WO2002071144A1

WO2002071144A1 - A telephotographic device and application system

Info

Publication number: WO2002071144A1
Application number: PCT/US2002/001711
Authority: WO
Inventors: Uri Milman; Mark M. Friedman
Original assignee: Kaufmann, Yaakov
Priority date: 2001-03-02
Filing date: 2002-01-23
Publication date: 2002-09-12
Also published as: WO2002071144A9

Abstract

A wide field of view optical device comprising a first reflector (43) having reflective surfaces (42, 43) and a second retroflector (46) positioned relative to the first retroflector so that light (50) incident in an incident direction on the first retroflector is reflected by the first retroflector in a first reflected direction to the second retroflector and then is reflected by the second retroflector in a second reflected direction substantially parallel to the incident direction. The device further includes an objective lens assembly (62) positioned between the first and second reflective surfaces and an eyepiece lens assembly (64) adjacent the second reflective surface.

Description

A TELEPHOTOGRAPHIC DEVICE AND APPLICATION SYSTEM

FIELD AND BACKGROUND OF THE INVENTION

The present invention relates to an optical device for personal use and, more particularly, to a binocular-type optical device whose center of gravity is close to the face of the user.

Watanabe, in US Patent No. 6,157,483, which patent is incorporated by reference for all purposes as if fully set forth herein, describes a binocular with low magnification and a wide field of view. This prior art binocular relies on a system of four planar reflective surfaces in each of its monoculars to fold the optical path. The method used by Watanabe to fold the optical path is illustrated in Figures 1 and 2. In these Figures, a Cartesian coordinate system is used in which the +x direction is left relative to the user of the binocular, the +y direction is up relative to the user of the binocular and the +z direction is forward relative to the user of the binocular. Figure 1 is a schematic side view of the left monocular 10. Figure 2 is a schematic partial front view of left monocular 10. The right monocular is the mirror image of the left monocular.

Monocular 10 includes four reflective surfaces 12, 14, 16 and 18. Reflective surface 12 is parallel to the plane y=z. Reflective surface 14 is parallel to the plane x=y. Reflective surface 16 is parallel to the plane x=-y and so is orthogonal to reflective surface 14. Reflective surface 18 is parallel to the plane y=-z and so is orthogonal to reflective surface 12. Watanabe uses mirrors as reflective surfaces 12, 14, 16 and 18.

Lines 20, 22, 24, 26 and 28 represent optical paths and optical axes of monocular 10. The arrowheads on lines 20, 22, 24 and 26 represent directions of propagation. Light from an observed target enters monocular 10 along optical path 20 and is reflected by reflective surface 12 along optical path 22 to reflective surface 14, by reflective surface 14 along optical path 24 to reflective surface 16, by reflective surface 16 along optical path 26 to reflective surface 18 and by reflective surface 18 along optical path 28 to the left eye 30 of the user.

Also shown in Figure 1 are an objective lens assembly 32, that may include two or more lenses but that is represented as a single convex lens for illustrational clarity; and an eyepiece lens assembly 34, that also may include two or more lenses but that also is represented as a single convex lens for illustrational clarity. Objective lens assembly 32 focuses light from the target onto an image plane (not shown) between reflective surface 18 and eyepiece lens assembly 34. Eyepiece lens assembly 34 magnifies the image. Also for illustrational clarity, objective lens assembly 32 is shown in front of reflective surface 12. In the preferred embodiment of monocular 10, objective lens assembly 32 is between reflective surfaces 12 and 14; and, indeed, lenses of objective lens assembly 32 may also be between reflective surfaces 14 and 16 and/or between reflective surfaces 16 and 18. A binocular based on monoculars 10 shares with most other binoculars the problem that the user must hold the binocular in order to use it. Binoculars mounted on eyeglass-type frames, thereby freeing the user's hands for other tasks, also are known. Two prior art patents that are particularly notable in this regard, and that share a common inventor (Beecher) are US 3,985,421 and US 4,488,790, both of which are incorporated by reference for all purposes as if fully set forth herein. Beecher achieves compactness and light weight by using mirrors in a Porro prism configuration. Figures 3 and 4 are schematic illustrations of a right monocular 40 as taught by Beecher. Figure 3 is a schematic side view of monocular 40. Figure 4 is a schematic top view of monocular 40. The coordinate system is as in Figures 1 and 2. Monocular 40 includes four reflective surfaces (mirrors) 42, 44, 46 and 48.

Reflective surface 42 is parallel to the plane x=z. Reflective surface 44 is parallel to the plane x=-z and so is orthogonal to reflective surface 42. Reflective surface 46 is parallel to the plane y=-z. Reflective surface 48 is parallel to the plane y=z and so is orthogonal to reflective surface 46. Monocular 40 also includes an objective lens assembly 62 in front of reflective surface 42 and an eyepiece lens assembly 64 behind reflective surface 48. Lens assemblies 62 and 64 are represented as single convex lenses for illustrational clarity. Typically, however, each of lens assemblies 62 and 64 includes two or more lenses. Objective lens assembly 62 focuses light from an observed target onto an image plane (not shown). Eyepiece lens assembly 64 magnifies the image.

Lines 50, 52, 54, 56 and 58 represent optical paths and optical axes of monocular 40. The arrowheads on lines 50, 52, 54, 56 and 58 represent directions of propagation. Light from the target enters monocular 40 along optical path 50 and is reflected by reflective surface 42 along optical path 52 to reflective surface 44, by reflective surface 44 along optical path 54 to reflective surface 46, by reflective surface 46 along optical path 56 to reflective surface 48, and by reflective surface 48 along optical path 58 to the right eye 31 of the user. Note that optical path 54 is antiparallel to optical paths 50 and 58. Incident optical axis 50 of reflective surface 42 also is the optical axis of objective lens assembly 62. Reflected optical axis 58 of reflective surface 48 also is the optical axis of eyepiece lens assembly 64.

