Illumination device

TECHNICAL FIELD

The present invention relates to an illumination device comprising a display unit for providing a video output.

TECHNICAL BACKGROUND

Recently, rapid developments have been made in the area of lighting and illumination. For example, solid-state lighting devices (LEDs) are used to provide large controllable pixel arrays, thus enabling great flexibility in lighting ambiance and patterns. At the same time, such LED arrays can also be used as a large screen display, e.g. Philips Vidiwall.

However, a problem in this context is that the light output from a LED array, or indeed any other type of traditional display, causes considerable variation of the ambient light (ambience). Therefore, if a specific ambience is desired (constant or varying), a simultaneous display of image content will interfere with the illumination.

OBJECTS OF THE INVENTION

It is an object of the present invention to mitigate this problem, and to provide an illumination device capable of providing a desired ambience lighting while displaying an image content.

SUMMARY OF THE INVENTION

According to the invention, this and other objects are achieved by an illumination device having a display unit, a display driver adapted to receive a video signal and to control a video output of said display unit based on said video signal, an illuminator unit comprising a plurality of additional light emitting elements, and a controller, adapted to receive said video signal and to control an additional light output from said illuminator unit in accordance with the video signal and a set point representing a desired total light output, such that said video output in combination with said additional light output approximates said desired total light output.

By enabling control of the total light output, an illumination device is achieved that can provide a desired illumination while at the same time displaying video content on the display unit. Therefore, video content can be displayed without interfering with the overall ambiance. The controller is adapted to control the emitted light from the additional light emitting elements in accordance with a desired total light output and the video signal. In other words, the additional light emitting elements are controlled to emit light that in combination with the video output results in the desired total light output. Therefore, even with changing video content displayed on the display unit, the total light output can be predicted and controlled, to avoid any undesired influence on ambient light (ambience).

A device according to this invention may be thought of in two ways: as an illumination device with the ability to display, or as a display device with the ability to illuminate. As an illumination device with the ability to display, it has applications where occasional or relatively unobtrusive video is desirable, which might even be a relatively static announcement in a foyer of a hotel or conference venue. As a display device with the ability to illuminate, it could take the place of a television and room light at home, where one member of a family wants to watch a TV program, while another wants to read. In another application area, it is possible that street advertising at night could become subject to legal controls where the light output must be constant, to avoid irritation to pedestrians and local inhabitants and to avoid excessive distraction to vehicle drivers.

The invention can be more economical with energy consumption than with a separate, fixed, source of illumination and an independent display device, since with the invention the energy used on the display side is effectively put to double use, whereas in the prior art, the illuminator provides the basic light level, and the display consumes extra energy.

The control can be effected in respect of intensity and/or color. In case of color control, the additional light emitting elements preferably include elements for emitting different colors, and most preferably include at least red, green and blue light emitting elements. Such a design will enable a flexible control of the additional light output, and enable realization of many different total light outputs.

The desired total light output can be variable, resulting in a varying ambient lighting. This can be achieved by allowing the set point to vary.

The display unit can be any display that actively emits light, such as a CRT or a LED. The additional light emitting elements are preferably an array of LEDs, most

preferably of different colors. When the display unit is a LED display, the display and the additional light emitting elements can be just different portions of one LED panel.

BRIEF DESCRIPTION OF THE DRAWINGS This and other aspects of the present invention will now be described in more detail, with reference to the appended drawings showing a currently preferred embodiment of the invention.

Figure 1 shows a schematic block diagram of a first embodiment of the present invention. Figure 2 shows a schematic block diagram of a second embodiment of the present invention.

Figure 3a-c illustrates the operation of the illumination device in figure 1. Figure 4a-c illustrates the operation of the illumination device in figure 1 in a situation where full color compensation cannot be achieved. Figure 5a-c illustrates the operation of the illumination device in figure 1 in a situation where full color compensation cannot be achieved.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The illumination device shown in figure 1 has a display unit 1 and an auxiliary illuminator 2 comprising a set of additional light emitting elements (not shown in detail). The display unit can be e.g. a LED-based display or a CRT, or any other type of display that actively emits light. The auxiliary illuminator can be an array of LEDs, and can be integrated with the display unit. According to one embodiment, the display unit and the auxiliary illuminator are formed by separate portions of the same large area LED array. The display unit is typically a color display, in which case the illuminator unit also must be capable of emitting light of different color, e.g. red, green and blue. Preferably, the illuminator unit is an array of LEDs comprising red green and blue LEDs 9.

The display unit 1 is controlled by a display driver 3, which operates the display unit to display a video content based on a video input signal 4. The same video signal 4 is also provided to a controller 5, arranged to control the light output from the auxiliary illuminator 2.

In operation, the controller is adapted to control the illuminator to emit light such that the total emitted light from both the illuminator and the display unit correspond to a desired ambient light (ambience). This desired ambience can be a fixed value, e.g. white

light, that does not change. Alternatively, desired ambience is allowed to change over time. The time profile that defines how the ambience changes over time may use as its origin the time from the start of a film, rather than time from some arbitrary origin. In any case, the desired ambience can be represented by a set point 6, which can be pre-stored in the controller (in case of a fixed set point) or be supplied to the controller through a suitable interface (fixed or varying set point).

The set point can represent a desired color content as well as a desired intensity. The set point is preferably represented in terms of color contributions from the primary colors of the illuminator unit 3, e.g. red, green and blue in a typical three primary system.

In the embodiment in figure 1 , the controller 5 is adapted to calculate complementary output levels based on the desired ambience and video input signal.

According to another embodiment, illustrated in figure 2, a film or video sequence can be provided with a pre-calculated complementary signal 7, intended to be used as control signal for the controller 5. The complementary signal 7 can be multiplexed into the video stream 4 and separated by the driver 3 as indicated in figure 2, or supplied via a separate channel. The use of a pre-calculated complementary signal 7 simplifies the controller 5, because the controller then does not have to calculate light levels itself, though it must retain synchronicity with the video. In a simple embodiment, synchronization would be done by having one light level signal per fixed unit of time: e.g. one signal per x microseconds

Figure 3a-c illustrates the control effected by the controller in the simple case of providing white ambient light. Figure 3a shows the aggregated RGB levels of the video signal at a given point in time. The desired total output is indicated by the level 8. Figure 3b shows the complementary RGB levels set by the controller, so that the combination of video output and illuminator output results in equal RGB levels, i.e. white light, as shown in figure 3c.

The level 8 indicates the desired intensity of the white light. This level can be as low as the maximum output level for any color of the video signal. If the desired intensity 8' is lower than this maximum level, full color compensation cannot be achieved without increasing intensity above the desired level. This is illustrated in figure 4a-c.

Figure 5a-c illustrates a different situation, where the desired total output 8" is not white. Here, it is possible that one of the RGB levels of the video signal (here the red

level) exceeds the desired level. In such a case, again a full color compensation cannot be achieved without departing from the desired intensity, as indicated in figure 5b and 5c.

In cases such as those described, where full color compensation cannot be provided, instead of exceeding the intensity level, the display levels can be adjusted downwards, so that the video content is slightly distorted. Yet another alternative is to accept a total light output departing from the desired value. Finally, the deviation can be handled by combining several actions, such as decreasing the display output levels while at the same time exceeding the desired intensity level.

The methods of this invention could be adapted where the set point defines not a desired level of illumination and color, but a minimum level of illumination. This would soften the effect of a film or video sequence which had periods of complete, or almost complete, darkness.

The person skilled in the art realizes that the present invention by no means is limited to the preferred embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims. For example, one display unit could be provided with a plurality of auxiliary illuminators, each providing a different contribution to a total desired light output.