Folded Line-Scan Imaging with Dynamic LED Illumination
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Solution Overview
Problem
Current line scan imaging systems require high F-stop lenses for long depth of field applications, making them inefficient in terms of illumination and requiring separate cameras for near and far fields, which limits their compactness and cost-effectiveness.
Innovation Solution
Implementing a line scan camera with LEDs, collimating lenses, and mirrors to achieve folded optics, allowing for both short and long depth of field imaging with a low F-stop value, enabling compact, cost-effective, and illumination-efficient imaging by bending the optical path and positioning the light source close to the target.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high F-stop lens is used to achieve long depth of field, then the depth of field coverage is improved, but the illumination efficiency deteriorates and the system becomes less compact
Solution Approach 1:
The patent introduces a temporal dimension by capturing images at different depths of field at different times and combining them computationally. This allows the system to achieve both near-field and far-field coverage without requiring a high F-stop lens, thereby maintaining illumination efficiency while expanding depth of field coverage across the temporal dimension.
Solution Approach 2:
The patent segments the depth of field coverage into multiple ranges (near-field and far-field), capturing images for each segment separately at different times and then combining them. This segmentation allows the use of a low F-stop lens for each segment while achieving comprehensive depth of field coverage when combined.
2Reliability
If a high F-stop lens is used to achieve long depth of field, then the depth of field coverage is improved, but the system complexity and cost increase due to requiring multiple cameras
Solution Approach 1:
The patent makes a single camera perform multiple functions by capturing images at different depths of field at different times and combining them computationally. This eliminates the need for multiple cameras or complex optical switching mechanisms, reducing system complexity while maintaining comprehensive depth of field coverage.
Solution Approach 2:
The patent creates a computational copy of the scene at different depth planes by capturing images at different times and combining them. This computational approach replaces the need for physical copies (multiple cameras) to simultaneously capture different depth ranges, simplifying the system architecture.
3Reliability
If the illumination is located far away from the target to cover wide view, then the depth of field is extended, but the illumination intensity at the target decreases
Solution Approach 1:
The patent makes the illumination dynamic by adjusting the LED intensity based on the captured image brightness. This allows the system to maintain high illumination intensity at the target when using a low F-stop lens while still achieving extended depth of field coverage through computational combining of multiple images.
Solution Approach 2:
The patent implements feedback control where the illumination intensity is adjusted based on the brightness of captured images. This feedback mechanism ensures optimal illumination intensity at the target while maintaining the low F-stop configuration that enables both near and far field coverage when combined computationally.
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
Enables efficient line scanning at both short and long depths of field using a single camera with low F-stop values, improving illumination efficiency and system compactness by allowing a single camera to capture images at various depths without the need for multiple lenses or cameras.
Implementation Method 1
The camera has a single line of pixels and either the camera or object is moved perpendicular to that line of pixels to build up a two-dimensional image of the object
Implementation Method 2
The illumination arrangement comprises a light source, a collimating lens and mirrors. The mirrors enable folded optics so that an optical path from the target to the camera is longer than a size of the imaging system
Data Source
AI summary
A line-scan imaging camera can scan an object at a near field and a far field using a low F-stop value by reading out different rows on an imager. A line LED provides a line illumination over an object. Additionally, the imaging camera captures the illumination portion of the object through an optical path that includes mirrors that allow folded optics. The optical path is longer than the distance between the object and the camera. A mirror is located close to or adjacent to the line LED to provide efficient illumination and to align the initial leg of the optical path with the line illumination.