Abstract:
Methods, apparatuses and systems for projecting an image, such as a diffused image, are disclosed herein.

Description:
RELATED APPLICATIONS 
   This application is a continuation of U.S. application Ser. No. 10/733,972 filed Dec. 11, 2003 now U.S. Pat. No. 6,883,917 titled “ILLUMINATION FIELD BLENDING FOR USE IN SUBTITLE PROJECTION SYSTEMS,” which is a continuation of U.S. application Ser. No. 10/020,516 filed Dec. 14, 2001 now U.S. Pat. No. 6,663,244 titled “ILLUMINATION FIELD BLENDING FOR USE IN SUBTITLE PROJECTION SYSTEMS.” 

   TECHNICAL FIELD 
   This invention relates to image projection systems that superimpose text onto a screen with an image of a projected film. 
   BACKGROUND OF THE INVENTION 
   Subtitles or text images that are projected onto a screen from a film having a movie or other image are commonly laser etched into the film itself. Subtitles etched onto film can be difficult to see, particularly if at any time the images in the film have a color that matches the color of the subtitles. The film image can temporarily camouflage the subtitles. In addition, because the subtitles are etched onto the film itself, a unique and separate film must be made having subtitles in each desired language. 
   To make subtitles more visible and to avoid the need to alter the film itself, a projection system which projects one image onto another image may be used to project subtitles onto another image on a screen. Such a projection system has a first projector that projects the movie or other images onto a screen and a second projector that projects a text box containing subtitles onto the screen. The second projector, instead of projecting subtitles that have been etched onto film, may project digital images from a compact disc. These digital images are clearer than text that has been etched onto film. In addition, a compact disc may have the subtitles in a variety of languages, making international distribution of movies simpler because the film can be distributed in its original form. 
   A disadvantage of using such a text projection system is that the text box sharply transitions from light to dark, making the border of the subtitle image sharp and clearly visible on the image. This sharp transition creates a sharply distinct box on the image, cutting out whatever portion of the image that would otherwise be seen where the box is located. Such a text box prevents the image from gradually blending into the text. 
   SUMMARY OF THE INVENTION 
   It is an object of this invention to provide a projector that projects a text box with a fade out transition region to enable a text box to appear to gradually fade out into the other image. 
   The projection system of the present invention projects a text box with a fade out transition region that minimizes visual disruption to the image onto which the text box is projected. The fade out transition region is created by the position of the optical elements of a text projector, as discussed below. The projection system includes an image projector and a text projector. The image projector projects an image onto a screen, and the text projector projects text or subtitles onto a portion of the image. The text or subtitles are projected in a text box. 
   The text projector has a light source or lamp adapted to project light as a text box. The text projector also has a light path modifier positioned to receive light from the light source. In one embodiment, the light path modifier is an integrator tunnel with reflective walls. In another embodiment, the light path modifier is a,pair of fly eye panels. The text projector further includes a relay lens that transmits light in the form of a text box from the light path modifier to a display device. The display device may be transmissive or reflective. A projection lens receives light from the display device and is positioned to project a text box onto the image projected by the image projector. The text projector preferably has an optional pair of condensing lenses positioned to condense light and direct it from the light path modifier to the relay lens. A single condensing lens may also be used. Alternatively, the relay lens may function as the condensing lens. 
   The sharpness of the borders of the text box are determined by the placement of the light path modifier relative to an object plane. The position of the object plane is defined by the position of the relay lens. Projectors which project a sharply defined text box onto another image have a relay lens that defines an object plane at the exit end of a light tunnel or other light path modifier. In order to decrease the sharpness of the borders of the text box, the exit end of the light path modifier is sufficiently offset from the object plane so that the contrast between the text box and the image projected by the image projector is diminished. The light path modifier may also be sufficiently offset so that the image projected by the image projector is at least partially visible through the text box and so that the text box has a fade out transition region. The borders of such a text box will blend into the image projected by the image projector. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic of the projection system with an image projector and a text projector projecting onto a screen. 
