Improved point source electromagnetic radiation emitters including a dispersing element that radiates electromagnetic radiation over a vary wide conical angle of approaching about 180°. This light dispersing element can be in any one or more of several illustrated forms such as a light diffusing spherical or hemispherical element, a planar diffusing plate, a tapered light guide, a piano-concave lens, a convex mirror, a light pipe with a large numerical aperture, or the like. The emitter of this invention may be fixed to an object and tracked in a 3-dimensional volume by a system using electro-optical position sensors in order to determine the spatial location of the emitters and therefore to determine, by geometry, the position or orientation of the object. The electromagnetic radiation generator is preferably disposed remote from the emitter and is electrically and magnetically isolated from the emitter. A common optical fiber provides transmission of the radiation from the generator to the emitter. The emitted radiation more nearly resembles point source of radiation and therefore enables more accurate determination of the location of the radiating element, and thereby more accurate determination of the position and orientation of the object on which the emitters reside. The preferred electromagnetic radiation generator is an LED, most preferably a laser diode.
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0. 60. A method of accurately determining the location of a point in three dimensional space which comprises:
electrically generating electromagnetic radiation;
non-electrically transmitting said electromagnetic radiation to at least one emitter comprising a radiation dispersing element adapted to emit electromagnetic radiation therefrom through a solid angle at least approaching a hemisphere; and
non-electrically emitting said electromagnetic radiation from said dispersing element in a pattern over a solid angle that at least approaches about a hemisphere.
0. 68. An electrically neutral system for radiating electromagnetic radiation from an effective point source and remotely receiving the same, comprising:
at least one source of electromagnetic radiation;
lens means adapted to couple said electromagnetic radiation to a plurality of non-electronic radiation transmission means;
at least one emitter, adapted to radiate electromagnetic radiation through a solid angle that at least approaches a hemisphere, electromagnetically coupled to at least one of said transmission means and spaced apart from said source; and
a plurality of means adapted to receive said radiated electromagnetic radiation spaced from said emitter(s) and not electrically connected to said emitters.
0. 56. An electrically neutral system for radiating electromagnetic radiation from an effective point source comprising:
an electromagnetic radiation generator;
an emitter of electromagnetic radiation comprising a radiation dispersing element that emits said electromagnetic radiation in a substantially conical pattern through a solid angle that at least approaches a hemisphere, and wherein said emitter is disposed a distance from said generator;
at least one optical fiber disposed in operative relationship to both said generator and said emitter such that it is adapted to transmit electromagnetic radiation from said generator to said emitter; and
an electric power source operatively associated with said electromagnetic radiation generator, wherein said generator is substantially electrically and magnetically isolated from said emitter.
39. A method of accurately determining the location of a point in three dimensional space which comprises:
electrically generating electromagnetic radiation;
non-electrically transmitting said electromagnetic radiation to an emitter, comprising a radiation dispersing element, so constructed as to emit electromagnetic radiation therefrom in a conical array through a solid angle at least approaching 180° a hemisphere;
non-electrically emitting said electromagnetic radiation from said dispersing element in a substantially conical pattern over a solid angle that at least approaches about 180° a hemisphere; and
thereby causing a centroid of said emitted electromagnetic radiation to at least closely approximate a point source of said radiation which is substantially invariant with respect to the emitter of said radiation regardless of the angle from which said emitted radiation is viewed.
0. 67. A method of accurately determining the location of a point in three dimensional space comprising:
generating electromagnetic radiation;
non-electrically transmitting and electromagnetic radiation to at least one emitter, comprising at least one radiation dispersing element adapted to emit electromagnetic radiation therefrom through a solid angle at least approaching about a hemisphere;
non-electrically emitting said electromagnetic radiation from said dispersing element at a solid angle approaching about a hemisphere;
receiving a plurality of electromagnetic rays, emitted by said emitter, by an electromagnetic radiation detector;
determining angles intercepted between said rays and at least one reference line that has a known angular relationship with said radiation detector; and
from said angle, calculating a location of said emitter in said three dimensional space.
