It is often desirable to transmit signals across a rotating interface. Well-known prior art solutions have provided slip rings and brushes to form electrical contacts across a rotatable interface, thereby enabling continuous, multiple 360 degree revolutions in each direction of rotation. Slip rings and brushes, however, need frequent replacement and often introduce noise into the signals being transmitted across the interface.

Nothing in the prior art is directed toward a coupler which, instead of using slip rings and brushes, uses inductively-coupled magnetic coils to transmit a power signal across a rotating interface and also uses optically-coupled optical signal transmission means to transmit one or more data and/or control signal(s) across the rotating interface, thereby enabling continuous, multiple 360 degree revolutions, in each direction of rotation, of one part of the rotating interface with respect to the other part of the rotating interface.

The following references may be relevant to the present invention: Divan et al., U.S. Patent No.

5,341,280, issued August 23, 1994; Hulsey, U.S. Patent No.

5,264,776, issued November 23, 1993; Chan et al., U.S.

Patent No. 5,245,248, issued September 14, 1993; Ishii et al., U.S. Patent No. 5,070,293, issued December 3, 1991; Grabbe, U.S. Patent No. 5,047,830, issued September 10,

1991; Dodier, U.S. Patent No. 4,838,797, issued June 13, 1989; Szabo, U.S. Patent No. 4,675,638, issued June 23, 1987; Steffen, U.S. Patent No. 4,419,783, issued December 13, 1983; Weston, U.S. Patent No. 3,995,209, issued November 30, 1976; and Crafts et al., U.S. Patent No.

3,387,606, issued June 11, 1968.

Additionally, the inventors are aware of Wheeler et al., U.S. Patent No. 4,673,268, issued June 16, 1987, which may be relevant to the present invention.

None of these references, either singly or in combination, disclose or suggest the present invention.

BRIEF SUMMARY OF THE INVENTION The present invention is a coupler for transmitting signals across a rotating interface. The coupler comprises a first part and a second part mounted for rotation about an axis with respect to the first part.

The first part comprises a first magnetic coil and first optical signal transmission means. The second part comprises a second magnetic coil being inductively coupled to the first magnetic coil and second optical signal transmission means. First and second optical signal transmission means are optically coupled for transmission of an optical signal therebetween.

It is an object of the present invention to provide a coupler which comprises means for transmitting a power signal across a rotating interface and which also comprises optically-coupled optical signal transmission means for transmitting data and/or control signal(s) across a rotating interface.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING Fig. 1 is a side sectional view of a first preferred embodiment of the present invention, taken substantially along a plane containing the axis of rotation of the first preferred embodiment.

Fig. 2 is a downward-looking sectional view a first preferred embodiment of the present invention, taken along the line 2-2 of Fig. 1.

Fig. 3 is a schematic block diagram of the present invention, shown electrically connected to a video camera.

Fig. 4 is a perspective view of a second preferred embodiment of the present invention.

Fig. 5 is a side sectional view of a second preferred embodiment of the present invention, taken substantially along a plane containing the axis of rotation of the second preferred embodiment.

DETAILED DESCRIPTION OF THE INVENTION Referring to Figs. 1 and 2, a first preferred embodiment of the present invention is seen to comprise a coupler 20 for transmitting signals across a rotating interface 22. Fig. 1 is a side sectional view of the coupler 20 taken substantially along a plane containing the axis of rotation of the coupler 20, and Fig. 2 is a downward-looking sectional view of the coupler 20 taken substantially along the line 2-2 of Fig. 1. The coupler 20 is seen to comprise a first, or bottom, part 24 and a second, or top, part 26 mounted for rotation about an axis with respect to the first part 24. The first part 24 comprises first optical signal transmission means 32 and a first magnetic coil 30, which preferably includes a first magnetic core 38 preferably formed into an upwardly-open first cylinder 56 having a circular base 58 for mounting to a stationary support, not shown. The circular base 58

has a first hole 60 therethrough for mounting first optical signal transmission means 32 along the axis of rotation. The first magnetic coil 30 is preferably wound, in a manner well-known to those skilled in the art, around the first cylinder 56. The material of first cylinder 56 that forms first magnetic core 38 is preferably a ferrous material capable of being induced with a magnetic field, such as, for example, iron.

