Extended working range illumination system for an imaging-based bar code reader
A method and apparatus for reading a target object having areas of differing light reflectivity on the target such as a handheld bar code reader having a first illumination pattern, a detector for measuring a distance from the reader to a target object, a system threshold, and a comparator for evaluating the measured distance against the threshold. Should the reader's internal circuitry and/or software determine that the measured distance is greater than the threshold, a second illumination pattern is activated that has power effective illumination for increasing the operable reading distance between the reader and the target object. The second illumination pattern can be generated from a secondary illumination source or through a lens internal to the reader.
1. An illumination assembly for emitting illumination for imaging a target object, the imaging assembly comprising:
a) an illumination source energizable to emit a first illumination pattern when a distance to the target object is less than or equal to a prescribed value; and
b) the illumination source energizable to emit a second illumination pattern when the distance to the target object is greater than the prescribed value, wherein the second illumination pattern is more concentrated than the first illumination pattern.
2. The illumination assembly of claim 1 , wherein said second illumination pattern is produced by a concentrating lens.
3. The illumination assembly of claim 1 , wherein said second illumination pattern is produced by a light emitting diode.
4. The illumination assembly of claim 1 , wherein said assembly is a bar code scanner and the target object is a bar code that is imaged and decoded.
5. The illumination assembly of claim 1 , wherein said second illumination pattern is produced by a reflective concentrator.
6. A bar code reader for imaging a target bar code comprising:
a) imaging assembly for imaging and decoding a bar code;
b) a range assembly for determining a distance from the imaging assembly to the target bar code;
c) illumination assembly for emitting illumination for imaging the target bar code the imaging assembly including:
1) an illumination source energizable to emit a first illumination pattern when a distance to the target bar code is less than a predetermined value; and
2) the illumination source energizable to emit a second illumination pattern when the distance to the target bar code is greater than the predetermined value, wherein the second illumination pattern is more concentrated than the first illumination pattern.
7. The bar code reader of claim 6 , wherein said second illumination pattern is generated from a concentrating lens.
8. The bar code reader of claim 6 , wherein said second illumination pattern is generated from at least one light emitting diode.
9. The bar code reader of claim 6 , wherein said second illumination pattern is generated from a reflective concentrator.
10. A reading apparatus for decoding areas of differing light reflectivity on a target comprising:
a) an illumination source for producing a first illumination pattern;
b) a detector for measuring a distance from said reading apparatus and a target object;
c) a system threshold;
d) a comparator for evaluating the measured distance against said threshold; and
e) a second illumination pattern that is activated when said measured distance is greater than said threshold, wherein the second illumination pattern is more concentrated than the first illumination pattern.
11. The reading apparatus of claim 10 , wherein said second illumination pattern is generated from a converging lens for increasing the concentration of the illumination on the target object.
12. The reading apparatus of claim 10 , wherein said second illumination pattern is generated from at least one light emitting diode.
13. The reading apparatus of claim 12 , wherein the light emitting diode is independent from said first illumination pattern.
14. The reading apparatus of claim 10 , wherein said second illumination pattern is generated from a reflective concentrator for increasing the concentration of the illumination on the target object.
15. The reading apparatus of claim 10 , wherein said second illumination pattern is dependent from said first illumination pattern.
16. The reading apparatus of claim 10 , wherein said a second illumination pattern is activated when said measured distance is greater than or equal to said threshold.
17. The reading apparatus of claim 10 , wherein said a threshold is autonomously configured.
18. The reading apparatus of claim 10 , wherein said a threshold is prescribed by external conditions.
19. The reading apparatus of claim 10 , wherein the reading apparatus is a bar code scanner and the target object is a bar code that is imaged and decoded.
