Abstract:
Image-intensifying glasses  100  are disclosed that are suitable for certain commercial and entertainment applications by virtue of their light weight, small size, and economical production, compared to certain other night vision products. In one disclosed embodiment, input light passes through two Amici prisms  144  and  148  and a field-flattening lens  150  to reach an image intensifier  152 . The intensified image it produces is reflected off a first folding mirror  162 , passes through a lens  154 , reflects off a curved mirror  156 , and passes back through the lens  154  the other way. The intensified image then passes through two additional, non-doublet lenses  158  and  160 , between which an intermediate image exists. The intensified image then reflects off the “lens,” or visor  130 , of the glasses and proceeds to the pupil of eye  131  of the wearer. Alternative embodiments use a helmet visor, mirror, or other (at least partially) reflective surface for the final reflection.

Description:
REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of and claims priority to U.S. application Ser. No. 12/497,645, titled “Night Vision Glasses” and filed Jul. 3, 2009, pending, which is an application under 35 USC §371 of international application PCT/US2009/044413, filed May 18, 2009, which claims priority to U.S. Provisional Application No. 61/053,843, titled “Night Vision Glasses” and filed May 16, 2008. This application claims priority to all of those prior applications, and incorporates herein the disclosures thereof by reference. This application is also related to U.S. application Ser. No. 12/404,087, titled “Visor Heads-Up Display,” and filed Mar. 13, 2009, and U.S. Provisional Application No. 61/036,281. 
     
    
     FIELD 
       [0002]    Some embodiments disclosed herein relate to optical systems and elements, and in particular to a system having significant infrared properties and a folded optical path, forming night vision glasses that provide the wearer with an intensified image of the real world. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0003]      FIG. 1  is a front view of a pair of night vision glasses according to one embodiment. 
           [0004]      FIG. 2  is a front view of the optical arrangement according to the embodiment of  FIG. 1 . 
           [0005]      FIG. 3  is a schematic view of the optical system in the embodiment of  FIG. 1 , unfolded at two planar fold mirrors and at two fold prisms for clarity. 
           [0006]      FIG. 4  is a top view of optical arrangement of the embodiment of  FIG. 1 . 
           [0007]      FIG. 5  is a rear view of optical arrangement in the embodiment of  FIG. 1 . 
       
    
    
