| 摘要 |
The first reflective lateral face of the first triangular-pyramidal retroreflective unit is on the same plane with the first lateral face of the tetrahedral retroreflective unit, the second reflective lateral face of the first triangular-pyramidal retroreflective unit is on the same plane with the second lateral face of the tetrahedral retroreflective unit, the third reflective lateral face of the first triangular-pyramidal retroreflective unit is parallel to one of the two lateral faces forming a V shaped groove, the third reflective lateral face of the second triangular-pyramidal retroreflective unit is identical with, or parallel to, the other of the two faces forming said V-shaped groove; and the third reflective lateral face of said tetrahedral retroreflective unit is same as one of the two faces forming said V-shaped groove. <IMAGE> |
