| 摘要 |
A visual tracking device (10) comprises a light screening member (12) having a relatively high light transmission region (50) and a relatively low light transmission region (52) substantially surrounding the relatively high light transmission region (50). By means of this arrangement, text, symbols or other markings underlying the high light transmission region (50) are readily discernible and text, symbols and other markings underlying the low light transmission region (52) are less readily discernable.
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