First and second laser devices irradiate a sample in a laser excitation with a laser probe pulse of the second laser device and a time resolved impulsive laser excitation via the first laser device. Coherent Raman signals are generated from the sample over a spatial extent (x- y). Raman signals received from the sample are diffracted via a grating (RG) to a condenser (CM) in order to pass through the tunable spectral filter (SLM) operating in the Fourier plane to keep the size of the spatial dependence minimal. The beam expander (SL+, SL2) and dispersion stage /TG) are arranged for expanding the signal by the beam expander; and propagating through the dispersion stage, such that the spatial dependence become the dominant part in the convolution product at the position of the image sensor (CCD).