Patent ID: 7937226

Claim:
A device for determining a physical feature of a sample ( 1 ), comprising: a light source ( 2 ) for producing radiation; a probe with at least a first and a second optical fiber ( 5 , 6 ), the first optical fiber ( 5 ) having a first diameter and being arranged to deliver the radiation on a sample ( 1 ) and to collect first backscattered radiation from the sample ( 1 ), the second optical fiber ( 6 ) having a second diameter and being arranged to collect second backscattered radiation, wherein the second optical fiber ( 6 ) is positioned alongside the first optical fiber ( 5 ); wherein at least one of said fibers both delivers light from the light source and measures scattered light from the sample ( 1 ); a spectrometer ( 7 ) for producing a first signal ( 1 ) based on the first backscattered radiation, and for producing a second signal (J) based on the second backscattered radiation; a processor ( 9 ) arranged to determine a measured differential backscatter signal as a function of wavelength (λ) using the first and second signals (I, J), wherein the processor is arranged to calculate the physical feature.