Scheimpflug Code Reader Lighting for Uniform Far-Side Illuminance
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Solution Overview
Problem
Code readers using a Scheimpflug optical system face issues with non-uniform brightness between near and far fields, leading to insufficient illuminance on the far side, which affects the readability of codes attached to workpieces.
Innovation Solution
A code reader is designed with multiple illumination units, including narrow-angle and wide-angle illumination units, to create a focal plane with varying light distribution angles and optical axis intersections, ensuring uniform brightness across the near and far sides by adjusting the overlap and distribution of illumination light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Scheimpflug optical system is used to deepen the depth of field, then the ability to read codes at different distances improves, but brightness uniformity deteriorates with the near side becoming brighter and far side becoming darker
Solution Approach 1:
The illumination system is divided into multiple illumination units with different characteristics (narrow-angle and wide-angle units). Each unit targets specific regions (near field and far field) to provide segmented illumination that compensates for the brightness non-uniformity caused by the Scheimpflug optical system, ensuring uniform brightness across the entire focal plane.
Solution Approach 2:
Different illumination units are assigned different light distribution angles and positions tailored to specific regions. The wide-angle illumination unit targets the far side with broader light distribution, while the narrow-angle unit targets the near side with concentrated light. This local quality approach ensures each region receives optimal illumination for uniform brightness.
2Measurement precision
If multiple illumination units with different light distribution angles are used to improve brightness uniformity, then reading accuracy improves, but device complexity increases
Solution Approach 1:
The multiple illumination units serve dual purposes: they collectively provide uniform brightness across the entire focal plane while individually targeting specific regions. The system achieves both brightness uniformity and reading accuracy without requiring separate complex illumination systems for different regions, as each unit contributes to both overall uniformity and regional optimization.
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 enhances the uniformity of brightness, allowing for efficient reading of codes both near and far from the imaging unit, improving reading speed and accuracy.
Implementation Method 1
an imaging unit that includes a Scheimpflug optical system including a lens collecting reflected light from the code attached to the workpiece and an image sensor having a light receiving surface inclined with respect to an optical axis of the lens
Implementation Method 2
a lens collecting reflected light from the code attached to the workpiece
Data Source
AI summary
A code reader includes: a plurality of illumination units that irradiate the workpiece with illumination light; an imaging unit that includes a Scheimpflug optical system and generates and outputs a code image; and a control unit that executes decoding processing on the code image. The Scheimpflug optical system is used to form a focal plane extending from a near side to a far side of the imaging unit and make light distribution angles of the plurality of illumination units different or make positions where optical axes of the plurality of illumination units intersect the focal plane different in a direction in which the focal plane extends to suppress insufficiency of illuminance on the far side with respect to the near side of the focal plane or to make illuminance on the far side equal to or higher than illuminance on the near side.