Abstract

We perform a bidimensional analysis to evaluate the variation of the fluorescence decay of europium thenoyltrifluoroacetonate (EuTTA) with temperature changes. We analyze how a specific thermal distribution modifies the spatial temperature of the sensing film and we study the corresponding fluorescence response using an integral functional of the emission decay. We present experimental results of a thermal distribution registered with the EuTTA-based thermal-to-visible conversion method. Furthermore, we analyze the spatial and temporal response of the proposed sensing element by using heat-transfer theory. Based on the presented analysis, we establish the optimal thermal and physical design for the sensing element of the proposed thermal-to-visible converter.

© 2012 Optical Society of America

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References

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  1. G. Paez, M. Alfaro, and M. Strojnik, “Thermal characterization of europium thenoyltrifluoroacetonate for its use in formation of thermal images,” Proc. SPIE 6307, 63070G (2006).
    [CrossRef]
  2. M. Alfaro, G. Paez, and M. Strojnik, “Calibration and evaluation of EuTTA fluorescence as active medium for IR-to-visible conversion,” Proc. SPIE 7082, 70820U (2008).
    [CrossRef]
  3. B. Dong, X. S. Xu, X. J. Wang, T. Yang, and Y. Y. He, “Infrared-to-visible up-conversion emissions and thermometric applications of Er3+-doped Al2O3,” Appl. Phys. B 89, 281–284 (2007).
    [CrossRef]
  4. V. V. Krishtop, E. V. Tolstov, V. I. Stroganov, and A. V. Syui, “Converting IR radiation with broad-band pumping in nonlinear-optical crystals,” J. Opt. Technol. 74, 243–245 (2007).
    [CrossRef]
  5. L. N. Asnis, L. N. Kaporski, T. K. Razumova, A. S. Tibilov, and S. A. Chizhov, “Estimating the possibility of creating an uncooled, direct-conversion bolometric array based on optical pumping of a thermal image into a visible image,” J. Opt. Technol. 75, 366–370 (2008).
    [CrossRef]
  6. V. A. Pilipovich, A. K. Esman, V. K. Kuleshov, and G. L. Zykov, “Estimating the main parameters of a waveguide microcavity converter of IR images,” J. Opt. Technol. 76, 251–254 (2009).
    [CrossRef]
  7. J. Gao, Q. Zhang, B. Jiao, and D. Chen, “Optical sensitivity analysis of a bent micro reflector array in uncooled infrared imaging,” J. Micromech. Microeng. 19, 095018 (2009).
    [CrossRef]
  8. L. Salmon, G. Molinar, D. Zitouni, C. Quintero, C. Bergaud, J. Micheaud, and A. Bousseksou, “A novel approach for fluorescent thermometry and thermal imaging purposes using spin crossover nanoparticles,” J. Mater. Chem. 20, 5499–5503 (2010).
    [CrossRef]
  9. M. Alfaro, G. Paez, and M. Strojnik, “Conversion of absorbed thermal radiation into visible using europium thenoyltrifluoroacetonate,” Appl. Opt. 49, 5444–5453 (2010).
    [CrossRef]
  10. M. Alfaro, M. Strojnik, and G. Paez, “EuTTA fluorescence lifetime and spectral power characterization for its use as an active medium for IR-to-visible conversion,” Proc. SPIE 6678, 66781J (2007).
    [CrossRef]
  11. A. Rogalsky, Infrared Detectors (Taylor and Francis, 2011).
  12. J. P. Holman, Heat Transfer (McGraw-Hill, 1997).
  13. J. W. Judy, “Microelectromechanical systems (MEMS): fabrication, design and applications,” Smart Mater. Struct. 10, 1115–1134 (2001).
    [CrossRef]
  14. J. Castrellon, G. Paez, and M. Strojnik, “Remote temperature sensor employing erbium-doped silica fiber,” Infrared Phys. Technol. 43, 219–222 (2002).
    [CrossRef]
  15. G. Paez and M. Strojnik, “Erbium-doped optical fiber fluorescence temperature sensor with enhanced sensitivity, a high signal-to-noise ratio, and a power ratio in the 520-530- and 550-560-nm bands,” Appl. Opt. 42, 3251–3258 (2003).
    [CrossRef]
  16. J. Sandoval, G. Paez, and M. Strojnik, “Heat transfer analysis of a dynamic infrared-to-visible converter,” Opt. Eng. 42, 3517–3523 (2003).
    [CrossRef]
  17. V. López, G. Paez, and M. Strojnik, “Sensitivity of a temperature sensor, employing ratio of fluorescence power in a band,” Infrared Phys. Technol. 46, 133–139 (2004).
    [CrossRef]
  18. J. Sandoval, G. Paez, and M. Strojnik, “Er-doped silica dynamic IR-to-visible image converter,” Infrared Phys. Technol. 46, 141–145 (2004).
    [CrossRef]
  19. M. Strojnik-Scholl and G. Paez, “Determination of temperature distributions with micrometer spatial resolution,” Opt. Eng. 46, 036401 (2007).
    [CrossRef]

