Patent Publication Number: US-2012032875-A1

Title: Scanned Image Projection System Employing Beam Folding Apparatus

Description:
BACKGROUND 
     1. Technical Field 
     This invention relates generally to scanned image projection systems, and more particularly to a scanned image projection system employing a beam folder to partially reflect scanned light. 
     2. Background Art 
     Scanned image projection systems, such as those employing scanned lasers, facilitate the production of brilliant images created with vibrant colors. These scanned laser projection systems are generally brighter, sharper, and have a larger depth of focus than do conventional projection systems. Further, the advent of semiconductor lasers and laser diodes allows laser projection systems to be designed as compact projection systems that can be manufactured at a reasonable cost. These systems consume small amounts of power yet deliver bright, complex images. 
     With traditional image projection systems, a presenter making a presentation must face the same projection surface as the audience to view the projected images. This results in the presenter generally having his back facing the audience, which is less than desirable. Additionally, to control the image, the presenter must use a control device that is tethered to the image projection system, such as a mouse or keypad. This “hard wire” restriction limits the mobility of the presenter while making a presentation. 
     It would be advantageous to provide from an image projection systems a plurality of images, and optionally the ability to control the image projection system without the need of a mouse or keyboard. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates one embodiment of a scanned image projection system employing a beam folding apparatus in accordance with embodiments of the invention. 
         FIG. 2  illustrates a schematic block diagram of one embodiment of a scanned image projection system employing a beam folding apparatus in accordance with embodiments of the invention. 
         FIG. 3  illustrates one embodiment of a spatial light modulator suitable for use with one or more embodiments of a scanned image projection system employing a beam folding apparatus in accordance with embodiments of the invention. 
         FIG. 4  illustrates another embodiment of a scanned image projection system employing a beam folding apparatus in accordance with embodiments of the invention. 
         FIG. 5  illustrates another embodiment of a scanned image projection system employing a beam folding apparatus in accordance with embodiments of the invention. 
         FIG. 6  illustrates another embodiment of a scanned image projection system employing a beam folding apparatus and incorporating a head-up display in accordance with embodiments of the invention. 
         FIG. 7  illustrates one embodiment of a projection surface suitable for use with one or more embodiments. 
         FIG. 8  illustrates one embodiment of head-up projection surface suitable for use with one or more embodiments, including the embodiment of  FIG. 6 . 
         FIG. 9  illustrates an exemplary head-up projection surface suitable for use with one or more embodiments, including the embodiment of  FIG. 6 . 
         FIG. 10  illustrates another embodiment of a head-projection surface suitable for use with one or more embodiments, including the embodiment of  FIG. 6 . 
     
    
    
     Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention. 
     DETAILED DESCRIPTION 
     Before describing in detail embodiments that are in accordance with the present invention, it will be appreciated that embodiments of the invention described herein may be comprised of one or more conventional processors and unique stored program instructions that control the one or more processors to implement, in conjunction with certain non-processor circuits, some, most, or all of the functions of presenting multiple images or permitting a user to control image content as described herein. 
     The non-processor circuits may include, but are not limited to, microprocessors, scanning mirrors, image encoding devices, memory devices, clock circuits, power circuits, and so forth. As such, these functions may be interpreted as steps of a method to perform multiple image delivery or image projection system control. It is expected that one of ordinary skill, notwithstanding possibly significant effort and many design choices motivated by, for example, available time, current technology, and economic considerations, when guided by the concepts and principles disclosed herein will be readily capable of generating such programs and circuits with minimal experimentation. 
     Embodiments of the invention are now described in detail. Referring to the drawings, like numbers indicate like parts throughout the views. As used in the description herein and throughout the claims, the following terms take the meanings explicitly associated herein, unless the context clearly dictates otherwise: the meaning of “a,” “an,” and “the” includes plural reference, the meaning of “in” includes “in” and “on.” Relational terms such as first and second, top and bottom, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, reference designators shown herein in parenthesis indicate components shown in a figure other than the one in discussion. For example, talking about a device ( 10 ) while discussing figure A would refer to an element,  10 , shown in figure other than figure A. 
