Patent Publication Number: US-2010118284-A1

Title: Angled light integrator for a display device

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority from U.S. Provisional Patent Application No. 61/114,145 of Ron Ferguson and David Kerry Kiser, entitled “ANGLED LIGHT TUNNEL FOR A PROJECTION DEVICE,” filed Nov. 13, 2008, the disclosure of which is hereby incorporated by reference in its entirety and for all purposes. 
    
    
     BACKGROUND AND SUMMARY 
     Display devices, such as projection devices, may be used in a variety of environments including, but not limited to, home environments and applications, education environments and applications, business facilities, conference rooms and other meeting facilities, etc. Display devices may be adapted to project a variety of multimedia materials including, but not limited to, images, text, graphics, video images, still images, presentations, etc. A user may desire to employ the use of a single display device in multiple locations. Therefore, a user may want to physically move the display device between the locations. To increase the display device&#39;s portability the size of the display device may be reduced. 
     However, difficulties may arise when attempting to reduce the size of the display device due to constraints of various optical components in the display device. For example, the image characteristics of the display device may be compromised when the size of various optical components are reduced, leading to degraded image quality. For example in some display devices, light emitted from a light source, may be reflected by at least one or more minors, through a light integrator including a light tunnel, and then to an imaging device, such as a liquid crystal display (LCD) panel. In the light integrator light rays are reflected multiple times off of the sides of the light tunnel prior to output thereby increasing the uniformity of the light distribution. The length of the light tunnel may affect how evenly the output light is distributed. Thus, when a shorter light tunnel is used, the uniformity of the output light distribution is decreased. The longer tunnel may produce more evenly distributed light, but results in an increase in the overall length and/or size of the display device, thereby adversely affecting the device&#39;s compactness. 
     Other attempts have been made to fold the light integrator at a right angle in an attempt to reduce the length of the display device. For example in U.S. Pat. No. 5,625,738 a light integrator having a first segment forming a right angle with a second segment is disclosed. However, the width of the display device may be increased when a right-angle folded light tunnel is utilized, preventing a reduction in the size of the display device. Furthermore, the light integrator shown in U.S. Pat. No. 5,625,738 may be constructed as a single component which may increase the manufacturing cost of the light integrator. 
     To address these issues and as disclosed in more detail herein, a light integrator for a display device is provided. The light integrator may include a first light tunnel configured to receive a light beam, increase the uniformity of the light distribution in the light beam, and output the light beam, the first light tunnel having a first optical axis. The light integrator may further include a redirection component configured to receive the light beam from the first light tunnel and redirect the light beam to a second light tunnel configured to further increase the uniformity of the light distribution in the light beam and transmit the light beam to downstream optical components, the second light tunnel having a second optical axis forming an angle less than 180 degrees and non-perpendicular with the first optical axis. 
     In this way, the shape of the light integrator may be adjusted (e.g. angled) to conform to the arrangement of components within a display device, facilitating a reduction in size of the display device while increasing the uniformity of the light distribution. In other words, the shape of the light integrator may be tailored to fit the packaging constraints of a compact display device, while retaining the image characteristics (e.g. light distribution) of a larger display device. 
     This Summary is provided to introduce concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Furthermore, the claimed subject matter is not limited to implementations that solve any or all disadvantages noted in any part of this disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  shows a schematic diagram of a display device including a light integrator. 
         FIG. 2  shows a first embodiment of the light integrator shown in  FIG. 1 . 
         FIG. 3  shows another embodiment of the light integrator shown in  FIG. 1 . 
         FIG. 4  shows an embodiment of the light integrator, shown in  FIG. 1 , forming an obtuse angle. 
         FIG. 5  shows an embodiment of the light integrator, shown in  FIG. 1 , including a first light tunnel having a length that is disproportional to a length of a second light tunnel. 
         FIG. 6  shows an embodiment of the light integrator, shown in  FIG. 1 , having tapered light tunnels. 
         FIGS. 7 and 8  show various embodiments of the light integrator, shown in  FIG. 1 , having a third light tunnel. 
         FIG. 9  shows a process flow for a light integrator included in a display device. 