2010 (2)

L. Salmon, G. Molinar, D. Zitouni, C. Quintero, C. Bergaud, J. Micheaud, and A. Bousseksou, “A novel approach for fluorescent thermometry and thermal imaging purposes using spin crossover nanoparticles,” J. Mater. Chem. 20, 5499–5503 (2010).
[CrossRef]

M. Alfaro, G. Paez, and M. Strojnik, “Conversion of absorbed thermal radiation into visible using europium thenoyltrifluoroacetonate,” Appl. Opt. 49, 5444–5453 (2010).
[CrossRef]

2009 (2)

J. Gao, Q. Zhang, B. Jiao, and D. Chen, “Optical sensitivity analysis of a bent micro reflector array in uncooled infrared imaging,” J. Micromech. Microeng. 19, 095018 (2009).
[CrossRef]

V. A. Pilipovich, A. K. Esman, V. K. Kuleshov, and G. L. Zykov, “Estimating the main parameters of a waveguide microcavity converter of IR images,” J. Opt. Technol. 76, 251–254 (2009).
[CrossRef]

2008 (2)

2007 (4)

B. Dong, X. S. Xu, X. J. Wang, T. Yang, and Y. Y. He, “Infrared-to-visible up-conversion emissions and thermometric applications of Er3+-doped Al2O3,” Appl. Phys. B 89, 281–284 (2007).
[CrossRef]

M. Alfaro, M. Strojnik, and G. Paez, “EuTTA fluorescence lifetime and spectral power characterization for its use as an active medium for IR-to-visible conversion,” Proc. SPIE 6678, 66781J (2007).
[CrossRef]

V. V. Krishtop, E. V. Tolstov, V. I. Stroganov, and A. V. Syui, “Converting IR radiation with broad-band pumping in nonlinear-optical crystals,” J. Opt. Technol. 74, 243–245 (2007).
[CrossRef]

M. Strojnik-Scholl and G. Paez, “Determination of temperature distributions with micrometer spatial resolution,” Opt. Eng. 46, 036401 (2007).
[CrossRef]

2006 (1)

G. Paez, M. Alfaro, and M. Strojnik, “Thermal characterization of europium thenoyltrifluoroacetonate for its use in formation of thermal images,” Proc. SPIE 6307, 63070G (2006).
[CrossRef]

2004 (2)

V. López, G. Paez, and M. Strojnik, “Sensitivity of a temperature sensor, employing ratio of fluorescence power in a band,” Infrared Phys. Technol. 46, 133–139 (2004).
[CrossRef]

J. Sandoval, G. Paez, and M. Strojnik, “Er-doped silica dynamic IR-to-visible image converter,” Infrared Phys. Technol. 46, 141–145 (2004).
[CrossRef]

2003 (2)

2002 (1)

J. Castrellon, G. Paez, and M. Strojnik, “Remote temperature sensor employing erbium-doped silica fiber,” Infrared Phys. Technol. 43, 219–222 (2002).
[CrossRef]

2001 (1)

J. W. Judy, “Microelectromechanical systems (MEMS): fabrication, design and applications,” Smart Mater. Struct. 10, 1115–1134 (2001).
[CrossRef]

Alfaro, M.

