Measuring arrangement for examining a subject with visible, NIR or IR light

• US 5,309,907 A
• Filed: 08/26/1992
• Issued: 05/10/1994
• Est. Priority Date: 09/04/1991
• Status: Expired due to Term

• Current Assignee: Siemens AG
• Original Assignee: Siemens AG
• Inventors: Fang, Ming, Reinfelder, Hans-Erich
• Primary Examiner(s): Sykes, Angela D.
• Application Number:
  US07/935,878
• Time in Patent Office: 622 Days
• Field of Search: 128/633-634, 128/664-665, 128/666-667
• US Class Current: 600/342
• CPC Class Codes: A61B 5/0073 by tomography, i.e. reconstruction of 3D images from 2D projections A61B5/0066 takes precedence
• CPC Class Codes: A61B 5/1455 using optical sensors, e.g. spectral photometrical oximeters

Abstract

An apparatus for examining tissue in vivo by means of the optical properties of the tissue generates a measuring chirp signal which is introduced into a tissue-containing subject as a coherent optical chirp signal. The parts of the measuring chirp signal emerging from the subject are superimposed with a reference chirp signal to form a superposition signal that is supplied to a filter that only allows those parts of the superposition signal to pass that represent those parts of the measuring chirp signal emerging from the subject which have traversed a defined, optical path length within the subject.

Claims

1. An apparatus for optically analyzing tissue in vivo comprising:

means for directing a measuring chirp signal at a tissue-containing subject, said measuring chirp signal being a coherent optical signal of light selected from the group consisting of visible, NIR and IR light, a part of said measuring chirp signal emerging from said subject after interacting therein with tissue to be analyzed and forming an emerging signal;

means for generating a reference chirp signal having a defined phase relationship to said measuring chirp signal;

means for superimposing said emerging signal with said reference chirp signal to form a superposition signal having sets of beats, each set of beats having a respective beat frequency;

filter means, for receiving said superposition signal and having a transmission range with an upper limit frequency, for generating from said superposition signal a filtered signal having at least one beat frequency within said transmission range; and

means for dimensioning parameters including the transit time of said measuring chirp signal outside said subject, the transit time of said reference chirp signal, and said upper limit frequency of said filter means for causing said filtered signal to represent substantially only parts of said emerging signal which have traversed an optical path length in said subject which does not exceed a defined maximum optical path length.

2. An apparatus as claimed in claim 1 wherein said filter means is a filter means having a transmission range which also has a lower limit frequency, and wherein said lower limit frequency is among said parameters dimensioned by said means for dimensioning.

3. An apparatus as claimed in claim 2 further comprising:

means for varying at least one of said parameters.

4. An apparatus as claimed in claim 2 further comprising:

evaluation means, for receiving said filtered signal, for calculating said optical path length traversed in said subject by said parts of said emerging signal represented in said filtered signal, based on said upper and lower limit frequencies of said filter means, said transit time of said measuring chirp signal outside said subject, and said transit time of said reference chirp signal.

5. An apparatus as claimed in claim 1 wherein said means for generating said measuring chirp signal and said means for generating said reference chirp signal comprise, in combination, at least one coherent light source, and wherein said apparatus further comprises:

signal generator means for generating a signal for frequency-modulating light from said coherent light source for causing said coherent light source to emit an optical chirp signal having an optical frequency varying in a defined manner over time;

beam splitter means for splitting said optical chirp signal into a first optical signal forming said measuring chirp signal and a second optical signal forming said reference chirp signal;

wherein said means for superimposing is a means for optically superimposing said measuring chirp signal and said reference chirp signal to form an optical superposition signal, and wherein said apparatus further comprises;

opto-electronic detector means for detecting said optical superposition signal and converting it into an electrical signal which is supplied to said filter means as said superposition signal.

6. An apparatus as claimed in claim 1 wherein said means for generating said measuring chirp signal and said means for generating said reference chirp signal comprise, in combination, at least one coherent light source, and wherein said apparatus further comprises:

signal generator means for generating a signal for amplitude-modulating light from said coherent light source for causing said coherent light source to emit an optical chirp signal having an optical intensity changing over time at a frequency varying in a defined manner over time;

beam splitter means for splitting said optical chirp signal into a first optical signal forming said measuring chirp signal and a second optical signal forming said reference chirp signal;

wherein said means for superimposing is a means for optically superimposing said measuring chirp signal and said reference chirp signal to form an optical superposition signal, and wherein said apparatus further comprises;

opto-electronic detector means for detecting said optical superposition signal and converting it into an electrical signal which is supplied to said filter means as said superposition signal.

7. An apparatus as claimed in claim 5 or 6 wherein said beam splitter means and said means for superimposing, in combination, consist of a semi-reflective mirror onto which said optical chirp signal from said coherent light source is incident at an angle deviating from 90°

thereby splitting said optical chirp signal into said measuring chirp signal and said reference chirp signal, propagating along different respective propagation paths, and reflector means, disposed in the propagation path of said reference chirp signal, for directly reflecting said reference chirp signal back along said propagation path.

8. An apparatus as claimed in claim 5 or 6 wherein said beam splitter means is an optical fiber fan-out coupler and wherein said means for superimposing is an optical fiber fan-in coupler, and said apparatus further comprising:

a first optical fiber conducting said reference chirp signal from said optical fiber fan-out coupler to said optical fiber fan-in coupler;

a second optical fiber conducting said measuring chirp signal from said optical fiber fan-out coupler to said subject; and

a third optical fiber conducting said emerging signal to said optical fiber fan-in coupler.

9. An apparatus as claimed in claim 1 wherein said means for generating said measuring chirp signal is a coherent light source, wherein said means for generating said reference chirp signal is an electrical generator means for generating a first electrical signal forming said reference chirp signal and being connected to said coherent light source for causing said coherent light source to emit an amplitude-modulated signal, forming said measuring chirp signal, having an optical intensity changing over time at a frequency varying in a defined manner over time, and wherein said apparatus further comprises:

opto-electronic detector means for converting said emerging signal into a second electrical signal, forming an electrical emerging signal,

and wherein said means for superimposing is a mixer means, supplied with said reference chirp signal and said electrical emerging signal, for generating a third electrical signal, forming said superposition signal, which is supplied to said filter means.

