Abstract:
Optical systems are described that use one or more lasers to project images onto a screen or projection surface. The optical systems can be direct view optical systems or vision projection optical systems. The described systems reduce costs and power consumption compared to the use of optical systems that use LCD screens. In addition, the described optical systems permit the image to be displayed anywhere on the screen, which in turn allows the screen to have improved light transmission for enhanced target identification in the case of gun/weapon sights and other devices that are used for target recognition.

Description:
FIELD 
     This disclosure relates to optical systems such as direct view optical systems and vision projection optical systems. 
     BACKGROUND 
     Target viewing devices such as gun/weapon sights, spotter scopes, telescopes, microscopes, monoculars, binoculars and the like are example forms of direct view optical devices. In devices such as gun/weapon sights, reticles are projected onto LCD screens incorporated into the gun/weapon sight. The LCD screens are typically full color display devices, and in most cases the projected reticle is monochromatic. So only a small portion of the capabilities of the LCD screens are used. In addition, LCD screens are expensive, generate a significant amount of heat, and consume a significant amount of power. 
     Moreover, LCD screens used in gun/weapon sights generally cover the entire field of view or project onto screens that cover the entire viewing area. A screen that obscures the entire field of view reduces the light transmission across the entire field of view. In low light vision applications, small reductions in visible light transmission significantly reduce the ability to identify targets through the sight. 
     SUMMARY 
     Optical systems are described that use one or more lasers to project images onto a screen or projection surface. The optical systems can be direct view optical systems or vision projection optical systems. The described systems reduce costs and power consumption compared to the use of optical systems that use LCD screens. In addition, the described optical systems permit the image to be displayed anywhere on the screen, which in turn allows the screen to have improved light transmission for enhanced target identification in the case of gun/weapon sights and other devices that are used for target recognition. 
     The concepts described herein can be used on gun/weapon sights, spotter scopes, telescopes, microscopes, monoculars, binoculars, cameras, virtual reality glasses, and other devices. A direct view optical system is one where a viewer is able to directly see light gathered by the system, such as telescopes, monoculars, microscopes, binoculars, gun/weapon sights and the like. A vision projection optical system is one where a viewer is able to view an image that is projected onto a screen or projection surface, where the screen can also be partially transparent to allow the viewer to see through the screen to the background to directly see light gathered by the system. 
     In one embodiment, a direct view optical system is provided that includes a viewing end, a light input aperture, a first laser that is configured to output a first laser beam, a steerable light reflecting device positioned to reflect the first laser beam output by the first laser, a first optical shutter device disposed in a light path between the first laser and the steerable light reflecting device, and a screen that includes a portion that is at least partially transparent to allow viewing of light that enters via the light input aperture. The screen also includes a portion that is at least partially reflective or fluorescent onto which an image, for example a reticle, is projected. The first laser beam output by the first laser can be a visible beam or a non-visible beam. When the beam is non-visible, the beam induces fluorescence on the screen. 
     In another embodiment, an optical system is provided that includes a first laser that is configured to output a first visible or non-visible laser beam, a steerable light reflecting device positioned to reflect the first laser beam output by the first laser, a first optical shutter device disposed in a light path between the first laser and the steerable light reflecting device, and a projection surface having a viewing side that is positioned to receive the first laser beam reflected by the steerable light reflecting device. The projection surface is at least partially reflective or fluorescent, and in some embodiments the projection surface may also be partially transparent. 
    
    
     
       DRAWINGS 
         FIG. 1  depicts a gun sight that can incorporate the direct view optical concepts described herein. 
         FIG. 2  is a schematic illustration of one embodiment of a direct view optical system described herein. 
         FIG. 3  is a schematic illustration of another embodiment of a direct view optical system that also includes a laser range finder. 
         FIG. 4  is a schematic illustration of an embodiment of an optical system that employs multiple lasers projecting an image onto a projection surface. 
         FIG. 5  is a schematic illustration of another embodiment of an optical system that employs multiple lasers projecting an image onto a projection surface. 
     
