In the field of biotechnology, the estimation of relevant process parameters is still a challenge. Particularly with regard to efficient control of processes with high product yields, a real-time and reliable documentation with process analytical sensors is essential. Moreover, stricter regulations of the US Food and Drug Administration for the pharmaceutical industry concerning process documentation, imposed by the Process and Analytical Technology Initiative, have increased the demand for sensors that are able to very accurately monitor and document the production process. For the monitoring and control of bioprocesses, a huge variety of sensors is used. Most systems are based on optical or electrochemical sensors. Furthermore, the market demand for disposable sensor systems increases rapidly as the application of disposable bioreactors represents the biggest technical advance in modern biotechnology. These presterilized plastic bags significantly reduce the cost/income ratio and build a meaningful concept for the design and implementation of standardized peripheral bioproduction. Simple and flexible adaptation of sensors is a bottleneck and high-production requirements of the sensor components have to be met. This contribution gives an overview on concepts of sensor systems and image-based techniques that allow the online estimation of relevant process parameters used in single-use bioreactor systems.