Abstract:
A projection screen has first transparent particles tinted a first color and second transparent particles tinted a second color.

Description:
BACKGROUND 
   Projection screens may display images projected thereon by projectors. Some types of projection screens may absorb colors of the projected light. This may result in lost light to the viewer as compared to the light from a fully diffusive surface. Additionally, these types of projection screens may act as diffuse reflectors and therefore a substantial portion of the reflected light may not be directed back toward the viewer. 

   
     DESCRIPTION OF THE DRAWINGS 
       FIG. 1  illustrates a portion of an embodiment of a frontal projection screen, according to an embodiment of the disclosure. 
       FIG. 2  illustrates a portion of an embodiment of a frontal projection screen, according to another embodiment of the disclosure. 
       FIG. 3A  illustrates a portion of an embodiment of a frontal projection screen, according to another embodiment of the disclosure. 
       FIG. 3B  illustrates a portion of an embodiment of a frontal projection screen, according to yet another embodiment of the disclosure. 
       FIG. 4A  illustrates a portion of an embodiment of a frontal projection screen, according to another embodiment of the disclosure. 
       FIG. 4B  illustrates a portion of an embodiment of a frontal projection screen, according to still another embodiment of the disclosure. 
       FIG. 5  illustrates a portion of an embodiment of a frontal projection screen, according to another embodiment of the disclosure. 
       FIG. 6  illustrates a portion of an embodiment of a frontal projection screen, according to another embodiment of the disclosure. 
       FIG. 7  illustrates a portion of an embodiment of a frontal projection screen, according to another embodiment of the disclosure. 
       FIG. 8  illustrates a portion of an embodiment of a rear projection screen, according to another embodiment of the disclosure. 
   

   DETAILED DESCRIPTION 
   In the following detailed description of the present embodiments, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific embodiments that may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice disclosed subject matter, and it is to be understood that other embodiments may be utilized and that process, electrical or mechanical changes may be made without departing from the scope of the claimed subject matter. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the claimed subject matter is defined only by the appended claims and equivalents thereof. 
     FIG. 1  illustrates a portion of a frontal projection screen  100 , according to an embodiment. Screen  100  includes a substrate  110  that may be flexible or substantially rigid. For one embodiment, substrate  110  may include a mirror reflector, e.g., is silvered or mirrored; for another embodiment, substrate  110  may include a diffusive reflector, e.g., is white; and for another embodiment, substrate  110  may include a dark light absorber, e.g., black or gray. Transparent particles  120 ,  122 , and  124 , such as spheres, ellipsoids, etc., e.g., of glass or plastic, may, in one embodiment, be adhered to substrate  110  using an opaque or transparent adhesive  115 . Particles  120 ,  122 , and  124  are in direct contact or otherwise in optical contact with substrate  110  so that light can pass through particles  120 ,  122 , and  124  and reach substrate  110 . For one embodiment each of particles  120 ,  122 , and  124  is tinted a different color, e.g., particle  120  is tinted green, particle  122  red, and particle  124  blue. For various embodiments, dyes, pigments, interference coatings, dichroic coatings, etc. can be used to tint particles  120 ,  122 , and  124 . For other embodiments, two different colors, such as magenta and green, four colors, e.g., cyan, magenta, yellow, and black, etc., are used instead of three. For another embodiment, particles  120 ,  122 , and  124  are respectively tinted cyan, magenta, and yellow. 
   For other embodiments, adhesive  115  may have a substantially different refractive index than particles  120 ,  122 , and  124  and covers a part of the rear surface of each of particles  120 ,  122 , and  124  to define how the screen reacts to ambient light coming from different angles. For these embodiments, substrate  110  may be a mirror reflector, diffusive surface, or dark absorber. Different colored particles are used so that the screen is tuned to the projector system lamp plus color filtering coming from the projector. 
   In operation, each of particles  120 ,  122 , and  124  receives light  128  from a projector. The light passes through particles  120 ,  122 , and  124  and is reflected by substrate  110 . The reflected light passes back through particles  120 ,  122 , and  124  and respectively exits particles  120 ,  122 , and  124  as beams  130 ,  132 , and  134 . Beams  130 ,  132 , and  134  are respectively the colors of particles  120 ,  122 , and  124 . That is, each of particles  120 ,  122 , and  124  passes its like color component of light  128 , e.g., particles  120 ,  122 , and  124  respectively pass green, red, and blue, and absorbs the other color components, e.g., particle  120  absorbs red and blue, particle  122  absorbs green and blue, and particle  124  absorbs green and red. 
