Variable Focus Lens Assembly for Bar Code Reader
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Solution Overview
Problem
Conventional imaging-based bar code readers face challenges in automatically selecting a region of interest for blur analysis, particularly in scenarios where objects at different depths within the field of view lead to varying degrees of blurriness, making it difficult to achieve clear imaging and decoding of bar codes.
Innovation Solution
A variable focus imaging lens assembly that includes a movable lens driven by an automatic focusing system, which generates a series of image frames, analyzes them to determine a region of interest containing the bar code, and selects the frame with minimal blurring for decoding, using contrast and edge detection analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed focus lens system is used, then the device complexity is reduced, but the image quality deteriorates at the limits of the working range due to blurriness
Solution Approach 1:
The patent applies the dynamics principle by implementing a variable focus lens system that can dynamically adjust its focal length based on the distance to the target bar code. The lens assembly includes a movable lens element that can be positioned at different locations along the optical axis to change the focal plane, thereby maintaining sharp focus across a extended working range from near to far distances.
2Manufacturing precision
If a variable focus lens system is used, then the image quality is improved across the working range, but the device complexity increases due to additional focusing mechanisms
Solution Approach 1:
The patent applies the self-service principle by implementing an automatic focusing system that uses image processing algorithms to analyze captured frames and automatically determine the optimal lens position. The system performs blur analysis on image frames to identify the sharpest focus condition and self-adjusts the lens position without requiring manual intervention or complex external control mechanisms.
Solution Approach 2:
The patent applies the feedback principle by using image quality analysis as feedback to control lens positioning. The system captures image frames, analyzes the sharpness and focus quality of the bar code in these frames, and uses this feedback information to automatically adjust the lens position to achieve optimal focus, creating a closed-loop control system.
3Measurement precision
If the entire field of view is analyzed for blur, then the measurement precision is maximized, but the processing time increases significantly
Solution Approach 1:
The patent applies the segmentation principle by dividing the image frame analysis into two stages: first, a rapid initial assessment of the entire frame to locate potential bar code regions; second, a detailed blur analysis focused only on the identified region of interest containing the bar code. This segmented approach reduces the amount of data requiring intensive processing while maintaining measurement precision for the critical decoding area.
Solution Approach 2:
The patent applies the local quality principle by applying different levels of analysis to different regions of the image. The system performs comprehensive blur analysis only on the region containing the bar code (region of interest), while using simpler or no analysis on the rest of the field of view. This localized approach concentrates computational resources on the critical area where precise focus measurement is essential for decoding.
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 approach enables efficient identification and decoding of bar codes by focusing on the region of interest, reducing blurriness and improving image quality across the field of view, even at the limits of the working range.
Implementation Method 1
a lens assembly focusing light from the field of view onto the sensor array
Data Source
AI summary
A variable focus imaging lens assembly for an imaging system of an imaging-based bar code reader for imaging and decoding a target bar code. The lens assembly includes an automatic focusing system for energizing a drive mechanism and imaging system to move a movable lens from the predetermined position along its path of travel and generate a series of image frames; analyzing one or more image frames of the series of image frames to determine a region of interest, the region of interest including an image of a target bar code; analyzing the region of interest in subsequent image frames of the series of image frames to determine an amount of blurring; selecting an image frame from the series of image frames having blurring less than a threshold amount of blurring; and utilizing a decoder to decode the image of the target bar code in the selected image frame.