     
    
    
     DETAILED DESCRIPTION 
     As described in more detail herein, a light integrator for a display device is provided. In one example, the light integrator may include a first light tunnel configured to receive a light beam, increase the uniformity of the light distribution in the light beam, and output the light beam, the first light tunnel having a first optical axis. The light integrator may further include a redirection component configured to receive the light beam from the first light tunnel and redirect the light beam to a second light tunnel configured to further increase the uniformity in the light distribution in the light beam and transmit the light beam to downstream optical components, the second light tunnel having a second optical axis forming an angle less than 180 degrees and non-perpendicular with the first optical axis. In this way, the uniformity of the light distribution may be increased while allowing the light integrator to be angled to conform to the contours of the display device. Therefore, the size of the display device may be reduced, if desired, while increasing the uniformity of the light distribution to a desired level. 
       FIG. 1  illustrates generally an exemplary display device  100 . As described and illustrated herein, display device  100  may be a projection device, such as a front projection device or front projector. In some examples, the projection device may be configured to be vertically mounted onto a ceiling or overhang. In other examples, the projection device may be configured to be positioned onto a surface such as a table, chair, etc. However, it should be appreciated that the display device may be another type of display device, including, but not limited to, a rear projector, a front projection television, a rear-projection television, etc. Further, the display device may be integrated within other systems, including but not limited to telephones, computers, etc. 
     Continuing with  FIG. 1 , display device  100  includes a housing or body  102 . As further elaborated below, housing  102  may contain a light source  104 , a light integrator  106 , optical components  108 , an imaging device  110 , as well as other components which may assist in the generation of a projected image. The housing may include heat-reduction elements, including venting panels, fans, blowers, etc. allowing external air to circulate within display device  100 , to cool the optical components (such as light source  104 ) as well as other electronic components within the display device and reduce any potential overheating during operation of the display device. 
     Light source  104  may be any suitable light source, including but not limited a high-intensity discharge (HID) lamp, light emitting diodes (LEDs), etc. In some examples, such as an HID lamp system, the light source may include a light gathering reflector and/or an arc lamp. The light gathering reflector may include an at least partially concave reflective surface, such as an ellipsoid, a parabola, etc. The arc lamp may comprise any of a variety of high intensity discharge lamps capable of producing sufficient light for display device  100 , such as a halogen lamp, a high pressure mercury arc lamp, etc. It will be appreciated that the light source may produce a wide spectrum light beam. In other words, the light source may be configured to emit a light beam having a wide spectrum. As another example, in an LED system, an LED-based light source may include a cluster or array of LED. However, in other examples, individual LEDs may be utilized. It will be appreciated that other suitable light sources configured to generate a light beam for propagation to downstream components may be utilized. As described herein a light beam may include a plurality of light rays having discrete energy packets. 
     Light integrator  106  may in part function to increase the uniformity of light distribution of a light beam, such as by distributing at least a portion of the light from light source  104 , substantially across an output aperture. The uniformity of the intensity of the distributed light may depend, at least in part, on the length of light integrator  106 . As further elaborated with reference to  FIGS. 2-8 , light integrator  106  may be folded in an angled configuration to enable lengthening of the optical path without substantially increasing the length and/or size of the display device. In this way, the portability of the display device may be increased without compromising image quality. 
     Light having an increased uniformity may then travel from light integrator  106  through a plurality of optical components  108  before being directed and/or focused towards imaging device  110 . The plurality of optical components  108  may include light filtering components, such as a color wheel, and one or more lenses, such as one or more focusing lenses, for focusing the distributed light towards the imaging device  110 . Imaging device  110  may include one or more reflective LCD panels, transmissive LCD panels, LCOS panels, and/or a variety of other image producing devices. Additionally, display device  100  may also include projection optics (not shown), such as projection lenses for example, for projecting the generated images onto a display surface. 
       FIG. 2  illustrates a first embodiment of light integrator  106 . In the depicted embodiment, the light integrator is in an acute angle configuration. However, as discussed in greater detail herein, the angle formed by the optical axes of the light integrator may be adjusted based on various factors such as the arrangement, size, and shape of other components in the display device. As previously discussed, the light integrator may be configured to receive a light beam from light source  104  and transmit a light beam having increased light distribution uniformity. In some examples, the light beam may be substantially homogenized upon passage through the light integrator such that the intensity of the light exiting the light integrator may be substantially uniform. However, in other examples, the light beam may not be substantially homogenized upon passage through the light integrator. 
