Patent attributes
A particulate determination method determines by onetime scanning, the size of a particulate included in a plurality of particulates of various sizes which are arranged on a disc. False recognition of the number of particulates is avoided even when a plurality of particulates are adjacent to each other. A photodector detection signal is judged using plural threshold values according to the sizes of particulates to be detected. Results of determinations corresponding to the respective threshold values are stored on mutually independent memory maps. When counting particulates, a particulate size and a particulate count value are determined from a combination of stored data appearing in a scanning window at the same position on the respective memory maps.
