Miniaturized optical spectrometers

Cost-effective implementation of numerous spectral channels

At present, the high cost of sensors with more than six spectral channels severely restricts their scope of application. They are rarely employed in price-sensitive areas such as mobile consumer products, scanning of field crops or in the cosmetics and food industries. Thanks to the nanoSPECTRAL technology developed by our Optical Sensor Systems group, however, the necessary optical filters can now be produced at very low cost.

With this technology, production costs remain practically constant regardless of the number of spectral channels to be implemented. This is achieved by structuring the metal layers in the CMOS semiconductor process. In contrast to conventional optical filters such as thin-film filters, these optical nanostructures require no additional production steps (e.g. deposition of the filters).

Thanks to CMOS integration of filters and photodiodes, as well as analog and digital signal processing, our nanoSPECTRAL technology enables highly integrated monolithic sensors. As the technology is being established in two commercial CMOS foundries, products based on it will be available in industrial quality.

The chip-scale spectrometer already has over 30 channels, making it suitable for applications including analysis of foodstuffs, environmental analysis, and smart lighting. The number of spectral channels can be increased and their wavelength adjusted according to the use case.

Another use case for cost-effective multispectral sensors is being explored in the INFIMEDAR research project, funded by the German Federal Ministry of Education and Research (BMBF). The goal of this project is to determine the condition of plants in the field and enable targeted application of weed control products such as herbicides with a view to reducing the amounts used. Our involvement in the project consists in the design and simulation of the spectral properties of the filters, and chip design of the sensor IC, as well as optical characterization of the multispectral sensors.