CN101876753B

Movatterモバイル変換

Info

Publication number: CN101876753B
Application number: CN2010102015323A
Authority: CN
Inventors: 霍露明
Original assignee: Hong Kong Applied Science and Technology Research Institute ASTRI
Current assignee: Hong Kong Applied Science and Technology Research Institute ASTRI
Priority date: 2010-06-03
Filing date: 2010-06-03
Publication date: 2012-06-27
Anticipated expiration: 2030-06-03
Also published as: CN101876753A

Abstract

A head-up display including a hybrid illumination system is disclosed. The light mixing unit provides a substantially homogeneous light source to the reflective display unit. The light collecting optical unit collects the ambient light and guides it to the light mixing unit. At the same time, the light emitted by the electrically driven light source is also directed to the light-mixing unit. One or more optical elements direct the ambient light and the light source light to the light mixing unit for homogenization. The light-gathering unit receives the uniformly mixed light and outputs the gathered light to a polarization beam splitter. The reflective display modulates the light from the polarizing beam splitter and passes it back to the polarizing beam splitter using information from an electrical signal source. The polarized light transmits through the projection lens unit to create an image on the windshield.

Description

Translated fromChinese

平视显示器的混合照明系统Hybrid lighting system for head-up display

【技术领域】【Technical field】

本发明通常涉及平视显示器(head-up display)，特别涉及平视显示器的照明系统。This invention relates generally to head-up displays, and more particularly to lighting systems for head-up displays.

【背景技术】【Background technique】

平视显示器(HUD)是将图像投影在一个可见表面上的系统，该可见表面所在的位置允许观察者始终保持一个姿势，显示器或仪表板的高度大致与观察者的眼睛成水平，让观察者始终保持平视的姿态，而不需要低头观看。平视显示器可用于各种环境如机动车辆、航空器、头盔和其它观察者不能分散其注视的重要情况。A head-up display (HUD) is a system that projects an image onto a visible surface in a position that allows the observer to maintain a posture at all times. Maintain an eye-level posture without looking down. Head-up displays can be used in a variety of environments such as motor vehicles, aircraft, helmets, and other critical situations where the observer cannot distract their gaze.

尽管平视显示器适用于这种环境，但有时在明亮环境光条件下辨别图像会很困难。因此，需要能够在高环境光条件下容易观看的显示器。在这之前，在收集平视显示器的环境光方面已经有许多努力。WO 95/13557是这种平视显示器的一个例子，其在显示器里使用一个环境光光源，其投影图象在挡风玻璃上。同样，在美国专利4,997,263和美国专利7,430,349里，也是聚合环境光和另一个光源。尽管都是使用环境光和另一个光源，前者有较低的环境光收集效率，而后者涉及复杂的收集光纤。此外，这两个专利聚合这两个光源，却都没有提供一个均匀光源用于显示。While the HUD is fine for this environment, it can sometimes be difficult to discern the image in bright ambient light conditions. Accordingly, there is a need for displays that can be easily viewed under high ambient light conditions. There have been many efforts to collect ambient light for HUDs before this. WO 95/13557 is an example of such a head-up display which uses an ambient light source in the display which projects an image on the windshield. Likewise, in US Patent 4,997,263 and US Patent 7,430,349, ambient light and another light source are aggregated. Although both use ambient light and another light source, the former has low ambient light collection efficiency, while the latter involves complex collection fibers. Furthermore, both patents aggregate the two light sources, but neither provides a uniform light source for display.

因此，需要改进平视显示器的光源，使得其既能够提供足够显示亮度又能提供一个均匀光源用于显示，以便能够允许在高环境光条件下清楚地观看。Therefore, there is a need for an improved light source for a head-up display that can provide both sufficient display brightness and a uniform light source for display to allow clear viewing in high ambient light conditions.

【发明概述】【Summary of Invention】

本发明是一个平视显示器(HUD)，其利用来自外界的环境光和来自电光源的可视光用于照明被投影的图像。其包括集光单元、第一光束成形光学单元、第二光束成形光学单元、混光单元、聚光单元、偏振分束器(PBS)、反射显示器单元、投影单元、散光膜和一个光源。根据各个组件的位置，可以选择性地使用反射镜来改变光路经。此外，其还可以包括一个亮度增强器和一个预偏器(pre-polarizer)。The present invention is a heads-up display (HUD) that utilizes ambient light from the outside world and visible light from an electric light source for illuminating the projected image. It includes a light collecting unit, a first beam shaping optical unit, a second beam shaping optical unit, a light mixing unit, a light collecting unit, a polarizing beam splitter (PBS), a reflective display unit, a projection unit, a diffuser film and a light source. Depending on the position of the individual components, mirrors can optionally be used to alter the light path. In addition, it may also include a brightness enhancer and a pre-polarizer.

