Imaging optical code reader having selectable depths of field

• US 20040118918A1
• Filed: 04/02/2003
• Published: 06/24/2004
• Est. Priority Date: 12/18/2002
• Status: Active Grant

• Current Assignee: Symbol Technologies, LLC (Zebra Technologies Corporation)
• Original Assignee: Symbol Technologies, Inc. (Zebra Technologies Corporation)
• Inventors: Carlson, Brad, Shi, Tsi David, Dvorkis, Paul, Krichever, Mark, Breytman, Alex
• Granted Patent: US 7,025,271 B2
• Time in Patent Office: Days
• US Class Current: 235/454
• CPC Class Codes: G06K 19/14 the marking being sensed by radiation
• CPC Class Codes: G06K 7/0004 Hybrid readers
• CPC Class Codes: G06K 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer
• CPC Class Codes: G06K 7/10386 the interrogation device being of the portable or hand-handheld type, e.g. incorporated in ubiquitous hand-held devices such as PDA or mobile phone, or in the form of a portable dedicated RFID reader
• CPC Class Codes: G06K 7/10722 Photodetector array or CCD scanning
• CPC Class Codes: G06K 7/10811 Focalisation

Abstract

Several optical systems for imaging engines of imaging optical code readers are disclosed. Each optical system includes the abilities to change the depth of field of the imaging field and to adjust a focus quality of the imaging field. The disclosed structures for changing the depth of field of the disclosed optical systems allow for the automatic or manual selection of one of a plurality of depths of field.

Claims

1. An optical system for an optical code reader including an image sensor, the optical system comprising:

an optical assembly including at least one optical element located in an optical path of the code reader for impinging an image of an optical code onto the image sensor; and

an image modification assembly having an actuator selectively moveable among a plurality of positions, wherein each position modifies the depth of field of said image impinged onto the image sensor.

2. The optical system of claim 1, wherein the actuator is an optical wedge having a first thickness corresponding to a first depth of field and a second thickness corresponding to a second depth of field.

3. The optical system of claim 1, wherein the actuator is an optical wedge having a plurality of thicknesses each corresponding to a particular depth of field, wherein said actuator is one of transversely or rotationally moveable with respect to the optical path.

4. The optical system of claim 1, wherein the image modification assembly comprises a manually actuated trigger assembly operatively coupled to the actuator for moving the actuator to one of the plurality of positions while substantially simultaneously imaging the optical code.

5. The optical system of claim 1, wherein the image modification assembly further comprises a switch for selectively switching the actuator among the plurality of positions.

6. The optical system of claim 1, further comprising an image focusing assembly in operative communication with the at least one optical element for adjusting the position of the at least one optical element for adjusting a focus quality of the image.

7. The optical system of claim 1, further comprising an image focusing assembly in operative communication with the image sensor for moving the image sensor for adjusting a focus quality of the image.

8. The optical system of claim 1, wherein the actuator modifies the diameter of an aperture aligned with the image sensor for modifying the depth of field.

9. An optical system for an optical code reader including an image sensor comprising:

an optical assembly including an optical element located in an optical path of the code reader for impinging an image of an optical code onto the image sensor;

an image modification assembly including an optical wedge having a first thickness defining a near depth of field and a second thickness defining a far depth of field, said optical wedge being selectively moveable between the first and second positions for modifying the depth of field of said image impinged onto the image sensor; and

an image focusing assembly for moving the optical element for adjusting a focus quality of the image onto the image sensor.

10. The optical system of claim 9, wherein the image focusing assembly controls the image modification assembly for controlling the depth of field.

11. The optical system of claim 9, wherein the image focusing assembly controls the position and/or orientation of the image sensor for controlling the focus quality of the image.

