Photonic Microsystem For Solar Illumination Monitoring

INTRODUCTION An innovative photonic microsystem intended for solar illumination monitoring has been developed and tested. The microsystem is based on a hemispherically shaped optical front-end that directs the solar light on an integrated circuit consisting of a 2-dimensional photodetector array combined with the necessary electronic processing elements. The detector array computes the azimuth, elevation and intensity of the sun in real-time. It can be used for example to control an airconditioning system. The developed microsystem is able to locate the sun within an azimuth angle of _C 120" and an elevation angle between 5" (horizon) and 90" (zenith). Monitoring of the power density of the sun light is possible between 1001000W/m2. Most conventional regulation devices intended for the monitoring of incident solar energy are based on the measurement of the induced temperature variation of the environment. The time responses of these systems are quite low and can be problematic when a rapid response is desired. A typical example is the monitoring of sudden solar illumination variations in the inside of a car. A variety of simple devices based on the use of a small number of photodiodes have been proposed [1,2]. With these systems it is possible to monitor the intensity of the sun, but the angular directivity is poor. Other systems use CCD arrays [3] which result in expensive devices. The present work concerns the development of a lowcost industrial sensor, using analog integrated detector technology. The required specifications of the sensor are: Figure 1. Photograph of the components of the photonic microsystem: refracting side of the optical front-end and detector array on TO-8 case 140 TRANSDUCERS '95 * EUROSENSORS IX The 8th International Conference on Solid-state Sensors and Actuators, and Eurosensors IX Stockholm, Sweden, June 2529, 1995