     Light integrator may include a first light tunnel  210  and a second light tunnel  212 . The first light tunnel may be configured to increase the uniformity of the light distribution of a light beam traveling through the light integrator and the second light tunnel may be configured to further increase the uniformity of the light distribution in the light beam. The light integrator may further include a redirection component  214 , interposed between the first light tunnel  210  and the second light tunnel  212 . The redirection component may be configured to redirect the light beam from the first light tunnel into the second light tunnel. In this way, the direction of the light may be altered, allowing the light integrator to be angled. 
     In some examples the first light tunnel, the second light tunnel, and the redirection component may be separately manufactured and subsequently assembled, to reduce the manufacturing cost of the light integrator. However in other examples, the first light tunnel, the second light tunnel, and the redirection component may be manufactured as a single component. 
     The first light tunnel  210  may include an input end  216  for receiving light and an output end  218  for transmitting light. Similarly, the second light tunnel  212  may include an input end  220  and an output end  222 . Redirection component  214  may also include an input end  224  and an output end  226 . Further the redirection components may include a reflective surface  228 . In the depicted embodiment reflective surface  228  is a reflective mirror. However, in other embodiments, such as shown in  FIG. 3 , the reflective surface may be a surface in a prism, such as a total internal reflection (TIR) prism. 
     In the depicted embodiment, output end  218  of the first light tunnel may be in direct contact with input end  224  of the redirection component. Likewise, input end  220  of the second light tunnel may be in direct contact with output end  226  of the redirection component. Alternatively, there may be a partial gap between the first light tunnel  210 , the redirection component  214 , and/or the second light tunnel  212 . For example the gap may be 100 microns or less. Further still in other examples, the first light tunnel and/or the second light tunnel may be positioned such that they are spaced apart from the redirection component. 
     The first light tunnel  210  may further include a first reflective outer casing  230  and a first transmissive core  232 . Similarly the second light tunnel  212  may include a second reflective outer casing  234  and a second transmissive core  236 . It will be appreciated that light rays included in an input light beam may be propagated through the first light tunnel via the reflection of the light rays off opposing sides of the reflective outer casing  230  Likewise, the light beam may be propagated through the second light tunnel via the reflection of light rays off opposing sides of the reflective outer casing  234 . In the depicted embodiment the first transmissive core  232  and the second transmissive core  236  are hollow. However, in other embodiments, such as the example depicted in  FIG. 3 , one or both of the transmissive cores ( 232  and  236 ) may be formed out of a solid and transparent material, such as glass (e.g. doped glass) or a polymeric material (e.g. plastic). Additionally, it will be appreciated that the reflective outer casing may be a reflective minor or other suitable reflective device. However, when a solid and transparent transmissive core is utilized the reflective outer casing may be a surface of the glass or plastic, in some embodiments. Further, in some embodiments the input ends ( 216  and  220 ) and the output ends ( 218  and  222 ) of the first and second light tunnels may be rectangular or square in shape and four reflective surfaces may extend down the length of the light tunnel from the input end. Thus, in such example, the reflective surfaces (e.g. the tunnel walls) may be perpendicular at their abutting edges. However, in other embodiments, alternate light tunnel configurations may be utilized. 
     The first light tunnel  210  has a first optical axis  238  and the second light tunnel has a second optical axis  240 . In this example, the optical axes are longitudinally aligned with the light tunnels. It will be understood that the optical axes are not in alignment with the reflected light rays within the light tunnels. However, in other examples alternate alignments are possible. The optical axes may define an angular relationship between the first and the second light tunnels. Therefore, the first optical axis and the second optical axis form an angle  242 . In the depicted embodiment the angle is acute. However, in other embodiments other suitable angles may be formed. For example, the angle may be obtuse. Thus in some examples, the angle may be non-perpendicular and less than 180 degrees. The angle formed between the first and second optical axes may be selected based on packaging considerations (e.g. component layout, size and shape of the housing, etc.) in the display device. Light integrators with alternate angles shown in  FIGS. 4-8  are discussed in greater detail herein. 
