Patent Abstract:
A multi channel video engine ( 10 ) for accepting, dividing, modifying and recombining light to project an image. A housing ( 12 ) encloses an optical assembly ( 28 ) having a dichroic mirror assembly ( 58 ) and a color cube ( 60 ). A plurality of LCD assemblies ( 30 ) accept light from the dichroic mirror assembly ( 58 ), modifies it, and reflects it to the color cube ( 60 ). A lens assembly ( 16 ) is affixed to a bulkhead ( 24 ) of the housing ( 12 ) using a lens cradle ( 14 ) and lens retainer ( 18 ). An output prism ( 54 ) aligns light onto a second plane ( 70 ) to coincide with an optical axis ( 72 ) of the lens assembly ( 16 ).

Full Description:
RELATED APPLICATIONS 
     This application is a continuation of U.S. Patent application Ser. No. 09/483,888, filed Jan. 18, 2000 now U.S. Pat. No. 6,377,318 by the same inventor, which is incorporated herein by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The present invention relates to the field of multi channel imaging devices, and more particularly to projection type imaging devices, wherein it is very important to accurately align physical components of the apparatus such that the color components of a resulting image will be aligned. The predominant current usage of the present inventive multi channel imaging engine is as a component of projection video display devices, wherein it is desirable to have a rugged and accurately aligned electro-optical unit for projecting well aligned color images therefrom. 
     BACKGROUND ART 
     The typical arrangement for multi-channel imaging systems will have a clamshell arrangement where the internal optics and components are assembled from above and the optical cavity is split along a horizontal plane into two halves. However, the construction of such a device results in two or more assembly planes. For example, at least one is horizontal for the placement of the splitting and combining optics, and at least one is vertical for the placement of the projection optics. This requires complex molded parts with expensive tooling. Since there are two or more assembly planes, the registration of the optics becomes more difficult. This problem is made worse in an off-axis design where the optics are not all on the same plane. 
     It would be desirable to have a multi-channel imaging system wherein the alignment problems discussed above are ameliorated. It would be of further benefit if such a device were sufficiently rigid to prevent distortion problems caused by flexing and vibration. However, such a solution, in order to be practical, should be inexpensive to produce and inexpensive to use in the production of a final multi channel image projection system. 
     To the inventor&#39;s knowledge, all previous apparatus or methods for producing a multi channel imaging engine have been difficult and/or expensive to manufacture and assemble, less than optimally rigid, and difficult to align and use. 
     DISCLOSURE OF INVENTION 
     Accordingly, it is an object of the present invention to provide a video projection engine that will provide sub-pixel accuracy over an entire image range. 
     It is still another object of the present invention to provide a video projection engine which is simple to construct and wherein components are readily aligned. 
     It is yet another object of the present invention to provide a video projection engine wherein there are no problems of mis-convergence due to twisting or bending of the optical housing. 
     It is still another object of the present invention to provide a video projection engine wherein artifacts from vibration introduced from external sources is minimized. 
     It is yet another object of the present invention to provide a video projection engine which is inexpensive to produce. 
     It is still another object of the present invention to provide a video projection engine which can be used with inexpensive auxiliary components. 
     It is yet another object of the present invention to provide a video projection engine which is inexpensive to install and align. 
     Briefly, an embodiment of the present invention is an assembly of mechanical components that aligns, supports and houses the optical, opto-mechanical and electronic components of a three color projection system. The architecture is executed in such a way that it solves many of the problems that are associated with high resolution multi-channel imaging systems. The total cost of the components is reduced because the number of components is less and the parts can be manufactured with high volume, low cost processes. The inter-channel stiffness and the mechanical stability between the individual color channels is superior to previous approaches. This is a direct consequence of the novel approach for enclosing the multi-channel cavity. There is no optical alignment required other than convergence of the discreet images. The components are all self-aligning with very low cost registration features. 
