Optical coherence tomography receiver
An Optical Coherence Tomography receiver may include prisms, polarizing beam splitters, reflectors, lenses, and a photodetector array arranged in a compact package. Sample and reference beams are combined into an interference beam and split in two. The two resulting interference beams are then split into two polarization sates each. The optical path lengths for both pairs of interference beams with the same polarization state are equal or nearly equal.
1. An Optical Coherence Tomography (OCT) receiver that receives a sample beam and a reference beam and combines the sample beam and the reference beam into an interference beam, the OCT receiver comprising:
first and second prisms aligned with each other, a first face of the first prism adjacent to a first face of the second prism, the first prism arranged to receive one of the sample beam or the reference beam, and the second prism arranged to receive the other of the sample beam or the reference beam, the interference beam created and split into a first interference beam and a second interference beam where the first face of the first prism and the first face of the second prism meet;
first and second polarizing beam splitters aligned with each other, the first and second polarizing beam splitters arranged adjacent to the first prism, the first and second polarizing beam splitters arranged to split the first interference beam into first and second polarization states;
a delay path arranged adjacent to the second polarizing beam splitter, the delay path configured to receive the second interference beam;
third and fourth polarizing beam splitters arranged adjacent to each other, the third and fourth polarizing beam splitters arranged adjacent to the delay path, the third and fourth polarizing beam splitters arranged to split the second interference beam into first and second polarization states; and
a photodetector array configured to receive the first polarization state of the first interference beam, the second polarization state of the first interference beam, the first polarization state of the second interference beam, and the second polarization state of the second interference beam.
2. The OCT receiver of claim 1 further comprising:
a first collimating lens arranged to receive one of the sample beam or reference beam and direct the one of the sample beam or reference beam to the first prism; and
a second collimating lens arranged to receive the other of the sample beam or reference beam and direct the other of the sample beam or reference beam to the second prism.
3. The OCT receiver of claim 1 further comprising four lenses:
a first lens arranged to receive the first polarization state of the first interference beam;
a second lens arranged to receive the second polarization state of the first interference beam;
a third lens arranged to receive the first polarization state of the second interference beam; and
a fourth lens arranged to receive the second polarization state of the second interference beam.
4. The OCT receiver of claim 3 wherein the first, second, third, and fourth lenses are each ball lenses.
5. The OCT receiver of claim 1 wherein the delay path comprises a prism, the prism having first and second faces, the first face of the prism adjacent to the second prism, and the second face of the prism adjacent to the third and fourth polarizing beam splitters.
6. The OCT receiver of claim 1 wherein the delay path comprises a pair of reflectors located between the second prism and the third and fourth polarizing beam splitters.
7. The OCT receiver of claim 1 wherein a first optical path length from the adjacent faces of the first and second prisms to a first photodetector of the photodetector array that receives the first polarization state of the first interference beam is equal or nearly equal to a second optical path length from the adjacent faces of the first and second prisms to a second photodetector of the photodetector array that receives the first polarization state of the second interference beam.
8. The OCT receiver of claim 1 wherein a third optical path length from the adjacent faces of the first and second prisms to a third photodetector of the photodetector array that receives the second polarization state of the first interference beam is equal or nearly equal to a fourth optical path length from the adjacent faces of the first and second prisms to a fourth photodetector of the photodetector array that receives the second polarization state of the second interference beam.
9. The OCT receiver of claim 1 wherein the first and second prisms, the delay path, and the first, second, third, and fourth polarizing beam splitters comprise a single assembly, the single assembly tilted by an angle of between one and five degrees from a horizontal plane containing the sample beam and the reference beam.
10. The OCT receiver of claim 1 wherein an angle of incidence of the both the sample beam and the reference beam on the first face of the first prism and the first face of the second prism is between one and five degrees.
11. The OCT receiver of claim 1 wherein, the first and second prisms, the delay path, and the first, second, third, and fourth polarizing beam splitters, comprise a single assembly that forms a compact package with a volume of less than 23 millimeters by 37 millimeters by 10 millimeters.
12. An Optical Coherence Tomography (OCT) receiver that receives a sample beam and a reference beam and combines the sample beam and reference beam into an interference beam, the OCT receiver comprising:
an assembly comprising a prism, a first reflector, and a second reflector, the first and second reflectors arranged on opposite sides of the prism, the prism arranged to receive one of the sample beam or the reference beam, and the first reflector arranged to receive the other of the sample beam or the reference beam, the interference beam created and split into a first interference beam and a second interference beam in the prism;
first and second polarizing beam splitters aligned with each other, the first and second polarizing beam splitters arranged adjacent to the first reflector, the first and second polarizing beam splitters arranged to split the first interference beam into first and second polarization states;
a delay path arranged adjacent to the non-polarizing beam splitter and second reflector, the delay path configured to receive the second interference beam;
third and fourth polarizing beam splitters arranged adjacent to each other, the third and fourth polarizing beam splitters arranged adjacent to the delay path, the third and fourth polarizing beam splitters arranged to split the second interference beam into first and second polarization states; and
a photodetector array configured to receive the first polarization state of the first interference beam, the second polarization state of the first interference beam, the first polarization state of the second interference beam, and the second polarization state of the second interference beam.
13. The OCT receiver of claim 12 further comprising:
a first collimating lens arranged to receive one of the sample beam or reference beam and direct the one of the sample beam or reference beam to the prism; and
a second collimating lens arranged to receive the other of the sample beam or reference beam and direct the other of the sample beam or reference beam to the second reflector.
14. The OCT receiver of claim 12 further comprising:
a first lens arranged to receive the first polarization state of the first interference beam;
a second lens arranged to receive the second polarization state of the first interference beam;
a third lens arranged to receive the first polarization state of the second interference beam; and
a fourth lens arranged to receive the second polarization state of the second interference beam.
15. The OCT receiver of claim 14 wherein the first, second, third, and fourth lenses are each ball lenses.
16. The OCT receiver of claim 12 wherein the delay path comprises a prism, the prism having first and second faces, the first face of the prism adjacent to the prism, and the second face of the prism adjacent to the third and fourth polarizing beam splitters.
17. The OCT receiver of claim 12 wherein the delay path comprises a pair of reflectors located between the prism and the third and fourth polarizing beam splitters.
18. The OCT receiver of claim 12 wherein a first optical path length from the non-polarizing splitter to a first photodetector of the photodetector array that receives the first polarization state of the first interference beam is equal or nearly equal to a second optical path length from the non-polarizing splitter to a second photodetector of the photodetector array that receives the first polarization state of the second interference beam.
19. The OCT receiver of claim 12 wherein a third optical path length from the non-polarizing splitter to a third photodetector of the photodetector array that receives the second polarization state of the first interference beam is equal or nearly equal to a fourth optical path length from the non-polarizing splitter to a fourth photodetector of the photodetector array that receives the second polarization state of the second interference beam.
20. The OCT receiver of claim 12 wherein the first and second reflector, the prism, the delay path, and the first, second, third, and fourth polarizing beam splitters comprise a single assembly tilted by an angle of between one and five degrees with respect to plane containing the sample beam and the reference beam.
21. The OCT receiver of claim 12 wherein an angle of incidence of the both the sample beam and the reference beam on the first face of the first prism and the first face of the second prism is between one and five degrees.
22. The OCT receiver of claim 12 wherein, the first and second reflectors, the prism, the delay path, and the first, second, third, and fourth polarizing beam splitters, comprise a single assembly that forms a compact package with a volume of less than 23 millimeters by 37 millimeters by 10 millimeters.