EP1877998A1

EP1877998A1 - Light source arrangement for backlighting display apparatuses and display apparatus

Info

Publication number: EP1877998A1
Application number: EP06742282A
Authority: EP
Inventors: Axel Schwab
Original assignee: Osram Opto Semiconductors GmbH
Current assignee: Ams Osram International GmbH
Priority date: 2005-04-30
Filing date: 2006-04-27
Publication date: 2008-01-16
Also published as: TWI358691B; KR20080014803A; DE102005020568A1; CN101167119B; CN101167119A; JP2008541141A; US20080106512A1; WO2006116974A1; TW200703198A

Abstract

The invention specifies a light source arrangement for backlighting a display apparatus, which arrangement contains a plurality of light sources (1) and a control device (4) which matches the luminous intensity of the light sources to the information (I) to be reproduced. In addition, the invention specifies such a display apparatus.

Description

description

Light source arrangement for backlighting of display devices and display device

The invention relates to a light source arrangement for the backlighting of display devices and to a display device.

With the growing demand for ever flatter display devices, the demand for LCD (Liquid Crystal Display) displays and TFT (Thin Film Transistor) displays has increased dramatically. LCD and TFT screens, like plasma screens, have the advantage of a flat design compared to conventional tube devices. LCD and TFT screens also have longer life and lower energy consumption compared to plasma screens.

Up to now, the backlighting of LCD and TFT displays has mostly been using cold cathode fluorescent lamps (CCFL). Lately, however, the backlighting of such screen types wins

Semiconductor light sources more and more important. For example, US 2002/0070914 A1 describes a backlight for an LCD display with a field of light-emitting diodes.

However, the low contrast ratio of the LCD and TFT screens of about 800: 1 at a luminance of 500 candela per m ² makes a wide application. In contrast, plasma devices achieve contrast ratios of 3000: 1 at very high luminances of up to 1000 candela per m ² . conventional Tube devices even achieve contrast values of 10000: 1. However, these tube devices can not be manufactured in a flat design.

A low contrast ratio has a particularly strong effect on LCD or TFT screens, for example in televisions, if, for example, image sequences with night scenes are to be displayed there. Due to the poor contrast ratio of previous LCD or TFT screens, they can not display rich or dark black.

Increasing the contrast ratio of LCD and TFT screens is possible with the improvement of the light valves used in these types of screen to pass or block light. The improvement of the light valves aims to increase the maximum filter attenuation of the light valves. However, the gain of the damping encounters technical limits. With strong backlighting of the display devices and limited filter attenuation, the contrast is limited, causing black spots to appear in a dark shade of gray.

The invention has for its object to provide a light source arrangement, which improves the contrast ratio of display devices. Furthermore, a display device with improved contrast ratio is to be specified.

This object is achieved by a light source arrangement having the features of claim 1 and a display device having the features of claim 21.

Advantageous embodiments and further developments are specified in the dependent claims, the disclosure of which hereby expressly included in the description by reference.

A light source arrangement for backlighting a display device according to the invention comprises a plurality of light sources and a control device which adjusts the light intensity of individual light sources or of groups of light sources to the information to be reproduced. The light intensity is defined as an SI unit and is often referred to as luminosity or brightness.

The contrast improvement - ie the increase in the ratio of the brightness of the brightest pixel to the brightness of the darkest pixel - is created by not only the effect of the light valves of a display device is used to produce the contrast, but also takes place a regulation of the light intensity of the corresponding light sources of the light source assembly.

Light valves are elements that are controlled to pass or block light. In LCD displays, these valves contain liquid crystals that can polarize light by their orientation. In TFT displays, the light valves contain transistors.

In particular, the light source arrangement can be used in LCD or TFT television sets, as the resolution of the television picture is generally lower than the technically possible resolution of the LCD or TFT picture matrix. In the area that is backlit by a light source, only contrast variations need to be displayed on a smaller scale.

Radiation-emitting semiconductor components, such as light-emitting diodes (LEDs), are preferred as light sources organic light-emitting diodes, or laser diodes used. Alternatively, other light sources that allow areal illumination and can be controlled individually or in groups in light intensity can be used.

