English:
[0001] The present invention is related to light emitting diodes (LEDs) with wavelength conversion and in particular to controlling the angular dependency of an LED to produce a desired non-uniformity.
[0002] Lighting devices that use light emitting diodes (LEDs) are becoming increasingly common in many lighting applications. Generally, LEDs use phosphor conversion of the primary emission to generate white light, but phosphors can also be used to create more saturated colors like red, green and yellow.
[0004] Current strategies for dealing with the color non-uniformity include reducing the angular dependency. By way of example, one strategy is to coat the sides of the phosphor material to prevent the side emission of light. Another strategy is to add scattering particles to the phosphor material to mix the converted and non-converted light so that the side emitted light and top emitted light have approximately the same color. Such solutions to the angular dependency, however, reduce the efficiency of the devices as well as increase the cost of production. Accordingly, other solutions for dealing with the angular dependency are desired.
[0005] A light source includes an LED with a wavelength converting element with a selected ratio of height and width to produce a desired non-uniform angular color distribution, e.g., a uniformity of Δu'v' >0.015 within an angular distribution from 0° to 90°. The light source is used with applications that translate the non-uniform angular color distribution from the light source into a uniform color distribution, e.g., with a uniformity of Δu'v' <0.01. Consequently, the efficiency of the system is increased relative to conventional systems designed around an LED that is configured to produce a uniform angular color distribution.
[0006] Fig. 1 illustrates a side view of a light source that includes an LED with a wavelength converting element that has a controlled non-uniform angular color distribution.
[0007] Fig. 2 illustrates a Δu'v' shift over angle for showing the angular color non-uniformity of the light source from Fig. 1.
[0008] Figs. 3 A and 3B illustrates an example of the light source used with a flash type application.
[0009] Fig. 4 illustrates a side view of the light source in a semi-side emitter configuration.
[0010] Fig. 5 illustrates another embodiment of the light source that emits light with a controlled non-uniform angular color dependency.
[0011] Figs. 6A and 6B, by way of example, illustrate a plan view and side view of a plurality of light sources used with a backlight type application.
[0012] Fig. 7 is a graph illustrating the absorption curve per 1 mm for PMMA acrylic, which is commonly used as a waveguide in a backlight application.
[0014] Fig. 9 is a graph illustrating the color shift due to a PMMA waveguide's (blue) absorption over distance.
[0015] Fig. 1 illustrates a side view of a light source 100, including a light emitting diode (LED) 101 with a wavelength converting element 110, which has a controlled non-uniform angular color distribution. Fig. 1 also illustrates a device 120 used with the light source 100 with a lens 122 arrangement for reflecting the light from light source 100 to the device 120. The device 120 may be an application such as a flash type application or back lighting or other appropriate applications. The angular color non-uniformity of the light source 100 is configured to be used with a light based device 120 so that the overall system, i.e., light source 100 and device 120, becomes more efficient than a system that includes a conventional light source 100 with a uniform angular LED.
[0016] The LED 101 is illustrated as a flip-chip device with bond pads 102 located on the bottom surface of the LED 101. The bond pads 102 are bonded to contact elements 104 on a substrate 106, which may be, e.g., ceramic or silicon. The substrate 106 may be mounted on a heat sink 108 if desired. If desired, support structures other than the substrate 106 and heat sink 108 may be used.
[0017] In one embodiment, the LED 101 may be a blue or ultraviolet (UV) LED and may be a high radiance device, such as the type described in U.S. Serial No. 10/652,348, entitled "Package for a Semiconductor Light Emitting Device", by Frank Wall et al., filed August 29, 2003, Pub. No. 2005/0045901, having the same assignee as the present disclosure and which is incorporated herein by reference. The angular emission pattern of the LED 101 can be lambertian (as illustrated in Fig. 1) or controlled using a photonic crystals such as lattice structures.
[0018] Mounted to the LED 101 is a wavelength converting element 110 that may be, e.g., a phosphor in a binder material, embedded in, e.g., silicone and molded over the LEDlOl, or in a rigid ceramic slab, sometimes referred to herein as a "luminescent ceramic". The ceramic slabs are generally self-supporting layers and may be translucent or transparent to particular wavelengths, which may reduce the scattering loss associated with non-transparent wavelength converting layers such as conformal layers. Luminescent ceramic layers may be more robust than thin film or conformal phosphor layers.
