Optical mapping apparatus with adjustable depth resolution

• US 5,975,697 A
• Filed: 11/25/1998
• Issued: 11/02/1999
• Est. Priority Date: 11/25/1998
• Status: Expired due to Term

• Current Assignee: Optos Plc (Nikon Corporation)
• Original Assignee: OTI Ophthalmic Technologies Inc.
• Inventors: Jackson, David A., Podoleanu, Adrian Gh.
• Primary Examiner(s): MANUEL, GEORGE C
• Application Number:
  US09/199,153
• Time in Patent Office: 342 Days
• Field of Search: 351/206, 351/207, 351/211, 351/212, 351/221, 351/246, 356/345, 356/346, 356/349, 356/357
• US Class Current: 351/206
• CPC Class Codes: A61B 3/102 for optical coherence tomography [OCT]
• CPC Class Codes: A61B 3/1025 for confocal scanning
• CPC Class Codes: G01B 9/02009 by using two or more low coherence lengths using different or varying spectral width
• CPC Class Codes: G01B 9/02012 using temporal intensity variation
• CPC Class Codes: G01B 9/02028 Two or more reference or object arms in one interferometer
• CPC Class Codes: G01B 9/02048 Rough and fine measurement
• CPC Class Codes: G01B 9/02058 by particular optical compensation or alignment elements, e.g. dispersion compensation
• CPC Class Codes: G01B 9/02091 Tomographic interferometers, e.g. based on optical coherence
• CPC Class Codes: G01N 21/4795 spatially resolved investigating of object in scattering medium in vivo A61B

Abstract

Optical mapping apparatus with adjustable depth resolution is provided. The optical mapping apparatus can display transversal images in an object, particularly the eye. The apparatus can deliver two or more images with different depth resolutions, or a combination of these images, or only one image with adjustable depth resolution. There is also provided optical mapping apparatus with adjustable depth resolution, where OCT images are corrected for the curvature at the back of the eye lens.

Claims

1. Optical mapping apparatus with adjustable depth resolution, comprising:

an interferometer chosen from the group consisting of fiberized interferometers and bulk interferometers, wherein said interferometer is excited by an optical source with adjustable coherence length, said interferometer comprising a first optical path and a second optical path leading to an object location, and to a reference reflector, respectively;

raster scanning means for transversally scanning an optical output from the said interferometer over a predetermined area about a point in a raster, or for moving the optical output from the interferometer to a point in a raster;

interface optics for transferring an optical beam from the raster scanning means to an object situated at the object location and for transferring an optical output beam reflected and scattered from the object back to the interferometer, along said first optical path;

means to alter at least one of the first optical path and the second path, so as to introduce intensity modulation, or phase modulation, or intensity modulation and phase modulation;

analyzing means, coupled to said raster scanning means, for demodulating the photodetected signal;

means for longitudinal scanning, to alter the length of the first optical path or the second optical path over a predetermined amount, for at least one of the points in the raster, in steps or continuously, at a pace synchronised with transversal scanning means; and

means for displaying or storing an image of at least part of said object.

2. Optical mapping apparatus according to claim 1, wherein said optical source comprises two superposed radiation sources, one first said source having a very short coherence length, and the other second said source having a coherence length greater than that of the first said first source;

wherein both sources have substantially the same central wavelength.

3. Optical mapping apparatus according to claim 2, wherein the coherence length of at least one of said optical sources is electrically adjustable to provide either a continuous range for the compound source from less than a few micrometers or a few tens of micrometers, to more than a few hundreds of micrometers, or to provide adjustability on some subintervals, by applying a combination of currents thereto.

4. Optical mapping apparatus according to claim 2, wherein said optical source comprises an electronic unit, for changing the ratio of the powers of said two radiation sources;

wherein, when changing the ratio of the powers of said two superposed radiation sources, said electronic unit ensures that the overall intensity is kept constant, or that the bias intensity in the final image is kept constant.

5. Optical mapping apparatus according to claim 2, wherein the optical source comprises an electro-optic element for balancing the contribution of the two component sources in the final output beam.

6. Optical mapping apparatus according to claim 5, wherein said electro-optic element is an electrically controllable directional coupler.

7. Optical mapping apparatus according to claim 2, wherein said optical source comprises two first fibers, each said first fiber being arranged for transmitting light from a respective optical source, and a second fiber for collecting light from said source fibers, said second fiber being translatable between said first fibers.