     DESCRIPTION 
       [0008]    For the purpose of promoting an understanding of the principles of the present invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will, nevertheless, be understood that no limitation of the scope of the invention is thereby intended; any alterations and further modifications of the described or illustrated embodiments, and any further applications of the principles of the invention as illustrated therein are contemplated as would normally occur to one skilled in the art to which the invention relates. 
         [0009]    For many years, night vision technology has enabled military personnel to view scenes in very low light conditions. However, many night vision systems had weight distributions and overall bulk that made them unsuitable for many applications, such as many civil and entertainment applications. These systems required additional support, which frequently came from an external structure (such as a vehicle frame), a pilot&#39;s helmet, or one or both of the user&#39;s hands. 
         [0010]    Generally, one form of the system disclosed herein is a pair of glasses that includes night vision technology to provide an intensified image to the wearer. Various embodiments are mounted on eyeglasses or other eyewear, and are balanced and light enough to stay on the user&#39;s face. Other forms include wrap-around glasses, helmet-based forms, mirror-based forms, and other embodiments that will occur to those skilled in the art in view of this disclosure. For clarity, the word “visor” will be used to refer to the object that is within the view of the wearer, and off which the generated image(s) reflect(s), though that object might just as well be a lens, mirror, or other (at least partially reflective) object, whether or not the word “visor” would typically be used to describe it. 
         [0011]    Turning to  FIG. 1 , night vision glasses  100  comprise a frame  110 , stems  120 , an optical module  140 , and a visor  130  as are customary or desirable. Optical module  140  converts received low light level energy into visible light that is seen by the wearer as an enhanced image reflected off the surface of the visor  130 . 
         [0012]    The components of optical module  140  are illustrated in more detail pictorially in  FIG. 2  and schematically in  FIG. 3 . The optical module  140  comprises an objective lens subsystem  501 , an image intensifier  152 , and an eyepiece lens subsystem  601 . The objective lens subsystem  501  comprises doublet  142 , fold prism  144 , singlet or doublet  146 , fold prism  148 , and field flattener lens  150 ; whereas the eyepiece lens subsystem  601  comprises flat mirror  162 , lens  154 , curved mirror  156 , lens  158 , flat mirror  164 , and lens  160 . 
         [0013]    In this embodiment, optical module  140  contains a total of five optical folds: two in the objective lens subsystem  501  and three in the eyepiece lens subsystem  601 . In addition to the folds in the optical module  140 , one additional fold is provided by visor  130  resulting in a total of six folds. These six folds are even in number and, therefore, maintain the correct handedness (reversion) of the image with respect to the real world. The image intensifier  152  is made with a simple glass window output and, therefore, the image seen through objective lens subsystem  501  and eyepiece lens subsystem  601  would not be properly oriented due to the normal image rotation of the objective lens subsystem  501 . To correct this, two modified Amici, or “roof,” prisms  144  and  148  are utilized to rotate the objective image back by 180 degrees and provide proper orientation as seen by the eye. 
         [0014]    As shown in  FIGS. 2 and 3 , a doublet  142  receives light from in front of the wearer. The light passes through fold prism  144 , a singlet or doublet  146 , and another fold prism  148  onto a field-flattening lens  150  and into the cathode (input) window of image intensifier  152 . In this embodiment, prism  144  and prism  148  are modified Amici, or “roof,” prisms and, in combination with the doublet  142 , singlet or doublet  146 , and field flattener  150 , focus an image on the image intensifier  152  with the correct position and orientation. It will be clear to those skilled in the art in view of this disclosure that other embodiments may employ simple Amici reflectors made up of simple, front surface mirrors instead of prisms. Note that, for clarity, the folds produced by fold prisms  144  and  148  are not shown in  FIG. 3 . 
         [0015]    In this embodiment, the image intensifier  152  has a 12-13 mm diameter image format with a thin glass, second generation (multi-alkali) cathode window and a thin glass output window. Note that the fiber optic twister that is used for the output window in certain existing night vision devices adds considerable size and expense, but is not needed in the present embodiment because of the inversions achieved by the Amici prisms (or reflectors). Other types of image intensifiers might be selected for different variations on size, weight, cost, commercialization potential, power consumption, and daylight protection. While other anodes might be selected based on these and other design considerations, yet still retain the spirit of the present invention, glass-type output (anode) windows offer substantially higher transmission of light from the phosphor than military-type fiber-optics-based windows. In these embodiments, the higher transmission from the glass-type output window offsets some of the losses inherent with the use of smaller aperture objective lens and the lower gain of the second-generation image intensifier. Some embodiments, for example, provide 65-75% of the intensified field of view compared to some military night vision systems, but weigh only 1/10 of what those military night vision systems weigh. 
         [0016]    The image produced by the image intensifier  152  passes through lens  154 , a thin, plastic, meniscus-type “corrector” lens, both before and after it is reflected off a curved (e.g., spherical, aspheric, hyperbolic, elliptical, parabolic, or toroid-shape) mirror  156 . In this embodiment, the combination of the mirror  156  and lens  154  corrects for astigmatism and distortion that is produced by the tilted spherical visor/reflector  130 . The mirror  156  in this embodiment is preferably a spherical front surface mirror, but can also be a rear surface mirror so as to act as a Margin mirror. It can be made of any suitable material, even plastic. Lens  158  in this embodiment is matched with lenses  160  and  154  to place and collimate the intensified image at the pupil  131  of the user&#39;s eye. Lenses  160 ,  158 , and  154  are plastic lenses in this embodiment, and an intermediate image appears between lens  160  and lens  158 . The various lenses and mirrors of the system can be made of glass, plastic, or any other suitable material. Employing a combination of different plastics for the various lenses and mirrors provides good achromatization of the system, reducing the need for bulkier, heavier glass-type achromats. Note that, for clarity, the folds produced by planar mirrors  162  and  164  have been removed from the schematic view shown in  FIG. 3 . 
         [0017]    Finally, the image reflects off the visor  130  of the night vision glasses  100  and to the pupil  131  of the observer. Visor  130  in this embodiment is spherical, though in other embodiments it can be aspheric, parabolic, or toroidal in shape, or still another shape as will occur to those skilled in the art. Further, visor  130  in this embodiment normally has uniform reflectivity, partial reflectivity, or reflectivity that varies vertically as in the lenses of some conventional sunglasses. The design with a spherical visor is more flexible and less sensitive to minor variations in manufacturing than certain other designs. 
         [0018]    Lenses  154  and  160  are preferably made of a light plastic material, such as acrylic or polycarbonate, though other lens materials can be used as will occur to those skilled in the art. Likewise, mirror  156  may be spherical, aspheric, parabolic, toroidal, or another shape to form a suitable combination with lens  154  and the rest of the system. In various embodiments, mirror  156  is made of plastic, glass, metal, or other materials as will appear to those skilled in the art. Mirrors  156 ,  162 , and  164  may even be made using a replication process. 
         [0019]    Lens  158  is preferably a polystyrene or polycarbonate type of plastic. Some of these plastic materials are made/distributed by companies such as General Electric. Other lenses may be used in other embodiments, as will occur to those skilled in the art. 
         [0020]    Visor  130  is also preferably plastic and in various embodiments is tinted, untinted, treated with variable and/or light-sensitive dynamic tinting, or coated with a thin film reflection coating on one side. This thin film could be applied to a whole side, or to just a patch. The visor  130  is preferably made of polycarbonate plastic or another shatterproof material for improved eye safety, and is attached to the frame  110  using any of a variety of means that will occur to those skilled in the art. 
         [0021]      FIG. 4  shows a top view of the optical arrangement of night vision glasses  100  in one embodiment of an optical system for projecting an intensified image onto the right side of the glasses as viewed from the rear, while  FIG. 5  shows a rear view of the same embodiment. The various optical folds throughout the optical system achieve improved spatial compactness. In particular, this embodiment includes planar folding mirrors  162  and  164 , curved mirror  156 , and fold prisms  144  and  148 . As shown in  FIG. 4 , the intensified image reflects off region  166  of visor  130  to a pupil  131  of a user. 
         [0022]    To summarize, the embodiment illustrated in  FIG. 1  includes an image intensifying system that uses an objective lens subsystem  501  that employs two Amici prisms or mirrors, an image intensifier that utilizes a simple glass output window instead of a fiber optic window, and an eyepiece lens subsystem  601  that, combined with the visor  130 , projects the intensified image to the user&#39;s eye as described in U.S. Provisional Application No. 61/036,281 and U.S. patent application Ser. No. 12/404,087. 
         [0023]    All publications, prior applications, and other documents cited herein are hereby incorporated by reference in their entirety as if each had been individually incorporated by reference and fully set forth. While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.