US5777314A
Expired / Lapsed
US
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Optical scanner with fixed focus optics
Assignee: Technologies Inc
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Filing: 1996-11-05
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Granted: 1998-07-07
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Expires: 2016-11-05
Abstract
Abstract Methods are provided to assist in selection of appropriate optical components for optimizing performance of the optical scanner for reading one-, two- and three-dimensional optically encoded information at a wide range of field depths and angles. The optical components are fixed in position relative to each other so that no position adjustments are required to obtain a reading at a desired distance once the optical components are optimized. Among the parameters that are considered are LEDs for emitting light within specific wavelength ranges, optical filters, lens focal lengths, magnification, etc. The Fourier transform of an input square wave signal generated by light reflected from a bar code is used to generate the appropriate resolution requirements. Selection of appropriate optical components is dependent upon the intended operation of the scanner. For example, depth of field is considered, as is scan angle and density of the code to be read. The performance models are based upon the modulation transfer function (MTF) of the optical system, comprising the encoded information, the lens system and the CCD array.
Inventors
- 👤 Alexander Roustaei
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 02:22
CPC Classifications
G; G06; G06K; G06K7/00; G06K7/10; G06K7/10544; G06K7/10712; G06K7/10722; G06K7/10742; G03; G03F; G03F7/00; G03F7/70; G03F7/70483; G03F7/70491; G03F7/705; G06K7/10732; G06K7/10792; G06K7/10801; G06K7/10811; G06K7/12
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
285 words
An optical assembly within an optical scanner for scanning a symbol comprising a plurality of contrasting regions representative of encoded information, each contrasting region having a bar width, wherein said symbol is illuminated by incident light to produce modulated reflected light providing a square wave input representative of said plurality of contrasting regions, said optical assembly comprising: at least two LEDs for generating the incident light; a detector array for detecting the square wave input and generating an electrical signal representative of the square wave input, said detector array comprising a plurality of CCDs and having an array area; a fixed focus multi-element lens system having a pre-selected magnification for receiving the modulated reflected light and providing focused reflected light to said detector array, the pre-selected magnification being selected so that the focused reflected light impinges upon a substantial portion of said array area over a range of distances to said symbol; wherein said at least two LEDs, said detector array, and elements of said multi-element lens system are selected by determining a spatial frequency of said plurality of contrasting regions, calculating a square wave modulation transfer function using the Fourier transform of the square wave input to determine an initial optical resolution, comparing the initial optical resolution to a minimum required optical resolution for a given density of the plurality of contrasting regions to determine whether a particular symbol with the given density can be read at a given distance from the symbol, and varying the elements of said multi-element lens system to provide an adjusted magnification and an adjusted optical resolution greater than the minimum required optical resolution at the given distance and to obtain equal resolvability for an entire field of view.
Claim 2
Dependent Claim
285 words
An optical assembly within an optical scanner for scanning a symbol comprising a plurality of contrasting regions representative of encoded information, each contrasting region having a bar width, wherein said symbol is illuminated by incident light to produce modulated reflected light providing a square wave input representative of said plurality of contrasting regions, said optical assembly comprising: at least two LEDs for generating the incident light; a detector array for detecting the square wave input and generating an electrical signal representative of the square wave input, said detector array comprising a plurality of CCDs and having an array area; a fixed focus multi-element lens system having a pre-selected magnification for receiving the modulated reflected light and providing focused reflected light to said detector array, the pre-selected magnification being selected so that the focused reflected light impinges upon a substantial portion of said array area over a range of distances to said symbol; wherein said at least two LEDs, said detector array, and elements of said multi-element lens system are selected by determining a spatial frequency of said plurality of contrasting regions, calculating a square wave modulation transfer function using the Fourier transform of the square wave input to determine an initial optical resolution, comparing the initial optical resolution to a minimum required optical resolution for a given density of the plurality of contrasting regions to determine whether a particular symbol with the given density can be read at a given distance from the symbol, and varying the elements of said multi-element lens system to provide an adjusted magnification and an adjusted optical resolution greater than the minimum required optical resolution at the given distance and to obtain equal resolvability for an entire field of view.
Claim 3
Dependent Claim
43 words
An optical assembly within an optical scanner as in claim 1 wherein each CCD within said detector array is assumed to have a modulation transfer function which is approximately 1.0 over a standard range of spatial frequencies for said plurality of contrasting regions.
Claim 4
Dependent Claim
26 words
An optical assembly within an optical scanner as in claim 1 wherein the minimum required optical resolution is determined according to the relationship: F.sub.s =1/(magnification)(bar width).
Claim 5
Dependent Claim
69 words
An optical assembly within an optical scanner as in claim 1 wherein a combination of said CCDs and said at least two LEDs is selected according to the relationship: V.sub.out =∫V(λ)F(λ)d(λ), where V(λ) is the CCD spectral sensitivity in volts/lumen/micron and F(λ) is the flux output in lumens/micron of each LED of said at least two LEDs so that an output voltage V out of the CCDs is maximized.
Claim 6
Dependent Claim
21 words
An optical assembly within an optical scanner as in claim 1 wherein said multi-element lens system includes an optical bandpass filter.
Claim 7
Dependent Claim
25 words
An optical assembly within an optical scanner as in claim 1 wherein the range of distances to said symbol is 0.5 inches to 20 inches.
