Pinhole SPECT for small animal has become a routine procedure in many applications of molecular biology and pharmaceutical development. There is an increasing demand in the whole body imaging of lab animals. A simple and direct solution is to scan the object along a helical trajectory, similar to a helical CT scan. The corresponding acquisition time can be greatly reduced, while the over-lappin...

The Crossed-Slits (X-Slits) camera is defined by two nonintersecting slits, which replace the pinhole in the common perspective camera. Each point in space is projected to the image plane by a ray which passes through the point and the two slits. The X-Slits projection model includes the pushbroom camera as a special case. In addition, it describes a certain class of panoramic images, which are...

We report on a novel diagnostics instrument for in-situ imaging and measurements of X-ray beam parameters in real-time. The instrument is based on the robust and simple idea of a pinhole camera that collects the weakly scattered radiation from a thin sheet of a low-Z material placed in the X-ray beam at an acute angle. We demonstrate how by recording the scattered radiation with an appropriate ...

We identify and study two types of “accidental” images that can be formed in scenes. The first is an accidental pinhole camera image. The second class of accidental images are “inverse” pinhole camera images, formed by subtracting an image with a small occluder present from a reference image without the occluder. Both types of accidental cameras happen in a variety of different situations. For ...

The majority of computer vision applications assumes that the camera adheres to the pinhole camera model. However, most optical systems will introduce undesirable effects. By far, the most evident of these effects is radial lensing, which is particularly noticeable in fish-eye camera systems, where the effect is relatively extreme. Several authors have developed models of fish-eye lenses that c...

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...