EP1992172A1

EP1992172A1 - Lighting device and display system with a lighting device

Info

Publication number: EP1992172A1
Application number: EP07726544A
Authority: EP
Inventors: Christian Breuer; Andreas Huber
Original assignee: Osram GmbH
Current assignee: Osram GmbH
Priority date: 2006-03-03
Filing date: 2007-02-28
Publication date: 2008-11-19
Also published as: JP2009528562A; TW200745605A; CA2642928A1; US20090026983A1; DE102006009975A1; KR20080109776A; WO2007099125A1; CN101395927A

Abstract

The invention discloses a lighting device (10, 11) having at least one light source (1, 1R, 1G, 1B) which is actuated by an operating unit (2) with an electrical signal on the basis of a light curve (3) stored in the operating unit (2). It also describes a display system having such a lighting device.

Description

Lighting device and display system with a lighting device

The invention relates to a lighting device with at least one light source and a display system with such a lighting device.

Display systems and their lighting devices are described for example in the publications US 5,633,755 and US 6,323,982. Display systems, such as DLP projectors (short for "digital light processing projector"), include a lighting device with a light source whose light is directed to a DMD chip (short for "digital mirror device chip"). The DMD chip comprises microscopically small pivoting mirrors which either direct the light onto the projection surface if the associated pixel is to be switched on or direct the light away from the projection surface, for example onto an absorber if the associated pixel is to be switched off. Each mirror thus acts as a light valve that controls the light flux of a pixel. These light valves are called DMD light valves in the present case. For color generation comprises a DLP projector in the case of a lighting device that emits white light, such as a filter wheel, which is arranged between lighting device and DMD chip and filters of different colors, such as red, green and blue. With the aid of the filter wheel, light of the respectively desired color is transmitted sequentially from the white light of the illumination device. The color temperature of such display systems is generally associated with the color location of the light of the illumination device. This usually changes with the operating parameters of the light sources of the illumination device, such as voltage, current and temperature. Furthermore, depending on the light sources used in the illumination device, the ratio between current intensity and light flux is not necessarily linear. This leads to a change in the current also to a change in the color location of the light of the light source and thus to a change in the color temperature of the display system.

Furthermore, the color depth of the display system is limited by the minimum duty cycle of a pixel. To increase the color depth, it is possible, for example, to use dithering, in which individual pixels are switched at a frequency lower than the regular frequency of 1/60 Hz. However, this usually leads to a visible to the human observer noise.

The contrast ratio of the display system is defined by the ratio of maximum light flux with fully opened light valves to minimal light flux with fully closed light valves. To increase the contrast ratio of a display system, for example, the minimum light flux can be further reduced with completely closed light valves by means of a mechanical diaphragm. However, a mechanical shutter takes up space in the lighting device or the display system, increases the weight of the lighting device or the display system, and also provides an additional potential source of interference. An object of the invention is to provide a

Indicate lighting device whose color location can be adjusted specifically. Another object is to provide a display system with such a lighting device. Furthermore, it is desirable to provide a lighting device for use in a display system, with the aid of which the color depth and / or the contrast ratio of the display system can be improved in a simple manner.

These objects are achieved by a lighting device having the features of claim 1 and by a display system having the features of claim 15.

Preferred embodiments of the illumination device or the display system are specified in the dependent claims 2 to 14 and 16 to 20.

An illumination device according to the invention comprises an operating device which activates at least one light source with an electrical signal in accordance with a light curve stored in the operating device.

In the present case, the term "light curve" is to be understood as meaning a function of the illuminance as a function of time.The operating device generates the electrical signal for controlling the light source in accordance with the light curve, so that the light source generates the respectively desired illuminance. In the electrical signal with which the light source is driven, it is preferably a current signal.

The illumination device can preferably be used in a display system whose colors are driven sequentially. With the aid of the light curve, the light flux of the illumination source for each color can advantageously be temporally varied in such a way that when using the illumination device in a display system with sequential color control, the light flux of the illumination device for each color can be adjusted separately in a desired manner such that the color temperature of the display system is adjusted to a desired value.

In a preferred embodiment of

Lighting device has the light curve segments with temporally constant illuminance. Particularly preferably, the light curve is composed of segments with temporally constant illuminance. This means that for a time t _x the light curve has a temporally constant illuminance B _x and the following time interval t _{x +} i has a likewise constant illumination intensity B _{x +} I. If the illumination device is used in a display system with sequential color control, a single color of the display system is preferably switched on during the time interval t _x and a different color during the subsequent time interval t _{x +} i.

