Classes on Biomedical Optics:Class 1-Radiative Sources

The Oregon Graduate Institute (OGI) has been an amazing source of information throughout the simulation part of this project.
Here is the link to their course on Biomedical Optics:
http://omlc.ogi.edu/classroom/ece532/
From what I have understood, this course deals with how light is transported through a biological tissue.I have summarised it to make it clear to myself:
Class 1:Radiative Sources
If we put a power source in a box,and capture all the energy radiating from it,the rate of increase of the box's energy,per second, is its radiant power.
If we leave it on for a certain time,the total power output gives its radiant energy.
They have also given the example of Laser immersed in black water.
Note to myself:Maybe I could do the same kind of experiment to measure the radiation from the LED source we are going to use.

On the other hand,Radiant Intensity is the power of a source radiating energy into a cone in a particular direction, and it gives the power radiated per unit solid angle.
For instance,if we beam a flashlight onto a wall,the radiant intensity is the
power radiated x (area it falls on)/(total area).
In this case the total area is 4*pi*R^2 and the area it falls on is A.

Similarly,the radiant power per unit surface area is known as the Irradiance.

The Fluence rate,which is similar,refers to the radiant power that is present per unit cross-sectional area of a sphere.

The opposite of irradiance is given by radiant exittance which is the amount of light leaving a surface area.

A more difficult concept is Radiance, which gives the amount of light per unit solid angle(very small),per unit area(again limiting case).

Finally,they have discussed how light is collected.
Firstly,normal laser light can be collected via an aperture,and the irradiance is measured as an exponentially decreasing function of the central axis of the beam.
Secondly,an aperture is used to collect light from conical surfaces.
Thirdly,an integrating sphere is used to collect light.
Finally,the manner in which light is collected and guided by an optical fiber is explained.
An isotropic collector,which collects light with equal efficiency from all directions is also explained.
That's all with the first lecture.
When I study the next lecture , I'll be plunging deeper into biomedical optics.