Uniform color illuminating device

Abstract

An illumination device (21) is described comprising a light guide (12) and an LED package (1) having two or more spatially separated LED chips (2, 3, 4). The LED package (1) generates two or more light outputs on two or more separate wavelengths which are optically coupled into the light guide (12). A portion of the two or more light outputs exit the light guide (12) via a light output surface (14). A wavelength dependent modification feature (22) is arranged to modify the intensity of at least one of the two or more light outputs to provide a uniform colour light output to the illumination device (21). The LED package (1) can comprise an RGB LED package and the wavelength dependent modification feature (22) is arranged to provide a uniform white light output. This provides an illumination device (21) capable of providing a low intensity light level over a large surface area which is thinner and less expensive to manufacture than those known in the art.

Description

[0001] This invention relates to the field of lighting, and more particularly to a homogeneous color lighting device that can be used for lighting, backlighting, signage, or display purposes. The described homogeneous color lighting device has been particularly well-received in the transportation sector, such as the automotive, railway, and aerospace industries. Background of the Invention

[0003] Lighting is a key means of making the interior spaces of vehicles—where passengers stand or sit during transport—more attractive and comfortable. One of the most effective ways to deliver light to these environments while saving space is to backlight the interior surfaces of vehicles. This requires providing a uniform, low-intensity level of light over large surface areas. This uniform, low-intensity light level is necessary to minimize glare experienced by passengers while transporting inside the vehicle, while also providing an attractive decorative and illuminating means for the interior surfaces.

[0004] Due to space and weight constraints within vehicles, any light source solution must be very thin, approximately 1 mm. Furthermore, due to vibration and integration limitations, the lighting device must also be able to be mechanically attached, bonded, connected, or molded to the interior surfaces of the vehicle.

[0005] There are many light source technologies that can be used in the transportation sector. Two such examples are electroluminescent thin films and organic light-emitting diodes (OLEDs). Both solutions involve active light-emitting materials that cover the entire surface for backlighting. However, both technologies are expensive and have low reliability and lifespan, making them unsuitable as comprehensive solutions for transportation interiors.

[0006] Inorganic light-emitting diodes (LEDs) are the most commonly used lighting technology in transportation lighting. LEDs are small, solid-state, semiconductor chip-based devices that can be designed to emit different colors of light, or, when combined with color-converting materials, provide white light. However, LEDs are small points of light, so external optical systems are needed to transform them into large-area, uniformly colored, and uniformly intense lighting surfaces.

[0007] Typically, multi-color or variable-color LEDs consist of two or more inorganic LED chips integrated within a single electronic package. However, the most common multi-chip LED package is the so-called RGB LED package, one type of which is schematically represented in Figure 1(a) and generally described by reference numeral 1. As can be seen, the RGB LED package 1 comprises a red LED chip 2, a green LED chip 3, and a blue LED chip 4, all mounted on the common surface 5 of the surface mount package lead frame 6. A transparent housing 7 covers the three individual chips 2, 3, and 4 to provide them with a physical protective barrier. Therefore, the RGB LED package 1 is designed to emit light generated by the three individual chips 2, 3, and 4 from all five surfaces that are not in contact with the PCB 6.

[0008] Figure 1(b) provides a schematic representation of a second type of RGB LED package known in the art, and is generally depicted with reference numeral 8. As can be seen, the RGB LED package 8 includes a red LED chip 2, a green LED chip 3, and a blue LED chip 4, all again mounted on the common surface 5 of the surface mount package lead frame 6. A transparent housing 9 again covers the three individual chips 2, 3, and 4 to provide them with a physical protective barrier. However, in this embodiment, the transparent housing 9 is transparent only on one surface 10 (i.e., the side opposite the common surface 5 of the lead frame 6). Therefore, the RGB LED package 8 is designed to emit light generated by the three individual chips 2, 3, and 4 from only one surface 10.

[0009] A known configuration for optical systems used to achieve large-area, uniformly tinted, and uniformly intensified illuminated surfaces involves deploying RGB LED packages 1 and 8 in a 2D matrix on a printed circuit board (PCB), with a diffuser layer placed on top of the 2D matrix. This is traditionally known as direct-illuminated LED backlighting. The advantage of the direct-illuminated LED backlighting method is that each RGB LED package 1 and 8 is independently addressable, thus allowing for pixelated area light sources. However, such systems either require very tight packing of the RGB LED packages 1 and 8, resulting in high power density and high cost per unit area, or require very thick optical systems (e.g., air gaps and / or diffuser thickness), making them unsuitable for deployment within limited internal transport space. For example, if the RGB LED packages 1 and 8 are spaced 20 mm apart, an optical system depth greater than 20 mm is required.