集光单元从外界收集环境光，并将其重新导向至集光单元的轴，使得其落在一个预定锥角(cone angle)内。在本发明第一实施例里，其中集光单元的轴和第一光束成形光学器件的轴平衡且重合，由集光单元整合的光被直接导入到第一光束成形光学单元内。在本发明第二实施例里，其中集光单元的轴和第一光束成形光学器件的轴不是平衡的，由集光单元整合的光通过一个反射单元被导入到光束成形光学单元内。第一光束成形光学单元的功能是准直收集的环境光，并通过一个反射镜将其导向混光单元。The light collecting unit collects ambient light from the outside and redirects it to the axis of the light collecting unit such that it falls within a predetermined cone angle. In the first embodiment of the present invention, wherein the axes of the light collecting unit and the first beam shaping optical device are balanced and coincident, the light integrated by the light collecting unit is directly guided into the first beam shaping optical unit. In the second embodiment of the present invention, wherein the axis of the light collecting unit and the axis of the first beam shaping optics are not balanced, the light integrated by the light collecting unit is guided into the beam shaping optical unit through a reflective unit. The function of the first beam shaping optical unit is to collimate the collected ambient light and direct it to the light mixing unit through a mirror.

来自光源的可视光穿过光束成形光学单元用于准直。随后，光束成形光学单元的准直光通过一个反射镜被导向混光单元。Visible light from the light source is passed through the beam shaping optics for collimation. Subsequently, the collimated light from the beam shaping optics is directed to the light mixing unit via a mirror.

混光单元混合并均匀化混光单元内的所有光，并控制将被投影到反射显示器单元上的混光的散射角，使得反射显示器单元接收到均匀照明。接着，从混光单元出来的混合光被导入到聚光单元，然后其将光导向PBS。The light mixing unit mixes and homogenizes all the light within the light mixing unit, and controls the scattering angle of the mixed light to be projected onto the reflective display unit, so that the reflective display unit receives uniform illumination. Next, the mixed light from the light mixing unit is introduced into the light concentrating unit, which then directs the light to the PBS.

若包含一个预偏器，其安装的最佳位置应在聚光单元和PBS之间。预偏器的朝向会使得仅有PBS阻止偏振态的光被透过。因此，来自预偏器的透射光将在PBS上被反射到反射显示器单元。在PBS，具有特别偏振的光被完全反射，而正交偏振的光被透过。然后，被反射离开PBS的光到达反射显示器单元。反射显示器单元，在运行使用期间其有一个视频信号作为其输入，通过偏振旋转来调制入射光。反射光包括了PBS阻止偏振态和PBS通过偏振态的光。仅有PBS通过偏振态的光，如图像光，才会通过PBS被传输到投影镜头单元，结果，投影镜头单元从视频信号投影一个图像到扩散膜上，其然后形成一个真实图像并被反射到挡风玻璃上而进入观察者视野。If a prepolarizer is included, it should be installed optimally between the condenser unit and the PBS. The prepolarizer is oriented such that only the PBS prevents the polarization state from being transmitted. Thus, transmitted light from the prepolarizer will be reflected on the PBS to the reflective display unit. In PBS, light with a particular polarization is completely reflected, while light with an orthogonal polarization is transmitted. The light that is reflected off the PBS then reaches the reflective display unit. A reflective display unit, which has a video signal as its input during operational use, modulates the incident light by polarization rotation. Reflected light includes both the PBS-blocked polarization state and the PBS-passed polarization state. Only light that passes the polarization state of the PBS, such as image light, is transmitted to the projection lens unit through the PBS, and as a result, the projection lens unit projects an image from the video signal onto the diffuser film, which then forms a real image and is reflected to the into the viewer's field of view through the windshield.

【附图说明】【Description of drawings】

图1描述本发明一个实施例的一个合并环境光的平视显示器。Figure 1 depicts a head-up display incorporating ambient light according to one embodiment of the present invention.