    
    
     DETAILED DESCRIPTION 
     With reference to  FIG. 1 , for purposes of describing the inventive concepts, a gun sight  10  is illustrated that can incorporate the direct view optical concepts described herein. It is to be realized that the concepts described herein can be employed on or with other types of optical devices, such as spotter scopes, telescopes, microscopes, monoculars, binoculars, cameras, virtual reality glasses, and other devices. 
     The gun sight  10  includes a housing  12  having a viewing end or aperture  14  at one end through which a user  16  looks into the gun sight, and a light input aperture  18  at the opposite end through which light from a target to be viewed enters the gun sight. On or within the housing  12  are various additional optical components discussed below with respect to  FIGS. 2 and 3 . 
     With reference to  FIG. 2 , the gun sight  10  includes a laser  20  that is configured to output a visible or a non-visible fluorescence-inducing laser beam  22 . As used herein, the terms visible and non-visible mean visibility or non-visibility by the human eye. The laser  20  can be any kind of laser that outputs a visible laser beam, including but not limited to an yttrium aluminum garnet (YAG) laser that outputs a green light laser beam, for example at 503 nm. Alternatively, the laser  20  can be of a type that outputs a non-visible beam which produces fluorescence on a surface  32  that is visible to the human eye. 
     A steerable light reflecting device  24  is positioned to reflect the laser beam  22  output by the laser. The light reflecting device  24  can be, for example, a mirror that is MEMS actuated in two dimensions to be able to steer the reflected beam. 
     An optical shutter device  26  is disposed in the light path between the laser  20  and the steerable light reflecting device  24  to turn the beam  22  on and off. The shutter device  26  is used to determine the image(s), for example a reticle, alphanumerics, range to target, wind information, etc., that are ultimately projected onto the display. The shutter device  26  can be any device suitable for creating the desired image(s), for example an LCD shutter. In addition, the shutter device  26  can be disposed at other locations in the light path. 
     A screen  28  is disposed within the housing  12  onto which the reflected beam from the reflecting device  24  is projected. The screen  28  includes a portion  30  that is at least partially transparent to allow direct viewing of light that enters via the light input aperture  18 . The transparent portion  30  facilitates target identification by maximizing the amount of direct light reaching the screen  28  for viewing by the viewer. The screen  28  also includes a portion  32  that is at least partially reflective or fluorescent. It is the portion  32  that receives the beam from the reflecting device  24  to allow viewing of the projected image by the user  16 . The portion  32  can be made partially reflective or fluorescent by a coating that is applied to the screen  28 . 
     In the illustrated embodiment, the transparent portion  30  comprises the upper half of the screen  28  while the portion  32  comprises the lower half of the screen. However, the portions  30 ,  32  can occupy any desired proportions, equal or unequal, of the screen  28 , for example the left and right halves of the screen  28 , ¼ and ¾, etc. 
     As shown in  FIG. 2 , the screen  28  includes a primary reticle  34  comprising crosshairs etched into the screen  28 . The optical system allows a new reticle  36  or aim point to be projected onto the portion  32  of the screen  28  by the laser  20 . The vertical and left and right positioning of the new reticle  36  can be altered by the steerable reflecting device  24  simply by steering the reflecting device  24  to change its angle. 
     The location of the new reticle  36  on the screen  28  can be the result of a new firing solution calculated based on various factors by a separate computing device (not illustrated). Once the user identifies the target through the transparent portion  30 , the user moves the gun sight until the new reticle  36  is on the target, thereby increasing the chances of an accurate shot. 
     To prevent laser light from escaping from the gun sight, a filter  38  is provided between the screen  28  and the light input aperture  18 . The filter  38  can be, for example, a 503 nm notch filter. 
       FIG. 3  is a schematic illustration of another embodiment of a direct view optical system that is similar in construction to the system in  FIG. 2 , but which also includes a laser range finder mechanism for use in determining range to target. The laser range finder mechanism includes a beam splitter  40  that receives the laser beam  22  and splits the beam  22  into a first laser beam  22   a  and a second laser beam  22   b . An optical shutter device  42  is disposed between the beam splitter  40  and a light output to receive the second laser beam  22   b  and output a range finding beam  44  for use in determining range to target. 
     In addition, a reflector  46  receives the first beam  22   a  and reflects the first laser beam through the shutter  26  and toward the steerable light reflecting device  24 . A frequency doubler  48  is provided in the light path between the beam splitter  40  and the reflector  46  to increase the frequency of the beam  22   a.    
