Vision Camera Assembly with Semi-Reflecting Mirror for Fiber Texture Imaging
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Solution Overview
Problem
Machine vision systems face challenges in acquiring high-resolution images of surfaces with fiber-like textures at short exposure times and short working distances, as existing technologies struggle to combine direct illumination, high resolution, and a short working distance effectively.
Innovation Solution
A vision system camera assembly with a removably attached optics and illumination module that projects structured illumination along the optical axis, using a semi-reflecting mirror, collimating optics, and a telecentric lens assembly to achieve a short working distance and prevent ghost images, while incorporating high-output LEDs and a heat sink for efficient operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If direct illumination is used to enhance high-speed imaging of fiber distribution, then exposure time can be shortened, but working distance increases and resolution decreases
Solution Approach 1:
A semi-reflecting mirror is introduced as an intermediary component to redirect structured illumination onto the optical axis. This allows the illumination source to be positioned off-axis while still achieving direct illumination of the surface, thereby maintaining short exposure times without compromising working distance or resolution
Solution Approach 2:
The illumination geometry is changed by projecting light at oblique angles rather than directly along the optical axis. This dimensional change in illumination approach allows short working distance to be maintained while still achieving the direct illumination effect needed for short exposure times
2Measurement precision
If a short working distance is used to achieve high resolution, then imaging capability is improved, but direct illumination becomes difficult to implement
Solution Approach 1:
The optical system is segmented into separate functional modules: an illumination module with structured light source, a beam-splitting mirror, and the imaging optics. This segmentation allows the illumination path to be independently optimized for direct illumination while the imaging path maintains short working distance for high resolution
Solution Approach 2:
The semi-reflecting mirror serves multiple functions: it redirects structured illumination onto the optical axis, allows light from the imaged scene to pass through to the imager, and enables the system to achieve both direct illumination and short working distance simultaneously
3Loss of information
If structured illumination is projected at oblique angles to enhance fiber texture visibility, then surface feature recognition is improved, but ghost images and stray light increase
Solution Approach 1:
The semi-reflecting mirror, which could potentially cause stray light and ghost images, is configured to redirect the structured illumination while blocking stray light paths. The mirror transforms the potential harmful effect of oblique illumination into a beneficial structured illumination pattern that enhances fiber visibility without generating ghost images
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 effective imaging of fiber-like textures with short exposure times and high resolution, enhancing the ability to recognize features such as paper fibers, and can be used for various surfaces requiring precise inspection.
Implementation Method 1
a semi-reflective mirror that allows light from the imaged surface to pass therethrough and into the camera lens assembly, and that reflects light generated by the illumination element along an illumination axis onto the optical axis
Implementation Method 2
a collimating optics assembly that collimates the light as it is projected onto the scene. The projected light defines, at least in part, a structured, off-axis light pattern
Implementation Method 3
incorporating high-output LEDs and a heat sink for efficient operation
Data Source
Figure 1
Figure 2
Figure 2A
AI summary
This invention provides a vision system camera assembly (120) that includes an optics and illumination module that is removably attached thereto, and that is arranged to project illumination along an optical axis of the imager. This arrangement allows for short exposure time and a short working distance from an imaged scene/surface under inspection. A semi-reflecting mirror (260) turns a structured illumination beam from an illumination axis (IA) onto the optical axis (OA) while allowing light from the imaged scene to pass through the mirror and into the imager optics (230). The front end of the module contains a collimating optics (292, 286) in which the light from a diffuser (286) residing within the focal point of the lens (292) is collimated to strike the surface at various off-axis angles. The collimating optics can form a telecentric lens assembly (294, 296, 230) that can comprise a pair of stacked lenses (294, 296) having a perimeter that is equal to or greater than the area of interest on the surface.