| 摘要 |
A luminescent address bar code is applied to a predetermined location of a postal item at an early stage in its handling by the Postal Authorities to provide in a machine readable form the destination address written on the postal item. This machine readable bar code is then sensed and used to route the postal item in automatic sorting machines. Errors in the reading of the luminescent address bar codes leads to the postal item being misrouted or being rejected. The quantity of light emitted from the luminescent address bar codes varies with the nature and properties of the surface of the postal item and it is this variation in the quantitiy of light emitted which leads to errors in reading the codes. To overcome this the reflectance of the surface of the postal item is monitored and then the quantity of flurescent or phosphorescent material applied to the postal item to form the bars of the address code is controlled in dependence upon the reflectance of the postal item, so that the visible light emitted from the code bars on every postal item is substantially constant. |
