Patent Application
20220155152
The present invention relates to infrared photodetection devices, infrared photodetection processes, computer programs, and computer-readable storage media containing a program.
Japanese Unexamined Patent Application Publication, Tokukai, No. 2007-183207 describes a conventionally known radiation thermometer. The radiation thermometer described in Japanese Unexamined Patent Application Publication, Tokukai, No. 2007-183207 includes a first sensor, a second sensor, a transmittance storage unit, a sensor correlation computation unit, a temperature correlation information storage unit, and a temperature computation unit. The first sensor detects the reception light level of transmitted light passing through a measurement object in a first wavelength range in which the measurement object has a lower emissivity for radiation light radiating from the measurement object than a prescribed value. The second sensor detects the reception light levels of the transmitted light and the radiation light in a second wavelength range in which the measurement object has, for the radiation light, an emissivity equal to a prescribed value that is higher than the emissivity in the first wavelength range. The transmittance storage unit stores both a constant related to a first transmittance of the measurement object for light in the first wavelength range and a constant related to a second transmittance of the measurement object for light in the second wavelength range. The sensor correlation computation unit stores a correlation between the level of radiation light radiating from a heat source as received by the first sensor and the level of radiation light radiating from the heat source as received by the second sensor. The sensor correlation computation unit also calculates the radiation level of the heat source in the second wavelength range from the correlation by using a value obtained by dividing the level of the light received and detected by the first sensor by the first transmittance stored in the transmittance storage unit. The temperature correlation information storage unit stores a correlation between the temperature of the measurement object and the reception light level detected by the second sensor of radiation light radiating from the measurement object. The temperature computation unit calculates the temperature of the measurement object on the basis of the radiation level of the heat source in the second wavelength range calculated by the sensor correlation computation unit, the transmittance constant of the measurement object stored in the transmittance storage unit, and the level of reception light detected by the second sensor, by using a prescribed correlation equation stored in the temperature correlation information storage unit.
Japanese Unexamined Patent Application Publication, Tokukai, No. 2012-202934 describes a conventionally known thermal imaging method. The imaging method described in Japanese Unexamined Patent Application Publication, Tokukai, No. 2012-202934 involves: estimating an infrared detection value from a thermal responsivity of an infrared imaging device and a difference between a first detection value and a second detection value; and estimating an infrared detection value of the infrared imaging device for the current scan period from a rate of change of the detection value of the infrared imaging device from the immediately preceding scan period to the current scan period, to estimate the temperature of an object for the current scan period.
Japanese Unexamined Patent Application Publication, Tokukai, No. 2017-184017 describes a conventionally known infrared photodetection device. The infrared photodetection device described in Japanese Unexamined Patent Application Publication, Tokukai, No. 2017-184017 calculates a difference between a first signal representing the amount of dark current flowing in a light-receiving element and a second signal representing the amount of current flowing in the light-receiving element during image capturing, to obtain photocurrent data. The infrared photodetection device includes a temperature sensor, so that the infrared photodetection device can measure the amount of dark current in response to a change in the temperature detected by the temperature sensor to generate a first signal representing the measurement of the amount of dark current. Patent Literature 3 thus discloses: detecting temperature around an infrared photodetection device by using a temperature sensor; and in response to a change in temperature around the infrared photodetection device, subtracting a first signal representing post-change temperature from a second signal to obtain photocurrent data.
Japanese Unexamined Patent Application Publication, Tokukai, No. 2007-183207, Japanese Unexamined Patent Application Publication, Tokukai, No. 2012-202934, and Japanese Unexamined Patent Application Publication, Tokukai, No. 2017-184017 all calculate temperature using a single wavelength range. It is therefore difficult to reduce error in calculating the temperature of a measurement object in these techniques. In addition, Japanese Unexamined Patent Application Publication, Tokukai, No. 2007-183207 and Japanese Unexamined Patent Application Publication, Tokukai, No. 2012-202934 lack the concept of using both thermal response and optical response.
In view of these issues, the present invention, in an embodiment thereof, provides an infrared photodetection device allowing for less error in calculating the temperature of a measurement object.
The present invention, in another embodiment thereof, provides an infrared photodetection process allowing for less error in calculating the temperature of a measurement object.
The present invention, in a further embodiment thereof, provides a computer program for implementing a temperature calculation process allowing for less error in calculating the temperature of a measurement object.
The present invention, in still another embodiment thereof, provides a computer-readable storage medium containing a computer program for implementing a temperature calculation process allowing for less error in calculating the temperature of a measurement object.
The present invention, in an embodiment thereof, is directed to an infrared photodetection device including: a detection unit and a calculation unit. The detection unit includes a detection element configured to detect infrared light in a first wavelength range and detect infrared light in a second wavelength range lying within the first wavelength range, the second wavelength range having a central wavelength toward a short wavelength end and/or a long wavelength end with respect to a central wavelength of the first wavelength range. The calculation unit includes a computation section capable of calculating temperature of an object from a first detection value obtained when infrared light is detected in the first wavelength range by the detection element and a second detection value obtained when infrared light is detected in the second wavelength range by the detection element.
In Configuration 1, the calculation unit calculates a ratio of the first and second detection values and calculates the temperature of the object from the calculated ratio.
In Configuration 1 or 2, the calculation unit calculates a thermal signal component from the first detection value, the thermal signal component representing an amount of change of a thermal signal caused by a rise in temperature when infrared light in the first wavelength range is incident on the detection element, calculates an optical signal component from the second detection value, the optical signal component being generated by infrared light in the second wavelength range, and calculates the temperature of the object from the calculated optical signal component and the calculated thermal signal component.
In Configuration 3, the calculation unit calculates the optical signal component and the thermal signal component from a time response of a detection value detected by the detection element and calculates the temperature of the object from the calculated optical signal component and the calculated thermal signal component.
The present invention, in an embodiment thereof, is directed to an infrared photodetection device including: a detection unit and a calculation unit. The detection unit includes a detection element configured to detect infrared light in a first wavelength range, detect infrared light in a third wavelength range lying within the first wavelength range, the third wavelength range having a central wavelength toward a short wavelength end with respect to a central wavelength of the first wavelength range, and detect infrared light in a fourth wavelength range lying within the first wavelength range, the fourth wavelength range having a central wavelength toward a long wavelength end with respect to the central wavelength of the first wavelength range. The calculation unit includes a computation section capable of calculating temperature of an object from a first detection value obtained when infrared light is detected in the first wavelength range by the detection element, a third detection value obtained when infrared light is detected in the third wavelength range by the detection element, and a fourth detection value obtained when infrared light is detected in the fourth wavelength range by the detection element.
In Configuration 5, the calculation unit calculates a first ratio obtained by dividing the first detection value by the third detection value, a second ratio obtained by dividing the first detection value by the fourth detection value, and a third ratio obtained by dividing the fourth detection value by the third detection value and calculates, as the temperature of the object, one of a first temperature of the object calculated from the first ratio and a second temperature of the object calculated from the second ratio that differs more from a third temperature of the object calculated from the third ratio.
In any one of Configurations 1 to 5, the first wavelength range lies within an atmospheric window.
In Configuration 7, the first wavelength range lies within any one of wavelength ranges of 3.4 to 4.2 μm, 4.4 to 5.5 μm, and 8 to 14 μm.
In any one of Configurations 1 to 5, the first wavelength range is a transmission wavelength range of an optical element disposed between the object and the detection unit.
In Configuration 5, the detection unit further includes: a first filter for detecting the first wavelength range; a second filter for detecting the third wavelength range; and a third filter for detecting the fourth wavelength range.
In any one of Configurations 1 to 9, the detection element includes a quantum-dot layer or a quantum-well layer.
In Configuration 11, the infrared photodetection device selects the third wavelength range and the fourth wavelength range by applying a voltage to the detection element.
In any one of Configurations 1 to 10, the detection element includes: a first detection element configured to detect infrared light in the first wavelength range; and a second detection element configured to detect infrared light in the second wavelength range. The first detection element is a thermal element.
In Configuration 13, the second detection element includes a detection element having a function identical to a function of the first detection element.
