Registers – Coded record sensors – Particular sensor structure
Reexamination Certificate
1995-06-07
2001-12-11
Tremblay, Mark (Department: 2165)
Registers
Coded record sensors
Particular sensor structure
C235S462190
Reexamination Certificate
active
06328212
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention generally relates to an electro-optical scanning system for reading symbols, especially bar code symbols and, more particularly, to non-laser-based scanners operative for focusing a light beam and the view of a light sensor in different planes exteriorly of a scanner housing.
It has heretofore been proposed to read bar code symbols, particularly of the Universal Product Code (UPC) type, by using laser and non-laser scanners of the type disclosed in, for example, U.S. Pat. Nos. 4,251,798; 4,387,297; 4,409,470; 4,806,742 and 4,825,057, all of which have been assigned to Symbol Technologies, Inc., the assignee of this invention, and are hereby incorporated by reference herein.
Typically, a laser beam generated by a laser source, for example, a gas laser tube or a semiconductor laser diode, is optically focused by an optical train into a generally circular laser beam spot on a symbol. The beam spot is swept by a scanning component over the symbol and forms a scan pattern thereon. Laser light reflected off the symbol is detected by a light sensor, e.g. a photodiode, mounted together with the laser source, the optical train, the scanning component, and the photodiode in a housing, preferably one having a handle to enable hand-held, portable operation.
The symbol itself is a code pattern comprised of a series of bars of various widths, the bars being spaced apart from one another to bound spaces of various widths, the bars and spaces having different light-reflective properties. Although dimensions may vary, depending on the particular application and the density of the symbol, each bar and space of a UPC symbol typically used in the retail industry to identify retail products measures on the order of thousandths of an inch (mils). In practice, the generally circular laser beam spot has a cross-sectional diameter on the order of 6 to 10 mils.
Although the known laser scanners have enjoyed considerable commercial success, there is nevertheless incentive to reduce the cost of the scanner unit. The laser devices produce a very intense light spot of small size, and thus have inherent advantages. However, the laser light sources are of relatively high cost compared, for example, to non-laser sources such as light emitting diodes (LEDs). The use of non-laser sources presents problems, since it is difficult to focus a non-collimated source to beam spot sizes measuring on the order of mils, at least not without resorting to expensive, heavy, multiple-element optical trains or loss of power. LED's can typically be focused to spot sizes on the order of millimeters. However, using such a large-sized beam spot to read bars and spaces which measure on the order of mils imposes a significant burden on the signal processing and decode circuitry for the scanner. Non-reads and reading errors are likely.
By contrast, in laser-based systems, where the laser beam spot dimensions are on the same order of magnitude as those of the bars and spaces to be decoded, the signal processing and decoding circuitry has no such burden. The photodiode in such laser-based systems typically “looks” at a large volume of space surrounding the beam spot and in a common plane therewith.
SUMMARY OF THE INVENTION
It is a principal object of this invention to provide improved electro-optical scanners. Another object is to provide improvements in practicality, reliability, freedom from errors, and/or cost reduction in low-cost, non-laser-based scanners. An additional object is to provide a method of focusing a light beam into a scan spot, and to focus the view of a photodiode into a viewing window which is sized to lie within the scan spot. A further object is to provide a method of positioning the scan spot and the viewing window in different planes exteriorly of a housing for the scanner. In addition, an object is to provide a scanner device which is of low cost and high reliability, and is simple and convenient to operate by unskilled users. Further, an object is to provide an improved scanner that automatically adapts to varying scanning conditions without operator intervention.
To achieve the objects and in accordance with the purpose of the invention, as embodied and broadly described herein, a system for reading data on a target in two different viewing planes includes a laser light source for generating a laser light beam and mirrors for focusing the laser beam toward the data in the two viewing planes. Sensors detect the light reflected from each of the two viewing planes and generates an electrical signal indicative of the detected light. A signal processor, responsive the electrical signal, processes and decodes the data associated with the viewing plane on which the beam is focused. In a preferred embodiment the system further provides for adjusting a bandwidth of the electrical signal.
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Barkan Edward
Metlitasky Boris
Swartz Jerome
Symbol Technologies Inc.
Tremblay Mark
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