JPH09266552A - Photoelectric conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the photoelectric conversion device which is not affected by temperature variation and has excellent S/N. SOLUTION: This converting device has a photoelectric converting element S1 which converts an incident light signal into an electric signal, a transistor(TR) T1 which performs transfer control over the electric signal from the photoelectric converting element S1, and a driving means 3 which applies a transfer control signal to the control electrode of the TR T1. In this case, the device has control means 6 and 7 which detect the temperature of the photoelectric converting element S1 and/or TR T1 and controls the driving means 3 so that the turn-on time of the TR T1 varies with the detected temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoelectric conversion device preferably used for X-ray photography and the like.

[0002]

2. Description of the Related Art FIG. 10 is a schematic circuit diagram showing a schematic configuration of a conventional photoelectric conversion device. In FIG. 10, S1 is a photoelectric conversion element, and is composed of a photodiode P1 and a capacitor C1 here. A power source 1 is connected to the photoelectric conversion element and applies a bias to the photodiode. T1 is a thin film transistor (hereinafter referred to as a thin film transistor) that transfers charges generated by the photoelectric conversion element S1 according to the amount of incident light to the readout circuit 2.
TFT). The readout circuit 2 is a capacitor C2, an amplifier A
1 and capacitor reset switch SW1. Further, 3 is a gate drive circuit for applying a voltage (gate pulse Vg) to the gate electrode of the TFT T1. In addition,
The photoelectric conversion element S1 and the TFT T1 are generally formed simultaneously by an amorphous silicon process.

FIG. 11 is a timing chart showing the read timing of the conventional photoelectric conversion device. FIG.
As indicated by a in the figure, the light is pulsed light that is emitted for the time T (light). After the photocharges are accumulated in the photoelectric conversion element S1 by the light irradiation, the gate drive circuit 3
Gate pulse Vg1 (pulse width T (Vg)) is applied from
T T1 is turned on and the electric charge due to light is transferred to the reading circuit 2. The transferred charges are amplified by the readout circuit 2 and output as an analog image signal Sig (c in the figure). After the analog image signal is output, the potential of the capacitor C2 of the readout circuit 2 is reset by the reset switch SW1 (d in the figure).

Generally, in a conventional photoelectric conversion device, a TFT
The time T (Vg) for turning on the gate of is set based on the time constant determined by the value of the ON resistance Ron of the capacitance C1 of the photoelectric conversion element and the capacitance C2 TFT of the readout circuit.

As shown in FIG. 12, the ON resistance Ron (reflecting the mobility) of a TFT of amorphous silicon greatly depends on the temperature, and the resistance value becomes high (that is, the mobility decreases) especially at a low temperature.

FIG. 13 shows the relationship between the charge transfer efficiency, the gate pulse time, and the temperature dependence when the charges generated in the photoelectric conversion element, that is, the charges accumulated in the capacitor C1 are transferred to the capacitor C2 of the reading circuit. The gate pulse time required to transfer the charges generated in the photoelectric conversion element varies depending on the temperature. When the temperature decreases, the gate pulse time required to transfer the charges becomes longer. In FIG. 13, the gate pulse time required for 99% transfer (transfer remaining 1%) at high temperature is T (Vg) H, and the gate pulse time required for 99% transfer at low temperature is T (Vg) L. The gate pulse time at each temperature has a relationship such as T (Vg) L> T (Vg) H.

Therefore, in the conventional photoelectric conversion device, the ON time of the TFT is set to T (V
g) It was set like L.

[0008]

However, the conventional photoelectric conversion device has the following problems. Dark current always flows through the photoelectric conversion element. As shown in FIG. 14, the dark current Id of the sensor also depends on the temperature, and the dark current increases as the temperature rises. That is, there is a relation of Id (HT)> Id (LT).

The dark current Id continues to flow in the photoelectric conversion element during the light irradiation and during the time when the TFT is turned on and the charges are read out after the light irradiation, which affects the read signal as noise. Therefore, if the ON time of the TFT is set as long as T (Vg) L in consideration of charge transfer at low temperature as in the conventional photoelectric conversion device, the charge due to the dark current at high temperature and at low temperature is Thus, the amount of charge due to dark current differs from the amount of charge due to light irradiation.