[0019] Examples of phosphors that may be used in a binder, molded over the LED 101, or in a luminescent ceramic include aluminum garnet phosphors with the general formula (Lui_x_y_a_bYxGdy)3(Ali_zGaz)5Oi2:CeaPrbwherein 03Al5O^Ce3+and Y3Al5O^iCe3+which emit light in the yellow-green range; and (Sri_x_yBaxCay)2-zSi5_aAlaN8-a0a:Euz2+wherein 0 2Si5NsIEu2+, which emit light in the red range. Suitable Y3Al5Oi2ICe3+ceramic slabs may be purchased from Baikowski International Corporation of Charlotte, N.C. Other green, yellow, and red emitting phosphors may also be suitable, including (Sri_a_bCabBac)SixNyOz:Eua+(a=0.002-0.2, b=0.0-0.25, c=0.0-0.25, x=1.5-2.5, y=1.5-2.5, z=1.5-2.5) including, for example, SrSi2N2O2)Eu+; (Sri_u_v-xMguCavBax)(Ga2-y-zAlyInzS4):Eu+including, for example, SrGa2S4)Eu2+; Sr^xBaxSiO4)Eu2+; and (Cai_xSrx)S:Eu2+wherein 02+and SrSiEu2+. As illustrated by the respective arrows 114 and 115, the light source 100 has both top emission and side emission of light, where the top emitted light 114 is bluish white and the side emitted light 115 is yellowish. By controlling the height H of the wavelength converting element 110, or more specifically, the height/width (HAV) ratio, the angular dependency of the light can be controlled to produce a desired amount of bluish white light 114 and yellowish light 115 that is appropriate for the device 120. By way of example, to produce less blue light, a wavelength converting element 110 with greater height H is used, while to produce more blue light, a wavelength converting element 110 with less height H is used.
[0020] Fig. 2A illustrates a Δu'v' shift over angle showing one embodiment of the angular color non-uniformity of the light source 100. The Δu'v' shift over angle is a measure of the color shift relative to a reference point. As can be seen in Fig. 2A, the light source 100 produces a Δu'v' shift of >0.015 between 0° and 90° with respect to the 0° reference point. This is the maximum color over angle variation as measured within the angular range. Fig. 2B shows an example of the Δu'v' for another light source 100 with a blue LED and Red/Green phosphors, that has been configured to produce a Δu'v'>0.05 over angle. By varying, e.g., the HAV ratio, different maximum Δu'v' over angle values can be created e.g. maximum Δu'v' over angle may be larger than 0.015, 0.03, 0.045 or 0.06 depending on the desired application, e.g., the device 120, the light source 100 is to be used with. The device 120 using the light source 100, in accordance with one embodiment, then produces a spatial color uniformity of Δu'v' less than 0.015, e.g., less than 0.01 or 0.005.
[0021] Accordingly, rather than try to eliminate the angular color dependency of the light, the light source 100 is designed to produce a controlled angular color non-uniformity that is optimized for the particular device 120 with which the light source 100 is to be used. Thus, as described above for example, the light source 100 is configured to produces a controlled angular color non-uniformity with a Δu'v' shift of >0.015 over angle, but when used with device 120, the device 120 produces a spatial color uniformity of Δu'v'<0.015. Different spatial color uniformities like Δu'v' <0.05 to Δu'v'<0.015 are possible depending on the application requirements. For example, medical monitors or other application that require a highly accurate representation of color may be produced with a backlight in accordance with one embodiment having a Δu'v' <0.05, whereas consumer monitors may be produced with a backlight having a Δu'v' <0.01, and applications such as a camera flash may have a Δu'v' <0.015. With the controlled angular color non-uniformity, the efficiency of the light source 100 can be increased as there is no need to block light from being emitted from the light source 100. Consequently, the overall performance of the system, including the device 120 and the light source 100 is improved compared to systems in which a uniform angular LED is used.
[0022] Figs. 3A and 3B illustrates an example of the light source 100 that may be used with a flash type device 120, e.g., for a camera. Fig. 2B illustrates light source 100 with an additional controlling element 112, such as a dichroic filter, overlying the wavelength converting element 110. The dichroic filter 112 transmits light differently as a function of angle, which further aids in the control of the angular dependency. Alternatively, a scattering element may be used to appropriately reduce or control the angular dependency. As illustrated in Fig. 2B, the light source 100 produces bluish white light 114 and yellowish light 115 that is reflected by the reflector 122 and mixed at the imaging target 124.
