Modular focus system for image based code readers

• US 8,134,116 B2
• Filed: 01/12/2009
• Issued: 03/13/2012
• Est. Priority Date: 01/12/2009
• Status: Active Grant

• Current Assignee: Cognex Corporation
• Original Assignee: Cognex Corporation
• Inventors: Nunnink, Laurens, Reuter, Richard
• Primary Examiner(s): LE, QUE TAN
• Application Number:
  US12/352,109
• Publication Number:
  US 20100176319A1
• Time in Patent Office: 1,156 Days
• Field of Search: 250/239, 250/216, 250/234, 250/235, 250/208.1, 2502011-2015, 235/454, 235/462.42, 235/462.22, 235/462.36, 235/462.43
• US Class Current: 250/234
• CPC Class Codes: G02B 3/14 of variable focal length
• CPC Class Codes: G02B 7/026 using retaining rings or springs G02B7/027 takes precedence
• CPC Class Codes: G02B 7/04 with mechanism for focusing or varying magnification
• CPC Class Codes: G02B 7/10 by relative axial movement of several lenses, e.g. of varifocal objective lens
• CPC Class Codes: G06K 7/10811 Focalisation
• CPC Class Codes: G06K 7/10831 Arrangement of optical elements, e.g. lenses, mirrors, prisms optical elements per se G02B
• CPC Class Codes: G06K 7/1092 sensing by means of TV-scanning

Abstract

A modular focus system for image based code readers includes swappable lens attachments enables fixed focus, manual focus, and variable focus operation from a single reader. A manual focus lens cap includes a manually adjustable focus ring to change the focus of the reader. A variable focus lens module includes a liquid lens that is manipulated by a voltage delivered via a pair of electrodes to adjust the focus of the reader. The lens attachments can be swapped out and replaced as needed.

Claims

1. An image-based code reader comprising:

a lens mount secured within a lens mount housing;

a lens barrel rotatably received by the lens mount;

a sensor for capturing image data reflected from a target object;

an imager lens assembly fixedly secured within the lens barrel about an optical axis, wherein the imager lens assembly focuses the image data onto the sensor; and

a modular focusing system including a first removable lens attachment having a focus ring disposed at a target-facing end and a flange disposed at a sensor-facing end and a second removable lens attachment comprising;

a liquid lens secured within a liquid lens housing; and

a pair of electrodes in electrical contact with the liquid lens;

wherein the code reader is focused by at least one of adjusting the first lens attachment when secured to the code reader or a voltage to the liquid lens when the second lens attachment is coupled to the lens barrel.

2. The image based code reader of claim 1, wherein when the first lens attachment is rotated, the imager lens assembly is axially displaced from the sensor to focus the code reader.

3. The image based code reader of claim 2, further including a cover comprising a locking tab, wherein the locking tab is configured to be received within a slot in the first lens attachment when connected to the lens mount housing so as to prevent rotation of the first lens attachment.

4. The image based code reader of claim 2, wherein the lens mount includes at least one aligning tab, wherein the first lens attachment includes at least one key slot aligned with at least one aligning tab when the first lens attachment is placed onto and removed from the lens barrel, and wherein the at least one aligning tab corresponds to a predetermined focal length of the imager lens.

5. The image based code reader of claim 4, wherein the at least one aligning tab is formed in a receptacle disposed in the lens mount and the at least one key slot is formed in the retaining flange.

6. The image based code reader of claim 1, wherein the liquid lens housing includes at least one key slot aligned with the at least one aligning tab when placed onto and removed from the lens barrel, and wherein the at least one aligning tab corresponds to a predetermined focal length of the imager lens assembly.

7. The image based code reader of claim 1, further comprising a controller configured to detect when the second removable lens attachment is coupled to the code reader.

8. The image based code reader of claim 7, further comprising a controller configured to detect at least one of out-of-focus image data, a target distance, and an operator input;

wherein the controller is further configured to generate an output voltage for the liquid lens when one of out-of-focus image data, a target distance, and an operator input is detected.

9. A modular focus system for an image-based code reader, the system comprising:

a lens mount;

a lens barrel received by the lens mount;

an imager lens secured about an optical axis within the lens barrel for converging reflected image data from an object onto a sensor; and

a plurality of removable lens attachments for adjusting the focus of the reader, the plurality of lens attachments including;

a manual focus lens module configured to be secured to the lens barrel such that rotation of the manual focus lens module translates into an axial movement of the imager lens relative to the sensor; and

a variable focus lens module configured to be secured to the lens barrel and electrically connected to a controller such that an output from the controller adjusts the focus of the code reader.

10. The modular focus system of claim 9, wherein the manual focus lens module is comprised of:

a focus ring disposed at a target-facing end; and

a retaining flange disposed at a sensor-facing end.

11. The modular focus system of claim 10, wherein the manual focus lens module is further comprised of a mechanical stop for limiting rotation of the lens barrel to a predetermined range.

