ZierSens - All-in-one CMOS image sensor with OLED microdisplay for the determination of plant constituents

Ornamental plant cultivation is locally anchored in almost all German districts, mainly with small and medium-sized farms. In 2022, the production value of flowers and ornamental plants produced in Germany amounted to around 1.2 billion euros. Sales of cut flowers, for example, amounted to around 3.1 billion euros.1 In order for the plant cultivation sector in Germany to remain competitive, it is dependent on secure and high yields. Decisive factors for this include successful plant breeding, plant protection and optimal fertilization in order to conserve resources and soils. As part of the ZierSens project, the Fraunhofer FEP has been working on a technology that can promptly detect deficits or nutrient surpluses in ornamental plants. The institute has decades of experience in the development of application-specific OLED microdisplays for a wide variety of purposes. It is also possible to combine OLED light sources and photodiodes on a silicon chip. So-called bidirectional microdisplays are thus able to emit and simultaneously detect light in a wavelength-specific manner. This technology enables the measurement and evaluation of small areas for surface inspection in various application areas. In the project, it was specifically used to detect the condition of an ornamental plant with regard to possible under- or oversupply. A leaf of an ornamental plant is pressed onto the microdisplay using a mechanism, which illuminates the leaf and can detect and evaluate the reflected light. In extensive plant cultivation experiments at the LfULG, plants were produced in different nutritional states and images of leaves at different stages were taken. These images were used to train artificial neural networks to automatically identify leaf characteristics. Compared to conventional measurement systems, which require a large number of measurements and use an averaged value within the measurement spot, bidirectional OLED microdisplays offer a spatially resolved measurement. This allows several measured values to be generated at one measuring point, which are directly related to each other. This should enable more targeted fertilization and thus a more efficient use of resources, thereby reducing the environmental impact.