Speckle reduction in holographic projection using temporal-multiplexing of spatial frequencies

Abstract

We present a method that significantly reduces the speckle effect in holographic projection. It is based on zero-padding the prede fined projected intensity and calculating an extended phase dis tribution using an optimized iterative approach based on the gen eralized projection method. The extended phase distribution is divided into several finite ones with the size of the spatial light modulator (SLM). The SLM manipulates an incident plane wave to generate the projected intensity at a remote plane. Utilizing the temporal-multiplexing property of a phase-only SLM and incoher ent superposition of the redundant intensities projected across the observation plane reduce the speckle effect. In contrast to the state of the art, no mechanical moving parts and no additional informa tion are required during the projection process. The basic principle of this technique and its experimental verification are described.

Three-dimensional visualization of brain tumor progression based accurate segmentation via comparative holographic projection

“…Speckle noise reduction. From the sate of the art [13,14,36,55], it is known that the optical reconstruction of a phase-only hologram is noisy. To overcome the speckle noise which is a common problem in displaying CGHs, a speckle reduction method proposed by Agour et.…”

“…al. [13] which is based on temporal multiplexing of spatial frequencies was applied. The algorithm is illustrated in Fig 12, where the size of MR slice was 320 × 260 pixels.…”

“…The signal to noise ratio (SNR) and the standard deviation (σ) were used to quantitatively evaluate the quality of the reconstructed images. The scaled SNR can be calculated from [13,60]:…”

“…Holographic projection is a method that provides three-dimensional (3D) information about an object without the need for special eyewear. Unlike the existing traditional photography that evaluates only the intensity distribution of a test object, computergenerated hologram (CGH) has been generated to permit direct access of both intensity and phase of the object field providing the complete 3D information [12][13][14][15][16]. Despite the generated CGH is a 2D distribution, it encodes the 3D information of the object [15][16][17][18][19][20].…”

“…In addition to the previously mentioned artifacts, there is arising speckle noise that deteriorates the projected image quality in the observation plane which is a result of the coherent light illumination. This effect can also be compensated using different multiplexing techniques [13,36]. Thus, the combination of CGH with the SLM allows a dynamic holographic projection in real-time with high efficiency and low power consumption [18,22,[37][38][39].…”