Intelligent method of tracking focus in machine vision applications

1. A method for tracking focus of an adjustable variable focus lens-based imaging system, the method comprising:

identifying, in the imaging system, an initial fixed focus position of an adjustable variable focus lens assembly of the imaging system for capturing an image of an object;

determining one or more focusing parameters of the adjustable variable focus lens assembly for the initial fixed focus position and comparing the one or more focusing parameters to a lens behavior model for the adjustable variable focus lens assembly;

determining a compensated fixed focus position of the imaging system based on the comparison to the lens behavior model; and

capturing, via the imaging system, at least one image of the object at the compensated fixed focus position.

2. The method of claim 1 , wherein the one or more focusing parameters comprise at least one of time, current temperature of the adjustable variable focus lens assembly, diopter of the adjustable variable focus lens assembly, voltage associated with the initial fixed focus position, voltage sweep associated with the initial fixed focus position, and modulation transfer function of at least a portion of an image captured by the imaging system at the initial fixed focus position.

3. The method of claim 1 , wherein determining the compensated fixed focus position of the imaging system based on the comparison to the lens behavior model comprises:

based on the comparison to the lens behavior model, identifying a focusing sweep range defined by a forward focus position forward of the initial fixed focus position and an aft focus position aft of the initial fixed focus position;

determining a compensated forward focus position and a compensated aft focus position based on the comparison to the lens aging model;

capturing, via the imaging system, a plurality of images of the object at focus positions at and/or between the compensated forward focus position and the compensated aft focus position; and

determining the compensated fixed focus position as one of the focus positions.

4. The method of claim 1 , wherein the initial fixed focus position is associated with an initial reference voltage, and wherein determining the compensated fixed focus position of the imaging system comprises:

based on the comparison to the lens behavior model, determining a forward focus position voltage and an aft focus position voltage;

capturing, via the imaging system, a plurality of images of the object at different focus positions by sweeping the imaging system across voltages at and/or between the forward focus position voltage and the aft focus position voltage; and

determining the compensated fixed focus position as one of the different focus positions.

5. The method of claim 1 , wherein the initial fixed focus position is associated with an initial reference voltage, and wherein determining the compensated fixed focus position of the imaging system comprises:

identifying a focusing sweep voltage range defined by a forward focus position voltage corresponding to a forward focus position forward of the initial fixed focus position and by an aft focus position voltage corresponding to an aft focus position aft of the initial fixed focus position;

determining a compensated forward focus position voltage and a compensated aft focus position voltage based on the comparison to the lens behavior model;

capturing, via the imaging system, a plurality of images of the object at different focus positions by sweeping the imaging system across voltages at and/or between the forward focus position voltage and the aft focus position voltage, wherein the different focus positions are between +1 diopter and −1 diopter of a center focus position; and

determining the compensated fixed focus position as one of the different focus positions.

6. The method of claim 1 , further comprising:

capturing a plurality of images of objects for machine vision analysis and storing one or more focusing parameters of the adjustable variable focus lens for each of the plurality of images captured for machine vision analysis;

determining image quality changes occurring over the plurality of images captured for machine vision analysis; and

developing the lens behavior model based the image quality changes,

wherein the image quality changes are changes in contrast or modulation transfer function over a feature of interest in the plurality of images.

7. The method of claim 1 , wherein the lens behavior model comprises time based compensation data, temperature based compensation data, diopter based compensation data, voltage based compensation data, voltage sweep based compensation data, and/or modulation transfer function based compensation data.

8. The method of claim 1 , wherein the adjustable variable focus lens assembly comprises a liquid lens.

9. The method of claim 1 , wherein the lens behavior model is an aging model comprising historical data for the one or more focusing parameters of the adjustable variable focus lens assembly.

10. The method of claim 1 , wherein the lens behavior model is a thermal model comprising thermal data for the one or more focusing parameters of the adjustable variable focus lens assembly.

11. The method of claim 1 , wherein the lens behavior model is a drift model comprising lens drift data for the one or more focusing parameters of the adjustable variable focus lens assembly.

