| 摘要 |
PROBLEM TO BE SOLVED: To automatically set a proper light amount area for determining defects adapted to a group of powder and grain which is to be actually inspected, while dispensing with laborious work such as adjustment as much as possible. SOLUTION: When a detecting position, through which a group of powder and grain as an object to be inspected passes in the form of single layer, is lighted, light from the detecting position is received by a light-receiving means, and a light receiving amount of the light-receiving means is sampled at a set time interval so as to provide a predetermined number of light-receiving amount data. As to the set number of light receiving amount data, the data ranging from the dark side to the bright side is divided into a plurality of steps, a frequency distribution hg of a light amount value in the respective steps is found, and on the basis of this frequency distribution hg, an upper limit value T1 and a lower limit value T2 of the proper light amount range are set.
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