Method and apparatus for providing omnidirectional lighting in a scanning device

• US 20060032921A1
• Filed: 08/05/2004
• Published: 02/16/2006
• Est. Priority Date: 10/24/2003
• Status: Active Grant

• Current Assignee: Cognex Technology & Investment Corporation (Cognex Corporation)
• Original Assignee: Cognex Technology & Investment Corporation (Cognex Corporation)
• Inventors: Testa, Justin, Equitz, William H., Nadabar, Sateesh G., Gerst, Carl W. III
• Granted Patent: US 7,604,174 B2
• Time in Patent Office: Days
• US Class Current: 235/455
• CPC Class Codes: G06K 7/10732 Light sources
• CPC Class Codes: G06K 7/10851 Circuits for pulse shaping, amplifying, eliminating noise signals, checking the function of the sensing device basic electronic circuitry H03
• CPC Class Codes: G06K 7/14 using light without selection of wavelength, e.g. sensing reflected white light G06K7/10831 - G06K7/1097 take precedence
• CPC Class Codes: G06K 7/146 the method including quality enhancement steps

Abstract

A system and method is provided for selectively controlling the illumination, and particularly dark field illumination, applied to a symbol to be decoded, and for determining a suitable or optimized level of lighting for decoding the symbol. A ring-shaped illuminator is provided, and is segmented into a plurality of individually-controllable lighting portions which can be, for example, quadrants. Initially, illumination is provided to the symbol through an initial set of lighting conditions. Feedback from acquired image data is then used to determine whether the lighting is suitable for decoding the symbol and, if not, a controller varies the lighting applied to the symbol, and additional image data is acquired. This process is continued until suitable conditions are met. Alternatively, activation and deactivation of the lighting segments can be manually selected by an operator to provide suitable conditions.

Claims

1. A digital scanning device for decoding a digitally encoded symbol comprising:

a light source comprising a plurality of individually-controllable lighting elements for providing dark field illumination to an encoded data symbol;

an image sensor for detecting image data reflected from the encoded data symbol when illuminated by the light source; and

a controller connected to each of the individually-controllable lighting elements, the controller being programmed to selectively activate the lighting elements to vary the lighting provided by the light source on the data encoded symbol and to process the image data collected by the image sensor to decode the symbol.

2. The digital scanning device as recited in claim 1, wherein the individually controllable lighting elements comprise portions of a circular ring.

3. The digital scanning device as recited in claim 2, wherein the portions of the circular ring comprise quadrants

4. The digital scanning device as recited in claim 2, wherein the individually-controllable lighting elements comprise a plurality of electrically-connected individual light elements.

5. The digital scanning device as recited in claim 1, wherein the individually controllable lighting elements provide a rectangular ring.

6. The digital scanning device as recited in claim 1, wherein the individually controllable listing elements provide an oval ring.

7. The digital scanning device as recited in claim 1, wherein the individually controllable lighting elements provide an elliptical ring.

8. The digital scanning device as recited in claim 1, wherein the controller is further programmed to evaluate the data acquired by the image sensor and to vary the light applied to the data symbol from the individually-controllable lighting elements to optimize symbol decoding.

9. The digital scanning device as recited in claim 1, wherein the light source comprises a passive illumination pipe.

10. The digital scanning device as defined in claim 1, wherein the scanning device is a handheld scanning device.

11. The digital scanning device as defined in claim 1, wherein the scanning device is a fixed mount scanning device.

12. The digital scanning device as defined in claim 1, wherein the light source comprises an active light pipe.

13. The digital scanning device as defined in claim 1, further comprising a manual control connected to the controller for manually selecting at least one of the individually-controllable light elements to be activated.

14. The digital scanning device as recited in claim 1, further comprising a memory component for storing data corresponding to the lighting elements activated for a successful decode.

15. The digital scanning device as recited in claim 1, wherein the controller is further programmed to vary the brightness of the individually-controllable light elements.

16. The digital scanning device as recited in claim 1, wherein the controller is further programmed to vary the exposure time of the image sensor.

