Laser Pointer Pen

A laser pointer pen is a portable, pen-sized laser designed to be held in the hand, and most commonly used to project a point of light to highlight items of interest during a presentation. A laser pointer pen has a low-enough power that the projected beam is not visible from the side in normal clear air, but is only visible as a point of light where the laser pointer pen’s beam strikes a diffusely reflective surface. Another type of higher powered laser pointer pen has visible laser via Rayleigh scattering when viewed from the side in moderately to dimly lit conditions.

Mostly an inexpensive laser pointer pen uses a deep red laser diode near 670/650 nm wavelength. A slightly more expensive laser pointer pen uses a brown-orange 635 nm diode, making them more easily visible than their 670 nm counterparts due to the greater sensitivity of the human eye at 635 nm. Other colors are possible too, with the 532 nm green laser pointer pen being the most common alternative. In the past few years, yellow-orange a laser pointer pen, at 593.5 nm, has been made available. In September 2005, a handheld blue laser pointer pen at 473 nm also became available.

The apparent brightness of a spot from a laser pointer pen beam depends not only on the optical power of the laser and the reflectivity of the surface, but also on the color response of the human eye. For the same optical power, the green laser pointer pen will seem brighter than other colors because the human eye is most sensitive in the green area of spectrum (for low light levels), with sensitivity decreasing as colors become redder or bluer.

The output power of a laser pointer pen is measured in milliwatts (mW). In Europe/UK the legal requirement is that laser pointer pen outputs not exceed 1 mW; in USA this output is limited to 5 mW for presentation lasers.

A laser pointer pen is often used in school and business presentations and visual demonstrations as an eye-catching pointing device. Red laser pointer pen can be used in almost any indoor or low-light situation where pointing out details by hand may be inconvenient, such as in construction work or interior decorating. Green laser pointer pen can be used for similar purposes as well as outdoors in daylight or for longer distances.

In pointing applications such as these, natural hand tremor may cause unwanted jittery motion of the laser pointer pen dot. A future laser pointer pen may solve this problem by stabilizing the laser beam from unwanted hand tremor.

A laser pointer pen can also be used as toys for pets, especially for cats in play. Some offer a selection of designs for the laser pointer pen beam to project (e.g. images of butterflies, mice, or flowers), to provide variety. Opinions are divided on the safety of a laser pointer pen used in this way. Some consider a laser pointer pen to be a healthier alternative to the more traditional string for cats because they reduce the risk of choking on the string. Others are concerned that the laser pointer pen beam may damage pets' eyes.

A green laser pointer pen can also be used for skygazing. On a moonless night, a green laser pointer pen beam can often be clearly seen, allowing someone to accurately point out individual stars to others nearby.

A laser pointer pen should never be directed into the eyes of a person or animal or into any moving vehicle in which the driver or pilot could be distracted. The output of a laser pointer pen is generally limited to 1 mW or 5 mW in order to prevent accidental damage to the retina of human eyes. Usually, a laser pointer pen has class 2 or class 3a lasers, which require extended viewing times to damage the retina severely. The Food and Drug Administration (FDA) has determined that a class 3a laser pointer pen could cause injury to the eye if viewed directly for approximately 0.25 seconds, although it has cited evidence that exposure to visible lasers is "usually" limited by the blink reflex of the eye, which they have timed at just under 0.25 seconds.

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