Why Plastic or Ploymer Optics?

WHY PLASTIC OPTICS?

There are many reasons why product designers decide to use .plastic optics essentially fall into two categories: relative low cost and the opportunity to use unique element configuration.

Plastic optics have a number of advantages over glass. Foremost of these are lower cost, higher impact resistance, lighter weight and more configuration possibilities for simplifying system assembly. Configuration flexibility is especially useful in systems that can use aspherical lenses to simplify system design and reduce pats count, weight and cost. Moreover, light transmittance is comparable to that of high-grade crown glasses. Finally, the plastics

that can break generally do not splinter like glass. The fragments are larger and tend to be more obtuse and less hazardous.

The chief disadvantages of plastic optics are comparative intolerance to severe temperature fluctuation in some systems and low resistance to scratching. These disadvantages,

however, are far outweighed by the advantages plastic brings to the majority of optical applications. Although plastic has less temperature tolerance than glass,most optical systems do not operate in ambient, temperatures beyond the thermal limits of plastic elements. For

that matter, glass optical systems often will not withstand much more physical abuse than their plastic counterparts and still function properly.

The variety of available glass optical raw materials is much greater than that for plastic. This abundance of glass options translates to greater design freedom because of the

wide selection of dispersions and indices of refraction.However, creative use of plastic aspherics often compensates for the narrower choice of materials.

Low Cost: The injection molding process, is ideal for producing large volumes of parts economically.

Multicavity molds allow a low-cost manufacturing process

Injection-molded optical elements are formed in steel molds that contain machined cavities with surfaces polished to an optical quality (top). The molten raw material is forced under pressure into the temperature-controlled mold (bottom). After cooling, the parts are removed from the gates and runners and require no further finishing process.

to be combined with comparatively inexpensive raw materials to create a powerful economic advantage for large production volumes. By carefully sizing the mold for required production volume, the break-even cost, compared to the glass alternative, can be surprisingly low,

Integral Mounting: The molding process permits mounting

and assembly features such as mounting brackets,

holes, slots and flanges to be integral with the optical element.

The result is a single-piece design that eliminates

mounting hardware and simplifies assembly and alignment.

Assembly costs often are more than that of the optic itself,

so the benefits of using imaginative configurations are obvious.

Furthermore, multiple elements can be combined in

unique optical configurations such as transceiver lenses for

transmitting and receiving simultaneously. Figures 1.3,

1.4, 1.5, 1.6 and 1.7 demonstrate special designs incorporating

both multiple elements and integral mounting.

Fig. 1.8 is a multielement lens with a special edge configuration

that aligns and centers the elements; this design is

economically beneficial for high production volume applications.