1970s Osram HBO 75W Lamp lit

Super high pressure mercury lamps were introduced a compact source of high intensity light, both in the visible and ultra violet wavelengths. The most common use was in the beginning as projector lamps. Small lamps were often used for light sources in microscopy, optical distance measurements and even small projectors. This particular lamp is unusual because it is one of the few lamps featuring an outer envelope.
This allows for a shorter lamp design because the Moly seal do not risk to oxidise due to it being sealed. The outer envelope also allows the passage of long and medium wavelength UV radiation while short wave radiation is blocked.

This lamp is designed to operate on a 220V AC choke making the control gear less complex then with their DC counterparts.

This picture is the lamp operated a t full power, fully warmed up after approx 15 minutes. It runs very well on a 125W Mercury vapour choke and ignites with a standard ignitor. Not however that th ballst is overloaded by the higher lamp current with this lamp being rated at 1,6A