Laser-based analytical techniques in cultural heritage science - Tutorial review.

This tutorial review combines the fundamentals of the design and operation of lasers with their usage in applications related to conservation and cultural heritage (CH) science - as components of analytical devices for the study of the chemical composition of materials. The development of laser instruments and their fundamental physical background, including a short explanation of their properties and parameters, are briefly summarised, and an overview of different laser-based analytical techniques is given. The analytical techniques covered in this tutorial are divided into three groups based on their technical aspects and properties: (1) vibrational spectroscopy, (2) elemental analysis, and (3) different molecular mass spectrometric techniques.

Measurement of stress build-up of ion-exchange strengthened lithium aluminosilicate glass.

A recently developed non-destructive method was used to investigate the stress build-up in chemically strengthened lithium aluminosilicate glass. We utilized an updated version of the gradient scattered light method, which now enables more precise determination of the depth coordinates, recovering a more detailed stress profile around the knee. The main motivation of the work was to characterize and optimize the development of the knee-shaped breaking point in stress profile in lithium aluminosilicate glass using Saunders-Kubichan method of 1-step strengthening in a mixture of KNO3+NaNO3 molten salt bath. In the industry, a 2-step process is still commonly used to build such a stress profile. 1-step strengthening will simplify the process as well as save the cost. Compared to previous studies, which used a destructive method based on transmitted light photoelasticity, we found that in the samples ion-exchanged for 24h the knee-shaped breaking points were situated two times deeper whereas the case-depths were 28% shallower. The measured stress profiles were validated by stress equilibrium and by comparison to Na+ ion concentration profiles.

Cataract diagnosis by measurement of backscattered light.

We present a portable optical cataract assessment technology which measures with a circular photodetector the fraction of light scattered backwards by the human eye lens when illuminated by a laser diode. As our signal arises directly from the fundamental pathology-increased scattering in the lens-it directly assesses cataract extent and progression. Initial clinical results in undilated human eyes show device reading correlations in agreement with clinical examination and Scheimpflug photography.