Claim 8
Dependent Claim
25 words
An optical assembly within an optical scanner as in claim 6 wherein the range of distances covers a field of view of up to 30°.
Claim 9
Dependent Claim
26 words
An optical assembly within an optical scanner as in claim 1 wherein said multi-element lens system is disposed at a fixed distance from said detector array.
Claim 10
Dependent Claim
24 words
An optical assembly within an optical scanner as in claim 1 wherein the magnification of said multi-element lens systems is optimized using ray tracing.
Claim 11
Dependent Claim
42 words
An optical assembly within an optical scanner as in claim 1 wherein said at least two LEDs produce sufficient illumination to obtain an output signal greater than the dark voltage noise from said detector array over the entire said range of distances.
Claim 12
Dependent Claim
269 words
A CCD optical scanner for scanning a symbol comprising a plurality of contrasting regions representative of encoded information, each contrasting region having a bar width, wherein the symbol is illuminated by incident light from at least two LEDs to produce modulated reflected light providing a square wave input representative of the plurality of contrasting regions, the square wave input being detected by a detector array comprising at plurality of CCDs and having an array area, the improvement comprising: a multi-element lens system having a fixed focus with a pre-selected magnification for receiving the modulated reflected light and providing focused reflected light to the detector array, the pre-selected magnification being selected so that the focused reflected light impinges upon a substantial portion of the array area over a range of distances to the symbol; wherein elements of said multi-element lens system are selected in combination with the at least two LEDs and the detector array by determining a spatial frequency of the plurality of contrasting regions, calculating a square wave modulation transfer function using the Fourier transform of the square wave input to determine an initial optical resolution, comparing the initial optical resolution to a minimum required optical resolution for a given density of said plurality of contrasting regions to determine whether a particular symbol with the given density can be read at a given distance from said symbol, and varying the elements of said multi-element lens system to provide an adjusted magnification and an adjusted optical resolution greater than the minimum required optical resolution at the given distance and to obtain equal resolvability for an entire field of view.
Claim 13
Dependent Claim
269 words
A CCD optical scanner for scanning a symbol comprising a plurality of contrasting regions representative of encoded information, each contrasting region having a bar width, wherein the symbol is illuminated by incident light from at least two LEDs to produce modulated reflected light providing a square wave input representative of the plurality of contrasting regions, the square wave input being detected by a detector array comprising at plurality of CCDs and having an array area, the improvement comprising: a multi-element lens system having a fixed focus with a pre-selected magnification for receiving the modulated reflected light and providing focused reflected light to the detector array, the pre-selected magnification being selected so that the focused reflected light impinges upon a substantial portion of the array area over a range of distances to the symbol; wherein elements of said multi-element lens system are selected in combination with the at least two LEDs and the detector array by determining a spatial frequency of the plurality of contrasting regions, calculating a square wave modulation transfer function using the Fourier transform of the square wave input to determine an initial optical resolution, comparing the initial optical resolution to a minimum required optical resolution for a given density of said plurality of contrasting regions to determine whether a particular symbol with the given density can be read at a given distance from said symbol, and varying the elements of said multi-element lens system to provide an adjusted magnification and an adjusted optical resolution greater than the minimum required optical resolution at the given distance and to obtain equal resolvability for an entire field of view.
Claim 14
Dependent Claim
44 words
A CCD optical scanner as in claim 11 further comprising the improvement that each CCD within the detector array is assumed to have a modulation transfer function which is approximately 1.0 over a standard range of spatial frequencies for said plurality of contrasting regions.
Claim 15
Dependent Claim
23 words
A CCD optical scanner as in claim 11 wherein the minimum required optical resolution is determined according to the relationship: F.sub.s =1/(magnification)(bar width).
Claim 16
Dependent Claim
70 words
A CCD optical scanner as in claim 11 further comprising the improvement that a combination of the CCDs and said at least two LEDs is selected according to the relationship: V.sub.out =∫V(λ)F(λ)d(λ), where V(λ) is the CCD spectral sensitivity in volts/lumen/micron and F(λ) is the flux output in lumens/micron of each LED of the at least two LEDs so that an output voltage V out of the CCDs is maximized.
Claim 17
Dependent Claim
18 words
A CCD optical scanner as in claim 11 wherein said multi-element lens system includes an optical bandpass filter.
Claim 18
Dependent Claim
22 words
A CCD optical scanner as in claim 11 wherein the range of distances to said symbol is 0.5 inches to 20 inches.
Claim 19
Dependent Claim
22 words
A CCD optical scanner as in claim 10 wherein the range of distances covers a field of view of up to 30°.
Claim 20
Dependent Claim
23 words
A CCD optical scanner as in claim 11 wherein said multi-element lens system is disposed at a fixed distance from the detector array.
Claim 21
Dependent Claim
21 words
A CCD optical scanner as in claim 11 wherein the magnification of said multi-element lens systems is optimized using ray tracing.
Claim 22
Dependent Claim
39 words
A CCD optical scanner as in claim 11 wherein the at least two LEDs produce sufficient illumination to obtain an output signal greater than the dark voltage noise from the detector array over the entire said range of distances.
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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) | 2001-07-06 | 2002-01-05 | 2002-07-07 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2005-07-06 | 2006-01-05 | 2006-07-07 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2009-07-06 | 2010-01-05 | 2010-07-07 | $7700.00 | Window Closed / Lapsed |