8. Optical mapping apparatus according to claim 2, wherein said optical source comprises two first fibers, each first fiber being arranged for transmitting light from a respective one of said sources, and a collecting mirror for collecting light from said first fibers.

9. Optical mapping apparatus according to claim 3, wherein the output beams of said two superposed radiation sources are orientated and focused to ensure an intersection of areas of their spatial distribution power.

10. Optical mapping apparatus according to claim 2, comprising a translatable collecting fiber for collecting light from said optical sources.

11. Optical mapping apparatus according to claim 2, wherein said optical source with adjustable coherence length is a subnanosecond tunable optical source which is adapted to be tuned under subnanosecond electrical pulse control in a bandwidth for which the associated correlation profile width secures a predetermined depth resolution.

12. Optical mapping apparatus according to claim 2, wherein said first optical source of largest bandwidth is modulated in intensity at a first frequency, and the second source of narrowest bandwidth is modulated in intensity at a second frequency, said first and second frequencies being different, and their ratio being an irrational numeral, and wherein said photodetected signal is sent to a first receiver tuned on said first frequency and to a second receiver tuned on a second frequency, so as to select the corresponding images, where the first corresponding image has a very narrow sectioning interval given by said first receiver tuned on said the first frequency, and where the second corresponding image has a wider sectioning interval given by said second receiver tuned on said second frequency;

and

wherein said first and second corresponding images are displayed simultaneously by way of a two input display device.

13. Optical mapping apparatus according to claim 12, wherein the depth resolution in the final image or in the two or three images produced by the apparatus is adjustable by choosing a step chosen from the group of steps consisting of:

(i) adjusting the depth sectioning interval of a confocal optical receiver image;

(ii) varying the sectioning interval of one of the interferometer images by changing the coherence length of the source or of one of the sources; and

(iii) weighting the contributions of the interferometer and confocal optical receiver in a compound image, so as to provide an adjustable resolution depth from a minimum given by the minimum coherence length of the said first source to a maximum given by either the confocal optical receiver or the maximum coherence length of the said second source.

14. Optical mapping apparatus according to claim 1, wherein said optical source with adjustable coherence length is a multi-electrode laser diode.

15. Optical mapping apparatus according to claim 1, wherein there is a reference beam for said interferometer, and wherein said apparatus is further provided with a blocking means to block said reference beam, and wherein, when said blocking means is activated, it synchronously switches the input of the displaying device to the output of a high gain amplifier for the photodetected signal.

16. Optical mapping apparatus according to claim 15, where said interferometer uses balance detection, and wherein said amplifier provides the addition of the photodetected signals, the result of which is then sent to a displaying device.

17. Optical mapping apparatus according to claim 15, wherein, when said photodetectors are avalanche, their gain is switched automatically by a reference power via the voltage drop on series resistors connected therewith, said optical mapping apparatus is switched between a confocal regime of operation and an OCT regime of operation.

18. Optical mapping apparatus according to claim 15, wherein, when said interferometer is a bulk interferometer, the depth resolution of the image obtained with the reference arm blocked can be adjusted by varying the numerical aperture of optics preceding a photodetector, when the photodetector is used, or by simultaneously varying the numerical apertures of optics preceding two photodetectors when balance detection is employed, said numerical apertures being varied by adjusting either the focal length of the lenses or by adjusting the diameter of the pinhole in the optics preceding the photodetector, or photodetectors when balance detection is used.

19. Optical mapping apparatus according to claim 1, comprising a feedback loop under synchronous control of said raster scanning means for providing a curvature-corrected transversal image.

20. Optical mapping apparatus according to claim 1, wherein the means to alter the length of the reference beam comprises at least one galvanometer-mirror.

21. Optical mapping apparatus according to claim 20, wherein said means to alter the length of a reference beam for said interferometer comprises a galvanometer-mirror placed at a distance f+δ

from a convergent lens, and a mirror at a distance f from said convergent lens, where f is the focal length of the convergent lens and where the incidence beam on the galvanometer-mirror is δ

away from the galvanometer-mirror axis.

22. Optical mapping apparatus according to claim 20, wherein the means to alter the length of a reference beam for said interferometer comprises a galvanometer-mirror, a convergent lens, and a first mirror at a distance f away from the lens, and a second mirror to implement a double pass on the galvanometer-mirror and so as to increase the path variation;

wherein the point of incidence of a beam on the galvanometer-mirror is on its axis and in the focal plane of the lens; and

wherein the lens is laterally shifted in the plane of the scanned rays to ensure that, at the maximum angle of deviation, light reflected by said first mirror and refracted by the lens falls on said galvanometer-mirror.

