Registers – Coded record sensors – Particular sensor structure
Reexamination Certificate
2000-02-10
2001-08-14
Lee, Michael G. (Department: 2876)
Registers
Coded record sensors
Particular sensor structure
C235S462320, C235S462350
Reexamination Certificate
active
06273336
ABSTRACT:
BACKGROUND OF THE INVENTION
The field of the present invention relates to data reading devices such as for example bar code scanning systems.
In data reading devices, a return light signal from the object or symbol being read is focused onto a detector or detector array. In the example of a bar code scanner reading the bars and spaces of a typical bar code, there needs to be sufficient difference in signal intensity between the signal corresponding to the light space and the signal corresponding to the dark bar in order for the processor to differentiate therebetween. In scanner applications there has been demand for increased depth of field, i.e., the range of distance over which the scanner can effectively scan.
There are several methods for improving depth of field, but there are essentially two areas which may be controlled, namely (1) outgoing beam generation and (2) collection. This application focuses on methods for improving depth of field and signal differentiation from the collection side.
SUMMARY OF THE INVENTION
The present invention is directed to a system and method by which an optical correction module or corrective optical element(s) are placed in the light collection path to the detector in a data reader, whereby the characteristics of light coming from sources in different locations and/or distances relative to the collection lens may be changed, thus rendering the return signal more uniform over greater distances and/or positions relative to the collection system.
In a preferred embodiment, a diffusion element is placed between a collection lens and the detector such that the amount of collected light from a far field target reaching the detector is maximized and the amount of collected light from a near field target reaching the detector is selectively inhibited rendering the total light intensity on the detector more uniform as between the far field signal and the near field signal.
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U.S. application No. 08/942,399, Michael J. Ahten and James W. Ring, filed Oct. 10, 1997, “Offset Optical Axes for Bar Code Scanner.”.
Ring James W.
Rudeen Robert W.
Lee Diane I.
Lee Michael G.
Lyon & Lyon LLP
PSC Scanning Inc.
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