   The respective particles  120 ,  122 , and  124  in concert with substrate  110  can have a retroreflective property. Retroreflectivity may be defined as reflecting light substantially parallel to incoming light. Therefore, the light is reflected back through particles  120 ,  122 , and  124  has a narrower viewing cone than diffuse reflections off of opaque particles. For example, the viewing cone of the light passed back through particles  120 ,  122 , and  124  will be narrow compared to a purely diffuse reflection, e.g., about less than 5 degrees reflecting substantially back to the projector, whereas a purely diffuse reflection, e.g., of a white surface, has nearly about a 180-degree viewing cone, i.e., 90 degrees on either side of the perpendicular to surface  112 . The smaller viewing cone results in screen (or optical) gain and enables more light to be reflected back the viewers. This acts to compensate for the lost light absorbed by the colored particles. 
   For some embodiments, particles  120 ,  122 , and  124  may be of the same size or of different sizes. Changing the particle size changes the amount of like colored light that is reflected by a particle and the amount of unlike colored light that is absorbed by that particle. Different ratios of one color to another can be used to achieve a similar purpose for other embodiments. 
     FIG. 2  illustrates a portion of a frontal projection screen  200 , according to another embodiment. For one embodiment, transparent particles  220 ,  222 , and  224  are respectively tinted different colors, e.g., particle  220  is tinted green, particle  222  red, and particle  224  blue, and are adhered to a substrate  210  using adhesive  115 . Substrate  210  may be as described for substrate  110  or may be a dark absorber to increase ambient absorption. For another embodiment, two different colors, such as magenta and green, four colors, e.g., cyan, magenta, yellow, and black, etc., are used instead of three. For another embodiment particles  220 ,  222 , and  224  are respectively tinted cyan, magenta, and yellow. A portion  228  of each of the particles  220 ,  222 , and  224  adjacent substrate  210 , e.g., the backs of particles  220 ,  222 , and  224 , are coated with a coating that is substantially a mirror reflector, e.g., a silvered or mirrored coating, and for another embodiment, a coating that is substantially a diffusive reflector, e.g., a white coating. Particles  220 ,  222 , and  224  may be of the same size or of different sizes. For other embodiments, adhesive  115  may have a substantially different refractive index than particles  220 ,  222 , and  224  and covers a part of the rear surface of each of particles  220 ,  222 , and  224  to define how the screen reacts to ambient light coming from different angles. 
   In operation, each of particles  220 ,  222 , and  224  receives light  128  from the projector. The light passes through particles  220 ,  222 , and  224  and is reflected by the coating. The reflected light passes back through particles  220 ,  222 , and  224  and respectively exits particles  220 ,  222 , and  224  as beams  230 ,  232 , and  234 , respectively having the colors of particles  220 ,  222 , and  224 . That is, each of particles  220 ,  222 , and  224  reflects its like color component of light  128  and absorbs the other color components. Each of particles  220 ,  222 , and  224  has a retroreflective property that narrows the viewing cone unless the beads have a diffuse coating. 
   For another embodiment, portion  228  of each of particles  220 ,  222 , and  224  is tinted a different color, e.g., green, red, or blue, magenta or green, cyan magenta, or yellow, etc., and the remaining portion of each of particles  220 ,  222 , and  224  is untinted or clear. For this embodiment, the light passes through particles  220 ,  222 , and  224  and is retroreflected by the respective one of the tinted portions  228 . The retroreflected light passes back through particles  220 ,  222 , and  224  and respectively exits particles  220 ,  222 , and  224  as beams  230 ,  232 , and  234 , respectively having the colors of colored coatings. That is, each of the colored coatings reflects its like color component of light  128  through its corresponding particle and absorbs the other color components. 
     FIG. 3A  illustrates a portion of a frontal projection screen  300 , according to another embodiment. Colored particles  330 ,  332 , and  334  are adhered to a substrate  310  of screen  300 , e.g., colored particle  330  is green, colored particle  332  red, and colored particle  334  blue. Substrate  310  may be as described for substrate  115  or may be gray, etc. Colored particles  330 ,  332 , and  334  may be opaque substantially diffusive reflectors (or color dots) or substantially mirror reflectors. Clear transparent particles  320 ,  322 ,  324  are respectively adhered to colored particles  330 ,  332 , and  334  by adhesive  115  so that they are in contact or otherwise in optical contact with their respective colored particle. Particles  320 ,  322 , and  324  and colored particles  330 ,  332 , and  334  may all be of the same size or be of different sizes. For another embodiment, two different colors, such as magenta and green, four colors, e.g., cyan, magenta, yellow, and black, etc., are used instead of three. For another embodiment colored particles  330 ,  332 , and  334  are respectively cyan, magenta, and yellow. 
