Abstract:
An optical device for viewing an image is provided. The optical device comprises a plurality of optical channels positioned adjacent one another, each optical channel having an image detector and a complimentary objective lens spaced by a respective distance. A focusing mechanism is coupled to the optical device and configured to simultaneously adjust the respective distance between the image detector and the objective lens of each optical channel.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a ganged focus mechanism for use with an optical device, particularly suited for night vision applications. 
     BACKGROUND OF THE INVENTION 
     Night vision systems are used in a wide variety of military, industrial and residential applications to enable sight in a dark environment. For example, night vision systems are utilized by military aviators during nighttime flights or military soldiers patrolling the ground. Security cameras use night vision systems to monitor dark areas and medical instruments use night vision systems to alleviate conditions such as retinitis pigmentosis (night blindness). 
     Conventional image enhancement night vision equipment utilize an Image Intensifier (I 2 ) to amplify an image. The image intensifier collects tiny amounts of light in a dark environment, including the lower portion of the infrared light spectrum, that are present in the environment but may be imperceptible to the human eye. The image intensifier amplifies the light so that the human eye can perceive the image. The light output from the image intensifier can either be supplied to a camera, external monitor or directly to the eyes of a viewer. The image intensifier devices are commonly employed in vision goggles, i.e. a monocular or binocular, that are worn on a user&#39;s head for transmission of the light output directly to the viewer. 
     Image enhancement night vision equipment utilizes available light such as starlight and moon light. Although the image enhancement equipment will work in very reduced lighting, it may not work in environments of absolute darkness, such as caves or caverns. Furthermore, image enhancement equipment effectiveness may be reduced by battlefield obscuration such as smoke, fog, rain, dust, and foliage. 
     Standard night vision devices may be enhanced with the addition of thermal imaging, i.e. infrared (IR) information. Whereas conventional night vision devices employing image intensifiers can only see visible wavelengths of radiation, the enhanced system provides additional situational awareness by providing infrared (i.e. heat) information to the image. A typical scenario where this might be important is where a camouflaged person cannot be seen with an image intensifier device. However, with the addition of infrared information to the same image, the camouflaged person&#39;s heat signature is seen. 
     The enhanced night vision device commonly includes two channels for transmitting a scene image to the user. The first channel includes a thermal camera (i.e. infrared detector) and a complementary objective lens to transmit a scene image in a first spectral band. The second channel includes an image intensifier camera and another complementary objective lens to transmit the same scene image in a second spectral band. A processing module within the device fuses the images together and superimposes the images on each other. Such a device is disclosed in U.S. Pat. No. 6,560,029 which is incorporated herein by reference in its entirety. 
     The focus of each channel of the enhanced night vision device is individually adjusted by the user. More particularly, the position of each objective lens relative to each detector or camera is adjusted by the user. The devices typically do not allow for tracking of one objective lens relative to another objective lens for the purpose of simultaneously focusing the channels, or determination of and compensation for parallax disparity. 
     Thus, it would be advantageous to supply an apparatus which simultaneously focuses both channels of a fused system and tracks the position of one channel relative to another channel to compensate for parallax disparity. 
     SUMMARY OF THE INVENTION 
     According to one aspect of this invention, an optical device for viewing an image is provided. The optical device comprises a plurality of optical channels positioned adjacent one another, each optical channel having an image detector and a complimentary objective lens spaced by a respective distance. A focusing mechanism is coupled to the optical device and configured to simultaneously adjust the respective distance between the image detector and the objective lens of each optical channel. 
     According to another aspect of this invention, a focusing mechanism configured for use with an optical device having a plurality of optical channels positioned adjacent one another is provided. Each channel includes an image detector and a complimentary objective lens spaced by a respective distance, wherein the focusing mechanism is adapted to simultaneously adjust the respective distance between each respective image detector and objective lens. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is best understood from the following detailed description when read in connection with the accompanying drawing. Included in the drawing are the following figures: 
         FIG. 1A  is a perspective view from the top left of an exemplary embodiment of a night vision optical device used in accordance with the present invention; 
         FIG. 1B  is a perspective view from the top right of the night vision optical device of  FIG. 1A ; 
         FIG. 1C  is an exploded view of the night vision optical device of  FIG. 1A  for purposes of clarity; 
         FIG. 2A  is a perspective view from the top left of the night vision optical device of  FIG. 1A  in a near focus configuration (various components of the device are omitted for clarity); 
         FIG. 2B  is a perspective view from the top left of the night vision optical device of  FIG. 1A  in a far focus configuration (various components of the device are omitted for clarity); 
         FIG. 3A  is a perspective view from the top rear of an exemplary collar illustrated in  FIG. 1A ; 
         FIG. 3B  is a top plan view of the collar of  FIG. 3A ; 
         FIG. 4A  is a perspective view from the top right of an exemplary cam driver illustrated in  FIG. 1A ; 
         FIG. 4B  is an elevation view from the left side of the cam driver of  FIG. 4A ; 
         FIG. 4C  is a top plan view of the cam driver of  FIG. 4A ; 
         FIG. 4D  is a bottom plan view of the cam driver of  FIG. 4A ; and 
         FIG. 5  is a top plan view of another exemplary embodiment of a focusing mechanism used in accordance with the present invention (various components of the mechanism are omitted for clarity). 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The invention will next be illustrated with reference to the figures. Such figures are intended to be illustrative rather than limiting and are included herewith to facilitate explanation of the present invention. The figures are not to scale, and are not intended to serve as engineering drawings. 
