Optical spectrometer designs

Traditional optical spectrometers for both mid-IR and NIR were based on a scanning monochromator. This design features a single source and detector, and a mechanically scanned dispersion element in combination... 

Double-beam instrument An optical instrument design that eliminates the need to alternate blank and analyte solutions manually in the light path. A beam splitter partitions the radiation in a double beam in space spectrometer a chopper directs the beam alternately between blank and analyte in a double beam in time instrument. 

Figure 12. Optical schematic representation of an aberration-corrected toroidal diffraction grating spectrometer designed for use with an I PDA detector system. (Reproduced with permission from Ref. 12.

The function of the interferometer in a Fourier transform infrared spectrometer has been presented. An FT-IR spectrometer optical layout is now described and information is provided for each element of a typical spectrometer design. A schematic of a typical FT-IR optical design is given in Figure 6. 

A single photon fluorometer consists of the following subsystems an optical spectrometer (including a pulsed light source), a data acquisition system (consisting of timing electronics) and a data analyser (composed of a computer with re-convolution software). Birch and Imhof [16] have widely published on instrumentation design and analytical methods. 

These effects have been used by investigators to reduce the background radiation levels in x-ray spectroscopy. For Bremsstrahlung radiation, the maximum polarization vector is parallel to the electron path in the x-ray tube. In many conventional-wavelength spectrometer designs, the specimen and crystal surfaces will become parallel when 26 equals the takeoff angle 2 ( 45°). In addition, the x-ray tube axis and the rotational axes of the crystal and detector are parallel. This so-called parallel optics cannot take advantage of the polarization of the white spectrum. If, however, the surface plane of the crystal and specimen remain perpendicular... 

The last 4 years have seen a tremendous increase in the use of Raman spectroscopy in general and there is nowhere where this is more noticeable than in the area of process analysis. In comparison to the other optical spectroscopic techniques available, Raman spectroscopy offers a unique combination of well-resolved features and the ability to perform the analysis remotely by interfacing the spectrometer to the sample via standard silica fiber optics. Adar et al. [1] and Lipp and Leugers [2] have both reviewed the development of Raman spectroscopy for process applications in terms of necessary instrumentation and illustrated this with a discussion of several successful applications. Developments in fiber-optic probe design for Raman spectroscopy, up to mid-1996, have been thoroughly reviewed by Lewis and Griffiths [3] and more recently by Lewis and Lewis [4]. 

J.F. James, R.S. Sternberg, The Design of Optical Spectrometers, Chapman and Hall, London, 1969. 

The first interferometer incorporating an air-bearing drive was the Block Engineering Model 296. This interferometer was the one used in the first commercial mid-infrared FT-IR spectrometer designed for laboratory use, the Digilab FTS-14 [4]. This instrument was introduced in 1969 and was followed a few years later by the Model 7199 spectrometer made by Nicolet Analytical Instruments which also featured an air-bearing drive. Both of these early FT-IR spectrometers were too large to be placed on a lab bench and the compressor was mounted inside the instrument s cabinetry. Over the next 10 or 15 years, the optics and electronics of FT-IR spectrometers became far more compact and bench-top instruments became commonplace. Since compressors are noisy and occupy too much bench space. 

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