REDUCING PERCEIVED BRIGHTNESS OF ILLUMINATION LIGHT SOURCE IN ELECTRO-OPTICAL READERS THAT ILLUMINATE AND READ TARGETS BY IMAGE CAPTURE

• US 20140131596A1
• Filed: 11/15/2012
• Published: 05/15/2014
• Est. Priority Date: 11/15/2012
• Status: Active Grant

• Current Assignee: Symbol Technologies, LLC (Zebra Technologies Corporation)
• Original Assignee: Symbol Technologies, Inc. (Zebra Technologies Corporation)
• Inventors: Vinogradov, Igor R., Liu, Rong, Mitelman, Yuly, Trongone, Eric S.
• Granted Patent: US 10,318,778 B2
• Time in Patent Office: Days
• US Class Current: 250/566
• CPC Class Codes: G06K 7/10831 Arrangement of optical elements, e.g. lenses, mirrors, prisms optical elements per se G02B

Abstract

Targets to be electro-optically read by image capture are illuminated with illumination light emitted from an illumination light source and directed along an illumination path through a window to the targets, and return light from the targets is captured through the window and projected along an imaging path to an array of light sensors of an imaging system. An optical element is located in both the illumination path and the imaging path, and has a light-reflecting, non-diffusing portion for directing the captured return light incident on the light-reflecting portion along a folded imaging path to the array, and a light-diffusing portion for diffusing the illumination light incident on the light-diffusing portion along a folded illumination path to scatter and blur an image of the illumination light source, to increase an apparent size of the illumination light source, and to reduce a perceived brightness of the illumination light source.

Claims

1. An apparatus for electro-optically reading targets by image capture, comprising:

a housing;

a window supported by the housing;

an illumination system supported by the housing, and operative for illuminating the targets with illumination light emitted from an illumination light source and directed along an illumination path through the window to the targets;

an imaging system including a solid-state imager supported by the housing and having an array of light sensors looking at an imaging field of view that extends through the window to the targets, and an imaging lens system operative for capturing return illumination light from the targets through the window, and for projecting the captured return illumination light along an imaging path to the array; and

an optical element located in both the illumination path and the imaging path, the optical element having a light-reflecting, non-diffusing portion for folding the imaging path and for directing the captured return illumination light incident on the light-reflecting portion along the folded imaging path to the array, and a light-diffusing portion for folding the illumination path and for diffusing the illumination light incident on the light-diffusing portion along the folded illumination path to scatter and blur an image of the illumination light source, to increase an apparent size of the illumination light source, and to reduce a perceived brightness of the illumination light source.

2. The apparatus of claim 1, wherein the window is substantially planar, and wherein the housing supports the window in one of a generally upright and a generally horizontal plane.

3. The apparatus of claim 1, wherein the illumination light source includes a plurality of light emitting diodes.

4. The apparatus of claim 1, wherein the optical element is of one-piece construction, and wherein the light-reflecting portion is located on one part of the optical element, and wherein the light-diffusing portion is located on an outer surface of a remaining part of the optical element.

5. The apparatus of claim 4, wherein the light-reflecting portion has a surface finish less than about five micrometers, and wherein the light-diffusing portion has a surface finish exceeding about five micrometers.

6. The apparatus of claim 1, wherein the optical element is constituted of one of glass and plastic.

7. The apparatus of claim 1, and a fold mirror also located in both the illumination path and the imaging path, the fold mirror being operative for folding the folded imaging path and for reflecting the captured return illumination light incident thereon to the optical element, and for folding the illumination path and for reflecting the illumination light from the optical element through the window.

8. An apparatus for electro-optically reading targets by image capture, comprising:

a housing;

a window supported by the housing;

an illumination system supported by the housing, and operative for illuminating the targets with illumination light emitted from an illumination light source and directed along an illumination path through the window to the targets;

an imaging system including a solid-state imager supported by the housing and having an array of light sensors looking at an imaging field of view that extends through the window to the targets, and an imaging lens system operative for capturing return illumination light from the targets through the window, and for projecting the captured return illumination light along an imaging path to the array; and

an optical element located in both the illumination path and the imaging path, the optical element having a light-reflecting, non-diffusing portion for directing the captured return illumination light incident on the light-reflecting portion along the imaging path to the array, and a light-diffusing portion for folding the illumination path and for diffusing the illumination light incident on the light-diffusing portion along the folded illumination path to scatter and blur an image of the illumination light source, to increase an apparent size of the illumination light source, and to reduce a perceived brightness of the illumination light source.

9. The apparatus of claim 8, wherein the optical element is of one-piece construction, and wherein the light-reflecting portion is located on one part of the optical element, and wherein the light-diffusing portion is located on an outer surface of a remaining part of the optical element.

10. The apparatus of claim 9, wherein the light-reflecting portion has a surface finish less than about five micrometers, and wherein the light-diffusing portion has a surface finish exceeding about five micrometers.

11. A method of electro-optically reading targets by image capture, comprising:

supporting a window on a housing;

illuminating the targets with illumination light emitted from an illumination light source and directed along an illumination path through the window to the targets;

capturing return illumination light from the targets through the window, and projecting the captured return illumination light along an imaging path to an array of light sensors of a solid-state imager;

locating an optical element in both the illumination path and the imaging path; and

configuring the optical element with a light-reflecting, non-diffusing portion for folding the imaging path and for directing the captured return illumination light incident on the light-reflecting portion along the folded imaging path to the array, and with a light-diffusing portion for folding the illumination path and for diffusing the illumination light incident on the light-diffusing portion along the folded illumination path to scatter and blur an image of the illumination light source, to increase an apparent size of the illumination light source, and to reduce a perceived brightness of the illumination light source.

12. The method of claim 11, and configuring the window to be substantially planar, and supporting the window in one of a generally upright and a generally horizontal plane.

13. The method of claim 11, and configuring the illumination light source as a plurality of light emitting diodes.

14. The method of claim 11, and constructing the optical element of one-piece, and locating the light-reflecting portion on one part of the optical element, and locating the light-diffusing portion on an outer surface of a remaining part of the optical element.

15. The method of claim 14, and configuring the light-reflecting portion with a surface finish less than about five micrometers, and configuring the light-diffusing portion with a surface finish exceeding about five micrometers.

16. The method of claim 11, and constituting the optical element of one of glass and plastic.

17. The method of claim 11, and also locating a fold mirror in both the illumination path and the imaging path, the fold mirror being operative for folding the folded imaging path and for reflecting the captured return illumination light incident thereon to the optical element, and for folding the illumination path and for reflecting the illumination light from the optical element through the window.