Method and apparatus for providing omnidirectional lighting in a scanning device

• US 8,061,613 B2
• Filed: 09/01/2009
• Issued: 11/22/2011
• 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: Gerst, Carl W. III, Testa, Justin, Nadabar, Sateesha, Equitz, William H.
• Primary Examiner(s): TRAIL, ALLYSON NEEL
• Application Number:
  US12/552,107
• Publication Number:
  US 20100025469A1
• Time in Patent Office: 812 Days
• Field of Search: 235/462.42, 235/462.01, 235/462.45
• 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 low angle dark field illumination to an encoded data symbol;

a bright field light source for providing bright field illumination to the 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 and to the bright field illumination source, the controller being programmed to selectively activate the lighting elements to vary the direction of the dark field illumination provided by the light source and to selectively activate the bright field 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 at least one of a circular ring, an oval ring, and an elliptical 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 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.

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

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

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

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

11. 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.

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

13. 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.

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

15. The digital scanning device as defined in claim 1, further comprising a memory component connected to the controller for storing light conditions.

16. The digital scanning device as defined in claim 1, 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.

17. The digital scanning device as defined in claim 1, 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.

18. The digital scanning device as recited in claim 1, wherein a ring light source comprises a plurality of individually-controllable lighting segments.

19. The digital scanning device as recited in claim 1, 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.

20. The digital scanning device as recited in claim 1, wherein the light source is arcuate.

21. 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 a low-angle dark field on an illumination surface and a bright field illuminator directed at the encoded data symbol to provide bright field illumination;

(b) selectively 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 direction of the dark field illumination on the data encoded symbol and to selectively activate the bright field illumination source; and

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

22. The method as defined in claim 21, further comprising the steps of arranging the individually controllable lighting elements in quadrants around the illumination surface.

23. The method as defined in claim 21, further comprising the step of (g) storing the parameter found to be suitable for decoding.

24. The method as defined in claim 21, wherein step (b) comprises retrieving the stored illumination setting.

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

26. The method as defined in claim 21, wherein step (d) comprises evaluating the acquired image date to decode the symbol.

27. The method as defined in claim 21, wherein step (d) comprises evaluating the acquired image data to evaluate the relative concentration of light and dark pixels.

28. The method as defined in claim 21, 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.

29. The method as defined in claim 21, wherein step (a) further comprises the steps of providing a bright field illumination element, and selectively providing each of a bright field illumination and a dark field illumination.

30. The method as defined in claim 21, 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.

31. The method as defined in claim 21, wherein step (e) comprises varying an exposure time for illuminating the symbol.

32. The method as defined in claim 21, wherein step (e) comprises varying the focus.

33. The method as defined in claim 21, wherein step (e) comprises selectively activating at least one of the individually-controllable lighting elements.

34. The method as defined in claim 21, wherein step (a) further comprises the step of angling the light emitted from the light elements to provide the low angle dark field illumination.