12. The modular focus system of claim 9, wherein the variable focus lens module is comprised of:

a liquid lens disposed within a housing; and

a pair of electrodes in electrical contact with the liquid lens.

13. The modular focus system of claim 12, wherein the variable focus lens module is further comprised of a biasing member for holding the liquid lens and electrodes together within the housing.

14. The modular focus system of claim 9, wherein the lens mount includes at least one inwardly extending aligning tab, and wherein each of the plurality of lens attachments includes at least one associated key slot such that each of the at least one aligning tabs and associated key slots are aligned to couple and decouple the lens attachments to the code reader.

15. The modular focus system of claim 14, wherein the lens mount further includes a cutout for receiving an extension formed in the variable focus lens module.

16. A removable variable focus lens module for an image based code reader, the variable focus lens module comprising:

a housing having a base and a cover, the base and cover defining a cavity and an opening extending through the housing about a module axis;

a first electrical contact disposed within the cavity having at least one electrode extending therefrom generally parallel to the module axis;

a liquid lens element;

a spacer configured to center the liquid lens element about the module axis;

a second electrical contact positioned in the cavity such that the first and second electrical contacts sandwich the liquid lens element; and

a biasing element disposed between one of the first and second electrical contacts and one of the base and cover to hold the first and second contacts in electrical and mechanical contact with the liquid lens element;

wherein the variable focus lens module is configured to be removably secured to the code reader such that the module axis generally aligns with an optical axis of the code reader.

17. The removable variable focus lens module of claim 16, wherein the housing further includes a key slot such that the key slot is aligned with a corresponding aligning tab formed in the code reader when the variable focus lens module is secured to or removed from the code reader.

18. An image-based code reader comprising:

a lens mount secured within a lens mount housing;

a lens barrel received by the lens mount;

a sensor for capturing image data reflected from a target object;

an imager lens assembly fixedly secured within the lens barrel about an optical axis, wherein the imager lens assembly focuses the image data onto the sensor; and

a modular focusing system including a first removable lens attachment having a focus ring and a second removable lens attachment comprising;

a variable focus element adapted to be secured to an element housing; and

a pair of electrodes in electrical communication with the variable focus element;

wherein the code reader is focused by at least one of adjusting the first lens attachment when secured to the code reader or supplying a voltage to the variable focus element when the second lens attachment is coupled to the lens barrel.

19. The image-based code reader of claim 18, wherein when the first lens attachment is rotated, the imager lens assembly is axially displaced from the sensor to focus the code reader.

20. The image-based code reader of claim 19, further including a cover comprising a locking tab, wherein the locking tab is configured to be received within a slot in the first lens attachment when connected to the lens mount housing so as to prevent rotation of the first lens attachment.

21. The image-based code reader of claim 18, wherein at least one alignment feature of the lens mount and the first lens attachment are configured such that the lens mount and the first lens attachment are received in only substantially one orientation.

22. The image-based code reader of claim 18, wherein at least one alignment feature on the lens mount is at least one aligning tab and the at least one alignment feature on the first lens attachment is at least one key slot which is aligned with the at least one aligning tab when the first lens attachment is placed onto and removed from the lens barrel, and wherein the at least one aligning tab corresponds to a predetermined focal length of the imager lens assembly.

23. The image-based code reader of claim 22, wherein the at least one aligning tab is formed in a receptacle disposed in the lens mount and the at least one key slot is formed in a retaining flange.

24. The image-based code reader of claim 18, where in the variable focus element is a liquid lens.

25. The image-based code reader of claim 18, wherein the element housing includes at least one key slot aligned with the at least one aligning tab when placed onto and removed from the lens barrel.

26. The image-based code reader of claim 18, further comprising a controller configured to detect when the second removable lens attachment is coupled to the code reader.

27. The image-based code reader of claim 26, further comprising a controller configured to detect at least one of out-of-focus image data, a target distance, and an operator input;

wherein the controller is further configured to generate an output voltage for the variable focus element when one of out-of-focus image data, a target distance, and an operator input is detected.

28. A modular focus system for an image-based code reader, the system comprising:

a housing;

a sensor adapted to capture image data reflected from a target object;

a lens barrel coupled to a imager lens, the lens barrel rotatably coupled to the housing; and

a plurality of removable lens attachments for adjusting the focus of the reader, the plurality of lens attachments including;

a manual focus lens module configured to be secured to the lens barrel such that rotation of the manual focus lens module translates into an axial movement of the imager lens relative to the sensor; and

a variable focus lens module configured to be secured to the lens barrel and electrically connected to a controller such that an output from the controller adjusts the focus of the code reader.

29. The image based code reader of claim 28, wherein the housing includes a receptacle.

30. The image based code reader of claim 29, wherein the lens barrel is at least partially disposed within the receptacle.

31. The image-based code reader of claim 28, where in the variable focus lens module is a liquid lens.