0. 50. An electrically neutral system for radiating electromagnetic radiation from an effective point source comprising:
at least one electromagnetic radiation generator;
at least one emitter of electromagnetic radiation comprising means for emitting radiation through a solid angle that at least approaches a hemisphere,
wherein said radiation emission has a centroid such that is at least closely approximates a point source of said radiation; and
wherein said emitter(s) is disposed a distance from said generator(s),
at least one optical fiber disposed in operative relationship to said generator(s) and said emitter(s) such that the fiber is adapted to transmit electromagnetic radiation from said generator(s) to said emitter(s); and
an electric power source operatively associated with said electromagnetic radiation generator, wherein said generator is substantially electrically and magnetically isolated from said emitter.
20. An electrically neutral system for radiating electromagnetic radiation from an effective point source comprising:
an electromagnetic radiation generators;
an emitter of electromagnetic radiation comprising a radiation dispersing element which emits said electromagnetic radiation in a substantially conical pattern through a solid angle which at least approaches 180° a hemisphere,
wherein said radiation emission has a centroid such that it at least closely approximates a point source of said radiation thereby causing said centroid of said electromagnetic radiation to be in a substantially invariant relationship to the emitter of said radiation regardless of the angle from which the centroid of emitted radiation is viewed, and
wherein said emitter is disposed a distance from said generator;
at least one optical filter disposed in operative relationship to both said generator and said emitter such that it is adapted to transmit electromagnetic radiation from said generator to said emitter; and
an electric power source operatively associated with said electromagnetic radiation generator, wherein said generator is substantially electrically and magnetically isolated from said emitter.
0. 51. A method of determining the position and orientation of at least one three dimensional object in a three dimensional space, defined by a coordinate system, which comprises:
disposing a plurality of electromagnetic emitters, comprising a dispersing element so constructed as to radiate electromagnetic radiation over a solid angle that at least approaches about a hemisphere in known spaced apart relationship to each other on a surface of said object;
providing at least one electromagnetic radiation generator spaced from said object;
providing at least one non-electric radiation guide means operatively associated with said emitter(s) and with said at least one generator(s);
generating electromagnetic radiation from generator(s);
transmitting said radiation, non-electrically through said radiation guide(s) to said emitter(s);
non-electrically radiating radiation from at least one of said dispersing elements;
receiving said emitted radiation by a plurality of electromagnetic radiation receivers;
determining the location of each emitter as a function of the angles between said received radiation and respective reference lines; and
converting said determined locations of said emitters to a position and orientation of said object in said three dimensional space.
0. 63. An apparatus for determining the location of at least one point in three dimensional space relative to a three dimensional coordinate system defining said space comprising:
at least one emitter of electromagnetic radiation, comprising a radiation dispersing element that disperses electromagnetic rays emitted from said emitter in a pattern that at least approaches a solid angle at least about equal to a hemisphere and has a radiation pattern that at least closely approximates that of a point source of said radiation over said solid angle;
a plurality of electromagnetic radiation sensors, each of which is adapted to detect at least one electromagnetic ray emitted from at least one of said emitters, and to convert said detected ray into a signal;
where there are a plurality of emitters, means to differentiate at least two of said emitters; and
a signal processor adapted to calculate the location of said emitter(s) relative to the three dimensional coordinate system from said signal information;
wherein, as a consequence of said emitter(s) emitting electromagnetic radiation through said solid angle, determining the location of the centroid(s) of said emitter(s) with greater accuracy than would have been the accuracy determined had that electromagnetic radiation been generated without said dispersing element.
42. A method of determining the position and orientation of at least one three dimensional object in a three dimensional space defined by a coordinate system which comprises:
disposing a plurality of electromagnetic emitters, comprising a dispersing element so constructed as to radiate electromagnetic radiation in a substantially conical pattern over a solid angle that at least approaches about 180° a hemisphere in known spaced apart relationship to each other on a surface of said object;
providing at least one electromagnetic radiation generator spaced from said object;
providing a non-electric radiation guide operatively associated with each emitter and with said at least one generator;
generating electromagnetic radiation from each of said generators;
transmitting said radiation, non-electrically through said radiation guides to said emitters;
non-electrically radiating a substantially conical pattern of radiation from at least one of said dispersing elements;
receiving said emitted radiation by a plurality of electromagnetic radiation receivers;
determining the location of each emitter as a function of the angles between said received radiation and respective reference lines; and
converting said determined locations of said emitters to a position and orientation of said object in said three dimensional space.
