Textured retro-reflective marker
An apparatus comprising a retro-reflective marker and a device configured to receive the retro-reflective marker in a socket located on the top surface of the device. The retro-reflective marker comprises a retro-reflective layer having a first retro-reflectance capability. The retro-reflective layer comprises a textured surface, a portion of the textured surface having a surface topology such that surface normal vectors positioned across the portion extend from the portion of the textured surface in different directions, and a plurality of retro-reflective micro elements distributed across the textured surface. The retro-reflective marker further comprises a border defining a retro-reflective area of the retro-reflective layer, where a portion of the border provides a second retro-reflectance capability lower than the first retro-reflectance capability.
1. An apparatus comprising:
a retro-reflective marker, comprising:
a retro-reflective layer having a first retro-reflectance capability, the retro-reflective layer comprising:
a textured surface, a portion of the textured surface having a surface topology such that surface normal vectors of the portion of the textured surface extend from the portion of the textured surface in different directions, and
a plurality of retro-reflective micro elements distributed across the textured surface; and
a border defining a retro-reflective area of the retro-reflective layer, wherein a portion of the border provides a second retro-reflectance capability lower than the first retro-reflectance capability; and
a base comprising at least one feature configured to guide the retro-reflective layer when the retro-reflective layer is placed on a top surface of the base such that the retro-reflective area aligns with a pre-determined location of the base.
2. The apparatus of claim 1 , wherein the base is part of a device for optical tracking, and wherein the at least one feature includes a socket configured to receive the retro-reflective marker.
3. The apparatus of claim 1 , wherein each of the plurality of retro-reflective micro elements has a retro-reflective axis aligned with a corresponding surface normal vector at a corresponding location that the retro-reflective micro element is adhered.
4. The apparatus of claim 1 , wherein the retro-reflective marker is visible for light incident relative to a surface normal vector of the textured surface at an angle above 55 degrees.
5. The apparatus of claim 1 , wherein the second retro-reflectance capability is lower than the first retro-reflectance capability by at least 20%.
6. The apparatus of claim 1 , wherein the portion of the border includes a ring-shape geometry with a width of at least 1 millimeter.
7. The apparatus of claim 1 , wherein the surface topology is periodic, wherein the surface topology includes a sinusoidal geometry that includes one or more waves, and a wavelength of the one or more waves of the surface topology ranges between 1% and 50% of a size of the retro-reflective area.
8. The apparatus of claim 1 , wherein the surface topology is periodic, wherein the surface topology includes a sinusoidal geometry that includes one or more waves, and an amplitude of the one or more waves of the surface topology ranges between 0.5% and 25% of a size of the retro-reflective area.
9. The apparatus of claim 1 , further comprising: a protective layer positioned over the retro-reflective layer.
10. The apparatus of claim 9 , wherein the protective layer comprises an anti-reflective coating applied to a top surface or a bottom surface of the protective layer.
11. The apparatus of claim 10 , wherein the anti-reflective coating comprises a near-infrared (NIR) wavelength-specific anti-reflective coating.
12. The apparatus of claim 9 , wherein the protective layer covers the retro-reflective layer, and the border partially covers the protective layer.
13. The apparatus of claim 1 , wherein the retro-reflective layer has a circular shape.
14. A marker comprising:
a retro-reflective layer having a first retro-reflectance capability, the retro-reflective layer comprising:
a textured surface, a portion of the textured surface having a surface topology such that surface normal vectors of the portion of the textured surface extend from the portion of the textured surface in different directions, and
a plurality of retro-reflective micro elements distributed across the textured surface; and
a base comprising a top surface where the retro-reflective layer is placed, the top surface providing a second retro-reflectance capability lower than the first retro-reflectance capability, wherein the base comprises a locating feature configured to guide the retro-reflective layer when the retro-reflective layer is placed on the top surface of the base such that a retro-reflective area of the retro-reflective layer aligns with a pre-determined location of the base.
15. The marker of claim 14 , wherein when the retro-reflective layer is placed on the top surface of the base, the center of the retro-reflective area aligns with a center of the base.
16. The marker of claim 14 , wherein the base comprises a central opening configured to releasably attach to a connector.
17. The marker of claim 16 , wherein the connector comprises:
a body having a top surface and a bottom surface,
a conical structure extending from the top surface, and
two projects extending from an outer surface of the conical structure, wherein the central opening is configured to receive the conical structure and the two projects.
18. The marker of claim 17 , wherein the central opening is configured to releasably couple with the connector by inserting and twisting the connector by a particular angle.
19. The marker of claim 18 , wherein the central opening further comprises a cavity at a position corresponding to the two projects so that when the two projects are twisted into the cavity, the connector is releasably coupled to the base.
20. The marker of claim 16 , wherein the connector is configured to releasably couple to the base by a snap-fit connection or threaded connection.