WO2001001849A1 - Closed loop optical coherence topography - Google Patents
Closed loop optical coherence topography Download PDFInfo
- Publication number
- WO2001001849A1 WO2001001849A1 PCT/AU2000/000802 AU0000802W WO0101849A1 WO 2001001849 A1 WO2001001849 A1 WO 2001001849A1 AU 0000802 W AU0000802 W AU 0000802W WO 0101849 A1 WO0101849 A1 WO 0101849A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- sample
- path length
- light
- topology
- path
- Prior art date
Links
- 230000003287 optical effect Effects 0.000 title claims abstract description 27
- 238000012876 topography Methods 0.000 title claims abstract description 9
- 238000000034 method Methods 0.000 claims abstract description 22
- 239000000835 fiber Substances 0.000 claims description 10
- 230000008859 change Effects 0.000 claims description 4
- 239000000523 sample Substances 0.000 description 49
- 238000012014 optical coherence tomography Methods 0.000 description 12
- 210000004087 cornea Anatomy 0.000 description 8
- 238000012360 testing method Methods 0.000 description 4
- 230000010355 oscillation Effects 0.000 description 3
- 239000012472 biological sample Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000001356 surgical procedure Methods 0.000 description 2
- 208000003556 Dry Eye Syndromes Diseases 0.000 description 1
- 206010013774 Dry eye Diseases 0.000 description 1
- 238000010420 art technique Methods 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000003384 imaging method Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
- 238000013519 translation Methods 0.000 description 1
Classifications
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B3/00—Apparatus for testing the eyes; Instruments for examining the eyes
- A61B3/10—Objective types, i.e. instruments for examining the eyes independent of the patients' perceptions or reactions
- A61B3/107—Objective types, i.e. instruments for examining the eyes independent of the patients' perceptions or reactions for determining the shape or measuring the curvature of the cornea
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
- G01B11/2441—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures using interferometry
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B9/00—Measuring instruments characterised by the use of optical techniques
- G01B9/02—Interferometers
- G01B9/0209—Low-coherence interferometers
- G01B9/02091—Tomographic interferometers, e.g. based on optical coherence
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B2290/00—Aspects of interferometers not specifically covered by any group under G01B9/02
- G01B2290/20—Dispersive element for generating dispersion
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B2290/00—Aspects of interferometers not specifically covered by any group under G01B9/02
- G01B2290/35—Mechanical variable delay line
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B2290/00—Aspects of interferometers not specifically covered by any group under G01B9/02
- G01B2290/65—Spatial scanning object beam
Definitions
- the present invention relates to the field of optical coherence topography, of particular but by no means exclusive application in the area of cornea1 topography.
- OCT Optical Coherence Tomography
- OCT systems generate volume rather than surface maps, as they detect light scattered from a series of depths in the Z-axis as the reference mirror of the OCT interferometer is correspondingly scanned along its Z-axis.
- the actual depth within the sample of a feature is determined from the Z coordinate of the scanned reference mirror at the time of detection.
- Detected features may be on the surface of the sample or, if the incident light can penetrate the sample (as is the case with many biological samples), within the sample. In either case, a large three dimensional data cube must be collected even though, in many applications, a surface topology is all that is of interest.
- the resolution of the three dimensional data is ordinarily limited by the coherence envelope (typically 10 to 20 ⁇ m) .
- This large OCT data set or "volume map” must then be analyzed to extract the desired information, a lengthy data reduction task.
- the results of an OCT scan will reveal the transitions or boundaries between layers of differing refractive index. The most significant of these will be between the air and the cornea itself, so extracting the three dimensional location of this boundary is equivalent to generating, from the original volume map, a surface map of the cornea.
- Figure 1 is a perspective view of the volume map 10 of OCT data that would be collected in order to obtain a surface map 12 of a cornea 14, which surface map 12 represents a small subset of the volume map 10.
- this technique is slow as a complete volume scan must first be performed - during which the sample must remain essentially motionless - and then the data set must be reduced to extract the desired information.
- the sample - such as an eye - may be difficult to immobilize, and the available computing resources may not be adequate to reduce the vast volume data set sufficiently quickly.