M. Alfaro, G. Paez, and M. Strojnik, “Conversion of absorbed thermal radiation into visible using europium thenoyltrifluoroacetonate,” Appl. Opt. 49, 5444–5453 (2010).
[CrossRef]

M. Alfaro, G. Paez, and M. Strojnik, “Calibration and evaluation of EuTTA fluorescence as active medium for IR-to-visible conversion,” Proc. SPIE 7082, 70820U (2008).
[CrossRef]

M. Alfaro, M. Strojnik, and G. Paez, “EuTTA fluorescence lifetime and spectral power characterization for its use as an active medium for IR-to-visible conversion,” Proc. SPIE 6678, 66781J (2007).
[CrossRef]

G. Paez, M. Alfaro, and M. Strojnik, “Thermal characterization of europium thenoyltrifluoroacetonate for its use in formation of thermal images,” Proc. SPIE 6307, 63070G (2006).
[CrossRef]

Asnis, L. N.

Bergaud, C.

L. Salmon, G. Molinar, D. Zitouni, C. Quintero, C. Bergaud, J. Micheaud, and A. Bousseksou, “A novel approach for fluorescent thermometry and thermal imaging purposes using spin crossover nanoparticles,” J. Mater. Chem. 20, 5499–5503 (2010).
[CrossRef]

Bousseksou, A.

L. Salmon, G. Molinar, D. Zitouni, C. Quintero, C. Bergaud, J. Micheaud, and A. Bousseksou, “A novel approach for fluorescent thermometry and thermal imaging purposes using spin crossover nanoparticles,” J. Mater. Chem. 20, 5499–5503 (2010).
[CrossRef]

Castrellon, J.

J. Castrellon, G. Paez, and M. Strojnik, “Remote temperature sensor employing erbium-doped silica fiber,” Infrared Phys. Technol. 43, 219–222 (2002).
[CrossRef]

Chen, D.

J. Gao, Q. Zhang, B. Jiao, and D. Chen, “Optical sensitivity analysis of a bent micro reflector array in uncooled infrared imaging,” J. Micromech. Microeng. 19, 095018 (2009).
[CrossRef]

Chizhov, S. A.

Dong, B.

B. Dong, X. S. Xu, X. J. Wang, T. Yang, and Y. Y. He, “Infrared-to-visible up-conversion emissions and thermometric applications of Er3+-doped Al2O3,” Appl. Phys. B 89, 281–284 (2007).
[CrossRef]

Esman, A. K.

Gao, J.

J. Gao, Q. Zhang, B. Jiao, and D. Chen, “Optical sensitivity analysis of a bent micro reflector array in uncooled infrared imaging,” J. Micromech. Microeng. 19, 095018 (2009).
[CrossRef]

He, Y. Y.

B. Dong, X. S. Xu, X. J. Wang, T. Yang, and Y. Y. He, “Infrared-to-visible up-conversion emissions and thermometric applications of Er3+-doped Al2O3,” Appl. Phys. B 89, 281–284 (2007).
[CrossRef]

Holman, J. P.

J. P. Holman, Heat Transfer (McGraw-Hill, 1997).

Jiao, B.

J. Gao, Q. Zhang, B. Jiao, and D. Chen, “Optical sensitivity analysis of a bent micro reflector array in uncooled infrared imaging,” J. Micromech. Microeng. 19, 095018 (2009).
[CrossRef]

Judy, J. W.

J. W. Judy, “Microelectromechanical systems (MEMS): fabrication, design and applications,” Smart Mater. Struct. 10, 1115–1134 (2001).
[CrossRef]

Kaporski, L. N.

Krishtop, V. V.

Kuleshov, V. K.

López, V.

V. López, G. Paez, and M. Strojnik, “Sensitivity of a temperature sensor, employing ratio of fluorescence power in a band,” Infrared Phys. Technol. 46, 133–139 (2004).
[CrossRef]

Micheaud, J.

L. Salmon, G. Molinar, D. Zitouni, C. Quintero, C. Bergaud, J. Micheaud, and A. Bousseksou, “A novel approach for fluorescent thermometry and thermal imaging purposes using spin crossover nanoparticles,” J. Mater. Chem. 20, 5499–5503 (2010).
[CrossRef]

Molinar, G.

