Optical train

The scanners commercially available today operate on the basis of the optical train illustrated in Figure 22. 

Fig. 22 Optical trains of the commercially available scanners. (A) absorption, (B) fluorescence quenching and true fluorescence.

However, the optical train illustrated in Figure 22B allows the determination of fluorescence quenching. The interfering effect described above now becomes the major effect and determines the result obtained. For this purpose the deuterium lamp is replaced by a mercury vapor lamp, whose short-wavelength emission line (2 = 254 nm) excites the luminescence indicator in the layer. Since the radiation intensity is now much greater than was the case for the deuterium lamp, the fluorescence emitted by the indicator is also much more intense and is, thus, readily measured. 

The optical train employed for photometric determinations of fluorescence depends on the problem involved. A spectral resolution of the emitted fluorescence is not necessary for quantitative determinations. The optical train sketched in Figure 22B can, therefore, be employed. If the fluorescence spectrum is to be determined the fluorescent light has to be analyzed into its component parts before reaching the detector (Fig. 28). A mercury or xenon lamp is used for excitation in such cases. 

When recording excitation and fluorescence spectra it must be ensured that monochromatic light falls on the detector This can best be verified in instruments built up on the kit principle or in those equipped with two monochromators (spectrofluonmeters) The majority of scanners commercially available at the moment do not allow of such an optical train, which was realized in the KM3 chromatogram spectrometer (Zeiss) So such units are not able to generate direct absorption or fluorescence spectra for the charactenzation of fluorescent components... 

Fig. 69. Schematic of the optical train for birefringence measure ments. For microphotographs, an instant camera replaced the photodetector...

Evaluation of chromatograms 133 ff -, optical trains 30, 39 -, peak area/height 31, 33,40 Evipan 339, 343... 

Evaluation of chromatograms la 133ff Evaluation, peak area or height la 31,33,40 -, optical trains la 30, 39 Evipan la 339,343 Excitation to fluorescence la 10,12,20,37 Explosion resulting from reagent residues la 82,253,261,315,365 Explosives lb 49,244,407-409 Exposure to vapors la 86... 

Saponins la 7,411,430 -, bioautographic determination la 109 Sarcosine Ia435 lbl24 Scandium cations, detection la 144 Scanner, optical trains la 30,39 S-Chamber (small chamber) la 126,127 SCHiFF s bases lb 52 Scintillators la 12 Scopolamine lb 231,252,255,323 Scopoletin lb 216-218,365 Screening process lb 45 Sebacic acid la 178,233,249,308 Sebuthylazine lb 418 Selectivity, enhancement by derivatiza-tion la 55... 

Sandwich chamber 126,127 Sapogenins 43,195, 206, 411 -, steroid 69, 206 -, trifluoroacetates 69 Saponins 7,109, 411, 430 Sarcosine 435 Scandium cations 144 Scanners, optical trains 30, 39 S-chamber see Sandwich chamber Scintillators 12 Sebacic acid 178,233,249, 308 Selectivity... 

Fig. 1 Schematic diagram of the integrating sphere portion of a diffuse reflectance spectrometer, illustrating the key elements of the optical train. Although the detecto has been placed in the plane of the sample and reference materials, in common practice it would be mounted orthogonal to the plane created by the intersection of the optica beams.

The optical train affords as much as twice the dispersion and the ultimate resolution is fairly comparable to any single-monochromator instrument (Figure 22.2),... 

The possible outcomes of measurements—combinations of scattering matrix elements—listed in Table 13.1 follow from multiplication of three matrices those representing the polarizer, the scattering medium, and the analyzer. If U is an element in the optical train, then the measured irradiance depends on only two matrix elements. In general, however, there are four elements in a combination, so that four measurements are required to obtain one matrix element. 

Figure 20-2 (cQ Varian Cary 3E Ultraviolet-Visible Spectrophotometer, (b) Optical train. [Courtesy Varian Australia Ply, lid., Victoria, Australia.]... 

Since the Maxwell equations involve the components of the Jones vector, it is normally easier to derive the Jones matrix, J, for complex, anisotropic media. Once J is obtained, it is generally convenient to transform it to the Mueller matrix representation for the purpose of analyzing the quantities measured in specific optical trains. This is because the components of the Stokes vector are observable, whereas the Jones vector components are not. Since it is the intensity of light that is normally required, only the first element of Sn,... 

Description of a typical element in the schematic of an optical train. 

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