Radiant energy – Photocells; circuits and apparatus – Photocell controlled circuit
Patent
1992-01-28
1993-10-05
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Photocell controlled circuit
315154, 315158, H01J 4014
Patent
active
052507998
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method for adapting the light intensity of the summation light of a room lit by internal light and external light to the external light, which varies with the time of day, in which the light intensity of the internal light is controlled in dependence on one or more control parameters according to a given function and the function can be varied according to individual preference.
Methods of this kind are used to compensate for variations in light intensity in a room caused by changes in the external light. To detect the light intensity of the external light an external light sensor is arranged outside the room to be lit. The light intensity of the internal light is controlled in substantially inverse dependence on the external light: when the external light decreases the light inside the room is made brighter.
In the "Journal of the Illuminating Engineering Society, (Winter 1989, pages 70-90) a method and a lighting system for carrying it out are described for a room, in which a light-sensitive sensor is connected to a control unit, which in turn controls a dimming unit. The dimming unit controls light sources arranged in the room which generate a dimmed light level. The light-sensitive sensor is arranged so that it cannot detect the dimmed light level of the light sources. The control of the light sources takes place in accordance with an inverse linear dependence of the dimmed light level on the detected sensor signal. The slope of this function defining the dependence is set by a scale factor. The calibration is performed on commissioning the lighting system at a desired time of day.
A method of this kind has the disadvantage that setting the slope of the linear function changes not only the dimmed light level at the time of the calibration but also the dimmed light levels associated with all other light intensities of the external light.
It is an object of the invention to provide a method and a circuit arrangement which give finer setting possibilities for adapting the light intensity in a room.
This object is achieved in a method of the kind described in the introduction in that the dependency function is determined by a plurality of function values that can be set independently of one another and in that each function value can be varied independently of other function values.
The invention makes use of the idea that an individual lighting requirement is not met by selecting a single parameter of the function, for example the slope or the parallel displacement, but rather it can only be met by determining the function through individual points or sections.
The invention takes advantage of the discovery that even a complicated dependency of the light intensity of the internal light on the light intensity of the external light, the summation light or the time can be defined by relatively few function values that can be determined independently of one another. This enables all individual lighting requirements to be taken account of in a user-friendly manner.
The present invention also takes into account the adaptation of the structural illumination of a room, which may depend not only upon the intensity of the external light but also on the direction of daylight. According to the invention the distribution of the light intensity in the room can be adapted in dependence on the daylight so that a particular and possibly non-uniform distribution of light in the room can be realised. This is accomplished by connecting one or more, preferably two, independent light sensors to an independent dimmer unit or units that control a plurality of internal light sources arranged at different positions (x,y) in the room such that the illumination of the room can be changed independently of the external light falling on the external light sensors.
An observer in a room perceives, as shown for example in FIG. 7, the sum of the light intensity of the incoming external light E.sub.i ' and of the artificially produced internal light E.sub.k as the total light intensity of the summation light E.su
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Masshardt, "Helligkeitsregulierung von Hochdruck-Gasentladungslampen," Technische Rundschau, No. 19, 1988.
Nelms David C.
Zumtobel Aktiengesellschaft
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