Grating, principle

Modal Transition in Nano-Coated Long Period Fiber Gratings Principle and Applications to Chemical Sensing... 

Figure Bl.18.6. Schematic representation of Zemike s phase contrast method. The object is assumed to be a relief grating in a transparent material of constant index of refraction. Phase and amplitude are varied by the Zemike diaphragm, such that an amplitude image is obtained whose contrast is, m principle, adjustable.

An important principle is that the coal becomes ignited from the fuel which is on top of it and further down the grate. This reduces carry-over of smalTunburned particles, as the burning coal on top filters them out. Volatiles released from the fresh coal are also ignited and consumed in the burning layer. This minimizes smoke formation which is caused by incomplete combustion of the volatiles. 

Fig. 19.2 Layout of an infrared spectrophotometer employing a diffraction grating for monochromation. Reproduced by permission from R. C. J. Osland, Principles and Practices of Infrared Spectroscopy, 2nd edn, Philips Ltd, 1985.

Thus far we have been considering—in Young s experiment, Michelson interference, and even measurements of mutual intensity—what is essentially two source interference. We now turn to multiple source interference. For example, a diffraction grating divides up a beam into an array of sources, which then interfere. By the principle of superposition, the disturbance in the far field is the sum over the sources... 

The equivalent of the grating equation for a prism is the application of Fermat s principle to the configuration shown in Fig. 12. 

PRINCIPLE OF MEASUREMENT, M MULTIPLE, S SINGLE, P POINT, R RINETIC WAVE LENGTH, F-FILTER, M MONOCHROMETER, G GRATING... 

Operating principle of a diffraction grating, cp is the angle of incidence d is the groove spacing 9 is the angle of reflection. 

The inset diagram in Figure 22.2 shows the use of a prism in place of the grating . However, underlying principle being identical, a rotating mirror affords the scanning of individual frequencies. 

The gratings can also be made in situ by holographic irradiation as was demonstrated for low molecular stilbenes in a polystyrene matrix [197]. Here, the spatial modulation of gain dominates over the refractive index modulation in its contribution to optical feedback. The principles of holographic irradiation will be described in Section VIII, which discusses photosensitive materials. 

Figure 2.23 Diffraction gratings. Each line in a grating acts as a separate source of radiation (a) but radiation transmitted at any angle 6 is retarded relative to radiation from the preceding line (b) by the distance x. In the transmitted radiation some wavelengths will undergo constructive interference while the majority will suffer destructive effects. Reflectance gratings (c) are frequently used and the principles of monochro-mation are the same as for transmission gratings.

Figure 15, (a) Principle of a grating, (b) Intensity patterns produced by diffraction gratings with two, three and four slits of width < with each having the same separation between adjacent slits. 

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