Abstract: A circuit for operating a high pressure discharge lamp comprising input terminals for connection to a supply voltage source, output terminals for connecting the high pressure discharge lamp, and apparatus, coupled to the input terminals, for supplying an alternating lamp current to the high pressure discharge lamp. The lamp current in each period has a mean value Im. At the start of each period, the lamp current is lowered with respect to the mean value Im so as to allow for stable diffuse attachment on the cathodic phase electrode. The circuit is particularly suited for operating a lamp in an optical projection system.

Abstract: The invention relates to a measuring circuit for detecting the amount of deposited electrode material on the wall of a lamp vessel of a discharge lamp by measuring the power of infrared radiation within a specific wavelength range, comprising a detector for generating an electrical signal constituting a measure for the power of the infrared light in said specific wave length range. According to the invention the measuring is done in a time lapse starting after a predetermined time interval following the extinguishing of the discharge lamp. An increased accuracy of the measurement is thereby realized.

Abstract: A circuit arrangement for operating a high pressure discharge lamp includes input terminals for connection to a supply voltage source and an apparatus coupled to the input terminals for supplying an alternating lamp current to the high pressure discharge lamp. A device (III) is provided for generating a current pulse in each half period of the lamp current. This current pulse has the same polarity as the lamp current and is superimposed on the lamp current in the latter part of a predetermined fraction of the half periods of the lamp current. The circuit substantially suppresses flickering of the discharge arc during lamp operation.

Abstract: The high pressure mercury discharge lamp comprises a quartz glass lamp vessel (1) having a region (2) surrounding a discharge space (3), spaced-apart tungsten electrodes (4) defining a discharge path (5) disposed in the lamp vessel, and connected to current conductors (6) which extend from the lamp vessel to the exterior and a filling of mercury, rare gas and bromine. The lamp has an operating pressure of at least about 200 bar. The discharge space (3) is spheroidal in shape and has specified dimensions. The lamp consumes a power of 70 to 150 W. The lamp has favourable properties which render the lamp suitable for use in optical systems, e.g. for projection purposes.

Abstract: A high-pressure mercury vapor discharge lamp whose envelope two tungsten electrodes disposed therein of tungsten and a filling containing a rare gas, a quantity of mercury larger than 0.2 mg/mm.sup.3 at a mercury a pour pressure of more than 200 bar and at least one of the halogens chlorine, bromine or iodine in a quantity between 10.sup.-6 and 10.sup.-4 .mu.mol/mm.sup.3. The wall load in operation is higher than 1 W/mm.sup.2.

Abstract: In a gas discharge lamp having a discharge vessel containing an ionizable gas filling and consisting of a translucent material, which is surrounded at a certain distance by a translucent outer bulb, the discharge vessel has a thermally insulating translucent envelope of a microporous aerogel.

Abstract: An electrode head for a high-pressure discharge lamp consists of tungsten sheet material formed as a flat or curved plate having an elongated end face having a transverse dimension at least three or five times the plate thickness. As a result the discharge arc terminates practically in pointed form on the electrode end face, and the electrode is heated relatively slightly but has a large surface for thermal emission.