| 摘要 |
<p>A substrate capable of receiving and retaining imaging is coded so as to maximize the amount of the scannable information that can be packed into an area, and/or to provide an effective security feature. A first machine readable identification code (12) (e.g. bar code) is imaged on a predetermined area of the substrate (30), and is opaque to a first predetermined wavelength range of electromagnetic energy (e.g. the infrared region of light). An overlay (13, 27) is applied over and a least partially covering the first code. The overlay is transparent to the first wavelength range, and opaque to a second wavelength range (e.g. the visible spectrum of light). The overlay may be a security block (27) which substantially completely covers the first code, or may be a second bar code (13) (or additional codes) which is transparent to the second range. The codes may be read by multiple passes of different scanner heads (15, 16) by relative movement between the heads and the substrate, or by a scanner (23) in which first and second (or more) different scanner heads are mounted together so that two different wavelength range bar codes on the substrate may be read at the same time.</p> |
