Difference between revisions of "AY Honors/Optics/Answer Key"

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(Deleted a rewording of sumary - fact that the brighter room can be seen from the other side)
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The '''opaque projector''', '''epidioscope''', '''epidiascope''' or '''episcope''' is a device which displays opaque materials by shining a bright lamp onto the object from above. A system of mirrors, prisms and/or imaging [[Lens (optics)|lenses]] is used to focus an image of the material onto a viewing screen. Because they must project the reflected light, opaque projectors require brighter bulbs and larger lenses than overhead projectors. Care must be taken that the materials are not damaged by the heat generated by the light source. Opaque projectors are not as common as the modern "overhead".
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A '''two-way mirror''', also called a  '''one-way mirror''', is a pane of glass with a partially reflective, partially transparent layer, used with a darkened room on one side and a well-lit room on the other, allowing those in the darkened room to see into the lighted room but not vice versa.
  
Opaque projectors are typically used to project images of book pages, drawings, mineral specimens, leaves, etc. They have been produced and marketed as artists’ enlargement tools to allow images to be transferred to surfaces such as prepared canvas, or for lectures and discourses.  
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==Design==
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The glass is coated with (or in some cases encases a layer of) a very thin almost [[transparent]] layer of metal (generally [[aluminum]]) to enhance its reflective nature. The result is what appears to be a mirror from one side, and tinted glass from the other. A viewer in the brightly lit area has difficulty seeing into the darkened room, through what appears to be a mirror.
  
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To take full advantage of the partially mirrored surface, the target side should be brightly lit, to obscure any hint of light coming through the glass from the viewer's side. The darkened room is only completely obscured when it is in complete darkness. Sometimes a darkened curtain or a double door type vestibule is used to keep the viewers side darkened.
  
==See also==
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A [[flashlight]] held against the glass can be used to assist peering through and illuminate the darkened viewers side.
* [[Projector]] for a directory of projector types.
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==Uses==
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Two-way mirrors are used for:
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* providing [[security]], through covert viewing, of public spaces
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* for the protection of covert [[camera]]s
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* for some [[police]] [[interrogation]] rooms
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[[Image:Teleprompter schematic.svg|right|350px|thumb|One-Way Glass (4) used to reflect a Script]]
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* The use of one-way glass is also apparent in the [[broadcast]] [[television]] where persons read from a '[[script]]' while seemingly looking directly at the Camera. This effect is achieved where the Camera is the viewer looking through the glass, upon which the 'script' is also reflected for the subject to read.  
  
==External links==
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* Techniques of camouflage can also be used with ordinary glass, for special effects such as [[Pepper's ghost]], which projects the image of a person from one room to another as an apparition, as used in Anaheim California's [[Disneyland]] exhibit "[[The Haunted Mansion]]". The effect can also be produced by a finely perforated white metal screen that is difficult to see through in one direction, depending on the relative light levels of the separated spaces.
  
* [http://www.luikerwaal.com/newframe_uk.htm?/epidia_uk.htm Episcopes and epidiascopes], photographs of a collection.
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==See also==
* [http://www.curzon.org.uk/collection/Epidiascope.html Historic Ross Epidiascope]
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*[[Mirror]]
* [http://www.firstcall-photographic.co.uk/pp/Projectors/35mm_Projectors_and_Epidiascopes/Braun_Paxiscope_XL_Epidiascope.html Another description] of the Braun Paxiscope unit.
 
  
[[Category:Projectors]]
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{{DEFAULTSORT:One-way Glass}}
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[[Category:Architecture]]
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[[Category:Security]]
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[[Category:Mirrors]]
  
[[de:Episkop]]
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[[pl:Lustro fenickie]]
[[lb:Episkop]]
 
[[ja:エピスコープ]]
 
[[pl:Episkop]]
 
[[uk:Епіскоп]]
 

Revision as of 14:33, 26 November 2007

A two-way mirror, also called a one-way mirror, is a pane of glass with a partially reflective, partially transparent layer, used with a darkened room on one side and a well-lit room on the other, allowing those in the darkened room to see into the lighted room but not vice versa.

Design

The glass is coated with (or in some cases encases a layer of) a very thin almost transparent layer of metal (generally aluminum) to enhance its reflective nature. The result is what appears to be a mirror from one side, and tinted glass from the other. A viewer in the brightly lit area has difficulty seeing into the darkened room, through what appears to be a mirror.

To take full advantage of the partially mirrored surface, the target side should be brightly lit, to obscure any hint of light coming through the glass from the viewer's side. The darkened room is only completely obscured when it is in complete darkness. Sometimes a darkened curtain or a double door type vestibule is used to keep the viewers side darkened.

A flashlight held against the glass can be used to assist peering through and illuminate the darkened viewers side.

Uses

Two-way mirrors are used for:

One-Way Glass (4) used to reflect a Script
  • The use of one-way glass is also apparent in the broadcast television where persons read from a 'script' while seemingly looking directly at the Camera. This effect is achieved where the Camera is the viewer looking through the glass, upon which the 'script' is also reflected for the subject to read.
  • Techniques of camouflage can also be used with ordinary glass, for special effects such as Pepper's ghost, which projects the image of a person from one room to another as an apparition, as used in Anaheim California's Disneyland exhibit "The Haunted Mansion". The effect can also be produced by a finely perforated white metal screen that is difficult to see through in one direction, depending on the relative light levels of the separated spaces.

See also

pl:Lustro fenickie