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Transcript of Overhead Projector
- main component of the overhead projector is the base
- contains a clear glass top, an interior light, a small fan and a vent
- the fan on the back of the unit removes the heat that is produced by the light and out through the vent, this prevents the projector from overheating
- when the light is turned on the only light escaping is through the glass top, this illuminates the glass top and anything placed on top of it
- the clear plastic sheets let light shine through the sheet to project an image Adjustable Arm and Head:
- an adjustable arm and head is attached to the base of the projector
- head of the unit contains a mirror and two lenses on the front and side
- the mirror is positioned so that it can reflect light coming in through the bottom lens
- when the light in the base is turned on it projects the image off the mirror and onto screen Mirror Positioning:
- moving the arm up or down will affect both the focus and the size of the image projected
- the angle of the projector head allows the projected image to be moved as needed
- it needs a few moments after adjustment to get the projected image to focus on the screen Lights : Most overhead projectors use a high-powered halogen lamp that may consume up to 750 watts yet produces a fairly dim, yellow image.
- The light is an important part to the function of the head
- The light necessary for the lens to detect the transparencies and darker print Mirrors:
-The mirrors in the head of the unit work together to reflect light and project an image onto a screen
- The 1st mirror works to capture the light from the base of the projector. The light from the mirror is then reflected to the 2nd mirror
- The 2nd mirror reflects the light through a magnifying lens for a larger projection Magnifying Lens:
- First the mirrors have to reflect the light towards the screen, the image would be small without the magnifying lens
- The lens captures the image reflected by the mirror and shines it on the screen so that it is longer and more legible
- The clarity of the image depends on how close the lens is to the transparent sheet and how close the projector is to the screen Breaking It Down: How It Works: By Kiera Kaminski and Jenna Van Huisstede October 2012 Light Source Lens Mirror Surface P Disadvantages: - for a large classroom of people to see items clearly the projector must be at the right distance and angle
- overhead projector light bulbs are costly, and average cost of $300
- overheads are very large and bulky and can be difficult to move around to other classrooms
- outdated technology, today we have more advanced, better quality overhead projectors