Optical Sensor Positioning for Deformed Object Topography
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Solution Overview
Problem
Existing automatic ballistic and tool mark comparison systems struggle to accurately capture the 3D topography of deformed or arbitrarily shaped objects with metallic surfaces, as they often experience occlusion and specular reflection issues when the surface is not perpendicular to the optical axis, leading to incomplete imaging of tool marks.
Innovation Solution
A method and system that utilize a set of motors to rotate and translate objects within an optical sensor system, computing the normal representative of the surface topography and adjusting the object's position to ensure the surface is perpendicular to the sensor axis, thereby preventing occlusion and improving image acquisition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the surface is not perpendicular to the optical axis, then the field of view can cover larger areas, but occlusion occurs and the bottom of the mark cannot be imaged properly
Solution Approach 1:
The patent implements dynamic adjustment of the object's orientation during the imaging process. The system computes the normal representative of the surface topography and determines the angle difference between the normal and the optical axis, then rotates the object to minimize this angle difference, ensuring the surface becomes perpendicular to the optical axis before imaging.
2Area of stationary object
If the surface is not perpendicular to the optical axis, then more surface area can be captured, but specular reflection prevents proper imaging of metallic surfaces
Solution Approach 1:
The system dynamically adjusts the object's orientation to ensure the surface normal aligns with the optical axis. This dynamic repositioning eliminates specular reflection issues by ensuring that reflected light returns directly to the sensor, thereby improving image quality and reliability for metallic surfaces.
3Productivity
If simple rotation is used for cylindrical objects, then the process is simple and fast, but deformed or arbitrary shapes cannot be properly captured
Solution Approach 1:
The patent employs a feedback mechanism where the system acquires an initial relief map, computes the normal representative of the surface topography, determines the angle difference between the normal and the optical axis, and uses this information to guide the rotation and translation movements. This closed-loop approach ensures that both cylindrical and deformed/arbitrary shapes are properly captured.
Solution Approach 2:
The system changes the orientation parameters (rotation angles and translation positions) based on the computed angle difference and normal representative. By dynamically adjusting these parameters, the system adapts to different object shapes while maintaining perpendicularity between the surface and optical axis during imaging.
4Area of stationary object
If multiple 3D images are acquired with motion applied between acquisitions, then larger areas can be measured, but the positioning and merging process becomes complex
Solution Approach 1:
The patent replaces complex mechanical positioning systems with a computational approach. The system uses image processing algorithms to compute the normal representative and determine angle differences, then uses these computational results to guide simple rotational and translational movements. This substitution of mechanical complexity with computational intelligence simplifies the overall system while enabling measurement of larger areas.
Data Source
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Figure 3A~3B
AI summary
There is described a method for positioning an object on an optical sensor system for acquiring a surface thereof, the sensor system having a set of motors for rotating the object around a motor axis perpendicular to an optical axis of the sensor system and for translating the object in X, Y and Z directions, the method comprising: (a) acquiring a relief map of an area in a field of view of the sensor system; (b) computing a normal representative of a topography of the relief map of the area; (c) determining an angle difference between the normal and the optical axis of the sensor system; (d) comparing the angle difference to a threshold angle to determine if the surface of the area is perpendicular to the sensor axis; (e) if the angle difference is greater than a threshold angle, rotating the object to obtain a new difference angle less than the threshold angle; and (f) translating the object to reposition the area in the field of view after the rotating has displaced the area.