| 摘要 |
PURPOSE: To correctly judge exhaustion of ink by a method wherein reflection densities of a mark recorded on recording paper and a white ground part of the recording paper are detected, and a reflection density difference between the mark and the white ground part is found so that judgement is less affected by a variation of a photoelectric sensor in sensitivity. CONSTITUTION: After forming a printing image on recording paper based on image data, a printing head 12 forms a mark. Reflection densities of the mark and a white ground part of the recording paper are detected by a reflection density detection part 5. A reflection density range representing a difference between a maximum value and a minimum value with respect to the detected reflection densities is computed by a system control part 1. The reflection density range is compared with a threshold value previously stored in a RAM part 3. If the reflection density range is smaller than the threshold, exhaustion of ink is judged by the system control part 1. A message of exhaustion of ink is displayed on an operation display part 4. |
