JP2006292437A - Temperature detection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a miniaturizable and inexpensive temperature detection device capable of performing easily optical adjustment or assembly. <P>SOLUTION: In this temperature detection device 10, a temperature detection element 11 is equipped in a casing 110 with a substrate 120, an optical system 130, an InGaAs photodiode 141, an Si photodiode 142 and a signal processing part 150. Each light receiving surface of the InGaAs photodiode 141 and the Si photodiode 142 is faced to the same side, and the InGaAs photodiode 141 is arranged on the surface of the Si photodiode 142. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a temperature detection device that detects the temperature of an object to be measured based on thermal radiation radiated from the object to be measured.

  Various temperature detection devices are known. For example, in addition to a contact temperature detection device including a temperature detection element such as a thermocouple or a thermistor, a non-contact temperature detection device is also known. The contact-type temperature detection device is provided with the temperature detection element in direct contact with the measurement object, and the temperature detection element is assumed to be at the same temperature as the measurement object. The response is poor. On the other hand, the non-contact type temperature detection device detects the temperature of the measurement object based on the thermal radiation radiated from the measurement object, and the light receiving element that receives the thermal radiation contacts the measurement object. Therefore, the response to the temperature change of the measurement object is good.

  As described in Patent Document 1, the non-contact type temperature detection device is, for example, a cooking heater device including an electric heating unit that heats an object to be heated (such as a pan or a frying pan). Used when detecting. In the cooking heater device described in this document, an object to be heated is placed on a top plate made of heat-resistant tempered glass, and a magnetic field generating coil and a temperature detection device are provided under the top plate. When a high-frequency alternating current flows through the magnetic field generating coil, an induced current flows through the object to be heated by electromagnetic induction, and the object to be heated itself generates heat. And based on the thermal radiation radiated | emitted from the to-be-heated to-be-heated object, the temperature of a to-be-heated object is detected by the temperature detection apparatus.

  Thus, by using a non-contact type temperature detection device in the cooking heater device, temperature detection can be performed with high responsiveness to the temperature change of the object to be heated, which is the measurement object, and as a result, the temperature can be detected at high speed. Since the temperature of the heated object can be electrically controlled, for example, when the content of the object to be heated is tempura oil, ignition of the tempura oil can be prevented.

In addition, such a non-contact type temperature detecting device generally includes two light receiving elements as described in Patent Document 1. That is, in a black body, which is a virtual object that radiates thermal radiation most efficiently, the wavelength dependence and temperature dependence of thermal radiation follow Planck's equation. On the other hand, the heat radiation from the object to be heated which is an actual object is smaller than the heat radiation from the black body, and the emissivity (ratio to the heat radiation from the black body) differs depending on the material of the object to be heated. Therefore, by detecting the thermal radiation at each of the two wavelengths by the two light receiving elements having different spectral sensitivity characteristics by the wavelength selection filter, the influence due to the difference in emissivity of the object to be heated is reduced, and the temperature The measurement accuracy is improved. Patent Document 1 exemplifies InGaAs (indium gallium arsenide), PbS (lead sulfide), PbSe (lead selenide), and the like as light receiving elements included in the temperature detection device.
JP 2003-109736 A

  However, in the temperature detection device disclosed in the above-mentioned patent document, since two light receiving elements are arranged in parallel, in order to guide thermal radiation radiated from a certain range of the measurement object to each of the two light receiving elements, 2 Two optical systems are required. As described above, in the conventional non-contact type temperature detection device, the temperature detection element including the two light receiving elements and the two optical systems is not easy to optically adjust and assemble, and is large. Further, the conventional non-contact type temperature detecting device is expensive because InGaAs or the like is used as a light receiving element.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide an inexpensive temperature detection device that is easy to optically adjust and assemble, can be downsized, and is inexpensive.

  The temperature detection element according to the present invention includes an InGaAs photodiode and an Si photodiode that each output a current signal having a value corresponding to the amount of incident light, and the light receiving surfaces of the InGaAs photodiode and the Si photodiode are directed to the same side. The InGaAs photodiode is arranged on the surface of the Si photodiode. Moreover, it is preferable that the temperature detection element according to the present invention further includes an optical system that guides thermal radiation radiated from a certain range of the surface of the measurement object to the InGaAs photodiode and the Si photodiode.

