US 6,307,633 B1Granted

Method and apparatus for performing scanning optical coherence confocal microscopy through a scattering medium

AssigneeOptical Biopsy Technologies, Inc.

InventorsMichael J. Mandella, Mark H. Garrett, Gordon S. Kino

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Abstract

An apparatus and method for performing optical coherence domain reflectometry. The apparatus preferably includes a single output light source to illuminate a sample with a probe beam and to provide a reference beam. The reference beam is routed into a long arm of an interferometer by a polarizing beamsplitter. A reflected beam is collected from the sample. A 90° double pass polarization rotation element located between the light source and the sample renders the polarizations of the probe beam and reflected beam orthogonal. The polarizing beamsplitter routes the reflected beam into a short arm of the interferometer. The interferometer combines the reference beam and the reflected beam such that coherent interference occurs between the beams. The apparatus ensures that all of the reflected beam contributes to the interference, resulting in a high signal to noise ratio.

Claims44

Dependent claims

An apparatus for performing scanning optical coherence confocal microscopy on a sample, the apparatus comprising:

a) a light source having a predetermined coherence length for producing a probe beam and a reference beam, wherein the light source is located such that a light path exists between the light source and the sample;
b) a scanning head disposed along the light path between the light source and the sample, comprising:
i) at least one silicon micromachined scanning mirror for deflecting the probe beam to the sample;
ii) a lens assembly comprising at least one lens for focusing the probe beam to a focal point at a predetermined depth within the sample, wherein the lens is disposed along an optical path between the silicon micromachined scanning mirror and the sample, and wherein a reflected beam emanates from the focal point;
iii) and
iv) a translation means for causing the silicon micromachined scanning mirror and the lens assembly to move relative to the sample along a direction substantially parallel to the probe beam, to provide vertical scanning;
wherein the silicon micromachined scanning mirror can be pivoted such that the probe beam is able to scan the sample along a direction substantially perpendicular to the probe beam, thereby providing transverse scanning;
c) an interferometer having at least two arms, wherein the interferometer is disposed in optical communication with the reference beam and the reflected beam, and wherein the arms have an optical path length difference selected to restore optical coherence between at least a portion of the reference beam and at least a portion of the reflected beam;
wherein a coherence gate interval at the focal point of the probe beam is established by means of the interferometer.

6 more elements

A method for performing scanning optical coherence confocal microscopy on a sample, the method comprising the steps of:

a) producing a reference beam and a probe beam from a light source having a predetermined coherence length;
b) transmitting the probe beam along a flexible optical fiber disposed between the light source and the sample;
c) using a silicon micromachined scanning mirror to deflect the probe beam emerging from an output end of the flexible optical fiber to the sample;
d) focusing the probe beam to a focal point at a predetermined depth within the sample by use of a lens assembly disposed along an optical path between the silicon micromachined scanning mirror and the sample;
e) using an interferometer to establish a coherence gate interval comprising a region of the sample substantially centered about the focal point;
g) pivoting the silicon micromachined scanning mirror such that the probe beam scans the sample along a direction substantially perpendicular to the probe beam, while collecting a reflected beam comprising a portion of the probe beam reflected from within the coherence gate interval;
h) passing the reflected beam into the output end of the flexible optical fiber;
i) sending the reference beam and the reflected beam through the interferometer, wherein the interferometer has at least two arms, and wherein an optical path length difference between the arms is selected to restore optical coherence between at least a portion of the reference beam and at least a portion of the reflected beam;
and
j) moving the silicon micromachined scanning mirror, the output end of the flexible fiber, and the lens assembly relative to the sample along a direction substantially parallel to the probe beam such that the focal point of the lens moves further into or away from the sample, while maintaining the coherence gate interval about the focal point, and repeating the steps of g) through j).

7 more elements

Dependencies are inferred from the claim text.