US 6,538,817 B1 · Method and apparatus for optical coherence tomography with a multispectral laser source

Abstract

A method and apparatus for performing optical coherence tomography using a wavelength multiplexed source is provided. The single output beam of the source is of a large bandwidth, thus providing a high resolution tomography system. In order to achieve high contrast as well, the wavelength multiplexed source has minimal wavelength separation between spectrally adjacent lasers and has an output beam with an approximately Gaussian spectral shape. The source is preferably comprised of one or more multi-gain element arrays multiplexed together within a single external resonator cavity. Interposed between the array and the resonator cavity output coupler are a collimating element and a diffraction grating. The collimating element can be a refractive optic, a reflective optic, or, for some applications, a ¼ pitch GRIN lens. The diffraction grating can either be transmissive or reflective. The combination of the diffraction grating and the collimating element forces each emitter within the array to lase at a distinct wavelength. In order to achieve an overall bandwidth greater than the gain bandwidth of a single emitter array, either multiple arrays of differing center wavelength are packaged together or a large array is used with a laterally varying quantum well thickness or epitaxy. An intracavity spatial filter can be used to improve the beam quality and reduce cross-talk. An optical coherence tomography imaging system is coupled to the resonator cavity.

Claims50

Dependent claims

A method of optical coherence tomography imaging, the method comprising the steps of:

multiplexing a plurality of laser beams into a single output beam, wherein said multiplexing step occurs within a single resonator cavity;
splitting said output beam into a reference beam and a sampling beam;
directing said reference beam at a reference;
translating said reference;
directing said sampling beam at a sample;
monitoring a reflected reference beam from said reference and a reflected sampling beam from said sample;
outputting a signal dependent on an amplitude and a phase corresponding to said monitored reflected reference beam and reflected sampling beam;
processing said signal to determine an image of said sample.

5 more elements

An optical coherence tomography system comprising:

a laser gain element array comprised of a plurality of laser gain elements;
a GRIN lens, wherein emissions from said plurality of laser gain elements pass through said GRIN lens;
a reflective diffraction grating, wherein emissions passing through said GRIN lens from said plurality of laser gain elements overlap on said diffraction grating and are reflected by said diffraction grating back through said GRIN lens;
an output coupler, wherein emissions from said plurality of laser gain elements reflected by said diffraction grating are focused onto said output coupler, said output coupler outputting a single output beam;
a beam splitter, said beam splitter splitting said output beam into a reference beam and a sampling beam;
a reference, wherein said reference beam impinges on said reference, said reference reflecting at least a portion of said reference beam;
a reference translation stage;
a detector, wherein said detector monitors said reflected reference beam and a reflected sampling beam, said detector outputting a signal corresponding to said monitored reflected reference beam and said reflected sampling beam;
and
a processor coupled to said detector, said processor processing said signal output by said detector.

7 more elements

An optical coherence tomography system comprising:

a first laser gain element array comprised of a first plurality of laser gain elements;
a second laser gain element array comprised of a second plurality of laser gain elements;
a beam combining element, said beam combining element combining a first plurality of emissions from said first plurality of laser gain elements with a second plurality of emissions from said second plurality of laser gain elements to form a plane of combined emissions;
a wave plate interposed between said first laser gain element array and said beam combining element;
a collimating optical element, said collimating optical element collimating said combined emissions;
a diffraction grating, wherein said collimated combined emissions are directed onto said diffraction grating;
an output coupler, said output coupler outputting a single output beam;
a beam splitter, said beam splitter splitting said output beam into a reference beam and a sampling beam;
a reference, wherein said reference beam impinges on said reference, said reference reflecting at least a portion of said reference beam;
a reference translation stage;
a detector, wherein said detector monitors said reflected reference beam and a reflected sampling beam, said detector outputting a signal corresponding to said monitored reflected reference beam and said reflected sampling beam;
and
a processor coupled to said detector, said processor processing said signal output by said detector.

10 more elements

An optical coherence tomography system comprising:

a laser gain element array comprised of a plurality of laser gain elements;
an optical element of a uniform optical index, wherein emissions from said plurality of laser gain elements pass through an entrance aperture on a leading surface of said optical element;
a reflective coating coupled to a shaped back surface of said optical element, wherein said reflective coating on said shaped back surface substantially collimates said emissions from said plurality of laser gain elements;
a reflective diffraction grating coupled to said leading surface of said optical element, wherein said substantially collimated emissions from said plurality of laser gain elements are reflected by said diffraction grating back through said optical element, wherein said reflective coating on said shaped back surface substantially focuses said emissions from said plurality of laser gain elements reflected by said diffraction grating, wherein said focussed emissions pass through an exit aperture on said leading surface of said optical element;
an output coupler proximate to said exit aperture, wherein emissions from said plurality of laser gain elements focussed by said reflective coating on said shaped back surface are focused onto said output coupler, said output coupler outputting a single output beam;
a beam splitter, said beam splitter splitting said output beam into a reference beam and a sampling beam;
a reference, wherein said reference beam impinges on said reference, said reference reflecting at least a portion of said reference beam;
a reference translation stage;
a detector, wherein said detector monitors said reflected reference beam and a reflected sampling beam, said detector outputting a signal corresponding to said monitored reflected reference beam and said reflected sampling beam;
and
a processor coupled to said detector, said processor processing said signal output by said detector.

8 more elements

Dependencies are inferred from the claim text.

Method and apparatus for optical coherence tomography with a multispectral laser source

Life of this patent

Method and apparatus for optical coherence tomography with a multispectral laser source

Life of this patent

Abstract

Claims50