Purpose : This study aims to design a compact and high-performance head-mounted display (HMD) optical system that enhances user immersion and wearing comfort. The system is based on a prism structure incorporating aspheric elements.
Methods : The optical system was designed using Code V software. The target specifications included a diagonal field of view of 40°, a total system thickness of approximately 11 mm, an eye relief (ER) of 15 mm, and an aperture size of 4 mm. The optical performance goals were to achieve a Root-Mean-Square (RMS) spot size smaller than 0.01 mm and a Modulation Transfer Function (MTF) of 0.4 or higher at 50 cycles/mm. The system consists of a total of 10 surfaces, including three prisms and one display panel. The prisms form nine optical surfaces, and the 10th surface corresponds to the display. Five of the optical surfaces were designed as aspheric to minimize aberrations. A folded off-axis layout was adopted to achieve both compactness and high imaging performance.
Results : The final design demonstrated an RMS spot size of less than 0.005 mm at the center and an average of less than 0.01 mm across the full field. The MTF was maintained at 0.4 at 50 cycles/mm, confirming high-resolution imaging. The distortion rate was maintained within +2.8%, outperforming several existing designs. Uniform optical performance was maintained across the full field of view, and the total system thickness was successfully reduced to approximately 11 mm.
Conclusion : This study presents a prism- and asphere-based optical design that achieves structural simplification and compactness while maintaining high-resolution performance. The proposed approach can serve as an effective lightweight design strategy for future wearable displays and miniature HMD systems.