Thermal imaging device and method

Claim 1

A thermal imaging device comprising: an objective lens for receiving and focusing invisible infrared light from a scene; a movable scanner for receiving and reflecting infrared light from said objective lens; a detector for receiving the reflected infrared light from said scanner and responsively providing electrical signals; a processing circuit for receiving the electrical signals from said detector and responsively providing imaging electrical signals; a display device for receiving the imaging electrical signals and responsively providing a visible image replicating the scene; said movable scanner carrying a circular magnetic track having alternating opposite magnetic domains providing circumferentially varying magnetic flux extending between said magnetic domains, said circumferentially varying magnetic flux having plural magnetic flux minima alternating with plural magnetic flux maxima both arrayed circumferentially around said magnetic track; a sensor head having plural magneto-resistive elements disposed to be affected by said alternating opposite magnetic domains as said scanner moves, said sensor head disposing said magneto-resistive elements to align in two groups of elements each including at least an alternate pair of said plural elements, each element of each of said two groups of elements individually aligning substantially simultaneously with one of a respective magnetic flux maxima or with a magnetic flux minima of said magnetic domains, and a bifurcated sensor circuit having a pair of opposite branches and connecting said magneto-resistive elements of one of said two groups of elements in series with one another in one of said opposite branches and also connecting said magneto-resistive elements of the other of said two groups in the other of said opposite branches, whereby all of said plural magneto-resistive elements in said two groups of elements are simultaneously exposed to one of a respective flux maxima and flux minima as said scanner moves.

Claim 8

A method of operating a thermal imaging device comprising steps of: providing an electrical detector for infrared light; providing a rotational multi-faceted scanner mirror receiving and reflecting infrared light from a scene to said detector; using said detector to responsively provide electrical signals; using a display device to receive said electrical signals and to responsively provide a visible image replicating the scene; providing an annular magnetic track on said scanner mirror which magnetic track provides a plurality of adjacent magnetic domains of known substantially uniform pitch dimension and alternating magnetic polarity disposed around said magnetic track, said plurality of magnetic domains providing magnetic flux fields varying circumferentially of said magnetic track, which magnetic flux fields alternate between a maxima value between adjacent domains and a minima value substantially at the center of each domain; providing a stationary sensor head having plural magneto-resistive elements disposed to be affected by said alternating opposite magnetic domains as said scanner mirror rotates, said sensor head disposing all of said magneto-resistive elements to align in alternate pairs with respective magnetic flux maxima and magnetic flux minima of said magnetic domains, and a bifurcated sensor circuit having a pair of opposite branches and connecting said magneto-resistive elements aligning with a magnetic flux minima in series with one another in one of said opposite branches and also connecting said magneto-resistive elements aligning with a magnetic flux maxima in series in the other of said opposite branches, whereby said magneto-resistive elements in said alternate pairs are substantially simultaneously exposed to respective flux maxima and flux minima as said scanner mirror rotates; applying a voltage between a center tap of said bifurcated electrical circuit and said opposite branches thereof, and using alternating voltage drop signals appearing between said opposite branches and said center tap in opposition to one another to sense relative rotation of said scanner mirror past said sensor head.

Claim 9

A method of operating a thermal imaging device comprising steps of: providing an electrical detector for infrared light; providing a rotational multi-faceted scanner mirror receiving and reflecting infrared light from a scene to said detector; using said detector to responsively provide electrical signals; using a display device to receive said electrical signals and to responsively provide a visible image replicating the scene; providing an annular magnetic track on said scanner mirror which magnetic track provides a plurality of adjacent magnetic domains of known substantially uniform pitch dimension and alternating magnetic polarity disposed around said magnetic track, said plurality of magnetic domains providing magnetic flux fields varying circumferentially of said magnetic track, which magnetic flux fields alternate between a maxima value between adjacent domains and a minima value substantially at the center of each domain; providing a stationary sensor head having plural magneto-resistive elements disposed to be affected by said alternating opposite magnetic domains as said scanner mirror rotates, said sensor head disposing all of said magneto-resistive elements to align in alternate pairs with respective magnetic flux maxima and magnetic flux minima of said magnetic domains, and a bifurcated sensor circuit having a pair of opposite branches and connecting said magneto-resistive elements aligning with a magnetic flux minima in series with one another in one of said opposite branches and also connecting said magneto-resistive elements aligning with a magnetic flux maxima in series in the other of said opposite branches, whereby said magneto-resistive elements in said alternate pairs are substantially simultaneously exposed to respective flux maxima and flux minima as said scanner mirror rotates; applying a voltage between a center tap of said bifurcated electrical circuit and said opposite branches thereof, and using alternating voltage drop signals appearing between said opposite branches and said center tap in opposition to one another to sense relative rotation of said scanner mirror past said sensor head.