Does anyone know the equation for this? I am trying to calculate the illuminance of a laser beam. I am shining a laser onto a solar cell. The solar cell's datasheet has graphs with illuminance (lux) and I am trying to convert watts to lux.
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\$\begingroup\$ This might be more of a physics (optics) question than EE, although EEs should know this stuff, too. Keep in mind that the solar cell's characteristics are specified under the assumption of uniform illumination. If your laser is only lighting up a small spot, the results will be different. \$\endgroup\$– Dave TweedCommented Mar 29, 2017 at 21:42
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1\$\begingroup\$ Not only that, but if the solar cell doesn't have some special coating to match its response to human eye response, the response on an illuminance basis will depend on the source spectrum. Since your laser has a different spectrum than they probably assumed (solar illumination), it won't get the same photocurrent on an illuminance basis anyway. \$\endgroup\$– The PhotonCommented Mar 29, 2017 at 23:15
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\$\begingroup\$ A link to the solar cell datasheet might help to clear this up. \$\endgroup\$– The PhotonCommented Mar 29, 2017 at 23:15
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\$\begingroup\$ You measure the luminescence of lasers in Watts, measured by a tool called a laser power meter. \$\endgroup\$– tuskiomiCommented Mar 30, 2017 at 4:35
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\$\begingroup\$ luminescence of the beam or the dot? \$\endgroup\$– tuskiomiCommented Jun 22, 2017 at 18:42
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As tuskiomi said above: Use a laser power meter, which will give you watts. (A solar cell will not give you an accurate power measurement because it is illuminated unevenly).
Once you have watts, find the luminous efficacy of your laser in lumens/watt. Specifically, you probably want the photopic luminous efficacy, as it is a bright light. This should be fairly straightforward as your laser is (hopefully) monochromatic. Having determined the luminous efficacy, you can now find the luminous flux. Based on the beam area and luminous flux, you can now find illuminance in lumens. Err, and I think you need to multiply by the luminosity function somewhere in there. (There's a reason it's much easier to express laser power in watts).