       FIG. 2A  illustrates a first example of a text box projected onto another image as it would appear on a screen when a prior art system is utilized. 
       FIG. 2B  illustrates a first example of a text box projected onto another image as it would appear on a screen when a system is used in accordance with the present invention. 
       FIG. 3A  illustrates a second example of a text box projected onto another image as it would appear on a screen when a prior art system is utilized. 
       FIG. 3B  illustrates a second example of a text box projected onto another image as it would appear on a screen when a system is utilized in accordance with the present invention. 
       FIG. 4A  is a schematic of the elements of the text projector of an embodiment of the present invention with an integrator tunnel 
       FIG. 4B  is a schematic of the elements of the text projector of an embodiment of the present invention with a pair of fly eye panels. 
       FIG. 5A  is a schematic of the optical architecture and the relationship of the object plane and the display device, as a function of the placement of the light path modifier before the light path modifier is offset from the object plane. 
       FIG. 5B  is a schematic of the optical architecture and the relationship of the object plane and the display device, as a function of the placement of the light path modifier after the light path modifier is offset from the object plane. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Different embodiments of the present invention, described by way of example, project an image and a text box, the text box having borders that enable the image to be seen along the borders. Skilled persons will readily appreciate that the present invention can be used in any projection system that projects one image onto another. 
   One embodiment of a projection system  10  is shown in  FIG. 1 , with an image projector  20  and a text projector  30 . Image projector  20  projects an image  120  onto a screen  100  and text projector  30  projects a smaller image, as text  132  in a text box  130 , onto the screen  100 . Together, text box  130  and image  120  form a composite image  110 . 
     FIGS. 2A and 3A  illustrate text boxes  130  projected by a text projector  30  of the prior art as the text boxes  130  would appear in composite image  110 . Text boxes  130  of the prior art have borders  134  that are sharply defined, making text box  130  distinct from image  120 . The sharp definition of border  134  completely blocks out precisely as much of image  120  as overlaps text box  130 . Text boxes  130  of the prior art also prevent image  120  from gradually blending into text  132 . 
     FIGS. 2B and 3B  illustrate the appearance of text boxes  130  when light is transmitted onto a screen through use of an embodiment of the present invention. Text boxes  130  of  FIGS. 2B and 3B  have a fade out transition region  136  that gradually fades out completely at border  134  of text box  130 , enabling more of image  120  to be viewed than text boxes  130  delivered in accordance with the prior art, as shown in  FIGS. 2A and 3A . Fade out transition region  136  enables text box  130  to blend with image  120 , making text box  130  less visually disruptive to composite image  110 . 
     FIGS. 4A and 4B  are schematic views of the elements required for text projector  30  of two different embodiments of a projection system  10 . Text projector  30  has a light source or lamp  40  adapted to project light to display text  132  and text box  130 . Text projector  30  also has a light path modifier. In the embodiment shown in  FIG. 4A , the light path modifier is an integrator tunnel  50  with an entry end  52  and an exit end  54 . Integrator tunnel  50  is a tunnel with reflective walls as disclosed in U.S. Pat. No. 5,625,738, which is incorporated herein by reference. 
   Integrator tunnel  50  is positioned to receive light from light source  40  at entry end  52 . Integrator tunnel  50  redistributes light from light source  40  so that, at exit end  54 , the light is uniformly distributed in a shape matching the that of text box  130 . In the embodiment shown in  FIG. 4B , the light path modifier is a pair of fly eye panels  50 ′, each of which corresponds to an array of small lenses, with a first fly eye panel  52 ′ and a second fly eye panel  54 ′. 