       FIG. 3  shows a second embodiment of light integrator  106 . As previously discussed, the light integrator may be configured to receive a light beam from light source  104  and transmit a light beam having an increased uniformity of light distribution to downstream components. As the light integrator depicted in  FIG. 3  includes similar components to the light integrator shown in  FIG. 2 , the components are labeled similarly. 
     As depicted in  FIG. 3  the first transmissive core  232  and the second transmissive core  236  may be solid. For example a transparent material such as glass, doped glass, a polymeric material (e.g. plastic), etc., may substantially fill the core of the first and/or second light tunnel. When a solid transmissive core is used the reflective outer casing may be a surface of the solid transparent material. However in other embodiments, the reflective outer casing may be a reflective minor. Further, in other examples, the first transmissive core  232  may be hollow and the second transmissive core  236  may be formed out of a solid and transparent material or visa-versa. In this way, at least one of the first transmissive core and the second transmissive core may be formed out of glass or plastic and at least one of the first transmissive core and the second transmissive core is hollow. Continuing with  FIG. 3 , the redirection component may be a prism, such as a total internal reflection (TIR) prism. The prism may be constructed out of a suitable material, such plastic or glass. However, in other embodiments the redirection component may include a reflective mirror, as previously discussed. 
     Output end  218  of the first light tunnel  210  may be spaced apart from the input end  224  of redirection component  214 . Likewise, input end  220  of the second light tunnel  212  may be spaced apart from the output end  226  of the redirection component. Alternatively, there may be a partial gap between the first light tunnel and/or second light tunnel and the redirection component. For example the partial gap may be 100 microns or less. Further still in other examples, the first light tunnel and/or the second light tunnel may be positioned such that they are in direct contact with the redirection component. 
       FIG. 4  illustrates another example of light integrator  106 . The light integrator depicted in  FIG. 4  includes similar components to the light integrator shown in  FIG. 2 . Thus, related, components are labeled accordingly. 
     As shown, angle  242  formed by first optical axis and the second optical axis may be opened beyond 90 degrees. For example,  FIG. 4  illustrates the light integrator wherein the first and second optical axes form an obtuse angle. However, it will be appreciated that the angle depicted in  FIG. 4  is exemplary in nature and numerous alternate angles may be formed between the first and second optical axes in other embodiments. 
       FIG. 5  illustrates another embodiment of light integrator  106 . The first light tunnel  210  may be configured to increase the uniformity of the light distribution in a light beam by a first amount and the second light tunnel  212  may be configured to increase the uniformity of the light distribution in the light beam by a second amount that is disproportional to the first amount. As previously discussed the length of a light tunnel may correspond to an amount by which the uniformity of the light distribution is increased. Therefore, as shown in  FIG. 5  the length of the first light tunnel  210  may be disproportional to the length of the second light tunnel  212 . 
     The lengths of the light tunnels may be selected based on the desired uniformity of the light distribution in the display device as well as various packaging considerations of the display device. For example, an overall light tunnel length (i.e. summation of the length of the first and second light tunnels) may be selected based on the desired uniformity of the light distribution. Accordingly the angle formed by the optical axes as well as the length of the light tunnels may be chosen based on the selected overall light tunnel length as well as the layout of various components within the display device. However, in other examples, alternate techniques may be used to select the angle formed by the optical axes and the lengths of the light tunnels. As such, the first light tunnel may be an extended length relative to the second light tunnel or vise versa. 
       FIG. 6  depicts another embodiment of light integrator  106 . In the depicted example, the first light tunnel  210  and the second light tunnel  212  are tapered. As such, the width and/or height of input end  216  of the first light tunnel may be larger than the width and/or height of output end  218  of the first light tunnel. Similarly the width and/or height of input end  220  of the second light tunnel may be larger than the width and/or height of output end  222  of the second light tunnel. In this way, the output of the light integrator may be sized to attach to downstream components. It will be appreciated that when a square or rectangular light tunnel is utilized each of the opposing walls may be correspondingly tapered, in some examples. In other examples, the first light tunnel may be tapered and the second light tunnel may be substantially straight or visa-versa. 