     Embodiments of the present invention provide an imaging system employing one or more light sources, which in one embodiment are semiconductor laser sources having the colors of red, green, and blue. Light from the sources is scanned or otherwise modulated by a spatial light modulator to form images on a projection surface. A selective or partial reflector is disposed between the imaging system and the projection surface and is configured to function as a beam folding apparatus. The selective reflector reflects a portion of the spatially modulated light in a second direction towards a second projection surface. In one embodiment, an alternate light source, such as an infrared light source, can be modulated along with the other light sources. Reflections from this additional light source, such as reflections from a user&#39;s hand, can be detected by the imaging system and used as a control input. The reflections can be used, for example, to move a cursor or other content within the image. Embodiments of the present invention thus provide an auxiliary image for a person to view. Some embodiments further provide a method of controlling the image content that does not require a hard-wired mouse or keyboard. 
     In one embodiment, the selective reflector is manufactured from a selective mirror, a dielectric coating, a customized reflective layer, or prism. The selective reflector is configured to pass one portion of the modulated light and reflect another. The selective reflector can cause the reflection based upon polarization or wavelength. Alternatively, the selective reflector can simply reflect a percentage of the modulated light to form a second image that is the same as the one passing through the selective reflector. 
     Illustrating by way of one simple example, where the light sources are emissions from a red laser, a green laser, and a blue laser, and the additional source is an infrared laser, the selective reflector can be configured to pass the visible light and reflect the infrared light in a different direction, which may be away from the projection surface. By passing a hand or other object within the reflected infrared projection cone, a user can cause reflections to be directed from the object back to the selective reflector and to a sensor in the imaging system. These reflections can be used as an input, such as to control a cursor or other image contents. The sensor can be configured, in conjunction with a processor or other control circuit, to recognize hand gestures or other motion to affect the image content. 
     In another embodiment, two sets of light sources are used. Each set of light sources is amplitude modulated with a different signal such that the resulting light is configured to produce different images. A first image can be passed through the selective reflector while a second image is reflected to a second projection surface. Accordingly, a user may be able to read a narrative created by the second image while viewers see video corresponding to the narrative in the first image. Either or both of the first image and second image can include a modulated alternate light source. The user may then use hand gestures made within either or both of the first image and second image to alter image content. 
     Turning now to  FIG. 1 , illustrated therein is one embodiment of an imaging system  100  configured in accordance with one or more embodiments of the invention. The imaging system  100  includes one or more light sources  101 , 102 , 103  that are configured to produce one or more light beams  104 , 105 , 106 . In one embodiment, the one or more light sources  101 , 102 , 103  are laser light sources, such as those created by semiconductor laser sources. In the illustrative embodiment of  FIG. 1 , the one or more light sources  101 , 102 , 103  comprise a red light source, a green light source, and a blue light source. A spatial light modulator  107  scans or otherwise modulates the light  108  to produce images  109  on a projection surface. 
     In one embodiment, an additional light source  111  is modulated along with the one or more light sources  101 , 102 , 103 . In the illustrative embodiment of  FIG. 1 , the additional light source  111  is a non-visible light source and is configured to produce an alternate, non-visible light beam  112 . While a non-visible light source, such as an infrared or ultraviolet light source is one suitable additional light source  111 , it will be clear to those of ordinary skill in the art having the benefit of this disclosure that other light sources could be used as the additional light source  111 . For instance, a designer may select a predefined color, such as purple or pink, to use as the additional light source  111  as well. A beam combiner  113  combines the output of the light sources  101 , 102 , 103 , 111  to produce a combined beam of light  108 . An optional collimation or focusing optical element may be included between the light sources  101 , 102 , 103 , 111  and the spatial light modulator  107 . 
     The spatial light modulator  107  is configured to produce images  109  by scanning the combined beam of light  108  along a projection surface  110 , which may be a wall, screen, or other surface. The spatial light modulator  107 , which may be a scanning mirror or other modulation device, is operable with and responsive to a controller  114 . In one embodiment, the spatial light modulator  107  receives the combined beam of light  108  and deflects in response to a drive signal  115  from a driver  116  that is operable with the controller  114 . This pivoting action scans the combined beam of light  108  within an image cone  118  extending in a first direction  119  to form the image  109 . In one embodiment, the scan occurs horizontally and vertically in a raster pattern. 
     A partial reflector  117  is disposed within the image cone  118  formed by the spatial light modulator  107 . The partial reflector  117  is configured to pass at least a portion of the combined beam of light  108  in the first direction  119  and reflect at least a portion of the additional light beam  112  within a second cone  120 . In one embodiment, the second cone  120  is oriented in a second direction  121  that is different from the first direction  119 . For example, the second direction can be substantially orthogonal with the first direction  119 , or can form either an acute or obtuse angle with the first direction  119 . Additionally, the second direction  121  can extend outward radially at any angle as well. While shown as extending down in the illustrative embodiment of  FIG. 1 , it could equally extend out of the page, upward, into the page, or at other radial angles relative to the first direction  119 . 