  Further, the temperature detection device according to the present invention is a temperature detection device for detecting the temperature of the measurement object based on the thermal radiation radiated from the measurement object, and (1) each according to the incident amount of the heat radiation. The temperature detection element according to the present invention including the InGaAs photodiode and the Si photodiode that outputs a current signal of a predetermined value, and (2) the current signal output from the InGaAs photodiode is input, and the value of this current signal is input. A first signal processing circuit for outputting a voltage signal having a value corresponding thereto; and (3) a second signal for inputting a current signal output from the Si photodiode and outputting a voltage signal having a value corresponding to the value of the current signal. And a processing circuit. In addition, the temperature detection device according to the present invention preferably further includes a calculation unit that obtains the temperature of the measurement object based on the value of the voltage signal output from each of the first signal processing circuit and the second signal processing circuit. is there.

  According to the present invention, the thermal radiation radiated from the measurement object is incident on the stacked InGaAs photodiode and Si photodiode. The current signal output from the InGaAs photodiode has a value corresponding to the spectral sensitivity characteristic of the InGaAs photodiode, and is input to the first signal processing circuit and converted into a voltage signal. The current signal output from the Si photodiode has a value corresponding to the spectral sensitivity characteristic of the Si photodiode, and is input to the second signal processing circuit and converted into a voltage signal. And based on the voltage signal output from each of the 1st signal processing circuit and the 2nd signal processing circuit, the temperature of a measuring object is calculated in the operation part.

  Therefore, since the temperature detection element and the temperature detection device according to the present invention are non-contact type using the stacked InGaAs photodiode and Si photodiode, the thermal radiation radiated from the measurement object is one. The optical system can lead to both InGaAs photodiodes and Si photodiodes, has excellent temperature detection responsiveness, is inexpensive and small, and is easy to optically adjust and assemble.

  The second signal processing circuit preferably includes sensitivity adjustment means for adjusting the relationship between the output voltage value and the input current value. More specifically, the second signal processing circuit includes: a current-voltage conversion circuit that converts an input current signal into a voltage signal; an amplification circuit that amplifies and outputs a voltage signal output from the current-voltage conversion circuit; And a means for adjusting the amplification factor of the amplifier circuit as the sensitivity adjusting means. In this case, in the second signal processing circuit that inputs the current signal output from the Si photodiode, the relationship of the output voltage value to the input current value (that is, the temperature detection sensitivity) can be adjusted by the sensitivity adjusting means.

  The second signal processing circuit preferably includes a temperature correction unit that corrects a change in spectral sensitivity characteristic due to a temperature change of the Si photodiode and outputs the corrected voltage signal. More specifically, the second signal processing circuit includes: a current-voltage conversion circuit that converts an input current signal into a voltage signal; an amplification circuit that amplifies and outputs a voltage signal output from the current-voltage conversion circuit; Preferably, the temperature correction means includes means for adjusting the amplification factor of the amplifier circuit according to the temperature. In this case, in the second signal processing circuit that inputs the current signal output from the Si photodiode, the variation in the spectral sensitivity characteristic due to the temperature change of the Si photodiode is corrected by the second temperature correction means, A corrected voltage signal is output.

  According to the present invention, the optical adjustment and assembly are easy, the size can be reduced, and the cost can be reduced.

  The best mode for carrying out the present invention will be described below in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a cross-sectional view of a main part of a cooking heater device 1 including a temperature detection device 10 according to the present embodiment. The cooking heater device 1 includes a temperature detection device 10, a top plate 20, a magnetic field generating coil 30, and a power supply circuit 40, and heats an object to be heated 2 (for example, a pan or a frying pan) placed on the top plate 20. Then, the thing in the to-be-heated material 2 is heated and cooked.

  The temperature detection device 10, the magnetic field generation coil 30, and the power supply circuit 40 are disposed below the top plate 20. When a high-frequency alternating current supplied from the power supply circuit 40 flows to the magnetic field generating coil 30, an induced current flows to the bottom of the object to be heated 2 due to electromagnetic induction by the magnetic field lines M generated from the magnetic field generating coil 30. The heated object 2 generates heat due to the electric resistance of 2. Then, the heat radiation radiated from the heated object 2 that has generated heat passes through the window portion 21 provided on the top plate 20 and reaches the temperature detection element 11 of the temperature detection device 10, and is heated by the temperature detection device 10. The temperature of the object 2 is detected. The position where the window portion 21 and the temperature detecting element 11 are provided may be on the center line of the magnetic field generating coil 30 or may be in the vicinity where the conducting wire of the magnetic field generating coil 30 deviates from the center line. Good.

