Overhead projector facts for kids
An overhead projector (OHP) is a cool device that helps you show pictures or information to a group of people. Imagine you have a drawing or some notes on a clear plastic sheet. You put this sheet on the OHP, and it shines a bright light through it. This light then projects a much bigger version of your drawing onto a screen or wall!
For a long time, OHPs were super popular in classrooms. Teachers used them to show lessons, diagrams, or notes to all the students at once. They could even write on the clear plastic sheet while projecting, which was like magic!
The OHP has a special flat surface where you place your clear sheets. Inside, there's a strong light bulb and a fan. The fan is important because it keeps the machine from getting too hot, especially when it's used for a long time.
Today, you might not see as many OHPs in schools or meeting rooms. Newer tools like document cameras and interactive whiteboards are often used instead. These new devices can project videos and files directly from a computer, which is very handy.
Contents
How Overhead Projectors Were Used
Overhead projectors were mainly used for showing presentations. They were great for displaying notes, drawings, or special transparent sheets called "transparencies."
Here's how they worked:
- You would create your notes or pictures on a clear plastic sheet.
- You'd place this sheet on the projector's glass surface.
- A bright light inside the OHP would shine through the sheet.
- Lenses in the projector would then focus this light.
- Finally, the image would appear much larger on a screen or wall.
Teachers loved them because they could write or draw on the transparency while talking. This made lessons more interactive and fun.
The History of Overhead Projectors
The idea of projecting images has been around for a long time! Before the OHP, there were machines called "magic lanterns." These were early projectors that showed images from glass slides.
Early Inventions
The first known overhead projection machine was created in 1853. A French scientist named Edmund Becquerel developed it. Later, in 1866, another person named Jules Duboscq used a similar device.
Growing Popularity
Overhead projectors became very important during World War II. The U.S. military used them a lot for training soldiers. After the war, schools started using them too.
By the late 1950s and early 1960s, OHPs were widely used in both schools and businesses. They became a common tool for teaching and giving presentations. As more people wanted OHPs in the 1950s, a company called Bruhl Industries was started in 1953. This company became one of the biggest makers of overhead projectors.
Images for kids
-
Mirror and lens
-
A worker loads documents into an Ozalid printer.
See also
In Spanish: Retroproyector para niños
