Abstract: An alignment detector that detects an alignment of a printhead of a printer, with the alignment detector including a photodetector and a single focusing element focusing a point on a media to a point on the photodetector. The alignment detector can be used to detect the alignment of the printer by scanning the alignment detector across the media and detecting predetermined marks previously printed on the media by imaging the predetermined marks using the alignment detector. The area between the single focusing element and the photodetector may be filled by a translucent material, such that there is no air gap between the two.