[0023] If desired, the light source 100 may be a side (or semi-side) emitter in which no there is little top emission and significant side emission. Fig. 4 illustrates light source 100 in a semi- side emitter configuration, in which no top reflector on the top surface 110topof the wavelength converting element 110 is necessary. As illustrated in Fig. 4, the angular emission pattern from the sides 110sldeof the light source 100 is lambertian. By replacing a top reflector with increased height H of the wavelength converting element 110 with respect to the width W of the wavelength converting element 110 (which in this embodiment is the same as the width of the LED 101), the number of reflections of the light to the LED 101 is reduced. Reflections to the LED 101 are inefficient and therefore by reducing the reflections to the LED 101 the losses in the system are reduced. Moreover, by increasing the height H, the sides 110Side of the wavelength converting element 110 have a greater area, which provides increased light extraction from the sides 110Side of the wavelength converting element 110. By increasing the height H of the wavelength converting element 110 with respect to the width W, the light source 100 is optimized for applications requiring light extraction, as opposed to light collection. For example, in applications such as flash optical design, a small designed source is desired, so that optics can be kept small, while collecting most of the light and aim the light at a target of 1.05x0.8meters at lmeter distance. By increasing the height of the wavelength converting element 110, the light extracted is increased. The Ce concentration within the wavelength converting element may be configured to produce the desired color point for the particular application. Additionally, scattering particles may be added to the wavelength converting element to assist in the light extraction into air.
[0024] Fig. 5 illustrates another embodiment of the light source 100 that emits light with a controlled angular color dependency. The light source 100 includes a thin optically coupled laminate element 116 to the top surface of the wavelength converting element 110, which may be, e.g., a dichroic layer, a scattering layer, or a red phosphor layer. If desired, the element 116 may be placed between the wavelength converting element 110 and the LED 101, particularly when the element 116 is a red phosphor layer, the wavelength converting element 110 is a greenish phosphor plate such as LUAG, and the LED 101 is a blue LED. Additionally, the light source 100 may include an overmolded dome lens 118, which may be silicon, epoxy, or other appropriate material, which may also be to assist in the control of the angular color non- uniformity. If desired, the overmolded dome lens 118 need not be used. The top emitted light, illustrated by arrow 114, is bluish white and has a lambertian emission profile. The side emitted light, illustrated by arrow 115, is yellowish and has an isotropic emission profile that is configured by the height H of the wavelength converting element as well as by scattering. The angular dependent emission of light source 100 may be translated into a uniform spatial color distribution in the desired application, such a backlight.
[0025] Figs. 6A and 6B, by way of example, illustrate a plan view and side view of a plurality of light source 100 used with a backlight type device 120. The backlight 120 extracts color, e.g., blue versus green/red, from a single light source 100 at different locations within the backlight. Thus, by using a number of light sources 100 and by controlling the angular color distribution of the emitted light, a uniform spatial distribution of color may be produced within the backlight application
[0026] Fig. 7 is a graph illustrating the absorption curve per 1 mm for PMMA acrylic, which is commonly used as a waveguide in a backlight application. The X axis represents wavelengths while the Y axis represents the percentage of absorption. Fig. 8 is a graph illustrates the effect of the spectral absorption of the waveguide illustrating the change of the spectrum from the edge (illustrated by curve 202) and the center (illustrated by curve 204) of a 72" PMMA waveguide. The X axis represents wavelengths while the Y axis represents relative spectral distribution. As can be seen in Fig. 8, the center 204 of the spectrum at the center of the waveguide includes less blue light than the edge 202 of the waveguide. Fig. 9 is a graph illustrating the theoretical color shift due to a PMMA waveguide's (blue) absorption in a 2- sided backlight over distance for a conventional light source having a uniform angular and spatial input. The X axis represents the diagonal position of the backlight in inches, while the Y axis represents the change in Δu'v' from the center to the edge. As illustrated, the conventional waveguide using a conventional uniform angular light source has a Δu'v' that is greater than 0.01 and in fact is up to 0.02.
[0027] Thus, as can be seen from the graphs in Figs. 7, 8, and 9, more blue light is absorbed over distance by a PMMA waveguide, with the result that such a waveguide has less blue light in the center of the waveguide than at the edge of the waveguide. Moreover, as illustrated in Fig. 9, the Δu'v' shift has an approximately linear variation over distance. With the use of the controlled non-uniform angular color distribution of light source 100, more blue light can be emitted directly towards the center of the waveguide to compensate for the blue absorption in the PMMA material to produce a more uniform color distribution in the backlight application.
[0028] Although the present invention is illustrated in connection with specific embodiments for instructional purposes, the present invention is not limited thereto. Various adaptations and modifications may be made without departing from the scope of the invention. Therefore, the spirit and scope of the appended claims should not be limited to the foregoing description.

