Multiple imaging technique for extending depth of focus in retinal displays

Area of Science:

• Optics and Photonics
• Display Technology
• Human-Computer Interaction

Background:

• See-through head-mounted displays (HMDs) face challenges with limited depth of focus.
• This limitation impacts the clarity and usability of displayed information, especially for tasks requiring focus at different distances.

Purpose of the Study:

• To propose and evaluate a novel solution for extending the depth of focus in retinal projection displays.
• To investigate the efficacy of coherent multiple imaging with a phase-only mask for improving HMD visual performance.

Main Methods:

• Utilized a phase-only mask within a retinal projection display system.
• Employed a schematic eye model and the SPLAT simulation tool for calculating projected retinal images.
• Assessed image quality using objective criteria and psychometric measurements under varying illumination conditions (partially coherent, fully coherent, incoherent).

Main Results:

• The coherent multiple imaging technique with a phase-only mask shows promise for enhancing depth of focus.
• Partially coherent illumination resulted in a significant extension of the depth of focus for reading text, up to a factor of 3.2.
• Fully coherent illumination led to structural degradation, while incoherent illumination caused contrast reduction in retinal images.

Conclusions:

• The proposed method offers a viable approach to overcome the depth of focus limitations in see-through HMDs.
• Partially coherent illumination is crucial for achieving the extended depth of focus benefits of this technique.
• Further research can explore optimizing phase-only masks and illumination conditions for practical HMD applications.