Optical Fiber Multipoint Light Measurement System for the Investigation of Plant Cultivation Light Environment

Abstract

In this study, we propose an optical fiber multipoint light measurement system to investigate quantitatively a proper light environment for plant cultivation. Especially, we focus on the light environment in a greenhouse. For better quality and faster cultivation, various vinyl films have been researched and commercialized to control the light environment inside the greenhouse. Those functional vinyl films are evaluated only subjectively by the plant cultivation results. Here, to evaluate the influence of functional vinyl film for greenhouse quantitatively, we investigate the light environment 3-dimensionally around a plant individual using the proposed light measurement system. The optical fiber multipoint light measurement system was designed to suitable for a real time and long-term measurement. To detect light environment 3-dimensionally around a plant individual, we fabricated a cubic shaped apparatus of 6 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> with a hole in each surface using a 3D printing technique. The light is received by about 0.1 mm diameter optical fibers. Each optical fiber was mounted in the hole located at center of each surface of the apparatus. Finally, the received light is analyzed by spectrometer. With the measurement system, we investigated the light environment in the greenhouse. As a result, we found that near plant root the intensity of infrared region becomes strong that was not absorbed into the leaf.