The second part 26 comprises a second magnetic coil 34 being inductively coupled to the first magnetic coil 30, and the second part 26 also comprises second optical signal transmission means 36. The second magnetic coil 34 preferably includes a second magnetic core 40 inductively coupled to the first magnetic core 38, with second magnetic core 40 being preferably formed into a downwardly-open second cylinder 62 having an outer diameter that is slightly smaller than the inner diameter of the first cylinder 56 so that a portion of the second cylinder 62 can be mounted within the first cylinder 56, and so that a slight circumferential gap 74 is maintained between the first cylinder 56 and the second cylinder 62.

The second part 26 also includes a circular top 64 for mounting an electronic device, such as a video camera and its associated electronics, as hereinafter described. The circular top 64 has a second hole 66 there through for mounting second optical signal transmission means 36 along the axis of rotation. The second cylinder 62 preferably extends above first cylinder 56 a sufficient height to expose a portion 67 of cylinder 62 around which is circumferentially wound the second magnetic coil 34. The material of second cylinder 62 that forms second magnetic core 40 is preferably a ferrous material capable of being induced with a magnetic field, such as, for example, iron.

To minimize magnetic core losses, the first 38 and second 40 magnetic cores are preferably constructed of well-known thin ferrous disks that are concentrically stacked on top of one another along the axis of rotation so as to form the respective cores 38 and 40. To maximize the inductive coupling between the first 38 and second 40 magnetic cores, the first 38 and second 40 magnetic cores are constructed so that, when the first 24 and second 26 parts are rotated, the circumferential air gap 74 is maintained at a minimum, preferably less than 0.005 inches. It is desirable to avoid fluctuations in the inductive coupling between the first 30 and second 34 magnetic coils as the second part 26 is rotated with respect to the first part 24. Constructing and mounting the first 38 and second 40 magnetic cores so that the change in the circumferential air gap 74 remains minimal as the first 24 and second 26 parts are rotated with respect to one another helps to avoid these undesirable fluctuations in the inductive coupling. Bearings 68 are preferably used to concentrically and rotatably mount the first part 24 to the second part 26 so as to form the rotating interface 22. The bearings 68 also act to maintain a vertical air gap 72 between the first 24 and second 26 parts. The bearings 68 are constructed from a non-magnetic, non-ferrous material, thereby ensuring that the first 38 and second 40 magnetic cores are not magnetically shunted together. Many other well-known friction-reducing devices may be used to mount the first part 24 to the second part 26, as will now be apparent to those skilled in the art. For illustrative purposes and for clarity, Figs. 1 and 2 show the vertical air gap 72 and the circumferential air gap 74 with exaggerated dimensions.

First 32 and second 36 optical signal transmission

means are optically coupled for transmission of an optical signal therebetween. One of first 32 and second 36 optical signal transmission means preferably includes electrical to optical signal conversion means 46, and the other of first 32 and second 36 optical signal transmission means preferably includes optical to electrical signal conversion means 48. Electrical to optical signal conversion means 46 and optical to electrical signal conversion means 46 are optically coupled for transmission of an optical signal therebetween. In Fig. 1, first optical signal transmission means 32 includes electrical to optical signal conversion means 46 and second optical signal transmission means 36 includes optical to electrical signal conversion means 48; however, the inclusion of the signal conversion means 46, 48 within the respective signal transmission means 36, 32 could be reversed for transmission of an optical signal therebetween in the other direction, as will now be understood. First optical signal transmission means 32 also preferably includes a first optical fiber 42 and second optical signal transmission means 36 also preferably includes a second optical fiber 44. Electrical to optical signal conversion means 46 is a well-known means for converting an electrical signal, such as a first electrical video signal responsive to a scene viewed by a video camera, into an optical signal, and optical to electrical signal conversion means 48 is a well-known complementary means for converting this optical signal back into an electrical signal, such as, for example, a second electrical video signal similar to the first electrical video signal. The optical signal preferably travels from electrical to optical signal conversion means 46 to optical to electrical signal conversion means 48 via the first 42 and second 44 optical fibers. An example of such well-known conversion means for converting a first electrical signal

