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METHOD AND APPARATUS FOR DISCRIMINATING OR LOCATING BAR CODES FOR AN OPTICAL MARK READER
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TECHNICAL FIELD
The present invention relates to a scanning system comprised of an optical mark reader having the capability to scan or read bar codes. More particularly, the 10 present invention relates to a method and apparatus for discriminating the presence of a bar code on a scannable form to be scanned by such a scanning system.
PRIOR ART
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Scanning systems of both the optical mark reader type and the bar code scanner type are well-known in the prior art. It has been recognized that the use of bar codes on scannable forms can substantially reduce the need for manual gridding of identification or back- 20 ground data on such forms. By integrating a bar code containing a multiple digit identification code with the scannable form, a scanning system can be given the ability to link the scannable form to a pre-existing data file containing identification or background data having 25 the same identification code. The accuracy and efficiency of such an scanning system is enhanced when the previously entered and edited identification or background data associated with the bar code is used to replace, verify or supplement similar information on the 30 scannable form.
While current bar code scanners are capable of discriminating a bar code from background marks or noise on a scannable form, they do so by actually reading and decoding the bar code and the amount of time necessary 35 to identify and decode a bar code on a scannable form is significantly greater than the typical time for the picking cycle of a high speed optical mark reader. More importantly, the time out period for current bar code scanners is often five to ten times longer than the time typically required to scan and decode a bar code, if one is present. Consequently, in applications where a bar code may or may not be present on a scannable form, it is not practical to examine every scannable form using 4J conventional bar code scanning techniques to determine whether a bar code is present. To do so would delay the optical mark reader by the full time out period each time a bar code was not present on the scannable form. 5q
Prior art bar code discriminating mechanisms are also not suitable for discriminating whether a bar code is present on a scannable form. For example, U.S. Pat. No. 4,667,089 discloses a Bar Code Discriminating Apparatus for Bar Code Reading based on a sequential analysis 55 of the width of the scanned signals. While this apparatus may be useful for some applications, the text and response bubbles on a typical scannable form may have a frequency content similar to the frequency of the signals generated by scanning a bar code. Consequently, an 60 analysis of the width or frequency of the signals generated by using this apparatus would not be effective in determining the presence or absence of a bar code on a scannable form.
Accordingly, it would be desirable to provide for a 65 method and apparatus for discriminating bar codes for an optical mark reader having the capability to scan or read bar codes that will quickly, efficiently and reliably
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determine the presence or absence of a bar code on a scannable form.
SUMMARY OF THE INVENTION
In accordance with the present invention, a method and apparatus for discriminating bar codes for an optical mark reader is provided comprising a scanning means for scanning a target area on a scannable form and producing a signal in response to certain indications, i.e., marks or spaces, in the target area, detection means for detecting indications having a width within a preselected range of widths, first comparator means for comparing the number of detected indications to a specified range of valid numbers of detected indications, and second comparator means for comparing the output of the first comparator means for two consecutive sweeps of the scanning means and enabling means for producing an enabling signal when the output of the first comparator means is valid for two consecutive sweeps, such that the enabling signal enables a bar code scanner to scan and decode the bar code, and a picking signal when the output of the first comparator means is not valid for two consecutive sweeps during a scan of the entire target area, such that the picking signal enables the optical mark reader to begin mark scanning of the scannable form without decoding the bar code.
In the preferred embodiment, the present invention utilizes the wide black marks and the wide white spaces of an interleaved 2 of 5 bar code symbology as the basis for detecting both the width of the indications and comparing the number of detected indications to a range of expected numbers of indications. Because non-bar code markings and spacings on a scannable form for an optical mark reader may produce a scanning signal having characteristics similar to that of a typical bar code, particularly the characteristics of narrow bars and narrow spaces of a bar code, the wide black marks and wide white spaces are the preferred indications in the bar code to analyze for discriminating whether a bar code is present in the target area. This is because the target area is less likely to contain wide black marks or wide white spaces that indicate the presence of a bar code, but is likely to contain text, response indicia or other marks or indications that may be subject to misinterpretation as the narrow bars and narrow spaces of a bar code. In addition, the invention requires that the scanned signal be within this range of valid indications for a bar code for two consecutive sweeps of the scanning means. By selecting a sweep pattern and rate that will pass over the bar code twice and requiring two consecutive valid sweeps, the method and apparatus of the present invention further assures that a valid bar code has been detected in the target area, rather than a random number of spaces and marks generated by text, response indicia, or other background noise on the scannable form. Thus, the present invention utilizes three different tests, an acceptable range of widths of the indications in a bar code, an acceptable range of counts of the number of indications in a bar code, and two consecutive acceptable sweeps to discriminate the presence of the bar code on a scannable form.
An object of the present invention is to provide a method and apparatus for discriminating bar codes for an optical mark reader having the capability to scan or read bar codes that will quickly and efficiently determine the presence or absence of a bar code on a scannable form.
