Apparatus and method for ranging and noise reduction of low coherence interferometry LCI and optical coherence tomography OCT signals by parallel detection of spectral bands

• US 7,630,083 B2
• Filed: 12/13/2007
• Issued: 12/08/2009
• Est. Priority Date: 01/24/2002
• Status: Expired due to Term

• Current Assignee: The General Hospital Corporation (Mass General Brigham, Inc.)
• Original Assignee: The General Hospital Corporation (Mass General Brigham, Inc.)
• Inventors: Bouma, Brett Eugene, Tearney, Guillermo J., de Boer, Johannes F.
• Primary Examiner(s): Connolly; Patrick J
• Application Number:
  US11/955,834
• Publication Number:
  US 20080100837A1
• Time in Patent Office: 726 Days
• Field of Search: 356/456, 356/479, 356/497, 356/521, 356/451
• US Class Current: 356/479
• CPC Class Codes: A61B 5/0059 using light, e.g. diagnosis by transillumination, diascopy, fluorescence A61B5/0093, A61B5/1455, A61B5/02416 and A61B5/0261 take precedence
• CPC Class Codes: A61B 5/0066 Optical coherence imaging
• CPC Class Codes: A61B 5/7257 using Fourier transforms
• CPC Class Codes: G01B 2290/45 Multiple detectors for detecting interferometer signals
• CPC Class Codes: G01B 9/02007 Two or more frequencies or sources used for interferometric measurement using only beat G01B9/02003
• CPC Class Codes: G01B 9/02008 by using a frequency comb
• CPC Class Codes: G01B 9/0201 using temporal phase variation
• CPC Class Codes: G01B 9/02032 generating a spatial carrier frequency, e.g. by creating lateral or angular offset between reference and object beam shearing interferometers G01B9/02098
• CPC Class Codes: G01B 9/02044 Imaging in the frequency domain, e.g. by using a spectrometer
• CPC Class Codes: G01B 9/02045 using the Doppler effect
• CPC Class Codes: G01B 9/02079 Quadrature detection, i.e. detecting relatively phase-shifted signals
• CPC Class Codes: G01B 9/0209 Low-coherence interferometers
• 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

Apparatus and method for increasing the sensitivity in the detection of optical coherence tomography and low coherence interferometry (“LCI”) signals by detecting a parallel set of spectral bands, each band being a unique combination of optical frequencies. The LCI broad bandwidth source is split into N spectral bands. The N spectral bands are individually detected and processed to provide an increase in the signal-to-noise ratio by a factor of N. Each spectral band is detected by a separate photo detector and amplified. For each spectral band the signal is band pass filtered around the signal band by analog electronics and digitized, or, alternatively, the signal may be digitized and band pass filtered in software. As a consequence, the shot noise contribution to the signal is reduced by a factor equal to the number of spectral bands. The signal remains the same. The reduction of the shot noise increases the dynamic range and sensitivity of the system.

Claims

1. An apparatus for optical imaging, comprising:

a) an interferometer configured to receive at least one electro-magnetic radiation from a transmissive reference, and generate the at least one signal at least one signal as a function of the at least one electro-magnetic radiation;

b) a spectral separating unit which splits the at least one signal received from the interferometer into a plurality of optical frequencies; and

c) a plurality of detectors, each detector being configured to detect at least a portion of the optical frequencies received from the spectral separating unit, wherein the spectral separating unit comprises at least one of (i) an addressable mirror array or (ii) a waveguide filter.

2. The apparatus according to claim 1, wherein the spectral separating unit splits the signal into the bands.

3. The apparatus according to claim 1, wherein the detectors are provided in a form of a two-dimensional array.

4. The apparatus according to claim 1, wherein a sample is scanned in a series of simultaneous illuminations of substantially all of areas of the sample to provide at least one radiation associated with the sample to be used by the interferometer to provide the at least one signal.

5. The apparatus according to claim 1, wherein the interferometer comprises an arrangement generating a path length difference that is a fraction of a ranging depth of the interferometer.

6. An apparatus for optical imaging, comprising:

a) an interferometer structured to provide at least one signal;

b) a spectral separating unit which splits the at least one signal received from the interferometer into a plurality of optical freguencies; and

c) a plurality of detectors, each detector being configured to detect at least a portion of the optical freguencies received from the spectral separating unit, wherein the spectral separating unit comprises at least one of (i) an addressable mirror array or (ii) a waveguide filter, wherein the spectral separating unit comprises a polarization separating unit.

7. An apparatus for optical imaging, comprising:

a) an interferometer structured to provide at least one signal;

b) a spectral separating unit which splits the at least one signal received from the interferometer into a plurality of optical freguencies;

c) a plurality of detectors, each detector being configured to detect at least a portion of the optical frequencies received from the spectral separating unit, wherein the spectral separating unit comprises at least one of (i) an addressable mirror array or (ii) a waveguide filter; and

d) an arrangement which configured to at least one of;

i. reconstruct the signal from the detectors by a mathematical manipulation of each plurality of signals obtained from the detectors, or

ii. track a phase of the signal of the interferometer.

8. An apparatus for optical imaging, comprising:

a) an interferometer structured to provide at least one signal;

b) a spectral separating unit which splits the at least one signal received from the interferometer into a plurality of optical frequencies; and

c) a plurality of detectors, each detector being configured to detect at least a portion of the optical frequencies received from the spectral separating unit, wherein the spectral separating unit comprises at least one of (i) an addressable mirror array or (ii) a waveguide filter, wherein the spectral separating unit splits the signal into a plurality of bands, whereby at least one of the bands comprises spectra that has a comb-like structure.

9. An apparatus for optical imaging, comprising:

a) an interferometer structured to provide at least one signal;

b) a spectral separating unit which splits the at least one signal received from the interferometer into a plurality of optical frequencies;

c) a plurality of detectors, each detector being configured to detect at least a portion of the optical frequencies received from the spectral separating unit, wherein the spectral separating unit comprises at least one of (i) an addressable mirror array or (ii) a waveguide filter; and

d) an arrangement which configured to track a phase of the at least one signal of the interferometer.

10. An apparatus for optical imaging, comprising:

a) an interferometer structured to receive at least one electro-magnetic radiation from a reference and provide at least one signal;

b) a spectral separating unit which splits the at least one signal received from the interferometer into a plurality of optical frequencies; and

c) a plurality of detectors, each detector being configured to detect at least a portion of the optical frequencies received from the spectral separating unit, wherein the spectral separating unit comprises at least one of (i) an addressable mirror array or (ii) a waveguide filter.