Region specific magnification on digital holograms at 100 frames per second

Abstract

We report a fast method for magnifying a selected region of the pictorial content that has been recorded in a digital hologram, without the need of regenerating the latter from the original object scene. In essence, the hologram is first back-projected to a complex, two dimensional virtual diffraction plane (VDP) which is located at close proximity to the original object points. Next, the fringe patterns in the selected region of the VDP, which corresponds to the complex light wave emerged from the part of the object within the coverage of the region, is transformed to achieve the magnification effect. Subsequently, the processed field distribution on the VDP is expanded into a full hologram. We have applied our proposed method to realize a magnifying glass effect, so that the reconstructed image of the hologram will zoom into a specific region of the object scene. For a medium size digital hologram comprising of 2048 × 2048 pixels, the magnifying process can be realized in less than 10ms (equivalent to a rate of around 100 frames per second). To the best of our knowledge, this is the first time region specific magnification at such a high frame rate is considered and achieved in the context of digital holography.