First reflective surfaces 42 and 44 constitute a first retroreflector. Second reflective surfaces 46 and 48 constitute a second retroreflector. Optical axis 50 is an incident optical axis of the first retroreflector. Optical axis 54 is both a reflected optical axis of the first retroreflector and an incident optical axis of the second retroreflector. Optical axis 58 is a reflected optical axis of the second retroreflector. Because reflective surfaces 42, 44, 46 and 48 are mirrors, light propagates within these retroreflectors via a rarefied medium (air). As described in US 4,488,790, a binocular that includes right monocular 40 of

Beecher and a matching left monocular is sufficiently light and compact to be mounted on an eyeglass-type frame. One problem with this prior art binocular-frame combination is the relatively low field of view of the binoculars, as compared with the wide-field-of-vie binocular of Watanabe. There is thus a widely recognized need for, and it would be highly advantageous to have, a wide-field-of-view binocular that is suitable for mounting on a support that holds the binocular close to the user's face, for example, eyeglass-type frames as in US 4,488,790, or diving-goggles-type frames.

SUMMARY OF THE INVENTION

According to the present invention there is provided an optical device including: (a) a first retroreflector; and (b) a second retroreflector positioned relative to the first retroreflector so that light incident in an incident direction on the first retroreflector is reflected by the first retroreflector in a first reflected direction to the second retroreflector and then is reflected by the second retroreflector in a second reflected direction substantially parallel to the incident direction; wherein the light propagates within one of the retroreflectors via a rarefied medium and within another of the retroreflectors at least partly via a condensed medium. According to the present invention there' is provided an optical device including: (a) a first reflective surface; (b) a second reflective surface substantially orthogonal to the first reflective surface, such that light incident on the first reflective surface in an incident direction along an incident optical path is reflected by the first reflective surface in a first reflected direction along a first reflected optical path and then is reflected by the second reflective surface in a second reflected direction, substantially antiparallel to the first reflected direction, along a second reflected optical path; (c) a third reflective surface, oriented so that at least a portion of the light that is reflected by the second reflective surface is further reflected in a third reflected direction, substantially orthogonal to a plane defined by the first and second reflected directions, along a third reflected optical path; (d) a fourth reflective surface substantially orthogonal to the third reflective surface, such that the at least portion of the light, that is reflected by the third reflective surface, then is reflected by the fourth reflective surface in a fourth reflected direction, substantially antiparallel to the second reflected direction, along a fourth optical path; and (e) a lens located between two of the reflective surfaces.

According to the present invention there is provided an apparatus for enabling a user to observe a target, including: (a) a rangefinder for measuring a range to the target; (b) an optical system wherethrough the user views the target; (c) a focusing mechanism for focusing the optical system on the target; and (d) a controller for operating the focusing mechanism in accordance with the measured range; wherein the focusing mechanism is alternately operable by the user and by the controller.

According to the present invention there is provided a method by which a user observes an observation target, including the steps of: (a) providing an apparatus including: (i) a rangefinder, (ii) an optical system, (iii) a focusing mechanism, and (iv) a controller; (b) calibrating the apparatus by steps including: for each of a plurality of calibration targets at different respective distances from the apparatus: (i) measuring a respective calibration range to the each calibration target, using the rangefinder, (ii) focusing the optical system on the each calibration target, by the user, using the focusing mechanism, thereby obtaining a respective calibration setting of the focusing mechanism, and (iii) storing the respective calibration range and the respective calibration setting in the controller; (c) measuring an observation range to the observation target, using the rangefinder; and (d) focusing the optical system on the observation target, by the controller, using the focusing mechanism in accordance with the observation range, the calibration ranges and the calibration settings.

According to the present invention there is provided an apparatus for photographing a target, by a user, including: (a) a camera, for photographing the target, including a first focusing mechanism for focusing the camera on the target; (b) an optical system including a second focusing mechanism wherewith the user focuses the optical system on the target; and (c) a controller operative to operate the first focusing mechanism to focus the camera on the target in accordance with a setting of the second focusing mechanism. According to the present invention there is provided a method of photographing a photographic target, by a user, including the steps of: (a) providing an apparatus including: (i) a camera including a first focusing mechanism, (ii) an optical system including a second focusing mechanism, and (iii) a controller; (b) calibrating the apparatus by steps including: for each of a plurality of calibration targets: (i) focusing the camera on the each calibration target, using the first focusing mechanism, thereby obtaining a respective calibration setting of the first focusing mechanism, (ii) focusing the optical system on the each calibration target, by the user, using the second focusing mechanism, thereby obtaining a respective calibration setting of the second focusing mechanism, and (iii) storing the respective calibration settings of the first and second focusing mechanisms in the controller; (c) focusing the optical system on the photographic target, by the user, thereby obtaining an operational setting of the second focusing mechanism; and (d) focusing the camera on the photographic target, by the controller, using the first focusing mechanism, in accordance with the calibration settings and the operational setting. According to the present invention there is provided an optical device for observing a target, including: (a) an objective lens assembly for creating an image of the target in a focal plane; (b) an eyepiece lens assembly for magnifying the image; and (c) a mechanism for inverting the image; wherein at least a portion of the objective lens assembly is laterally adjacent the eyepiece lens assembly. According to the present invention there is provided an optical device for observing a target, including: (a) an objective lens assembly for creating an image of the target in a focal plane; (b) an eyepiece lens assembly for magnifying the image; and (c) a mechanism for inverting the image; the objective lens assembly, the eyepiece lens assembly and the mechanism being arranged so that an axial coordinate of a center of gravity of the optical device is less than an axial coordinate of a center of volume of the optical device by at least one-quarter of an axial length of the optical device. The present invention includes three improvements of the monocular of

Beecher. As discussed below, the first two improvements are particularly effective in moving the center of gravity of a monocular of the present invention close to the user's face.

The first improvement is the replacement of one of the retroreflectors of monocular 40 with a retroreflector within which the light propagates at least partly via a condensed medium such as glass. The light propagates within the other retroreflector only via a rarefied medium such as air. Preferably, the retroreflector that is replaced in this manner is the first retroreflector, i.e., the retroreflector that is constituted by reflective surfaces 42 and 44, in order to move the center of gravity of monocular 40 closer to the user's face. Preferably, the light propagates within the replaced retroreflector only via the condensed medium.