   Text projector  30  further includes a relay lens  70  positioned to receive light from light path modifier  50  or  50 ′ and to transmit light to a display device  80 . As shown in  FIG. 4B , the text projector preferably includes a pair of condensing lenses  62 ,  64 . A single condensing lens may also be used. Condensing lenses  62 ,  64  are positioned to direct and condense light from light path modifier  50  or  50 ′ to relay lens  70 . Condensing lenses  60  operate to condense light so that display device can be smaller, reducing the overall cost of text projector  30 . In an alternative embodiment, the text projector has no condensing lenses and relay lens  70  operates both as a relay lens and a condensing lens, as shown in  FIG. 4A . 
   Display device  80  receives light in the shape of text box  130  as it is to be projected on screen  100 . Display device  80  may be transmissive or reflective. For example, display device  80  may be a transmissive LCD panel or a reflective array of mirrors. A projection lens  90  is positioned to receive light transmitted or reflected by display device  80 . The focus of text  132  in text box  130  is determined by the position of projection lens  90  relative to display device  80 . Projection lens  90  is also positioned to superimpose text box  130  onto image  120 , forming composite image  110 . 
   As shown in  FIGS. 5A and 5B , the position of relay lens  70  defines the position of an object plane  44 .  FIG. 5A  shows exit end  54  of integrator tunnel  50  at object plane  44 . In similar projectors that utilize fly eye panels, second fly eye panel  54 ′ is at object plane  44 . Text projector  30 , configured as shown in  FIG. 5A  with exit end  54  or second fly eye panel  54 ′ at object plane  44 , projects a sharply defined image, with a border that abruptly transitions from image  120 . 
     FIG. 5B  shows an embodiment of the present invention with an integrator tunnel  50  as the light path modifier. Exit end  54  is sufficiently offset from object plane  44  and away from relay lens  70  such that the light from light source  40  is concentrated on the center of display device  80  and increasingly diffuse as the light approaches the edges of display device  80 . The same effect may be achieved by offsetting exit end  54  from object plane  44  towards relay lens  70 . The decrease in light concentration from the center of text box  130  to borders  134  of text box  130  minimizes the contrast between text box  130  and image  120 . Stated otherwise, exit end  54  of integrator tunnel  50  is sufficiently offset from object plane  44  to enable image  120  to be at least partially visible through text box  130  at fade out transition region  136 . Borders  134  of text box  130  projected by text projector as shown in  FIG. 5B  blend into image  120  along fade out transition region  136 . Such a gradual transition causes less visual disruption to composite image  110  while still enabling text  132  to be completely legible. Similarly, in embodiments containing fly eye panels, front fly eye panel  54  is offset from object plane  44  as described above for exit end  54 . 
   There are several steps involved in a method for projecting composite image  110  that minimizes the contrast at the transition from text box  130  around text  132  to image  120 . After obtaining image projector  20  and obtaining text projector  30  with optical elements adapted to project text  132  in a text box  130 , as described above, the optical elements are modified. More particularly the optical elements of text projector  30  are adjusted so that exit end  54  or front fly eye panel  54  is offset from object plane  44  away from relay lens  70  from exit end  54  or front fly eye panel  54 . Alternatively, exit end  54  or front fly eye panel  54  may be offset toward object plane  44  toward relay lens  70 . 
   As described above in connection with  FIGS. 4A and 4B , adjusting the optical elements involves identifying the position of object plane  44  as defined by the position of relay lens  70  and positioning light path modifier  50 ,  51 ′ relative to object plane  44  so that the light path modifier  50 ,  50 ′ is offset from object plane  44 . The light path modifier  50 ,  50 ′ is offset from object plane  44  away from relay lens  70  sufficiently to diffuse light at borders  134  and concentrate light towards text  132  in text box  130  and to display device  80 , thereby decreasing the sharpness of borders  134  so that contrast between text box  130  and image  120  is diminished. As discussed above, a similar effect is achieved by offsetting light path modifier  50  from object plane  44  toward relay lens  70 . 
   It will be obvious to those having skill in the art that many changes may be made to the details of the above-described embodiments of this invention without departing from the underlying principles thereof. The scope of the present invention should, therefore, be determined only by the following claims.