A gear includes a gear main body and a plurality of teeth projecting on the outer circumferential surface of the gear main body. A measure is determined of errors occurring in communication over a wireless link. If the result of determination indicates output not allowed, a stroke of the character is omitted to reduce the size of the character to allow the correct output according to the predetermined resolution. A color filter is sufficient to create the dark-field background required for fluorescent imaging, without the need for expensive thin-film interference filters. Based upon the multiplicity-specific distribution, one estimates, for each multiplicity category, the number of trigger pulses lost due to neutron detector dead time that would have been assigned to the multiplicity category.