Patent ID: 7864311

Claim:
Method for generating and detecting a Raman spectrum of a medium to be investigated, the method comprising the following steps: producing electromagnetic excitation radiation with a laser diode at least two different wavelengths by driving the electric current applied to the laser diode according to at least two different defined excitation conditions, coupling the excitation radiation into the medium to be investigated, coupling the electromagnetic radiation scattered by the medium to be investigated into an optical spectrum analyzer for spectral analysis of the scattered radiation, detecting at least one Raman spectrum from the scattered radiation for each of the different excitation wavelengths and determining the Raman spectrum of the medium to be investigated from the at least two detected Raman spectra, wherein the step of producing electromagnetic excitation radiation comprises using a laser diode with an internal frequency-selective element as an excitation light source, wherein the laser diode is driven in such a way that the laser diode alternately emits at least two defined wavelengths with a wavelengths separation of at least 0.5 nm, and wherein the electric current applied to the laser diode is driven alternately according to at least two different defined excitation conditions, wherein switching back and forth between the excitation conditions is performed with a frequency higher than 0.1 Hz.