Component simplified design of the freeform reflective imaging systems based on optical-digital integration

Area of Science:

• Optical Engineering
• Image Processing
• System Design

Background:

• Off-axis reflective systems use freeform surfaces for aberration correction but increase fabrication complexity and cost.
• Reducing elements simplifies systems but degrades image quality due to uncorrected aberrations.
• High-quality imaging in wide field-of-view systems requires effective aberration management.

Purpose of the Study:

• To propose a simplified design method for off-axis reflective systems using optical-digital integration.
• To reduce the complexity of optical systems while maintaining high image quality.
• To develop a method for correcting off-axis aberrations in imaging systems.

Main Methods:

• Constructed a wavefront aberration model using Zernike polynomials based on wavefront aberration theory.
• Established a point spread function (PSF) model via Fourier transform and developed an Aberration-Correlated Homogenized PSF (ACH-PSF) model.
• Employed a Richardson-Lucy deconvolution algorithm with a Total Variation (TV) regularization term to process degraded images.

Main Results:

• A three-mirror system with freeform surfaces was simplified to a two-mirror system for an 8–12 µm waveband system.
• The simplified design achieved a focal length of 97.2 mm, F-number of 1.5, and a field of view of 8°×6°.
• Image quality metrics improved significantly: Peak Signal-to-Noise Ratio (PSNR) increased from 29.21 dB to 34.48 dB, and Structural Similarity Index (SSIM) improved from 0.8530 to 0.9410.

Conclusions:

• The proposed optical-digital integration method effectively simplifies off-axis reflective system design.
• The method successfully eliminates the impact of off-axis aberrations, enhancing image quality.
• This approach offers a novel strategy for simplified design in off-axis optical systems, validated by significant improvements in PSNR and SSIM.