The second improvement is the placement of one of the lenses, either of objective lens assembly 62 or of eyepiece lens assembly 64, between two of the reflective surfaces, to obtain a wider field of view in the manner of Watanabe. More generally, any element of objective lens assembly 62 or of eyepiece lens assembly 64, for example the stop of objective lens assembly 62, may be between two of the reflective surfaces. For example, an element of objective lens assembly 62, or a lens of eyepiece lens assembly 64, may be between the two retroreflectors, or may be between the two orthogonal mirrors of the rarefied medium retroreflector. The third improvement is the arrangement of objective lens assembly 62 and eyepiece lens assembly 64 so that at least a portion of objective lens assembly 62 is laterally adjacent eyepiece lens assembly 64, meaning that the z-coordinate of that portion of objective lens assembly 62 is less than the maximum z-coordinate of eyepiece lens assembly 64. This improvement also moves the center of gravity of monocular 40 closer to the user's face.

The figure of merit appropriate to the present invention is the product of the field of view (in degrees) and the magnification of the image obtained by eyepiece lens assembly 64. Preferably, this figure of merit is at least 68 degrees. The combination of the first and third improvements of the present invention produces a monocular whose center of gravity is closer to the user than the monocular's center of volume by at least one quarter of the total axial length (the length in the z-direction) of the monocular. In the present invention, the mutual relationship of the two retroreflectors is defined by two planes: a first plane that includes optical axes 50 and 54 and a second plane that includes optical axes 54 and 58. Specifically, these two planes are mutually orthogonal.

Preferably the retroreflectors of the present invention each have two mutually orthogonal reflective surfaces, as illustrated, although the scope of the present invention also includes retroreflectors such as cube corner prisms that have three mutually orthogonal reflective surfaces.

Preferably, reflective surfaces 42, 44, 46 and 48 all are flat, as in prior art monoculars 10 and 40, although the scope of the present invention also includes the use of curved surfaces 42, 44, 46 and/or 48 to provide magnification instead of or supplemental to the magnification provided by objective lens assembly 62 and eyepiece lens assembly 64.

Preferably, a monocular of the present invention includes a focusing mechanism for focusing eyepiece lens assembly 64 on the focal plane, preferably by varying a distance between objective lens assembly 62 and eyepiece lens assembly 64 as measured along the relevant optical paths 50, 52, 54, 56 and/or 58.

Preferably, an optical device of the present invention includes a rangefinder operationally connected to the focusing mechanism, a camera operationally connected to the focusing mechanism and a transmitter for transmitting images acquired by the camera.

Two monoculars of the present invention constitute a binocular. Preferably, the monoculars are mounted on a frame that is adapted to be worn by the user, using a mount that allows the monoculars to be moved between a first position, in which the monoculars are held in front of the user's eyes so that light reflected by reflective surfaces 48 enters respective eyes of the user, and a second position, in which the monoculars are held away from the user's eyes, allowing normal vision.

The scope of the present invention also includes the use of a monocular of the present invention as a finderscope of a larger telescope. A monocular of the present invention can be configured for observing distant targets, for observing targets at intermediate distances, or for magnifying nearby targets.

The scope of the present invention also includes an apparatus for enabling a user to observe an observation target, and a method of using that apparatus. The apparatus includes a rangefinder, an optical system with a focusing mechanism (preferably but not necessarily a binocular of the present invention) and a controller. Preferably, the operational axis of the rangefinder and the optical axis of the optical system are parallel. The focusing mechanism is adapted to be operated alternately by the user, and by the controller in accordance with the range to the target that is measured by the rangefinder.

The apparatus is calibrated, using a plurality of calibration targets at different respective distances, in three steps. In the first step, the rangefinder measures respective calibration ranges to each of the calibration targets. In the second step, the user focuses the optical system successively on each of the calibration targets to obtain respective calibration settings of the focusing mechanism. In the third step, the calibration ranges and the calibration settings are stored in the controller. Subsequent to calibration, the user observes an observation target by measuring the range to the observation target using the rangefinder and by allowing the controller to focus the optical system on the observation target based on the measured range to the observation target and on the calibration parameters. Because the operational axis of the rangefinder is parallel to the optical axis of the optical system, the rangefinder is pointed at the observation target whenever the optical system is pointed at the observation target. This frees the user's hands for activities other than focusing the optical system.

The scope of the present invention also includes an apparatus for photographing a photographic target, and a method of using that apparatus. The apparatus includes a camera with a focusing mechanism, an optical system with a focusing mechanism (preferably a binocular of the present invention) and a controller that operates the focusing mechanism of the camera in accordance with the setting of the focusing mechanism of the optical system. Preferably, the camera and the optical system have parallel optical axes. The apparatus is calibrated, using a plurality of calibration targets at different respective distances, in three steps. In the first step, the camera is focused successively on each of the calibration targets to obtain respective calibration settings of the camera's focusing mechanism. In the second step, the user focuses the optical system successively on each of the calibration targets to obtain respective calibration settings of the optical system's focusing mechanism. In the third step, the calibrations settings are stored in the controller. Subsequent to calibration, the user photographs a photographic target by aiming both the camera and the optical system at the photographic target, focusing the optical system at the photographic target using the optical system's focusing mechanism, and using the controller to focus the camera on the photographic target in accordance with the current setting of the optical system's focusing mechanism. This method is useful in situations in which the camera's focusing mechanism, if left to its own devices, would not focus on the photographic target, for example if the camera's default focusing mechanism is based on the travel time of an ultrasound pulse and there is a transparent acoustic reflector such as a windowpane between the camera and the photographic target.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is herein described, by way of example only, with reference to the accompanying drawings, wherein:

FIGs. 1 and 2 are schematic depictions of the prior art monocular of Watanabe;

FIGs. 3 and 4 are schematic depictions of the prior art monocular of Beecher;

FIGs. 5, 6 A and 6B are schematic depictions, corresponding to FIG. 4, of three monoculars of the present invention;

FIG. 7 is an external perspective view of the monocular of FIG. 6;

