Studies on Automatic Sorting of Agricultural Products (I)

Surface Color Detecting of Agricultural Products

Abstract

The peel color, as well as the shape, is considerable factor in grading agricultural products that is mainly discriminated by people in fact. In this paper, automatic detecting for the peel colors of agricultural products were attemped by using an opto-electronic system consisting of four color sensors and a 4W fluorescence lamp. The color sensor was made by combining two different spectral sensitivity photo diodes and infrared cut off filter into one (Dual junction photo diode).
In order to detect the peel colors, these color sensors were set to receive the reflective rays from the both sides of equatoral part and stem part, or apidal part (blossom end part) of a fruit. Hence, from the output voltages of these color sensors, colored degree C_m and colored uneveness C_v(1), C_v(2), C_v(3) were calculated to express the status of color.
Tomatoes and satsuma oranges were tested and the following results were obtained:
As the peel colors progressed from matured green to dart red (Hue θ=120°-20° (Hunter's chromaticity)) the values of C_m decreased in proportionally.
The peel colors of satsuma oranges in SHU group (good group) were more even (values of C_v(1), C_v(2), C_v(3) were small) and progressive (values of C_m were small) than those in YU proup (fair group). It shows that the status of peel color seems to be discriminated by this method availably.