TARGET ACQUIRING TELESCOPE

Abstract: A telescopic device adapted for bifocal vision, comprising: optical means for viewing a field-of-view; a housing for containing and supporting the optical means, said optical means comprising an objective lens located at one side of said housing with a first optical axis and an eyepiece lens located at the opposite side of said housing with a second optical axis; means for tilting said first optical axis with respect to said second optical axis to enable simultaneous view of the target and its magnified image; and target acquisition means.

Description: APPLICATION FOR PATENT Title: TARGET ACQUIRING TELESCOPE FIELD AND BACKGROUND OF THE INVENTION The present invention relates to optical devices and means for magnifying vision. More particularly, the invention relates to hand-held, tripod-mounted, and head-mounted telescopic devices. Optical direct view telescopic devices can be categorized according to several classifications: - Keplerian vs. Galilean telescopes. - Monocular versus binocular (stereoscopic) telescopes. - Distant viewing vs. close viewing telescopes. - Head-mounted vs. hand-held and tripod-mounted telescopes. Keplerian telescopes, wherein the eyepiece lens group has a positive power, have better image quality, larger field-of-view and an exit pupil which is external to the eyepiece. In addition, they have an internal real image that enables the entire field of view to be presented with sharp borders as well as superimposition of a reticule on the magnified image. The disadvantage of the Keplerian telescope is that an image erection system is needed. For this reason, this telescope is relatively bulky and heavy. Galilean telescopes, wherein the eyepiece lens group has a negative power, are limited to low magnifications and a relatively narrow field-of-view. The field-of-view does not have clearly defined borders and no reticule can be superimposed on the image. In addition, unless the eyepiece almost touches the observer's eye, the field-of-view is even further reduced. The only advantage of the Galilean telescope is that no image erection system is needed. Therefore, it is relatively compact and light-weight. For the above reasons, Galilean telescopes are employed mainly as toy binoculars and as opera glasses, i.e., where the performance is not critical. For professional applications such as field binoculars and telemagnifiers, Keplerian telescopes are almost exclusively utilized. Prior art telescopic means, whether hand-held or tripod mounted, do not enable smooth switching between the natural (unmagnified) view of the target and its magnified view. An auxiliary acquisition telescope is sometimes used in parallel with tripod mounted telescopes to ease the task of continuous area observation. In an effort to help the user, as well as to free his hands, head-mounted telescopic means have been proposed. US 4,577,347 and US 5,128,807 describe helmet-mounted monocular telescopes, while US 4,488,790 describes a spectacle-frame mounted binocular telescope intended for magnifying the visible image of distant objects. In practice, the only head-mounted telescopic devices that have found practical use are the stereoscopic telemagmfiers, used in the medical field by dentists and surgeons, as well as aids for the visually handicapped. A conventional telemagnifier includes a pair of telescopes that are focused to, and converge at, a point located typically about 30 cm in front of the wearer's eyes. These telemagmfiers are mounted on a head strap but more often on a spectacle frame, or on spectacle lenses. The main disadvantage of the above telescopic means is that they obscure the natural view in front of the aided eye whereas the viewer may be interested in both the unmagnified natural view of the object and in its magnified image to make target acquisition easy. Relatively recently, Spitzberg has made an advancement in head-mounted telemagmfiers by displacing the magnified view-of-the-object of interest relative to its natural view thereby enabling access to both images, and an easier target acquisition - as described in US 4,795,235 and US 5,028,127. In general, however, these bifocal telescopes, which are more fully described later, provide only a partial answer to the target acquisition problem, thus enabling only a limited number of applications in view of all the above telescope classifications. US 4,795,235 describes a spectacle lens mounted Keplerian monocular telescope which is intended for the visually handicapped wherein the optical axis of the eyepiece lens is tilted 40° with respect to the optical axis of the objective lens in order to present the magmfied image beside its natural image and minimize obscuration of the natural field-of-view by the magnified image. This type of telescope suffers from two disadvantages: (i). the off-axis position of the magnified image strains the eye; and (ii). It cannot be used as a binocular since the two eyes would have to stare at different directions. US 5,028,127 describes a Galilean spectacle-mounted monocular telescope which is also intended for the visually handicapped, and in which the optical axis of the eyepiece lens is tilted with respect