Optical Scanner Autofocus Selection for Low-Latency Long-Range Reading
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Solution Overview
Problem
Active autofocus systems in optical scanners face interference issues that affect their accuracy and reliability, particularly in long-distance scanning applications where the target surface and symbol constitute a small fraction of the captured images, leading to increased latency and reduced usability.
Innovation Solution
An optical scanner system with multiple image-capture devices and an adaptive autofocus mechanism that dynamically selects the correct configuration based on scene changes, using techniques like laser triangulation and optical flow to quickly adjust focus and camera settings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If passive autofocus is used to ensure reliable focus evaluation, then focus accuracy is improved, but scanning speed deteriorates due to complete focus sweep requirement
Solution Approach 1:
The system performs preliminary scene evaluation during idle phases to detect scene changes before actual scanning occurs. This advance detection allows the system to prepare appropriate focus settings in advance, eliminating the need for complete focus sweeps during active scanning operations.
Solution Approach 2:
The system dynamically adjusts the autofocus strategy based on detected scene changes. When scene changes are detected, the system activates active autofocus modes (laser triangulation, phase-shift) that provide rapid focus adjustment without complete sweeps, adapting the evaluation thoroughness to the actual scanning needs.
2Speed
If active autofocus with auxiliary measurement systems is used to increase scanning speed, then scanning speed is improved, but reliability deteriorates due to interference from other light sources
Solution Approach 1:
The system uses image processing algorithms as an intermediary to distinguish between auxiliary signal reflections (desired) and other light sources (interference). By analyzing the characteristics of reflected light and comparing against known interference patterns, the system can reliably identify valid focus measurements even in the presence of competing light sources.
Solution Approach 2:
The system implements feedback mechanisms where focus evaluation results are continuously monitored and used to adjust auxiliary measurement parameters. When interference is detected, the system adjusts the auxiliary signal characteristics or re-evaluates using alternative methods, ensuring reliable focus determination maintains scanning speed.
3Measurement precision
If multiple cameras with different fields of view are used to capture multiple images, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The system segments the scanning operation into distinct phases (idle scene evaluation, active scanning, focus adjustment) and assigns different camera configurations to different phases. During idle phases, all cameras may be active for comprehensive scene monitoring. During active scanning, only the appropriate camera for the detected distance range is activated, reducing overall system complexity while maintaining precision when needed.
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 the snappiness and performance of optical scanners by reducing latency and enhancing accuracy in various applications, including long-range barcode reading and other automated vision tasks.
Implementation Method 1
Active autofocus uses an auxiliary measurement system that emits a signal which is not part of the image to be captured, and senses a reflection of the emitted signal from the target's surface. These include such technologies as time-of-flight sensors
Implementation Method 2
Active autofocus uses an auxiliary measurement system that emits a signal which is not part of the image to be captured, and senses a reflection of the emitted signal from the target's surface. These include such technologies as laser triangulation
Implementation Method 3
capturing a digital image of a subject using a camera with an image sensor
Data Source
AI summary
An optical scanner determines ranging to a subject using a localization phase in which a series of image frames is received which collectively contains an aimer spot captured as a reflection off of a surface of the subject. The optical scanner includes an idle phase in which the optical scanner remains idle with respect to parameter setting and evaluation but is configured to detect scene changes within its field of view, an initial phase that is entered into after the idle phase responsive to an activation event and not detecting a scene change, the initial phase including a configuration based operational parameter setting with a plurality of different configurations, and a decode phase that is entered into after the idle phase responsive to an activation event and detecting a scene change.