Interferometeric imaging with a grating based phase control optical delay line

• US 6,421,164 B2
• Filed: 06/13/2001
• Issued: 07/16/2002
• Est. Priority Date: 04/29/1991
• Status: Expired due to Fees

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Bouma, Brett E., Tearney, Guillermo, Fujimoto, James G.
• Primary Examiner(s): Epps, Georgia
• Assistant Examiner(s): Spector, David N.
• Application Number:
  US09/880,120
• Publication Number:
  US 20010036002A1
• Time in Patent Office: 398 Days
• Field of Search: 250/227.12, 250/227.27, 356/450, 356/477, 356/479, 356/484, 356/485, 356/488, 356/496, 356/497, 359/197, 359/205, 359/285, 359/287, 359/331, 359/566, 359/578, 359/583
• US Class Current: 359/287
• CPC Class Codes: A61B 1/00096 Optical elements
• CPC Class Codes: A61B 1/00172 with means for scanning
• CPC Class Codes: A61B 1/00183 for variable viewing angles
• CPC Class Codes: A61B 2562/0242 for varying or adjusting the optical path length in the tissue
• CPC Class Codes: A61B 3/1005 for measuring distances inside the eye, e.g. thickness of the cornea A61B3/11 takes precedence
• CPC Class Codes: A61B 3/102 for optical coherence tomography [OCT]
• CPC Class Codes: A61B 3/1225 using coherent radiation
• CPC Class Codes: A61B 5/0064 Body surface scanning
• CPC Class Codes: A61B 5/0066 Optical coherence imaging
• CPC Class Codes: A61B 5/0084 for introduction into the body, e.g. by catheters A61B5/1459 takes precedence
• CPC Class Codes: A61B 5/441 Skin evaluation, e.g. for skin disorder diagnosis
• CPC Class Codes: A61B 5/6852 Catheters
• CPC Class Codes: B82Y 15/00 Nanotechnology for interacting, sensing or actuating, e.g. quantum dots as markers in protein assays or molecular motors
• CPC Class Codes: G01B 11/00 Measuring arrangements characterised by the use of optical techniques
• CPC Class Codes: G01B 11/002 for measuring two or more coordinates
• CPC Class Codes: G01B 11/026 by measuring distance between sensor and object G01B11/0608 takes precedence
• CPC Class Codes: G01B 11/12 internal diameters
• CPC Class Codes: G01B 11/2441 using interferometry
• CPC Class Codes: G01B 2290/20 Dispersive element for generating dispersion
• CPC Class Codes: G01B 2290/35 Mechanical variable delay line
• CPC Class Codes: G01B 9/02002 : using two or more frequencies
• CPC Class Codes: G01B 9/02091 : Tomographic interferometers, e.g. based on optical coherence
• CPC Class Codes: G01J 1/00 : Photometry, e.g. photographic exposure meter spectrophotometry G01J3/00; specially adapted for radiation pyrometry G01J5/00 ; exposure meters built in cameras G03B17/06
• CPC Class Codes: G01N 21/4795 : spatially resolved investigating of object in scattering medium in vivo A61B
• CPC Class Codes: G02B 26/06 : for controlling the phase of light G02B26/08 takes precedence , measuring optical phase difference G01J9/00
• CPC Class Codes: G02B 27/4233 : having a diffractive element [DOE] contributing to a non-imaging application diffusers having a diffractive element G02B5/0252; filters having a diffractive element G02B5/203; systems for controlling the direction of light having diffractive elements G02B26/0808; scanning systems having diffractive elements G02B26/106; beam shaping systems using diffractive optical elements G02B27/0944; beam splitting or combining systems operating by diffraction G02B27/1086
• CPC Class Codes: G02B 27/4244 : in wavelength selecting devices spectrometry G01J
• CPC Class Codes: G02B 27/4255 : for alignment or positioning purposes optical displacement encoding scales G01D5/347
• CPC Class Codes: G02B 5/1828 : having means for producing variable diffraction controlling the direction of light by means of one or more diffracting elements G02B26/0808; acousto-optical elements G02F1/11, G02F1/33; electro- or magneto-optical diffraction G02F1/292, G02F1/2955
• CPC Class Codes: G11B 2007/0013 : for carriers having multiple discrete layers
• CPC Class Codes: G11B 7/005 : Reproducing G11B7/0065 takes precedence
• CPC Class Codes: G11B 7/08564 : using galvanomirrors
• CPC Class Codes: G11B 7/127 : Lasers; Multiple laser arrays lasers per se H01S
• CPC Class Codes: G11B 7/1353 : Diffractive elements, e.g. holograms or gratings diffraction gratings per se G02B5/18; holograms per se G02B5/32; grating systems G02B27/44
• CPC Class Codes: G11B 7/24 : Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the arrangement of information on the carrier G11B7/007
• CPC Class Codes: H01S 5/141 : using a wavelength selective device, e.g. a grating or etalon H01S5/146 takes precedence