L. Salmon, G. Molinar, D. Zitouni, C. Quintero, C. Bergaud, J. Micheaud, and A. Bousseksou, “A novel approach for fluorescent thermometry and thermal imaging purposes using spin crossover nanoparticles,” J. Mater. Chem. 20, 5499–5503 (2010).
[CrossRef]

Paez, G.

M. Alfaro, G. Paez, and M. Strojnik, “Conversion of absorbed thermal radiation into visible using europium thenoyltrifluoroacetonate,” Appl. Opt. 49, 5444–5453 (2010).
[CrossRef]

M. Alfaro, G. Paez, and M. Strojnik, “Calibration and evaluation of EuTTA fluorescence as active medium for IR-to-visible conversion,” Proc. SPIE 7082, 70820U (2008).
[CrossRef]

M. Strojnik-Scholl and G. Paez, “Determination of temperature distributions with micrometer spatial resolution,” Opt. Eng. 46, 036401 (2007).
[CrossRef]

M. Alfaro, M. Strojnik, and G. Paez, “EuTTA fluorescence lifetime and spectral power characterization for its use as an active medium for IR-to-visible conversion,” Proc. SPIE 6678, 66781J (2007).
[CrossRef]

G. Paez, M. Alfaro, and M. Strojnik, “Thermal characterization of europium thenoyltrifluoroacetonate for its use in formation of thermal images,” Proc. SPIE 6307, 63070G (2006).
[CrossRef]

V. López, G. Paez, and M. Strojnik, “Sensitivity of a temperature sensor, employing ratio of fluorescence power in a band,” Infrared Phys. Technol. 46, 133–139 (2004).
[CrossRef]

J. Sandoval, G. Paez, and M. Strojnik, “Er-doped silica dynamic IR-to-visible image converter,” Infrared Phys. Technol. 46, 141–145 (2004).
[CrossRef]

G. Paez and M. Strojnik, “Erbium-doped optical fiber fluorescence temperature sensor with enhanced sensitivity, a high signal-to-noise ratio, and a power ratio in the 520-530- and 550-560-nm bands,” Appl. Opt. 42, 3251–3258 (2003).
[CrossRef]

J. Sandoval, G. Paez, and M. Strojnik, “Heat transfer analysis of a dynamic infrared-to-visible converter,” Opt. Eng. 42, 3517–3523 (2003).
[CrossRef]

J. Castrellon, G. Paez, and M. Strojnik, “Remote temperature sensor employing erbium-doped silica fiber,” Infrared Phys. Technol. 43, 219–222 (2002).
[CrossRef]

Pilipovich, V. A.

Quintero, C.

L. Salmon, G. Molinar, D. Zitouni, C. Quintero, C. Bergaud, J. Micheaud, and A. Bousseksou, “A novel approach for fluorescent thermometry and thermal imaging purposes using spin crossover nanoparticles,” J. Mater. Chem. 20, 5499–5503 (2010).
[CrossRef]

Razumova, T. K.

Rogalsky, A.

A. Rogalsky, Infrared Detectors (Taylor and Francis, 2011).

Salmon, L.

L. Salmon, G. Molinar, D. Zitouni, C. Quintero, C. Bergaud, J. Micheaud, and A. Bousseksou, “A novel approach for fluorescent thermometry and thermal imaging purposes using spin crossover nanoparticles,” J. Mater. Chem. 20, 5499–5503 (2010).
[CrossRef]

Sandoval, J.

J. Sandoval, G. Paez, and M. Strojnik, “Er-doped silica dynamic IR-to-visible image converter,” Infrared Phys. Technol. 46, 141–145 (2004).
[CrossRef]

J. Sandoval, G. Paez, and M. Strojnik, “Heat transfer analysis of a dynamic infrared-to-visible converter,” Opt. Eng. 42, 3517–3523 (2003).
[CrossRef]

Stroganov, V. I.

Strojnik, M.

