JP5264418B2 - Thermal infrared detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermal type infrared detection element which restrains negative return effect by wiring resistance and has high sensitivity. <P>SOLUTION: This thermal infrared detection elements includes a diode 101, a power source Vdd which supplies a constant supply voltage to the positive electrode of the diode through first wiring, a voltage setting circuit 106 which sets up the voltage applied to both ends of the diode, and a current reading circuit 108 which is connected to the negative electrode of the diode through second wiring and the voltage setting circuit and reads the current of the diode. The voltage setting circuit 106 controls the voltage Vref of a connecting point 105 of the second wiring and the voltage setting circuit to a voltage subtracted by a voltage drop generated by the resistance 102 of the first wiring, the resistance 103 of the second wiring, and a current If of the diode. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a thermal infrared detection element (or also referred to as a “thermal infrared imaging element”) that detects a temperature change caused by incident infrared radiation with a two-dimensionally arranged semiconductor sensor, and in particular, a thermal type using a diode as a temperature sensor. The present invention relates to an infrared detection element.

  Conventionally, various techniques have been developed for thermal infrared solid-state imaging devices that detect temperature changes caused by incident infrared rays using semiconductor sensors arranged in an array.

  For example, Patent Document 1 discloses a thermal infrared detection element that applies a constant forward voltage to a diode and uses the temperature dependence of a current flowing through the diode. A high-sensitivity thermal infrared detection element can be realized by a constant voltage driving method in which a constant forward voltage is applied to such a diode. In other words, the forward current of the diode increases exponentially with respect to the voltage, so that when the constant forward voltage is applied rather than detecting the forward voltage change when the constant forward current is applied, Since a larger change rate can be obtained by detecting the forward current, a highly sensitive thermal infrared detector can be realized. A thermal infrared detecting element having a similar concept is also disclosed in Patent Documents 2 to 4.

Japanese Patent Laid-Open No. 2003-110938 JP 2000-019015 JP 2001-044400 A JP 2001-264176 A

  In a conventional thermal infrared detection element, a plurality of diodes are arranged in an array as a temperature sensor, each diode is connected to a row selection line and a signal line, and a detection result is obtained from one pixel by the row selection line and the signal line. Read out.

  An important point in driving the diode at a constant voltage is how to give the diode a predetermined bias.

  Usually, a thermal infrared detecting element using a diode has a hollow heat insulating structure in which a thermoelectric conversion portion is supported by two elongated heat insulating support legs. A diode is incorporated in the thermoelectric converter, and wiring to the diode is embedded in the heat insulating support leg. Furthermore, an infrared ray absorbing portion is provided on the upper surface of the thermoelectric conversion portion. When the incident infrared ray to the infrared absorbing portion changes, the infrared energy absorbed by the infrared absorbing portion changes, and the change is converted into a temperature change of the thermoelectric conversion portion by the heat insulating structure. The temperature change is read by the change in the current flowing through the diode incorporated in the thermoelectric converter. In order to increase the detection sensitivity in such a configuration, it is necessary to increase the thermal resistance of the heat insulating support legs. Furthermore, it is preferable that the metal forming the wiring embedded in the heat-insulating support legs is also thinned and made thin and long. In this way, the electrical resistance of the wiring increases, usually from several K to several ten KΩ.

  When a predetermined bias is applied to the diode under the electrical resistance of the high wiring as described above, there are the following problems.

  When a predetermined bias voltage is applied from the external circuit between the wiring in the support leg and the connection point of the row selection line and the signal line, the temperature of the thermoelectric converter rises and the current of the diode increases. The voltage drop in the wiring inside increases. For this reason, the forward voltage of the diode is reduced, and the current flowing through the diode is reduced. On the contrary, when the temperature of the thermoelectric conversion unit decreases and the current of the diode decreases, the voltage drop in the wiring in the support leg decreases. For this reason, the forward voltage of the diode increases and acts to increase the current of the diode. As described above, a phenomenon occurs in which a change in the current of the diode is suppressed due to the influence of the voltage drop due to the wiring resistance. That is, when the diode temperature changes and the current flowing through the diode fluctuates, the effective bias voltage applied to the diode fluctuates due to fluctuations in the voltage drop caused by the resistance of the diode and wiring, and the change in the diode current accompanying the temperature change Is suppressed, and the temperature detection sensitivity decreases. Hereinafter, the effect of suppressing a change in the current of the diode by such wiring resistance is referred to as a “negative feedback effect”. This negative feedback effect is caused by the resistance from the constant voltage supply to the diode, and the main cause of the resistance is the wiring resistance in the support leg, but the resistance of the row selection line and the signal line is not small. Has contributed. Due to this negative feedback effect, there is a problem that the characteristic of high sensitivity, which is a feature of the constant voltage driving method, cannot be fully exhibited.

  Patent Document 1 discloses that a negative feedback effect is a means for converting a diode current into a voltage in order to read out the current, for example, when a load resistor or a capacitor is connected, voltage fluctuation at the resistor or capacitor affects the diode bias. (See [0021] of Patent Document 1). As a solution to this problem, Patent Document 1 discloses a method in which the voltage at the connection point between the signal line and the column transistor group, which is the voltage conversion means, is always kept constant using the voltage conversion means. However, this method cannot solve the negative feedback effect due to the resistance of the signal line, the selection line, and the wiring in the pixel up to the column transistor group as the voltage conversion means.

  Patent Document 2 discloses an infrared detection element that utilizes the temperature dependence of the forward characteristics of a diode. Specifically, the bias of the diode is controlled so as to suppress a current change (drift current) when the environmental temperature changes. Is changed by a variable voltage source (see [0012], [0024], [0026] of Patent Document 2). Patent Document 2 does not disclose details of a method for changing the bias of the diode. For example, when the ambient temperature increases and the diode current increases, the diode bias is lowered to decrease the current in order to keep the output constant. Understandable. However, it is clear that such a method does not eliminate the negative feedback effect due to the wiring resistance generated when infrared light is incident, and the problem regarding the negative feedback effect is not recognized in the first place.

  Patent Document 3 discloses a structure in which the junction area of the diode is widened, and the readout circuit has a configuration similar to that of Patent Document 2 (see [0030] of Patent Document 3). Therefore, Patent Document 3 does not solve the problem of the negative feedback effect due to the wiring resistance generated when infrared light is incident, and does not recognize the problem related to the negative feedback effect in the first place.

  Patent Document 4 discloses a temperature measuring device or a thermal infrared image sensor in which a bias voltage circuit is inserted in series with a diode and a forward current is read via the circuit, as in Patent Document 2. Patent Document 4 describes the negative feedback effect due to resistance, but the inventor of Patent Document 4 points out that the negative feedback effect becomes a problem if the resistance is increased by increasing the resistance by connecting the resistance during current reading. (See [0009] of Patent Document 4). Then, with the same problem recognition as Patent Document 1, an accurate bias is given to the diode regardless of the resistance of the current reading unit ([0011] of Patent Document 4). In Patent Document 4, when applied to a thermal insulation sensor, a bias circuit is usually formed on a substrate without a thermal insulation structure. Therefore, wiring from the wiring in the support leg in the heat insulating structure to the bias circuit is required, and the negative feedback effect is generated by the wiring to the bias circuit.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a high-sensitivity thermal infrared detection element by suppressing the negative feedback effect due to wiring resistance.

  In order to solve the above problems, in the present invention, in the thermal infrared detector, the bias voltage applied to both ends of the diode is controlled to a constant value regardless of the current flowing through the diode having the heat insulating structure and the infrared absorbing portion. As a result, even if the temperature of the diode changes and the diode current changes, the voltage applied to the diode always becomes a constant value, so that the negative feedback effect due to the wiring resistance can be reduced. Specifically, the thermal infrared detection element according to the present invention has the following configuration.

The thermal infrared detection element according to the present invention includes one or more diodes connected in series as a thermoelectric conversion part, a hollow heat insulation structure that supports the thermoelectric conversion part with two heat insulation support legs, and absorbs infrared rays. An infrared absorption part that conducts heat corresponding to the absorbed infrared rays to the diode, and a power source that supplies a constant power supply voltage are connected to the anode side of the diode via the first wiring that is one of the heat insulating support legs. The cathode side of the diode is connected to the input terminal of the voltage setting circuit via the second wiring which is the other of the heat insulating support legs. In the voltage setting circuit, the current flowing through the input diode is divided or duplicated into a first current and a second current, and the first current is output to the output terminal of the voltage setting circuit, Using the current, a voltage drop caused by the resistance of the first wiring, the resistance of the second wiring, and the current of the diode is extracted, and the input of the voltage setting circuit, which is a connection point between the second wiring and the voltage setting circuit The terminal voltage is controlled to a voltage obtained by subtracting the extracted voltage drop from a predetermined bias voltage. A current reading circuit for reading the first current is connected to the output terminal of the voltage setting circuit.

  According to the present invention, even if the temperature of the diode changes and the current changes, the voltage applied to the diode is always a value obtained by subtracting a predetermined bias voltage from the power supply voltage. A highly sensitive thermal infrared detector can be realized.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

Embodiment 1 FIG.
(1. Overall configuration of thermal infrared detector)
FIG. 1 shows the configuration of a thermal infrared detection element according to Embodiment 1 of the present invention. The thermal infrared detection element includes a diode 101 for infrared detection. The anode of the diode 101 for infrared detection is connected to the power supply terminal 104 via the resistor 102, and the cathode is connected to the voltage setting circuit 106 via the resistor 103 and the terminal 105. The current If flowing through the diode 101 flows to the current reading circuit 108 via the voltage setting circuit 106 and the terminal 107 and is detected via the terminal 109. Note that the terminals 105 and 107 are expressed as terminals for convenience of explanation, but may not be in the form of terminals as long as they are electrically connected.

