CS1 and CS2 are enabled, column scanning from P1(1,1) to P1(n,1) and P2(1,1) to P2(n,1) is performed, and chip select CS1 and Disable CS2. With the above, column scanning for one row of the three sub-arrays 120 is completed.

Next, reading of signals from the second row onward of each sub-array 120 will be described. The control unit 109 controls to enable the row signal line V2 of the row scanning circuit 203 by inputting one pulse of CLKV to the sub-array 120. When the row signal line V2 is enabled, the control unit 109 enables the outputs of the sensor rows P0(1,2) to P2(n,2) shown in FIG. 7 selected by the row signal line V2.

After that, by sequentially switching the row signal line of the row scanning circuit 203 of the sensor array 105 to Vm by CLKV, the column scanning is repeated from the row of the final sensor of P0(1,m) to P2(n,m), thereby performing the sub-array. The reading of all the sensors for 120 sheets is completed. In this way, by reading using the CS signal corresponding to each sub-array 120 and the temperature sensor 127, the signals of the sub-array 120 and the temperature sensor 127 can be easily made to correspond to each other. Although the above describes three sub-arrays 120 and one AD converter 108, it is not limited to this. For example, one sub array 120 and one AD conversion 108 may be used. Further, four or more sub-arrays 120 and one AD converter 108 may correspond to each other. In this way, by associating the plurality of sub-arrays 120 with the AD converter 108, the data of the sub-arrays and the data of the temperature sensor can be associated with each other with a simpler circuit configuration.

As described above, the temperature of the sensor array can be appropriately acquired in the image pickup apparatus having the temperature sensor. In an image pickup apparatus having a plurality of temperature sensors and a plurality of sub-arrays, it is possible to easily associate the data of the sub-arrays with the data of the temperature sensors.

Then, the control unit 109 can change and correct the frame data for offset based on the acquired plurality of temperature sensors. For example, the relationship between the relative temperature difference and the offset frame data is acquired in advance with reference to the offset frame data of the standard temperature data of each sub-array. Then, the offset frame data can be appropriately changed and used for correction. By doing so, the image pickup apparatus can appropriately perform offset correction.

(Example 2)
A second embodiment will be described with reference to FIG. The second embodiment is different from the other embodiments in that a plurality of temperature sensors are arranged in one sub array.

With this configuration, since the temperature information of a wide range within one sub-array can be measured, the temperature of the sensor array can be corrected more accurately. Hereinafter, the second embodiment will be described in detail.

FIG. 7 is a diagram showing an example of the internal structure of the sub-array 120 when the temperature sensor 127 is provided corresponding to a plurality of sensors.

In the sub-array 120 of this embodiment, the temperature sensor 127 is provided in parallel with a plurality of sensors. The control unit 109 can enable the TSEL signal and switch the output to the signal reading unit 20. In FIG. 7, the temperature sensor 127 is provided along with some of the sensors 202, but this is not a limitation. The temperature sensor 127 can be arranged corresponding to a plurality of rows and columns. There may be more temperature sensors 127 than the number of sensors. With this configuration, the temperature characteristic of the entire sub-array 120 can be detected.

Next, an example of the arrangement of the temperature sensor 127 in this embodiment will be described. In this embodiment, the temperature sensor 127 is preferably installed on the back side of the sub array 120 so as not to block the incidence of radiation or light on the sub array 120. In the case of this configuration, it is preferable to dispose the temperature sensor 127 between the sub-array 120 and the cooling panel 130.

As described above, in the image pickup apparatus having the temperature sensor, the temperature of the sensor array can be acquired in a wider range.

(Example 3)
A third embodiment will be described with reference to FIGS. 8 and 9. The difference from the other embodiments is that it is possible to determine whether or not a signal can be read from the temperature sensor according to the amount of change in the temperature of the sensor panel according to a signal different from the signal for operating the sensor array. different. With this configuration, it is possible to set the timing of supplying the voltage to the temperature sensor to any timing. Therefore, the temperature rise can be detected even when the EN signal to the sensor array is not enabled. Hereinafter, the third embodiment will be described in detail.

FIG. 8 shows a temperature sensor in which voltage application to the diode can be controlled by an EN signal different from the sensor array. M91 is a transistor that functions as a switch that limits the voltage application to the diode according to the EN1 signal. When EN1 is asserted (hereinafter, high level), the control unit 109 can control to apply the voltage to the diode. On the other hand, the control unit 109 can control the voltage application by setting EN1 to the negate state (hereinafter, low level).

An example of the read driving timing of the signal from the temperature sensor 127 when the constant current to the temperature sensor 127 is limited will be described with reference to FIG.

First, the control unit 109 performs reset drive at time t110. In this case, EN1 is set to the low level to limit the driving of the temperature sensor 127. Next, at time t111, the control unit 109 sets EN1 to a high level prior to sampling driving. After that, the control unit 109 performs sampling drive at time t112, and data reading is started at time t113. Therefore, it is possible to prevent the temperature sensor 127 from being controlled at the timing of reset driving.