  The temperature detection device 10 includes a temperature detection element 11 and a calculation unit 12. The temperature detection element 11 is disposed below the window portion 21 of the top plate 20, receives heat radiation radiated from the bottom of the heated object 2 to be measured and transmitted through the window portion 21, and the light reception result is received. The voltage signal to be expressed is output to the calculation unit 12. The calculation unit 12 receives the voltage signal output from the temperature detection element 11 and obtains the temperature of the object to be heated 2 based on the value of the voltage signal. When calculating the temperature of the object to be heated 2 from the input voltage value in the calculation unit 12, the relationship between the two measured and stored in advance is referred to.

  Moreover, the calculating part 12 controls the power supply circuit 40 based on the calculated | required temperature. For example, when the calculation unit 12 determines that the obtained temperature exceeds a predetermined temperature, the calculation unit 12 adjusts the magnitude of the alternating current supplied from the power supply circuit 40 to the magnetic field generating coil 30, or generates a magnetic field. The supply of alternating current to the coil 30 is stopped. The calculation unit 12 may display the obtained temperature on a display unit (not shown), or generate a warning when determining that the obtained temperature exceeds a predetermined temperature. May be.

  FIG. 2 is a cross-sectional view of the temperature detection element 11 of the temperature detection apparatus 10 according to the present embodiment. The temperature detection device 10 includes a substrate 120, an optical system 130, an InGaAs photodiode 141, a Si photodiode 142, and a signal processing unit 150 in a housing 110 in the temperature detection element 11. An InGaAs photodiode 141 and a Si photodiode 142 are fixed to the upper surface of the substrate 120 (the surface on the heated object 2 side). An optical system 130 is disposed above the substrate 120. A signal processing unit 150 is provided on the lower surface of the substrate 120. In addition, the signal processing unit 150 may be provided together with the calculation unit 12 separately from the temperature detection element 11.

  The light receiving surfaces of the InGaAs photodiode 141 and the Si photodiode 142 are directed to the same side, and the InGaAs photodiode 141 is disposed on the surface of the Si photodiode 142. The optical system 130 guides thermal radiation radiated from a certain range at the bottom of the object to be heated 2 to both the InGaAs photodiode 141 and the Si photodiode 142. The optical system 130 is specifically a convex lens.

  The InGaAs photodiode 141 has a first spectral sensitivity characteristic, and outputs a current signal having a value corresponding to the incident amount of thermal radiation based on the first spectral sensitivity characteristic. The Si photodiode 142 has a second spectral sensitivity characteristic, and outputs a current signal having a value corresponding to the amount of incident thermal radiation based on the second spectral sensitivity characteristic. The first spectral sensitivity characteristic of the InGaAs photodiode 141 and the second spectral sensitivity characteristic of the Si photodiode 142 are different from each other. For example, the InGaAs photodiode 141 has a sensitivity peak near a wavelength of 1.55 μm, and the Si photodiode 142 has a sensitivity peak near a wavelength of 0.96 μm.

  The signal processing unit 150 provided on the lower surface of the substrate 120 is electrically connected to each of the InGaAs photodiode 141 and the Si photodiode 142 provided on the upper surface of the substrate 120 by through electrodes provided on the substrate 120. . The signal processing unit 150 receives the current signals output from the InGaAs photodiode 141 and the Si photodiode 142, and outputs a voltage signal having a value corresponding to the value of each current signal.

  The board 120 further includes a connector (not shown) for sending the voltage signal output from the signal processing unit 150 to the arithmetic unit 12, and a screw hole (not shown) for fixing the board 120 to the housing 110. Is provided.

  The casing 110 is preferably made of a material having high thermal conductivity (for example, Al die cast). Since the InGaAs photodiode 141, the Si photodiode 142, and the signal processing unit 150 are housed in the casing 110 made of a material having a high thermal conductivity in this manner, these temperatures become substantially equal to each other. This is convenient for performing correction.

