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In surplus catalogs I often see Lasers from scanners at stores advertised. Always they have a warning about their power and dangers . I would like to know how come there clerks and who use these scanners are not in any danger? These things must have considerable more power than our

There are two parts to the answer. First, the scanner beams are moving very fast. Even if you looked directly into the scanner (Do not DO IT!) the exposure would last only a very short time. As with the sun, some things are in the appropriate brightness range that staring at them can do damage which a quick glance would not cause. Second, the lasers used are fairly low power, much less than a watt. The problem is that the power is concentrated in a small beam which can focus very tightly on the retina and cause damage even when a lightbulb with comparable power output would barely be visible. Remember, the retina is irreplacable. Always use appropriate eye protection measures when working with lasers or other high power density light sources. To find out the appropriate safety measures consult with the manufacturer.

gregory r bradburn

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