Virtual Spectral Selectivity in a Modulated Thermal Infrared Emitter with Lock-In Detection
The need for affordable low-power devices has led MEMS-based thermal emitters to become an interesting option for optical gas sensors. Since these emitters have a low thermal mass, they can be easily modulated and combined with a lock-in amplifier for detection. In this paper, we show that the signa...
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| Format: | Article |
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MDPI AG
2022-07-01
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| Series: | Sensors |
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| Online Access: | https://www.mdpi.com/1424-8220/22/14/5451 |
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| author | David Santalices Juan Meléndez Susana Briz |
| author_facet | David Santalices Juan Meléndez Susana Briz |
| author_sort | David Santalices |
| collection | DOAJ |
| description | The need for affordable low-power devices has led MEMS-based thermal emitters to become an interesting option for optical gas sensors. Since these emitters have a low thermal mass, they can be easily modulated and combined with a lock-in amplifier for detection. In this paper, we show that the signal measured by a lock-in amplifier from a thermal emitter that varies its temperature periodically can have different spectral profiles, depending on the reference signal used. These virtual emitters appear because the Fourier series expansion of the emitted radiance, as a function of time, has different coefficients for each wavelength, and this spectral signature, which is different for each harmonic, can be retrieved using a reference signal that corresponds to its frequency. In this study, the effect is first proved theoretically and then is measured experimentally. For this purpose, we performed measurements with an IR camera provided with six different spectral filters of a modulated emitter, in combination with lock-in amplification via software. Finally, we show a potential application of this effect using multiple virtual emitters to gain spectral selectivity and distinguish between two gases, CO<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mrow></mrow><mn>2</mn></msub></semantics></math></inline-formula> and CH<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mrow></mrow><mn>4</mn></msub></semantics></math></inline-formula>. |
| first_indexed | 2024-03-09T10:12:21Z |
| format | Article |
| id | doaj.art-3c87cadcdd2d4699b0806b0ac67a2665 |
| institution | Directory Open Access Journal |
| issn | 1424-8220 |
| language | English |
| last_indexed | 2024-03-09T10:12:21Z |
| publishDate | 2022-07-01 |
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| series | Sensors |
| spelling | doaj.art-3c87cadcdd2d4699b0806b0ac67a26652023-12-01T22:41:10ZengMDPI AGSensors1424-82202022-07-012214545110.3390/s22145451Virtual Spectral Selectivity in a Modulated Thermal Infrared Emitter with Lock-In DetectionDavid Santalices0Juan Meléndez1Susana Briz2LIR—Infrared Laboratory, Department of Physics, Universidad Carlos III de Madrid, 28911 Leganés, SpainLIR—Infrared Laboratory, Department of Physics, Universidad Carlos III de Madrid, 28911 Leganés, SpainLIR—Infrared Laboratory, Department of Physics, Universidad Carlos III de Madrid, 28911 Leganés, SpainThe need for affordable low-power devices has led MEMS-based thermal emitters to become an interesting option for optical gas sensors. Since these emitters have a low thermal mass, they can be easily modulated and combined with a lock-in amplifier for detection. In this paper, we show that the signal measured by a lock-in amplifier from a thermal emitter that varies its temperature periodically can have different spectral profiles, depending on the reference signal used. These virtual emitters appear because the Fourier series expansion of the emitted radiance, as a function of time, has different coefficients for each wavelength, and this spectral signature, which is different for each harmonic, can be retrieved using a reference signal that corresponds to its frequency. In this study, the effect is first proved theoretically and then is measured experimentally. For this purpose, we performed measurements with an IR camera provided with six different spectral filters of a modulated emitter, in combination with lock-in amplification via software. Finally, we show a potential application of this effect using multiple virtual emitters to gain spectral selectivity and distinguish between two gases, CO<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mrow></mrow><mn>2</mn></msub></semantics></math></inline-formula> and CH<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mrow></mrow><mn>4</mn></msub></semantics></math></inline-formula>.https://www.mdpi.com/1424-8220/22/14/5451thermal emitterblackbodylock-in amplifierFourier seriesoptical gas sensorgas detection |
| spellingShingle | David Santalices Juan Meléndez Susana Briz Virtual Spectral Selectivity in a Modulated Thermal Infrared Emitter with Lock-In Detection Sensors thermal emitter blackbody lock-in amplifier Fourier series optical gas sensor gas detection |
| title | Virtual Spectral Selectivity in a Modulated Thermal Infrared Emitter with Lock-In Detection |
| title_full | Virtual Spectral Selectivity in a Modulated Thermal Infrared Emitter with Lock-In Detection |
| title_fullStr | Virtual Spectral Selectivity in a Modulated Thermal Infrared Emitter with Lock-In Detection |
| title_full_unstemmed | Virtual Spectral Selectivity in a Modulated Thermal Infrared Emitter with Lock-In Detection |
| title_short | Virtual Spectral Selectivity in a Modulated Thermal Infrared Emitter with Lock-In Detection |
| title_sort | virtual spectral selectivity in a modulated thermal infrared emitter with lock in detection |
| topic | thermal emitter blackbody lock-in amplifier Fourier series optical gas sensor gas detection |
| url | https://www.mdpi.com/1424-8220/22/14/5451 |
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