| 摘要 |
A retroreflective device comprising a substantially spherical graded refractive index lens, referred to as a GRIN-sphere lens ( 2 ), a reflective part for retroreflecting ( 6 ) a radiation beam (B) passing through the graded refractive index lens and, at least partially surrounding the lens, a transparent material ( 4 ) having a substantially uniform refractive index.
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