- a surface may be the external surface, or - in some applications - a surface defined by the boundary between two layers within the sample.
- an optical coherence topography apparatus for determining the topology of a surface of or within a sample, having: a light source for providing a beam of light; a beam splitter for splitting said beam into first and second components; a sample arm for receiving said sample and characterized by a first path length; scanning means for scanning said sample with said first component of said beam; a reference arm with a reference means for receiving said second component, said reference arm characterized by a second path length; and a light detector for detecting interference patterns due to interference of a reference beam from said reference means and a sample beam from said sample; wherein one of said first and said second path lengths is controllably adjustable and said apparatus includes control means responsive to changes in said interference patterns due to differences in said first path length as said sample is scanned, by adjusting said one of said first and said second path lengths to compensate for said changes in said first path length, whereby said adjustment in said one of first and second path lengths is indicative of said changes in said first path length and thereby of said topology
- the light source may comprise a broadband source of low coherence light or a narrowband source.
- a broadband source has a short coherence function, which therefore 'gates' the region from which reflections may be detected.
- one of said first and second path lengths is said second path length, and said control means is operable to adjust said second path length by controlling said reference means.
- the control means may be operable to adjust said first path length, such as by moving said sample or, where said sample arm includes an optic fibre, stretching said optic fibre.
- the topology of the sample can be deduced from the degree, at any point in the scanning of the sample, that the first or second path length is adjusted to compensate for variations in the first or sample arm path length due to that topology.
- the scanning means is preferably operable for scanning the sample in two orthogonal axes perpendicular to the direction of the first component of the beam.
- the beam splitter may comprise a partially silvered mirror or, preferably, an optical coupler such as a fused biconical taper coupler.
- said light source is a superluminescent diode or other broad bandwidth source.
- the light source may be an incandescent source, a mode-locked laser or a narrowband continuous wave laser.
- said reference arm includes an optical delay line, including dispersing means (such as a diffraction grating) for dispersing light received by said reference arm and a reflecting means with adjustable tilt for receiving light from said dispersing means and introducing a path difference according to said tilt.
- dispersing means such as a diffraction grating
- a reflecting means with adjustable tilt for receiving light from said dispersing means and introducing a path difference according to said tilt.
- said optical delay line is operable to decouple phase and group delay so that said phase delay can be used to provide a control signal and said group delay can be used to gate the zone from which a reflection can be received .
- the optical delay line may be implemented using acousto-optic or electro-optic devices.
- said light source comprises a narrowband laser and said reference arm includes an optical delay line, said delay line includinga reflecting means with adjustable tilt for introducing a path difference according to said tilt.
- the reflecting means may comprise any suitable mirror or prism (such as a 90° retro-reflector prism) .
- an apparatus for determining the topology of a corneal surface including the apparatus described above.
- the present invention further provides a method for determining the topology of a sample, comprising: splitting a beam of light into first and second components; scanning said sample characterized by a first path length with said first component and directing said second component to a reference means characterized by a second path length; forming an interference pattern of light reflected by said sample and from said reference means; detecting changes in said interference pattern due to variations in said first path length due to said topology of said sample; adjusting one of said first and second path lengths to compensate for said changes; and determining said topology from said adjustments.
- the beam of light may be a beam of low coherence light, and the beam may be a narrowband beam of light.
- Preferably said one of said first and second path length is said second path length.
- Preferably said adjusting of said second path length is by means of said reference means .
- said reference means includes dispersing means for dispersing light received by said reference means, and a reflecting means with adjustable tilt for receiving light from said dispersing means and introducing a path difference according to said tilt.
- said method includes providing said beam of light by means of a narrowband continuous wave laser, and said reference means includes a reflecting means with adjustable tilt for introducing a path difference according to said tilt.
- said scanning said sample is in a manner which minimises the rate of change of the first path length due to said topology.
- said scanning is in a spiral pattern.
- the present invention still further provides a method for determining the topology of a corneal surface, said method including the method described above.
