A fluorescence temperature measurement signal processing method based on phase demodulation

Abstract

A fluorescence temperature measurement signal processing method based on phase demodulation, which relates to the technical field of temperature measurement. In the present invention, a cosine signal is used to drive a light source; after being excited by the light source, a fluorescent material emits fluorescence of the same frequency; after AC amplification, the fluorescence signal and the cosine drive signal form a set of elliptical curves; the least square fitting algorithm is used to obtain the elliptical curve coefficients and calculate the fluorescence lifetime; polynomial fitting is used to obtain the conversion relationship between the fluorescence lifetime and the temperature. This method can effectively improve the accuracy of fluorescence temperature measurement and reduce noise interference.

Description

Technical Field

[0001] The present invention relates to the technical field of temperature measurement, and particularly to a fluorescence temperature measurement signal processing method based on phase demodulation. Background Art

[0002] The working mechanism of fluorescence temperature measurement is based on the physical phenomenon of photoluminescence, and has the characteristics of being insensitive to light intensity changes, not affected by electromagnetic interference, high reliability, strong adaptability, etc., and can be widely applied to various industrial environments. Theoretically, after the excitation light disappears, the fluorescence afterglow decays exponentially. By measuring the decay time, the temperature at the measurement point can be obtained. However, affected by system noise and the non-monochromaticity of the fluorescence signal, the actually measured fluorescence decay curve often does not satisfy the single exponential decay relationship, resulting in inaccurate fluorescence lifetime inversion and relatively poor temperature measurement accuracy. Summary of the Invention

[0003] In view of the above problems, the present invention provides a fluorescence temperature measurement signal processing method based on phase demodulation to further improve the temperature measurement accuracy.

[0004] The object of the present invention is achieved by the following technical solutions:

[0005] A fluorescence temperature measurement signal processing method based on phase demodulation, characterized in that the steps are as follows:

[0006] Step 1: Use a cosine signal to drive a light source to emit cosine light;

[0007] Step 2: After the fluorescent material is excited by the light source, it emits fluorescence of the same frequency. After AC amplification, the relationship between the fluorescence signal and time is obtained;

[0008] Step 3: Draw an ellipse curve with the cosine drive signal as the abscissa and the fluorescence signal obtained in step 2 as the ordinate;

[0009] Step 4: Use the least squares fitting algorithm to obtain the ellipse curve coefficients and calculate the fluorescence lifetime;

[0010] Step 5: Use the least squares method for quadratic polynomial fitting to obtain the conversion relationship between the fluorescence lifetime and the temperature, and obtain the temperature value through the fluorescence lifetime.

[0011] In step 1, the relationship between the cosine signal and time is as follows:

[0012] S = cos(2πft)

[0013] Where S is the drive signal, f is the signal frequency, and t is the time.

[0014] In step 2, the relationship between the fluorescence signal and time is as follows:

[0015]

[0016] Among them, I is the fluorescence signal, and A is the fluorescence intensity. is the phase difference; the phase difference has the following relationship with the fluorescence lifetime:

[0017]

[0018] Among them, τ is the fluorescence lifetime.

[0019] The drive signal and the fluorescence signal in step 3 satisfy the following relationship:

[0020] S 2 + C1I 2 - C2SI + C3 = 1

[0021] Among them, C1, C2, and C3 are fitting coefficients, and the values are determined by least-squares fitting calculation of the drive signal and the fluorescence signal according to the above formula.

[0022] The following formula is used for calculating the fluorescence lifetime in step 4:

[0023]

[0024] The quadratic polynomial in step 5 is:

[0025] T = a0τ 2 + a1τ + a2

[0026] Among them, T is the temperature to be measured, and a0, a1, and a2 are polynomial fitting coefficients, and the values are obtained through temperature calibration.

[0027] The beneficial effects of the present invention are:

[0028] By comparing the phase difference between the excitation light signal and the fluorescence signal, the decay time can be directly calculated by the method of the present invention, avoiding the error caused by the inconsistency between the theoretical model and the actual signal, and improving the accuracy of fluorescence temperature measurement.

[0029] The present invention calculates the fluorescence lifetime by using the elliptic curve relationship between the drive signal and the fluorescence signal, has no high requirements for the sampling rate of the fluorescence signal, and does not require integer-period sampling, reducing the performance requirements and design difficulty of the hardware sampling module.

[0030] The least-squares fitting algorithm adopted by the present invention can effectively reduce the interference of system random noise and improve the accuracy of fluorescence temperature measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a flowchart of the fluorescence temperature measurement signal processing method based on phase demodulation of the present invention;

[0032] Figure 2 The elliptic curve of the drive signal and the fluorescence signal of the present invention.

[0033] Figure 3 The fitting curve of the fluorescence lifetime obtained by the present invention and the measured temperature. Detailed implementation manners

[0034] The following combines the accompanying drawings and embodiments to further describe in detail the specific implementation manners of the present invention. The following embodiments are used to illustrate the present invention, but are not used to limit the scope of the present invention.

