| 摘要 |
PURPOSE:To prevent accurately light information from being read incorrectly by providing a storage means which stores such an electric characteristic of an AC power source that the illuminance of a lighting means driven by the AC power source is larger than a specific value as an adequate value and a readout control means which performs conversion to an electric signal only when the AC power source has the adequate value. CONSTITUTION:The electric power from the commercial AC power source connected to power input terminals 21a and 21b is supplied to a fluorescent lamp 5 from terminals 27a and 27b through a phase detecting circuit 23 and a stabilizer 25. The phase detecting circuit 23 detects the phase of the AC source voltage supplied from the power input terminals 21a and 21b and supplies it to a phase comparing circuit 29. The phase comparing circuit 29 is supplied with a reference phase signal stored in a phase storage circuit 31 and compares this reference phase signal with the phase of the AC source voltage detected by the phase detecting circuit 23. The control circuit 33 receives reference phase signals P1-P4 from the phase comparing circuit 29 to control a main scanning control circuit 35.
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