| 摘要 |
PROBLEM TO BE SOLVED: To perform highly accurate conveyance control and printing control, for a sheet to be printed having a low whiteness degree and a sheet to be printed including a positioning mark, which is lowered in a blackness degree.SOLUTION: In a portable printer 1, a white corresponding voltage value Vw0, an initial black corresponding voltage value Vb0, and an initial threshold Vb0+k0(Vw0-Vb0) are stored, and a black mark PM is detected by setting the value from k0 to k1, from Vw0 to Vw1, and from Vb0 to Vb1 based on a detected voltage value V by a photodetector 35B in a period in which the sheet to be printed 53 is conveyed by a predetermined distance by a platen roller 11 according to an updating indication signal, and using an effect that the detected voltage value V by the photodetector 35B reaches a new set threshold Vb1+k1(Vw1-Vb1). |
