| 摘要 |
1,168,111. Electric synchronizing. INSTITUTE FOR SCIENTIFIC INFORMATION. 19 Jan., 1967 [21 March, 1966], No. 2846/67. Heading H2L. [Also in Division H4] A document to be copied is scanned linewise by a photo-electric strip element 30, Fig. 1, which is moved down the document by hand to introduce the other component of scan, the resulting electric signals being applied to a xerographic recorder 14 in which the recording strip 50 is caused to move in synchronism with the movements imparted to element 30. A rotatable apertured drum is mounted on the side of the housing for element 30 so as to engage the document and co-operates with a lamp (not shown) and a photo-cell 82 to generate pulses representing by their number the distance moved. The recording strip is moved by a motor 66 whilst a similar drum and photo-cell assembly 92, 98 produces pulses representing the strip movement. The pulses from photo-cell 82 drive an up-down bit counter 88, Fig. 2, in one direction, whilst the pulses from photo-cell 98 drive the counter in the reverse direction back to zero. Departure of the count from zero is detected by threshold logic 90 which controls motor 66. The photo. electric element comprises a known assembly of a photo-sensitive strip and a linear array of biased diodes. The arrangement is controlled by a ramp or staircase generator 34 which brings the diodes into conduction in sequence thereby simultating a line scan. The line scan in the xerographic recorder is effected by an electrode wheel assembly 44 which rotates in a direction transverse the direction of movement of strip 50. Each electrode is in the form of a spoke which terminates at the wheel rim and co-operates with an earthed plate 42 to lay down charges on the strip. Signals are applied to the electrodes via brush 38 bearing on the wheel hub. Commencement of line scan by the operative electrode is detected by a photo-cell 122 when the spoke interrupts the light beam from lamp 118. The photo-cell triggers generator 34 by way of a NOR gate 116 which is controlled as shown in Fig. 2, by a signal from a NAND gate 112 which in turn receives signals from flip-flops 110 and 114 triggered at each pulse from photo-cells 82 and 98. The circuit operates to synchronize the line scan in photo-electric element 30 to the recording electrode scan such that one scan only is made in response to each incremental movement which gives rise to a pulse from photo-cell 82. The recording is developed in known manner by apparatus 52. Photo-electric element 30 is exposed to the document through a slit 81, the housing having also an opening so that the user may see what is being copied. |