When changing to the other color, the light curve changes to a different time constant illuminance, if for the setting of a certain color temperature a different brightness of this color should be necessary. Thus, the light source is supplied with a corresponding electrical signal for each color to adjust the color temperature of the display system to a desired value.

The change between the illuminance levels of the individual segments can be achieved for example by a variation of the operating current and / or control of the light sources by means of a pulse width modulated signal (PWM signal). A variation of the operating current is preferably used in gas discharge lamps, while PWM signals is generally used for driving light emitting diodes. A pulse width modulated signal, preferably a square wave signal within a fixed pitch period for a certain time t _e i _n the state "on" and for the remainder of the fundamental period t _from the "off" state. The ratio of on-time and basic period tein / (t _e in + t _off ) is called the duty cycle. It indicates the percentage of time over which the square wave signal is turned on within the fundamental period.

If the light curve contains short segments with very low illumination intensity, the light quantity emitted by the illumination device can thereby be reduced for the same switch-on duration of the light valves, whereby advantageously the color depth of the display system can be increased without, for example, producing visible noise, as in the case described above dithering. The minimum duration that a short segment may have depends on the light valves used. For DMD light valves, this is preferably about 8 μs, for LCD light valves about 1 ms. In the present case, "LCD light valve" refers to a light valve that is realized by means of a liquid-crystalline matrix, the illuminance during these short segments preferably having one of the following values: 50%, 25%, 12.5% Usually an extra bit of color depth.

Preferably, the light curve has a periodic signal whose period is between 16 ms and 20 ms, with the limits included, or consists of such. A periodic repetition with a period between 16 ms and 20 ms offers the advantage that no flicker can be detected for the human eye.

In a further preferred embodiment of the illumination device, the operating device is suitable for purposefully changing the light curve during operation, for example, by a user or by an external control signal. As a result, for example, by varying the light curve, the color locus of the light of the illumination device can be adapted such that the color temperature of the display system in which the illumination device is used is adapted by a user or automatically to a desired application.

Particularly preferably, the operating device scales the light curve in proportion to a predetermined reference value. In this way, the average luminous flux of the illumination device can be lowered or also raised by means of the operating device, depending on which color locus of the illumination device is desired for the respective application. Particularly preferably, the Scaling linear. By lowering or raising the luminous flux by means of the light curve, the contrast ratio of the display system in which the illumination device is used can advantageously be improved.

In a further preferred embodiment of the illumination device, the operating device detects operating parameters of the light source. Operating parameters of the light source are, for example, voltage, temperature, current and color of the light. If the operating device stores the dependence of the spectrum of the light source on its operating parameters, the operating device can advantageously regulate the electrical signal for controlling the light source in such a way that changes in the spectrum of the light source are compensated due to changed operating parameters and thus the color locus of the illumination device and the color temperature of the display system in which the lighting device is used is kept constant. Furthermore, non-linearities in the illuminance-current intensity characteristic curve can be compensated dynamically in this way.

In a particularly preferred embodiment, the operating device keeps the light flux of the light source constant by means of a control loop from the operating parameters of the light source and the predetermined reference value. As a result, the color location of the illumination device can advantageously be kept constant.

Furthermore, the operating device preferably changes the reference value during operation, for example, on the basis of the input of corresponding values by a human User. Thus, the color location of the illumination device can advantageously be changed during operation by a user in the desired manner.

In a further preferred embodiment of the illumination device, the current intensity-illuminance characteristic of the light source is stored in the operating device. This allows the operating device to regulate the electrical signal for driving the light source such that the light flux of the light source is kept constant. Furthermore, it is possible to maintain the relative relationships of the illuminance of individual segments with each other despite a non-linear current intensity-illuminance characteristic. If the illumination device comprises a plurality of light sources, then either a current intensity / luminance characteristic can be stored in the operating device if the light sources all have the same current intensity / luminance characteristic, or a plurality of current intensity / luminance characteristic can be stored in the operating device, if such Light sources have different amperage-illuminance characteristic. The latter is usually the case when light sources of different colors are used in the lighting device.

