Laser Linear Array Calibration for Shock-Distorted PIV Images
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Solution Overview
Problem
Conventional PIV image calibration methods fail to accurately obtain spatial resolutions in hypersonic wind tunnels due to shock waves causing optical diffraction and distortion, which are not replicable in windless conditions and complicate distortion in windy conditions.
Innovation Solution
A device and method using laser linear arrays to form a laser grating in the test observation region, combined with a neural network-based distortion-restoring calibration algorithm, to calibrate and restore distorted images caused by shock waves without interfering with the true flow field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a black and white checkerboard target is placed in the tested region for calibration, then spatial resolutions can be obtained in windless conditions, but shock waves are generated causing optical diffraction and distortion in hypersonic wind tunnels
Solution Approach 1:
The patent uses a laser grating as a virtual copy of the traditional physical checkerboard target. The laser grating projects a pattern of parallel laser lines onto the flow field, creating a measurable distortion pattern that replicates the calibration function without the harmful physical presence of a solid target in the hypersonic flow.
Solution Approach 2:
The patent replaces the mechanical physical target (checkerboard) with an optical field-based calibration method (laser grating). Instead of using a solid object that generates shock waves, the system uses laser light to create a calibration pattern that can be captured and processed to determine spatial resolution without mechanical interference with the flow.
2Adaptability or versatility
If a physical target is used for calibration in hypersonic wind tunnels, then calibration can be performed, but the target generates shock waves that cause complex distortion making accurate spatial resolution measurement impossible
Solution Approach 1:
The laser grating creates a virtual calibration pattern that copies the essential calibration function of a physical target without the harmful physical properties. The pattern of parallel laser lines provides sufficient geometric information for calibration while avoiding shock wave generation.
Solution Approach 2:
The patent changes the physical state of the calibration object from solid (physical target) to optical field (laser grating). This parameter change eliminates the shock wave generation mechanism while preserving the calibration functionality through the laser-induced distortion pattern in the flow field.
3Object-affected harmful factors
If no target is placed in the tested region to avoid shock waves, then optical diffraction is avoided, but spatial resolutions cannot be obtained in windless conditions
Solution Approach 1:
The laser grating system is self-calibrating in the sense that it creates its own distortion pattern within the flow field that serves as the calibration reference. The system uses the laser lines themselves as the calibration target, eliminating the need for separate physical calibration objects while maintaining calibration capability.
Solution Approach 2:
The patent substitutes the mechanical target approach with an optical field-based system that generates calibration patterns dynamically. The laser grating creates measurable distortion patterns in the flow field that enable spatial resolution calibration without requiring physical objects that would cause optical diffraction.
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
Accurately obtains spatial resolutions at various positions of the image by calibrating and restoring distorted laser grating images, achieving high-accuracy image calibration without contact or interference.
Implementation Method 1
a laser emission component configured to emit equidistant laser linear arrays to form a laser linear array light path
Implementation Method 2
an optical component configured to perform light splitting on laser rays in the laser linear array light path to form a laser grating in a test observation region
Implementation Method 3
optical diffraction is caused locally in the tested region, the recorded particle trajectory image is distorted
Data Source
AI summary
The present disclosure provides a device and method for calibrating a particle image velocimetry (PIV) image based on laser linear arrays, and relates to the technical field of laser velocity measurement and image restoration. The present disclosure can solve the problem of image distortion caused by a shock wave of a model in a hypersonic wind tunnel, thereby realizing distortion capture and correction. The device includes a laser emission component configured to emit equidistant laser linear arrays; an optical component configured to perform light splitting on laser rays to form a laser grating in a test observation region; a camera configured to acquire a distorted laser grating image when a working condition of a wind tunnel test section model is adjusted to a working condition of a PIV test; and a background processor configured to calibrate and restore the distorted laser grating image with a neural network-based distortion-restoring calibration algorithm.