The present invention, in an embodiment thereof, is directed to an infrared photodetection process including: a first step of a detection element detecting infrared light in a first wavelength range and detecting infrared light in a second wavelength range lying within the first wavelength range, the second wavelength range having a central wavelength toward a short wavelength end or a long wavelength end with respect to a central wavelength of the first wavelength range; and a second step of receiving a first detection value obtained when infrared light is detected in the first wavelength range by the detection element and a second detection value obtained when infrared light is detected in the second wavelength range by the detection element, calculating a ratio of the received first and second detection values, and calculating temperature of an object from the calculated ratio.
In Configuration 15, the second step calculates a thermal signal component from the first detection value, the thermal signal component representing an amount of change of a thermal signal caused by a rise in temperature when infrared light in the first wavelength range is incident on the detection element, calculates an optical signal component from the second detection value, the optical signal component being generated by infrared light in the second wavelength range, and calculates the temperature of the object from the calculated optical signal component and the calculated thermal signal component.
In Configuration 15, the second wavelength range includes a third wavelength range lying within the first wavelength range and a fourth wavelength range lying within the first wavelength range, the third wavelength range having a central wavelength toward a short wavelength end with respect to a central wavelength of the first wavelength range, the fourth wavelength range having a central wavelength toward a long wavelength end with respect to the central wavelength of the first wavelength range, and the second step calculates a first ratio obtained by dividing the first detection value by a third detection value, a second ratio obtained by dividing the first detection value by a fourth detection value, and a third ratio obtained by dividing the fourth detection value by the third detection value from the first detection value, the third detection value, and the fourth detection value, the third detection value being obtained when infrared light is detected in the third wavelength range by the detection element, the fourth detection value being obtained when infrared light is detected in the fourth wavelength range by the detection element, and calculates, as the temperature of the object, one of a first temperature of the object calculated from the first ratio and a second temperature of the object calculated from the second ratio that differs more from a third temperature of the object calculated from the third ratio.
The present invention, in an embodiment thereof, is directed to a computer program for causing a computer to calculate temperature of an object from a first detection value obtained when infrared light is detected in a first wavelength range by a detection element and a second detection value obtained when infrared light is detected in a second wavelength range by the detection element, the second wavelength range lying within the first wavelength range and having a central wavelength toward a short wavelength end or a long wavelength end with respect to a central wavelength of the first wavelength range, the computer program causing the computer to implement: a first step of a reception means receiving the first detection value and the second detection value; a second step of a calculation means calculating a ratio of the first and second detection values from the first and second detection values received in the first step; and a third step of the calculation means calculating the temperature of the object from the calculated ratio.
In Configuration 18, the second wavelength range includes a third wavelength range lying within the first wavelength range and a fourth wavelength range lying within the first wavelength range, the third wavelength range having a central wavelength toward a short wavelength end with respect to the central wavelength of the first wavelength range, the fourth wavelength range having a central wavelength toward a long wavelength end with respect to the central wavelength of the first wavelength range, the reception means, in the first step, receives the first detection value, a third detection value obtained when infrared light is detected in the third wavelength range by the detection element, and a fourth detection value obtained when infrared light is detected in the fourth wavelength range by the detection element, the calculation means, in the second step, calculates a first ratio obtained by dividing the first detection value by the third detection value, a second ratio obtained by dividing the first detection value by the fourth detection value, and a third ratio obtained by dividing the fourth detection value by the third detection value from the first detection value, the third detection value, and the fourth detection value, and the calculation means, in the third step, calculates a first temperature of the object from the first ratio, a second temperature of the object from the second ratio, and a third temperature of the object from the third ratio and calculates, as the temperature of the object, one of the first and second temperatures that differs more from the third temperature.
The present invention, in an embodiment thereof, is directed to a computer-readable storage medium containing the computer program of Configuration 18 or 19.
The present invention allows for less error in calculating the temperature of a measurement object.
The following will describe embodiments of the present invention in detail with reference to drawings. Identical and equivalent members will be denoted by the same reference signs throughout the drawings, and description thereof is not repeated.
A description is now given of some of the terms used in this specification.
A “quantum-dot layer” is composed primarily of quantum dots, a wetting layer, an intermediate layer, a quantum-dot underlayer, a quantum-dot partial capping layer, and an insertion layer.
“Quantum dots” are semiconductor fine particles having a particle size of less than or equal to 100 nm and surrounded by a semiconductor material that has a larger band gap than does the semiconductor material for the quantum dots. In Stranski-Krastanov (S-K) growth, a wetting layer is formed before a transition to quantum dot growth.
A “quantum-dot underlayer” is an underlayer for the growth of quantum dots and a wetting layer and is made of a semiconductor material that has a larger band gap than does the semiconductor material for the quantum dots.
A “quantum-dot partial capping layer” is a layer that grows on quantum dots and is made of a semiconductor material that has a larger band gap than does the semiconductor material for the quantum dots, and covers at least parts of the quantum dots.
An “intermediate layer” is a base layer for a quantum-dot layer and is made of a semiconductor material that has a larger band gap than does the semiconductor material for the quantum dots. The intermediate layer may be made of the same semiconductor material as the quantum-dot underlayer and the quantum-dot partial capping layer. The intermediate layer here refers to an intermediate layer in a quantum-dot layer.
A “quantum-well layer” includes, for example, quantum wells and an intermediate layer.
“Quantum wells” form a semiconductor layer with a thickness of less than or equal to 100 nm and is interposed between semiconductor materials that have a larger band gap than does the semiconductor material for the quantum wells.
An “intermediate layer” is made of a semiconductor material that has a larger band gap than does the semiconductor material for the quantum wells and has the same meaning as an intermediate layer in a quantum-dot layer. The intermediate layer here refers to an intermediate layer in a quantum-well layer.
The detection unit 1 includes a detection element 11 and a reference element 12. The detection element 11 includes a quantum-dot infrared photodetector (QDIP) or a quantum-well infrared photodetector (QWIP). The quantum-dot infrared photodetector or the quantum-well infrared photodetector may be either a single element or an imager. Under an application voltage from the operation unit 2, the detection element 11 detects infrared light, emitted by a measurement object 30, in a certain specific wavelength range (second wavelength range) and outputs an analog signal as a detection spectrum to the operation unit 2. The analog signal is a voltage or current signal in accordance with the radiation intensity of the detected infrared light. The second wavelength range is a range of wavelengths of the light to which the detection unit 1 has detection sensitivity.
The reference element 12 outputs a detection intensity that changes with the heat produced by incident light. The reference element 12 is, for example, a thermal element. Specific examples of such a thermal element include a bolometer and a thermopile. The reference element 12 detects a thermal signal component that represents an amount of change of a thermal signal caused by a rise in temperature under incident infrared light and outputs the detected thermal signal component to the operation unit 2. The reference element 12 detects a thermal signal component, but not an optical signal component. More particularly, the reference element 12 detects the thermal signal component detected by the detection element 11, but not the optical signal component detected by the detection element 11. The reference element 12 detects a thermal signal component in a particular range that is referred to as a first wavelength range. The first wavelength range represents an overlap between a wavelength range (A) of the infrared light radiating from an object and being actually incident on the reference element 12 and a wavelength range (B) of the infrared light detectable as a thermal signal component by the reference element 12. The wavelength range (A) varies with the transmittance of infrared light from the object to the reference element 12 (hereinafter, the “transmittance”). The wavelength range (B) is a range of wavelengths of the light to which the reference element 12 has detection sensitivity.
The operation unit 2 applies an application voltage V to the detection element 11. The application voltage V may have a constant value. Alternatively, the application voltage may be cyclically changed as in, for example, V=V0+ΔV sin(2λt/TS) when the detection element 11 detects different wavelengths under different application voltages. V0 and ΔV are set in accordance with the desired detectable wavelength range. TS is a time cycle at which the application voltage V is modulated.
The operation unit 2 receives, from the detection element 11, a detection spectrum detected by the detection element 11 under the application voltage V and outputs the received detection spectrum to the calculation section 3. The operation unit 2 also receives a thermal signal component from the reference element 12 and outputs the received thermal signal component to the calculation section 3.