23. Optical mapping apparatus according to claim 20, comprising a display scanning device in which a vertical display thereof performs in alternate directions which are changed at each change of a voltage ramp slope of a voltage applied to said galvanometer.

24. Optical mapping apparatus according to claim 23, where the galvanometer scanner giving the line in the raster can be used only to create the phase modulation to carry parts of the OCT image signal.

25. Optical mapping apparatus according to claim 24, where a combination of the modulation due to the galvanometer scanner giving the line in the raster, and of the modulation due to an extra phase modulator, is employed to carry all of the OCT image signal.

26. Optical mapping apparatus according to claim 24, where an electronic filter in a receiver may discard parts of the low frequency spectrum, and pass frequencies up to the maximum phase modulation frequencies resulting by the pass modulation introduced by transversal scanning the object.

27. Optical mapping apparatus according to claim 24, where the frequency of the carrier created by the said galvanometer scanner can be increased by shifting the incident optical beam away from the centre of the galvanometer mirror.

28. Optical mapping apparatus according to claim 20, wherein said means to alter the length of a reference beam for said interferometer comprises a first galvonmeter-mirror, a first convergent lens, a second galvonmeter-mirror, and a second convergent lens, where each respective lens is placed at a distance f+s from the respective galvonmeter-mirror, wherein f is the focal length of each respective convergent lens;

wherein the incidence beam on the first galvonmeter-mirror is redirected to said second galvonmeter-mirror and thence to a second optical output path.

29. Optical mapping apparatus according to claim 1, wherein said apparatus includes software which can generate a transversal image O_s with different equivalent depth resolutions, by combining transversal OCT images collected at different depths, wherein said software generated image has a depth resolution between the minimum ensured by the coherence length of the optical source up to a maximum determined by the range of transversal images which have been collected;

and

wherein each image contribution to the final image is weighted according to a predetermined profile.

30. Optical mapping apparatus according to claim 1, where a processor can be introduced in each input of a display device to provide either a linear, logarithmic, or squared version of an input signal thereto.

31. Optical mapping apparatus with adjustable depth resolution, comprising:

an interferometer chosen from the group consisting of fiberized interferometers and bulk interferometers, wherein said interferometer is excited by an optical radiation source or a source with adjustable coherence length, said interferometer comprising a first optical path and a second optical path leading to an object location and to a reference reflector, respectively;

a confocal optical receiver with adjustable focal depth;

an optical splitter for internally directing light returned from an object situated at said object location to said optical confocal receiver;

raster scanning means for raster scanning an optical output from the interferometer over a line, or over a predetermined area;

interface optics for transferring an optical beam from said raster scanning means to the object and for transferring an optical output beam reflected and scattered from the object back to said optical splitter through said raster scanning means, and from said optical splitter to both of said interferometer and said optical confocal receiver, in a ratio determined by said optical splitter;

means to alter at least one of the first optical path and the second optical path, to introduce intensity modulation, or phase modulation, or intensity modulation and phase modulation;

analyzing means, coupled to said raster scanning means, for demodulating the photodetected signal;

means for longitudinal scanning, to alter the length of the first optical path or the second optical path over a predetermined amount, for at least one point in the raster, in steps or continuously, at a pace synchronised with transversal scanning means;

means for processing an image created by said interferometer and an image created by said confocal receiver; and

means for the simultaneous display of the said respective images created by said interferometer and by said confocal receiver.

32. Optical mapping apparatus according to claim 31, wherein said optical source comprises two superposed radiation sources, one first said source having a very short coherence length, and the other second said source having a coherence length greater than that of the first said first source;

wherein both sources have substantially the same central wavelength.

33. Optical mapping apparatus according to claim 32, wherein the coherence length of at least one of said optical sources is electrically adjustable to provide either a continuous range for the compound source from less than a few micrometers or a few tens of micrometers, to more than a few hundreds of micrometers, or to provide adjustability on some subintervals, by applying a combination of currents thereto.

34. Optical mapping apparatus according to claim 32, wherein said optical source comprises an electronic unit, for changing the ratio of the powers of said two radiation sources;

wherein, when changing the ratio of the powers of said two superposed radiation sources, said electronic unit ensures that the overall intensity is kept constant, or that the bias intensity in the final image is kept constant.

