Reflective devices

A fourth category of PV technologies, concentrator photovoltaics, uses small but very efficient cells Uluminated with concentrated sunlight. PV concentrators use lenses or reflective devices and track the sun through daUy cycles. The tracking maintains the concentrated light at intensities up to several hundred times normal sunlight. 

In order to compensate for the distortions in the wavefront due to the atmosphere we must introduce a phase correction device into the optical beam. These phase correction devices operate by producing an optical path difference in the beam by varying either the refractive index of the phase corrector (refractive devices) or by introducing a variable geometrical path difference (reflective devices, i.e. deformable mirrors). Almost all AO systems use deformable mirrors, although there has been considerable research about liquid crystal devices in which the refractive index is electrically controlled. 

Figure 10.19—Specular reflection device for FTIR. a) Optical path in a specular reflection device at a fixed angle b) raw signal obtained by specular reflection of a sample of methyl polymethacrylate (Plexiglas) ...

Figure 10.20—Devices allowing the study of samples by reflection, a) Diffuse reflection device b) attenuated total reflection (ATR) device c) comparison of the spectra of benzoic acid obtained by transmission (KBr disc) and by diffuse reflection using the Kubelka Munk correction. The depth of penetration of the IR beam depends on the wavelength. The absorbance for longer wavelengths would be overestimated if no correction was applied.

Figure 10.16 ATR three reflection device and examples of spectra. The small diamond disc (diameter 0.75 mm) enables the isolation of the sample examined from the ZnSe crystal. Chemically inert and resistant, diamond is appropriate for examination of aU sorts of hard samples which are pressed against its surface or contain water. Above right, are reproduced two spectra obtained with such a device. Spectra obtained from a drop of sulfuric acid (H2SO41M) deposited as a sample (reproduced courtesy of SensIR). Below, spectrum of water at 25 °C and of heated water vapour (250 °C) Inti Lab 32,(2), 2002).

Figure 10.17 Devices allowing the study of samples by reflection, (a) Schematic representation of two ATR devices (attenuated total reflection) a model with a trapezium crystal for multiple reflections and a model for single reflection with solid microsamples (the application of a weight improves the contact of the sample with the crystal s rounded form). Basic formula and notion of critical angle (h) Specular reflection device. Optical pathway of the apparatus at a fixed angle of 30 ° for highly reflecting samples and of 60 ° for the contrary (c) Optical scheme for a diffuse reflection device and diagram of a Spectra Tech model.

Reflective devices include capillaries, Bragg-Fresnel lens, and mirrors. Capillaries, typically tapered, rely on internal reflection to concentrate photons into small spots defined by the downstream aperture (Bilderback and Thiel 1995 Heald et al. 1997 Dhez et al. 1999 Bilderback and Huang 2001). Sub-micrometer beams have been achieved whereas the small working distances tend to be the main limitation. Bragg-Fresnel lens (Hayakawa et al. 1989 Chevalier et al. 1995 Snigirev et al. 1995 Dhez et al. 1999) are similar to FZPs but operate in reflection mode. 

Fig. 4.11. Schematic diagram of a modular modem photodiode spectrometer containing a light source, bifurcated fibre optics, and the optical components in a ceramic block. With a different arrangement of the fibres a transmittance, fluorescence, and reflectance device can be...

CFR 392.33 — Obscured lamps or reflective devices/material. 49 CFR 393.11 — Lamps and reflective devices. 

All required lamps and reflective devices/material must not be obscured by the tailboard, by any part of the load, or be covered by dirt or other added vehicle or work eqmpment. 

The table below lists the required lamps, reflective devices, and associated equipment by type of commercial motor vehicle. The illustrations that follow the table illustrate the position of the lamps, reflective devices, and associated eqmpment as specified in the table. 

Pole trailers and trailer converter dollies must meet the Part 393 requirements for lamps, reflective devices, and electrical equipment in effect at the time of manufacture. Trailers which are equipped with conspicuity material which meets the requirements of 393.11(b) are not required to be equipped with the reflex reflectors listed in the table above if ... 

CFR 571.108 — Standard No. 108 Lamps, reflective devices, and associated equipment. 

Polyaniline films have not only been shown to exhibit electrochromism in the visible region, but also in the microwave and far-IR regions of the electromagnetic spectrum. A polyaniline film doped with camphorsulfonic add and incorporated into a sohd state microwave shutter demonstrated that the transmittance and reflectance of X-band microwave energy could be modulated [6]. At a wavelength of 10 GHz, the shutter could be switched between 4.8% transmission when the polymer is oxidized and 42% transmission when the polymer is neutral. When utilized in a reflective device configuration in combination with poly(diphenylamine), polyamline yields a high reflective modulation in the far-IR [119,120]. This device shows a reflectance contrast of 53% at 10.5 p,m, 28% at 16.5 p,m, and 46% at 620 nm. 

Reduction potential, 13-2, 13-19 Reductive elimination, 9-8, 9-10-9-11, 9-21 Reflectance spectra, 15-25-15-26, 15-66-15-67 Reflective cholesteric LCD, 8-42-8-43 Reflective devices,... 

For a mirror application, a totally reflective device is necessary. The reflector may be either behind the counter electrode or included into the... 

No/defective lighting devices/reflective devices/ projected... 

The production of patterned, rapid-switching, reflective ECDs has been demonstrated by Aubert et al. with active electrochromic materials such as PEDOT, (PProDOT) and the dimethyl-substituted derivative PProDOT-Me2, whose resulting switching times were 0.1-0.2 s (5-10 Hz) [51, 56]. In another dual-type polymer PEDOT and PBEDOT-B(OCi2H2s)2 reflective device, a 2 x 2 pixelated lateral configuration has been shown. 

Cholesteric LCs (CLCs) are of particular interest due to their unique ability to self-organize into a helical supramolecular architecture. CLC structures are also found in nature including living matter. They have been used in temperature sensors, optical filters, reflective devices, cosmetics, etc. A CLC reflects light owing to its helical... 

Several technologies able to be used for the development of communicative textile devices have been presented. Some of them are already used for the development of textile displays. Their emission of reflective characteristics allow their use for different types of applications. Emissive devices such as luminescent stmctures or optical fibres are preferred for high-visibility outfits for personal safety, for art and fashion design or for advertising events. Reflective devices offer a softer, more discreet colour change, which could preferentially be used for everyday applications such as communicative clothes, home furnishings or fashion. 

The patented device developed by Acosta et al. [3]. In this reflectance device, the glucose content is directly modeled from the collected spectra. Reference values come from glucose testers available to diabetic patients. 

Rather than generating a completely new waveform, some jammers prefer to intentionally introduce a multipath component. These jammers are reflective devices, where the friendly signal is received and then reflected or retransmitted in the direction of the receiver. In military systems the repeat-back jammer may be an active device however, in commercial applications it is typically known as multipath interference. Multipath is a significant problem in urban areas where signals can reflect off buildings and in indoor wireless communication systems where high carrier frequencies make a host of structures and equipment effective reflectors of EM radiation. 

Directional/directional geometry offers a number of advantages over sphere-based diffuse reflectance devices. The primary advantage is that there is no sphere to become dirty or contaminated, which is why directional/directional geometry is often used in on-line applications in... 

U.S. Department of Transportation. Eederal motor vehicle safety standards standard no. 108 Lamps, reflective devices and associated equipment. United States of America US Government Publishing Office 2007. 

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