Optical systems nonimaging

As Raman scattering is a weak process, photons are precious and high collection efficiency is desired for a higher signal-to-noise ratio. Specialized optics such as Cassegrain microscope objectives and nonimaging paraboloidal mirrors have been employed to increase both the collection spot size and the effective numerical aperture of the optical system.10... 

Figure 4 Nonimaging (left) versus imaging (right) optical systems. In the latter all light rays coming from a point in the source must be imaged to a point in the receiver.

Nonimaging optics Optical theory and design that departs from traditional methods and develops techniques for maximizing the collecting power of concentrating elements and systems. 

Figure 25 Relative silica Raman performance for an unfiltered nonimaging 6-around-l probe and a Kaiser Optical Systems, Inc, Mk II imaging probe (a) unfiltered A -around-1 (b) imaging probe.

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