Registers – Coded record sensors – Particular sensor structure
Reexamination Certificate
2000-08-21
2001-11-27
Pitts, Harold I. (Department: 2876)
Registers
Coded record sensors
Particular sensor structure
C235S472010, C235S462320
Reexamination Certificate
active
06321988
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 a piezoelectric reflector arrangement to increase apparent resolution of a photosensor.
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, for inventory control, tracking, production control and expediting, quality assurance and other purposes.
Bar code dataforms come in a variety of different formats including one and two dimensional bar codes, matrix codes and graphic codes, as well as words and numbers and other symbols, which may be printed or etched on paper, plastic cards and metallic and other items. For example, a one dimensional bar code dataform typically consists of a series of parallel light and dark rectangular areas of varying widths. The light areas are often referred to as “spaces” and the dark areas as “bars”. Different widths of bars and spaces define different characters in a particular bar code dataform.
Data originally encoded in a dataform is recovered for further use in a variety of ways. For example, a printed bar code may be illuminated to derive reflectance values which are digitized, stored in buffer memory and subsequently decoded to recover the data encoded in the bar code. The printed bar code may be illuminated using a laser, an array of LEDs, ambient light, or the like. The light reflected from the printed bar code typically is captured using a photosensor such as, for example, a CCD detector or CMOS detector.
A problem associated with conventional dataform readers is that the readers are designed to read dataforms located within a limited range therefrom. For example, a dataform reader may be designed to read dataforms located within the range of three inches to twelve inches from the reader. The maximum distance at which a dataform reader is able to read a dataform is limited by a resolution of the photodetector used to capture the dataform. For example, using a conventional 640 horizontal pixel photosensor, one dimensional bar code dataforms can be read so long as the distance the reader is placed from the dataform is such that the 640 horizontal pixels are suitable to distinguish among the narrowest bars and spaces forming the dataform. As the dataform reader is moved further away from a dataform, the images of the bars and spaces appear smaller at the photosensor thereby limiting the range at which the dataform reader is able to read a dataform.
One way to allow the dataform reader to read the dataform at longer distances is to increase the resolution of the photosensor. For example, rather than providing 640 horizontal pixels, the photosensor may include 1000 or more horizontal pixels. In this manner, the photosensor is able to distinguish among smaller features of the dataform thereby enabling reading of dataforms located farther away. A significant drawback to increasing the number of horizontal pixels on the photosensor is that a width of the photosensor becomes proportionately larger in order to accommodate the additional pixels. As the width of the photosensor increases, so does the overall width of the reader module. Unfortunately, due to customer demand for smaller and more compact dataform readers, the ability to increase the width of the reader module is often not a feasible option.
Accordingly, there is a strong need in the art for a dataform reader which is capable of reading dataforms at longer distances which overcomes the aforementioned drawbacks.
SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention, a range at which a dataform reader is able to read a dataform is improved by increasing an apparent resolution of a photosensor capturing the image of the dataform. The apparent resolution of the photosensor is increased by providing a reader module having a piezoelectric reflector that scans an indicia and a single lens with partially overlapping fields of views. Each field of view is set to capture a respective portion of a full dataform image. For instance, the field of view from each piezoelectric reflector may be set to capture a respective portion of a one-dimensional bar code label. A voltage can then be applied to at least one of the piezoelectric reflectors so that the field of view of the piezoelectric reflector can be varied. This allows for a second reading in which the overlapping portions of the field of views is changed. The two readings can then be compared to determined the integrity of readings. A number of samples can be captured for the same dataform image, so that an optimal image reading can be obtained. Furthermore, the number of samples can be employed to determine if a reading is valid. For example, multiple readings can be taken and a valid reading can be determined based on any two readings matching. The piezoelectric reflectors can also be adjusted to eliminate the overlapping portions to obtain a maximum capture range of the pixels for a given dataform image.
In order to increase the apparent resolution of the photosensor, each of the piezoelectric reflectors is preferably arranged to focus a respective image of the dataform onto different zones of the photosensor. For instance, each piezoelectric reflector may be arranged to direct images onto rectangular shaped zones arranged vertically with respect to one another. Upon capturing an image from the lens in different zones, the full image of the dataform is reconstructed. In particular, the images from each zone is preferably provided to an image processor whereby overlapping data from each zone is accounted for and a single image representative of a combined field of view from the lens and piezoelectric reflectors is obtained. The integrity of the combined image can be improved by sampling the dataform a multiple number of times with different overlapping data. Since an image from each piezoelectric reflector is focused onto different zones and then combined, the apparent resolution of the photosensor is increased. For instance, if a multiple reflector dataform reader has a two-dimensional photosensor with 640 horizontal pixels and the piezoelectric reflectors are arranged to project respective images on three different rectangular zones of the photosensor, the apparent horizontal resolution of the photosensor increases from 640 pixels to 1920 (640×3) pixels less the number of pixels providing overlapping data in each zone. It will be appreciated that since the photosensor itself need not be increased in width to accommodate such higher horizontal resolution imaging, the overall width of the reader module may remain unchanged. Thus, the dataform reader is able to read dataforms at longer ranges by increasing the apparent resolution of the photosensor, without increasing the overall width of the reading module itself. Furthermore, by varying the reflection angle of the piezoelectric reflectors, the overlap portions of the field of view (FOV) can be eliminated maximizing the pixels captured for the dataform.
According to one aspect of the invention, a dataform reading system is provided. The dataform reading system includes at least one photosensor providing a plurality of different zones for image capture, a lens for focusing a respective image representing a portion of a dataform taken along a target line onto a respective one of the plurality of different zones, at least two piezoelectric reflectors configured to direct an image of adjacent and partially overlapping portions of the dataform taken along the target line onto the lens, and an illuminating device for illuminating the dataform.
According to ano
Merchant Peter
Stoner Paul D.
Amin & Turocy LLP
Pitts Harold I.
Telxon Corporation
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