PURPOSE: To properly detect paper widths of various recording paper sheets by setting a threshold value of light sensor output to detect a recording medium existent area according to a kind of recording medium.
CONSTITUTION: Before paper width detecting operation is performed by a paper width detecting means 204 which is arranged in a carriage and has a reflection type optical detecting means, preliminary detecting operation similar to this operation is performed, and a threshold value when to detect a recording paper sheet end part is automatically set. A paper width sensor 204 has an infrared light emitting diode 101 and a light receiving element 104, and light emitted from the light emitting diode 101 is constituted so as to be made incident by being reflected by a recording paper 105 or a platen 20 after being condensed by an optical lens. An output value from the paper width sensor 204 is read by a MPU 213 in a control circuit 201 through an A/D port, and a paper width is detected by comparing it with the threshold value. Thereby, since a detecting threshold value is set by the preliminary detecting operation, dispersion of sensitivity of a detecting system and the possibility of erroneous detection by a secular change are restrained, and an application range of the recording paper sheet is also widened.
NAKAGAWA YOSHIHIRO
NAKADA KAZUHIRO
KASAHARA TAKASHI
MASAKI TOMOAKI
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