WO2008106942A1 - Lighting device, display device, and method for the operation thereof - Google Patents

Abstract

A lighting device comprises, in a housing (15), one or more semiconductor elements (12, 13, 14) that are suitable for the radiation of light, and a light sensor (11). The light sensor is suited to generate an output signal that is dependent upon receiving light.

Description

description

Lighting device, display device and method for their operation

This patent application claims the priority of German patent applications 102007010554.3 and 102007012381.9, the disclosure of which is hereby incorporated by reference.

Technical field of the invention

The invention relates to a lighting device in which a semiconductor body suitable for emitting light is arranged in a space enclosed by a housing. The invention also relates to a display device suitable for displaying information that is illuminated by the illumination device. Moreover, the invention relates to a method by which the illumination device can be operated and a method by which the display device can be operated.

Background of the invention

Conventional lighting devices comprise a housing with a recess which defines a space in which a semiconductor body suitable for emitting light is arranged. Such lighting devices are also referred to as LED - light emitting device. A potting compound covers and protects the light-emitting semiconductor chip. The housing may be suitable for mounting on a circuit board. The light emission by the semiconductor chip is subject to fluctuations which are caused by aging processes in the semiconductor chip and within the arrangement and which, moreover, can be dependent on the temperature. Therefore, corresponding arrangements are used to achieve a predetermined luminance by the LED, which is resistant to aging and / or temperature. Such arrangements may include a light sensor, which reacts by means of appropriate control measures on the LED and compensates for any deviation from a predetermined value.

Such an arrangement is described, for example, in US patent application US 2006/0066265 A1. The known arrangement uses a discrete light sensor located outside the LEDs on a circuit board. Such an arrangement is less integrated and the optical coupling between LED and light sensor corresponds to the discrete structure. For possible applications in modern display devices with backlighting, therefore, the known arrangement is only partially suitable.

An object of the present invention is to provide a lighting device in which the optical coupling between LED and sensor is improved.

In addition, an advantageous use for the lighting device in a backlit display device should be specified. Likewise, appropriate operating methods of the invention are to be based. Summary of the invention

According to one embodiment of the invention, a lighting device according to the features of claim 1 is given.

A display device with such a lighting device is the subject of patent claim 10. A method for operating a lighting device or a display device are the subject of claims 12 and 13. Refinements and developments of the lighting device, and the display device are specified in the dependent claims. The disclosure of the claims is hereby expressly incorporated by reference to the description.

The invention relates to a lighting device which contains a housing with a space surrounded by the housing. The illumination device has a semiconductor body suitable for emitting light during operation, which is arranged inside the space. Further, it has a photosensitive sensor which is disposed within the space and is adapted to produce an output signal dependent on reception of light.

According to one embodiment, the semiconductor body suitable for emitting light and the sensor device, that is to say in particular the sensor, are integrated in a single housing. As a result, a sufficient optical coupling between the light emitting semiconductor body and the light sensor device is achieved. The light-emitting semiconductor body and the light sensor device can each be realized as semiconductor chips. The light sensor can, for example be formed as a silicon photodiode sensor. A sufficient portion of the light emitted by the LED chip is reflected on the walls of the housing, which also serve as a reflector, so that the photosensor chip can receive directly emitted and / or reflected light. In some embodiments, a potting compound may be provided which covers LED chip and / or photosensor chip and provides good optical coupling between the arranged in the reflector housing components. The potting compound can also be omitted in other versions.

In one embodiment, the sensor, which is in particular a photosensor chip, is connected to corresponding signal lines so that the electrical signals generated by it, representing a detected photo event, can be emitted to the outside, outside the housing. By way of example, corresponding metallic signal lines are led through the housing wall in order to contact the photo-chip in the interior of the housing with a connection section of the signal line. The contacting can be produced for example by direct contact or via a bonding wire or via alternative bonding technologies. A generated in response to the light received by the photo-chip output signal is fed via the signal lines to the outside and can be tapped outside the housing. The housing can be mounted on a circuit board, for example by means of SMT (Surface Mount Technology). The signal line is then connected to a corresponding signal line on the circuit board. In another embodiment, the sensor is connected to corresponding signal lines with a control circuit, which is included in the lighting device itself, ie in particular in the housing. Various arrangements of LED chips and sensor chips are possible. For example, there are three LED chips that emit light at different wavelength ranges. This makes it possible to produce a desired color by mixing. The light sensor is arranged in the immediate vicinity of the three semiconductor chips and detects the light emitted by them. Of course, it is possible to arrange less than two or more than three light-emitting chips within the housing interior. In addition, it is possible to provide more than one light sensor there.