     The partial reflector  117  can be formed from any of a number of materials. In one embodiment, the partial reflector  117  comprises a prism. In another embodiment, the partial reflector  117  comprises a selective mirror that is configured to reflect some light beams and transmit others. In one embodiment, the selective reflection is based upon wavelength, where some wavelengths are transmitted and others are reflected. In another embodiment, the selective reflection is based on polarization, where light beams having a first polarization are transmitted, while light beams having a second polarization are reflected. In yet another embodiment, the selective reflection is simply a percentage of the scanned beam  122 , such that a first portion of the whole is transmitted and a second portion of the whole is reflected. 
     In one embodiment, the partial reflector  117  comprises an optical coating, which may be disposed on a substrate. The optical coating functions as a selective coating or filter. A suitable optical coating may comprise a multilayer, thin film, dielectric coating that includes materials such as magnesium oxide or magnesium fluoride. In certain coatings, some layers may be thicker than others. Further, the layers may have indices of refraction that differ from each other by varying amounts. The coatings can be configured to provide the selective reflection properties as described herein. As is known in the art, many optic coating manufacturers are capable of receiving reflective and transmissive requirements associated with a particular application and delivering a coating tailored to those requirements. For instance, exemplary coatings may be obtained from optical product suppliers such as Cascade Optical Corporation of Santa Ana, Calif., USA or Deposition Sciences Inc of Santa Rosa, Calif., USA. 
     In one embodiment, the second cone  120  comprises only the additional light beam  112 . In this embodiment, where the additional light beam  112  is non-visible, the image  109  is produced by the visible light beams  104 , 105 , 106  that are transmitted through the partial reflector  117 . The partial reflector  117  is configured to reflect the additional light beam  112  along the second direction  121 . 
     In another embodiment, the second cone  120  comprises at least a portion of the additional light beam  112  and a portion of the visible light beams  104 , 105 , 106 . Accordingly, a second image  123  can be formed on a second projection surface  124 . In such an embodiment, the second image  123  will be a replication of the original image  109 . In this embodiment, all of the additional light beam  112  can be reflected within the second cone  120 , or only a portion. In the latter scenario, the first image cone  118  would include a portion of the additional light beam  112  as well. 
     A sensor  125 , which can be a photodetector or other sensor and which is operable with the controller  114 , is then configured to detect reflections  126  of the additional light beam  112  from the partial reflector  117 . The sensor  125  can convert the reflections  126  into analog or digital signals indicative of, for example, location and intensity. The signals are then delivered to the controller  114 . In one embodiment, the sensor  125  can include a filter configured to keep the signal to noise ratio within a predetermined limit. For example, where infrared light is used for the additional light beam  112 , the sensor  125  may include an integrated infrared filter to ensure that signals detected by the sensor  125  only from infrared light. 
     In one embodiment, the controller  114  is then configured to use the reflections  126  as an input to control the imaging system  100 . Illustrating by example, in one embodiment a user may make hand gestures  128  or other motions within the second cone  120 . Accordingly, the reflections  126  comprise reflections from the user&#39;s hand  127 . The controller  114  can be configured with executable instructions configured as software or firmware to recognize the hand gestures  128  as control signals. These control signals can be used to move, for example, a cursor  129  within the image  109 . Such movement would be useful in making a presentation, as the presented would be able to make the hand gestures  128  within the second cone  120 , thereby preventing the addition of shadows or other unnecessary artifacts from appearing in the image  109  being viewed by the audience. Where the second cone includes both the visible light beams  104 , 105 , 106  and the additional light beam  112 , the presenter would instantly know where his hand  127 , and therefore the corresponding cursor  129 , was by looking at the second image  123 . Note that while a user&#39;s hand  127  is one object suitable for control, it will be clear those of ordinary skill in the art having the benefit of this disclosure that embodiments of the invention are not so limited. Rather than reflecting from a hand, the additional light beam  112  could reflect from a stylus, pointer, or other object being held by the user. Further, such objects could be configured with reflective layers to enhance the reflections  126 . 