This appears as a decrease in the S / N ratio at high temperature. Further, when the relationship between the light irradiation time T (Light) and T (Vg) for turning on the TFT is T (Vg)> T (Light), the decrease in the S / N ratio becomes remarkable.

Further, the problem due to the dark current (reduction of S / N ratio) becomes more remarkable when a plurality of photoelectric conversion elements and TFTs are provided as shown in FIG. 15 and sequentially read by using a shift register or the like. .

In FIG. 15, S1 to Sn are photoelectric conversion elements,
Here, photodiodes P1 to Pn and capacitors C1-1 to C1
It consists of -n. A power source 1 is connected to the photoelectric conversion elements S1 to Sn and applies a bias to the photodiodes P1 to Pn. T1 to Tn are TFTs that transfer the charges generated in the photoelectric conversion elements S1 to Sn according to the amount of incident light to the reading circuit 2. Here, the readout circuit 2 includes capacitors C2-1 to C2-n, amplifiers A1-1 to A1-n, and a capacitor reset switch SW1-.
It is composed of 1 to SW1-n. Reference numeral 4 denotes an analog multiplexer that sequentially selects the output of the reading circuit 2 and outputs it as an analog image signal. Furthermore, 5 is the TFT of each pixel
It is a shift register that applies a gate pulse to T1 to Tn.

FIG. 16 is a timing chart showing the read timing of the conventional photoelectric conversion device. As indicated by a in FIG. 16, the light is pulsed light that is emitted for the time T (light). After photoelectric charges are accumulated in the photoelectric conversion element by light irradiation, gate pulses Vg1 to VgN are applied from the shift register 5 as shown in b to e of FIG.
Tn is sequentially turned on and the electric charge by light is transferred to the reading circuit 2. The transferred charges are amplified by the readout circuit 2 and sequentially transferred to the analog image signal Si by the analog multiplexer 4.
It is output as g (f in FIG. 16).

As shown in FIG. 15, in the case of a configuration in which n TFTs T1 to Tn are sequentially turned on by using the shift register 5 to read out a signal, the time required for reading is T (Vg) × n. Increases proportionally as the number of lines driven increases.

In each photoelectric conversion element, not only the charge Qp due to light but also the charge Qd due to the dark current Id is accumulated by the time the TFT is turned on after the light irradiation and the charges are read out. For example, in the photoelectric conversion element Sn of FIG. 15, until Vgn is applied to the TFT Tn, a charge due to a dark current such as Qd = (T (light) + (N-1) × T (Vg)) × Id is generated. Accumulated.

Therefore, as in the case described with reference to FIG. 10, the ON time of the TFT is set to T (Vg) in consideration of charge transfer at low temperature.
When it is set to a long value such as L, the amount of the charge Qd due to the dark current is different from the optical signal (charge Qp due to light) read out at the time of high temperature and the temperature at low temperature. For example, when the dark current at high temperature is Id (HT) and the dark current at low temperature is Id (LT), the S / N of the photoelectric conversion element Sn at each temperature is S / N (high temperature) = (Qp / Qd (HT)) = Qp / (T (light) + (N-1) × T (Vg) L) × Id (HT) S / N (low temperature) = (Qp / Qd (LT)) = Qp / It becomes like (T (light) + (N-1) × T (Vg) L) × Id (LT). Where (T (light) + (N-1) × T (Vg) L) × Id (HT)> (T (light) + (N-1) × T (Vg) L) × Id (LT) Qd (HT)> Qd (LT) That is, when the temperature is high, the component due to the dark current is large in the electric charge accumulated in the capacitor C1, and when the number of lines n is larger, the ratio of the component due to the dark current is further increased. Therefore, S / N is most disadvantageous when the number of lines is large at high temperature.

That is, in the conventional photoelectric conversion device,
There was a problem that S / N was different between high temperature and low temperature, and sufficient S / N could not be obtained especially at high temperature.

