Optical imaging interference optics

Optical interferometry can be used to measure surface features without contact. Light reflected from the surface of interest interferes with light from an optically flat reference surface. Deviations in the fnnge pattern produced by the interference are related to differences in surface height. The interferometer can be moved to quantify the deviations. Lateral resolution is determined by the resolution of the magnification optics. If an imaging array is used, three-dimensional (3D) information can be provided. 

Observation. The time of observation is about 2-4 hocus for vital preparation and several days for fixed preparations. All the preparations may be analyzed by 3-channel simultaneous detection to receive common complicated interference image of the object and details of its structure (see experiment 1) by receiving 20 visual slices (optical sections) or the complete volume (the information must be also quantitatively extracted) (see experiment 2) by computer modelling the images as well as mathematical analysis (experiments). 

In video microscopy, for instance, background is normally subtracted using differential interference contrast (DIC) [18]. This technique, which requires a number of manipulations from the user, may now be automated using a new method called polarization-modulated (PMDIC) [19,20], It requires the introduction of a liquid crystal electro-optic modulator and of a software module to handle difference images. PMDIC has been shown to bring improvements in imaging moving cells, which show a low contrast, as well as thick tissue samples. 

Y. Zhang, D. H. Brooks, M. A. Franceschini, and D. A. Boas. Eigenvector-based spatial filtering for reduction of physiological interference in diffuse optical imaging. Journal of Biomedical Optics, 10 011014-1-011014-11, 2005. 

The schematic processing steps for the two-layer deep-UV PCM system are shown in Table III for near-UV and e-beam exposures, resulting in capped and uncapped profiles respectively. Step 5a is required only for near-UV exposures to average out optical interference effects discussed in Section 6.2.a. Step 6a is used to enhance the AZ to PMMA adhesion and cap retention. Figure 15 shows uncapped 1 - nm lines in a 2 - /im thick PMMA layer. Figure 16 shows the capped image with 0.3 fim AZ on 2 -iLim PMMA. The AZ layer was delineated by a 30 - /iC/cm 25 - keV e-beam in both cases. 

Figure 2. Series of optical interference images showing the decay of a 1-D grating on a Ni(lOO) surface at 1219C[11]. The interference fringes represent contour intervals of 0.27pm. The...

Another important optical phenomena that relies on light interference and diffraction is holography, the process by which holograms (interference patterns) are produced. Whilst holograms are best known for the reproduction of near perfect 3D images of an object in the graphic arts, they also find apphcations in newer areas such as laser eye protection, LCDs, diffractive optical elements, optical processing... 

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