0. 61. A method of determining the position and orientation of at least one three dimensional object in a three dimensional space defined by a three dimensional coordinate system which comprises:
disposing a plurality of electromagnetic emitters, comprising a dispersing element adapted to radiate electromagnetic radiation in a substantially conical pattern over a solid angle that at least approaches about a hemisphere, in known spaced apart relationship to each other on a surface of said object;
providing at least one electromagnetic radiation generator spaced from said emitter(s);
providing a non-electric radiation guide operatively associated at least one of said emitters and with said at least one generator;
generating electromagnetic radiation by said generator(s);
non-electrically transmitting electromagnetic radiation through said radiation guides to said emitter(s);
non-electrically radiating a pattern of radiation at least approaching a hemisphere from at least one of said dispersing elements;
receiving said emitted radiation by a plurality of electromagnetic radiation receivers;
determining the location of each emitter as a function of angles between said received radiation and respective reference lines; and
converting said determined locations of said emitters to a position and orientation of said object in said three dimensional space.
0. 52. An apparatus for determining the location of at least one point in three dimensional space relative to a three dimensional coordinate system defining said space comprising:
at least one emitter of electromagnetic radiation, comprising a radiation dispersing element that is adapted to emit said radiation in a substantially conical pattern that at least approaches a solid angle at least about equal to a hemisphere;
an electromagnetic radiation generator operatively associated with at least one of said emitters;
means for transmitting electromagnetic radiation generated by said generator to said associated emitter;
a plurality of electromagnetic radiation sensors, each of which is adapted to detect at least one electromagnetic ray emitted from at least one of said emitters;
where there are a plurality of emitters, means to differentiate electromagnetic radiation emitted by at least two of said emitters; and
means for determining the location of said emitter(s) relative to said three dimensional coordinate system as a function of a plurality of angles intercepted between rays of said radiation and at least one reference line;
wherein, as a consequence of said emitters emitting electromagnetic radiation at a solid angle at least approaching a hemisphere, determining the location of said emitters with greater accuracy that would have been the accuracy determined had the electromagnetic radiation been generated without said dispersing element.
1. An apparatus for determining the location of at least one point in three dimensional space relative to a three dimensional coordinate system defining said space comprising:
at least one emitter of electromagnetic radiation, comprising a radiation dispersing element which emits said radiation in a substantially conical pattern which at least approaches a solid angle of about 180° hemisphere, wherein said radiation emission pattern has a centroid such that it at least closely approximates a point source of said radiation thereby causing said centroid of said electromagnetic radiation to be in a substantially invariant relationship to said emitter of said radiation regardless of the angle from which the centroid of the emitted radiation is viewed;
an electromagnetic radiation generator operatively associated with each of said emitters;
means for transmitting electromagnetic radiation generated by said generator to said emitter;
a plurality of electromagnetic radiation sensors, each of which is adapted to detect at least one electromagnetic ray emitted from at least one of said emitters;
a power supply for said electromagnetic radiation generator;
where there are a plurality of emitters, means to differentiate electromagnetic radiation emitted by at least two of said emitters; and
means for determining the location of said emitter relative to the three dimensional coordinate system;
wherein, as a consequence of said emitters emitting electromagnetic radiation at a solid angle of at least approaching 180 ° a hemisphere determining the location of a said emitters with greater accuracy than would have been the accuracy determined had the electromagnetic radiation been generated without said dispersing element.
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This invention relates to improved emitters of electromagnetic rays. It more particularly refers to such emitters that are more nearly perfect point sources of electromagnetic rays than have been available in the prior art. It also refers to a novel method of determining the location of points in three dimensional space using such nearly perfect point sources of electromagnetic radiation.
The electromagnetic rays to which this invention refers are often, but not necessarily, in the viable spectrum. The substantially point source emitters of this invention are suited to be disposed on a supporting object, of known size and shape, whose position and orientation are being determined in a three dimensional coordinate system from a determination of the locations of these emitters in the same coordinate system. They may also be disposed on one or more stationary and/or moving objects, of known size and shape, whose position(s) and orientation(s) and being tracked as it moves in space within a three dimensional coordinate system. In this use as a position and orientation determinant, the emitter is seen by a plurality of electromagnetic ray receptors, which are generally referred to herein as cameras.