  The voltage setting circuit 106 is a circuit that controls the potential of the terminal 105 and controls the voltage applied to both ends of the diode 101 to be constant. The voltage setting circuit 106 controls the potential of the terminal 105 according to the current If flowing in the diode 101 in order to control the voltage across the diode 101 to a constant value. A more detailed operation of the voltage setting circuit 106 will be described later.

  The current reading circuit 108 converts an input current into a voltage and can be realized by a known technique. As an example, the configuration shown in FIG. 2 can be considered. FIG. 2A shows an example realized by a transimpedance amplifier, which has a configuration in which feedback from the output of the operational amplifier 201 is applied to the inverting input terminal by a load resistance RL, and an output having a value obtained by multiplying the current by the resistance RL is obtained. It is done. Alternatively, an integrator may be used in which the output of the operational amplifier 301 as shown in FIG. 2B is fed back to the inverting input terminal with the capacitor Ci and the reset switch 302 is provided at both ends of the capacitor Ci. In this configuration, an output of a value obtained by dividing the reset operation cycle of the reset switch 302 by the integration time Ti and the value obtained by multiplying the current by the integration time Ti by the integration capacitance Ci is obtained. In the example of FIG. 2B, since the integration operation is performed, there is also a noise reduction effect.

  The diode 101 has a heat insulation structure and an infrared absorption structure as shown in FIG. Such a configuration is well known. In FIG. 3, the infrared absorption structure (thermoelectric conversion part) including the main part of the diode 101 is supported on a hollow portion 403 provided on the substrate by two elongated heat insulating support legs 401 and 402. Connection wires (not shown) to the diode 101 are embedded in the heat insulating support legs 401 and 402. The heat insulating support legs 401 and 402 are connected to the anode-side power supply wiring 404 and the cathode-side signal line 405, respectively. An infrared absorption film 406 is formed on the portion where the diode 101 exists. The resistors 102 and 103 correspond to the wiring resistance in the heat insulating support legs 401 and 402.

(2. Voltage setting circuit)
The operation of the voltage setting circuit 106 will be described. The voltage setting circuit 106 controls the voltage Vref at the terminal 105 as follows.
Vref = Vc-If ・ Rc (1.1)
Rc is a combined resistance of the resistors 102 and 103, If is a current flowing through the diode 101, and Vc is a predetermined bias voltage.

On the other hand, assuming that the power supply voltage applied to the terminal 104 is Vdd, the forward bias voltage Vf of the diode 101 applied to the diode 101 is obtained by the following equation.
Vf = Vdd-If ・ Rc-Vref (1.2)

From the expressions (1.1) and (1.2), the forward bias voltage Vf is as follows.
Vf = Vdd-Vc (2)

  That is, the forward bias voltage Vf becomes a constant voltage regardless of the current If. Therefore, the sensitivity reduction due to the negative feedback effect, which has been a problem in the prior art, is eliminated, and a highly sensitive thermal infrared detector can be realized.

  FIG. 4 shows a configuration example of the voltage setting circuit 106 having such a function. The current flowing through the input terminal 105 and the output terminal 107 of the voltage setting circuit 106 is divided into two PMOS transistors 501 and 502 having the same size. The drain of one PMOS transistor 501 is connected to the output terminal 107, and the drain of the other transistor 502 is connected to a current mirror circuit composed of N-channel transistors 503 and 504. In the current mirror circuit, a current If that is twice the shunt current If / 2 is formed by the transistor 504. That is, the W / L ratio of the transistor 504 is set to twice the W / L ratio of the transistor 503. The drain of the transistor 504 is connected to a predetermined bias voltage Vc via a resistor Rc. The resistance value of the resistor Rc matches the combined value of the resistance values of the resistors 102 and 103 of the infrared detection unit. Specifically, it is conceivable as an example that the diode portion is short-circuited with a thick wiring having a small resistance in the configuration shown in FIG. As a result, a voltage of (Vc−If · Rc) is applied to the drain of the transistor 504. This voltage is input to the non-inverting terminal of the operational amplifier 507, and the voltage of the terminal 105 is input to the inverting terminal. The output of the operational amplifier 507 is input to the gates of the transistors 501 and 502. The operation of the operational amplifier 507 causes a feedback operation so that the voltage of the inverting input terminal, that is, the input terminal 105 of the voltage setting circuit 106 is always the voltage of the non-inverting input terminal (Vc−If · Rc).

  Consider the operation when the current If increases, the voltage drop across the resistors 102 and 103 increases, and the voltage at the terminal 105 decreases. In this case, since the voltage at the inverting input terminal of the operational amplifier 507 is decreased, the output of the operational amplifier 507 is increased, the gate voltages of the PMOS transistors 501 and 502 are increased, and the currents of the PMOS transistors 501 and 502 are decreased. Since the current from the diode 101 does not flow except for the PMOS transistors 501 and 502, the surplus diode current If charges the source voltage nodes of the PMOS transistors 501 and 502. As a result, the source voltage of the PMOS transistors 501 and 502 and the voltage at the inverting input terminal of the operational amplifier 507 are increased, and the gate voltages of the PMOS transistors 501 and 502 are decreased. As a result, the current flowing through the PMOS transistors 501 and 502 increases and eventually exceeds the current flowing through the diode 101. When this happens, the reverse phenomenon occurs, the source voltage nodes of the PMOS transistors 501 and 502 are discharged, and the source voltage of the PMOS transistors 501 and 502 and the voltage at the inverting input terminal of the operational amplifier 507 are also lowered. Thereafter, the same operation as described above is repeated, and finally stabilizes when the source voltage of the PMOS transistors 501 and 502 matches the voltage (Vc−If · Rc) of the non-inverting input terminal of the operational amplifier 507.

  Due to the operation of the voltage setting circuit 106 as described above, the voltage at the terminal 105 is controlled to the voltage (Vc-If · Rc), whereby the voltage applied across the diode 101 can be controlled to (Vdd-Vc). On the other hand, a constant bias independent of the current If can be applied. In other words, even if the temperature of the diode 101 changes and the current If changes, the voltage applied to the diode 101 is always a value obtained by subtracting a constant bias voltage Vc from the power supply voltage Vdd, so there is no negative feedback effect due to wiring resistance. A high-sensitivity thermal infrared detection element can be realized.

  In the present embodiment, the configuration of the thermal infrared detection element including one pixel has been described. Needless to say, the idea of the present embodiment can be applied to a thermal infrared detection element in which a plurality of pixels are arranged in an array. (The same applies to the following embodiments).

Embodiment 2. FIG.
FIG. 5 shows the configuration of the thermal infrared detection element according to the second embodiment of the present invention. The difference from the first embodiment is that a current source 601 is connected to the terminal 107. In order to explain the operation of the present invention, the equivalent circuit shown in FIG. 6 is used. In FIG. 6, the resistor 102 and the resistor 103 are collectively referred to as a resistor 701, the diode 101 and the resistor 701 are connected via a terminal 702, and the voltage at the terminal 702 is Vx. Similarly to the first embodiment, the voltage at the terminal 105 is Vref, and the value of the resistor 701 is Rc.

  FIG. 7 shows the voltage-current characteristics of the circuit shown in FIG. In FIG. 7, the horizontal axis represents voltage Vx, and the vertical axis represents current If. The characteristic of the diode 101 is 0 bias when the voltage Vx is equal to the power supply voltage Vdd, a known forward characteristic when the voltage Vx falls below the power supply voltage Vdd, and a current increasing characteristic as the temperature rises. On the other hand, the current flowing through the resistor 701 is (Vx−Vref) / Rc from Ohm's law. Since the current flowing through the diode 101 and the current flowing through the resistor 701 are equal, the intersection of these two characteristic curves becomes the operating point.

  In general, the forward current of the diode is several μA or more, but the temperature change rate of the diode current is about 6% per C. When viewed as an infrared detector, the pixel size is 40 μm, the thermal conductance of the heat insulating support leg is 100 nW / K, the infrared absorptivity is 80%, and the optical system F value is 1, although it depends on the setting of the optical system and the heat insulation characteristics. Then, the temperature of the diode 101 changes by about 5 millidegrees C per degree of temperature change of the subject. Even if the imaging temperature range of the subject is about room temperature ± 30 degrees C, the temperature change of the diode 101 is 0.3 degrees Cp-p at most. That is, it can be seen that the current change of the diode 101 is about 1.8% p-p (≈6% × 0.3), and even if a current of several μA is flowing, only a part thereof becomes a signal current. Therefore, it is not necessary to send all of the diode current If to the current reading circuit as in the first embodiment, and only a part of the diode current If may be sent to the current reading circuit 108. By doing so, it is possible to design the current reading circuit 108 so that the dynamic range can be effectively used, and it is possible to realize a highly sensitive thermal infrared detecting element having a large dynamic range. The bias current Ib of the current source 601 is for realizing this, and as shown in FIG. 6, the part obtained by removing the current Ib from the current If flows into the current extraction unit 108 as the signal current Ii. The value of the current Ib of the current source 601 may be set according to the imaging temperature range and pixel characteristics as described above. When the diode current changes greatly due to a change in ambient temperature, the current Ib may be changed according to the ambient temperature.