An advantageous embodiment of the light source arrangement has one or more light guides in order to guide the light of the semiconductor light sources to the corresponding screen areas. Each light source is preferably arranged downstream of a light guide in the emission direction such that a majority of the radiation coupled out of the light source passes into the light guide.

But also possible is a direct backlight waiving fiber optics. In the case of direct backlighting, the radiation coupled out by the light sources is preferably formed by means of one or more beam shaping elements. Beam shaping elements are, for example, lenses, collimators and / or diffusers. The beam shaping is particularly preferably such that the area illuminated by a light source is increased. The beam shaping elements are arranged downstream of the light sources in the emission direction such that a majority of the light coupled out of a light source passes through a beam shaping element.

In an advantageous embodiment, a light source is formed by a lighting group. An illumination group is the combination of one or more radiation-emitting semiconductor components to form a light source, which in turn is itself designed as a separate component in an advantageous embodiment. Such a lighting group is formed for example by a multi-chip design, in the a plurality of radiation-emitting semiconductor chips are arranged in a common housing.

A light source preferably illuminates a certain area of the display device to be backlit, for example an LCD or TFT display device. An advantageous embodiment of the invention provides that a light source backlit a region within the display device, which contains a plurality of light valves.

This has the advantage that a light source covers the backlighting for a specific area of the light valve arrangement. As a result, a larger area lighting can be modularly constructed by light tiles.

The backlighting device for a single area is called a light tile. As a rule, a light tile backlights a plurality of pixels of a display device. In the case of rectangular light tiles, a light tile backlighs a range of n * m pixels of the display device, wherein in the special case of square light tiles m is equal to n. The number of pixels of such a region is preferably directly proportional to the number of light valves contained in this region.

A light tile preferably backlights 4096 pixels, particularly preferably 1024 pixels, of a display device. Square light tiles therefore preferably illuminate a range of 64 × 64 pixels, particularly preferably 32 × 32 pixels.

Light tiles for backlighting such a number of pixels are advantageously so small that the contrast differences within a light tile are usually low. In addition, the brightness of the areas that differ from neighboring light tiles are backlit, often only slightly, so that during operation of the light source arrangement adjacent light sources can be operated with a similar intensity. As a result, finely graded, substantially uniform transitions between strongly and slightly backlit areas of the backlit display device are advantageously achieved. If the information to be reproduced is an image sequence, the brightness of the region of the display device illuminated by a light tile often changes only slightly in successive images of the image sequence. Abrupt changes in the intensity of a light tile are avoided as possible. Advantageously, based on the number of pixels, only a comparatively small number of light sources are necessary for the backlighting.

A further advantageous embodiment of the invention provides that the adaptation of the luminous intensity of the individual light sources or groups of light sources is achieved in that the control device controls the power supply for the individual light sources or the groups of light sources. This is preferably achieved by supplying the light sources with a temporally varying current, for example an analog current or a digitally timed current. In a pulsed power supply, the power is provided in individual pulses, for which different types of modulation are possible. For example, the light intensity of the light source is preferably changed by a pulse width control, ie a change in the duration of a pulse at the same clock frequency, by a frequency control, ie a change in the duration of a clock in particular constant duration of a pulse, or by a combination of the two. For example, the extension of the clock frequency calls at the same pulse duration In the operation of a light source in the temporal average in the viewer, the sensation of a lower brightness, since the light source is provided on average less energy.

The clock frequency is chosen in each case so high that the human eye is not able to resolve the individual light pulses generated thereby separately. The eye of the observer registers a reduced number of light pulses, which are individually no longer resolvable, as reduced brightness of the light source. For example, the control device uses this effect to vary the light intensity by a modulation such as a pulse width control and / or frequency control for the viewer. The pulse width control and / or frequency control is preferably carried out with the aid of a q-bit (qualifier bit) technology.

A further advantageous embodiment of the invention provides that the adjustment of the light intensity of the individual light sources or groups of light sources is achieved by changing the height of the operating current. A change in the current amplitude by a light source causes a change in their intensity. A correspondingly configured control device thus varies the current intensity at the individual light sources or groups of light sources, in order thereby to adapt the light intensity.