into an optical signal and then for converting an optical signal back into a second electrical signal are the CX- series light emitting diodes having connectors for attachment to a fiber optic bundle, and the complementary CR-series photodiodes for a similar attachment to a fiber optic bundle. These CX-series light emitting diodes and CR-series photodiodes are manufactured by Math Associates Inc., 5500 New Horizons Blvd., Amityville, NY 11701.

Fiber optic connectors for optically coupling two fiber optic cables together are those similar to the SPB-series, FCPC-series, SMAS-series, SMA6-series, and STC-series, also manufactured by Math Associates Inc. Such connectors could be used at the rotating interface to optically couple the two fiber optic cables 42 and 44 together, although the chosen connectors preferably would be of the type that allow free rotation at the connector interface.

The first optical fiber 42 extends through the first hole 60 and one end 92 of the first optical fiber 42 is mounted along the axis of rotation. The second optical fiber 44 extends through the second hole 66 and is preferably mounted within the second part 26 using a solid lightweight non-magnetic material 82, such as cork, for example. One end 94 of the second optical fiber 44 is mounted in close proximity and axially aligned with end 92 of the first optical fiber so that the first 42 and the second 44 optical fibers are optically coupled for transmission of an optical signal therebetween.

With respect to the first part 24, the second part 26 can be continuously rotated through multiple 360 degree rotations in either direction of rotation using rotation means well-known to those skilled in the art. The inductively-coupled magnetic coils 30, 34 enable electrical power to be transmitted between the first 24 and second 26 parts, and the optically-coupled optical

signal transmission means 32, 36 enable an optical signal to be transmitted between the first 24 and second 26 parts. It should be readily apparent that the coupler 20 can be used to transmit signals between numerous devices which can be inductively and optically coupled between opposite parts of the rotating interface 22.

Fig. 4 shows a perspective view and Fig. 5 shows a side sectional view taken substantially along a plane containing the axis of rotation of a second preferred embodiment of the present invention. Identifying reference designators are marked similarly to those of the first preferred embodiment, except with the prefix "2".

It shall be understood that many aspects of the two embodiments are substantially the same, and only the differences will be treated in detail, it being understood that similar structural features of both embodiments perform similar functions.

Referring to Figs. 4 and 5, a second preferred embodiment of the present invention is seen to comprise a coupler 2.20 for transmitting signals across a rotating interface 2.22. The coupler 2.20 is seen to comprise a first, or bottom, part 2.24 and a second, or top, part 2.26. The first part 2.24 comprises a first circular disk 84 having a first channel 86 that is concentric with the central axis of the first circular disk 84 and which partially extends into the depth of the first circular disk 84, as best seen in the view shown in Fig. 5. A first magnetic coil 2.30, preferably having a first magnetic core 2.38, is affixed within the first channel 86. The first circular disk 84 also has a first hole 2.60 therethrough for mounting first optical signal transmission means 2.32 along the central axis of the first circular disk 84. The second part 2.26 comprises a second circular disk 88 having a second channel 90 that is

concentric with the central axis of the second circular disk 88 and which partially extends into the depth of the second circular disk 88, as best seen in Fig. 5. The first 86 and second 90 channels are preferably constructed so that each channel 86, 90 has the same depth and width and so that the two channels 86 and 90 are in concentric alignment with each other. A second magnetic coil 2.34, preferably having a second magnetic core 2.40, is affixed within the second channel 90. The second circular disk 88 has a second hole 2.66 therethrough for mounting second optical signal transmission means 2.36 along the central axis of the second circular disk 90. The first 2.24 and second 2.26 parts are concentrically mounted for rotation with respect to each other about the common central axis of discs 84 and 88 so that the first 2.30 and second 2.34 magnetic coils are inductively coupled, the first 2.38 and second 2.40 magnetic cores are inductively coupled, and first 2.32 and second 2.36 optical signal transmission means are optically coupled. For the sake of clarity and in order to clearly show other features, Figs. 4 and 5 omit the rotatable mounting of first part 2.24 to second part 2.26, but means for such rotatable mounting of one object to another, e.g., bearings and the like, are well- known to those skilled in the art.

