| 摘要 |
<p>Machine engraved identification cards. Prior identification cards required an opaque base of one color overlaid with an opaque layer of a contrasting color so that light impinging on the engraved surface of the card is variably reflected back to the eye of the observer according to the location and amount of the top layer removed to expose the bottom layer to form an observable image. Prior cards rely solely upon the variable reflectivity of light from the two opaque layers on the front of the engraved card. Thus, background light is irrelevant. The present card (10) has a translucent base layer (30) with engraved scores (36) extending through an opaque top layer (34) into the base layer whereby a "negative" image appears when the background light is below a determinable value and a latent, "positive" image appears when the background light passing through the translucent base is above the determinable value.</p> |