     Referring generally to the figures, a multiple channel optical device is designated by the numeral “ 10 .” Briefly, multiple channel optical device  10  may be used, for example, with a man-mounted night vision monocular arrangement, such as the one illustrated in U.S. Pat. No. 6,560,029. The multiple channel optical device  10  is adapted to observe and transmit an image to a prismatic video display (not shown) positioned in front of a user&#39;s eye. The subsequent description will concentrate on the details of optical device  10 . 
     In an exemplary embodiment, illustrated in  FIGS. 1A–1C , optical device  10  includes two channels for transmitting a scene image. The first channel (i.e. top channel) includes infrared detector  22  (or IR camera) and complementary objective lens  12  adapted to transmit a scene image in a first spectral band. The second channel (i.e. bottom channel) includes image intensifier assembly  24  (or image intensifier camera) and a separate complementary objective lens  26  adapted to transmit the same scene image in a second spectral band. The components of the first channel are optionally positioned above the components of the second channel. In the interest of clarity, further description will reference the first channel (i.e. top channel) of optical device  10 , as the mechanical structure of the two channels is similar. 
     According to an exemplary embodiment, the first channel includes two separate assemblies (i.e. the first assembly and the second assembly) that cooperate together to control the longitudinal distance between IR detector  22  and objective lens  12 . The distance between IR detector  22  and objective lens  12  characterizes the focus of the first channel. The longitudinal and transverse directions are indicated by the arrows pointing to “L” and “T”, respectively, in  FIG. 1B . 
     The first assembly includes objective lens  12  which is threadedly engaged and fixed onto faceplate  14 . A set of brackets  44  and  45  abut the rear side of faceplate  14  and are retained in a substantially fixed position by a set of fasteners  48  installed through the faceplate. More particularly, the fasteners threadedly engage a longitudinally threaded hole (see  FIG. 1C ) disposed in each bracket  44  and  45 . 
     The opposing end of brackets  44  and  45  are positioned in a slot disposed in opposing cam drivers  40  and  50 . A left and right handed screw  42 , best illustrated in  FIG. 1C , is threadedly engaged with threaded apertures disposed in both cam drivers and both brackets  44  and  45  so that a clockwise or counterclockwise rotation of screw  42  translates cam drivers  40  and  50  in opposite directions along a transverse axis. Both right-handed threads and left-handed threads are disposed on the exterior surface of the screw. The functionality of the left and right handed screw should be understood by one skilled in the art. 
     Although not shown, a wheel, knob, handle or other apparatus may be coupled to screw  42  to effect rotation of the screw and the resultant translation of the cam drivers. The wheel may be coupled to the ends of screw  42 . It is also envisioned that a motor or other mechanized apparatus may be coupled to screw  42  for automated operation of device  10 . 
     The cam drivers  40  and  50  include cam surface  46  that bears on another cam surface  48  of a floating collar  18 . As the cam drivers translate along the transverse direction, they urge cam surface  48  of floating collar  18  in the longitudinal direction. More particularly, the cam drivers and the collar have angled surfaces to convert the transverse motion of the cam drivers into longitudinal motion of the collar. As will be explained further detail later, cam drivers  40  and  50  simultaneously bear on collar  18  of the first channel and collar  18 ′ of the second channel. Thus, the translation of the cam drivers induces the simultaneous translation of the collars of the first and second channels. The interaction between cam drivers and the collars will be described in further detail later with reference to the remaining figures. 
     The collar  18  floats between the aforementioned first assembly and a second assembly. The second assembly includes a hollow sleeve  16  that is positioned about the cylindrical body of objective lens  12  and is adapted to float over the body of the objective lens. The sleeve includes a cylindrical body and knurled shoulder  52 , whereby collar  18  is positioned about the cylindrical body of sleeve  16  and abuts the knurled shoulder of the sleeve. Thus, by virtue of the contact between the collar and the shoulder, the longitudinal translation of the collar induces the longitudinal translation of the sleeve. 
