Chi Shing Cheung

• Nottingham Trent University

Historical buildings are prone to deterioration due to moisture and salt activity. Salt weathering affects the appearance of monuments, resulting in mechanical degradation. Many laboratory-based studies have been performed focusing on understanding salt formation in building materials and the resulting damage mechanisms. However, large-scale in sit...

Long-term condition monitoring of works of art can provide new insights into object-specific deterioration mechanisms. Detecting change over time allows us to determine whether deterioration is active, to investigate its cause and to establish the efficacy of conservation interventions. However, long-term condition monitoring poses both logistical...

This paper presents a novel multimodal remote sensing setup to analyze the complex stratigraphy of historical wall paintings at distances of order 10 m. The proposed method enables comprehensive investigation of the chemical composition of multilayer paint stratigraphy by combining standoff laser-induced breakdown spectroscopy for elemental profili...

Colloidal suspensions are the basis of a wide variety of coatings, prepared as liquids and then dried into solid films. The processes at play during film formation, however, are difficult...

The increased adoption of non-invasive laser-based techniques for analysis of cultural assets has recently called into question the non-invasiveness of the techniques in practical operation. The methods to assess the occurrence of radiation-induced alteration on paintings are very limited and none of them can predict damage. Here we present a novel...

We describe a novel in situ non-invasive and non-contact technique for simultaneous measurement of refractive index and dispersion of transparent solid materials using optical coherence tomography (OCT). The technique requires multi-angle OCT imaging. It gives typical precision of 0.02 for the refractive index and 0.03 $$\mu$$ μ m $$^{-1}$$ - 1 for...

A mobile remote standoff Raman spectroscopy system operational at typical distances of 10 m was developed specifically for research of historical sites and wall paintings recently. Here we present an upgrade to that system informed by a thorough experimental investigation of the relevant laser-induced degradation issues. Reflectance spectroscopy as...

A spatially periodic voltage was used to create a dielectrophoresis induced periodic micro wrinkle deformation on the surface of a liquid film. Optical Coherence Tomography provided the equilibrium wrinkle profile at submicron accuracy. The dynamic wrinkle amplitude was derived from optical diffraction analysis during sub-millisecond wrinkle format...

Egyptian faience is a non-clay ceramic semi-transparent material formed of a quartz core and alkali-lime glaze. Previous investigations have identified production techniques by using microstructure images obtained from invasive methods. Optical coherence tomography (OCT) is a non-invasive 3D imaging technique that produces virtual cross-sections of...

This paper investigates the use of Optical Coherence Tomography (OCT) and Short-wave Infrared (SWIR) spectral imaging to study the deterioration of a Limoges enamel panel. Limoges enamels are formed of glass layers applied on a metal substrate and are prone to glass disease. However, the level of deterioration in Limoges enamels is generally diffic...

Portable and mobile Raman spectroscopy systems are increasingly being adopted in in situ non-invasive examination of artworks given their high specificity in material identification. However, these systems typically operate within centimeter range working distances, making the examination of large architectural interiors such as wall paintings in c...

The formation and growth of metal soaps is of interest in heritage science, as soaps have been linked to a range of alteration and degradation phenomena potentially affecting works of art. However, current approaches detect metal soaps mainly in an invasive way or only at a late formation stage when the metal soaps are formed on the surface of the...

Egyptian faience is a non-clay ceramic semi-transparent material, formed of a quartz core and alkali lime glaze with some cases exhibiting an interaction layer between them. Several possible glazing methods have been identified. Previous investigations have tried to identify the glazing technique by using the microstructure images obtained from pol...

In the evaporation of microlitre liquid droplets, the accepted view is that surface tension dominates and the effect of gravity is negligible. We report, through the first use of rotating optical coherence tomography, that a change in the flow pattern and speed occurs when evaporating binary liquid droplets are tilted, conclusively showing that gra...

The bacterial flora of nasogastric feeding tubes and faecal samples were analysed for a low-birth weight (725 g) neonate EGA 25 weeks in intensive care. Samples were collected at age 6 and 8 weeks of life. Optical coherence tomography (OCT) was used to visualise bacterial biofilms inside the nasogastric feeding tubes. The biofilm was heterogeneousl...

This paper examines for the first time the potential complementary imaging capabilities of Optical coherence tomography (OCT) and non-linear microscopy (NLM) for multi-modal 3D examination of paintings following the successful application of OCT to the in situ, non-invasive examination of varnish and paint stratigraphy of historic paintings and the...

Cultural heritage plays a significant role in our identities and well-being. The aim of conservation is to manage change to cultural heritage objects. Non-destructive techniques offer an opportunity to quantify deterioration objectively and at an earlier stage than observation. There are limitations for using the techniques on precious artefacts. T...

