Patent ID: 7868878

Claim:
A modular unit for an electronic pen having a writing implement, said modular unit comprising: a carrier having a receiver for receiving the writing implement, a printed circuit board mounted on the carrier, the printed circuit board having at least one hole, a two-dimensional radiation sensor surface-mounted on the printed circuit board, the sensor positioned on the printed circuit board with respect to the least one hole, an imaging unit designed to control a spatial origin of radiation reaching the radiation sensor, the imaging unit defining an image plane and an object plane, the imaging unit having a body and a holder that is associated with an outer part of the body, the imaging unit further having at least one pin, and a radiation source for illuminating the object plane, the radiation source being held by the holder of the imaging unit, wherein the imaging unit is aligned with the printed circuit board such that the at least one pin of the imaging unit is inserted in the at least one hole of the printed circuit board to align the imaging unit to locate the image plane on the radiation sensor, and wherein the carrier, the printed circuit board, and the imaging unit are coupled together such that the printed circuit board is positioned between the carrier and the imaging unit.