35. Optical mapping apparatus according to claim 32, wherein the optical source comprises an electro-optic element for balancing the contribution of the two component sources in the final output beam.

36. Optical mapping apparatus according to claim 32, wherein said electro-optic element is an electrically controllable directional coupler.

37. Optical mapping apparatus according to claim 32, wherein said optical source comprises two first fibers, each said first fiber being arranged for transmitting light from a respective optical source, and a second fiber for collecting light from said source fibers, said second fiber being translatable between said first fibers.

38. Optical mapping apparatus according to claim 32, wherein said optical source comprises two first fibers, each first fiber being arranged for transmitting light from a respective one of said sources, and a collecting mirror for collecting light from said first fibers.

39. Optical mapping apparatus according to claim 32, wherein the output beams of said two superposed radiation sources are orientated and focused to ensure an intersection of areas of their spatial distribution power.

40. Optical mapping apparatus according to claim 32, comprising a translatable collecting fiber for collecting light from said optical sources.

41. Optical mapping apparatus according to claim 32, wherein said optical source with adjustable coherence length is a subnanosecond tunable optical source which is adapted to be tuned under subnanosecond electrical pulse control in a bandwidth for which the associated correlation profile width secures a predetermined depth resolution.

42. Optical mapping apparatus according to claim 32, wherein said first optical source of largest bandwidth is modulated in intensity at a first frequency, and the second source of narrowest bandwidth is modulated in intensity at a second frequency, said first and second frequencies being different, and their ratio being an irrational numeral, and wherein said photodetected signal is sent to a first receiver tuned on said first frequency and to a second receiver tuned on a second frequency, so as to select the corresponding images, where the first corresponding image has a very narrow sectioning interval given by said first receiver tuned on said the first frequency, and where the second corresponding image has a wider sectioning interval given by said second receiver tuned on said second frequency;

and

wherein said first and second corresponding images are displayed simultaneously by way of a three input display device.

43. Optical mapping apparatus according to claim 31, wherein said optical source with adjustable coherence length is a multi-electrode laser diode.

44. Optical mapping apparatus according to claim 31, wherein said optical source is broadband.

45. Optical mapping apparatus according to claim 31, wherein said optical splitter is a bulk beamsplitter.

46. Optical mapping apparatus according to claim 45, wherein said confocal receiver comprises an adjustable pinhole behind a lens or between lenses and a photodetector, and the focal depth interval is adjustable independently of the said interferometer.

47. Optical mapping apparatus according to claim 46, wherein said optical source is broadband, and wherein the depth resolution in a final image produced by said optical mapping apparatus is adjustable by choosing a step chosen from the group of steps consisting of:

(i) adjusting the depth sectioning interval of the image produced by the confocal optical receiver; and

(ii) balancing the amplitudes of an interferometer image signal and of an optical confocal receiver signal sent to display means, so as to provide an adjustable resolution depth from a minimum given by the coherence length of the broadband source to a maximum given by the confocal optical receiver.

48. Optical mapping apparatus according to claim 46, wherein the depth resolution in a final image produced by the apparatus choosing a step chosen from the group of steps consisting of:

(i) adjusting the depth sectioning interval of a confocal optical receiver image;

(ii) varying the sectioning interval of an interferometer image by changing the coherence length of the source; and

(iii) weighting the contributions of the interferometer and confocal optical receiver to a compound image, so as to provide an adjustable resolution depth from a minimum given by the minimum coherence length of said first source to a maximum given by either the confocal optical receiver or the maximum coherence length of said second source.

49. Optical mapping apparatus according to claim 45, wherein said confocal receiver comprises a fiber pigtail terminated on a photodetector.

50. Optical mapping apparatus according to claim 49, wherein said optical source is broadband;

wherein the depth resolution in a final image produced by said optical mapping apparatus is adjustable by balancing the amplitudes of an interferometer image signal and of an optical confocal receiver signal sent to a display means, so as to provide an adjustable resolution depth from a minimum given by the coherence length of the broadband source to a maximum given by the confocal optical receiver.

51. Optical mapping apparatus according to claim 31, wherein said optical splitter is a fiberized directional coupler terminated on a pigtailed photodetector provided on said optical confocal receiver, and wherein the fiber input of the directional coupler acts as the aperture of said confocal optical receiver, and said optical splitter is part of said first optical path of said interferometer.

