Case Study : A 10 nano-Watt Light Source for Routine Production
Generating a precise, stable low intensity light pulse can be a complex design problem. Measuring low light levels whether with a calibrated PIN photodiode or thermopile is fraught with difficulties such as back ground light, sources of heat and instrumentation drift. The Phos-4 can be used to provide a solution to this problem. The method is based on making a pair of measurements at high and low current. This allows the ratio of the intensities between the two currents to be known. First pair of measurements is made with the LED Module positioned adjacent to the fibre optic mount to maximise the powers. The LED module is then moved away until the power at the maximum current is the desired output intensity times the intensity ratio. The LED current is then simply switched to the lower current, giving the desired optical intensity.