17. A method for decoding an encoded data symbol, the method comprising the following steps:

(a) arranging a plurality of individually-controllable lighting elements around an encoded data symbol to provide at least one of a dark field and a bright field illumination on an illumination surface;

(b) illuminating the data encoded symbol with at least one of the individually-controllable lighting elements;

(c) acquiring an image data set;

(d) evaluating the image data set to determine suitability for decoding;

(e) selectively varying a lighting parameter for varying the light emitted from individually-controllable lighting elements to vary the illumination on the data encoded symbol; and

(f) repeating steps (d) and (e) until the image data set is suitable for decoding.

18. The method as defined in claim 17, further comprising the steps of arranging the individually controllable lighting elements in quadrants around the illumination surface.

19. The method as defined in claim 17, further comprising the step of (g) storing the setting of selectively activate and deactivated lighting elements found to be suitable for decoding.

20. The method as defined in claim 17, wherein step (b) comprises retrieving the stored illumination setting.

21. The method as defined in claim 17, wherein step (b) comprises retrieving default parameters for activating each of the light elements.

22. The method as defined in claim 17, wherein step (d) comprises evaluating the acquired image date to decode the symbol.

23. The method as defined in claim 17, wherein step (d) comprises evaluating the acquired image data to evaluate the relative concentration of light and dark pixels.

24. The method as defined in claim 17, wherein step (a) comprises arranging the light elements in quadrants, and wherein successive occurrences of step (b) comprise sequentially activating one of more combinations of the quadrants.

25. The method as defined in claim 17, wherein step (a) comprises selectively providing each of a bright field illumination and a dark field illumination.

26. The method as defined in claim 17, wherein step (e) comprises varying the light emitted by modulating a signal applied to at least one of the individually controllable lighting elements to vary the brightness of the illumination.

27. The method as defined in claim 17, wherein step (e) comprises varying an exposure time for illuminating the symbol.

28. The method as defined in claim 17, wherein step (e) comprises varying the focus.

29. The method as defined in claim 17, wherein step (e) comprises selectively activating at least one of the individually-controllable lighting elements.

30. A digital scanning device, comprising:

a ring light source providing dark field illumination to an adjacent surface including a symbol to be decoded;

a controller connected to the ring light source for selectively varying the light projected from the light source; and

an image sensor connected to the controller for acquiring image data of the symbol, wherein the controller is programmed to evaluate the image data to determine whether the image data is sufficient to decode the symbol and to vary the light projected from the light source until the image data is sufficient to decode the symbol.

31. The digital scanning device as defined in claim 30, further comprising a memory component connected to the controller for storing light conditions.

32. The digital scanning device as defined in claim 30, wherein the controller is further programmed to determine whether the data is sufficient to decode the symbol based on a statistical analysis of the data.

33. The digital scanning device as defined in claim 30, wherein the controller is further programmed to determine whether the data is sufficient to decode the symbol based on an attempt to decode the symbol.

34. The digital scanning device as defined in claim 30, further comprising a bright field light source for providing bright field illumination to the adjacent surface, wherein the controller is further programmed to selectively activate the bright field light source to illuminate the symbol.

35. The illuminator as defined in claim 30, wherein the ring light source comprises a passive light pipe.

36. The illuminator as defined in claim 30, wherein the ring light source comprises an active light pipe.

37. The illuminator as defined in claim 30, wherein the ring light source comprises a plurality of individually-controllable lighting segments.

38. The illuminator as defined in claim 30, further comprising an image sensor connected to the controller for detecting light reflected from the symbol and for providing feedback to the controller for varying the lighting conditions.

39. A digital scanning device, comprising:

an arcuate light source;

a controller connected to the arcuate light source for selectively varying the light projected from the light source; and

an image sensor connected to the controller for acquiring image data at the symbol, wherein the controller is programmed to evaluate the image data to determine whether the image data is sufficient to decode the symbol and to vary the light projected from the light source until the image data is sufficient to decode the symbol.

40. The digital scanning device as defined in claim 39, wherein the arcuate light source comprises a portion of a ring.

41. The digital scanning device as defined in claim 39, wherein the arcuate light source comprises a ring.

42. The digital scanning device as defined in claim 39, wherein the arcuate light source comprises a plurality of individually-controllable lighting elements.