Embodiment 3 FIG.
FIG. 8 shows the configuration of a thermal infrared detection element according to Embodiment 3 of the present invention. In the present embodiment, a configuration capable of automatically changing the current of the current source 601 (corresponding to a current mirror circuit including transistors 907 and 908) in the configuration of the second embodiment according to the ambient temperature. Will be explained.

  For this purpose, a diode (hereinafter referred to as “reference diode”) 901 having no infrared absorption structure and / or heat insulation structure is provided, and the same circuit element as that for the diode 101 for infrared detection is connected in series to this diode 901. To do.

  The anode of the reference diode 901 is connected to the power supply terminal 904 via the resistor 902. The power supply terminal 904 is usually supplied with the same power supply voltage as that of the power supply terminal 104. The cathode of the reference diode 901 is connected to the voltage setting circuit 906 via a resistor 903 and a terminal 905. The resistors 902 and 903 and the voltage setting circuit 906 are the same as the resistors 102 and 103 and the voltage setting circuit 106, respectively. Since the reference diode 901 does not have an infrared absorption structure and / or a heat insulation structure, the reference diode 901 does not respond to infrared rays, and a current corresponding to a change in ambient temperature flows. This current is duplicated by a current mirror circuit composed of NMOS transistors 907 and 908, subtracted from the current If flowing in the diode 101, and the remaining current flows into the current reading circuit 108. Thus, the current flowing into the current reading circuit 108 is obtained by subtracting the current corresponding to the temperature of the detection element. That is, the bias current Ib removed from the current If of the diode 101 is controlled so that the output corresponding to the reference diode 901 is always a constant voltage. As a result, it is possible to realize a high-sensitivity thermal infrared detection element having a large dynamic range and a small output fluctuation, that is, temperature drift due to a change in ambient temperature.

Embodiment 4 FIG.
FIG. 9 shows the configuration of a thermal infrared detection element according to Embodiment 4 of the present invention. In the example shown in FIG. 9, the current determined by the NMOS transistor 907 is subtracted from the current flowing through the reference diode 901, and the current value obtained by the subtraction is obtained by the current reading circuit 1001 having the same configuration as the current reading circuit 108. Converted to voltage. The outputs of the current reading circuits 108 and 1001 have such a polarity that the output voltage increases as the input current increases. The output voltage of the current reading circuit 1001 with respect to the reference diode 901 is input to the non-inverting input of the operational amplifier 1003, the reference voltage is input to the inverting input terminal 1002, and the output of the operational amplifier 1003 is input to the gate voltages of the NMOS transistors 907 and 908. In this way, a feedback loop for matching the output of the current reading circuit 1001 with the reference voltage (input voltage of the terminal 1002) is formed. By doing so, the gate voltage of the NMOS transistors 907 and 908, that is, the value of the current Ib subtracted from the diode current If is determined so that the output voltage of the current reading circuit 1001 with respect to the reference diode 901 matches the reference voltage. If the polarity of the output of the current reading circuits 108 and 1001 is reversed, the polarity of the input of the operational amplifier 1003 may be reversed. According to the configuration of the present embodiment, the circuit 906, 907, 108, and 1001 are corrected including the temperature drift, and the output corresponding to the reference diode 901 is always equal to the predetermined reference voltage, compared with the third embodiment. This makes it possible to suppress temperature drift with higher accuracy.

Embodiment 5 FIG.
In the fourth embodiment, the thermal infrared detection element including one diode 101 has been described. However, the above technical idea can also be applied to a thermal infrared imaging element in which the diodes 101 are arranged in a two-dimensional array. FIG. 10 shows a configuration when the diodes 101 are arranged in an array. FIG. 10 shows an example in which the circuit disclosed in the fourth embodiment is applied to the configuration of a thermal infrared imaging element in which diodes are arranged in an array, but the idea disclosed in the other embodiments is also similar. Needless to say, the present invention can be applied to a configuration of a thermal infrared imaging device in which diodes are arranged in an array.

  In FIG. 10, the diodes 101 are arranged in an array, and one pixel P includes one diode 101 to form a 3 × 3 pixel image sensor. The plurality of pixels P arranged in an array form a pixel array. A reference diode 901 is arranged at the right end of each row. The anodes of the diodes 101 and 901 are commonly connected in units of rows, and the power supply voltage is sequentially supplied from the power supply terminal 104 in units of rows by the vertical scanning circuit 1101. The cathodes of the diodes 101 and 901 are commonly connected in units of columns. A voltage setting circuit 1102 provided for each column is connected to the cathode of the diode 101, and a voltage setting circuit 906 is connected to the cathode of the reference diode 901. Outputs of the voltage setting circuits 1102 and 906 are connected to current sources 1103 and 907 and current reading circuits 1104 and 1001.

  Outputs of the current reading circuits 1104 and 1001 are connected to a horizontal selection switch 1105. The horizontal selection switch 1105 is sequentially turned on by a control signal from the horizontal selection circuit 1106, and guides the outputs of the current reading circuits 1104 and 1001 to the output terminal 1107.

  When an output corresponding to the reference diode 901 is output, the sample hold circuit 1108 samples and holds the output and inputs the output to the non-inverting input terminal of the operational amplifier 1003. A reference voltage is input from the terminal 1002 to the inverting input terminal of the operational amplifier 1003. Since the reference diode 901 is provided in units of rows, the current flowing through the current sources 1103 and 907 is controlled so that the output thereof matches the reference voltage. Note that a low-pass filter may be inserted into the output of the operational amplifier 1003. Thereby, the feedback effect by the output from the reference diode 901 is averaged, and a more stable output can be obtained. Thereby, it is possible to realize a thermal infrared imaging device in which temperature drift is suppressed with high sensitivity, high dynamic range, and high accuracy.

  The resistance contribution of the drive line 1109, which is the wiring that commonly connects the anodes of the diodes 101 and 901, differs between the left and right pixels in the row, and the resistance contribution of the signal line 1110, which is the wiring that commonly connects the cathodes of the diode 101, is within the column. The pixel at the top and bottom of the pixel is different. For this reason, it is preferable to make the resistance of these wirings sufficiently small with respect to the resistance of the heat insulating support leg provided in the diode 101.

  The voltage setting circuits 1102 and 906 convert the voltage at the connection point between the signal line 1110 and the voltage setting circuits 1102 and 906 from the predetermined bias voltage, the resistance of the heat insulating support leg (first and second wiring resistance), and the signal line. The voltage is controlled by subtracting the voltage drop caused by the resistance of 1110 and the drive line 1109 and the current If of the diodes 101 and 901.

  In order to avoid the influence of the wiring resistance as much as possible, the resistance (resistor 505 in FIG. 4) provided in the voltage setting circuits 1102 and 906 is changed step by step in units of rows, and the vertical scanning circuit 1101 is further changed from the power supply terminal 104. The resistance of a power supply line (shown by a broken line) that runs vertically in the inside may be set to 1 / (the number of horizontal pixels) of the resistance of each wiring 1110 that commonly connects the cathodes of the diodes 101 and 901. Here, the reason why the ratio is 1 / (number of horizontal pixels) is as follows. Since the current corresponding to the number of horizontal pixels flows in the power supply line running vertically in the vertical scanning circuit 1101, the power supply line running vertically in the vertical scanning circuit 1101 apparently has the resistance of the wiring that commonly connects the cathodes of the diodes. This is because it contributes as a resistance several times the number of horizontal pixels.

Embodiment 6 FIG.
In the fifth embodiment, if the contribution of the resistance of the wiring that commonly connects the anodes of the diodes in units of rows and the resistance of the wiring that commonly connects the cathodes of the diodes in columns is not negligible compared to the resistance of the heat insulating support legs, Not only is it difficult to correct the resistance difference between them, but the following problems may occur. When strong infrared light is incident on one pixel, the current of the diode of that one pixel increases. Since the anode sides of the diodes are connected in common, the voltage drop on the common connection wiring changes under the influence of the current change of one pixel. The anode voltage of the diodes of other pixels in the same row as the one pixel may be changed to generate a “false signal”. In particular, when the pixel size is reduced, the wiring width must be reduced, and this effect becomes remarkable. A configuration for solving this problem will be described below.

  FIG. 11 shows the configuration of a thermal infrared detection element according to the sixth embodiment of the present invention. The pixel P includes a diode 101 and a selection MOS switch 1201 connected in series. The cathode of the diode 101 is connected to one terminal of the selection MOS switch 1201. The gates of the selection MOS switches 1201 are connected in common by a selection line 1202 in units of rows, and row selection signals are sequentially applied from the vertical scanning circuit 1101. The anodes of the diodes 101 are commonly connected in units of columns by a power line 1203, and the other terminals of the selection MOS switches 1201 are commonly connected in units of columns by a signal line 1204. The power supply line 1203 is commonly connected between the columns by the common power supply line 1205 and is connected to the power supply terminal 104. Here, since the common power supply line 1205 is outside the pixel array, even if the pixel size is reduced, the wiring width can be set sufficiently wide so that the contribution of resistance can be ignored. The voltage setting circuits 1102 and 906 convert the voltage at the connection point between the signal line 1204 and the voltage setting circuits 1102 and 906 from the predetermined bias voltage to the resistance of the heat insulating support legs of the diode (first and second wiring resistances), The voltage is controlled by subtracting the voltage drop caused by the ON resistance of the MOS transistor 1201, the resistance of the signal line 1204 and the power supply line 1203, and the current If of the diode.