The calculation section 3 receives a detection spectrum and a thermal signal component from the operation unit 2 to calculate the temperature of the measurement object 30 from the received detection spectrum and thermal signal component by using a technique which will be detailed later.
The buffer layer 22 is disposed on the semiconductor substrate 21 in contact with one of the surfaces of the semiconductor substrate 21. The n-type semiconductor layer 23 is disposed on the buffer layer 22 in contact with the buffer layer 22.
The photoelectric conversion layer 24 is disposed on the n-type semiconductor layer 23 in contact with the n-type semiconductor layer 23. The n-type semiconductor layer 25 is disposed on the photoelectric conversion layer 24 in contact with the photoelectric conversion layer 24.
The electrodes 26 and 27 are disposed on the n-type semiconductor layer 25 in contact with the n-type semiconductor layer 25 and are separated by a distance from each other. The electrode 28 is disposed on the n-type semiconductor layer 23 in contact with the n-type semiconductor layer 23.
The semiconductor substrate 21 is made of, for example, semi-insulating GaAs. A buffer layer 23 is made of, for example, GaAs. The buffer layer 23 has a thickness of, for example, 100 nm to 500 nm.
The n-type semiconductor layers 23 and 25 are made of, for example, n-GaAs. The n-type semiconductor layers 23 and 25 each have a thickness of, for example, 100 nm to 1000 nm.
The electrodes 26 to 28 are n-type electrodes and made of, for example, any of Au/AuGeNi, AuGe/Ni/Au, Au/Ge, and Au/Ge/Ni/Au. The electrodes 26 to 28 each have a thickness of, for example, 10 nm to 500 nm.
The photoelectric conversion layer 24 has a layered structure including a stack of quantum-dot layers 241.
The quantum-dot layers 241 may be made of any material, but are preferably made of a III-V compound semiconductor.
Quantum dots 411 are preferably made of a semiconductor material that has lower band gap energy than does an intermediate layer 415.
The quantum-dot layers 241 are preferably made of any of, for example, GaAsxSb1-x, AlSb, InAsxSb1-x, GaxIn1-xSb, AlSbxAs1-x, AlAszSb1-z, InxGa1-xAs, AlxGa1-xAs, AlyGa1-yAszSb1-z, InxGa1-xP, (AlyGa1-y)zIn1-zP, GaAsxP1-x, GayIn1-yAszP1-z, and InxAl1-xAs, where 0≤x≤1, 0≤y≤1, and 0≤z≤1 in these materials and throughout the rest of the specification. Alternatively, the quantum-dot layers 241 may be made of a mixed crystal of any of these materials.
As another alternative, the quantum-dot layers 241 may be made of a compound semiconductor of a Group V semiconductor material and either a Group IV semiconductor or a Group III semiconductor material and may be made of a compound semiconductor of a Group H semiconductor material and a Group VI semiconductor material, as can be found in the periodic table. Alternatively, the quantum-dot layers 241 may be made of a mixed crystal of any of these compound semiconductors. As a further alternative, the quantum-dot layers 241 may be made of a chalcopyrite-based material or a non-chalcopyrite-based semiconductor material.
The photoelectric conversion layer 24 may be either an i-type semiconductor layer or a semiconductor layer containing a p-type impurity or a n-type impurity.
Referring to
The buffer layer 22 is then formed on the semiconductor substrate 21 by MBE (step (b) in
Subsequent to step (b), the n-type semiconductor layer 23 is formed on the buffer layer 22 by MBE (step (c) in
Subsequently, one of the quantum-dot layers 241 including the quantum dots 411 and the intermediate layer 415 is formed on the n-type semiconductor layer 23 by MBE (step (d) in
The quantum dots 411 are formed here by a technique called Stranski-Krastanov (S-K) growth.
More specifically, a GaAs (crystal) layer is grown as the intermediate layer 415. After that, an Al0.4Ga0.6As crystal layer is grown as an underlayer 412 (barrier layer; not shown) for the quantum dots 411, and the quantum dots 411 of InAs are formed by self-assembly mechanism. An Al0.4Ga0.6As crystal layer is then grown as a partial capping layer 414 (not shown) to cap the quantum dots 411. Thereafter, a GaAs crystal layer is grown as an intermediate layer, which completes the formation of the quantum-dot layer 241.
Step (d) is repeated, for example, 10 times, to form on the n-type semiconductor layer 23 the photoelectric conversion layer 24 including a stack of the quantum-dot layers 241 (step (e) in
The thickness of the intermediate layer 415 is, for example, 40 nm, which is sufficiently large in comparison with the thickness of the barrier layers (underlayer 412 and partial capping layer 414). The thickness of the barrier layers (underlayer 412 and partial capping layer 414) is, for example, 1 nm because the barrier layers need to be so thin that the excited carriers can tunnel through to the intermediate layer 415.
After step (e) in
Subsequently, the laminate is removed from the MBE device and subjected to photolithography and wet etching to partially remove the photoelectric conversion layer 24 and the n-type semiconductor layer 25. The electrodes 26 and 27 are then formed on the n-type semiconductor layer 25, and the electrode 28 is formed on the n-type semiconductor layer 23, which completes the manufacture of the quantum-dot infrared photodetector 20 (step (g) in
A description is now given of how to calculate the temperature of the measurement object 30. The radiation spectrum of a measurement object 30 agrees generally with the Planck equation given below:
where equation (1) λ is a wavelength, h is the Planck's constant, kB is the Boltzmann's constant, c is the speed of light, and T is the absolute temperature of the measurement object 30.
The detection value that can be detected by the detection unit 1 is theoretically a product of a radiation spectrum I(λ) multiplied by a solid angle α in which heat radiation is detectable (a detectable proportion of the black-body radiation intensity, alternatively referred to as a detection proportion), a transmittance τ(λ) through air, the emissivity ε(λ) of the measurement object 30, and a detection sensitivity A(λ) of the detection unit 1, integrated over the detection wavelength range. It is the detection sensitivity A(λ) of the detection unit 1 and the detection wavelength range that are dependent on the detection unit 1.
In the detection unit 1, the detection value DR of the reference element 12 is given by the following formula:
[Math. 2]
D
R=α∫R
When the reference element 12 is a thermal infrared sensor, the detection wavelength range is dependent on the transmittance because the high-transmittance wavelength range through air is narrower than the detectable wavelength range for the thermal infrared sensor.
The detection value DD of the detection element 11 is a sum of an optical signal component DL and an amount of change (thermal signal component) DN of a thermal signal caused by a rise in the temperature of the detection element 11 under infrared light radiation and is given by the following formula:
[Math. 3]
D
D
=D
L
+D
N (3)
The optical signal component DL in equation (3) is given by the following formula:
[Math. 4]
D
L=α∫L
The amount of change DN of the thermal signal in equation (3) is given by the following formula:
[Math. 5]
D
N=α∫N
The wavelength range for which the detection element 11 can generate an optical signal is characteristic to the detection element 11. A quantum-dot or quantum-well detection element can generate an optical signal for a particularly narrow wavelength range.
Meanwhile, the thermal signal of the detection element 11 is not dependent on the detection sensitivity of the detection element 11. The wavelength range N1 to N2 for which the detection element 11 can generate a thermal signal is the wavelength range R1 to R2 shown in
[Math. 6]
D
N=α∫R
The detection value DR of the reference element 12 in equation (2) only differs from the amount of change DN of the thermal signal in equation (6) in detection sensitivities AR(λ) and AN(λ), which shows that the amount of change DN of the thermal signal has a correlation with the detection value DR of the reference element 12. It is therefore possible to calculate the amount of change DN of the thermal signal from the detection value DR of the reference element 12. The optical signal component DL can be hence calculated by plugging the detection value DD of the detection element 11 and the amount of change DN of the thermal signal into equation (3).