An advantageous embodiment of the light source arrangement provides that the adaptation of the light intensity of the light sources takes place in rows and / or columns. An embodiment of this type has the advantage that the control device does not have to individually control all the light sources, but can access them in rows and / or columns. This simplifies the necessary control effort in this embodiment. A further advantageous embodiment of the light source arrangement provides that the light sources are arranged corresponding to a regular grid, the arrangement being selected from the group of rectangular, parallelogram-like, hexagonal and rhombic grid arrangements. For example, a rectangular grid arrangement allows a particularly simple control, since the light sources can then be controlled in a simple manner in rows and / or columns. However, in particular embodiments of the invention, it may be desirable to choose a different grid arrangement. For example, hexagonal grating assemblies generally allow more dense packing of the individual light sources, thereby allowing greater overall illuminance.

A particularly advantageous embodiment of the invention provides that at least one diffuser is arranged downstream of the light sources in the emission direction in such a way that a large part of the radiation coupled out of the light sources reaches the diffuser. The use of such a diffuser causes a more homogeneous distribution of light at the surface of the display device or information reproduction device backlit by the light sources.

A further advantageous embodiment of the

Light source arrangement provides that each light source in each case at least one homogenization element (white box element) is arranged downstream in the emission direction such that a majority of the radiation coupled out of the light source passes into the homogenization element. The homogenizing elements are in particular associated with backlit areas (pixel fields) of the display device. A white box element preferably comprises a reflector which is that of the light source emitted light is homogenized, so preferably the surface illuminated by the white box element appears to the viewer at all points substantially the same light, and / or used for beam shaping.

A white box element, a light guide and / or a combination of light guide and white box element improve the homogeneity of the backlighting of a portion of the display device that is backlit by a light source. Preferably, the homogenization elements are arranged so that no sharp light-dark transitions between the luminous areas, in particular individual light tiles, occur.

A further preferred embodiment of the light source arrangement provides that at least one BEF (Brightness Enhancement Film) film is assigned to the light sources. Such a BEF film enhances the light emission perpendicular to the display plane by focusing the radiation in the direction of the surface normal of the display plane. A viewer, in front of the

Display device sits, therefore, the radiation perceives as brighter, if such a BEF film is arranged downstream of the light sources in the emission direction.

A further advantageous embodiment of the light source arrangement provides that the light sources or the lighting groups are arranged on a common carrier. Possible carriers may be all forms of circuit boards, in particular metal core boards, which have an increased thermal conductivity.

Appropriately, light sources, in particular individual light sources or groups of light sources, which preferably backlight different areas of the display device, operated by the control device, in particular at the same times, with mutually different light intensity. Areas in which the information to be displayed should have a low brightness for the viewer are in this way backlit with low light intensity, while areas in which the information to be displayed should have a greater brightness for the viewer are backlit with higher light intensity. Advantageously, in this way, for example, the ratio of the brightness of the brightest to the brightness of the darkest pixel is increased.

A particularly advantageous embodiment of the invention provides that the control device controls the light intensity of the light sources, in particular of individual light sources or groups of light sources. The control device thus adjusts the light intensity of the light sources according to their algorithm automatically. By the control means for controlling the light intensity of the individual light sources or groups of light sources, a contrast enhancement is achieved, for example, by increasing the ratio of the brightness of the brightest to the brightness of the darkest pixel. For control, the controller uses an algorithm. In this algorithm, at least one of the following input variables is processed. These include the contrast values, that is to say in particular the standardized brightnesses of the pixels of the information to be reproduced, which are backlit by a light source (light tile), in particular the mean value of the brightnesses and / or the greatest and smallest brightness of these pixels, the contrast values of adjacent light tiles, in particular the mean value of the brightnesses and / or the maximum and minimum brightness of a pixel of one, several or each of these light tiles, the contrast values of the total information reproduced by the display device, that is, for example, the brightness of the brightest and the brightness of the darkest pixel, and / or the brightness of the surroundings of the display device.

