Abstract: A light pen input system includes a light sensing device (10) having a row and column array of light sensing elements (14) over which a light pen (12) is moved to write in information, e.g. for display on a display screen, the light beam emitted by the pen producing a light spot (20) on the array which covers, and is sensed by, adjacent elements and which, with the beam directed perpendicularly to the array, is substantially non-circular in shape, having dimensions in two directions over the array which differ from one another. Rotation of the pen around its axis is then detectable, providing additional functionality. An elongated light spot, e.g. elliptical, rectangular or triangular, provides further capabilities in enabling the width of a written stroke to be varied by twisting the pen.

Abstract: The image sensor (1a) has a transparent substrate (2) supporting a two dimensional array (3) of photosensitive and switching elements (4) with switching signal conductors (5) and data signal conductors (6) connected to the photosensitive and switching elements (4) for enabling individual photosensitive elements to be accessed. The photosensitive and switching elements (4) and the conductors (5 and 6) are arranged such that at least half of the area of the image sensor is transparent during operation. Each photosensitive element is electrically coupled to a respective capacitor (7) for storing charge generated as a result of light being incident on the photosensitive element. The capacitors (7) are formed so as to be transparent and so as to occupy a significant part of the entire area of the array (3).