Variable Focus Lens Stabilization for Barcode Scanning
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Solution Overview
Problem
Electrically tunable variable focus lenses in barcode scanners lack feedback on current focus, leading to misreads and operational delays due to ambient temperature variations, lens aging, and other factors, especially in hands-free operation modes with varying object distances.
Innovation Solution
A focus stabilization system that uses a variable focus lens, controller, and imaging sensor to capture images at multiple focus planes, determining image quality values and tuning parameters to maintain optimal focus, allowing for faster and accurate image capture of barcodes across varying distances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a variable focus lens is used to enable autofocus capability, then the system can adapt to different object distances, but the system loses feedback on current focus status leading to misreads and operational delays
Solution Approach 1:
The patent implements a feedback mechanism by capturing multiple images at different focus planes and using image quality analysis to determine the current focus status. The processor analyzes image sharpness and other quality metrics to generate feedback signals that indicate whether the variable focus lens is properly focused, allowing the system to compensate for the lack of direct focus feedback from the lens itself.
Solution Approach 2:
The system performs preliminary actions by capturing a set of images at multiple predetermined focus planes before actual barcode scanning occurs. This allows the system to pre-determine the optimal focus plane and prepare focus adjustment commands in advance, reducing the time required when the actual scanning operation needs to occur.
2Adaptability or versatility
If conventional autofocus camera systems are used, then the system can focus on objects, but operational delays occur as the system focuses on different objects and distances
Solution Approach 1:
The system captures images at multiple focus planes in advance and stores them for later use. When barcode scanning is required, the system can quickly select and process pre-captured images from the appropriate focus plane without needing to perform time-consuming autofocus operations, significantly reducing operational delays.
Solution Approach 2:
The patent segments the focus range into multiple discrete focus planes, each with its own captured images. This segmentation allows the system to treat different focus distances as separate, pre-processed data sets, enabling rapid switching between focus planes during operation without requiring continuous refocusing.
3Adaptability or versatility
If the lens aperture is made larger for autofocus capability, then the system can focus on objects, but the depth of focus becomes shallower making it unsuitable for hands-free operation
Solution Approach 1:
The system segments the working distance range into multiple discrete focus planes, each captured at a specific focal distance. By capturing images at these segmented focus planes in advance, the system effectively creates multiple shallow depth-of-field images that can be quickly selected and processed, overcoming the limitation of shallow depth of focus in hands-free operation mode.
Data Source
AI summary
A method and apparatus for the focus stabilization of an imaging system with variable focus lenses is disclosed herein. As example imaging system includes a variable focus (VF) lens for imaging an object of interest (OOI), a controller configured to provide a voltage to the VF lens, an imaging sensor, and a processor. The processor obtains a calibration parameter, and the imaging system obtains a plurality of images of the OOI. The processor identifies a region of interest of one or more of the images, and an alignment parameter is determined from the images. The processor then determines a tuning parameter from comparing the determined alignment parameter with the obtained calibration parameter. The controller tunes the VF lens according to the determined tuning parameter.