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 7,872,757 B2
• Filed: 09/30/2009
• Issued: 01/18/2011
• 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:
  US12/570,443
• Publication Number:
  US 20100094576A1
• Time in Patent Office: 475 Days
• Field of Search: 356/456, 356/479, 356/497
• US Class Current: 356/456
• 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 tracking a phase of at least one electro-magnetic signal associated with at least one portion of a sample, comprising:

a) a detecting arrangement obtaining at least one first interferometric signal comprising a plurality of spectral bands separated from the at least one electro-magnetic signal;

b) a phase modulator driver having a modulating frequency, and configured to modulate the at least one first signal based on the modulating frequency so as to generate at least one second signal;

c) a mixer configured to mix the at least one first signal with the at least one second signal so as to generate a resultant signal; and

d) a processing arrangement configured to (i) generate an offset based on the resultant signal, (ii) control a phase of the at least one first signal based on the offset to generate further information, and (iii) generate an image based on at least a portion of the sample using the further information.

2. A software arrangement for tracking a phase of at least one electro-magnetic signal associated with at least one portion of a sample, which, when executed by a processing arrangement, configures the processing arrangement to execute the steps comprising of:

a. obtaining at least one first interferometric signal comprising a plurality of spectral bands separated from the at least one electro-magnetic signal;

b. modulating the at least one first signal based on a modulating frequency of a modulating arrangement so as to generate at least one second signal;

c. mixing the at least one first signal with the at least one second signal so as to generate a resultant signal

d. generating an offset based on the resultant signal;

e. controlling a phase of the at least one first signal based on the offset to generate further information; and

f. generating an image based on at least a portion of the sample using the further information.

3. A method for tracking a phase of at least one electro-magnetic signal associated with at least one portion of a sample, comprising the steps of:

a. obtaining at least one first interferometric signal comprising a plurality of spectral bands separated from the at least one electro-magnetic signal;

b. modulating the at least one first signal based on a modulating frequency of a modulating arrangement so as to generate at least one second signal;

c. mixing the at least one first signal with the at least one second signal so as to generate a resultant signal;

d. generating an offset based on the resultant signal;

e. controlling a phase of the at least one first signal based on the offset to generate further information; and

f. generating an image based on at least a portion of the sample using the further information.