The straight ray lines between a plurality of either the emitter(s), or the camera(s), or both, can be compared to straight reference lines to thus form a plurality of angles from which geometric information is obtained. This geometric information can, in turn, be used to determine the precise location(s) of the emitter(s) in space, and from these emitter locations, if the shape and size of the object are known, the position and orientation of the object on which the emitter(s) reside can be determined geometrically. Since the location of the emitter(s) can be tracked substantially continuously, or at least very frequently, movements of the object on which they are disposed can be tracked. The more frequently the locations of the emitters are determined, the more precise is the movement tracking ability of the system. Further, the smaller and less variant the emitter source of the electromagnetic rays, the more accurately can its location be determined. That is, the closer the emitter assembles a point source, which is in the same apparent location Aseen≅Asunset≅ sunset situation, the centroid of the visible portion of the square will shift away from the geometrical center of the sphere.
The sunset situation can be eliminated by using a planar diffuser, such as the one shown in the configuration depicted in
A second embodiment of the optical element 26 of this invention is shown in FIG. 4. In this case the light is widely dispersed by means of a special optical fiber bundle 26b called an image guide or a light pipe. It is preferably tapered to concentrate the light into a smaller spot and it has a high numerical index to widen the emission angle of the cone of radiation. Such fiber bundles are available from Collimated Holes, Inc., (Campbell, Calif.).
In any embodiment of this invention, the optical fiber bundles may be randomly organized and need not preserve image geometry because they are only being used as light transmitters. If the fibers of the light pipe have a high index of refraction (a numerical aperture value near 1.0), the light will be radiated through out substantially, a full hemispherical pattern. Even though the intensity of light diminishes with the cosine of the angle of the direction of radiation (measured relative to the optical axis of the fibers, far more light is radiated in directions which are substantially parallel to the axis of the fibers and much less at steeper angles) Even so, there is sufficient radiated light to be “seen” by the camera array. This is shown in
Note that in the embodiment shown in this figure, the whole optical fiber 24 and the light pipe 26b could be one and the same element if they were properly designed. That is, the optical fiber 24 may simply be a long flexible light guide with a large (wide) numerical aperture at its end. Conventional optical fibers have not been found to produce satisfactory large conical emission angles, without first being modified. Therefore, this aspect of this large conical emission angles, without first being modified. Therefore, this aspect of this invention has been developed specifically to overcome this deficiency.
Note should be taken that, in the embodiment shown in this
A third embodiment of the optical element 26 is shown in
A fourth embodiment of the optical element 26 of this invention is shown in FIG. 7. In this embodiment, the light coming out of the transmitting optical fibers is reflected off of a tiny curved (hyperbolic) mirror 26d. This is the reflective optical counterpart to the refractive element 26c shown in other figures. The advantage of this arrangement is that the light can be spread over a wide annular ring of angles. The drawback to this arrangement is that the optical fiber or the mirror itself eclipses the reflected light at angles near the optical axis (both forward and backward).
The above description has presented four specific embodiments of the operationally substantially at least hemispherical optical radiating elements of this invention. Each of these embodiments is illustrative of the instant invented means of making optical fibers practical for use in an electro-optical system for tracking an object, such as a probe or pointer, with two or more point source light emitters. The optical elements facilitate increased accuracy, nearly perfect electrical and magnetic isolation, and no generation of spurious radiation. The passive optical fibers on the object itself potentially reduce the cost enough that disposable surgical probes would be economically feasible. Further, the optical fibers are more robust than LED's and are therefore more suitable for autoclaving in medical environments. Lastly, the optical light source can be a laser (diode or gas) which has the potential for generating more light than the simple LED used in the prior art.
While this invention has been described above with reference to several preferred embodiments, a person of ordinary skill in the art should be able to readily visualize alternative embodiments which do not materially depart from the scope of this invention. Therefore, the scope and content of this invention are not limited by the foregoing description. Rather, the scope and content are to be defined by the following claims.
Harrison, Daniel J., Faul, Ivan, Schulz, Waldean A., Pasquini, Ronald M.
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