Light scattering optical configuration

The reflecting surface can be a mirror or a membrane with a light-scattering surface. In any case, the sensor has the appearance of a monolithic probe (i.e., a dip-stick probe). Optical sensors based on absorption, fluorescence, phosphorescence, and luminescence can employ such a configuration. Various highly optimized fiberoptic probes for UV-Vis, NIR, and IR ranges are now commercially available, and their designs are shown in Fig. 9.23. 

Figure 2. Optical configuration of the two-angle light-scattering photometer used in these studies.

Figure 4 (bottom) shows the configuration of the optics to irradiate the seawater and to detect the subsequent signal through the window. A set of lenses, and L2, focuses the fiber image on the water channel. (The diameter of the laser beam at the measuring position was determined to be about 0.6 mm.) The fluorescence emitted and the light scattered in the focused volume are collected by the lens L3 on the surfaces of the fibers F1 and F2 with a two-to-one reduction factor. A dichroic filter transmits the fluorescence radiation to the fiber F j and the scattered radiation to the fiber F2. 

After a final centrifugation, resuspend cells in fresh fixative to an optical density of about 0.3 at 600 nm (light scattering depends on the configuration of the spectrophotometer and higher or lower values may be needed) and drop about 200 p.1 from about 5 cm on slightly slanted slides. 

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