     The embodiment of  FIG. 1  can also be expanded in other ways. Where, for example, the controller  114  is applying amplitude modulation to the light sources  101 , 102 , 103  to create video, the hand gestures  128  can be used by the controller to alter the video content. Where, for example, the video content was an animation of a bear walking through the woods, the hand gestures  128  could cause the bear to move. Numerous other extensions of embodiments of the invention will be readily apparent to those of ordinary skill in the art having the benefit of this disclosure. 
     Turning now to  FIG. 2 , illustrated therein is a schematic block diagram of an alternate embodiment of an image projection system  200  configured in accordance with embodiments of the invention.  FIG. 2  illustrates a general block diagram of the scanned image projection system, with one or more laser sources  241  configured to produce a plurality of light beams. In one embodiment, the one or more laser sources  241  comprise a red laser  201 , a blue laser  202 , and a green laser  203 , as indicated by the “R,” “G,” and “B.” The lasers can be any of various types of lasers. For example, in one embodiment, each laser source  241  is a semiconductor laser, such as an edge-emitting laser or vertical cavity surface emitting lasers. Such semiconductor lasers are well known in the art and are commonly available from a variety of manufacturers. 
     A spatial light modulator  207  is then configured to produce images by spatially encoding the light from the laser sources  241  along a projection surface  210 . In one embodiment, the spatial light modulator  207  comprises a Micro-Electro-Mechanical-System (MEMS) scanning mirror, such as those manufactured by Microvision, Inc. Examples of MEMS scanning mirrors, such as those suitable for use with embodiments of the present invention, are set forth in commonly assigned U.S. patent application Ser. No. 11/786,423, filed Apr. 10, 2007, entitled, “Integrated Photonics Module and Devices Using Integrated Photonics Module,” which is incorporated herein by reference, and in U.S. Published patent application Ser. No. 10/984,327, filed Nov. 9, 2004, entitled “MEMS Device Having Simplified Drive,” which is incorporated herein by reference. While a scanning mirror is one type of spatial light modulator suitable for use with embodiments of the invention, it will be clear to those of ordinary skill in the art having the benefit of this disclosure that the invention is not so limited. Other types of spatial light modulators, such as a spinning wheel found digital light projection technology systems, can also be used. 
     To permit the designer to orient the one or more laser sources  241  in various ways relative to the spatial light modulator  207 , one or more optical alignment devices  231 , 230 , 229  may optionally be used to direct light beams  204 , 205 , 206  from the one or more laser sources  241  to the spatial light modulator  207 . For example, the one or more optical alignment devices  231 , 230 , 229 , in one embodiment, are used to orient the plurality of light beams  204 , 205 , 206  into a single, collimated light beam  208 . Where the one or more laser sources  241  comprise a red laser  201 , blue laser  202 , and green laser  203 , the one or more optical alignment devices  231 , 230 , 229  can blend the output of each laser to form a collinear beam of light. 
     In one embodiment, dichroic mirrors are used as the one or more optical alignment devices  231 , 230 , 229 . Dichroic mirrors are partially reflective mirrors that include dichroic filters that selectively pass light in a narrow wavelength bandwidth while reflecting others. In one embodiment, polarizing coatings can be incorporated into the dichroic mirrors as well. Dichroic mirrors and their use in laser-based projection systems are known in the art and, as such, will not be discussed in further detail here. Note that the location, as well as the number, of the optical alignment devices  231 , 230 , 229  can vary based upon application. For example, in some MEMS-type scanning systems, the plurality of light beams  204 , 205 , 206  can be delivered directly into the spatial light modulator  207 . Alternatively, some applications may not require optical alignment devices  231 , 230 , 229 . 
     An additional light source  211 , which in one embodiment is a non-visible light source, is co-located with the laser sources  241 . In the illustrative embodiment of  FIG. 2 , the additional light source  211  can be, for example, an infrared light source or an ultraviolet light source. As with the laser sources  241 , the additional light source  211  can be a semiconductor light source such as a light emitting diode. One example of a non-visible light source suitable for use as the additional light source  211  is an infrared light emitting diode having a wavelength of around 800-810 nanometers. Another example of a non-visible light source suitable for use as the additional light source  211  is an ultraviolet light emitting diode having a wavelength of around 400-410 nanometers. It will be clear to those of ordinary skill in the art having the benefit of this disclosure that the invention is not so limited, as any number of other non-visible light sources or visible light sources can be used as the additional light source  211  as well. 