中文:
[0001]本发明涉及具有波长转换的发光二极管(LED),且尤其涉及控制LED的角度依赖性以产生希望的非均匀性。
[0002]使用发光二极管(LED)的照明器件在许多照明应用中正变得越来越常见。通常,LED使用初级发射的磷光体转换以产生白色光,但是磷光体也可以用来形成更饱和的颜色,比如红色、绿色和黄色。
[0004]处理颜色非均匀性的当前策略包括降低角度依赖性。举例而言,一种策略是涂敷磷光体材料的侧面以防止光的侧面发射。另一种策略是向磷光体材料添加散射颗粒以便混合转换光和非转换光,使得侧面发射的光和顶部发射的光具有近似相同的颜色。然而,对于角度依赖性的这类解决方案降低了器件的效率,也增大了生产成本。因此,处理角度依赖性的其他解决方案是所希望的。
[0005]一种光源包括具有波长转换元件的LED,该波长转换元件具有选定的高度和宽度的比率以产生希望的非均匀角度颜色分布,例如在从0°到90°的角度分布内的均匀性Δu’v’>0.015。该光源与这样的应用一起使用,所述应用将来自光源的非均匀角度颜色分布转化成均匀颜色分布,例如均匀性为Δu’v’<0.01。因此,相对于围绕被配置成产生均匀角度颜色分布的LED而设计的常规系统,该系统的效率增加。
[0006]图1说明了包括具有波长转换元件的LED的光源的侧视图,该光源具有受控的非均匀角度颜色分布。
[0007]图2说明了随着角度的Δu’v’偏移,用于示出图1的光源的角度颜色非均匀性。
[0008]图3A和图3B说明了与闪光灯类型的应用一起使用的光源的实例。
[0009]图4说明了半侧面发射器配置的光源的侧视图。
[0010]图5说明了发射具有受控的非均匀角度颜色依赖性的光的光源的另一实施例。
[0011]图6A和图6B通过实例说明了与背光类型应用一起使用的多个光源的平面图和侧视图。
[0012]图7为说明针对PMMA丙烯酸的每1mm的吸收曲线的曲线图,所述PMMA丙烯酸在背光应用中常用作波导。
[0014]图9为说明由于PMMA波导的随着距离的(蓝色)吸收而引起的颜色偏移的曲线图。
[0015]图1说明了包括具有波长转换元件110的发光二极管(LED)101的光源100的侧视图,该光源具有受控的非均匀角度颜色分布。图1也说明了与光源100一起使用的具有镜片122布置的器件120,所述镜片布置用于将来自光源100的光反射到器件120。器件120可以是诸如闪光灯类型应用或背光照明或者其他适当应用之类的应用。光源100的角度颜色非均匀性被配置成与基于光的器件120一起使用,使得整个系统(即光源100和器件120)变得比包括具有均匀角度LED的常规光源100的系统更加有效。
[0016]LED 101被示为倒装芯片器件,其中焊盘102位于LED 101的底部表面上。焊盘102结合到衬底106上的接触元件104,所述衬底可以是例如陶瓷或硅。如果希望的话,可以将衬底106安装到散热器108上。如果希望的话,可以使用不同于衬底106和散热器108的支撑结构。
[0017]在一个实施例中,LED 101可以是蓝色或紫外(UV)LED并且可以是高辐射器件,例如Frank Wall等人2003年8月29日提交的、公开号为No. 2005/0045901的、题为“Package for a Semiconductor Light Emitting Device”的、美国序列号为No. 10/652348中描述的类型,该文献与本公开具有相同的受让人并且通过引用合并于此。LED 101的角度发射模式可以是朗伯型(如图1中所示),或者使用诸如晶格结构之类的光子晶体进行控制。
[0018]波长转换元件110安装到LED 101,该波长转换元件例如可以是嵌入到例如硅树脂中且模制在LED 101上的粘合剂材料中的或者在这里有时称为“发光陶瓷”的刚性陶瓷板中的磷光体。陶瓷板通常为自支撑层并且对于特定波长可以是半透明或透明,这可以减少与诸如共形层之类的非透明波长转换层关联的散射损失。发光陶瓷层可以比薄膜或共形磷光体层更鲁棒。