52. Optical mapping apparatus according to claim 51, wherein said optical source is broadband;

wherein the depth resolution in a final image produced by said optical mapping apparatus is adjustable by balancing the amplitudes of an interferometer image signal and of an optical confocal receiver signal sent to a display means, so as to provide an adjustable resolution depth from a minimum given by the coherence length of the broadband source to a maximum given by the confocal optical receiver.

53. Optical mapping apparatus according to claim 51, wherein the depth resolution in a final image produced by the apparatus is adjustable by choosing a step from the group of steps consisting of:

(i) varying the sectioning interval of an image produced by the interferometer by changing the coherence length of the source; and

(ii) weighting the contributions of the interferometer and confocal optical receiver, so as to provide an adjustable resolution depth from a minimum given by the minimum coherence length of the source to a maximum given by the confocal optical receiver.

54. Optical mapping apparatus according to claim 31, wherein the image given by said confocal optical receiver is used in the storage process of the image given by an OCT channel, to compensate during its acquisition, for the transversal object movement.

55. Optical mapping apparatus according to claim 54, wherein the means for processing images can perform mathematical operations in a pixel-by-pixel format using the image obtained by said storage process.

56. Optical mapping apparatus according to claim 31, wherein the means for processing an image can perform mathematical operations in a pixel-by-pixel format using the interferometer image and the confocal optical receiver image.

57. Optical mapping apparatus according to claim 31, wherein there is a reference beam for said interferometer, and wherein said apparatus is further provided with a blocking means to block said reference beam, and wherein, when said blocking means is activated, it synchronously switches the input of the displaying device to the output of a high gain amplifier for the photodetected signal.

58. Optical mapping apparatus according to claim 57, wherein, when said interferometer is a bulk interferometer, the depth resolution of the image obtained with the reference arm blocked can be adjusted by varying the numerical aperture of optics preceding a photodetector, when the photodetector is used, or by simultaneously varying the numerical apertures of optics preceding two photodetectors when balance detection is employed, said numerical apertures being varied by adjusting either the focal length of the lenses or by adjusting the diameter of the pinhole in the optics preceding the photodetector, or photodetectors when balance detection is used.

59. Optical mapping apparatus according to claim 31, wherein said optical splitter has an optimized splitting ratio, so as to ensure optimal signal-to-noise ratios in images generated by both the interferometer and the optical confocal receiver.

60. Optical mapping apparatus according to claim 31, comprising a feedback loop under synchronous control of said raster scanning means for providing a curvature-corrected transversal image.

61. Optical mapping apparatus according to claim 31, wherein the means to alter the length of the reference beam comprises at least one galvanometer-mirror.

62. Optical mapping apparatus according to claim 61, wherein said means to alter the length of a reference beam for said interferometer comprises a galvanometer-mirror placed at a distance f+δ

from a convergent lens, and a mirror at a distance f from said convergent lens, where f is the focal length of the convergent lens and where the incidence beam on the galvanometer-mirror is δ

away from the galvanometer-mirror axis.

63. Optical mapping apparatus according to claim 61, wherein the means to alter the length of a reference beam for said interferometer comprises a galvanometer-mirror, a convergent lens, and a first mirror at a distance f away from the lens, and a second mirror to implement a double pass on the galvanometer-mirror and so as to increase the path variation;

wherein the point of incidence of a beam on the galvanometer-mirror is on its axis and in the focal plane of the lens; and

wherein the lens is laterally shifted in the plane of the scanned rays to ensure that, at the maximum angle of deviation, light reflected by said first mirror and refracted by the lens falls on said galvanometer-mirror.

64. Optical mapping apparatus according to claim 61, comprising a display scanning device in which a vertical display thereof performs in alternate directions which are changed at each change of a voltage ramp slope of a voltage applied to said galvanometer.

65. Optical mapping apparatus according to claim 64, where the galvanometer scanner giving the line in the raster can be used only to create the phase modulation to carry parts of the OCT image signal.

66. Optical mapping apparatus according to claim 65, where a combination of the modulation due to the galvanometer scanner giving the line in the raster, and of the modulation due to an extra phase modulator, is employed to carry all of the OCT image signal.

67. Optical mapping apparatus according to claim 65, where an electronic filter in a receiver may discard parts of the low frequency spectrum, and pass frequencies up to the maximum phase modulation frequencies resulting by the pass modulation introduced by transversal scanning the object.

68. Optical mapping apparatus according to claim 65, where the frequency of the carrier created by the said galvanometer scanner can be increased by shifting the incident optical beam away from the centre of the galvanometer mirror.

