Handheld 3D Reconstruction Using Off-Axis Apertures and Laser Dot Defocusing
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Solution Overview
Problem
Existing three-dimensional imaging techniques face challenges in achieving high accuracy and depth measurement, particularly when using aperture coded systems, which often require tradeoffs in defocused information and have limitations in working depth and camera pose determination.
Innovation Solution
A camera system with off-axis apertures and a projector that projects a grid of laser dots at an angle relative to the camera, utilizing defocusing and active stereo methods to determine the pose and deformation of the projected pattern, allowing for accurate 3D shape measurement and increased working depth by averaging centroid detection and using feature matching algorithms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If aperture coded systems are used for 3D imaging, then depth measurement capability is improved, but measurement precision deteriorates due to tradeoffs in defocused information
Solution Approach 1:
The camera lens is divided into multiple off-axis aperture segments that are spatially separated. Each aperture captures defocused information from different angular perspectives, allowing the system to segment the depth measurement task across multiple optical paths. This segmentation enables recovery of defocused information that would otherwise be lost in conventional single-aperture systems.
Solution Approach 2:
The system transitions from conventional 2D image capture to 4D information capture by adding two spatial dimensions through off-axis aperture arrangement. The apertures are positioned at different lateral positions (x, y coordinates) in addition to the standard optical axis, creating a multi-dimensional aperture code that encodes both spatial and depth information simultaneously, thereby recovering defocused information across multiple dimensions.
2Length of stationary object
If conventional 3D imaging systems are used, then system complexity is reduced, but working depth is limited
Solution Approach 1:
The off-axis aperture camera system performs multiple functions simultaneously: it captures standard focused images for 2D reconstruction while also capturing defocused information through the off-axis apertures for extended depth measurement. This multi-functionality allows a single device to operate in both conventional and extended depth modes without requiring separate systems, thereby increasing working depth without proportionally increasing overall system complexity.
3Measurement precision
If camera pose determination is improved using feature matching, then 3D reconstruction accuracy is improved, but computation time increases
Solution Approach 1:
The system performs preliminary pose estimation using the geometric constraints provided by the known off-axis aperture configuration and projected grid pattern. This preliminary pose information is then used to guide the feature matching algorithm, reducing the search space and number of iterations required for accurate pose determination. The preliminary action of using aperture-based geometric constraints accelerates the subsequent feature matching computation while maintaining high accuracy.
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
The system achieves high accuracy in 3D shape measurement and increased working depth by accurately determining the pose and deformation of the projected pattern, enabling more applications, even at lower angles and greater depths, through the combination of defocusing and active stereo imaging.
Implementation Method 1
A projector projects an optical pattern toward a surface... projects a grid of laser dots... The way that the pattern projected by the light deforms based on the varying surface depth
Implementation Method 2
The camera has at least two off-axis apertures thereon, arranged to obtain an image of the projected pattern including defocused information... utilizing defocusing and active stereo methods
Implementation Method 3
U.S. Pat. No. 7,006,132 describes a geometric analysis in which a camera lens of focal length f is located at z=0. Two small apertures are placed within the lens, separated a distance d/2 away from the optical centerline... to solve for the image separation
Implementation Method 4
utilizing defocusing and active stereo methods to determine the pose and deformation of the projected pattern... combination of defocusing and active stereo imaging
Implementation Method 5
projects a grid of laser dots and uses laser-dot defocusing for approximate Z and thus grid correspondence
Data Source
AI summary
A camera has a lens and aperture device for determining 3D information. A projector projects an optical pattern toward a surface. The camera has at least two off-axis apertures thereon, arranged to obtain an image of the projected pattern including defocused information. The camera is movable between different positions to image the surface from said different positions, and the projector is at a specified angle of at least 5° relative to said camera. A processor carries out a first operation using information received through the apertures to determine a pose of said camera, and to determine three dimensional information about the object based on a degree of deformation of said optical pattern on said surface indicative of a three dimensional surface. An embodiment projects a grid of laser dots and uses laser-dot defocusing for approximate Z and thus grid correspondence, which can greatly increase the working depth of the system.