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• Reflecting-type photo-interrupter method
At the end of printing, light is emitted from the LED (light-emitting sec-
tion) in the direction of the footer mark (black) printed on the trailing edge
of the recording paper, and the reflected light is detected by a photo-tran-
sistor (light-receiving section). The presence of ink is detected from the
output of the photo-transistor at this time. For the duration that ink is
present, the light is absorbed by the footer mark and does not reach the
photo-transistor. When there is no more ink, the footer mark is not printed,
and so light is reflected on the recording paper (white) and reaches the
photo-transistor.
Ink detection sensor
(reflecting-type photo-interrupter)
Footer mark on trailing
edge of recording
Fig. 4-69 Reflecting-type Photo-interrupter Method
RECORDING SECTION
paper
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