It is also possible to calculate an integrated radiation illuminance over the wavelength range shown in
A description is given of a technique for calculating the temperature of the measurement object 30. The transmittance τ(λ), emissivity ε(λ), and a detection sensitivity AN(λ) are typically considered not dependent on wavelength (constant over the detection wavelength range) in calculation. The wavelength range shown in
Equations (2), (4), and (6) described above give the following equations (7), (8), and (9) respectively:
[Math. 7]
D
R
=α×ε×τ×A
R∫R
[Math. 8]
D
L
=α×ε×τ×A
L∫L
[Math. 9]
D
N=α×ε×τ×ΔN∫R
Plugging equations (8) and (9) into equation (3), an output DD of the detection element 11 is given by the following formula:
The ratio of the detection value DD of the detection element 11 and the detection value DR of the reference element 12 is given by the following formula:
Hence, the ratio of the detection value DD and the detection value DR has a value not dependent on α×ελτ.
The detection sensitivities AL and AN of the detection element 11 and the detection sensitivity AR of the reference element 12 are known because they can be measured in advance. Therefore, a temperature T of the measurement object 30 included in the radiation spectrum I(λ) represented by equation (1) can be calculated by plugging the detection sensitivities AL, AN, and AR and a ratio DD/DR of the detection value DD of the detection element 11 and the detection value DR of the reference element 12 into equation (11).
The temperature of the measurement object 30 can be alternatively calculated by evaluating the right-hand side of equation (11) using a different temperature and finding a temperature that matches the left-hand side of equation (11).
The first term in the right-hand side can be calculated using equation (11). This numerator represents an optical signal component and is therefore free from thermal effect. Accordingly, the effect of the amount of change DN of a thermal signal caused by a rise in the temperature of the detection element 11 under infrared light radiation is removed by calculating the temperature T of the measurement object 30 using equation (11). Additionally, by using DR that corresponds to a thermal signal component DN detected by the detection element 11, the temperature T of the measurement object 30 can be calculated.
The temperature calculating technique described above may be considered as an application, to two wavelength ranges with an overlapping detection wavelength range, of a so-called “two-color method” whereby temperature is calculated from a ratio of detection values for different wavelength ranges.
However, a common two-color method only deals with two non-overlapping wavelength ranges and for this reason, will likely to lead to error if the detection values of the reference element and the detection element are calculated on an assumption that the reference element and the detection element have an equal emissivity and transmittance.
Meanwhile, in the above-described technique, the detection wavelength range of the detection element 11 lies within the detection wavelength range of the reference element 12 (the detection wavelength range of the detection element 11 partially overlaps the detection wavelength range of the reference element 12). The technique hence does not lead to error even if it is assumed that the reference element and the detection element have an equal emissivity and transmittance. Accordingly, the temperature of the measurement object 30 can be calculated with less error by using the above-described technique.
Under the application voltage V, the detection element 11 detects the detection value DD (step S2) and outputs the detected detection value DD to the operation unit 2. The operation unit 2 outputs the detection value DD received from the detection element 11 to the calculation section 3.
The reference element 12 detects the detection value DR (step S3) and outputs the detected detection value DR to the operation unit 2. The operation unit 2 outputs the detection value DR received from the reference element 12 to the calculation section 3.
The calculation section 3 receives the detection values DD and DR from the operation unit 2 and calculates the ratio DD/DR of the detection value DD and the detection value DR from the received detection values DD and DR (step S4).
The calculation section 3 then plugs the known detection sensitivities AL, AR, and AN, the ratio DD/DR, and the radiation spectrum I(λ) represented by equation (1) into equation (11) to calculate the temperature T of the measurement object 30 (step S5), which completes the infrared photodetection process.
The flow chart shows an example where the detection value DD and the detection value DR are detected one after the other. Alternatively, the detection value DD and the detection value DR may be detected in parallel.
A description is now given of the precision of the calculated temperature of the measurement object 30. In equation (11), it is the ratio of integrated values of a black-body radiation brightness spectrum that is dependent on temperature.
The detectable wavelength range for the reference element 12 shown in
The ratio of integrated values of a black-body radiation brightness spectrum are plotted in
For instance, the ratio of integrated values of black-body radiation brightness grows with a rise in temperature for the detection value, 8 to 14 μm, detected by the reference element 12 rather than for the detection value detected by the detection element 11 for a central wavelength of 13.5 μm and a width of 1 μm (in other words, 13 μm to 14 μm) because there occurs an increase in black-body radiation brightness in 8 to 14 μm due to a rise in the temperature of the measurement object 30 (see white circles in
When the detection wavelength range of the detection element 11 is from 8 to 9 μm, almost the opposite is true (see black circles in
When the detection wavelength range of the detection element 11 is in the center of the detection wavelength range of the reference element 12, the temperature dependency of black-body radiation brightness appears equally in both elements. The temperature dependency of the ratio of integrated values of black-body radiation brightness is therefore reduced.
The ratio of integrated values of black-body radiation brightness changes more with a change in the temperature of the measurement object 30 when the temperature of the measurement object 30 is lower. This is especially evident when the detection wavelength range of the detection element 11 is from 8 to 9 μm. This is, as can be understood from
Accordingly, when the detectable temperature range is as relatively low as, for example, 20 to 40° C., 8.5 μm is preferred to the central wavelength of 13.5 μm.
When the detection wavelength range of the detection element 11 is from 13 to 14 μm, there is no influence of this. Therefore, the ratio of integrated values of black-body radiation brightness changes substantially linearly with the temperature of the measurement object 30, which facilitates analysis.
The detection wavelength ranges of the detection element 11 and the reference element 12 have been so far described as being symmetric with respect to the central wavelength. Alternatively, the detection wavelength ranges may be asymmetric.
In Embodiment 1, the operations of the calculation section 3 may be implemented using software. In such a case, the calculation section 3 includes: an ALU (arithmetic logic unit); a CPU (central processing unit) including a computation-enabled computation section such as an adder or a multiplier; a ROM (read-only memory); and a RAM (random access memory).
The ROM contains a program Prog_A including: step S1-1 where the detection values DD and DR are received from the detection element 11 and the reference element 12 respectively; and steps S4 and S5 shown in
The CPU retrieves the program Prog_A from the ROM and executes the program Prog_A to calculate the temperature T of the measurement object 30 using the above-described technique. In such a case, the CPU sequentially executes steps S1-1, S4, and S5.
The CPU, which calculates the ratio DD/DR and the temperature T of the measurement object 30, constitutes at least a part of a calculation means. The CPU, which receives the detection values DD and DR, constitutes at least a part of a reception means.
The program Prog_A may be contained in a storage medium (e.g., CD or DVD) for distribution. In such a case, the computer (CPU) retrieves the program Prog_A from the storage medium and executes the program Prog_A to calculate the temperature of the measurement object 30 using the above-described technique. Accordingly, the CD, DVD, and other like storage media containing the program Prog_A are computer-(CPU-)readable storage media containing the program Prog_A.
The detection unit 1A includes a detection element 13 in place of the reference element 12 in the detection unit 1 shown in
The detection element 13 includes the same detection element as the detection element 11. The reflector 14 is disposed on the infrared-light-incident side of the detection element 13 so as to face the detection element 13. The reflector 14 reflects infrared light incident on the detection element 13 and is preferably highly reflective to infrared light. The detection elements 11 and 13 are disposed on the heat conductor 15 in contact with the heat conductor 15. The heat conductor 15 transfers a thermal signal component detected by the detection element 11 to the detection element 13. Therefore, the detection element 13 detects DR corresponding to the amount of change DN of a thermal signal caused by a rise in the temperature of the detection element 11 under infrared light radiation described above and outputs a detected amount of change DR to the operation unit 2. In other words, the detection element 13 detects a thermal signal component (DR), but not an optical signal component. More particularly, the detection element 13 detects the thermal signal component detected by the detection element 11, but not the optical signal component detected by the detection element 11. If the detection element 13 is capable of detection over a sufficiently broad wavelength range as a thermal signal component here, the second wavelength range is practically the wavelength range (A) of the infrared light radiating from an object and being actually incident on the detection element 13.
The calculation section 3A calculates the ratio DD/DR of the detection value DD of the detection element 11 and the detection value DR of the detection element 13. The calculation section 3A then calculates the temperature T of the measurement object 30 using equation (11) and the technique described in Embodiment 1.
