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
Existing 3D displays and technologies • Color Filter glasses (used in some modern 3D movies) • Polarizing glasses ( used in some modern 3D movies) • Shutter glasses • Separate display for each eye ( used in HMDs) • 3DTV
How does the 3-D effect work? • Our ability to see in three dimensions (also referred to as Stereo vision) comes from each our eyes seeing a slightly different view of the world. Our brain integrates these two images into one three dimensional picture. • A key element in producing 3D vision is parallax. Parallax is the horizontal distance between corresponding left and right image points.
Color Filter Glasses • Each eye has a different color filter in front of them • The brain integrates the two images together and combined image is 3 dimensional. • Common color filter combinations include red and green, and blue and green.
Advantages and Disadvantages • 3D material can be stored to any standard video media, and viewed with normal display devices • Glasses are inexpensive • Few possible color combinations causes images not of exceptional quality • Causes colors in the image to be compromised, causing objects coming out screen to appear gray.
Polarizing Glasses • This method is used with projection displays when 3D material needs to be displayed. • Glasses consist of 2 polarizing lens which have their polarization direction to be 90 degrees different. • The material which has to be shown is typically projected using 2 projectors,where each have polarizing lenses in front of them.
Advantage and Disadvantage • Pictures can be in full color • Glasses are still inexpensive • Projection surface must be specially made so as not to affect the polarization.
LCD Shutter Glass Method • Alternates images rapidly on the monitor screen for left and right images. • Viewer looks at screen through the shuttering eyewear. • Signal is a normal signal that has been specially recorded with the left and right images stored on the even and odd fields of the video signal.
Disadvantages • Image must be refreshed fast enough to avoid flicker • Synchronization errors, and occasional ghost images.
Head Mount Displays • Helmet like device where there are two separate displays installed. • Used in many high-end virtual reality systems, they deliver very realistic 3D graphics, and allow the viewer to turn their heads, giving the impression of a 3D world. • The only disadvantage to HMD devices is the extremely high price.
Hines Lab 3D TV • This device is built around a single liquid crystal panel, on which multiple images are arranged and projected to a rear-projection screen where they form the 3-D image. Stereo and motion parallax allow the viewer to confirm the position and roundness of objects as the observer changes positions.
Advantages of 3D TV • The signal can be broadcast by a single television station over air ways or cable • Can be used as a computer display, or for video games • Can be projected to virtually any screen size • Projects all images simultaneously, in full color, and creates no flicker • Can be produced economically, because it uses a single LC panel and conventional optics.