Image analyser using pierced mask - for scanning image on rotating drum, and photodiodes for detecting light intensity passing through holes

摘要

The image analyser comprises a transparent rotatable drum (1) made of e.g. glass, and containing a light source (6). The drum carries an elongate mask (7) extending axially of the drum (1) along its outer surface and having a line of fine holes (8) of dia. 0.1mm through which light from the light source (6) can pass. The mask is closed by a plate (10) containing photodiodes (12) which detect the light passing through the holes (8). The mask (7) and plate (10) are supported on rollers (18) and coupled to the drive motor (5) of the drum such that when the drum (1) is rotated the mask (7) and plate (10) are axially moved to scan a document secured on the drum (1) surface beneath the mask (7). A magnetic strip (25) on the drum circumference is sensed by a sensing head (26) which causes the photodiodes to be read each 0.1mm rotation of the drum. A 1m2 document can be scanned to a precision of 108 points.