In a further embodiment of the

Lighting device comprises this one or more light sources that emit light with a color location in the white area of the CIE standard color chart. Such a lighting device is particularly suitable for use in a display system whose colors are generated sequentially by means of a color modulator, such as a filter wheel. In a further embodiment of the

Lighting device comprises these at least two light sources that emit light of different colors. Such a lighting device can be used in particular in a display system that has no color modulator. In this embodiment, the colors are generated directly by the light sources, which are sequentially driven in accordance with the light curve with an electrical signal. In an expedient embodiment, the light curve in this case has segments with constant illuminance in each case during the time intervals in which the individual colors are turned on. In this way, the brightness of each color is adjusted according to the illuminance of the respective light curve segment, and thus the color locus of the illumination device is set to a desired value.

Particularly preferably, the illumination device comprises a red, a green and a blue light source. Such a lighting device can generate red, green and blue light sequentially in succession with the aid of the light curve, so that a white color impression is produced in a human observer.

As light sources, for example, gas discharge lamps, semiconductor light-emitting diodes, organic light-emitting diodes or laser diodes are used in the illumination device.

The illumination device is particularly suitable for use in a display system. Preferably, the display system is a DLP projector. Farther For example, the illumination device can also be used in an LCD screen in which the light valves are produced by means of a liquid-crystalline matrix. The colors can be generated in an LCD display either directly by the backlighting or by means of a filter plate. If the colors are to be generated directly by the backlight, then, for example, a lighting device is suitable which has at least two light sources of different colors, as described above.

Furthermore, the illumination device is particularly suitable for use with a display system whose colors are driven sequentially.

In a preferred embodiment of the display system, the light curve is adapted via a communication interface to the image content to be displayed (in particular the power / average illuminance). This offers the advantage that, for example, the illuminance of the light source (s) can be adapted dynamically to the brightness of the image content. As a result, both contrast and color depth can be improved.

In a further preferred embodiment of the display system, the operating device adapts the light curve to the speed of the synchronization signal by time scaling. The synchronization signal usually has a frequency of 50 Hz or 60 Hz and thus corresponds to the frequency of a video signal. The synchronization is performed such that all segments of the light curve are linearly scaled until a full period of the light curve is in a full period of the synchronization signal fits. Thereafter, the phase relationship of the two signals is set to a fixed value. The light curve then usually has a duration of 16.67 ms or 20 ms. If a filter wheel is used, the filter wheel will play all colors between once and eight times during this time. The light curve thus usually contains several color filter periods.

In a further preferred embodiment of the display system, the synchronization signal is connected to a sequential color modulator. A sequential color modulator is a device which selects different colors one after the other from light having a color location in the white region of the CIE standard color plate, ie sequentially. For example, a color modulator may be a filter wheel.

In one embodiment of the display system a plurality of light curves are stored in the operating device, which can be selected depending on the synchronization signal from the operating device to output corresponding electrical signals for controlling the light sources. In this way it is possible to adjust the color temperature of the display system by selecting the light curve.

Further advantages, embodiments and preferred developments of the invention will become apparent from the embodiments described below in conjunction with FIGS.

Show it: FIGS. 1A and 1B show schematic representations of two exemplary embodiments of the illumination device,

2A, a schematic sectional view of a first embodiment of a display system,

FIG. 2B is a schematic diagram of a light curve used in the first embodiment of the display system.

FIG. 3, a schematic sectional view of a second exemplary embodiment of a display system,

FIGS. 4A to 4C are schematic diagrams of three exemplary light curves for operating a lighting device according to the invention;

4D, a tabular representation of the light curve of Figure 4C, and

FIGS. 4E to 4G are schematic diagrams of three further exemplary light curves for exemplifying the structure of a light curve;

FIG. 5 shows a schematic diagram of an exemplary current intensity illuminance characteristic of a light source for operating a lighting device according to the invention.

In the exemplary embodiments and figures, identical or identically acting components are each provided with the same reference numerals. The illustrated elements are basically not to be considered as true to scale. Much more For example, individual elements, such as light sources, may be exaggerated for better understanding.

The illumination device 10 according to the exemplary embodiment of FIG. 1A comprises a light source 1, in the present case a gas discharge lamp, which emits light with a color location in the white region of the CIE standard color plate. In the gas discharge lamp 1 is a point light source with a very small arc distance, which has a high energy density of about 300 W / mirW.

