Apparatus and methods for uniform frequency sample clocking

• US 8,593,641 B2
• Filed: 09/23/2011
• Issued: 11/26/2013
• Est. Priority Date: 07/12/2007
• Status: Active Grant

• Current Assignee: Volcano Corporation (Koninklijke Philips N.V.)
• Original Assignee: Volcano Corporation (Koninklijke Philips N.V.)
• Inventors: Kemp, Nathaniel J., Kuranov, Roman, McElroy, Austin Broderick, Milner, Thomas E.
• Primary Examiner(s): Toatley, Gregory J
• Assistant Examiner(s): BOLOGNA, DOMINIC JOSEPH
• Application Number:
  US13/243,399
• Publication Number:
  US 20120013914A1
• Time in Patent Office: 795 Days
• Field of Search: 356/479, 356/497, 25022719-22727
• US Class Current: 356/497
• CPC Class Codes: A61B 5/0066 Optical coherence imaging
• CPC Class Codes: A61B 5/0073 by tomography, i.e. reconstruction of 3D images from 2D projections A61B5/0066 takes precedence
• CPC Class Codes: A61B 5/6852 Catheters
• CPC Class Codes: A61B 5/7257 using Fourier transforms
• CPC Class Codes: G01B 2290/25 Fabry-Perot in interferometer, e.g. etalon, cavity
• CPC Class Codes: G01B 9/02004 using frequency scans
• CPC Class Codes: G01B 9/02057 by using common path configuration, i.e. reference and object path almost entirely overlapping
• CPC Class Codes: G01B 9/02062 Active error reduction, i.e. varying with time
• CPC Class Codes: G01B 9/02067 by electronic control systems, i.e. using feedback acting on optics or light
• CPC Class Codes: G01B 9/02069 Synchronization of light source or manipulator and detector
• CPC Class Codes: G01B 9/02083 characterised by particular signal processing and presentation
• CPC Class Codes: G01B 9/02091 Tomographic interferometers, e.g. based on optical coherence
• CPC Class Codes: G01M 11/3127 using multiple or wavelength variable input source
• CPC Class Codes: G01M 11/3172 Reflectometers detecting the back-scattered light in the frequency-domain, e.g. OFDR, FMCW, heterodyne detection
• CPC Class Codes: G01N 21/4795 spatially resolved investigating of object in scattering medium in vivo A61B

Abstract

The invention provides systems and methods for producing an OCT image from a swept laser source. In certain embodiments, methods of the invention involve producing light from a swept laser source, splitting the light into a first and a second portion, in which the first portion is sent to an OCT interferometer to produce an OCT signal and the second portion is sent to a uniform frequency sample clock, processing the second portion into an external clock signal that is accepted by a digitizer, sending the OCT signal and the clock signal to the digitizer, and generating an OCT image from a combination of the OCT signal and the clock signal.

Claims

1. A method for generating an optical coherence tomography (OCT) image, the method comprising:

producing light from a swept laser source;

splitting the light into a first and a second portion, wherein the first portion is sent to an OCT interferometer to produce an OCT signal and the second portion is sent to a uniform frequency sample clock;

processing the second portion into an external clock signal that is accepted by a digitizer, wherein processing comprises the steps of coupling the swept source laser to a uniform frequency sample clock generator and generating the clocking signal, wherein the uniform frequency sample clock generator further comprises a gas cell providing a metric on the absolute lasing wavelength at digitized sampling times and an optical wavemeter coupled to a digitizer providing the relationship between the sampling time and lasing wavelength, further comprising determining the wavenumber bias of the swept laser source;

sending the OCT signal and the clock signal to the digitizer; and

generating an OCT image from a combination of the OCT signal and the clock signal.

3. The method according to either claim 1 or 2, wherein the OCT interferometer comprises a Mach-Zehnder interferometer configuration.

4. The method according to either claim 1 or 2, wherein the OCT interferometer comprises a Michelson interferometer configuration.

5. The method according to either claim 1 or 2, wherein splitting is accomplished using optical couplers.

6. The method according to claim 5, wherein 90% of the first portion comprises 90% of the light.

7. The method according to either claim 1 or 2, wherein the OCT interferometer is coupled to a catheter probe.

8. The method according to either claim 7, wherein the catheter probe is a rotating catheter probe.

2. A method for generating an optical coherence tomography (OCT) image, the method comprising:

producing light from a swept laser source;

splitting the light into a first and a second portion, wherein the first portion is sent to an OCT interferometer to produce an OCT signal and the second portion is sent to a uniform frequency sample clock;

processing the second portion into an external clock signal that is accepted by a digitizer, wherein processing comprises the steps of coupling the swept source laser to a uniform frequency sample clock generator and generating the clocking signal, wherein the uniform frequency sample clock generator further comprises a detector channel and a gas cell channel to generate a gas cell pulse, differentiating the gas cell pulse to replace the maximum absorption gas cell lines with a zero crossing voltage, producing a transistor-transistor logic pulse with rising edges corresponding to the central wavelength of the absorption gas cell lines, repeatedly outputting the shape of the laser source sweep, and producing a window pulse to select one of the gas cell pulses;

sending the OCT signal and the clock signal to the digitizer; and

generating an OCT image from a combination of the OCT signal and the clock signal.