In August of 2017, CRR invented tailorable truncated retroreflector array (TTRA) technology while working to improve retroreflectors used in CRR’s long-distance modulating reflector tag system. TTRA technology involves truncating triangular trihedral corner reflectors and tiling together multiple instances of resulting truncated triangular trihedral corner reflectors to produce truncated retroreflector arrays that have retroreflection characteristics substantially the same as conventional retroreflector arrays. But unlike these conventional arrays, where non-retroreflected energy has typically been treated as signal loss, arrays designed using TTRA technology enable non-retroreflected energy such as light to be redirected to specific locations other than an energy source in order to meet specific application requirements.
Truncation of a triangular trihedral corner reflector is accomplished in a manner similar to cutting cookie dough using a truncating object having a certain shape and truncation rotation angle relative to the orientation of the triangular trihedral corner reflector being truncated. A truncating object can have a rectangular shape, an equilateral triangular shape, a right isosceles triangle shape, or an isosceles triangle shape, where the length-to-width ratio of the rectangular shape can vary and the non-congruent angle of the isosceles triangle shape can vary. Figure 1 depicts vertical truncation of a trihedral triangular corner reflector using an equilateral triangular truncation object having a 60° truncation rotation.
A truncation can be either a vertical truncation or a non-vertical truncation, where a non-vertical truncation angle can vary. A vertical or non-vertical truncation can be centered on the symmetrical axis of the triangular trihedral corner reflector or offset from the axis.
Figure 2 depicts non-vertical truncation of a trihedral triangular corner reflector using an equilateral triangle both without and with an offset from the symmetrical axis of the corner reflector.
Figure 3 presents plan views looking down the symmetrical axis (or boresight) of a triangular trihedral retroreflector and corresponding truncated retroreflectors having been vertically truncated using an equilateral triangle truncating object with 5°, 10°, 20°, 30°, 40°, 50°, and 60° truncation rotations.
Figures 4 and 5 present plan and side views of a retroreflector array made up of six triangular trihedral corner reflectors and seven truncated retroreflector arrays each made up of six truncated retroreflectors. The six truncated retroreflectors that make up the seven truncated retroreflector arrays were truncated using equilateral triangle truncating objects having 5°, 10°, 20°, 30°, 40°, 50°, and 60° truncation rotations, respectively. In Figure 5, the dashed lines indicate the a boundary between the remaining retroreflector portions of the arrays that are below the dashed lines and the redirecting portions of the arrays that are above the dashed lines.
Figure 6 presents the same plan views of Figure 4 with added dashed lines indicating the retroreflector portions of the truncated retroreflector arrays and with solid darker lines indicated the redirecting portions of the truncated retroreflector arrays, where the portions of the array outside the retroreflector portions are also redirecting portions.
Figure 7 depicts oblique projection views of larger truncated retroreflector arrays similar to those shown in Figures 4-6.
Generally, by varying truncation parameters, essentially an infinite number of array designs can be produced allowing engineering trades to be made regarding retroreflection vs. energy redirecting characteristics so as to efficiently retroreflect energy (e.g., light) back to a source while also controlling the redirecting of the remaining (i.e., non-retroreflected) energy to locations other than the source, where energy can be directed in a deterministic manner.
TTRA technology can be used in numerous applications such as:
Safety reflectors on roads, vehicles, buildings, bicycles, motorcycles, trailers, etc.
Reflective sheeting used on road signs
Safety and hazard signage (e.g., reflective device on a bridge, a buoy, a jetty, a tree, etc.)
Reflective surfaces on walls (e.g., beneath kitchen cabinets, on bathroom walls)
Wall tiles, ceiling tiles, architectural tiles, ceiling medallions
Lighting covers including overhead light diffusers
Reflective surfaces in lighting including LED lighting
Home decor: coasters, mirrors, candle holders, picture frames, clocks, holiday decorations, switch and electrical outlet covers
Targets used with sensors such as LIDAR or radar sensors (e.g., autonomous vehicle and robot guidance systems)
Tracking system targets (i.e., reference points)
Reflective surfaces to support imaging (e.g., MRI)
Reflective surfaces used in liquid crystal display (LCD) screens
CRR has developed product prototypes based on the TTRA technology in several application areas: