ABSTRACT
This chapter introduces the types of lenses which are used in building optic and optical fibre devices and instruments. A typical lens is made of glass or plastic. Lenses are classified in two categories: thin lenses and thick lenses. Lenses are commonly used to form images by the refraction of light. Lenses are used in building optic/optical fibre devices and instruments, such as cameras, microscopes, slide projectors, and fibre optical switches. Radial graded-index (GRIN) lenses are often specified in terms of their pitch lengths and operating wavelengths. Coupling light into a fibre cable can be accomplished by using a quarter-pitch GRIN lens, which focuses the collimated beam from the laser source onto a small spot on the core of the fibre cable. GRIN lenses are used to focus and collimate light within a variety of fibre optical components. Ball lenses couple fibres from micro-optic components to light sources, from laser diodes to fibre cables, and from fibre cables to detectors.
