3D MEMS scanner for real-time cross-sectional endomicroscopy
An optical probe scanning assembly for use in an optical probe includes a mirror assembly that focuses an illumination beam path and a collection beam path at a region of interest within the sample. The illumination beam and the collection beam overlap to form a confocal beam region. The mirror assembly is movable in an x-axis direction and in a y-axis direction to scan the confocal beam region within the sample. The scanning assembly further includes a scanning suspension system including a gimbal assembly connected to the mirror assembly to allow the mirror assembly to rotate about one or more axes. The mirror is thereby adapted to scan along at least two different orthogonal planes, one of which extends vertically into the sample.
1. An optical probe scanning assembly for use in an optical probe having a housing having a proximal end and a distal end positioned at a sample, the scanning assembly comprising:
a mirror assembly configured to focus an illumination beam path and a collection beam path at a region of interest within the sample where the illumination beam and the collection beam overlap to form a confocal beam region, the mirror assembly being movable in an x-axis direction, a y-axis direction, and a z-axis direction to scan the confocal beam region within the sample; and
a scanning suspension system comprising a gimbal assembly connected to the mirror assembly to cause the mirror assembly to rotate in the x-axis direction and the y-axis direction and to be movably displaced along the z-axis direction, such that the mirror is adapted to scan along at least two different orthogonal planes, one of which extends vertically into the sample along the z-axis direction.
2. The scanning assembly of claim 1 , wherein the mirror assembly is configured to scan the confocal beam region across a three-dimensional volume in the sample.
3. The scanning assembly of claim 1 , wherein the vertical scanning assembly is configured to scan the confocal beam region over a three-dimensional volume that extends from an vertical depth of the sample extending from an upper surface of the sample to a depth of at least 400 pm below the upper surface.
4. The scanning assembly of claim 3 , wherein the vertical scanning assembly is configured to scan the confocal beam region to a depth of 400 pm below the upper surface of the sample.
5. The scanning assembly of claim 1 , wherein the scanning suspension assembly further comprises:
opposing lever arms disposed on each side of the mirror assembly and deflectable from a flattened position of the mirror to an erected position, each lever arm coupled to the mirror through a serpentine spring mechanism to allow for rotation of the mirror assembly when the mirror assembly is in the erected position.
6. The scanning assembly of claim 1 , wherein the scanning suspension assembly further comprises:
an inner spring assembly for scanning the mirror about a first axis; and
an outer spring assembly for scanning the mirror about a second axis orthogonal to the first axis.
7. The scanning assembly of claim 1 , further comprising a controller having a processor and a memory, the controller being configured with executable instructions (i) to excite the gimbal assembly to scan the mirror in orthogonal directions in response to a control signal having a frequency, (ii) to switch the mirror assembly from a flattened position to an erected position for scanning over a three-dimensional volume of the sample, (iii) to provide the control signal at or near integer multiples of a structural resonance of the scanning assembly, (iv) to provide the control signal having a Lissajous scan pattern, (v) to parametrically excite the mirror assembly for scanning, and/or (vi) to provide the control signal having a duty cycle chosen to drive the mirror assembly into scanning along one of a plurality of different orthogonal two-dimensional regions, where different duty cycles result in the scanning along different regions.
8. The scanning assembly of claim 1 , wherein the mirror assembly comprises a micro-mirror having a first reflector pad for reflecting the illumination beam into the sample and a second reflector pad for reflecting the collection beam out of the sample.
9. The scanning assembly of claim 8 , wherein the first reflector pad and the second reflector pad are connected by a strut to achieve dual movement of the first reflector pad and the second reflector pad.
10. The scanning assembly of claim 9 , wherein the mirror assembly further comprises a comb drive capable of deflecting the micro-mirror for scanning the confocal beam region along one or more transverse directions.
11. The scanning assembly of claim 9 , wherein the mirror assembly further comprises multiple comb drives that are collectively capable of deflecting the micro-mirror for scanning the confocal beam region along two orthogonal transverse directions.
12. The scanning assembly of claim 1 , wherein the micro-mirror is a MEMS fabricated mirror.
13. The scanning assembly of claim 1 , wherein the mirror assembly further comprises a mirror element.
14. The scanning assembly of claim 13 , wherein the mirror element is a parabolic mirror.
15. The scanning assembly of claim 1 , wherein the probe housing assembly has a diameter of approximately 10 mm or below.
16. The scanning assembly of claim 1 , wherein the probe housing assembly has a diameter of approximately 5 mm.
17. The scanning assembly of claim 1 , further comprising a controller having a processor and a memory, the controller being configured with executable instructions to:
excite the gimbal assembly to rotate the mirror along the x-axis direction and the y-axis direction in response to a control signal having a first frequency; and
displace the mirror assembly along the z-axis direction from a flattened position to an erected position for scanning over a three-dimensional volume of the sample in response to a control signal having a second frequency.