FEATURE COSMETICS
Interference fringe profilometry is used to assess skin topography in cosmetics testing
‘We can see if a product modifies the secretion of sebum, and reduces the volume of a pore’
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get these images, as well as the values,’ said Radionov. Interference fringe profilometry is another
much-loved method used to assess skin topography in cosmetics testing. The technique calculates a phase image from an interference fringe image projection, providing data on the altitude of each point. Widely used to evaluate the impact of anti-ageing products on wrinkles, especially crow’s feet, cosmetic testing companies are now looking for ways to use this method. As Dr Francis Vial, deputy CEO and scientific director of Spincontrol, highlighted, his company uses Aeva-HE fringe projection units, which also combine stereo imaging, to assess wrinkles on the neck, chest around the mouth and more. Fringe projection units can provide
different fields of view, depending on whether the user wants to study localised structures or larger regions of skin. ‘We will use a small field-of-view to study, say pores and fine lines at high resolution,’ said Vial. ‘We might look at the astringent effect
14 Electro Optics July 2021
on a pore in 3D – we can see if a product modifies the secretion of sebum and reduces the volume and diameter of a pore.’ The company will use a larger field of
view to capture entire faces, as well as body parts such as the abdomen and thigh, with software creating 3D profiles of, perhaps, sagging at the jaw and the volume of the chin bone. ‘When we age, the adipose tissue in our cheeks decreases... and some cosmetic products use these molecules to have a plumping effect on the cheek. We can look at this,’ explained Vial. ‘[We also look at] any uplifting effects of the chest, and the effects of slimming products on the abdomen and volume of the thighs.’ In the early days of using interference
fringe projection in cosmetic testing – more than 20 years ago – measurements would have to be acquired from silicone elastomer replicas of the skin surface. However, according to Vial, instruments are more accurate and less sensitive to motion, so readings can be taken directly from the volunteer. And thanks to developments in high-resolution digital light projectors and 3D measurement algorithms, imaging resolution has improved from around 200µm to nearly 1µm. But beyond moisture mapping and
fringe projection, Raman spectroscopy has become an indispensable testing method for clinical studies on volunteers. The technique uses near infrared light to examine skin in vivo, and according to Bio-EC’s Radionov, can provide reliable analysis to skin depths of around 30µm, meaning that stratum corneum effects can be investigated. As part of its Raman-based testing, Bio- EC has been working closely with Professor Ali Tfayli from the University of Paris- g
Bio-EC
@electrooptics |
www.electrooptics.com
Spincontrol
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