11Pick up a handout.Pick up polarizing 3d glasses. Return them when class is over.22Lec. 28, Thursday, Dec. 2End Ch. 8, start Ch. 14, Holography• Chapter 8, Binocular vision– Why two eyes– Binocular disparity– Conveying depth in art– Stereo images5 Concept questions• Chapter 14, Holography – How to make a hologram– Clever observations about holograms– Integral hologram– White light hologram2We are here2We only did 20 of these slides today.233How do polarized 3-d glasses work?1. The two images are projected onto a screen. 2. The light passes through polarizing filters leaning 45 degrees to the left and 45 degrees to the right.3. The person wears polarizing glasses so each eye sees just one of the images. 4. The projection screenmust be special to preserve the polarization. 5. The effect is lost if the persons leans their head!344Stereo Photographytwo cameras make two images to reproduces binocular disparity4The three-d view looks “just right” when the cameras have the same spacing apart as your eyes. Is this answer a surprise? The spacing of eyes is about 6.5 cm or about 2 ½ inches.3555Special “lenticular” or “silver” screen that does not “scramble”polarizationDemo: we will look at some homemade 3D slides6What 3d technology was used in Avatar?1. RealD Cinema uses circular polarization. 2. The electric field direction is rotating either clockwise or counterclockwise. There are filters for circular polarization. This “works” if you tilt your head. 3. A lenticular (silver) screen is used to preserve polarization. 4. Alternate images are projected with different polarization. 48 frames per second is the total.47Cicularly polarized light has the electric field rotating clockwise or counterclockwise.xyzhttp://en.wikipedia.org/wiki/Circular_polarization8LCD “shutter” 3d glasses for games• The LCD panel is either “on” or “off” (clear or opaque)• Alternate sides are on and off. The left eye sees “even numbered” images and the right side sees “odd numbered” images. The glasses must have a battery and receive a synchronizing signal.59Ch. 8 Concept test 1Which method for determining depth does not work on the Moon:A. OverlayB. Previous knowledgeC.Binocular disparityD.Light and shadow E. Both C and D 10Ch. 8 Concept test 2Which drawing shows two-point perspective done correctly?ABCD611Ch. 8 Concept test 3Is this stereo pair done correctly?A. Yes B. NoLeft eye view Right eye view12Ch. 8 Concept test 3This drawing is very wrong about:A. HighlightsB. OverlayC. Contrast D. Perspective713Ch. 8 Concept test 4This drawing conveys depth mostly by:A. PerspectiveB. OverlayC. Light and shadowD. HighlightsE. Contrast 14Ch. 8 Concept test 5This drawing has incorrect:A. OverlayB. ContrastC. HighlightsD. Light and shadow E. Perspective81515Lec. 28, Thursday, Dec. 2End Ch. 8, start Ch. 14, Holography• Chapter 8, Binocular vision– Why two eyes– Binocular disparity– Conveying depth in art– Stereo imagesConcept questions• Chapter 14, Holography – How to make a hologram– Clever observations about holograms– Integral hologram– White light hologram15We are here1516HologramA hologram looks like a 3-D image. What is it really?A hologram is a photograph of an interference pattern (which is also called a diffraction pattern.)Example: two laser beams hitting a screen create an interference pattern of light and dark areas:917Clever observationOne laser beam (beam 1) falling on the recorded pattern will be scattered from the pattern in a way that reconstructs the missing beam 2. Do this first to record the pattern:18Then this happens with one beam falling on the pattern: The hologram recreates the “missing” light when one beam is shined on it.1019Second clever observationThis also works if beam 1 is a laser beam and beam 2 is laser light scattered off some object (coffee cup). Then the beam 2 that is recreated looks like light from that object (a coffee cup). 20The holographic image appears if the film is viewed from front or back (but some holograms are one-sided):1121Third clever observationThe holographic image is 3-dimensional. Why?When viewing the hologram, the left eye sees light scattered in the direction of the left eye and the right eye sees light scattered in the direction of the right eye, so the images seen by the two eyes are different. 22Fourth clever observationCut the hologram in half and you see the whole image, with some fine detail lost. Sounds like a great computer memory. Data is not lost if part of memory goes bad.1223Fifth clever observationLaser light is not always necessary for viewing. 24Integral hologramThese go 360 degrees around the object. 1. The object is rotated on a turntable. 2. The film is passed through the camera simultaneously so that different views are on different sections of the film.1325What do I see in the integral hologram?As you move around the curved film you see views from different directions. The image appears to rotate, or a dancer appears to dance. 26Technical details 1. Film has fine grain (0.0005 mm). The image has details on the scale of the wavelength of light. Ordinary film records details of 0.01 mm. 2. The silver bromide film coating is thicker so that the pattern is many wavelengths deep. 3. The objects can’t move during the picture-taking (except for integral holograms) 4. The laser beam must be expanded with lenses so that the light covers the