Abstract:
An optical system is capable of enhancing vision of low vision individuals using a simple adjustment mechanism that requires a minimum length of travel to effect a desired adjustment. First and second substantially perpendicular mirrors are mounted in a cluster for pivotable movement. An entrance mirror is pivoted in response to pivoting movement of the mirror cluster so as to ensure proper convergence when the object to be viewed is close to the objective lens or lenses in a binocular system. The system also includes an objective lens and an eyepiece lens and is readily mounted to a conventional eyeglasses frame.

Description:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       [0001] This invention was made with Government support under SBIR Grant 5R44EY09322-03. The Government has certain rights in this invention. 
     
    
     
       CROSS-REFERENCE TO RELATED APPLICATIONS  
         [0002]    (NOT APPLICABLE)  
         BACKGROUND OF THE INVENTION  
         [0003]    The present invention relates to vision enhancing optical systems and, more particularly, to a lightweight efficiently focusable optical system, especially for use by low vision persons such as in association with eyeglasses.  
           [0004]    Vision enhancing systems for low vision individuals have made significant advances in the past years. As shown by U.S. Pat. Nos. 4,704,000 and 5,680,195, vision enhancing systems now may be provided that are light enough to be mounted on a user&#39;s eyeglasses. As shown in an article entitled “Self-Focusing Infrared Telescope Glasses May Restore Sight to Millions,”  Electronic Design,  Goldberg, Apr. 14, 1997, such low vision systems may include auto-focusing. While enormous strides have been made, it is desirable to provide an optical system for low vision individuals that is even lighter and has more effective and efficient focusing and that is well suited for auto-focusing.  
           [0005]    One system that attempts to achieve this object is described in U.S. Pat. No. 6,065,835, which is incorporated herein by reference. In this system, a mirror cluster includes two mirrors that are mounted at an angle of about 90° to each other and for substantially linear movement. With the 90° mirror cluster, two units of focus are achieved for every one unit of travel, making focusing quicker and easier. The patent recognizes that while the same basic results could be achieved by moving prisms instead of mirrors, mirrors are much lighter in weight than prisms and therefore are much more suitable to wearable vision systems, particularly those that must be light enough to be mounted on eyeglasses. This system, however, must be sized to accommodate the linear movement of the mirror cluster. In a binocular system, the linear movement of two mirror clusters must be accommodated. As a consequence, the size of the device is larger than desirable, and the device itself tends to interfere with normal and peripheral vision.  
         SUMMARY OF THE INVENTION  
         [0006]    With the system of the present invention, it is an object to provide a lightweight, efficiently, universally and effectively focusable optical system, especially for use by low vision persons such as in association with eyeglasses. It is a further object to provide such a system within a compact housing that minimizes interference with central and peripheral vision.  
           [0007]    It is yet another object to ensure that a magnified image viewed by the system at any distance appears in the same spatial location as normally viewed except for image size.  
           [0008]    In an exemplary embodiment of the invention, a vision enhancing optical system includes an objective lens disposed in an optical path, an eyepiece lens disposed in the optical path, and a mirror cluster disposed in the optical path and having first and second substantially planar mirrors that are disposed at an angle of substantially 90° relative to each other. The mirror cluster is pivotable about an axis substantially perpendicular to the optical path at the mirror cluster. The system may further include a third mirror disposed in the optical path reflecting incoming light toward the objective lens. A fourth mirror may be disposed in the optical path reflecting the incoming light toward the mirror cluster. In sequence, the system preferably includes the third mirror reflecting incoming light toward the objective lens, the objective lens, the fourth mirror reflecting the incoming light toward the mirror cluster, the mirror cluster, and the eyepiece lens.  
           [0009]    The first and second mirrors of the mirror cluster are preferably coupled to arms of a bracket disposed substantially 90° relative to each other. In this context, the bracket is coupled with a rotatable mirror arm. The system includes structure for rotating the mirror arms such as a motor or the like. The third mirror disposed in the optical path that reflects the incoming light toward the mirror cluster is also pivotable relative to the objective lens. In this context, the mirror arm supporting the third mirror preferably includes a cam, and the third mirror is coupled with a cam follower engaging the cam. The position of the third mirror is adjusted based on a position of the mirror arm.  
           [0010]    The optical system may be a binocular or monocular system. In one embodiment of the monocular arrangement, an entrance mirror reflects incoming light toward the mirror cluster, wherein the entrance mirror is spaced from the mirror cluster by a distance substantially corresponding to the distance between a person&#39;s eyes. In a second embodiment, an entrance mirror reflects light toward a prism. In both embodiments, the entrance mirror is preferably pivotable relative to the optical path to enable image position correction as previously described.  
           [0011]    In another embodiment, an eyepiece houses the eyepiece lens, and the optical system is attachable to a frame of a pair of glasses. When the optical system is attached to the glasses frame, only the eyepiece and eyepiece lens impinge an area inside the glasses frame.  
