| 摘要 |
The intensity of each lamp (16) which illuminates an object (12) at an inspection station (10) is controlled by controlling driving voltage applied to a power supply (22) which supplies electrical power to the lamp (16). A phototransistor (30) is used to sense the intensity of the lamp (16) through an optical fiber (28). The sensor (30) is followed by a digitally-controlled, variable gain circuit whose outputs is fed to an A-D converter. A microprocessor (26) analyzes the digital signal from the A-D converter and corrects the driving voltage to the power supply (22) to keep the intensity output of the lamp constant. In this way, feedback corrects for a degraded lamp output due to aging.
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