As described above, in the imaging device having the temperature sensor, the temperature sensor can be read out by the same method while controlling the temperature sensor separately from the sensor array. Therefore, the signal from the temperature sensor can be read at a desired timing.

The embodiment of the present invention can also be realized by a computer or a control computer executing a program (computer program). Further, means for supplying the program to the computer, for example, a computer-readable recording medium such as a CD-ROM storing the program or a transmission medium such as the Internet for transmitting the program is also applied as an embodiment of the present invention. be able to. The above program can also be applied as an embodiment of the present invention. The above program, recording medium, transmission medium, and program product are included in the scope of the present invention. Further, an invention based on a combination that can be easily imagined from the embodiments is also included in the scope of the present invention.

Although the present invention has been described in detail above based on the embodiments, the present invention is not limited to these specific embodiments, and various forms within the scope of the present invention are also included in the scope of the present invention. included. Furthermore, the above-described examples merely show one embodiment of the present invention, and inventions that can be easily imagined from the above-described examples are also included in the scope of the present invention.

100 Radiation Imaging Device 105 Sensor Array 120 Sub-array 127 Temperature Sensor 202 Sensor

Claims (15)

A sensor array, each having a plurality of sub-arrays in which a plurality of sensors each having a conversion element that converts radiation into an electric charge and that outputs a signal according to the electric charge are arranged,
A plurality of temperature sensors outputting a signal according to the temperature of the sensor array,
A sub-array of one of the plurality of sub-arrays, the conversion element including a photoelectric conversion element that performs photoelectric conversion that converts light converted by the scintillator that converts the radiation into light; One temperature sensor of the plurality of temperature sensors including at least one or a plurality of diodes that are supplied with a directional voltage and output a signal according to the temperature of the sensor array and the forward voltage is commonly connected. An image pickup apparatus, wherein a signal output from the one sub-array and a signal from the one temperature sensor are read out via a wiring. The image pickup apparatus according to claim 1, further comprising a control unit that controls the sensor array and the temperature sensor so as to read a signal from the sensor array and a signal from the temperature sensor. The control unit controls the sensor array and the temperature sensor so as to read out from the temperature sensor for each frame during a period in which a signal is read out from a sensor to be read out for one frame in the sensor array. The image pickup apparatus according to claim 2. The image pickup apparatus according to claim 2 , wherein the photoelectric conversion element includes a photodiode. 5. The control unit calculates the amount of change in the temperature of the sensor array or the temperature of the sensor array based on a signal corresponding to the temperature of the sensor array and the forward voltage. The imaging device according to any one of 1. The image sensor according to claim 4, wherein the temperature sensor includes a signal amplification unit that amplifies a signal of the diode, and a signal holding unit that holds a signal output from the signal amplification unit. apparatus. The temperature sensor includes a second signal amplification unit different from the signal holding unit that amplifies a reference signal serving as a temperature reference of the sensor array, and a reference that holds a signal output from the second signal amplification unit. The imaging device according to claim 6, further comprising a holding unit. The image pickup apparatus according to claim 6, wherein the signal amplification unit includes at least one transistor. The sub-array and the temperature sensor are arranged on a common semiconductor substrate,
9. The image pickup device according to claim 2, wherein the temperature sensor is arranged in a region different from a region in which the sub-array is arranged on the semiconductor substrate. The image pickup apparatus according to claim 2, further comprising a signal reading unit that reads out a signal from the sensor array and a signal from the temperature sensor via the wiring. The sub-array, the plurality of sensors are arranged in a matrix,
Further comprising a row scanning circuit for scanning the plurality of the sensors of the sub-array row by row,
The image pickup apparatus according to claim 2, wherein the row scanning circuit scans a predetermined row of the sensor and the temperature sensor in common. The imaging device according to any one of claims 2 to 11, wherein a plurality of the temperature sensors are arranged in the sub-array. The control unit controls the temperature sensor to determine whether to read a signal according to a change amount of the temperature of the sensor array, in response to a signal different from a signal for operating the sensor array. The image pickup apparatus according to claim 2, wherein The image pickup apparatus according to any one of claims 1 to 13,
A processing unit that processes an image captured by the image capturing device;
An imaging system comprising: A sensor array having a plurality of sub-arrays each having a plurality of sensors each of which has a conversion element for converting radiation into an electric charge and outputs a signal according to the electric charge, and outputs a signal according to the temperature of the sensor array. A plurality of temperature sensors, and an imaging method of an imaging device,
A sub-array of one of the plurality of sub-arrays, the conversion element including a photoelectric conversion element that performs photoelectric conversion that converts light converted by the scintillator that converts the radiation into light; One temperature sensor of the plurality of temperature sensors including at least one or a plurality of diodes that are supplied with a directional voltage and output a signal according to the temperature of the sensor array and the forward voltage is commonly connected. through the wire, a first step of acquiring a signal from said plurality of temperature sensors,
Through the wiring, and a second step of acquiring a signal from said one sub-array,
And an imaging method.

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