Page 49 - Chapter 3 - Fundamentals of Laser/IPL Hair Removal

Chapter 3 – Fundamentals of Laser/IPL Hair Removal 1st Edition
The Important Science and Biology Involved with Hair Removal
In Chapter 1 we discussed many of the ‘fundamentals’ of light and the skin. Here, we review some of that information, briefly:
Figure 16 - Light is scattered and absorbed throughout the depth of the skin
The figure above shows how the intensity (this may be thought of as fluence too) drops as light propagates into the skin. Most of the absorption occurs in the most superficial ‘layer’ – up to 63% may be absorbed here. In the next ‘layer’, around 23% is absorbed, leaving the remaining 14% in the deeper layers. Here, a ‘layer’ is defined by the general absorption coefficient of the tissues.
This is a basic optical definition – the top ‘layer’ extends to a depth, z, where this equals one divided by the absorption coefficient (z = 1/𝜇!) where 𝜇!is the absorption coefficient. However, this is a grossly simplified definition which doesn’t really apply very well to laser/IPL skin treatments. For more about this topic, please watch our video on ‘Useful Penetration Depths’.
Basic Terms You Really Should Understand
There are a bunch of important laser terms and expression which you really should understand. These terms are used by laser users, engineers, operators, technicians etc all over the world. By understanding these expressions you will gain a deeper insight into how and why the laser treatments work. These terms are:
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