Patent ID: 7490918

Claim:
A droplet determination device for a droplet discharge apparatus, comprising: a droplet discharge device having a droplet discharge port surface in which droplet discharge ports which discharge liquid droplets are arranged in a staggered matrix in such a manner that each of the rows of the droplet discharge ports in the staggered matrix is substantially parallel with a lengthwise direction of the droplet discharge port surface; a detection device in which a light source and a single light sensor for the light source are disposed in such a manner that an optical axis of a light beam formed between the light source and the single light sensor is substantially perpendicular to a direction of flight of the droplets discharged from the droplet discharge ports, and the optical axis of the light beam is substantially parallel to the droplet discharge port surface; an optical system which forms the light beam into substantially parallel light, when the optical axis is viewed from a direction perpendicular to the optical axis, of which a cross-sectional shape in the direction perpendicular to the optical axis of the substantially parallel light is elongated in the direction of flight of the droplets; and a discharge judgment device which judges a discharge status of the droplet according to a detection signal obtained from the detection device when the droplet is discharged into the substantially parallel light, wherein the cross-sectional shape of the substantially parallel light, perpendicular to the optical axis of the substantially, parallel light, has a first beam width in the direction of flight of the droplets and a second beam width in a breadthways direction of the droplet discharge port surface perpendicular to the lengthwise direction, where the first beam width is set to be greater than a maximum droplet length realizable by a droplet after discharge from the droplet discharge port while remaining narrower than a distance between the droplet discharge port surface and a recording sheet onto which the droplet is to be discharged, the second beam width is set to encompass only the droplets discharged from the droplet discharge ports in only one of the rows in the staggered matrix, the first beam width is greater than the second beam width and a ratio of the first beam width to the second beam width is greater than or equal to 2.