12. An optical system for an optical code reader including an image sensor comprising:

an optical assembly including an optical element located in an optical path of the code reader for impinging an image of an optical code onto the image sensor;

an image modification assembly including an adjustable aperture assembly having a first diameter defining a near depth of field and a second diameter defining a far depth of field, said aperture assembly being selectively moveable between the first and second positions for modifying the depth of field of said image impinged onto the image sensor; and

an image focusing assembly for moving the optical element for adjusting a focus quality of the image onto the image sensor.

13. The optical system of claim 12, wherein the image focusing assembly controls the image modification assembly for controlling the depth of field.

14. The optical system of claim 12, wherein the image focusing assembly controls the position and/or orientation of the image sensor for controlling the focus quality of the image.

15. An optical system for an optical code reader comprising:

first and second lens assemblies having respective first and second depths of field, and respective first and second input optical axes;

at least one optical element having a transmissive state and a reflective state positioned in at least the first input optical axis to provide incident light from the first lens assembly to an image sensor when the at least one optical element is in the transmissive state and to provide incident light from the second lens assembly to the image sensor when the at least one optical element is in the reflective state; and

a control circuit assembly for applying a voltage to the at least one optical element for switching the at least one optical element between the transmissive and reflective states to switch between the first and second depths of field.

16. An optical code reading system comprising:

a photo sensor employing an array of cells for producing electrical signals responsive to an image directed to said sensor;

an optical system for focusing one of at least two images corresponding to at least two depths of field which do not completely overlap to the photo sensor, the optical system including at least one moveable optical element for switching between said depths of field, said optical element having at least two different thicknesses corresponding to the at least two depths of field;

means for controlling said optical element to switch between the depths of field; and

means for decoding data from the electrical signals corresponding to an optical code contained in at least one of the images focused on the photo sensor.

17. The optical code reading system of claim 16, wherein the optical system includes at least one lens through which an input optical path of the system passes and wherein the at least two thicknesses of the moveable optical element traverse the optical path for switching between said fields of view.

18. An imaging system for reading an optical code comprising:

a photo sensor employing an array of cells for producing electrical signals responsive to an image directed to said sensor;

an optical system for directing images to the photo sensor, wherein the optical system includes an optical element for switching between at least two states to vary the optical properties of the image directed to the photo sensor, wherein the optical element is an optical wedge having at least two different thicknesses corresponding to the at least two states; and

means for controlling the optical wedge to select an image of the optical code that is readily decodable.

19. The imaging system of claim 18, wherein the optical element is switched between the at least two states to provide at least two different depths of field.

20. The imaging system of claim 18, wherein the optical element is switched between the at least two states to provide at least two different focal distances.

21. The imaging system of claim 18, further comprising automatically focusing means for controlling at least one of the optical system and the photo sensor for focusing the image.

22. The imaging system of claim 18, wherein the at least two different thicknesses have a difference of approximately 0.7 mm.

23. An optical code reading system comprising:

a photo sensor employing an array of cells for producing electrical signals responsive to an image directed to said sensor;

an optical system for focusing one of at least two images corresponding to at least two depths of field which do not completely overlap to the photo sensor, the optical system including an actuator assembly for selectively altering the diameter of an aperture whose center is substantially aligned with an optical path of the optical system for switching between said depths of field;

means for controlling said actuator assembly to switch between the depths of field; and

means for decoding data from the electrical signals corresponding to an optical code contained in at least one of the images focused on the photo sensor.

24. An imaging system for reading an optical code comprising:

a photo sensor employing an array of cells for producing electrical signals responsive to an image directed to said sensor;

an optical system for directing images to the photo sensor, wherein the optical system includes at least one electrically operative optical element for electronically switching between at least two states to vary the optical properties of the image directed to the photo sensor, wherein the at least one optical element is at least one electronic mirror; and

means for controlling the at least one electronic mirror to select an image of the optical code that is readily decodable.

27. The imaging system of claim 24, wherein the at least one optical element is switched between the at least two states to provide different depths of field.

28. The imaging system of claim 24, wherein the at least one optical element is switched between the at least two states to provide different focal distances.