  FIG. 3 is a configuration diagram of the signal processing unit 150 of the temperature detection device 10 according to the present embodiment. The signal processing unit 150 includes a first signal processing circuit 151 and a second signal processing circuit 152. The first signal processing circuit 151 receives the current signal output from the InGaAs photodiode 141 and outputs a voltage signal having a value corresponding to the value of the current signal. The first signal processing circuit 151 outputs the current signal input from the InGaAs photodiode 141. A current-voltage conversion circuit that converts the signal into a voltage signal; and an amplification circuit that amplifies and outputs the voltage signal output from the current-voltage conversion circuit. Similarly, the second signal processing circuit 152 inputs a current signal output from the Si photodiode 142 and outputs a voltage signal having a value corresponding to the value of the current signal. A current-voltage conversion circuit that converts the input current signal into a voltage signal; and an amplification circuit that amplifies and outputs the voltage signal output from the current-voltage conversion circuit.

  The second signal processing circuit 152 that inputs the current signal output from the Si photodiode 142 includes sensitivity adjustment means that adjusts the relationship of the output voltage value with respect to the input current value. It is preferable to include means for adjusting the amplification factor of the amplifier circuit. Further, the second signal processing circuit 152 includes a temperature correction unit that corrects the fluctuation of the second spectral sensitivity characteristic due to the temperature change of the Si photodiode 142, and specifically, the resistance value depending on the temperature as the temperature correction unit. Preferably, the amplifier circuit includes a resistor that varies.

  FIG. 4 is a circuit diagram of the second signal processing circuit 152 of the temperature detection device 10 according to the present embodiment. The second signal processing circuit 152 includes a current-voltage conversion circuit 161, a low-pass filter 162, an amplifier circuit 163, and a low-pass filter 164.

The current-voltage conversion circuit 161 receives the current signal output from the Si photodiode 142, converts the current signal into a voltage signal, and outputs the voltage signal to the low-pass filter 162. The current-voltage conversion circuit 161 includes an amplifier A ₁ , a resistor R _1, and a capacitive element C ₁ . The non-inverting input terminal of the amplifier A ₁ is grounded, and the inverting input terminal of the amplifier A ₁ is connected to the Si photodiode 142. The resistor R ₁ and the capacitive element C ₁ are connected in parallel to each other and provided between the inverting input terminal and the output terminal of the amplifier A ₁ .

Low pass filter 162 includes a resistor _{R 2} and capacitor element _{C 2.} One end of the resistor R ₂ is connected to the output terminal of the amplifier A ₁ of the current-voltage conversion circuit 161. The other end of the resistor R ₂ is connected to the non-inverting input terminal of the amplifier A ₃ of the amplifier circuit 163. Capacitive element C ₂ is provided between the other end of the resistor R ₂ and the constant voltage point.

The amplifier circuit 163 receives the voltage signal output from the current-voltage conversion circuit 161 and passed through the low-pass filter 162, amplifies the voltage signal, and outputs the amplified voltage signal to the low-pass filter 164. The amplifier circuit 163 includes an amplifier A ₃ , resistors R _{31 to} R _33, and a capacitive element C ₃ . The resistor R ₃₂ and the resistor R ₃₃ are connected in series, and the resistors R ₃₂ and R ₃₃ and the capacitive element C ₃ are connected in parallel to each other, and the inverting input terminal and the output terminal of the amplifier A ₃ are connected to each other. It is provided between. Resistor R ₃₁ is provided between the inverting input terminal of the amplifier A ₃ and constant voltage point.

Resistor R ₃₁ is a heat-sensitive resistor whose resistance value changes with temperature, a large resistance value higher temperatures. The resistor R ₃₂ has a fixed resistance value. The resistor R ₃₃ has a variable resistance value. When the resistance value of the resistor _{R 31} represents a _{R 31,} the resistance value of the resistor _{R 32} represents a _{R 32,} also the resistance value of the resistor _{R 33} and is represented as _{R 33,} the amplification factor of the amplifier circuit 163 G is represented by the following formula (1).