   According to another embodiment,  FIG. 3B  illustrates that particles  320 ,  322 , and  324  do not have to have a one-to-one relationship with colored particles  330 ,  332 , and  334 , as in  FIG. 3A . Rather, particles  320 ,  322 , and  324  can be located between successive colored particles  330 ,  332 , and  334 , and/or more than one of particles  320 ,  322 , or  324  can be adhered to a respective colored particle  330 ,  332 , or  334 . 
   In operation, each of particles  320 ,  322 , and  324  receives light  128  from the projector. The light passes through particles  320 ,  322 , and  324  and is reflected by the respective one of colored particles  330 ,  332 , and  334 . The reflected light passes back through particles  320 ,  322 , and  324  and respectively exits particles  320 ,  322 , and  324  as beams  336 ,  338 , and  340 , respectively having the colors of colored particles  330 ,  332 , and  334 . That is, each of colored particles  330 ,  332 , and  334  reflects its like color component of light  128  through its corresponding particle and absorbs the other color components. Each of particles  320 ,  322 , and  324  and its corresponding one of colored particles  330 ,  332 , and  334  has a retroreflective property that narrows the viewing cone. 
     FIG. 4A  illustrates a portion of a frontal projection screen  400 , according to another embodiment. Tinted mirror reflectors  420 ,  422 , and  424 , such as mica particles, each tinted a different color, e.g., reflector  420  is tinted green, reflector  422  red, and reflector  424  blue, are adhered to a substrate  410  of screen  400 . For various embodiments dyes, pigments, interference coatings, dichroic coatings, etc. can be used to tint mirror reflectors  420 ,  422 , and  424 . Substrate  410  may be as described for substrate  110  or may be gray, etc. Reflectors  420 ,  422 , and  424  may all be of the same size or be of different sizes and of different color ratios. For another embodiment, two different colors, such as magenta and green, four colors, e.g., cyan, magenta, yellow, and black, etc., are used instead of three. For another embodiment reflectors  420 ,  422 , and  424  are respectively tinted cyan, magenta, and yellow. According to another embodiment,  FIG. 4B  illustrates that reflectors  420 ,  422 , and  424  can be randomly distributed, do not necessarily lie flat on substrate  410 , or may overlap each other. 
   In operation, each of reflectors  420 ,  422 , and  424  receives light  128  from the projector and respectively reflects it as beams  430 ,  432 , and  434 , respectively having the colors of reflectors  420 ,  422 , and  424 . That is, each of reflectors  420 ,  422 , and  424  reflects its like color component of light  128  and absorbs the other color components. Each of reflectors  420 ,  422 , and  424  has a narrower viewing cone than a diffusive reflector. The narrower viewing cone results in screen gain and enables more light to be reflected back toward the viewers. This acts to compensate for the lost light absorbed by the colored reflectors. 
     FIG. 5  illustrates a portion of a frontal projection screen  500 , according to another embodiment. For one embodiment, frontal projection screen  500  is as described above for screen  100 ,  200 ,  300 , or  400  respectively of  FIGS. 1 ,  2 ,  3 A and  3 B, and  4 A and  4 B, and includes colored elements  520 ,  522 , and  524 , each corresponding to a different color, adhered to a substrate  510 . For one embodiment, colored elements  520 ,  522 , and  524  represent the colored elements in  FIGS. 1 ,  2 ,  3 A and  3 B, and  4 A and  4 B, i.e., tinted transparent particles affixed to a diffuse, mirror, or light absorbing screen substrate ( FIG. 1 ) or having a diffuse or mirror coating applied to the backs thereof ( FIG. 2 ), clear particles with a tint applied to the backs thereof ( FIG. 2 ), clear particles in optical contact with a color dot ( FIGS. 3A  or  3 B), and/or a tinted mirror reflector ( FIG. 4 ). Note that each of colored elements  520 ,  522 , and  524  may represent a plurality of colored elements, each plurality including colored elements from  FIGS. 1 ,  2 ,  3 A and  3 B, and/or  4 A and  4 B. Screen  500  also includes diffusive reflectors  540 , such as color dots, of different colors adjacent colored elements  520 ,  522 , and  524 . For one embodiment, the colors of diffusive reflectors  540  are the same colors as colored elements  520 ,  522 , and  524 . That is, each diffusive reflector  540  may be green, red or blue, magenta or green, cyan, magenta, yellow, or black, cyan, magenta, or yellow, etc. Diffusive reflectors  540  act to tone down retroreflectivy or mirror reflectivity. 
