Introduction

In this chapter, we will look further at the optical properties of single or simple lenses, some special lenses and some interesting examples of more complex lens systems.

We study the properties of single lenses to learn more about how they image beams. Such knowledge also helps us to understand the properties of more complex optical systems because these more complex systems are composed of single lenses and an understanding of the role of each single lens helps us to understand the operation of the system as a whole.

There are a wide range of simple lenses. We will initially classify them according to whether they are rotationally symmetric or non-rotationally symmetric and start with the symmetric lenses.

In this chapter, we will assume the lenses are in air, unless it is specifically stated otherwise and there will be such cases. There are some interesting situations where the lenses are not in air and we will look at some examples in Section 6.4.

Rotationally symmetric simple lenses

Rotationally symmetric lenses are constructed with surfaces that are rotationally symmetric and the axes are co-linear. These lenses may be made with spherical or aspheric surfaces. Non-rotationally symmetric lenses will be discussed in the next major section, Section 6.2.

Spherical lenses

Most lenses are constructed using spherical surfaces with co-linear centres of curvature. The line joining the centres is the optical axis. Lenses are usually made with spherical surfaces because of the low manufacturing cost relative to that of other surface forms.