     In one embodiment, the additional light source  211  is disposed within the image projection system  200  such that the additional light beam  112  is generally collinear with the other light beams  204 , 205 , 206 . Where necessary, an additional optical alignment device  242  can be used to orient the additional light beam  212  so as to be collinear with the combined light beam  208 . The spatial light modulator  207  is then able to modulate or encode the additional light beam  212  along with the other light beams  204 , 205 , 206 . 
     A selective reflector  217  is disposed within an image cone  218  created by the spatial light modulator  207 . The selective reflector  217 , like the partial reflector ( 117 ) from  FIG. 1  above, is configured to reflect a portion  220  of the image cone  218  in a second direction  221 . In one embodiment, the portion  220  comprises only the additional light beam  112 , with the other light beams  204 , 205 , 206  being passed through the selective reflector  217  so as to produce an image on the projection surface  210 . In another embodiment, the portion  220  comprises at least a portion of the additional light beam  212  and a portion of the other light beams  204 , 205 , 206 . Accordingly, a second image can be formed on a second projection surface  224 . All of the additional light beam  212  can be reflected, or only a portion. 
     A sensor  225  is then configured to receive reflections  226  of at least some of the portion  220  and create electrical signals corresponding to the reflection intensity, location, or other data as sensed by a detector in the sensor  225 . In one embodiment, the sensor  225  is configured as a charge coupled device photodetector. In another embodiment, the sensor  225  is configured as a CMOS photodetector. Other types of sensors  225  may also be used. The sensor  225  effectively captures an “image” of the reflection  226  from the selective reflector  217  and delivers a corresponding signal to a control circuit  214 . 
     The control circuit  214 , which may be a microcontroller, a microprocessor, ASIC, logic chip, or other device, serves as the brain of the image projection system  200 . The control circuit  214  can include other processing units dedicated to performance of specific functions. For example, an integrated or stand-alone digital signal processor may handle the processing of incoming communication signals or data. In the illustrative embodiment of  FIG. 2 , the control circuit  214  is shown for simplicity as an integrated circuit, but shall be understood to be representative of any processing architecture known to those skilled in the art. 
     The control circuit  214  can be a single processor, such as a microprocessor integrated circuit, or alternatively may comprise one or more processing units or components. The control circuit  214  is coupled to a memory  243  or other computer readable medium. By executing operable code  244  stored in the memory  243 , the control circuit  214  is capable of causing the various components of the image projection system  200  to execute their respective functions. 
     In one embodiment, the control circuit  214  executes operable code  244  comprising one or more routines stored in the memory  243 . The memory  243  may comprise a separate and distinct integrated circuit connected and operable with the control circuit  214  via a data bus. Further, the memory  243  may include one or more read-only memories, dynamic or static random-access memory, or any other type of programmable memory, such as one or more EPROMs, EEPROMs, registers, and the like. In some embodiments, the memory  243  can comprise non-traditional storage devices as well. The routines stored in the memory  243  can be stored in the form of executable software, firmware, or in any other fashion known to those skilled in the art. 
     In one embodiment, the control circuit  214  is configured to use the reflections  226  as input for controlling the image projection system  200 . A user may make hand gestures  228  or other motions within the portion  220 , which causes reflections  226  from the user&#39;s hand  227  or other objects to reflect off the selective reflector  213  to the sensor  225 . The operable code  244  in the memory  243  can instruct the control circuit  214  to recognize the hand gestures  228  as control signals. As described above, these control signals can be used to move a cursor within an image  109 , or to control content of images being displayed on the projection surface  210 . 
     Turning now to  FIG. 3 , illustrated therein is one example of a spatial light modulator  307  suitable for use with various embodiments of the invention. As noted above, one or more embodiments can employ a MEMS scanning platform such as that described in commonly assigned U.S. patent application Ser. No. 12/496,892, filed on Jul. 2, 2009, entitled, “Phase Locked Resonant Scanning Display Projection,” which is incorporated herein by reference. Such a spatial light modulator  307  is shown in  FIG. 3 . Note that there are many different ways in which a spatial light modulator can be constructed, and the MEMS scanning platform is but one example. Further, other spatial light modulators can be substituted for the spatial light modulator  307  of  FIG. 3 , which is illustrative only. 
