Optical power of Smartphone (Galaxy S20) torch

AI Thread Summary
The discussion centers on using a smartphone torch as an illumination source for a project involving phototransistors. The main challenge is determining the effective optical power to calculate the surface power density from the induced current. Despite extensive online searches and contacting Samsung tech support, specific information on the smartphone's light output was not found. A light meter was suggested as a potential solution, recalling its importance in photography. Ultimately, a Thorlabs photodetector was utilized to measure light intensity. The user noted that the photodetector's responsivity varies with wavelength, but an average responsivity provided a satisfactory estimation. The final calculated surface power density of the optical light was approximately 1.92 mW/cm² at a distance of 2.5 cm from the torch.
Techni
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Looking for effective optical power of smartphone torch
In doing a project on phototransistors I am using my smartphone as illumination source.

In order to find the responsivity of the induced current from the light, I need to know the surface power density, which I could estimate, if I knew the effective optical power of the light from the smartphone torch.

I have scoured the internet (and even contacted Samsung tech support) with no luck, and am hoping someone can help me find a source for the info.
 
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Algr said:
Perhaps a light meter would help? They used to be a critical tool in photography.

https://duckduckgo.com/?q=light+meter&atb=v314-1&ia=web
Thank you for the response.

I ended up using a Thorlabs photodetector (https://www.thorlabs.com/thorproduct.cfm?partnumber=PDA100A-EC).

While I ran into the problem with the responsivity of the photodetector being wavelength dependent, due to the smartphone torch covering a wide spectrum, choosing an average responsivity of the photodetector gives a decent enough order of magnitude estimation.
 
Techni said:
average responsivity of the photodetector gives a decent enough order of magnitude estimation.
And what number did you get?
 
I ended up with a rough estimate for the surface power density of the optical light of 1.92 mW/cm^2 at a distance of 2.5 cm normal to the torch plane (backside of the phone)
 
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