M. Alfaro, G. Paez, and M. Strojnik, “Conversion of absorbed thermal radiation into visible using europium thenoyltrifluoroacetonate,” Appl. Opt. 49, 5444–5453 (2010).
[CrossRef]

M. Alfaro, G. Paez, and M. Strojnik, “Calibration and evaluation of EuTTA fluorescence as active medium for IR-to-visible conversion,” Proc. SPIE 7082, 70820U (2008).
[CrossRef]

M. Alfaro, M. Strojnik, and G. Paez, “EuTTA fluorescence lifetime and spectral power characterization for its use as an active medium for IR-to-visible conversion,” Proc. SPIE 6678, 66781J (2007).
[CrossRef]

G. Paez, M. Alfaro, and M. Strojnik, “Thermal characterization of europium thenoyltrifluoroacetonate for its use in formation of thermal images,” Proc. SPIE 6307, 63070G (2006).
[CrossRef]

J. Sandoval, G. Paez, and M. Strojnik, “Er-doped silica dynamic IR-to-visible image converter,” Infrared Phys. Technol. 46, 141–145 (2004).
[CrossRef]

V. López, G. Paez, and M. Strojnik, “Sensitivity of a temperature sensor, employing ratio of fluorescence power in a band,” Infrared Phys. Technol. 46, 133–139 (2004).
[CrossRef]

G. Paez and M. Strojnik, “Erbium-doped optical fiber fluorescence temperature sensor with enhanced sensitivity, a high signal-to-noise ratio, and a power ratio in the 520-530- and 550-560-nm bands,” Appl. Opt. 42, 3251–3258 (2003).
[CrossRef]

J. Sandoval, G. Paez, and M. Strojnik, “Heat transfer analysis of a dynamic infrared-to-visible converter,” Opt. Eng. 42, 3517–3523 (2003).
[CrossRef]

J. Castrellon, G. Paez, and M. Strojnik, “Remote temperature sensor employing erbium-doped silica fiber,” Infrared Phys. Technol. 43, 219–222 (2002).
[CrossRef]

Strojnik-Scholl, M.

M. Strojnik-Scholl and G. Paez, “Determination of temperature distributions with micrometer spatial resolution,” Opt. Eng. 46, 036401 (2007).
[CrossRef]

Syui, A. V.

Tibilov, A. S.

Tolstov, E. V.

Wang, X. J.

B. Dong, X. S. Xu, X. J. Wang, T. Yang, and Y. Y. He, “Infrared-to-visible up-conversion emissions and thermometric applications of Er3+-doped Al2O3,” Appl. Phys. B 89, 281–284 (2007).
[CrossRef]

Xu, X. S.

B. Dong, X. S. Xu, X. J. Wang, T. Yang, and Y. Y. He, “Infrared-to-visible up-conversion emissions and thermometric applications of Er3+-doped Al2O3,” Appl. Phys. B 89, 281–284 (2007).
[CrossRef]

Yang, T.

B. Dong, X. S. Xu, X. J. Wang, T. Yang, and Y. Y. He, “Infrared-to-visible up-conversion emissions and thermometric applications of Er3+-doped Al2O3,” Appl. Phys. B 89, 281–284 (2007).
[CrossRef]

Zhang, Q.

J. Gao, Q. Zhang, B. Jiao, and D. Chen, “Optical sensitivity analysis of a bent micro reflector array in uncooled infrared imaging,” J. Micromech. Microeng. 19, 095018 (2009).
[CrossRef]

Zitouni, D.

L. Salmon, G. Molinar, D. Zitouni, C. Quintero, C. Bergaud, J. Micheaud, and A. Bousseksou, “A novel approach for fluorescent thermometry and thermal imaging purposes using spin crossover nanoparticles,” J. Mater. Chem. 20, 5499–5503 (2010).
[CrossRef]

Zykov, G. L.