In the infrared photodetection device 10A, the heat conductor 15 renders the detection value DR of the detection element 13 equal to the amount of change DN of a thermal signal caused by a rise in the temperature of the detection element 11 under infrared light radiation. The detection element 13 thus enables accurate detection of the amount of change DN of a thermal signal caused by a rise in the temperature of the detection element 11.
The detection unit 1B includes an absorber 16 in place of the heat conductor 15 in the detection unit 1A shown in
In the detection unit 1B, the detection element 13 is disposed on the absorber 16 in contact with the absorber 16. The absorber 16 absorbs the light radiating from the measurement object 30 over a broader range (e.g., 8 to 14 μm) than the detectable wavelength range for the detection element 13 to transfer the heat produced by the light to the detection element 13.
Without the absorber 16, the environmental temperature of the detection element 13 would rise less under infrared light having wavelengths from 8 to 14 μm than the environmental temperature of the detection element 11 by as much as the reflected infrared light. That could render the detection element 13 less sensitive to the thermal component. The absorber 16 is preferably adjusted in such a manner that the environmental temperature of the detection element 13 can rise as much as the environmental temperature of the detection element 11. This adjustment renders the detection value DR of the detection element 13 equal to the amount of change DN of the thermal signal of the detection element 11.
Referring to
Under the application voltage V, the detection element 11 detects the detection value DD (step S12) and outputs the detected detection value DD to the operation unit 2. The operation unit 2 outputs the detection value DD received from the detection element 11 to the calculation section 3A.
The detection element 13 detects the detection value DR under the application voltage V (step S13) and outputs the detected detection value DR to the operation unit 2. The operation unit 2 outputs the detection value DR received from the detection element 13 to the calculation section 3A.
The calculation section 3A receives the detection values DD and DR from the operation unit 2 and calculates the ratio DD/DR of the detection value DD and the detection value DR from the received detection values DD and DR (step S14).
The calculation section 3A then plugs the known detection sensitivities AL, AR, and AN, the ratio DD/DR, and the radiation spectrum I(λ) represented by equation (1) into equation (11) to calculate the temperature T of the measurement object 30 (step S15), which completes the infrared photodetection process.
The flow chart shows an example where the detection value DD and the detection value DR are detected one after the other. Alternatively, the detection value DD and the detection value DR may be detected in parallel.
A common two-color method detects infrared light using two detection wavelengths and, for this reason, needs two different detection elements and/or two different wavelength filters. On the other hand, Embodiment 2 needs only one type of detection element, thereby reducing device cost and development cost.
Besides, Embodiment 2 additionally achieves the various effects described in Embodiment 1.
In Embodiment 2, the operations of the calculation section 3A may be implemented using software. In such a case, the calculation section 3A includes a CPU (including a computation section), a ROM, and a RAM.
The ROM contains a program Prog_B including: step S1-1 where the detection values DD and DR are received from the detection element 11 and the detection element 13 respectively; and steps S14 and S15 shown in
The CPU retrieves the program Prog_B from the ROM and executes the program Prog_B to calculate the temperature T of the measurement object 30 using the above-described technique. In such a case, the CPU sequentially executes steps S1-1, S14, and S15.
The CPU, which calculates the ratio DD/DR and the temperature T of the measurement object 30, constitutes at least a part of a calculation means. The CPU, which receives the detection values DD and DR, constitutes at least a part of a reception means.
The program Prog_B may be contained in a storage medium (e.g., CD or DVD) for distribution. In such a case, the computer (CPU) retrieves the program Prog_B from the storage medium and executes the program Prog_B to calculate the temperature of the measurement object 30 using the above-described technique. Accordingly, the CD, DVD, and other like storage media containing the program Prog_B are computer-(CPU-)readable storage media containing the program Prog_B.
In Embodiment 2, when the detection element 13 exhibits polarization-dependent characteristics in light absorption, a polarizer is used as the reflector 14. The polarized light to be detected is adjusted using the polarizer in such a manner that no optical signal component can be detected.
The description of Embodiment 1 applies to Embodiment 2 unless otherwise mentioned explicitly.
The detection unit 1C has the same structure as the detection unit 1 shown in
Referring to
Because the equilibrium value of the optical signal component is not distinguishable in the detection signal, analysis is done using the following formula:
[Math. 12]
D
D
=D
N(1−exp[−(t−t0)/τ])+DL (12)
In equation (12), r is a heat diffusion time.
The calculation section 3B calculates DN and DL by fitting from the detection signal at time t1 and onwards using equation (12), with time t1 being 1 to 2 seconds, which is sufficiently longer than the time response of the optical signal component and shorter than the time response of the thermal signal component.
This technique enables distinguishing between the optical signal component and the thermal signal component for separate detection thereof by using the detection element 11. If the detection element 11 is capable of detection over a sufficiently broad wavelength range, the second wavelength range is practically the wavelength range (A) of the infrared light radiating from an object and being actually incident on the detection element 11.
The calculation section 3B then calculates a ratio DD/DN of DD and DN by either plugging calculated DN and DL into equation (3) and thus calculating DD or using the value of DD in the equilibrium state.
Accordingly, the calculation section 3B plugs the known detection sensitivities AL, AR, and AN, the ratio DD/DN, and the radiation spectrum I(λ) represented by equation (1) into an equation obtained from equation (11) by replacing DD/DR with DI/DN therein, to calculate the temperature T of the measurement object 30.
Precision increases with fewer parameters being subjected to fitting. For instance, because the heat diffusion time is dictated by the detection unit, the surrounding structure, and the environmental temperature, data may be stored beforehand for each environmental temperature, so that values may be specified in based on the results of separate measurement of the environmental temperature. Meanwhile, DN and DL are subjected to fitting every time because DN and DL vary from one detection to the other.
Referring to
The detection element 11 then detects a time response of the detection value DD under the application voltage V (step S22) and outputs the detected time response of the detection value DD to the operation unit 2. The operation unit 2 outputs the time response of the detection value DD received from the detection element 11 to the calculation section 3B.
The calculation section 3B receives the time response of the detection value DD from the operation unit 2, subjects the received time response of the detection value DD to fitting using equation (12), and calculates the optical signal component DL and the thermal signal component DN (step S23).
The calculation section 3B then determines DD from the calculated optical signal component DL and the calculated thermal signal component DN (see equation (3)) and calculates the ratio DD/DN (step S24).
Accordingly, the calculation section 3B plugs the known detection sensitivities AL, AR, and AN, the ratio DD/DN, and the radiation spectrum I(λ) represented by equation (1) into an equation obtained from equation (11) by replacing DD/DR with DD/DN therein, to calculate the temperature T of the measurement object 30 (step S25), which completes the infrared photodetection process.
The flow chart in
Referring to
Subsequent to step S23, the calculation section 3B plugs the detection proportion α (which has a constant value), the emissivity a (which has a constant value), the transmittance τ (which has a constant value), the detection sensitivity AL, the optical signal component DL, and the radiation spectrum I(λ) represented by equation (1) into equation (8), to calculate the temperature T of the measurement object 30 (step S26), which completes the infrared photodetection process.
Embodiment 3 requires no reference element 12 of Embodiment 1, thereby enabling reducing the size and cost of the infrared photodetection device. In addition, since it is possible to calculate a thermal signal component for each detection element, the thermal signal component can be accurately corrected even when the thermal signal component varies from one detection element to the other.
Besides, Embodiment 3 additionally achieves the various effects described in Embodiment 1.
In Embodiment 3, the operations of the calculation section 3B may be implemented using software. In such a case, the calculation section 3B includes: a CPU (including a computation section), a ROM, and a RAM.
The ROM contains either a program Prog_C including: step S1-2 where the time response of the detection value DD is received from the detection element 11; and steps S23 to S25 shown in
The CPU retrieves the program Prog_C from the ROM and executes the program Prog_C to calculate the temperature T of the measurement object 30 using the above-described technique. In such a case, the CPU sequentially executes steps S1-2 and S23 to S25. The CPU alternatively retrieves the program Prog_D from the ROM and executes the program Prog_D to calculate the temperature T of the measurement object 30 using the above-described technique. In such a case, the CPU sequentially executes steps S1-2, S23, and S26.