     The invention has a housing that is constructed in such a way that the entire optical cavity is contained inside the single formed part. The cavity is enclosed with a bulkhead that serves as a frame to align and support the optics and opto-mechanics. There is only a single assembly plane that is the plane of the bulkhead. The splitter and combiner optics are attached to the bulkhead as well as the projection lens. The cavity is enclosed when the kernel housing is attached to the bulkhead. The kernel housing can be formed as a single piece and there are no secondary operations required. The bulkhead can be stamped or molded and the bracket that holds the splitter dichroics, the combiner prism, the polarizer/analyzer assembly, and/or any additional optical devices can be molded (also with no secondary operations). There is a novel focussing mount for the projection lens that allows for a simple, low cost, fixed focus lens. 
     An advantage of the present invention is that a relatively inexpensive video projection engine is provided for incorporation into video projection imaging devices. 
     A further advantage of the present invention is that sub-pixel accuracy is provided over an entire image. 
     Yet another advantage of the present invention is that effects of vibration are essentially eliminated, such that cooling fans can be mounted on the video projection engine without adverse effects. 
     Still another advantage of the present invention is that the rigidity of the video projection engine essentially eliminates problems of mis-convergence due to twisting or bending of the optical housing. 
     Yet another advantage of the present invention is that the video projection engine is rugged in construction and reliable in operation. 
     Still another advantage of the present invention is that it is inexpensive to produce. 
     Yet another advantage of the present invention is that it is inexpensive to install, align, and use. 
     These and other objects and advantages of the present invention will become clear to those skilled in the art in view of the description of modes of carrying out the invention, and the industrial applicability thereof, as described herein and as illustrated in the several figures of the drawing. The objects and advantages listed are not an exhaustive list of all possible advantages of the invention. Moreover, it will be possible to practice the invention even where one or more of the intended objects and/or advantages might be absent or not required in the application. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is perspective view of a multi channel imaging engine according to the present invention; 
         FIG. 2  is an exploded perspective view of the multi channel imaging engine of  FIG. 1 ; 
         FIG. 3  is an exploded perspective view of the lens unit of  FIGS. 1 and 2 ; 
         FIG. 4  is an exploded perspective view of the bulkhead and the optical assembly of  FIGS. 1 and 2 ; 
         FIG. 5  is an exploded perspective view of the optical assembly of  FIGS. 1 ,  2  and  4 ; 
         FIG. 6  is a perspective view of another embodiment of a multi channel imaging engine according to the present invention; and 
         FIG. 7  is an exploded perspective view of the example of the multi channel imaging engine of FIG.  6 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The embodiments and variations of the invention described herein, and/or shown in the drawings, are presented by way of example only and are not limiting as to the scope of the invention. Unless otherwise specifically stated, individual aspects and components of the invention may be omitted or modified, or may have substituted therefore known equivalents, or as yet unknown substitutes such as may be developed in the future or such as may be found to be acceptable substitutes in the future. The invention may also be modified for a variety of applications while remaining within the spirit and scope of the claimed invention, since the range of potential applications is great, and since it is intended that the present invention be adaptable to many such variations. 
     The mode for carrying out the invention, as described herein, is a multi channel imaging engine. An example of the inventive multi channel imaging engine is depicted in a perspective view in FIG.  1  and is designated therein by the general reference character  10 . The multi channel imaging engine  10  has a housing  12  with a lens cradle  14  affixed thereto. The lens cradle  14  supports a lens assembly  16  which is held in place, thereon, by a lens retainer  18 . The assembled lens cradle  14 , lens assembly  16 , and lens retainer  18  will be referred to, herein, as a lens unit  19 . 
     This example of the invention has two cooling fans  20  affixed to the housing  12 . While the cooling fans  20  are not a necessary part of the invention, it is instructive to note that the present inventive multi channel imaging engine  20  is sufficiently rigid that the cooling fans  20  can be mounted thereon without the adverse effects of vibration which would result from a less rigid device. 
