Abstract: The single heads (40) mounted on a single print carriage of an ink jet printer comprise a column (50) of phototransistors (51-i), built directly into the chip of each head in the same process steps as used for the circuits for selecting and driving the actuating resistors; an illuminating device (43) on board the printer focuses a light spot (70) on the column (50) of phototransistors (51-i) which, scanned in sequence, provide the electronic controller of the printer a video output (57); from the output (57), processing and computing means produce a measurement of the vertical and horizontal misalignment of each head (40), a measurement used subsequently to automatically compensate this misalignment.

Abstract: The individual monochromatic printheads mounted simultaneously on the scanning carriage of an ink jet printer are provided with an opto-electronic position detector of the four-quadrant type, which is integrated directly in the chip of each head by means of the same MOS technology used for the circuits for selection and driving of the emission resistors; an illumination device fixed onto the printer focuses a light spot on the position detector which thus provides the electronic control unit of the printer with a measurement of both the vertical and horizontal misalignment of each head, a measurement which is subsequently used in order to compensate automatically for the misalignment thereof.