10. An apparatus as claimed in claim 9 wherein said means for directing said measuring chirp signal at said subject has a light exit zone from which said optical chirp signal exits toward said subject, and wherein said detector means has a light entry zone into which said emerging signal enters said detector means, said light exit zone and said light entry zone being disposed on opposite sides of said subject, and said apparatus further comprising means for generating relative movement between said light exit and light entry zones, in combination, and said subject for scanning said subject.

11. An apparatus as claimed in claim 10 wherein said detector means is formed by at least one photodiode.

12. An apparatus as claimed in claim 10 wherein said detector means is formed by at least one photomultiplier.

13. An apparatus as claimed in claim 9 wherein said means for directing said measuring chirp signal at said subject has a light exit zone from which said optical chirp signal exits toward said subject, and wherein said detector means has a light entry zone into which said emerging signal enters said detector means, said light exit zone and said light entry zone being disposed in close proximity on the same side of said subject, and said apparatus further comprising means for generating relative movement between said light exit and light entry zones, in combination, and said subject for scanning said subject.

14. An apparatus as claimed in claim 9 wherein said means for directing said measuring chirp signal at said subject has a light exit zone from which said optical chirp signal exits toward said subject, wherein said detector means consists of a plurality of separate detector elements, each detector element having a light entry zone into which a part of said emerging signal enters that detector element, and said apparatus further comprising means for generating a relative movement between said light exit zone and said subject for scanning said subject, and multiplexer means for successively connecting said individual detector elements to said means for superimposing during said scanning.

15. An apparatus as claimed in claim 14 wherein said detector elements are annularly disposed around said subject.

16. An apparatus as claimed in claim 15 wherein said light exit zones are annularly arranged around said subject in alternation with said detector elements.

17. An apparatus as claimed in claim 10, 13 or 14 further comprising evaluation means for calculating an at least two-dimensional absorption array of absorption coefficients of a region of said subject from said filtered signal.

18. An apparatus as claimed in claim 17 further comprising graphic display means for displaying the calculated absorption arrays with different chromatic values respectively allocated to different absorption coefficients.

19. An apparatus as claimed in claim 17 further comprising graphic display means for displaying the calculated absorption arrays with different grayscale values respectively allocated to different absorption coefficients.

20. An apparatus as claimed in claim 9 wherein said means for directing said measuring chirp signal at said subject has a plurality of light exit zones from which said optical chirp signal exits, one at a time, toward said examination subject, wherein said detector means consists of a plurality of separate detector elements corresponding in number to said plurality of light exit zones, each detector element having a light entry zone into which a part of said emerging signal enters that detector element, each light exit zone having one detector element, and thus one light entry zone, uniquely allocated thereto, and wherein said means for directing includes means for successively directing said optical chirp signal out of each of said light exit zones for scanning said subject.

21. An apparatus as claimed in claim 20 wherein said means for directing said measuring chirp signal at said subject includes a plurality of separate optical fibers, each optical fiber having a first end and having a second end forming one of said light exit zones, an optical fiber array in which said first ends of said optical fibers are mounted, and means for moving a source of said coherent optical chirp signal through successive positions relative to said array for successively coupling said optical chirp signal into each of said first ends of said optical fibers.

22. An apparatus as claimed in claim 9 wherein said means for superimposing includes a plurality of mixers, corresponding in number to said plurality of detector elements, and said mixers being respectively connected to said detector elements for mixing the signal from the detector element connected thereto with said reference chirp signal, wherein said filter means comprises a plurality of filter elements corresponding in number to said plurality of mixers, said filter elements being respectively connected to said mixers, and said apparatus further comprising evaluation means, connected to the outputs of all of said filter elements, for calculating said optical path length traversed by said part of said emerging signal in said subject.

23. An apparatus as claimed in claim 9 wherein said means for directing said measuring chirp signal at said subject has a light exit zone from which said optical chirp signal exits toward said subject, and wherein said means for superimposing has a light entry zone into which said emerging signal enters said means for superimposing, said light exit zone and said light entry zone being disposed on opposite sides of said subject, and said apparatus further comprising means for generating relative movement between said light exit and light entry zones, in combination, and said subject for scanning said subject.

24. An apparatus as claimed in claim 1 wherein said means for directing said measuring chirp signal at said subject includes at least one laser diode as a source for said coherent optical chirp signal.

25. An apparatus as claimed in claim 1 further comprising light guide means for conducting said optical chirp signal from said means for directing to said subject.

26. An apparatus as claimed in claim 1 further comprising light guide means for conducting said emerging signal from said subject to said means for superimposing.

27. An apparatus as claimed in claim 1 further comprising detector means for detecting said emerging signal and transmitting said emerging signal to said means for superimposing, wherein said means for directing said measuring chirp signal at said subject has a light exit zone from which said optical chirp signal exits toward said subject, and wherein said detector means has a light entry zone into which said emerging signal enters said detector means, said light exit zone and said light entry zone being disposed on opposite sides of said subject, and said apparatus further comprising means for generating relative movement between said light exit and light entry zones, in combination, and said subject for scanning said subject.

28. An apparatus as claimed in claim 27 wherein said detector means is formed by at least one photodiode.

29. An apparatus as claimed in claim 27 wherein said detector means is formed by at least one photomultiplier.

30. An apparatus as claimed in claim 1 further comprising detector means for detecting said emerging signal and transmitting said emerging signal to said means for superimposing, wherein said means for directing said measuring chirp signal at said subject has a light exit zone from which said optical chirp signal exits toward said subject, and wherein said detector means has a light entry zone into which said emerging signal enters said detector means, said light exit zone and said light entry zone being disposed in close proximity on the same side of said subject, and said apparatus further comprising means for generating relative movement between said light exit and light entry zones, in combination, and said subject for scanning said subject.

