Registers – Coded record sensors – Particular sensor structure
Patent
1978-05-26
1980-08-12
Kilgore, Robert M.
Registers
Coded record sensors
Particular sensor structure
35 48B, 235455, G06K 710, G09B 2706
Patent
active
042174872
ABSTRACT:
After certain checks have been automatically made, and answer document is continuously scanned by successively and repeatedly switching the various phototransistors, one for each column of response positions or bubbles printed with ink visible to infrared energy, into a conductive or light-responsive state. In this way, between timing marks, each phototransistor is constantly employed to determine the light transmittivity of the document as far as that particular phototransistor is concerned. When an opaque timing mark is not passing by an additional phototransistor assigned to sense light passing through the document at that period, the data obtained is used to determine what the level of paper translucency is, an average paper level being stored for each cell that is subsequently compared with acquired data obtained between later arriving timing marks, the average being modified as required. Whereas a number of scanning loops occur during the periods when there are no timing marks, additional scanning loops, owing to the constant scanning, take place during the interval when a timing mark is passing by and it is during these additional loops that the data is examined to see how dark any response bubble in that particular row is and the reading thus obtained is compared against the paper level, here again the comparison being for each particular phototransistor.
REFERENCES:
patent: 3201569 (1965-08-01), Conron
patent: 3536894 (1970-10-01), Travioli
patent: 3539777 (1970-11-01), Rohland
patent: 3628031 (1971-12-01), Azure
patent: 3643066 (1972-02-01), Coliz
patent: 3737628 (1973-06-01), Azure
patent: 3829662 (1974-08-01), Furahashi
Thomas-Tyndall-"Digital Feedback Light-Emitting Diode Control", IBM Tech. Disc. Bull., vol. 16, No. 8, Jan. 1974, pp. 2598-2600.
Kilgore Robert M.
National Computer Systems, Inc.
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