Nano Second LED Pulse

Nanosecond LED light pulses are used in a variety of applications:

• Time-resolved spectroscopy: This technique is used to study the fluorescence decay times of molecules. The short pulse of light excites the molecules, and the time it takes for the fluorescence to decay is measured. This information can be used to determine the structure and properties of the molecule

• LIDAR: LIDAR (light detection and ranging) is a remote sensing technique that uses light to measure distances. A nanosecond LED pulse is emitted, and the time it takes for the pulse to reflect off of an object and return to the detector is measured. This information can be used to create a 3D map of the environment.

• Optical communications: Nanosecond LED pulses can be used to transmit data over fiber optic cables. The pulses are modulated with the data, and the detector at the other end of the cable decodes the data.

• Biomedical imaging: Nanosecond LED pulses can be used to image cells and tissues. The pulses are used to excite fluorescent molecules, and the emitted light is used to create a map of the fluorescence intensity. This information can be used to diagnose diseases and monitor the progress of treatment.

• High-speed photography: Nanosecond LED pulses can be used to freeze motion in high-speed photography. The short pulse of light is used to illuminate the scene for a very short time, allowing the camera to capture a sharp image of the moving object.

At the rising edge of the input voltage pulse the LED starts to light. Initially L1 rejects current flowing through it, as inductors initially reject change. If L1 is small then after a nano second or 2 all the current available form R1 flows through L1, extinguishing the LED.

Of course in practical circuits you have to deal with issues like the steepness of the pulse applied to R1 and back EMF from the inductor.