     The interior surface of sleeve  16  is threadedly engaged and fixed onto threaded flange  21  of translating carriage  20 . The infrared detector  22  is mounted to the translating carriage with threaded fasteners or any other fastener known in the art. The translating carriage includes a cylindrical aperture through which the body of objective lens  12  passes through. More particularly, the carriage translates (i.e. rides) along the exterior surface of objective lens  12 . 
     It should be understood that since the sleeve is fixed to carriage  20 , and detector  22  is mounted to the carriage, the detector translates along with the sleeve in the longitudinal direction. Although not illustrated, a gap exists between the rear side of faceplate  14  and sleeve  16  to accommodate the longitudinal translation of the sleeve. 
     A spring  30  is compressed between the objective lens (of the first assembly) and the translating carriage (of the second assembly) to urge the assemblies apart. Moreover, the spring urges sleeve  16  and objective lens  12  apart since the sleeve is threadedly coupled to carriage  20 . A protective ring  28  is positioned between the spring and the objective lens to shield the objective lens from harm (e.g. scratch or abrasion) by the spring. In use, as the IR detector translates relative to the objective lens, the spring compression changes. The functionality of the spring will be described in further detail later with reference to  FIGS. 2A and 2B . 
     Referring still to  FIGS. 1A through 1C , although sleeve  16  floats over the body of lens  12 , the travel range of the sleeve is limited. As best illustrated in  FIG. 1C , several pins  54  are fixedly inserted through holes  57  that are radially positioned on the sleeve. The pins are positioned to engage slots  56  that are radially positioned on the exterior surface of the objective lens. The engagement between the pins and slots restricts the float of the sleeve over objective lens  12 . More particularly, the boundary of the slots define the range of motion for the pins (and sleeve). The total travel range of sleeve  16  over objective lens  12 , which is the total travel of the first channel, may be about ½ of a millimeter. However, the channels of device  10  are not limited to any specific range of motion. 
     In summary, the first channel includes collar  18  that floats between two assemblies urged apart by spring  30 . In the first assembly, objective lens  12  and brackets  44  and  45  are fixed to faceplate  14  and cam drivers  40 ,  50  are engaged with the brackets by virtue of screw  42 . In the second assembly, sleeve  16  and IR detector  22  are fixed to opposite sides of carriage  20 . The cam drivers  40 ,  50  bear on floating collar  18  which bears on sleeve  16 . The transverse translation of the cam drivers (by virtue of the rotation of screw  42 ) induces a longitudinal translation of collar  18 , sleeve  16  and IR detector  22  thereby changing the longitudinal distance between IR detector  22  and objective lens  12 . 
     The distance separating detector  22  and objective lens  12  is also controlled by the distance sleeve  16  is threaded onto carriage  20 . The knurled surface  52  is also provided to facilitate rotation of the sleeve onto the carriage: In assembly, the sleeve is threaded onto the carriage a pre-determined distance. The device  10  is subsequently enclosed so that the user is restricted from manually rotating the knurled surface. However, the user is provided a handle (not shown) that is coupled to screw  42 , which is not enclosed within the device, so that the user may set the focus of both channels. It should be understood that the rotation of the knurled surface of the sleeve controls the focus setting of a single channel, whereas the rotation of screw  42  simultaneously controls the focus setting of both channels, i.e. the first channel and the second channel. 
     The ganged focus mechanism of the optical device includes screw  42 , the spring, the cam drivers, the collars, the sleeves and the carriages. The interaction and inter relationship between those components simultaneously controls the focus setting of both channels. The term “ganged focus mechanism” implies that a mechanism simultaneously controls the focus of multiple channels. The ganged focus mechanism also facilitates individual focusing of each channel to tune the objective lenses to their respective focal plane position to match a prescribed focus distance. 
     Referring now to  FIGS. 2A and 2B , various components of the prior exemplary embodiment are omitted for the purpose of clarity. The figures illustrate the cooperation between cam drivers  40  and  50  and collars  18  and  18 ′. The device is illustrated in a near focus configuration in  FIG. 2A  and is illustrated in a far focus configuration (i.e. focus at infinity) in  FIG. 2B . 
