UPDATE OF TECHNICAL INFORMATION REGARDING LONG TERM STABILITY OF LUNT SOLAR FILTERS.
To ensure long term stability and safety of all filters that are required in the production of a solar telescope system, Lunt Solar Systems is pleased to announce newly designed, Induced Transmission Filters (ITF). A vital part of the safety and performance of these systems, the ITF is used to block unwanted out of band transmissions while providing a high transmission at the desired wavelength.
The metal layer used in the filter works to block IR to the safety levels required for visual use. Without the induced part (matching metal oxide layers), the metal layer would simply act as a neutral density filter. Generally these filters were used primarily in laser systems where thermal loading and cycling are kept to a minimum. Under these ideal conditions the filter can provide years of service.
Utilizing these filter systems for solar applications can result in high thermal load cycles and exposure to varying humidity. This cycling can lead to premature failure of currently available ITFs.
Lunt Solar has taken a 2 step approach so that we may provide a guarantee to our customers that none of our filters will fail during normal use.
- The newly designed ITF system has been tested to and can now be backed with the MIL-STD-810C specification. This specification specifically addresses long term environmental stability of our unique system and application.
- Lunt Solar will also be providing an Energy Rejection Filter (ERF) early in the optical system to remove unwanted heat from the filters including the etalon. Although a piece of red filter glass is a generic to current design and is used to block unwanted Ultra Violet radiation, the addition of the IR reflector will make this element a true ERF, blocking the transmission of ALL harmful wavelengths.