InfraRed (IR) photothermal techniques are candidates for in-situ characterisation of tokamak Plasma Facing Components (PFC) surfaces, by means of an external thermal excitation coupled with an IR temperature measurement. Among these techniques, the Laser Lock-In Thermography (LLIT) uses a modulated laser excitation which gives 2 major advantages: enhancement of signal to noise ratio and emissivity independence, which is a plus when the components have various and unpredictable surface quality. With this method, it is possible to develop a process which could be used remotely, either mounted onto an in-situ inspection device (articulated arm) or in a PFC test bed. This paper presents the results obtained with a continuous modulated laser heat source on particular samples (W coating on CFC substrate, C layer on graphite substrate). The identification of the experimental data with a theoretical model allows a quantitative characterisation of the layers.