| 摘要 |
A two-beam detection method causes two beams to differ in light intensity and converging the two beams to enter a common photosensitive element, a photoreception surface of the photosensitive element being configured such that the two beams differ in time required to pass the photoreception surface, processes an output from the photosensitive element using a plurality of threshold levels so as to obtain rectangular signals, one of the rectangular signals obtained using one of the plurality of threshold levels being designated as a detection signal for one of the two beams, and performs a predetermined calculation on the rectangular signals so as to obtain a detection signal for the other of the two beams.
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