A laser pointer or laser pen is a small portable and visible laser designed to highlight something of interest by projecting a small bright spot of colored light onto it. The small width of the beam and low power of typical laser pointers make the beam itself invisible in a reasonably clean atmosphere, showing a point of light when striking an opaque surface.
Some super-powerful laser pointers project a visible beam via scattering from dust particles or water fog droplets along the beam path. Blue laser pointers and green laser pens may have a visible beam even in clean air because of Rayleigh scattering from air molecules, especially when viewed in moderately-to-dimly lit conditions. The intensity of such scattering increases when these beams are viewed from angles near the beam axis. Such led lasers, particularly the Green laser pointers are used as astronomical-object pointers for teaching purposes, in the same general manner as flashlights.
The recent low-cost availability of infrared (IR) diode laser modules of up to 1000 mW (1 watt) output has created a generation of IR-pumped frequency-doubled (DPSS) green laser pointer pens, blue led laser pen pointers, and violet laser pens, of super powerful laser (100–300 mW). Because the IR in the beams of LED lasers is difficult to filter and contributes heat which is difficult to dissipate in a pocket laser pointer package, it is often left as a beam component in cheaper higher power laser pointers.
