diance for a light source can be altered with various 

 types of "filters" covering the lamp. These include 

 undesirable coatings of dust and dirt. 



Spectral Reflectance 



Spectral reflectance of an object is basically the 

 "color" of the object -- the ability of a fruit to reflect 

 certain colors of light in the presence of natural light. In 

 fruits, the chlorophyll, anthocyanin, or other natural 

 pigments dictate the item's color. The apparent color of 

 an item can be altered by changing the light source or by 

 incomplete color receptor capability. Some defective 

 and nondefective measurements for the same commod- 

 ity vary in their reflectance over the entire spectrum 

 while others either vary only in certain regions of the 

 spectrum or they vary httle at all. 



Many defects that need to be detected on fruits and 

 vegetables are of brown or grayish color. One might 

 assume, therefore, that simply finding the light source 

 with the most energy in the color regions making up the 



brown color would be ideal for all applications. The 

 objective in selecting the best light source for a given 

 task, however, is to light a commodity with a source that 

 will accentuate the color difference between the sound 

 tissue and the defects. For example, if we wish to find 

 brown discoloration on red cherries, then we want to use 

 an inspection light of a color that will accentuate brown 

 against the normal red color of the cherry. The key is 

 to fiTKi a color of inspection lighting that wiU make the 

 defects show up the most, i.e., to make the commodity 

 look its worst. 



Receptor Sensitivity 



The third component in perceiving a color is the 

 receiving or sensing of the light. In this case, the human 

 eye is the receptor. There is no adjustment to the human 

 eye. The only variability is in the individual's sensitiv- 

 ity to the color and quantity of the light. Sensitivity 

 decreases with age and this should be a consideration 

 during lighting design. 



Fruit Notes, Fall, 1994 