[0010] It is also known in the art to use light guides to distribute light from a light source (e.g., RGB LED packages 1 and 8) to areas requiring illumination. One known type of light guide is an optical fiber, which is typically composed of a transparent material (glass or plastic) with filaments capable of transmitting light. Another known type of light guide is a planar light guide. These are plate or panel light guides, which are typically formed as thin cuboids.

[0011] Both light guide designs utilize the refractive effect caused by two materials with different refractive indices. Specifically, the light guide transmits light from one location to another by utilizing the total internal reflection effect experienced by light propagating within the material when it encounters the boundary surrounding the material. Another useful characteristic of the aforementioned light guides is their ability to capture the intensity of light output from RGB LED packages 1 and 8 and diffuse it uniformly, as well as, or modify its shape or distribution to achieve desired results.

[0012] The aforementioned light guide method has been further developed to attempt to meet the spatial constraints of backlighting in the transportation field. One approach is to distribute RGB LED packages 1 and 8 in a 2D matrix on a planar light guide, and then optically couple the light emitted from the RGB LED packages 1 and 8 into the planar light guide. Figure 2 and Figure 3 An example of such a system is presented. Specifically, Figure 2 A two-dimensional cross-sectional side view of a lighting device 11 is presented, the lighting device 11 including a cavity 13 (for simplicity, Figure 2 The planar light guide 12 (only one cavity is shown in the diagram) is located inside the cavity 13, and the RGB LED package 1 is located inside the cavity 13. Figure 3 Presented Figure 2 The diagram shows a planar view of the lighting device 11. Light extraction features (not shown) inside or on the surface of the planar light guide 12 are then used to provide a means for light to exit the light guide structure via the light output surface 14. The design of the light extraction features (variations in size, density, etc.) again provides a means for increasing the intensity uniformity of the backlight on the surface material of the light output surface 14.

[0013] However, it is known in the art that the spatial separation of chips 2, 3, and 4 in RGB LED packages 1 and 8 results in an optical system designed around such RGB LED packages 1 and 8 effectively having three separate colored light sources located at different positions, typically separated by a scale of several hundred micrometers. This arrangement leads to non-uniform coloring effects within the optical system, particularly when viewed close to the RGB LED packages 1 and 8.

[0014] Reference Figure 2 and Figure 3 The lighting device 11 shown further describes the problematic features in detail. From Figure 2As can be seen, the red light emitted from the red LED chip 2 and the blue light emitted from the blue LED chip 4 converge at a common point 17 on the light output surface 14. The optical path length of the blue light 16 is greater than that of the red light 15. Due to the inverse square law of irradiance, at point 17, the amount of light from the blue LED chip 4 will be less than the amount of light from the red LED chip 2.

[0015] The overall result is the formation of three separate regions on the light output surface 14, such as Figure 3 As shown, that is: red region 18, in which the irradiance generated by red LED chip 2 will be higher than the irradiance generated by green LED chip 3 or blue LED chip 4; green region 19, in which the irradiance generated by green LED chip 3 will be higher than the irradiance generated by red LED chip 2 or blue LED chip 4; and blue region 20, in which the irradiance generated by blue LED chip 4 will be higher than the irradiance generated by red LED chip 2 or green LED chip 3.

[0016] Due to the spatial separation of chips 2, 3, and 4 in RGB LED packages 1 and 8, color variations exist on the light output surface 14. Specifically, when all the differently colored chips 2, 3, and 4 are powered, the separated red, green, and blue light sources cause slightly different areas of white. Therefore, when observed close to RGB LED packages 1 and 8, the emitted light from the illuminator 11 results in a visible non-uniform coloring effect.

[0017] Refractive optical systems, with their relatively long optical path lengths, and the use of light guides and fiber optic mats, can eliminate this problem of non-uniform coloring. For lamps based on these types of RGB LED packages 1 and 8, a known solution to this problem is to incorporate projection optics, which must be carefully designed to avoid noticeable separation of red, green, and blue light on the surface where the output light is projected. This typically requires a very complex refractive color mixing optical system. The use of diffuser layers is also known to mitigate the problematic non-uniform coloring effect. However, if the thickness of the diffuser layer is reduced to a level required for use in the transportation field, each of the RGB LED packages 1 and 8 begins to exhibit the aforementioned non-uniform coloring effect again within its emitted light.

