| 摘要 |
PROBLEM TO BE SOLVED: To correctly detect whether or not an ink drop is discharged from each ink nozzle without enhancing sensitivity of a sensor. SOLUTION: Ink drops 3 are discharged from each ink nozzle 2 to pass a detection area 43 of a photosensor 4. The presence/absence of the discharging of ink drops from each ink nozzle is judged on the basis of a decrease of the amount of light detected by the photosensor. In this case, a discharge interval L2 of ink drops 3 from each ink nozzle 2 is set smaller than an interval L1 at a normal printing operation, so that a count of ink drops 3 passing the detection area 43 per unit time is increased. An area of the detection area 43 shut by the ink drops 3 is accordingly increased. As a result, the amount of light detected at a photodetecting element 42 is reduced more and therefore whether or not the ink drops are discharged from each ink nozzle 2 can be detected correctly without enhancing sensitivity of the photosensor 4. |