69. Optical mapping apparatus according to claim 61, wherein said means to alter the length of a reference beam for said interferometer comprises a first galvonmeter-mirror, a first convergent lens, a second galvonmeter-mirror, and a second convergent lens, where each respective lens is placed at a distance f+s from the respective galvonmeter-mirror, wherein f is the focal length of each respective convergent lens;

wherein the incidence beam on the first galvonmeter-mirror is redirected to said second galvonmeter-mirror and thence to a second optical output path.

70. Optical mapping apparatus according to claim 31, wherein said apparatus includes software which can generate a transversal image O_s with different equivalent depth resolutions, by combining transversal OCT images collected at different depths, wherein said software generated image has a depth resolution between the minimum ensured by the coherence length of the optical source up to a maximum determined by the range of transversal images which have been collected;

and

wherein each image contribution to the final image is weighted according to a predetermined profile.

71. Optical mapping apparatus according to claim 31, where a processor can be introduced in each input of a display device to provide either a linear, logarithmic, or squared version of an input signal thereto.

80. Optical mapping apparatus according to claim 68, comprising a display scanning device in which a vertical display thereof performs in alternate directions which are changed at each change of a voltage ramp slope of a voltage applied to said galvanometer.

81. Optical mapping apparatus according to claim 80, where the galvanometer scanner giving the line in the raster can be used only to create the phase modulation to carry parts of the OCT image signal.

82. Optical mapping apparatus according to claim 81, where a combination of the modulation due to the galvanometer scanner giving the line in the raster, and of the modulation due to an extra phase modulator, is employed to carry all of the OCT image signal.

83. Optical mapping apparatus according to claim 81, where an electronic filter in a receiver may discard parts of the low frequency spectrum, and pass frequencies up to the maximum phase modulation frequencies resulting by the pass modulation introduced by transversal scanning the object.

84. Optical mapping apparatus according to claim 81, where the frequency of the carrier created by the said galvanometer scanner can be increased by shifting the incident optical beam away from the centre of the galvanometer mirror.

72. Optical mapping apparatus with adjustable depth resolution, comprising:

an interferometer chosen from the group consisting of fiberized interferometers and bulk interferometers, wherein said interferometer is excited by an optical source chosen from the group consisting of broadband optical sources and sources having adjustable coherence length;

wherein said interferometer comprises a first optical path and a second optical path leading to an object location, and to a reference reflector, respectively;

an optical element for producing an enlargement of the correlation function of the optical source when placed in either of said first path or said second path;

raster scanning means for transversally scanning an optical output from said interferometer over a predetermined area;

interface optics, for transferring an optical beam from said raster scanning means to an object situated at said object location, and for transferring an optical output beam reflected and scattered from said object back to said interferometer, along said first optical path;

means to alter at least one of said first optical path and said second optical path, to introduce intensity modulation, or phase modulation, or intensity modulation and phase modulation;

analyzing means, coupled to said raster scanning means, for demodulating the photodetected signal;

means for longitudinal scanning, to alter the length of the first optical path or the second optical path over a predetermined amount, for at least one point in the raster, in steps or continuously, at a pace synchronised with transversal scanning means; and

means for displaying or storing an image of at least part of said object.

73. Optical mapping apparatus according to claim 72, wherein said optical element for enlarging the correlation profile of the optical source is a dispersive element which causes an increase in the associated coherence length.

74. Optical mapping apparatus according to claim 73, wherein said dispersive element can be gradually introduced into the first or second path for a continuous adjustment of the coherence length and consequently of the depth resolution in an image generated by said optical mapping apparatus.

75. Optical mapping apparatus according to claim 72, wherein said optical element for enlarging the correlation profile of the optical source is a multi-step echelon.

76. Optical mapping apparatus according to claim 72, comprising a feedback loop under synchronous control of said raster scanning means for providing a curvature-corrected transversal image.

77. Optical mapping apparatus according to claim 72, wherein the means to alter the length of the reference beam comprises at least one galvanometer-mirror.

78. Optical mapping apparatus according to claim 77, wherein said means to alter the length of a reference beam for said interferometer comprises a galvanometer-mirror placed at a distance f+δ

from a convergent lens, and a mirror at a distance f from said convergent lens, where f is the focal length of the convergent lens and where the incidence beam on the galvanometer-mirror is δ

away from the galvanometer-mirror axis.

