Reflectivity, light sensors

Figure Bl.18.10. Scaimmg microscope in reflection the laser beam is focused on a spot on the object. The reflected light is collected and received by a broad-area sensor. By moving the stage, the object can be scaimed point by point and the corresponding reflection data used to construct the image. Instead of moving the stage, the illuminating laser beam can be used for scaiming.

Diffused silicon sensor, 20 655 Diffusely reflected light, measuring, 24 111... 

Fig. 13. Schematic design of the Aquasant probe. This is a sensor for optical density measuring the reflected light. Precision optics focus and collect the incident and the reflected light. Internally, light is guided through optical fibers. Left cross section right front view...

Fig. 11 (a) Schematic drawing of the colorimetric resonant reflection sensor. White light illuminates the sensor surface by an optical fiber. A second fiber guides the reflected light to a spectrometer, (b) Schematic spectrum... 

The utihzation of fluorescence dyes for analytical measurements enhances the sensitivity for the detection of the molecules of interest. First, Cronick and Little made use of evanescent wave excitation for a fluorescence immunoassay, in 1975. By using totally internally reflected light, they excited the fluorescence of a fluorescein-labeled antibody which has become bound to a hapten-protein conjugate adsorbed on a quartz-plate in an antibody solution [41]. Contrary to the label-free high-refractive-index sensors where the mass of the molecule of interest is... 

Surface plasmon resonance (SPR) biosensors exploit special electromagnetic waves-surface plasmon-polaritons-to probe interactions between an analyte in solution and a biomolecular recognition element immobilized on the SPR sensor surface. A surface plasmon wave can be described as a light-induced collective oscillation in electron density at the interface between a metal and a dielectric. At SPR, most incident photons are either absorbed or scattered at the metal/dielectric interface and, consequently, reflected light is greatly attenuated. The resonance wavelength and angle of incidence depend upon the permittivity of the metal and dielectric. 

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