| 摘要 |
PURPOSE:To attain miniaturization, high resolution and high reliability by providing a laser diode to an original face as near as possible and extracting the change in a current supplied to the laser diode. CONSTITUTION:An output light 13 and a monitor light 16 are irradiated to an LD12 connected to a constant current source 17. The output light 13 reaches an original 15 through a thin transparent protection layer 14, is reflected in it and then returned to the LD12 again. In such a case, the strength of a monitor light 16 is changed, measured by a photodetector 18 and an electric signal appears at an output terminal. Thus, the original 15 is read by checking the change in the current.
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