[0018] Therefore, in the area surrounding RGB LED packages 1 and 8, especially within the 2D LED matrix array coupled to the light guide plate, this non-uniform coloring effect remains a significant problem.

[0019] Another challenge with multi-chip LED packages is achieving color uniformity directly above the LED package. In the past, filters or absorbing materials were used to reduce light intensity in these areas. However, such solutions result in visible inhomogeneities in the spatial positioning of the multi-chip light source within the LED package and in any color compensation features. Invention Overview

[0021] Therefore, the object of embodiments of the present invention is to provide an alternative lighting device that provides uniform color light output.

[0022] Another object of the present invention is to provide a lighting device that provides a thinner uniform color light output than those lighting devices known in the art.

[0023] According to a first aspect of the invention, a lighting device is provided, the lighting device comprising a light guide and one or more LED packages having two or more spatially separated LED chips that generate two or more light outputs at two or more individual wavelengths.

[0024] Two or more optical outputs are optically coupled into the light guide, and a portion of the two or more optical outputs exits the light guide via the optical output surface.

[0025] The light guide also includes one or more wavelength-dependent modification features arranged to modify the intensity of at least one of two or more light outputs to provide an illumination device with uniform color light output.

[0026] Optionally, one or more wavelength-dependent modification features are located on the optical output surface. Alternatively, one or more wavelength-dependent modification features are located within the light guide.

[0027] Optionally, the light guide includes a planar light guide having one or more cavities for accommodating one or more LED packages.

[0028] Alternatively, the LED package can be optically coupled to a cavity-free planar light guide by other methods known in the art, such as directly embedding it inside the light guide material or having additional coupling optical features on the surface.

[0029] Optionally, the lighting device also includes a diffuser and an opaque mask located between one or more LED packages and the diffuser, wherein the opaque mask includes one or more holes. The one or more holes effectively form a mixed light source, but at an intensity level much lower than that generated by the LED packages themselves. The diffuser is then used to break the angle dependence of different colors from the individual LED chips, thereby producing output light from the lighting device comprising a uniform, average mixed light.

[0030] Optionally, one or more LED packages include RGB LED packages having red LED chips, green LED chips, and blue LED chips that emit light from five surfaces of the package.

[0031] In this embodiment, one of the wavelength-dependent modification features may be cyan and arranged closer to the red LED chip than either the green or blue LED chip. Preferably, the cyan wavelength-dependent modification feature is equidistant from the green and blue LED chips. As a result of this arrangement, uniform color light output is provided from the light output surface 14 near the red LED chip.

[0032] In this embodiment, one of the wavelength-dependent modification features may be magenta and is arranged closer to the green LED chip than either the red or blue LED chip. Preferably, the magenta wavelength-dependent modification feature is equidistant from the red and blue LED chips. As a result of this arrangement, uniform color light output is provided from the light output surface near the green LED chip.

[0033] In this embodiment, one of the wavelength-dependent modification features may be yellow and arranged closer to the blue LED chip than either the red or green LED chip. Preferably, the yellow wavelength-dependent modification feature is equidistant from the red and green LED chips. As a result of this arrangement, uniform color light output is provided from the light output surface near the blue LED chip.

[0034] Alternatively, one or more LED packages may include RGB LED packages having red LED chips, green LED chips, and blue LED chips that emit light from a single surface of the package.

[0035] In this embodiment, one of the wavelength-dependent modification features may be cyan and arranged further away from the red LED chip than either the green or blue LED chip. Preferably, the cyan wavelength-dependent modification feature is equidistant from the green and blue LED chips. As a result of this arrangement, uniform color light output is provided from the light output surface near the red LED chip.

[0036] In this embodiment, one of the wavelength-dependent modification features may be magenta and arranged further away from the green LED chip than either the red or blue LED chip. Preferably, the magenta wavelength-dependent modification feature is equidistant from both the red and blue LED chips. As a result of this arrangement, uniform color light output is provided from the light output surface near the green LED chip.

