Abstract:
An apparatus, system and method are provided to inject an image into a viewing optical system, which is used for viewing a scene. An image injector includes first and second optical elements with first and second sides, respectively, and a reflective material. The first side adjoins the second side and the reflective material is between the adjoining sides. An image generator is optically coupled to the second optical element and generates an image. The image injector is placed at the aperture of the viewing optical system and passes energy from the scene into the viewing optical system. The reflective material reflects energy from the image generator into the viewing optical system. The image generator may produce the image based upon an information signal from an information generator. The reflective material may reflect energy from the scene into an output optical system and the information generator produce the information signal based on the energy received in the output optical system.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This patent application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application No. 60/860,592 entitled “Optical Injector System for Image Display or Image Receiving Applications” filed on Nov. 22, 2006, which is hereby incorporated by reference. 

   TECHNICAL FIELD 
   This disclosure is generally directed to optical systems and more particularly to a system and method for optical image generation and injection. 
   BACKGROUND 
   Often, it is desirable to inject an image or visual indicator into an image as viewed through a rifle sight, telescope, video camera or other viewing optical system. Such an injected image may supplement an image of a scene being viewed through the viewing optical system, for example by highlighting a portion of the image of the scene or by overlaying the image of the scene with a visual image of the scene in a non-visible portion of the electromagnetic spectrum. A visual indicator other than an image may be injected to provide a user of the viewing optical system with an indicator that may be viewed within the image of the scene. Such an indicator may provide an alert, warning, failure or other sort of indication. 
   Typically, image injectors are undesirably large and/or heavy. Known image injectors may also be fragile or subject to degraded performance in inclement operating conditions. 
   SUMMARY 
   Aspects of the invention may be found in an apparatus for use with a viewing optical system, where the viewing optical system is used for viewing a scene. The apparatus includes an image injector and an image generator. The image injector includes a first optical element that has a first side, a second optical element that has a second side, and a reflective material. The first side adjoins the second side and the reflective material is positioned between the first and second sides. The image generator is optically coupled to the second optical element and generates an image. The image injector is adapted to be placed adjacent to an input of the viewing optical system and energy from the scene passes through the image generator into the input of the viewing optical system. The reflective material reflects energy from the image generated by the image generator into the viewing optical system. 
   The apparatus may also include an output optical system that is optically coupled to the first optical element, where the reflective material reflects energy from the scene into the output optical system. 
   Other aspects of the invention may be found in an information display system for use with a viewing optical system, where the viewing optical system is used for viewing a scene. The information display system includes an information generator, an image injector, and an image generator. The information generator has an input signal and generates an information signal responsive to the input signal. The image injector includes a first optical element that has a first side, a second optical element that has a second side, and a reflective material. The first side adjoins the second side and the reflective material is positioned between the first and second sides. The image generator is optically coupled to the second optical element and generates an image responsive to the information signal. The image injector is adapted to be placed adjacent to an input of the viewing optical system and energy from the scene passes through the image generator into the input of the viewing optical system. The reflective material reflects energy from the image generated by the image generator into the viewing optical system. 
   The information display system may also include an output optical system that is optically coupled to the first optical element, where the reflective material reflects energy from the scene into the output optical system. The information generator may be coupled to an output of the output optical system and may generate the information signal responsive to a signal received from the output optical system. 
   Still other aspects of the invention may be found in method of injecting an image for use with a viewing optical system, where the viewing optical system is used for viewing a scene. The method includes transmitting energy from the scene through an image injector into the viewing optical system. The image injector includes a first optical element that has a first side, a second optical element that has a second side, and a reflective material. The first side adjoins the second side and the reflective material is positioned between the first and second sides. The method also includes generating an image with an image generator that is optically coupled to the second element. The method further includes reflecting energy from the image generated by the image generator into the viewing optical system, where the energy from the image is reflected by the reflective material. 
   The method may include receiving energy from the scene at an output optical system that is optically coupled to the first optical element, wherein the energy received at the output optical system is reflected by the reflective material, and generating the image responsive to the energy received at the output optical system. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a more complete understanding of this disclosure and its features, reference is now made to the following description, taken in conjunction with the accompanying drawings, in which: 
       FIG. 1  depicts a schematic diagram of a system embodying the present invention; and 
       FIG. 2  presents an exploded view of an image injector according to the present invention. 
   

   DETAILED DESCRIPTION 
   An image injector according to the present invention mounts in front of, or may be integrated into, a viewing optical system. The image injector passes energy from a scene to the viewing optical system and reflects energy from an image generator to the viewing optical system. The image generator produces an optical indication or an image. An image controller may send a signal to the image generator representing the optical indication or image to be injected into the viewing optical system&#39;s view of the scene. The image injector may also intercept and reflect energy from the scene to an output optical system. 