图2描述本发明一个实施例的一个合并环境光的平视显示器的外部示意图。FIG. 2 depicts an external schematic view of a head-up display incorporating ambient light according to an embodiment of the present invention.

图3描述本发明的一个平视显示器实施例内的光学器件示意图。Figure 3 depicts a schematic diagram of the optics within an embodiment of the head-up display of the present invention.

图4描述图2平视显示器的内部构造。FIG. 4 depicts the internal structure of the head-up display of FIG. 2 .

图5是本发明另一个实施例的一个合并环境光的平视显示器的外部示意图。FIG. 5 is an external schematic diagram of a head-up display incorporating ambient light according to another embodiment of the present invention.

图6描述图5平视显示器的内部构造。FIG. 6 depicts the internal structure of the head-up display of FIG. 5 .

【发明详述】【Detailed description of the invention】

附图中，在每个示意图里相同号码表示相同或类似的特征。图1描述本发明一个实施例的一个平视显示器10的示意图。如图1所示，本发明收集环境光以用来增强平视显示器里的显示亮度。环境光与一个电驱动光源如发光二极管(LED)或激光二极管的可视光聚合在一起，用来形成一幅具有增强亮度级的图像。In the drawings, like numbers indicate like or similar features throughout each illustration. FIG. 1 depicts a schematic diagram of a head-updisplay 10 according to one embodiment of the present invention. As shown in FIG. 1, the present invention collects ambient light to enhance display brightness in a head-up display. Ambient light is combined with visible light from an electrically driven light source such as a light emitting diode (LED) or laser diode to form an image with enhanced brightness levels.

当本发明用于图1所述的车辆时，一个由平视显示器(HUD)单元10形成的图像20将被投影到扩散膜220上，并被反射到挡风玻璃30上，然后其让驾驶者看到。可选择地，HUD单元可以安装在仪表板的顶部，因为这样能够对驾驶者前端的视野构成最小的障碍。另外，HUD单元也可以安置在车辆的其它合适位置，如部分地或全部地安装在仪表板上，车厢顶部等。When the present invention is used in the vehicle shown in FIG. 1, animage 20 formed by the head-up display (HUD)unit 10 will be projected onto thediffuser film 220 and reflected onto thewindshield 30, which then allows the driver to See. Optionally, the HUD unit can be mounted on top of the instrument panel, as this poses the least obstruction to the driver's front view. In addition, the HUD unit can also be arranged in other suitable positions of the vehicle, such as being partially or completely installed on the instrument panel, the top of the compartment, and the like.

如图2所示的HUD单元10的外部示意图。环境光通过窗口40进入单元10，投影光学器件的出口在投影仪窗口50。由于HUD单元10的紧凑设计，在车辆上的售后安装可以非常简容地完成。这种情况下，HUD 10可以形成部分导航/GPS系统，其可以简容地安装在任何车辆上。The external schematic diagram of theHUD unit 10 is shown in FIG. 2 . Ambient light enters theunit 10 through thewindow 40 and the exit of the projection optics is at theprojector window 50 . Due to the compact design of theHUD unit 10, aftermarket installation on vehicles can be done very simply. In this case, theHUD 10 can form part of a navigation/GPS system which can be easily installed on any vehicle.

用于本发明一个实施例的光学器件示意图在图3内描述。如图3所示，环境光和来自光源如一个或多个LED/激光的光，被聚合以形成一个单一的均匀光源用于HUD内。环境光100进入集光光学单元110，然后可选择地，由镜120反射，再由第一光束成形光学单元130进行整形。集光光学单元110收集环境光，并重新引导它使其落在一个指定的锥角内。集光光学单元110可以从各种光学装置中选择，如光导、非球面透镜、和菲涅耳透镜。但是，该列表并不是限制性的，任何能够有效地收集并传递环境光到HUD的光学装置都可以补充用于本发明。A schematic diagram of the optics used in one embodiment of the invention is depicted in FIG. 3 . As shown in Figure 3, ambient light and light from a light source, such as one or more LEDs/lasers, are combined to form a single uniform light source for use within the HUD. The ambient light 100 enters the light collectingoptical unit 110 , and is optionally reflected by themirror 120 and then shaped by the first beam shapingoptical unit 130 . Thecollection optics unit 110 collects ambient light and redirects it to fall within a specified cone angle. The light collectingoptical unit 110 may be selected from various optical devices such as light guides, aspheric lenses, and Fresnel lenses. However, this list is not limiting, and any optical arrangement that can efficiently collect and deliver ambient light to the HUD can be used in addition to the present invention.

