Fluorescence sensing system

1. A portable fluorescence sensing device comprising:

a light source for exciting a sensor material;

a photo-detector for collecting the fluorescence emitted from the sensor material; and

a controller coupled to the photo-detector;

wherein the controller is configured to:

analyse the fluorescence signal collected by the photo-detector;

analyse a peak intensity, Vp, and a valid fluorescence intensity signal, V valid intensity , of the fluorescence signal; and

adjust the output power of the light source based on the analysis.

2. The device of claim 1 , wherein the valid fluorescence intensity signal, V valid intensity , of the fluorescence signal is calculated by the equation V valid intensity =V p −V b , wherein V b corresponds to the intensity of ambient light.

3. The device of claim 2 , further wherein the controller is configured to measure the intensity of the ambient light before the light source is powered on.

4. The device of claim 1 , wherein the controller is configured to compare the measured peak intensity of the fluorescence signal, V p , to a saturation intensity threshold value; and

decrease the output power of the light source if the peak intensity of the fluorescence signal is determined to be greater than the saturation intensity threshold value.

5. The device of claim 4 , further wherein if the controller determines that the peak intensity of the fluorescence signal is less than the saturation intensity threshold value, the controller is configured to determine whether the measured valid fluorescence intensity signal of the fluorescence signal, V valid intensity , is within a predefined operating range, and;

if the valid fluorescence intensity signal is greater than the predefined operating range, the controller is configured to decrease the output power of the light source; and

if the valid fluorescence intensity signal is less than the predefined operating range, the controller is configured to increase the output power of the light source.

6. The device of claim 5 , wherein the saturation intensity threshold value and the predefined operating range are programmable.

7. The device of claim 1 , wherein the light source comprises a variable resistive load, and wherein the output power of the light source is adjusted by varying the resistive load.

8. The device of claim 7 , wherein the resistive load comprises a plurality of channels, each channel comprising a resistor in series with a switch, and wherein the controller controls the operation of each of the switches to vary the resistive load.

9. The device of claim 8 , wherein each of the resistors comprises a different resistive value.

10. The device of claim 9 , wherein the resistive load comprises five channels, and wherein the values of the resistors in the channels are set to R, 2R, 4R, 8R and 16R.

11. The device of claim 1 , wherein the controller comprises a Field Programmable Gate Array, FPGA or a micro-controller.

12. The device of claim 1 , wherein the sensor material comprises a fluorescent substance which is present in a sample for detection.

13. A method for adjusting the incident light power in a portable fluorescence sensing device, the fluorescence sensing device comprising a light source for exciting a sensor material, and a photo-detector for collecting the fluorescence emitted from the sensor material, the method comprising the steps of:

analysing the fluorescence signal collected from the photo-detector;

analyse a peak intensity, Vp, and a valid fluorescence intensity signal, V valid intensity , of the fluorescence signal; and

adjusting the output power of the light source based on the analysis.

14. A computer program product, comprising a computer usable medium having a computer readable program code embodied therein, said computer readable program code adapted to be executed to implement a method according to claim 13 .