Calculate optical power output of LEDs

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To calculate the optical power output of LEDs, a photodiode is used to measure photocurrent at various wavelengths, applying the formula R = I/P, where R is responsivity, I is photocurrent, and P is optical power. The user reports obtaining a very low optical power output of 0.027 mW for an LED rated at 17,000 lumens, raising concerns about the accuracy of the calculation. The discussion suggests reviewing raw data and methods, questioning whether a sum is appropriate instead of an integral for accurate results. There is a need for clarification on the calculation approach to ensure correct optical power measurements. Accurate calculations are essential for reliable LED performance assessments.
Sophie MC
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Hi guys,

I have to calculate de optical power output of a set of LEDs. For that I used a photodiode to measure the photocurrent at each wavelength and then calculate the optical power at each wavelength using the following formula:

R (A/W) = I/P,

where R is the responsivity of the photodiode at each wavelength,
I is the photocurrent measure with the photodiode at each wavelength and
P is the optical power output at each wavelength that I want to measure.

I have de responsivity curve of my photodiode and I have measure the photocurrent. However when calculating de optical power output I obtain very small values.

For example, for a LED with typical 17000 mlm (from datasheet), I only obtain 0,027 mW (summation of all wavelegths) of optical power. I think that this is a very small value comparing with the value in lumens (17000 mlm).

Can any on help with this? Am I right? Am I wrong? Is this the right way of calculate optical power?

Thank you so much
 
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We would have to see your raw data and your methods to comment.

Are you using a sum where an integral is needed?
 
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