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Cathode Ray Tube Displays
Published in John G. Webster, Halit Eren, Measurement, Instrumentation, and Sensors Handbook, 2017
Color has been a part of the CRT world since the early 1950s. A sound understanding of human color perception is important for a detailed understanding of color in CRTs. Readers interested in an excellent comprehensive treatment of color science should refer to Wyszecki and Stiles [21] or Robertson and Fisher [22] for a brief overview. The most common method of introducing color to the CRT is the three-gun shadow mask technique. The shadow mask is a metal grid of many tiny apertures held in place immediately before the phosphor screen. The phosphor screen is an array of three different phosphor subpixels. Three electron guns are placed closely together in the neck of the tube, one gun for each one of the primary colors (red, green, and blue). The guns make a small angle with respect to each other. The shadow mask and beams are aligned so that each beam falls on the appropriate phosphor dot. The dots are placed closely together so the eye spatially integrates the subpixels into a continuous blend of color. There are two common configurations: delta and in-line. Delta, the traditional method, arranges the electron guns and the phosphor dots in a triad. This requires a shadow mask consisting of a grid of circular apertures. More recently, Sony introduced the Trinitron™ design. In the Trinitron tube the guns are placed in line, the shadow mask consists of vertical slots, and the phosphors are in vertical stripes. The design offers improved vertical resolution and is easier to converge, but the mask is slightly more difficult to support and is subject to thermal stress problems.
P
Published in Splinter Robert, Illustrated Encyclopedia of Applied and Engineering Physics, 2017
[biomedical, general, geophysics] Phase in “shadow” pattern created by an opaque object irradiated from behind. The source can be a particle source or emit electromagnetic radiation. The three phases recognized are umbra, penumbra, and antumbra. During a penumbra only a portion (edge) of an emission source is obscured by the object, casting a shadow resembling a finger-nail clipping, as seen during the onset of a total eclipse of the Sun or generally a partial eclipse. The umbra represents a total blackout of the source on a projected surface, or when observed straight on (Note: Not advisable during the observation of a solar eclipse, since when the Sun peaks back out the radiance can literally be blinding.) and the antumbra has light passing around the object. Note that for a point source, only the umbra is produced. In biomedical applications, this applies to radiation therapy, where the penumbra represents the biological space in the periphery of the spot irradiation location, and is generally defined as the tissue volume receiving only a partial dose, between 80% and 20% of the therapeutically intended isodose (see Figure P.32).
Principles of Radiation
Published in Don E. Bray, Roderic K. Stanley, Nondestructive Evaluation, 2018
Don E. Bray, Roderic K. Stanley
Earlier discussion on the geometric unsharpness indicated that greater distances from the source to the object would increase the sharpness of the image. This is because at larger distances, the width of the source becomes smaller compared to the source to object distance and the size of the shadow off of the edges is decreased. Increasing the distance from the source to the test sample also has the positive effect of decreasing the amount of secondary scatter due to fact that the circumferential energy front of the radiation becomes increasingly flat at larger distances from the source, thus approaching a narrow-beam configuration.
Shadow play
Published in Spatial Cognition & Computation, 2018
The visual properties of shadows create opportunities for visual jokes, jokes that at the same time illuminate the visual properties and make you see the world differently. Size is one. The size of a shadow depends on the distances between the light source, the caster, and the surface on which the shadow is projected. And so we can have a photograph of a shadow with an enormous hand, index finger outstretched to hold up a woman; in another, a woman grasping the index finger of a shadow hand to hold herself up off the ground (http://s630.photobucket.com/user/j4jokes12/media/funny/funny2/funnypictures4078.jpg.html); in a third, an enormous shadow of a hand, index finger and thumb together grasping the back of the shirt of a woman to lift her off the ground (http://s630.photobucket.com/user/j4jokes12/media/funny/funny2/funnypictures4077.jpg.html). In these as in some previous examples, the shadows are personified as well.
Condition assessment of ship structure using robot assisted 3D-reconstruction
Published in Ship Technology Research, 2021
Faisal Mehmood Shah, Tomaso Gaggero, Marco Gaiotti, Cesare Mario Rizzo
A shadow appears when an object comes completely or partially directly in front of the source of illumination. Shadow types can be categorized into two modules: self-shadow and cast-shadow. A self-shadow shows up when the segment of an object is not illuminated by directed light source whereas a cast shadow appears when segment of an object is directed in direction of light. Shadow detection and removal are very challenging tasks in reconstruction process. In the context of ship surveys, shadows are particularly hazardous because they can hide defects in the structures.
A method of using image-view pairs to represent complex 3D objects
Published in Cogent Engineering, 2018
Lihong Luo, Jianqing Mo, Xian Yang
A shadow is created when an object blocks light, creating a silhouette of the object on the opposite wall or floor. An IVP model has no shape but has corresponding images matching every light direction. Therefore, given the direction of the light, we can process the matching image, including resizing, binarization, and edge cleaning, to acquire the shadow image. Finally, we can apply the shadow image as a texture on the object on which the shadow appears.