The present invention has been made in view of the above problems in the conventional photoelectric conversion device, and an object of the present invention is to provide a photoelectric conversion device having a good S / N which is not affected by temperature change. .

[0019]

DISCLOSURE OF THE INVENTION The present invention for solving the above problems includes a photoelectric conversion element for converting an incident optical signal into an electric signal, a transistor for controlling transfer of an electric signal from the photoelectric conversion element, In a photoelectric conversion device having a driving unit that applies a transfer control signal to a control electrode of the transistor, the temperature of the photoelectric conversion element or / and the transistor is detected, and the conduction time of the transistor is detected according to the detected temperature. It has a control means for controlling the drive means so as to change.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings.

(First Embodiment) FIG. 1 shows a schematic circuit diagram of a first embodiment of a photoelectric conversion device of the present invention. FIG.
The same reference numerals are used for the same functions as those of the conventional example shown in FIG. In FIG. 1, S1 is a photoelectric conversion element, and here, a photodiode P1 and a capacitor C1
And a bias is applied by the power supply 1.
T1 is a TFT for transferring the charges generated in the photoelectric conversion element S1 to the reading circuit 2. Normal photoelectric conversion element S1 and TFT T1
Are simultaneously formed and formed by an amorphous silicon process or the like. Here, the reading circuit 2 is composed of a capacitor C2, an amplifier A1, and a switch SW1 for resetting the capacitor. Generally, this read circuit is an external IC. Further, the gate electrode (control electrode) of the TFT T1 is connected to a gate drive circuit 3 (drive means) for applying a gate pulse Vg for turning the gate ON / OFF.

A temperature sensor 7 for detecting temperature and outputting a temperature signal is provided in the vicinity of the photoelectric conversion element S1 and / or the TFT T1.
(Temperature detecting means) is arranged. The temperature signal from the temperature sensor 7 is input to the control circuit 6, and TF
A gate control signal for changing the gate pulse time of T is output to the gate drive circuit 3. The gate drive circuit 3 operates in accordance with the above-mentioned gate control signal to convert the photoelectric conversion element S1 or TFT T1.
The time for turning on the TFT, that is, the gate pulse time is changed in accordance with the temperature detected in. In particular, In this way, the control circuit 6 generates a gate control signal so that the time for turning on the TFT gate is shortened when the temperature is high and the time is long when the temperature is low. In this embodiment, the control circuit 6 and the temperature sensor 7 constitute a control means.

FIG. 2 is a timing chart in the embodiment of the present invention described with reference to FIG. 2A shows the timing of irradiating the object to be read with the photoelectric conversion element with light (in this figure, pulsed light is used for explanation). FIG.
Symbols b and c in the figure respectively show the gate pulse Vg1 and the analog image signal Sig from the readout circuit when the temperature detected by the temperature sensor is low. Similarly, b ′ and c ′ in FIG. 2 indicate the gate pulse and the analog image signal when the temperature is high. 2d shows the timing for resetting the capacitor C2 in the read circuit 2 of FIG. In the timing diagram of Figure 2, capacitor C2
The timing of resetting is constant with respect to the temperature detected by the temperature sensor 7, but like the gate pulse time.
The configuration may be such that the C2 reset interval is changed.

Here, the gate pulse time at each temperature is determined in consideration of the temperature dependence of the transfer efficiency shown in FIG. 13 and the temperature dependence of the sensor dark current shown in FIG. As described above, if the gate pulse time of the TFT is changed based on the temperature information from the temperature sensor provided near the photoelectric conversion element and the TFT, the S / N will decrease due to the dark current of the photoelectric conversion element even if the temperature changes. A small photoelectric conversion device can be realized.

The specific photoelectric conversion elements of the photoelectric conversion device, the layer structure of the TFT, the arrangement of the temperature sensor, and the schematic circuit structure will be described below.

FIG. 17 shows a photoelectric conversion element TF of the photoelectric conversion device.
FIG. 18 is a schematic circuit diagram in which the temperature sensor is embodied.

