Improving computed tomography of chemiluminescence under projection angle limitations via camera layout optimization

Area of Science:

• Fluid Dynamics and Combustion Science
• Optical Imaging and Tomography

Background:

• High-quality bulk tomography imaging under limited projection angles is crucial for complex flow and combustion diagnostics.
• Supersonic wind tunnel experiments face challenges with limited optical access, restricting the number of deployable high-speed cameras.

Purpose of the Study:

• To propose a camera layout optimization method for computed tomography of chemiluminescence (CTC) using fiber-optic endoscopes (FBEs) in limited-angle conditions.
• To improve reconstruction accuracy and stability by reducing projection weight matrix correlation and data redundancy.

Main Methods:

• Combining CTC technology with FBEs for enhanced data acquisition.
• Maximizing the angle between subspaces of the weight matrix rows to minimize correlation.
• Utilizing a simulated annealing algorithm to optimize camera projection angles and spatial distribution based on wind tunnel geometry.
• Leveraging geometric characteristics of wind tunnels with multiple windows for effective information capture.

Main Results:

• Achieved an average cross-correlation coefficient of verified projections above 0.98, a 2.1% improvement over uniform layouts.
• Effectively suppressed reconstruction artifacts caused by limited projection angles.
• Demonstrated reduced reconstruction error and good adaptability/robustness to flame direction changes.

Conclusions:

• The proposed camera layout optimization method significantly enhances the accuracy and stability of limited-angle CTC.
• This approach is robust and adaptable for complex flow and combustion diagnostics in supersonic wind tunnels.
• The integration of FBEs and optimized camera placement overcomes optical access limitations effectively.