Car mirror

We can now explain how an electrochromic car mirror operates. The mirror is constructed with II in its colourless form, so the mirror functions in a normal way. The driver activates the mirror when the anti-dazzle state of the mirror is required, and the coloured form of methylene blue (MB+) is generated oxidatively according to Equation (7.24). Coloured MB+ blocks out the dazzling reflection at the mirror by absorbing about 70 per cent of the light. After our vehicle has been overtaken and we require the mirror to function normally again, we reduce MB+ back to colourless MB0 via the reverse of Equation (7.24), and return the mirror to its colourless state. These two situations are depicted in Figure 7.6. 

The main application areas for electrochromic systems are in electrically switchable rear-view car mirrors for anti-dazzle, in glazing units for temperature and light control and in visnal displays. The main advantage offered by electrochromic systems in the first two of these applications is the fact that the cells can be made very large, i.e. one cell can comprise a whole glazing unit. 

A notable application of electrochromic cells is in car mirrors, which can be electrically dimmed so as to cut down dazzling reflections from bright lights. These do not use LT but instead rely upon the decomposition of atmospheric water vapour to... 

In a mirror-polished metal electrode substitute for the tungsten electrode we have a smart mirror. A similar photodetector-actuator automatically darkens a smart mirror in a car when a rear car uses high-beam lights. 

Electrochromic mirrors are now a common feature in expensive cars. 

Figure 7.6 Mirrors (a) an ordinary car driver s mirror reflects the lights of a following car, which can dazzle the driver (b) in an electrochromic mirror, a layer of optically absorbing chemical is electro-generated in front of the reflector layer, thereby decreasing the scope for dazzle. The width of the arrows indicates the relative light intensity...

Attractive metallic effects can be obtained by incorporating very thin, small flakes of aluminium, copper or copper/zinc alloys in otherwise transparent surface coatings. The metal flakes act as tiny mirrors within these paints, which are particularly effective on the curved surfaces of cars since the colour changes with the angle from which the surface is viewed. The orientation of the flakes within the paint film also changes the colour seen by the eye, so that careful dispersion of the metal components of the paint is essential. 

The materials that change colour on passing a charge are called electrochromes, and these can be classified into three groups. In the first type the colouring species remain in solution in the second type the reactants are in solution but the coloured product is a solid the third type are those where all the materials are solids, e.g. in films. The first type is used in car, anti-dazzle, rear-view mirrors, the second type in larger mirrors for commercial vehicles and the third type in smart windows (see section 1.5.4.2). 

Several other organic systems have been stndied as potential electrochromes because of their redox behaviour. These include carbazoles, methoxybiphenyls, fluorenones, benzoquinones, naphthaquinones and anthraqninones, tetracyanoquinodimethane, tetrathiafnlvalene and pyrazolines. ° Of particnlar interest are the 1,4-phenylenedi-amines, which form highly colonred species on oxidation. These, known as Wurster s salts, exemplified by Wnrster s Bine (1.97), are anodically colouring and this type of material has found nse in composite electrochromic systems for car rearview mirrors (see 1.5.4.1). 

Electrically switchable rear-view mirrors for cars and trucks have been in commercial production since the early 1990s, the leading company being the Gentex Corporation. The Gentex mirror consists of an ITO-glass surface, with the conductive side inwards, and a reflective metallic surface, spaced less than a millimetre apart. In the gap between these two electrodes is the solution electrolyte that is coloured at the anode by formation of the stable radical cation, similar to Wurster s... 

The electrochromic, self-dimming mirror market is expanding rapidly, comprising around 6 M of the estimated 150 M total for mirrors in cars and trucks in 2000. The market is set to grow to around 15 M by 2010, with additional growth in self-dim-mable sunroofs and sun visors. 

FIGURE 5.8 (a) CARS energy diagram, (b) Experimental setup BS, 15% beam splitter VA, variable attenuator A/2, half-waveplate Dl, 950 nm longpass dichroic mirror D2, 750 nm longpass dichroic mirror F, three 670 nm bandpass filters LI, aspheric lens L2, 10 cm concave lens. 

FIGURE 10.10 An experimental system of tip-enhanced CARS microscopy. See the text for detail. ND nentral-density filter, P polarizer, DM dichroic mirror, BE beam expander, BS beam splitter, APD avalanche photo diode. 

Compounds with the same chemical formula are called isomers. If two monosaccharide iso mers differ in configuration around one specific carbon atom (with the exception of the car bonyl carbon) they are defined as epimers of each other. If a pair of sugars are mirror images of each other (enantiomers), the two members of the pair are designated as D- and L-sugars. 

Fig. 6.8. A Principle of frequency-multiplexed CARS microspectroscopy A narrow-bandwidth pump pulse determines the inherent spectral resolution, while a broad-bandwidth Stokes pulse allows simultaneous detection over a wide range of Raman shifts. The multiplex CARS spectra shown originate from a 70 mM solution of cholesterol in CCI4 (solid line) and the nonresonant background of coverglass (dashed line) at a Raman shift centered at 2900 cm-1. B Energy level diagram for a multiplex CARS process. C Schematic of the multiplex CARS microscope (P polarizer HWP/QWP half/quarter-wave plate BC dichroic beam combiner Obj objective lens F filter A analyzer FM flip mirror L lens D detector S sample). D Measured normalized CARS spectrum of the cholesterol solution. E Maximum entropy method (MEM) phase spectrum (solid line) retrieved from (D) and the error background phase (dashed line) determined by a polynomial fit to those spectral regions without vibrational resonances. F Retrieved Raman response (solid line) calculated from the spectra shown in (E), directly reproducing the independently measured spontaneous Raman response (dashed line) of the same cholesterol sample...

Later, he couldn t tell how much, it stepped him out of the car and walked him across a quiet square to a larger, fancier car. Sat him in the back of that one, and a uniformed chauffeur checked his mirror to make sure Fitz was settled in, before taking him off on another drive. 

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