Radiometry, photocurrent in optics simulation

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SUMMARY

The discussion focuses on estimating the photocurrent produced by a photodiode in a simulation setup involving an LED and a wall acting as a radiometer film. The photodiode and LED are positioned 2 cm apart and tilted at 70 degrees towards the wall, which is 10 cm away. The irradiance on the wall element, dAw, is approximately 10-3 W/cm2. The user seeks to relate the known irradiance to the photocurrent using the formula for flux, incorporating the geometry and angles involved, but encounters difficulties in converting between radiance and irradiance. Alternative approaches using simulation to model the photodiode as a source are also considered.

PREREQUISITES
  • Understanding of radiometry and photocurrent generation
  • Familiarity with LED and photodiode characteristics
  • Knowledge of geometric optics, specifically angles and distances in light propagation
  • Proficiency in using simulation tools for optical modeling
NEXT STEPS
  • Research the relationship between radiance and irradiance in optical systems
  • Explore the use of Lambertian reflectance in optical simulations
  • Learn about the Invariance of radiance principle and its applications
  • Investigate simulation software capabilities for modeling photodiodes as light sources
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Optical engineers, researchers in photonics, and simulation specialists looking to understand photocurrent estimation in optical setups involving LEDs and photodiodes.

vst98
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Hi all,

I have to estimate a photocurrent produced in the following simulation setup.
Photodiode (detector) and LED (spaced 2cm) lie on one axis, oriented toward a wall (radiometer film) which is parallel to the axis and at a distance of about 10cm from the axis. How much photocurrent would an area dAw of the wall produce on the photodiode if irradiance on dAw received from the LED is known.

Further details:
- The photodiode and LED don't point directly to the wall but are tilted to 70 degrees.
- Irradiance on the dAw is in the order of 10-3 W/cm2, I will assume that the wall is totally reflecting and behaves like Lambertian scatterer.
- Geometry is known, that is detector (photodiode) area, dAw area, their distance and normal angles to the connection line are known.

It seems to me that I could use

\phi_1 = L_1\frac{dA_1*cos\theta_1*dA_2*cos\theta_2}{r^{2}}

L_1 = \frac{I_1 }{dA_1*cos\theta_1}

Φ1 is the flux (power) received by the photodiode of detector area dA1 , dA2 is the area of the
wall elment, θ1 and θ2 are angles normals of the dA1 and dA2 make with connecting line r.

If I could supstitute radiance L1 in the equation for the Φ1 I could get to the photocurrent, but L1 is expressed in terms of intensity I1 emitted from the
wall element dA1 which is in [W/sr] units and I know iradiance E, which is [W/m2].
so I got stuck here.There is also another way I can approach this problem. In simulation, I can turn the photodiode to be a source,
and get irradiance on the same dAw element from the photodiode-source and from the LED. But I am not sure if i could use this somehow to estimate the photocurrent.
 
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I'll try again to explain my problem clearly.
If I found irradiance on the wall element dAw from the LED diode to be Eled and
then independently found irradiance on the same dAw from the photodiode to be Epd
(I can make a detector area of the photodiode to be a source of rays in simulation).
Could I estimate power, or anything, which would be received on the photodiode (detector now)
from dAw when I switch on my LED source ?

Could take advantage of the Invariance of radiance here?
Anyone who has some thoughts ?