Tuesday, February 16, 2010

What Makes a Good Laser Pointer

Best 5mW Laser Pointers Part 2

The first step to shopping for a good laser pointer is to know what we are looking for. What are the criteria that you might want to use when choosing a good 5mW presenter laser pointer?

  • APC Power regulation: the power is constantly measured by the laser circuitry, and properly regulated to remain at 5mW or whatever the nominal power is -this regulation is typically referred to as APC, Auto Power Control. Lasers without APC may see their output power vary: at any time they may become more powerful than their nominal power calls for and become more dangerous, or, conversely, weaker than their nominal power, and therefore less useful.
  • IR Filter: in some wavelengths, in particular green, good pointers also have an infrared (IR) filter for better eye protection. Even though the output power we are looking for is 5mW, the actual diodes (or other devices) generating the original beam use much higher power, such as, for instance, 250mW. In some cases (green is one) there can be significant leakage in the IR wavelengths, meaning that, unless there is an IR filter on the pointer, the damage to eyes or materials can be equivalent to a device many times more powerful than 5mW. What makes IR radiation is so dangerous is that it will severely and permanently damage the eye without being noticed by the user before it is too late, since the IR beam is  invisible to the eye. Red lasers do not leak in the IR range, do not need a filter, and are therefore intrinsically safer.
  • Size: it is compact, small enough to be put on a keyring, or to wear as a pen in a pocket
  • Storage: there is a pocket clip for larger ones, or a way to store it on a key ring for smaller ones
  • Laser power: the actual laser power is reliably close to nominal, for all units manufactured, and is reliably the same, time after time, when you use your laser pointer. Some brands are known for often providing under- or over-powered devices. In many off brand devices, power changes from use to use due to poor connections or engineering.
  • Power source: the battery is a commonly used battery (AAA, or AA, if at all possible) that is small enough to keep the device compact, yet large enough to provide many hours of use. Avoid "watch" batteries, which power most cheap laser pointers.
  • Reliability: the casing is solid, if possible metal, the threads are deep, the device is sturdy and well engineered.  The on/off switch feels good and lasts for a long time. Most laser pointers are not branded or, if branded, carry unknown brands, and suffer from low reliability. 
  • Brand: The average unbranded laser pointer is a pointer without APC or IR filter, and may be dangerous to its user, even if nominally a 5mW device. To pick a good laser pointer, it is essential to specifically choose brands and models with proven reliability and track record. If you pick a cheap, no-name laser, then let it be a red one so that at least there is no IR danger.
  • Cost: always one element of choice

Tomorrow, we will discuss how we researched the best options in selecting laser pointers... So come back soon!

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