     With reference to  FIG. 4 , an optical system  100  is illustrated that employs multiple lasers projecting an image onto a projection surface. The optical system  100  can function as a vision projection optical system as well as a direct view optical system. 
     The system  100  includes a plurality of lasers  102   a, b, c . . . n , each of which outputs a visible or non-visible fluorescence-inducing laser beam  104 . Some of the lasers  102   a, b, c . . . n  might output beams of the same color. This would increase the total intensity of that color for the display. Some of the lasers might output different colors in order to encode color and intensity for the display. For example, the laser  102   a  can output a green laser beam, the laser  102   b  can output a blue laser beam, the laser  102   c  can output a red laser beam, etc. The laser beams  104  are each passed through optical shutter devices  106   a, b, c . . . n , for example opto-electronic attenuators/shutters, disposed in the light paths of the laser beams  104 , and are then combined in beam combiners  108   a, b, c . . . n  to form a combined beam  110 . This encodes the color and intensity for the resulting projected display. 
     A steerable light reflecting device  112  is positioned to reflect the combined beam  110 . The light reflecting device  112  can be, for example, a mirror that is MEMS actuated in two dimensions to be able to steer the beam. The steering can be performed as a 2D raster pattern or in any general fashion. 
     Co-alignment of the beams  104  from the lasers  102   a, b, c . . . n  may require a calibration procedure in which the alignment of the individual beam combiners  108   a, b, c . . . n  is adjusted. With the reflecting device  112  in a fixed position, the beam combiners  108   a, b, c . . . n  can be adjusted to move the projected laser spots to the same position on the projection surface. 
     The beam reflected by the reflecting device  112  is projected onto a projection surface  114  for viewing by a viewer  116 . The projection surface  114  can be totally or partially reflective or fluorescent. An example of a suitable projection surface  114  includes, but is not limited to, a flat white surface. The projection surface  114  can also be partially transparent to allow the viewer  116  to see through the projection surface  114  to the background when the system is turned off. 
       FIG. 5  also illustrates an optical system  150  that employs multiple lasers projecting an image onto a projection surface, and which can function as a vision projection optical system as well as a direct view optical system similar to the optical system  100  illustrated in  FIG. 4 . 
     The system  150  includes a plurality of lasers  152   a, b, c . . . n  each of which outputs a visible or fluorescence-inducing laser beam. Some of the lasers might output beams of the same color. This would increase the total intensity of that color at a particular display location, or in this configuration of the system  150 , could allow for display of the same color at multiple locations simultaneously. Some of the lasers might output different colors in order to encode color and intensity for the display. For example, the laser  152   a  can output a green laser beam, the laser  152   b  can output a blue laser beam, the laser  152   c  can output a red laser beam, etc. The laser beams  154  are each passed through optical shutter devices  156   a, b, c  . . . n, for example opto-electronic attenuators/shutters, disposed in the light paths of the laser beams  154 . This encodes the color and intensity for the resulting projected display. 
     The individual beams are then directed to steerable light reflecting devices  158   a, b, c . . . n  positioned to reflect the beams. The light reflecting devices  158   a, b, c . . . n  can be, for example, mirrors that are MEMS actuated in two dimensions to be able to steer the beams. The steering can be performed as a 2D raster pattern or in any general fashion. 
     The beams reflected by the reflecting devices  158   a, b, c . . . n  are then projected onto a projection surface  160  for viewing by a viewer  162 . The projection surface  160  can be totally or partially reflective or fluorescent. An example of a suitable projection surface  160  includes, but is not limited to, a flat white surface. The projection surface  160  can also be partially transparent to allow the viewer  162  to see through the projection surface  160  to the background when the system is turned off. 
     Co-alignment of the laser spots from the lasers  152   a, b, c . . . n  may require a calibration procedure in which offset angles from the individual steerable reflecting devices  158   a, b, c . . . n  would be determined such that the spots from the lasers  152   a, b, c . . . n  are made coincident at multiple positions on the display surface. 
     With respect to the embodiments in  FIGS. 2-5 , in certain instances it may be possible to substitute a light emitting diode(s) and lens combination for the laser(s). 
     The examples disclosed in this application are to be considered in all respects as illustrative and not limitative. The scope of the invention is indicated by the appended claims rather than by the foregoing description; and all changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein.