Page 58 - Lasers and IPLs in Medical/Aesthetic Applications v1.2
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Chapter 1 – Fundamentals of Medical/Aesthetic Lasers and IPLs v1.2
The power density of sunlight hitting the Earth’s surface on any typical day is typically around 1000 watts/metre2. (on average) - which is only 0.1 watts/cm2.
Unless you live in Scotland, where it is more like 0.00000001 W/cm2 on a good day.....
● However, the most important thing to understand about power density is that it absolutely determines what happens in tissue. Fluence determines whether anything happens at all, power density determines what actually happens.
● This is where many people become confused. An IPL system may generate a maximum fluence of, say, 20 J/cm2. A laser may generate a maximum fluence of only 5 J/cm2. On the face of it you may think that the IPL is the superior device. However, this is only part of the story.
● That same IPL may deliver its energy in a pulse of 10 ms, while the laser might deliver it in 10 nanoseconds (if it is a Q-switched laser).
     Power Density
Over 2.5 km
     1 cm
Around 100 – 5000 cm
Typical lasers
       © The Laser-IPL Guys 2021
QS lasers
Figure 29: Comparison of Power Densities between IPLs, lasers and QS lasers
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Chapter 1 LEVEL A Fundamentals of Lasers/IPLs

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