31. An apparatus as claimed in claim 1 wherein said means for directing said measuring chirp signal at said subject has a light exit zone from which said optical chirp signal exits toward said subject, and wherein said means for superimposing has a light entry zone into which said emerging signal enters said means for superimposing, said light exit zone and said light entry zone being disposed on opposite sides of said subject, and said apparatus further comprising means for generating relative movement between said light exit and light entry zones, in combination, and said subject for scanning said subject.

32. An apparatus as claimed in claims 27, 30 or 31 further comprising evaluation means for calculating an at least two-dimensional absorption array of absorption coefficients of a region of said subject from said filtered signal.

33. An apparatus as claimed in claim 32 further comprising graphic display means for displaying the calculated absorption arrays with different chromatic values respectively allocated to different absorption coefficients.

34. An apparatus as claimed in claim 32 further comprising graphic display means for displaying the calculated absorption arrays with different grayscale values respectively allocated to different absorption coefficients.

35. An apparatus for optically analyzing tissue comprising:

a coherent light source for generating a coherent optical chirp signal of light selected from the group consisting of visible, NIR and IR light;

beam splitter means for splitting said optical chirp signal into a measuring chirp signal and a reference chirp signal having a defined phase relationship to said measuring chirp signal;

a first group of optical fibers, having respectively different combinations of refractive index and length, said optical fibers in said first group being used one at a time to conduct said measuring chirp signal from said beam splitter means to a tissue-containing subject, a part of said measuring chirp signal emerging from said subject after interacting with tissue therein to be analyzed and forming an emerging signal;

means for superimposing said emerging signal with said reference chirp signal to form an optical superposition signal having sets of beats, each set of beats having a respective beat frequency;

a second group of separate optical fibers, having respectively different combinations of refractive index and length, said optical fibers in said second group being selected for use one at time to conduct said reference chirp signal from said beam splitter means to said means for superimposing;

a third group of separate optical fibers, having respectively different combinations of refractive index and length, said optical fibers in said second group being selected for use one at a time to conduct said emerging signal from said subject to said means for superimposing;

detector means for converting said optical superposition signal into an electrical superposition signal;

filter means, for receiving said electrical superposition signal and having a transmission range with an upper limit frequency, for generating from said superposition signal a filtered signal having at least one beat frequency within said transmission range; and

means for selecting said upper limit frequency, in combination with the transit time of said measuring chirp signal outside said subject defined by the selected one of said optical fibers in said first and third groups and the transit time of said reference chirp signal defined by the selected one of said optical fibers in said second group, for causing said filtered signal to represent substantially only parts of said emerging signal which have traversed an optical path length in said subject which does not exceed a defined maximum optical path length.

36. An apparatus as claimed in claim 35 wherein the selected one of said optical fibers in said first group has an end facing said subject forming a light exit zone from which said measuring chirp signal exits toward said subject and wherein the selected one of said optical fibers in said third group has an end facing said subject forming a light entry zone into which said emerging signal enters, said light entry zone and said light exit zone being disposed in close proximity on a same side of said subject.

37. An apparatus as claimed in claim 35 wherein the selected one of said optical fibers in said first group has an end facing said subject forming a light exit zone from which said measuring chirp signal exits toward said subject and wherein the selected one of said optical fibers in said third group has an end facing said subject forming a light entry zone into which said emerging signal enters, said light entry zone and said light exit zone being disposed on opposite sides of said subject.

38. An apparatus as claimed in claim 35 wherein the selected one of said optical fibers in said first group has an end facing said subject forming a light exit zone from which said measuring chirp signal exits toward said subject and wherein the selected one of said optical fibers in said third group has an end facing said subject forming a light entry zone into which said emerging signal enters, said light entry zone and said light exit zone being disposed in close proximity on a same side of said subject and said apparatus further comprising means for generating relative motion between said light entry and exit zones, in combination, and said subject for scanning said subject.

39. An apparatus as claimed in claim 35 wherein the selected one of said optical fibers in said first group has an end facing said subject forming a light exit zone from which said measuring chirp signal exits toward said subject and wherein the selected one of said optical fibers in said third group has an end facing said subject forming a light entry zone into which said emerging signal enters, said light entry zone and said light exit zone being disposed on opposite sides of said subject and said apparatus further comprising means for generating relative motion between said light entry and exit zones, in combination, and said subject for scanning said subject.

40. An apparatus for optically analyzing tissue in vivo comprising:

a coherent light source generating a coherent optical chirp signal of light selected from the group consisting of visible, NIR and IR light, said optical chirp signal propagating along a first propagation path;

a semi-reflective mirror disposed in said first propagation path at an angle deviating from 90°

which splits said optical chirp signal into a measuring chirp signal which continues to propagate along said first propagation path toward a tissue-containing subject, and a reference chirp signal propagating along a second propagation path, different from said first propagation path, a part of said measuring chirp signal emerging from said subject after interacting with tissue therein to be analyzed and forming an emerging signal propagating back along said first propagation path toward said semi-reflective mirror;

a fully-reflective mirror disposed a distance from said semi-reflective mirror in said second propagation path which directly and fully reflects said reference chirp signal back along said second propagation path toward said semi-reflective mirror so that said reference chirp signal has a defined phase relationship to said measuring chirp signal;

said fully-reflected reference chirp signal passing through said semi-reflective mirror and said emerging signal being deflected by said semi-reflective mirror so that both signals are superimposed forming an optical superposition signal having sets of beats, each set of beats having a respective beat frequency;

detector means, for receiving said optical superposition signal, for generating a corresponding electrical superposition signal;

filter means, supplied with said electrical superposition signal and having a transmission range with an upper limit frequency, for generating from said superposition signal a filtered signal having at least one beat frequency within said transmission range;

first adjustment means for adjusting the distance between said semi-reflective mirror and said fully reflective mirror;

second adjustment means for adjusting the distance between said semi-reflective mirror and said examination subject;

third adjustment means for adjusting the distance between said semi-reflective mirror and said detector means;

means for selecting said upper limit frequency of said filter means; and

said first, second and third adjustment means and said means for adjusting said upper limit frequency forming, in combination, means for dimensioning the transit time of said measuring chirp signal outside said subject, the transit time of said reference chirp signal, and said upper limit frequency of said filter means for causing said filtered signal to represent substantially only parts of said emerging signal which have traversed an optical path length in said subject which does not exceed a defined maximum optical path length.

