Handheld Scanner Illumination Compensation for Skew and Pitch
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Solution Overview
Problem
Handheld scanners experience non-uniform illumination and increased power consumption when held at an angle relative to a scanning surface due to uneven illumination from LEDs driven at the same current, degrading scanning performance and decoding accuracy.
Innovation Solution
An imaging-based data capture device with two illumination sources and a processor that adjusts LED currents based on brightness differences in initial frames to achieve uniform illumination across the field of view, using reduced resolution slit frames to quickly compensate for skew and pitch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If all LEDs are driven at the same current to ensure uniform illumination over the FOV, then illumination uniformity is improved, but power consumption increases and scanning performance degrades when held at an angle
Solution Approach 1:
The patent divides the illumination assembly into multiple independently controllable LED groups (e.g., first through fourth LED groups arranged in pairs). Each group can be driven at different current levels based on the specific illumination needs of different regions of the FOV. This allows localized adjustment of illumination intensity rather than uniformly driving all LEDs at the same current, thereby reducing overall power consumption while maintaining illumination uniformity when the scanner is held at angles.
2Illumination intensity
If all LEDs are driven at the same current to ensure uniform illumination over the FOV, then illumination uniformity is improved, but scanning performance degrades when held at an angle
Solution Approach 1:
The patent implements dynamic control of LED current levels based on detected illumination non-uniformity. The processor monitors the FOV for non-uniform illumination patterns caused by scanner angle (skew and pitch) and dynamically adjusts the current levels for different LED groups in response. This dynamic adaptation allows the system to maintain optimal scanning performance across various holding angles by compensating for illumination variations in real-time.
Solution Approach 2:
The system incorporates a feedback mechanism where the processor continuously monitors illumination uniformity across the FOV and uses this information to adjust LED driving currents. When non-uniform illumination is detected (indicating the scanner is held at an angle), the processor modifies the current distribution to different LED groups to compensate for the uneven illumination, thereby maintaining scanning and decoding performance.
3Measurement precision
If multiple frames are captured at different illumination levels to determine brightness differences, then illumination compensation accuracy is improved, but processing time increases
Solution Approach 1:
The patent captures a first frame at a first illumination level and a second frame at a second illumination level (or with illumination deactivated) before capturing the final third frame at the compensated illumination level. By preliminarily capturing these reference frames and calculating brightness differences in advance, the system establishes the illumination non-uniformity profile before the actual scanning operation, enabling rapid compensation without delaying the primary image capture.
Solution Approach 2:
The system uses reduced resolution slit frames for the initial brightness comparison rather than full-resolution frames. This partial action approach captures only the essential illumination pattern information needed for compensation calculations, significantly reducing processing time and data volume while still providing sufficient accuracy to determine brightness differences and guide the compensation of the full-resolution third frame.
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
Improves scanning and decoding performance by ensuring uniform illumination and reduces power consumption by dynamically adjusting LED currents, allowing for efficient image capture and processing.
Implementation Method 1
various handheld scanners have an illumination assembly formed of a series of light emitting diodes (LEDs) that illuminate a field of view (FOV)
Data Source
AI summary
Imaging devices, systems, and methods for capturing and processing images for vision applications in a non-fixed environment are described herein. An example system includes: an imaging assembly, an aiming assembly, and one or more imaging processors configured to: (a) receive a first image; (b) analyze at least a portion of the first image to determine a first focus value; (c) configure a focus parameter of the imaging assembly based on the first focus value; (d) receive a subsequent image; (e) determine a blurriness value for at least a portion of the subsequent image; (f) responsive to the blurriness value being less than a predetermined threshold value, transmit the subsequent image to a decode module; and (g) responsive to the blurriness value exceeding the predetermined threshold value: determine a subsequent focus value; (ii) configure the focus parameter based on the subsequent focus value; and (iii) repeat (d) through (g).