In vivo camera with multiple sources to illuminate tissue at different distances
An in vivo endoscope illuminates tissue using multiple sources. Light from a short-range source exits a tubular wall of the endoscope through a first illumination region that overlaps an imaging region, and the light returns through the imaging region after reflection by tissue, to form an image in a camera. Light from a long-range source exits the tubular wall through a second illumination region that does not overlap the imaging region. The endoscope of some embodiments includes a mirror, and light from an emitter for the short-range source is split and reaches the first illumination region from both sides of an optical axis of the camera. Illuminating the first illumination region with split fractions of light results in greater uniformity of illumination, than illuminating directly with an un-split beam. The energy generated by each source is changed depending on distance of the tissue to be imaged.
1. A device comprising:
a plurality of emitters of electromagnetic radiation enclosed within a housing, the housing comprising a tubular wall, said plurality of emitters being located in a ring around a camera;
an optical element enclosed within said housing, the optical element being located in a path of a portion of electromagnetic radiation emitted by at least one emitter in the plurality of emitters so as to direct at least a first fraction of said portion of electromagnetic radiation out through the housing, at least a portion of the optical element being on a first side of a lateral plane and said at least one emitter being on a second side of the lateral plane, wherein the optical element comprises a concentrator shaped to reduce angular divergence of at least said portion of electromagnetic radiation;
wherein all electromagnetic radiation from said at least one emitter is emitted on the second side of the lateral plane;
wherein the lateral plane is perpendicular to a longitudinal axis of the housing, the housing having a dimension along the longitudinal axis larger than any dimension within the lateral plane;
wherein the camera is positioned within the housing such that at least a portion of an image is formed in said camera by at least a second fraction of said portion of electromagnetic radiation entering through the tubular wall on the first side of the lateral plane after reflection outside the housing.
2. The device of claim 1 wherein:
the concentrator comprises a mirrored surface.
3. The device of claim 2 wherein the mirrored surface is at least partially annular.
4. The device of claim 1 wherein said portion of electromagnetic radiation is hereinafter a first portion, and wherein:
a second portion of electromagnetic radiation exits the housing without being directed by the optical element.
5. The device of claim 4 wherein:
at least one ray in the second portion of electromagnetic radiation passes through apertures in the optical element from a location of said at least one emitter.
6. The device of claim 1 wherein the housing has a near and a far end, the housing comprising a dome at the far end, wherein said portion of electromagnetic radiation is hereinafter a first portion, and wherein:
the optical element comprises a mirrored surface offset in a longitudinal direction from an optical axis of the camera towards the far end;
each emitter in the plurality of emitters is offset in the longitudinal direction from the optical axis of the camera towards the far end; and
the mirrored surface is located in a path of a second portion of electromagnetic radiation emitted by said at least one emitter in the plurality of emitters so as to reflect at least a fraction of said second portion of electromagnetic radiation out through the housing.
7. The device of claim 6 wherein said plurality of emitters are hereinafter a first plurality of emitters and wherein:
the device further comprises a second plurality of emitters; and
the second plurality of emitters are offset in said longitudinal direction from said optical axis toward the near end.
8. The device of claim 7 wherein:
the second plurality of emitters are positioned between another dome and an additional mirror, and the additional mirror acts as a baffle to block rays originating in at least one emitter in the second plurality of emitters from forming a virtual image that can be captured by the camera.
9. The device of claim 7 further comprising a baffle enclosed within the housing, wherein:
the second plurality of emitters are positioned behind the baffle to block rays originating in at least one emitter in the second plurality of emitters from forming a virtual image that can be captured by the camera.
10. The device of claim 1 wherein:
the concentrator has an input aperture facing said at least one emitter and an output aperture at which said portion of electromagnetic radiation has reduced angular divergence; and
the optical element has an additional input aperture and an additional output aperture such that an additional portion of electromagnetic radiation emitted by said at least one emitter enters the optical element through said additional input aperture and exits the optical element at said additional output aperture.
11. The device of claim 1 wherein:
the optical element comprises a mirrored surface on one side of a layer; and
said layer has another side that reflects at least a fraction of an additional portion of electromagnetic radiation emitted by said at least one emitter.
