Constraint-driven DMD-integrated off-axis freeform four-mirror relay imaging for active suppression of laser and intense-light interference.

Imaging detectors under intense light suffer from local saturation and reduced visibility. We propose a co-design methodology for active front-end interference suppression. This framework formulates the coupled physical constraints of beam separation, conjugate transfer, and non-rotationally symmetric aberration correction inherent to tilted modulation planes. By integrating digital micromirror device (DMD) spatial modulation with a two-stage off-axis freeform four-mirror architecture, we reveal the joint governing mechanisms of local masking, plane orientation, and aberration correction. Simulations over 0.35-1.0 µm yield a full-field MTF above 0.725 at 50 lp/mm and a maximum distortion of 2.29%. Independent validation of the second-order DMD-to-detector mapping yields residuals of 0.407 µm RMS and 0.763 µm maximum. An ideal 20×20µm OFF-state mask rejects 89.07% of selected interference energy, corresponding to 9.61 dB suppression and demonstrating system-level feasibility.