     The principal scanning component of the spatial light modulator  307  is a scanning mirror  331 . A driver  316 , which may be integrated with a control circuit, delivers a drive signal  315  to a drive coil  332  disposed about the scanning mirror  331 . The drive signal  315  causes a corresponding current to pass through the windings of the drive coil  332 . An external magnetic field source disposed near the light encoder (not shown) imposes a static magnetic field on the coil  332 . The magnetic field has a component  333  in the plane of the coil, and is oriented non-orthogonally with respect to the two drive axes  334 , 335 . The in-plane current in the windings of the coil  332  interacts with the in-plane magnetic field component  333  to produce out-of-plane Lorentz forces on the conductors of the coil  332 . As the drive current forms a loop, the current reverses sign across the scan axes, which causes the Lorentz forces to also reverse sign across the scan axes, thereby causing the application of mechanical torque. This combined torque produces responses in the two scan directions, depending on the frequency content of the torque, thereby causing motion about the axes  334 , 335 . This motion permits the driver  316 , or the control circuit via the driver, to scan an image on a projection surface. 
     Turning now to  FIG. 4 , illustrated therein is another imaging system  400  configured in accordance with embodiments of the invention. Many of the imaging system  400  components are the same as in  FIG. 1 , such as the spatial light modulator  407 , the light sources  401 , 402 , 403 , and the additional light source  411 . These components function substantially in the same way as described with reference to  FIG. 1  above. 
     The embodiment of  FIG. 4  differs from the embodiment of  FIG. 1  in that an additional set of light sources is provided. Specifically, a second set of light sources comprising light sources  441 , 442 , 443  is provided. Thus, the imaging system  400  includes a first set of light sources having light sources  401 , 402 , 403  and a second set of light sources having light sources  441 , 442 , 443 . 
     The second set of light sources permits the controller  414  to create two different images. Specifically, the controller can drive the first set of light sources with a first amplitude modulation to form a first image or series of images, as in the case of video. The second set of light sources can be driven with a second amplitude modulation so as to create a second image or series of images. The partial reflector  417  can then be configured to substantially transmit the first image  409  in the first direction  419  while substantially reflecting the second image  423  in a different direction  421 . 
     An additional light source may be included with one or both sets of light sources. For example, the imaging system  400  can include one additional light source  411  that is associated with the first set of light sources. Alternatively, the imaging system  400  can include one additional light source  444  that is associated with the second set of light sources. The imaging system  400  can further include both additional light source  411  and additional light source  444 . Accordingly, the partial reflector  417  can be configured to reflect or transmit either or both additional light sources  411 , 444  as desired. For example, the partial reflector can be configured to transmit additional light beam  412  while reflecting additional light beam  445 . Accordingly, reflections of additional light beam  412  can be interpreted by the controller  414  as control input from gestures within the first image  409 , while reflections of additional light beam  444  can be interpreted by the controller as control input form gestures within the second image  423 . This multi-image, multi-gesture system gives a user additional degrees of control in moving components of the images. 
     Turning now to  FIG. 5 , illustrated therein is another image projection system  500  configured in accordance with embodiments of the invention. The operation of the image projection system  500  can be similar to that of  FIG. 1  where only a first set of light sources  501 , 502 , 503 , 511  is included. Alternatively, the operation of the image projection system  500  can be similar to that of  FIG. 5 , when a second set of light sources  541 , 542 , 543 , 544  is included. As noted above, the image projection system  500  can include one or both of alternate light sources  544  and  511 . 
     The major difference between the embodiment of  FIG. 5  and previously described embodiments includes the use of a diffuser  550  disposed within the second cone  520  along the second direction  521 . The diffuser  550  is configured as a second projection surface for the second cone  520  reflected from the partial reflector  517 . The diffuser  550  permits the user to see the image  523  delivered within the second cone  520  from the back of that projection surface. 
     In one embodiment, the diffuser  550  is configured to at least partially transmit the alternate light beam  512 . Accordingly, the user can make hand gestures  528  from the backside of the diffuser  550  with reflections  526  still being delivered to the sensor  525 . As with previous embodiments, these reflections  526  can be used as control input by the controller  514 . 
     Turning now to  FIG. 6 , illustrated therein is another image projection system  600  configured in accordance with embodiments of the invention. The operation of the image projection system  600  can be similar to that of  FIG. 1  where only a first set of light sources is included. Alternatively, the operation of the image projection system  600  can be similar to that of  FIG. 5 , when a second set of light sources is included. As noted above, the image projection system  500  can include one or two additional light sources. 
