Canon (Australia)

Abstract The mission of the 2000 kg Cassini spacecraft concluded on 2017 September 15, by its deliberate entry into Saturn’s atmosphere at some 31.1 km s−1. Observations, using Hubble and groundbased observatories, to attempt optical detection of this 0.25 kT “artificial meteor” are summarized. No signatures were identified. A challenge with observing the event is that due to atmospheric drag, its timing was not completely deterministic months or even days in advance, a particular problem for space observatories. While imaging observations needed no geometric specification more than “Saturn,” observations with spectrometers required pointing the instrument aperture or slit at the specific impact site. Since giant planet longitude systems are not always familiar, distribution of an unambiguous “finder chart” showing the location of the predicted entry site on the disk is essential, as is clarity on whether stated times are spacecraft event time, or Earth received time (light-travel time, 83 minutes, later).

Small bowel obstruction (SBO) is a common cause of emergency presentations for abdominal pain and can be complicated by mesenteric ischemia. Computed tomography is currently central to diagnosis and management planning. Currently accepted signs identify secondary effects of the root physiological insult, which is vascular obstruction. We hypothesized that with advancements in CT technology and reconstruction algorithms, we can now more closely interrogate the mesenteric vasculature for obstruction and more accurately predict the need for surgical intervention. We retrospectively audited the charts of all patients presenting with a clinical diagnosis of SBO at a single institution in a 12-month period. Two blinded consultant radiologists were then asked to analyze 3D MIP reconstruction CT scans for vascular obstruction in addition to any currently accepted signs of ischemia. Comparison between vascular cutoff and accepted current signs in the need for surgical intervention and the presence of any signs of ischemia in theater were recorded. Vascular cutoff had a comparable, with a trend towards superiority, sensitivity and specificity and inter-observer agreement to currently accepted signs of ischemia. The absence of a cut off sign has an excellent negative predictive value for ischemia with only 2 (3.7%) patients demonstrating ischemia at surgery where the vascular cutoff sign was not seen to be present. Interrogating vascular obstruction using 3D MIP reconstructions in small bowel obstruction may be a more sensitive and specific sign for prediction of surgical intervention, possibly occurring earlier in the obstruction pathway.

This special issue of Applied Optics contains selected papers from OSA's Imaging Congress with particular emphasis on work from mathematics in imaging, computational optical sensing and imaging, imaging systems and applications, and 3D image acquisition and display.

Pipeline of processors allow the execution of a sequential streaming program on multiple processors. However, partitioning sequential code for Multiprocessor Systems-on-Chips (MPSoCs), and then creating the MPSoC platform for the sequential code to execute, is a challenging problem. Parallelizing/pipelining statements within a control loop will improve the throughput of each iteration and the overall performance. Existing techniques, such as OpenMP, for parallelizing control loops is agnostic of the underlying MPSoC architecture, thus limiting the possibilities for further parallelisation. Previous techniques related to distribution of statements to MPSoCs considered homogeneous processors and not automated. In this paper, we propose a novel automated parallelization/ pipelining approach to synthesize a heterogeneous distributed pipelined MPSoC to improve the throughput of a loop (critical for streaming applications). An Integer Linear Programming (ILP)-based formulation to map statements to processor configurations is presented, in order to find the most suitable heterogeneous processor configurations for maximal throughput. Our approach complements state-of-the-art parallelization techniques, such as OpenMP, to further improve the performance of an application. A complete MPSoC platform, for the Tensilica framework, is automatically generated within minutes using our approach for the tested applications.

This paper presents a parallel implementation of geodesic distance transform using OpenMP. We show how a sequential-based chamfer distance algorithm can be executed on parallel processing units with shared memory such as multiple cores on a modern CPU. Experimental results show a speedup of 2.6 times on a quad-core machine can be achieved without loss in accuracy. This work forms part of a C implementation for geodesic superpixel segmentation of natural images.

Image quality is a complex and multi-disciplinary field of research. Its applications cover a broad gamut including image engineering, photography, display technology and printing. Image quality is frequently an important consideration in optimizing technologies such as imaging device design, image compression, image encoding, colour management and broadcast transmission.In display and printing image quality plays an important role in design factors such as colour gamut, tone scale, resolution and spatial uniformity.The paper begins by reviewing the development of image quality concepts from simple engineering measures of fidelity, through attempts to improve these measures by accounting for low level features of the human visual system.In the case of photographic capture and rendering, the issue of fidelity of the image to the original scene is discussed, taking account of the consequences of colour appearance phenomena and colour preference.Finally, the relationship between image quality and higher order cognitive factors including naturalness, composition and region of salience are examined.

In this study, the authors examine the process of authenticating paper media using the unique fibre structure of a piece of paper (the so-called ‘paper fingerprint’) In particular, the authors look at methods to authenticate a paper fingerprint when text has been printed over the authentication zone. The authors show how alpha-masked correlation can be applied to this problem and develop a modification to this technique that is more closely matched to the requirements of this problem and produces an improvement in performance. They also investigate two methods of pixel inpainting to remove printed text or marks from the authentication zone and allow ordinary correlation to be performed. The authors show that these methods can perform as well as alpha-masked correlation. They derive confidence estimates for one of the matching processes. Finally, the authors investigate some methods for improving the robustness to forgery and rotation of the matching process.

Probabilistic Latent Semantic Analysis (PLSA) is one of the latent topic models and it has been successfully applied to visual recognition tasks. However, PLSA models have been learned mainly in batch learning, which can not handle data that arrives sequentially. In this paper, we propose a novel on-line learning algorithm for learning the parameters of PLSA. Our contributions are two-fold: (i) an on-line learning algorithm that learns the parameters of a PLSA model from incoming data; (ii) a codebook adaptation algorithm that can capture the full characteristics of all the features during the learning. Experimental results demonstrate that the proposed algorithm can handle sequentially arriving data that batch PLSA learning cannot cope with, and its performance is comparable with that of the batch PLSA learning on visual recognition.

In this paper, we examine the problem of authenticating media using the unique fiber structure of each piece of (the so-called paper fingerprint). In particular, we look at methods to authenticate media when text has been printed over the authentication zone. We show how alpha-masked correlation [Fitch05] can be applied to this problem and develop a modification to alpha-masked correlation that is more closely matched to the requirements of this problem and produces an improvement in performance. We also investigate two methods of pixel inpainting to remove printed text or marks from the authentication zone and allow ordinary correlation to be performed. We show that these methods can perform as well as alpha-masked correlation. Finally two methods of improving the robustness to forgery are investigated.

We propose a coherent mathematical model for human fingerprint images. Fingerprint structure is represented simply as a hologram - namely a phase modulated fringe pattern. The holographic form unifies analysis, classification, matching, compression, and synthesis of fingerprints in a self-consistent formalism. Hologram phase is at the heart of the method; a phase that uniquely decomposes into two parts via the Helmholtz decomposition theorem. Phase also circumvents the infinite frequency singularities that always occur at minutiae. Reliable analysis is possible using a recently discovered two-dimensional demodulator. The parsimony of this model is demonstrated by the reconstruction of a fingerprint image with an extreme compression factor of 239.