Civil Rights
Movements, leaders, victories and the continuing fight for equality.
q2K BHP
Black History Portal
THE BHP WIRE —
HIDDEN TRUTHS
What's New!
Explore the people, places, events, achievements, struggles and stories that shaped our journey.
Movements, leaders, victories and the continuing fight for equality.
Innovation, patents, science, technology and world-changing contributions.
Pioneers, champions, Negro Leagues, records, activism and excellence.
Meet the people whose lives, choices and achievements shaped the journey.
Black towns, communities, institutions and places where history happened.
Moments that changed communities, movements, institutions and the nation.
In August 1908, a white mob attacked Springfield, Illinois’s Black community, destroying homes and businesses and lynching two Black men. National outrage over the violence helped spur the movement that created the NAACP the following year.
MORE →Reflects the personal views, recollections, and perspective of the author, Mike Davis.
This is a personal recollection on the Move fire on May 13, 1985
 | This article needs more citations. (December 2009) |
A transparency, also known variously as a viewfoil or foil (from the French word "feuille" or sheet), or viewgraph, is a thin sheet of transparent flexible material, typically polyester (historically cellulose acetate), onto which figures can be drawn. These are then placed on an overhead projector for display to an audience. Many companies and small organizations use a system of projectors and transparencies in meetings and other groupings of people, though this system has been largely replaced by video projectors and interactive whiteboards.
Transparencies can be printed using a variety of technologies. In the 1960s and 70s the GAF OZALID "projecto-viewfoil" used a diazo process to make a clear sheet framed in cardboard and protected by a rice paper cover.[1] In the 1980s, laser printers or copiers could make foil sheets using standard xerographic processes. Specialist transparencies are available for use with laser printers that are better able to handle the high temperatures present in the fuser unit. For inkjet printers, coated transparencies are available that can absorb and hold the liquid ink—although care must be taken to avoid excessive exposure to moisture, which can cause the transparency to become cloudy; they must also be loaded correctly into the printer as they are only usually coated on one side.
Uses for transparencies are as varied as the organizations that use them.
Certain classes, such as those associated with mathematics or history and geography use transparencies to illustrate a point or problem. Until the advent of LaTeX, math classes in particular used rolls of acetate to illustrate sufficiently long problems and to display mathematical symbols missing from common computer keyboards.
Aerospace companies, like Boeing and Beechcraft, used transparencies for years in management meetings in order to brief engineers and relevant personnel about new aircraft designs and changes to existing designs, as well as bring up illustrated problems.[2]
Some churches and other religious organizations used them to show song lyrics, sermon outlines, and illustrate certain topics such as Old Testament battles and Jewish artifacts during worship services, as well as outline business meetings.
|
Many overhead projectors are used with a flat-panel LCD which, when used this way, is referred to as a spatial light modulator or SLM. Data projectors are often based on some form of SLM in a projection path. An LCD is a transmissive SLM, whereas other technologies such as Texas Instrument's DLP are reflective SLMs. Not all projectors use SLMs (e.g., some use devices that produce their own light rather than function as transparencies). An example of non-SLM system are organic light-emitting diodes (OLEDs).
| National | |
|---|---|
| Other | |
Source: Wikipedia. Article content is retrieved live through the MediaWiki API.
A transparency, also known variously as a viewfoil or foil (from the French word "feuille" or sheet), or viewgraph, is a thin sheet of transparent flexible material, typically polyester (historically cellulose acetate), onto which figures can be drawn. These are then placed on an overhead projector for display to an audience. Many companies and small organizations use a system of projectors and transparencies in meetings and other groupings of people, though this system has been largely replaced by video projectors and interactive whiteboards.
A Projection panel (also called overhead display or LCD panel) is a device that, although no longer in production, was used as a data projector is today. It works with an overhead projector. The panel consists of a translucent LCD, and a fan to keep it cool. The projection panel sits on the bed of the overhead projector, and acts like a piece of transparency. The panels have a VGA input, and sometimes Composite (RCA) and S-Video input. Later models have remotes, with functions such as 'freeze' which lets you freeze the image, useful for when you want to leave something on the screen whilst you do other things. Earlier models only had 640x480 resolution, while newer ones had up to SVGA resolution. Proxima, one maker of the panels, included a magic wand and sensor, which worked with the sensor detecting where you put the wand, to create and interactive effect, the equivalent of today's smart boards. Although they are not produced anymore, used panels can be purchased for a fraction of the price of a data projector. The panels are quite dim, as they do not let a great deal of light through, so brightness can be a problem, even with a powerful overhead projector.
In photography, the terms reversal film, slide film, positive film, and transparency film describe a type of photographic film that produces a positive image on a transparent film base. In place of negatives and printed photographs, reversal film produces diapositive photographs, known as diafilm and dia images. A diapositive slide is a mounted frame of transparency film intended for large-format projection of the image onto a screen by a slide projector. Such large-format projection permits many spectators to view the diapositive image at one time. The usual transparency-film format is the 35 mm slide, wherein one frame of film is mounted into a 2 in. ×2 in. square made either of cardboard or of a plastic material. Reversal film is produced in format sizes that range from 35 mm to roll film to 8 in. ×10 in. sheet film. Moreover, specialized photographic processing laboratories produce diapositive slides from digital-camera images in formats such as the JPEG, from computer-generated presentation graphics, and from images of physical materials such as fingerprints, microscopic evidence, paper documents, astronomic images, etc. Reversal film also is used as motion picture film in the 16 mm, Super 8 and 8 mm cine film formats, and produces a positive-image film that was originated in the cinematographic camera. In terms of film-production costs, such a cinematographic application of reversal film is more cost-effective than filming with negative film that then must be developed into a positive-image film for projection in a cinema.
A spatial light modulator (SLM) is a device that can control the intensity, phase, or polarization of light in a spatially varying manner. A simple example is an overhead projector transparency. Usually when the term SLM is used, it means that the transparency can be controlled by a computer. SLMs are primarily marketed for image projection, displays devices, and maskless lithography. SLMs are also used in optical computing and holographic optical tweezers. Usually, an SLM modulates the intensity of the light beam. However, it is also possible to produce devices that modulate the phase of the beam or both the intensity and the phase simultaneously. It is also possible to produce devices that modulate the polarization of the beam, and modulate the polarization, phase, and intensity simultaneously. SLMs are used extensively in holographic data storage setups to encode information into a laser beam similarly to the way a transparency does for an overhead projector. They can also be used as part of a holographic display technology. In the 1980s, large SLMs were placed on overhead projectors to project computer monitor contents to the screen. Since then, more modern projectors have been developed where the SLM is built inside the projector. These are commonly used in meetings for presentations. Liquid crystal SLMs can help solve problems related to laser microparticle manipulation. In this case spiral beam parameters can be changed dynamically.
Before the 1921 destruction of Tulsa’s Greenwood District, Black residents had created a remarkable center of business and community life. The district included stores, professional offices, entertainment venues and homes owned by Black citizens. Understanding Greenwood means learning what was built—not only what was burned.
MORE →Mae Jemison, aboard Space Shuttle Endeavour in 1992.
