A method for determining characteristics of a layer-based structure, characterized in that the method comprises - irradiating the layer-based structure repetitively with a continuous wave electromagnetic radiation of substantially one frequency in the range 0.1 GHz to 100 THz, the electromagnetic wave comprising a transient part from zero to a monochromatic steady state, and the steady state part and wherein a sum of the duration of the transient part and the duration of the steady state part is at least equal to a full round trip time of the electromagnetic wave inside the layer-based structure, the layer-based structure being sufficiently transparent to the used electromagnetic radiation, - capturing from the repetitive irradiating as a function of time a transient part of the reflection of the electromagnetic wave reflected at different interfaces of the layer-based structure or a transient part of the transmission of the electromagnetic wave transmitted through the different interfaces of the layer-based structure by sampling at a frequency of at least the repetition frequency of the emitted radiation, - deriving from the transient part of the reflected or transmitted electromagnetic wave as function of time information regarding different contributions in the transient part of the reflected or transmitted electromagnetic wave stemming from the reflections at or transmissions through the different interfaces of the layer-based structure, wherein said deriving comprises the deconvolution of the transient part of the reflected or transmitted electromagnetic wave based on a superposition model of the different contributions in the transient part of the reflected or transmitted electromagnetic wave, and - determining from said information at least geometric information and/or electromagnetic properties of the different layers of the layer-based structure. - irradiating the layer-based structure repetitively with a continuous wave electromagnetic radiation of substantially one frequency in the range 0.1 GHz to 100 THz, the electromagnetic wave comprising a transient part from zero to a monochromatic steady state, and the steady state part and wherein a sum of the duration of the transient part and the duration of the steady state part is at least equal to a full round trip time of the electromagnetic wave inside the layer-based structure, the layer-based structure being sufficiently transparent to the used electromagnetic radiation, - capturing from the repetitive irradiating as a function of time a transient part of the reflection of the electromagnetic wave reflected at different interfaces of the layer-based structure or a transient part of the transmission of the electromagnetic wave transmitted through the different interfaces of the layer-based structure by sampling at a frequency of at least the repetition frequency of the emitted radiation, - deriving from the transient part of the reflected or transmitted electromagnetic wave as function of time information regarding different contributions in the transient part of the reflected or transmitted electromagnetic wave stemming from the reflections at or transmissions through the different interfaces of the layer-based structure, wherein said deriving comprises the deconvolution of the transient part of the reflected or transmitted electromagnetic wave based on a superposition model of the different contributions in the transient part of the reflected or transmitted electromagnetic wave, and - determining from said information at least geometric information and/or electromagnetic properties of the different layers of the layer-based structure. <EOS>