= E. R. C. Draper
{c}
\b[E. R. C. Draper] coauthored the 2005 demonstration of <spatially offset Raman spectroscopy> with <P. Matousek> and colleagues. The method distinguishes contributions from different depths by changing where scattered light is collected relative to the illuminated spot.<Subsurface Probing in Diffusely Scattering Media Using Spatially Offset Raman Spectroscopy by P. Matousek and others>[byline and Abstract, lateral collection displacement]{ref}
An original two-layer model makes the separation concrete. Let $S$ and $B$ be fixed surface and buried-layer <Raman spectra>. Suppose two collection arrangements measure $y_0=3S+B$ and $y_1=S+2B$. The <linear combination> $3y_1-y_0=5B$ removes the surface spectrum exactly in this ideal model. The result depends on knowing the relative surface coefficients; it is not a claim that real tissue always follows these two numbers.
This example explains why a displaced detector can supply useful information even when a <scattering> sample prevents a sharp optical image of its interior. The two measurements have different mixture coefficients. Recovering the buried signal depends on that difference and on measurement <noise>, not solely on collecting more light.
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