Optical coherence tomography microscopy apparatus and method for detecting a three-dimensional image of an object

Patent metadata

Field	Value
Publication number	US-10215552-B2
Application number	US-201515321467-A
Country	US
Kind code	B2
Filing date	Jun 30, 2015
Priority date	Jul 1, 2014
Publication date	Feb 26, 2019
Grant date	Feb 26, 2019

Abstract

An optical coherence tomography microscopy apparatus (1) is presented for detecting a three-dimensional image of an optically translucent or reflective sample object (OS), the apparatus comprising an interferometric optical setup including a photo sensor unit (20). A sense signal Si from the photo sensor unit (20) is detected using a detection reference signal. The detection reference signal is derived from a signal indicative for a relative displacement of the sample object (OS) with respect to a reference object.

First claim

The invention claimed is:

1. An optical coherence tomography microscopy apparatus for detecting a three-dimensional image of an optically translucent or reflective sample object, the apparatus comprising an interferometric optical setup including:
a light source comprising one or more light emitting elements, to emit a beam of light having an emission bandwidth,
a photo sensor unit including at least one photo sensor able to sense a light intensity in a sensing region and to generate a sense signal indicative for said light intensity, the sensed light intensity being dependent on interference in said sensing region between a first and a second sub-beam impingent on the sensing region, and that are split off from said emitted beam, said first sub-beam being directed along a first optical path extending from the light source to the sensing region via the optically translucent or reflective sample object, and the second sub-beam being directed along a second optical path extending from the light source to the sensing region via the optically translucent or reflective reference object,
a displacement unit to change a difference in path length between said first optical path and said second optical path, therewith causing a modulation in the sensed light intensity,
a demodulator to demodulate the sense signal,
characterized in that the apparatus further includes a displacement sensor to generate a displacement signal indicative for said change in said path length difference and a reference signal generator to generate a detection reference signal from the displacement signal and in that said demodulator comprises a detector using said detection reference signal.

2. An optical coherence tomography microscopy apparatus according to claim 1 , wherein a reference period of the reference signal corresponds to a predetermined change in path length difference and wherein said reference period further corresponds to a fraction ½N of a period of a central wavelength of the light source, wherein N is a positive integer.

3. An optical coherence tomography microscopy apparatus according to claim 2 , characterized in that a ruler-encoder type of displacement sensor is used to generate the detection reference signal.

4. The apparatus according to claim 3 , wherein the reference period, of said detection reference signal generated by the ruler-encoder type of displacement sensor and corresponding to said fraction ½N of the period of the central wavelength of the light source, is obtained by said displacement meter having markings at a mutual distance.

5. The apparatus according to claim 3 , wherein the ruler-encoder type of displacement sensor is arranged to provide a first output signal indicative for a sine function of a detected displacement and a second output signal indicative for a cosine function of the detected displacement, which first and second output signal in combination indicate a phase that linearly varies with the displacement, the apparatus further being provided with a linear interpolator that outputs the reference signal as a signal having a phase that is a multiplication factor times the phase of the signal indicated by the first and the second output signal, said multiplication factor being specified in accordance with the specification of the light source to provide the reference signal to sample the sense signal.

6. An optical coherence tomography microscopy apparatus according to claim 1 , characterized in that the displacement sensor includes a further photo sensor to measure a temporal change in interference in a sensing bandwidth narrower than said emission bandwidth, said interference occurring between a third sub-beam being directed along a third optical path including the sample object and a fourth sub-beam directed along a fourth optical path including the reference object, said third and fourth sub-beam originating from a common light source, wherein a path length difference between the third and the fourth optical path changes corresponding to said changing difference between the path length of the first optical path and the path length of the second optical path and wherein the detection reference signal is used to sample the sense signal.

7. An optical coherence tomography microscopy apparatus according to claim 6 , characterized in that the further photo sensor is sensitive only for light in the sensing bandwidth.

8. An optical coherence tomography microscopy apparatus according to claim 7 , characterized in that the further photo sensor is arranged to sense an interference pattern for light within said sensing bandwidth in that a band pass filter is arranged in at least one of the third and the fourth optical paths, the band pass filter selectively passing light corresponding to said sensing bandwidth to the further photosensor.

9. An optical coherence tomography microscopy apparatus according to claim 8 , further including a beam splitter arranged at a location common to the third and the fourth optical path and subsequent to a location of the sample object in said third optical path and subsequent to a location of the reference object in said fourth optical path, wherein said beam splitter splits incoming light into a fifth beam directed towards the photo sensor unit and a sixth beam directed to said further photo sensor.

10. An optical coherence tomography microscopy apparatus according to claim 6 , wherein said common light source is the light source, wherein the photosensor arranged to sense an interference pattern for light within said sensing bandwidth is included in said photo sensor unit and wherein the apparatus is configured to alternate a bandwidth of said light source between said emission bandwidth and a sub-band of said emission bandwidth corresponding to said sensing bandwidth, and to measure a first interference when the light source is caused to emit light in said emission bandwidth and to measuring a second interference when the light source is caused to emit light in said sub-band of the emission bandwidth.

11. An optical coherence tomography microscopy apparatus according to claim 10 , wherein said light source comprises a first light emitting element to emit light in said emission bandwidth and a second light emitting element to emit light in said sub-band of said emission bandwidth and wherein the apparatus is configured to alternate the bandwidth of said light source between said emission bandwidth and the sub-band of said emission bandwidth by alternatingly activating the first light emitting element and the second light emitting element.

12. An optical coherence tomography microscopy apparatus according to claim 11 , wherein at least one of the first light emitting element and the second light emitting element has a controllable central emission wavelength, and wherein the apparatus further comprises a feedback module to minimize a difference between the central emission wavelength of the first light emitting element and the second light emitting element.

13. An optical coherence tomography microscopy apparatus according to claim 12 , wherein said first light emitting element is a LED and said second light emitting element is a laser, wherein said laser has a central emission wavelength that is controllable by its temperature.

14. An optical coherence tomography microscopy apparatus according to claim 6 , comprising a semitransparent mirror to split off the first and the second sub-beam from the emitted beam.

15. An optical coherence tomography microscopy apparatus according to claim 6 , wherein the paths of the third and the fourth sub-beam at least substantially coincide with the paths of th

Assignees

• TNO

Inventors

• Snel Robert
• Jonker Wouter Andries
• Liebig Thomas
• Winters Jasper

Classifications

• G01B2290/60

  Reference interferometer, i.e. additional interferometer not interacting with object · CPC title

• G01B9/02091 Primary

  Tomographic interferometers, e.g. based on optical coherence · CPC title

• G01B9/02071

  by measuring path difference independently from interferometer · CPC title

• G01B9/0201

  using temporal phase variation · CPC title

• A61B5/0066

  Optical coherence imaging · CPC title