     More particularly, starting from the near focus configuration of the optical device  10 ′ illustrated in  FIG. 2A , the entire face of the cam surfaces of the cam drivers are maintained in frictional contact with the cam surfaces of collars  18  and  18 ′. [The cam surfaces  46 ,  46 ′ of the cam drivers are best illustrated in  FIGS. 4A–4D  and cam surfaces  48  of collar  18  are best illustrated in FIGS.  3 A and  3 B.] As screw  42  rotates in a counterclockwise direction, the cam drivers translate outwardly in a transverse direction. The cam drivers are substantially restricted from translation in the longitudinal direction since they are fixed to brackets  44  and  45 . As the cam drivers translate, the cam surfaces  46 ,  46 ′ of the cam drivers slide along cam surfaces  48  of the collar thereby translating the collar in a forward longitudinal direction, as illustrated in the far focus configuration of  FIG. 2B . The forward and reverse longitudinal directions are indicated by the arrows pointing towards “F” and “R”, respectively. The cam surfaces  46 ,  46 ′ of the cam drivers then partially contact cam surfaces  48  of the collar, as shown in  FIG. 2B . As described previously, sleeve  16  and IR detector  22  translate forward along with the collar. The spring  30  compresses as the IR detector translates forward, thereby decreasing the longitudinal distance between IR detector  22  and objective lens  12 . 
     Conversely, starting from the far focus configuration of the optical device  10 ″ illustrated in  FIG. 2B , as screw  42  rotates in a clockwise direction, the cam drivers translate inwardly in the transverse direction. As the cam drivers translate, cam surfaces  46 ,  46 ′ of the cam drivers slide along cam surfaces  48  of the collar. The spring  30  is permitted to expand, thereby translating the carriage, IR detector and the sleeve in a reverse longitudinal direction. The knurled shoulder  52  of the sleeve bears against the collar and urges the collar to also translate in the reverse longitudinal direction until the entire face of the cam driver cam surfaces  46 ,  46 ′ are in frictional contact with the collar cam surfaces  48 , as shown in the near focus configuration of  FIG. 2A . It should be understood that as the IR detector translates in the reverse longitudinal direction the distance between IR detector  22  and objective lens  12  increases. 
     Referring now to  FIGS. 3A and 3B , an exemplary embodiment of collar  18  configured for use with the first channel is illustrated. The collar  18 ′ configured for use with the second channel is substantially similar to collar  18 . The collar  18  is substantially cylindrical and includes two extended cam surfaces  48 . The angle “A” of the cam surface may be any angular dimension. As mentioned previously, the collar is hollow to accommodate the cylindrical body of sleeve  16  therethrough. 
     Referring now to  FIGS. 4A–4D , an exemplary embodiment of cam driver  50  is illustrated. Although one cam driver is illustrated, cam drivers  40  and  50  are symmetrical and substantially similar. A threaded hole  58  (right handed thread) provided on a side of the cam driver is threadedly engaged with screw  42 . Alternatively, the opposing cam driver  40  includes a left handed threaded hole that is threadedly engaged with an opposing end of screw  42 . Thus, the cam drivers translate in opposite transverse directions in response to a rotation of the screw. The cam driver comprises two semi-circular cam surfaces  46  and  46 ′ configured for contact with collars  18  and  18 ′, respectively. The angle “B” of cam surface  46  and the angle “C” of cam surface  46 ′ may be any angular dimension. It should be understood that both cam surfaces  46  and  46 ′ are integral with the cam drivers, and they simultaneously translate both collars  18  and  18 ′, thereby simultaneously altering the focus of both channels. Although the cam drivers include two cam surfaces  46  and  46 ′, each cam driver may optionally include a single cam surface that is positioned in frictional contact with the cam surfaces of the collars. 
     In use and referring to  FIGS. 3A ,  3 B and  4 A– 4 D, cam surfaces  46 ,  46 ′ of the cam drivers slide along cam surfaces  48  of collar  18 . Each cam driver includes at least one sloping cam surface  46  to bear against at least one cam surface  48  of collar  18  to thereby control the focus of the first channel. Furthermore, each cam driver includes at least one sloping cam surface  46 ′ to bear against at least one cam surface of collar  18 ′ to thereby control the focus of the second channel. 
     The cam surfaces of collars  18  and  18 ′ and the cam drivers are angled to convert the transverse translation of the cam drivers into longitudinal translation of the collar. The cam surfaces  46 ,  46 ′ and  48  may be optionally planar, as shown, so that the translational relationship between the cam driver and the collar is linear. Angle “A” and angle “B” are desirably equivalent so that the cam surfaces of the collar and cam driver are maintained in sufficient frictional contact. Moreover, although the cam surface of collar  18 ′ is not illustrated, the angle of that cam surface is desirably equivalent to angle “C” of cam surface  46 ′. By way of non-limiting example, angle “A” may be about 22 degrees, angle “B” may be about 22 degrees and angle “C” may be about 45 degrees. It should be understood that the cam surfaces  46 ,  46 ′ and  48  may optionally be non-planar (i.e. curved), so that the translational relationship between the cam driver and the collar is non-linear, if so desired. 
