A DMD-Based Adaptive Modulation Method for High Dynamic Range Imaging in High-Glare Environments

TL;DR

The paper tackles sensor saturation under extreme glare in optical metrology by introducing a DMD-based adaptive modulation framework capable of achieving over $120\ \mathrm{dB}$ HDR, with a measured dynamic range of $127\ \mathrm{dB}$. It combines a DMD optical modulation unit and an adaptive computational imaging pipeline, including a double-telecentric optical design validated by Zemax (MTF ~ $0.55$ at $60\ \mathrm{lp/mm}$ and grid distortion < $0.1\%$) to maintain pixel-level registration. A real-time Adaptive Mask Generation algorithm and instantaneous intensity modulation enable artifact-free HDR within a single acquisition at $28$--$66$ Hz, yielding a $78\%$ reduction in strain error and preservation of measurement area in high-glare conditions. Overall, the method provides robust, high-fidelity DIC in challenging illumination scenarios, offering significant potential for optical metrology and structural analysis in welding and polished-surface contexts; future work targets acceleration and miniaturization for field deployment.

Abstract

Background The accuracy of photomechanics measurements critically relies on image quality,particularly under extreme illumination conditions such as welding arc monitoring and polished metallic surface analysis. High dynamic range (HDR) imaging above 120 dB is essential in these contexts. Conventional CCD/CMOS sensors, with dynamic ranges typically below 70 dB, are highly susceptible to saturation under glare, resulting in irreversible loss of detail and significant errors in digital image correlation (DIC). Methods This paper presents an HDR imaging system that leverages the spatial modulation capability of a digital micromirror device (DMD). The system architecture enables autonomous regional segmentation and adaptive exposure control for high-dynamic-range scenes through an integrated framework comprising two synergistic subsystems: a DMD-based optical modulation unit and an adaptive computational imaging pipeline. Results The system achieves a measurable dynamic range of 127 dB, effectively eliminating satu ration artifacts under high glare. Experimental results demonstrate a 78% reduction in strain error and improved DIC positioning accuracy, confirming reliable performance across extreme intensity variations. Conclusion The DMD-based system provides high fidelity adaptive HDR imaging, overcoming key limitations of conventional sensors. It exhibits strong potential for optical metrology and stress analysis in high-glare environments where traditional methods are inadequate.

Figures (9)

• Figure 1: Schematic of the high dynamic imaging system based on DMD: (a) DMD optical switch structure; (b) Microscopic view of DMD micromirror array; (c) System setup integrating DMD modulator and high-speed camera; (d) Representative image results before and after DMD modulation.
• Figure 2: Zemax simulation results for the double-telecentric optical system: (a) 3D optical layout, (b) Modulation Transfer Function (MTF), (c) Spot diagram, and (d) Grid distortion ($<$ 0.1%).
• Figure 3: Double-Telecentric System Design: (a) Schematic of the double-tilted double-telecentric system on the object surface's image plane; (b) Imaging result using the double-telecentric lens.
• Figure 4: Flowchart of the HDR imaging process based on DMD.
• Figure 5: The light attenuation of high brightness light is realized by DMD modulation. (a) Experimental scene; (b) Image acquisition before modulation; (c) Partial suppression of images; (d) Completely suppress the image.