Analogue reflectance- Optical

The requirements for an instrumental method of specifying reflected color include a light source, the colored object and a detector. What this means is that all we need is a source, an object and a detector. However, since the response characteristics of these optical components are not linear, nor flat, we need an analogue system in order to be able to measure color. 

However, these analogues are actually hypothetical. The reason for this is that it is nearly impossible to obtain optical measurement components, such as the source and the detector, whose response to light across the visible spectrum is flat (or nearly so). However, this is not an impossible task and we find that an excellent match can be obtained to the transmission functions of 7.8.21., i.e.-those of the Standard Observer. This is typical for commercially available instruments. Now, we have an instrument, called a Colorimeter, capable of measuring reflective color. 

The actual analogue values we need to measure reflectance are given on the next page as 7.8.30. as follows. Note that the optical response curves of the measuring parts, i.e.- the non-linearity of the source and detector, are now corrected in the response of the overall instrument. 

An important application for garnets is for isolators in optical communications systems. Reflections from end-faces of components and interconnections in an optical transmission line have a destabilizing effect on the operation of the laser sources and have to be eliminated. This is achieved using an optical isolator , the optical analogue (2 typically in the range 1.30—1.55 /mi) of the microwave isolator described in Section 9.5.5. 

Figure 4.6-13 Optical rotation q recorded as outlined in Fig. 4.6-12 Spectra of two differently concentrated solutions of S-tyrosine-methylester in the nematic mixture EBBA/MBBA (equimolar mixture of N-(p-ethoxybenzylidene)-p - -butylaniline and its methoxy analogue 2 of Table 4.6-1 Riedel-de Haen), left RCE (molar fraction x fa 0.024) related to the selective reflection band indicating pitch and handedness of the. structure, thus characterizing the chirality of the solute molecules by the helical twisting power right Sequence of ACE (,v se 0.0024, therefore the RCE should occur around 200 cm ) each of which indicates the induced handedness and therefore, discriminates enantiomers (Koite, 1978).

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