  In the pixel P, since the selection of the row is performed by the selection MOS switch 1201, there is no current component flowing in the row direction in the pixel as in the fifth embodiment. Here, if the widths of the power supply line 1203 and the signal line 1204 are the same, the resistances of the two become the same. Therefore, as shown in FIG. 12, regardless of which row is selected, the resistance connected to the diode 101 is not limited to the resistance of a heat insulating support leg (first wiring) (not shown), but a single signal. The line resistance (power supply line resistance) and the ON resistance of the selection MOS switch 1201 are obtained. This is the same for any pixel column. Therefore, not only the resistance becomes the same in all the pixels, but also only the current of the selected diode flows through the power supply line and the signal line in the pixel, so the above-mentioned false signal does not occur. As a result, there is no resistance difference between pixels due to the diode array as shown in FIG. 10, so there is no generation of false signals, high sensitivity, high dynamic range, and thermal infrared imaging in which temperature drift is suppressed with high accuracy. An element can be realized.

Embodiment 7 FIG.
In the above-described embodiment, the voltage setting circuit is provided on the cathode side of the diode, but it may be provided on the anode side. FIG. 13 shows a configuration example of the thermal infrared detection element in this case. In FIG. 13, the voltage setting circuit 1401 is provided between the power supply terminal 104 and the resistor 102 connected to the anode side of the diode 101. The voltage setting circuit 1401 controls the voltage Vref of the terminal 1402 as follows.
Vref = Vc + If ・ Rc (3.1)
Rc is a combined resistance value of the resistors 102 and 103, If is a current flowing through the diode 101, and Vc is a predetermined bias voltage.

On the other hand, the forward bias voltage Vf applied to the diode 101 is obtained by the following equation.
Vf = Vref-If ・ Rc (3.2)

From the equations (3.1) and (3.2), the forward bias voltage Vf is as follows.
Vf = Vc (4)

  That is, the forward bias voltage Vf becomes a constant voltage regardless of the current If. Therefore, the sensitivity reduction due to the negative feedback effect, which has been a problem in the prior art, is eliminated, and a highly sensitive thermal infrared detector can be realized.

  FIG. 14 shows the configuration of the voltage setting circuit 1401. The configuration of the voltage setting circuit 1401 shown in FIG. 14 is obtained by inverting the polarity of the transistor and reversing the relationship between the power supply and the ground in the configuration shown in FIG. That is, the current If of the diode 101 is supplied by the NMOS transistors 1501 and 1502 whose sources are connected in common. The gate potentials of the NMOS transistors 1501 and 1502 are controlled by the operational amplifier 507 so that the source potentials of the NMOS transistors 1501 and 1502 become (Vc + If · Rc). The inverting input terminal of the operational amplifier 507 is connected to the sources of the NMOS transistors 1501 and 1502, and the non-inverting input terminal is connected to the drain of the PMOS transistor 1504.

  A current mirror circuit composed of PMOS transistors 1503 and 1504 connected in series to the NMOS transistor 1502 replicates the diode current If. The potential of (Vc + If · Rc) created using the replicated current If and the resistor 505 having a resistance value equal to the combined resistance value of the wiring resistors 102 and 103 is input to the non-inverting input terminal of the operational amplifier 507. Is done.

  The basic operation of the voltage setting circuit 1401 of the present embodiment is the same as that shown in FIG. 4, but if the forward current If is the same as that shown in FIG. 4, the current flowing into the current reading circuit 108 is as shown in FIG. In the case of FIG. 14, it is If / 2, whereas in the case of FIG. 14, it is If. Therefore, the configuration of FIG. 14 can realize a thermal infrared detection element with higher sensitivity. However, although the terminal 506 is fixed to the fixed bias VC, since a current flows into the terminal 506 side, it is necessary to prepare a power source that has a small voltage change with respect to the inflow current as a power source for generating the fixed bias VC. In this embodiment, since the potential of the anode of the diode is controlled, it is necessary that the potential of the cathode terminal 107 is always constant. Therefore, it is preferable to apply the circuit shown in FIG. 2A in which the input potential is always constant as the current reading circuit 108. Also in this embodiment, the technical idea of the second embodiment may be applied, and the remaining current obtained by subtracting the constant current Ib from the diode current If may be caused to flow into the current reading circuit 108.

Embodiment 8 FIG.
As described in the seventh embodiment, in the first embodiment (FIG. 4), if the current flowing through the diode is If, the current flowing through the current readout circuit 108 is halved and the sensitivity is lowered. In the present embodiment and the ninth embodiment, an embodiment for solving this problem will be described.

  FIG. 15 is a diagram showing the configuration of the voltage setting circuit according to the present embodiment. Except for the voltage setting circuit, the configuration is the same as that shown in FIG. In the present embodiment, unlike the case of FIG. 4, the W / L ratio of the PMOS transistor 1601 and the PMOS transistor 1602 are not the same, and the W / L ratio of the PMOS transistor 1601 is n times that of the PMOS transistor 1602 (n> 1). ). Accordingly, the W / L ratio of the NMOS transistor 1604 and the NMOS transistor 1603 of the current mirror circuit that replicates the current is (n + 1): 1. As a result, the current flowing into the current reading circuit increases by 2n / (n + 1) times as compared with the case of FIG. 4, and the sensitivity also increases by that ratio.

Embodiment 9 FIG.
FIG. 16 is a configuration diagram of a voltage setting circuit according to the ninth embodiment of the present invention. Except for the voltage setting circuit, the configuration is the same as that of FIG. In this embodiment, unlike the case of FIG. 4, an NMOS transistor 1701 having a gate-drain connection is connected to the drain of a PMOS transistor 501 whose source potential is controlled by the operational amplifier 507 to (Vc−If · Rc). The flowing current If is duplicated by the NMOS transistors 1702 and 1703. A resistor 505 having a resistance value Rc that matches the combined resistance value of the wiring resistors 102 and 103 is connected between the drain of the NMOS transistor 1702 and the bias voltage Vc. Thus, the drain voltage of the NMOS transistor 1702 is controlled to (Vc−If · Rc). This voltage is input to the non-inverting input terminal of the operational amplifier 507. The current If flowing in the NMOS transistor 1703 is input to the current reading circuit 108 via the terminal 107 and read out as an output signal. In the present embodiment, the current If flowing in the diode 101 is not directly read out, but a current having the same magnitude can be taken out. That is, a current having the same magnitude as the current If of the diode 101 flows through the current reading circuit 108. For this reason, the sensitivity fall which becomes a problem by the circuit structure shown in FIG.

Embodiment 10 FIG.
FIG. 17 shows another configuration of the voltage setting circuit. Also with the voltage setting circuit of this embodiment, as shown in FIG. 5, it is possible to remove the bias current Ib and supply only the differential current to the current reading circuit 108. In FIG. 17, a bias current source 1801 is connected in series with an NMOS transistor 1703. The method for setting the bias current Ib is exactly the same as that shown in FIG. Further, as shown in FIGS. 8 and 9, the value of the bias current may be determined using a reference diode 901. Even with the voltage setting circuit of the present embodiment, a current of the same magnitude as the current obtained by removing the bias current Ib from the diode current If flows through the current reading circuit 108, so that a more sensitive thermal infrared detection element can be realized. .

Embodiment 11 FIG.
FIG. 18 shows the configuration of a thermal infrared detection element according to the eleventh embodiment of the present invention. In the example shown in FIG. 18, the current determined by the NMOS transistor 907 is subtracted from the current of the reference diode 901, and then converted into a voltage by the current reading circuit 1001 similar to the current reading circuit. A predetermined bias voltage 1300 is applied to the gates of the NMOS transistors 907 and 908. At this time, the polarities of the outputs of the current reading circuits 108 and 1001 are set such that the output voltage increases as the input current increases. The output voltage of the current reading circuit 1001 for the reference diode 901 is input to the non-inverting input of the operational amplifier 1003, and the reference voltage is input to the inverting input terminal 1002. The output of the operational amplifier 1003 is input to the voltage VC input terminal (corresponding to the voltage input terminal 506 in FIG. 4) of the second voltage setting circuit 906 and the voltage VC input terminal of the voltage setting circuit 106. In this way, a feedback loop for matching the output of the current reading circuit 1001 with the reference voltage (input voltage of the terminal 1002) is formed. By doing so, the VC input voltage of the second voltage setting circuit 906 and the VC input voltage of the voltage setting circuit 106 are determined so that the output voltage of the current reading circuit 1001 with respect to the reference diode 901 matches the reference voltage. When the polarity of the current reading circuits 108 and 1001 is reversed, the polarity of the input of the operational amplifier 1003 may be reversed. Here, an example in which the current If is subtracted using the current source by the NMOS transistors 907 and 908 has been described. However, as in the first embodiment, the subtraction by the current source may not be performed.

