Abstract:
Improved methods and apparatus for imaging comprising a base, an outer dome mounted on said base, a central shaft intersecting said base, an imaging array including at least one imaging chip mounted on said shaft, means for focusing light onto said imaging chip having at least one pixel, at least one signal processing system, means for rotating said shaft, and means for transmitting data from said imaging chip to said signal processing system and from said signal processing system to an external receiver.

Description:
RELATED CASES 
     This invention is described in my Provisional Application Ser. No. 61/088,043, filed Aug. 12, 2008. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to the field of imaging and more particularly to an imaging device and a method for forming an image. 
     BACKGROUND 
     Imaging devices and cameras which develop 360 degree views, e.g. panoramic imaging systems, are currently known. Such systems provide a relatively wide field of view and may be used for a variety of different purposes. Such applications include, but are not limited to, the areas of surveillance, robotics and machine vision. 
     In general, such devices are capable of imaging a wide angle of a scene. The wide angle may be up to approximately 360 degrees as measured both an azimuth and an elevation. Often, these devices require the use of multiple cameras, where the cameras are spaced apart, such that each camera may effectively capture a portion of a scene, which may or may not be reflected off of a mirrored surface. Additional methods which may be utilized to capture a wide field of view include, for example, convex mirrors, coupled with image processing algorithms, fish eye lenses or single cameras with conventional lenses that rotate. The use of such systems often requires mechanical means necessary to focus or zoom on an object. 
     However, it would be desirable to provide an imaging device which is capable of producing a 360 degree by 180 degree view or greater, without the necessity for lenses or mirrors that focus or require multiple optical elements. 
     BRIEF SUMMARY AND OBJECTS OF INVENTION 
     These disadvantages of the prior art are overcome with the present invention and an improved method and apparatus for imaging are provided which permit imaging a full field of view of a hemisphere or full sphere in real time without the use of mirrors. 
     These advantages of the present invention are preferably attained by providing which permit imaging a full field of view of a hemisphere or full sphere in real time without the use of mirrors. 
     Accordingly, it is an object of the present invention to provide improved methods and apparatus for imaging. 
     Another object of the present invention is to provide improved methods and apparatus for imaging which permit imaging a full field of view of a hemisphere or full sphere in real time without the use of mirrors. 
     A further object of the present invention is to provide which permit imaging a full field of view of a hemisphere or full sphere in real time without the use of mirrors. 
     A specific object of the present invention is to provide improved methods and apparatus for imaging comprising a base, an outer dome mounted on said base, a central shaft intersecting said base, an imaging array including at least one imaging chip mounted on said shaft, means for focusing light onto said imaging chip having at least one pixel, at least one signal processing system, means for rotating said shaft, and means for transmitting data from said imaging chip to said signal processing system and from said signal processing system to an external receiver. 
     These and other objects and features of the present invention will be apparent from the following detailed description, taken with reference to the figures of the accompanying drawing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         FIG. 1A  is perspective view of a camera in accordance with an embodiment of the present invention; 
         FIG. 1B  is a perspective view of the direction of rotation of the imaging device of  FIG. 1A ; 
         FIG. 2  is a perspective view of an imaging device in accordance with another embodiment of the present invention; 
         FIG. 3  is a schematic view of a SEAM in accordance with an embodiment of the present invention; 
         FIGS. 4A-4C  illustrate introduction of light at various angles to a photo element on an imaging chip with a SEAM in accordance with an embodiment of the present invention; 
         FIG. 5A  is a perspective view of an imaging device according to an embodiment of the present invention including image sensors, a corrective lens and a SEAM assembly; 
         FIG. 5B  is an end view of the imaging device of  FIG. 5A ; 
         FIG. 6  is an exploded view of an imaging chip, lens and SEAM assembly according to an embodiment of the present invention; 
         FIG. 7  is a perspective view of light rays from a source entering a SEAM assembly according to an embodiment of the present invention; 
         FIG. 8  is a perspective view of the operation of the corrective lens according to an embodiment of the present invention; 
         FIG. 9  is a diagrammatic representation of a plano-concave lens for a SEAM assembly according to an embodiment of the present invention; 
         FIG. 10A  is a side view of an alternative SEAM assembly which does not require a corrective lens; and 
         FIG. 10B  is a front view of an alternative SEAM assembly which does not require a corrective lens, the SEAM being split into two halves in an exploded view, so that the imaging chip can also be seen. 
     
