Patent ID: 8066348

Claim:
A method of detecting a defective nozzle in an image forming apparatus that includes a recording head having a plurality of nozzles aligned in a first direction used to eject droplets of a liquid therefrom, the method comprising: (a) controlling each of the plurality of nozzles to eject the liquid to form a detection pattern on a water-repellent surface, the detection pattern being formed by multiple droplets ejected from each operational nozzle of the plurality of nozzles, the multiple droplets ejected by the operational nozzle being sequentially arranged and spaced apart from each other both in the first direction and in a second direction orthogonal to the first direction to form together a generally rectangular configuration extending in both of the first and second directions on the water-repellent surface; (b) reading the detection pattern by a read sensor illuminating the detection pattern on the water-repellent surface, and receiving specular light reflected from the detection pattern, the read sensor having a detecting range; (c1) outputting a first read result when sensing a first area of the detection pattern on the water-repellent surface, the first area not having an ink droplet disposed thereon, due to the defective nozzle failing to eject liquid droplets, and therefore the first area reflecting a relatively large amount of specular light, and (c2) outputting a second read result when sensing a second area of the detection pattern on the water-repellent surface, the second area having a plurality of ink droplets disposed thereon with a hemispherical shiny surface to reflect a relatively small amount of specular light; and (d) detecting the defective nozzle according to the first and second read results collectively indicating an edge formed between the first area and second area, wherein the first area of the detection pattern, created due to the defective nozzle failing to eject liquid droplets onto the water-repellent surface, is larger than the detecting range of the read sensor detecting the detection pattern in at least one of the first and second directions.