Lasers, we do love our lasers! From the classic Red, to the bright Green, to the sneaky, changing Violet we love the fact that we can have such a unique pointing device in our hands.
But laser pointers have undergone a few changes in recent years, and some of the changes may be hard to figure out. Times were they were all like flashlights: one end would screw off and you would insert the batteries (AAA or button cell). They would resemble this laser pointer:
Once upon a time laser pointers were pretty much a high-cost luxury item. Back in the very late 80’s they could cost around $75-100 dollars for a simple red pointer that was nothing special. It was handy for those who had to do a lot of pointing work, but other than that it was a bit too much for most people to spend on a toy.
In the 90’s the prices on red laser pointers dropped a whole lot. Now you could get simple keychain models for under $5 and entertain your cat for less than a stuffed mouse. More fancy models still existed, but even they had come down in price. All of these laser pointers had one thing in common: they used a low cost red LED diode that projected a beam at 630nm. This was ok, but not a very visible pointer. Today a decent pen-length model can go from $10 to $30
Then came green laser pointers. At first they were very expensive: A basic model cost around $500 in 1999. But like the red models they soon came down in price, although they never quote reached the $5 level of the red models, they certain became more affordable. Now a green laser goes from $30-$150 depending on who is selling it.
Green laser pointers project a beam at a 532nm wavelength and generally have no greater output than the red laser pointers. Yet they are still very popular. Why? Because the human eye perceives the wavelength region around 532nm much better than the region around 630nm (red laser pointers). This video we made years ago illustrates this effect quite nicely:
Green lasers are bright enough that their beams can be visible under night conditions, so they are even used in astronomy to point towards objects in the night sky.
These days a third color of laser pointer has entered the fray (ignoring the very expensive ‘True Blue’ models, mind you). This is the 405nm wavelength Violet/Blue laser pointer.
405nm is not as visible as the 532nm Green Laser pointers, but 405nm does have other advantages. It is a wavelength that has industrial uses, and since it is a wavelength that is verrry close to the upper end of the human eye’s spectrum it actually is almost in the Ultraviolet spectrum. This has many uses, but one of the most interesting effects with how the human perceives the beam point. If it sits on a bright, white surface the point appears to be one color, but aim it at a not so bright, white surface and it appears a different color. This is an effect similar to what happens when you point an ultraviolet light at piece of bleached white clothing.
More fun, however, is what happens when you point the Violet/Blue laser pointer at popular Glow-In-The-Dark toys. We illustrate what happens in this video:
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