Robust barcode and reader for rod position determination

Abstract

A barcode reader and processing circuitry are disclosed for identifying a position of a cylinder rod, for example, along a path of movement. The barcode is marked on a surface of the rod and constitutes a series of markings extending along a portion of the length of the rod. The markings represent encoded information based on numbers calculated with a random number generator, and are grouped into subsets, each of which corresponds to a particular rod position. A portion of the rod including a subset of barcode markings is exposed to light emitted from the reader. Light reflected off the barcode is sensed with an array of photosensors provided in the reader. The photosensors generate electrical signals, and using Bayesian probability, a likely subset of markings is determined corresponding to the received electrical signals. Once identified, the markings subset is associated with a location corresponding to the position of the rod. A barcode reader is also described that is relatively easy to assemble and provides uniform illumination of the barcode.

1 - 47 . (canceled)  
   
   
       48 . An apparatus for reading an image provided on a surface, said apparatus comprising: 
 a plurality of photosensors;    a lens, said lens being configured to receive light from said image and direct said light to said plurality of photosensors;    a carrier, said lens and said plurality of photosensors being attached to said carrier; and    a housing, said housing having an external surface and an internal surface, said external surface having a first reference portion and said internal surface having a second reference portion, said second reference portion being aligned with said first reference portion, said carrier being attached to said second reference portion such that upon said first reference portion being positioned at a predetermined distance away from said image, said light is substantially focused onto said plurality of photosensors.    
   
   
       49 . An optical device in accordance with  claim 48 , wherein said housing has an opening, said light passing through said opening, said optical device further including at least one optical emitter provided in said housing, each of which being configured to direct light through said opening to said image.  
   
   
       50 . An optical device in accordance with  claim 49 , wherein said surface is substantially uniformly exposed by said light.  
   
   
       51 . An optical device in accordance with  claim 49 , further comprising a cylindrical lens provided between said at least one optical emitter and said image.  
   
   
       52 . An optical device in accordance with  claim 48 , wherein a first point on said first reference portion and a second point on said second reference portion define a reference line located between said plurality of photosensors and said lens such that as said housing thermally expands said plurality of photosensors moves in a direction opposite to the direction in which said lens moves, and said light remains substantially focused onto said plurality of photosensors.  
   
   
       53 . An optical device in accordance with  claim 48 , further including a casing provided between said first reference portion and said second reference portion, said casing having a thickness, said thickness corresponding to said predetermined distance.  
   
   
       54 . An optical device in accordance with  claim 48 , wherein said image is a barcode.  
   
   
       55 . An optical device in accordance with  claim 49 , wherein said at least one optical emitter includes an LED.  
   
   
       56 . An optical device comprising: 
 a housing having an opening;    first and second optical emitters provided in said housing, said first and second optical emitters being configured to output light through said opening;    a circuit configured to supply substantially the same electrical current to said first and second optical emitters; and    a plurality of photosensors provided in said housing, said plurality of photosensors receiving a portion of said light reflected off a surface external to said housing.    
   
   
       57 . An optical device in accordance with  claim 56 , wherein said circuit includes first and second transistors, the emitter of said first transistor and the emitter of said second transistor being coupled to a common terminal via respective resistors, said common terminal being maintained at a predetermined potential, and a collector of said first transistor being coupled to said first optical emitter and a collector of said second transistor being coupled to said second optical emitter, and the bases of said first and second transistors being connected together.  
   
   
       58 . An optical device in accordance with  claim 57 , wherein said circuit further includes a diode coupled between said collector of said first transistor and the base of said first transistor.  
   
   
       59 . An optical device in accordance with  claim 57 , wherein first and second optical emitters include first and second electrodes, respectively, said first and second electrodes being connected in common, said optical device further including a power supply being coupled to said commonly connected first and second electrodes, said power supply being configured to intermittently bias said first and second electrodes to thereby pass said electrical current through said first and second optical emitters.  
   
   
       60 . An optical device in accordance with  claim 59 , wherein said first and second optical emitters are LEDs.  
   
   
       61 . An optical device in accordance with  claim 58 , further comprising a resistor coupled between said base and said collector of said second transistor.  
   
   
       62 . An optical device in accordance with  claim 58 , wherein said diode includes a Schottky diode.  
   
   
       63 . An optical device in accordance with  claim 56 , further comprising a plurality of lenses provided between said plurality of optical emitters and said image, said plurality of lenses including a selfoc lens array.  
   
   
       64 . An optical device in accordance with  claim 56 , wherein said optical emitters and said plurality of photosensors are formed integrally with said carrier.  
   
   
       65 - 76 . (canceled)