to the optical axis of the objective lens such that the magnified image appears below its natural image. However, the adaptation of this type of bifocal telescope to the medical field as a stereoscopic telemagnifier is of limited utility due to the following reasons: - The area of interest in medical applications lies in the lower portion of the natural field of view, therefore, some of it is still obscured by the magnified image; - An image rotation may be induced in such telescope by the combined effect of the tilt angle of the eyepiece optical axis and the convergence angle of the objective optical axis. The two separate images would rotate in opposite directions and their binocular fusion will strain the eyes, if at all practical; - Additional disadvantages that further limit their usefulness for medical applications, as well as their adaptation for long distance observation, such as watching nature, sports events, opera shows, etc.; - A Galilean telescope has a limited magnification, field-of-view, and image quality; - Acquisition of a target, in particular a moving one, in the magmfied field of view is still tedious. Prior art bifocal telescopes were thus limited to head-mounted close viewing, monocular telescopes and were not even suggested for long distance viewing. These limitations are fully overcome by the invention. It is an object of the invention to provide a telescope in which the optical axis of the eyepiece lens is tilted relative to that of the objective lens and which includes target acquisition means for essentially instantaneous switch between the magmfied view -and the natural view, even while following moving objects. This type of telescope is hereinafter referred to as "target acquisition telescope" . It is another object of the invention to provide said telescope in two head mounting forms, one optimized for closed object magnification, and the other for distant objects magnification, which does not suffer from the above mentioned limitations. It is a further object of the invention to provide such a telescope that can be hand-held. It is yet another object of the invention to provide head-mounted telescopic means, wherein the target area of the natural field-of-view is essentially unobscured by the magnified field-of-view. It is still another object of the invention to provide telescopic means as mentioned above having a rectangular landscape-shaped field-of-view. It is another object of the invention to provide telescopic means as mentioned above having horizontally elongated exit pupil. It is still another object of the invention to provide telescopic means as above having a rectangular landscape-contoured eyepiece. It is a further object of the invention to provide telescopic means adapted for a relatively small field-of-view and a relatively long eye relief. It is still another object of the invention to provide spectacle mounted stereoscopic magnifier which has no relative rotation between the images seen by each one of the two eyes. Further advantages of the invention will become apparent as the description proceeds. SUMMARY OF THE INVENTION The telescopic device adapted for bifocal vision according to the invention comprises optical means for viewing a field-of-view, optional target acquisition means, a housing for containing and supporung the optical means, said optical means comprising an objective lens located at one side of said housing with a first optical axis, and an eyepiece lens located at the opposite side of said housing with a second optical axis, and means for tilting said first optical axis with respect to said second optical axis. The lenses of the optical means according to the invention include refractive, diffractive and/or refractive/diffractive lenses. According to a preferred embodiment of the invention, the first optical axis is tilted by an amount suitable for close objects viewing, or by an amount suitable for distant objects viewing. More particularly, the first axis is tilted with respect to the second axis, by an angle of about 40° in a device adapted for close-viewing, and about 25° in a device adapted for distant viewing. The means for tilting the light path comprise reflective and/or refractive and/or diffractive optical elements and wherein a magnified image appears above or below the natural unmagnified image, i.e., the device can be either top or low mounted (above or below the observer's eye level). The device according to another preferred embodiment of the invention may optionally be provided with a rectangular eyepiece contour and a rectangular field-of-view, and further may be provided with focusing means and/or target acquisition means which are a foldable or detachable frame type or reticule type. A device according to another preferred embodiment of the invention may be a monocular which is provided with an occlusion to the unaided eye, or a binocular. Further, the device of the invention may be hand-held, or mounted on a head support or on a spectacle frame. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 shows a conceptual view of telescopic means according to me invention which is optimized for distant objects viewing. Fig. 2 illustrates a side view of a hand held distant viewing device according to a preferred embodiment of the invention. Fig. 3 illustrates a side view of a top mounted spectacle-frame monocular telescopic means according to me invention optimized for close objects viewing. Fig. 4 illustrates a front view of a spectacle-frame low mounted telescopic monocular means according to the invention optimized for distant objects viewing. Fig 5 illustrates a possible adaptation of a conventional telescope to a telescope according to the invention. Fig. 6 illustrates a target acquisition means based on the projection of a virtual aiming point. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Fig. 1 illustrates in schematic form an embodiment of the mvention. The telescopic device 1 is assembled along two optical axes X and X', wherein axis X intersects with the center of the unmagnified (natural) field-of-view, and axis X' intersects with the center of the magmfied field-of-view as seen by the observer. The device further comprises an objective lens 3 which produces an inverted image (not shown) inside the telescopic device. Said device further comprises an image erecting system which is known to those skilled in the art (not shown), and an eyepiece lens 4 having a tilted angle of typically 25° with respect to the optical axis of the objective lens. Conventionally, the observer's eye pupil 10 essentially coincides with the exit pupil (not shown) of said device. The exit pupil is centered along axis X' and displaced typically 20 to 25 mm from the eyepiece lens. The preferred embodiment of the device further comprises acquisition means 11 that encompasses the portion of the natural field-of-view which is to be magnified. The center point of said acquisition means and the point located typically 5 mm above the center of the exit pupil define an axis X" that is substantially parallel to axis X and can thus serve for aligning the telescopic means with the direction to the target. Said acquisition means is stowable and is depicted in solid lines in its operational condition and in dotted lines in its stowed position. It is especially useful for acquiring moving objects, such as a birds, or for watching sports events. It was found that a simple wire-frame means, rather than a more complex optically collimated sight-like means is preferable since its image is blurred and is easy to ignore. The inherent inaccuracy of this means is compatible with its function, since in effect, after a relatively short learning period the average user is capable of acquiring the target with no acquisition means at all. it was found that in viewing distant targets the absolute value of the tilt angle between the optical axes X and X' should be approximately 25°. The sign of this angle can be either positive or negative, whereas in this context a negative angle signifies that for a horizontal X axis the magmfied image appears below the horizon and the telescope mounted below the eye level, while a negative angle signifies that a magnified image appears above the horizon and the telescope mounted above the eye level. It was also found that in hand-held telescopes of the present invention a negative tilt angle is preferable whereas for head mounted and particularly for spectacle mounted telescopes the tilt angle should preferably be positive for the eyepiece to minimally interfere with the natural field of view. Fig. 2 depicts a side view of a hand-held binocular according to the invention. The internal optical layout of the telescope may be any layout except that the optical axes of the objective and eyepiece lenses which are conventionally parallel are now tilted with respect to each other. The external outline of the binocular should be convenient to fit in the hands (not shown), and comfortably rest against the user's cheek bones. Aiming mean 11 is preferably collapsible and is erected in front of the dominant eye only. Focusing knob 19 serves to individually bring into focus the image that is presented to each eye. Such knob is convenient as an alternative to conventional threaded eyepiece focus mechanism, especially where the eyepiece is not round, as later described and elaborated. When axis X" in Fig. 1 is aligned with the target, i.e., when the observer sees the natural view of the target through acquisition means 11, as a result of the above relationships between axes X, X', and X", the magnified image of the target appears substantially at the center of the magmfied field-of-view presented at the eyepiece. By shifting his gaze between axes X' and X" the observer is thus able to instantaneously switch between the natural and the magmfied images of the target and to acquire a target by merely gazing at it through acquisition means 11. A preferable spectacle mounting of the telescope of the invention is shown in Fig. 3. The telescope, preferably binocular, is mounted on the upper portion of the spectacle frame and includes means for individually adjusting its position relative to the eye and the interpupillary distance (not shown). The particular telescope in Fig. 3 is optimized for close object viewing and the tilt angle is approximately 40°. The magnified field of view 12 is defined by aiming