Selective light absorption filter

In this section, the preparation and properties of the selective light absorption filter is described. This filter film has been developed to promote the color contrast of the color television based on a new concept, that is, the use of the selective light absorption filter. 

Figure 34-3. Structure and spectral transmittance of the selective light absorption filter.

Contrast and color purity are the most important qualities of the picture color television. In order to promote these qualities, the selective light absorption filter called black-enhance filter has been developed on the basis of the sol-gel technique (Ito, 1990 Matsuda, 1992). 

Base Techniques for Preparing the Selective Light Absorption Filter... 

For the practical use the selective light absorption filter has to fill the following requirements. 

The dispersive anti-reflecting coating has been manufactured by the same process as the selective light absorption filter. The differences are double spin coating and higher heating condition. 

Excitation filter selects wavelengths of light from a light source that fall in the maximum absorption region of a specific fluorophore. 

Simpler, cheaper and more practical approaches adopted subsequently to compensate for the interference colours of STN-LCDs involve the use of a passive optical element, such as selective polarisers and colour filters, see Chapter 2. A black-on-white appearance is produced most efficiently by using optical retardation layers with a high birefringence and an opposite twist sense to the STN-LCD. However, this also reduces the brightness of the display due to additional light absorption. 

There is little that is new this year on the photochemistry of polychlorobiphenyls, except that the differing selectivity towards chlorine loss in neutral or alkaline solution (reported previously for polychlorobenzenes) is confirmed for biphenyls. The major difference is that the preference for loss of ortho-C in neutral solution becomes a competition between ortho- and para-C loss in the presence of alkali. Polychlorobiphenyls are used as examples in a paper that gives equations to determine quantum yields in solution for situations where products act as inner filters in competing for light absorption. 

Nonmetallic inorganic materials are widely used for optical purposes lenses, pigments, interference filters, laser hosts, luminescent coatings, displays, solar cells, fiber optics, lamp bulbs, and tubes. For optical applications use is made of the refractory index, light absorption, luminescence, and nonlinear optical behavior of materials. These are intrinsic but may depend on the concentration of impurities. Refraction index and optical absorptivity in insulators are atomic properties and are only indirectly related to the structure, but the structure affects the selection rules and the term splitting in the atomic chromophores. The coordination number determines the intensity and wavelength of absorption and... 

Schematic diagram of a breathalyzer. The alcohol in the driver s breath is reacted with a potassium dichromate solution. The change in the absorption of li t due to the formation ofchromiumflll) sulfate is registered by the detector and shown on a meter, which directly displays the alcohol content in blood. The filter selects only one wavelength of light for measurement.

In the gas correlation techniques, gas-filled cells mounted on a rotating disk cross the analyzing infrared beam in turn. One correlation cell is filled with a gas that will not absorb infrared light, such as nitrogen (N2). The other cell (or cells) are filled with a high concentration of the gas to be measured. The wavelength range is selected at the absorption band of the gas to be measured by an optical band-pass filter. 

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