Hermetic Windows and Lens Caps
SCHOTT offers two main glass types as molded glass. The main workhorse (St) is usable for visible and NIR light. A second glass expands this range into the UV region (UV). The usual glass type used for making window caps with solder glass technology is SCHOTT D263 glass (PI). The following chart shows the glass transmittance spectrum for these glasses. All data is for uncoated glass.
SCHOTT offers optical coatings on lens and window caps for special applications that require a unique performance. Commonly applied coatings include:
AR (anti-reflective) coating
Beam splitter (interference or metal attenuation coating)
Ball lens caps can be manufactured using a large variety of optical glasses. Ranging from a refractive index of 1.5 to 2.0, widely used glasses include:
Optical properties for lens caps
SCHOTT has all the necessary equipment to calculate and measure the optical properties of glass for our lens caps. We can supply all necessary data, such as effective focal length, position of principal planes in the lens, and lens radius.
Because of the highly accurate sphericity (typical specification: sphericity < 0.5 µm), it is very easy to calculate the effective focal distance (EFL) with respect to the back focal distance (BFL) of the ball lenses.
SCHOTT can also help with questions concerning how to effectively couple the light into fibers for data communication.
Hermetic windows and lens caps are often distinguished by their production method – whether the glass and metal components are joined together by molding or soldering.
Molded or 'Direct Seal' caps
- Glass and metal are sealed without the use of any other interface material.
- The sealing process must be designed in a way that ensures the glass cools down without the formation of bubbles or inclusions, and obtains the correct optical properties.
- The highly robust glass-to-metal connection of SCHOTT caps provides excellent mechanical stability and processability during the customer production process.
- This production method is typically used for all conventional types of optical signal transmission.
- Metal and glass are fused with the aid of a solder glass.
- This production method is typically used for ultra-high precision applications with special optical components.
- To ensure that extremely narrow tolerances of the optical properties can be met, the components are soldered together in a cleanroom environment.
- Our technological leadership ensures that the lenses and windows are developed and processed to an extremely high quality standard.
Head of R&D Opto-electronics