Physics behind 3D Movies Ng Boon Hian
Case Study – 3D movies With 3D viewing technology offered in cinemas, many people are fast to snap up on the tickets to 3D movies. I watched Alice in Wonderland in 3D version at Shaw Theatre recently and wondered what was the science behind the 3D glasses.
How do our eyes work • Our eyes project a 3D image in the brain by seeing things from two different viewpoints as noted by the gap between our eyes and these 2 2D images are formed in the brain into 1 3D image. Thus, 3D images are formed and everything in the real world is 3D.
2D Movies 2D movies work on a film being projected onto the screen. Everything is on the screen and in 2D. The light is unpolarized.
Polarized light and Unpolarized ight • Light is an electromagnetic wave • Electromagnetic waves consist of electric and magnetic component • Electric component (electric force field) moves up and down as the electromagnetic waves forward
Unpolarized light • From Sun, bulbs, candles • No fixed plant of oscillation • Yellow plane arrow changes angles but keeps direction of light • Random changes in direction of light 3D animation
Polarized Light • Filtered Light • Fixed plane of oscillation • Half of the intensity of unpolarized light
Unpolarized VS Polarized • For unpolarized light, no matter how the arrow turns, electric forces are always perpendicular to ray direction Polarized light Unpolarized light
Polarizers • Filters out the unpolarized light into single light planes • Have lines aligned in 1 direction and only allow 1 plane of light to pass • Circular polarization and linear polarization
Circular polarizer and linear polarizer • Circular polarizer used for 3D glasses
Circular polarizer and linear polarizer • Circular polarizer is just a quarter wave plate in addition to the linear polarizer • Linear polarized 3D glasses will work with all the old stereo projectors, StereoJet prints, and modern projector systems with linear polarizers attached • Circular polarized 3D glasses are specifically for the StereoGraphics Z-Screen and some 3-D digital projection systems.
Circular polarizer and linear polarizer • Not much difference as both saturates colors and eliminates reflections from water and windows for cameras • Circular polarizers are more expensive but can eliminate possible metering errors while linear polarizers are unable to
Filters to transform unpolarized light to polarized light • Polaroid filter • Enables only 1 polarization of light to pass through.
3D Movies • Eyes are two inches apart, two different angles on viewing the same things creates a 3D image • 3D movies trick the brain by projecting two 2D images separately to the two eyes and recreate a 3D image in the brain
3D Movies • 3D movies not viewed with the glasses are very fuzzy and eye-straining to look at • The same scene is projected simultaneously from two sources • Previous 3D movies used colour as filter but polarization is used
Colour and Polarization • Colour 3D uses contrast of colours • An anaglyph image is formed • Each lens is made up of a chromatically different colour – blue and red • Colour used to provide separation • Red part allows blue light to enter while blue part allows red light to enter
Colour as filter • A severe disadvantage is that film cannot have much colour as colour is used as filter in this case Stereo Monochrome image
Polarization • Two synchronised projectors project two respective views, each with a different polarization • Each side of the glasses allows 1 plane of light to enter
3D Movies • Due to the 3D effect, viewers can feel the thrill of being in the movie themselves and get really close to the characters
Bites • 3D glasses if not cleaned properly can pass on eye infections to others • Can cause headaches and blurred vision • Forces viewers to focus on things in the foreground (which causes eyes to converge) and distance (which causes them to separate) simultaneously • Vergence accomodation conflict
Build your own 3D glasses activity • Cardboard • Scissors • Tape • Red and Blue acetate (Available from art store)
Build your own 3D glasses activity • Trace a pattern on the paper of the three parts of spec mainly the two sides and a middle portion • Place them on the cardboard and cut out the shapes • Cut eyeholes • Tape the blue and red acetate separately on the two eyeholes and you have a 3D glasses
Other Facts • 3D glasses used will not produce a 3D effect on home TV as light is unpolarized
Thank you! • http://www.colorado.edu/physics/2000/polarization/polarizationII.html • http://www.physicsclassroom.com/class/light/U12l1e.cfm • http://science.hq.nasa.gov/kids/imagers/ems/waves2.html • http://library.thinkquest.org/C006027/html-ver/op-polar.html • www.wikipedia.com • www.google.com • http://www.3dglassesonline.com/how-do-3d-glasses-work/ • http://www.howstuffworks.com/3dgraphics.htm • http://www.bobatkins.com/photography/technical/polarizers.html • http://www.berezin.com/3D/3dglasses.htm • http://www.articlesnatch.com/Article/Difference-Between-2d-And-3d-Animation/921882 • http://stereo.gsfc.nasa.gov/classroom/glasses.shtml • http://wiki.answers.com/Q/Why_do_Real_D_3D_glasses_work_in_the_cinema_but_they_wont_work_with_any_other_3D_images_at_home_Are_there_any_images_that_do_work