  In this embodiment, the temperature drift of the circuits 906, 907, 108, and 1001 is corrected, and not only the output corresponding to the reference diode 901 is always equal to a constant reference voltage, but also the amount of current flowing through the reference diode 901 is always constant. It becomes possible to control to a constant current amount. Thereby, temperature drift can be suppressed with higher accuracy than in the fourth embodiment.

Embodiment 12 FIG.
In this embodiment, the configuration shown in Embodiment 11 is applied to the configuration of a thermal infrared detection element in which diodes are arranged in a two-dimensional array. FIG. 19 shows the configuration. Needless to say, the present invention can be similarly applied to other embodiments.

  In FIG. 19, the diodes 101 are arranged in an array to form an image sensor with 3 × 3 pixels. The plurality of pixels arranged in an array form a pixel array. A reference diode 901 is arranged at the right end of each row. The anodes of the diodes 101 and 901 are commonly connected in units of rows, and the power supply voltage is sequentially supplied from the power supply terminal 104 in units of rows by the vertical scanning circuit 1101. The cathodes of the diodes 101 and 901 are commonly connected in units of columns. A voltage setting circuit 1102 provided for each column is connected to the cathode of the diode 101, and a voltage setting circuit 906 is connected to the cathode of the reference diode 901. Outputs of the voltage setting circuits 1102 and 906 are connected to current sources 1103 and 907 and current reading circuits 1104 and 1001.

  A predetermined bias voltage 1300 is input to the gates of the current sources 1103 and 907, and a constant current flows. Outputs of the current reading circuits 1104 and 1001 are connected to a horizontal selection switch 1005. The horizontal selection switch 1005 is sequentially turned on by a control signal from the horizontal selection circuit 1106, and guides the outputs of the current reading circuits 1104 and 1001 to the output terminal 1107.

  When an output corresponding to the reference diode 901 is output, the sample hold circuit 1108 samples and holds the output and inputs the output to the non-inverting input terminal of the operational amplifier 1003. A reference voltage is input from the terminal 1002 to the inverting input terminal of the operational amplifier 1003. Since the reference diode 901 is provided in units of rows, the input voltage with respect to VC of the voltage setting circuit 1102 and the voltage setting circuit 906 is controlled so that the output from the reference diode 901 matches the reference voltage. Note that a low-pass filter may be inserted into the output of the operational amplifier 1003. Thereby, the feedback effect by the output from the reference diode 901 is averaged, and a more stable output can be obtained. As a result, it is possible to realize a thermal infrared detection element in which temperature drift is suppressed with high sensitivity, high dynamic range, and high accuracy.

  Within the pixel P, a diode 101 and a selection MOS switch 1201 are connected in series. That is, the cathode of the diode 101 and one terminal of the selection MOS switch 1201 are connected. The gates of the selection MOS switches 1201 are connected in common by a selection line 1202 in units of rows, and row selection signals are sequentially applied from the vertical scanning circuit 1101. The anodes of the diodes 101 are commonly connected in units of columns by a power line 1203, and the other terminals of the selection MOS switches 1201 are commonly connected in units of columns by a signal line 1204. The power supply line 1203 is commonly connected between the columns by the common power supply line 1205 and is connected to the power supply terminal 104. Here, since the common power supply line 1205 is outside the pixel array, even if the pixel size is reduced, the wiring width can be set sufficiently wide so that the contribution of resistance can be ignored. In the pixel P, since the selection of the row is performed by the selection MOS switch 1201, there is no current component flowing in the row direction in the pixel as in the fifth embodiment. Here, if the widths of the power supply line 1203 and the signal line 1204 are the same, the resistances of the two become the same. Therefore, regardless of which row is selected, the resistance connected to the diode 101 is not only the resistance of a heat insulating support leg (not shown) but also the resistance of one signal line (power line resistance) and the selection MOS switch 1201. ON resistance. This is the same for any pixel column. Therefore, not only the resistance becomes the same in all the pixels but also only the current of the selected diode flows through the power supply line and the signal line in the pixel, so that the above-mentioned false signal does not occur. As a result, there is no resistance difference between pixels due to the diode array, so there is no false signal, and it is possible to realize a thermal infrared detecting element with high sensitivity, high dynamic range, and temperature drift suppressed with high accuracy.

  Of course, an array configuration in which the selection MOS switch 1201 is not formed in the pixel P as shown in the fifth embodiment may be used.

  In the present embodiment, not only the output related to the reference diode 901 is always equal to a predetermined reference voltage, but also the amount of current flowing through the reference diode 901 can be controlled to a constant amount of current. Thereby, temperature drift can be suppressed with higher accuracy than in the fifth and sixth embodiments.

Embodiment 13 FIG.
FIG. 20 shows the configuration of the voltage setting circuit of the thermal infrared detection element of this embodiment. As shown in the figure, the voltage setting circuit of the present embodiment does not have a reference diode (infrared absorption structure and / or heat insulation structure) as the bias current source 1801 in the configuration shown in Embodiment 10 (FIG. 17). A diode 2000 having no supporting leg structure (hereinafter referred to as “reference diode having no supporting leg structure”) 2000 is used. The thermal infrared detection element of this embodiment has the same configuration as that of FIG. 1 except for the voltage setting circuit. For example, the reset integrator shown in FIG. 2B can be used for the current reading circuit 108, and the voltage of the input terminal 107 of the current reading circuit 108 is the same as that of the non-inverting input terminal of the operational amplifier 301 shown in FIG. The voltage is equal to the voltage VB.

  The voltage of the terminal 2001 and the voltage of the terminal 107 are applied to both ends of the reference diode 2000 having no support leg structure, a bias current Ib flows, and the differential current (Ib−If) flows to the subsequent current reading circuit 108 via the terminal 107. ) Only.

  Further, the area and the number of the reference diodes are formed to be the same as the area and the number of the pixel diodes, and a voltage equal to the voltage (Vdd−Vc) applied to the pixel diode (see Expression (2)) The voltage of the terminal 2001 and the voltage of the terminal 107 may be set so as to be applied to the reference diode 2000 that is not provided. As a result, only the current increased in response to the infrared light can be taken out as the differential current (Ib−If) input to the current reading circuit 108. As a result, it is possible to realize a high-sensitivity thermal infrared detection element having a large dynamic range and a small output fluctuation, that is, temperature drift due to a change in ambient temperature. In addition, a diode having a small differential resistance is added in parallel to the NMOS transistor 1703 having a high differential resistance due to the saturation operation, so that it can be connected to the input terminal of the subsequent current reading circuit with a low impedance. Thereby, noise is reduced and a high-performance thermal infrared detection element can be realized. Here, the reference diode 2000 having no support leg structure may be a reference diode having a support leg structure.

Embodiment 14 FIG.
FIG. 21 shows the configuration of the voltage setting circuit of the thermal infrared detection element of this embodiment. As shown in the figure, the voltage setting circuit according to the present embodiment uses a resistance element 2002 as the bias current source 1801 in the configuration shown in the tenth embodiment (FIG. 17). The thermal infrared detection element of this embodiment has the same configuration as that of FIG. 1 except for the voltage setting circuit. For example, the reset integrator shown in FIG. 2B can be used for the current reading circuit 108, and the voltage of the input terminal 107 of the current reading circuit 108 is the same as that of the non-inverting input terminal of the operational amplifier 301 shown in FIG. The voltage is equal to the voltage VB.

  The voltage of the terminal 2003 and the voltage of the terminal 107 are applied to both ends of the resistance element 2002, the bias current Ib flows, and only the differential current (Ib−If) can be supplied to the current reading circuit 108 in the subsequent stage. As a result, it is possible to realize a high-sensitivity thermal infrared detection element having a large dynamic range and a small output fluctuation, that is, temperature drift due to a change in ambient temperature. In addition, the resistance element 2002 has a resistance value smaller than the differential resistance value of the NMOS transistor 1703 that increases to perform a saturation operation. As a result, it is possible to connect to the input terminal 107 of the current reading circuit 108 in the subsequent stage with low impedance, so that noise is reduced and a high-performance thermal infrared detection element can be realized.

Embodiment 15 FIG.
FIG. 22 shows the configuration of the voltage setting circuit of the thermal infrared detection element of this embodiment. The thermal infrared detection element of this embodiment has the same configuration as that of FIG. 1 except for the voltage setting circuit.

  In this embodiment, an NMOS transistor 1701 having a gate-drain connection is connected to the drain of the PMOS transistor 501 whose source potential is controlled to (Vc-If · Rc) by the operational amplifier 507, and the current If flowing therethrough is connected to the NMOS transistor. Duplicate at 1702. A resistor 505 having a resistance value Rc matching the combined resistance value of the wiring resistors 102 and 103 is connected between the drain of the NMOS transistor 1702 and the terminal 107.

  Since the reset integrator shown in FIG. 2B can be used for the current reading circuit 108, for example, the voltage at the terminal 107 serving as the input terminal of the current reading circuit 108 is the non-voltage of the operational amplifier 301 shown in FIG. The voltage is equal to the voltage of the inverting input terminal (described as VB in FIG. 2B but described as VC in FIG. 22). As a result, the drain voltage of the NMOS transistor 1702 is controlled to (Vc−If · Rc). This voltage is input to the non-inverting input terminal of the operational amplifier 507. A current If flowing in the NMOS transistor 1702 is input to the current reading circuit 108 via the terminal 107 and read as an output signal.

