Patent Application
20160076731
The present invention relates to an optical arrangement and a display device.
Modern display devices such as displays are often based on an arrangement of a multiplicity of picture elements or pixels. The resolution of such displays depends to a first approximation on the size of the picture elements themselves. Light-emitting chips on the basis of light-emitting diodes or LEDs can be used for producing high-resolution displays. A multiplicity of small light-emitting LED chips in the three primary colors such as red, green, blue (RGB) have to be assembled for displaying colors. Approximately 6 million chips are required in the case of HDTV (high-definition television). This approach has various disadvantages. Firstly, placing and contacting a multiplicity of small chips require a not insubstantial amount of time and technical outlay. Furthermore, the efficiency and area use of small chips are reduced by area losses during the production process, for example, by separation and contacting. Finally, small chips are more susceptible to small current problems than larger chips.
Alternatively, use can be made of pixilated LED chips having one primary color, usually blue, and the pixels thereof can alternately be provided with suitable conversion elements for other colors such as green and red. In addition to the lack of highly efficient and stable red converters, it is the necessary thickness of the conversion elements of approximately 100 μm in particular that constitutes a geometric limitation of the realizable minimal pixel dimensions.
Embodiments of the present invention provide an optical arrangement and a display device that is producible by way of a simpler process and that can provide a high resolution.
In one embodiment, an optical arrangement comprises a multiplicity of light-emitting chips on a carrier. The optical arrangement comprises first light-emitting chips which each have a plurality of pixels of a first group. Furthermore, the arrangement comprises second light-emitting chips, which each have a plurality of pixels of a second group. Furthermore, in each case one of the first light-emitting chips and one of the second light-emitting chips are arranged in a first unit cell in an areal manner on the carrier. The optical arrangement moreover comprises an optical element, which is disposed downstream of the light-emitting chips in the emission direction.
The optical element is configured to combine light emitted by the pixels of the first and second group in second unit cells in a decoupling plane in such a way that at least one second unit cell has an area that is smaller than the area of respectively one of the first unit cells. It is furthermore possible for each second unit cell to have an area that is smaller than the area of respectively one of the first unit cells. By way of example, the optical arrangement comprises a first unit cell and at least two second unit cells, wherein the second unit cells each have an area that is smaller than the area of the first unit cell.
By way of example, the carrier is manufactured from ceramic material and comprises electrical connections in order to be able to connect the optical arrangement to a controller. Here, preferably, the pixels of the first group are configured to emit light with a first wavelength while the pixels of the second group are configured to emit light with a different wavelength. By way of example, the pixels of the first group emit red light while the pixels of the second group emit green light, or vice versa. However, it is also possible for the pixels of the first group or the pixels of the second group to emit blue light. The individual pixels, which are also referred to as picture elements, are preferably implemented using light-emitting diodes. The optical element preferably comprises optical components such as lenses, in particular Fresnel lenses, gratings or binary diffractive elements.
The term “unit cell” relates to the arrangement of the light-emitting chips or to the luminous areas, ordered to form groups, of the individual light-emitting chips. One or more light-emitting chips with pixels of the first group and one or more light-emitting chips with pixels of the second group are respectively arranged within the first unit cells, wherein, preferably, the number and/or arrangement of the respective chips are the same in the first unit cell. Pixels of one group are preferably adjacent to one another. Furthermore, they are preferably similar to one another within the meaning of pixels of one group having the same peak or dominant wavelength or emitting in the same spectral range or being of the same manufactured type. Production-dependent deviations, such as different emission intensities, may occur. A light-emitting chip with a group of pixels is adjacent to a further light-emitting chip with a further, preferably different, group of pixels. In particular, the smallest unit of adjacent light-emitting chips that can be used to describe the optical element forms a first unit cell within the meaning of this application. Furthermore, the phrase “areal arrangement on the carrier” should be understood to mean that the light-emitting chips can be arranged both next to one another, for example, in one row, and also in the style of a matrix.
The second unit cells are defined in the decoupling plane. They comprise the light, guided by the optical element, from the pixels of different groups. In particular, a second unit cell is the smallest unit of adjacent pixels in the decoupling plane that can be used to describe the light redistribution in the decoupling plane.
A simplified production method is possible by using light-emitting chips with in each case groups of similar light-emitting picture elements or pixels. Similar groups of pixels are combined in the respective light-emitting chip. This is advantageous for the production because it is possible to dispense with a filter arrangement with different color filters, for example, in the style of a Bayer matrix, or with converters assigned to the individual pixels. This makes the production method not only simpler but also more cost-effective.