79. Optical mapping apparatus according to claim 77, wherein the means to alter the length of a reference beam for said interferometer comprises a galvanometer-mirror, a convergent lens, and a first mirror at a distance f away from the lens, and a second mirror to implement a double pass on the galvanometer-mirror and so as to increase the path variation;

wherein the point of incidence of a beam on the galvanometer-mirror is of its axis and in the focal plane of the lens; and

wherein the lens is laterally shifted in the plane of the scanned rays to ensure that, at the maximum angle of deviation, light reflected by said first mirror and refracted by the lens falls on said galvanometer-mirror.

85. Optical mapping apparatus according to claim 77, wherein said means to alter the length of a reference beam for said interferometer comprises a first galvonmeter-mirror, a first convergent lens, a second galvonmeter-mirror, and a second convergent lens, where each respective lens is placed at a distance f+s from the respective galvonmeter-mirror, wherein f is the focal length of each respective convergent lens;

wherein the incidence beam on the first galvonmeter-mirror is redirected to said second galvonmeter-mirror and thence to a second optical output path.

86. Optical mapping apparatus according to claim 72, wherein said apparatus includes software which can generate a transversal image O_s with different equivalent depth resolutions, by combining transversal OCT images collected at different depths, wherein said software generated image has a depth resolution between the minimum depth resolution in a single OCT image up to a maximum determined by the range of depth wherefrom transversal images have been collected;

and

wherein each image contribution to the final image is weighted according to a predetermined profile.

87. Optical mapping apparatus according to claim 72, where a processor can be introduced in each input of a display device to provide either a linear, logarithmic, or squared version of an input signal thereto.

88. Optical mapping apparatus with adjustable depth resolution, comprising:

at least two interferometers excited by an optical source consisting of broadband optical sources and sources having adjustable coherence length;

wherein each of said interferometers comprises an at least partly common first optical path leading to an object location, and a respective second optical path for each interferometer, wherein each of said second optical paths leads to a respective reference reflector;

at least one device for producing an enlargement of the correlation function of the source when placed in at least one of said optical second paths;

adjustable raster scanning means for transversally scanning an optical output from said interferometers over a predetermined area;

interface optics for transferring an optical beam from said raster scanning means to an object situated at the object location, and for transferring an optical output beam reflected and scattered from the object back to said interferometers, along said first optical path;

means to alter said first optical path, or one of said second optical paths, to introduce intensity modulation, phase modulation, or intensity modulation and phase modulation;

analyzing means, coupled to said raster scanning means, for demodulating the photodetected signal;

longitudinal scanning means to alter the length of said first optical path or said second optical path in each interferometer simultaneously over a predetermined amount, for at least one point in the raster, in steps or continuously, at a pace synchronised with transversal scanning means; and

means for displaying or storing two images of at least part of said object.

89. Optical mapping apparatus according to claim 88, wherein said first optical path is completely shared by said interferometers, and wherein said analyzing means uses a single photo receiver for all of said interferometers, and for each said second optical path;

wherein said optical mapping apparatus comprises a phase modulator in each interferometer, where each respective phase modulation is driven at a different frequency sufficiently distant apart from the other respective phase modulation frequencies for said analyzing means to be able to separate the respective signals in said interferometers, by means of subsequent frequency band pass filtering.

90. Optical mapping apparatus according to claim 89, further comprising means for processing signals in said interferometers using mathematical operations in a pixel-by-pixel format in a controllable ratio using respective images created by each said interferometer.

91. Optical mapping apparatus according to claim 89, wherein said optical element for enlarging the correlation profile of said optical source can be gradually introduced into the second path of one of the interferometers, for continuous adjustment of the depth resolution of an image provided by that interferometer.

92. Optical mapping apparatus according to claim 89, wherein said optical element for enlarging the correlation profile of the optical source is a dispersive element which causes an increase in the associated coherence length.

93. Optical mapping apparatus according to claim 92, wherein an image in the one of the said interferometers which has the poorest depth resolution, obtained by using said optical element for enlarging the correlation profile, is used in a process for storing an image with the best depth resolution, obtained using another interferometer with no such optical element, in order to compensate for transversal object movement during image acquisition.

94. Optical mapping apparatus according to claim 89, wherein said optical element for enlarging the correlation profile of the optical source is a multi-step echelon.

95. Optical mapping apparatus according to claim 88, further comprising means for processing signals in said interferometers using mathematical operations in a pixel-by-pixel format in a controllable ratio using respective images created by each said interferometer.