The CPU, which calculates the ratio DD/DN (or the optical signal component DL and the thermal signal component DN) and the temperature T of the measurement object 30, constitutes at least a part of a calculation means. The CPU, which receives the time response of the detection value DD, constitutes at least a part of a reception means.
The program Prog_C (or program Prog_D) may be contained in a storage medium (e.g., CD or DVD) for distribution. In such a case, the computer (CPU) retrieves the program Prog_C (or program Prog_D) from the storage medium and executes the program Prog_C (or program Prog_D) to calculate the temperature of the measurement object 30 using the above-described technique. Accordingly, the CD, DVD, and other like storage media containing the program Prog_C (or program Prog_D) are computer-(CPU-)readable storage media containing the program Prog_C (or program Prog_D).
The description of Embodiment 1 applies to Embodiment 3 unless otherwise mentioned explicitly.
The detection unit 1C includes a detection element 17 and wavelength filters 31 to 33. The detection element 17 includes, for example, an electromagnetic wave detection element such as a thermopile or a bolometer. The detection element 17 may be either a single element or an imager including a plurality of such elements.
The detection element 17 detects infrared light passing through the wavelength filter 31 and outputs a first detection value obtained upon the detection of the infrared light to the operation unit 2A. The detection element 17 also detects infrared light passing through the wavelength filter 32 and outputs a second detection value obtained upon the detection of the infrared light to the operation unit 2A. The detection element 17 further detects infrared light passing through the wavelength filter 33 and outputs a third detection value obtained upon the detection of the infrared light to the operation unit 2A.
Each wavelength filter 31 to 33 includes, for example, a multilayered interference filter. The wavelength filter 31 to 33 has a transmission range which will be detailed later. The wavelength filter 31 may be disposed on the detection element 17 or realized by utilizing the inherent detection sensitivity of the detection element 17.
The operation unit 2A receives the first detection value, the second detection value, and the third detection value from the detection element 17 and outputs the received first detection value, the received second detection value, and the received third detection value to the calculation section 3C. The operation unit 2A switches between the wavelength filters 31 to 33.
The calculation section 3C receives the first detection value, the second detection value, and the third detection value from the operation unit 2A and calculates the temperature of an object 30 on the basis of the received first detection value, the received second detection value, and the received third detection value using a technique which will be detailed later.
As described here, the wavelength range B is from λ1 to λ2, lying toward the short wavelength end with respect to the central wavelength λc of the wavelength range A and also within the wavelength range A (λ1 to λ4). The wavelength range C is from λ3 to λ4, lying toward the long wavelength end with respect to the central wavelength λc of the wavelength range A and also within the wavelength range A (λ1 to λ4).
The wavelength filter 31 passes infrared light in the wavelength range A. The wavelength filter 32 passes infrared light in the wavelength range B. The wavelength filter 33 passes infrared light in the wavelength range C. Therefore, the first wavelength range corresponds to the wavelength range A, and the second wavelength range corresponds to the wavelength ranges B and C. Here, the wavelength range B and the wavelength range C are the third wavelength range and a fourth wavelength range respectively.
Referring to
The detection intensity detected by the detection element 17 is the product, black-body radiation brightness×detection proportion×emissivity×transmittance, integrated over a range of wavelengths. The black-body radiation brightness is given by equation (1) above representing the Planck equation and is dependent on the temperature of the object. In Embodiment 4, it is assumed that the detection sensitivity of the detection element 17 has no wavelength dependency.
Curved line k15 represents calculated values of A/B. Curved line k16 represents measured values of A/B. Curved line k17 represents calculated values of A/C. Curved line k18 represents measured values of A/C. Curved line k19 represents calculated values of C/B. Curved line k20 represents measured values of C/B.
Referring to
Conventionally, C/B is calculated using a two-color method from results for the wavelength range B (=8 to 9 μm) and results for the wavelength range C (=13 to 14 μm), and the temperature of an object is calculated on the basis of thus-calculated C/B (see curved line k19). Refer to the right-side vertical axis in
The temperature at the point where the arrow originating at the measured value at 50° C. intersects with a calculated value is the temperature obtained in measurement. In other words, the temperature difference corresponding to the length of the arrow is a temperature error.
The wavelength dependency of emissivity often changes monotonically. Here, the result obtained when the wavelength filter 32 (=wavelength range B) or the wavelength filter 33 (=wavelength range C) is used has a maximum error from a calculated value. For emissivity change 1 (see curved line k13) in
Upon receiving the detection value DV_A from the detection element 17, the operation unit 2A sets the wavelength filter 32 between the object 30 and the detection element 17. The detection element 17 then detects the detection value DV_B obtained when infrared light is detected in the wavelength range B through the wavelength filter 32 (step S32) and outputs the detected detection value DV_B to the operation unit 2A.
Upon receiving the detection value DV_B from the detection element 17, the operation unit 2A sets the wavelength filter 33 between the object 30 and the detection element 17. The detection element 17 then detects the detection value DV_C obtained when infrared light is detected in the wavelength range C through the wavelength filter 33 (step S33) and outputs the detected detection value DV_C to the operation unit 2A.
Upon receiving the detection value DV_C from the detection element 17, the operation unit 2A outputs the detection values DV_A, DV_B, and DV_C to the calculation section 3C.
Upon receiving the detection values DV_A, DV_B, and DV_C from the operation unit 2A, the calculation section 3C calculates a ratio RT_1 (=DV_A/DV_B) of the detection value DV_A and the detection value DV_B (step S34), calculates a ratio RT_2 (=DV_A/DV_C) of the detection value DV_A and the detection value DV_C (step S35), and calculates a ratio RT_3 (=DV_C/DV_B) of the detection value DV_C and the detection value DV_B (step S36).
Thereafter, the calculation section 3C calculates a temperature T_1 of the object 30 from the ratio RT_1 (=DV_A/DV_B) using a two-color method (step S37), calculates a temperature T_2 of the object 30 from the ratio RT_2 (=DV_A/DV_C) using a two-color method (step S38), and calculates a temperature T_3 of the object 30 from the ratio RT_3 (=DV_C/DV_B) using a two-color method (step S39).
Accordingly, the calculation section 3C calculates one of the temperatures RT_1 and RT_2 that differs more from the temperature T_3 as the temperature of the object 30 (step S40), which completes the infrared photodetection process.
In the infrared photodetection process shown in
In Embodiment 4, the operations of the calculation section 3C may be implemented using software. In such a case, the calculation section 3C includes: a CPU (including a computation section), a ROM, and a RAM.
The ROM contains a program Prog_E including: step S1-3 where the detection values DV_A, DV_B, and DV_C are received from the detection element 17, and steps S34 to S40 shown in
The CPU retrieves the program Prog_E from the ROM and executes the program Prog_E to calculate the temperature T of the measurement object 30 using the above-described technique. In such a case, the CPU sequentially executes steps S1-3 and S34 to S40.
The CPU, which calculates the ratios RT_1 to RT_3 and the temperatures T_1 to T_3, constitutes at least a part of a calculation means. The CPU, which receives the detection values DV_A, DV_B, and DV_C, constitutes at least a part of a reception means.
The program Prog_E may be contained in a storage medium (e.g., CD or DVD) for distribution. In such a case, the computer (CPU) retrieves the program Prog_E from the storage medium and executes the program Prog_E to calculate the temperature of the measurement object 30 using the above-described technique. Accordingly, the CD, DVD, and other like storage media containing the program Prog_E are computer-(CPU-)readable storage media containing the program Prog_E.
The detection unit IE includes no reference element 12 in the detection unit 1 shown in
The operation unit 2B applies an application voltage V1 or an application voltage V2 to the detection element 11. The application voltage may be manually or automatically switched between V1 and V2 and may be varied at a time cycle TS beforehand as in, for example, V=(V2−V1)sin(2πt/TS)+V1. In such a case, the voltage V has an amplitude V2−V1 and varies with time t between V1 and V2 along a sine curve. The voltage V1 is equal to the voltage V when time t is equal to t1 (V=(V2−V1)sin(2πt1/TS)+V1). The voltage V2 is equal to the voltage V when time t is equal to t2 (V=(V2−V1)sin(2πt2/TS)+V1).