     FIG. 1  depicts a schematic diagram of an optical system  100  embodying the present invention. An image injector  101  in close proximity to an input or aperture  109  of a viewing optical system  108  and passes energy (indicated by rays or beams  110   a ,  110   b  and  110   c ) from a scene (not shown) into the input  109 . The optical injector  101  also reflects energy (represented by a ray or beam  114 ) from an image generator  112  into the input  109  of the viewing optical system  108 . In one embodiment, the image injector  101  is in contact with the input  109  of the viewing optical system  108  or is close enough that it does not obscure the entire aperture  109  of the viewing optical system  108 . 
   The optical injector  101  includes a first optical element  102  and a second optical element  104 . The first and second optical elements  102  and  104  have adjoining faces  103  and  105 , respectively, which physically and optically couple the first and second optical elements  102  and  104  and define the mating surface  106 , which will be further described with reference to  FIG. 2 . The rays  110   a  and  110   c  pass through the first optical element  102  and the second optical element  104 , respectively, to the input  109  of the viewing optical system. The ray  110   b  passes through first optical element  102 , the mating surface  106 , and the second optical element  104  to the input  109  of the viewing optical system. 
   The image generator  112  is optically coupled to the second optical element  104  at another face  113  of the second optical element  104 . The ray  114  from the image generator  112  passes through the face  113  and the second optical element  104  and is reflected by the mating surface  106  into the aperture  109  of the viewing optical system  108 . 
   The face  113  may have a shape (such as flat or spherical) chosen to facilitate optical coupling between the image generator  112  and the second optical element  104 . The index of refraction of the second optical element  104  material may be chosen to reduce an angular extent of the beam  114  incident on the mating surface  106  when compared to an equivalent angular extent of the beam  114  in air. As a result, the optical extent of the beam  114  at the edge of the second optical element  104  is smaller than the equivalent optical extent in air, allowing for smaller optics to be used in the image generator  112  when compared to an image generator used in an air-based image injector. Preferably, the beam  114  remains entirely within the second optical element  104  between the face  113  and the mating surface  106 . 
   In some embodiments, an output optical system  116  is optically coupled to another face  115  of the first optical element  102 . The mating surface  106  reflects a beam  118  through the first optical element  102  and the face  115  into the output optical system  116 . The beam  118  includes all or part of the beam  110   b.    
   The output optical system  116 , in one embodiment, generates a visible image of the beam  118  for projection or direct viewing by a user of the optical system  100 . In another embodiment, the output optical system  116  produces an electrical or optical signal on an output  117  that is representative of a characteristic of the scene being viewed by the optical system  100 . For example, such a signal may represent an overall brightness level of the scene; whether a certain object is present or absent in the scene; an image of the scene in the visible, infrared, or other range of the electromagnetic spectrum; or other signal derived from the beam  118 . 
   As described for the image injector  112 , the face  115  may have a shape (such as flat or spherical) chosen to facilitate optical coupling between the output optical system  116  and the first optical element  102 . The index of refraction of the first optical element  102  material may be chosen to reduce an angular extent of the beam  118  reflected from the mating surface  106  when compared to an equivalent angular extent of the beam  114  in air, allowing for smaller optics to be used in the output optical system  116  when compared to an air-based image injector. Preferably, the beam  118  remains entirely within the first optical element  102  between the mating surface  106  and the face  115 . 
   An information generator  120  receives a signal on an input  122  and generates a signal on an output  124 . The signal on the output  124  is an information signal representative of one or more characteristics of the signal on the input  122 . The output  124  is coupled to the image generator  112 , which generates an image according to the information signal on the output  124 . The image generator  112  projects the generated image into the image injector  101  through the face  113 , as represented by ray  114 . 
   In one embodiment, the output  117  of the output optical system  116  is coupled to the input  122  of the information generator  120 . In such an embodiment, the information signal generated by the information generator  120  is representative of the characteristic of the scene sensed by the output optical system  116 . In another embodiment, the output  117  is coupled to a device or system outside the optical system  100 . 
   In the embodiment shown in  FIG. 1 , the image injector  101  extends across substantially all of the aperture  109  of the viewing optical system  108  in the vertical direction. The image injector  101  and the mating surface  106  may extend across substantially all, or only a narrow strip, of the aperture  109  of the viewing optical system  108  in the horizontal direction (as shown in  FIG. 1 , into the page). 
   Because the mating surface  106  subtends only a portion of the aperture  109  of the viewing optical system  108 , the image injector  101  has a depth dimension (horizontal in  FIG. 1 ) that is significantly smaller than its vertical dimension. As shown in  FIG. 1 , the vertical dimension of the image injector  101  is substantially perpendicular to, and the depth dimension is substantially parallel to, the optical axis of the viewing optical system  108 . It will be understood that in other embodiments the image injector may be oriented at an angle other than 90 degrees to the optical axis of the viewing optical system  108 . 
   In other embodiments, the image injector  101 , the image generator  112 , and the output optical system  116  are integrated into, or fabricated as part of, the viewing optical system  108 . In still other embodiments, one or both of the image generator  112  and the output optical system  116  are separately mounted to the integrated image injector and optically coupled to the faces  113  and  115 , respectively. 