[0019]可以在模制在LED 101上的粘合剂中或者在发光陶瓷中使用的磷光体的实例包括铝石榴石磷光体,其具有通式(Lu1-x-y-a-b YxGdy)3(Al1-zGaz)5O12:CeaPrb,其中03Al5O12:Ce3+和Y3Al5O12:Ce3+,其发射黄色-绿色范围内的光;以及(Sr1-x-yBaxCay)2-zSi5-aAlaN8-aOa:Euz2+,其中0 ≤ a2Si5N8:Eu2+,其发射红色范围内的光。适当的Y3Al5O12:Ce3+陶瓷板可以从北卡罗来纳州夏洛特市的Baikowski International Corporation购买。其他的绿色、黄色和红色发射磷光体也可能是适当的,包括(Sr1-a-bCabBac)SixNyOz:Eua2+ (a=0.002-0.2、b=0.0-0.25、c=0.0-0.25、x=1.5-2.5、y=1.5-2.5、z=1.5-2.5),其包括例如SrSi2N2O2:Eu2+;(Sr1-u-v-xMguCavBax)(Ga2-y-zAlyInzS4):Eu2+,其包括例如SrGa2S4:Eu2+;Sr1-xBaxSiO4:Eu2+;以及(Ca1-xSrx)S:Eu2+,其中02+和SrS:Eu2+。如各箭头114和115所示,光源100具有顶部发射和侧面发射的光这两者,其中顶部发射的光114为蓝白色并且侧面发射的光115为淡黄色。通过控制波长转换元件110的高度H或者更特别地控制高度/宽度(H/W)比率,可以控制光的角度依赖性以产生对于器件120合适的希望数量的蓝白色光114和淡黄色光115。举例而言,为了产生更少的蓝色光,使用具有更大高度H的波长转换元件110,而为了产生更多的蓝色光,使用具有更小高度H的波长转换元件110。
[0020]图2A说明了随着角度的Δu’v’偏移,其示出光源100的角度颜色非均匀性的一个实施例。随着角度的Δu’v’偏移是相对于参考点的颜色偏移的度量。由图2A可见,光源100在0°与90°之间相对于0°参考点产生>0.015的Δu’v’偏移。这是在所述角度范围内测量的最大的颜色随着角度的变化。图2B示出了具有蓝色LED和红色/绿色磷光体的另一光源100的Δu’v’的实例,该光源被配置成产生随着角度的Δu’v’>0.05。通过改变例如H/W比率,可以产生随着角度值的不同的最大Δu’v’,例如,根据希望的应用,例如光源100与其一起使用的器件120,随着角度的最大Δu’v’可以大于0.015、0.03、0.045或0.06。依照一个实施例,使用光源100的器件120于是产生小于0.015,例如小于0.01或者0.005的空间颜色均匀性Δu’v’。
[0021]因此,不是试图消除光的角度颜色依赖性,而是光源100被设计成产生受控的角度颜色非均匀性,该角度颜色非均匀性对于光源100要与其一起使用的特定器件120而言被优化。因此,如上面所描述的,例如,光源100被配置成产生随着角度的Δu’v’偏移>0.015的受控的角度颜色非均匀性,但是当与器件120一起使用时,器件120产生Δu’v’<0.015的空间颜色均匀性。根据应用的要求,不同的空间颜色均匀性是可能的,比如Δu’v’<0.05至Δu’v’<0.015。例如,可以利用依照一个实施例的具有Δu’v’<0.05的背光产生需要高度精确的颜色表示的医疗监视器或其他应用,但是,可以利用具有Δu’v’<0.01的背光产生消费类监视器,并且诸如照相机闪光灯之类的应用可以具有Δu’v’<0.015。利用受控的角度颜色非均匀性,可以增加光源100的效率,因为无需阻挡光从光源100发射。因此,与其中使用了均匀角度LED的系统相比,包括器件120和光源100的系统的总体性能提高。
[0022]图3A和图3B说明了可以与闪光灯类型的器件120(例如用于相机)一起使用的光源100的实例。图2B说明了具有覆盖波长转换元件110的诸如二向色滤光器之类的附加控制元件112的光源100。二向色滤光器112作为角度的函数而不同地透射光,这进一步有助于控制角度依赖性。可替换地,可以使用散射元件以便适当地降低或控制角度依赖性。如图2B中所示,光源100产生蓝白色光114和淡黄色光115,淡黄色光被反射器122反射并且在成像目标124处混合。