Fig. 3 illustrates preferred applications of the present invention. A first preferred application of the coupler 20 is in combination with a video camera 28. Fig.

3, depicts a block diagram showing the coupler 20 electrically and optically coupled to the video camera 28, with coupler 20 being enclosed within dashed lines, it being understood that either the first embodiment 20 or the second embodiment 2.20 of the coupler could be equivalently used in the block diagram shown in Fig. 3.

The coupler 20 transmits electrical power from an external

power source 78 across the rotating interface to the video camera 28, and is configured to transmit a video signal from the video camera 28 across the rotating interface 22 to the video recorder or display 76. For illustrative purposes, the video camera 28 is shown spaced apart from the coupler 20, although preferably the video camera 28 is, directly or indirectly, physically mounted on the second part 26. Preferably, coupler 20 will be included and mounted within a well-known "pan and tilt" mechanism 70 at a rotating interface therewithin.

The first part 24 is mounted on a base, not shown, to support the coupler 20 and the video camera 28. First optical signal transmission means 32 includes optical to electrical signal conversion means 48 and the first optical fiber 42; second optical signal transmission means 36 includes electrical to optical signal conversion means 46 and the second optical fiber 44. The first magnetic coil 30 is electrically coupled to a power source 78, which supplies an alternating current voltage so as to induce a magnetic field from the second magnetic coil 34, with the induced magnetic field providing power for the video camera 28. The video camera 28 includes video camera power input means, such as wires 50, operably connected to the second magnetic coil 34 for receiving electrical power therefrom and for distributing the induced electrical power to the video camera 28.

Depending upon the power requirements of the video camera 28, the second magnetic coil 34 could be directly operably connected to video camera power input means 50, thereby providing alternating current power to camera 28, or could be operably connected through a well-known alternating current to direct current ("A.C. to D.C.") converter 80, as shown in Fig. 3.

Video camera 28 also includes a signal output means, such as wires 54, operably connected to well-known electrical to optical signal conversion means 46 to provide an electrical video signal to electrical to optical signal conversion means 46. Electrical to optical signal conversion means 46 converts the electrical video output signal into an optical signal, the optical signal then travels from the second optical fiber 44 to the optically-coupled first optical fiber 42, and well-known optical to electrical signal conversion means 48 then converts the optical signal back into an electrical video signal similar to the video signal produced by camera 28.

The video camera 28 can thus be continuously rotated through multiple 360 degree rotations in either direction of rotation, and the electrical video signal that is transmitted across the rotating interface by coupler 20 can then be processed by one or more of numerous electrical equipment well-known in the art, such as video recorder/display 76, for example.

It should also be understood that second optical signal transmission means 36, in addition to being a well- known uni-directional electrical to optical signal conversion means 46, could instead also be bi-directional and also include well-known optical to electrical signal conversion means. Similarly, first optical signal transmission means 32, in addition to being a well-known optical to electrical signal conversion means 48, could instead also be bi-directional and include well-known electrical to optical signal conversion means. By such a structure, optical signals and/or control signals could flow bi-directionally across the rotating interface 22.