光束成形光学单元130可以包括一组共轭透镜(conjugated lenses)或TIR透镜。光束成形光学单元130的目的是在光被导向混光装置之前准直聚集的环境光。The beam shapingoptical unit 130 may include a set of conjugated lenses or TIR lenses. The purpose of the beamshaping optics unit 130 is to collimate the collected ambient light before it is directed towards the light mixing device.

另一个光源140用于发射光，以便与集光光学单元110收集的环境光聚合。光源140可以是一个单色LED、多色LED、激光、白炽灯、卤素灯、弧光灯、或任何其它足够照明液晶元件的发光器、或以上发光器的任何组合。Anotherlight source 140 is used to emit light for aggregation with ambient light collected by the light collectingoptical unit 110 . Thelight source 140 can be a single-color LED, multi-color LED, laser, incandescent lamp, halogen lamp, arc lamp, or any other light emitter sufficient to illuminate the liquid crystal element, or any combination of the above light emitters.

接着，光源140的光进入第二光束成形光学单元150。当使用一个可选的反馈控制系统时，光源的光强度是可以根据收集的环境光强度而进行调整的。第二光束成形光学单元的目的是在将光导向混光单元170之前准直光源的光。Then, the light of thelight source 140 enters the second beam shapingoptical unit 150 . When using an optional feedback control system, the light intensity of the light source can be adjusted according to the collected ambient light intensity. The purpose of the second beam shaping optical unit is to collimate the light of the light source before directing the light to thelight mixing unit 170 .

反射镜160的安置和朝向会使得光源140的光和收集的环境光被导向混光单元170。反射镜160可以包括平面镜、曲面镜、直角棱镜、或多个以上透镜和/或多个以上透镜组合。反射镜160可以是单个单元或作为两个或多个独立单元。反射镜也可以由直角棱镜或其它光学器件代替，只要其能够改变光的方向。The placement and orientation of thereflector 160 will cause the light from thelight source 140 and collected ambient light to be directed to thelight mixing unit 170 . Thereflective mirror 160 may include a flat mirror, a curved mirror, a rectangular prism, or a plurality of the above lenses and/or a combination of the above lenses.Mirror 160 may be a single unit or as two or more separate units. Mirrors can also be replaced by rectangular prisms or other optical devices as long as they can change the direction of light.

对液晶元件而言，入射光的均匀度是非常重要的，混光单元170可以从各种装置中选择，只要其能够混合光源140的光和环境光，并输出一个充分均匀的光束。这类装置包括但不限于积分光棒(integrating rod)或宏焦距集光器(macrofocal concentrator)。宏焦距集光器的例子包括复合抛物面聚光器(CPC)、复合椭球面聚光器(CEC)和复合双曲面聚光器(CHC)。但是，任何能够均匀混合这两个光源并提供一个均匀输出的光学元件都可以补充作为本发明的混光单元170。为了进一步增强环境光和光源140的光的均匀化，利用混合器，混光单元的侧壁可以发散性地反射光。在混光单元内，聚集的和准直的环境光与来自光源140的准直光混合在一起。混光元件的功能是混合并均匀化在混光元件内的所有光，并控制将被投影到反射显示器单元上的混合光的扩散角。结果，从混光元件输出的光是被充分均匀化的。For the liquid crystal element, the uniformity of the incident light is very important, thelight mixing unit 170 can be selected from various devices, as long as it can mix the light of thelight source 140 and the ambient light, and output a sufficiently uniform light beam. Such devices include, but are not limited to, integrating rods or macrofocal concentrators. Examples of macrofocal concentrators include compound parabolic concentrators (CPC), compound ellipsoidal concentrators (CEC), and compound hyperbolic concentrators (CHC). However, any optical element that can uniformly mix the two light sources and provide a uniform output can be used as thelight mixing unit 170 of the present invention. In order to further enhance the uniformity of the ambient light and the light of thelight source 140, by using a mixer, the sidewall of the light mixing unit can reflect light divergently. In the light mixing unit, the concentrated and collimated ambient light is mixed with the collimated light from thelight source 140 . The function of the light mixing element is to mix and homogenize all the light within the light mixing element and to control the spread angle of the mixed light to be projected onto the reflective display unit. As a result, the light output from the light mixing element is sufficiently homogenized.

