Dual-Imaging Vision System for Extended Depth of Focus
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Solution Overview
Problem
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 when reading smaller codes at shorter distances or larger codes at longer distances.
Innovation Solution
A dual-imaging system configuration is employed, comprising a standard on-axis imaging system for longer distances and larger codes, and an extended-depth of focus (DOF) Scheimpflug imaging system for shorter distances and smaller codes, with the latter's image sensor positioned vertically to enhance focus range, and a structured light aimer to assist in centering and focusing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the ID reader optics are configured for 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 imaging system is divided into two separate optical paths: a first imaging system with a first image sensor for standard imaging, and a second imaging system with a second image sensor for extended depth of field imaging. Each sensor captures images of the same object from the same viewpoint, allowing the system to switch between standard and extended DOF modes depending on the distance and size of the code being read.
2Manufacturing precision
If the ID reader is configured for small codes at short distances, then the depth of focus is improved, but the ability to image larger codes at longer distances is compromised
Solution Approach 1:
The imaging system is divided into two separate optical paths: a first imaging system with a first image sensor for standard imaging, and a second imaging system with a second image sensor for extended depth of field imaging. Each sensor captures images of the same object from the same viewpoint, allowing the system to switch between standard and extended DOF modes depending on the distance and size of the code being read.
3Device complexity
If a single imaging system is used, then the device complexity is reduced, but the system cannot maintain focus across varying distances and code sizes
Solution Approach 1:
The imaging system is divided into two separate optical paths: a first imaging system with a first image sensor for standard imaging, and a second imaging system with a second image sensor for extended depth of field imaging. Each sensor captures images of the same object from the same viewpoint, allowing the system to switch between standard and extended DOF modes depending on the distance and size of the code being read.
Solution Approach 2:
The dual-imaging system provides multi-functionality by enabling both standard imaging and extended depth of field imaging through two parallel optical paths. The system can automatically or manually switch between modes to handle various scanning scenarios including close-up small codes and distant large codes, making a single device adaptable to multiple reading conditions.
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 configuration extends the reading range for both large and small ID codes, maintaining focus and accuracy across varying distances, thereby improving the overall performance of ID-code-reading vision systems.
Implementation Method 1
an extended-depth of focus (DOF) Scheimpflug imaging system for shorter distances and smaller codes
Data Source
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 can allow 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. An aimer can project structured light onto the object surface around the system optical axis.