Physics behind 3D Movies

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Physics behind 3D Movies - PowerPoint PPT Presentation

Physics behind 3D Movies. 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.

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Physics behind 3D Movies

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.
• 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.
• 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.
• Image must be refreshed fast enough to avoid flicker
• Synchronization errors, and occasional ghost images.