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US5545888A
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US
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Digitizer circuit for a bar code reader
Assignee: Symbol Technologies LLC
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Filing: 1995-05-22
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Granted: 1996-08-13
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Expires: 2015-05-22
Abstract
Abstract A circuit for digitizing an analog signal generated from a photoelectric conversion of reflected light when scanning indicia having spatially-separated, light-reflective portions bounded by edges includes a differentiator for differentiating the analog signal. An inverter inverts the differentiated signal to generate an inverted signal. A negative peak detector detects negative amplitude peaks and a positive peak detector detects positive amplitude peaks of the differentiated signal and generate, respectively, a negative and positive peak signal. Adders are used to add the positive peak signal to the inverted signal, and the negative peak signal to the inverted signal. A comparator compares the two summed signals to the differentiated signal and generates pulse signals indicative of the edges of the analog signal. A controller, in response to the pulse signals, generates a digital signal corresponding to the indicia being scanned.
Inventors
- 👤 Edward Barkan
- 👤 Raj Bridgelall
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 14:12
CPC Classifications
G; G06; G06K; G06K7/00; G06K7/10; G06K7/10544; G06K7/10821; G06K7/10861; G06K7/10871; G06K7/10554; G06K7/10564; G06K7/10584; G06K7/10594; G06K7/10603; G06K7/10633; G06K7/10643; G06K7/10653; G06K7/10673; G06K7/10683; G06K7/10693; G06K7/10792; G06K7/10801; G06K7/10811; G06K7/10851; G06K7/10881; G06K7/10891; G06K7/109; G06K7/14; G06K7/1404; G06K7/146; G06K7/1478; G06K2207/00; G06K2207/1011; G06K2207/1016; G06K2207/1018
Claims Analysis
Total Claims: 30
Claim 1
Independent Claim
132 words
A circuit for digitizing an analog signal generated from a photoelectric conversion of reflected light when scanning indicia having spatially-separated, light-reflective portions bounded by edges, comprising: differentiating means for differentiating the analog signal to generate a differentiated signal; inverter means for inverting the differentiated signal to generate an inverted signal; a positive and negative peak detecting means for detecting positive and negative amplitude peaks of the differentiated signal to generate peak signals; summing means for summing each of the peak signals with the inverted signal to generate sum signals; comparator means for comparing sum signals with the differentiated signal, the comparator means generating pulse signals indicative of the edges of the analog signal; and control means responsive to the pulse signals for constructing a digital signal corresponding to the indicia being scanned.
Claim 2
Dependent Claim
132 words
A circuit for digitizing an analog signal generated from a photoelectric conversion of reflected light when scanning indicia having spatially-separated, light-reflective portions bounded by edges, comprising: differentiating means for differentiating the analog signal to generate a differentiated signal; inverter means for inverting the differentiated signal to generate an inverted signal; a positive and negative peak detecting means for detecting positive and negative amplitude peaks of the differentiated signal to generate peak signals; summing means for summing each of the peak signals with the inverted signal to generate sum signals; comparator means for comparing sum signals with the differentiated signal, the comparator means generating pulse signals indicative of the edges of the analog signal; and control means responsive to the pulse signals for constructing a digital signal corresponding to the indicia being scanned.
Claim 3
Dependent Claim
54 words
The circuit according to claim 1, wherein the positive and negative peak detecting means comprises: a positive peak detector for detecting positive amplitude peaks of the differentiated signal and generating a positive peak signal; and a negative peak detector for detecting negative amplitude peaks of the differentiated signal and generating a negative peak signal.
Claim 4
Dependent Claim
48 words
The circuit according to claim 2, wherein the summing means comprises: first means for summing the positive peak signal and the inverted signal and generating a first sum signal; and second means for summing the negative peak signal and the inverted signal and generating a second sum signal.
Claim 5
Dependent Claim
36 words
The circuit according to claim 3, wherein the comparator means comprises: first means for comparing the first sum signal to the differentiated signal; and second means for comparing the second sum signal to the differentiated signal.
Claim 6
Dependent Claim
46 words
The circuit according to claim 4, wherein the first comparing means includes means for generating a first pulse signal corresponding to negative-going edges of the indicia and the second comparing means includes means for generating a second pulse signal corresponding to positive-going edges of the indicia.
Claim 7
Dependent Claim
35 words
The circuit according to claim 5, wherein the control means includes a first circuit for receiving the first and second pulse signals and producing an output signal, the digital signal corresponding to the output signal.
Claim 8
Dependent Claim
36 words
The circuit according to claim 6, wherein the control means further includes: a second circuit for receiving the output signal and generating the digital signal; and means for generating a clock signal for the second circuit.
Claim 9
Dependent Claim
18 words
The circuit according to claim 7, wherein said differentiating means generates a first derivative of the analog signal.
Claim 10
Dependent Claim
46 words
The circuit according to claim 8, wherein the clock signal generating means includes: means for differentiating the first derivative signal to generate a second derivative signal of the analog signal; and means for detecting zero crossing of the second derivative signal and generating corresponding clock pulses.
Claim 11
Dependent Claim
28 words
The circuit according to claim 9, wherein the clock signal generating means further includes a time delay circuit to delay the clock pulses and producing the clock signal.
Claim 12
Dependent Claim
14 words
The circuit according to claim 7, wherein the first and second circuits are flip-flops.
Claim 13
Dependent Claim
22 words
The circuit according to claim 7, wherein the control means includes a margin threshold circuit for controlling output of the digital signal.
Claim 14
Dependent Claim
19 words
The circuit according to claim 1, further comprising scaling means for changing the amplitude peaks of the peak signal.
Claim 15
Dependent Claim
23 words
The circuit according to claim 13, wherein the scaling means includes a voltage divider for reducing the amplitude peaks of the peak signal.
