| CPC G02B 5/136 (2013.01) [G02B 1/11 (2013.01); G02B 5/13 (2013.01); G02B 5/132 (2013.01); G02B 26/0833 (2013.01); G01S 17/66 (2013.01)] | 20 Claims |

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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.
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