     In this embodiment of the invention, the housing  12  has a kernel housing  22  and a bulkhead  24 . The kernel housing  22  described herein is die cast from aluminum alloy, although other construction techniques including but not limited to alternative molding methods are within the scope of the invention. Another example of a construction technique would be to press form the housing from a single piece of sheet steel, or to cut and bend sheet metal into the desired shape. The bulkhead  24  is affixed to the kernel housing  22  by screws  26 , as shown by way of example in the view of  FIG. 1  such that an interior  27  of the housing  12  is generally enclosed by the bulkhead  24  and the kernel housing  22 . 
     An optical assembly  28  is affixed to the bulkhead  24  within the housing  12 , and three LCD assemblies  30  are affixed to the outside of the housing  12 . The LCD assemblies  30  may optionally be of essentially any reflective type, wherein light projected onto one of the LCD assemblies  30  is modified according to an image electronically provided to the LCD assembly and the light, modified to conform to the image, is reflected therefrom. One skilled in the art will be familiar with such devices. In this present embodiment of the multi channel imaging engine  10 , the LCD assemblies  30  are of the commercially available type. The LCD assemblies  30  are each affixed to the kernel housing  22  using an alignment mount  32  whereby the LCD assemblies  30  may be aligned, as necessary, during final assembly of the multichannel imaging engine  10 . One skilled in the art will also be familiar with the alignment mount  32 , and variations of such that are available. 
       FIG. 2  is an exploded perspective view of a portion of the multichannel imaging engine  10  of FIG.  1 . In the view of  FIG. 2 , it can be seen that the optical assembly  28  is affixed to the bulkhead  24 . Also, in the view of  FIG. 2  it can be seen that the lens cradle  14  has an additional plurality (three are visible in the view of  FIG. 2 ) of the screws  26  for affixing the lens cradle  14  to the bulkhead  24 . 
     A light entry port  34  can be seen in the bulkhead  24  wherethrough white light is introduced into the housing  12 . Also visible in the view of  FIG. 2  are two of the three LCD ports  36  wherethrough light is projected onto, and reflected form the LCD assemblies  30  (FIG.  1 ). One of the two cooling ports  38  of this embodiment of the invention, whereon the cooling fans  20  ( FIG. 1 ) are affixed, is also visible in the view of FIG.  2 . 
       FIG. 3  is an exploded perspective view of the lens unit  19 , previously discussed herein in relation to  FIGS. 1 and 2 . The fixed focus lens assembly  16  has a positioning projection  40 , and the lens cradle  14  has two retaining rings  42  for accepting the lens assembly  16 . Each of the retaining rings  42  has a gap  44  therein such that the lens assembly can be inserted into the lens cradle  14  with the positioning projection  40  aligned with the gaps  44 . The lens assembly  16  is then secured in position in the lens cradle  14  by the lens retainer  18  using a pair of cap screws  46 . As can be seen in the view of  FIG. 3 , a positioning slot  48  in the lens retainer  18  is angled such that, when the positioning projection  40  is within the positioning slot  48 , the rotating the lens assembly  16  (with the cap screws  46  appropriately loosened), as indicated by arrow  50 , will cause the fixed focus lens assembly  16  to move forward or backward in the lens cradle  14 , as indicated by arrow  52 , such that the lens assembly  16  can be focused, as required. 
       FIG. 4  is an exploded view of the bulkhead  14  and optical assembly  28  wherein the optical assembly  28  can be more readily viewed. As can be seen in the view of  FIG. 2 , an output truncated doublet  54  (which is effectively used as a prism for redirecting light) of the optical assembly  28  projects partially through a light exit port  56  in the bulkhead  14  when the optical assembly  28  is affixed to the bulkhead  14 . Also visible in the view of  FIG. 4  are a dichroic mirror assembly  58 , and a color cube  60 , which will be discussed in more detail, hereinafter. The output truncated doublet  54 , the dichroic mirror assembly  58  and the color cube  60  are each affixed to an optical frame  62 . 