The brightnesses or contrast values of the pixels of the information to be reproduced are preferably determined by the control unit from the signal fed into the display device, which contains the information to be reproduced.

The brightness of the environment is measured, for example, by a sensor, in particular an AL sensor (Ambient Light Sensor). An ambient light sensor is a brightness sensor whose spectral sensitivity is preferably matched to that of the human eye.

The contrast values are in particular two-dimensional values. The control device thus preferably creates a matrix, in particular when the light sources are arranged in rows (x-direction) and columns (y-direction). The number of rows and columns of the matrix preferably corresponds to those of the light sources, so that each light source is assigned one cell of the matrix. The contrast values, for example the averaged brightnesses, of the pixels of the information to be displayed assigned to the individual light sources are expediently entered into the cells of the matrix. The desired light intensity of the light tiles, for example, including the light intensity of adjacent light tiles, can then be determined simply by means of matrix operations.

In particular, in the case of the representation of image sequences, for example of films, the control device is particularly preferably adapted to the intensity of the Controlling light sources in the representation of an image of the image sequence in dependence on the brightness or contrast values of one or more temporally preceding and / or subsequent images of the image sequence. The brightness or contrast values are, for example, the contrast values of the pixels assigned to a light tile, the contrast values of the pixels that are backlit by adjacent light sources, and / or the contrast values of the entire image, ie, for example, the brightness of the brightest and the brightness of the darkest pixel. This makes it possible to respond even to rapid contrast changes within a range of representation. For example, flickering of the light sources is preferably suppressed in the case of rapid brightness changes within a light tile. In order to display an image of the image sequence, the brightness or contrast values of one or more preceding images and, in particular with time-shifted representation, particularly preferably also the contrast values of one or more subsequent images are evaluated and used for the control.

In a preferred embodiment, special control algorithms will additionally be used by the controller. For example, another algorithm is used to recognize superimposed subtitles when playing a sequence of pictures, in particular a movie. For example, when a white text is superimposed against a dark, especially black background, high contrast differences are produced within the region of the display device that is illuminated by a light source. In order that such extremely high contrast differences do not disturb the contrast reproduction of the entire image information of the image sequence, the control device makes, for example, the extremely high contrast of a white font by one reduced contrast, for example those of a gray font, varies.

Since the contrast values represent substantially normalized brightness values, in one expedient embodiment the control device is designed in such a way that the corresponding brightness values are processed as input variables of the algorithms instead of the contrast values. The brightness values of the individual pixels can easily be determined in conventional codings of information to be reproduced for transmission to a display device and can therefore be processed particularly easily by the control device.

In a further advantageous embodiment, the control device additionally controls the light valves in order in particular to adapt the graphic resolution of the reproduced information. As a result, the control device adapts, for example, the resolution of the information to be reproduced to the grid of the light tiles. For example, the control device adjusts the resolution of an information to be displayed such that the edge of the representation coincides exactly with edges of the light tiles of the backlighting arrangement.

In addition, such a control allows optimal utilization of the individual backlit areas. Optimal in this context means an adjustment made according to an optimization criterion of the information reproduced by the light valve grid information to the grid of the backlighting arrangement. The adaptation of the information takes place, for example, by a change in the resolution and / or a shift in the representation within the light valve grid. Thus, the control device preferably shifts the information to be reproduced relative to the original one It also changes the size of the information to be displayed, for example by rescaling the information to be reproduced, that is to say the representation on the display device becomes relative to the originally intended size of the information to be reproduced enlarged or reduced.

Particularly broadband cinema films or other information whose aspect ratio does not correspond to the aspect ratio of the display device are adapted by such control to the screen format of the display device, in particular to the grid of the light tiles of the light source arrangement. For example, it is possible to adapt the video image so that it falls in the x and / or y direction into the appropriate grid of the light tiles. The control device is then preferably suitable for recognizing black bars, in particular on the upper and lower image edges, and then possibly completely switching off the backlighting in the corresponding areas.

