Optical observation in glass furnaces is important for the adjustment of the flame, optimisation of batch feeding and for evaluation of the condition of the refractories, among other things. Unfortunately, observation with the naked eye is restricted necessitating firmly installed telecameras and mobile furnace periscopes.

The HVG furnace periscopes manage with small windows and their lightweight design corresponds to the itinerant use.

The periscopes may be used up to 1600 °C furnace temperature. They are suitable for visual observation as well as for photographic and TV monitoring of glass furnaces. In addition, movements of the batch can be represented by rendition of the photos in fast motion.

The radiation from the reaction zone of the flame in the UV range is used for the visualisation of nonluminescent flames in hot furnace chambers. With narrow-band optical filters, the UV information of the flame is separated from the background that is strongly radiating in the visible and IR range. A UV permeable furnace periscope facilitates optical access to the combustion chamber. A UV telecamera supplies the graphic representation of the non-visible flame via a rendition of the field-by-field distribution of the UV radiating OH and/or CH radicals of the reaction zone.