Abstract

An apparatus for performing high speed scanning of an optical delay and its application for performing optical interferometry, ranging, and imaging, including cross sectional imaging using optical coherence tomography, is disclosed. The apparatus achieves optical delay scanning by using diffractive optical elements in conjunction with imaging optics. In one embodiment a diffraction grating disperses an optical beam into different spectral frequency or wavelength components which are collimated by a lens. A mirror is placed one focal length away from the lens and the alteration of the grating groove density, the grating input angle, the grating output angle, and/or the mirror tilt produce a change in optical group and phase delay. This apparatus permits the optical group and phase delay to be scanned by scanning the angle of the mirror. In other embodiments, this device permits optical delay scanning without the use of moving parts.

Claims

1. A method for producing an image of a sample, comprising:

providing an optical delay line apparatus, the optical delay line apparatus comprising;

an optical input;

an optical output; and

a plurality of optical elements in optical communication with each other;

guiding an optical signal having an optical spectrum from said optical input to said optical output by said plurality of optical elements, wherein at least one of said plurality of optical elements is a dispersive element and wherein at least one of said plurality of optical elements is adjustable;

spatially dispersing the optical spectrum produced by the sample to provide a spatially dispersed optical signal; and

,

repetitively scanning at least one of a phase delay and a group delay of the spatially dispersed optical signal to produce an image.

2. The method according to claim 1, wherein the optical delay line apparatus comprises an optical imaging module and a reflective element, each in optical communication with said dispersive element, the method further comprising

generating an angularly dispersed optical signal having spectral components by said dispersive element;

producing an image of the angularly dispersed optical signal by said optical imaging module at said reflective element; and

,

altering the angle of said reflective element to adjust the group delay.

3. The method according to claim 1, wherein said dispersive element is a diffraction grating, the method further comprising

adjusting the group delay by altering the relative angle between the diffraction grating normal and the incident light beam.

4. The method according to claim 1, wherein said dispersive element has a spatially periodic structure, the method further comprising

spatially dispersing wavelength components of the optical spectrum of the optical signal by said spatially periodic structure;

and,

adjusting the group delay by altering the spatially periodic structure of said dispersive element.

5. The method according to claim 1, wherein said dispersive element comprises an acousto-optic modulator having an adjustable spatially periodic structure, the method further comprising

varying the response of the periodic structure to a radio frequency drive waveform received by said acousto-optic modulator.

6. The method according to claim 5, further comprising

repetitively altering said radio frequency drive waveform to produce a repetitive and substantially constant rate of change of the group delay.

7. The method according to claim 5, further comprising

repetitively altering said radio frequency drive waveform to produce a repetitive change in group delay with a substantially constant optical throughput efficiency.

8. The method according to claim 5, wherein another of said plurality of optical elements is a double-pass mirror, wherein the method further comprises

positioning said double-pass mirror;

and,

receiving said spatially dispersed optical signal by said double-pass mirror.

9. The method according to claim 1, further comprising

interferometrically combining the optical signal transmitted through said optical delay line with a portion of the optical signal not transmitted through said delay line to achieve a non-zero frequency heterodyne signal.

10. The method according to claim 1, further comprising

adjusting at least one of said plurality of optical elements to independently affect the phase delay and the group delay of said optical signal.