Optical: systems and elements – Holographic system or element – Using a hologram as an optical element
Patent
1989-10-03
1992-07-14
Heyman, John S.
Optical: systems and elements
Holographic system or element
Using a hologram as an optical element
359 52, 359 99, G02F 113
Patent
active
051308282
ABSTRACT:
Liquid crystal temperature indicating compositions, preferably absent cholesteric liquid crystal material, and the containing of such compositions in volumes formed in a containment medium (29) that tends to distort the liquid crystal structure (36) when the temperature thereof is below a transition or clearing point temperature (FIG. 4). The containment medium (29) is water resistant, e.g. insoluble in water, and preferably has heat and optical stability, e.g., does not brown or otherwise discolor, at relatively high temperatures, e.g. above 100.degree. C. Plural liquid crystal materials having different transition temperatures may be mixed to form a liquid crystal material having a transition temperature intermediate those of the ingredients (FIG. 11). In such distorted or curvilinearly aligned mesomorphic phase, the index of refraction of the liquid crystal is different, preferably greater, than that of the containment medium; therefore, incident light (11) will be scattered (21), preferably isotropically, and such scattered light can be used as a temperature identifier (FIG. 1). However, above a transition temperature, the liquid crystal material changes to an isotropic phase (30), which is substantially optically transparent, on the one hand; and the liquid crystal is so selected such that in the isotropic phase it has an index of refraction substantially matching that of the containment medium (29) (FIG. 5). Incident light (11) is transmitted (24) by the isotropic liquid crystal (23) and, accordingly, provides another temperature identifier (FIG. 3). The scattering liquid crystal material will appear visually brighter than the transmitting liquid crystal material, especially when illumination is provided by light from a source (7) independent of ambient light (FIG. 1). Moreover, dye can be used to color the scattered light.
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Heyman John S.
Mai Huy K.
Manchester R&D Partnership
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