Model of Ocular Ambient Irradiance

This code is an initial simple implementation of the model described in Marro et al. 2024, "A model of ocular ambient irradiance at any head orientation".

This model allows for the calculation of ocular irradiance (irradiance received by the ocular area) based on local ambient irradiance (DNI, DHI and albedo), the sun's position (zenith and azimuth angles), and orientation of the head (pitch and yaw).

Install requirements

To use this code, it is necessary to install the two libraries it relies on: numpy and scipy. If you do not have these libraries, you can install them by running the following command:

pip install -r requirements.txt

Alternatively, you can install them one at a time using the following commands:

pip install numpy
pip install scipy

Quick Start

To use the model, you need to import the corresponding class and provide the necessary inputs.

Let's assume you have a DNI = 1.4 W/m2, a Solar Zenith Angle (SZA) of 45°, a Solar Azimuth Angle (SAA) of 180°, and you want to calculate the direct ocular irradiance with the head oriented vertically toward East.

import numpy as np
import OcularAmbientIrradiance as OAI

DNI = 1.4 # W / m2

theta = np.array([np.pi/4])
phi = np.array([np.pi])
beta = np.array([np.pi/2])
alpha = np.array([np.pi/2])

ocuIrr = OAI.OcularAmbientIrradiance()
intens = DNI * ocuIrr.F_dir(theta=theta, 
                            phi=phi,
                            beta=beta,
                            alpha=alpha)

print(intens) # result is: 0.25141949 W/m2

Example with rotating head

Consider that the head rotates 180 degrees (from 90 to 270) and is tilted downward by 15 degrees (a typical orientation for a walking person). We assume the rotation is fast enough that no change in the sun's direction is appreciable.

import numpy as np
import OcularAmbientIrradiance as OAI

ocuIrr = OAI.OcularAmbientIrradiance()

theta = np.ones(100) * np.pi/4
phi = np.ones(100) * np.pi
beta = np.ones(100) * np.radians(105)
alpha = np.array([np.pi/2 + i*np.pi/100 for i in range(100)])

DNI = 1.4 # W / m2

I_dir = DNI * ocuIrr.F_dir(theta, phi, beta, alpha)

print(I_dir)

Cite this work

@article{Marro_2024,
title = {A model of ocular ambient irradiance at any head orientation},
journal = {Computers in Biology and Medicine},
volume = {179},
pages = {108903},
year = {2024},
issn = {0010-4825},
doi = {https://doi.org/10.1016/j.compbiomed.2024.108903},
url = {https://www.sciencedirect.com/science/article/pii/S0010482524009880},
author = {Michele Marro and Laurent Moccozet and David Vernez},
}