Managing effective use of overhead projectors (OTP/OHPs) in education
B.Choose
one module that you think is difficult for you and write to your lecturer
briefly the things that you need to know.
ANNSWER
Managing effective use of overhead
projectors (OTP/OHPs) in education
An overhead
projector (OHP), like a film or slide projector, uses light to project an
enlarged image on a screen. In the overhead projector, the source of the image
is a page-sized sheet of transparent plastic film (also known as 'foils') with
the image to be projected either printed or hand-written/drawn. These are
placed on the glass surface of the projector, which has a light source below it
and a projecting mirror and lens assembly above it (hence, 'overhead'). They
were widely used in education and business before the advent of computer-based
projection
Overhead projectors were widely used in education
and business before the advent of computer-based projection
Educational
uses of the overhead projector and its various strengths and weaknesses. Basic
guidelines for using the overhead projector effectively are then offered, which
include ways to avoid some common problems. Finally, detailed guidelines for
designing and producing overhead projector software are provided which cover
the following topics:
(1) The two basic forms of overhead projector
software the continuous roll and the single transparency--and their respective
(2) Basic principles for designing overhead
projector transparencies;
(3)
Producing the transparencies by hand, with typewriter, from opaque originals,
or using a computer-based system; and
(4) Display techniques such as use of
progressive disclosure, overlays, and animation. An annotated list of two items
recommended for further reading is included. (MES)
The overhead projector facilitates an easy low-cost
interactive environment for educators. Teaching materials can be pre-printed on
plastic sheets, upon which the educator can directly write using a
non-permanent, washable color marking pen. This saves time, since the
transparency can be pre-printed and used repetitively, rather than having
materials written manually before each class.
The overhead is typically placed at a comfortable
writing height for the educator and allows the educator to face the class,
facilitating better communication between the students and teacher. The
enlarging features of the projector allow the educator to write in a
comfortable small script in a natural writing position rather than writing in
an overly large script on a blackboard and having to constantly hold their arm
out in midair to write on the blackboard.
When the transparency sheet is full of written or
drawn material, it can simply be replaced with a new, fresh sheet with more
pre-printed material, again saving class time vs a blackboard that would need
to be erased and teaching materials rewritten by the educator. Following the
class period, the transparencies are easily restored to their original unused
state by washing off with soap and water.
LCD overhead displays[
In the early 1980s–1990s, overhead projectors were
used as part of a classroom computer display/projection system. A
liquid-crystal panel mounted in a plastic frame was placed on top of the
overhead projector and connected to the video output of the computer, often
splitting off the normal monitor output. A cooling fan in the frame of the LCD
panel would blow cooling air across the LCD to prevent overheating that would
fog the image.
The first of these LCD panels were monochrome-only,
and could display NTSC video output such as from an Apple II computer or VCR. In the late 1980s color
models became available, capable of "thousands" of colors (16-bit
color), for the color Macintosh and VGA PCs.
The displays were never particularly fast to refresh or update, resulting in
the smearing of fast-moving images, but it was acceptable when nothing else was
available.
The Do-It-Yourself community has started using this
idea to make low-cost home theater projectors. By removing the casing and
backlight assembly of a common LCD monitor, one can use the exposed LCD screen
in conjunction with the overhead projector to project the contents of the LCD
screen to the wall at a much lower cost than with standard LCD projectors. Due
to the mirroring of the image in the head of the overhead projector, the image
on the wall is "re-flipped" to where it would be if one was looking
at the LCD screen normally.
verhead projectors were once a common fixture
in most classrooms and business conference rooms in the United
States, but in 2000s they were slowly being replaced by document cameras, dedicated computer projection systems
and interactive
whiteboards. Such
systems allow the presenter to project video directly from a computer file,
typically produced using software such as Microsoft
PowerPoint and LibreOffice. Such
presentations can also include animations, interactive components, or even
video clips, with ease of paging between slides. The relatively expensive
printing or photocopying of color transparencies is eliminated.
The primary reason for this
gradual replacement is the deeply ingrained use of computing technology in
modern society and the inability of overheads to easily support the features
that modern users demand. While an overhead can display static images fairly
well, it performs poorly at displaying moving images. The LCD video display
panels that were once used as an add-on to an overhead projector have become obsolete,
with that combination of display technology and projection optics now optimally
integrated into a modern video projector.
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