Registers – Coded record sensors – Particular sensor structure
Reexamination Certificate
1999-05-12
2001-11-20
Frech, Karl D. (Department: 2876)
Registers
Coded record sensors
Particular sensor structure
C235S462320, C235S472010
Reexamination Certificate
active
06318635
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a portable data collection device including an imaging based dataform reader and, more particularly, to a portable data collection device including an imaging based dataform reader utilizing multiple focal lengths to capture and identify an imaged dataform.
BACKGROUND OF THE INVENTION
Portable data collection devices are widely used in manufacturing, service and package delivery industries to perform a variety of on-site data collection activities. Such portable data collection devices often include integrated bar code dataform readers adapted to read bar code dataforms affixed to products, product packaging and/or containers in warehouses, retail stores, shipping terminals, etc. for inventory control, tracking, production control and expediting, quality assurance and other purposes. Various bar code dataform readers have been proposed for portable data collection devices including laser scanners and one dimensional (1D) charge coupled device (CCD) imaging assemblies, both of which are capable of reading 1D bar code dataforms, that is, bar codes consisting of a single row of contrasting black bars and white spaces of varying widths. Both laser scanners and CCD imaging assemblies are also capable of reading a “stacked” two dimensional (2D) bar code dataforms, such as PDF417, which is comprised of a plurality of adjacent rows of bar code data. The stacked 2D bar code PDF417 includes row indicator patterns utilized by the dataform reader for vertical synchronization to permit reading successive rows of bar code data.
A two dimensional (2D) imaging based dataform reader has been proposed in U.S. application Ser. No. 08/544,618, filed Oct. 18, 1995, now issued as U.S. Pat. No. 5,702,059 (the '059 patent) and entitled “Extended Working Range Dataform Reader Including Fuzzy Logic Image Control Circuitry”. The 2D dataform reader disclosed in the '059 patent, which is assigned to the assignee of the present application, includes an imaging assembly having a two dimensional array of photosensors adapted to read 2D bar code dataforms (e.g., PDF417, SuperCode, etc.) with vertical synchronization row indicator patterns as well as matrix dataforms (e.g., MaxiCode, DataMatrix, etc.) which do not include vertical synchronization patterns. The individual photosensors correspond to image picture elements or pixels of the resulting image generated with the photosensors are read out after an exposure period or periods. The 2D dataform reader disclosed in '059 patent utilizes an open loop feedback control system including fuzzy logic circuitry to determine proper exposure time and gain parameters for a camera assembly. The '059 patent is incorporated in its entirety herein by reference.
A problem associated with dataform readers in the past has been that the readers are designed to read dataforms located within a limited range from the reader. For example, a dataform reader may be designed to read dataforms located within the range of 3 inches to 12 inches from the reader. Unfortunately, oftentimes it is necessary to read a dataform which is located a greater distance away (e.g., several feet away). However, the dataform reader is unable to image the dataform satisfactorily at such range. This requires that the operator gain closer access to the dataform which at times can be inconvenient or impossible. As an example, in a warehouse an operator may have to utilize a ladder or lift in order to get close enough to a dataform on a shelf so that the dataform may be read.
In view of the aforementioned shortcomings associated with conventional dataform readers, there is a strong need in the art for a dataform reader which is capable of reading dataforms over a wider range of distances. In particular, there is a strong need for a dataform reader which quickly and accurately captures and identifies an imaged dataform at relatively low cost.
SUMMARY OF THE INVENTION
According to one aspect of the invention, a dataform reading module, is provided. The dataform reading module includes a 2D photosensor array, a first optic for focusing a first image representing a target dataform onto a first portion of the array, the first optic having a first best focus length, a second optic for focusing a second image representing the target dataform onto a second portion of the array, the second optic having a second best focus length different than the first best focus length, and an illuminating device for illuminating the target dataform.
According to another aspect of the invention, a dataform reader for reading a dataform is provided. The dataform reader includes a hand-portable sized housing, a reading module included within the housing, and means within the housing for selecting between a first image and a second image in accordance with a predefined focus criteria. The reading module includes a 2D photosensor array, a first optic for focusing a first image representing a target dataform onto a first portion of the array, the first optic having a first best focus length, a second optic for focusing a second image representing the target dataform onto a second portion of the array, the second optic having a second best focus length different than the first best focus length, and an illuminating device for illuminating the target dataform, wherein the first portion and the second portion each have a width substantially equal to a width of the array.
According to yet another aspect of the invention, a method for reading a dataform using a dataform reading module is provided. The method includes the steps of forming a first image of the dataform on a first portion of a photosensor array, the first image formed from an optic having a first best focus length from the image assembly, forming a second image of the dataform on a second portion of the photosensor array, the second image formed from an optic having a second best focus length from the image assembly which is different than the first best focus length, and wherein the first portion and the second portion each have a width substantially equal to a width of the photosensor array, and selecting between the first image and the second image in accordance with a predefined focus criteria.
According to still yet another aspect of the invention, a method for compensating for angular variations between a dataform reader and a target dataform is provided. The method includes the steps of capturing an image of the target dataform on a photosensitive array, grouping a plurality of rows of data from the photosensitive array into a plurality of adjacent row groups, each row group including at least two adjacent rows of data, summing signals representative of the data for a plurality of columns in each of the plurality of row groups, comparing the summed signals for the plurality of columns in each of the plurality of row groups, and compensating for the angular variations based on the comparison.
These and other aspects, features and advantages of the invention will become better understood from the detailed description of the preferred embodiments of the invention which are described in conjunction with the accompanying drawings.
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U.S. application Ser. No. 08/544,618, filed Oct. 18, 1995. 5702059.
U.S. applica
Amin & Turocy LLP
Cyr Daniel St.
Frech Karl D.
Telxon Corporation
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