Alternatively, the use of, for example, organic light emitting diodes (OLED), semiconductor light emitting diodes (LED) or laser diodes (LD) is possible.

Furthermore, the illumination device 10 according to FIG. 1A comprises an operating device 2, such as a function generator, which can provide electrical signals with a power of 300 W. The operating device 2 controls the light source 1 with an electric current signal, which follows a light curve 3. Light curves 3 will be explained later in connection with FIGS. 2A and 4A to 4C.

The illumination device 11 according to FIG. 1B comprises an operating device 2 such as that of the illumination device 10 according to FIG. 1A, with the difference that the

Lighting device 11 comprises three light sources 1, which emit light of different colors. In the present case, this is an LED that emits red light (hereafter referred to as "red LED"), an LED that emits green light (hereafter referred to as "green LED"), and an LED that emits blue light (hereafter "blue The red LED is identified by the reference symbol IR in the figures, the green LED by the reference symbol IG and the blue LED by the reference symbol IB.

As with the illumination device 10 according to FIG. 1A, the operating device 2 activates the light sources IR, IG, IB of the illumination device 11 with an electrical signal which corresponds to a light curve 3. The LEDs IR, IG, IB are mounted on a support 4, such as a metal core board and electrically connected to the operating device 2. In the operating device 2 of the illumination device 11 according to FIG. 1B, as in the operating device 2, the illumination device 10 according to FIG. 1A stores a light curve 3, according to which electrical signals are generated by the operating device 2 for driving the LEDs IR, IG, IB.

The display system according to FIG. 2A comprises a

Lighting device 10 according to the embodiment of Figure IA. This illumination device 10 emits white light, which is focused by means of optics 51, for example a lens, on colored filters of a filter wheel 6. The filter wheel 6 is in the emission of the illumination device 10, a further optics 52, for example, also a lens downstream, which directs the light selected by the filter wheel 6 on a DMD chip 71.

As already described in the introduction to the description, the DMD chip 71 comprises microscopically small pivoting mirrors which direct the colored light either onto or away from a projection optics 8, depending on whether the associated pixel is to be switched off or not. Of the In other words, DMD chip 71 comprises the light valves for controlling the individual pixels of the display system. In the present case, the filter wheel 6 functions as a color modulator, which sequentially selects individual colors from the white light of the illumination device 10 one after the other. In the present embodiment, the filter wheel 6 includes a red filter, a green filter, and a blue filter. An alternative filter wheel 6 with further colors is described below in connection with FIG. 4C.

The light curve 3 of FIG. 2B stored in the operating device 2 of the display system according to FIG. 2A in the present case comprises three segments S _R , S _G , S _{B associated} with the individual colors of the filters of the filter wheel 6, red, green and blue. The first segment S _R has a time interval t 1, during which the light curve 3 has a constant illuminance B _R. The first segment S _R is associated with the color red, that is, during the time interval t _R, the red filter of the filter wheel 6 selects red light from the white light of the illumination device 10. After the time interval t R, the illuminance of the light curve changes to the illuminance B _Q , which is kept constant during a time interval tg of the second segment S _{G associated with} the color green. Therefore, during the time interval tg, the green filter of the filter wheel 6 selects green light from the white light of the illumination device 10. After the time interval tg has elapsed, the filter wheel 6 changes to the blue filter and the light curve 3 changes to the third segment S _B. This means that the illuminance of the light curve 3 changes to the value Bg, which is kept constant during a time interval tg. Due to the different values of the illuminance within the different segments S _R , S _G , S _{B of} the light curve 3, the individual colors red, green and blue are associated with the filter of the filter wheel 6, the illuminance of the illumination device 10 is adjusted so that the brightnesses of the individual colors red, green and blue correspond to a desired value, which lead to a predetermined color temperature of the display system. The three segments S _R , S _G , S _{B of} the light curve 3 form a period of the light curve 3, which has a duration between 16 ms and 20 ms, the limits being included.

The display system of the exemplary embodiment according to FIG. 3 comprises a lighting device 11 according to FIG. 1B. Furthermore, the display system according to FIG. 3 does not include a sequential color modulator 6, such as a filter wheel, such as the display system according to FIG. 2A. The individual pixels of the display system according to FIG. 3 are not switched on and off by means of a DMD chip 71, but by means of a liquid-crystalline matrix 72. This liquid-crystalline matrix 72 is arranged downstream of the illumination device 11 in its emission direction. For color generation in the present case, the operating device 2 switches on the individual light sources of different colors IR, IG, IB of the illumination device successively individually according to a light curve 3 stored in the operating device 2 by means of an electrical signal. As the light curve 3, for example, the light curve 3 described above can be used in accordance with Figure 2B or a similar light curve 3, by means of which the brightness of the individual light sources IR, IG, IB different color are controlled according to a predetermined color temperature of the display system.

