Optical source for diffuse optical tomography
Optical sources having multiple optical emitters are described, which may be used in a sensor array used to detect optical properties of a subject, including hemoglobin and deoxygenated hemoglobin concentrations. Multiple optical emitters can be positioned within an optical source. The optical source may include a diffuser and one or more optics, which may direct light from the multiple optical emitters along substantially the same optical direction to the diffuser. The diffuser may receive light from the one or more optics and transmit light from the optical source where the transmitted light has a greater angular distribution than light emitted by one of the optical emitters.
1. An optical source comprising:
a plurality of optical emitters arranged on a substrate and configured to emit light having different characteristic wavelengths in a direction away from the substrate;
at least one optic positioned and configured to direct light from each of the plurality of optical emitters along substantially the same optical direction; and
a diffuser positioned on a side of the at least one optic opposite the plurality of optical emitters, wherein the diffuser is configured to receive light from the at least one optic and transmit light from the optical source that has greater angular distribution than the light emitted from the plurality of optical emitters, and wherein the diffuser transmits the light in a forward direction,
wherein the at least one optic includes a positive lens having a focal length, and the diffuser is positioned within the optical source at a distance from the positive lens equal to approximately the focal length.
2. The optical source of claim 1 , wherein the plurality of optical emitters includes a plurality of lasers.
3. The optical source of claim 2 , wherein the plurality of lasers includes a plurality of vertical-cavity surface-emitting lasers (VCSELs).
4. The optical source of claim 2 , wherein the plurality of lasers includes a plurality of edge emitting lasers.
5. The optical source of claim 1 , wherein the diffuser is a transmissive diffuser.
6. The optical source of claim 1 , wherein the diffuser is configured to transmit the light from the optical source in a Lambertian distribution.
7. The optical source of claim 1 , wherein the diffuser is configured to transmit the light from the optical source in a quasi-Lambertian distribution.
8. The optical source of claim 1 , wherein the at least one optic further includes a negative lens positioned between the positive lens and the plurality of optical emitters.
9. The optical source of claim 1 , wherein the at least one optic further includes a lens array positioned between the positive lens and the plurality of optical emitters.
10. The optical source of claim 1 , wherein the at least one optic is configured to direct light emitted by each of the plurality of optical emitters to overlap in a common plane at the diffuser.
11. The optical source of claim 1 , wherein the at least one optic is configured to direct light emitted by each of the plurality of optical emitters to be substantially coincident at the diffuser.
12. The optical source of claim 1 , wherein the at least one optic is configured to direct light emitted by each of the plurality of optical emitters to overlap in a common plane beyond the diffuser.
13. A sensor array comprising a plurality of optical sources and a plurality of optical detectors, wherein the plurality of optical sources comprises the optical source of claim 1 .