G - Physics – 06 – K
Patent
G - Physics
06
K
G06K 9/18 (2006.01) G06K 7/10 (2006.01)
Patent
CA 2168491
A data carrier such as a card, disc, or badge, may have digital data encoded in a surface thereof, or in a plurality of stacked transparent surfaces,where the data is encoded as either positive-going or negative-going surface irregularities. The data may be decoded from the surface by passing the data- carrying surface beneath a focusing lens through which light from a single wavelength laser diode is directed at the surface. Light from the surface is reflected back through the focusing lens to the single wavelength laser diode, where that reflected light impinging on the laser diode causes interference at the pn junction within the diode. If, at the same time, alternating current is being passed through the diode ? say, at 1.5 MHz ?, then the current anomalies occurring in the diode as a consequence of the pn interference may be detected such as by the voltage drop across a shunt device in series with the diode. A signal is derived which is indicative of the current anomalies, and it together with the alternating signal are fed to a mixer. The product of that mixer can be decoded such as by fourier analysis, delta analysis, or transient analysis, and so on. The resultant signal may also be fed through a filter before being analyzed.The result is that a data reading device having the laser emitter and data detector mounted in a single unit is provided. By filtering and/or such as fourier analysis, the reflection from one or other of several data carrying surfaces maybe decoded, provided that each data-carrying stratum is transparent, at least tothe light emitted from the single wavelength laser diode.
Bogdan Alexei
Sagalovich Emil S.
LandOfFree
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