- Figure 1 is a perspective view of an OCT data volume map collected in order to obtain a surface map of a cornea according to a prior art technique
- Figure 2 is a schematic view of an optical coherence tomograph apparatus according to a preferred embodiment of the present invention
- Figure 3 is a schematic representation of delay line of the apparatus of figure 2;
- Figure 4 is an interferogram depicting three possible interferograms from the apparatus of figure 2;
- Figure 5 is a schematic view of the apparatus of figure 2 in a test configuration with a mirror as a test sample and PZT fibre stretcher for simulating variations in the path length of the sample arm;
- Figures 6a, 6b and 6c are graphs of results from the test configuration
- Figure 7 depicts a preferred scanning pattern for the apparatus of figure 2;
- Figure 8 is a schematic view of a typical post- cut or operative) corneal profile
- Figure 9 depicts the path that the tracking system would need to follow if the corneal profile in figure 8 were traced using the spiral of figure 7.
- An optical coherence tomography apparatus is shown generally at 16 in figure 2, for determining the topology of a sample, for example cornea 18.
- a broadband light source in the form of superluminescent diode 20 illuminates a fibre-based ichelson interferometer, including optic fibres 22a,b,c,d, optical coupler 24, sample arm 26 (including focussing lens 28 and orthogonal scanners 30), reference arm 32 and detector 33.
- the detector 33 detects interference fringes only if the optical paths of the sample arm 26 and reference arm 32 match to within the coherence length of the source ( ⁇ 10 ⁇ m) .
- the apparatus 16 also includes a lock-in amplifier 34 and PID controller 36. In some embodiments the lock-in amplifier 34 may not be required.
- the reference arm 32 comprises a grating-based optical delay line (ODL), which utilizes the phase delay generated by tilted mirror to generate a control signal and the group delay in combination with the coherence function of the source to gate the zone in the sample from which a reflection can be detected.
- ODL grating-based optical delay line
- the light beam entering the reference arm 32 along fibre 22d is collimated by collimator 40 and dispersed by grating 42 before passing through lens 44 and impinging upon piezo- tilted mirror 46.
- the mirror 46 is controlled by PID controller 36 (see figure 2) .
- the beam then passes back through lens 44, via grating 42 to second pass mirror 48, before retracing the same optical path and exiting the reference arm 32.
- the grating 42 and lens 44 may clearly be replaced by a concave grating.
- the optical phase associated with the path length of the reference arm 32 is thus adjustable, and determined by the angle of mirror 46.
- This piezo-tilted mirror 46 provides the phase ramp, and the angle of tilt corresponds to an effective linear translation of the mirror 46.
- the proportionality is set by mirror tilt angle ⁇ and the offset of the pivot of the piezo-tilted mirror x 0 from the optical axis of the grating and lens.
- the operation of the grating based ODL is based on the Fourier correspondence between the phase ramp in the frequency domain and the group delay in time domain.
- the frequency of the interference fringes is controlled by the offset x 0 .
- Three interferograms 50 generated by scanning the tilt angle ⁇ are shown schematically in figure 4. Complete demodulation at zero offset results in the envelope 52, which does not produce a zero crossing and therefore cannot be used as a control signal.
- the higher frequency oscillation represents an up-converted fringe pattern 54.
- the lower frequency oscillation represents a down-converted fringe pattern 56.
- the frequency of the fringe pattern will, therefore, determine the angle of the zero-crossing point (of fringes with horizontal axis), and therefore the resolution with which this point - and therefore the sample 18 - can be located.
- the advantage of the adjustability of the fringe frequency is that one can trade off high stability of the apparatus (i.e. with low fringe frequency) versus high resolution (i.e. with high fringe frequency) as preferred or required.
- Figure 5 depicts a test arrangement of the apparatus of figure 2, where the sample is a plane mirror 60 and sample arm fibre 22c has been provided with a PZT fibre stretcher 62 for simulating variations in the path length of the sample arm 26.
- the bandwidth was about 10 Hz and the tracking range about 1 ⁇ m.
- PZT fibre stretcher 62 was driven with a saw-toothed signal 64 to effect an optical path variation in the sample arm 26: the effect on the position of the sample 60 is shown in figure 6b, where the corresponding movement of the sample is clearly visible.
- Figure 8 shows schematically a typical corneal profile after surgery in section.
- Figure 9 shows schematically the change in Z-axis coordinate of the tracking reference arm when the optical beam traces out a spiral path 72 on the cornea, plotted as delay d versus time t.
- An optical coherence tomography apparatus while generally similar to apparatus 16, employs a continuous wave laser light source, and a mirror rather than a diffraction grating.
- the laser can lock on to any fringe, so if there were two reflectors in a system that both produce approximately equal signals, it may be difficult to deduce which reflector is being tracked.
- the apparatus 16 with a broadband source in the form of superluminescent diode 20 one only detects a reflection when the reflection location matches the group delay (also set by the tilt and offset) to within the coherence length, thereby discriminating other reflectors that are located more than this length from the matched location.
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- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
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- General Physics & Mathematics (AREA)
- General Health & Medical Sciences (AREA)
- Ophthalmology & Optometry (AREA)
- Medical Informatics (AREA)
- Biophysics (AREA)
- Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
- Engineering & Computer Science (AREA)
- Biomedical Technology (AREA)
- Heart & Thoracic Surgery (AREA)
- Radiology & Medical Imaging (AREA)
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Abstract
Description
Claims
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP00940060A EP1204366A1 (en) | 1999-07-02 | 2000-06-30 | Closed loop optical coherence topography |
AU55143/00A AU5514300A (en) | 1999-07-02 | 2000-06-30 | Closed loop optical coherence topography |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AUPQ1398A AUPQ139899A0 (en) | 1999-07-02 | 1999-07-02 | Closed loop optical coherence topography |
AUPQ1398 | 1999-07-02 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2001001849A1 true WO2001001849A1 (en) | 2001-01-11 |
Family
ID=3815587
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/AU2000/000802 WO2001001849A1 (en) | 1999-07-02 | 2000-06-30 | Closed loop optical coherence topography |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP1204366A1 (en) |
AU (1) | AUPQ139899A0 (en) |
WO (1) | WO2001001849A1 (en) |
Cited By (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2003052345A1 (en) * | 2001-12-18 | 2003-06-26 | Massachusetts Institute Of Technology | System and method for measuring optical distance |
WO2003098312A1 (en) * | 2002-05-22 | 2003-11-27 | Carl Zeiss Meditec Ag | Optical coherence tomography scanner with negative field curvature |
GB2435322A (en) * | 2006-02-15 | 2007-08-22 | Oti Ophthalmic Technologies | Measuring curvature or axial position using OCT |
US7365858B2 (en) | 2001-12-18 | 2008-04-29 | Massachusetts Institute Of Technology | Systems and methods for phase measurements |
EP1975550A1 (en) * | 2007-03-28 | 2008-10-01 | Kabushiki Kaisha Topcon | Optical image measurement device |
US7557929B2 (en) | 2001-12-18 | 2009-07-07 | Massachusetts Institute Of Technology | Systems and methods for phase measurements |
CN107752985A (en) * | 2017-11-17 | 2018-03-06 | 苏州阿格斯医疗技术有限公司 | OCT image method, OCT image conduit and OCT systems |
WO2019227170A1 (en) * | 2018-06-01 | 2019-12-05 | OncoRes Medical Pty Ltd | A method and device for evaluating a mechanical property of a material |
JP2020039667A (en) * | 2018-09-12 | 2020-03-19 | 株式会社トプコン | Ophthalmic imaging apparatus, control method thereof, program, and recording medium |
WO2021131020A1 (en) * | 2019-12-27 | 2021-07-01 | 株式会社ニコン | Scanning method, scanning device, and scanning program |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
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WO1994018523A1 (en) * | 1993-02-01 | 1994-08-18 | Zygo Corporation | Method and apparatus for the rapid acquisition of data in coherence scanning interferometry |
WO1994018521A1 (en) * | 1993-02-08 | 1994-08-18 | Zygo Corporation | Method and apparatus for surface topography measurement by spatial-frequency analysis of interferograms |
WO1999001716A1 (en) * | 1997-07-01 | 1999-01-14 | David Macpherson | Ablation profiler |
-
1999
- 1999-07-02 AU AUPQ1398A patent/AUPQ139899A0/en not_active Abandoned
-
2000
- 2000-06-30 EP EP00940060A patent/EP1204366A1/en not_active Withdrawn
- 2000-06-30 WO PCT/AU2000/000802 patent/WO2001001849A1/en not_active Application Discontinuation
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1994018523A1 (en) * | 1993-02-01 | 1994-08-18 | Zygo Corporation | Method and apparatus for the rapid acquisition of data in coherence scanning interferometry |
WO1994018521A1 (en) * | 1993-02-08 | 1994-08-18 | Zygo Corporation | Method and apparatus for surface topography measurement by spatial-frequency analysis of interferograms |
WO1999001716A1 (en) * | 1997-07-01 | 1999-01-14 | David Macpherson | Ablation profiler |
Cited By (20)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2003052345A1 (en) * | 2001-12-18 | 2003-06-26 | Massachusetts Institute Of Technology | System and method for measuring optical distance |
US6934035B2 (en) | 2001-12-18 | 2005-08-23 | Massachusetts Institute Of Technology | System and method for measuring optical distance |
US7365858B2 (en) | 2001-12-18 | 2008-04-29 | Massachusetts Institute Of Technology | Systems and methods for phase measurements |
US7557929B2 (en) | 2001-12-18 | 2009-07-07 | Massachusetts Institute Of Technology | Systems and methods for phase measurements |
US8334982B2 (en) | 2001-12-18 | 2012-12-18 | Massachusetts Institute Of Technology | Systems and methods for phase measurements |
US9528817B2 (en) | 2001-12-18 | 2016-12-27 | Massachusetts Institute Of Technology | Systems and methods for phase measurements |
WO2003098312A1 (en) * | 2002-05-22 | 2003-11-27 | Carl Zeiss Meditec Ag | Optical coherence tomography scanner with negative field curvature |
GB2435322A (en) * | 2006-02-15 | 2007-08-22 | Oti Ophthalmic Technologies | Measuring curvature or axial position using OCT |
US7841719B2 (en) | 2006-02-15 | 2010-11-30 | Oti Ophthalmic Technologies Inc | Method and apparatus for determining the shape, distance and orientation of an object |
EP1975550A1 (en) * | 2007-03-28 | 2008-10-01 | Kabushiki Kaisha Topcon | Optical image measurement device |
CN107752985A (en) * | 2017-11-17 | 2018-03-06 | 苏州阿格斯医疗技术有限公司 | OCT image method, OCT image conduit and OCT systems |
CN107752985B (en) * | 2017-11-17 | 2024-08-06 | 苏州阿格斯医疗技术有限公司 | OCT imaging method, OCT imaging catheter and OCT system |
WO2019227170A1 (en) * | 2018-06-01 | 2019-12-05 | OncoRes Medical Pty Ltd | A method and device for evaluating a mechanical property of a material |
US11293746B2 (en) | 2018-06-01 | 2022-04-05 | OncoRes Medical Pty Ltd | Method and device for evaluating a mechanical property of a material |
JP2020039667A (en) * | 2018-09-12 | 2020-03-19 | 株式会社トプコン | Ophthalmic imaging apparatus, control method thereof, program, and recording medium |
WO2020054280A1 (en) * | 2018-09-12 | 2020-03-19 | 株式会社トプコン | Ophthalmological imaging device, control method thereof, program, and storage medium |
JP2023014190A (en) * | 2018-09-12 | 2023-01-26 | 株式会社トプコン | ophthalmic imaging equipment |
US12096983B2 (en) | 2018-09-12 | 2024-09-24 | Topcon Corporation | Ophthalmic imaging apparatus, controlling method of the same, and recording medium |
WO2021131020A1 (en) * | 2019-12-27 | 2021-07-01 | 株式会社ニコン | Scanning method, scanning device, and scanning program |
JPWO2021131020A1 (en) * | 2019-12-27 | 2021-07-01 |
Also Published As
Publication number | Publication date |
---|---|
AUPQ139899A0 (en) | 1999-07-29 |
EP1204366A1 (en) | 2002-05-15 |
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