Claim 16
Dependent Claim
21 words
The circuit according to claim 6, wherein the voltage divider reduces the amplitude peaks of the peak signal to approximately 50%.
Claim 17
Dependent Claim
17 words
The circuit according to claim 1, wherein the digitized signal corresponds to the edges of the indicia.
Claim 18
Independent Claim
145 words
A method for digitizing an analog signal generated from a photoelectric conversion of reflected light when scanning indicia having spatially-separated, light-reflective portions bounded by edges, the method comprising the steps of: differentiating the analog signal to generate a differentiated signal; inverting the differentiated signal to generate an inverted signal; detecting positive amplitude peaks of the differentiated signal and generating a positive peak signal; detecting negative amplitude peaks of the differentiated signal and generating a negative peak signal; summing the positive peak signal and the inverted signal and generating a first sum signal; summing the negative peak signal and the inverted signal and generating a second sum signal; comparing the first and second sum signals to the differentiated signal and generating pulse signals indicative of the edges of the analog signal; and generating, responsive to the pulse signals, a digital signal from the indicia being scanned.
Claim 19
Independent Claim
145 words
A method for digitizing an analog signal generated from a photoelectric conversion of reflected light when scanning indicia having spatially-separated, light-reflective portions bounded by edges, the method comprising the steps of: differentiating the analog signal to generate a differentiated signal; inverting the differentiated signal to generate an inverted signal; detecting positive amplitude peaks of the differentiated signal and generating a positive peak signal; detecting negative amplitude peaks of the differentiated signal and generating a negative peak signal; summing the positive peak signal and the inverted signal and generating a first sum signal; summing the negative peak signal and the inverted signal and generating a second sum signal; comparing the first and second sum signals to the differentiated signal and generating pulse signals indicative of the edges of the analog signal; and generating, responsive to the pulse signals, a digital signal from the indicia being scanned.
Claim 20
Dependent Claim
202 words
A circuit for digitizing an analog signal generated from a photoelectric conversion of reflected light when scanning indicia having spatially-separated, light-reflective portions bounded by edges, comprising: a differentiator for differentiating the analog signal to generate a differentiated signal; an inverter for inverting the differentiated signal to generate an inverted signal; a positive peak detector for detecting positive amplitude peaks of the differentiated signal and generating a positive peak signal; a negative peak detector for detecting negative amplitude peaks of the differentiated signal and generating a negative peak signal; an adder for summing the positive peak signal and the inverted signal and generating a first sum signal; an adder for summing the negative peak signal and the inverted signal and generating a second sum signal; a comparator for comparing the first sum signal with the differentiated signal, the comparator generating a first pulse signal indicative of the negative-going edges of the analog signal; a comparator for comparing the second sum signal with the differentiated signal, the comparator generating a second pulse signal indicative of the positive-going edges of the analog signal; and a controller responsive to the first and second pulse signals for constructing a digital signal corresponding to the indicia being scanned.
Claim 21
Dependent Claim
202 words
A circuit for digitizing an analog signal generated from a photoelectric conversion of reflected light when scanning indicia having spatially-separated, light-reflective portions bounded by edges, comprising: a differentiator for differentiating the analog signal to generate a differentiated signal; an inverter for inverting the differentiated signal to generate an inverted signal; a positive peak detector for detecting positive amplitude peaks of the differentiated signal and generating a positive peak signal; a negative peak detector for detecting negative amplitude peaks of the differentiated signal and generating a negative peak signal; an adder for summing the positive peak signal and the inverted signal and generating a first sum signal; an adder for summing the negative peak signal and the inverted signal and generating a second sum signal; a comparator for comparing the first sum signal with the differentiated signal, the comparator generating a first pulse signal indicative of the negative-going edges of the analog signal; a comparator for comparing the second sum signal with the differentiated signal, the comparator generating a second pulse signal indicative of the positive-going edges of the analog signal; and a controller responsive to the first and second pulse signals for constructing a digital signal corresponding to the indicia being scanned.
Claim 22
Dependent Claim
19 words
The circuit according to claim 18, further comprising scaling means for changing the amplitude peaks of the peak signal.
Claim 23
Dependent Claim
23 words
The circuit according to claim 19, wherein the scaling means includes a voltage divider for reducing the amplitude peaks of the peak signal.
Claim 24
Dependent Claim
21 words
The circuit according to claim 20, wherein the voltage divider reduces the amplitude peaks of the peak signal by approximately 50%.
Claim 25
Dependent Claim
17 words
The circuit according to claim 18, wherein the digitized signal corresponds to the edges of the indicia.
Claim 26
Dependent Claim
34 words
The circuit according to claim 18, wherein the controller includes a control circuit for receiving the first and second pulse signals and producing an output signal, the digital signal corresponding to the output signal.
Claim 27
Dependent Claim
18 words
The circuit according to claim 23, wherein said differentiator means generates a first derivative of the analog signal.
Claim 28
Dependent Claim
53 words
The circuit according to claim 24, including a clock signal generating means which includes: means for differentiating the first derivative signal to generate a second derivative signal of the analog signal; and means for detecting zero crossing of the second derivative signal and generating corresponding clock pulses for output to the control circuit.
Claim 29
Dependent Claim
12 words
The circuit according to claim 23, wherein the control circuit includes flip-flops.
Claim 30
Dependent Claim
22 words
The circuit according to claim 23, wherein the control circuit includes a margin threshold circuit for controlling output of the digital signal.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1999-08-13 | 2000-02-12 | 2000-08-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2003-08-13 | 2004-02-12 | 2004-08-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2007-08-13 | 2008-02-12 | 2008-08-13 | $7700.00 | Window Closed / Lapsed |