Calculation method of long-distance laser light
If the visibility of one laser is twice that of the other, it does not mean that the visual hazard distance is also twice. In fact, the visual hazard distance will be the square root of the color difference; or 1.4 times (1.4 is the square root of 2). To understand this more accurately, check the chart above comparing 1 watt lasers. The green 1-watt laser with 88% brightness has a visual hazard distance of 25.5 NM, and the blue 1-watt laser with 3% brightness has a visual hazard distance of 4.8 NM. The apparent brightness is 88/3 or 29 times the difference, but the visual interference hazard distance is only 25.5/4.8 or 5.3 times the difference. The square root of 29 is 5.4. (The calculation result deviates from 0.1 because the graph uses rounded numbers instead of exact numbers.) This also explains why in the example of 5 mW red and green pointers, the green hazard distance (1.8 NM) is approximately red ( .9 NM), even though the visible light of the green laser is four times the visible light of the red eye (88% vs. 23%).
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Have you ever played with a Laser pointer and want to know how far its light can travel? First of all, if we assume that the laser is optimized so that its divergence angle is at the theoretical minimum, then we can use this equation to calculate its beam divergence (in radians) to get the laser pointer's launch distance. (Laser wavelength)/(π × laser aperture) Then, a little geometric figure will provide us with the size of the final illumination point of the destination. π × (beam divergence angle in radians × distance) Finally, the brightness of the target is given by dividing the output power of the laser by the spot area. In perfect darkness, the darkest light visible to the naked eye is about one billionth of a watt per square meter. However, due to the existence of urban light pollution, people usually cannot see stars that are darker than Polaris, which has an intensity of about 4 parts per billion per square meter. In contrast, the brightness of the full moon is almost one million times that of one thousandth of a watt per square meter. Finally, the power of the sun at noon is as high as 1,000 watts per square meter, which is about 500,000 times brighter than the moon.
2021-09-18 06:24:04
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