Non-orthogonal cube corner elements and arrays thereof made by end milling

Abstract

A new technique for making cube corner elements that involves end milling is used in the fabrication of cube corner elements having non-orthogonal dihedral angles and dihedral angle errors, and arrays of such cube corner elements. A given optical face of a cube corner element may be a compound face with two constituent faces. In some cases, the constituent faces may be parallel and coplanar such that a given dihedral angle error pertains to the entire optical face, while in other cases, the two constituent faces may not be parallel, and may be associated with different dihedral angle errors.

1 . An article comprising a cube corner element defined in a structured surface, the structured surface extending along a reference plane, the cube corner element including a first rounded edge that is inclined relative to the reference plane, the cube corner element also including a first, second, and third optical face, wherein at least part of the first optical face deviates from orthogonality relative to at least part of the second optical face by a first angle error whose magnitude is at least 1 minute of arc but no more than 2 degrees. 
     
     
         2 . The article of  claim 1 , wherein the first optical face is a compound face having a first and second constituent face that meet along a first break line, and the second optical face is a compound face having a third and fourth constituent face that meet along a second break line, and wherein the first constituent face deviates from orthogonality relative to the third constituent face by the first angle error. 
     
     
         3 . The article of  claim 2 , wherein the second constituent face also deviates from orthogonality relative to the fourth constituent face by the first angle error. 
     
     
         4 . The article of  claim 1 , wherein the first, second, and third optical faces are each compound faces having two constituent faces that meet along a first, second, and third break line respectively, and for each of the first, second, and third optical faces, the two constituent faces are parallel to each other to within 1 minute of arc. 
     
     
         5 . The article of  claim 1 , wherein the rounded edge is a dihedral edge of the cube corner element. 
     
     
         6 . The article of  claim 1 , wherein the rounded edge is a non-dihedral edge of the cube corner element. 
     
     
         7 . The article of  claim 1 , wherein the structured surface also includes other cube corner elements, and wherein the at least part of the first optical face is not coplanar with any optical face, or portion thereof, of any of the other cube corner elements that are adjacent to the first cube corner element.