Abstract:
A drive system for optical components particularly useful with night vision devices. The drive system uses a single motor to rotate a selected one of two components between its operative and inoperative positions while retaining the other component in its inoperative position.

Description:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
       [0001]    This invention was made under U.S. Government Contract Number FA8650-03-C-5943 and the United States Government may have certain rights in this invention. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    This invention relates to a drive system and more particularly to a drive system useful in, among other things, a night vision device for rotating one of a plurality of optical components into an operative position with respect to the night vision device. 
         [0003]    Night vision devices include binoculars or monoculars that are used for intensifying low levels of ambient light to enable the user to see in the night. These devices generally include an image intensification tube having an objective lens that receives ambient light which is intensified by the image intensification tube and presented to the user. Night vision devices are well known in the art and may be hand carried or mounted to a helmet or a head mounted harness, worn by the user, to facilitate their use by soldiers in various vehicles or on the ground. 
         [0004]    Image intensification tubes are susceptible to interference from laser light and in some cases the tube can be damaged by laser light. 
         [0005]    To protect the night vision device from laser light, it is known to use a single laser interference filter that is operatively arranged with the objective lens to protect the image intensification tube from the effects of laser light. See for example U.S. Pat. No. 6,075,661 issued on Jan. 13, 2000 to Ted J. Gross et al. In the Gross patent there is provision for a single laser interference filter that fits over the free end of the objective lens to filter laser light. It has been found that a single laser interference filter is not completely satisfactory and that a filter system including two filters is, in some situations, preferable to protect the image intensification tube. Each of these two filters has a different filtering capability such that one or the other is best used depending on the characteristics of the laser light, e.g., its wavelength or its power density, whether it is continuous or pulsed and other like characteristics. The filters are stowed in an inoperative position in which they are out of the path of the ambient light. When a filter is needed, the desired filter is selected and is driven to an operative position adjacent the objective lens to protect the tube. The other filter is retained in an inoperative position. 
         [0006]    Providing a drive system or actuator for moving the selected filter to its operative position can be accomplished by the use of two motors, one for each filter, whereby the selected filter is moved by energizing it associated motor. Such arrangements are rather expensive, bulky and heavy. Accordingly, it is desirable to have an inexpensive, light weight arrangement for actuating the selected filter. 
       SUMMARY OF THE INVENTION 
       [0007]    A drive system comprising a housing and a screw rotatably mounted therein. A nut is operatively arranged on the screw for movement axially along the screw; and, a pair of optical components each having a rotatable sleeve are carried in the housing adjacent the nut. A pin is provided adjacent each end of the nut and a track is provided along the axial length of each sleeve. Each pin is operatively arranged with a different one of the tracks. Each track is configured so that upon axial movement of the nut, one pin holds one sleeve against rotation and the other pin rotates the other sleeve whereby the optical component associated with the other sleeve rotates from between a first and second position. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a perspective view illustrating a helmet mounted night vision binocular device including a laser interference filter and drive system in accordance with this invention; 
           [0009]      FIG. 2  is a partial section view taken along the line  2 - 2  of  FIG. 1  and illustrating the drive system according to this invention with the filters in their inoperative positions; 
           [0010]      FIG. 3  is a top view, partially in section illustrating the drive system according to this invention with the filters in their inoperative positions; 
           [0011]      FIG. 4  is a partial section view similar to  FIG. 2  but illustrating the drive system with one of the filters in its operative position; and 
           [0012]      FIG. 5  is a view similar to  FIG. 3  but illustrating the drive system with one of the filters in its operative position. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0013]    Referring to  FIG. 1  there is illustrated a night vision device in the form of a binocular  10  mounted on a helmet  12  by any suitable mounting arrangement shown generally at  14 . The helmet  12  is, of course, worn by a soldier, either a field soldier or pilot or other vehicle driver utilizing night vision equipment. It should be understood that the drive system according to this invention is useful with other apparatus including monoculars that are either hand held or mounted to a weapon. The binocular  10  includes a pair of monoculars  16 ,  16  which can be any image intensification device, thermal night vision device or other useful night vision device. Each monocular,  16 ,  16  includes an objective lens  18  and an image intensification tube (not shown). Such image intensification tubes are well known in the art and are operative to intensify the low levels of light received on the free end of the objective lens  18  and provide a visible image at eyepieces which is viewed by the user. 
         [0014]    Each monocular  16 ,  16  includes a laser interference filter assembly  20  (only one of which is shown in  FIG. 1 ). Each filter assembly  20  is the same and each includes a housing having a first generally cylindrical portion  22  of a size and shape to fit on the monocular  16  around the objective lens  18 . The filter assembly  20  housing is retained with its associated monocular  16  by any suitable fastening arrangement between the cylindrical portion  22  and the monocular housing adjacent the free end of the objective lens  18 . 
         [0015]    The filter assembly housing also includes a second portion  24  having an opening  26  of the same size and general shape as the objective lens  18  and the opening is adjacent to and in front of the objective lens so that light passes through the opening  26  and is incident on the lens. The second housing portion  24  includes an elliptically or other shaped portion extending below the opening  26  and this second housing portion is formed with an internal recess  28 , as best seen in  FIGS. 3 and 4 . Two laser interference filters  32  and  34 , only one of which is partially shown in  FIG. 1 , are located in the recess  28 . Each filter  32  and  34  has a different filtering capability and only one needs to be used depending on the characteristics of the laser light. 