The light curve 3 in the embodiment according to FIG. 4A comprises a periodic sequence of three each Segments S _R , S _G , S _B. The first segment S _B is associated with the color blue, the second segment S _{R with} the color red and the third segment S _{G with} the color green. As an alternative to the light curve 3 according to FIG. 2B, this light curve 3 can be stored in the operating device 2 of the lighting devices 10, 11 that are used in the display systems according to FIGS. 2A and 3, for example.

The first segment S _{B of} the light curve of FIG. 4A is associated with the color blue and has a duration t _B of approximately 1300 μs. During this time interval t _B , the luminous flux of the illumination device 10, 11 is approximately 120%.

The first segment S _B is followed by a second segment S _R , which is associated with the color red and has a duration of t _R. During a first time interval t _{Ri of} the time interval t _R , the light flux is the

Lighting device 10, 11 in the short term about 150%, while the light flux in a second time interval t _R2 , which directly adjoins the first time interval t _Ri and forms with this the time interval t _R , about 120%. The time interval t _R i is significantly shorter than the time interval t _R2 . In the present case, the time interval t _Ri is approximately 100 μs, while the time interval t _{R2 in the} present case amounts to approximately 1200 μs.

The second segment S _R is followed by a third segment S _G , which is associated with the color green and has a duration t _G of likewise approximately 1300 μs. Also, the time interval t _G is divided as the time interval t _R in two time intervals t _G i and t _G2 , wherein the first time interval t _G i is significantly longer than the second time interval t _G2 . The first time interval t _G i is presently about 1200 μs, while the second Time interval t _{G2 of} the green segment has a duration of about 100 microseconds. During the first time interval t _G i, the light curve 3 has a constant value of approximately 85%, which is temporarily lowered for the time interval t _G 2 to a value of approximately 45%.

After expiration of these three segments S _R , S _G , S _B takes place a substantially periodic repetition of these three segments S _R , S _G , S _B , wherein the arrangement of the short time intervals t _Ri , t _G2 within the segments in which the light flux relative to the remaining segment S _R , S _G significantly raised or lowered is different from the periodicity. The short time intervals of the light curve 3, in which the illuminance is greatly reduced, serve to increase the color depth as already described in the general description part. The short segments within which the illuminance is greatly increased are provided for stabilizing the electrodes of gas discharge lamps, if used as light sources 1. If other light sources 1, for example LEDs are used, such short raised segments within the light curve 3 are not necessary.

FIG. 4B shows two light curves 3. The diagrams represent the illuminance and the color as a function of time. They each contain a full period of the light curve shape, as a rule with a duration between 16 and 20 ms. With white light sources, the colors are generated by color filters, with several colored light sources, such as LEDs, the operating device 2 switches between the colors. The light curve of the embodiment of Figure 4C is designed on a filter wheel 6 with six different filters with the colors yellow, green, magenta, red, cyan and blue. Accordingly, the light curve 3 is composed of a periodic sequence of six different segments S _γ , S _G , S _M , S _R , S _C , S _B , which are assigned to the respective color. The segments S _γ , S _G , S _M , S _R , S ₀ , S _B are denoted below by the color to which they are assigned. Each segment S _γ , S _G , S _M , S _R , S _C , S _{B of} the light curve 3 in this case has a constant value of the light flux during most of the duration of the respective segment.