[0037] In this embodiment, one of the wavelength-dependent modification features may be yellow and arranged further away from the blue LED chip than either the red or green LED chip. Preferably, the yellow wavelength-dependent modification feature is equidistant from the red and green LED chips. As a result of this arrangement, uniform color light output is provided from the light output surface near the blue LED chip.

[0038] Most preferably, one or more wavelength-dependent modification features include ink, dye, or pigment. The wavelength-dependent modification features may be inherently uniform or patterned.

[0039] According to a second aspect of the invention, a lighting device is provided, comprising one or more LED packages, a diffuser, and an opaque mask located between one or more LED packages and the diffuser, wherein the opaque mask includes one or more apertures. The one or more apertures effectively form a mixed light source, but at an intensity level much lower than that generated by the LED packages themselves. The diffuser is then used to break the angle dependence of different colors from the individual LED chips, thereby generating output light from the lighting device comprising uniform, average-mixed light.

[0040] Embodiments of the second aspect of the present invention may include one or more features of the first aspect of the present invention or embodiments thereof, and vice versa.

[0041] According to a third aspect of the present invention, a method for generating uniform color light output is provided, the method comprising:

[0042] Optically couple two or more spatially separated optical outputs at two or more individual wavelengths into an optical guide;

[0043] Arrange a portion of two or more optical outputs to exit the light guide via the optical output surface; and

[0044] An optical guide is provided having one or more wavelength-dependent modification features, which are arranged to modify the intensity of at least one of two or more optical outputs.

[0045] Optionally, one or more wavelength-dependent modification features are provided on the optical output surface. Alternatively, one or more wavelength-dependent modification features are provided within the light guide.

[0046] Methods for generating uniform color light output may also include:

[0047] Provides a diffuser and an opaque mask, wherein the opaque mask is located between two or more spatially separated light outputs and the diffuser; and

[0048] Provide an opaque mask with one or more holes.

[0049] Preferably, optically coupling two or more spatially separated light outputs includes optically coupling a red light output, a green light output, and a blue light output into a light guide.

[0050] In this embodiment, providing a light guide with one or more wavelength-dependent modification features may include providing a cyan wavelength-dependent modification feature that is closer to the red light output than either the green or blue light output. Preferably, the cyan wavelength-dependent modification feature is provided equidistant from the green and blue light outputs.

[0051] In this embodiment, providing a light guide with one or more wavelength-dependent modification features may include providing a magenta-colored wavelength-dependent modification feature that is closer to the green light output than either the red or blue light output. Preferably, the magenta-colored wavelength-dependent modification feature is provided equidistant from the red and blue light outputs.

[0052] In this embodiment, providing a light guide with one or more wavelength-dependent modification features may include providing a yellow wavelength-dependent modification feature that is closer to the blue light output than either the red or green light output. Preferably, the yellow wavelength-dependent modification feature is provided equidistant from the red and green light outputs.

[0053] In an alternative embodiment, providing a light guide with one or more wavelength-dependent modification features may include providing a cyan wavelength-dependent modification feature that is further away from the red light output than either the green or blue light output. Preferably, the cyan wavelength-dependent modification feature is provided equidistant from the green and blue light outputs.

[0054] In this alternative embodiment, providing a light guide with one or more wavelength-dependent modification features may include providing a magenta-colored wavelength-dependent modification feature that is further away from the green light output than either the red or blue light output. Preferably, the magenta-colored wavelength-dependent modification feature is provided equidistant from the red and blue light outputs.

[0055] In this alternative embodiment, providing a light guide with one or more wavelength-dependent modification features may include providing a yellow wavelength-dependent modification feature that is further away from the blue light output than either the red or green light output. Preferably, the yellow wavelength-dependent modification feature is provided equidistant from the red and green light outputs.

[0056] Embodiments of the third aspect of the present invention may include one or more features of the first aspect or the second aspect or embodiments thereof, or vice versa.

[0057] According to a fourth aspect of the present invention, a method for generating uniform color light output is provided, the method comprising:

[0058] This allows two or more spatially separated light outputs at two or more individual wavelengths to propagate through a diffuser.

[0059] Provide an opaque mask between two or more spatially separated light outputs and diffusers; and

[0060] Provide an opaque mask with one or more holes.