41. An apparatus for optically analyzing tissue in vivo comprising:

a coherent light source generating a coherent optical chirp signal of light selected from the group consisting of visible, NIR and IR light;

signal generator means for generating an electrical reference chirp signal supplied to said coherent light source for modulating said optical chirp signal so that said optical chirp signal has a defined phase relationship to said reference chirp signal;

a light exit zone, optically coupled to said coherent light source, from which the modulated optical chirp signal is directed, as a measuring chirp signal, at a tissue-containing subject, a part of said measuring chirp signal emerging from said subject after interacting with tissue therein to be analyzed and forming an optical emerging signal;

detector means, having a light entry zone into which said optical emerging signal enters, for converting said optical emerging signal into a corresponding electrical emerging signal;

mixer means for electronically mixing said electrical emerging signal with said reference chirp signal to form an electrical superposition signal having sets of beats, each set of beats having a respective beat frequency;

filter means, for receiving said electrical superposition signal and having a transmission range with an upper limit frequency, for generating from said superposition signal a filtered signal consisting of an electrical superposition signal having at least one beat frequency within said transmission range;

means for adjusting at least one of a distance between said signal generator means and said coherent light source, a distance between said signal generator means and said mixer means, a distance between said coherent light source and said light exit zone, a distance between said light entry zone and said mixer means, and said upper limit frequency for, in combination, dimensioning the transit time of said measuring chirp signal outside said subject, the transit time of said reference chirp signal and said upper limit frequency of said filter means for causing said filtered signal to represent substantially only parts of said optical emerging signal which have traversed an optical path length in said subject which does not exceed a defined maximum optical path length.

42. An apparatus as claimed in claim 41 further comprising means for disposing said light entry zone and said light exit zone in close proximity on a same side of said subject.

43. An apparatus as claimed in claim 42 further comprising means for generating relative motion between said light entry and exit zones, in combination, and said subject for scanning said subject.

44. An apparatus as claimed in claim 41 further comprising means for disposing said light exit zone and said light entry zone on opposite sides of said subject.

45. An apparatus as claimed in claim 44 further comprising means for generating relative motion between said light entry and exit zones, in combination, and said subject for scanning said subject.

46. An apparatus for optically analyzing tissue in vivo comprising:

a coherent light source generating a coherent optical chirp signal of light selected from the group consisting of visible, NIR and IR light;

signal generator means for generating an electrical reference chirp signal supplied to said coherent light source for modulating said coherent optical chirp signal;

a single light exit zone, optically coupled to said coherent light source, from which the modulated optical chirp signal, as a measuring chirp signal, exits toward a tissue-containing subject, a part of said measuring chirp signal emerging from said subject after interacting with tissue therein to be analyzed and forming an optical emerging signal;

a plurality of detector elements arranged around said subject at respective positions which are stationary relative to said subject;

means for generating relative motion between said light exit zone and said subject so that a part of said optical emerging signal is successively incident on said detector elements for scanning said subject, each detector element generating an electrical signal corresponding to the part of the optical emerging signal incident thereon;

a plurality of mixers corresponding in number to the plurality of detector elements, all of said mixers receiving said electrical reference chirp signal and said mixers respectively receiving said electrical signals from said detector elements, and each mixer superimposing the electrical signal from the detector element connected thereto with said electrical reference chirp signal to form a superposition signal having sets of beats, each set of beats having a respective beat frequency;

a plurality of filters corresponding in number to the plurality of mixers, said filters respectively receiving said superposition signals from said mixers, each filter having an identical upper limit frequency and generating from a superposition signal supplied thereto from a mixer a filtered signal having at least one beat frequency within said transmission range;

means for combining said filtered signals to form a combined filtered signal; and

means for adjusting at least one of a distance between said signal generator means and said mixers, a distance between said coherent light source and said light exit zone and said upper limit frequency for, in combination, dimensioning the transit time of said measuring chirp signal outside said subject, the transit time of said electrical reference chirp signal, and said upper limit frequency of said filters for causing said combined filtered signal to represent substantially only parts of said optical emerging signal which have traversed an optical path length in said subject which does not exceed a defined maximum optical path length.

47. An apparatus for optically analyzing tissue in vivo comprising:

a coherent light source generating a coherent optical chirp signal of light selected from the group consisting of visible, NIR and IR light;

signal generator means for generating an electrical reference chirp signal supplied to said coherent light source for modulating said coherent optical chirp signal;

a plurality of light exit zones arranged around said subject at respective positions which are stationary relative to said subject, and means for successively, optically coupling said light exit zones one at a time to said coherent light source, from which the modulated optical chirp signal, as a measuring chirp signal, exits toward a tissue-containing subject, a part of said measuring chirp signal emerging from said subject after interacting with tissue therein to be analyzed and forming an optical emerging signal;

a plurality of detector elements arranged around said subject at respective positions which are stationary relative to said subject in alternation with said light exit zones, each detector element disposed to receive light from only one light exit zone;

each detector element generating an electrical signal corresponding to the part of the optical emerging signal incident thereon as said light zones are successively coupled to said coherent light source for scanning said subject;

a plurality of mixers corresponding in number to the plurality of detector elements, all of said mixers receiving said electrical reference chirp signal and said mixers respectively receiving said electrical signals from said detector elements, and each mixer superimposing the electrical signal from the detector element connected thereto with said electrical reference chirp signal to form a superposition signal having sets of beats, each set of beats having a respective beat frequency;

a plurality of filters corresponding in number to the plurality of mixers, said filters respectively receiving said superposition signals from said mixers, each filter having an identical upper limit frequency and generating from a electrical superposition signal received from a mixer a filtered signal having at least one beat frequency within said transmission range;

means for combining said filtered signals to form a combined filtered signal; and

means for adjusting at least one of a distance between said signal generator means and said mixers, a distance between said coherent light source and said light exit zone and said upper limit frequency for, in combination, dimensioning the transit time of said measuring chirp signal outside said subject, the transit time of said electrical reference chirp signal, and said upper limit frequency of said filters for causing said combined filtered signal to represent substantially only parts of said optical emerging signal which have traversed an optical path length in said subject which does not exceed a defined maximum optical path length.