接着，从混光元件170出来的混合光进入到聚光单元180内。聚光单元180可以包括一组共轭透镜或一组自由曲面透镜。可选择地，如果有预偏器(pre-polarizer)，聚光单元将混合光导向预偏器，否则，混合光一旦从聚光单元180中出来，被导向偏振分光器(PBS)190。Then, the mixed light from thelight mixing element 170 enters into thelight concentrating unit 180 . Thelight concentrating unit 180 may include a set of conjugate lenses or a set of free-form surface lenses. Optionally, if there is a pre-polarizer, the concentrating unit directs the mixed light to the pre-polarizer, otherwise, the mixed light is directed to a polarizing beam splitter (PBS) 190 once it exits the concentratingunit 180 .

预偏器的安置和朝向会使得仅有PBS阻止偏振态(blockpolarization)的光被透过。因此，透过预偏器的光将在PBS上被反射到反射显示器单元200。The placement and orientation of the prepolarizer is such that only the PBS blocks polarization of light from being transmitted. Therefore, light transmitted through the prepolarizer will be reflected on the PBS toreflective display unit 200 .

在PBS 190上，具有特别偏振的光被完全反射，而具有正交偏振的光被透过。偏振可以是线型、圆型、或胆甾型(cholesteric)。线型偏振器的例子包括聚合物多层偏振膜(polymeric multiple layer polarizing film)或有线栅偏振器(wire grid polarizer)。将会注意到，使用胆甾型偏振器也可能需要引入四分波延迟器，以便在线型和圆型偏振之间转换光。例如，如果反射显示器单元在线型偏振光上运行，并且光源的光也是线性偏振，那么胆甾型偏振器可以在其前表面上有一个四分波延迟层，以便使光圆形偏振后再入射到胆甾型偏振器的表面。此外，四分波延迟器会使反射光线性偏振后再传播到反射图像显示器单元。如果来自光源的光是圆形偏振，那么在反射图像显示器单元输入上可以有一个四分波延迟器，从而使胆甾型偏振器反射的光线性偏振。此外，PBS 190可以在一个或多个方向上是平坦的或弯曲的。OnPBS 190, light with a particular polarization is completely reflected, while light with an orthogonal polarization is transmitted. Polarization can be linear, circular, or cholesteric. Examples of linear polarizers include polymeric multiple layer polarizing films or wire grid polarizers. It will be noted that the use of cholesteric polarizers may also require the introduction of quarter-wave retarders to convert light between linear and circular polarization. For example, if a reflective display unit operates on linearly polarized light, and the light from the source is also linearly polarized, the cholesteric polarizer can have a quarter-wave retardation layer on its front surface in order to circularly polarize the light before it enters the to the surface of the cholesteric polarizer. In addition, the quarter-wave retarder linearly polarizes the reflected light before it propagates to the reflective image display unit. If the light from the source is circularly polarized, there can be a quarter-wave retarder on the input of the reflective image display unit, so that the light reflected by the cholesteric polarizer is linearly polarized. Additionally,PBS 190 can be flat or curved in one or more directions.

具有PBS的阻止偏振态(block polarization)的光将在PBS 190上被反射，并将行进到反射显示器单元200。反射显示器单元可以是一个液晶显示器(LCD)单元，如硅基液晶(LCoS)显示器、数字光处理(DLP)显示器、或任何其它合适的显示器单元。当本发明运行时，一个视频信号输入到反射显示器单元200，该视频信号可能是从一个GPS单元、一个导航单元、一个或多个仪表板装置(如速度计、测速计、油量表)、机载计算机、或任何能够产生合适视频信号用于反射显示器单元的装置产生的。反射显示器单元200通过偏振旋转，能够空间地调制入射光。反射光包括PBS阻止偏振态和PBS通过偏振态(pass polarizations)的光。仅PBS 190通过偏振态的光，如图像光，将通过PBS被传输到投影仪单元210。Light with block polarization of the PBS will be reflected on thePBS 190 and will travel to thereflective display unit 200. The reflective display unit may be a liquid crystal display (LCD) unit, such as a liquid crystal on silicon (LCoS) display, a digital light processing (DLP) display, or any other suitable display unit. When the present invention is in operation, a video signal is input toreflective display unit 200, which may be from a GPS unit, a navigation unit, one or more instrument panel devices (such as speedometer, speedometer, fuel gauge), onboard computer, or any device capable of generating a suitable video signal for use in the reflective display unit. Thereflective display unit 200 is capable of spatially modulating incident light through polarization rotation. Reflected light includes light of polarization states blocked by the PBS and light of polarization states passed by the PBS. Only light that passes the polarization state of thePBS 190, such as image light, will be transmitted to theprojector unit 210 through the PBS.