[0061] Embodiments of the fourth aspect of the present invention may include one or more features of the first to third aspects or embodiments thereof, or vice versa. Brief description of the attached diagram

[0063] Various embodiments of the invention will now be described by way of example only with reference to the accompanying drawings, in which:

[0064] Figure 1(a) presents a schematic representation of a first type of RGB LED package known in the art, while Figure 1(b) presents a schematic representation of a second type of RGB LED package known in the art.

[0065] Figure 2 A two-dimensional cross-sectional side view of a lighting device known in the art is presented.

[0066] Figure 3 Presented Figure 2 The diagram shows a plan view of the lighting device.

[0067] Figure 4 A two-dimensional cross-sectional side view of a lighting device according to an embodiment of the present invention is presented.

[0068] Figure 5 Presented Figure 4 The diagram shows a plan view of the lighting device.

[0069] Figure 6 A two-dimensional cross-sectional side view of a lighting device according to an alternative embodiment of the present invention is presented.

[0070] Figure 7 Presented Figure 6 The diagram shows a plan view of the lighting device.

[0071] Figure 8 A two-dimensional cross-sectional side view of a lighting device according to another alternative embodiment of the present invention is presented.

[0072] In the following description, similar parts are labeled with the same reference numerals throughout the specification and drawings. The drawings are not necessarily drawn to scale, and some parts have been exaggerated to better illustrate the details and features of embodiments of the invention.

[0073] Detailed Description of Preferred Embodiments

[0074] Figure 4 The image presents a two-dimensional cross-sectional side view of a lighting device 21 according to an embodiment of the present invention. It can be seen that the lighting device 21 is similar to the one described above. Figure 2 The described lighting device 11 includes a planar light guide 12 with a cavity 13 (for simplicity, Figure 4 (Only one cavity is shown in the image), the first type of RGB LED package 1 is located in cavity 13. Figure 5 Presented Figure 4 The diagram shows a plan view of the lighting device 21. Light extraction features (not shown) inside or on the surface of the planar light guide 12 can again be used to provide a means for allowing light to exit the lighting device 21 via the light output surface 14. The design of the light extraction features (variations in size, density, etc.) again provides a means for increasing the uniformity of the output light intensity.

[0075] and Figure 2 Unlike the lighting device 11, the lighting device 21 also includes a (see) located on the light output surface 14. Figure 4 ) or more (see Figure 5 Wavelength-related modification feature 22.

[0076] exist Figure 5 In this process, the wavelength-dependent modification feature 22 includes a cyan ink spot 22a printed on the light output surface 14, positioned closer to the red LED chip 2 than either the green LED chip 3 or the blue LED chip 4, i.e., it is located within the red region 18 of the light output surface 14. Preferably, the cyan ink spot 22a is equidistant from the green LED chip 3 and the blue LED chip 4. Due to the color selection of the wavelength-dependent modification feature 22a, its function is to selectively reduce the red content of the output light from the illuminator 21, while keeping the green and blue content substantially unchanged. As a result, uniform color light output is provided from the RGB LED package 1 within the red region 18 of the light output surface 14.

[0077] from Figure 5 As can be seen, the use of wavelength-dependent modification feature 22 can be extended to ensure uniform color light output from RGB LED package 1 within the green region 19 and blue region 20 of light output surface 14. In green region 19, wavelength-dependent modification feature 22 includes a magenta ink dot 22b printed on light output surface 14, such that it is closer to green LED chip 3 than either red LED chip 2 or blue LED chip 4. Preferably, the magenta ink dot 22b is equidistant from red LED chip 2 and blue LED chip 4. Due to the color selection of wavelength-dependent modification feature 22b, its function is to selectively reduce the green content of the output light from illuminator 21, while retaining the red and blue content substantially unchanged.

[0078] Similarly, within the blue region 20, the wavelength-dependent modification feature 22 includes a yellow ink dot 22c printed on the light output surface 14, positioned closer to the blue LED chip 4 than either the red LED chip 2 or the green LED chip 3. Preferably, the yellow ink dot 22c is equidistant from both the red LED chip 2 and the green LED chip 3. Due to the color selection of the wavelength-dependent modification feature 22c, its function is to selectively reduce the blue content of the output light from the illuminator 21, while retaining the red and green content substantially unchanged.

[0079] The presence of three colored ink dots 22a, 22b and 22c eliminates the problem of uneven coloring in the output light generated by the illuminator 21, because the wavelength-dependent modification feature 22 works by altering the amount of light emitted from the associated LED chips 2, 3 and 4 through selective absorption at the associated wavelength of the output light.

