Hi Vahid,

I've never done this before, but this is what comes to mind. Essentially, the total power would be calculated by integrating over the entire SPD, say from 380 to 780 nm. This would mean that the total power is equivalent to the total area under the curve. The first step would be to scale the entire SPD so that the area under the curve was equal to 20. Then, you could integrate over any wavelength range to get specific allocations of power.

Tony Esposito

I do appreciate your valuable reply.

This chart is from CREE company and demonstrates the light composition of two same LEDs with different temperature colors (3000K and 6500K) so the power consumption of both is 20W with the same light intensity in terms of lumens.

So your idea was one of the ways I thought of, but is it possible to have different areas under the curve for two LEDs with the same light intensity?

this made me doubtful, although it may be possible as the light compositions differ.

What's your idea, Please?

If they are both 20 W, my guess is that they would have the same area under the curve. To get the lumens, you have to take the absolute SPD (once you've scaled it) and compute its sumproduct with the V-lambda curve.

You could also reach out to CREE and ask them for the absolute SPDs.

Tony Esposito

Thank you so much for your valuable answers, Tony.

That was a precious help.

Bests

Vahid Shoaleh

If you want to calculate optical power from specific range of wavelength. You can just integrate the SPD for the range.

Same ligh intensity in terms of lumens can have different area under the curve for two LEDs. Because, light intensity in terms of lumens is calculated through sumproduct of SPD with the V-lambda curve.

And 20W is power dissipation calculated as product of current with voltage.

So, even if two LEDs has same Watt, area under curve can be different.