Optical coherence tomography system for subsurface inspection
An OCT system includes a broadband light source, and a beam splitter that splits the broadband light into a reference beam and an illumination beam. A reference mirror reflects the reference beam. Illumination optics passes the illumination beam and has a reflective surface with an optical power. Collection optics has a transparent region and a reflective surface with an optical power. The collection optics is configured so that the illumination beam is reflected from the reflective surface of the collection optics to the reflective surface of the illumination optics such that the illumination beam is redirected to a surface of a sample at an angle that results in scattering from within the sample that forms a sample beam propagating normal to a surface of the sample and through the transparent region of collection optics and through the transparent region of the illumination optics. An interferometric combiner is configured to interferometrically combine light from the sample beam and the reference beam. A spectrometer is configured to receive the interferometrically combined light from the sample beam and the reference beam and to generate spectral interferometric information. A processor processes the spectral interferometric information to determine information about the sample.
1 . An optical coherence tomography system comprising:
a) a broadband light source that generates broadband light at an output;
b) a beam splitter that splits the generated broadband light into a reference beam and an illumination beam;
c) a reference mirror that is positioned in a path of the reference beam, the reference mirror reflecting the reference beam;
d) illumination optics positioned in a path of the illumination beam and having a transparent region that passes the illumination beam and having a reflective surface with an optical power;
e) collection optics positioned in a path of the illumination beam and having a transparent region and having a reflective surface with an optical power, the collection optics being configured so that the illumination beam is reflected from the reflective surface of the collection optics to the reflective surface of the illumination optics such that the illumination beam is redirected to a surface of a sample at an angle that results in scattering from within the sample that forms a sample beam propagating normal to a surface of the sample and through the transparent region of collection optics and through the transparent region of the illumination optics;
f) an interferometric combiner positioned in the path of the sample beam and in the path of the reference beam, the interferometric combiner being configured to interferometrically combine light from the sample beam and the reference beam;
g) a spectrometer having an input coupled to an output of the interferometric combiner, the spectrometer configured to receive the interferometrically combined light from the sample beam and the reference beam and to generate spectral interferometric information; and
h) a processor having an input coupled to an output of the spectrometer, the processor processing the spectral interferometric information to determine information about the sample.
2 . The optical coherence tomography system of claim 1 wherein the reference mirror reflects the reference beam though the beam splitter to the interferometric combiner.
3 . The optical coherence tomography system of claim 1 wherein the broadband light source is a laser driven light source.
4 . The optical coherence tomography system of claim 1 wherein the broadband light source is a superluminescent diode.
5 . The optical coherence tomography system of claim 1 wherein the broadband light source is a supercontinuum broadband light source.
6 . The optical coherence tomography system of claim 1 wherein the broadband light source comprises a short-pulse laser.
7 . The optical coherence tomography system of claim 1 wherein the broadband light source generates at least some light having a wavelength that is less than 400 nm.
8 . The optical coherence tomography system of claim 1 wherein the broadband light source generates at least some light having a wavelength that is less than 300 nm.
9 . The optical coherence tomography system of claim 1 wherein the broadband light source generates at least some light in a visible region of the spectrum.
10 . The optical coherence tomography system of claim 1 wherein the broadband light source generates at least some light in a near-infrared region of the spectrum.
11 . The optical coherence tomography system of claim 1 wherein the broadband light source generates at least some light having wavelengths in an ultraviolet, a visible and a near-infrared region of the spectrum.
12 . The optical coherence tomography system of claim 1 wherein the interferometric combiner comprises a free space combiner.
13 . The optical coherence tomography system of claim 1 wherein the illumination optics is configured to project the generated broadband light to a sample with a polished surface.
14 . The optical coherence tomography system of claim 1 wherein the processor is configured to process the spectral interferometric information to determine defect locations in the sample.
15 . The optical coherence tomography system of claim 1 wherein the processor is configured to process the spectral interferometric information to determine a defect density in the sample.
16 . The optical coherence tomography system of claim 1 wherein the interferometrically combined light from the sample beam and the reference beam is projected through an optical fiber.