As can be seen from FIG. 17, the photoelectric conversion element of this embodiment and the TFT have the same layer structure, and therefore can be formed simultaneously by the amorphous silicon film forming process. A thermocouple (adhesive) is attached as a temperature sensor to the surface (rear surface) opposite to the surface of the substrate on which the photoelectric conversion elements and the like are provided. This thermocouple converts the substrate temperature into a voltage (thermoelectromotive force), detects the temperature, and outputs the control circuit 6
Input the temperature signal to. The thermocouple can be provided on the surface of the substrate on which the photoelectric conversion element and the like are provided.

FIG. 19 shows a photoelectric conversion element TF of the photoelectric conversion device.
FIG. 20 is a schematic circuit diagram embodying the temperature sensor. FIG. Here, a side temperature diode (pin diode) is used as a temperature sensor on the surface of the substrate on which the photoelectric conversion element and the like are provided.
Is installed. The temperature of the substrate is detected by utilizing the temperature dependence of V _F of this side temperature diode. The side temperature diode is shielded from light (provided by providing an upper metal electrode) so that light does not enter. The layer structure of the photoelectric conversion element, the TFT, and the connection portion is the same as the layer structure of FIG. The operation of the photoelectric conversion element shown in FIGS. 17 and 19 will be described in the fourth embodiment.

(Second Embodiment) FIG. 3 shows a schematic circuit diagram of a second embodiment of the photoelectric conversion device of the present invention. In addition, FIG. 4 is a timing diagram illustrating driving of the photoelectric conversion device according to the second embodiment. In the configuration of this embodiment, a separate temperature sensor is not used for temperature detection of the photoelectric conversion element and the TFT. Instead, it reads that the dark current of the photoelectric conversion element itself changes with temperature and uses it as a temperature signal. In FIG. 3, components having the same functions as those of the first embodiment of FIG. 1 and the conventional example of FIG. 10 are designated by the same reference numerals.

In the photoelectric conversion device according to the second embodiment of the present invention shown in FIG. 3, as shown in the timing chart of FIG. 4, the "temperature detection mode" for detecting the temperature of the photoelectric conversion element and the TFT and the image from the subject are displayed. It has two driving modes, a "reading mode" for reading information. In order to realize such driving, the control circuit 6 of FIG.
The light source control signal is further output to the light source 8 to control ON / OFF of light. In this embodiment, the control circuit 6 constitutes a control means.

First, in the "temperature detection mode", the temperatures of the photoelectric conversion element and the TFT are detected in the following steps. (1) A light source control signal is applied from the control circuit 6 to the light source 8 to turn off the light as shown in FIG. The photoelectric conversion element is in a dark state. (2) In the dark state, charges due to a dark current are accumulated in the photoelectric conversion element S1 for a certain period. (3) Turn on the TFT gate for the period of T (Vg) pre as shown in Fig. 4b.
Then, the charge due to the dark current is read by the read circuit 2. As shown in FIG. 14, the dark current of the photoelectric conversion device has temperature dependence. Therefore, as shown by c in FIG. 4, when the temperature is high (broken line of c in the figure), the amount of accumulated charges is large, and when the temperature is low (solid line of c in the figure), it is small. That is, the image signal during dark can be used as a temperature signal. (4) The dark image signal obtained in (3) above is input to the control circuit 6. The control circuit 6 determines the temperature of the photoelectric conversion element based on the size of the image signal.

Next, the "reading mode" is performed in the following steps. (1) The control circuit 6 outputs a light source control signal to the light source 8 to illuminate the subject for T (Light). Photoelectric conversion element S1
A charge corresponding to the information light from the subject is accumulated in the. (2) According to the temperature judged by the control circuit 6 in the above-mentioned “temperature detection mode”, the TFT is driven by the gate drive circuit 3.
A gate pulse is applied to the gate electrode of T1 so that high temperature → short gate on / low temperature → long gate on. (3) When the TFT T1 is turned on, the charges accumulated in the photoelectric conversion element S1 by the subject information light are transferred to the reading circuit 2 and output as the analog image signal Sig (c in FIG. 4).

