In this paper we use a simple, active-camera model to estimate the time-to-contact (TTC) of a moving object. We estimate TTC by enforcing a \uniform scale" constraint on the moving object. By actively adjusting the focal length of the pinhole model, the projected object maintains a xed image scale regardless of its motion. These adjustments on the ideal pinhole focal length are translated into ...

An improved tomographic algorithm in the scheme of Tikhonov-Phillips regularisation method, has been employed for multi-pixel bolometric measurements in order to get as much information as possible while keeping the assumptions to a minimum. The effects of finite detector size have been taken into account with a full three dimensional treatment of the detector geometry. The application of tomog...

INTRODUCTION BACKGROUND Vision screening study in primary school children has not been done in Bayelsa State. This study aims to screen for refractive error among primary school children in Bayelsa State and use the data to plan for school Eye Health Program. METHODS A cross sectional study on screening for refractive error in school children was carried out in Yenagoa Local Government Are...

Coherent diffraction microscopy requires a well-defined illumination wave such as a plane wave on a specimen. Experimentally, a small pinhole or a focused beam is often used to reduce the illumination area but they unavoidably distort the waves. The distortion of the illumination wave causes artifacts in the phase retrieval of oversampled diffraction patterns. Using computer simulations, we sea...

This work aims to develop a Monte Carlo (MC) model for pinhole K-shell X-ray fluorescence (XRF) imaging of metal nanoparticles using polychromatic X-rays. The MC model consisted of two-dimensional (2D) position-sensitive detectors and fan-beam X-rays used to stimulate the emission of XRF photons from gadolinium (Gd) or gold (Au) nanoparticles. Four cylindrical columns containing different conce...

We developed a compact and high-power modelocked fiber laser for multilayered optical memories. The average power and pulse width of the output pulse from the fiber laser that we developed were 109 mW and 2.1 ps, respectively. The dispersion of the output pulse was compensated with an external single-mode fiber of 2.5 m length. The pulse was compressed from 2.1 ps to 93 fs by dispersion compens...

Vol. 26 No. 5, 2014 659 Received April 3, 2013, Revised September 9, 2013, Accepted for publication October 13, 2013 Corresponding author: Sung-Yul Lee, Department of Dermatology, Soon Chun Hyang University Hospital Cheonan, 31 Suncheonhyang 6-gil, Dongnam-gu, Cheonan 330-721, Korea. Tel: 82-41-570-2270, Fax: 82-41-570-2783, E-mail: [email protected] This is an Open Access article distribute...

We developed SPECT imaging capability on an animal PET scanner to provide a cost effective option for animal SPECT imaging. The SPECT add-on sub-system was enabled by mechanically integrating a multiple-pinhole collimator in the PET detector ring. This study introduces a method to calibrate the geometrical parameters of the SPECT add-on using the PET imaging capability of the scanner. The propo...

We characterize and compare the axial and lateral performance of fluorescence confocal systems imaging in turbid media. The aperture configurations studied are a single pinhole, a slit, a Nipkow disk, and a linear array of pinholes. Systems with parallelized apertures are used clinically because they enable high-speed and real-time imaging. Understanding how they perform in highly scattering ti...

Nuclear angiocardiography with a gamma camera, a pinhole collimator, and 99mTc pertechnetate was performed on 43 children aged 3 years or less, including 10 neonates. Twenty-six children had congenital heart disease, which was confirmed at cardiac catheterization; the rest had no structural cardiac anomaly. Use of the pinhole collimator allowed magnification of cardiac images, with enhancement ...