Optical glass types

Highly pure lanthanum oxide is used to make optical glass of high refractive index for camera lenses. It also is used to make glass fibers. The oxide also is used to improve thermal and electrical properties of barium and strontium titanates. Other applications are in glass polishes carbon arc electrodes fluorescent type phosphors and as a diluent for nuclear fuels. In such apph-cations, lanthinum oxide is usually combined with other rare earth oxides. 

Figure <8. Optical map designating glass groups (letters) and glass types (numbers) as defined by index of refraction (n ) and Abbe-number (vj...

It is due to these stringent requirements on raw material purity along with the type of glass making oxides used that optical glasses in general are rather expensive compared to other commercial glasses. 

Figure 7.25 Examples of spectral sensitivities of a photodiode (a) and of two types of photomultipliers (b). The window transmissions are shown as q (silica) and g (optical glass). Horizontal axes, A in nm/100 vertical axes,

Optical glass Optical glass is a special type of glass. It is made... 

Fig. 3.120. Scheme of the devices (three types - a, b and c) for formation and study of asymmetric films a 1 - microscrews 2 - tube with organic liquid 3 - tube with air and vapour of the liquids 4 - films holder 5 - tube with aqueous solution b 1 - glass cuvette 2 - liquid substrate (water phase) 3 - glass plate with an orifice 4 -capillary (orifice) where the film forms 5 - porous material 6 - microvalve for regulating the liquid level c I -capillary tube 2 - glass tube with the surfactant solution 3 - a drop of organic liquid or bubble 4 - optical glass 5 - microscope eye-piece. 

Figure 7.9 Refractive index profiles of three common types of optical glass fiber multimode step index, multimode graded index, and single mode.

Currently mass produced types of optical glasses are melted in small continuous tanks of special design, provided with mechanical stirrers the glass melt is formed... 

Optical glasses are used in optical devices and instruments, and are characterized by specified and precisely maintained values of refractive index and dispersion. The other main properties required are high chemical and physical homogeneity, colourlessness and a high optical transmissivity. The optical industry has at its disposal hundreds of types of optical glasses, but only a limited number suffice to meet current requirements. 

FIG. 145. Optical properties of various types of optical glasses (Eastman Kodak Company). 

The earlier types of optical glasses which were melted from the traditionally employed oxides, exhibited approximately direct proportionality between refractive index and dispersion. Deviation from this rule has arisen by the introduction of new components (B2O3, BaO, ZnO, LajOj, etc.)and of quite new types of glasses. The main types and their optical properties are shown in Fig. 145. The current optical crowns and flints occupy a comparatively small region compared with that corresponding to the attainable properties of special optical glasses. 

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