   The colored elements  520 ,  522 , and  524  may be evenly distributed so that each has an unlike colored element next to it. Alternatively, as illustrated in  FIG. 6 , according to another embodiment, a frontal projection screen  600  has regions  612 ,  614 , and  616  that may respectively include groups  620 ,  622 , and  624  of like colored elements, i.e., colored elements  520 ,  522 , and  524 , respectively. For example, region  612  may include group  620  that may include only green colored elements, region  614  group  622  that may include only red colored elements, and region  616  group  624  that may include only blue colored elements. 
   For other embodiments, the colored elements  520 ,  522 , and  524  may be randomly distributed, as shown for a portion of a frontal projection screen  700  in  FIG. 7 , according to another embodiment. It is seen that for a random distribution unlike colored elements may be immediately next to each other and like colored elements may be immediately next to each other. 
     FIG. 8  illustrates a rear projection screen  800 , according to another embodiment. Screen  800  includes a transparent substrate  810  having color tinted transparent particles  820 ,  822 , and  824  adhered thereto by a transparent or opaque adhesive  815 . Transparent particles  820 ,  822 , and  824  are in direct contact or otherwise optical contact with transparent substrate  810  so that light can pass through particles  820 ,  822 , and  824  and reach substrate  810 . For one embodiment, particles  820 ,  822 , and  824  are respectively tinted green, red, and blue. Particles  820 ,  822 , and  824  may all be of the same size or be of different sizes. For another embodiment, two different colors, such as magenta and green, etc., are used instead of three. For another embodiment particles  820 ,  822 , and  824  are respectively tinted cyan, magenta, and yellow. Particles  820 ,  822 , and  824  may be distributed as described above. That is, particles  820 ,  822 , and  824  may be evenly distributed, randomly distributed, or be evenly distributed in groups of like colored elements. 
   In operation, each of particles  820 ,  822 , and  824  receives light  828  from a rear projector. Particles  820 ,  822 , and  824  respectively pass a like color component of light  828  as beams  830 ,  832 , and  834 , which are subsequently transmitted through substrate  810 , and absorb unlike color components of light  828 . For example, particle  820  passes green and absorbs red and blue; particle  822  passes red and absorbs green and blue; and particle  824  passes blue and absorbs green and red. Particles  820 ,  822 , and  824  act to reinforce their like color components. 
   For some embodiments, colored elements, such as tinted transparent particles, colored diffusive reflecting opaque particles, (or color dots), and/or tinted mirror reflecting particles (e.g., mica particles), are mixed together, e.g., in equal or unequal ratios by color and/or size, and are subsequently dispensed on an adhesive layer on a substrate of a frontal projection screen. For one embodiment, a transparent or an opaque film having adhesive on two sides can be used. For this embodiment, the mixed colored elements are dispensed onto one of the adhesive sides and the film containing the mixed colored elements is affixed to the substrate by the adhesive of the other side. This method can be used to apply color-tinted particles  820 ,  822 , and  824  to substrate  810  of the rear projection screen  800  of  FIG. 8 . 
   Another method includes depositing (printing) adhesive in a pattern on an adhesive-backed transparent or opaque sheet, affixing colored elements of one color to that adhesive pattern, repeating for the remaining colors, and adhering the adhesive-backed material to a frontal projection screen. Alternatively, this method can be used to affix the colored elements to a flexible opaque (mirrored or diffuse) or transparent substrate of the projection screen. This method can be used to apply color-tinted particles  820 ,  822 , and  824  to substrate  810  of the rear projection screen  800  of  FIG. 8 . 
   In another method, the colored elements are electrically charged so that they are attracted to a rotating drum and held in place. The colored elements are then transferred, according to a particular pattern, to a portion of an adhesive surface of a flexible or substantially rigid transparent sheet that also has an adhesive backing. Subsequently, the sheet is applied to a substrate of a frontal projection screen. Specifically, the drum is rotated through a reservoir containing colored elements of one of the colors to be deposited on the substrate, and these colored elements are written to the drum in a particular pattern and are subsequently transferred to the portion of the adhesive. The drum is rotated through a reservoir containing colored elements of another of the colors to be deposited on the substrate, and these colored elements are written to the drum in a particular pattern and are subsequently transferred to another portion of the adhesive. This is repeated for each of the colors. Alternatively, this method can be used to affix the colored elements to an adhesive applied to flexible or substantially rigid opaque (mirrored or diffuse) or transparent substrate of the projection screen. This method can be used to apply color-tinted particles  820 ,  822 , and  824  to substrate  810  of the rear projection screen  800  of  FIG. 8 . 
   CONCLUSION 
   Although specific embodiments have been illustrated and described herein it is manifestly intended that the scope of the claimed subject matter be limited only by the following claims and equivalents thereof.