FIG. 8 shows a binocular of the present invention;

FIGs. 9A, 9B and 9C show alternate configurations of the retroreflector housings of the monocular of FIGs. 3-5; FIG. 10 shows a Nagler-type eyepiece adapted for use with the present invention;

FIG. 11 is a schematic depiction, corresponding to FIG. 3, of a fourth monocular of the present invention; FIG. 12 is a partly schematic block diagram of a digital camera and a transceiver adapted for use with the present invention;

FIG. 13 illustrates the procedure for calibrating the focusing mechanisms of FIGs. 5 and 12; FIG. 14 illustrates autofocusing according to the present invention using a

Galilean periscope monocular;

FIGs. 15 and 16 illustrate two Galilean periscope monoculars that may be substituted for the monocular of FIG. 14;

FIG. 17 illustrates a system of the present invention that combines most of the features of FIGs. 5 and 12.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is of a wide field of view optical device which can be worn comfortably as a binocular. Specifically, the present invention can be used to observe a distant target while freeing the user's hands for other tasks.

The principles and operation of an optical device according to the present invention may be better understood with reference to the drawings and the accompanying description.

Referring again to the drawings, Figure 5 is a schematic top view of a monocular 40a of the present invention. Monocular 40 a is similar to prior art monocular 40, but the center of gravity of monocular 40a is closer to the user's face than the center of gravity of monocular 40, and the field of view of monocular 40a is wider than the field of view of monocular 40, by virtue of monocular 40a having objective lens assembly 62 between reflective surfaces 42 and 44. In monocular 40a, reflective surfaces 42 and 44 are mirrors, and the medium of propagation in the retroreflector constituted by reflective surfaces 42 and 44 is air. Also shown schematically in Figure 5 is a focusing mechanism 140 for moving objective lens assembly 62 along optical path 52 to vary the distance, along optical paths 52, 54, 56 and 58, between objective lens assembly 62 and eyepiece lens assembly 64 in order to focus monocular 40a. The operation of focusing mechanism 140 is discussed in detail below.

Figure 6A is a schematic top view of another monocular 40b of the present invention. Like monocular 40a, monocular 40b is similar to prior art monocular 40, but the center of gravity of monocular 40b is closer to the user's face than the center of gravity of monocular 40, by virtue of reflective surfaces 42 and 44 being reflective surfaces of a glass prism 43, rather than mirrors. As in monocular 40, reflective surfaces 46 and 48 are mirrors, and the medium of propagation between reflective surfaces 46 and 48 is air.

Figure 6B is a schematic top view of a variant 40c of monocular 40b. In monocular 40c, prism 43 is split into two prisms 43a and 43b, with reflective surface 42 being a reflective surface of prism 43 a and reflective surface 44 being a reflective surface of prism 42b; and one or more of the lenses of objective lens assembly 62, represented schematically in Figure 6B by a convex lens 62b, are placed between prisms 43a and 43b. The remaining lens or lenses of objective lens assembly 62, represented schematically in Figure 6B by a convex lens 62 a, remain on the +z side of prism 43a. Transferring part of objective lens assembly 62 from optical path 50 to optical path 52 in this manner moves the center of gravity of monocular 40c even closer to the user's face than the center of gravity of monocular 40.

Figure 7 is an external perspective view of monocular 40b. The optical • components of monocular 40b are housed in an objective housing 70 in which is mounted objective lens assembly 62, a distal retroreflector housing 72 in which is mounted prism 43, a proximal retroreflector housing 74 in which are mounted reflective surfaces 46 and 48, and an eyepiece housing 76 in which is mounted eyepiece lens assembly 64 of Figure 6A. In the present context, "proximal" and "distal" are with respect to eye 30 along optical paths 58, 56, 54, 52 and 50. Reflective surfaces 42, 44, 46 and 48 are shown in phantom in Figure 7. Also shown in Figure 7, mounted atop distal retroreflector housing 72, is a digital camera 90 whose operation is discussed below. The optical axis 92 of camera 90 is parallel to optical axis 50 of objective lens system 62.

Focusing mechanism 140 of monocular 40a also is used in monocular 40b, to focus monocular 40b by varying the distance of objective lens assembly 62 along optical path 50 rather than along optical path 52. Figure 8 shows a binocular 100 of the present invention, including monocular

40b as a left monocular, and a corresponding right monocular 40b', both mounted on an eyeglasses-type frame 102. The portion of frame 102 that is hidden by monoculars 40 and 40' is shown in phantom. As in Figure 7, left monocular 40b includes objective housing 70, distal retroreflector housing 72, proximal retroreflector housing 74 and an eyepiece housing (not shown). Right monocular 40b' is a mirror image of left monocular 40b, and includes an objective housing 70', a distal retroreflector housing 72', a proximal retroreflector housing 74' and an eyepiece housing (not shown). Note that only left monocular 40b includes a camera (camera 90). Frame 102 includes a nose bridge 104, earpieces 106 and 106' and two vertical tracks 108 and 108' upon which monoculars 40b and 40b' actually are mounted and along which monoculars 40b and 40b' slide. A groove 78 in distal retroreflector housing 72 and a groove 80 in eyepiece housing 76 (Figure 7) accommodate track 108, and similar grooves in distal retroreflector 72' and in the eyepiece housing of monocular 40b' accommodate track 108'. For enhanced mechanical stability, monoculars 40b and 40b' are rigidly com ected by two braces 110. Conventional mechanisms (not shown) secure monoculars 40b and 40b' to tracks 108 and 108' and reversibly lock monoculars 40b and 40b' alternately in one of two positions, the active position shown, with the eyepiece lens assemblies of monoculars 40b and 40b' in front of the user's eyes, and an inactive position shown in phantom, with monoculars 40b and 40b' raised out of the user's field of vision.

The mutual orientation of the distal and proximal retroreflector housings shown in Figure 8, with the distal retroreflector housings shifted above and laterally outward from the proximal retroreflector housings, is only illustrative. Other possible configurations are illustrated in Figures 9A, 9B and 9C. In addition, the housings themselves may be at other angles, for example 45 degrees, relative to each other, as long as the retroreflectors are mutually perpendicular to invert the image.

