Image-Quality Enhancement for a Holographic Wavefront Color Printer by Adaptive SLM Partitioning

Abstract

The wavefront printer records a volume-reflection hologram as a two-dimensional array of elemental holograms from computer-generated holograms (CGHs) displayed on a spatial light modulator (SLM). The wavefront coming from the object is extracted by filtering in the spatial-frequency domain. This paper presents a method to improve color reproduction in a wavefront printer with spatial division of exposures at primary colors, by adaptive partitioning of the SLM in accordance with the color content encoded in the input CGHs, and by the controllable change of exposure times for the recording of primary colors. The method is verified with a color wavefront printer with demagnification of the object beam. The quality of reconstruction achieved by the proposed method proves its efficiency in eliminating the stripe artifacts that are superimposed on reconstructed images in conventional mosaic recording.

Efficient Hogel-Based Hologram Synthesis Method for Holographic Stereogram Printing

“…For hogels with a resolution of 200 × 200 pixels as shown in Figure 6b, larger hogels improve the angular resolution of an HS, and the accuracy of orienting the plane waves created locally within a hogel. It is confirmed by measurement results from Equation (5).…”

“…For hogels with a resolution of 200 × 200 pixels as shown in Figure 6b, larger hogels improve the angular resolution of an HS, and the accuracy of orienting the plane waves created locally within a hogel. It is confirmed by measurement results from Equation (5). The conventional pixel re-arrangement technique re-arranges hogel with 50 × 50 pixels, according to Equation (3), and this process makes perspective image blurring at lower resolution, as shown in Figure 6a.…”

“…The 3D virtual models can be easily implemented by a holographic printer, which can be divided into two main types: wavefront printer and a holographic stereogram (HS) printer. The wavefront printer records an arbitrary object field while retaining full control of both the amplitude and phase distributions of the 3D object as does the traditional analogue hologram [4][5][6][7][8]. Among the various holographic representation approaches, the holographic stereogram (HS) is the most common incoherent reconstruction technique.…”