CHAPTER 4. HOW PROJECTORS WORK
PART 1.
We enjoy seeing movies in the theatre and also usea projector daily in our classrooms but how
does this technology help us see larger than lifecharacters and our favourite movies, pictures,
books with high details and bright colours on bigscreens.
The projector is a device that uses lenses, computerdata, colour wheels and many other
gadgets to produce a beam of light into what we wantto see and project it on a big white
screen. But it was not that easy in earlier timesand the design made by Charles Francis
Jenkins in 1894 was not at all close to what we havenow. The projector made by him worked by
blasting light through celluloid film and mixing soundand images together with technology very
primitive. But now projectors are very complex usingmodern technology.
There are many different types of the projector but3 types are commonly used-
The first type is LCD- Liquid crystal display, whichuses polarized light to show the image.
Polarized light is a beam of white light which bypassing through polarized glasses shows a
particular colour and by mixing all such colours theimage is projected.
Polarized light is white light beam made of differentcolours vibrating at different angles so when
glasses of particular angles are used known as polarizedglasses the colour vibrating at that
angle passes by and other colours are blocked. Ina similar way, there are glasses for mainly
three primary colours Red, Green, Blue along witha prism, a lamp and a filter to create our
image and lens through which the image is projected.
In the LCD Projector there are mainly 3 liquid crystal
panels. The beam of light displays image on first
panels, this image is then split into the primarycolours
by a series of dichroic mirrors. These primary colours
are then passed through the 2nd panel which decided
which part to be reflected and which part to be passed
through. Each panel shines different colours red,green,
blue and sends them to the final LCD panel which
decides how much to bend a light depending on the
electrical current.
Finally, the image of red, green, blue colour is converted
into completed by the third panel and the image ismagnified by a lens and projected on the
screen.