Paper roll detection apparatus and method, and printer

A method for detecting an amount of paper left in a roll of paper, the method comprising:

• detecting, by a first sensor, whether an outer periphery of the roll of paper reaches a first outer diameter;
• detecting, by a second sensor, whether the outer periphery of the roll of paper reaches a second outer diameter smaller than the first outer diameter;
• and
• estimating, by an estimating unit, a remaining amount of the paper left in the roll of paper based on a thickness of the paper, wherein the thickness of the paper is estimated based on a length of paper discharged during a time interval between a point of time when the first sensor detects the outer periphery of the roll of paper at the first outer diameter and a point of time when the second sensor detects the outer periphery of the roll of paper at the second outer diameter.

A printer for printing information on a roll of paper, the printer comprising:

• a main body with a plurality of mounting portions;
• a print mechanism provided in the main body;
• a container provided in the main body, the container including a support surface;
• first and second recessed portions connected to each other on the support surface, wherein the roll of paper can be contained in one of the first and second recessed portions;
• a first sensor configured to detect whether an outer periphery of the roll of paper reaches a first outer diameter smaller than the predetermined diameter;
• a second sensor configured to detect whether the outer periphery of the roll of paper reaches a second outer diameter smaller than the first outer diameter;
• and
• an estimation unit configured to estimate a remaining amount of paper in the roll of paper based on a thickness of the paper, wherein the thickness of the paper is estimated based on a length of paper discharged during a time interval between a point of time when the first sensor detects the outer periphery of the roll of paper at the first outer diameter and a point of time when the second sensor detects the outer periphery of the roll of paper at the second outer diameter.