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The light meter I have is not currently available for rent but I don't mind bringing it out to games to help gauge what the output strength is of a device at 850nm wavelength.
As I explained in my previous post a light meter measuring a specific wavelength is not a reliable means of declaring a laser eye-safe. It does not tell you what the operating wavelength of the laser is so you might be getting an inaccurate reading. Before I would approve an untrusted laser for use I would test it first on a spectrum analyzer to see what the peak wavelenth is and how powerful the output is at that frequency.
For these DBAL clones for instance, can anyone answer the following questions:
Is the peak wavelength emitted by the laser 850nm?
What is the spectral width of the laser?
Think of a radio for instance, if you tune near the station you start picking up the signal but at a lower strength. As you tune to the exact center frequency of the station you see the full strength. This is a similar concept, the light meter is set for 850nm, but the laser's peak wavelength (or center frequency) could be 900nm, the light meter measuring at 850nm at this point will give a value that is below the actual output power of the 900nm laser. This value would be either larger or smaller depending on the spectral width of the laser.
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In short, using light meters alone to measure the strength of an unknown laser is not sufficient evidence to deem the laser eye-safe.
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