Imaging reader and method with internal window reflections directed away from imager

• US 20070194119A1
• Filed: 02/22/2006
• Published: 08/23/2007
• Est. Priority Date: 02/22/2006
• Status: Active Grant

• Current Assignee: Symbol Technologies, LLC (Zebra Technologies Corporation)
• Original Assignee: Symbol Technologies, Inc. (Zebra Technologies Corporation)
• Inventors: Barkan, Edward, Vinogradov, Igor, Dryzmala, Mark
• Granted Patent: US 7,571,854 B2
• Time in Patent Office: Days
• US Class Current: 235/454
• CPC Class Codes: G06K 7/10722 Photodetector array or CCD scanning

Abstract

A target is illuminated with illumination light for image capture by a solid-state imager of an imaging reader. Internal reflections of the illumination light at a window are minimized, if not eliminated, by configuring the window as a non-planar optical element operative for redirecting the internal reflections away from the imager to enhance reader performance.

Claims

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

a) a housing having a window; and

b) a solid-state imager in the housing and including an array of image sensors for capturing target light through the window from the target over a field of view;

c) an illuminator in the housing for directing illumination light to and through the window to illuminate the target during reading, a portion of the illumination light incident on the window being reflected therefrom into the housing away from the window; and

d) the window being configured as a non-planar optical element for redirecting the reflected portion of the illumination light away from the imager to enhance reader performance.

2. The reader of claim 1, wherein the optical element is curved and has a radius of curvature.

3. The reader of claim 2, wherein the curved optical element has outer and inner spherical surfaces.

4. The reader of claim 2, wherein the illuminator is spaced from the window by a distance about equal to the radius of curvature of the curved optical element.

5. The reader of claim 2, wherein the curved optical element collects and focuses the reflected portion of the illumination light to a focal point spaced from the imager.

6. The reader of claim 2, wherein the curved lens has an optical power of about zero.

7. The reader of claim 1, wherein the imager captures the target light over an exposure time period, and a controller for controlling at least one of the exposure time period and the illumination light.

8. The reader of claim 1, wherein the illuminator includes a plurality of light emitting diodes (LEDs).

9. The reader of claim 1, wherein the target is at least one selected from a group including a one-dimensional symbol, a two-dimensional symbol, and a document.

10. The reader of claim 1, wherein the imager is one of a charge coupled device and a complementary metal oxide silicon device.

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

a) mounting a window on a housing of an electro-optical reader;

b) capturing target light with an array of image sensors of a solid-state imager through the window from the target over a field of view;

c) illuminating the target during reading by directing illumination light to and through the window, a portion of the illumination light incident on the window being reflected therefrom into the housing away from the window; and

d) configuring the window as a non-planar optical element for redirecting the reflected portion of the illumination light away from the imager to enhance reader performance.

12. The method of claim 11, wherein the configuring step is performed by forming the optical element with a curve having a radius of curvature.

13. The method of claim 12, wherein the configuring step is performed by forming the curved optical element with outer and inner spherical surfaces.

14. The method of claim 12, and the step of spacing the illuminator from the window by a distance about equal to the radius of curvature of the curved optical element.

15. The method of claim 12, wherein the redirecting step is performed by having the curved optical element collect and focus the reflected portion of the illumination light to a focal point spaced from the imager.

16. The method of claim 12, wherein the configuring step is performed by forming the curved optical element with an optical power of about zero.

17. The method of claim 11;

and the step of selecting the target from a group including a one-dimensional symbol, a two-dimensional symbol, and a document.