Information Content and Resolution Aspects in Thermal Mappings using C holester ic Compounds

Lukianoff, G. V.

doi:10.1080/15421406908084916

Cited by 11 publications

(3 citation statements)

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“…The phosphors mentioned above, however, have one disadvantage which limits their usefulness, i.e., the luminescent decay curve is very nonexponential. Bril et al (3) report that for Y3Al~O12: Ce 3+ the emission i n t e nsity is still 6% of its m a x i m u m value 80 ~sec after * Electrochemical Society Active Member. K e y words: luminescence, phosphors, cerium, Y3A2~O~.…”

Section: Spatial Resolutionmentioning

confidence: 98%

“…Under electron beam excitation these phosphors typically have a decay time (Imax/e) of less than 100 nsec and have a b r o a d -b a n d emission spectrum peaking in the near ultra violet or blue. Several recently developed phosphor materials have moved the cerium emission peak to much longer wavelengths, green emission being reported for CaS: Ce z+ (1) and green to yellow-orange for various garnet hosts (2)(3)(4).…”

Section: Spatial Resolutionmentioning

confidence: 99%

“…The thermal characteristics of the liquid crystal are operationally specified by two parameters: (i) the lowest temperature at which color first appears, which we call the transition temperature; and (ii) the temperature range over which the entire spectrum is displayed, which is referred to as the thermal bandwidth (3). The crystal can be simply considered to be a thermometer which translates the thermal gradient around the powered short into a color pattern.…”

Section: Ibm System Products Division East Fishkill Facility Hopewementioning

confidence: 99%

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Nondestructive Location of Oxide Breakdowns on MOSFET Structures

Garbarino

Sandison

1973

J. Electrochem. Soc.

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Section: Spatial Resolutionmentioning

confidence: 98%

Section: Spatial Resolutionmentioning

confidence: 99%

Section: Ibm System Products Division East Fishkill Facility Hopewementioning

confidence: 99%

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Nondestructive Location of Oxide Breakdowns on MOSFET Structures

Garbarino

Sandison

1973

J. Electrochem. Soc.

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Thermography Using Liquid Crystals

Gleeson¹

1998

Handbook of Liquid Crystals Set

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The dramatic variation of liquid crystalline properties with respect to temperature has resulted in the widespread use of cholesteric (chiral nematic) liquid crystals for thermography. The property that has been exploited most in liquid crystal thermography is the critical temperature dependence of the selective reflection from cholesteric liquid crystals, though other temperature dependent properties of mesophases have been utilized (e.g. the birefringence of nematic systems and selective reflection from other chiral phases). The helicoidal structure of cholesteric materials results in the selective reflection of visible light within a band of wavelengths of width Ahcentered at a wavelength ho, such that:Here, p is the pitch of the helical structure, An is the birefringence of the medium and ii is the average refractive index, (no + n J 2 .The temperature range over which the cholesteric material selectively reflects visible light is known as the colorplay of the material. The temperature dependence of the selective reflection from a cholesteric material is a consequence of the temperature variation of the pitch of the system, defined by the twist elastic constants. A critical divergence of the selective reflection occurs if a cholesteric material cools when an underlying SmA phase is approached. This happens because the twist deformation is not allowed within a SmA phase, and the twist elastic constants (and therefore pitch) show pretransitional divergence. The pitch of the system increases rapidly as the temperature reduces towards the SmA phase transition temperature, typically resulting in the reflection of red light at lower temperatures. In cholesteric materials without a SmA phase, the critical divergence of the selective reflection is less pronounced. Indeed, in some materials the selective reflection is at a constant wavelength over the entire temperature range. Thus materials that exhibit a low lying SmA phase possess the most useful thermal properties for most thermography applications, though temperature insensitive materials have found application as shear sensitive systems (see Sec. 3.3). At higher temperatures within the cholesteric phase (above any pretransitiona1 region) the pitch may either increase or decrease with increasing temperature, due

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