Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Reexamination Certificate
1999-03-04
2001-05-01
Epps, Georgia (Department: 2873)
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
C250S566000, C250S281000, C250S235000, C250S234000
Reexamination Certificate
active
06225641
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to optical readers, and more particularly to image-based optical readers for scanning and decoding optical indicia such as bar code symbols and the like.
BACKGROUND OF THE INVENTION
Optical readers for scanning and decoding bar code symbols are generally known. A typical optical reader scanning system includes a light source, such as a laser, for providing a light beam; and an optical system for scanning the light beam in a predetermined pattern throughout a defined scanning region. In addition, the scanning system includes a detection system for detecting light having at least a predetermined intensity reflected from the bar code symbol and for providing an electrical signal in response to detection of such reflected light. Moreover, an optical system is included for directing light from the scanned light beam that is reflected from the bar code symbol to the detection system.
Recently, optical readers using one-dimensional and two-dimensional multi-photosensor array charge-coupled devices (CCDs) have become more and more prevalent. The multi-photosensor array CCDs are used to image an entire bar code symbol, and the resultant electronic image is then processed using pattern recognition techniques to decode the bar code symbol.
Both laser-based optical readers and CCD-based optical readers perform adequately. However, laser-based optical readers at times experience regulatory problems, can draw an unacceptable amount of electrical power and are subject to strict optical alignment requirements. CCD-based optical readers are at present still too expensive to enjoy widespread usage and have a very limited depth of field. The CCDs themselves are relatively expensive. In addition, significant computational power is required to decode in a timely manner.
In view of the aforementioned shortcomings associated with current optical readers, there is a strong need in the art for an optical reader which does not suffer from some of the same drawbacks as conventional optical readers. For example, there is a strong need in the art for an optical reader which does not require a laser or a CCD. Moreover, there is a strong need in the art for an image-based optical reader which is able to image and decode the bar code symbol even over a wide range of object distances between the optical reader and the bar code symbol.
SUMMARY OF THE INVENTION
According to one aspect of the invention, an optical reader is provided for reading optical indicia. The optical reader includes an imaging element for forming an image of the optical indicia at an image plane. The optical reader further includes an aperture positioned at the image plane and having a width smaller than the width of a smallest element in the image to be discerned by the optical reader, the aperture permitting illumination from a portion of the image to impinge upon a photodetector. Moreover, the optical reader includes a displacement system which produces relative movement between the image and the aperture to produce an output of the photodetector indicative of the optical indicia.
To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative embodiments of the invention. These embodiments are indicative, however, of but a few of the various ways in which the principles of the invention may be employed. Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings.
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German John Dee
Rainone Michael D.
Stoner Paul D.
Tocci Michael David
Tocci Nora Christina
Epps Georgia
Lucas Michael A.
Renner , Otto, Boisselle & Sklar, LLP
Telxon Corporation
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