A second preferred application of the coupler 20 is for use in combination with a pan and tilt mechanism 70 having a variable elevation and a variable azimuth. Using

a video camera 28 with the combination of the coupler 20 and the pan and tilt mechanism 70 enables continuous multiple 360 degree rotations of the video camera 28 in each direction of rotation, and enables the video camera 28 to be upwardly and downwardly tilted. As with the first preferred application, electrical power, control and video signals are transmitted across the rotating interface 22 of the coupler 20. The construction of pan and tilt mechanisms are well-known in the art, and one example of a pan and tilt mechanism for mounting a video camera thereupon is shown in Wheeler et al., U.S. Patent No. 4,673,268, issued Jun. 16, 1987, which is herein incorporated fully by reference.

Referring to Fig. 3, the second preferred application of the coupler 20 can also be seen. First 32 and second 36 optical signal transmission means are constructed to be bi-directional, as previously discussed, so that each includes electrical to optical signal conversion means and optical to electrical signal conversion means. The pan and tilt mechanism 70 includes a pan and tilt mechanism control input/output means, such as wires 52, operably connected to the optical to electrical signal conversion means 46 included as a part of second optical signal transmission means 36, for receiving a first electrical control signal. Well-known pan and tilt control means 71, responsive to the first electrical control signal, are provided for selectively altering the azimuth and elevation of the pan and tilt mechanism in response to the first electrical control signal, in a manner well-known to those skilled in the art. A second electrical signal flows from the operators panel 96 to electrical to optical signal conversion means 48 included with first optical signal transmission means 32. Electrical to optical signal conversion means 48 converts the electrical signal to an optical signal, the optical signal then travels from

the first optical fiber 42 to the optically-coupled second optical fiber 44, and optical to electrical signal conversion means 46 included with second optical signal transmission means 36 converts the optical signal back to an electrical signal. This electrical signal is then received by the pan and tilt mechanism control input/output means 52 and is passed to pan and tilt control means 71 to cause selective alteration of the azimuth and elevation of the pan and tilt mechanism 70 in response to manipulation of the operator's panel 96.

Pan and tilt mechanism 70 includes pan and tilt mechanism power input means, such as wires 100, operably connected to the second magnetic coil 34 for receiving electrical power therefrom and distributing the electrical power to the pan and tilt mechanism 70 and to pan and tilt control means 71. Electrical power is supplied to the pan and tilt mechanism power input means 100 from the second magnetic coil 34 in a manner similar to that already discussed regarding video camera power input means 50.

Referring to Fig. 3, the third preferred application of the coupler 20 in combination with a video camera 28 can also be seen. First 32 and second 36 optical signal transmission means are constructed to be bi-directional, as previously discussed, so that each includes electrical to optical signal conversion means and optical to electrical signal conversion means. The video camera 28 is, directly or indirectly, physically mounted on the second part 26. The video camera 28 includes variable focus means 102 for varying the focus of camera 28, and includes a video camera control input/output means, such as wires 98, operably connected to optical to electrical signal conversion means 46 included with second optical signal transmission means 36. An electrical control

signal flows from the operators panel 96 to electrical to optical signal conversion means 48 included with first optical signal transmission means 32. Electrical to optical signal conversion means 48 converts the electrical control signal from the operator's panel to an optical signal, the optical signal travels from the first optical fiber 42 to the optically-coupled second optical fiber 44, and optical to electrical signal conversion means 46 included with second optical signal transmission means 36 converts the optical signal back to an electrical control signal similar to that emitted from the operator's panel 96. This electrical control signal is received by the video camera control input/output means 98 and is supplied to variable focus means 102, which is responsive to this electrical control signal, and which responds by varying the focusing of the video camera 28, in a manner well- known to those skilled in the art. The video camera 28 includes video camera power input means 50 for receiving electrical power from coil 34 and for distributing the electrical power to the video camera 28, in a manner similar to that already heretofore described.

It is now apparent that all of the aforementioned applications could be combined so that electrical power, video signals, signals to control the focusing of the video camera 28, and signals to control the pan and tilt mechanism 70 are transmitted across the rotating interface 22 of the coupler 20.

Although the present invention has been described and illustrated with respect to a preferred embodiment and a preferred use therefor, it is not to be so limited since modifications and changes can be made therein which are within the full intended scope of the invention.