Triangulation Scanner Retroreflector Registration
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Solution Overview
Problem
Existing triangulation scanners face challenges in accurately registering images, especially when dealing with large flat or curved surfaces, due to the lack of distinct features, which affects the creation of precise three-dimensional models.
Innovation Solution
A method and system that combines a six-degree of freedom triangulation scanner with a retroreflector and a camera, using a laser tracker to determine 3D coordinates and form composite 3D images by identifying common feature points in multiple 2D images, thereby improving image registration and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a triangulation scanner is used to scan large flat or curved surfaces, then scanning coverage is improved, but image registration accuracy deteriorates due to lack of distinct features
Solution Approach 1:
The patent introduces a retroreflector target as an intermediary object placed on the surface being scanned. This target provides distinct, easily detectable features (the retroreflector's reflective properties) that enable accurate image registration between multiple scans. The retroreflector serves as a mediator that bridges the gap between the scanner and the surface, providing reliable registration points even on featureless large flat or curved surfaces.
Solution Approach 2:
The patent changes the parameter of surface features by adding retroreflector targets with specific optical properties. Instead of relying on the natural features of the surface (which may be absent on large flat or curved surfaces), the system introduces artificial features with controlled reflective characteristics that can be reliably detected and used for registration across multiple scan positions.
2Area of stationary object
If multiple 2D images are captured from different positions to create 3D models, then measurement coverage is improved, but registration difficulty increases due to feature matching challenges
Solution Approach 1:
The retroreflector target acts as a common intermediary reference that appears in multiple 2D images from different scanner positions. Its distinct reflective properties make it easily detectable and identifiable across all images, providing a reliable basis for registering the images to each other and to the scanner's coordinate system.
Solution Approach 2:
The retroreflector target serves multiple functions simultaneously: it provides a registration feature for image alignment, serves as a distance measurement reference, and establishes a common coordinate reference frame. This multi-functionality simplifies the overall registration process by providing a single reference element that handles multiple measurement tasks.
3Measurement precision
If a laser tracker is used to determine 3D coordinates of a retroreflector, then measurement accuracy is improved, but system complexity increases
Solution Approach 1:
The laser tracker is used for multiple purposes: determining the 3D coordinates of the retroreflector, establishing the coordinate system, and providing distance measurements for triangulation. This multi-use approach justifies the complexity by extracting maximum utility from a single sophisticated instrument.
Solution Approach 2:
The system uses the retroreflector target to enable the laser tracker to self-calibrate and establish its own coordinate reference frame. The retroreflector's known geometric properties allow the tracker to automatically determine its position and orientation relative to the target, reducing the need for external calibration equipment or procedures.
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 approach enables the creation of accurate three-dimensional models by effectively registering multiple 2D images into a composite 3D representation, enhancing the precision and reliability of surface measurements and augmenting reality applications.
Implementation Method 1
The laser tracker is a particular type of coordinate measuring device that tracks the retroreflector target with one or more laser beams it emits. The laser tracker is thus a 'time-of-flight' type of measurement device.
Implementation Method 2
A common type of retroreflector target is the spherically mounted retroreflector (SMR), which comprises a cube-corner retroreflector embedded within a metal sphere.
Implementation Method 3
A scanning system that determines the 3D coordinates of an object surface based on triangulation principles. Since the camera and projector are arranged in a fixed relationship to each other, the distance and angles to the object surface may be determined from the projected line or pattern, the captured camera images and a baseline distance separating the projector and the camera according to trigonometric principles.
Data Source
AI summary
A method and system of combining 2D images into a 3D image. The method includes providing a coordinate measurement device and a triangulation scanner having an integral camera associated therewith, the scanner being separate from the coordinate measurement device. In a first instance, the coordinate measurement device determines the position and orientation of the scanner and the integral camera captures a first 2D image. In a second instance, the scanner is moved, the coordinate measurement device determines the position and orientation of the scanner, and the integral camera captures a second 2D image. A common feature point in the first and second images is found and is used, together with the first and second images and the positions and orientations of the scanner in the first and second instances, to create the 3D image.