In a preferred embodiment it is provided that the control device adapts the degree of opening of the light valves backlit by a light tile to the light intensity of the light tile. For example, the control device opens a light valve at a low light intensity stronger than at a higher light intensity, so that preferably the brightness of the light valve associated pixel is substantially independent of the light intensity of the light source, which backlit the light valve.

A further advantageous embodiment of the invention provides that the control device in the case of a direct backlighting of the light valves, the superposition of the emission Adjacent light sources or lighting groups in the adaptation of the light intensity of the individual light sources or light groups in an algorithm considered as input. In this case, a direct backlight means a waiver of optical elements between the light sources and the backlit display device, for example, the waiver of white box elements and / or light guide. If the use of optical elements in the backlighting of a display device is dispensed with, starting from the light sources, light cones are formed which overlap one another. This overlay is in one embodiment by the controller in the calculation of

Adjusted light intensity of the individual light sources or lighting groups. For example, the controller preferably operates a lower intensity light source when pixels within the illuminated portion of the display device that are to have high brightness are also backlit by an adjacent light source.

Further advantages and advantageous embodiments and developments of the invention will become apparent from the embodiments described below in conjunction with FIGS. 1 to 5.

Show it:

1, a schematic representation of the operation of a first embodiment of a display device according to the invention,

FIG. 2 shows a schematic representation of the mode of operation of a further embodiment of a display device according to the invention, 3, a schematic representation of the operation of a third embodiment of a display device according to the invention,

Figure 4, a schematic representation of the operation of a fourth advantageous embodiment of a display device according to the invention and

Figure 5, a schematic representation of the structure of a display device with light valves.

All figures shown are schematic and serve to explain. The illustrated elements and their proportions with each other are basically not to be considered as true to scale.

FIG. 1 shows the schematic view of a first embodiment of a display device according to the invention. In this case, information I is displayed or displayed with the aid of a light valve arrangement 2 and a light source arrangement 1, which can be recorded by a viewer. The preferred viewing direction is indicated in the figures 1 to 4 in each case by an arrow.

In this embodiment, information I to be reproduced is fed to the display device.

The information I is forwarded to a control device 4 and a control unit 5. Control unit 5 serves to control the light valves. Such control units 5 are already known in principle from conventional display devices with light valves. In the embodiment according to FIG. 1, the light source arrangement 1 is used as backlight is used for the light valve assembly 2, with the help of the control device 4 also used to reproduce the information I. For this purpose, the control device 4 controls the brightness of the individual light sources 55 of

Light source arrangement 1, which in the present case are semiconductor light sources.

The control device 4 takes from the information signal to be displayed, which transmits the information I to be reproduced to the display device, one or more of the following information and uses them as input variables for an algorithm or several algorithms for controlling the light intensity of the individual light sources 55: the contrast information over the whole to be displayed area

in the present case, the normalized brightness of the brightest and the darkest pixel of the information I, the contrast information of one or more regions of the

Surface, each of which is backlit by a single light source or a group of light sources - in this case, the normalized brightness of the brightest and the darkest pixel of the information I within this

Area or these areas, the corresponding contrast information of the respectively directly adjacent light sources illuminated areas or areas, optionally one or more of the above

Contrast information of the temporally preceding and / or subsequent image, and / or the ambient brightness.

In particular, when displaying a sequence of images, for example a video film or a television signal, the contrast information from a previous image or, in particular in the case of a time-shifted representation, also the Contrast information from a subsequent image is used to enhance the contrast of displaying an image of the sequence. The contrast improvement takes place in that the control device 4 evaluates the input variables taken from the incoming information by one or more algorithms and regulates the brightness of the individual light sources in accordance with a desired value. Preferably, the controller 4 includes a microelectronic controller, not shown, that stores the available information and processes it according to one or more algorithms and outputs appropriate control signals.

In this specific embodiment, it is further provided that at least one sensor 3 of the control device 4 supplies additional information about the ambient brightness in the region of the display device. This additional information is also evaluated by one or more algorithms and the controller 4 adjusts the light intensity of the individual light sources accordingly. For example, the control device 4 preferably increases the light intensity of the light sources 55 during operation when high ambient brightness is present. One or more brightness sensors (ambient light sensors) are particularly preferably used to determine the ambient brightness. Ambient light sensors are sensors whose sensitivity spectrum is preferably optimized for the sensitivity of the human eye, ie the eye of the observer.

