Rotating Mirror Laser Scanner Synchronization for 3D Color Mapping
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Solution Overview
Problem
Current 3D scanning systems face challenges in capturing clear color image information during laser scanning due to parallax issues, motion blur, and rolling shutter effects, which complicates the reconstruction of 3D color maps from point cloud data.
Innovation Solution
A method and system that synchronize the exposure time of an imaging camera with the rotation of a rotatable mirror in a laser scanner, allowing each pixel to capture image information along a defined trajectory, and use processing circuits to solve a system of linear equations to reconstruct the image information, correlating it with 3D data to create a 3D color map.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a color camera captures pictures through a rotating mirror during laser scanning, then image information can be acquired simultaneously with 3D data, but the captured images become highly blurred due to motion blur from high-speed mirror rotation
Solution Approach 1:
The patent converts the harmful motion blur caused by high-speed mirror rotation into a beneficial averaging effect. By capturing images during the mirror rotation and then deconvolving with a known motion blur kernel, the system recovers sharp image information. The blur that was initially harmful becomes a known transformation that can be mathematically reversed, allowing simultaneous 3D scanning and color imaging without quality loss.
Solution Approach 2:
The system uses feedback by incorporating knowledge of the exact mirror rotation state and camera orientation during exposure into the image reconstruction process. By using the known motion blur kernel derived from the mirror rotation parameters, the system can accurately deconvolve the captured images to recover the original sharp image information, turning the motion artifact into a recoverable signal.
2Productivity
If the laser scanner rotates at high speed to improve scanning efficiency, then productivity increases, but the kernel size for deconvolution becomes larger than the camera picture making reconstruction impractical
Solution Approach 1:
The patent applies partial action by selectively processing only the necessary portions of the blurred image data for reconstruction. Rather than attempting to deconvolve the entire high-speed scan data which would be computationally excessive, the system focuses on recovering image information at specific points where trajectory intersections occur, reducing the computational burden while maintaining reconstruction quality.
3Loss of information
If secondary cameras are used to capture color images for mapping to point cloud data, then color information can be acquired, but parallax issues result in lack of color information on parts of the point cloud
Solution Approach 1:
The patent makes the rotating mirror and single camera system universal by ensuring that the mirror directs light from all regions of the scanned environment to the camera during its rotation. This allows the same optical path used for 3D scanning to also capture color information from all points in the point cloud, eliminating parallax issues and ensuring complete color coverage without requiring separate secondary cameras.
4Illumination intensity
If the exposure time is increased to capture sufficient light during mirror rotation, then image brightness improves, but motion blur increases making deconvolution even more difficult
Solution Approach 1:
The patent changes the parameter of exposure time to be synchronized with the mirror rotation period. By setting the exposure time to match integer multiples of the rotation period, the system captures complete rotation cycles, ensuring that the motion blur kernel is periodic and can be accurately modeled. This parameter synchronization allows for sufficient light capture while keeping the blur pattern predictable and reversible through deconvolution.
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 simultaneous acquisition of 3D coordinate data and image information, reducing the time to generate a colorized point cloud and improving the accuracy of 3D color mapping by averaging image information over a full mirror rotation, thus overcoming the limitations of motion blur and parallax.
Implementation Method 1
a rotatable mirror configured and disposed to receive light from an environment and to direct at least a portion of the received light onto an imaging camera
Data Source
AI summary
Methods and systems for capturing image information of an environment using a laser scanner are described. The systems include a rotatable mirror arranged to direct light received onto an imaging camera of the laser scanner. The mirror is rotatable relative to the imaging camera and the camera is stationary relative to a rotational axis of the mirror. The methods include rotating the mirror relative to the camera and capturing, via the camera, an image containing image information of the received light. Each pixel of the image contains image information of an accumulation of the received light along a corresponding trajectory during a mirror rotation and each individual trajectory has a trajectory that crosses another of the individual trajectories within the image.