A measurement system is disclosed for light-based measurement of collagen, using a first light intensity and a second light intensity. The measurement system comprises a light source for emitting a light beam having a source wavelength range and an optical system to polarize light within the source wavelength range, thereby generating a polarized light beam, and to direct and focus the polarized light beam to a target position inside the skin at a predetermined focus depth below an outer surface of the skin. The measurement system further comprises a first detector, and a second detector for detecting the first light intensity and the second light intensity within, respectively, a first detection wavelength range and a second detection wavelength range of light reflected from the target position. The measurement system further comprises a comparator, coupled to the first detector and the second detector and configured and arranged to determine a difference between the first light intensity and the second light intensity. When natural collagen is present at the target position, a reflected spectrum of light of the polarized light beam reflected by said natural collagen comprises a plurality of adjacent first and second wavelength ranges, wherein in said first wavelength ranges constructive interference prevails between the polarized light beam and the natural collagen, and wherein in said second wavelength ranges destructive interference prevails between the polarized light beam and the natural collagen.