Estimation of Light Intensity Distribution on a Canopy Surface from Reflection Images

Abstract

The intensity of light falling on the leaf surface of a plant is critical information to accurately evaluate its photosynthetic status and/or the management of the light environment in protected cultivation. In this study, the relationship between the light intensity (expressed as the photosynthetic photon flux density; PPFD) irradiating the leaf surface and the pixel value (PV) in the reflection image was investigated for several plant canopies to examine the possibility of using reflection images to estimate the distribution of light intensity on a canopy surface. Reflection images of the plant canopies were acquired from several directions with a monochrome 14-bit CCD camera through a blue-green band-pass filter. High correlations were observed between the PPFD and the average PVs in the reflection images from three different directions for strawberry canopies under artificial light and tomato and rose canopies in a greenhouse. These results suggest that the distribution of light intensity on a canopy surface could possibly be estimated by reflection images from different directions. A simple method is proposed for the estimation of the PPFD distribution on a plant canopy in a greenhouse using reflection images.