In the previous chapter, we discussed some of the issues that determine whether or not plastic optics are appropriate for a particular application. One of the issues was the properties of the plastic optical materials themselves. In this chapter, we discuss in more detail the characteristics of the typically available plastic optical materials, focusing on their optical and mechanical properties. We also discuss the selection and specification of the materials.
2.1 Plastic Versus Glass Maps
When comparing optical plastics and optical glasses, two things are readily apparent. One, there are significantly fewer optical plastics than optical glasses to choose from. Two, compared to optical glasses, there are no optical plastics with relatively high refractive indices. One way of seeing this is to compare the âglass mapsâ of the two types of materials. Figure 2.1 shows a glass map for optical glasses and plastics, with the glasses shown as triangles and the plastics shown as diamonds. Figure 2.2 shows a similar map for just the optical plastics. For those unfamiliar with these maps, they are a plot of the refractive index of the material (vertical axis) versus the Abbe number or dispersion (horizontal axis) of the materials. Each point displayed on the map represents a specific material.
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