As described above, by detecting the temperature of the photoelectric conversion device in the "temperature detection mode" and changing the time for turning on the gate of the TFT in accordance with the temperature in the "reading mode", sufficient charge transfer of the TFT is performed. It is possible to realize a photoelectric conversion device that is less affected by the dark current of the photoelectric conversion element while ensuring efficiency.

(Third Embodiment) FIG. 5 shows a schematic circuit diagram of a third embodiment of the photoelectric conversion device of the present invention. In this embodiment, S1 to Sn and T1 to Tn are one-dimensional or two-dimensional.
These are a photoelectric conversion element and a TFT, which are arranged in a dimensional array. Each T
The shift register 5 is connected to the gate electrode of the FT, and the output from each pixel is connected to the analog multiplexer 4, which are sequentially selected and output as the image signal Sig. 5, those having the same functions as those of the second embodiment of FIG. 3 and the conventional example of FIG. 15 are denoted by the same reference numerals.

Similar to the second embodiment, in this embodiment,
By reading the charges accumulated in the photoelectric conversion elements S1 to Sn at the dark time, the temperature is detected and the time for turning on the gate of each TFT T1 to Tn is changed. The time for turning on the gate of each TFT may be changed for each TFT. The control circuit 6
As shown in FIG. 5, the temperature signal input to
It may be output from Amp or may be output from the analog multiplexer 4.

(Fourth Embodiment) FIG. 6 shows a schematic circuit diagram of a fourth embodiment of the photoelectric conversion device of the present invention. The photoelectric conversion device in this embodiment uses X-rays as a light source. Also, a MIS structure sensor is used as the photoelectric conversion element. FIG. 7 shows an equivalent circuit of one pixel of the photoelectric conversion device of this embodiment. FIG. 8 is a cross-sectional view showing the layer structure of the photoelectric conversion element and TFT of this embodiment. 6 and 7, components having the same functions as those in the third embodiment shown in FIG. 5 are designated by the same reference numerals.

In FIG. 6, reference numeral 9 is an X-ray power source, and when the switch is turned on, thermoelectrons are emitted from the cathode. An X-ray target (anode) 10 generates X-rays due to collisions with thermoelectrons. The generated X-rays are applied to the subject 11, and the X-rays that have passed through the subject 11 are converted into visible light by the phosphor 12 and enter the photoelectric conversion elements S1 to Sn. The X-ray power source 9 is controlled by an X-ray control signal output from the control circuit 6.

As can be seen from FIG. 8, the photoelectric conversion element of this embodiment and the TFT have the same layer structure, and therefore can be formed simultaneously by the amorphous silicon film forming process.

The operation of the MIS type photoelectric conversion element used in this embodiment will be described here. FIG. 9 (a),
7B is an energy band diagram of the photoelectric conversion element showing the operation of the refresh mode and the photoelectric conversion mode of the present embodiment, and shows the state of each layer in the thickness direction of FIG. 7B. Reference numeral 102 denotes a lower electrode (hereinafter referred to as a G electrode) made of Cr. Reference numeral 107 denotes an insulating layer formed of SiN that blocks passage of both electrons and holes, and its thickness is set to 500 angstroms or more, which is a thickness at which electrons and holes cannot move due to a tunnel effect. 1
Reference numeral 04 is a photoelectric conversion semiconductor layer formed of an intrinsic semiconductor i layer of hydrogenated amorphous silicon a-Si, 105 is an injection blocking layer of an n-layer of a-Si that blocks injection of holes into the photoelectric conversion semiconductor layer 104, and 106 is It is an upper electrode (hereinafter referred to as a D electrode) formed of Al. In the present embodiment, the D electrode does not completely cover the n layer, but since electrons can freely move between the D electrode and the n layer, the potentials of the D electrode and the n layer are always the same potential. The explanation assumes that.
This photoelectric conversion element has two kinds of operations, a refresh mode and a photoelectric conversion mode, depending on how the voltages of the D electrode and the G electrode are applied.

In the refresh mode shown in FIG. 9A, the D electrode is given a negative potential with respect to the G electrode, and the holes indicated by black circles in the i layer 104 are guided to the D electrode by the electric field. . At the same time, the electron indicated by the white circle is i layer 1
Injected at 04. At this time, some holes and electrons recombine in the n-layer 105 and the i-layer 104 and disappear. If this state continues for a sufficiently long time, the holes in the i layer 104 are i
Swept from layer 104.

