Q. What is the feature of LED pens?

Answer

A LED pen is a cathode ray tube housed in the shape of a light-sensitive wand used as a light-sensitive pointing instrument. The sensors in a light pen scan all of the pixels at once to create 2D or 3D representations of whatever is being scanned. Since the entire pixel is scanned in one go, the time it takes for the electron beam from the CRT to traverse the complete display may be measured. For use in low-light situations, light pens feature an internal battery and an LED light at their tip. The scanning speed and angle of a light pen's calibration probe determine its precision.