Near-end of roll detecting apparatus for detecting near-end of roll of recording medium, and printer

摘要

To improve precision in identifying the amount that remains of a recording medium, an apparatus includes a paper holder that supports an outer circumferential surface of a recording medium that is biased downward in a vertical direction by the weight of the recording medium, such that a position of a center of the recording medium moves on a straight-line trace, associated with consumption of the recording medium; and a light-reflecting sensor that is provided at a predetermined position at a side face of the paper holder and senses displacement per unit time at a position facing the predetermined position of the recording medium that is rotated by being pulled out of the paper holder, associated with the consumption of the recording medium, where based on the displacement sensed by the light-reflecting sensor, a radius of the recording medium at the time the light reflecting sensor senses the displacement is calculated.