12. The method of claim 1 , wherein comparing the one or more focusing parameters to the lens behavior model comprises;

capturing a plurality of images of the object and identifying a feature of interest in the plurality of images;

determining a contrast or modulation transfer function corresponding to the feature of interest for each of the plurality of images;

determining a change in the contrast or the modulation transfer function between the plurality of images; and

comparing the change in the contrast or the modulation transfer function to the lens behavior model and determining a change in the one or more focusing parameters corresponding to the change in the contrast or the modulation transfer function.

13. An imaging system comprising:

an imaging assembly having an adjustable variable focus lens assembly;

one or more processors; and

a non-transitory machine-readable memory storing machine-readable instructions that, when executed by the one or more processors, cause the imaging system to:

identify an initial fixed focus position of the adjustable variable focus lens assembly for capturing an image of an object;

determine one or more focusing parameters of the adjustable variable focus lens assembly for the initial fixed focus position and compare the one or more focusing parameters to a lens behavior model for the adjustable variable focus lens assembly;

determine a compensated fixed focus position of the imaging system based on the comparison to the lens behavior model; and

capture at least one image of the object at the compensated fixed focus position.

14. The imaging system of claim 13 , wherein the one or more focusing parameters comprise at least one of time, current temperature of the adjustable variable focus lens assembly, diopter of the adjustable variable focus lens assembly, voltage associated with the initial fixed focus position, voltage sweep associated with the initial fixed focus position, and modulation transfer function of an image captured by the imaging system at the initial fixed focus position.

15. The imaging system of claim 13 , the memory storing further machine-readable instructions that, when executed by the one or more processors, cause the imaging system to:

based on the comparison to the lens behavior model, identify a focusing sweep range defined by a forward focus position forward of the initial fixed focus position and an aft focus position aft of the initial fixed focus position;

determine a compensated forward focus position and a compensated aft focus position based on the comparison to the lens behavior model;

capture a plurality of images of the object at focus positions at and/or between the compensated forward focus position and the compensated aft focus position; and

determine the compensated fixed focus position as one of the focus positions.

16. The imaging system of claim 13 , the memory storing further machine-readable instructions that, when executed by the one or more processors, cause the imaging system to:

based on the comparison to the lens behavior model, determine a forward focus position voltage and an aft forward position voltage; and

capture a plurality of images of the object at different focus positions by sweeping the imaging system across voltages at and/or between the forward focus position voltage and the aft focus position voltage; and

determine the compensated fixed focus position as one of the different focus positions.

17. The imaging system of claim 13 , wherein the initial fixed focus position is associated with an initial reference voltage, the memory storing further machine-readable instructions that, when executed by the one or more processors, cause the imaging system to:

identify a focusing sweep voltage range defined by a forward focus position voltage corresponding to a forward focus position forward of the initial fixed focus position and by an aft focus position voltage corresponding to an aft focus position aft of the initial fixed focus position;

determine a compensated forward focus position voltage and a compensated aft focus position voltage based on the comparison to the lens behavior model;

capture a plurality of images of the object at different focus positions by sweeping the imaging system across voltages at and/or between the forward focus position voltage and the aft focus position voltage; and

determine the compensated fixed focus position as one of the different focus positions.

18. The imaging system of claim 13 , the memory storing further machine-readable instructions that, when executed by the one or more processors, cause the imaging system to:

capture a plurality of images of objects for machine vision analysis and storing one or more focusing parameters of the adjustable variable focus lens for each of the plurality of images captured for machine vision analysis;

determine image quality changes occurring over the plurality of images captured for machine vision analysis; and

develop the lens behavior model based the image quality changes,

wherein the image quality changes are changes in contrast or modulation transfer function over a feature of interest in the plurality of images.

19. The imaging system of claim 13 , wherein the lens behavior model comprises time based compensation data, temperature based compensation data, diopter based compensation data, voltage based compensation data, voltage sweep based compensation data, and/or modulation transfer function based compensation data.

20. The imaging system of claim 13 , wherein the lens behavior model is an aging model comprising historical data for the one or more focusing parameters of the adjustable variable focus lens assembly.

21. The imaging system of claim 13 , wherein the lens behavior model is a thermal model comprising thermal data for the one or more focusing parameters of the adjustable variable focus lens assembly.

22. The imaging system of claim 13 , wherein the lens behavior model is a drift model comprising lens drift data for the one or more focusing parameters of the adjustable variable focus lens assembly.