     In practice and according to this exemplary embodiment, although cam surfaces  46 ,  46 ′ of the cam drivers translate in the transverse direction at the same rate, collars  18  and  18 ′ do not longitudinally translate at equal rates, by virtue of the unequal angles “B” and “C” of the cam driver. Therefore, since collars  18  and  18 ′ translate at unequal rates, the rate of focus of the first and second channels are unequal, i.e. the change in distance separating the respective lenses and detectors is unequal. However, the angles “B” and “C” may be equal if so desired to achieve equal focus of both channels. Furthermore, the angles “B” and “C” of the cam driver and/or the angle of the cam surface of the collars may be any dimension. 
     In summary, although the focus of the first and second channels are simultaneously adjusted by virtue of the ganged focus mechanism, the rate of focus of each channel may not be equal by virtue of the aforementioned unequal cam surface angles. 
     The focusing components of the optical device, such as the cam drivers, collars, left and right handed screw, sleeves and carriages may be formed from any material, such as aluminum or steel and formed by any fabrication process such as casting, molding or machining. 
     Another exemplary embodiment of a focusing mechanism  110  is illustrated in  FIG. 5  and various components are omitted for clarity. This embodiment is similar to the prior embodiment, however, focusing mechanism  110  includes a cam and slot interface in lieu of spring  30  (refer to  FIG. 1C ). More specifically, a pin  160  extends from each cam driver  140  and  150 . Each pin engages a slots  165  positioned on the collar  118 , that is, each pin translates along the boundary of the slots. In practice, as screw  142  rotates, the cam drivers and pins  160  translate in a transverse direction and the pins engages slots  165  to translate (i.e. drive) the collar  118  in a longitudinal direction. Similar to the last embodiment, the sleeve, carriage and detector also translate in the longitudinal direction along with collar  118 , thereby altering the longitudinal distance between the detector and the objective lens, and, thus, altering the focus setting of the channels. 
     Referring back to  FIGS. 1A and 1B , objective lenses  12  and  26  are separated by a vertical distance. One skilled in the art will understand that the vertical separation introduces a parallax disparity, which is an inherent problem in most multiple channel optical systems. Superimposing the images projected through the channels upon one another (i.e. overlay) causes the parallax disparity to manifest itself as a mismatch of the two images. The mismatch of the images is proportional to the degree of separation between the objective lenses relative to the distance between the optical device and the object being observed. 
     The ganged focus mechanism provides a reference for positional disparity between the objective lenses that can be used as an input for parallax correction in either a mechanical, analog or digital imaging system. It has been discovered that a positioning feedback device coupled to device  10  provides parallax adjustment throughout the entire focus range. 
     Although not illustrated, a positional feedback device, e.g. a strain gage, hall-effect device, or encoder may be incorporated with the device to measure the distance between an objective lens and its accompanying detector. This measurement can be used to derive the focal distance (i.e. the distance to the subject being imaged) of multiple channels and to provide an input to a table, algorithm or mechanism that can shift either one or more of the detectors themselves or their output images to the prismatic display device (not shown). In this manner, an object viewed at infinity through two channels would appear on the display as a singular image comprising two superimposed images. As the object is moved closer and the separation of the two channels would normally become apparent as an overlay mismatch on the prismatic display, the input from the feedback device of this embodiment would provide an open-circuit instruction for the imaging system to compensate for the parallax disparity. 
     In an embodiment, a digital imaging system cooperates with the positional feedback device to vertically shift one image relative to the other image by the appropriate number of pixels on the prismatic display to compensate for the parallax disparity. The mechanical, analog or digital imaging system may also be adapted to translate the image displayed on the prismatic display horizontally to compensate for a lateral displacement error. 
     Although the invention is illustrated and described herein with reference to specific embodiments, the invention is not intended to be limited to the details shown. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims and without departing from the invention. In particular, although the device is intended for use with a monocular night vision system, it may also be used with a binocular night vision system or any other optical system. Furthermore, although the detectors  22  and  22 ′ translate along the stationary objective lenses in practice, in another embodiment not illustrated herein, the objective lenses may translate along detectors that are maintained in a stationary position. The optical device is also not limited to detector  22  and image intensifier assembly  24 , as any wavelength detector or image intensifier may be used. Also, the embodiments selected for illustration in the figures are not shown to scale and are not limited to the proportions shown.