     FIG. 2  presents an exploded view of the image injector  101  according to the present invention. The first optical element  102  and the face  103  have been separated from the second optical element  104  and the face  105 . Elements  206 ,  208  and  210  of the mating surface  106  are indicated on the face  105  of the second optical element  104 , however it will be understood that the mating surface  106  may be located on the face  103  of the first optical element  102 . It will also be understood that the mating surface  106  may be one or more materials that are separate from, but positioned between, the faces  103  and  105 . 
   A portion  206  of the mating surface  106  is reflective. The portion  206 , as shown, has a size smaller than one or both of the faces  103  and  105 ; however, it will be understood that the portion  206  may be coextensive with the faces  103  and  105 . The portion  206  may be a coating on the face  103  or the face  105 . Such a coating may be a metallic or dielectric material. 
   While the reflective portion  206  is shown in  FIG. 2  in the center of the mating surface  106 , it will be understood that the reflective portion  206  may be located anywhere in the mating surface  106 . In one embodiment, the first and second optical elements  102  and  104  are bonded together at the mating surface  106  in order to maintain optical alignment between the faces  113  and  115  and the mating surface  106  despite rough physical treatment of the image injector  101 . 
   The reflective portion  206  may have a reflectivity between 1 percent and 100 percent, inclusive. The portion  206  may reflect energy in the visible spectrum, all or part of the infrared spectrum, or in any other part of the electromagnetic spectrum. The portion  206  may reflect one portion of the spectrum and transmit other portions of the spectrum. The portion  206  may have any combination of these characteristics of reflectivity, transmissivity, and spectral response. 
   Where the portion  206  has a size less than the size of one or both of the faces  103  and  105 , remaining portions  208  and  210  of the mating surface  106  may include an optical adhesive having an index of refraction that closely matches the index of refraction of the first and second optical elements  102  and  104 , so as to minimize reflections from the portions  208  and  210 . The portions  208  and  210  may additionally or alternatively include an antireflective coating on one or both of the faces  103  and  105 . In other embodiments, the portions  208  and  210  of the mating surface  106 , the first optical element  102 , and the second optical element  104  may be untreated. 
   While the beam  114  is depicted as a single ray, it will be understood that the image generator  112  may be designed to generate a beam that converges on or near a reflective portion of the mating surface  106  and diverges again to fill the input  109  of the viewing optical system  108 . 
   Because the image injector  101  is significantly closer to the viewing optical system  108  than the scene being viewed, when the scene is in focus, the reflective portion  206  and other elements of the mating surface  106  will be greatly out of focus to the user of the viewing optical system  108 . When the image generator  112  is not generating an image, the presence of the reflective portion  206  will be undetectable to the user. 
   In one embodiment, the image generator  112  generates an image that has an apparent focus at a location that is closer to the viewing optical system than the scene being viewed by a user of the viewing optical system  108 , for example, at or near the mating plane  106 . In such an embodiment, by bringing the scene into focus with the viewing optical system  108 , the user throws the image from the image generator  112  out of focus. As a result, the image will be perceived by the user as a ‘wash’ of light over all or part of the scene. Such an image may convey information by varying a color, intensity, rate or duty cycle of the image. 
   In another embodiment, the image generator  112  generates an image that has an apparent focus at a location that is substantially at the same distance from the viewing optical system  108  as the scene being viewed by a user of the viewing optical system  108 . In such an embodiment, by bringing the scene into focus with the viewing optical system  108 , the user would also bring the image generated by the image generator  112  into focus and be able to perceive detail in the image. Such an image could therefore include, for example, numbers, text and/or symbols. Such an image could include a processed image of the scene, acquired by the output optical system  116  or another sensor; an image of the scene with information removed or added; or an image of the scene acquired with a sensor observing the scene in a different region of the electromagnetic spectrum than the user. It will be understood that the image could include any combination of the above described image content. 
   In an embodiment intended for use with a viewing optical system responsive to energy in another part of the spectrum than visible light (for example, infrared), the image generator  112  generates an image in that other part of the spectrum. In an embodiment intended for use with a binocular viewing optical system, two image injectors are placed in front of two inputs to the binocular viewing optical system and either one image generator coupled to both image injectors or a separate image generator coupled to each of the image injectors. 
   It may be advantageous to set forth definitions of certain words and phrases used in this patent document. The term “couple” and its derivatives refer to any direct or indirect communication between two or more elements, whether or not those elements are in physical contact with one another. The terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation. The term “or” is inclusive, meaning and/or. The phrases “associated with” and “associated therewith,” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like. 
   While this disclosure has described certain embodiments and generally associated methods, alterations and permutations of these embodiments and methods will be apparent to those skilled in the art. Accordingly, the above description of example embodiments does not define or constrain this disclosure. Other changes, substitutions, and alterations are also possible without departing from the spirit and scope of this disclosure, as defined by the following claims.