Intercharacter gap detector for MICRS

• US 4,381,494 A
• Filed: 10/06/1980
• Issued: 04/26/1983
• Est. Priority Date: 10/06/1980
• Status: Expired due to Term

• Current Assignee: Unisys Corporation
• Original Assignee: Burroughs Incorporated (Terreno Realty Corp.)
• Inventors: Wisner, Daniel A.
• Primary Examiner(s): Boudreau, Leo H.
• Application Number:
  US06/194,045
• Time in Patent Office: 932 Days
• Field of Search: 340/146.3 C, 340/146.3 AG, 340/146.3 SG, 340/146.3 Y, 235/449, 235/450, 235/474, 235/92 T, 235/92 LG, 235/92 PB, 360/25, 360/32, 360/57, 360/137, 360/50
• US Class Current: 382/320
• CPC Class Codes: G06V 30/2253 Recognition of characters printed with magnetic ink G06V30/2247 takes precedence

Abstract

System for determining whether magnetic ink is present on specific areas of a document bearing magnetic ink characters. Signals are produced as a magnetic read head passes over the area in question on the face of the document. These signals are routed to apparatus which operates in response to the signals by providing outputs of a first kind when magnetic ink is present and outputs of another kind when ink is not present or is not present in sufficient amount to produce a signal exceeding a threshold value. Logic means responsive to the signals of the first and second kinds establish the presence or absence of magnetic material.

Claims

1. In a character recognition system, means for determining whether magnetic material is present in a particular concentration in an area of a document scanned by a magnetic character read head, comprising:

means responsive to raw signals from a magnetic character read head for providing output signals, said output signals including first signals which are generated by passage of the read head past magnetic material which is present in a particular concentration and second signals denoting passage of the read head past areas where magnetic material is present in less than the particular concentration;

said means responsive to raw signals including a threshold detector including two differential comparators coupled to produce said first signals and said second signals, where the first signals include extraneous noise and the second signals are substantially free of noise; and

means coupled responsive to said first signals and said second signals to establish the presence or absence of magnetic material in the particular concentration for periods determined in accordance with said signals.

2. The invention as claimed in claim 1, in which:

the means coupled to establish the presence or absence of magnetic material in the particular concentration includes a counter;

said counter is reset by logic ZERO among said first and second signals, said counter responding to being reset by starting the count of clock pulses;

and

said counter providing a logic ONE output when a count of pulses representing two feature periods is reached.

3. In a character recognition system, means for determining whether magnetic material is present under a read head, comprising:

threshold detector means coupled responsive to signals from a magnetic character read head for providing logic signals of which first logic signals denote the presence of a strong concentration of magnetic material and second logic signals denote a weaker concentration of magnetic material; and

means coupled responsive to said second logic signals to measure the duration of said signals and establish the presence of the weaker concentration of magnetic material.

4. The invention as claimed in claim 3, in which:

the detector means operates as a threshold detector including two differential comparators coupled to distinguish between said first logic signals and said second logic signals, where the first logic signals include extraneous noise and the second logic signals are substantially free of noise.

5. The invention as claimed in claim 3 or 4, in which:

the means coupled responsive to said second logic signals to measure the duration of said signals and establish the presence of the weaker concentration of magnetic material includes a counter;

said counter is reset by logic ZERO among said first and second signals, said counter responding to being reset by starting the count of clock pulses; and

said counter providing a logic ONE output coupled to stop the counter when a count of pulses representing two feature periods is reached.

6. In a character recognition system, means for determining whether magnetic material is present in critical quantities in areas of a document being scanned by a magnetic character read head, comprising:

means responsive to raw signals from a magnetic character read head for providing output signals, said output signals including first signals of a kind denoting passage of the read head past areas of a document bearing critical quantities of magnetic material and second signals of a kind denoting passage of the read head past areas bearing less than critical quantities of magnetic material;

counter means coupled to distinguish between said first and second signals;

said counter means being responsive to selected ones of said first signals to reset to zero count and then prevent the accumulation of a count,

said counter means being responsive to said second signals to continue a count, unless disturbed by a first signal, and to provide a logic ONE after a count of said second signals which is two feature periods long, where said count two feature periods long denotes an intercharacter space two feature periods wide containing an amount of magnetic material which is less than that required to produce a signal of the first kind.

7. The invention as claimed in claim 6, in which:

the means responsive to raw signals includes a threshold detector including two differential comparators coupled to distinguish between said first signals and said second signals, where said first signals include extraneous noise and said second signals are substantially free of noise.

8. In a character recognition system for discriminating between areas of a document bearing magnetic material in sufficient quantity to form a character and areas of a document bearing less magnetic material, means comprising:

a threshold detector coupled to accept input signals from a magnetic read head,

said detector providing first output signals representing excursions of a first group of said input signals beyond certain threshold levels corresponding to areas on a document in which a minimum concentration of magnetic material is found;

said detector providing second output signals representing excursions of a second group of said input signals within certain threshold levels corresponding to areas on a document in which the concentration of magnetic material is less than the minimum required to provide signals of the first group;

counter means coupled responsive to said first and said second group of input signals;

said counter means responding to input signals of the first group to reset repeatedly to zero and provide a fixed value at its output;

said counter means responding to input signals of the second group by continuing to count, unless disturbed by a first signal, to provide a logic ONE after a count which is two feature periods long where said count two feature periods long denotes the presence of an intercharacter space two feature periods wide.

9. In a character recognition system, means for determining whether magnetic material is present in a particular concentration in an area of a document scanned by a magnetic character read head, comprising:

means responsive to raw signals from a magnetic character read head for providing output signals, said output signals including first signals which are generated by passage of the read head past magnetic material which is present in a particular concentration and second signals denoting passage of the read head past areas where magnetic material is present in less than the particular concentration;

means coupled responsive to said first signals and said second signals to establish the presence or absence of magnetic material in the particular concentration for periods determined in accordance with said signals;

said means coupled to establish the presence or absence of magnetic material in the particular concentration including a counter;

said counter being reset by logic ZERO among said first and second signals, said counter responding to being reset by starting the count of clock pulses; and

said counter providing a logic ONE output when a count of pulses representing two feature periods is reached.