    
    
     GLOSSARY 
     The term “field of view”, as used herein, shall mean an area which a camera can see at any given moment or as a result of movement of the imaging device in a manner similar to a flatbed scanner to build and image which includes an entire field of view. 
     The term “frames per second”, as used herein, shall mean the number of full pictures that are taken by an imaging device per second. 
     The term “photo element”, as used herein, shall mean a region on an imaging chip that creates an individual pixel. It can be a photo capacitor, a photo transistor or photo diode and is synonymous to a pixel when referring to an imaging chip, such as a CCD. 
     The term “circle of confusion”, as used herein, shall mean an optical spot caused by a cone of light rays from a lens which does not come to a perfect focus when imaging a point source. 
     The term “hemispherical imaging array”, as used herein, shall mean a combination of a printed circuit board and reinforced fiberglass mount that holds multiple imaging chips, processing circuitry for the imaging chips with other support circuitry, corrective lens and SEAM. It is a rotating part that has a central axis which divides the mount into two sections, in most cases, only 90 degrees of the hemisphere will have imaging chips. 
     The term “positional feedback”, as used herein, shall mean a means of obtaining an exact position from a motor. The system works almost identically to a computer hard drive in that the position of the motor, at all times, is known and is reading data from that position. In the case of a hard drive, it is a magnetic medium. 
     The term “real time image”, as used herein, shall mean a rate of 1 or more FPS (frames per second) for the total field of view, which is 360 degrees of rotation. 
     The term “Imaging device”, as used herein, shall mean any device that converts light within a bandwidth of from 1 micrometer in wavelength (infrared) to 100 nm in wavelength (ultraviolet), including the visible spectrum, into an electrical signal for the purpose of creating image or light analysis. 
     DETAILED DESCRIPTION OF THE INVENTION 
     In that form of the present invention chosen for purposes of illustration,  FIG. 1A  shows a hemispherical configuration of an imaging device  10  having an outer shell base  12  with a dome  14 . Within the dome  12  is a hemispherical imaging array  16  which provides a first processing component (not shown) comprising a system for imaging and signal processing and rotation mount for the imaging charged couple devices (CCDs) or chips  18 . In one embodiment, one or more slip rings  20 , for operational power or optional video information or signals, are operably coupled to a central shaft  28 , having an upper rotating portion  28   a  and a lower stationary portion  28   b , and which is hollow to accommodate cable. A fiber optic transmitter  29  (not shown) is mounted inside shaft  28  on the upper rotational portion  28   a . A fiber optic receiver  31  (not shown) is mounted inside the lower portion  28   b  of the shaft  28 . 
     In another embodiment, one or more light rings  24 , for sending a signal via a series of light receivers rather than by the slip rings  20 , are provided. The device, in some embodiments, may only use a series of slip rings  20  to transmit power and electrical signals, in lieu of the fiber optic transmitter  29 , fiber optic receiver  31  or the light rings  24 . A motor  22  rotates the imaging PCB and imaging chips  18 . A second processing component  26 , comprising a system from motor positioning, drive circuitry and digital signal processing (DSP) is located near the base  12  of the device  10 . In one embodiment, the second processing system  26  can contain driver signals for imaging chips  18  and raw video signals, which can be optically linked to the second processing system  26  or sent through slip rings  20 . 
       FIG. 1B  shows the direction of rotation  32  of the imaging device  10  around the central shaft  28 . Each imaging photo element or pixel (See  FIG. 3 ) is assigned a particular latitude of rotation. Within the 180 degree field of view, there can be at least 200 pixels. As the imaging device  10  rotates, each single point of light in a 360×180 degree hemisphere is scanned to form an image. The field of view can be expanded by increasing the number of imaging chips  18 , increasing the arc of the dome  14  or placing the imaging device  10  on a stalk. 
     In another embodiment, as illustrated in  FIG. 2 , the imaging device  10  comprises a cylindrical configuration, having an outer dome  34  mounted on a base  36  and intersected by a central shaft  38 . A first processing system  40 , with circuitry for the support of the imaging devices  42  and data processing, is affixed in a vertical position within the dome  34 . Located at the base of the central shaft  38  is a bearing  46 , which serves to support the shaft  38 . One or more slip rings  50  are positioned around the bearing  46 . A second processing system  52 , with DSP or other imaging processing, is located near the base of the device  10 . The second processing system  52  can also include motor drivers and power regulation. 
     Operationally, images are captured by one or more single element aperture masks (SEAM)  60 . The SEAM serves to focus light onto an imaging chip by restricting the field of view and reducing the circle of confusion for each pixel of an imaging device. This can be accomplished by having a single or limited number of holes from which a single pixel receives only light passing through a single or limited number of apertures in the SEAM  60 . There is illustrated, in  FIG. 3 , one embodiment of the SEAM  60  comprising a plate  62  having at least one aperture  64  per pixel  68  and mounting holes  66   a ,  66   b  for attaching the SEAM  60  to the imaging device  10 . In the embodiment illustrated, imaging chip pixels  68  are 10 microns in size, apertures  64  are 6 microns and the SEAM  60  will be aligned perpendicular to the pixel  68  of the imaging chip. 
