System optical imaging

With a special optical system at the sample chamber, combined with an imagir system at the detector end, it is possible to construct two-dimensional images of the sample displayed in the emission of a selected Raman line. By imaging from their characteristic Raman lines, it is possible to map individual phases in the multiphase sample however, Raman images, unlike SEM and electron microprobe images, have not proved sufficiently useful to justify the substantial cost of imaging optical systems. 

Collecting optics, radiation detectors and some form of indicator are the basic elements of an industrial infrared instrument. The optical system collects radiant energy and focuses it upon a detector, which converts it into an electrical signal. The instrument s electronics amplifies the output signal and process it into a form which can be displayed. There are three general types of instruments that can be used for predictive maintenance infrared thermometers or spot radiometers line scanners and imaging systems. 

Tor the purpose of this brief account we will provide only a notional definition of optical aberrations. In an optical system, the angular coordinates of incident rays are transformed according to sequential applications of Descarte s law from one optical surface to the next. Aberrations are essentially the non-linear terms of the transformation, the angular coordinates of emerging rays not being strictly proportional to those of the incident ones -thereby generating distorted and/or blurred images. 

Figure 9. The entrance and exit pupils are the surfaces where the entrance and exit rays coming from the different field positions cross each other. In different terms, the entrance pupil is the aperture of the optical system as seen by an observer located at the position of the object, or at the location of the image for the exit one.

Entrance and exit pupils are conjugates i.e. images of each other through the optical system. The real physical aperture may be neither of them, hut set hy a physical diaphragm or component contour, located... 

Thus by a series of calculations of ray height and position we can determine the location of an individual ray as it traverses an optical system. If we trace a series of rays all emanating from a single point on an object and discover that they all intersect at a single point we determine the image location for that point. 

At distances that are very large compared to either the source dimensions, or the aperture of our optical system the complex amplitude is just the Fourier transform of the object complex amphtude. Furthermore, it can be shown that the complex amplitude in the image plane of an optical system is just the Fourier transform of the complex amplitude at the aperture plane, (for a complete derivation of this see Goodman, 1996). 

The effect of overall slope on the wavefront can be removed by re-centering the speckle image, and in most adaptive optics systems this is performed by a planar tip/tilt mirror (Roddier and Roddier, 1993). 

Figure 1 shows the simulation of a galaxy observed with a PSF which is typical of an adaptive optics system. The noisy blurred image in Fig. 1 will be used to compare various image reconstruction methods described in this course. 

Measuring FRET by fluorescence lifetime imaging microscopy (FRET-FLIM) offers the ability to see beyond the resolution of the optical system ( 10-100 times that of modern far field microscopes [5]). FRET efficiency can be used as a proxy for molecular distance, thereby allowing the easy detection and somewhat more challenging quantification of molecular interactions. Although many types of assay exist, FRET-FLIM is a highly suitable technique that is capable of in situ measurements of molecular interactions and conformation in living and fixed cells. 

Sokolov, K., Aaron, J., Hsu, B., Nida, D., Gillenwater, A., Follen, M., Macaulay, C., Adler-Storthz, K., Korgel, B., Discour, M., Pasqualini, R., Arap, W., Lam, W. and Richartz-Kortum, R. (2003) Optical systems for in vivo molecular imaging of cancer. Technology in Cancer Research ei Treatment, 2, 491-504. 

The basic instrumentation for CL imaging includes an ultrasensitive video camera, an optical system, and appropriate software for image analysis [21],... 

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