In order to switch from this state to the photoelectric conversion mode shown in FIG. 9B, the D electrode gives a positive potential to the G electrode. Then, the electrons in the i layer 104 are instantly guided to the D electrode. However, holes are not guided to the i layer 104 because the n layer 105 functions as an injection blocking layer. When light enters the i-layer 104 in this state, the light is absorbed and electron-hole pairs are generated. The electrons are guided to the D electrode by the electric field, and the holes move in the i layer 104 and reach the interface between the i layer 104 and the insulating layer 107. However, since it cannot move into the insulating layer 107, it remains inside the i layer 104. At this time, the electrons move to the D electrode and the holes move to the interface of the insulating layer 107 in the i layer 104, so that a current flows from the G electrode in order to maintain electrical neutrality in the element. This current is proportional to the incident light because it corresponds to electron-hole pairs generated by the light. After maintaining the photoelectric conversion mode of FIG. 9B for a certain period and then returning to the refresh mode of FIG. 9A, the holes remaining in the i layer 104 are guided to the D electrode as described above, At the same time, a current corresponding to this hole flows. This amount of holes corresponds to the total amount of light incident during the photoelectric conversion mode period. At this time, a current corresponding to the amount of electrons injected into the i layer 104 also flows, but since this amount is approximately constant, it may be detected by subtracting it. That is, the photoelectric conversion element in this embodiment can output the amount of light that is incident in real time, and at the same time, can output the total amount of light that is incident during a certain period. This can be said to be a major feature of the photoelectric conversion element of this embodiment.

However, if the period of the photoelectric conversion mode is long or the illuminance of the incident light is strong for some reason, the current may not flow although the light is incident as in D. This is i as shown in FIG.
Many holes remain in the layer 104 and are
This is because the electric field in the layer 104 becomes small, and the generated electrons are not guided to the D electrode and are recombined with the holes in the i layer 104. When the light incident state changes in this state, the current may flow unstablely, but when the refresh mode is set again, the holes in the i layer 104 are swept out, and in the next photoelectric conversion mode, it is proportional to the light again. Electric current is obtained.

Further, in the above description, when sweeping out the holes in the i layer 104 in the refresh mode, it is ideal to sweep out all the holes, but sweeping out only some of the holes is effective, and is equal to the above. The current is obtained and there is no problem. That is, it is sufficient if the state of FIG. 9C is not obtained at the next detection opportunity in the photoelectric conversion mode, the potential of the D electrode with respect to the G electrode in the refresh mode, the period of the refresh mode, and the injection blocking layer of the n layer 105. The characteristics of should be decided. Further, in the refresh mode, injection of electrons into the i layer 104 is not a necessary condition, and the potential of the D electrode with respect to the G electrode is not limited to be negative. This is because when a large number of holes remain in the i layer 104, the electric field in the i layer is applied in the direction of guiding the holes to the D electrode even if the potential of the D electrode with respect to the G electrode is positive. Similarly, the characteristics of the injection blocking layer of the n-layer 105 are not required to be able to inject electrons into the i-layer 104.

[0044]

As described above, according to the present invention,
It is possible to realize a photoelectric conversion device that provides a good image with a simple structure that is less affected by S / N due to temperature changes.

[Brief description of drawings]

FIG. 1 is a schematic circuit diagram of a first embodiment of the present invention.

FIG. 2 is a timing diagram illustrating an operation of the first exemplary embodiment of the present invention.

FIG. 3 is a schematic circuit diagram of a second embodiment of the present invention.

FIG. 4 is a timing diagram illustrating an operation of the second exemplary embodiment of the present invention.

FIG. 5 is a schematic circuit diagram of a third embodiment of the present invention.

FIG. 6 is a schematic circuit diagram of a fourth embodiment of the present invention.

FIG. 7 is an equivalent circuit diagram of one pixel of the photoelectric conversion device of the present invention.