The operation unit 2B receives, from the detection element 11, a detection spectrum SP1 detected by the detection element 11 under the application voltage V1 and a detection spectrum SP2 detected by the detection element 11 under the application voltage V2 and outputs the received detection spectra SP1 and SP2 to the calculation section 3D.
The calculation section 3D receives the detection spectra SP1 and SP2 from the operation unit 2B and calculates the temperature of the object 30 from the received detection spectra SP1 and SP2 using a technique which will be detailed later.
Referring to
The detection sensitivity spectrum SP3 has a peak wavelength λ5 with infrared light in a wavelength range D being absorbed. The detection sensitivity spectrum SP4 has a peak wavelength λ6 with infrared light in a wavelength range E being absorbed. The detection sensitivity spectrum SP4 has an absorption wavelength range partially overlapping the detection sensitivity spectrum SP3.
The wavelength range D of the detection sensitivity spectrum SP3 corresponds to the wavelength range B of Embodiment 4. The result SP4−(SP3×Hk) of subtraction from the detection sensitivity spectrum SP4 of SP3×Hk, which is a result of multiplication of the detection sensitivity spectrum SP3 and a correction coefficient Hk, corresponds to the wavelength range C of Embodiment 4. Additionally, the result of weighting β×SP3+(1−β)×SP4, which is a sum of the products of the detection sensitivity spectra SP3 and SP4 and a weight coefficient, corresponds to the wavelength range A of Embodiment 4, where β is a real number that satisfies 0<β<1.
Therefore, the temperature of the object 30 can be calculated from the detection sensitivity spectrum SP3, the result of subtraction SP4−(SP3×Hk), and the result of weighting β×SP3+(1−β)×SP4 by using the technique described in Embodiment 4.
Referring to
Upon receiving the detection spectrum SP1 from the detection element 11, the operation unit 2B applies the voltage V2 to the detection element 11. The detection element 11 then detects the detection spectrum SP2 of infrared light under the applied voltage V2 (step S42) and outputs the detected detection spectrum SP2 to the operation unit 2B.
Upon receiving the detection spectrum SP2 from the detection element 11, the operation unit 2B outputs the detection spectra SP1 and SP2 to the calculation section 3D.
Upon receiving the detection spectra SP1 and SP2 from the operation unit 2B, the calculation section 3D calculates the result of subtraction SP2−(SP1×Hk) from the detection spectra SP1 and SP2 and the correction coefficient Hk (step S43). In addition, the calculation section 3D calculates the result of weighting β×SP1+(1−β)×SP2 from the detection spectra SP1 and SP2 and a weight coefficient β (step S44).
Accordingly, the calculation section 3D assigns the result of weighting β×SP1+(1−β)×SP2 to the detection value DV_A, the detection value of the detection spectrum SP1 to the detection value DV_B, and the result of subtraction SP2−(SP1×Hk) to the detection value DV_C (step S45).
Thereafter, the calculation section 3D sequentially executes steps S34 to S40 described in Embodiment 4 to calculate the temperature of the object 30, which completes the infrared photodetection process.
The calculation of the temperature of the object 30 represented by the flow chart in
In Embodiment 5, the operations of the calculation section 3D may be implemented using software. In such a case, the calculation section 3D includes: a CPU (including a computation section), a ROM, and a RAM.
The ROM contains a program Prog_F including: step S1-4 where the detection spectra SP1 and SP2 are received from the detection element 11; and steps S43 to S45 and S34 to S40 shown in
The CPU retrieves the program Prog_F from the ROM and executes the program Prog_F to calculate the temperature T of the measurement object 30 using the above-described technique. In such a case, the CPU sequentially executes steps S1-4, S43 to S45, and S34 to S40.
The CPU, which calculates the result of weighting β×SP1+(1−β)×SP2, the result of subtraction SP2−(SP1×Hk), the ratios RT_1 to RT_3, and the temperatures T_1 to T_3, constitutes at least a part of a calculation means. The CPU, which receives the detection spectra SP1 and SP2, constitutes at least a part of a reception means.
The program Prog_F may be contained in a storage medium (e.g., CD or DVD) for distribution. In such a case, the computer (CPU) retrieves the program Prog_F from the storage medium and executes the program Prog_F to calculate the temperature of the measurement object 30 using the above-described technique. Accordingly, the CD, DVD, and other like storage media containing the program Prog_F are computer-(CPU-)readable storage media containing the program Prog_F.
The description of Embodiment 1 applies to Embodiment 5 unless otherwise mentioned explicitly.
The operation unit 2C applies a voltage V3 to the detection element 11 to set the detection wavelength range of the detection element 11 to the wavelength range A described in Embodiment 4. The operation unit 2C also applies a voltage V4 to the detection element 11 to set the detection wavelength range of the detection element 11 to the wavelength range B described in Embodiment 4. The operation unit 2C also applies a voltage V5 to the detection element 11 to set the detection wavelength range of the detection element 11 to the wavelength range C described in Embodiment 4.
The operation unit 2C receives the detection value DV_A detected by the detection element 11 under the applied voltage V3 from the detection element 11, receives the detection value DV_B detected by the detection element 11 under the applied voltage V4 from the detection element 11, and receives the detection value DV_C detected by the detection element 11 under the applied voltage V5 from the detection element 11. The operation unit 2C then outputs the detection values DV_A to DV_C to the calculation section 3C.
The calculation section 3C receives the detection values DV_A to DV_C from the operation unit 2C and calculates the temperature of the object 30 from the received detection values DV_A to DV_C by using the technique described in Embodiment 4.
Referring to
The voltages V3 and V4 may be automatically changed. The voltages V3 and V4 may be varied at a time cycle TS beforehand as in, for example, V=(V4−V3)sin(2πt/TS)+V3. In such a case, the voltage V has an amplitude V4-V3 and varies with time t between V3 and V4 along a sine curve. The voltage V3 is equal to the voltage V when time t is equal to t3 (V=(V4−V3)sin(2πt3/TS)+V3). The voltage V4 is equal to the voltage V when time t is equal to t4 (V=(V4−V3)sin(2πt4/TS)+V3).
The detection element 11 then detects the detection value DV_B under the applied voltage V3 and the detection value DV_C under the applied voltage V4. The detection element 11 detects a detection value in increments of ΔV from the voltage V3 to the voltage V4 with a resolution N. In other words, the detection element 11 detects a detection value DV_nΔV under the applied voltage V3+nΔV, where n is an integer from 1 to N−1. The comprehensive sum of DV_B, DV_C, and the sum of DV_nΔV as n goes from 1 to N−1 corresponds to the detection value DV_A for the wavelength range A described in Embodiment 4.
The calculation section 3C can therefore calculate the temperature of the object 30 by using the technique described in Embodiment 4.
Referring to
Upon receiving the detection value DV_B from the detection element 11, the operation unit 2C sets n to 1 (step S52) to apply the voltage V3+nΔV to the detection element 11. The detection element 11 then detects the detection value DV_nΔV obtained when infrared light is detected under the applied voltage V3+nΔV (step S53) and outputs the detected detection value DV_nΔV to the operation unit 2C.
Upon receiving the detection value DV_nΔV from the detection element 11, the operation unit 2C determines whether or not n is equal to N−1 (step S54). If it is determined in step S54 that n is not equal to N−1, the operation unit 2C sets n to n+1 (step S55). Thereafter, the process proceeds to step S53 where steps S53 to S55 are repeated until it is determined in step S54 that n=N−1.
If it is determined in step S54 that n=N−1, in other words, if the operation unit 2C receives a detection value DV_(N−1)ΔV from the detection element 11, the operation unit 2C applies the voltage V4 to the detection element 11. The detection element 11 then detects the detection value DV_C obtained when infrared light is detected in the wavelength range C under the applied voltage V4 (step S56) and outputs the detected detection value DV_C to the operation unit 2C.