  In the present embodiment, the current If flowing in the diode 101 is not directly read out, but a current having the same magnitude can be taken out. That is, a current having the same magnitude as the current If of the diode 101 flows through the current reading circuit 108. For this reason, the sensitivity fall which becomes a problem by the circuit structure shown in FIG. 4 does not arise. Further, since the NMOS transistor 1703 is not required as in the configuration of the tenth embodiment, the circuit area is reduced compared to the tenth embodiment, the chip area of the thermal infrared detection element is reduced, and the cost is reduced. The

Embodiment 16 FIG.
FIG. 23 shows the configuration of the voltage setting circuit of the thermal infrared detection element of this embodiment. The voltage setting circuit of the present embodiment shown in the figure has a bias current source 2005 added to the configuration shown in FIG. 22, and supplies a differential current between the current Ib and the current If flowing through the bias current source 2005 to the terminal 107. Reading is performed. As a result, it is possible to realize a high-sensitivity thermal infrared detection element having a large dynamic range and a small output fluctuation, that is, temperature drift due to a change in ambient temperature.

  As the bias current source 2005, a current mirror current source using a MOS transistor can be used. Alternatively, as the bias current source 2005, the reference diode (see FIG. 24) without the support leg structure shown in the thirteenth embodiment or the resistance element (see FIG. 25) shown in the fourteenth embodiment can be used.

Embodiment 17. FIG.
In this embodiment, an example in which the voltage setting circuit shown in Embodiment 13 (FIG. 20) is applied to a configuration of a thermal infrared detection element in which diodes are arranged in a two-dimensional array will be described. FIG. 26 shows the configuration.

  In the configuration shown in FIG. 26, the diodes 101 are arranged in an array and constitute a 3 × 3 pixel imaging device. The plurality of pixels arranged in an array form a pixel array. The anodes of the diodes 101 are commonly connected in units of rows and connected to the vertical scanning circuit 1101. A power supply voltage Vdd is sequentially supplied from the power supply terminal 104 to the diode 101 in units of rows by the vertical scanning circuit 1101. The cathodes of the diodes 101 are commonly connected in units of columns. A voltage setting circuit 3000 provided for each column is connected to the cathode of the diode 101. Voltage setting circuit 3000 has the configuration shown in the thirteenth embodiment. A reference circuit 4000 is added to the right end of the voltage setting circuit 3000 provided for each column. The reference circuit 4000 is not connected to the pixel array. FIG. 27 shows a specific configuration of the reference circuit 4000. Reference circuit 4000 includes a reference diode 2000b that does not have a support leg structure for generating a differential current, and a current source 2010 that draws current If_ref.

  The voltage setting circuit 3000 has a configuration shown in FIG. In this case, the terminal 105 of the voltage setting circuit 3000 is connected to the cathode of the pixel diode, the terminal 107 is connected to the current reading circuit 1104, the terminal 506 is connected to the output of the operational amplifier 1003, and the terminal 2001 is a terminal for supplying the power supply voltage Vdd. 104 is connected.

  Outputs of the voltage setting circuit 3000 and the reference circuit 4000 are connected to a current reading circuit 1104 and a current reading circuit 4001, respectively. Outputs of the current reading circuits 1104 and 4001 are connected to a horizontal selection switch 1105. The horizontal selection switch 1105 is sequentially turned on by a control signal from the horizontal selection circuit 1106 and guides the outputs of the current reading circuits 1104 and 4001 to the output terminal 1107. In the present embodiment, the current reading circuits 1104 and 4001 have the configuration shown in FIG.

  When an output corresponding to the reference circuit 4000 is output, the sample hold circuit 1108 samples and holds the output and inputs the output to the non-inverting input terminal of the operational amplifier 1003. The output voltage 4003 of the operational amplifier 1003 is input to the inverting input terminal of the operational amplifier 1003. The output voltage 4003 of the operational amplifier 1003 is input to the VC voltage (terminal 506 in FIG. 20) of the voltage setting circuit 3000 as the voltage VC. Further, the output voltage 4003 of the operational amplifier 1003 is applied to the non-inverting input terminal (terminal denoted as VB in FIG. 2B) of the operational amplifier (the operational amplifier 301 in FIG. 2B) of each of the current reading circuits 1104 and 4001. Entered. In the reference circuit 4000, the anode terminal 2008 of the reference diode 2000b that does not have a support leg structure for generating a differential current is connected to the power supply voltage Vdd of the terminal 104.

  With the above configuration, the current flowing through the reference diode 2000b in the reference circuit 4000 becomes equal to the current If_ref of the reference current source 2010 of the reference circuit 4000 (that is, from the reference circuit 4000 to the current reading circuit 4001 via the output terminal 2009). So that the output of the current reading circuit 4001 becomes equal to the voltage VC of the non-inverting input terminal of the operational amplifier of the current reading circuit 4001 (for example, the operational amplifier 301 shown in FIG. 2B). The output voltage 4003 (that is, the bias voltage VC) of the operational amplifier 1003 is controlled.

  In the present embodiment, even if the ambient temperature changes, the bias voltage VC is controlled so that the current flowing through the reference diode 2000b in the reference circuit 4000 is always equal to the current If_ref of the reference current source 2010. The voltage applied to the reference diodes 2000 and 2000b is Vdd-VC, which is equal to the voltage applied to the pixel diode 101. By setting the bias voltage VC as described above, the current that flows through the pixel diode 101 when the incidence of infrared rays is zero regardless of the ambient temperature is If_ref. Therefore, the current of the pixel diode can be measured with reference to the current If_ref regardless of the ambient temperature. Therefore, finally, the current reading circuit 1104 can read only the current increased by the incidence of infrared rays in the current of the pixel diode measured on a constant basis regardless of the ambient temperature. As a result, it is possible to realize a thermal infrared detection element in which temperature drift is suppressed with high sensitivity, high dynamic range, and high accuracy.

  Here, the voltage Vdd is applied with a constant voltage and the voltage VC is feedback controlled. However, the voltage VC may be applied with a constant voltage and the voltage Vdd may be feedback controlled. Here, the configuration shown in Embodiment 13 is applied, but the configuration shown in FIG. 24 in Embodiment 16 may be applied.

  Further, a low-pass filter may be inserted into the output of the operational amplifier 1003. Thereby, the feedback effect by the output from the reference circuit 4000 is averaged, and a more stable output can be obtained. Therefore, it is possible to realize a thermal infrared detection element in which temperature drift is suppressed with high sensitivity, high dynamic range, and high accuracy.

Embodiment 18 FIG.
In the present embodiment, a voltage setting circuit using a current mirror current source using a PMOS transistor as the bias current source 1801 in the configuration shown in the tenth embodiment is replaced with a thermal infrared detecting element in which diodes are arranged in a two-dimensional array. An example applied to the configuration will be described. FIG. 28 shows the configuration.

  In the figure, diodes 101 are arranged in an array and constitute a 3 × 3 pixel imaging device. The plurality of pixels arranged in an array form a pixel array. Two columns of diodes (reference diodes) 901 having no infrared absorption structure and / or heat insulation structure are formed at the right end of each row. The anodes of the diodes 101 and 901 are commonly connected in units of rows. The anodes of the diodes 101 and 901 are supplied with the power supply voltage Vdd from the power supply terminal 104 in order by the vertical scanning circuit 1101 in units of rows. The cathodes of the diodes 101 and 901 are commonly connected in units of columns. A voltage setting circuit 5000 provided for each column is connected to the cathodes of the diodes 101 and 901.

  The voltage setting circuit 5000 is obtained by configuring the bias current source 1801 as a current mirror current source using a PMOS transistor 5001 in the configuration shown in the tenth embodiment (FIG. 17). FIG. 29 shows the configuration of the voltage setting circuit 5000. In FIG. 29, the terminal 105 is connected to the pixel diode, the terminal 107 is connected to the current reading circuit 1104, and the terminal 506 is connected to the output of the operational amplifier 1003. The terminal 5003 is connected to the gate of another PMOS transistor 5001 and the gate of the PMOS transistor 5006.

  The voltage setting circuit 5200 in the second column from the right end connected to the reference pixel also has a configuration similar to that shown in FIG. In the voltage setting circuit 5200 in the second column from the right end connected to the reference pixel, the gate electrode and the drain electrode of the PMOS transistor 5006 are connected. Therefore, a current mirror operation is performed by the PMOS transistor 5006 and the PMOS transistor 5001. Therefore, a current equal to the current flowing through the reference diodes 901 in the second column from the right end flows as a current Ib1 in the PMOS transistor 5001 in the voltage setting circuit 5000 connected to each column of the pixel array. In the voltage setting circuit 5000, the difference current between the current If flowing in the pixel diode 101 of each column of the pixel array and the current (Ib1) flowing in the reference diode 901 is supplied to the current reading circuit 1104 in the next stage. Thereby, it is possible to read only the increase in the current of the pixel diode, which has been increased by the incidence of infrared rays, by the current reading circuit 1104.