23. The imaging system of claim 13 , the memory storing further machine-readable instructions that, when executed by the one or more processors, cause the imaging system to:

capture a plurality of images of the object and identify a feature of interest in the plurality of images;

determine a contrast or modulation transfer function corresponding to the feature of interest for each of the plurality of images; and

determine a change in the contrast or the modulation transfer function between the plurality of images and determine a change in the one or more focusing parameters corresponding to the change in the contrast or the modulation transfer function; and

compare the change in the contrast or the modulation transfer function to the lens behavior model.

24. The imaging system of claim 13 , wherein the adjustable variable focus lens assembly comprises a liquid lens.

25. The imaging system of claim 13 , wherein the imaging assembly is a barcode reader.

26. The imaging system of claim 13 , wherein the imaging assembly is a machine vision system.

27. A machine vision method comprising:

identifying, in a machine vision system having an adjustable variable focus lens assembly, one or more current operating conditions of the adjustable variable focus lens assembly, the adjustable variable focus lens assembly having a first operating parameter value set;

comparing the one or more current operating conditions to a lens behavior model for the adjustable variable focus lens assembly;

in response to the comparison, determining a compensated parameter value set for compensating for age related changes to the adjustable variable focus lens assembly; and

capturing, via the machine vision system, at least one image of an object using the compensated parameter value set.

28. The machine vision method of claim 27 , wherein the one or more current operating conditions of the machine vision system comprise at least one of time, current temperature of the adjustable variable focus lens assembly, diopter of the adjustable variable focus lens assembly, voltage associated with the initial fixed focus position, voltage sweep of the adjustable variable focus lens assembly, and modulation transfer function of an image captured by the adjustable variable focus lens assembly.

29. The machine vision method of claim 27 , wherein first operating parameter value set comprises a first fixed focus position of the adjustable variable focus lens assembly, and wherein the compensated parameter value set comprises a compensated fixed focus position different than the first fixed focus position.

30. The machine vision method of claim 27 , wherein first operating parameter value set comprises a focusing sweep distance range, and wherein the compensated parameter value set comprises a compensated focusing sweep distance range different than the focusing sweep distance range.

31. The machine vision method of claim 27 , wherein first operating parameter value set comprises a voltage associated with a first fixed focus position of the adjustable variable focus lens assembly, and wherein the compensated parameter value set comprises a compensated voltage associated with a compensated fixed focus position different than the first fixed focus position.

32. A machine vision system comprising:

an imaging assembly having an adjustable variable focus lens assembly;

one or more processors; and

a non-transitory machine-readable memory storing machine-readable instructions that, when executed by the one or more processors, cause the machine vision system to:

identify one or more current operating conditions of the adjustable variable focus lens assembly, the adjustable variable focus lens assembly having a first operating parameter value set;

compare the one or more current operating conditions to a lens behavior model for the adjustable variable focus lens assembly; and

in response to the comparison, determine a compensated parameter value set for compensating for age related changes to the adjustable variable focus lens assembly; and

capture, via the machine vision system, at least one image of an object using the compensated parameter value set.

33. The machine vision system of claim 32 , wherein the one or more current operating conditions of the machine vision system comprise at least one of time, current temperature of the adjustable variable focus lens assembly, diopter of the adjustable variable focus lens assembly, voltage associated with the initial fixed focus position, voltage sweep of the adjustable variable focus lens assembly, and modulation transfer function of an image captured by the adjustable variable focus lens assembly.

34. The machine vision system of claim 32 , wherein first operating parameter value set comprises a first fixed focus position of the adjustable variable focus lens assembly, and wherein the compensated parameter value set comprises a compensated fixed focus position different than the first fixed focus position.

35. The machine vision system of claim 32 , wherein first operating parameter value set comprises a focusing sweep distance range, and wherein the compensated parameter value set comprises a compensated focusing sweep distance range different than the focusing sweep distance range.

36. The machine vision system of claim 32 , wherein first operating parameter value set comprises a voltage associated with a first fixed focus position of the adjustable variable focus lens assembly, and wherein the compensated parameter value set comprises a compensated voltage associated with a compensated fixed focus position different than the first fixed focus position.