IMAGING READER WITH NON-UNIFORM MAGNIFICATION WITHIN A FIELD OF VIEW

• US 20120325909A1
• Filed: 06/23/2011
• Published: 12/27/2012
• Est. Priority Date: 06/23/2011
• Status: Active Grant

• Current Assignee: Symbol Technologies, LLC (Zebra Technologies Corporation)
• Original Assignee: Symbol Technologies, Inc. (Zebra Technologies Corporation)
• Inventors: VINOGRADOV, Igor, TRAJKOVIC, Miroslav
• Granted Patent: US 8,777,106 B2
• Time in Patent Office: Days
• US Class Current: 235/454
• CPC Class Codes: G02B 27/0075 with means for altering, e.g. increasing, the depth of field or depth of focus
• CPC Class Codes: G06K 7/10722 Photodetector array or CCD scanning

Abstract

An imaging lens assembly captures return light through a window of a vertical slot scanner from a target located in a range of working distances along an optical axis away from the window, and projects the captured return light onto an array of a solid-state imager. The imaging lens assembly is optically modified for non-uniform magnification within, and for increasing resolution at an outer peripheral region of, a field of view of the array, in an imaging plane generally perpendicular to the optical axis. The magnification is at least partly increased in the imaging plane with increasing radial distance away from the optical axis, to enable reading of the target when tilted relative to the optical axis and located at the outer peripheral region of the field of view.

Claims

1. A reader for electro-optically reading a target by image capture, comprising:

a housing having a window;

a solid-state imager supported by the housing, and having an array of sensors with a field of view in which the target is located during reading; and

an imaging lens assembly having an optical axis, and operative for capturing return light through the window from the target located in a range of working distances along the optical axis away from the window, and for projecting the captured return light onto the array, the imaging lens assembly being optically modified for non-uniform magnification within, and increasing resolution at an outer peripheral region of, the field of view in an imaging plane generally perpendicular to the optical axis, the magnification at least partly increasing in the imaging plane with increasing radial distance away from the optical axis, to enable reading of the target when tilted relative to the optical axis and located at the outer peripheral region of the field of view.

2. The reader of claim 1, wherein the window is located on the housing in a generally upright plane.

3. The reader of claim 1, wherein the array is one of a charge coupled device (CCD) array and a complementary metal oxide semiconductor (CMOS) array.

4. The reader of claim 1, and further comprising an illumination system supported by the housing, for illuminating the target with illumination light, and wherein the optically modified imaging lens assembly is operative for projecting the captured return illumination light onto the array.

5. The reader of claim 1, and further comprising a controller for processing electrical signals produced by the imager, and for decoding a target symbol.

6. The reader of claim 1, wherein the optically modified imaging lens assembly comprises non-rotationally symmetrical optics.

7. The reader of claim 6, wherein the non-rotationally symmetrical optics include at least one of a toroidal lens, a cylindrical lens, an aspherical toroidal lens and an aspherical cylindrical lens.

8. The reader of claim 1, wherein the optically modified imaging lens assembly comprises rotationally symmetrical optics.

9. The reader of claim 1, wherein the optically modified imaging lens assembly gradually increases the magnification in the imaging plane with increasing radial distance away from the optical axis.

10. The reader of claim 1,wherein the optically modified imaging lens assembly gradually increases the magnification in the imaging plane with increasing radial distance away from the optical axis until the outer peripheral region of the field of view is reached, and then gradually decreases the magnification in the imaging plane with increasing radial distance away from the optical axis as the outer peripheral region of the field of view is traversed.

11. A method of electro-optically reading a target by image capture, comprising the steps of:

locating the target in a field of view of an array of sensors of a solid-state imager during reading;

capturing return light through a window from the target located in a range of working distances along an optical axis of an imaging lens assembly;

projecting the captured return light onto the array; and

optically modifying the imaging lens assembly for non-uniform magnification within, and for increasing resolution at an outer peripheral region of, the field of view, in an imaging plane generally perpendicular to the optical axis, by at least partly increasing the magnification in the imaging plane with increasing radial distance away from the optical axis, to enable reading of the target when tilted relative to the optical axis and located at the outer peripheral region of the field of view.

12. The method of claim 11, and orienting the window to lie in a generally upright plane.

13. The method of claim 11, and configuring the array as one of a charge coupled device (CCD) array and a complementary metal oxide semiconductor (CMOS) array.

14. The method of claim 11, and illuminating the target with illumination light, and wherein the projecting step is performed by projecting the captured return illumination light onto the array.

15. The method of claim 11, and processing electrical signals produced by the imager, and decoding a target symbol.

16. The method of claim 11, and configuring the optically modified imaging lens assembly of non-rotationally symmetrical optics.

17. The method of claim 16, and configuring the non-rotationally symmetrical optics as at least one of a toroidal lens, a cylindrical lens, an aspherical toroidal lens, and an aspherical cylindrical lens.

18. The method of claim 11, and configuring the optically modified imaging lens assembly of rotationally symmetrical optics.

19. The method of claim 11, wherein the optically modifying step is performed by gradually increasing the magnification in the imaging plane with increasing radial distance away from the optical axis.

20. The method of claim 11, wherein the optically modifying step is performed by gradually increasing the magnification in the imaging plane with increasing radial distance away from the optical axis until the outer peripheral region of the field of view is reached, and then gradually decreasing the magnification in the imaging plane with increasing radial distance away from the optical axis as the outer peripheral region of the field of view is traversed.