Food for thought, the AEL for a Class IIA laser is .95 mW into a 7 mm eye pupil. AEL = Accessable Emission Limits. Class IIA basically means the blink reflex of your eye will protect you 99.9999 percent of the time. Most of us here can tell you that 1 millwatt in the eye hurts like a bitch.
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For industrial and certain public use the license free limit pops up to 4.95 mW. Prolonged eye exposure to a non-moving, high quality, 5 mW beam hurts like a half kick in the balls, can be very dis-orienting, and you wont do it very often.
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Some place around 15-20-25 mW CW, temporary scarring of the retina can happen for a very high quality beam, in some individuals. Ten mW of Qswitched light with its very high peak power would be more then enough to scare me. I'd have to look at a chart and do some math, but lets call just 10-20 mW of what you could have as being very damaging with a small beam diameter. I may be way off, but that is the number that sticks in my head for a Q-Switched Yag...
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We've seen video cameras get dead pixels with 5-10 Milliwatts of CW light, if they have a decent lens.
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So it does not take much. The exact threshold for retinal damage is difficult to assess in a single post.
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That Q-Switch in your laser lets it discharge the laser rod in a quick spike or series of spikes. Think capacitor discharge into a shorted load. ND:Yag has a storage time constant of about 250 microseconds, and a huge storage depth per unit volume. For yours, a guess would be a 40 to 150 nanosecond pulse if the Q-switch is active. Which makes the pulsed laser a whole new ballgame in terms of safety! When the Acoustic Q-Switch is active, it causes a loss in the cavity, preventing lasing. Energy gets stored in the rod, waiting to be dumped. When the Q-Switch opens, that rod will lase again in a pulse with very high peak power. If your laser is what I think it is, an optimal rate would be between 6,000 and 15,000 fast pulses per second.
Yet it can also lase CW, and will at greatly reduced power.
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If your working with VFDs for motors, I'm starting to be encouraged.
Steve
Last edited by mixedgas; 07-28-2016 at 15:27.
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