           [0012]    In another exemplary embodiment of the invention, a binocular vision enhancing optical system includes first and second objective lenses disposed in first and second optical paths, respectively; first and second eyepiece lenses disposed in the first and second optical paths, respectively; and first and second mirror clusters disposed in the first and second optical paths, respectively. Each of the first and second mirror clusters includes first and second substantially planar mirrors that are disposed at an angle of substantially 90° relative to each other. The mirror clusters are pivotable about an axis substantially perpendicular to the respective optical paths at the mirror clusters.  
           [0013]    In yet another exemplary embodiment of the invention, a vision enhancing optical system includes a pair of glasses including a frame and the vision enhancing unit according to the invention secured to the glasses frame. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    These and other aspects and advantages of the present invention will be described in detail with reference to the accompanying drawings, in which:  
         [0015]    [0015]FIG. 1 shows the vision enhancing optical system according to the invention attached to a pair of eyeglasses;  
         [0016]    [0016]FIG. 2 is a perspective view showing an optical path defined by the lenses and mirrors of the system;  
         [0017]    [0017]FIG. 3 is a simplified side view with the mirror cluster shown in position for far focus;  
         [0018]    [0018]FIG. 4 is a simplified side view with the mirror cluster shown in position for near focus;  
         [0019]    [0019]FIG. 5 is a side view of the mirror arm axle rotation system and convergence system;  
         [0020]    [0020]FIG. 6 illustrates a monocular version of the vision enhancing optical system according to the present invention; and  
         [0021]    [0021]FIG. 7 shows an alternative embodiment of the invention, illustrating image position correction. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0022]    [0022]FIG. 1 is a view from a user&#39;s perspective of the vision enhancing optical system  10  according to the present invention attached to the frame  12  of a pair of eyeglasses. Generally, the optical system  10  includes a main housing  14  containing or supporting the components of the optical system  10 . An auto-focus component  16  and electronics therefor are contained within the main housing  14 . The auto-focus component  16  and the electronics therefor are generally known and do not form part of the present invention. Further details thereof will thus not be described. Left and right eyepieces  18  house an eyepiece lens  20  and are configured to impinge an area inside the glasses frame  12  in front of a user&#39;s pupils. As seen in FIG. 1, only the eyepiece  18  and eyepiece lens  20  impinge the area inside the glasses frame  12 .  
         [0023]    [0023]FIG. 2 shows a preferred arrangement of lenses and mirrors of the optical system  10  according to the invention that define an optical path  22 . The system includes an objective lens  24  that may be placed anywhere along the optical path, the eyepiece lens  20  discussed above, and a mirror cluster  26  including first  28  and second  30  substantially planar mirrors that are disposed at an angle with respect to each other of substantially 90°. The system also includes a third mirror  32  that, in a preferred embodiment, reflects incoming light through the objective lens  24  toward a fourth mirror  34  that reflects the incoming light toward the first mirror  28  of the mirror cluster  26 . The image is then reflected to the second mirror  30  of the mirror cluster  26  and through the eyepiece lens  20 .  
         [0024]    With continued reference to FIG. 2 and with reference to FIGS. 3 and 4, the first  28  and second  30  mirrors of the mirror cluster  26  are secured to respective arms  36 ,  38  of a bracket  40 . The bracket  40  is coupled with a rotatable mirror arm  42  that effects controlled pivotal movement of the bracket  40  and thus the mirror cluster  26 . It has been discovered that the linear movement of the mirror cluster described in the above-mentioned U.S. Pat. No. 6,065,835 can be eliminated to provide a more compact and lightweight system by pivoting the mirror cluster  26  for far focus and near focus applications. FIG. 3 shows an exemplary position of the mirror cluster  26  in position for far focus operation (for example, 3′ or farther). When the system detects that a near focus operation is required, the mirror cluster  26  is pivoted to the position illustrated in FIG. 4 via rotation of the mirror arm  42 . In this manner, focusing for near images (for example, 3′ or less) can be accurately achieved.  
         [0025]    With reference to FIG. 5, pivoting of the mirror cluster  26  via bracket  40  is accomplished by rotating the mirror arm  42  about its axis. The mirror arm is connected to one end of a lever arm  44 , which in turn is connected at its other end to a trunion  46 . The trunion  46  is coupled with a motor  48  via a lead screw  50 . A torsion spring  51  holds the mirror arm  42  and associated parts against the frame and also applies a preload against the motor  48 . As the motor  48  drives the trunion  46  forward and back via the lead screw  50 , the lever arm  44  is pivoted thereby rotating the mirror arm  42 , and thereby pivoting the bracket  40  and mirror cluster  26 . Alternatively, the lever arm  44  can be pivoted manually.  