The light sensor can record emitted light in a wide spectral range or be provided with a color filter, so that only light of a specific wavelength or a narrow spectral range is added to the active part of the light sensor. Depending on the application, different conditions are conceivable.

In one embodiment, for example, three LED chips and a light sensor can be used, which are in particular positioned in each case in the vicinity of corners of a quadrilateral, in particular a rectangle or square. This results in a point-symmetrical arrangement of the three LED chips and the light sensor. On the other hand, it is also possible to position all the LED chips and the light sensor aligned linearly along a straight line. The light sensor can be arranged on the edge of the three LEDs or can be arranged between two LEDs. Finally, combinations of linearly arranged and arranged in a rectangular shape positioning are possible. The invention can be used in all applications of lighting equipment. For example, an illumination device according to an embodiment of the invention can be used in a conventional LED array for illuminating an environment. Regular light detection, comparison of the received light intensity with a threshold value and feedback of the light emission of the light-emitting LED (s) can be used to calibrate the brightness of each LED. The brightness adjustment can be performed unnoticed for a viewer briefly during operation or, for example, when switching on or off the lighting device. This makes it possible to compensate for aging processes. As is known, aging processes take place differently with different LED chips and therefore cause different LEDs after aging to have a different state of aging and to be able to emit different light intensity. The specified illumination device with the light sensor integrated in the same housing makes it possible to dynamically determine the respective individual aging state of an LED during operation and then compensate it.

A lighting device of the type described here can be used particularly advantageously for the backlighting of an LC (liquid crystal) display (LCD). For this purpose, located on the environment and in particular a viewer facing side of the LCD LCD layers, which display a mostly digitally supplied information. Underneath, with respect to the LCD layer facing away from the environment, there is a light source. For a larger area LCD, multiple of the lighting devices described herein may be provided in matrixed form. It is necessary that all Provide lighting equipment in the background equal light intensity, so that homogeneity of the backlighting is ensured. In some embodiments, the backlighting within the LCD may be controlled in sections depending on the information displayed in the LCD. This increases the contrast of the displayed image information.

For example, a control device is provided which receives and evaluates the output signals of the respective sensor chips of each individual lighting element and feeds back a control signal to the LED chips in order to compensate for aging and / or temperature-induced light intensity fluctuations.

The illumination device described here, in which LED chips and sensor chip are integrated in a housing, are not limited in their application to the application examples shown here in particular, but can in principle be used for any illumination arrangement which has at least a portion of the same homogeneous light emission intensity needed to be used.

Brief description of the figures

The invention will be explained in detail with reference to the figures shown in the drawing. Identical or corresponding elements in different figures are designated by like reference numerals. The figures and the elements shown in the figures are not to be considered as true to scale. Rather, individual elements for exaggerated understanding and / or better representability can be exaggerated. Show it: FIG. 1 shows a schematic plan view of a lighting device,

FIG. 2 shows a schematic plan view of another illumination device,

FIG. 3 shows a schematic cross section through the illumination device of FIG. 2,

4 shows a schematic plan view of an LC display with an array of illumination devices for backlighting and

FIG. 5 shows a schematic cross section through part of the LCD display of FIG. 4.

Detailed description of embodiments

FIG. 1 shows a plan view of a lighting device according to one exemplary embodiment. The lighting device 10 has a housing 15 which surrounds an interior 16. In the interior 16, in the exemplary embodiment shown, there are four semiconductor chips, namely three chips 12, 13, 14 suitable for emitting light and a chip 11 suitable for the detection of light. The chips or LED chips 12, 13, 14 suitable for emitting light are respectively suitable. To emit light at different wavelengths. By way of example, the semiconductor chip 12 is an LED which predominantly emits red light, semiconductor chip 13 an LED which predominantly emits green light, and semiconductor chip 14 an LED which emits predominantly blue light. LEDs for R, G and B allow all colors, including white light, to be mixed. It is also possible that other colors are generated by the respective LED chips.

The semiconductor chip 11 is a photodiode designed as a silicon detector, which is sensitive to the incidence of light and generates a dependent on the intensity of the incident light dependent electrical output signal.

All chips 11, ..., 14 are aligned along a line 17. Expediently, the sensor chip 11 is arranged between the G chip 13 and the B chip 14. Other arrangements in the order of the chips are also possible. For example, all of the R, G, B chips can be arranged one behind the other and the sensor chip 11 is located outside of the triple arrangement adjacent to the edge of the housing. In any case, in all cases the sensor chip 11 is arranged together with the light-emitting chips 12,..., 14 within the same interior 16 enclosed by the housing 15. It is also possible for the sensor chip 11 to be arranged with any other number of light-emitting semiconductor chips within the interior of a housing. These can be a single light-emitting semiconductor chip or two light-emitting semiconductor chips or more than three light-emitting semiconductor chips.

