Optical sensors are highly sensitive to a number of environmental conditions, and are particularly vulnerable to damage caused by humidity and certain chemicals. They can be protected by welding protective caps to the headers in which they are housed. However, at the same time, it is vital to ensure that the caps meet a range of optical requirements to ensure the consistent transmission of optical signals.
Molded caps are sealed hermetically by fusing the glass directly to the metal frame without the use of any other interface materials. This is achieved by reheating cooled glass and then fusing it with the metal. The fusion process must be designed in such a way to ensure that the glass cools down without the formation of bubbles and inclusions and obtains the correct optical properties, which is often subject to very low tolerance limits.
Fusion molded caps can also be manufactured with windows and convex (plano and biconvex) lenses, and with various kinds of filters for special applications. Windows and lenses can be supplied in a range of designs and according to customer specifications.