Page 101 - Chapter 3 - Fundamentals of Laser/IPL Hair Removal

Chapter 3 – Fundamentals of Laser/IPL Hair Removal 1st Edition
% Energy in IPL wavebands
% energy
40
35
30
25
20
15
10
5 0
600-700 700-800
800-900 900-1000 Wavebands (nm)
1000-1100
1100-1200
Figure 37 – The energy in each 100nm waveband from an IPL unit
So, in the range 600 to 800nm, there is 57% of all the energy in the full 600-1200nm range, while in the range 600 to 900nm there is about 76% of the total energy. Between 600 and 1000nm the total percentage is 89%. So, we don’t really need anything above 1000nm – where absorption in dermal water becomes much stronger than in the lower wavelengths, leading to potentially more thermal pain!!
IPL ‘Pulse Trains’
When an IPL ‘pulse’ is fired, it actually comprises several sub-pulses, in, what is known as, a ‘pulse train’. This train of sub-pulses is so fast that the human eye cannot discriminate between each sub-pulse – so we only see one bright flash of light.
The reason for this is purely engineering!! If an IPL continually fired long pulses, the flashlamp would rapidly burn out. So, the design engineers break up the overall pulse into a series of shorter pulses, which allows cooling water to cool the lamp between each sub-pulse. This cooling is usually sufficient to protect the lamp and lengthen its lifetime.
In Figure 38 three sub-pulses are fired with two cooling gaps between them. The duration of each of the sub-pulses are T1, T2 and T3, while the durations of the cooling gaps are D1 and D2. We normally recommend that the cooling gaps (D1 and D2) are kept to as short as possible, to improve the heating process in the targets (longer gaps between pulses allows for more cooling of the absorbing target – which is not desirable).
________________________________________________________________________ 101 Chapter 3 Laser/IPL Hair Removal
© The Laser-IPL Guys, 2022