Appl. Opt. (2)

Appl. Phys. B (1)

B. Dong, X. S. Xu, X. J. Wang, T. Yang, and Y. Y. He, “Infrared-to-visible up-conversion emissions and thermometric applications of Er3+-doped Al2O3,” Appl. Phys. B 89, 281–284 (2007).
[CrossRef]

Infrared Phys. Technol. (3)

J. Castrellon, G. Paez, and M. Strojnik, “Remote temperature sensor employing erbium-doped silica fiber,” Infrared Phys. Technol. 43, 219–222 (2002).
[CrossRef]

V. López, G. Paez, and M. Strojnik, “Sensitivity of a temperature sensor, employing ratio of fluorescence power in a band,” Infrared Phys. Technol. 46, 133–139 (2004).
[CrossRef]

J. Sandoval, G. Paez, and M. Strojnik, “Er-doped silica dynamic IR-to-visible image converter,” Infrared Phys. Technol. 46, 141–145 (2004).
[CrossRef]

J. Mater. Chem. (1)

L. Salmon, G. Molinar, D. Zitouni, C. Quintero, C. Bergaud, J. Micheaud, and A. Bousseksou, “A novel approach for fluorescent thermometry and thermal imaging purposes using spin crossover nanoparticles,” J. Mater. Chem. 20, 5499–5503 (2010).
[CrossRef]

J. Micromech. Microeng. (1)

J. Gao, Q. Zhang, B. Jiao, and D. Chen, “Optical sensitivity analysis of a bent micro reflector array in uncooled infrared imaging,” J. Micromech. Microeng. 19, 095018 (2009).
[CrossRef]

J. Opt. Technol. (3)

Opt. Eng. (2)

M. Strojnik-Scholl and G. Paez, “Determination of temperature distributions with micrometer spatial resolution,” Opt. Eng. 46, 036401 (2007).
[CrossRef]

J. Sandoval, G. Paez, and M. Strojnik, “Heat transfer analysis of a dynamic infrared-to-visible converter,” Opt. Eng. 42, 3517–3523 (2003).
[CrossRef]

Proc. SPIE (3)

G. Paez, M. Alfaro, and M. Strojnik, “Thermal characterization of europium thenoyltrifluoroacetonate for its use in formation of thermal images,” Proc. SPIE 6307, 63070G (2006).
[CrossRef]

M. Alfaro, G. Paez, and M. Strojnik, “Calibration and evaluation of EuTTA fluorescence as active medium for IR-to-visible conversion,” Proc. SPIE 7082, 70820U (2008).
[CrossRef]

M. Alfaro, M. Strojnik, and G. Paez, “EuTTA fluorescence lifetime and spectral power characterization for its use as an active medium for IR-to-visible conversion,” Proc. SPIE 6678, 66781J (2007).
[CrossRef]

Smart Mater. Struct. (1)

J. W. Judy, “Microelectromechanical systems (MEMS): fabrication, design and applications,” Smart Mater. Struct. 10, 1115–1134 (2001).
[CrossRef]

Other (2)

A. Rogalsky, Infrared Detectors (Taylor and Francis, 2011).

J. P. Holman, Heat Transfer (McGraw-Hill, 1997).

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Figures (12)

Fig. 1.
Fig. 1.

Proposed fluorescence-based converter. The EuTTA fluorescence emission P(t,TF) is modified by the change in film temperature TF(x,y,t), caused by the absorbed thermal distribution T(x,y). The integral value for each pixel of the visible detection system is proportional to the local temperature of the corresponding point of the film.

Fig. 2.
Fig. 2.

(a) Thermal distribution used to simulate the functional integral response to a temperature change. x and y are the spatial dimensions. (b) Change in temperature of line 50 in the x direction. We model two peaks with distinct maximums to demonstrate that our thermal-to-visible conversion method resolves temperature differences within the registered thermal distribution.

Fig. 3.
Fig. 3.

Time-dependent fluorescence decay responding to thermal changes of the sensing film. The functional value presented by each pixel over the x direction is calculated, integrating the corresponding P(t,TF) decay curve. Then, the changes in integral functional are due to differences in emission power and lifetime.

Fig. 4.
Fig. 4.

(a) Functional distribution obtained after the thermal distribution (Fig. 2) has impinged the fluorescent film. (b) Values of the integral in the x direction (y=50). The zones with smaller values of the integral are related to higher temperatures due to thermal quenching of the fluorescence of EuTTA.

Fig. 5.
Fig. 5.

Representation of a thermal image acquired with the visible emission of EuTTA. This image is the contour map of Fig. 3. The hotter zones have lower values of integral functional and, therefore, appear darker. The brighter zones correspond to higher integral values.

