Photoluminescence imaging of speleothem microbanding with a high- resolution confocal scanning laser macroscope

Hyperspectral imaging of speleothems

“…Although these can provide good-quality images, microscopy (under both visible and fluorescent illumination) has been required to identify finer resolved features. Subsequent digital image processing has identified such things as grey-level changes throughout individual stalagmite lamina and within a group of laminae captured under polarised visible light (Xiaoguang et al, 1998), luminescence properties under UV-light (Baker et al, 1993;Ribes et al, 2000), and crystalline fabric and calcite porosity (Kendall and Broughton, 1978;Genty, 1993;Frisia et al, 2000). Such studies have aided the recognition of sub-annual lamina made up of white porous calcite lamina (WPL) and dark compact calcite lamina (DCL), which together make up an annual lamination (Genty, 1993); they also identified organic acid layers (humic and fulvic acids), which may be used to determine variations in the annual growth rate (Baker et al, 1993) as well as an indicator of paleoprecipitation (Proctor et al, 2002).…”

“…Other limitations are the destructive nature of creating thin sections of stalagmite often used for imaging work, which may use up large portions of samples, the time it takes to capture images by microscopy when working with field of views in the order of mm or less (especially if multiple transects are taken), the process of moving the sample in order to take the next image and subsequently tiling images which can cause non-uniformity between images and discontinuities (Ribes et al, 2000). Ribes et al (2000) describe the set-up of a confocal scanning laser macroscope to take photoluminescence images of speleothem microbanding. The confocal lens eliminates light from outside the focal plane which may blur any captured image, whilst the macroscope set-up allows for a much larger field of view up to 7.5 Â 7.5 cm (or down to 200 Â 200 mm), without loosing image resolution.…”

Infrared photoluminescence imaging of infrared materials: HgCdTe/Cd(Zn)Te heterostructures

“…(as several examples, see Refs. [1][2][3][4][5][6]). Regarding to semiconductors, the main advantage of IRPL technique is the possibility to visualize the spatial distribution of structural defects all over the volume of investigated sample.…”