Patent ID: 7815278

Claim:
An ink droplet discharge-condition detecting unit, comprising: at least one light emitting element, wherein each light emitting element is configured to emit a single light beam; a light receiving element positioned to face one light emitting element to define an area there between through which an ink droplet discharged from an ink droplet-discharging device is configured to pass; and a first diaphragm plate disposed near a front surface of the light receiving element, the first diaphragm plate having a plurality of apertures arranged at a pitch in a discharge direction of the ink droplet, wherein when the one light emitting element emits a single light beam towards the light receiving element in a fixed state, the single light beam travels across the area and is separated into a plurality of detection beams as a result of passing through all the apertures of the plurality of apertures in the first diaphragm plate so that the plurality of detection beams is configured to be received by the light receiving element, wherein the plurality of detection beams includes a first detection beam and a second detection beam, wherein if a discharged ink droplet blocks only a portion of the single light beam, then a first quantity of light received by the light receiving element from the first detection beam will be different from a second quantity of light received at the same time by the light receiving element from the second detection beam, wherein a difference between the received first quantity of light and second quantity of light causes an output of the light receiving element to change, and wherein the ink droplet discharge-condition detecting unit is configured to detect a discharge condition of the ink droplet based on the change in the output of the light receiving element.