48. An apparatus for optically analyzing tissue in vivo comprising:

a plurality of coherent light sources each generating a coherent optical chirp signal of light selected from the group consisting of visible, NIR and IR light, said coherent light sources being arranged around a tissue-containing subject at respective positions which are stationary relative to said subject;

signal generator means for generating an electrical reference chirp signal supplied to said coherent light source for modulating said coherent optical chirp signal;

means for successively energizing said coherent light sources, one at a time for directing the modulated optical chirp signal, as a measuring chirp signal, at said containing subject for scanning said subject, a part of said measuring chirp signal emerging from said subject after interacting with tissue therein to be analyzed and forming an optical emerging signal;

a plurality of detector elements arranged around said subject at respective positions which are stationary relative to said subject, in alternation with said coherent light sources, each detector element disposed to receive light from only one of said coherent light sources so that a part of said optical emerging signal is successively incident on said detector elements as said coherent light sources are successively energized, each detector element generating an electrical signal corresponding to the part of the optical emerging signal incident thereon;

a plurality of mixers corresponding in number to the plurality of detector elements, all of said mixers receiving said electrical reference chirp signal and said mixers respectively receiving said electrical signals from said detector elements, and each mixer superimposing the electrical signal from the detector element connected thereto with said electrical reference chirp signal to form a superposition signal having sets of beats, each set of beats having a respective beat frequency;

a plurality of filters corresponding in number to the plurality of mixers, said filters respectively receiving said superposition signals from said mixers, each filter having an identical upper limit frequency and generating from an electrical superposition signal received from a mixer a filtered signal having at least one beat frequency within said transmission range;

means for combining said filtered signals to form a combined filtered signal; and

means for adjusting at least one of a distance between said signal generator means and said mixers, a distance between said coherent light source and said light exit zone and said upper limit frequency for, in combination, dimensioning the transit time of said measuring chirp signal outside said subject, the transit time of said electrical reference chirp signal, and said upper limit frequency of said filters for causing said combined filtered signal to represent substantially only parts of said optical emerging signal which have traversed an optical path length in said subject which does not exceed a defined maximum optical path length.

49. A method for optically analyzing tissue in vivo comprising the steps of:

directing a measuring chirp signal at a tissue-containing subject, said measuring chirp signal being a coherent optical signal of light selected from the group consisting of visible, NIR and IR light, a part of said measuring chirp signal emerging from said subject after interacting therein with tissue to be analyzed and forming an emerging signal;

generating a reference chirp signal having a defined phase relationship to said measuring chirp signal;

superimposing said emerging signal with said reference chirp signal to form a superposition signal having sets of beats, each set of beats having a respective beat frequency;

filtering said superposition signal through a transmission range with an upper limit frequency, for generating from said superposition signal a filtered signal having at least one beat frequency within said transmission range; and

dimensioning parameters including the transit time of said measuring chirp signal outside said subject, the transit time of said reference chirp signal, and said upper limit frequency of said filter means for causing said filtered signal to represent substantially only parts of said emerging signal which have traversed an optical path length in said subject which does not exceed a defined maximum optical path length.

50. A method as claimed in claim 49 wherein said transmission range also has a lower limit frequency, and wherein the step of dimensioning parameters includes dimensioning said lower limit frequency.

51. A method as claimed in claim 50 further comprising the step of:

varying at least one of said parameters.

52. A method as claimed in claim 50 further comprising the steps of:

calculating, from said filtered signal, said optical path length traversed in said subject by said part of said emerging signal represented in said filtered signal, based on said upper and lower limit frequencies of said filter means, said transit time of said measuring chirp signal outside said subject, and said transit time of said reference chirp signal.

53. A method as claimed in claim 49 or 50 comprising the additional step of calculating an at least two-dimensional absorption array of absorption coefficients of a region of said subject from said filtered signal.

54. A method as claimed in claim 53 comprising the additional step of graphically displaying the calculated absorption arrays with different chromatic values respectively allocated to different absorption coefficients.

55. A method as claimed in claim 53 comprising the additional step of graphically displaying the calculated absorption arrays with different grayscale values respectively allocated to different absorption coefficients.

56. A method as claimed in claim 49 wherein the steps of generating said measuring chirp signal and for generating said reference chirp signal are defined by generating said measuring chirp signal and said reference chirp signal in combination, from at least one coherent light source, and wherein said method comprises the additional steps of:

generating a signal for frequency-modulating light from said coherent light source for causing said coherent light source to emit an optical chirp signal having an optical frequency varying in a defined manner over time;

splitting said optical chirp signal into a first optical signal forming said measuring chirp signal and a second optical signal forming said reference chirp signal;

wherein the step of superimposing is further defined by optically superimposing said measuring chirp signal and said reference chirp signal to form an optical superposition signal, and wherein said method comprises the additional step of;

opto-electronically detecting said optical superposition signal and converting it into an electrical signal which is filtered as said superposition signal.

57. A method as claimed in claim 49 wherein the steps of generating said measuring chirp signal and generating said reference chirp signal are further defined by generating said measuring chirp signal and said reference chirp signal, in combination, from at least one coherent light source, and wherein said method comprises the additional steps of:

generating a signal for amplitude-modulating light from said coherent light source for causing said coherent light source to emit an optical chirp signal having an optical intensity changing over time at a frequency varying in a defined manner over time;

splitting said optical chirp signal into a first optical signal forming said measuring chirp signal and a second optical signal forming said reference chirp signal;

wherein the step of superimposing is further defined by optically superimposing said measuring chirp signal and said reference chirp signal to form an optical superposition signal, and wherein said method comprises the additional step of;

opto-electronically detecting said optical superposition signal and converting it into an electrical signal which is received by said filter means as said superposition signal.

