S.V. Smirnov - Post-graduate Student, SPIIRAS

Historical documents are thus a set of documents for mass recognition that not enough is to use only the existing recognition systems. Because if the data contains spelling errors or inaccuracies recognition, they are heavy to handle, and no standard system of full text search will not return them to the user. This implies that to meet the needs of the application, the results obtained at the output of the recognition system must be subjected to further post-processing in order to correct mistakes and committed errors of recognition. The quality of the adjustment process is largely dependent on the accuracy of detecting errors and their correct classification. All types of errors can be divided into two categories: the vocabulary and non-verbal mistakes. Preprocessing methods of recognition results include methods for the replacement pattern, adjusting alphanumeric errors, clean up noise and excessive punctuation error correction does not detect hyphenation. Before attempting to adjust their recognition errors should be identified. Methods for detection of recognition errors are divided into two groups: methods of detection of word errors and non-verbal methods of detecting errors. The most important methods for the detection of word errors: assessment of the likelihood OCR, n-gram analysis, dictionary lookup. There are the following categories of non-verbal methods for correcting errors: measurement of the minimum distance between words, the definition of similarity between the words, the replacement of symbols according to predefined rules, n-grams of characters, probabilistic methods and neural network. All OCR error correction methods can be divided into two groups: the adjustment is based on comparing the results of several OCR systems, and adjustment using OCR recognition results of one system. The most commonly used methods and algorithms for error correction OCR are: Levenshtein distance, anagram hashing, OCR-key, n-gram analysis, neural networks. The best results are achieved when building systems that use a combination of the above methods.