 E. R. C. Draper

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.^[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.