Abstract:
A method and apparatus for generating a video signal representing an image of a scene, by: providing a photodetector having a light sensitive surface with a given area; providing a first focusing lens; positioning the first lens to focus an image of a scene on the photodetector so that only a portion of the image is focused on the light sensitive surface; and effecting relative displacement between the first lens and the photodetector parallel to the light sensitive surface in order to change the portion of the image that is focused on the light sensitive surface.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to video cameras and methods for generating video image signals.  
         BRIEF SUMMARY OF THE INVENTION  
         [0002]    According to the present invention, video signals representing images of multiple fields of view of a scene are generated by providing two or more lenses and a photodetector array wherein the lenses form images in a common plane containing the photodetector array and at least one of the lenses has an image formation area substantially larger than the area of the photodetector array, and effecting relative movement between the lenses and the photodetector array in a direction parallel to the common plane. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0003]    [0003]FIGS. 1 and 2 are simplified perspective views showing the basic components of two embodiments of the invention.  
         [0004]    [0004]FIG. 3 is a pictorial view of a system containing a video camera according to the invention.  
         [0005]    [0005]FIG. 3A is an elevational, cross-sectional view of a practical embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0006]    [0006]FIG. 1 is a perspective view illustrating a first preferred embodiment of the invention. This embodiment includes a photodetector  12 , which is shown in a first position in solid lines and, at  12 ′, in a second position in broken lines. Photodetector  12  is mounted for movement over a plane P to positions other than those illustrated. [Note: It is not clear from the disclosure whether the entire photodetector is represented by the reference SP or by the reference P. Please clarify this point.] 
         [0007]    Above plane P there are disposed two lenses, a relatively short focal length lens  16  and a relatively long focal length lens  18 . When lens  18  is positioned to focus an image of a scene on plane P, this image will cover an area larger then the area of detector  12 , so that only a portion of that scene will be detected. By moving detector  12  in plane P, different portions of the scene being viewed by lens  18  can be imaged on detector  12 .  
         [0008]    The focal length of lens  16  can be selected to have a field of view which is such that when detector  12  is in position  12 ′ aligned with the optical axis of lens  16 , substantially the entire field of view of lens  16  is imaged on the detector area.  
         [0009]    Thus, by shifting detector  12  in plane P, a scene can be viewed with different magnifications and, when detector  12  is in the field of view of lens  18 , different portions of the scene can be imaged by displacing detector  12  in plane P.  
         [0010]    One advantage of this arrangement is that the scene imaged on detector  12  by lens  18  is, in effect, an enlarged view of a portion of a scene that will be imaged by lens  16  on detector  12 , but with the same resolution as the scene imaged by lens  16 .  
         [0011]    When detector  12  is displaced within the field of view of the longer focal length lens  18 , the result corresponds to pan and tilt scanning. In addition, it is possible to capture and store images of a plurality of regions in the field of view of the longer focal length lens  18 .  
         [0012]    [0012]FIG. 2 is a view similar to that of FIG. 1 showing essentially the same structural arrangement, with the exception that detector  12  is essentially maintained stationary and lenses  16  and  18  are mounted on a carriage  20  that is movable in a plane parallel to plane P.  
         [0013]    Of course, it would also be possible to mount detector  12  and carriage  20  so that each is movable relative to some fixed reference. In an embodiment of this type, which will be described below with reference to FIG. 3A and which combines the techniques described above with respect to FIGS. 1 and 2, detector  12  can be displaced along one of the X and Y axes, while the lenses are displaced along the other axis. This facilitates fast changes in the fields of view of the lenses and allows the detector  12  to be brought more rapidly to a particular region in the field of view of one of the lenses.  
         [0014]    In addition, in the case of each illustrated embodiment, lenses  16  and  18  can be readily mounted for movement perpendicular to plane P for focusing purposes.  
         [0015]    [0015]FIG. 3 is a perspective view showing a scanning camera according to FIG. 1 or  2 , associated with a conventional computer system that can be used for display and editing of images viewed by the camera.  
         [0016]    In the illustrated embodiment, carriage  20  is mounted for translational movement relative to detector  12 . For this purpose, there may be provided, in a conventional manner, a support base supporting a first plate that is movable by a translator  101  in a first direction parallel to the base, and a second plate that is movable by a translator  102  relative to the first plate in a second direction perpendicular to the first direction. Carriage  20  may be fixed to the second plate and detector  12  may be fixed either to the support base or to the first plate.  
         [0017]    Each of translators  101  and  102  may be constituted by a servomotor driving a conventional feed screw mechanism.  