In the embodiment illustrated in FIG. 1, the control device 4 additionally influences the control unit 5, indicated by an action arrow. In this case, the control device 4 influences the resolution of the information to be reproduced I, which is passed from the control unit 5 to the light valve assembly 2. This influence the resolution is particularly advantageous since the grid of the light valve arrangement 2 in the present case does not coincide with the grid of the light source arrangement 1. The grid of the light valve assembly 2 is finer than that of the light source assembly 1. While the resolution is predetermined in conventional display devices by the control unit 5 alone, by means of a predetermined by the controller 4 adjustment of the resolution optimal and uniform division of the light valves of the light valve assembly 2 on the Grid of the light source assembly 1 achieved.

In this context, a resolution with optimum division is to be understood, for example, as meaning that the envelope of the surface formed by the light valves used for the representation, when projected onto the light source arrangement 1, does not intersect regions which are backlit by individual light sources, but instead each coincides with their boundaries. The resolution is thus adapted so that the reproduction area determined thereby is ideally congruent with an area formed by light tiles of the backlighting arrangement. In other words, the total number of pixels per row is preferably an integer multiple of the number of pixels per row of a light tile, and / or the total number of pixels per column is an integral multiple of the number of pixels per column of a light tile.

FIG. 2 shows a further advantageous embodiment of a display device according to the invention. Information to be reproduced I is fed to the display device. The information is forwarded to a control device 24 and a control unit 25, wherein the control device 24 for acting on the Control unit 25 is provided. However, the embodiments of the present invention are not limited to the fact that the control device 24 and the control unit 25 or their equivalents are made separately in the other embodiments, but both may also be implemented together as an integrated unit. The control unit 25 controls the light valve assembly 22 while the controller 24 controls the light source assembly 21.

A viewer registers the light which emanates from the light source arrangement 21 and to which the information I to be reproduced is impressed by the light valve arrangement 22.

In this exemplary embodiment, the control device 24 uses one or more of the information or input variables also described with reference to FIG. 1 in order to control the brightness of the individual light sources 55 of the light source arrangement 21. In contrast to FIG. 1, no brightness sensor is provided.

The grid of the light source arrangement 21 arises because individual light sources 55 backlight portions of the light valve arrangement. These sub-areas or light tiles form the backlighting arrangement of the area. The number of light tiles is presently less than the number of light valves. As a result, the light source arrangement and the light valve arrangement have different rasters. Therefore, it is advantageous to achieve a change in the resolution by influencing the control unit 25 by the control device 24. A change in the resolution of the information is particularly advantageous when used to display the information by means of the light valve assembly 22 whole light tiles of the light source assembly 21 for backlighting. In other words, the Resolution adjusted so that the edge of the resulting representation, projected onto the light source assembly 21, exactly hits the edges of individual light tiles.

FIG. 3 shows a third embodiment of a display device according to the invention. In this embodiment, information I to be reproduced is fed to the display device shown schematically. The information is forwarded to the control device 34 and the control unit 35. In this case, the control unit 35 evaluates the information and controls the light valves of the light valve arrangement 32 accordingly. The controller 34 extracts one or more of the above-described contrast information from the information I to be reproduced and evaluates it. For this purpose, it uses one or more algorithms, as described on the basis of the exemplary embodiments according to FIGS. 1 and 2.

Depending on the contrast information evaluated by one or more algorithms, the control device 34 controls the brightness of the individual light sources of the light source arrangement 31, which in the present case are semiconductor light sources.

Since the contrast information is generally normalized brightness information, further advantageous embodiments of the invention process the corresponding brightness information instead of the aforementioned contrast information as input information.

As an effect of the control device 34, the observer sees through the activation of the light source arrangement 31 Contrast enhanced representation of the information shown by means of the light valve assembly 32.