[0035] In this embodiment, a red fluorescent material is used as a sensing substance to provide a fluorescence temperature measurement signal processing method based on phase demodulation. As Figure 1 shown, it includes the following steps:

[0036] Step 1: Use a cosine signal to drive the light source to emit cosine light;

[0037] In this embodiment, the cosine frequency f = 20 Hz;

[0038] The relationship between the cosine signal and time is as follows:

[0039] S = cos(2πft)

[0040] where S is the drive signal, f is the signal frequency, and t is the time;

[0041] Step 2: After the fluorescent material is excited by the light source, it emits fluorescence of the same frequency. After AC amplification, the relationship between the fluorescence signal and time is as follows:

[0042]

[0043] where I is the fluorescence signal, A is the fluorescence intensity, is the phase difference;

[0044] In this embodiment, the fluorescence signal is normalized, and A = 1 is set;

[0045] The phase difference has the following relationship with the fluorescence lifetime:

[0046]

[0047] where τ is the fluorescence lifetime;

[0048] Step 3: Draw an elliptic curve with the cosine drive signal as the abscissa and the fluorescence signal as the ordinate;

[0049] The drive signal and the fluorescence signal satisfy the following relationship:

[0050] S2 + C1I 2 - C2SI + C3 = 1

[0051] Among them, C1, C2, and C3 are fitting coefficients, and their values are determined by least squares fitting calculation of the driving signal and the fluorescence signal according to the above formula.

[0052] In this embodiment, the fluorescence signal for 1 s was collected at a sampling rate of 1 kHz, and the elliptical curve relationship between the driving signal and the fluorescence signal as shown in Figure 2 was plotted. Through fitting calculation, the coefficients of the elliptical equation are: C1 = 0.99970885, C2 = 0.79835229, C3 = 0.63762297;

[0053] Step 4: Use the least squares fitting algorithm to obtain the coefficients of the elliptical curve and calculate the fluorescence lifetime;

[0054] The fluorescence lifetime is calculated using the following formula:

[0055]

[0056] In this embodiment, through calculation, the fluorescence lifetime τ = 0.00599913 s;

[0057] Step 5: Use the least squares method to perform quadratic polynomial fitting to obtain the conversion relationship between the fluorescence lifetime and the temperature;

[0058] The quadratic polynomial is:

[0059] T = a0τ 2 + a1τ + a2

[0060] Among them, T is the temperature to be measured, and a0, a1, and a2 are polynomial fitting coefficients. Their values are obtained through temperature calibration. The specific method is: set several standard temperatures, measure the corresponding fluorescence lifetimes, and perform least squares polynomial fitting calculation on the two according to the above formula to obtain the polynomial coefficients;

[0061] In this embodiment, through temperature calibration, the curve relationship between the temperature and the fluorescence lifetime between 20°C and 150°C was obtained, as shown in Figure 3 shown.

[0062] Through least squares fitting, the polynomial coefficients are: a0 = -1.0884, a1 = -51.9352, a2 = 360.26338.

Claims

1. A fluorescence temperature measurement signal processing method based on phase demodulation, characterized in that The steps are as follows: Step 1: Use a cosine signal to drive a light source to emit cosine light. Step 2: After the fluorescent material is excited by the light source, it emits fluorescence of the same frequency. After AC amplification, the relationship between the fluorescence signal and time is obtained. Step 3: Plot an elliptical curve with the cosine drive signal as the abscissa and the fluorescence signal obtained in Step 2 as the ordinate. Step 4: Use the least squares fitting algorithm to obtain the elliptical curve coefficients and calculate the fluorescence lifetime. Step 5: Use the least squares method for quadratic polynomial fitting to obtain the conversion relationship between the fluorescence lifetime and temperature, and obtain the temperature value through the fluorescence lifetime.

2. The method for processing fluorescence temperature measurement signals based on phase demodulation according to claim 1, characterized in that, In Step 1, the relationship between the cosine signal and time is as follows: S = cos(2πft) where S is the drive signal, f is the signal frequency, and t is the time.

3. A fluorescence temperature measurement signal processing method based on phase demodulation according to claim 1, characterized in that, In Step 2, the relationship between the fluorescence signal and time is as follows: where I is the fluorescence signal and A is the fluorescence intensity, is the phase difference; the phase difference has the following relationship with the fluorescence lifetime: where τ is the fluorescence lifetime.

4. A fluorescence temperature measurement signal processing method based on phase demodulation according to claim 1, characterized in that In Step 3, the drive signal and the fluorescence signal satisfy the following relationship: S 2 +C1I 2 -C2SI + C3 = 1 where C1, C2, and C3 are fitting coefficients, and the values are determined by least squares fitting calculation of the drive signal and the fluorescence signal according to the above formula.

5. A fluorescence temperature measurement signal processing method based on phase demodulation according to claim 1, characterized in that, In Step 4, the fluorescence lifetime is calculated using the following formula:

6. The fluorescence temperature measurement signal processing method based on phase demodulation according to claim 1, wherein, In Step 5, the quadratic polynomial is: T = a0τ 2 + a1τ + a2 where T is the temperature to be measured, and a0, a1, and a2 are polynomial fitting coefficients, and the values are obtained through temperature calibration.

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