FIG. 2 shows a plan view of another illumination device, in which the four semiconductor chips are positioned within the space 16 enclosed by the housing 15 in a square arrangement. The semiconductor housing 15 has a recess with a round cross section, which encloses the space 16. Within the recess or space 16, the semiconductor chips are arranged near corners of a square 18. In particular, the focus of the respective semiconductor chips at the corners 181, 182, 183, 184 of the square 18 are arranged. The sensor chip 11 is located near the corner 184. The R, G, B chips 12, 13, 14 are located at the other corners of the square 18. In this embodiment, as compared to the embodiment of FIG of the sensor chip 11 to the LED chips 12, 13, 14 lower. The interior 16 of the housing is expediently filled with a potting compound. This provides good optical coupling between the elements. In addition, the potting compound protects against mechanical external influences. In other embodiments, the potting compound can also be omitted. Optionally, depending on the application, a lens body may also be provided, which is placed on the potting compound or on the housing base to bundle or expand the emitted light (not shown).

In operation, the LED chips 12, 13, 14 are supplied with supply voltage and emit light of the characteristic wavelength range for them. The emitted light is scattered, partially reflected by the side wall 161 of the reflective housing and radiated after passage through the potting compound. A portion of the emitted light is coupled into the sensor chip 11. The sensor chip 11, for example a photodiode, then generates an electrical output signal which depends on the received light intensity. The sensor chip 11 may be sensitive within a wide range of light wavelengths. If the semiconductor chip 11 is to receive only within a certain wavelength range, ie light of a specific color, the semiconductor chip 11 can be covered with a corresponding color filter material. FIG. 3 shows a cross section through the illumination device illustrated in FIG. 2 along the section line AA. The cross-section shows the reflective sidewalls 161 of the reflector 15. The sidewalls enclose a space 16 which is filled with potting compound 162. At the bottom of the recess 16 forming the space 16 in the housing, the B chip 14, that is to say the semiconductor body emitting in the blue spectral range, and the photosensitive photodetector 11 are shown in cross section. Both chips are connected to a common ground line 143 and otherwise have respective further signal terminals of another pole. Thus, the B-chip 14 is connected to the metallic signal line 141 via a bonding wire 142. Supply voltage is supplied via the line 141, so that the semiconductor chip 14 emits blue light during operation. The light emitted by the semiconductor chip 14 is emitted, for example, directly via the potting compound 162 to the outside. A portion of the light generated in the chip 14 is reflected by the side walls 161 and reaches the photodetector 11. The photodetector 11 is connected to a signal line 111 via a bonding wire 112. This signal line 111 leads from the inner space of the housing via the housing wall to the outside. The metallic lines 141, 111 are correspondingly shaped such that the illumination device 10 can be arranged and electrically connected to a circuit board by means of SMT (Surface Mount Technology). For this purpose, the housing has a rear side 162, which is designed so that the housing with its rear side 163 can be placed on the circuit board. The distal ends of the metal traces 141, 111 are also bent in the same plane. While the conductor track 141 serves to supply a supply voltage, the output signal generated by the semiconductor sensor 11 outside the housing 15 can be picked off via the conductor track 111. Beispiels- For example, line 111 is connected in an extension to a controller chip, such as a microprocessor.

FIG. 4 shows a plan view of a backlit LC display (LCD). The LCD shows a matrix arrangement of lighting devices of the kind previously described and illustrated in Figs. 2 and 3. Each of these lighting devices, e.g. B. 20, 21, 22, 23, serves to backlight a certain surface portion of the LCD. As is known, LEDs age differently and therefore emit light of varying intensity. In addition, the emitted light intensity varies with temperature. It is therefore necessary that as far as possible all illumination devices of the backlighting of the LCD be corrected, so that they emit as constant a light intensity and / or light as possible a constant color locus regardless of any deviation due to aging and / or temperature. This achieves a homogeneous backlighting.

By means of the illumination device described, the light intensity emitted by the respective LEDs present there can be individually determined by each sensor chip 11 of each illumination element 20, 21, 22, 23, and then a correction and corresponding activation for the respective LEDs take place in the connected control device 120. The evaluation and control algorithm, which the control device 120 handles, is designed in such a way that the feedback loop controls that all illumination devices 20, 21, 22, 23 emit the same light intensity and / or light with the same color location. The backlighting can be individually controlled, for example, depending on the image content displayed in the LCD. For example, brightly displayed image content is more strongly backlit, while dark image content is little backlit. This increases the image contrast. Since in this case individually controllable lighting elements 20, 21, 22, 23 are present in the backlighting of the LCD, it is necessary for them to radiate a reference light intensity which is as constant as possible.