G = 1 + (R ₃₂ + R ₃₃ ) / R ₃₁ (1)
The resistor R ₃₃ can adjust the amplification factor G of the amplifier circuit 163 by adjusting its resistance value, and thus can function as the sensitivity adjusting means described above. Further, the resistor R ₃₁ is the resistance value with temperature changes, thereby, it is possible to correct the gain G of the amplifier circuit 163 may act as a temperature compensation means described above.

Low pass filter 164 includes a resistor _{R 4} and the capacitor _{C 4.} One end of the resistor R ₄ is connected to the output terminal of the amplifier A ₃ of the amplifier circuit 163. The other end of the resistor R ₃ is connected to the calculation unit 12. Capacitive element C ₄ is provided between the other end and the ground potential of the resistor R _4.

Resistor R ₀₁ and resistor R ₀₂ are connected in series. One end of the resistor R ₀₁ is the power supply voltage Vcc is applied, one end of the resistor R ₀₂ is grounded. A capacitive element C ₀ is provided in parallel with the resistor R ₀₂ . The connection point between the resistor R ₀₁ and the resistor R ₀₂ is a constant voltage obtained by dividing the power supply voltage Vcc, is connected to one end of the capacitive element C ₂ of the low-pass filter 162, and is connected to the resistance of the amplifier circuit 163. with one end of the vessel _{R 31} are connected. The power supply voltage Vcc, for example, is supplied from the arithmetic unit 12 via the connector on the board 120 of the temperature detecting element 11, also it is applied to the capacitor C ₂ and a resistor R ₃₁ each end through a low pass filter The The power supply voltage Vcc is also supplied to each of the amplifier A ₁ of the current-voltage conversion circuit 161 and the amplifier A ₃ of the amplifier circuit 163.

An example of specific characteristic values of each element included in the second signal processing circuit 152 is as follows. Current - resistance value of the resistor _{R 1} included in the voltage conversion circuit 161 is 22Emuomega, capacitance of the capacitor _{C 1} is 10 pF. Resistance value of the resistor _{R 2} that is included in the low-pass filter 162 is a 10 k.OMEGA, capacitance of the capacitor _{C 2} is 0.1ĩF. Resistance value of the resistor _{R 31} included in the amplifier circuit 163 is 1 k [Omega, resistor resistance of _{R 32} is 22Keiomega, maximum resistance value of the resistor _{R 33} is 100 k.OMEGA, the capacitance of the capacitor _{C 3} Is 0.1 μF. The resistance value of the resistor _{R 4} contained in the low-pass filter 164 is 1.8Keiomega, capacitance of the capacitor _{C 4} is 0.1ĩF. The resistance value of the resistor R ₀₁ is 43 kΩ, the resistance value of the resistor R ₀₂ is 10 kΩ, and the capacitance value of the capacitive element C ₀ is 0.1 μF.

  The first signal processing circuit 151 has substantially the same configuration as the second signal processing circuit 152. However, since the variation in temperature detection between individual InGaAs photodiodes is small and the temperature dependence of the spectral sensitivity characteristics of the InGaAs photodiodes is small, the amplification circuit included in the first signal processing circuit 151 includes sensitivity adjustment means and It is not necessary to have any temperature correction means.

  FIG. 5 and FIG. 6 are diagrams each showing a configuration example of the temperature detection element 11 of the temperature detection device 10 according to the present embodiment. In these drawings, a plan view and a cross-sectional view of the stacked InGaAs photodiode 141 and Si photodiode 142 are shown. In each semiconductor region shown in these drawings, the n-type and p-type may be reversed.

  FIG. 5A is a plan view of the stacked InGaAs photodiode 141 and Si photodiode 142, and FIG. 5B is a cross-sectional view taken along line AA in FIG.

  An InGaAs photodiode 141 shown in FIG. 5 has an n-type InGaAs substrate 211 formed with a p-type region 212, an insulating film 213 formed on the surface thereof, and a metal wiring layer 214 formed thereon. And a pad 215 is formed. One end of the metal wiring layer 214 is electrically connected to the p-type region 212 through the contact hole 216, and the other end is connected to the pad 215. The pad 215 is wire bonded to the pad on the substrate 120.