     The redirection component may be sized to receive a light beam from the first tapered light tunnel and redirect the light beam to the second tapered light tunnel. As depicted, the first optical axis and the second optical axis form an acute angle. However, in other examples, alternate angles may be formed depending on the size and layout of other optical and electronic components in the display device. 
       FIGS. 7 and 8  illustrate alternate embodiments of light integrator  106 . In the illustrated embodiments the light integrator includes a third light tunnel  700  which may be used to further increase the uniformity of the light distribution in a light beam travelling through the light integrator. Additionally a second redirection component  702  configured to redirect a light beam may also be included in the light integrator. 
     The second redirection component may include an input end  704  configured to receive light from the second light tunnel  212 . The second redirection component may also include a reflective surface  706  and an output end  708 . The reflective surface may be a reflective mirror, a surface of a prism, etc. The second redirection component may direct a light beam to an input end  710  of the third light tunnel. The third light tunnel may be configured to further increase the uniformity of the light distribution in the light beam travelling through the light integrator. Additionally the third light tunnel may include a reflective outer casing  712 , a transmissive core  714 , and an output end  715 . The third light tunnel may also include a third optical axis  716 . The second optical axis  240  and the third optical axis  716  may form an angle  718 . In  FIG. 7  angle  718  is an obtuse angle and in  FIG. 8  angle  718  is a right angle. It will be appreciated that alternate angles may be formed in other embodiments, such as an acute angle. 
     Further, as shown in  FIG. 7  the third optical axis  716  may be parallel to a plane defined by the first and second optical axes ( 238  and  240 ). In  FIG. 8 , the third optical axis may extend through the plane defined by the first and second optical axes. In particular the third optical axis is perpendicularly arranged with respect to the first and second optical axes. However, in other examples, the orientation of the third optical axis may be altered. In either case the third optical axis forms an angle with the second optical axis that is less than 180 degrees. In some embodiments, the third optical axis may form an acute angle with the second optical axis. 
       FIG. 9  illustrates a method  900  for operation of a light integrator included in a display device. The method  900  may be implemented using the systems, devices, and components described herein, and/or via any other suitable systems, devices, and components. 
     At  902 , method  900  includes receiving a light beam at an input of a first light tunnel having a first optical axis. At  904  the method includes increasing the uniformity of the light distribution in the light beam in the first light tunnel and at  906  the method includes directing the light beam from the first light tunnel to a redirection component. 
     Next at  908  the method includes redirecting the light beam in the redirection component to a second light tunnel having a second optical axis forming an angle less than 180 degrees and non-perpendicular with the first optical axis. In this way, the direction of the light beam may be altered allowing the light integrator to be angled. At  910  the method includes further increasing the uniformity of the light distribution of the light beam in the second light tunnel and at  912  directing the light beam from the second light tunnel to downstream optical components. 
     In one embodiment, the downstream optical components may include one or more lenses, an imaging device, etc. However in another embodiment the downstream optical components may include a second redirection component and a third light tunnel configured to further increase the uniformity of light distribution of the light beam. Therefore, at  914  the method may further include receiving the light beam in a second redirection component and at  916  redirecting the light beam to a third light tunnel having a third optical axis forming an angle less than 180 degrees and non-perpendicular with the second optical axis. 
     At  918  the method includes further increasing the uniformity of the light distribution of the light beam in the third light tunnel. Next at  920  the method includes directing the light beam from the third light tunnel to downstream optical components. After  920  the method ends. In other examples, steps  914 - 920  may not be included in method  900 . 
     It will further be understood that the configurations and/or approaches described herein are exemplary in nature, and that these specific embodiments or examples are not to be considered in a limiting sense, because numerous variations are possible. The specific routines or methods described herein may represent one or more of any number of processing strategies. As such, various acts illustrated may be performed in the sequence illustrated, in other sequences, in parallel, or in some cases omitted. Likewise, the order of any of the above-described processes is not necessarily required to achieve the features and/or results of the embodiments described herein, but is provided for ease of illustration and description. The subject matter of the present disclosure includes all novel and nonobvious combinations and subcombinations of the various processes, systems and configurations, and other features, functions, acts, and/or properties disclosed herein, as well as any and all equivalents thereof.