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

Revision as of 13:50, 5 July 2007

The opaque projector, epidioscope, epidiascope or episcope is a predecessor to the overhead projector. It displays opaque materials by shining a bright lamp, often limelight, onto the object from above. A system of mirrors, prisms and/or imaging 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".

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. In the early and middle parts of the 20th century, low-cost opaque projectors were produced and marketed as toys for children.

In educational settings, the specific role of the opaque projector has been superseded by the presenter, a lighted table with a fixed video camera above it. The image from the camera is displayed using a separate projector. The desktop presenter unit is sometimes called an opaque projector.

External links

Episcopes and epidiascopes, photographs of a collection.
Historic Ross Epidiascope
Another description of the Braun Paxiscope unit.

de:Episkop ja:エピスコープ pl:Episkop uk:Епіскоп

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-{{Wikify|date=February 2007}}
+The '''opaque projector''', '''epidioscope''', '''epidiascope''' or '''episcope''' is a predecessor to the [[overhead projector]]. It displays opaque materials by shining a bright lamp, often [[limelight]], 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".
-The so-called '''one-way glass''', '''two-way mirror''' or '''mirrored glass''' is a technique that exploits the use of an enclosed darkened room and an enclosed well-lit room separated by a pane of highly reflective glass.  This is not an ordinary mirror, but something that only appears to be a mirror.  This glass is coated with a very thin almost transparent layer of metal to enhance its reflective nature.  The result is what appears to be a mirror from one side, and slightly tinted glass from the other.  A person on the brightly lit room has difficulty seeing into the darkened room, through what appears to be a mirror.
+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. In the early and middle parts of the 20th century, low-cost opaque projectors were produced and marketed as toys for children.
-This is sometimes used for providing security through covert viewing of public spaces like stores from private offices, for protection of covert cameras, and for police interrogation rooms where witnesses can view the proceedings.  It has even been used by nefarious landlords to spy on tenants most private spaces. But, it can be detected by the wary.
+In educational settings, the specific role of the opaque projector has been superseded by the ''presenter'', a lighted table with a fixed [[video camera]] above it.  The image from the camera is displayed using a separate projector.  The desktop presenter unit is sometimes called an opaque projector.
-Other 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==
+* [[Projector]] for a directory of projector types.
-To take full advantage of the partially mirrored surface to appear like a mirror, one side should be brightly lit, to camouflage any hint of light coming through the glass from the darkened side.  The darkened room is only completely secure or non-viewable, when it is completely dark there.  Sometimes a darkened curtain or an airlock type vestibule with double doors are used on that side to keep out light.  Careful control of the lighting must also be used.  Detectives or witnesses on the darkened side should be cautioned not to light a cigarette when close to the glass.  Wily criminals in the examination room, have been known to put their eyes near the glass and cup their hands around their face and peer through.  A flashlight held against the glass can also be used to peer through and illuminate the opposite side.
+==External links==
-Office workers who work in offices with reflective glass on the outside, should know that their activities, not visible during the daytime from the outside, are quite visible at night in their well-lit areas.
+* [http://www.luikerwaal.com/newframe_uk.htm?/epidia_uk.htm Episcopes and epidiascopes], photographs of a collection.
+* [http://www.curzon.org.uk/collection/Epidiascope.html Historic Ross Epidiascope]
+* [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:Architecture]]
+[[Category:Projectors]]
+[[de:Episkop]]
+[[ja:エピスコープ]]
+[[pl:Episkop]]
+[[uk:Епіскоп]]