PSI is a high-tech company for more than 25 years PSI has been specializing in the design and manufacture of sophisticated, high-end instrumentation for research in the biological sciences. The company is a world expert in manufacturing instrumentation for advanced measurement and imaging of optical signals in plants and algae, particularly in the field of chlorophyll fluorescence/reflectance techniques. The instrumentation we have developed is used for monitoring a wide range of physiological signals from individual cells to mature crop plants. As the first company to offer a chlorophyll fluorescence imaging system.