Multiple-pinhole (MPH) glasses are currently sold in many countries with unproven advertisements; however, their objective and subjective effects have not been investigated. Therefore, to investigate the effects of MPH glasses excluding the single-pinhole (SPH) effect, we compared the visual functional changes, reading speed, and ocular discomfort after reading caused by MPH and SPH glasses. He...

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...

We analyze the coherence properties of a partially coherent field emerging from two pinholes in an opaque screen and show that the spectral degree of coherence possesses phase singularities on certain surfaces in the region of superposition. To our knowledge, this is the first illustration of the singular behavior of the spectral degree of coherence, and the results extend the field of singular...

Seven-pinhole emission tomography has been studied under conditions that simulate clinical myocardial imaging with thallium-201, and is compared with planar imaging with a heart phantom. The seven-pinhole technique produces reconstructed images that offer a tomographic presentation of the object but do not quantitatively represent true cross sections of the object's activity distribution. Tomog...

PURPOSE This paper presents new spectral measurements of a tungsten-target digital breast tomosynthesis (DBT) system, including spectra of 43-49 kVp. METHODS Raw x-ray spectra of 20-49 kVp were directly measured from the tube port of a Selenia Dimensions DBT system using a CdTe based spectrometer. Two configurations of collimation were employed: one with two tungsten pinholes of 25 μm and 200...

Soft x-ray emission from plasmas produced by ablation from a magnesium target employing a ruby laser is studied using a grazing incidence spectrograph in the spectral region 3–12 nm. Emission intensities are investigated for different ionic lines as a function of position, time after the maximum of the laser pulse and laser irradiance. A gated pinhole camera is employed for studying the evoluti...

where c is the column and r is the row. (This is a Point Grey convention, and it assumes the camera center is exactly in the center column and row of the image. In fact, proper camera calibration can be done to get a better estimate of the center.) The (X,Y,Z) coordinate system is shown in Fig. 1, and the (u, v) system in Fig. 2: Z points along line of sight, away from camera; X (and also u) po...

This paper presents a feasibility study of a Compton scattering enhanced (CSE) multiple pinhole imaging system for gamma rays with energy of 140keV or higher. This system consists of a multiple-pinhole collimator, a position sensitive scintillation detector as used in standard Gamma camera, and a Silicon pad detector array, inserted between the collimator and the scintillation detector. The pro...

This paper analyzes the tradeo between spatial resolution and noise for simple pinhole imaging systems with photon-counting detectors. We consider image recovery algorithms based on density estimation methods using kernels that are based on apodized inverse filters. This approach allows a continuous-object, continuous-data treatment of the problem. The analysis shows that the pinhole size that ...

We introduce an application of thermionic emission in a PMT photocathode. Because of the nonlinear dependence of thermionic emission on absorbed laser power, a conventional PMT is found to produce a virtual pinhole effect that rejects unfocused light at least as strongly as a physical pinhole. This virtual pinhole effect is exploited in a scanning transmission confocal microscope equipped with ...