The individual segments S _γ , S _G , S _M , S _R , S ₀ , S _B are again assigned time intervals t _γ , t _G , t _M , t _R , t _c , t _B , which are divided into two or three time intervals t _γi, t _γ2, t _G1, t _G2, t _m i, t _m, t _m, Ri, t _R2, t _C i, t _C2A t _C 3 t, _B i, t _B2 split, wherein each one of said time intervals significantly is longer than the others. These time intervals are referred to below as "long time intervals." The values of the light flux in the long time intervals of the individual segments are shown in the table in FIG. 4D in the "segment light level" line. The yellow and green segments S _γ , S _G have a constant luminous flux of 80% during the long time interval. The magenta and red segments S _M , S _R have a luminous flux of 120% during the long time interval, while the cyan segment S _{c has} a luminous flux of 80% during the long time interval and the blue segment S _{B has} a luminous flux of 120%. during the long time interval. At the end of each segment is a short period of time during which the light level is lowered more than the long time interval. These values can be found in the table in Figure 4D under the line "negative pulse light level" in the yellow and the green Segment S _γ , S _G is the flux of light to a value of 40%, in the magenta and the red segment S _M , S _R to a value of 60%, in the cyan segment S ₀ , to a value of 40% and lowered to the blue segment S _B to a value of 60%. Furthermore, a communication takes place at the end of the magenta segment S _M and at the end of the cyan segment S ₀ , which is symbolized by arrows and is in each case linked to a light flux which has been raised relative to the long time interval.

The segment sizes of the different colors are not identical, as can be seen in the table in FIG. 4D in the "segment size" row, but are 60 ° for the yellow and green segments S _γ , S _G , for the magenta segment S _{M has} a value of 40 °, the value of 70 ° for the red segment S _R , a value of 62 ° for the cyan segment S ₀ and a value of 68 ° for the blue segment S _B. These values are based on the light curve 3 coordinated.

In conjunction with a light curve 3, whose segments S _R , S _G , S _{B are associated with} the colors red, green and blue, as shown for example in Figures 2B and 4A, usually finds a filter wheel 6 with two red, two blue and two green filters application. The filters are preferably arranged in the order of red, green, blue, red, green, blue. The sizes of the individual color filter segments can be the same (60 ° for all six filters) or different, matched to the light curve used. 3

The functions of the individual time intervals within the segments S _R , S _G , S _B will be explained in more detail below by way of example with reference to FIGS. 4E, 4F and 4G. The light curve 3 according to FIG. 4E, like the light curve 3 according to FIG. 4A, comprises a periodic sequence of a segment S _{B associated} with the color blue, a segment S _{R associated} with the color red and a segment S _G containing the color S Color is associated with green. Each segment S _R , S _G , S _B has a duration of approximately 1500 μs. The time interval t _B , the time interval t _R and the time interval t _G , which are assigned to the respective segment S _R , S _G , S _B , therefore have the same length. Within a segment S _R , S _G , S _B , the light curve 3 in each case has a constant value. During the time interval t _B , the light curve 3 has a value of about 95%, during the time interval t _R a value of about 100% and during the time interval t _G a value of about 110%. By means of the different levels of the light curve 3, the light flux of the illumination device is adapted such that a display system with this illumination device has a desired color temperature.

The light curve 3 according to FIG. 4F shows by way of example short time intervals t _B2 , t _B3 , t _R2 , t _Gi , t _G2 , t _G3 at the end of each segment S _R , S _G , S _B , similar to those already described above in connection with FIG 4A. The light curve 3 is in turn composed of a periodic sequence of a segment S _B , which is associated with the color blue, a segment S _R , which is associated with the color red and a segment S _G , which is associated with the color green together. The time interval t _B , t _R , t _{G of} each segment is divided here into three time intervals of a long time interval ti _B , tiR, ti _G at the beginning of each segment S _R , S _G , S _B and two short time intervals t _B2 , t _B , t _R2 , t _G i, t _G2 , t _G 3 respectively to the end of each segment S _R , S _G , S _B. During the short Time intervals t _B2 , t _B 3, t _R2 , t _G i, t _G2 , t _G 3, the light flux of the light curve 3 is gradually lowered. By way of example, the segment S _{B associated} with the color blue is described here. During the time interval t _B i, the light curve 3 is a value of about 110%. In the time interval t _B2 , which follows directly on the time interval t _B i, the light curve 3 is a value of about 55%, while the value of the light curve 3 in the time interval t _B 3 following the time interval t _{B2 is} about 30 % is lowered. The time interval t _B i has a duration of approximately 1300 μs, while the time intervals t _B2 and T _B3 each have a duration of approximately 10 μs. The remaining segments S _R , S _{G of} the light curve are constructed identically, as the segment S _B , which is associated with the color blue. The lowering of the light curve 3 during the short time intervals t _B2 , t _B3 , t _R2 , t _Gi , t _G2 , t _G3 serves to improve the color depth of the display system in which the illumination device is used. The light curve 3 according to FIG. 4G shows the two forms of light curves already explained with reference to FIGS. 4E and 4F together in a light curve 3, as can also be used in a lighting device. The description of the short segments t _B2 , t _B3 , t _R2 , t _Gi , t _G2 , t _G3 at the end of each segment S _R , S _G , S _B of FIG. 4F is here also for the short time intervals t _B2 , t _B3 , t _R2, t _Gi, _G2, t _G3 of FIG 4G valid, while the levels of the light curve 3 during the long time intervals t _B t i, _R2, _G3 of each segment S _R, S _G, S _B t the value according to the light curve 3 corresponds to FIG. 4E.