       FIG. 5  is an exploded perspective view of the optical assembly  28 , according to this presently described embodiment of the invention. One skilled in the art will recognize that the dichroic mirror assembly  58  has three dichroic mirrors  64  arranged in an “X” configuration such that white light projected onto the dichroic mirror assembly  58  is divided into its three basic component wavelength colors, with one of each such colors being directed toward a corresponding one of the LCD assemblies  30  (FIG.  1 ). One skilled in the art will also recognize that the color cube  60  is made up of four color cube prisms  65  with the contiguous surfaces thereof having dichroic surfacing such that three primary color light beams reflected from the three LCD assemblies  30  are recombined and directed toward the output truncated doublet  54 . 
     It is important to note that, in this embodiment of the invention, light us directed slightly upward (from a perspective where the color cube  60  is above the dichroic mirror assembly  58 ) as light enters the housing  12  through the light entry port  34  (FIG.  2 ), as indicted by a light input path arrow  66  in FIG.  1 . Accordingly, as light travels through the multi channel imaging engine  10 , the light is divided by the dichroic mirror assembly  58 , modified by and reflected from the LCD assemblies  30 , and recombined by the color cube  60  relative to a first plane  68 . The light is also moving relative to a second plane  70  (generally upward, as discussed previously herein) such that the light first passes through the dichroic mirror assembly  58 , is then reflected at an upward angle from the LCD assemblies  30 , and then passes through, and is recombined by, the color cube  60 . Since an optical axis  72  of the lens assembly  16  is aligned generally along the first plane  68 , the output truncated doublet  54  is shaped and configured to realign the (slightly upward canted) light with the optical axis  72  of the lens assembly  16 . 
     Accordingly, the described embodiment of the multi channel imaging engine  10  is assembled generally as follows; The optical assembly  28  is assembled as described herein and affixed to the bulkhead  24 . The bulkhead is affixed to the kernel housing  22  generally enclosing the interior  27  thereof. The LCD assemblies  30  are affixed to the exterior of the kernel housing  22 , using the alignment mounts  32 , as previously described herein. In this manner, the bulkhead  24  and the kernel housing  22  serve as mounting means for mounting the optical assembly  28  with respect to the LCD assemblies  30 . Except as otherwise stated, or as may be necessitated by a particular application or variation of the invention, the order of assembly operations is not critical and is not an inherent part of the invention. 
     Another embodiment of the multi channel imaging engine is depicted in a perspective view in FIG.  6  and is designated therein by the general reference character  10   a . This embodiment of the multi channel imaging engine  10   a  is not greatly different in kind and in components from the previously described multi channel imaging engine  10 , previously described herein. The multi channel imaging engine  10   a  is presented here in order to illustrate some possible variations in shape and construction as described herein and as depicted in the drawings. As can be seen in the view of  FIG. 6 , the multi channel imaging engine  10   a  has a housing  12   a  with a lens cradle  14   a  affixed thereto. The lens cradle  14   a  supports a lens assembly  16   a  which is held in place, thereon, by a lens retainer  18   a . The assembled lens cradle  14   a , lens assembly  16   a , and lens retainer  18   a  will be referred to, herein, as a lens unit  19   a . As can be seen in the view of  FIG. 6 , two of the cooling fans  20  are affixed to the housing  12   a  in this embodiment of the invention, as well. 
     In this embodiment of the invention, also, the housing  12   a  has a kernel housing  22   a  and a bulkhead  24   a , each of which are constructed by methods similar to those previously described in relation to the first described embodiment of the invention, herein, and shaped as shown in the view of FIG.  6  and the subsequent figures of the drawing. 
     An optical assembly  28   a  is affixed to the bulkhead  24 . within the housing  12   a , and three LCD assemblies  30 , which are not significantly different from the LCD assemblies  30  previously described herein, are affixed to the outside of the housing  12   a . The bulkhead  24   a  and the kernel housing  22   a  when fixed to each other, provide mounting means for mounting the optical assembly  28   a  with respect to the LCD assemblies  30 . 
