Browse Prior Art Database

Low Resolution Bar Code Reading

IP.com Disclosure Number: IPCOM000035062D
Original Publication Date: 1989-May-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 2 page(s) / 14K

Publishing Venue

IBM

Related People

Kishi, G: AUTHOR [+2]

Abstract

Using bar codes is a standard way of identifying materials. Typically, bar codes are read by scanners that read a single horizontal line across the bar code. This disclosure covers reading a barcode (Bar Code 39) with a camera, specifically with low resolution. With a camera system the tradeoffs are between higher resolution or larger field of view. If a bar code is to be automatically read by a camera, and if it is not accurately placed on the object, a large field of view is required so the camera can see the entire barcode and "find" it in its (the camera's) field of view. Often, since the resolution of the camera is limited (usually by price), this field of view means that the resolution of the camera will not be high enough to read the bar code.

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Low Resolution Bar Code Reading

Using bar codes is a standard way of identifying materials.

Typically, bar codes are read by scanners that read a single horizontal line across the bar code. This disclosure covers reading a barcode (Bar Code 39) with a camera, specifically with low resolution. With a camera system the tradeoffs are between higher resolution or larger field of view. If a bar code is to be automatically read by a camera, and if it is not accurately placed on the object, a large field of view is required so the camera can see the entire barcode and "find" it in its (the camera's) field of view.

Often, since the resolution of the camera is limited (usually by price), this field of view means that the resolution of the camera will not be high enough to read the bar code. Normally, the bar code is read by assuming that the reader (in this case a camera) can accurately resolve the width of each bar. This means that each bar must probably be at least 10 pixels in width. The camera's software would determine whether the bar is wide or not by the width of pixels. At lower resolution, it is not possible to accurately determine the width of each bar because the resolution in pixels is too low. We have discovered, however, due to the integrating nature of the camera, wide dark bars appear darker than narrow dark bars and wide bright bars appear brighter than narrow bright bars. This disclosure takes advantage of this fact to read bar codes with a camera with low resolution. The advantage is that more potential bar code reading applications become economically feasible - a cheaper camera can be used to read bar codes (less resolution = cheaper). In our specific usage - card identification, we have a tool that already has a camera mounted on it to inspect the card. This disclosure can be used to allow the camera to read bar codes on the card, which was previously impossible. The image is decoded as follows: Starting at the end of the white zone - the first dark local minimum (minimum intensity=black) is found. The minimum is the value at which the slope of the image intensity turns pos...