Optical Backscatter Sunscreen Testing
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Solution Overview
Problem
Current methods for determining sun protection factors (SPF) are invasive, cause skin damage, and inadequately assess UVA protection, as they rely on erythema induction or non-physiological skin models, failing to account for long-term skin damage from UVA radiation and lacking reliability in in-vitro UVA SPF determination.
Innovation Solution
A non-invasive method using controlled radiation sources and detectors with defined distances to measure light backscatter before and after applying a radiation protection agent, allowing for damage-free determination of SPF across various spectral ranges by calculating the transmission factor and sun protection factor without causing skin damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If erythema induction methods are used to determine SPF, then measurement precision is improved, but test subjects suffer skin damage
Solution Approach 1:
The patent uses optical backscatter measurements to create an optical copy or model of skin protection rather than relying on biological erythema responses. By measuring how light scatters off the skin surface with and without sunscreen, the system determines SPF through optical properties rather than biological damage, eliminating the need to harm test subjects while maintaining measurement accuracy
Solution Approach 2:
The patent replaces the biological mechanism (erythema induction and observation) with an optical measurement system. Instead of using UV radiation to induce visible skin redness and measuring that biological response, the system uses controlled light sources and detectors to measure optical backscatter, substituting a mechanical/optical system for a biological one to avoid skin damage
2Object-affected harmful factors
If in-vitro methods with plastic plates are used, then test subject harm is reduced, but measurement precision deteriorates due to unrealistic skin models
Solution Approach 1:
The patent creates an optical measurement model that copies the essential light-skin interaction properties without using unrealistic plastic substrates. By measuring optical backscatter from actual skin or more realistic models with proper optical coupling, the system captures the true optical behavior of sunscreen on skin, providing accurate UVA protection factors without the artifacts introduced by roughened plastic surfaces
Solution Approach 2:
The patent changes the measurement parameters from transmission spectroscopy (which requires unrealistic plastic substrates and scaling) to optical backscatter measurement. This parameter change allows direct measurement on more realistic skin models or actual skin, eliminating the need for scaling to in-vivo data and providing direct, accurate UVA protection factor determination
3Measurement precision
If multiple test subjects are required for SPF determination, then measurement precision is improved by reducing inter-individual variation, but loss of time increases
Solution Approach 1:
The patent uses optical backscatter measurements that can be performed on a single individual multiple times, creating reproducible optical signatures. By measuring the same person's skin optical properties with and without sunscreen across multiple sessions, the system eliminates inter-individual variation while reducing the need for large cohorts, thereby decreasing testing time while maintaining or improving precision
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method enables accurate, non-invasive SPF determination without harming test subjects, providing reliable results for both UVA and UVB protection, and extends the assessment to visible and infrared ranges, improving the reliability of sunscreen testing.
Implementation Method 1
measuring the light backscatter on the skin surface before and after application of the radiation protection agent
Data Source
AI summary
The invention is used to ascertain a sun protection factor for light, for example for cosmetics and sunscreens for which a sun protection factor (SPF) is specified. Two measurements of the light backscattering on the skin surface are carried out in vivo or in vitro or on skin models (animal skin models or artificial skin models) before and after applying the radiation protection means onto the skin, and the sun protection factor is ascertained therefrom. In contrast to standard methods used until now, the distance between the lighting surface and the detection surface on the skin is ascertained for the irradiation path of the measurement method. The skin lighting dose used during the measurement lies below harmful limits. The sun protection factor can be ascertained according to previous standards or for additional wavelengths or wavelength ranges (e.g. UVA, VIS, NIR, IR).