  The Si photodiode 142 shown in FIG. 5 has an n-type Si substrate 221 formed with a p-type region 222, an insulating film 223 formed on the surface, and a metal wiring layer 224a thereon. , 224b and pads 225a, 225b. One end of the metal wiring layer 224a is electrically connected to the p-type region 222 through the contact hole 226, and the other end is connected to the pad 225a. One end of the metal wiring layer 224b is electrically connected to the back surface of the n-type substrate 211 of the InGaAs photodiode 141, and the other end is connected to the pad 225b. Each of the pads 225a and 225b is wire-bonded to the pad on the substrate 120. The back surface of the n-type substrate 221 is electrically connected to the metal wiring on the substrate 120 substrate 120.

  In the configuration example shown in FIG. 5, the current signal output from the InGaAs photodiode 141 is electrically connected to the pad 215 that is electrically connected to the p-type region 212 that is the anode and to the n-type substrate 211 that is the cathode. It is output between the connected pads 225b. Further, the current signal output from the Si photodiode 142 is supplied from a pad 225a electrically connected to the p-type region 222 that is an anode and a substrate 120 electrically connected to the back surface of the n-type substrate 221 that is a cathode. Output between the upper metal wiring.

  6A is a plan view of the stacked InGaAs photodiode 141 and Si photodiode 142, and FIG. 6B is a cross-sectional view taken along line BB in FIG. 6A.

  The InGaAs photodiode 141 shown in FIG. 6 has an n-type InGaAs substrate 311 formed with a p-type region 312, an insulating film 313 is formed on the surface, and a metal wiring layer 314 is further formed thereon. And a pad 315 is formed. One end of the metal wiring layer 314 is electrically connected to the p-type region 312 via the contact hole 316, and the other end is connected to the pad 315. The pad 315 is wire bonded to the pad on the substrate 120. A die bond metal pad 317 is formed on the back surface of the n-type substrate 311.

  The Si photodiode 142 shown in FIG. 6 has an n-type Si substrate 321 in which a p-type region 322 is formed in an annular shape, an insulating film 323 is formed on the surface, and a metal wiring is further formed thereon. A layer 324 and a pad 325 are formed. One end of the metal wiring layer 324 is electrically connected to the p-type region 322 via the contact hole 326 a and the other end is connected to the pad 325. The pad 325 is wire bonded to the pad on the substrate 120. The back surface of the n-type substrate 321 is electrically connected to the metal wiring on the substrate 120 substrate 120. The surface of the n-type substrate 321 is electrically connected to the pad 317 through the contact hole 326b. The contact hole 326 b is formed above the n-type region 321 surrounded by the annular p-type region 322.

  In the configuration example shown in FIG. 6, each of the InGaAs photodiode 141 and the Si photodiode 142 has a common n-type region 311 and 321 electrically connected to each other via a pad 317 and a contact hole 326b. The structure has a cathode. The current signal output from the InGaAs photodiode 141 is generated on the pad 315 electrically connected to the p-type region 312 that is the anode and the substrate 120 electrically connected to the back surface of the n-type substrate 321 that is the common cathode. Output between the metal wiring. In addition, the current signal output from the Si photodiode 142 is supplied from a pad 325 that is electrically connected to the p-type region 322 that is an anode and a substrate that is electrically connected to the back surface of the n-type substrate 321 that is a common cathode. It is output between the metal wiring on 120.

  As shown in FIG. 5 and FIG. 6 respectively, in this embodiment, the light-receiving surfaces of the InGaAs photodiode 141 and the Si photodiode 142 are directed to the same side, and the InGaAs photodiode 141 is a Si photo diode. It is disposed on the surface of the diode 142. Therefore, the thermal radiation radiated from a certain range at the bottom of the article to be heated 2 can be guided to both the InGaAs photodiode 141 and the Si photodiode 142 by one optical system 130. In addition, optical adjustment and assembly are easy, and downsizing is possible. Furthermore, compared with the case where two conventional InGaAs photodiodes are used, in this embodiment, since the InGaAs photodiode 141 and the Si photodiode 142 are used, the cost can be reduced.

