US5286960A — Method of programmable digitization and bar code …

Claim 1

Independent Claim 137 words

A method of accurately reconstructing from a sampled analog signal bar-to-space and space-to-bar transition points in a symbol comprising the steps of: accepting as input successive samples from an analog signal, said samples being representative of levels of reflectivity of a symbol being scanned; determining a white value associated with a space and a black value associated with a bar on said symbol; determining a threshold between said black value and said white value; determining from said input a preceding sample and a succeeding sample having values that bracket said threshold; and determining a transition point and an offset of said transition point from said preceding sample to define a first time interval therebetween by performing an interpolation that is limited to an interval between said preceding sample and said succeeding sample in the absence of upsampling.

Claim 2

Independent Claim 137 words

A method of accurately reconstructing from a sampled analog signal bar-to-space and space-to-bar transition points in a symbol comprising the steps of: accepting as input successive samples from an analog signal, said samples being representative of levels of reflectivity of a symbol being scanned; determining a white value associated with a space and a black value associated with a bar on said symbol; determining a threshold between said black value and said white value; determining from said input a preceding sample and a succeeding sample having values that bracket said threshold; and determining a transition point and an offset of said transition point from said preceding sample to define a first time interval therebetween by performing an interpolation that is limited to an interval between said preceding sample and said succeeding sample in the absence of upsampling.

Claim 3

Dependent Claim 167 words

The method of claim 1, further comprising the steps of generating an output, said output undergoing a transition between a first value representative of one of said black and white values to a second value representative of another of said black and white values after elapse of said first time interval following said determination of said transition point; and wherein said step of determining a threshold is performed by steps comprising: calculating an excursion as the unsigned difference between said white value and said black value; calculating a magnitude as the product of said excursion and a constant; when said output is indicative of a high level of reflectivity, adjusting said white value by said magnitude in a direction that indicates decreasing reflectivity and determining said threshold as said adjusted white value; and when said output is indicative of a low level of reflectivity, adjusting said black value by said magnitude in a direction that indicates increasing reflectivity, and determining said threshold as said adjusted black value.

Claim 4

Dependent Claim 64 words

The method of claim 1, further comprising the step of generating an output prior to completely scanning the symbol, said output undergoing a transition between a first value representative of one of said black and white values to a second value representative of another of said black and white values after elapse of said first time interval following said determination of said transition point.

Claim 5

Dependent Claim 25 words

The method of claim 3, wherein said step of generating an output further comprises the step of initially generating said output at a predefined state.

Claim 6

Dependent Claim 23 words

The method of claim 4, wherein said predefined state has a value that corresponds to a high level of reflectivity in said symbol.

Claim 7

Dependent Claim 23 words

The method of claim 4, wherein said predefined state has a value that corresponds to a low level of reflectivity in said symbol.

Claim 8

Dependent Claim 27 words

The method of claim 4, wherein said predefined state has a value that is indicative of an initial reflectivity in accordance with a value from said input.

Claim 9

Dependent Claim 32 words

The method of claim 3, wherein said white value and said black value are determined from samples that are indicative of the highest and lowest levels of reflectivity in said symbol respectively.

Claim 10

Dependent Claim 50 words

The method of claim 3, wherein said step of generating an output comprises the step of generating a digitizer output that has a logical state at another logical state when a transition point is determined, whereby said digitizer output is indicative of high and low reflectivity levels in said symbol.

Claim 11

Dependent Claim 37 words

The method of claim 3, wherein said step of generating an output comprises the step of outputting a signal having a value that is indicative of a elapsed second time interval since said signal was last generated.

Claim 12

Dependent Claim 121 words

The method of claim 9 wherein said step of determining a threshold is performed by steps comprising: calculating an excursion as the unsigned difference between said white value and said black value; calculating a magnitude as the product of said excursion and a constant; when said digitizer output has a logical state indicative of a high level of reflectivity, adjusting said white value by said magnitude in a direction that indicates decreasing reflectivity and determining said threshold as said adjusted white value; and when said digitizer output has a logical state indicative of a low level of reflectivity, adjusting said black value by said magnitude in a direction that indicates increasing reflectivity, and determining said threshold as said adjusted black value.

Claim 13

Dependent Claim 17 words

The method of claim 11 wherein said constant is in a range of between 0.2 and 0.6.

Claim 14

Dependent Claim 13 words

The method of claim 11 wherein said constant has a value of 0.25.

Claim 15

Dependent Claim 34 words

The method of claim 3, wherein said white value and said black value are respectively determined from averages of samples that are associated with analog inputs indicative of high and low levels of reflectivity.

Claim 16

Dependent Claim 24 words

The method of claim 3, wherein said step of determining said white value and said black value is performed by assigning predetermined values thereto.

