We present experimental results obtained by applying imaging techniques to the operation of edge emitting diode lasers. Standard Si-based CCD cameras, short-wave infrared (IR) and thermal cameras (for the medium IR range) were used for stationary and transient measurements. Time resolutions in the sub-microsecond range were achieved by operating diode lasers with short pulses and using the cameras as time-integrating monitors. Both GaAs and GaN-based diode lasers are involved in the study. The presented type of imaging analysis allows the detection of spatial temperature profiles, defect distributions, and non-equilibrium carrier distributions. Knowledge of these parameters is helpful for the development of new device architectures and the elimination of deficiencies in existing device designs. The time-resolved measurement of moving defect fronts reveals the kinetics of sudden degradation processes. Thus, in-situ imaging techniques represent versatile tools that complement standard failure analysis of diode lasers.