A high resolution of the whole optical arrangement is obtained by using the optical element since light from pixels of different groups is combined in each case in the second unit cells, even though the light-emitting chips with groups of similar pixels are respectively adjacent to one another in the first unit cells. In particular, the resolution is not restricted by the size of the light-emitting chips, for example, by the edge length thereof. Rather, the achievable resolution depends on the size of the pixels themselves, the emitted light of which is redistributed by the optical element.
The redistribution leads to light with different wavelengths being combined in the second unit cells and these unit cells having a smaller area than the first unit cells which are substantially formed by the light-emitting chips with groups of similar pixels. Thus, the optical arrangement redistributes the light emitted by the chips in such a way that the resulting second unit cells (consisting of pixels) are smaller than the first unit cells (consisting of chips). In other words, the optical arrangement can deflect and moreover focus the light emitted by the chips. By way of example, the second unit cells of the pixels have an edge length that is smaller than that of the first unit cells by a factor of 4. As a result, advantages emerge for the design of directly emitting RGB displays.
According to a further embodiment, third light-emitting chips are arranged in an areal manner on the carrier and respectively have a plurality of pixels of a third group. The first unit cell now comprises respectively one of the first, the second and the third light-emitting chips.
The pixels of the third group can emit light with a wavelength that respectively differs from the wavelength of the light emitted by the pixels of the first group and of the light emitted by the pixels of the second group. In particular, the pixels of the first, the second and the third group can emit light that in each case has a different spectral color than the light of the pixels of the other two groups. By way of example, pixels of one group therefore produce red light, pixels of a further group produce green light and pixels of the last group produce blue light. The first, the second and the third light-emitting chips therefore produce light with three different colors.
Here, the optical element is configured to combine light emitted by the pixels of the first, second and third group in such a way in second unit cells in the decoupling plane that at least one second unit cell has an area that is smaller than the area of respectively one of the first unit cells.
By using third light-emitting chips with a third group of pixels it is possible to display more colors using the optical arrangement. By way of example, this provides a basic configuration for displaying a specific color model. By way of example, the pixels of the first, second and third group can be assigned to the primary colors red, green and blue of the RGB color model. The optical element is then able to provide second unit cells which have three primary colors and therefore, for example, have all RGB primary colors.
According to a further embodiment, a first light-emitting chip, a second light-emitting chip and a third light-emitting chip are in each case arranged laterally or in a matrix arrangement next to one another on the carrier.
According to a further embodiment, at least fourth light-emitting chips are arranged on the carrier in an areal manner and each have a plurality of pixels of at least one fourth group. In this case, the first unit cell comprises respectively one of the first light-emitting chips, the second light-emitting chips, the third light-emitting chips and at least one fourth light-emitting chip. By way of example, the pixels of the fourth group can emit green light.
Here, the optical element is configured to combine light emitted by the pixels of the first, second, third and at least fourth group in second unit cells in the decoupling plane in such a way that at least one second unit cell has an area that is smaller than the area of respectively one of the first unit cells.
The use of at least fourth light-emitting chips constitutes a development of the previously presented arrangement on the basis of two or three different light-emitting chips. Here, what is possible is that a fourth color is respectively assigned to the pixels of the fourth group such that the optical arrangement can display a color model on the basis of four primary colors. However, it is also possible that two of the total of four light-emitting chips or their respective groups of pixels emit the same wavelength and thus, for example, are able to represent a Bayer matrix with the colors red, two times green and blue. Other assignments are likewise possible, just like fifth light-emitting chips with in each case a plurality of pixels of a fifth group, etc.
According to a further embodiment, at least one of the first unit cells has a multiplicity of first or second light-emitting chips.
According to a further embodiment, the carrier has a flat or curved surface. In this manner, the optical arrangement can be used in a plane, for example, as a luminous surface or display. However, it is likewise possible for the arrangement to be embodied in accordance with a three-dimensional form by means of a curved carrier.
In accordance with a further embodiment, the first, second, third and/or fourth light-emitting chips are arranged in a regular two-dimensional lattice on the carrier. In particular, the regular two-dimensional lattice can be periodic or quasi-periodic.
By way of example, the lattice emerges from periodic or quasi-periodic repetition of the arrangement of light-emitting chips, defined in the first unit cells, on the carrier. Preferably, the repetition is defined by translation in two different directions along the face of the carrier. What also emerges thus as a result of the embodiment of the optical element is a repeating lattice in the decoupling plane on the basis of the second unit cells.
According to a further embodiment, the regular two-dimensional lattice has a quadratic, a hexagonal or a quasi-crystalline lattice.