Finally, FIG. 5 also shows a cross section through the LC display shown in FIG. 4 along the line B-B. Near the surface, so the outer environment 123 and in particular facing a viewer, there is the layer arrangement 121 of the liquid crystal display. Below this is an optical matching layer 122. The optical matching layer 122 serves, for example, to ensure homogeneous mixing of the light generated by the three LEDs of a respective lighting element 20, 21, so that, for example, homogeneous white light is generated. Below these are the lighting elements 20, 21.

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 lighting device comprising: - A housing with a housing (15) surrounded space (16); a semiconductor body (12, 13, 14) adapted to emit light in operation and disposed within the space (16); - A photosensitive sensor (11) which is disposed within the space (16) and is adapted to produce a signal dependent on the reception of light output. 2. Illumination device according to claim 1, wherein the semiconductor body (12, 13, 14) suitable for emitting light is a light-emitting semiconductor diode and the light-sensitive sensor (11) is a semiconductor photodiode. 3. Lighting device according to claim 1 or 2, wherein a plurality, preferably three, suitable for emitting light semiconductor body (12, 13, 14) in the space (16) are arranged, wherein the plurality of semiconductor bodies are adapted to emit light at each different wavelength ranges , 4. Lighting device according to one of claims 1 to 3, wherein the photosensitive sensor (11) is adapted to detect received light of a predetermined color. 5. Lighting device according to one of claims 1 to 4, wherein the photosensitive sensor (11) is connected to at least one electrical signal line (111) from the Space (16) through the housing (15) is guided in an outer region surrounding the housing, wherein the signal line (111) in the surrounding area has a connection for tapping the output signal generated by the sensor. 6. Lighting device according to one of claims 1 to 5, wherein the suitable for emitting light semiconductor body (12, 13, 14) and the photosensitive sensor (11) are optically coupled together. 7. Lighting device according to claim 6, wherein the semiconductor body (12, 13, 14) suitable for emitting light and the photosensitive sensor (11) are enclosed by a potting compound (162). 8. Lighting device according to one of claims 1 to 7, wherein at least three at different wavelength in operation for emitting light suitable semiconductor body (12, 13, 14) are provided, wherein each one of the at least three semiconductor body and the photosensitive sensor (11) are respectively positioned in the region of corners (181, 182, 183, 184) of an imaginary rectangle (18) in the space (16) surrounding the housing (15). 9. Lighting device according to one of claims 1 to 8, wherein at least three at different wavelength in operation for emitting light suitable semiconductor body (12, 13, 14) are provided, wherein the at least three semiconductor body and the photosensitive sensor (11) along a straight line (17) are aligned and in the housing (15) surrounding space (16) are arranged. 10. Display device comprising: - A first of the external environment (123) facing planar trained functional element (121), which is adapted to visually represent supplied information, and - At least one of the external environment (123) facing away and the functional element (121) backlit lighting device (20, 21) according to one of claims 1 to 9. 11. A display device according to claim 10, further comprising: - A control device (120), by which the brightness of the emitted from the semiconductor bodies (12, 13, 14) in operation light is adjusted in response to the arranged in the same housing photosensitive sensor (11) and the control device (120) supplied signal , 12. A method for operating a lighting device according to one of claims 1 to 9, comprising the steps: Applying a supply voltage to the semiconductor body (12, 13, 14) suitable for emitting light and emitting light, Receiving at least a portion of the radiated light through the light-sensitive sensor (11) arranged in the same space (16) surrounded by the housing (15) as the semiconductor body (12, 13, 14), Generating an output signal as a function of the light received in the sensor (11) and outputting the output signal outside the housing (15) of the illumination device, and - Driving the semiconductor body (12, 13, 14) of the illumination device in dependence on the output signal output. 13. A method for operating a display device according to claim 10 or 11, comprising the steps: Emitting light through the semiconductor body (12, 13, 14) in a plurality of existing illumination devices, Receiving at least a portion of the radiated light through the photosensitive sensors (11) arranged in each case in the same housing (15) as the semiconductor body, Generating respective output signals by the sensors (11) and supplying to a control device (120), - Driving the semiconductor body (12, 13, 14) of the plurality of lighting devices differently, so that all of the plurality of lighting devices radiate an independent of aging and / or temperature the same light intensity.