Claim 17

Dependent Claim 20 words

The method of claim 3, wherein said step of determining said threshold is performed by assigning a predetermined value thereto.

Claim 18

Dependent Claim 45 words

The method of claim 3, wherein said white value and said black value are determined from samples that are accepted subsequent to a generation of said output and are respectively indicative of the highest and lowest levels of reflectivity in a portion of said symbol.

Claim 19

Dependent Claim 20 words

The method of claim 17, wherein said samples are accepted subsequent to no more than two generations of said output.

Claim 20

Dependent Claim 10 words

The method of claim 3, wherein said interpolation is linear.

Claim 21

Dependent Claim 23 words

The method of claim 19 wherein said linear interpolation has a precision that is limited to 1/8th of the interval between successive samples.

Claim 22

Dependent Claim 10 words

The method of claim 3 wherein said interpolation is non-linear.

Claim 23

Dependent Claim 242 words

A bar code scanner, comprising: light receiving means for detecting light reflected from said symbol, and for generating a sampled analog signal in response thereto that is indicative of the bar-space pattern of said bar code symbol; analog to digital converting means for converting said analog signal to a digital signal; microprocessor means, accepting said digital signal as an input, for determining transition points that correspond to bar-to-space and space-to-bar transitions in said bar code symbol, said microprocessor means having a program resident in a memory thereof for determining a threshold, said program executing the steps of: determining a white value associated with a space and a black value associated with a bar on said bar code symbol; determining a threshold between said black value and said white value; determining from said digital signal a preceding sample and a succeeding sample having values that bracket said threshold; determining a transition point and an offset of said transition point from said preceding sample to define a first time interval therebetween by performing an interpolation that is limited to an interval between said preceding sample and said succeeding sample in the absence of upsampling; and generating an output that undergoes a transition between a first value representative of one of a high and low reflectivity levels to a second value representative of another of said high and low reflectivity levels after elapse of said first time interval following said determination of said transition point.

Claim 24

Dependent Claim 242 words

A bar code scanner, comprising: light receiving means for detecting light reflected from said symbol, and for generating a sampled analog signal in response thereto that is indicative of the bar-space pattern of said bar code symbol; analog to digital converting means for converting said analog signal to a digital signal; microprocessor means, accepting said digital signal as an input, for determining transition points that correspond to bar-to-space and space-to-bar transitions in said bar code symbol, said microprocessor means having a program resident in a memory thereof for determining a threshold, said program executing the steps of: determining a white value associated with a space and a black value associated with a bar on said bar code symbol; determining a threshold between said black value and said white value; determining from said digital signal a preceding sample and a succeeding sample having values that bracket said threshold; determining a transition point and an offset of said transition point from said preceding sample to define a first time interval therebetween by performing an interpolation that is limited to an interval between said preceding sample and said succeeding sample in the absence of upsampling; and generating an output that undergoes a transition between a first value representative of one of a high and low reflectivity levels to a second value representative of another of said high and low reflectivity levels after elapse of said first time interval following said determination of said transition point.

Claim 25

Dependent Claim 16 words

The bar code scanner of claim 22, wherein said scanner is contained in a single housing.

Claim 26

Dependent Claim 12 words

The bar code scanner of claim 22, wherein said output is digitized.

Claim 27

Dependent Claim 27 words

The bar code scanner of claim 22, further comprising means responsive to said microprocessor means for generating a signal that is indicative of said first time interval.

Claim 28

Dependent Claim 35 words

The bar code scanner of claim 25, wherein said means for generating generates a signal having a value that is indicative of a second time interval that has elapsed since a signal was last generated.

Claim 29

Dependent Claim 75 words

The bar code scanner of claim 22 wherein said step of determining a threshold further comprises the steps of: calculating an excursion as the unsigned difference between said white value and said black value; calculating a magnitude as the product of said excursion and a constant; adjusting said white value by said magnitude in a direction that indicates decreasing reflectivity; and adjusting said black value by said magnitude in a direction that indicates increasing reflectivity.

Claim 30

Dependent Claim 19 words

The bar code scanner of claim 27 wherein said constant is in a range of between 0.2 and 0.6.

Claim 31

Dependent Claim 15 words

The bar code scanner of claim 27 wherein said constant has a value of 0.25.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1997-02-14	1997-08-16	1998-02-15	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	2001-02-14	2001-08-16	2002-02-15	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2005-02-14	2005-08-16	2006-02-15	$7700.00	Window Closed / Lapsed

Method of programmable digitization and bar code scanning apparatus employing same

Abstract

Inventors

Bibliographic Details

Claims Analysis

References Cited (Backward Citations)

USPTO Annuity & Maintenance Windows

Assigned Categories & Tags

Assign Category Tag