58. A method as claimed in claim 56 or 57 wherein the step of splitting and superimposing are further defined, in combination, by directing said optical chirp signal onto a semi-reflective mirror at an angle deviating from 90°

and thereby splitting said optical chirp signal into said measuring chirp signal and said reference chirp signal, propagating along different respective propagation paths, directly reflecting said reference chirp signal propagating away from said semi-reflective mirror back along said propagation path toward said semi-reflective mirror.

59. A method as claimed in claim 56 or 57 wherein the step of splitting is further defined by splitting said optical chirp signal in an optical fiber fan-out coupler and wherein the step of superimposing is further defined by superimposing said emerging signal and said reference chirp signal in an optical fiber fan-in coupler, and said method comprising the additional steps of:

conducting said reference chirp signal from said optical fiber fan-out coupler to said optical fiber fan-in coupler in a first optical fiber;

conducting said measuring chirp signal from said optical fiber fan-out coupler to said subject in a second optical fiber; and

conducting said emerging signal to said optical fiber fan-in coupler in a third optical fiber.

60. An apparatus as claimed in claim 49 wherein the step of generating said measuring chirp signal is further defined by generating said measuring chirp signal from a coherent light source, wherein the step of generating said reference chirp signal is further defined by generating a first electrical signal forming said reference chirp signal and supplying said reference chirp signal to said coherent light source for causing said coherent light source to emit an amplitude-modulated signal, forming said measuring chirp signal, having an optical intensity changing over time at a frequency varying in a defined manner over time, and wherein said method comprises the additional step of:

opto-electronically converting said emerging signal into a second electrical signal, forming an electrical emerging signal, and wherein the step of superimposing is further defined by electronically mixing said reference chirp signal and said electrical emerging signal, for generating a third electrical signal, forming said superposition signal, which is filtered in the filtering step.

61. A method as claimed in claim 60 wherein the step of directing said measuring chirp signal at said subject is further defined by emitting said measuring chirp signal from a light exit zone from which said optical chirp signal exits toward said subject, and wherein said method comprises the additional steps of:

receiving said emerging signal via a light entry zone;

disposing said light exit zone and said light entry zone on opposite sides of said subject; and

generating relative movement between said light exit and light entry zones, in combination, and said subject for scanning said subject.

62. An apparatus as claimed in claim 60 wherein the step of directing said measuring chirp signal at said subject is further defined by emitting said measuring chirp signal from a light exit zone from which said optical chirp signal exits toward said subject, and wherein said method comprises the additional steps of:

receiving said emerging signal via a light entry zone;

disposing said light exit zone and said light entry zone being close proximity on the same side of said subject;

generating relative movement between said light exit and light entry zones, in combination, and said subject for scanning said subject.

63. A method as claimed in claim 60 wherein the step of directing said measuring chirp signal at said subject is further defined by emitting said measuring chirp signal from a light exit zone from which said optical chirp signal exits toward said subject, wherein the step of opto-electronically converting is further defined by respectively converting a part of said emerging signal into a plurality of electrical emerging signals in a plurality of separate detector elements, each detector element having a light entry zone into which said part of said emerging signal enters that detector element, and said method comprising the additional steps of:

generating a relative movement between said light exit zone and said subject for scanning said subject;

successively superimposing each of said plurality of electrical emerging signals with said reference chirp signal during said scanning.

64. A method as claimed in claim 60 wherein the step of directing said measuring chirp signal at said subject is further defined by emitting said measuring chirp signal from a plurality of light exit zones from which said optical chirp signal exits, one at a time, toward said examination subject for scanning said subject, and wherein said method comprises the additional steps of:

receiving said emerging signal in a plurality of separate detector elements corresponding in number to said plurality of light exit zones, each detector element having a light entry zone into which a part of said emerging signal enters that detector element, each light exit zone having one detector element, and thus one light entry zone, uniquely allocated thereto; and

successively directing said optical chirp signal out of each of said light exit zones for scanning said subject.

65. A method as claimed in claim 64 wherein the step of directing said measuring chirp signal at said subject is further defined by directing said optical chirp signal at said subject through a plurality of separate optical fibers, each optical fiber having a first end and having a second end forming one of said light exit zones, and wherein the step of successively directing said optical chirp signal out of each said light exit zone is further defined by moving a source of said coherent optical chirp signal through successive positions relative to said first ends for successively coupling said optical chirp signal into each of said first ends of said optical fibers for scanning said subject.

66. A method claimed in claim 60 wherein the step of directing said measuring chirp signal at said subject is further defined by emitting said measuring chirp signal from a light exit zone from which said optical chirp signal exits toward said subject, and wherein said method comprises the additional step of:

disposing said light exit zone and said light entry zone on opposite sides of said subject; and

generating relative movement between said light exit and light entry zones, in combination, and said subject for scanning said subject.

67. A method for optically analyzing tissue in vivo comprising the steps of:

generating a coherent optical chirp signal of light selected from the group consisting of visible, NIR and IR light;

splitting said optical chirp signal, at a splitting location, into a measuring chirp signal and a reference chirp signal having a defined phase relationship to said measuring chirp signal;

selecting one fiber from a first group of optical fibers, having respectively different combinations of refractive index and length, to conduct said measuring chirp signal from said splitting location to a tissue-containing subject, a part of said measuring chirp signal emerging from said subject after interacting with tissue therein to be analyzed and forming an emerging signal;

superimposing said emerging signal, at a superimposing location, with said reference chirp signal to form an optical superposition signal having sets of beats, each set of beats having a respective beat frequency;

selecting one fiber from a second group of separate optical fibers, having respectively different combinations of refractive index and length, for conducting said reference chirp signal from said splitting location to said superimposing location;

selecting one fiber from a third group of separate optical fibers, having respectively different combinations of refractive index and length, for conducting said emerging signal from said subject to said superimposing location;

converting said optical superposition signal into an electrical superposition signal;

filtering said electrical superposition signal through a transmission range with an upper limit frequency, for generating from said electrical superposition signal a filtered signal having at least one beat frequency within said transmission range; and

selecting said upper limit frequency, in combination with the transit time of said measuring chirp signal outside said subject defined by selecting respective ones of said optical fibers in said first and third groups and the transit time of said reference chirp signal defined by selecting one of said optical fibers in said second group, for causing said filtered signal to represent substantially only parts of said emerging signal which have traversed an optical path length in said subject which does not exceed a defined maximum optical path length.

