Infrared displays

Due to the unique nature of liquid crystals, they have been widely used in medical and technical fields such as thermal mapping of human skin, diagnosis of vascular diseases [2], cancer diagnosis [3], pharmacological tests [4], skin grafting [5], infrared display units [6], microwave fields 7], etc. 

The above concept can be utilized to build an infrared display unit [9] (Fig. 1) consisting basically of a temperature-controlled chamber that can be evacuated and which has windows at opposite ends. One window is transparent to infrared wavelengths and is made, for example, of sodium chloride. The other window is transparent to wavelengths between 400 nm and 750 nm, i.e. the visible spectrum, and is made of glass. Between these two windows and parallel to them the actual image converter is located a polyester foil about 5 jim thick is coated on the incident radiation side with a 1 nm to 3 /rm layer capable of quantitatively absorbing infrared radiation, for example finely distributed gold or nickel. The other side is... 

Figure 1. Scheme of an infrared display unit based on cholesteric liquid crystals (after reference [9]). 

To perform a vibrational analysis, choose Vibrationson the Compute menu to invoke a vibrational analysis calculation, and then choose Vibrational Dectrum to visualize the results. The Vibrational Spectrum dialog box displays all vibrational frequencies and a simulated infrared spectrum. You can zoom and pan in the spectrum and pick normal modes for display, using vectors (using the Rendering dialog box from Display/Rendering menu item) and/or an im ation. 

Fig. 1. Schematic for thermographic imaging. The ambient thermal radiation is imaged on the focal plane which converts the infrared to an electrical signal for display on a video monitor. Sensors with uncooled focal planes are now the size of a minicam and cost 5 to 10 times as much.

In order to develop the dyes for these fields, characteristics of known dyes have been re-examined, and some anthraquinone dyes have been found usable. One example of use is in thermal-transfer recording where the sublimation properties of disperse dyes are appHed. Anthraquinone compounds have also been found to be usehil dichroic dyes for guest-host Hquid crystal displays when the substituents are properly selected to have high order parameters. These dichroic dyes can be used for polarizer films of LCD systems as well. Anthraquinone derivatives that absorb in the near-infrared region have also been discovered, which may be appHcable in semiconductor laser recording. 

Isotherm A line in a flow system or on a graph connecting points of equal temperature, or a mathematical or graphical relationship between two variables at constant temperature. Or a display using lines on a drawing to show constant-temperature contour lines, as from thermal imaging with infrared techniques. 

Display 1-octyne as a ball-and-spoke model. Examine the individual vibrations (> 1400 cm only), and classify the bands in the experimental infrared spectrum as due to specific motions, e.g., CH, CC and C=C stretching, and HCH and CCC bending motions. 

Collecting optics, radiation detectors and some form of indicator are the basic elements of an industrial infrared instrument. The optical system collects radiant energy and focuses it upon a detector, which converts it into an electrical signal. The instrument s electronics amplifies the output signal and process it into a form which can be displayed. There are three general types of instruments that can be used for predictive maintenance infrared thermometers or spot radiometers line scanners and imaging systems. 

More complicated molecules, with two or more chemical bonds, have more complicated absorption spectra. However, each molecule has such a characteristic spectrum that the spectrum can be used to detect the presence of that particular molecular substance. Figure 14-17, for example, shows the absorptions shown by liquid carbon tetrachloride, CCfi, and by liquid carbon disulfide, CS2. The bottom spectrum is that displayed by liquid CC14 containing a small amount of C. The absorptions of CS2 are evident in the spectrum of the mixture, so the infrared spectrum can be used to detect the impurity and to measure its concentration. 

All infrared spectrophotometers are provided with chart recorders which will present the complete infrared spectrum on a single continuous sheet, usually with wavelength and wavenumber scales shown for the abscissa and with absorbance and percentage transmittance as the ordinates. More advanced instruments also possess visual display units on which the spectra can be displayed as they are recorded and on which they can be compared with earlier spectra previously obtained or with spectra drawn from an extensive library held in a computer memory. These modern developments have all led to quantitative infrared spectrophotometry being a much more viable and useful analytical procedure than it was just a few years ago. 

FIGURE 3 The infrared spectrum of an amino acid, with the groups contributing to some ol the peaks identified. Notice that the spectrum displays the intensity of absorption. 

Luminescence can be defined as the emission of light (intended in the broader sense of ultraviolet, visible, or near infrared radiation) by electronic excited states of atoms or molecules. Luminescence is an important phenomenon from a basic viewpoint (e.g., for monitoring excited state behavior) [1] as well as for applications (lasers, displays, sensors, etc.) [2,3]. 

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