In order to develope the machine vision sorting and grading system for the fruits，the optical properties of the FUJI apple and the NIJISSEIKI pear were measured by a spectrophtometer（Model UV−3100 by SHIMAZU co.）
The spectral reflectances of the normal surface and the defectives（scar，bruise，cut，compression，puncture，friction，and etc.）were measured in the wave length between 290nm and 2500nm. And the standard deviation of the optical properties about the normal fruits and the defects were investigated.
The optical properties of normal fruits in visible wave length region（290-780nm）were complicated because of the variation in color over the surface，but in near infrared region，they were about same values of spectral reflectance expecially and the defference of the spectral reflectance between all the defects and normal fruits（excepted the compress defects）were over 10% in the wave length between 500nm and 900nm.
Because the color variance of fruits surface did not affect in near infrared region，this study concludes that the detection of the defects with the machine vision system should be carried out in the near infrared region between 800nm and 900nm.