         [0016]    The filter assembly housing also includes a second cylindrical portion  30  having an axis extending generally parallel to the first cylindrical portion  22  and, of course, to the monocular  16 . 
         [0017]    In their inoperative positions, the filters  32  and  34  are located below the objective lens  18  in the recess  28  formed in the second housing portion  24 . When one of the filters is required to protect the goggle, the required filter is moved from its inoperative position to an operative position, preferably, in front of the objective lens  18  while the other filter remains in its inoperative position. Light will impinge on the selected filters  32  or  34  and the selected filter is operative to protect the tubes from the laser light. Such filters are known in the art and need not be described here. It is sufficient to note that they allow the ambient light to pass to the objective lens  18  and its image intensification tube while filtering out the laser light. 
         [0018]    Referring now to  FIGS. 2 through 5  there is illustrated a drive system in accordance with this invention that drives the selected filter from its inoperative to its operative position while leaving the other filter in its inoperative position. This drive system is located in the second cylindrical housing portion  30  and includes a single reversible electric motor  36  which may be located within or outside of the filter assembly housing. The motor  36  is operatively coupled to a threaded lead screw  38  which is rotatably mounted in the housing portion  30 . Any suitable coupling between the motor and the lead screw  38  is usable provided that it is operative to rotate the lead screw in either direction depending on the direction of rotation of the motor  36 . A nut  40  is carried on the thread formed on the lead screw  38  and, as will be explained, when the lead screw is rotated, the nut translates axially along the screw in one direction or the other depending on the direction of rotation. It can be seen that the nut  40  is an internally threaded elongated member having a pair of pins  42  and  44  or similar protruberances. Each pin  42 ,  44  extends radially outwardly from the nut&#39;s outer surface adjacent the free ends of the nut adjacent the outer ends of the housing portion  30 . 
         [0019]    Each filter  32  and  34  is formed with or is otherwise operatively coupled to a generally cylindrical sleeve  46  and  48 , respectively. Each sleeve extends from the circumferential surface of its associated filter  32  or  34  into the housing portion  30 . These sleeves  46  and  48  are generally cylindrical members arranged so that the sleeve is adjacent the screw  38  and preferably encases the screw  38  and the nut  40  to prevent the nut from rotating. 
         [0020]    Each sleeve  46  and  48  is formed with a track that cooperates with the pins  42  and  44 , respectively, to rotate the selected filter  32  or  34  from its inoperative position to its operative position while it maintains the other filter in its inoperative position. In this embodiment, the tracks are in the form of elongated slots  50  and  52 , that extend axially along the length of its associated sleeve  46  and  48 , respectively. Each slot  50  and  52  includes an axially extending generally straight segment  54  and  56 , respectively, and each axial segment has an open end adjacent the other slot so that the axially extending segments form a continuous track extending through both sleeves  46  and  48 . The axial segments  54  and  56  extend generally coextensive with the axial length of the nut  40 . At their other end, that is, the ends adjacent the outer ends of the housing portion  30 , the slots  50  and  52  are formed with generally arcuate segments  58  and  60 , respectively, that extend at an angle to the axial segments  54  and  56  in a direction generally toward the filters  32  and  34 , respectively. 
         [0021]    As shown in  FIGS. 2 and 3 , in the inoperative position of the filters  32  and  34 , each pin  42  and  44  is located generally adjacent the intersection of its associated axial slot segment  54  or  56  and their respective arcuate segments  58  and  60 . Because the pins  42  and  44  are seated in the axial segments  54  and  56  of the slots  50  and  52 , rotation of the screw  38  in one direction or the other presents the nut  40  from rotating and drives the nut axially along the screw in a direction dependant on the direction of rotation of the screw  38 . As the nut  40  moves, the pins slide along the axial segment  54  and  56  of the slot and the lead pin, pin  42  as shown in  FIG. 3 , slides into the arcuate segment  58  and rotates the sleeve  46  and its associated filter  32  into its operative position. At the same time, the other pin  44  rides along the straight line segment  56  until it is adjacent the straight line segment  54 . Such axial movement of the other pin  44  does not rotate its associated sleeve  48  and its associated filter  34  remains in its inoperative position. 
         [0022]    When filter  32  is in its operative position, rotation of the screw  38  in the opposite direction slides the pins  40  and  42  back to the position shown in  FIG. 2 . As the pin  40  slides along arcuate segment  58  it rotates the sleeve  46  and its associated filter  32  to its inoperative position. 
         [0023]    It should be understood that when the filters are in their inoperative position, rotation of the screw  38  in the direction opposite that described above will move the other filter  34  between its inoperative and operative positions in the same manner described for filter  32 . 
         [0024]    In use, the motor can be operated manually by a suitable switch arrangement or it can be associated with appropriate laser light sensors and software to automatically select and drive the selected filter between its operative and inoperative positions. 
         [0025]    While the foregoing describes an exemplary embodiment of the invention, the scope of the invention is recited in the claims appended hereto.