device 11. The lower portion of the natural field-of-view is thus undisturbed, and the user can smoothly switch his attention from the natural to the magmfied image and back. As mentioned above, an opposite image rotation usually be induced in each of the individual images in telemagnifier applications which makes their fusion difficult and strains the observer's eyes. The reason of the image rotation was traced to the combined effect of the tilt angle of the eyepiece optical axes and the convergence angle of the objective optical axes. It occurs when the interpupillary distance of the two individual telescopes is adjusted by means of a mechanism based on an horizontal shaft as in conventional field glasses. The image rotation is not induced if the interpupillary distance is adjusted by means of a mechanism based on a vertical shaft. A proper corrective fixed image rotation in each of the telescopes was found to correct this problem. In prior art telescopic means such as hand-held binoculars the magnified target is acquired in the eyepiece field-of-view after aligning the telescopic means to the approximate direction of the target. To facilitate the acquisition, said field-of-view usually extends as much as possible, typically 50° to 70°. In the present invention target acquisition does not depend on the size of the field-of-view, which can therefore be made significantly smaller, typically 25° to 30°. It is well known to those skilled in the art that an eyepiece with a smaller field-of-view necessitates a smaller number of lens elements, and thus more compact lighter in weight and cheaper to manufacture. In addition, the smaller field-of-view enables longer eye-relief without increasing the size of the eyepiece lens as may be seen in Fig. 1 thus minimizing the natural vision obscuration. It was also found that if the field-of-view of the device of the invention is made rectangular similar to a TV screen, or more particularly, if the width to height ratio is approximately 1.7, the view is more realistic and aesthetically appealing than in prior art round field-of-view telescopic means. The fact that the telescopic means of the present invention does not obscure the natural view of the target is more fully utilized if it is constructed such that its contour, as seen by the observer, is minimized so as to be essentially unnoticed by the user while using his unaided vision. This can be achieved if the obscuration due to the eyepiece is contoured to substantially match the magmfied field-of-view. The obscuration is thus particularly small since the field-of-view is both relatively small and its contour is rectangular. To avoid obscuration due to other components of the device, said components should be contained within said eyepiece contour. In applications where the device is head-mounted, i.e., fixed relative to the eye, the motion of the eye in its socket while it scans the magmfied field-of-view, results in displacement of its pupil relative to the exit pupil of the device, this relative displacement cannot be compensated for by re-centering the eye with respect to the telescope, as in hand-held telescopic devices, and may result in obscuration (vignetting) particularly at the edges of the field-of-view. As is well known in telescopic devices, the exit pupil is a reduced image of the objective lens, and this effect may be particularly noticeable if the field-of-view is stretched horizontally (rectangular) while the objective lens is round. In a preferred embodiment of the invention this is remedied by increasing the horizontal dimension of the objective lens to assume a chamfered rectangular shape thereby increasing the horizontal extent of the exit pupil. The spectacle mounting shown in Fig. 3 is adaptable for either a binocular or a monocular telescopic means. A front view of the monocular version is shown in Fig. 4 where the right eye is aided by the device 1. Monocular operation has the advantage that one eye is completely unobscured and complements the portion of the natural field-of-view obscured by the eyepiece contour 16 of the telescopic device. This enables the user to ignore the monocular when no scene magnification is desired. The disadvantage of monocular operation is that when the user gazes downward at the magnified image, the unaided eye sees a different image that may be distracting by mentally being superimposed on the magnified image. It was found, however, that if the aided eye is the dominant one, it is fairly easy to ignore the second image. An optional, preferably detachable , occlusion may advantageously be placed in front of the unaided eye on pedestal 18, the angular coverage of this occlusion, depicted as dotted rectangle 17, substantially coincides with the eyepiece field-of-view, as seen by the other eye. A preferred optical layout for the spectacle mounted telescope is described in an Israeli patent application number 111427 filed October 27, 1994 by the same applicant herein, however any other layout could be used, such as the one described in U.S. patent number 4,488,790. A binocular operation has the advantage that the magmfied image is more comfortably viewed and is preferable in simations where the