         [0018]    The video camera is connected to the computer system via a data line  112 , which may be a bus, cable or any other type of data conductor. The computer system constitutes, in effect, a transformation and display device and may be constituted by a conventional personal computer having appropriate software.  
         [0019]    The computer system preferably includes a frame grabber  202 , a CPU chip  204 , a diskette drive  206 , a monitor  210  and a keyboard  212 . As is conventional, the computer system may also include other storage devices, such as hard drives, CD drives, communications devices such as modems, sound cards, etc.  
         [0020]    [0020]FIG. 3A is an elevational, cross-sectional view of one suitable embodiment of the camera shown in FIG. 3. In the arrangement shown in FIG. 3A, a stationary support base  210  supports translator  101  and a first plate  220 . Plate  220 , in turn, supports translator  102  and a second plate  230 . Each of plates  220  and  230  is in the form of a frame having an essentially hollow interior. Detector  12  may be embedded in the upper surface of base  210 , or may be carried by a support member  240  that is fixed to plate  220 . Carriage  20  is fixed to plate  230 .  
         [0021]    Plate  220  is displaceable along the surface of base  210  parallel to the plane of FIG. 3A by the operation of translator  101 . Plate  230  is displaceable parallel to the plane of base  210 , but in a direction perpendicular to the plane of FIG. 3A, by the action of translator  102 .  
         [0022]    When detector  12  is embedded in the upper surface of base  210 , translators  101  and  102  act to displace carriage  20  in two mutually perpendicular directions relative to detector  12 . When, on the other hand, detector  12  is carried by support member  240 , detector  12  will be displaced in a first horizontal direction by the operation of translator  101  and carriage  20  will be displaced in a second horizontal direction, perpendicular to the first direction, by operation of translator  102 .  
         [0023]    According to a further embodiment of the invention, two photodetectors can be provided, one at the position of detector  12  and the other at position  12 ′ in FIG. 1. One detector, such as  12 ′, can be stationary relative to its associated lens  16 , while the other detector,  12 , is movable in plane P relative to its associated lens  18 .  
         [0024]    Returning to FIG. 3, frame grabber  202  includes a virtual array in which date transmitted via line  112  is stored. The data will be stored conventionally in a rectangular format, corresponding to the pattern of sensor cell locations in detector  12 . Video data supplied to monitor  210  can produce two display portions, a portion D 1  showing the wide field of view imaged by lens  16  and a portion D 2  showing the narrow field of view imaged by lens  18 . Since the data for the images to be displayed in portions D 1  and D 2  are obtained at different times, the data for one display portion will be stored for a selected period of time while the image for the other display portion is being generated.  
         [0025]    Software may be provided to correlate the displays associated with the two lenses. For example, the software can allow the user to point to a certain region of display portion D 1  and click on that region to cause translators  101  and  102  to bring lens  18  to a position relative to detector  12  to form an enlarged image of that region with a magnification equal to the ratio of the focal length of lens  18  to the focal length of lens  16 .  
         [0026]    Thus, the present invention provides a camera which has both a lens providing a wide field of view, such lens having a relatively short focal length, and a lens having a relatively narrow field of view and a relatively long focal length. An image of a scene can first be focused on detector  12  by the short focal length lens and then stored and/or displayed, after which detector  12  and/or carriage  20  can be moved so that a selected portion of the scene can be focused on detector  12  by the long focal length lens, and the resulting data can also be stored and/or displayed.  
         [0027]    Detector  12  is preferably of the CCD television type, although any other suitable detector technology can be employed. In addition, one or both lenses can be mounted for movement along their respective optical axes A, A′, for focusing purposes.  
         [0028]    If two detectors are provided, the image formed by the detector at position  12 ′ can provide the data for display portion D 1 , while the image formed by the detector at position  12  can be used to provide the data for display portion D 2 . This arrangement provides, in effect, two cameras in which the position of detector  12  can be adjusted while viewing the image provided by the second detector at position  12 ′, thereby providing a master-slave relationship.  
         [0029]    The foregoing description of the specific embodiments will so fully reveal the general nature of the invention that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without undue experimentation and without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. The means, materials, and steps for carrying out various disclosed functions may take a variety of alternative forms without departing from the invention.  
         [0030]    Thus the expressions “means to . . . ” and “means for . . . ”, or any method step language, as may be found in the specification above and/or in the claims below, followed by a functional statement, are intended to define and cover whatever structural, physical, chemical or electrical element or structure, or whatever method step, which may now or in the future exist which carries out the recited function, whether or not precisely equivalent to the embodiment or embodiments disclosed in the specification above, i.e., other means or steps for carrying out the same functions can be used; and it is intended that such expressions be given their broadest interpretation.