68. A method as claimed in claim 67 wherein the selected one of said optical fibers in said first group has an end facing said subject forming a light exit zone from which said measuring chirp signal exits toward said subject and wherein the selected one of said optical fibers in said third group has an end facing said subject forming a light entry zone into which said emerging signal enters, and wherein said method comprises the additional step of disposing said light entry zone and said light exit zone in close proximity on a same side of said subject.

69. A method as claimed in claim 67 wherein the selected one of said optical fibers in said first group has an end facing said subject forming a light exit zone from which said measuring chirp signal exits toward said subject and wherein the selected one of said optical fibers in said third group has an end facing said subject forming a light entry zone into which said emerging signal enters, and wherein said method comprises the additional step of disposing said light entry zone and said light exit zone on opposite sides of said subject.

70. A method as claimed in claim 67 wherein the selected one of said optical fibers in said first group has an end facing said subject forming a light exit zone from which said measuring chirp signal exits toward said subject and wherein the selected one of said optical fibers in said third group has an end facing said subject forming a light entry zone into which said emerging signal enters, and wherein said method comprises the additional steps of disposing said light entry zone and said light exit zone in close proximity on a same side of said subject;

and

generating relative motion between said light entry and exit zones, in combination, and said subject for scanning said subject.

71. A method as claimed in claim 67 wherein the selected one of said optical fibers in said first group has an end facing said subject forming a light exit zone from which said measuring chirp signal exits toward said subject and wherein the selected one of said optical fibers in said third group has an end facing said subject forming a light entry zone into which said emerging signal enters, and wherein said method comprises the additional steps of disposing said light entry zone and said light exit zone on opposite sides of said subject;

and

generating relative motion between said light entry and exit zones, in combination, and said subject for scanning said subject.

72. A method for optically analyzing tissue in vivo comprising the steps of:

generating a coherent optical chirp signal of light selected from the group consisting of visible, NIR and IR light, said optical chirp signal propagating along a first propagation path;

directing said optical chirp signal at a semi-reflective mirror disposed in said first propagation path at an angle deviating from 90°

for splitting said optical chirp signal into a measuring chirp signal which continues to propagate along said first propagation path toward a tissue-containing subject, and a reference chirp signal propagating along a second propagation path, different from said first propagation path, a part of said measuring chirp signal emerging from said subject after interacting with tissue therein to be analyzed and forming an emerging signal propagating back along said first propagation path toward said semi-reflective mirror;

disposing a fully-reflective mirror a distance from said semi-reflective mirror in said second propagation path for directly and fully reflecting said reference chirp signal back along said second propagation path toward said semi-reflective mirror so that said reference chirp signal has a defined phase relationship to said measuring chirp signal;

passing said fully reflected reference chirp signal through said semi-reflective mirror and deflecting said emerging signal by said semi-reflective mirror for superimposing both signals to form an optical superposition signal having sets of beats, each set of beats having a respective beat frequency;

converting said optical superposition signal, at a converting location into a corresponding electrical superposition signal;

filtering said electrical superposition signal through a transmission range with an upper limit frequency, for generating from said electrical superposition signal a filtered signal having at least one beat frequency within said transmission range;

adjusting the distance between said semi-reflective mirror and said fully reflective mirror;

adjusting the distance between said semi-reflective mirror and said examination subject;

adjusting the distance between said semi-reflective mirror and said converting location;

selecting said upper limit frequency; and

selectively adjusting said distances and said upper limit frequency, in combination, for dimensioning the transit time of said measuring chirp signal outside said subject, the transit time of said reference chirp signal, and said upper limit frequency for causing said filtered signal to represent substantially only parts of said emerging signal which have traversed an optical path length in said subject which does not exceed a defined maximum optical path length.

73. A method for optically analyzing tissue in vivo comprising the steps of:

generating a coherent optical chirp signal from a coherent light source emitting light selected from the group consisting of visible, NIR and IR light;

generating, from a generator source, an electrical reference chirp signal supplied to said coherent light source for modulating said optical chirp signal so that said optical chirp signal has a defined phase relationship to said reference chirp signal;

optically coupling a light exit zone, to said coherent light source, from which the modulated optical chirp signal is directed, as a measuring chirp signal, at a tissue-containing subject, a part of said measuring chirp signal emerging from said subject after interacting with tissue therein to be analyzed and forming an optical emerging signal;

receiving said optical emerging signal via a light entry zone and converting said optical emerging signal into a corresponding electrical emerging signal;

electronically mixing said electrical emerging signal, at a mixing location, with said reference chirp signal to form an electrical superposition signal having sets of beats, each set of beats having a respective beat frequency;

filtering said electrical superposition signal through a transmission range with an upper limit frequency, for generating from said electrical superposition signal a filtered signal having at least one beat frequency within said transmission range;

adjusting at least one of a distance between said generator source means and said coherent light source, a distance between said signal generator source and said mixing location, a distance between said coherent light source and said light exit zone, a distance between said light entry zone and said mixing location, and said upper limit frequency for, in combination, dimensioning the transit time of said measuring chirp signal outside said subject, the transit time of said reference chirp signal and said upper limit frequency of said filter means for causing said filtered signal to represent substantially only parts of said optical emerging signal which have traversed an optical path length in said subject which does not exceed a defined maximum optical path length.

