Error Patterns in Historical OCR: A Comparative Analysis of TrOCR and a Vision-Language Model

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Main Authors: Vesalainen, Ari, Mäkelä, Eetu, Ruotsalainen, Laura, Tolonen, Mikko
Format: Preprint
Published: 2026
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author Vesalainen, Ari
Mäkelä, Eetu
Ruotsalainen, Laura
Tolonen, Mikko
author_facet Vesalainen, Ari
Mäkelä, Eetu
Ruotsalainen, Laura
Tolonen, Mikko
contents Optical Character Recognition (OCR) of eighteenth-century printed texts remains challenging due to degraded print quality, archaic glyphs, and non-standardized orthography. Although transformer-based OCR systems and Vision-Language Models (VLMs) achieve strong aggregate accuracy, metrics such as Character Error Rate (CER) and Word Error Rate (WER) provide limited insight into their reliability for scholarly use. We compare a dedicated OCR transformer (TrOCR) and a general-purpose Vision-Language Model (Qwen) on line-level historical English texts using length-weighted accuracy metrics and hypothesis driven error analysis. While Qwen achieves lower CER/WER and greater robustness to degraded input, it exhibits selective linguistic regularization and orthographic normalization that may silently alter historically meaningful forms. TrOCR preserves orthographic fidelity more consistently but is more prone to cascading error propagation. Our findings show that architectural inductive biases shape OCR error structure in systematic ways. Models with similar aggregate accuracy can differ substantially in error locality, detectability, and downstream scholarly risk, underscoring the need for architecture-aware evaluation in historical digitization workflows.
format Preprint
id arxiv_https___arxiv_org_abs_2602_14524
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Error Patterns in Historical OCR: A Comparative Analysis of TrOCR and a Vision-Language Model
Vesalainen, Ari
Mäkelä, Eetu
Ruotsalainen, Laura
Tolonen, Mikko
Computer Vision and Pattern Recognition
Optical Character Recognition (OCR) of eighteenth-century printed texts remains challenging due to degraded print quality, archaic glyphs, and non-standardized orthography. Although transformer-based OCR systems and Vision-Language Models (VLMs) achieve strong aggregate accuracy, metrics such as Character Error Rate (CER) and Word Error Rate (WER) provide limited insight into their reliability for scholarly use. We compare a dedicated OCR transformer (TrOCR) and a general-purpose Vision-Language Model (Qwen) on line-level historical English texts using length-weighted accuracy metrics and hypothesis driven error analysis. While Qwen achieves lower CER/WER and greater robustness to degraded input, it exhibits selective linguistic regularization and orthographic normalization that may silently alter historically meaningful forms. TrOCR preserves orthographic fidelity more consistently but is more prone to cascading error propagation. Our findings show that architectural inductive biases shape OCR error structure in systematic ways. Models with similar aggregate accuracy can differ substantially in error locality, detectability, and downstream scholarly risk, underscoring the need for architecture-aware evaluation in historical digitization workflows.
title Error Patterns in Historical OCR: A Comparative Analysis of TrOCR and a Vision-Language Model
topic Computer Vision and Pattern Recognition
url https://arxiv.org/abs/2602.14524