Dual-Imaging Vision System for Extended Depth of Focus
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Solution Overview
Problem
Existing machine vision systems face challenges in accurately finding and decoding small-scale ID codes, such as DataMatrix codes, due to limited depth of focus, especially at short distances, and difficulty in stabilizing handheld devices for proper focusing.
Innovation Solution
A dual-imaging system configuration with a standard on-axis imaging system for longer distances and an extended-depth-of-focus (EDOF) Scheimpflug configuration for shorter distances, combined with aimer assemblies projecting structured light to assist in focusing and determining object distance, allowing for improved focus and decoding capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the ID reader optics are configured to read at longer distances, then the reading range is extended, but the depth of focus is reduced making it impossible to read small codes at short distances
Solution Approach 1:
The patent divides the imaging system into two separate optical paths: a first optical path with a first image sensor optimized for long-distance reading, and a second optical path with a second image sensor optimized for short-distance reading with extended depth of focus. Each optical path independently handles specific distance ranges, resolving the contradiction between long reading distance and sufficient depth of focus.
Solution Approach 2:
The patent introduces a vertical dimension by stacking two image sensors at different positions along the optical axis. The first image sensor is positioned to receive light from long distances, while the second image sensor is positioned to receive light from short distances. This spatial arrangement in the vertical dimension allows simultaneous optimization for both distance ranges without compromising either performance.
2Manufacturing precision
If the ID reader is configured for small code reading at short distances, then the depth of focus is sufficient, but the reading range for larger IDs at longer distances is limited
Solution Approach 1:
The patent segments the imaging functionality by dedicating the second optical path and second image sensor specifically to short-distance, small-code reading applications where extended depth of focus is critical. Simultaneously, the first optical path and first image sensor are dedicated to long-distance reading of larger codes, ensuring each subsystem operates within its optimal performance range.
Solution Approach 2:
The dual-optical-path system provides universal functionality by enabling the ID reader to handle both short-distance small code scanning and long-distance large code scanning through a single integrated device. The system automatically selects or switches between optical paths based on the target distance and code size, achieving multi-functionality without requiring separate devices.
3Ease of operation
If a handheld device is used for flexibility, then the ease of operation is improved, but the ability to stabilize and properly focus on the object is compromised
Solution Approach 1:
The system incorporates an autofocus mechanism that automatically adjusts the focus of each optical path based on the detected target distance. When the user points the handheld device at a target, the system autonomously determines the appropriate focus setting for the selected optical path and adjusts lens elements or sensor positioning accordingly, eliminating the need for manual focus stabilization by the user.
Solution Approach 2:
The system employs feedback through image acquisition and analysis to determine whether the target is within the optimal focus range. The processor analyzes the captured images from both optical paths and provides feedback to adjust the focus mechanism, ensuring stable and accurate focus even when the handheld device experiences minor movements during operation.
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
The dual-imaging system enhances the reading range for both large and small ID codes, providing extended depth of focus and enabling accurate decoding of small codes at varying distances with improved user guidance for handheld devices.
Implementation Method 1
The illuminated scene is then acquired by an image sensor within the imaging system through optics
Implementation Method 2
a second imaging system defining an extended-depth of focus (DOF) configuration with second optics
Implementation Method 3
a primary aimer assembly and a secondary aimer assembly that each project a discrete beam of structured light onto the surface
Data Source
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AI summary
This invention provides a vision system, typically having at least two imaging systems/image sensors that enable a multi-function unit. The first imaging system, typically a standard, on-axis optical configuration can be used for long distances and larger feature sets and the second imaging system is typically an extended-depth of focus/field (DOF) configuration. This second imaging system allows reading of smaller feature sets/objects and/or at shorter distances. The reading range of an overall (e.g.) ID-code-reading vison system is extended and relatively small objects can be accurately imaged. The extended-DOF imaging system sensor can be positioned with its longest dimension in the vertical axis. The system allows vision system processes to compute the distance from the vision system to the object to generate an autofocus setting for variable optics in the standard imaging system. A single or dual aimer can project structured light onto the object surface around the system optical axis.