[0080] Technical readers will understand that the wavelength-dependent modification features 22 can take various forms and spatial locations. They can be located on the light output surface 14 or inside the planar light guide 12. Furthermore, the wavelength-dependent modification features 22 can be uniform in nature or patterned. In alternative embodiments, the wavelength-dependent modification features 22 may include dyes or pigments.

[0081] The selection of components for wavelength-dependent modification feature 22 can also be chosen to alter the amount of light from one or more of the multiple light sources 2, 3, and 4 through an additive rather than an absorption process (i.e., the colored ink dot 22a does not selectively reduce the red content of the output light from illuminator 21, but rather increases the green and blue content of the output light within the red region 18 of the light output surface 14). Similarly, colored ink dot 22b can be selected to increase the red and blue content of the output light within the green region 19 of the light output surface 14, while keeping the green content of the output light substantially unchanged. In the same manner, colored ink dot 22c can be selected to increase the red and green content of the output light within the blue region 20 of the light output surface 14, while keeping the blue content of the output light substantially unchanged.

[0082] In alternative embodiments, the LED package can be optically coupled to a planar light guide without using a cavity. Many alternatives are known in the art, such as embedding the LED package directly within the light guide material or having additional coupling optical features on its surface.

[0083] During the development of this invention, the applicant has discovered that when the lighting device 23 is Figure 6 and Figure 7 When the type presented is such that it includes the second type of RGB LED package 8, the position of the wavelength-dependent modification feature 22 must be changed. In these embodiments, the wavelength-dependent modification feature 22 needs to be positioned such that the LED chip intended to interact with it is located further away from the wavelength-dependent modification feature 22 than the other two LED chips.

[0084] Reference Figure 6 and Figure 7 The wavelength-dependent modification feature 22 includes a cyan ink dot 22a printed on the light output surface 14, such that it is further away from the red LED chip 2 than either the green LED chip 3 or the blue LED chip 4, i.e., it is located outside the red region 18 of the light output surface 14. Also preferably, the cyan ink dot 22a is equidistant from the green LED chip 3 and the blue LED chip 4.

[0085] Regarding the green LED chip 3, the wavelength-dependent modification feature 22 includes a magenta ink dot 22b printed on the light output surface 14, such that it is further away from the green LED chip 3 than either the red LED chip 2 or the blue LED chip 4. Preferably, the magenta ink dot 22b is again equidistant from both the red LED chip 2 and the blue LED chip 4.

[0086] Similarly, regarding the blue LED chip 4, the wavelength-dependent modification feature 22 includes a yellow ink dot 22c printed on the light output surface 14, such that it is further away from the blue LED chip 4 than either the red LED chip 2 or the green LED chip 3. Preferably, the yellow ink dot 22c is again equidistant from both the red LED chip 2 and the green LED chip 3.

[0087] The applicant believes that the reason for the reversal requirement in the spatial position of the wavelength-dependent modification feature 22 is the result of the reflection of the output light from LED chips 2, 3 and 4 from the inner wall of the transparent housing 9.

[0088] Figure 8 A two-dimensional cross-sectional side view of a lighting device according to another alternative embodiment of the present invention is presented. Figure 8 As shown, one or more RGB LED packages 1 and 8 are positioned together with a diffuser 25 such that light 26 emitted from one or more RGB LED packages 1 and 8 propagates through the diffuser 25 before leaving the illuminator via the light output surface 14. An opaque mask 27 is located between the RGB LED packages 1 and 8 and the diffuser 25. One or more apertures 28 are formed in the opaque mask 27 to allow light 26 from the red LED chip 2, green LED chip 3, and blue LED chip 4 to mix at the location of one or more apertures 28. The one or more apertures 28 effectively form a mixed light source, but at an intensity level much lower than that generated by the RGB LED packages 1 and 8 themselves. The diffuser 25 is then used to break the angular dependence of the different colors from the individual LED chips 2, 3, and 4, thereby producing output light 29 from the illuminator 24, which comprises uniformly, evenly mixed light.

[0089] It will be understood that the opaque mask 27 may be arranged to interact with two or more RGB LED packages 1 and 8 within the lighting device 24, or alternatively, there may be a dedicated opaque mask 27 for each RGB LED package 1 and 8.