FIG. 7 is a diagram showing black body radiation characteristics, Si photodiode sensitivity characteristics, and InGaAs photodiode sensitivity characteristics. In this figure, as black body radiation characteristics, black body radiation characteristics M _{1 at} a temperature of 538K, black body radiation characteristics M _{2 at} a temperature of 573K, black body radiation characteristics M _{3 at} a temperature of 598K, and temperature blackbody radiation characteristic _{M 4} in the case of 623K is shown. As the sensitivity characteristic of the Si photodiode, Si photodiode sensitivity characteristics S ₁ of the type S _1, and the sensitivity characteristics S ₂ of Si photodiode type S ₂ having different spectral sensitivity characteristics of a type S ₁ is shown Has been. Further, as the sensitivity characteristic of the InGaAs photodiode, the sensitivity characteristics _{G 1} of InGaAs photodiode type _{G 1,} and the sensitivity characteristic of the InGaAs photodiode type _{G 2} having different spectral sensitivity characteristics of a type _{G 1 G 2} It is shown.

  As described above, black body radiation is thermal radiation from a black body, which is a virtual object that radiates thermal radiation most efficiently, and the wavelength dependence and temperature dependence of the thermal radiation follow Planck's equation. On the other hand, the heat radiation from the object to be heated, which is an actual object, is smaller than the heat radiation from the black body, and the emissivity (ratio to the heat radiation from the black body) depends on the material of the object to be heated 2 as the measurement object. ) Is different. Therefore, by detecting the thermal radiation at each of the two wavelengths by the two light receiving elements, the influence due to the difference in the emissivity of the object to be heated is reduced to improve the accuracy of temperature measurement.

In the case where InGaAs photodiodes of type G ₁ and G ₂ are used as the two light receiving elements, the heat radiation from the object to be heated 2 that is the measurement object is compared in the wavelength range in which these InGaAs photodiodes are sensitive. Therefore, the temperature of the object to be heated 2 can be detected with high sensitivity. However, a temperature detection device using an InGaAs photodiode can detect thermal radiation with high sensitivity, but is expensive.

In contrast, when Si photodiodes of types S ₁ and S ₂ are used, the heat from the object to be heated 2 as the measurement object is near the wavelength at which the sensitivity of these Si photodiodes reaches a peak. Radiation is extremely small, and it is extremely difficult to detect the temperature of the object 2 to be heated. Therefore, when a Si photodiode is used, it is not near the wavelength at which the sensitivity of the Si photodiode reaches a peak, but at a wavelength longer than this peak wavelength and a certain amount of thermal radiation from the object to be heated 2 exists. detecting the thermal radiation with the light receiving sensitivity of (around 1.1μm from the vicinity of the peak wavelength 840nm type _{S 2).}

However, even when detecting the thermal radiation with the light receiving sensitivity wavelength (around 1.1μm from the vicinity of the peak wavelength 840nm Type S _2), the sensitivity of Si photodiodes is small. Therefore, in the present embodiment, the area of the light receiving region of the Si photodiode 142 having a low sensitivity is made larger than the area of the light receiving region of the InGaAs photodiode 141 having a high sensitivity. Accordingly, the Si photodiode 142 can be stacked on the InGaAs photodiode 141, thereby reducing the size as a whole.

  In general, the spectral sensitivity characteristics of Si photodiodes vary greatly among individuals, and are highly temperature dependent. FIG. 8 is a graph showing an example of the wavelength dependence of the temperature coefficient of the spectral sensitivity characteristic of the Si photodiode. As shown in this figure, the temperature dependence of the spectral sensitivity characteristic of the Si photodiode is large in the vicinity of the wavelength of the thermal radiation to be detected.

Therefore, in the present embodiment, as described above, the signal processing circuit 152 includes sensitivity adjustment means for adjusting the relationship of the output voltage value with respect to the input current value. Specifically, each amplifier circuit is used as this sensitivity adjustment means. Means for adjusting the amplification factor (resistor R ₃₃ whose resistance value is variable). The signal processing circuit 152 includes a temperature correction unit that corrects fluctuations in spectral sensitivity characteristics due to the temperature change of the Si photodiode 142. Specifically, as the temperature correction unit, a resistance whose resistance value varies with temperature is used. The amplifier R ₃₁ is included in the amplifier circuit.

  As described above, the temperature detection device 10 according to the present embodiment is a non-contact type using stacked InGaAs photodiodes and Si photodiodes, and therefore has excellent temperature detection responsiveness, and is inexpensive and compact. In addition, optical adjustment and assembly are easy. Further, even if there is a large variation in temperature detection between individual Si photodiodes, the temperature detection apparatus 10 can improve the accuracy of temperature detection because the signal processing circuit 152 includes a sensitivity adjustment means. Furthermore, even if the temperature dependence of the spectral sensitivity characteristic of the Si photodiode is large, the temperature detection apparatus 10 also improves the temperature detection accuracy in this respect because the signal processing circuit 152 includes the temperature correction means.