Here, it is possible to arrange the light-emitting chips in accordance with the two-dimensional lattice in the form of squares, hexagonal or quasi-crystalline lattices. By way of example, if the target application is a curved, areal direct display, correspondingly curved chip arrangements can be considered, just like a two-dimensional lattice in the style of pentagons and hexagons is suitable, for example, for building up a sphere-shaped football.
Furthermore, it is conceivable that the respective groups of pixels of the light-emitting chips are arranged in the form of a quadratic, a hexagonal or a quasi-crystalline pattern. The respective two-dimensional lattices can then be realized in such a way that the respective light-emitting chips are arranged adjacent to one another at the outer edges thereof or directly adjoining one another, and hence form the two-dimensional lattice in the form of a square, a hexagon or, in general, a polygonal form.
A regular lattice can be constructed by periodic repetition of the unit cell in the three spatial directions and therefore only has 2-fold, 3-fold, 4-fold and 6-fold symmetries. However, a double unit cell (or unit cell of higher order) can also be repeated in a non-periodic manner and denotes a quasi-crystalline lattice within the meaning of this application. An example is, for example, a so-called Penrose lattice.
In a further embodiment, further light-emitting chips are arranged in an areal, in particular plane, manner on the carrier and respectively comprise a further group of pixels. The first unit cells then respectively comprise one of the first, the second, the third, the fourth and the further light-emitting chips, for example, fifth light-emitting chips with in each case a plurality of pixels of a fifth group.
Then, the optical element is configured to combine light emitted by the pixels of the first, second, third, fourth and the further group in such a way in second unit cells in the decoupling plane that at least one second unit cell has an area that is smaller than the area of respectively one of the first unit cells. Furthermore, each second unit cell can have an area that is less than the area of respectively one of the first unit cells.
The use of further light-emitting chips and further groups of pixels thus, as it were, constitutes a generalization of the principle of the optical arrangement present. Using this, it is possible in a flexible manner to combine light-emitting chips with different light-emitting pixels to form a relatively large arrangement.
According to a further embodiment, the hybrid made of carrier, light-emitting chips and optical element is integrated. In this case, a component with component parts that are already aligned in relation to one another during the production and are consequently secured against adjustment emerges within the scope of producing the optical arrangement. Alternatively, it is possible for the carrier to be equipped with the light-emitting chips and the optical element. In this case, the optical arrangement is modular and the individual components can be produced separately from one another. Thus, it is possible, for example, to produce the optical arrangement on the basis of a wafer. Preferably, a light-emitting wafer and a micro-optics wafer, which comprises the optical element, are produced separately and then connected.
According to a further embodiment, the optical element comprises an arrangement of micro-lenses. Here, the micro-lenses are configured to collimate divergent radiation beams of the light emitted by the light-emitting chips. Moreover, it is possible to merge parallel radiation beams. Thus, beam guidance is realized with the aid of the micro-lenses such that light from the respective pixels of the light-emitting chips is guided into the second unit cells.
According to a further exemplary embodiment, the optical element comprises a prism arrangement. Here, the prism arrangement is configured to guide and/or deflect light.
With the aid of the prism arrangement there is a redistribution of the light from the respective groups of pixels in the different light-emitting chips from the first unit cells to the second unit cells. The prism arrangement can be embodied in such a way that the angle of inclination and the alignment of the individual prisms are different in each case for different pixels.
In a further embodiment, the micro-lens arrangement and the prism arrangement are integrated monolithically in the optical element.
According to a further embodiment, the micro-lens arrangement and the prism arrangement are embodied as separate elements.
According to a further embodiment, the pixels arranged on the carrier can each be actuated separately. In particular, the intensity of the light emitted in each case by an actuated pixel is adjustable.
In this manner, it is possible to realize, e.g., a display such as an LED direct display, i.e., a display without an LCD imager. Otherwise, an imaging element, e.g., an LCD, must be disposed downstream for displays with LEDs having homogeneously luminous pixels. Inter alia, an advantage thereof is a comparatively higher resolution.
According to a further embodiment, the pixels arranged on the carrier are configured to emit light in accordance with a color model standard. In particular, the color model standard can comprise an RGB or RGBY color model.
According to one embodiment, a display device comprises an optical arrangement as shown above. Moreover, the display device comprises a controller for actuating the pixels arranged on the carrier.
The multiplicity of light-emitting chips can be arranged on a carrier with suitable dimensions. Here, the first unit cell constitutes the smallest unit. In this manner, the optical arrangement can be combined to form, and operated as, a display device such as a screen, television or monitor. In the case of a given resolution, e.g., for an HDTV (high definition television) display, a display device of the proposed type, which has pixelated chips and the above-described optical element, requires significantly fewer chips than a comparable display device made of small individual chips.
