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Optical Sensor Array

In the field of data processing and communication, long existing limits of standalone devices have been overcome by the networking of different systems. The possibility to compute large amounts of data enables the analysis of complex phenomena in a very fast and secure manner. Consequently, the next step is the connection of these sensing systems within a network, as has already happened with data analyzing systems. In the future, networks will consist of many single sensors which are connected to each other in order to be able to acquire data sets of complex processes. Thus, the opportunity to obtain such data sets will allow detailed analysis of phenomena that could not be analyzed before. The use of the described sensors in vast quantities in complex networks requires them to be very small and to be manufactured with low production costs. Scientists at the INA are researching in exactly this direction in the development of a highly miniaturized spectrometer.
It will be able to detect the concentration of different substances without getting into contact with them. Conventional spectrometers have already hit the boundary of miniaturization. This is due to the fact that there is a necessity for a finite optical path length between a dispersive element and the detector. This length influences the resolution of the spectrometer as much as the ability of the dispersive element to spread the light. A further miniaturization automatically worsens the resolution achievable.

It is the aim to develop a miniaturized optical Nanospectrometer that is suitable for mass production and has a low price. Additionally, a very high resolution will be achieved by a thin film system which allows the Nanospectrometer to have extremely small dimensions. The Nanospectrometer developed consists of a field of many single Fabry-Pérot filters directly placed on commercial CMOS-chips that are well-known from their application in digital cameras. Every single filter is placed on a single pixel of the CMOS-chip. This way, every pixel detects one single colour, which corresponds to one very narrow wavelength range. This method allows the bulk production of miniaturized optical Nanospectrometers, which would not be possible, if conventional technologies were used.

The determination of the intensity of a single optical wavelength is achieved by reflecting all light irradiating a filter except for a single well-defined wavelength which is transmitted by the filter and can be detected by the sensor.  The consideration of all the intensities measured results in the spectrum of the incident light. Changes in the spectra reveal the concentration of the matter.

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