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US Patent 5073700 - Mark sense detector with variable threshold
US Patent Issued on December 17, 1991
Estimated Patent Expiration Date:
January 10, 2010Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
Estimated Patent Expiration Date:
January 10, 2010Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.AbstractA mark sense detector with a threshold detector having a weighted and variable threshold discriminates reflective variations on an illuminated surface such as a hand-marked lottery entry card having a plurality of tracks with potential reflective variations occurring at discrete positions thereon. The card is fed relative to an array of photodetectors for the tracks, each photodetector producing an input signal for a respective one of the tracks in response to reflections of the illuminated surface, the input signal varying with marks and with parameters of the illumination and feeding. The track input signals are applied to follower amplifiers for each of the tracks. An integrator for each of the tracks averages the output of the follower amplifier, the average being divided and applied as the threshold input to a comparator for each of the tracks. The integrator has different time constants for charging and discharging and is blocked by a diode against discharging through the follower, thereby favoring detection of marks. The division of the average level applied as the comparator threshold can be switchable as a function of card parameters. One of the detector channesl can be used for edge detection. | InventorApplicationNo. 462817 filed on 01/10/1990US Classes:235/436, Readout control235/455, Light level control235/456, Multiple column code250/556, Document verification or graph reader250/557With means to position, direct, or detect recordField of Search235/436, Readout control235/454, Optical235/455, Light level control235/456, Multiple column code250/556, Document verification or graph reader250/557With means to position, direct, or detect recordExaminersPrimary: Trafton, David L.Attorney, Agent or FirmUS Patent References3303329, 3692983, 3747066, 3751636, 3814944, 3846623, 3872329, 3949233, Hand held bar code reader with constant linear amplifier outputIssued on: 04/06/1976 Inventor: Gluck4047023, Color mark detector with pulsed source and synchronous demodulation Issued on: 09/06/1977 Inventor: Key , et al.4162408, Optical mark sense detector Issued on: 07/24/1979 Inventor: Hansen4196845, Bar-coded data input terminals Issued on: 04/08/1980 Inventor: Chesters4230265, Adaptive threshold optical reader Issued on: 10/28/1980 Inventor: Casaly4335301, Wave shaping circuit for electro-optical code readers Issued on: 06/15/1982 Inventor: Palmer , et al.4356389, Bar code scanner interface Issued on: 10/26/1982 Inventor: Quirey , et al.4578568, Data reader Issued on: 03/25/1986 Inventor: Tsuzuki4724307, Marked card reader Issued on: 02/09/1988 Inventor: Dutton , et al.4870262Signal processing apparatus and binary encoder circuit for the same Issued on: 09/26/1989 Inventor: Hasegawa International ClassG06K 007/00 |