Below, the invention will be explained in more detail using a plurality of exemplary embodiments on the basis of figures. To the extent that parts or components have a corresponding function, the description thereof will not be repeated in each one of the following figures.
In detail:
The system carrier 1 and the pixelated light-emitting chips 2 can be a monolithic component. Alternatively, the system carrier can be manufactured separately and subsequently be equipped with the individual chips. Electrical wiring and details of the design and the corresponding components such as, e.g., adhesives, solder, solder pads, bond wires and the like are not shown in the drawing. The pixels of the individual chips typically have a diameter Wp in the region of 50 μm and are arranged in a pixel grid of 20 to 30 μm in relation to one another. The chips have an edge length Λc of the order of 1000 μm.
Disposed downstream of the light-emitting chips in the emission direction is an array of micro-lenses 3, followed by a prism array 4, a further prism array 5 and a further micro-lens array 6. These optical components form an optical element for collimating and guiding the light emitted by the pixels of the different groups. Alternatively, or in a complementary manner, use can also be made of gratings, holographic elements, Fresnel lenses and binary diffractive elements instead of the micro-lenses and/or prisms. Furthermore, a decoupling plane 7 (which is also denoted an evaluation plane) is shown and it, as will be shown below, corresponds to a new light source with emission surfaces redistributed in a pixel-by-pixel manner.
Further details of the optical element are not shown in
During operation of the optical arrangement, which is shown in section with three pixelated light-emitting chips with the groups 21, 22 and 23 in this
On the micro-lens array 3 the individual beams in each case impact on corresponding micro-lenses 3 disposed downstream of the individual pixels. These micro-lenses 3 collimate the light of the individual pixels, which light was emitted in a divergent manner in each case by said pixels. The individual light beams now fall in a collimated, preferably parallel, manner on the prism array 4 arranged downstream, with this element deflecting the collimated light by a predetermined angle. The respective angle can be different from pixel to pixel. However, the angles are selected in such a way that, subsequently, the respective deflected light beams are deflected to the second prism array 5 and, there, are deflected parallel back to a normal of the array 5. Additionally, the second micro-lens array 6 is situated in such a position that the light beams previously deflected by the first and second prism arrays 4, 5 can be registered and focused on the decoupling plane 7 which is disposed downstream. To this end, the position of individual lenses in the second micro-lens array 6 is likewise adapted to the deflection angles of the light beams previously deflected by the prism arrays 4, 5.
Therefore, there is a redistribution of the light beams, emitted by the pixels of the light-emitting chips, in the decoupling plane 7 by way of the micro-lens arrays 3, 6 and the prism arrays 4, 5 such that, as indicated by dashed lines in the drawing, three colors are respectively adjacent to one another in a second unit cell E2 as redistributed pixels 21′, 22′ and 23′. In other words, the redistribution caused by the optical element allows an increase in the resolution of the optical arrangement to be obtained.
In
In a similar manner, as shown schematically in
The embodiment of the micro-lens arrays 3, 6 and of the prism arrays 4, 5 is similar to the embodiments in accordance with
The diameter of the micro-lenses is preferably no less than 50 μm so that the optical properties thereof are substantially refractive. It is advantageous for the angle deflection by the prism arrays to be small, for example, less than 30°, preferably less than 15°, particularly preferably less than 10°. This is the case if the light emitted by a pixel on the chip is only deflected to an adjacent pixel in the decoupling plane 7 in a top view.
The shown optical arrangement redistributes the light emitted by the light-emitting chips, e.g., LED chips, in such a way that the resultant second unit cells E2, which have the pixel groups 21, 22, 23, are smaller than the first unit cells E1, which are defined by the chip arrangement itself. In
Lattice constant chip/lattice constant pixel=(Λc/Λp)=5
Area chip/area pixel=(Λc/Λp)2=25.
In the case of a given resolution (e.g., for HDTV), a direct LED display made of pixelated chips and with the described optical arrangement requires 25 times fewer chips than a direct LED display made of small individual chips.
The invention is not restricted by the description on the basis of the exemplary embodiments. Rather, the invention comprises each new feature and each combination of features; this, in particular, includes every combination of features in the patent claims, even if this feature or this combination itself is not explicitly specified in the patent claims or in the exemplary embodiments.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2013 104 046.2 | Apr 2013 | DE | national |
This patent application is a national phase filing under section 371 of PCT/EP2014/057644, filed Apr. 15, 2014, which claims the priority of German patent application 10 2013 104 046.2, filed Apr. 22, 2013, each of which is incorporated herein by reference in its entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2014/057644 | 4/15/2014 | WO | 00 |
