DOCUMENT SCANNING AND DISPLAY SYSTEMS

1307147 Sorting letters by television NATIONAL CASH REGISTER CO 22 June 1971 [2 Oct 1970] 29167/71 Heading H4F Remote control of the destinations of a succession of objects, e.g. letters 10-on a conveyer 13 is enabled by illuminating each letter when it enters a viewing station, such that a television camera 20 can view each letter in turn and send the video signal to selected respective channels on a recording medium 32, the recorded signals being fed in parallel to respective monitor displays 34 viewed by operators who, by means of key boards 36, direct the respective letters to their destinations. Each letter has its trailing edge detected by a light source 14, photo diode 16 and detector station 12, the resulting signal being fed to a control unit where it causes, after a prescribed delay (such that the letter is now passing the camera) the operation of flash lamps 22. The duration of the flash is such that a two field interlaced-picture can be taken by the camera. Each field is recorded on a single track of the recording medium 32-e.g. a magnetic drum, the two adjacent tracks containing the recordings of the two fields being termed, "a channel". Due to the rapid fade of the charge image on the vidicon target, the second field. signal has to be boosted to make it equal to the first. This may be done by: (a) operating with low beam current for the first field and high beam current for the second field, (b) increasing the average D.C. voltage level of the second field to equalize the brightnesses; (c) increasing the gain of the video amplifier during the second field. The video signal is converted to an f.m. modulation at 26 and is directed to the correct channel track by track selector 27 and control unit 18. The track number and time of recording is recorded in a respective sector of a sector memory track on the drum 32. The recorded video signals are read out as selected by unit 30 and demodulated in units 33. The demodulated signals are fed via directing means 35 to respective display monitors 34. The outputs of the keyboards 36 are fed to a channel director 28, for recording on the respective sector of the sector memory track, and direction to the letter sorting mechanism. Direction of a letter enables the channel to be cleared for the recording of the next letter image. The recording which has been longest on the drum, is next fed to the now unused monitor. Clock signals, from which the camera and monitor seam signals are derived, are recorded on a