[0023]如果希望的话,光源100可以是侧面(或半侧面)发射器,其中存在很少的顶部发射和大量的侧面发射。图4说明了半侧面发射器配置的光源100,其中波长转换元件110的顶部表面110top上的顶部反射器是不必要的。如图4中所示,来自光源100的侧面110side的角度发射模式是朗伯型。通过利用相对于波长转换元件110的宽度W(其在本实施例中与LED 101的宽度相同)增大波长转换元件110的高度H来代替顶部反射器,减少了到LED 101的光反射的次数。到LED 101的反射是低效的,并且因此通过减少到LED 101的反射,降低了系统中的损耗。而且,通过增大高度H,波长转换元件110的侧面110side具有更大的面积,这提供了增大的来自波长转换元件110侧面110side的光提取。通过相对于宽度W增大波长转换元件110的高度H,光源100对于与光收集相对比的要求光提取的应用而言被优化。例如,在诸如闪光灯光学设计之类的应用中,小的设计的源是所希望的,使得光学器件可以保持较小,同时收集大多数光,并且将光瞄准到1米距离处的1.05x0.8米的目标。通过增大波长转换元件110的高度,增加了提取的光。波长转换元件内的Ce浓度可以被配置成对于特定的应用产生希望的色点。此外,可以将散射颗粒添加到波长转换元件以便帮助将光提取到空气中。
[0024]图5说明了发射具有受控的角度颜色依赖性的光的光源100的另一实施例。光源100包括到波长转换元件110的顶部表面的薄光学耦合层压元件116,其可以是例如二向色层、散射层或红色磷光体层。如果希望的话,特别是当元件116为红色磷光体层、波长转换元件110为诸如LUAG之类的淡绿色磷光体板并且LED 101为蓝色LED时,元件116可以置于波长转换元件110与LED 101之间。此外,光源100可以包括包覆成型(overmolded)圆顶镜片118,其可以是硅、环氧树脂或其他适当的材料,其也可以帮助控制角度颜色非均匀性。如果希望的话,不必使用包覆成型圆顶镜片118。由箭头114示出的顶部发射的光为蓝白色并且具有朗伯型发射轮廓。由箭头115示出的侧面发射的光为淡黄色并且具有由波长转换元件的高度H以及由散射配置的各向同性发射轮廓。在诸如背光之类的希望的应用中,可以将光源100的角度依赖发射转化成均匀的空间颜色分布。
[0025]图6A和图6B通过实例说明了与背光类型的器件120一起使用的多个光源100的平面图和侧视图。背光120在背光内的不同位置处提取来自单个光源100的颜色,例如蓝色对绿色/红色。因此,通过使用一定数量的光源100并且通过控制发射的光的角度颜色分布,可以在背光应用中产生均匀的空间颜色分布。
[0026]图7为说明针对PMMA丙烯酸的每1mm的吸收曲线的曲线图,所述PMMA丙烯酸在背光应用中常用作波导。X轴代表波长,而Y轴代表吸收百分比。图8为说明波导的光谱吸收效应的曲线图,其示出来自72’’ PMMA波导的边缘(由曲线202示出)和中心(由曲线204示出)的光谱变化。X轴代表波长,而Y轴代表相对光谱分布。由图8可见,波导中心处的光谱中心204包括比波导边缘202更少的蓝色光。图9为说明针对具有均匀角度和空间输入的常规光源的由于双侧背光中PMMA波导的随着距离的(蓝色)吸收而引起的理论颜色偏移的曲线图。X轴代表以英寸为单位的背光的对角位置,而Y轴代表从中心到边缘的Δu’v’变化。如所示,使用常规均匀角度光源的常规波导具有大于0.01且事实上高达0.02的Δu’v’。
[0027]因此,从图7、8和9中的曲线图可见,更多的蓝色光随着距离而被PMMA波导吸收,结果是这种波导在波导中心处比在波导边缘处具有更少的蓝色光。而且,如图9中所示,Δu’v’偏移具有随着距离的近似线性的变化。借助于光源100的受控的非均匀角度颜色分布,更多的蓝色光可以朝波导中心直接发射以便补偿PMMA材料中的蓝色吸收,从而在背光应用中产生更均匀的颜色分布。举例而言,图10说明了类似于图9中所示的理论PMMA波导的吸收,但是使用了具有随着角度>0.01的Δu’v’偏移的受控角度颜色非均匀性的光源。如图10中所示,得到的空间颜色均匀性具有小于0.01的Δu’v’。
[0028]尽管出于教导的目的结合具体实施例说明了本发明,但是本发明并不限于此。在不脱离本发明的范围的情况下可以做出各种不同的调适和修改。因此,所附权利要求的精神和范围不应当限于前面的描述。