Upon receiving the detection value DV_C from the detection element 11, the operation unit 2C outputs the detection values DV_B, DV_ΔV to DV_(N−1)ΔV, and DV_C to the calculation section 3C. Upon receiving the detection values DV_B, DV_ΔV to DV_(N−1)ΔV, and DV_C from the operation unit 2C, the calculation section 3C calculates the detection value DV_A, which is a sum of the received detection values DV_B, DV_ΔV to DV_(N−1)ΔV, and DV_C (step S57).
To obtain the sum here, the detection values DV_B, DV_ΔV to DV_(N−1)ΔV, and DV_C are added up after the detection values DV_ΔV to DV_(N−1)ΔV are multiplied by respective coefficients in such a manner as to match with the detection value for the wavelength range A. If the shift width of the detection wavelength of the detection element 11 when the voltage applied to the detection element 11 has changed by a voltage ΔV is more than the shift width of the detection wavelength before the voltage applied to the detection element 11 is changed by the voltage ΔV, the calculation section 3C calculates a sum of the detection values DV_B, DV_ΔV to DV_(N−1)ΔV, and DV_C after multiplying the detection values DV_ΔV to DV_(N−1)ΔV by respective coefficients that are larger than 1. On the other hand, if the shift width of the detection wavelength of the detection element 11 when the voltage applied to the detection element 11 has changed by the voltage ΔV is less than the shift width of the detection wavelength before the voltage applied to the detection element 11 is changed by the voltage ΔV, the calculation section 3C calculates a sum of the detection values DV_B, DV_ΔV to DV_(N−1)ΔV, and DV_C after multiplying the detection values DV_ΔV to DV_(N−1)ΔV by respective coefficients that are smaller than 1. Suitable coefficients can be calculated if the shift width of the detection wavelength of the detection element 11 when the voltage has changed by ΔV is measured beforehand and stored in the calculation section 3C in the form of a table.
Then, subsequent to step S57, the calculation section 3C also sequentially executes steps S34 to S40 described above to calculate the temperature of the object 30.
The calculation of the temperature of the object 30 represented by the flow chart in
In Embodiment 6, the operations of the calculation section 3C may be implemented using software. In such a case, the calculation section 3C includes: a CPU (including a computation section), a ROM, and a RAM.
The ROM contains a program Prog_G including: step S1-5 where the detection values DV_B, DV_nΔV (n=1 to N−1), and DV_C are received from the detection element 11; and steps S34 to S40 shown in
The CPU retrieves the program Prog_G from the ROM and executes the program Prog_G to calculate the temperature T of the measurement object 30 using the above-described technique. In such a case, the CPU sequentially executes steps S1-5 and S34 to S40.
The CPU, which calculates the ratios RT_1 to RT_3 and the temperatures T_1 to T_3, constitutes at least a part of a calculation means. The CPU, which receives the detection values DV_B, DV_nΔV (n=1 to N−1), and DV_C, constitutes at least a part of a reception means.
The program Prog_G may be contained in a storage medium (e.g., CD or DVD) for distribution. In such a case, the computer (CPU) retrieves the program Prog_G from the storage medium and executes the program Prog_G to calculate the temperature of the measurement object 30 using the above-described technique. Accordingly, the CD, DVD, and other like storage media containing the program Prog_G are computer-(CPU-)readable storage media containing the program Prog_G.
The description of Embodiments 1 and 5 applies to Embodiment 6 unless otherwise mentioned explicitly.
Embodiments 1 and 2 described earlier describe that the ratio DD/DR is calculated from the detection values DD and DR detected respectively using the second wavelength range and the first wavelength range which is broader than the second wavelength range. Embodiments 1 and 2 also describe that the temperature T of the measurement object 30 is calculated by plugging into equation (11) the calculated ratio DD/DR, the radiation spectrum I(λ) represented by equation (1), and the detection sensitivities AL, AR, and AN.
Embodiment 3 described earlier describes that the optical signal component DL and the thermal signal component DN are calculated from the time response of the detection value DD, that DD is determined from the calculated optical signal component DL and the calculated thermal signal component DN to calculate the ratio DD/DN, and that the temperature T of the measurement object 30 is calculated by plugging the calculated ratio DD/DN, the radiation spectrum I(λ) represented by equation (1), and the detection sensitivities AL, AR, and AN into an equation obtained from equation (11) by replacing DD/DR with DD/DN therein. The optical signal component DL is a signal component for the second wavelength range described in Embodiments 1 and 2. The thermal signal component DN is a signal component for the first wavelength range described in Embodiments 1 and 2. Accordingly, the temperature of the object 30 is calculated using the signal component for the second wavelength range and the signal component for the first wavelength range in Embodiment 3.
Embodiments 4 and 5 describe that the temperature of the object 30 is calculated from the detection values DV_A, DV_B, and DV_C detected respectively for the wavelength range A, the wavelength range B, and the wavelength range C. The wavelength range B is from wavelength λ1 to wavelength λ2, lying toward the short wavelength end with respect to a central wavelength kc of the wavelength range A, over which infrared light is transmitted. The wavelength range C is from wavelength λ3 to wavelength λ4, lying toward the long wavelength end with respect to the central wavelength λc of the wavelength range A, over which infrared light is transmitted.
Embodiment 5 describes that the temperature of the object 30 is calculated from the detection values detected for a wavelength range corresponding to the wavelength range A, a wavelength range corresponding to the wavelength range B, and a wavelength range corresponding to the wavelength range C.
Therefore, Embodiments 1 to 6 share a common feature that the temperature of the object 30 is calculated from infrared light detection values detected for two different, but partially overlapping wavelength ranges.
Accordingly, the present invention, in an embodiment thereof, is directed to an infrared photodetection device including: a detection unit including a detection element configured to detect infrared light in a first wavelength range and detect infrared light in a second wavelength range lying within the first wavelength range and toward a short wavelength end or a long wavelength end with respect to a central wavelength of the first wavelength range; and a calculation unit configured to receive, from the detection unit, a first detection value obtained when infrared light is detected in the first wavelength range by the detection element and a second detection value obtained when infrared light is detected in the second wavelength range by the detection element, calculate A ratio of the received first and second detection values, and calculate temperature of an object from the calculated ratio.
The present invention, in an embodiment thereof, is directed to an infrared photodetection process including: a first step of a detection element detecting infrared light in a first wavelength range and detecting infrared light in a second wavelength range lying within the first wavelength range and toward a short wavelength end or a long wavelength end with respect to a central wavelength of the first wavelength range; and a second step of receiving a first detection value obtained when infrared light is detected in the first wavelength range by the detection element and a second detection value obtained when infrared light is detected in the second wavelength range by the detection element, calculating a ratio of the received first and second detection values, and calculating temperature of an object from the calculated ratio.
The present invention, in an embodiment thereof, is directed to a computer program for causing a computer to calculate temperature of an object from a first detection value obtained when infrared light is detected in a first wavelength range by a detection element and a second detection value obtained when infrared light is detected in a second wavelength range by the detection element, the second wavelength range lying within the first wavelength range and toward a short wavelength end or a long wavelength end with respect to a central wavelength of the first wavelength range, the computer program causing the computer to implement: a first step of a reception means receiving the first detection value and the second detection value; a second step of a calculation means calculating a ratio of the first and second detection values from the first and second detection values received in the first step; and a third step of the calculation means calculating the temperature of the object from the calculated ratio.
Each calculation section 3, 3A, 3B, 3C, and 3D constitutes at least a part of a calculation unit in an embodiment of the present invention.
The embodiments and examples disclosed herein are for illustrative purposes only in every respect and provide no basis for restrictive interpretations. The scope of the present invention is defined only by the claims and never bound by the embodiments or examples. Those modifications and variations that may lead to equivalents of claimed elements are all included within the scope of the invention.
This invention is applicable to infrared photodetection devices, infrared photodetection processes, computer programs, and computer-readable storage media containing such a computer program.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2019-045184 | Mar 2019 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2020/010609 | 3/11/2020 | WO | 00 |
