But note that if you scan a bar code (at a particular steady scan speed) that a "wide white bar" could actually be a range of 10 -> 16 ones while the narrow black bar could be 3 -> 9 zeros. This variation can occur due to....

+ Variation of bar widths due to printing transfer process.

+ Sharpness of the printed bar code edges.

+ Printer resolution if the printer itself is digital in nature.

+ Scan parallelism to the orthagonal axis of the bar code.

+ Scan speed instantaneous variation.

+ Scan "slotting width" relating to the sensitivity of the photo pickup.

+ Light intensity used to illuminate the bar code during scanning.

+ Reflectivity of dark bars in the printed bar code.

+ Reflectivity of light bars in the printed bar code.

+ Contrast ratio between the light ahd dark bars of the code.

+ Thermal and humity characteristics of the medium the bar code is printed upon.

+ Optical sensor digitizing frequency.

+ Synchronization of the sampling points to the actual edges of the bar code.

+ Oversampling ratio of the scan digitize rate versus the fundamental bar frequency determined by the scan speed.

As you can see there are many factors that make the bar code detection difficult. However it is not impossible as MANY MANY bar code scanners have been successfully built and deployed.

Michael Karas