20. A method for imaging a target bar code, the steps of the method comprising:
a) determining a distance from the imaging assembly to the target bar code;
b) energizing an illumination assembly for emitting illumination for imaging a target bar code an illumination source energizable to emit a first illumination pattern when a distance to the target bar code is less than or equal to a predetermined value; and
c) the illumination source energizable to emit a second illumination pattern when the distance to the target bar code is greater than the predetermined value, wherein the second illumination pattern is more concentrated than the first illumination pattern.
21. The method for imaging a target bar code of claim 20 , wherein said second illumination pattern is generated from a converging lens.
22. The method for imaging a target bar code of claim 20 , wherein said second illumination pattern is generated from at least one light emitting diode.
23. The method for imaging a target bar code of claim 20 , wherein said second illumination pattern is generated from a reflective concentrator.
24. A method of reading a target article comprising:
a) projecting a first illumination pattern from an imaging system across a target article;
b) reflecting said first illumination pattern from said target article to a lens located in said imaging system;
c) directing said reflected illumination across a pixel array generating an image;
d) reading said image produced in the pixel array in a CCD imager;
e) comparing a measured distance from said imaging system to said target article against a threshold of said imaging system;
f) sustaining the first illumination pattern if when comparing the measured distance against the threshold of imaging system its determined that the measured distance is less than said threshold; and
g) employing a second illumination pattern if when comparing the measured distance against the threshold of imaging system its determined that the measured distance is greater than said threshold, wherein the second illumination pattern is more concentrated than the first illumination pattern.
25. The method of reading a target article of claim 24 , wherein the concentrated illumination pattern is produced by a lens having a concentrating effect.
26. The method of reading a target article of claim 24 , wherein the concentrated illumination pattern is produced by at least one light emitting diode.
27. The method of reading a target article of claim 24 , wherein the threshold is prescribed by interpolation techniques of the imaging system based on the quality of the image produced by the pixel array.
28. The method of reading a target article of claim 24 , wherein the threshold is prescribed by software parameters of the imaging system.
29. The method of reading a target article of claim 24 , wherein the threshold is prescribed by environmental conditions surrounding the imaging system.
30. The method of reading a target article of claim 24 , wherein the imaging system is a bar code reader and the target article is a bar code that is imaged and decoded.
31. The method of reading a target article of claim 24 , wherein the concentrated illumination pattern is produced by a reflective concentrator.
32. An automatic imaging system having a first illumination pattern that is directed at a target object when the system is actuated and an imaging system including a pixel array, a focusing lens to focus an image of the target object onto the pixel array, the automatic imaging system comprising:
a) software and/or circuitry for analyzing an image of the illumination reflected from the target object and projected onto the pixel array by the lens;
b) an analytical technique to establish a measured variable;
c) an imaging system threshold;
d) a comparator for evaluating said measured variable to said imaging system threshold; and
e) a second illumination pattern that is activated when said measured variable is greater than said imaging system threshold, wherein the second illumination pattern is more concentrated than the first illumination pattern.
33. The automatic imaging system of claim 32 , wherein said imaging system threshold is autonomous based on surrounding environmental conditions.
34. The automatic imaging system of claim 32 , wherein said imaging system threshold is prescribed.
35. The automatic imaging system of claim 32 , wherein said second concentrated illumination is produced from concentrating the first illumination on the target object.
36. The automatic imaging system of claim 32 , wherein said second concentrated illumination is produced from at least one light emitting diode that is independent of said first illumination.
37. The automatic imaging system of claim 32 , wherein said second concentrated illumination is produced from a lens that concentrates the first illumination on the target object.
38. The automatic imaging system of claim 32 , wherein the imaging system is a bar code reader and the target object is a bar code that is imaged and decoded.
39. The automatic imaging system of claim 32 , wherein the analytical technique to establish a measured variable is a range finding technique.
40. The automatic imaging system of claim 32 , wherein the analytical technique to establish a measured variable is an automatic focusing technique.
41. The automatic imaging system of claim 32 , wherein the analytical technique to establish a measured variable is an auto exposure control technique.