[0090] Therefore, the illuminator 24 provides a low level of uniform, evenly mixed colored light (e.g., white) above the RGB LED packages 1 and 8. This solves the problem of color uniformity directly above the LED packages, as well as the requirement to balance the illuminance in this area with that in areas farther away from the RGB LED packages 1 and 8. Since only a very small amount of light is needed above the RGB LED packages 1 and 8, this solution is particularly suitable for backlighting the interior surfaces of vehicles. The low level of light from the diffuser 25 is balanced with the light emitted from areas farther away from the RGB LED packages 1 and 8, creating an overall uniform appearance across the entire illuminator 24 using the matrix array of the RGB LED packages 1 and 8.

[0091] Compared to devices known in the art, the present invention provides many alternative uniform color lighting devices that can provide low intensity light levels over a larger surface area.

[0092] A significant advantage of this invention is that it allows for the production of much thinner uniform-color lighting devices than those known in the prior art, without introducing the problem of color inhomogeneity artifacts. In other words, it enables the production of thin devices that exhibit highly uniform white light output from light sources of different tints over a large surface area.

[0093] Compared to known alternative solutions in the art, the disclosed uniform color lighting device also has a lower manufacturing cost and higher reliability and lifespan.

[0094] Since uniform color lighting devices can include multiple individual light sources, they exhibit the further advantage that each light source can be addressed independently, thus enabling the production of pixelated area light sources.

[0095] Due to the aforementioned advantages, the uniform color lighting device of the present invention has found particular application in the transportation sector (e.g., the automotive, train, and aerospace industries, where thin, robust devices are required that can be mechanically attached, bonded, connected, or molded onto the inner surface of a vehicle).

[0096] Throughout this specification, unless the context otherwise requires, the terms "comprise" or "include," or variations such as "comprises" or "comprising," "includes," or "including," will be understood to imply inclusion of the stated integers or groups of integers, but not to exclude any other integers or groups of integers. Furthermore, unless the context otherwise requires, the term "or" will be interpreted as inclusive rather than exclusive.

[0097] For purposes of illustration and description, the foregoing description of the invention has been presented; it is not intended to be exhaustive or to limit the invention to the precise forms disclosed. The described embodiments were chosen and described in order to best explain the principles of the invention and its practical application, so that others skilled in the art can best utilize the invention in various implementations and with various modifications suitable for the particular intended use. Therefore, further modifications or improvements can be combined without departing from the scope of the invention as defined by the appended claims.

Claims

1. A lighting device, comprising: A light guide and one or more LED packages having two or more spatially separated LED chips, each LED chip generating light output, wherein the light output from a first LED chip is at a first wavelength, and the light output from a second LED chip is at a second wavelength different from the first wavelength of the first LED chip, wherein the two or more light outputs are optically coupled to the light guide, and a portion of the two or more light outputs exits the light guide via a light output surface, wherein the light guide further includes two or more wavelength-dependent modification features located on the light output surface, wherein a first wavelength-dependent modification feature is located on a first region of the light output surface and is arranged to selectively modify the intensity of the light output generated by the first of the two or more spatially separated LED chips, and a second wavelength-dependent modification feature is located on a second region of the light output surface and is arranged to selectively modify the intensity of the light output generated by the second of the two or more spatially separated LED chips, to provide the lighting device having uniform color light output.

2. The lighting device according to claim 1, wherein, The lighting device further includes a diffuser and an opaque mask located between one of the one or more LED packages and the diffuser, wherein the opaque mask includes one or more holes.

3. The lighting device according to claim 1 or 2, wherein, The one or more LED packages include RGB LED packages having red LED chips, green LED chips, and blue LED chips that emit light from five surfaces of the package.

4. The lighting device according to claim 3, wherein, One of the two or more wavelength-related modification features is cyan and is arranged closer to the red LED chip than either the green LED chip or the blue LED chip.

5. The lighting device according to claim 3, wherein, One of the two or more wavelength-related modification features is magenta and is arranged closer to the green LED chip than either the red LED chip or the blue LED chip.

6. The lighting device according to claim 3, wherein, One of the two or more wavelength-related modification features is yellow and is arranged closer to the blue LED chip than either the red LED chip or the green LED chip.

7. The lighting device according to claim 1 or 2, wherein, The one or more LED packages include RGB LED packages having red LED chips, green LED chips, and blue LED chips that emit light from a single surface of the package.