       FIG. 7  is an exploded perspective view of a portion of the multichannel imaging engine  10   a  of FIG.  6 . In the view of  FIG. 7 , it can be seen that the optical assembly  28   a  is affixed to the bulkhead  24   a . Indeed, in this embodiment of the multi channel imaging engine  10 , the components of the optical assembly  28   a  are affixed directly to the bulkhead  24   a , as will be discussed in more detail, hereinafter. In this embodiment also, a light entry port  34   a  can be seen in the bulkhead  24   a  wherethrough white light is introduced into the housing  12   a . Also visible in the view of  FIG. 7  are two of the three LCD ports  36   a  wherethrough light is projected onto, and reflected form the LCD assemblies  30  (FIG.  6 ). One of two cooling ports  38   a  of this embodiment of the invention, whereon the cooling fans  20  ( FIG. 6 ) are affixed, is also visible in the view of FIG.  7 . The fixed focus lens assembly  16   a , the lens cradle  14   a , and the lens retainer  18   a  function much like the fixed focus lens assembly  16  and the lens cradle  14  previously discussed herein in relation to  FIG. 3 , although the actual shape is somewhat different, as can be seen by comparison of the views of  FIGS. 2 and 7 . 
     As can be seen in the view of  FIG. 7 , an output doublet  54   a  is positioned in relation to a light exit port  56   a , and performs functions previously as described herein in relation to the truncated doublet  54  of the previously described embodiment. 
     In this presently described embodiment  10   a  of the present invention, the dichroic mirrors  64  are assembled within a mirror receptacle  74  which is formed as a part of the bulkhead  24   a , and the color cube  60  is affixed to the bulkhead  24   a . The dichroic mirrors  64  and the color cube  60  are essentially the same as, and function in an similar manner to like elements previously discussed herein in relation to the first described embodiment  10  of the invention. 
     Various modifications may be made to the invention without altering its value or scope. For example, the housing  12  could be molded and/or made from another material. 
     All of the above are only some of the examples of available embodiments of the present invention. Those skilled in the art will readily observe that numerous other modifications and alterations may be made without departing from the spirit and scope of the invention. Accordingly, the disclosure herein is not intended as limiting and the appended claims are to be interpreted as encompassing the entire scope of the invention. 
     INDUSTRIAL APPLICABILITY 
     The inventive multi channel imaging engine  10  is intended to be widely used in the production of video image projection systems such as high resolution projection television devices, and particularly computer video output projection display devices. The invention allows convergence to sub-pixel accuracy over the entire image. The assembly is simplified by the self-aligning features and there is no alignment of optics other than the convergence of the three image channels. The inter-channel stiffness is substantially high so that there are no problems of misconvergence due to twisting or bending of the optical housing. There is a substantial cost advantage because the construction of the mechanics allows for simple molded and stamped parts with no secondary machining operations. The focussing mount can be molded and allows the projection lens to be purchased as a low cost fixed focus lens. 
     This mechanical architecture is a departure from the typical method of projection system assembly. It permits low cost system solutions, especially with (but not exclusive to) off-axis projection systems. This will allow off-axis reflective projection systems to complete effectively in the market for high resolution, low cost display systems. 
     One skilled in the art will readily understand the alignment procedures used in conjunction with the present invention. For example, the alignment mounts  32  are used to adjust the LCD assemblies such that the three color component images properly align when recombined in the color cube  60 . Similarly, the lens retainer  18  will be loosened and the lens assembly rotated, as briefly discussed herein before, to properly adjust the focal aspect of the lens assembly  16 . 
     Since the multi channel video projection engine  10  of the present invention may be readily produced and integrated with existing video creation and display systems and devices, and since the advantages as described herein are provided, it is expected that it will be readily accepted in the industry. For these and other reasons, it is expected that the utility and industrial applicability of the invention will be both significant in scope and long-lasting in duration.

Technology Classification (CPC): 7