Page 37 - Lasers and IPLs in Medical/Aesthetic Applications v1.2
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Chapter 1 – Fundamentals of Medical/Aesthetic Lasers and IPLs v1.2
For example, the target chromophore in hair removal is the melanin in the hair shaft. If we used all of the light from a Xenon lamp, it would also damage capillary blood vessels just below the epidermal/dermal junction. This is not desirable!
So, to get around this, we employ filters which ‘remove’ the unwanted wavelengths. In figure 18 (below), we can see a 650 nm filter designed to absorb all wavelength below that wavelength. In doing so, only wavelengths longer than 650 nm will emerge from the filter – these wavelengths are useful for hair removal (photo-epilation) because they will be preferentially absorbed by melanin, with virtually zero absorption in blood. Click here for a video of this.
Whereas, a 550nm filter is typically used to allow yellow light through to the skin, which is strongly absorbed by blood and/or melanin.
Most professional IPL systems offer a number of filter options. While, many salon IPL systems only offer either one or two filters, thereby limiting their clinical effectiveness and versatility. Careful selection of these filters can help to enhance absorption in the target tissues.
605nm filter
Figure 18: By using filters we can select which wavelengths we want to use. A ‘605 nm’ filter absorbs all the light energy with wavelengths lower than 605 nm, and so only allows red and infra-red light energy through.
Most lasers used in aesthetic/medical applications today do not allow the user to choose the wavelength. They are ‘designed’ into the laser by choice of the lasing medium. IPLs usually offer
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Chapter 1 LEVEL A Fundamentals of Lasers/IPLs
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