RT Book,_Section T1 Exploring Open-Vocabulary Models for Category-Free Detection A1 García Fernández, Pablo A1 Mucientes Molina, Manuel A1 Cores Costa, Daniel K1 Category-free K1 Open-vocabulary object detection K1 Captioning AB Object detection models typically rely on a predefined setof categories, limiting their applicability in real-world scenarios whereobject classes may be unknown. In this paper, we propose a novel,training-free framework that enables off-the-shelf open-vocabulary ob-ject detectors (OvOD) to perform category-free detection —localizingand classifying objects without any prior category knowledge. Our ap-proach leverages image captioning to dynamically generate descriptiveterms directly from the image content, followed by a WordNet-based fil-tering process to extract semantically meaningful category names. Thesediscovered categories are then embedded and matched with visual regionfeatures using a frozen OvOD model to perform detection. We evaluateour method on the COCO dataset in a fully zero-shot setting and demon-strate that it significantly outperforms strong multimodal large languagemodel baselines, achieving an improvement of over 30 AP points. Thishighlights our method as a promising direction for more adaptive solu-tions to real-world detection challenges. PB Springer SN 978-3-032-04968-1 YR 2025 FD 2025-09-22 LK https://hdl.handle.net/10347/43664 UL https://hdl.handle.net/10347/43664 LA eng NO Garcia-Fernandez, P., Cores, D., Mucientes, M. (2026). Exploring Open-Vocabulary Models for Category-Free Detection. In: Castrillón-Santana, M., et al. Computer Analysis of Images and Patterns. CAIP 2025. Lecture Notes in Computer Science, vol 15621. Springer, Cham. https://doi.org/10.1007/978-3-032-04968-1_24 NO Paper presented in The 21st International Conference in Computer Analysis of Images and Patterns NO This work was partially supported by the Spanish Ministerio de Ciencia e In- novación (grant numbers PID2020-112623GB-I00, PID2023-149549NB-I00), and the Galician Consellería de Cultura, Educación e Universidade (2024-2027 ED431G- 2023/04). These grants are co-funded by the European Regional Development Fund (ERDF). Pablo Garcia-Fernandez is supported by the Spanish Ministerio de Universidades under the FPU national plan (grant number FPU21/05581). DS Minerva RD 24 abr 2026