It is principal part sectional drawing of the cooking heater apparatus 1 provided with the temperature detection apparatus 10 which concerns on this embodiment. It is sectional drawing of the temperature detection element 11 of the temperature detection apparatus 10 which concerns on this embodiment. It is a block diagram of the signal processing part 150 of the temperature detection apparatus 10 which concerns on this embodiment. It is a circuit diagram of the 2nd signal processing circuit 152 of temperature detector 10 concerning this embodiment. It is a figure which shows the structural example of the temperature detection element 11 of the temperature detection apparatus 10 which concerns on this embodiment. It is a figure which shows the structural example of the temperature detection element 11 of the temperature detection apparatus 10 which concerns on this embodiment. It is a figure which shows the black body radiation | emission characteristic, the sensitivity characteristic of Si photodiode, and the sensitivity characteristic of an InGaAs photodiode. It is a graph which shows an example of the wavelength dependence of the temperature coefficient of the spectral sensitivity characteristic of Si photodiode.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Cooking heater apparatus, 2 ... Heated object, 10 ... Temperature detection apparatus, 11 ... Temperature detection element, 12 ... Operation part, 20 ... Top plate, 21 ... Window part, 30 ... Magnetic field generation coil, 40 ... Power supply circuit, 110 ... Case, 120 ... Substrate, 130 ... Optical system, 141 ... InGaAs photodiode, 142 ... Si photodiode, 150 ... Signal processing unit, 151 ... First signal processing circuit, 152 ... Second signal processing circuit, 161 ... Current -Voltage conversion circuit 162 ... low pass filter, 163 ... amplification circuit, 164 ... low pass filter.

Claims (8)

Each includes an InGaAs photodiode and a Si photodiode that output a current signal having a value corresponding to the amount of incident light.
The light receiving surfaces of the InGaAs photodiode and the Si photodiode are directed to the same side, and the InGaAs photodiode is disposed on the surface of the Si photodiode.
A temperature detecting element characterized by that.   The temperature detecting element according to claim 1, further comprising an optical system for guiding thermal radiation radiated from a predetermined range of the surface of the measurement object to the InGaAs photodiode and the Si photodiode. A temperature detection device that detects the temperature of the measurement object based on thermal radiation radiated from the measurement object,
The temperature detection element according to claim 1, comprising an InGaAs photodiode and a Si photodiode that each output a current signal having a value corresponding to the amount of incident thermal radiation.
A first signal processing circuit for inputting a current signal output from the InGaAs photodiode and outputting a voltage signal having a value corresponding to the value of the current signal;
A second signal processing circuit for inputting a current signal output from the Si photodiode and outputting a voltage signal having a value corresponding to the value of the current signal;
A temperature detecting device comprising:   4. The temperature detection according to claim 3, further comprising a calculation unit that calculates a temperature of the measurement object based on a value of a voltage signal output from each of the first signal processing circuit and the second signal processing circuit. apparatus.   4. The temperature detection device according to claim 3, wherein the second signal processing circuit includes sensitivity adjustment means for adjusting a relationship between an output voltage value and an input current value.   The second signal processing circuit converts the input current signal into a voltage signal, a current-voltage conversion circuit, an amplification circuit that amplifies and outputs the voltage signal output from the current-voltage conversion circuit, and the sensitivity adjustment 6. The temperature detecting device according to claim 5, further comprising means for adjusting an amplification factor of the amplifier circuit.   4. The temperature correction unit, wherein the second signal processing circuit includes a temperature correction unit that corrects a change in spectral sensitivity characteristics due to a temperature change of the Si photodiode and outputs the corrected voltage signal. The temperature detection device described.   The second signal processing circuit converts a current signal into a voltage signal, a current-voltage conversion circuit, an amplification circuit that amplifies and outputs a voltage signal output from the current-voltage conversion circuit, and the temperature correction 8. The temperature detecting device according to claim 7, further comprising: means for adjusting an amplification factor of the amplifier circuit according to temperature.

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