Optical characteristics of oil palm fresh fruits bunch (FFB) under three spectrum regions influence for harvest decision

Abstract

In current practice, appearance was used to determine ripeness for oil palm fresh fruits bunch (FFB), that accompanied by detachment of fruit-lets from the bunch. The FFB from marihat clone harvested at five ripeness stages, under ripeness (F0), ripeness (F1, F2, F3), and over ripeness (F4). At every ripeness stages, differences of oil content and pigment accumulation were observed on the bunch. All samples recorded using a digital camera (10 MPixels) from 2, 7, 10, and 15 meter distance, simulating variation of light intensity upon recording. During image recording, three lighting were used, namely ultraviolet lamp (320-380 nm), visible light lamp (400-700 nm) and infrared lamp (720-1100 nm), all have similar power output of 600watt. Camera point of view was set to cover a square area of 12,5cm by 12,5cm of the frontal area of FFB, each picture produced has 3888 by 2952 pixel. Image processing software created to extract digital RGB information from the images, and displayed the information in histogram. From the experiment, it was observed that the changes of intensity influence the RGB value of recorded image with reverse correlation, and longer wave light spectrum produce smaller RGB value. The correlation model among image recording distance and RGB of the image display similar nature. From three color channels, G_mean represents better correlation for sample's oil content determination. Using UV and visible lighting, the FFB samples may be determined for harvest decision, up to seven meter observation distance.