Page 275 - Chapter 3 - Laser/IPL Hair Removal

Chapter 3 – Fundamentals of Laser/IPL Hair Removal 2nd Edition
Note: it’s a good idea to convert any spot size measurement into centimetres!!
So, if we have a laser which is generating a pulse of 1.3 Joules of energy in a 4 mm diameter spot, then:
E = 1.3 Joules d=4mm=0.4cm
Then, the fluence = 1.3 / (0.4/2)2 which is 1.3 / 0.1256 which yields a fluence of approx. 10.4 J/cm2.
An alternative and ‘quick and easy’ way to calculate the fluence is to use ‘multiplying factors’:
2 32 48 6 3.5 82
Now, all we need to do is take the measured energy form your laser pulse, say 1.3 J, as above, and then select the multiplying factor for the measured spot diameter – in this case a diameter of 4 mm yields ‘8’;
Then simply multiply them together: 1.3 * 8 = 10.4 J/cm2.
For a 3mm spot diameter this would be 1.3 * 14 = 18.2 J/cm2, while for a larger 8 mm spot it becomes 2.6 J/cm2.
This is more than accurate enough for most clinical applications. There’s no real point going beyond one decimal place since the measurement of both the laser energy and the spot diameter will not be that accurate!
Read more here...
________________________________________________________________________ 275 Chapter 3, Ed. 2.0 Laser/IPL Hair Removal
© The Laser-IPL Guys, 2025
Spot diameter (mm)
Multiplying Factor
1
127
3
14
5
5
7
2.6