8. The lighting device according to claim 7, wherein, One of the two or more wavelength-related modification features is cyan and is arranged further away from the red LED chip than either the green LED chip or the blue LED chip.

9. The lighting device according to claim 7, wherein, One of the two or more wavelength-related modification features is magenta and is arranged further away from the green LED chip than either the red LED chip or the blue LED chip.

10. The lighting device according to claim 7, wherein, One of the two or more wavelength-related modification features is yellow and is arranged further away from the blue LED chip than either the red LED chip or the green LED chip.

11. The lighting device according to claim 4 or 8, wherein, The wavelength-related modified features, which are cyan, are equidistant from the green LED chip and the blue LED chip.

12. The lighting device according to claim 5 or 9, wherein, The wavelength-related modified features, in magenta, are equidistant from the red LED chip and the blue LED chip.

13. The lighting device according to claim 6 or 10, wherein, The wavelength-related modified features, marked in yellow, are equidistant from the red and green LED chips.

14. The lighting device according to claim 1 or 2, wherein, The two or more wavelength-related modification features include inks, dyes, or pigments.

15. The lighting device according to claim 1 or 2, wherein, The wavelength-dependent modification features are essentially uniform or patterned.

16. A method for generating uniform color light output, the method comprising: Two or more spatially separated optical outputs are optically coupled into an optical guide, wherein a first optical output is at a first wavelength and a second optical output is at a second wavelength different from the first wavelength; A portion of the two or more spatially separated optical outputs exits the light guide via the optical output surface; and The light guide is provided with two or more wavelength-dependent modification features located on the light output surface, wherein a first wavelength-dependent modification feature is located on a first region of the light output surface and is arranged to selectively modify the intensity of a first light output of the two or more spatially separated light outputs, and a second wavelength-dependent modification feature is located on a second region of the light output surface and is arranged to selectively modify the intensity of a second light output of the two or more spatially separated light outputs.

17. The method for generating uniform color light output according to claim 16, wherein, The method further includes: A diffuser and an opaque mask are provided, wherein the opaque mask is located between the two or more spatially separated light outputs and the diffuser; and Provide the opaque mask having one or more holes.

18. The method for generating uniform color light output according to claim 16 or 17, wherein, Optically coupling the two or more spatially separated light outputs into the light guide includes optically coupling red light output, green light output, and blue light output into the light guide.

19. The method for generating uniform color light output according to claim 18, wherein, The light guide providing two or more wavelength-dependent modification features includes: providing a cyan wavelength-dependent modification feature that is closer to the red light output than either the green light output or the blue light output.

20. The method for generating uniform color light output according to claim 18, wherein, The light guide providing two or more wavelength-dependent modification features includes: providing a magenta wavelength-dependent modification feature that is closer to the green light output than either the red light output or the blue light output.

21. The method for generating uniform color light output according to claim 18, wherein, The light guide that provides two or more wavelength-dependent modification features includes providing a yellow wavelength-dependent modification feature that is closer to the blue light output than either the red light output or the green light output.

22. The method for generating uniform color light output according to claim 18, wherein, The light guide providing two or more wavelength-dependent modification features includes: providing a cyan wavelength-dependent modification feature that is further away from the red light output than either the green light output or the blue light output.

23. The method for generating uniform color light output according to claim 18, wherein, The light guide providing two or more wavelength-dependent modification features includes: providing a magenta wavelength-dependent modification feature, the magenta wavelength-dependent modification feature being further away from the green light output than either the red light output or the blue light output.

24. The method for generating uniform color light output according to claim 18, wherein, The light guide providing two or more wavelength-dependent modification features includes: providing a yellow wavelength-dependent modification feature, the yellow wavelength-dependent modification feature being further away from the blue light output than either the red light output or the green light output.

25. The method for generating uniform color light output according to claim 19 or 22, wherein, The wavelength-dependent modification feature of the cyan light is provided to be equidistant from the green light output and the blue light output.

26. The method for generating uniform color light output according to claim 20 or 23, wherein, The wavelength-dependent modification feature of the magenta light is provided to be equidistant from the red light output and the blue light output.

27. The method for generating uniform color light output according to claim 21 or 24, wherein, The wavelength-related modification feature of the yellow light is provided to be equidistant from the red light output and the green light output.

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