Ball Lens – A Micro Millimeter Device to Transform Optical to Electrical Energy
Optoelectronics combines the concept of optics and electronics together. The study of optoelectronics is based on the principle of quantum mechanics which occurs on a nanoscopic scale. Instruments that use optical to electrical or electrical to optical transducers are optoelectronic devices. Ball lens is the optical component used in these devices and they are easily placed due to their compact sizes. It is shaped in the form a sphere in order to refract an optical beam. The sizes of these glass balls range from as small as 0.001 mm to 5 mm in diameter.
The glass ball lens is molded precisely in the following steps:
- A gob of glass is placed on the bottom half of the mold
- The process chamber is subjected to nitrogen gas for removing the oxygen
- The mold and the glass are placed in an isothermal chamber
- When the temperature of the chamber reaches to the softening point of glass, the top half of the mold is closed
- The glass is pressurized between the molds in a controlled process till the required thickness has been achieved
- The glass is then cooled down by filling the chamber with nitrogen
- The glass lens is removed from the mold.
The molding machine is specialized to control the pressure and the temperature during the process of molding the glass lens. This process is called precision glass molding. The preforms of glass that are used in the molds have different shapes like spherical, biconcave, plano, gob and biconvex. The lenses are coated with anti reflective material using physical vapor deposition (lens is coated by the vaporization of the oxide materials) or plasma enhanced deposition (lens is coated by the chemical reaction which is created in vacuum). The coating is done to enhance the optical reflection and to improve its mechanical and electrical properties.
Optical elements like glass ball are used in fiber optic communication devices for coupling light from fiber to fiber, as they are easy to align and position in the device. These elements are attached to the ends of the fibers to enable emission for maximum efficiency. They are also used in aeronautical field and in medical devices, most commonly in endoscopes. The medical devices are small and precise and hence half ball lens may be used, due to the physical constraint of a compact design.
Optoelectronics has advanced into everyday life in the form of devices that change electric signals to optical energy!
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