74. A method as claimed in claim 73 comprising the additional step of disposing said light entry zone and said light exit zone in close proximity on a same side of said subject.

75. A method as claimed in claim 74 comprising the additional step of generating relative motion between said light entry and exit zones, in combination, and said subject for scanning said subject.

76. A method as claimed in claim 74 comprising the additional step of disposing said light exit zone and said light entry zone on opposite sides of said subject.

77. A method as claimed in claim 76 comprising the additional step of generating relative motion between said light entry and exit zones, in combination, and said subject for scanning said subject.

78. A method for optically analyzing tissue in vivo comprising the steps of:

generating a coherent optical chirp signal from a coherent light source emitting light selected from the group consisting of visible, NIR and IR light;

generating, from a generator source, an electrical reference chirp signal supplied to said coherent light source for modulating said coherent optical chirp signal;

optically coupling a single light exit zone, to said coherent light source, from which the modulated optical chirp signal, as a measuring chirp signal, is directed at a tissue-containing subject, a part of said measuring chirp signal emerging from said subject after interacting with tissue therein to be analyzed and forming an optical emerging signal;

arranging a plurality of detector elements around said subject at respective positions which are stationary relative to said subject;

generating relative motion between said light exit zone and said subject so that a part of said optical emerging signal is successively incident on said detector elements for scanning said subject, each detector element generating an electrical signal corresponding to the part of the optical emerging signal incident thereon;

superimposing each of the respective electrical signals from the detector elements at a mixing location with said electrical reference chirp signal to form a plurality of superposition signals each having sets of beats, each set of beats having a respective beat frequency;

separately fitting each of said superposition signals through transmission ranges identical upper limit frequency and thereby generating from said electrical superposition signals a plurality of respective filtered signals each having at least one beat frequency within said transmission range;

combining said filtered signals to form a combined filtered signal; and

adjusting at least one of a distance between said generator source and said mixing location, a distance between said coherent light source and said light exit zone and said upper limit frequency for, in combination, dimensioning the transit time of said measuring chirp signal outside said subject, the transit time of said electrical reference chirp signal, and said upper limit frequency for causing said combined filtered signal to represent substantially only parts of said optical emerging signal which have traversed an optical path length in said subject which does not exceed a defined maximum optical path length.

79. A method for optically analyzing tissue in vivo comprising the steps of:

generating a coherent optical chirp signal from a coherent light source emitting light selected from the group consisting of visible, NIR and IR light;

generating, from a generator source an electrical reference chirp signal supplied to said coherent light source for modulating said coherent optical chirp signal;

arranging a plurality of light exit zones around said subject at respective positions which are stationary relative to said subject, and for successively, optically coupling said light exit zones one at a time to said coherent light source, from which the modulated optical chirp signal, as a measuring chirp signal, exits toward a tissue-containing subject, a part of said measuring chirp signal emerging from said subject after interacting with tissue therein to be analyzed and forming an optical emerging signal;

arranging a plurality of detector elements arranged around said subject at respective positions which are stationary relative to said subject in alternation with said light exit zones, each detector element disposed to receive light from only one light exit zone;

generating from each detector element an electrical signal corresponding to the part of the optical emerging signal incident thereon as said light zones are successively coupled to said coherent light source for scanning said subject for scanning said subject;

superimposing each electrical signal from each detector element at a mixing location with said electrical reference chirp signal to form a plurality of superposition signals having sets of beats, each set of beats having a respective beat frequency;

separately filtering said superposition signals through transmission ranges having an identical upper limit frequency and thereby generating from said electrical superposition signals supplied thereto from a mixer a plurality of respective filtered signals each having at lease one beat frequency within said transmission range;

combining said filtered signals to form a combined filtered signal; and

adjusting at least one of a distance between said generator source and said mixing location, a distance between said coherent light source and said light exit zone and said upper limit frequency for, in combination, dimensioning the transit time of said measuring chirp signal outside said subject, the transit time of said electrical reference chirp signal, and said upper limit frequency for causing said combined filtered signal to represent substantially only parts of said optical emerging signal which have traversed an optical path length in said subject which does not exceed a defined maximum optical path length.

80. A method for optically analyzing tissue in vivo comprising the steps of:

generating a plurality of coherent optical chirp signals from a plurality of coherent light sources each emitting light selected from the group consisting of visible, NIR and IR light;

arranging said coherent light sources being arranged around a tissue-containing subject at respective positions which are stationary relative to said subject;

generating, from a generator source, an electrical reference chirp signal supplied to said coherent light source for modulating said coherent optical chirp signal;

successively energizing said coherent light sources, one at a time for directing the modulated optical chirp signal, as a measuring chirp signal, at said containing subject for scanning said subject, a part of said measuring chirp signal emerging from said subject after interacting with tissue therein to be analyzed and forming an optical emerging signal;

arranging a plurality of detector elements around said subject at respective positions which are stationary relative to said subject, in alternation with said coherent light sources, each detector element disposed to receive light from only one of said coherent light sources so that a part of said optical emerging signal is successively incident on said detector elements as said coherent light sources are successively energized, and generating from each detector element an electrical signal corresponding to the part of the optical emerging signal incident thereon;

superimposing each electrical signal from each detector element at a mixing location with said electrical reference chirp signal to form a plurality of superposition signals each having sets of beats, each set of beats having a respective beat frequency;

separately filtering said superposition signals through transmission ranges having an identical upper limit frequency and thereby generating from said superposition signals a plurality of respective filtered signals each having at least one beat frequency within said transmission range;

combining said filtered signals to form a combined filtered signal; and

adjusting at least one of a distance between said generator source and said mixing location, a distance between said coherent light source and said light exit zone and said upper limit frequency for, in combination, dimensioning the transit time of said measuring chirp signal outside said subject, the transit time of said electrical reference chirp signal, and said upper limit frequency for causing said combined filtered signal to represent substantially only parts of said optical emerging signal which have traversed an optical path length in said subject which does not exceed a defined maximum optical path length.