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Fingerprinting Art and Cultural Heritage - In Situ 3D Non-Contact Microscale Documentation and Identification of Paintings and Polychrome Objects

Final Report Summary - FING-ART-PRINT (Fingerprinting Art and Cultural Heritage - In Situ 3D Non-Contact Microscale Documentation and Identification of Paintings and Polychrome Objects)

The FING-ART-PRINT project aimed to develop a system that offers advanced protection for works of art in terms of illicit trafficking and damaging during transportation and exhibition. The increased movement of cultural heritage brings with it major concerns for conservators and curators. Problems associated with loans and special exhibitions of objects include not only the well-known dangers of (irreparable) damage in transport or due to poor exhibition conditions, but also increasing exposure of objects to the possibility of loss or theft.

The FING-ART-PRINT technique involved taking a unique 'fingerprint' of an object without coming in contact with the object. This fingerprint consists of the measurement of the roughness and reflectance spectra (colour) of an object at some position on the object, for example, a square centimetre, selected by the owner.

The fingerprint is stored in a digital file containing a combination of the following information for a selected area(s) of the surface of an object:
- three dimensional (3D) roughness / texture information on a (sub)micron scale (the roughness fingerprint)
- high resolution spectral information about pigments and dyes used (spectral fingerprint)
- a high resolution 3D accurate colour digital image of the selected area(s).

The project had the following four main objectives / work packages (WPs):
WP 1 - develop individual roughness and spectral reflectance measurement equipment for the specific application of taking fingerprints.
WP 2 - develop a user friendly version of all required software for (re)taking fingerprints for integration into the FING-ART-PRINT system as well as for post-processing.
WP 3 - integrate the hardware and software developed in WP's 1-2 into a complete, compact FING-ART-PRINT system for finger-printing objects.
WP 4 - verify that the FING-ART-PRINT can take a legitimate fingerprint of an object of art or cultural heritage, and that this fingerprint is a unique and lasting characteristic of an object.

The FING-ART-PRINT project was successfully completed, and virtually all objectives were accomplished. A user-friendly prototype apparatus for taking fingerprints was developed and optimised within the project, with the help of end users from museums and other cultural heritage institutes.

For the FING-ART-PRINT system, a commercial confocal microscope, miuSurf, from NanoFocus was adapted for use for taking fingerprints, and for operation on a flexible robot system. The profilometer can take roughness fingerprints of up to one square centimetre, at a lateral and depth resolution of less than one micrometer.

The multi-spectral camera for obtaining spectral fingerprints was a new development by partner ELDIM. ELDIM originally planned to develop an innovative spectral imager based on Fourier transform spectrometry. However, this was not successful due to mechanical stability problems. The multi-spectral camera, MSColor32 was thus developed based on band pass filter technology, and makes use of 31 band pass filters across the visible light spectrum. The camera can be used to image areas down to several square millimeters.

The integration of the hardware was conducted by NanoFocus. The robot system was specially constructed for the prototype, and includes a number of special parts of a Kuka robot system to combine them to a special positioning machine. Both the confocal profilometer and the multi-spectral camera were reduced in weight to less than 5 kg to allow the robot to operate at maximum performance capacity. A sensor changing system was developed so that the robot could take measurements with one instrument, and then exchange it for the other. A confocal stitching procedure was implemented into the robot control software to allow the confocal profilometer to take fingerprints of larger areas than the profilometer can take at one time. The multi-spectral camera could not be integrated into the FING-ART-PRINT prototype but can operate stand-alone.

The operation of the FING-ART-PRINT system was controlled via a user interface software created by UOS. This software helps non-technical users control the movement of the robot, and to take measurements in a user-friendly manner. NanoFocus optimised its miuSoft software for use in the interface. An important feature of the user interface is to assist users in 'refingerprinting' an object, that is finding the original position of the fingerprint so that a new fingerprint can be made, or that an old fingerprint can be checked.

In summary, the FING-ART-PRINT system is compact and allows fast, easy measurements of object surfaces in situ. It is user-friendly, so that a non-technical person from the museum world such as an art historian, collection manager, or conservator can easily use it for routine measurements in real time to allow analyses in front of the work of art. The system is transportable to any location (for example, the storage room or exposition room of a museum), and can be easily assembled and disassembled. Routine fingerprint measurements can be carried out in reasonable time (several minutes per object) and without any special room conditions. The only crucial condition is the sensitivity to vibrations which has to be taken into account.

FING-ART-PRINT is expected to have an enormous impact on the identification and protection of moveable cultural heritage. The system is compact and allows fast, easy measurements of object surfaces in situ. It will give curators a non-contact method for 'marking', identifying, and tracing works of art, precluding the need for stickers or markers. It will give conservation scientists the possibility for studying changes of the surfaces of artworks due to cleaning and other surface treatments on the object itself, as well as the effects of climate and aging on the condition of objects. Finally, the instrument is user-friendly, so that a non-technical person from the museum world such as an art historian, collection manager, or conservator can easily use it and evaluate the results. The results should be recorded in real time to allow analyses in front of the work of art in the presence of curators, conservators, etc.

Besides use for existing collections around the world, FING-ART-PRINT will have an enormous impact in fighting illegal trafficking and protecting objects from theft and commercial resale. FING-ART-PRINT makes innovative use of advanced technologies developed for 'normal' industrial use in order to provide fingerprint records of objects of art and cultural heritage, this without any physical contact with the object, and non-destructively. The uniqueness of the fingerprints will allow the improvement of international databases such as those mentioned above for such objects. As an extension to the identification task to be addressed by FING-ART-PRINT, the system will also have a significant impact on the analysis and detection of frauds. It will allow museums and law enforcement authorities to clearly mark and identify objects which are already known to be authentic. In the case of the loss and recovery of an object, a fingerprint of the object can be taken and compared with the above-mentioned databases containing objects which have been fingerprinted, in exactly the same manner as law enforcement officers use fingerprints, DNA, or dental records to identify missing persons, criminals, or potential personnel security problems.

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