International audienceProbing in real time thin film processes is an efficient way to unravel the impact of key parameters as this approach offers a direct insight on the involved mechanisms. MBE has benefited from a large number of in-situ techniques like RHEED, reflectivity, or optical thermometry. Despite the direct measurement of stress in the growing layers that they allow, curvature measurement tools based on laser deflectometry have not been widely adopted by the MBE community, due to intrinsic technological limitations. We have developed a novel curvature measurement technique, named Magnification Inferred Curvature (MIC), that overcomes these limitations. We will explain the principle of the measurement and illustrate its unique capabilities with a few selected examples, focusing on the GaAs1-xBix alloy. Keywords: in-situ, curvature, stress, dilute bismid