Abstract: A method comprises a) radiating at least one measurement light pulse having a pulse duration and intensity onto a measurement area of the inhomogeneous sample; b) detecting at least one pressure transient at the measurement area; and c) calculating a value for the energy density absorbed by the sample during the pulse duration from a curve of the at least one pressure transient at the start and at the end of the at least one measurement light pulse. The method further includes: repeating steps a) to c) for different angles of incidence of the measurement light; modelling the inhomogeneous sample as a stack of layers, each layer being assigned at least a layer thickness and an absorption coefficient, at least one absorption coefficient of a layer being a fitting parameter; and performing a fitting procedure for the fitting parameters; outputting the fitted fitting parameters.

Abstract: The invention relates to a photoacoustic method comprising a measurement light having a predefined wavelength range for determining properties of an inhomogeneous sample, the sample having a mean absorption length ? from the range of 1 to 100 micrometers for the predefined wavelength range, the method comprising the following steps: a) radiating at least one measurement light pulse having a predefined pulse duration and a predefined intensity onto a measurement area of the area F with ?F>>? in the surface of the inhomogeneous sample; b) detecting at least one pressure transient at the measurement area, the pressure transient resulting from the absorption of the at least one measurement light pulse in the inhomogeneous sample with production of a pressure wave propagating to the measurement area; c) calculating a value for the energy density absorbed by the sample during the pulse duration from the curve of the at least one pressure transient at the start and at the end of the at least one measurement li