Enhanced compactness and a still wider field of view can be attained by using a Nagler-type eyepiece. Background on Nagler-type eyepieces can be found in Nagler, US Patents No. 4,286,844, 4,525,935 and 4,747,675. That the lenses of a Nagler-type eyepiece are spaced apart allows the insertion of reflective surface 48 amidst these lenses. Figure 10 shows a Nagler-type eyepiece 120 with seven lenses 122, 124, 126, 128, 130, 132 and 134, and with reflective surface 48 between lenses 130 and 132. Obviously, in a variant of monocular 40a or 40b that uses eyepiece 120, only lenses 132 and 134 are mounted in eyepiece housing 76; lenses 122, 124, 126, 128 and 130 are mounted in proximal retroreflector housing 74, between reflective surfaces 46 and 48. Figure 11 is a partial schematic side view of a fourth monocular 40d of the present invention. Monocular 40d includes a distal retroreflector housing 272, a proximal retroreflector housing 274 and an eyepiece housing 276. Within distal retroreflector housing 272 is mounted a glass prism 243 that is similar to prism 43 of monocular 40b, so that two of the surfaces of prism 243 are reflective surfaces 42 and 44. Reflective surfaces 46 and 48 are mounted within proximal retroreflector housing 274, as mirrors. A lens 262 of objective lens assembly 62 also is mounted in distal retroreflector housing 272, optically between reflective surfaces 44 and 46. Within eyepiece housing 276 are mounted six lenses 222, 224, 226, 228, 230 and 232 that constitute the eyepiece lens assembly of monocular 40d.

Figure 11 serves to illustrate geometric aspects of the present invention. The coordinate system in Figure 11 is chosen so that the axial (z) coordinate of the left end of monocular 40d, i.e., the end of monocular 40d closest to the user, is z=0. The total axial length of monocular 40d is L. The center of volume of monocular 40d, i.e., the geometric point whose coordinates are obtained by performing an unweighted average of the volume occupied by monocular 40d, is shown at 210. The center of gravity of monocular 40d, i.e. the geometric point whose coordinates are obtained by performing a density- weighted average of the volume occupied by monocular 40d, is shown at 212. The first geometric aspect of the present invention that is illustrated in Figure 11 is that objective lens 262 is laterally adjacent the eyepiece lens assembly, in the sense that the smallest z-coordinate of objective lens 262 is less than the largest z-coordinate of rightmost eyepiece lens 232. The second geometric aspect of the present invention that is illustrated in Figure 11 is that because of the high density of the components of distal retroreflector housing 272 and eyepiece housing 274 relative to the components of proximal retroreflector housing 274, the z-coordinate of point 212 is less than the z-coordinate of point 210 by at least X/4.

As in US 3,985,421, monoculars 40a, 40b, 40c and 40d preferably are constructed of lightweight materials. For example, housings 70, 72, 74 and 76 preferably are made of a lightweight metal such as magnesium or of plastic; and the mirrors whose reflective surfaces are reflective surfaces 46 and 48 (and reflective surfaces 42 and 44 of monocular 40a) preferably are made of plastic or of glass-laminated magnesium. Although the description herein is directed primarily towards monoculars and binoculars for viewing distant targets (ranges from two meters to infinity), it will be appreciated that the principles of the present invention are equally applicable to monoculars and binoculars intended for viewing targets at intermediate distances (ranges from thirty centimeters to thirty meters), as well as to monoculars and binoculars intended for magnification of close-up objects (ranges up to four meters), for example as taught by Malis in US Patent No. 4,196,966 in the context of surgery. Other applications of such monoculars and binoculars include the inspection of gemstones and the inspection of electronic components mounted on printed circuit boards. The use of a monocular of the present invention to magnify a nearby target requires that the optical path between objective lens assembly 62 and eyepiece lens assembly 64 be longer than when a monocular of the present invention is used to observe a distant target; so that the third improvement of the present invention, i.e., the arrangement of objective lens assembly 62 and eyepiece lens assembly 64 so that a portion of objective lens assembly 62 is laterally adjacent eyepiece lens assembly 64, often is not feasible in a monocular of the present invention intended for magnification of nearby targets.

Figure 12 is a partial schematic block diagram of digital camera 90, in operative association with a radio frequency transceiver 182, such as a cellular telephone, a partial schematic block diagram of which also is included in Figure 12. The optical system of camera 90 includes a lens system 162 and a suitable sensor array 164, for example a CCD array or a CMOS array, on which lens system 162 focuses an image of a photographic target. Optical axis 92 is the optical axis of lens system 162. Camera 90 also includes a focusing mechanism 172 that in turn includes a rangefinder 160 for measuring a range to the photographic target, a sensor 168 for sensing the position of lens system 162 along optical axis 92, a motor 170 for moving lens system 1 2 back and forth along optical axis 92, and controller 146 for operating motor 170, in accordance with the range measured by rangefinder 160 and the position sensed by sensor 168 to focus the image of the photographic target on sensor array 164. Note that controller 146 is the same as controller 146 of Figure 5: controller 146 serves as the controller of both focusing mechanism 140 of monocular 40 (or 40a) and focusing mechanism 172 of camera 90. Rangefinder 166 has an operational axis 166, parallel to optical axis 92, along which rangefinder 166 sends a pulse of wave energy, for example an ultrasound pulse or an infrared pulse, towards the target. The range to the target is determined from the round trip travel time to the target, i.e., the time between the transmission of the pulse and the receipt of a reflected pulse from the target. Controller 146 is based on a microprocessor and also includes a non- volatile memory, such as a flash memory, for storing adjustable operating parameters even when power to controller 146 is turned off, as described below.

