Image analysis – Pattern recognition – Template matching
Patent
1995-06-30
1998-08-11
Couso, Yon J.
Image analysis
Pattern recognition
Template matching
382151, 382294, G06K 962, G06K 900, G06K 932
Patent
active
057938873
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method and apparatus for aligning images, in particular the image of an empty template and the image of a filled-in template, in order to be able to separate the information written into the template by eliminating the image of the empty template. The invention is of particular interest in areas where information filled into an invariant form is to be processed separately from the part of the image which does not contribute to the information content as such.
BACKGROUND OF THE INVENTION
The handling of paper documents is a daily routine in today's office environments. When trying to make the handling of documents--such as forms--more efficient, one has to digitise them in order to be able to employ modern data processing means such as computers or data transmission networks. Once a document is available to such a system, it is possible to load it in a storage from where it later can be retrieved. The storage and retrieval of documents is just one aspect in this connection, the other, possibly more important aspect is the treatment of the information contained in the documents.
The treatment of the information contained in documents generally involves the acquisition of the information by a reading device, the transformation of the acquired information into a machine-readable code, the storing of the coded information for later, and possibly repeated processing, the actual processing of the information and finally the output of the results of the processing.
The acquisition of the information by a reading device, such as an optical scanner, should be performed with sufficiently high resolution lest the information content should become mutilated or partially lost. Reading devices usually produce a high volume of scan data which in turn require powerful computers for fast and reliable processing and a large memory capacity for storage. As a typical example, a page of the A4 size (279.times.210 mm), scanned at 100 pels/cm (where "pel" stands for picture element and is either a white or black dot), requires about 700 kBytes of storage space. Even a rather modest number of documents would call for an unreasonable big memory.
Since most of an image of a filled-in form does not contribute to the information content, different methods have been developed for the separation of the standard or constant part (CP), which is the empty form, and the variable part (VP), which is the filled-in data. Such a separation of the constant part (CP) and the variable part (VP), also known as template elimination, has the following advantages: variable parts (VP) superimposed with a single copy of the constant part (CP). Typically, the varying part's (VP) size is just a fraction of the size of the whole image, and 90% saving in storage are possible. constant (CP) and variable parts (VP) saves up to a magnitude in communication volume and thus eliminates one of the common bottlenecks of forms processing systems. situations the constant part (CP) of a form might interfere with automatic character recognition. Having access to the variable part (VP) alone, frequently eliminates this problem.
One method for the elimination of the constant part (CP), i.e. the form as such, has for example been implemented and reported by D. E. Nielsen et al., in "Evaluation of Scanner Spectral Response for Insurance Industry Documents", 16/A44 NCI Program, Working Paper No. 2, May 1973. This method, also known as "dropout ink" technique, is based on the idea to use a special colour ink when printing a form which is transparent to conventional scanners. If a completed form of this type is scanned, the basic pattern (i.e. CP) would be invisible to the scanner, and only the variable part (VP) would be entered into the computer. An evident disadvantage of this approach is that the use of special-ink-sensitive scanners would exclude the application of this approach to existing archives. Also, the use of special ink is certainly more cumbersome and costly. It is a further disadvantage of the "dropout ink
REFERENCES:
patent: 5182656 (1993-01-01), Chevion et al.
patent: 5542007 (1996-07-01), Chevion et al.
Wang, Ynjiun P. and Pavlidis, Theo, "Optimal Correspondence of String Subsequences", IEEE Transactions on Pattern Analysis and Machine Intelligence, vol. 12, No. 11, pp. 1080-1087, Nov. 1990.
Couso Yon J.
Emile Volel
International Business Machines - Corporation
Nguyen Ha Tran
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