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Beamer with light measurement by means of optical fibre

IP.com Disclosure Number: IPCOM000010540D
Publication Date: 2002-Dec-13
Document File: 1 page(s) / 6K

Publishing Venue

The IP.com Prior Art Database

Abstract

ID610588

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ID610588

Beamer with light measurement by means of optical fibre

    In an optical system such as a beamer comprising a discharge lamp, such as a UHP lamp it is essential that the light output of the lamp is maintained at a constant level.

    This is done by measuring the light output of the lamp making use of a sensor. The signal generated by the sensor is coupled to the operating circuit (driver) that supplies the lamp and one or more operation parameters are adjusted so as to maintain the light output of the lamp at a desired level. The signal generated by the sensor is usually a DC signal. Since mains isolation is desirable the DC signal is first converted into a pulse width modulated signal that is transferred by means of an optocoupler taking care of the mains isolation. Subsequently the pulse width modulated signal is converted back into a DC signal and coupled to the operating circuit. A disadvantage of this light level control is that comparatively many components are needed and that some of these components are large. Furthermore, it is often necessary that at least part of these components are placed in the direct vicinity of the lamp, interfering with the light radiated by the lamp. These disadvantages can be solved by making use of an optical fibre with an in-coupling part that is placed in the vicinity of the lamp and guides the sensed light to a sensor that is located in or in the vicinity of the operating circuit. The sensor generates a DC signal out of...