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.
Electrical – How to calculate the illuminance of a laser beam
laserpowersolar cell
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For a somewhat larger photodetector, use a 10 mm, through-hole, diffused package (not water-clear), green LED as your sensor.
Something like this one:
The diffusion will provide better sensing when the laser is off-axis to the LED, compared to a water-clear one.
The reason to use a green LED is, LEDs, when used as photodetectors, are most sensitive to their predominant emission wavelength, or actually slightly shorter wavelengths.
See this link for LED as a light sensor, which touches upon the above.
In general, you can detect laser with solar panels. There is intensive research on possibilities of employing lasers in wireless power transmission (Laser Power Beaming). Laser Power Beaming have already been used in order to provide energy for remotely controlled machines (example).
It is my belief that we are 20-30 years from the point when Laser Power Beaming from orbital based photovoltaic power collectors (satellites) will be possible (remember SimCity?).
That said, it seems like you are not that into wireless power transmission. I guess you want to use laser as means of transmitting some information to an electrical circuits which get attached to humans clothes, right?
Well, I've seen (and used) few military combat simulation systems which employ lasers in order to allow soldiers to shoot at each other (without killing each other). Even those systems which are vehicle mounted did not use photovoltaic cells in order to detect laser radiation.
We could provide you with a bunch of information about photovoltaics and lasers, but I believe that your initial direction is incorrect. You can use several photodiodes scattered over the body in order to increase the coverage of your system - it will be cheaper, simpler and much more durable approach.
If sensitivity is your concern, you might want to check out for photomultiplier. These devices have very high sensitivity, but are more complex and more expensive than photodiodes. They are also much more prone to mechanical damage.
Best Answer
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).