Curved Exit Window for Barcode Scanner Stray Light Control
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Solution Overview
Problem
Imaging scanners face the challenge of stray light from the illuminating source causing hot spots within the field of view due to reflection between the folding mirror and exit window, leading to suboptimal performance and increased device size and cost when attempting to position the illuminating source after the mirror and before the exit window.
Innovation Solution
A curved exit window is configured to direct stray light away from the imaging lens, allowing the illuminating source to be integrated closer to the imaging sensor on a single PCB, minimizing parallax and reducing the need for additional components and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the illuminating source is positioned after the folding mirror and before the exit window, then stray light causing hot spots is reduced, but device size and cost increase due to additional components and complex positioning requirements
Solution Approach 1:
The patent combines the illuminating source with the imaging sensor on a single PCB, eliminating the need for separate positioning of these components. This integration simplifies the overall device structure while maintaining effective stray light management through the curved window design.
Solution Approach 2:
The patent employs a curved exit window instead of a flat one. This curvature is specifically designed to redirect stray light away from the imaging lens, preventing hot spots while allowing the illuminating source to be positioned closer to the sensor without increasing device complexity.
2Device complexity
If the illuminating source is positioned close to the imaging sensor on a single PCB, then device size and cost are reduced, but parallax between image and illumination fields of view increases
Solution Approach 1:
The curved exit window is designed to compensate for the parallax effect introduced by positioning the illuminating source close to the imaging sensor. The specific curvature of the window redirects light paths to minimize the angular difference between illumination and imaging fields of view, effectively reducing parallax while maintaining component integration.
3Ease of manufacture
If a flat exit window is used, then manufacturing is simpler, but stray light reflects back into the imaging lens causing hot spots
Solution Approach 1:
The patent transitions from a flat window to a curved window design. While curved windows are slightly more complex to manufacture than flat ones, the curvature provides the necessary optical function of redirecting stray light away from the imaging lens, preventing hot spots while remaining manufacturable with standard optical fabrication processes.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enables a compact, cost-effective imaging scanner with minimal parallax between image and illumination fields of view, reducing the risk of stray light and allowing for efficient illumination design with reduced power consumption and device size.
Implementation Method 1
A curved exit window is configured to direct stray light away from the imaging lens
Data Source
AI summary
An apparatus operative to decode a barcode on a target object includes a mirror located within the housing at a position generally facing both the curved window and the imaging lens arrangement of the scan engine. The curved window is configured to operate together with the mirror to direct any of the illumination light reflected by the curved window away from the imaging lens arrangement to avoid the detrimental hot spots in the image.