Selection of optimal spectral metrics for classification of inks in historical documents using hyperspectral imaging data

Ana B. López-Baldomero; M. A. Martínez-Domingo; Eva M. Valero; Ramón Fernández-Gualda; Ana López-Montes; Rosario Blanc-García; Teresa Espejo

doi:10.1117/12.2672962

9 August 2023 Selection of optimal spectral metrics for classification of inks in historical documents using hyperspectral imaging data

Ana B. López-Baldomero, M. A. Martínez-Domingo, Eva M. Valero, Ramón Fernández-Gualda, Ana López-Montes, Rosario Blanc-García, Teresa Espejo

Author Affiliations +

Proceedings Volume 12620, Optics for Arts, Architecture, and Archaeology (O3A) IX; 126200E (2023) https://doi.org/10.1117/12.2672962
Event: SPIE Optical Metrology, 2023, Munich, Germany

Abstract

Hyperspectral imaging has been increasingly used for non-destructive analysis of historical documents. Spectral reflectance data allow material identification and mapping using a library of reference spectra. Similarity metrics are crucial for quantifying the differences between reference and test spectra. Despite the apparent simplicity of the metrics, little work has been done on comparing their performance in the classification of historical inks. In this work, we propose three methods for selection of optimal spectral metrics, with an application to classification of historical inks. Hyperspectral images of laboratory and real historical samples are acquired in VNIR [400-1000 nm] and SWIR [900- 1700 nm] spectral ranges. Two spectral reflectance libraries are obtained (one for each range) including eight inks: iron gall, sepia, and carbon-based inks, and some mixtures. Six spectral similarity metrics are used: RMSE, SAM, SID, SIDSAM, NS3, and JMSAM. Firstly, metrics values in laboratory samples are studied to determine the classification confidence threshold of each metric. Then, the optimal metrics found for classification are selected using diverse approaches: (1) considering the confidence threshold; (2) evaluating classification performance metrics; (3) studying the probability of spectral discrimination and the power of spectral discrimination of each metric. Finally, inks of historical samples are classified by searching through the spectral libraries using optimal spectral metrics. Our method can correctly identify inks in both laboratory and historical samples in a simple and semi-supervised way.

Conference Presentation

Citation Download Citation

Ana B. López-Baldomero, M. A. Martínez-Domingo, Eva M. Valero, Ramón Fernández-Gualda, Ana López-Montes, Rosario Blanc-García, and Teresa Espejo "Selection of optimal spectral metrics for classification of inks in historical documents using hyperspectral imaging data", Proc. SPIE 12620, Optics for Arts, Architecture, and Archaeology (O3A) IX, 126200E (9 August 2023); https://doi.org/10.1117/12.2672962

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available