Patent ID: 7118187

Claim:
An inkjet recording apparatus, comprising: a recording medium feeding section to feed a recording medium on a platen; a recording head including a plurality of nozzles to eject ink droplets onto the recording medium; a recording head moving section to move the recording head in a direction perpendicular to a feeding direction of the recording medium; a mark recording section to record a plurality of marks, which are perpendicular to the feeding direction of the recording medium, on the recording medium using a plurality of the nozzles, while the recording head is moved by the recording head moving section; and a mark detecting unit which is moved together with the recording head and detects the plurality of marks; wherein the recording medium feeding section calculates and assumes a position which gives a smallest detection error from a distance interval calculated by a nozzle pitch of the recording head, referring to a position of each mark detected by the mark detecting unit; and wherein a feeding amount of the recording medium is determined based on the calculated and assumed position; and wherein the mark detecting unit comprises a light reflection type sensor, which includes: a light emitting element which emits detecting light onto a recording medium; a condenser lens which condenses detecting light emitted from the light emitting element; and a light receiving sensor which detects light reflected from a surface of the recording medium on which the detecting light is focused by the condenser lens, wherein an optical axis of the light emitting element and an optical axis of the condenser lens are approximately perpendicular to the surface of the recording medium, and wherein the light emitting element, the condenser lens and the recording medium are arranged so as to satisfy an inequality k×b<a×m, where: k is a length of the light emitting element in a sub-scanning direction, a is a distance between the condenser lens and the surface of the recording medium, b is a distance between the condenser lens and the surface of recording medium, and m is a pitch of the plurality of marks in the sub-scanning direction.