| 摘要 |
A substrate for an optical sensor, the substrate having an image printed in a frequency modulated manner and a randomly textured surface ( 27 ) overlying said image. In one embodiment the substrate comprises an image bearing layer ( 24 ) and an overlying transparent layer ( 26 ), the image bearing layer being provided with an image printed in a frequency modulated manner and the transparent layer ( 26 ) being randomly textured. |
