Daguerreotypes are historical photographic images made on mirror-like metallic plates. These are heritage objects whose shape cannot be measured with invasive techniques, like contact probes, but the high reflectivity of their surfaces makes the use of non-invasive, 3D-measuring optical techniques challenging. Moreover, the dark areas resulting from their degradation produce a very high contrast, which add extra difficulties to their measurement. In the last few years, several strategies have been developed to overcome the limitations of optical techniques when measuring reflective metallic surfaces. Many of these solutions are not applicable to the study of cultural heritage artifacts, as they are invasive. We attempted the use of conoscopic holography in a 3D-scanning system using a double-exposure strategy. This is a promising option for 3D measuring of daguerreotypes, as we experimentally demonstrated in this work. We present the results obtained from the analyses of two 19th-century daguerreotypes with different superficial conditions. The double-exposure allowed us to obtain high-quality data from the entire object surface. This enabled the measurement of micro-scale details related to the manufacturing process and/or to the corrosion deposits. The proposed methodology can be exploited to monitor the overall health of highly reflective metallic objects but also the outcomes of some conservation treatments, such as cleaning.

This study presents a novel platform for the non-invasive analysis of painted surfaces, integrating sequentially shifted excitation (SSE ^TM ) Raman mapping with 3D scanning. Designed for hardware-registered data acquisition, the system enables automated macro-Raman mapping across extended and uneven surfaces with precise spatial control. To demonstrate the platform potential in accurate material mapping, we showcase the results acquired from purposely prepared acrylic mock-ups and a painting. The coupling of 3D surface information with subsequent Raman spectral acquisition was exploited for precise focus adjustment and co-registration of datasets. We demonstrate the potential of combined 3D and SSE ^TM Raman mapping—so far not implemented in cultural heritage contexts—for non-invasive analyses, even in scenarios with high fluorescent signals. The system’s modular design permits future integration of additional imaging modalities, making it a promising tool for advanced analysis in conservation science.

We present a custom platform for multimodal analysis that is currently integrating 3D scanning, Reflectance Imaging Spectroscopy (RIS) in the visible range (420–720 nm), and Sequentially Shifted Excitation macro-Raman mapping (SSE ^TM -MA-Raman) within a single, fully spatially hardware-registered framework. The system was conceived to overcome one of the major limitations in multimodal cultural heritage diagnostics: the difficulty of reliably registering Regions of Interest (ROIs) and aligning heterogeneous datasets acquired with independent instruments. The core of the platform is an optical breadboard, moved by a three-axis motorised stage with micrometric repeatability, and custom control software enabling automated acquisition, instrument synchronisation, and intrinsic spatial co-registration across modalities. Here, we describe the system architecture, the acquisition pipeline, and the Raman handshaking routine, demonstrating how the integration of topography-driven autofocusing with coordinated RIS and SSE ^TM -MA-Raman mapping enhances accuracy, reproducibility, and facilitates data interpretation. The potential and performance of the platform were evaluated on a real-case scenario: a contemporary painting by Gastone Novelli (1925–1968) from the Peggy Guggenheim collection (Venice, Italy), currently under restoration at the Opificio delle Pietre Dure (OPD) in Florence, Italy. The results confirm the strength of this new hardware-registered system as a robust solution for advanced multimodal investigations in heritage science, producing co-registered datasets containing complementary morphological and spectroscopic information.