     The SEAM  60  is formed by drilling at least one aperture  64  into plate  62 . Plate  62  can be from about 0.05 to about 0.5 inches in thickness and can be formed of a ceramic or metal material, such as aluminum or copper, and the like. Apertures  64  can be from about 5 to about 50 microns in size, as determined by the size of the pixels  68  of the imaging device utilized. The diameter of an aperture  64  is determined by the size of a single pixel  68  and will range in size from about half the size of an individual pixel up to 5 pixels  68 . A variation of construction can also have the apertures  64  formed by channels into a material then fully assembled after the channels are manufactured, resulting in holes with the desired angle and depth. An alternate embodiment of the SEAM, seen in  FIG. 10 , shows the apertures  64  varying in angle to the individual pixels  68  of an imaging chip  18 . This alternative may not require any form of corrective lens, however, light will not always be entering the individual pixels  68  of the imaging chip  18  at a perpendicular angle to the chip  18  and pixels  68  thereof. 
     A additional alternative of the SEAM  60  can employ a series of micro-fiber optics which would produce the identical effect of the reduction of the circle of confusion. This would also have the benefit of limiting the angle at which light is received onto the imaging chip  18 , again accomplishing the goal of the SEAM. In the case of this variation, glass of other light conductive (transparent) material simply takes the place of the air or vacuum that is present in the SEAM itself. 
     In  FIGS. 4A-4C , there are illustrated examples of the introduction of light rays  70  at various angles to a photoelement  72  on an imaging chip (not shown) with a SEAM  60 . Preferably, light passing through as aperture  64  in the SEAM  60  will be aligned perpendicular to the pixel  68  of the imaging chip. Thus, by having each individual photo diode on an imaging chip sampling light from a particular angle, at a particular moment, each pixel  68  is pointed are such an angle as to scan every vertical line possible, thus allowing for increased vertical resolution, e.g. in the thousands of pixels  68  of vertical lines. 
     In one embodiment, imaging chips  18  are curved to fit an arc required for each pixel to scan an individual latitude. By “latitude, it is meant the location of a pixel on a y axis, which is also in conjunction with the central shaft  28  of the imaging device  10 . 
     So that the imaging device  10  can aim each pixel  68  at a subdivision of a degree of the minimum 90 degree arc, a corrective lens  75  ( FIG. 5 ) is interposed between the SEAM  60  and imaging chips  18  in order to direct pixels (not shown) to the angle required to scan in order to develop an image. Apertures  64  (not shown) are located along the outer edge  76  of the SEAM  60 . The chip  18 /lens  75 /SEAM  60  combination will be referred to herein as a “SEAM assembly”  78 . The lens  75  redirects light from entering from an angle into a photo element on the imaging chip  18 , such that it is perpendicular to the imaging chip  18 . It is contemplated that each imaging chip  18  be offset laterally in order to allow for overlap of scanning of each imaging/optical/SEAM assembly  78 . 
     Referring to  FIG. 7 , there is shown an exploded view of the SEAM assembly  78  of  FIG. 6 , including imaging chips  18 , corrective lens  75  and SEAM  60 . Apertures  64  (not shown) in the SEAM  60  can be aligned along a curved surface, but will remain perpendicular to the circumference of the outer edge  76  of the SEAM  60 , as well as the inner edge  80 /Light rays  70  passing through the SEAM  60  pass through apertures  64  (not shown) in the SEAM  60 . The corrective lens  75  changes the angle of the light rays  70  to be perpendicular to a pixel (not shown) on the imaging chip  18 , as shown in  FIG. 7 . 
     In  FIGS. 5-7 , in one embodiment, the corrective lens  78  is illustrated as a plano-concave lens. In normal operation, light enters the plano-concave lens  78  from the flat side and is then dispersed according to the center of the radius (R1) to the curved side of the lens and the refraction factor of the material being used (n). According to an embodiment of the present invention, the light rays  70  enter the lens  75  from the curved side and, rather than being dispersed, are turned into a series of parallel beams, allowing for maximum absorption of light for each pixel of an area or imaging chip  18 , as shown in  FIG. 8 . In  FIG. 8 , “F” is the focal point, “f” is the focal length and “C” is the center of the lens. The focal point of the plano-concave lens can thus be determined according to:
 
1 /F =( n− 1)·(1 /R )
 
     Where F is the focal point of the lens 
     n is the refractive index of the lens material; and 
     R 1  is the radius of one side of the lens; 
     A design of a plano-concave lens  78  for a SEAM  60  and imaging chip  18  of the invention can be determined with reference to  FIG. 9  and the following formulas. In one implementation, as illustrated in  FIG. 9 , the following parameters may be utilized: 
     A is the distance of the focal point of the SEAM assembly; 
     a is the angle)(90°/number of the imaging chips/2; 
     O is the imaging area/2; 
     C s  is the center of the radius of the SEAM; 
     F is the focal point of the lens; and 
     R L  is the radius of the lens. 
     Thus, the distance of the focal point of the assembly may be determined according to:
 
 A=O /tan( a )
 
     Such that A is equal to C s  which is equal to F according to:
 
 A=C   s   =F  
 
     Then R L =A·(n−1) 
     Obviously, numerous other variations and modifications can be made without departing from the spirit of the present invention. Therefore, it should be clearly understood that the forms of the present invention described above and shown in the figures of the accompanying drawing are illustrative only and are not intended to limit the scope of the present invention.