Page 90 - An Introduction to Laser Tattoo Removal

Chapter 2 – Fundamentals of Laser Tattoo Removal v1.0
‘Focal drift’ occurs when the handpiece tip is moved away from the skin. Because of the way the light is usually focussed (in most lasers) the beam emitted from your handpiece tip is not parallel – it is ‘conical’ in shape. So, as you pull the handpiece tip away from the skin surface, the beam may become smaller (or larger), which directly changes the ‘power density’ (and ‘energy density’). Most lasers will have a handpiece with some sort of ‘spacer’ attached to it. This has been designed by the laser engineers to ensure you use the correct spot size (see figure 39).
Watch this video which demonstrates what happens to the spot size as you pull away from the skin surface (plus this one which Mike did on his own skin).
Remember....
To achieve good clinical results with your laser you MUST use the proper settings – wavelength, pulse duration, spot size and fluence (energy density).
If you set up your laser, using the correct setting for the job, then use the handpiece in the wrong position, you have lost all your prep work!
Laser Energy Distribution Across a Spot
Figure 44: A fairly typical laser spot showing the distribution of energy
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Chapter 2 LEVEL A Laser Tattoo Removal
© The Laser-IPL Guys, 2021
The energy distribution across a spot area can vary enormously. It depends on the alignment of the mirrors inside the laser cavity, the ‘pumping efficiency’ of the laser medium, the power output of the flashlamp and a couple of other issues.
As a consequence, we typically find that the energy profile is rarely flat meaning that the output spot will have ‘hotspots’ in it where the fluence is higher than in surrounding regions!