Fig. 6.
Fig. 6.

(a) Lateral view of the converter sensing element. We consider that the sensing element has layers of heat absorber (carbon black) and EuTTA embedded in polymer film. Each pixel is insulated from its neighbors, minimizing lateral heat diffusion. We use the values of thermal resistivity and capacity for heat absorber Rabs, Cabs, and polymer Rp and Cp in the heat-transfer analysis based on the lumped-heat-capacity formulation. (b) Node scheme utilized to model transient heat transfer within a pixel. The heat transfer takes place in one dimension, i.e., only into the pixel. qr is the thermal radiation absorbed by the sensing film. We simulate the heat transfer in order to calculate pixel dimensions and d.

Fig. 7.
Fig. 7.

Calculated step response of the polymer node as well as the fitted curve for different pixel dimensions. (a) Step response of a pixel with thermal time response τth equal to 31 ms. The pixel size corresponding to this case has the optimal dimensions to allow dynamic conversion. (b) and (c) illustrate how the physical dimensions of the pixel determine the temporal heat-transfer process. (b) Step response of a pixel with τth=2.6s, 3 orders of magnitude greater that the optimal pixel. In this case, the pixel dimensions are 1 order of magnitude larger that the pixel in (a). (c) Step response of a pixel with thermal time response equal to 3 ms. This pixel has dimensions diminished by 1 order of magnitude with respect to pixel (a). ΔTmin in each graph represents the minimum temperature change that can be measured with a variation in the integral functional IP(TF). A pixel with a thermal-response time of 3 ms is not optimal because, after τth has elapsed, the temperature change is not resolvable with EuTTA fluorescence.

Fig. 8.
Fig. 8.

Implemented experimental layout for fluorescent measurements. A thermal distribution is absorbed by the sensing film. An array of LEDs emitting at 365 nm excites the fluorescence of EuTTA. We acquire the fluorescence response with a CCD camera to register thermal distributions using fluorescence-based thermal-to-visible conversion.

Fig. 9.
Fig. 9.

(a) Experimental thermal distribution absorbed by the sensing film. (b) Thermal profile at the center of the image [dashed line in (a)]. The profile is two peaks of energy separated by 10.8 mm and with different magnitudes of maximum temperature. The sensing film absorbs this thermal distribution and changes its fluorescence properties due to temperature changes.

Fig. 10.
Fig. 10.

(a) Thermal distribution registered with the fluorescent sensing film. The converted image is captured with a CCD system. (b) Absolute value of the variation in fluorescence power. This profile is comparable with the thermal profile represented with the dashed curve.

Fig. 11.
Fig. 11.

Experimental setup for measuring thermal temporal response of the implemented fluorescent sensing film. A millimetric spot of thermal radiation heats the sensing film and we measure the thermal-response time. The physical dimensions of the spot replicate the conditions established for the theoretical analysis section, i.e., uniform temperature over a limited area and heat transfer mainly into the film.

Fig. 12.
Fig. 12.

Experimental and fitted thermal response of the sensing film. We heat the sensing film with a millimetric spot to replicate the response of a pixel. The measured τth is approximately 0.644 s. According to the calculation, such thermal-response time corresponds to a pixel with a physical of thickness of 700 μm. A pixel with a comparable time of response has 250 μm of side. These values are estimates, because in the experiment, lateral heat transfer does occur. Both curves are normalized to compare the corresponding response times.

Tables (2)

Tables Icon

Table 1. Parameters Used in the Heat-Transfer Analysis of a Pixel of the Sensing Elementa

Tables Icon

Table 2. Calculated Physical Dimensions for a Pixel of the Proposed Sensing Elementa

Equations (5)

Equations on this page are rendered with MathJax. Learn more.

IP(TF)=t0t1P0(TF)exp[tτ(TF)]dt.
·[kTF(x,y,z,t)]q(x,y,z,t)=ρcTF(x,y,z,t)t.
CeqdTFdt+GeqTF=αPth(t).
Ti,t+1=(qi+jTj,pRij)ΔτCi+(1ΔτCij1Rij)Ti,t.
T4(t)=A(1et/τth);t>0.

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