| 摘要 |
PROBLEM TO BE SOLVED: To measure information as to illuminance while saving space, without increasing the cost. SOLUTION: An emitted beam is received to measure the information about the illuminance of the beam. This instrument is provided with a photoreceiver 21 for photoreceiving the beam, a specifying device 23 for specifying a photoreceiving area for the beam emitted to the photoreceiver 21 in plural ranges, and a switching device for driving the specifying device 23 to switch the range of the photoreceiving area.
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