eyepiece obscuration of the surroundings is less objectionable. When intended as a stereoscopic magnifier for close objects viewing, a binocular structure is mandatory, and individual fields of view of the two telescopic means should converge at the plane of the object to be magmfied. Spectacle mounting of the telescopic means in front of a corrective glasses has the advantage that it does not have to correct for accommodation limitations of the eye since they are already corrected by the spectacle lenses. Thus, a telescopic means intended for distant viewing can be permanently focused at infinity and does not need a focusing mechanism, as in conventional telescopes and binoculars. This significantly simplifies the construction, and enables further weight reduction. Fig. 5 depicts a periscopic device 21 that can be added to a conventional telescope 22 in order to modify it according to the invention. The periscopic device includes two mirrors 23 and 24 and an optional target acquisition frame 11. A telescope design that is very suitable for the present invention is described in a copending Israeli patent application number 111427 filed October 27, 1994, by the same applicant herein , the description of which is incorporated herein by reference. A different target acquisition means is depicted in Fig. 6. As opposed to the first target acquisition means 11 in Fig. 1 the second target acquisition means does not rely on any mechanical addition external to the telescope. Instead, it is based on superimposing two lines 25 and 26 on the magnified image appearing at the eyepiece. The two lines converge at a virtual point 27 that is at the center of the unmagnified field of view i.e., defining the axis X" in Fig. 1, by superimposing point 27 on the unmagnified target the observer can align the telescopic means at the target direction and center its image in the magmfied field of view. The two lines as seen by the viewer are the infinity projected images of two lines engraved inside the field aperture at the image plane inside the telescopic device. All the above has been provided for the purpose of illustration. Many modifications can be carried out in the invention. For instance, any optical element can be substituted with an equivalent one, e.g., hollow prisms or mirrors by a solid prism, all without exceeding the scope of the invention.

Claims: WHAT IS CLAIMED IS: 1. A telescopic device adapted for bifocal vision, comprising: optical means for viewing a field-of-view; a housing for containing and supporting the optical means, said optical means comprising an objective lens located at one side of said housing with a first optical axis and an eyepiece lens located at the opposite side of said housing with a second optical axis; means for tilting said first optical axis with respect to said second optical axis to enable simultaneous view of the target and its magmfied image; and target acquisition means. 2. A device according to claim 1 wherein the above lenses include refractive and/or diffractive and/or refractive/diffractive lenses. 3. A device according to claim 1 wherein the first optical axis is tilted by an amount suitable for close objects viewing. 4. A device according to claim 1 wherein the first optical axis is tilted by an amount suitable for distant objects viewing. 5. A device according to any one of claims 3 and 4 wherein the means for tilting the light path comprise reflective and/or refractive and/or diffractive optical elements and wherein a magnified image appears above or below the natural unmagnified image. 6. A device adapted for close view according to any one of claims 1 to 5, wherein the first axis is tilted with respect to the second axis, by an angle of about 40°. 7. A device adapted for distant view according to any one of claims 1 to 5, wherein the first axis is tilted with respect to the second axis, by an angle of about 25°. 8. A device according to claim 2, wherein the field-of-view is rectangular. 9. A device according to claim 2, wherein the eyepiece contour is rectangular. 10. A device according to claims 1 to 9, comprising focusing means. 11. A device according to claims 1 to 10, comprising a fixed focus. 12. A device according to claim 1 comprising foldable or detachable frame type target acquisition means. 13. A device according to claim 1 comprising reticule type target acquisition means. 14. A device according to any one of claims 1 to 13, wherein the device is a monocular. 15. A monocular device according to claim 14, which is provided with an occlusion to the unaided eye. 16. A device according to any one of claims 1 to 13, wherein the device is a binocular. 17. A device according to claim 16, wherein the binocular includes an image rotation correction. 18. A device according to any one of claims 1 to 16, adapted for hand-held use. 19. A device according to any one of claims 1 to 17, which is mounted on a head support. 20. A device according to any one of claims 1 to 17 which is mounted on a spectacle frame.

Inventors: NETZER YISHAY, NETZER, YISHAY
Applicants: NETZER YISHAY, NETZER YOHAY, NETZER, YISHAY, NETZER, YOHAY
Application year: 1995
Main classification: G01C
IPC codes: G02B23, G02B27, G02C7