Since the ‘rediscovery’ of the Selden map of China, an early seventeenth century map of Asia, in the Bodleian Library in Oxford, the importance of the map in our understanding of globalisation in the early seventeenth century has been recognised. One of the unresolved questions is the origin of the map. This paper addresses the question through mat...

We correct a mistake in the OCT system sensitivity given in our recent paper [Opt. Express 23(3), 1992 (2015) 10.1364/OE.23.00199225836070].

Optical Coherence Tomography has been successfully applied to the non-invasive imaging of subsurface microstructure of a variety of materials from biological tissues to painted objects of art. One of the limitations of the technique is the low depth of penetration due to the strong scattering and absorption in the material. Previous studies found t...

In the last 10 years, Optical Coherence Tomography (OCT) has been successfully applied to art conservation, history and archaeology. OCT has the potential to become a routine non-invasive tool in museums allowing cross-section imaging anywhere on an intact object where there are no other methods of obtaining subsurface information. While current co...

A 220 nm bandwidth supercontinuum source in the two-micron wavelength range has been developed for use in a Fourier domain optical coherence tomography (FDOCT) system. This long wavelength source serves to enhance probing depth in highly scattering material with low water content. We present results confirming improved penetration depth in high opa...

A wavelength-swept thulium-doped fiber laser system employing two parallel cavities with two different fiber gain stages is reported. The fiber gain stages were tailored to provide emission in complementary bands with external wavelength-dependent feedback cavities sharing a common rotating polygon mirror for wavelength scanning. The wavelength-swe...

An optical coherence tomography system using a compact fiber source emitting amplified spontaneous emission at central wavelength of 1960 nm with bandwidth of 40 nm is developed to enhance the probing depth in a highly scattering material with low water content. Examples of application to paint are used to demonstrate significantly improved penetra...

PRISMS (Portable Remote Imaging System for Multispectral Scanning) is designed for in situ, simultaneous high resolution spectral and 3D topographic imaging of wall paintings and other large surfaces. In particular, it can image at transverse resolutions of tens of microns remotely from distances of tens of metres, making high resolution imaging po...

A wavelength-swept thulium-doped silica fiber laser using an intracavity rotating slotted-disk wavelength scanning filter in combination with an intracavity solid etalon for passive control of temporal and spectral profiles is reported. The laser yielded a wavelength swept output in a step-wise fashion with each laser pulse separated from the previ...

Wavelength-swept operation of cladding-pumped and core-pumped thulium-doped fiber lasers using a novel intracavity rotating disk wavelength-scanning arrangement is reported. Scanning ranges from 1905-2049nm (for cladding pumping) and 1768-1956nm (for core pumping) were obtained.

Wavelength-swept laser sources with broad wavelength tunability and narrow instantaneous linewidth in the two-micron band have potential applications in a number of areas, including spectroscopic characterisation and optical coherence tomography (OCT). The use of OCT for non-invasive investigation of paintings to provide the information necessary f...

Optical Coherence Tomography has been successfully applied to the imaging of painted objects in recent years. However, a significant limitation is the low penetration depth of OCT in paint because of the high opacity of paint due to either scattering or absorption. It has been shown that the optimum spectral window for OCT imaging of paint layers i...

While OCT has been applied to the non-invasive examination of the stratigraphy of paint layers in recent years, it has been recognized that the resolutions of commercially available OCT cannot compete in depth resolution with conventional microscopic examination of cross-sections of paint samples. It is necessary to achieve resolutions better than...

The response of the transmission spectrum of a fibre optic long period grating operating near the phase matching turning point to the deposition of a nanostructured coating is investigated. The dual-resonant bands characteristic of operation in this regime are observed to show a high sensitivity to the thickness of the coating, but with opposite si...

Nanostructured coatings have been deposited onto tapered optical fibres using the Langmuir–Blodgett technique. The response of the transmission spectrum of the tapered fibres to changes in thickness of the coating has been analysed. The effects observed are shown to be dependent on the diameter of the tapered region.

The response of the dual resonant bands of a fiber-optic long-period grating operating near the phase-matching turning point to the deposition of a nanostructured coating is investigated. The dual central wavelengths of the resonant bands are observed to show a high sensitivity to the thickness of the coating but with opposite signs. Appropriate de...

The sensitivity of attenuation bands corresponding to the 2nd order coupling to cladding modes by a fibre optic long period grating (LPG) to the deposition of nanostructured coatings is investigated and compared with that of the 1st order coupling. The experimental observations support previously reported theoretical descriptions of LPGs with nanos...

A study of the fabrication process and optical characterization of Ni indiffusion into x and y cut LiNbO3 substrate. The formation of waveguides in air ambient is clean and fast with the diffusion time well away from the T-c and out-diffusion regime of LiNbO3. Optical characterization of the planar waveguides uses prism measurement technique and IW...