Underwater 3D Reconstruction Stereo Camera Refraction Compensation
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Solution Overview
Problem
Existing methods for underwater fish size measurement using stereo cameras face inaccuracies due to refractions across different mediums, leading to variable camera parameters and incorrect 3D reconstruction.
Innovation Solution
A device employing a stereo camera system calibrated at multiple distances, with stored sets of intrinsic and extrinsic parameters, including distortion coefficients, to select the most appropriate set for accurate 3D reconstruction based on the target's distance, accounting for refractions in a multi-medium environment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a pinhole camera model is used for underwater size measurement, then the device structure is simple, but measurement precision deteriorates due to refraction effects
Solution Approach 1:
The patent applies parameter changes by storing multiple sets of intrinsic and extrinsic parameters calibrated at different distances. When measuring fish at a specific distance, the system selects the parameter set that best matches that distance, thereby adapting the camera model to compensate for refraction effects without changing the physical camera structure.
2Ease of manufacture
If camera parameters are calibrated at a single distance, then calibration process is simple, but measurement precision deteriorates when target distance varies
Solution Approach 1:
The patent segments the calibration process by performing calibration at multiple discrete distances and storing separate parameter sets for each distance. This divides the single calibration task into multiple distance-specific calibrations, allowing accurate measurement across varying distances by selecting the appropriate segment (parameter set) based on the target distance.
3Measurement precision
If water housing with transparent window is used to eliminate refraction, then measurement precision improves, but device complexity increases
Solution Approach 1:
Instead of physically modifying the camera housing with water-filled transparent windows, the patent changes the software parameters by using multiple calibrated parameter sets that account for refraction effects. This virtual compensation approach achieves measurement precision without increasing mechanical device complexity.
4Measurement precision
If multiple sets of parameters are stored for different distances, then measurement precision improves across varying distances, but device complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing multiple sets of camera parameters at different distances before actual measurement. The calibration work is performed in advance for various distances, and during measurement, the system simply retrieves the pre-computed parameter set matching the target distance, avoiding complex real-time calculations.
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 accurate 3D reconstruction and fish size measurement by compensating for refractions, eliminating the need for complex water housings and providing precise size calculations across varying distances.
Implementation Method 1
As a ray of light that reflects from an underwater target (e.g., a fish) to a camera, it has to travel through different mediums i.e., water, transparent window, and air causing refractions.
Data Source
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AI summary
The disclosure relates to a 3D image reconstruction device (100) that includes a stereo camera (105, 110), a data storage device (130), and a 3D reconstruction module (150). The stereo camera (105, 110) includes a first camera and a second camera that take a pair of pictures in an underwater environment of a target. The data storage device (130) stores a plurality of sets of parameters, each set of the plurality of sets of parameters modelling the stereo camera that produces pictures of an underwater target at a distance from the stereo camera. The plurality of sets of parameters model the stereo camera at different distances. The 3D reconstruction module (150) calculates a 3D position of the target based on a 2D position of the target on the pair of pictures and a selected set selected from the plurality of sets of parameters.