如图1所示，投影仪单元210投影图像光在扩散膜220上。扩散膜可以被连接到投影仪单元。一个真实的镜像将通过扩散膜形成，并且该真实镜像将被反射到在挡风玻璃上而进入观察者视野。可以理解，扩散膜220的使用是可选择性的，可以设置反射显示器200与投影光学器件以便直接将一个合适图像直接从投影仪单元210显示到挡风玻璃上。As shown in FIG. 1 , theprojector unit 210 projects image light on thediffusion film 220 . A diffuser film can be attached to the projector unit. A true mirror image will be formed through the diffuser film, and this true mirror image will be reflected onto the windshield into the viewer's field of view. It will be appreciated that the use ofdiffuser film 220 is optional and thatreflective display 200 and projection optics may be provided to display a suitable image directly fromprojector unit 210 onto the windshield.

图4描述图2平视显示器10的光学元件的内部配置。图4元件类似于图3所示的那些元件，如对应的元件号码所示。FIG. 4 depicts the internal configuration of the optical components of the head-updisplay 10 of FIG. 2 . Components of FIG. 4 are similar to those shown in FIG. 3, as indicated by corresponding component numbers.

图5描述本发明平视显示器的一个卧式实施例10的外部示意图。如之前的实施例，环境光进入窗口40，图像光是从投影口50出来。图6描述在平视显示器10内部的光学元件配置。图6元件类似于图3所示的那些元件，如对应的元件号码所示。如图6所示，用于环境光的集光光学器件110的配置允许HUD高度低于图2HUD的高度。该实施例特别适用于售后安装在车辆仪表板上，因为其更能够提供更好的视野。FIG. 5 depicts an external schematic view of ahorizontal embodiment 10 of the head-up display of the present invention. As in the previous embodiments, ambient light enters thewindow 40 and image light exits theprojection port 50 . FIG. 6 depicts the arrangement of optical elements inside the head-updisplay 10 . Components of FIG. 6 are similar to those shown in FIG. 3, as indicated by corresponding component numbers. As shown in FIG. 6, the configuration of thecollection optics 110 for ambient light allows for a lower HUD height than that of the HUD of FIG. 2 . This embodiment is particularly suitable for aftermarket mounting on vehicle dashboards as it provides better visibility.

应该理解，本发明上述元件的实际位置和朝向可以调整以改变图像的尺寸、亮度和清晰度。It should be understood that the actual positions and orientations of the above elements of the present invention can be adjusted to change the size, brightness and clarity of the image.

尽管本发明已经在上下文里描述了专为机动车辆设计的用于显示相关驾驶信息如车辆速度、发动机速度(rpm)和全球定位系统(GPS)数据的平视显示器(HUD)单元，应该理解，本发明同样适用于其它交通工具涵义下的平视显示器，如航空器和船舶。此外，本发明同样适用于其它需要增强照明的情况，如头盔显示单元或微型投影仪。Although the present invention has been described in the context of a head-up display (HUD) unit designed for motor vehicles to display relevant driving information such as vehicle speed, engine speed (rpm) and global positioning system (GPS) data, it should be understood that the present invention The invention is also applicable to head-up displays within the meaning of other vehicles, such as aircraft and ships. In addition, the present invention is equally applicable to other situations that require enhanced lighting, such as helmet display units or micro-projectors.

尽管已经描述了本发明的特别实施例，应该理解，本发明不受限于在此所述的具体构造，从以上述描述可以明显地对其作出各种修改、改变和变化。这些修改、改变和变换被看作是所附权利要求内阐述的本发明范围的一部分。Although particular embodiments of the invention have been described, it is to be understood that the invention is not limited to the specific constructions described herein, and various modifications, changes and variations will be apparent from the foregoing description. Such modifications, changes and transformations are considered to be part of the scope of the present invention as set forth in the appended claims.