         [0026]    A binocular system needs to ensure convergence of the image being viewed. When an object to be viewed is three feet or closer to the objective lens or lenses of a binocular system, unless some adjustment of the optical components is effected, it is not possible to maintain a fused binocular image. Convergence is provided according to the invention by mounting each third mirror  32  pivotally, for pivotal movement about a pivot axis relative to the objective lens  24 . Preferably, structure is provided for automatically pivoting each third mirror  32  in response to a pivot position of the mirror cluster  26  to maintain a substantially constant optical relationship between the mirror cluster  26  and the third mirror  32  and to provide a fused binocular image for objects about 3′ or less from the system.  
         [0027]    In order to automatically pivot the third mirror  32  with pivoting of the mirror cluster  26 , automatic pivoting structure is coupled with the lever arm  44 . The automatic pivoting structure may include any conventional structure that effects pivotal movement of one component to which it is connected while allowing relative movement of that component with respect to another. In a preferred embodiment, with continued reference to FIG. 5, the automatic pivoting structure includes a cam surface  52  on the lever arm  44  and a cam follower  54  coupled with the third mirror  32 . In the binocular arrangement, the third mirrors  32  and respective cam followers  54  are biased against the cam surfaces  52  via a spring connected between them. With this structure, as the motor  48  drives the lead screw  50  to pivot the lever arm  44  and rotate the mirror arm  42 , the cam follower  54  rides on the cam surface  52  to adjust a position of the third mirror  32 .  
         [0028]    The vertical position of the point of view shifts along with focus to compensate for the vertical distance between the viewer&#39;s eye level and the incoming light path. This compensation can be understood as caused by the vertical displacement of a center ray due to the vertical shift of the vertex of the third  32  and fourth  34  mirrors from their rotational motion as a unit. The position of the mirror arm  42  axle center of rotation is chosen so as to cause the point of view to appear approximately as if it were directly in front of the eyes over the full range of focus from infinity to about 10″. As the focus is shifted, the horizontal point of view is also moved so that both eyes perceive the same points on the object together (i.e., the left and right images “fuse”). This is effected by pivoting the third mirror  32  in coordination with the focus motion via the mirror cluster  26  as described above.  
         [0029]    The pupillary distance (i.e., the distance between an individual&#39;s pupils) can be accommodated by allowing de-coupling of various components in the system of the invention, and reattachment once adjusted. An easy to adjust (but also easy to move out of adjustment) mechanism for this purpose such as found in conventional binoculars is not necessary because the system of the invention will not normally be used by more than one or a few people. Preferably, pupillary distance adjustment is effected by sliding the lens holder against the frame and the mirror arm in or out of the axle. An extension of the mirror arm may be provided to engage a surface on the lens holder so that the two parts move in unison.  
         [0030]    To compensate for alignment errors caused by tolerances in production and assembly of components, the fourth mirror  34  is provided with an adjustment system including a kinematic arrangement that is typical of mirror mounts used in optical research labs. The mirror is bonded to a plate pre-loaded by a spring to bear against three screws. One pointed screw engages a hole in the plate, a second pointed screw engages a v-groove in the plate, and a rounded tip screw bears against a flat on the plate.  
         [0031]    In addition to the horizontal and vertical alignment permitted by the aforementioned mirror mounting system, it may become necessary to provide for adjustment of scene angle between left and right sides if economical production of parts precludes sufficiently accurate deterministic mounting. There are several ways this might be done, with the choice to be determined if needed, such as by twisting the mirror arm  42  or incorporating another adjustment mechanism similar to and orthogonal to the above-mentioned kinematic mount.  
         [0032]    In a monocular variant according to the present invention, in addition to simply using one-half of the device, the entrance mirror or third mirror  32  is positioned adjacent the user&#39;s eye opposite the ocular (that is, if the ocular is at the right eye, the entrance mirror will be on the side of the left eye). The preferred construction of the monocular variant according to the invention is illustrated in FIG. 6. In FIG. 6, the ocular is positioned adjacent the user&#39;s right eye, and the third mirror  32  is positioned adjacent the user&#39;s left eye. Otherwise, the system and components are the same as that for the binocular variant described above, and the components will not be described again. This construction allows for a much longer optical path than the binocular system, with the benefits attendant to the optical path.  
         [0033]    Still another variation is illustrated in FIG. 7. This embodiment incorporates the pivoting entrance mirror  32 ′ in place of a prism in the vision enhancing system disclosed in U.S. Pat. No. 4,704,000, the disclosure of which is hereby incorporated by reference. That is, the Amici prism in the noted U.S. patent is replaced with a pivoting third mirror  32 ′ of the present invention. The mirror  32 ′ reflects incoming light to an objective  24 ′ and reflects the image to the ocular via a penta prism PP. With this construction, the image space of an object can be brought into alignment with the ocular at close distance, instead of being in front of and perpendicular to the device at the entrance mirror.  
         [0034]    It will thus be seen that according to the present invention a highly advantageous optical system has been provided that is readily mounted to conventional eyeglasses.  
         [0035]    While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.