     The major difference between the embodiment of  FIG. 6  and previously described embodiments includes the use of a head-up display  660  disposed within the second cone  620 . The head-up display  660  is configured as a second projection surface for the second cone  620  reflected from the partial reflector  617 . The head-up display  617  permits the user  661  to see the image  623  delivered within the second cone  620  while also seeing the image  609  delivered to the projection surface. Such a configuration can be advantageous for presenters with the image  623  delivered within the second cone  620  comprises, for example, the text of a presentation that corresponds to the image content presented on the projection surface. Other applications will be readily available to those of ordinary skill in the art having the benefit of this disclosure. 
     In one embodiment, the head-up display  650  is configured to at least partially transmit an alternate light beam  612 . Accordingly, the user can make hand gestures  628  while viewing both the head-up display  660  and the projected image  609  with reflections  626  still being delivered to the sensor  625 . To accomplish this, the head-up display  660  may be configured with one or more reflective layers configured to reflect the additional light beam  612 , as will be described below. As with previous embodiments, the reflections  626  can be used as control input by the controller  614 . 
     Turning now to  FIG. 7 , illustrated therein is an optical device  700  configured for use as a projection surface for the head-up display ( 660 ) of  FIG. 6 . The optical device  700  includes reflective layer  701  comprising one or more reflective layers being configured to reflect visible light and the additional light beam while still permitting a user to substantially see through the optical device  700 . Such reflective layers are described, for example, in commonly assigned U.S. patent application Ser. No. 12/424,129, filed Apr. 15, 2009 and entitled “Wide Field of View Head-Up Display System,” commonly assigned U.S. Pat. No. 7,715,103, filed Sep. 10, 2007 and entitled “Buried Numerical Aperture Expander Having Transparent Properties,” commonly assigned U.S. patent application Ser. No. 12/194,466, filed Aug. 19, 2008 and entitled “Embedded Relay Lens for Head-Up Displays or the Like,” and commonly assigned U.S. patent application Ser. No. 12/843,424, filed Jul. 26, 2010, and entitled “Variable Reflectivity Notch Filter and Optical Devices Using Same,” each of which is incorporated herein by reference. 
     The reflective layer  701  is integrated within a body  302 . Where the projection system uses red, blue and green lasers, the reflective layer  701  can be configured with a notch filter having a transmission curve configured to substantially reflect  705  red, blue, and green light, as well as the alternate light beam. Light  707  having other wavelengths is permitted to pass through the reflective layer  801 . 
     As will be shown in more detail in the discussion of  FIGS. 9 and 10 , the reflective layer  701  can be integrated with an exit pupil expander  703  so as to work more effectively with laser based systems. The reflective layer  701  can be applied directly on the surface of the exit pupil expander  703  or attached with optical filler materials or epoxy. In one embodiment, the reflective index of the substrate, the exit pupil expander  703 , the epoxy, and the cover plate are very similar. 
     The exit pupil expander  703  can be configured as one or more of a micro lens array, microspheres, nanospheres, a diffuser, or a diffraction grating. The exit pupil expander  703  is configured to expand reflected light. For example, the exit pupil expander  703  can have optical properties resulting from a selected pitch, radius, or spacing of its constituent parts that work to expand incident light when reflected. Further, the exit pupil expander  703  may include various holographic elements, a diffractive grating, or other optical elements capable of optically expanding reflected light rays to result in a controlled angle of reflection or interference pattern. 
     Turning now to  FIG. 8 , illustrated therein is a head-up display monitor  800  having a head-up display surface  801  integrated therein. The head-up display surface  801  comprises an exit pupil expander integrated with a selective reflectivity notch filter as described with reference to  FIG. 7 . The inclusion of an exit pupil expander is still advantageous as the exit pupil expander still works to “spread” reflected light so that the projection surface does not act as a flat mirror reflecting light in accordance with an angle of incidence without distribution. Wavelengths other than those selected for reflection or partial reflection by the transmission curve are transmitted without substantial distortion through the selective reflectivity notch filter. 
     Turning now to  FIGS. 9 and 10 , illustrated therein are sectional views of optical devices including selective reflectivity notch filters and exit pupil expanders, either of which is suitable for use as a display monitor in the head-up display ( 660 ) of  FIG. 6 . 
     Beginning with  FIG. 9 , the optical device  900  is constructed to substantially reflect certain incident light rays  990  in accordance with a transmission curve. For example, in one embodiment the incident light rays  990  can comprise red, blue, infrared, or green light. The resulting reflected light rays  991  may be expanded to a desired output expansion cone  992  to provide a larger field of view of a reflected image to a viewer. This expansion of reflected light rays  991  may be referred to as “numerical aperture” expansion. 