Other forms of rangefinders are known that are software-based rather than hardware-based. In a digital camera equipped with such a rangefinder, the rangefinder determines the optimal focusing position of the lens by performing image processing on the images acquired by sensor array 164. Such software-based rangefinders are included in the scope of the term "rangefinder" as used herein. The "operational axis" of a software-based rangefinder is the optical axis of the camera's optical system. Transceiver 182 operates under the control of its own microprocessor-based controller 190. A socket 184 in camera 90 accommodates a jack 186 that allows analog signals from sensor array 164 to be sent to an A/D converter 188 in transceiver 182. A/D converter 188 digitizes these analog signals under the control of controller 190. Controller 190 stores the digitized signals, that constitute a digital representation of the image focused by lens system 162 onto sensor array 164, in a memory 192. As taught by Hull et al. in US Patent No. 5,806,005, the images of photographic targets that are acquired using camera 90 and stored in memory 192 may be transmitted to a remote location, for which purpose transceiver 182 includes a radio frequency transmitter 194 and an antenna 196. Returning briefly to Figure 5, automatic focusing mechanism 140 includes, in addition to controller 146, a sensor 142 for sensing the position of objective lens assembly 62 along optical path 50 (in monocular 40b) or along optical path 52 (in monocular 40a) and motor 144 for moving objective lens assembly 62 back and forth along optical path 50 (in monocular 40b) or along optical path 52 (in monocular 40a). Controller 146 receives signals from sensor 142 that indicate the position of objective lens assembly and sends operating signals to motor 144. Monoculars 40a and 40b also are provided with a manual override mechanism 145 that allows the user to use motor 144 to move objective lens assembly 62 to focus monocular 40a or 40b manually.

In binocular 100, monocular 40b' is provided with its own sensor, similar to sensor 142, and its own motor, similar to motor 144, that also are coupled to controller 146. Monocular 40b' also is provided with its own manual override mechanism to allow manual focusing of monocular 40b'.

That controller 146 is shared by both focusing mechanisms 140 and 172 allows monocular 40a, monocular 40b or binocular 100 to be used in an autofocusing mode in which the user never has to manipulate the manual focusing mechanism. For this purpose, the manual focusing mechanism must be calibrated relative to automatic focusing mechanisms 140 and 172, as illustrated in Figure 13. In Figure 13, monocular 40b is represented by objective lens assembly 62 and by reflective surface 42; and camera 90 is represented by lens system 162 and sensor array 164. Note that optical axis 50 of objective lens assembly 62, optical axis 92 of lens system 162 and operational axis 166 of rangefinder 160 all are parallel, so that aiming monocular 40b at a target also aims camera 90 at the target, and vice versa. Also shown in Figure 13 are five calibration targets 180 at five different respective distances from monocular 40b and camera 90. A set of exemplary respective distances for targets 180 is 20 meters for target 180D, 50 meters for target 180C, 100 meters for target 180B, 500 meters for target 180 A and infinity (e.g., an astronomical object such as the Moon) for target 180∞. Objective lens assembly 62 and lens system 162 are shown at respective distances from reflective surface 42 and sensor array 164, respectively, at which objective lens assembly 62 and lens system 162 are focused on target 180D. Corresponding positions of objective lens assembly 62 and lens system 162, at which objective lens assembly 62 and lens system 162 are focused on the other targets 180, are shown in phantom.

To calibrate monocular 40b and camera 90 together, the user aims monocular 40b and camera 90 together at each target 180 in succession, focuses monocular 40b manually on the target 180, and allows controller 146 to focus camera 90 on the target 180 using the range measured by rangefinder 160. As each target is brought into focus both manually (using manual override 145) and automatically (using automatic focusing mechanism 172), controller 146 records a corresponding calibration table entry that includes the range measured by rangefinder 160, the setting of objective lens assembly 62 as measured using sensor 142, and the setting of lens system 162 as measured using sensor 168. Subsequently, whenever the user aims monocular 40b and camera 90 at an observation target, controller 146 measures a range to the observation target using rangefinder 160, interpolates a corresponding setting of objective lens assembly 62 in the calibration table, and uses motor 144 to move objective lens assembly 62 to this interpolated setting. The result is that monocular 40b is focused automatically on the observation target.

The calibration for this autofocusing mode also allows the combination of monocular 40b and camera 90 to be used for photography, in a manual focusing mode, in situations in which rangefinder 160 would give an incorrect range to a photographic target. For example, suppose that rangefinder 160 works by measuring the round trip travel time of an ultrasonic pulse, and that a barrier, such as a plate glass window, that is acoustically opaque and optically transparent, intervenes between camera 90 and the photographic target. The user aims monocular 40b and camera 90 at the photographic target, and focuses monocular 40b manually on the photographic target. Controller 146 reads the setting of objective lens assembly 62 using sensor 142, interpolates a corresponding setting of lens system 162 in the calibration table, and uses motor 170 to move lens system 162 to this interpolated setting. The result is that camera 90 is focused on the photographic target despite the presence of the barrier.

Another application of rangefinder 160 is in conjunction with an embodiment of binocular 100 that includes a track motor for raising and lowering monoculars 40b and 40b' along tracks 108 and 108'. Controller 146 is provided with a threshold range. When the range measured by rangefinder 160 exceeds the threshold range, controller 146 operates the track motor to lower monoculars 40b and 40b' in front of the user's eyes to enable the user to view a distant target. When the range measured by rangefinder 160 is less than the threshold range, controller 146 operates the track motor to raise monoculars 40b and 40b' away from the user's eyes to enable the user to view nearby objects with normal vision. As noted above, the aspects of the present invention that relate to automatic focusing are applicable to any suitable optical device, not just to the optical device of the present invention. Figure 14 shows an alternative optical device configured to implement these aspects of the present invention. Specifically, the optical device of Figure 14 is a binocular 101 based on two Galilean periscope monoculars. Insofar as is possible, the reference numerals in Figure 14 refer to the same components as in previous Figures. Note that rangefinder 160 is external to camera 90. The monocular shown in Figure 14 is the right monocular, that includes an objective lens housing 71 within which is mounted a convex objective lens (not shown), two periscope mirrors Ml and M2, and a concave eyepiece lens 65. Controller 146 focuses this Galilean periscope monocular as described above, by sliding objective lens housing 71 back and forth to change the optical path length between the objective lens and eyepiece lens 65. Figures 15 and 16 illustrate other configurations of a Galilean periscope monocular that may be used in monocular 101 instead of the configuration illustrated in Figure 14.