Figure 4 shows a fourth embodiment of a display device according to the invention, in which the information to be reproduced I is fed into the system. The information I is forwarded to a control device 44 and a control unit 45. However, embodiments of the invention are not limited to the fact that the control unit 45 and the control device 44 must be designed separately, but in particular also include the possibility of integrating the control device 44 and the control unit 45 together in an overall control.

The control unit 45 serves to control the light valve arrangement 42. The control unit 44 evaluates with the aid of one or more algorithms input variables which are taken from the information I. The input quantities may be brightness and / or contrast information of the fed-in information to be reproduced, as described in the preceding exemplary embodiments. In addition, a control device 44 can receive and evaluate the information of at least one sensor 43, which measures the ambient brightness of the room in which the display device is operated, as an input variable.

The evaluation is done by means of one or more of the previously described algorithms. As a result of this evaluation, an activation of the light sources 55 of the light source arrangement 41 is effected. In this case, the brightness of individual light sources is preferably varied to improve the contrast of the overall presentation. Alternatively, the brightness of groups of light sources, for example, individual lines or Columns of light sources can be varied. The control device thus controls the light intensity or the brightness of individual light tiles or the brightness of groups of light tiles, for example the rows or columns of the grid formed by the light tiles.

By a targeted evaluation of the incoming information, the control device 44 thus produces a contrast enhancement of the displayed information, which can be perceived by a viewer.

FIG. 5 shows the schematic structure of a display device with light valves. FIG. 5a shows a schematic cross-section of the structure of such a display device, and FIG. 5b shows a schematic plan view of such a display device.

In FIG. 5 a, a plurality of light sources 55, in the present case semiconductor light sources, are arranged on a support 56. The light sources 55 are preferably light groups, so that a light source 55 comprises a plurality of light-emitting semiconductor components, which are particularly preferably arranged in a common housing. The carrier 56 is presently a circuit board, in particular a metal core board. Metal core boards allow, due to their higher thermal conductivity, a particularly efficient cooling of the light sources 55. The light sources 55 couple their emitted light into homogenizing elements, so-called white-box elements 54. The dimension of the white box elements on their

Light exit side determines the size of the light tiles in this embodiment. These white box elements include reflectors for beam shaping. The reflectors are present shaped so that the entire light exit side of the Light tiles lit as evenly as possible when operating the light source.

The relationship between the dimensions of the light exit side of the white box elements and the size of the light tiles is shown by the dashed lines connecting Figures 5a and 5b. Subsequent to the light exit side, there is a diffuser 53 and at least one BEF (Brightness Enhancement Film) film 52 for the light sources or luminous groups. The diffuser 53 ensures an improved homogenization of the emitted light. The BEF foil 52 serves to improve the emission characteristic of the display device by focusing the radiation in the direction of the observer and is commercially available, for example, from 3M. This backlighting is a light valve assembly 51, which modulates the radiated light information, downstream. Such a light valve arrangement is generally of multilayer construction and expediently contains a plurality of filters, for example polarization filters.

In Figure 5b, the schematic structure of the display device is shown in plan. The backlighting of the display device is composed of individual light tiles 57a, 57b, 57c. In the x and in the y direction, a number v or w of light tiles for the backlighting of the

Radiation exit surface of the display device arranged. The number v, w of the light tiles is expediently adapted to the size of the display device. The light valve arrangement 51 arranged downstream of the light tiles is shown in FIG. 5b only within the light tile 57a and is schematically indicated by a checkerboard pattern. The grid of the light valve arrangement 51 is finer in this embodiment than the grid of light tiles. For example, specific embodiments of the invention contemplate that the display device is a 32 "TFT television, with the light valve arrangement having a pixel resolution of 1366 x 768 pixels or more, with a 16: 9 aspect ratio. This light valve grid is backlit by an array of light tiles For example, this light tile arrangement comprises 22 × 12 (vxw) light tiles, ie a total of 264 light tiles.These light tiles preferably contain LEDs of the product designation MultiLED or Advanced Power TopLED or light groups constructed thereof as light sources In this exemplary embodiment, therefore, each light tile has a backlight of approximately 64 x 64 pixels of the light valve arrangement.

