- Joined
- Oct 26, 2007
- Messages
- 5,438
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- 83
That's not right. Under the same beam conditions (power, spot size), red will never look as bright as green under any viewing conditions (e.g. photopic, scotopic vision). In fact, as view conditions become darker, the eye becomes even less sensitive to red, and more sensitive to greens around 532nm (and more sensitive to blues). The only way light from a red laser may appear brighter is if the 532 spot is much larger, and therefore less concentrated, than the 635/638/640nm at the same distance. That may be the case due to the 532nm lasers usually having poor divergence, which is really more of a collimation issue.
Also, for brightness, the only reason you should tolerate a shift towards longer wavelengths is if the beam profile is better. Brightness drops off rapidly the longer the wavelength for reds. If anything, you want them shifted more towards shorter wavelengths, as this makes them brighter. I've been suspecting that there's a sweet spot in terms of brightness for these high-powered 638nm diodes: where the wavelength shift due to power output reduces the perceived brightness more than the additional power. That would be the optimal power level for tuning lasers.
The best overall everything would be a 635nm, or shorter wavelength red like red HeNe wavelengths, with great beamspecs. The closest thing we have to that, cheaply, is the single-mode 638nm laser diode that is currently out, or perhaps those multimode variants if you can tame the divergence.
Maybe the solution will be some awful multimode 635nm-ish diodes that put out so much power that it isn't really that terrible to waste some on a lens that cuts off the sides to gain a better looking beam (like Lazereer's long-focal length lens).
Nice units. Thanks.