Figure 15 illustrates a Galilean periscope monocular that provides magnification of distant targets viewed through a narrow field of view. The optical system of the monocular of Figure 15 includes two right-angle prisms 328 and 329 constructed together with curved, fixed lenses, specifically, convex objective lens 330 and concave eyepiece lens 332. Optionally, objective lens 330 and eyepiece lens 332 are permanently affixed with transparent optical adhesive applied to contact surfaces SI and S4 of supporting materials 334 and 336, respectively, for each add-on lens. Supporting materials 334 and 336 are made of any optically suitable material, such as high quality plastic, matched to the refractive index of the adjoining prism 328 or 329 to which they are fitted.

The larger prism 328 captures and reflects light from a distant target 338. The light from target 338 follows a ray path 340 that passes through convex objective lens 330. Lens 330 is attached to or molded together as one piece with prism 328 at contact surface SI. Ray path 340 is reflected from the inner mirror surface A of prism 328. Surface A redirects ray path 340 so that ray path 340 exits prism 328 through face S2, traverses a distance D between prisms 328 and 329, and enters prism 329 at face S3. The light propagating along ray path 340 then is reflected from inner mirror face B in small prism 329 and is redirected at a 90 degree angle from inner mirror face B so that ray path 340 passes through face S4 and eyepiece lens 332 and then enters the user's eye 342. Thus, eye 342 sees a magnified image of target 338. Focal adjustments of the magnified object image are preformed by changing the distance D between prisms 328 and 329. A magnification of between 3X and 3 OX is achieved, with respective fields of view between 14 degrees and a fraction of a degree. Both surfaces S2 and S3 can be flat as illustrated, spherical, or aspherical for the purpose of correcting optical aberrations. In general, surfaces SI through S4 of prisms 328 and 329 can be of any type, for example, aspherical, spherical, conical or the like. Furthermore, a filter or polarizer can be placed between surfaces S2 and S3 to prevent unwanted radiation from entering eye 342.

Figure 16 illustrates another Galilean periscope monocular in which an optical element 344 includes rhomboids formed form one piece of transparent material to operate as a single, fixed focus optical system in conjunction with movable objective 330 and eyepiece 332 lenses which provide for focal adjustment over distance D which varies the overall distance of the path of ray 340 between objective lens 330 and eyepiece lens 332. Focusing is accomplished by moving either objective lens 330 or eyepiece lens 332 in the focal plane of the composite prism constituted by optical element 344 so that eye 342 receives a focused magnified image of target 338.

Figure 17 is a schematic block diagram of a system 200 of the present invention that includes monocular 40a, camera 90 and transceiver 182, but without the autofocus feature described above. Instead of the electromechanical components discussed above, such as rangefinder 160 and controller 146, for focusing monocular 40a and camera 90, system 200 includes a purely mechanical, manual focusing mechanism 147 that slaves camera 90 to monocular 40a. In essence, monocular 40a is used as a viewfinder for camera 90. The user of system 200 uses manual focusing mechanism 147 to move objective lens assembly 62 along optical path 52, and/or eyepiece lens assembly 64 along optical path 56, until a distant target is perceived to be in focus. Simultaneously, manual focusing mechanism 147 moves lens system 162 to focus an image of the target onto sensor array 164. As described above, transceiver 182 stores the image acquired by camera 90 in memory 192 and/or transmits the image acquired by camera 90 to a remote location using transmitter 194 and antenna 196.

While the invention has been described with respect to a limited number of embodiments, it will be appreciated that many variations, modifications and other applications of the invention may be made.

Claims

WHAT IS CLAIMED IS:

1. An optical device comprising:

(a) a first retroreflector; and

(b) a second retroreflector positioned relative to said first retroreflector so that light incident in an incident direction on said first retroreflector is reflected by said first retroreflector in a first reflected direction to said second retroreflector and then is reflected by said second retroreflector in a second reflected direction substantially parallel to said incident direction; wherein said light propagates within one of said retroreflectors via a rarefied medium and within another of said retroreflectors at least partly via a condensed medium.

2. The optical device of claim 1, wherein said rarefied medium is air.

3. The optical device of claim 1, wherein said retroreflector, wherein said light propagates via said rarefied medium, includes two orthogonal mirrors.

4. The optical device of claim 1, wherein said light propagates within said other retroreflector only via said condensed medium.

5. The optical device of claim 1, wherein said condensed medium includes glass.

6. The optical device of claim 1, wherein said retroreflector, wherein said light propagates at least partly via said condensed medium, is said first retroreflector.

7. The optical device of claim 1, wherein said first reflected direction is substantially antiparallel to both said incident direction and said second reflected direction.

8. The optical device of claim 1 : wherein said first retroreflector has an incident optical axis parallel to said incident direction and a reflection optical axis antiparallel to said incident direction, said incident optical axis of said first retroreflector and said reflection optical axis of said first retroreflector defining a first plane; wherein said second retroreflector has an incident optical axis parallel to said first reflected direction and a reflection optical axis antiparallel to said first reflected direction, said incident optical axis of said second retroreflector and said reflection optical axis of said second retroreflector defining a second plane; and wherein said first and second planes are substantially mutually orthogonal.

9. The optical device of claim 1, wherein at least a portion of said light is from a target, the device further comprising:

(c) an objective lens assembly for creating an image of said target in a focal plane.

10. The optical device of claim 9, wherein one of said at least one retroreflector, wherein said light propagates via said rarefied medium, includes two orthogonal mirrors; and wherein at least one element of said objective lens assembly is between said two orthogonal mirrors.

11. The optical device of claim 9, wherein at least one element of said objective lens assembly is between said two retroreflectors.

12. The optical device of claim 11 , further comprising:

(d) an eyepiece lens assembly for magnifying said image.

13. The optical device of claim 12, wherein one of said at least one retroreflector, wherein said light propagates via said rarefied medium, includes two orthogonal mirrors; and wherein said eyepiece lens assembly includes at least one lens between said two orthogonal mirrors.