     The optical device  900  can also be constructed to allow certain light rays  993  and  994  to be transmitted, at least in part. Such light rays  993 , 994  therefore travel through either side of the variable reflectivity notch filter integrated within the optical device. Accordingly, the optical device  900  has both reflective and transmissive properties, which are defined by the transmission curve. This configuration works well in head-up display applications where it can be desirable to display an image from a corresponding image projection source on optical device  900  while still allowing the optical device  900  to be at least partially transparent so as to allow a user to see through the optical device while simultaneously viewing the displayed image. 
     The exit pupil expander  995  may be either an ordered array of microstructures or a randomized light diffuser. The exit pupil expander  995  can be, for example, a micro lens array (MLA). The exit pupil expander  995  can be manufactured from a molded liquid polymer, or may be formed via other methods. In one embodiment, the exit pupil expander  995  may be embossed by a roll embossing process. In another embodiment, the exit pupil expander  995  may comprise glass or plastic beads, or microspheres or nanospheres, or similarly shaped objects capable of functioning as an optical diffuser or lens. The exit pupil expander  995  may have optical properties resulting from a selected pitch, radius, or spacing of its constituent parts to expand incident light that is reflected. The selective reflectivity notch filter  996  may be disposed on the exit pupil expander  995  to impart selective reflective properties in accordance with a transmission curve. The selective reflectivity notch filter  996  may comprise a thin coating having reflective properties at desired wavelengths so as to allow some light to be substantially reflected, some light to be partially reflected, and some light to be substantially transmitted. 
     Turning now to  FIG. 10 , illustrated therein is a cross sectional view of an alternate embodiment of an optical device  1000  configured with embodiments of the invention. The optical device  1000  of  FIG. 10  is similar to that of  FIG. 9  in that it includes a selective reflectivity notch filter  1096 . The optical device  1000  of  FIG. 10  differs from that of  FIG. 9  in that it includes an asymmetrical exit pupil expander  1095  that is coupled with a variable reflectivity notch filter. 
     The exit pupil expander  1095  of  FIG. 10  is designed to have an asymmetrical structure so that reflected light rays  1091  are directed in a desired direction according to the structures of the exit pupil expander  1095 . For example, the exit pupil expander  1095  may have an asymmetrical structure to cause reflected light rays  1091  to have a directional bias from the angle of reflection that would not otherwise occur if exit pupil expander  1095  were symmetrical. 
     In the illustrative embodiment of  FIG. 10 , the exit pupil expander  1095  has an asymmetry to bias reflected light rays  1091  downward, which results in the output expansion cone  1010  to also be directed downward. Alternatively, the exit pupil expander  1095  may have an asymmetry to bias reflected light rays  651  upward as desired. Such an asymmetrical structure may be utilized to direct the output expansion cone  1010  to a desired location according to the particular application. It is well to note that the “asymmetricalness” of the elements of the exit pupil expander  1095  may vary from element to element. For example, the asymmetry of the elements located toward the ends of the exit pupil expander  1095  may have more asymmetry than elements located toward the center of the exit pupil expander  1095 . Additionally, centrally located elements may have very little or no asymmetry. Such varying asymmetry directed toward the center of the exit pupil expander  1095  may be utilized to result in a smaller, narrower output expansion cone. Varying asymmetry directed away from the center of the exit pupil expander  1095  may result in a larger, wider output expansion cone. 
     As set forth herein, a selective reflector is used as a beam folder in an imaging system to pass one image cone while reflecting another. The selective reflector can perform the reflection based upon polarization, wavelength, or even by passing a portion of a cone and reflecting another portion. Depending upon the number of light sources, one or multiple images can be created. An additional light source can be included and reflected off the selective reflector. Reflections of the light from the additional light source can be detected by a sensor and delivered to a control circuit, which can use the reflections as control inputs. 
     In the foregoing specification, specific embodiments of the present invention have been described. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the present invention as set forth in the claims below. Thus, while preferred embodiments of the invention have been illustrated and described, it is clear that the invention is not so limited. Numerous modifications, changes, variations, substitutions, and equivalents will occur to those skilled in the art without departing from the spirit and scope of the present invention as defined by the following claims. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of present invention. The benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential features or elements of any or all the claims.