ABSTRACT
The spherical computer-generated hologram is inevitably suffered from the speckle noise since it is necessary to add random phase to the object to ensure the scattering characteristic of reconstructed image. The speckle noise seriously degrades the quality of reconstructed image especially for a spherical phase-only hologram (SPOH). In this paper, spherical self-diffraction iteration (SSDI) algorithm is proposed to suppress the speckle noise in the SPOH. The algorithm is based on spherical self-diffraction (SSD) model which is a special case of spherical back-propagation (SBP) model at limit condition. The correctness of SBP and SSD as well as the effectiveness of SSDI algorithm are verified by numerical simulations. Meaningfully, the proposed method significantly outperforms the conventional methods in speckle suppression performance and computing speed. As far as we known, models of SBP and SSD as well as conception of SSDI are firstly proposed and applied for speckle suppression of SPOH.
ABSTRACT
Recently, great progress has been made in the research of cylindrical holography as a promising technique of 360° display. However, there is an unsolved issue of occlusion culling, which is critical to cylindrical holography and degrades the reconstructed images due to overlapping. To our knowledge, the occlusion issue in cylindrical holography has never been deeply discussed. In this paper, a method of occlusion culling is proposed for computer-generated cylindrical holograms based on a horizontal optical-path-limit function. In cylindrical diffraction, the propagation characteristics of light waves can be described by the point spread function, which is mainly obtained by analyzing the meaning of the obliquity factor in the concentric cylinder model. Different from the planar diffraction, the diffraction area of each source point is limited within the tangents in cylindrical diffraction. Therefore, a horizontal optical path limit function that acts directly on the point spread function for occlusion culling is established. Besides, the proposed method can be applied to the three-dimensional object by using the layer-oriented method. Moreover, the effectiveness of the proposed occlusion culling method is verified by the numerical simulation results and error analysis of the reconstructed images.
ABSTRACT
BACKGROUND: Summer acupoint herbal patching (SAHP) has been widely used in China for thousands of years. This bibliometric analysis aims to provide a comprehensive review of the characteristics of clinical studies on SAHP for any condition. METHODS: We included clinical studies such as randomized clinical trials (RCTs), controlled clinical studies (CCTs), case series (CSs), case reports (CRs), and cross-sectional studies on SAHP for any condition. Six databases were searched from date of inception to March 2015. Bibliometric information and study details such as study type, characteristics of participants, details of the intervention and comparison, and outcome were extracted and analyzed. RESULTS: A total of 937 clinical studies were identified and which were published between 1977 and 2015. This included 404 RCTs, 52 CCTs, 458 CSs, 19 CRs and 4 cross-sectional studies and involved 232,138 participants aged 2 to 90 years from two countries. Almost all studies were from China (936, 99.89%). The five conditions most commonly treated by SAHP were asthma (401, 42.80%), chronic bronchitis (146, 15.58%), allergic rhinitis (117, 12.49%), chronic obstructive pulmonary disease (73, 7.79%), and recurrent respiratory tract infection (42, 4.48%). Among 502 controlled studies, the majority compared SAHP alone with different controls (16 categories, 275 comparisons). The most commonly used controls were western medicine, placebo, traditional Chinese medicine, no treatment and non-pharmaceutical traditional Chinese therapies. Composite outcome measures were the most frequently reported outcome (512, 69.19%). CONCLUSION: A substantial amount of research on SAHP has been published in China and which predominantly focuses on respiratory conditions. The findings from this study can be used to inform further research by highlighting areas of greatest impact for SAHP.
