Electro-optical Scanner Exit Window Light Collection Lens
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Solution Overview
Problem
Non retro-reflective scanners face a parallax effect due to the spacing of the light collection lens from the scanning beam axis, requiring an additional field of view orthogonal to the beam axis, which increases ambient light and decreases the signal-to-noise ratio, making it difficult to decode bar codes effectively.
Innovation Solution
The integration of a light collection lens system with a reflective surface between the lens and its focal point, where the focal point lies on the scanning beam plane, eliminates parallax and reduces the need for additional field of view, directing reflected light directly to the photodetector circuitry and minimizing ambient light exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the light collection lens is spaced from the scanning beam axis, then the scanner can collect reflected light, but parallax effect occurs requiring additional field of view which increases ambient light and decreases signal-to-noise ratio
Solution Approach 1:
The patent combines the light collection lens with the exit window into a single integrated optical element. The exit window serves dual functions: protecting internal components and collecting reflected light. This merging eliminates the need for a separate light collection lens spaced from the beam axis, thereby eliminating parallax effects while maintaining effective light collection and improving signal-to-noise ratio
2Adaptability or versatility
If the focal point of the light collection lens is not on the scanning beam plane, then the lens can collect light from a broader area, but parallax effect increases making bar code decoding difficult
Solution Approach 1:
The patent positions the focal point of the light collection lens precisely on the scanning beam plane, creating a localized optimal focal region where reflected light from the scan line converges accurately. This precise local positioning ensures that light is collected effectively from the intended area without introducing parallax errors, thereby maintaining both light collection efficiency and bar code decoding accuracy
3Quantity of substance
If additional field of view is added orthogonal to the beam axis, then more reflected light can be collected, but ambient light exposure increases decreasing signal quality
Solution Approach 1:
The patent uses the exit window as an intermediary optical element that collects reflected light and directs it through the light collection lens to the photodetector circuitry. This intermediary structure enables effective light collection while maintaining a compact optical path that does not require additional field of view orthogonal to the beam axis, thereby collecting sufficient reflected light without increasing exposure to harmful ambient light
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 substantially reduces parallax effects, improves the signal-to-noise ratio, and enhances the quality of the signal output by focusing reflected light precisely on the photodetector, allowing for more accurate bar code decoding.
Implementation Method 1
a light collection lens receiving reflected light from the target bar code and directing the reflected light toward a focal point
Implementation Method 2
a reflective surface disposed between the collection lens and the collection lens focal point to redirect the reflected light passing through the collection lens toward the photodetector circuitry
Implementation Method 3
photodetector circuitry receiving light from the target bar code
Data Source
AI summary
A portable electro-optical scanner for reading a target bar code having a plurality of bar code elements. The portable scanner includes: a housing supporting a scanning module and an optic system. The scanning module electro-optically scans the target bar code with a scanning beam and collects reflected light returning from the bar code. The scanning module includes a beam source emitting a scanning beam, beam directing apparatus causing the scanning beam to be repetitively scanned along a scanning plane intersecting the target bar code and photodetector circuitry receiving light from the target bar code. The optic system includes an exit window, a light collection lens and a reflective surface. The scanning beam passes through the exit window upon exiting the housing. The light collection lens receives reflected light from the target bar code and directing the reflected light toward a focal point. The focal point lying on the scanning plane of the scanning beam. The reflective surface is disposed between the light collection lens and the focal point to redirect the reflected light passing through the light collection lens toward the photodetector circuitry.