Today I made the led (1050nm) circuit inside a box as given in my previous elog. Steve drilled a 1mm hole in the box as an aperture for led light.
Resistance (R) used = 665 .
We connected a power supply and IR has been detected using the card.
Later we changed the input voltage and measured the optical power using a powermeter.
Since the optical power values are very less, we may need to drill a larger hole.
Now the hole is approximately 7mm from led, therefore aperture angle is approximately 2*tan-1(0.5/7) = 8deg. From radiometric curve given in the datasheet of LED1050E, most of the power is within 20 deg. So a hole of size 2* tan(10) *7 = 2.5mm may be required.
I have also attached a photo of the led beam spot on the IR detection card.