The amperage-illuminance characteristic of the embodiment according to FIG. 5 is approximately linear. It indicates a current in percent on the y-axis and a light level in percent on the y-axis. By means of the amperage-illuminance characteristic, which may also be stored in the operating device 2 of the lighting device 10, 11, it is possible that, with changed lamp operating parameters, such as the current intensity, the brightness of the light source 1, IR, IG, IB of the lighting device 10, 11 is maintained at the predetermined by the light curve 3 illuminance.

The invention is not limited by the description with reference to the embodiments. Rather, the invention encompasses any novel feature as well as any combination of features, including in particular any combination of features in the claims, even if this feature or combination itself is not explicitly stated in the patent claims or exemplary embodiments.

Claims

claims

1. lighting device (10, 11) with at least one light source (1, IR, IG, IB) by an operating device (2) with an electrical signal according to a in the operating device

(2) stored light curve (3) is driven.

2. Lighting device (10, 11) according to claim 1, wherein the light curve (3) is a function of the illuminance

(B) is a function of time (t).

3. Lighting device (10, 11) according to claim 2, wherein the light curve (3) has segments (S) with a time constant illuminance (B).

4. lighting device (10, 11) according to any one of the above claims, wherein the light curve (3) has a periodic signal whose period is between 16 ms and 20 ms, the limits are included.

5. Lighting device (10, 11) according to any one of the above claims, wherein the operating device (2) changes the light curve (3) during operation targeted.

6. lighting device (10, 11) according to any one of the above claims, wherein the operating device (2) scales the light curve (3) in proportion to a predetermined reference value.

7. Illumination device (10, 11) according to one of the above claims, wherein the operating device (2) detects operating parameters of the light source (1, IR, IG, IB).

8. lighting device (10, 11) according to claim 7 with reference to claim 6, wherein the operating device (2) the light flux of the light source (1, IR, IG, IB) by means of a control loop from the operating parameters of the light source (1, IR, IG, IB) and the predetermined reference value keeps constant.

9. lighting device (10, 11) according to any one of claims 6 to 8, wherein the operating device (2) during operation, the reference value changes purposefully.

10. Lighting device (10, 11) according to one of the above claims, wherein in the operating device (2) the current intensity-illuminance characteristic of the light source (1, IR, IG, IB) is stored.

11. Lighting device (10, 11) according to any one of the above claims, wherein the light source (1, IR, IG, IB) emits light with a color in the white area of the CIE standard color chart.

12. Lighting device (10, 11) according to one of claims 1 to 10, which comprises at least two light sources (1, IR, IG, IB) emitting light of different colors.

13. Lighting device (10, 11) according to claim 12, which has at least one red, one green and one blue light source

(1, IR, IG, IB).

14. Lighting device (10, 11) according to any one of the above claims, wherein as light sources (1, IR, IG, IB) gas discharge lamps, semiconductor light-emitting diodes, organic light-emitting diodes or laser diodes are used.

15. Display system with a lighting device (10, 11) according to one of the above claims.

16. A display system according to claim 15, whose colors are driven sequentially.

17. Display system according to one of claims 15 to 16, wherein the light curve (3) is adapted via a communication interface to the displayed image contents.

18. A display system according to claim 17, wherein the operating device (2) adapts the light curve (3) by time scaling to the speed of the synchronization signal.

19. A display system according to any one of claims 17 to 18, wherein the synchronization signal is connected to a sequential color modulator (6).

20. Display system according to one of claims 17 to 19, wherein in the operating device (2) a plurality of light curves (3) are stored, depending on the

Synchronization signal from the operating device (2) are selected to modulate the electrical signal to drive the light source (1, IR, IG, IB).