  Outputs of the current reading circuits 1104 and 5007 are connected to a horizontal selection switch 1105. The horizontal selection switch 1105 is sequentially turned on by a control signal from the horizontal selection circuit 1106 and guides the outputs of the current reading circuits 1104 and 5007 to the output terminal 1107. When an output corresponding to the reference diode at the right end of the column is output, the sample hold circuit 1108 samples and holds the output and inputs the output to the non-inverting input terminal of the operational amplifier 1003. The output voltage 4003 of the operational amplifier 1003 is input to the inverting input terminal of the operational amplifier 1003. The output voltage 4003 of the operational amplifier 1003 is input to the VC voltage (terminal 506 in FIG. 29) of the voltage setting circuit 5000 as the voltage VC. Further, the output voltage 4003 of the operational amplifier 1003 is input to the non-inverting input terminals (terminals denoted as VB in FIG. 2B) of the operational amplifiers of the current reading circuits 1104 and 5007.

  A bias current source 5005 for supplying a reference current Ib is connected to the voltage setting circuit 5100 corresponding to the reference diode in the rightmost column instead of the PMOS transistors 5001 and 5006. A circuit 5110 in the voltage setting circuit 5100 has a configuration similar to that of the circuit 5010 shown in FIG. The output of the voltage setting circuit 5000 corresponding to each column of the pixel diodes 101 is connected to the current reading circuit 1104. The output of the voltage setting circuit 5200 corresponding to the reference diodes in the second column from the right end is not connected to the current reading circuit 1104. The output of the voltage setting circuit 5100 corresponding to the rightmost reference diode is connected to the current reading circuit 5007. With this configuration, the current flowing through the reference diode in the rightmost column is made equal to the current Ib of the reference current bias current source 5005 (that is, the current input to the current reading circuit 5007 is zero), and the current reading circuit 5007 The output voltage 4003 of the operational amplifier 1003 is controlled so that the output corresponding to is equal to the voltage VC of the non-inverting input terminal of the operational amplifier of the current reading circuit 5007.

  Note that a low-pass filter may be inserted into the output of the operational amplifier 1003. Thereby, the feedback effect by the output corresponding to the current reading circuit 5007 is averaged, and a more stable output can be obtained.

  In the present embodiment, even if the ambient temperature changes, the current flowing through the rightmost reference diode is always equal to the current Ib of the reference current bias current source 5005. Furthermore, as described above, only the contribution of the increase in the current of the pixel diode that is increased by the incidence of infrared rays is output. As a result, it is possible to realize a thermal infrared detection element in which temperature drift is suppressed with high sensitivity, high dynamic range, and high accuracy.

Circuit diagram of thermal infrared detection element according to the first embodiment of the present invention The figure which shows the example of the electric current reading circuit of the thermal type infrared rays detection element of embodiment of this invention The figure which shows the structure of the diode of the thermal type infrared detection element in Embodiment 1 Circuit diagram of voltage setting circuit of thermal-type infrared detection element in embodiment 1 Circuit diagram of thermal infrared detection element in embodiment 2 of the present invention Equivalent circuit diagram of the circuit shown in FIG. The figure which shows the voltage-current characteristic of the thermal type infrared rays detection element in Embodiment 2. Circuit diagram of thermal infrared detecting element according to Embodiment 3 of the present invention Circuit diagram of thermal infrared detection element in embodiment 4 of the present invention Circuit diagram of thermal infrared imaging device in embodiment 5 of the present invention Circuit diagram of thermal infrared imaging device in Embodiment 6 of the present invention Circuit diagram for one column of pixels of thermal infrared imaging device in the sixth embodiment Circuit diagram of thermal infrared detection element in embodiment 7 of the present invention Circuit diagram of voltage setting circuit of thermal-type infrared detection element in embodiment 7 Circuit diagram of voltage setting circuit of thermal infrared detection element in embodiment 8 Circuit diagram of voltage setting circuit of thermal infrared detecting element in embodiment 9 Circuit diagram of voltage setting circuit of thermal-type infrared detection element in embodiment 10 Circuit diagram of thermal infrared detection element in embodiment 11 Circuit diagram of thermal infrared detection element in embodiment 12 of the present invention Circuit diagram of voltage setting circuit of thermal infrared detecting element in the embodiment 13 of the present invention Circuit diagram of voltage setting circuit of thermal infrared detecting element according to embodiment 14 of the present invention Circuit diagram of voltage setting circuit of thermal infrared detecting element in embodiment 15 of the present invention Circuit diagram of voltage setting circuit of thermal infrared detection element in embodiment 16 of the present invention The circuit diagram of the modification of the voltage setting circuit of the thermal type infrared detection element in Embodiment 16 of this invention The circuit diagram of the modification of the voltage setting circuit of the thermal type infrared detection element in Embodiment 16 of this invention Circuit diagram of thermal infrared detection element in embodiment 17 of the present invention Circuit diagram of a reference circuit of a thermal infrared detection element in the seventeenth embodiment of the present invention Circuit diagram of thermal infrared detection element according to Embodiment 18 of the present invention Circuit diagram of voltage setting circuit of thermal infrared detecting element according to Embodiment 18 of the present invention

Explanation of symbols

  101 diode, 102 1st wiring resistance, 103 2nd wiring resistance, 106 voltage setting circuit, 108 current reading circuit, 401 insulation support leg, 402 insulation support leg, 406 infrared absorption film, 601 bias current source, 901 reference diode 902, third wiring resistance, 903 fourth wiring resistance, 906 second voltage setting circuit, 1001 second current reading circuit, 1101 vertical scanning circuit, 1106 horizontal scanning circuit, 1201 MOS switch, 1202 selection line, 1203 Power line, 1204 signal line, 1205 common power line, 2000 Reference diode without support leg structure for generating differential current, 2001 Terminal for applying voltage to the anode of reference diode without support leg structure, 2002 For generating differential current Resistor element, 2003 terminal for applying voltage to the differential current generating resistor element, 2004 anode terminal of the bias current source for differential current generation, 2005 bias current source for generating differential current, 2008 support leg structure Terminal that applies voltage to the anode of the reference diode that does not have, Output terminal of 2009 reference circuit, Bias current source used for 2010 reference circuit, 3000 Voltage setting circuit, 4000 reference circuit, Current reading circuit corresponding to 4001 reference circuit, 4003 VC Op-amp output terminal for voltage control, 5000 voltage setting circuit, 5001 PMOS transistor forming current mirror, 5002 PMOS transistor power supply terminal forming current mirror, 5003 PMOS transistor gate electrode terminal forming current mirror, 5004 current mirror A power supply terminal of a PMOS transistor to be formed, a bias current source for a 5005 reference current, a PMOS transistor to form a current mirror, 5007, a current reading circuit corresponding to a reference diode on the right end, P pixel.

Claims (12)