96. Optical mapping apparatus according to claim 88, wherein said optical element for enlarging the correlation profile of said optical source can be gradually introduced into the second path of one of the interferometers, for continuous adjustment of the depth resolution of an image provided by that interferometer.

97. Optical mapping apparatus according to claim 88, wherein said optical element for enlarging the correlation profile of the optical source is a dispersive element which causes an increase in the associated coherence length.

98. Optical mapping apparatus according to claim 97, wherein an image in the one of the said interferometers which has the poorest depth resolution, obtained by using said optical element for enlarging the correlation profile, is used in a process for storing an image with the best depth resolution, obtained using another interferometer with no such optical element, in order to compensate for transversal object movement during image acquisition.

99. Optical mapping apparatus according to claim 88, wherein said optical element for enlarging the correlation profile of the optical source is a multi-step echelon.

100. Optical mapping apparatus according to claim 88, comprising a feedback loop under synchronous control of said raster scanning means for providing a curvature-corrected transversal image.

101. Optical mapping apparatus according to claim 88, wherein the means to alter the length of the reference beam comprises at least one galvanometer-mirror.

102. Optical mapping apparatus according to claim 101, wherein said means to alter the length of a reference beam for said interferometer comprises a galvanometer-mirror placed at a distance f+δ

from a convergent lens, and a mirror at a distance f from said convergent lens, where f is the focal length of the convergent lens and where the incidence beam on the galvanometer-mirror is δ

away from the galvanometer-mirror axis.

103. Optical mapping apparatus according to claim 101, wherein the means to alter the length of a reference beam for said interferometer comprises a galvanometer-mirror, a convergent lens, and a first mirror at a distance f away from the lens, and a second mirror to implement a double pass on the galvanometer-mirror and so as to increase the path variation;

wherein the point of incidence of a beam on the galvanometer-mirror is on its axis and in the focal plane of the lens; and

wherein the lens is laterally shifted in the plane of the scanned rays to ensure that, at the maximum angle of deviation, light reflected by said first mirror and refracted by the lens falls on said galvanometer-mirror.

104. Optical mapping apparatus according to claim 101, comprising a display scanning device in which a vertical display thereof performs in alternate directions which are changed at each change of a voltage ramp slope of a voltage applied to said galvanometer.

105. Optical mapping apparatus according to claim 104, where the galvanometer scanner giving the line in the raster can be used only to create the phase modulation to carry parts of the OCT image signal.

106. Optical mapping apparatus according to claim 105, where a combination of the modulation due to the galvanometer scanner giving the line in the raster, and of the modulation due to an extra phase modulator, is employed to carry all of the OCT image signal.

107. Optical mapping apparatus according to claim 105, where an electronic filter in a receiver may discard parts of the low frequency spectrum, and pass frequencies up to the maximum phase modulation frequencies resulting by the pass modulation introduced by transversal scanning the object.

108. Optical mapping apparatus according to claim 105, where the frequency of the carrier created by the said galvanometer scanner can be increased by shifting the incident optical beam away from the centre of the galvanometer mirror.

109. Optical mapping apparatus according to claim 101, wherein said means to alter the length of a reference beam for said interferometer comprises a first galvonmeter-mirror, a first convergent lens, a second galvonmeter-mirror, and a second convergent lens, where each respective lens is placed at a distance f+s from the respective galvonmeter-mirror, wherein f is the focal length of each respective convergent lens;

wherein the incidence beam on the first galvonmeter-mirror is redirected to said second galvonmeter-mirror and thence to a second optical output path.

110. Optical mapping apparatus according to claim 88, where said optical mapping apparatus can be used to generate longitudinal images by using said transversal scanning means to generate a 1D sample over the object, and by replacing one of the transversal coordinates in the image with the longitudinal coordinate corresponding to the optical path difference introduced by said longitudinal scanning means.

111. Optical mapping apparatus according to claim 88, wherein said apparatus includes software which can generate a transversal image O_s with different equivalent depth resolutions, by combining transversal OCT images collected at different depths, wherein said software generated image has a depth resolution between the minimum depth resolution in a single OCT image up to a maximum determined by the range of depth wherefrom transversal images have been collected;

and

wherein each image contribution to the final image is weighted according to a predetermined profile.

112. Optical mapping apparatus according to claim 88, where a processor can be introduced in each input of a display device to provide either a linear, logarithmic, or squared version of an input signal thereto.