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pleochroism of a crystal so that it exhibits two different colors when viewed from two different directions

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2014/12/16 17:34:48」(JST)

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Lampworked dichroic glass bead

In optics, a dichroic material is either one which causes visible light to be split up into distinct beams of different wavelengths (colours) (not to be confused with dispersion), or one in which light rays having different polarizations are absorbed by different amounts.^[1]

The original meaning of dichroic, from the Greek dikhroos, two-coloured, refers to any optical device which can split a beam of light into two beams with differing wavelengths. Such devices include mirrors and filters, usually treated with optical coatings, which are designed to reflect light over a certain range of wavelengths, and transmit light which is outside that range. An example is the dichroic prism, used in some camcorders, which uses several coatings to split light into red, green and blue components for recording on separate CCD arrays, however it is now more common to have a Bayer filter to filter individual pixels on a single CCD array. This kind of dichroic device does not usually depend on the polarization of the light. The term dichromatic is also used in this sense.

The second meaning of dichroic refers to a material in which light in different polarization states traveling through it experiences a different absorption coefficient. This is also known as diattenuation. When the polarization states in question are right and left-handed circular polarization, it is then known as circular dichroism. Since the left- and right-handed circular polarizations represent two spin angular momentum (SAM) states, in this case for a photon, this dichroism can also be thought of as Spin Angular Momentum Dichroism.

In some crystals, the strength of the dichroic effect varies strongly with the wavelength of the light, making them appear to have different colours when viewed with light having differing polarizations.^{[dubious – discuss]} This is more generally referred to as pleochroism, and the technique can be used in mineralogy to identify minerals. In some materials, such as herapathite (iodoquinine sulfate) or Polaroid sheets, the effect is not strongly dependent on wavelength.

Which meaning of dichroic is intended can usually be inferred from the context. A mirror, filter, or beam splitter is referred to as dichroic in the colour-separating first sense; a dichroic crystal or material refers to the polarization-absorbing second sense.

Dichroism in liquid crystals

Dichroism, in the second meaning, occurs in liquid crystals due to either the optical anisotropy of the molecular structure or the presence of impurities or the presence of dichroic dyes. The latter is also called a guest–host effect.^[2]

References

^ University Physics 6th ed. F.W. Sears, M.W. Zemansky, H.D. Young ISBN 0-201-07199-1
^ Stephen M. Kelly (2000). Flat Panel Displays: Advanced Organic Materials. Royal Society of Chemistry. p. 110. ISBN 0-85404-567-8.

English Journal

Epi-fluorescence microscopy.

Webb DJ, Brown CM.SourceDepartment of Biological Sciences, Vanderbilt University, Nashville, TN, USA.
Methods in molecular biology (Clifton, N.J.).Methods Mol Biol.2013;931:29-59. doi: 10.1007/978-1-62703-056-4_2.
Epi-fluorescence microscopy is available in most life sciences research laboratories, and when optimized can be a central laboratory tool. In this chapter, the epi-fluorescence light path is introduced and the various components are discussed in detail. Recommendations are made for incident lamp lig
PMID 23026996

Interactions of different polyphenols with bovine serum albumin using fluorescence quenching and molecular docking.

Skrt M, Benedik E, Podlipnik C, Ulrih NP.SourceBiotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia.
Food chemistry.Food Chem.2012 Dec 15;135(4):2418-24. doi: 10.1016/j.foodchem.2012.06.114. Epub 2012 Jul 14.
Polyphenols are responsible for the major organoleptic characteristics of plant-derived foods and beverages. Here, we investigated the binding of several polyphenols to bovine serum albumin (BSA) at pH 7.5 and 25°C: catechins [(-)-epigallocatechin-3-gallate, (-)-epigallocatechin, (-)-epicatechin-3-
PMID 22980822