LED for hyperspectral imaging - a new selection method.

Hyperspectral imaging (HSI) has become a sophisticated technique in modern applications such as food analyses, recycling technology, medicine, pharmacy and forensic science. It allows one to analyse both spatial and spectral information from an object. But hyperspectral cameras are still expensive due to their extended wavelength range. The development of new light-emitting diodes (LED) in the recent past enables another approach to HSI using a monochrome camera in combination with a LED-based illumination. However, such a system has a lower spectral resolution. Additionally, the growing supply of LED on the market complicates the selection of LED. In this paper, we propose a new time efficient selection method for the design process of an illumination. It chooses an optimised LED combination from an existing database to match a predefined spectral power distribution. Therefore, an algorithm is used to evaluate various LED combinations. Furthermore, the method considers the spectral behaviour of each LED in dependence of forward current and temperature of the solder point. Our method has already shown promise during the selection process for even spectral distributions which is demonstrated in the study. Additionally, we will show its potential for HSI illuminations.

Review on Hydrogel-based pH Sensors and Microsensors.

Stimuli-responsive hydrogels are materials with great potential for development of active functionalities in fluidics and micro-fluidics. Based on the current state of research on pH sensors, hydrogel sensors are described qualitatively and quantitatively for the first time. The review introduces the physical background of the special properties of stimuli-responsive hydrogels. Following, transducers are described which are able to convert the non-electrical changes of the physical properties of stimuli-responsive hydrogels into an electrical signal. Finally, the specific sensor properties, design rules and general conditions for sensor applications are discussed.