14. The optical device of claim 12, further comprising: (e) a focusing mechanism for focusing said eyepiece lens assembly on said image.

15. The optical device of claim 14, wherein said focusing mechanism is operative to vary a distance along said optical paths between said objective lens assembly and said eyepiece lens assembly.

16. The optical device of claim 14, further comprising:

(f) a rangefinder operationally connected to said focusing mechanism.

17. The optical device of claim 14, further comprising:

(f) a camera operationally connected to said focusing mechanism.

18. The optical device of claim 17, further comprising:

(g) a transmitter for transmitting images acquired using said camera.

19. The optical device of claim 12, wherein said eyepiece lens assembly is substantially adjacent said first retroreflector.

20. The optical device of claim 1, further comprising:

(c) a frame, adapted to be worn by a user of the optical device; and

(d) a mount, for mounting said retroreflectors on said frame in at least one position relative to said frame, one of said at least one position being such that light, that is reflected by said second retroreflector, enters an eye of said user.

21. The optical device of claim 1, wherein one of said retroreflectors includes a curved reflective surface.

22. The optical device of claim 1, having a magnification-field-of-view product of at least about 68 degrees.

23. A finderscope comprising the optical device of claim 1.

24. A binocular comprising two optical devices of claim 1.

25. The optical device of claim 1, configured for the observation of a distant target.

26. The optical device of claim 1, configured for the magnification of a nearby target.

27. The optical device of claim 1, configured for the observation of a target at an intermediate distance.

28. An optical device comprising:

(a) a first reflective surface;

(b) a second reflective surface substantially orthogonal to said first reflective surface, such that light incident on said first reflective surface in an incident direction along an incident optical path is reflected by said first reflective surface in a first reflected direction along a first reflected optical path and then is reflected by said second reflective surface in a second reflected direction, substantially antiparallel to said first reflected direction, along a second reflected optical path;

(c) a third reflective surface, oriented so that at least a portion of said light that is reflected by said second reflective surface is further reflected in a third reflected direction, substantially orthogonal to a plane defined by said first and second reflected directions, along a third reflected optical path;

(d) a fourth reflective surface substantially orthogonal to said third reflective surface, such that said at least portion of said light, that is reflected by said third reflective surface, then is reflected by said fourth reflective surface in a fourth reflected direction, substantially antiparallel to said second reflected direction, along a fourth optical path; and (e) a lens located between two of said reflective surfaces.

29. The optical device of claim 28, wherein at least one of said reflective surfaces is curved.

30. The optical device of claim 28, wherein said lens is an element of an objective lens assembly.

31. The optical device of claim 28, wherein said lens is an element of an eyepiece lens assembly.

32. An apparatus for enabling a user to observe a target, comprising:

(a) a rangefinder for measuring a range to the target;

(b) an optical system wherethrough the user views the target;

(c) a focusing mechanism for focusing said optical system on the target; and

(d) a controller for operating said focusing mechanism in accordance with said measured range; wherein said focusing mechanism is alternately operable by the user and by said controller.

33. The apparatus of claim 32, wherein an operational axis of said rangefinder is parallel to an optical axis of said optical system.

34. A method by which a user observes an observation target, comprising the steps of:

(a) providing an apparatus including: (i) a rangefinder,

(ii) an optical system,

(iii) a focusing mechanism, and

(iv) a controller;

(b) calibrating said apparatus by steps including: for each of a plurality of calibration targets at different respective distances from the apparatus: (i) measuring a respective calibration range to said each calibration target, using said rangefinder, (ii) focusing said optical system on said each calibration target, by the user, using said focusing mechanism, thereby obtaining a respective calibration setting of said focusing mechanism, and (iii) storing said respective calibration range and said respective calibration setting in said controller;

(c) measuring an observation range to the observation target, using said rangefinder; and

(d) focusing said optical system on the observation target, by said controller, using said focusing mechanism in accordance with said observation range, said calibration ranges and said calibration settings.

35. An apparatus for photographing a target, by a user, comprising:

(a) a camera, for photographing the target, including a first focusing mechanism for focusing said camera on the target;

(b) an optical system including a second focusing mechanism wherewith the user focuses said optical system on the target; and

(c) a controller operative to operate said first focusing mechanism to focus said camera on the target in accordance with a setting of said second focusing mechanism.

36. The apparatus of claim 35, wherein said camera and said optical system have parallel optical axes.

37. A method of photographing a photographic target, by a user, comprising the steps of:

(a) providing an apparatus including:

(i) a camera including a first focusing mechanism,

(ii) an optical system including a second focusing mechanism, and

(iii) a controller;

(b) calibrating said apparatus by steps including: for each of a plurality of calibration targets: (i) focusing said camera on said each calibration target, using said first focusing mechanism, thereby obtaining a respective calibration setting of said first focusing mechanism,

(ii) focusing said optical system on said each calibration target, by the user, using said second focusing mechanism, thereby obtaining a respective calibration setting of said second focusing mechanism, and

(iii) storing said respective calibration settings of said first and second focusing mechanisms in said controller;

(c) focusing said optical system on the photographic target, by the user, thereby obtaining an operational setting of said second focusing mechanism; and

(d) focusing said camera on the photographic target, by said controller, using said first focusing mechanism, in accordance with said calibration settings and said operational setting.

38. An optical device for observing a target, comprising:

(a) an objective lens assembly for creating an image of the target in a focal plane;

(b) an eyepiece lens assembly for magnifying said image; and

(c) a mechanism for inverting said image; wherein at least a portion of said objective lens assembly is laterally adjacent said eyepiece lens assembly.

39. The optical device of claim 38, having a magnification-field-of-view product of at least about 68 degrees.

40. An optical device for observing a target, comprising:

(b) an eyepiece lens assembly for magnifying said image; and

(c) a mechanism for inverting said image; said objective lens assembly, said eyepiece lens assembly and said mechanism being arranged so that an axial coordinate of a center of gravity of the optical device is less than an axial coordinate of a center of volume of the optical device by at least one-quarter of an axial length of the optical device.

41. The optical device of claim 40, having a magnification-field-of-view product of at least about 68 degrees.