Apparatus for and method of minimizing specular reflections in imaging field of view of workstation that reads targets by image capture
A workstation electro-optically reads targets by image capture, and includes a housing, a generally planar window, an imaging module, and a generally planar fold mirror between the window and the module. The module has an illuminating light assembly for directing illumination light along an illumination path through the window at a target for return therefrom during reading, and an image sensing assembly for detecting return illumination light through the window along an imaging path over an imaging field of view during reading. The fold mirror folds the illumination and the imaging paths. The fold mirror and the window lie in planes that are substantially parallel to each other to prevent reflections of the illumination light off of the fold mirror and the window from entering the imaging field of view as virtual images that degrade target detection by the image sensing assembly.
1. A workstation for electro-optically reading targets by image capture, comprising:
a housing for supporting a light-transmissive window;
an imaging module mounted in the housing, the imaging module including an illuminating light assembly for directing illumination light along an illumination path in the housing through the window at a target for return therefrom during reading, and an image sensing assembly for detecting return illumination light returning from the target through the window along an imaging path in the housing over an imaging field of view during reading;
a fold mirror mounted in the illumination and the imaging paths in the housing between the window and the imaging module, and operative for folding the illumination and the imaging paths, the fold mirror lying in a plane and facing the window, and the window lying in a plane and oriented relative to the plane of the fold mirror to prevent reflections of the illumination light off of the fold mirror and the window from entering the imaging field of view as virtual images that degrade target detection by the image sensing assembly; and
wherein the plane of the window is oriented in a range of plus or minus 10 degrees out of exact parallelism with the plane of the fold mirror.
2. The workstation of claim 1 , wherein the housing is fixed relative to a support surface at the workstation, and wherein the window is elevated relative to the support surface.
3. The workstation of claim 1 , wherein the illuminating light assembly includes a pair of light emitting diodes (LEDs) spaced apart from each other, and a pair of illumination lenses through which the illumination light passes en route to the fold mirror.
4. The workstation of claim 3 , wherein the image sensing assembly includes a solid-state, image sensor having an array of pixels for detecting the return illumination light returning from the target, and an imaging lens assembly for capturing the return illumination light over the imaging field of view and over a range of working distances relative to the window.
5. The workstation of claim 4 , wherein the imaging module includes a printed circuit board on which the illuminating light assembly and the image sensing assembly are commonly mounted, and wherein the LEDs are mounted at opposite sides of the image sensor on the board.
6. The workstation of claim 1 , wherein the plane of the window is substantially parallel to the plane of the fold mirror.
7. The workstation of claim 1 , wherein the fold mirror is mounted at an elevation above the imaging module.
8. The workstation of claim 1 , wherein the image sensing assembly is operative for generating an electrical signal indicative of the detected return illumination light; and further comprising a controller for processing the electrical signal into data corresponding to the target.
9. A workstation for electro-optically reading targets by image capture, comprising:
a housing for supporting a light-transmissive window;
an imaging module mounted in the housing, the imaging module including an illuminating light assembly for directing illumination light along an illumination path in the housing through the window at a target for return therefrom during reading, and an image sensing assembly for detecting return illumination light returning from the target through the window along an imaging path in the housing over an imaging field of view during reading;
a fold mirror mounted in the illumination and the imaging paths in the housing between the window and the imaging module, and operative for folding the illumination and the imaging paths, the fold mirror lying in a plane and facing the window, and the window lying in a plane that is substantially parallel to the plane of the fold mirror to prevent reflections of the illumination light off of the fold mirror and the window from entering the imaging field of view as virtual images that degrade target detection by the image sensing assembly; and
wherein the plane of the window is oriented in a range of plus or minus 10 degrees out of exact parallelism with the plane of the fold mirror.
10. A method of electro-optically reading targets by image capture, comprising:
supporting a light-transmissive window on a housing;
directing illumination light along an illumination path in the housing through the window at a target for return therefrom during reading;
detecting return illumination light returning from the target through the window along an imaging path in the housing over an imaging field of view during reading;
folding the illumination and the imaging paths by mounting a fold mirror in the illumination and the imaging paths in the housing;
configuring the fold mirror to lie in a plane;
positioning the fold mirror to face the window;
configuring the window to lie in a plane;
orienting the plane of the window relative to the plane of the fold mirror to prevent reflections of the illumination light off of the fold mirror and the window from entering the imaging field of view as virtual images that degrade target detection; and
wherein the orienting is performed by orienting the plane of the window to be in a range of plus or minus 10 degrees out of exact parallelism with the plane of the fold mirror.
11. The method of claim 10 , and fixing the housing relative to a support surface at the workstation, and elevating the window relative to the support surface.
12. The method of claim 10 , wherein the directing is performed by a pair of light emitting diodes (LEDs) spaced apart from each other, and a pair of illumination lenses through which the illumination light passes en route to the fold mirror.
13. The method of claim 12 , wherein the detecting is performed by a solid-state, image sensor having an array of pixels for detecting the return illumination light returning from the target, and by an imaging lens assembly for capturing the return illumination light over the imaging field of view and over a range of working distances relative to the window.
14. The method of claim 13 , and mounting the LEDs at opposite sides of the image sensor on a printed circuit board.
15. The method of claim 10 , wherein the orienting is performed by orienting the plane of the window to be substantially parallel to the plane of the fold mirror.
16. The method of claim 10 , and further comprising generating an electrical signal indicative of the detected return illumination light; and
processing the electrical signal into data corresponding to the target.