As the thermoelectric converter, one or a plurality of diodes connected in series,
A hollow heat insulating structure for supporting the thermoelectric conversion part with two heat insulating support legs;
An infrared absorption part that absorbs infrared rays and conducts heat corresponding to the absorbed infrared rays to the diode;
A power supply for supplying a constant power supply voltage is connected to the anode side of the diode via the first wiring that is one of the heat insulating support legs,
An input terminal of a voltage setting circuit is connected to the cathode side of the diode via a second wiring that is the other of the heat insulating support legs,
In the voltage setting circuit,
    The input current flowing in the diode is divided or replicated into a first current and a second current,
The first current is output to an output terminal of the voltage setting circuit;
Using the second current, a voltage drop caused by the resistance of the first wiring, the resistance of the second wiring, and the current of the diode is extracted,
The voltage at the input terminal of the voltage setting circuit, which is a connection point between the second wiring and the voltage setting circuit, is controlled to a voltage obtained by subtracting the extracted voltage drop from a predetermined bias voltage,
A current reading circuit for reading the first current is connected to an output terminal of the voltage setting circuit.
A thermal infrared detecting element. As the thermoelectric converter, one or a plurality of diodes connected in series,
A hollow heat insulating structure for supporting the thermoelectric conversion part with two heat insulating support legs;
An infrared absorption part that absorbs infrared rays and conducts heat corresponding to the absorbed infrared rays to the diode;
A power supply that supplies a constant power supply voltage is connected to the input terminal of the voltage setting circuit,
The anode of the diode is connected to the output terminal of the voltage setting circuit via the first wiring that is one of the heat insulating support legs,
A current reading circuit is connected to the cathode side of the diode via a second wiring that is the other of the heat insulating support legs,
In the voltage setting circuit,
The input current flowing in the diode is divided or replicated into a first current and a second current,
The first current is output to an output terminal of the voltage setting circuit;
Using the second current, a voltage drop caused by the resistance of the first wiring, the resistance of the second wiring, and the current of the diode is extracted,
The voltage at the connection point between the voltage setting circuit and the first wiring, which is an output terminal of the voltage setting circuit, is controlled to a voltage obtained by adding the extracted voltage drop to a predetermined bias voltage,
The current reading circuit reads the first current.
A thermal infrared detecting element. As the thermoelectric converter, one or a plurality of diodes connected in series,
A hollow heat insulating structure for supporting the thermoelectric conversion part with two heat insulating support legs;
An infrared absorption part that absorbs infrared rays and conducts heat corresponding to the absorbed infrared rays to the diode;
A power supply for supplying a constant power supply voltage is connected to the anode side of the diode via the first wiring that is one of the heat insulating support legs,
An input terminal of a voltage setting circuit is connected to the cathode side of the diode via a second wiring that is the other of the heat insulating support legs,
In the voltage setting circuit,
The input current flowing through the diode is replicated in the first current,
The first current is output to the output terminal of the voltage setting circuit,
Using the first current, a voltage drop caused by the resistance of the first wiring, the resistance of the second wiring, and the current of the diode is extracted,
The voltage at the input terminal of the voltage setting circuit, which is a connection point between the second wiring and the voltage setting circuit, is controlled to a voltage obtained by subtracting the extracted voltage drop from a predetermined bias voltage,
A current reading circuit for reading the first current is connected to an output terminal of the voltage setting circuit.
A thermal infrared detecting element. Means for subtracting a constant current from the first current;
The remaining current subtracted by the means is input to the current reading circuit,
The thermal infrared detection element according to any one of claims 1 to 3. As the thermoelectric converter, one or a plurality of first diodes connected in series;
A hollow heat insulating structure for supporting the thermoelectric conversion part with two heat insulating support legs;
An infrared absorber that absorbs infrared rays and conducts heat corresponding to the absorbed infrared rays to the first diode;
A second diode that does not have the hollow heat insulating structure and / or the infrared absorbing portion;
Two separate thermal support legs supporting the second diode;
With
A first power supply for supplying a constant power supply voltage is connected to the anode side of the first diode via a first wiring that is one of the heat insulating support legs,
The input terminal of the first voltage setting circuit is connected to the cathode side of the first diode via the second wiring which is the other of the heat insulating support legs.
In the first voltage setting circuit,
The input current flowing through the first diode is divided or replicated into a first current and a second current,
The first current is output to an output terminal of the first voltage setting circuit;
Using the second current, a voltage drop caused by the resistance of the first wiring, the resistance of the second wiring, and the current of the first diode is extracted,
The voltage at the input terminal of the first voltage setting circuit, which is a connection point between the second wiring and the first voltage setting circuit, is a voltage obtained by subtracting the extracted voltage drop from a predetermined bias voltage. Controlled,
A first current reading circuit for reading the first current is connected to an output terminal of the first voltage setting circuit,
A second power supply for supplying a constant power supply voltage is connected to the anode side of the second diode via a third wiring that is one of the other heat insulating support legs,
The input terminal of the second voltage setting circuit is connected to the cathode side of the second diode via a fourth wiring which is the other of the other heat insulating support legs,
In the second voltage setting circuit,
The current that flows through the input second diode is divided or replicated into a third current and a fourth current,
The third current is output to an output terminal of the second voltage setting circuit;
Using the fourth current, another voltage drop caused by the resistance of the third wiring, the resistance of the fourth wiring, and the current of the second diode is extracted,
The voltage at the input terminal of the second voltage setting circuit, which is a connection point between the fourth wiring and the second voltage setting circuit, is controlled to a voltage obtained by subtracting the other voltage drop from a predetermined bias voltage. And
A second current reading circuit for reading the third current is connected to an output terminal of the second voltage setting circuit,
The output of the second current reading circuit is compared with a reference voltage, and the first and second bias currents, which are constant currents subtracted from the first and third currents, respectively, according to the difference are obtained. A bias current determining means for determining;
The bias current determining means converts the output of the second current reading circuit to the reference voltage.
A feedback loop is formed to match
A thermal infrared detecting element. The voltage setting circuit includes:
The source is connected in common, and the drain of one PMOS transistor is the output of the voltage setting circuit
A pair of PMOS transistors connected to the terminals;
A current collector connected to the drain of the other PMOS transistor and replicates the current of the diode.
Mirror circuit,
Using the replicated current, a voltage obtained by subtracting the voltage drop from a constant bias voltage.
Means to create,
Means for controlling a gate voltage of the pair of PMOS transistors based on a voltage difference between the created voltage and a source voltage of the pair of PMOS transistors;
including,
The thermal infrared detection element according to claim 1. Each of the first voltage setting circuit and the second voltage setting circuit is
The source is connected in common, and the drain of one PMOS transistor is the output of the voltage setting circuit
A pair of PMOS transistors connected to the terminals;
A current collector connected to the drain of the other PMOS transistor and replicates the current of the diode.
Mirror circuit,
Using the replicated current, a voltage obtained by subtracting the voltage drop from a constant bias voltage.
Means to create,
Means for controlling a gate voltage of the pair of PMOS transistors based on a voltage difference between the created voltage and a source voltage of the pair of PMOS transistors;
including,
The thermal infrared detection element according to claim 5. The voltage setting circuit includes:
The source is connected in common, and the drain of one NMOS transistor is the input of the voltage setting circuit
A pair of NMOS transistors connected to the terminals;
A current collector connected to the drain of the other NMOS transistor and replicates the current of the diode.
Mirror circuit,
Means for generating a voltage obtained by adding a voltage drop caused by the resistance of the first and second wirings to a constant bias voltage using the replicated current;
Based on the difference voltage between the created voltage and the source voltage of the NMOS transistor, the one
Means for controlling the gate voltage of a pair of NMOS transistors;
including,
The thermal infrared detection element according to claim 2. The voltage setting circuit includes:
A PMOS transistor whose source is connected to the input terminal of the voltage setting circuit;
Connected to the drain of the PMOS transistor to replicate the current of the diode,
A current mirror circuit having an output terminal;
Using the replicated current provided through one of the output terminals, the predetermined bias
Means for creating a voltage by subtracting the voltage drop from the voltage;
Based on the voltage difference between the created voltage and the source voltage of the PMOS transistor, the PMOS
Means for controlling the gate voltage of the transistor,
The other of the output terminals is used as the output terminal of the voltage setting circuit.
The thermal infrared detection element according to claim 1 or 3, The first voltage setting circuit and the second voltage setting circuit are:
A PMOS transistor whose source is connected to the input terminal of the voltage setting circuit;
Connected to the drain of the PMOS transistor to replicate the current of the diode,
A current mirror circuit having an output terminal;
Using the replicated current provided through one of the output terminals, the predetermined bias
Means for creating a voltage by subtracting the voltage drop from the voltage;
Based on the voltage difference between the created voltage and the source voltage of the PMOS transistor, the PMOS
Means for controlling the gate voltage of the transistor;
Including
The other of the output terminals is used as the output terminal of the voltage setting circuit.
The thermal infrared detection element according to claim 5. One or a plurality of the thermoelectric conversion units including a hollow heat insulating structure that supports the thermoelectric conversion unit with two heat insulating support legs and an infrared absorption unit that conducts heat corresponding to the infrared ray absorbed and absorbed to the diode. A diode connected in series includes a group of diodes arranged two-dimensionally,
The anodes of the diodes in each row are connected to a plurality of commonly connected drive lines via a first wiring that is one of the heat insulating support legs,
The cathodes of the diodes in each column are connected to a plurality of signal lines that are commonly connected via the second wiring that is the other of the heat insulating support legs,
A vertical scanning circuit for sequentially applying a power supply voltage to each drive line is connected to each drive line,
A current reading circuit is connected to the end of each signal line via a voltage setting circuit,
A horizontal scanning circuit for sequentially reading the output of the current reading circuit is connected to the output terminal of the current reading circuit,
In the voltage setting circuit,
Of the diode group, the current flowing through the selected diode at the time of reading is divided or duplicated into a first current and a second current,
The first current is output to an output terminal of the voltage setting circuit;
Using the second current, a voltage drop caused by the resistance of the first wiring, the resistance of the second wiring, the resistance of the signal line and the driving line, and the current of the diode is extracted,
The voltage at the input terminal of the voltage setting circuit, which is a connection point between the signal line and the voltage setting circuit, is controlled to a voltage obtained by subtracting the extracted voltage drop from a predetermined bias voltage,
A current reading circuit for reading the first current is connected to an output terminal of the voltage setting circuit.
A thermal infrared detecting element. A pixel array in which a plurality of pixels are arranged two-dimensionally;
The pixel is
As the thermoelectric converter, one or a plurality of diodes connected in series,
A hollow heat insulating structure for supporting the thermoelectric conversion part with two heat insulating support legs;
An infrared absorption part that absorbs infrared rays and conducts heat corresponding to the absorbed infrared rays to the diode;
A MOS transistor connected in series to the diode;
Including
The cathode of the diode is connected to the drain of the MOS transistor through a first wiring resistance which is one of the heat insulating support legs,
A plurality of power supply lines commonly connecting the anodes of the diodes in each row via a second wiring resistance which is the other of the heat insulating support legs;
A plurality of select lines commonly connecting the gates of the MOS transistors in each row;
A plurality of signal lines commonly connecting the sources of the MOS transistors in each column;
A common power supply line connected to the power supply terminal by commonly connecting the power supply line outside the pixel array;
A vertical scanning circuit for sequentially applying a selection pulse to each of the selection lines;
A voltage setting circuit for setting a voltage applied to both ends of the series circuit of the diode and the MOS transistor;
A current reading circuit connected to the end of the signal line via a voltage setting circuit;
A horizontal selection circuit for sequentially reading the outputs of the current reading circuit;
Further comprising
The power line and the signal line have substantially the same resistance value,
The voltage setting circuit includes:
Dividing or replicating the input current of the diode into a first current and a second current;
Outputting the first current to an output terminal of the voltage setting circuit;
Using the second current, extract a voltage drop caused by the resistance of the first wiring, the resistance of the second wiring, the resistance of the signal line and the driving line, and the current of the diode,
The voltage at the input terminal of the voltage setting circuit, which is a connection point between the signal line and the voltage setting circuit, is controlled to a voltage obtained by subtracting the extracted voltage drop from a predetermined bias voltage.
A thermal infrared detecting element.

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