Alternatively, the display device can also be backlit by 43 × 24 (v × w), ie 1032 light tiles, each light tile containing, for example, a power top LED. As a result, approximately 32 × 32 pixels of the light valve arrangement are backlit in each case by a light tile which, for example, in each case comprises a power top LED.

MultiLED, Power TopLED and Advanced Power TopLED are names of semiconductor light sources, which are distributed by Osram.

In a further advantageous embodiment, the display device comprises a 45-inch TFT screen. With a picture format of 16: 9, the light valve arrangement thus has a pixel resolution of 1920 x 1080 pixels. For backlighting, for example, 30 × 17 (vxw), ie 510 light tiles, are used here, which preferably each contain a MultiLED or an Advanced Power TopLED as the light source. In this particular embodiment, each light tile backlit then each a portion of the light valve assembly, which comprises approximately 64 x 64 pixels.

This patent application claims the priority of German Patent Application 10 2005 020 568.2, the disclosure of which is hereby incorporated by reference.

The invention is not limited by the description based on the embodiments of these. 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

A light source arrangement for backlighting a display device, which contains a plurality of light sources (1) and a control device (4), which adjusts the light intensity of individual light sources or groups of light sources to be reproduced information (I).

2. Light source arrangement according to claim 1, wherein the light sources comprise at least one radiation-emitting semiconductor component.

3. The light source assembly of claim 2, wherein each light source comprises a plurality of radiation-emitting semiconductor devices.

4. Light source arrangement according to one of claims 1 to 3, which contains a light valve arrangement (2), which in particular comprises a plurality of light valves.

5. A light source assembly according to claim 4, wherein a light source backlit a region having a plurality of light valves.

6. Light source arrangement according to one of the preceding claims, wherein the control means controls the light intensity of the light sources by a timing of the power supply.

A light source assembly according to any one of the preceding claims, wherein the control means controls the light intensity of the light sources by changing their operating current.

8. Light source arrangement according to one of the preceding claims, wherein the light sources are arranged in rows and columns.

9. light source arrangement according to claim 8, wherein the control device, the light intensity of the light sources line and / or column-wise controls.

10. Light source arrangement according to one of the preceding claims, wherein the light sources are arranged corresponding to a regular grid.

11. The light source arrangement according to claim 10, wherein the grid has rectangular, parallelogram-like, hexagonal or rhombic basic units.

12. Light source arrangement according to one of the preceding claims, wherein the light sources at least one diffuser (53) is arranged downstream in the emission direction.

13. Light source arrangement according to one of the preceding claims, wherein the light sources at least one homogenizing element (54) and / or a light guide is arranged downstream in the emission direction.

14. Light source arrangement according to one of the preceding claims, wherein the light sources at least one BEF (Brightness Enhancement FiIm) -FoIIe downstream in the emission direction.

15. Light source arrangement according to one of the preceding claims, wherein the light sources are arranged on a common carrier, in particular a circuit board.

16. Light source arrangement according to one of the preceding claims, wherein the control device is adapted to operate light sources that backlight different areas of the display device at the same times with different light intensity.

17. Light source arrangement according to one of the preceding claims, in which the control device is configured to influence the light intensities of the light sources as a function of at least one of the following input variables:

Contrast values within the backlit area of a

Light source

Contrast values of the backlit areas of adjacent

Light sources,

Contrast values reproduced by the display device

Information,

Ambient brightness.

18. Light source arrangement according to one of the preceding claims, wherein the control device is adapted to the light intensity of the individual light sources or groups of light sources in the case of playback of an image sequence, in particular a film, depending on the contrast values of an image or multiple images of the image sequence vary.

19. Light source arrangement according to one of the preceding claims, wherein the control device additionally controls the light valve arrangement, in particular to adjust the graphic resolution of the reproduced information.

20. Light source arrangement according to one of the preceding claims, wherein the control device in a direct backlighting the superposition of the emission of adjacent Considered light sources in the adjustment of the luminous intensity of the individual light sources.

21. Display device with a light source arrangement according to one of the preceding claims.

22. A display device according to claim 21, comprising an LCD or TFT screen.