| 摘要 |
<p>992, 578. Automatic character reading. ELECTRIC & MUSICAL INDUSTRIES Ltd. Aug. 28, 1961 [Aug. 30, 1960], No. 29805/60. Heading G4R. In character reading apparatus there are means for scanning the character and means for obtaining "black" signals during two predetermined periods of the scan at the top and bottom ends and means responsive to differences in integrated black signals in the two periods for changing the position of the scan raster so as to register with the character. Figs. 3a, 3b show the relationship between sampling pulses P 1 , P 2 and the parts A 1 , A 2 of the waveform of the output of a photomultiplier, when a scanned character is symmetrically located relative to the scan, parts A 1 , A 2 corresponding to the unmarked white portions above and below the character which are scanned. In the arrangement of Fig. 4 the photomultiplier output is applied via amplifier 1 to a stage 2 which fixes the upper and lower levels of the signal. The output is fed to two AND gates 3, 4 to which are applied respectively sampling pulses P 1 , P 2 . If a 'black' signal occurs at the output of the photomultiplier while pulse P 1 and/or pulse P 2 is being applied to the gates, indicating a misalignment of the raster and the character, an output will be derived from gate 3 and/or gate 4 and will be fed through integrators 5, 6 and peak rectifiers 7, 8 respectively to a differential amplifier 9, the output from which is applied to the scan generator to alter the relative position of the character and the raster in such a direction as to locate the character symmetrically with respect to the raster. In an alternative arrangement, Fig. 6, two-state devices 15, 16 are used, devices 15, 16 being triggered into their '1' state by the occurence of a 'black' signal during the duration of pulses P 1 , P 2 respectively, and are returned to their 'O' state respectively in response to the end of pulse P 1 , detected by an end gate 13, and to the end of a black signal detected by an end gate 14. When in their ' 1' state, the outputs of devices 15, 16 are connected through circuits 5, 7 and 6, 8 respectively, as before, to differential amplifier 9 to alter the position of the raster relative to the character. Other arrangements, not shown, for deriving scan position correcting signals are described.</p> |