12. The device of claim 1 wherein:
a longitudinal plane passes through a point (hereinafter “intersection point”) formed by intersection of a surface of said housing with an optical axis of said camera, the longitudinal plane further passes through a center of curvature C of an arc AB, the arc AB being defined by intersection of said surface of said housing with an additional lateral plane parallel to the optical axis and passing through said intersection point, the additional lateral plane and the longitudinal plane being oriented perpendicular to one another; and
the optical element limits angular divergence of at least some illumination rays emitted from said at least one emitter such that a projection on to said longitudinal plane, of an illumination ray in said majority, after reflection from said intersection point, makes an angle θi with a normal to said surface of said housing such that θi>θ FOV +α wherein θ FOV is half angle of a field of view of the camera projected in the longitudinal plane and α is an angle between said normal and said optical axis.
13. The device of claim 1 wherein:
a first illumination ray emitted by said at least one emitter is incident on the housing with angle of incidence θ i and is reflected with an identical angle of reflection relative to a line N that bisects an angle formed by said first illumination ray and a reflected ray resulting from reflection of said first illumination ray by said housing;
a point U exists at the intersection of a first line collinear with the incident ray and a second line collinear with the reflected ray;
a first image forming ray forms an angle σ with line N, said first image forming ray being comprised in a plurality of image forming rays, said plurality of image forming rays forming a cropped portion of said image supplied to a transmitter comprised in said device;
additional illumination rays from said at least one emitter are restricted in angle such that θ i >σ for a majority of pairs of any additional illumination ray incident on the housing and a corresponding additional image forming ray comprised in said plurality of image forming rays;
the first image forming ray, when located within a free space between the housing and the camera, is collinear to a line passing through said point U and a pupil of the camera; and
said line is coplanar with said first illumination ray and said reflected ray.
14. The device of claim 1 wherein:
the optical element has an annular shape; and
the optical element comprises multiple concentrators including said concentrator.
15. The device of claim 14 wherein:
the optical element comprises a plurality of spokes between an inner sidewall and an outer sidewall; and
a mirrored surface is located between walls of two adjacent spokes; and
the mirrored surface is formed on one of the inner sidewall or the outer sidewall.
16. The device of claim 15 wherein the mirrored surface is hereinafter a first mirrored surface, and wherein:
a second mirrored surface is located between walls of two adjacent radial spokes;
the spokes are located between an inner sidewall and an outer sidewall; and
the second mirrored surface is formed on one of the inner sidewall or the outer sidewall.
17. The device of claim 15 wherein:
the mirrored surface and said walls of the two adjacent spokes and an additional mirrored surface define a boundary of an input aperture of the optical element; and
said at least one emitter is located directly facing the input aperture.
18. The device of claim 1 wherein:
said at least one emitter comprises a light emitting diode (LED) encapsulated within a cavity of a package; and
the optical element is mounted on the package with at least a portion of an outer sidewall of the optical element overhanging an opening of the cavity.
19. The device of claim 18 wherein:
said opening of the cavity is of an area larger than an area of an input aperture of said optical element facing said at least one emitter.
20. The device of claim 1 wherein:
the optical element is entirely on the first side of the lateral plane and said at least one emitter is in a cavity of a package on the second side of the lateral plane.
21. The device of claim 1 comprising a wall enclosed within the housing, wherein:
a plurality of paths correspond to a plurality of rays originating from a specific emitter in the plurality of emitters, the plurality of paths pass through the wall to reach the housing and the rays reflect therefrom to form within said housing, a mirror image of the specific emitter, in the absence of the wall; and
the wall is opaque and positioned adjacent to the specific emitter to block passage of the plurality of rays along said paths to prevent said formation of said mirror image by said plurality of rays.
22. The device of claim 21 wherein:
the wall is annular.
23. The device of claim 1 further comprising a baffle enclosed within the housing, wherein:
the baffle is positioned to block rays originating in at least one emitter in the plurality of emitters from forming a virtual image that can be captured by the camera.
24. The device of claim 1 wherein:
the concentrator comprises a lens.
25. The device of claim 24 wherein:
the lens is a collimating lens.
26. The device of claim 1 wherein:
the concentrator has an optical axis that passes through a location of said at least one emitter.
27. The device of claim 1 wherein:
the camera comprises a pupil;
at least the second fraction of said portion of electromagnetic radiation passes through the pupil after entering the housing; and
the pupil is closer to the optical element than to said at least one emitter.
28. The device of claim 1 wherein:
the camera has at least one optical axis; and
said at least one optical axis is closer to the optical element than to said at least one emitter.
