| 摘要 |
An optical reading apparatus is described for reading documents which contain information in the form of optical markings which deflect a reading beam coming from a light source in at least one given direction of deflection. A first light sensor detects a deflected partial beam. A second light sensor, the optical axis of which lies in a given direction of deflection, is only receptive to those light rays deflected at the document which lie outside a first cone and inside a second cone which is coaxial with the second light sensor. A comparator compares the electrical signals of both light sensors. Altered markings, which cause additional dispersion of the reading beam, can be reliably distinguished from the unaltered markings. |
