Delivering light via optical waveguide and multi-view optical probe head
Techniques, apparatus and systems that use an optical probe head to deliver light to a target and to collect light from the target for imaging, monitoring, medical diagnostics and medical treatment applications.
1. A device for delivering light to and collecting light from a target, comprising:
a sheath structured to include a hollow channel along a sheath longitudinal direction, the sheath having a proximal end configured to receive input polarized light and a distal end configured to export the input polarized light as probe light outside the sheath to a target;
a polarization maintaining (PM) fiber movably placed inside the hollow channel of the sheath and structured to exhibit a first principal polarization direction and a second, orthogonal principal polarization direction, both perpendicular to a longitudinal direction of the PM fiber;
an optical probe head located inside the sheath and engaged to a distal end of the PM fiber with a fixed orientation relative to the first principal polarization axis of the PM fiber to receive the input polarized light from the PM fiber, the optical probe head operable to direct the probe light polarized in the first principal polarization direction to exit the optical probe head at a first exit angle with respect to the sheath longitudinal direction and the probe light polarized in the second principal polarization direction to exit the optical probe head at a second, different exit angle with respect to the sheath longitudinal direction, respectively; and
a rotation mechanism coupled to the optical head and operable to rotate the optical head inside the sheath about the sheath longitudinal direction to change a direction of light existing the optical probe head at the first exit angle and at the second exit angle.
2. The device of claim 1 , wherein:
the optical probe head comprises a lens to receive light from the PM fiber and a polarizing beam splitter to receive the light from the lens and to produce the probe light, the polarizing beam splitter transmitting the probe light polarized in the first principal polarization direction at the first exit angle and reflecting the probe light polarized in the second principal polarization direction at the second exit angle, respectively.
3. The device of claim 2 , wherein:
the PM fiber includes an angled end facet facing the lens to direct the light towards the polarizing beam splitter at a direction different from the sheath longitudinal direction.
4. The device of claim 1 , wherein:
the optical probe head comprises a GRIN lens having an angled end facet which is coated with a polarization coating that transmits light polarized in the first principal polarization direction as the probe light and reflects light polarized in the second principal polarization direction through a side surface of the GRIN lens as the probe light.
5. The device of claim 1 , comprising:
a transparent liquid filled in the sheath between the optical head and an inner wall of the sheath, wherein the liquid has a refractive index greater than a refractive index of the sheath.
6. The device of claim 5 , wherein:
the optical probe head is structured so that the probe light at the first exit angle undergoes a total internal reflection at an interface between the liquid and a side inner wall of the sheath and the probe light at the second exit angle is incident at a side inner wall of the sheath at an angle less than a critical angle for the total internal reflection.
7. The device of claim 6 , comprising:
a pulling mechanism coupled to the PM fiber to push and pull the PM fiber and the optical probe head to change a longitudinal position of the optical probe head inside the sheath relative to a distal end of the sheath between a first position at which the probe light at the first exit angle hits the distal end of the sheath to exit the distal end and a second position at which the probe light at the first exit angle hits a side inner wall of the sheath without reaching the distal end of and thus is totally reflected.
8. The device of claim 1 , comprising:
a pulling mechanism coupled to the PM fiber to push and pull the PM fiber and the optical probe head to change a longitudinal position of the optical probe head inside the sheath relative to a distal end of the sheath.
9. The device of claim 1 , comprising:
an input PM fiber; and
a rotary joint that rotatably engages a distal end of the input PM fiber to the first distal end of the PM fiber to couple the input polarized light from the input fiber into the PM fiber while preserving a polarization of the input polarized light,
wherein the rotation mechanism rotates the PM fiber and the optical probe head relative to the input PM fiber in changing the direction of the probe light exiting the sheath.
10. The device of claim 9 , wherein:
the rotary joint comprises:
an input collimator lens coupled to the distal end of the input PM fiber;
a first quarter waveplate located to receive light from the input collimator and oriented to transform light polarized in either of two orthogonal principal polarization directions of the input PM fiber into a circularly polarized light;
a second quarter waveplate spaced from the first quarter waveplate by an air gap to transform the circularly polarized light from the first quarter waveplate into a linearly polarized light, the second quarter waveplate and the PM fiber being oriented at a fixed relative orientation to each other to align a polarization of the linearly polarized light from the second quarter waveplate with one of the first and second principal polarization axes of the PM fiber; and
an output collimator lens coupled to the first distal end of the PM fiber to couple the linearly polarized light from the second quarter waveplate into the PM fiber,
wherein the second waveplate and the output collimator are fixed to the PM fiber and the optical probe head to form a rotary assembly, and the rotary assembly is rotated relative to the first waveplate, the input collimator and the input PM fiber by the rotation mechanism in changing the direction of the probe light exiting the sheath.
11. The device of claim 9 , comprising:
a polarization controller coupled to the input PM fiber to control a linear polarization of the input light to the input PM fiber to control a direction of the probe light that exits the optical probe head.
12. The device of claim 1 , comprising:
a polarization controller to control a linear polarization of the input light to the PM fiber to control a direction of the probe light that exits the optical probe head.
13. The device of claim 1 , comprising:
a mask engaged to the distal end of the sheath and structured to have an aperture on the distal end of the sheath to transmit the probe light at the first exit angle,
wherein the optical probe head is movable along the sheath longitudinal direction to a first position to transmit the probe light at the first exit angle through the aperture while probe light at the second exit angle is blocked by the mask, and to a second position to transmit the probe light at the second exit angle to exit the sheath without being blocked by the mask while the mask blocks the probe light at the first exit angle from exiting the sheath.