29. The device of claim 1 wherein:
the first fraction of said portion of electromagnetic radiation exits the housing through the tubular wall.
30. A method of imaging comprising:
emitting electromagnetic radiation by at least one emitter in a plurality of emitters enclosed within a housing, the housing comprising a tubular wall;
wherein the plurality of emitters are located in a ring around a camera;
wherein an optical element is enclosed within said housing and the optical element is located in a path of a portion of electromagnetic radiation emitted by said at least one emitter in the plurality of emitters so as to direct at least a first fraction of said portion of electromagnetic radiation out through the housing, at least a portion of the optical element being on a first side of a lateral plane and said at least one emitter being on a second side of the lateral plane, wherein the optical element comprises a concentrator shaped to reduce angular divergence of at least said portion of electromagnetic radiation;
wherein all electromagnetic radiation from said at least one emitter is emitted on the second side of the lateral plane;
wherein the lateral plane is perpendicular to a longitudinal axis of the housing, the housing having a dimension along the longitudinal axis larger than any dimension within the lateral plane; and
sensing an image in the camera;
wherein at least a portion of the image is created in the camera by at least a second fraction of said portion of said electromagnetic radiation entering through the tubular wall on the first side of the lateral plane after reflection outside the housing.
31. The method of claim 30 wherein:
the optical element comprises a mirrored surface.
32. The method of claim 30 wherein:
the optical element is annular.
33. The method of claim 30 , wherein the concentrator has an optical axis that passes through a location of said at least one emitter.
34. The method of claim 30 wherein the housing has a near and a far end, and wherein:
the housing further encloses a mirrored surface offset in a longitudinal direction from an optical axis of the camera towards the near end; and
each emitter in the plurality of emitters is offset in a longitudinal direction from the optical axis of the camera towards the far end; and
the mirrored surface is located in a path of a second portion of electromagnetic radiation emitted by said at least one emitter in the plurality of emitters so as to reflect at least a fraction of said second portion of electromagnetic radiation out through the housing.
35. The method of claim 34 wherein:
the housing additionally encloses a second plurality of emitters;
the housing further encloses a second mirrored surface on a mirror positioned as baffle to block rays originating in at least one emitter in the second plurality of emitters from forming a virtual image in said camera.
36. The method of claim 30 wherein:
the optical element is entirely on the first side of the lateral plane and said at least one emitter is in a cavity of a package on the second side of the lateral plane.
37. The method of claim 30 further comprising:
calculating, by using at least one processor enclosed within the housing, an average luminance value for each sector in a plurality of sectors used to sense said image;
calculating, using the at least one processor, a difference between the average luminance value calculated for each sector and a target luminance value for said each sector; and
computing, using the at least one processor, a drive current for generating the electromagnetic radiation, based at least partially on said difference.
38. The method of claim 37 wherein:
a change in said drive current is obtained, using the at least one processor, based on a linear combination of a plurality of said differences individually calculated for each sector in said plurality of sectors.
39. The method of claim 30 wherein:
the optical element comprises a lens.
40. The method of claim 30 wherein:
the first fraction of said portion of electromagnetic radiation exits the housing through the tubular wall.
41. An apparatus comprising:
means for imaging;
means for emitting electromagnetic radiation, the means for emitting being enclosed within a housing, the housing comprising a tubular wall, the means for emitting being located in a ring around the means for imaging; and
means for directing electromagnetic radiation, the means for directing being enclosed within said housing, the means for directing comprising an optical element located in a path of a portion of electromagnetic radiation emitted by the means for emitting so as to direct at least a first fraction of said portion of electromagnetic radiation out through the housing, at least a portion of the optical element being on a first side of a lateral plane and said at least one emitter being on a second side of the lateral plane, wherein the optical element comprises a concentrator shaped to reduce angular divergence of at least said portion of electromagnetic radiation;
wherein all electromagnetic radiation from said means for emitting is emitted on the second side of the lateral plane;
wherein the lateral plane is perpendicular to a longitudinal axis of the apparatus, the apparatus having a dimension along the longitudinal axis larger than any dimension within the lateral plane;
the means for imaging being positioned within the housing such that at least a portion of an image is formed in the means for imaging by at least a second fraction of said portion of electromagnetic radiation entering through the tubular wall on the first side of the lateral plane after reflection outside the housing.