Image quality assessment: from error visibility to structural similarity

Multiple imaging technique for extending depth of focus in retinal displays

Limited depth of focus is among the main problems of todays see-through head-mounted displays. In this paper we propose and evaluate a new solution to this problem: the use of the coherent multiple imaging technique in a retinal projection display by incorporating an appropriate phase-only mask. The evaluation is based on a schematic eye model and on the partial coherence simulation tool SPLAT which allows us to calculate the projected retinal images of a text target. Objective image quality criteria demonstrate that this approach is promising provided that partially coherent illumination light is used. In this case, psychometric measurements reveal that the depth of focus for reading text can be extended by a factor of up to 3.2. For fully coherent and incoherent illumination, however, the retinal images suffer from structural and contrast degradation effects, respectively.