FIG. 8 is a cross-sectional view of one pixel of the photoelectric conversion device of the present invention.

9 is a diagram illustrating an operation of the photoelectric conversion element illustrated in FIG.

FIG. 10 is a schematic circuit diagram of a conventional technique.

FIG. 11 is a timing diagram illustrating an operation of the related art.

FIG. 12 is an explanatory diagram of temperature dependence of ON resistance of TFT.

FIG. 13 is an explanatory diagram of temperature dependence of charge transfer efficiency of TFT.

FIG. 14 is an explanatory diagram of temperature dependence of dark current of a photoelectric conversion element.

FIG. 15 is a schematic circuit diagram of a conventional technique.

FIG. 16 is a timing diagram illustrating the operation of the conventional technique.

FIG. 17 is a cross-sectional view showing a photoelectric conversion element, a TFT, a layer structure of a connection portion, and a temperature sensor of a photoelectric conversion device.

FIG. 18 is a schematic circuit diagram embodying a temperature sensor.

FIG. 19 is a cross-sectional view showing a photoelectric conversion element, a TFT, a layer structure of a connecting portion, and another temperature sensor of the photoelectric conversion device.

FIG. 20 is a schematic circuit diagram embodying a temperature sensor.

[Explanation of symbols]

 1 Power Supply 2 Readout Circuit 3 Gate Drive Circuit 4 Analog Multiplexer 5 Shift Register 6 Control Circuit 7 Temperature Sensor 8 Light Source 9 X-ray Power Supply 10 X-ray Target 11 Subject 12 Phosphor S1 to Sn Photoelectric Conversion Element T1 to Tn Thin Film Transistor (TFT)

Claims (12)

[Claims] 1. A photoelectric conversion element for converting an incident optical signal into an electric signal, a transistor for controlling transfer of an electric signal from the photoelectric conversion element, and driving means for applying a transfer control signal to a control electrode of the transistor. In the photoelectric conversion device including: a control unit that detects the temperature of the photoelectric conversion element or / and the transistor and controls the driving unit so that the conduction time of the transistor changes according to the detected temperature. A photoelectric conversion device having. 2. The photoelectric conversion element and the transistor are provided on the same substrate, the control means includes temperature detection means for detecting the temperature of the substrate, and the control means is detected by the temperature detection means. The photoelectric conversion device according to claim 1, wherein the driving unit is controlled such that the conduction time of the transistor changes according to the temperature of the substrate. 3. The control means shortens the time for transferring the electric signal by the transistor when the detected temperature is high, and the time for transferring the electric signal by the transistor when the detected temperature is low. The photoelectric conversion device according to claim 1 or 2, wherein the photoelectric conversion device is a device for controlling so as to lengthen. 4. The photoelectric conversion device according to claim 2, wherein the temperature detecting means is provided on the same substrate as the photoelectric conversion element and the transistor. 5. The method according to claim 1, further comprising a reading unit that reads the electric signal transferred from the transistor, and the control unit determines the temperature based on an output signal from the reading unit. The photoelectric conversion device described. 6. The photoelectric conversion device according to claim 5, wherein the control unit determines the temperature based on an output signal from the reading unit in a dark state. 7. The light source for giving an optical signal to be incident on the photoelectric conversion element, and a means for controlling ON / OFF of the light source, according to any one of claims 1 to 6. The photoelectric conversion device described in 1. 8. The photoelectric conversion device has means for switching between a temperature detection mode and a reading mode, and in the temperature detection mode, the light source is turned off to bring it into a dark state. The photoelectric conversion device described. 9. The photoelectric conversion device according to claim 7, wherein the light source has an X-ray source and a phosphor that converts at least a part of X-rays emitted from the X-ray source into light. . 10. The photoelectric conversion device according to claim 1, wherein the photoelectric conversion element and the transistor are formed by an amorphous silicon process. 11. The photoelectric conversion element is a PIN type photodiode, and the photoelectric conversion element is preferably a PIN type photodiode.
The photoelectric conversion device described in 1. 12. The photoelectric conversion device according to claim 1, wherein the photoelectric conversion element is an MIS type sensor.