3D Measurement Correction for Projector Lens Distortion
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Solution Overview
Problem
Conventional three-dimensional measurement systems using projected pattern light suffer from lens distortion, leading to inaccurate object reconstruction due to the effect of projector lens distortion.
Innovation Solution
An image processing system that includes a light projection apparatus, an imaging apparatus, and a control apparatus with a calculation unit capable of determining a first point on the pattern image, calculating a second point in the projection plane, correcting for lens distortion using a nonlinear line and epipolar line analysis, and calculating three-dimensional coordinates based on these points to accurately account for distortion effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional three-dimensional measurement technology is used to determine correspondence of pixels between projected pattern light and captured pattern image, then the measurement process is simple, but the object cannot be three-dimensionally reconstructed with sufficiently high precision due to lens distortion
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing correspondence relationships between distorted projection plane coordinates and corrected three-dimensional space coordinates in a correspondence table before actual measurement. This allows the system to compensate for lens distortion without performing complex real-time calculations, thereby improving measurement precision while keeping the device complexity manageable.
Solution Approach 2:
The patent introduces an intermediary correspondence table that mediates between the distorted projection plane coordinates and the corrected three-dimensional space coordinates. This intermediary structure allows the system to handle distortion correction efficiently by looking up pre-computed values rather than performing complex geometric transformations during measurement, resolving the contradiction between precision and complexity.
2Measurement precision
If lens distortion correction is performed using complex coordinate transformation and iterative calculation methods, then measurement precision improves, but calculation time and computational resources increase
Solution Approach 1:
The patent performs the complex coordinate transformations and iterative calculations in advance to build a correspondence table, separating the computationally intensive work from the actual measurement process. During measurement, the system only needs to perform simple table lookups, thereby achieving high coordinate accuracy without incurring significant calculation time delays.
Solution Approach 2:
The patent implements a dynamic approach where the system adapts its calculation strategy based on the measurement requirements. For high-precision applications, it uses the pre-computed correspondence table with fine resolution, while for faster measurements, it can use coarser tables or simplified models, thus balancing precision and speed according to actual needs.
Data Source
AI summary
An image processing system comprises: a projector for projecting pattern light whose coordinate component at least in one direction is determinable; an imaging apparatus for imaging an object illuminated with the pattern light to acquire a pattern image; and a controller including a calculator for calculating the 3D coordinates of a point on the object based on the pattern light and the pattern image. The calculator determines a first point on the pattern image; calculates a second point corresponding to the first point in a pattern-light projection plane; calculates a third point based on the second point in the projection plane, a nonlinear line in the projection plane calculated by analyzing the pattern image, and an epipolar line in the projection plane calculated based on the first point; and calculates the three-dimensional coordinates of the point on the object based on the first point and the third point.