Segmentation, retardation and mass approximation of birefringent particles on a standard light microscope

Using the traditional microscope for mineral grain orientation determination: A prototype image analysis pipeline for optic-axis mapping (POAM)

This paper reports on the development of an open-source image analysis software 'pipeline' dedicated to petrographic microscopy. Using conventional rock thin sections and images from a standard polarising microscope, the pipeline can classify minerals and subgrains into objects and obtain information about optic-axis orientation. Five metamorphic rocks were chosen to test and illustrate the method. Thin sections were imaged using reflected and cross- and plane-polarised transmitted light. Images were taken at different angles of the polariser and analyser (360° with 10° steps), both with and without the full-lambda plate. The resulting image stacks were analysed with a modular pipeline for optic-axis mapping (POAM). POAM consists of external and internal software packages that register, segment, classify, and interpret the visible light spectra using object-based image analysis (OBIAS). The mapped fields-of-view and grain orientation stereonets of interest are presented in the context of whole-slide images. Two innovations are reported. First, we used hierarchical tree region merging on blended multimodal images to classify individual grains of rock-forming minerals into objects. Second, we assembled a new optical mineralogy algorithm chain that identifies the mineral slow axis orientation. The c-axis orientation results were verified with scanning electron microscopy electron backscattered diffraction (SEM-EBSD) data. For quartz (uniaxial) in a granite mylonite the test yielded excellent correspondence of c-axis azimuth and good agreement for inclination. For orthorhombic orthopyroxene in a deformed garnet harzburgite, POAM produced acceptable results for slow axis azimuth. In addition, the method identified slight anisotropy in garnet that would not be appreciated by traditional microscopy. We propose that our method is ideally suited for two commonly performed tasks in mineralogy. First, for mineral grain classification of entire thin sections scans on blended images to provide automated modal abundance estimates and grain size distribution. Second, for prospective fields of view of interest, POAM can rapidly generate slow axis crystal orientation maps from multiangle image stacks on conventionally prepared thin sections for targeting detailed SEM-EBSD studies.

Cellular morphological trait dataset for extant coccolithophores from the Atlantic Ocean

Calcification and biomass production by planktonic marine organisms influences the global carbon cycle and fuels marine ecosystems. The major calcifying plankton group coccolithophores are highly diverse, comprising ca. 250-300 extant species. However, coccolithophore size (a key functional trait) and degree of calcification are poorly quantified, as most of our understanding of this group comes from a small number of species. We generated a novel reference dataset of coccolithophore morphological traits, including cell-specific data for coccosphere and cell size, coccolith size, number of coccoliths per cell, and cellular calcite content. This dataset includes observations from 1074 individual cells and represents 61 species from 25 genera spanning equatorial to temperate coccolithophore populations that were sampled during the Atlantic Meridional Transect (AMT) 14 cruise in 2004. This unique dataset can be used to explore relationships between morphological traits (cell size and cell calcite) and environmental conditions, investigate species-specific and community contributions to pelagic carbonate production, export and plankton biomass, and inform and validate coccolithophore representation in marine ecosystem and biogeochemical models.

Random depolarization film design for real-color displays

Liquid crystal displays and organic light-emitting diode displays emit polarized light through polarizers and quarter-wave plates, which cause blackout and color change problems when the displays are viewed through polarizers, such as polarized sunglasses. Random depolarization films (RDFs) are polymer films doped with calcite particles, which randomize the polarization of light emitted from displays to resolve polarization problems. To realize displays without any color change, we investigate the retardation values and fabrication conditions required for RDFs. Analysis of the transmittance spectra and interference colors of different RDFs suggested that retardation values of approximately 600-1200 nm are sufficient to realize real-color displays. In addition, the color change measurements of displays with the RDFs revealed that an optimal dopant particle size exists and that the RDFs doped with 3.6 and 7.3 µm calcite particles achieved chromaticity changes of less than 0.02 for all 24 colors in the Macbeth chart.

Real-color displays realized by randomized polarization

This study achieves real-color displays using a randomizing effect based on the concept of "natural light." At present, most displays emit linearly polarized light, which causes essential blackout and color degradation problems when the displays are viewed through polarizers such as sunglasses. To address this, complex polarization-control technologies are added to existing displays, but the problems remain unresolved. In contrast, this study randomizes the polarization using a polymer film called a random depolarization film (RDF) that is doped with specific birefringent crystal particles. The RDF placed on a display reproduces colors that are very close to the natural colors seen in reality without the need for complex polarization technologies. We believe that it has the potential to change the approach to color-reproducing technology for displays.