February 25, 2010
| by Stephen Hopkins
Welcome to 3D Thursdays, class. This is an introductory lesson in 3D, which you’ve no doubt heard is taking over the video landscape this year. Along with the daily coverage of product introductions, announcements and news regarding 3D, we will be providing informational and other elements about 3D every Thursday on ElectronicHouse.com.
There will be quizzes. If everyone has their notebooks out and 3D glasses on, we’ll go ahead and get started. We’re going to start with a basic introduction of how 3D works, some basics about equipment, and a few history tidbits.
1.) What is 3D?
3D Imaging, classically known as Stereoscopy, “is any technique capable of recording three-dimensional visual information or creating the illusion of depth in an image.” Stereoscopy dates back nearly as far as photography itself and derives its name from the Stereoscope.
2.) How is the 3D effect created?
The visual effect of depth in an image (static or moving) is created using Stereopsis (from stereo meaning “solid,” and opsis meaning sight). Two slightly different images are projected on to each retina, and, due to the different locations of each eye in the head, the brain resolves the binocular disparities in the image to generate the perception of depth.
In 3D Film and 3D video in the home, the different image for each eye is projected in an interlaced fashion, relying on glasses (color key, passive polarized, or active shutter) to allow each eye see its prescribed image at the correct time.
3.) What are the different types of glasses and how do they work?
There are three types of glasses used to aid each eye in seeing the correct image at the correct time; Color Key (or anaglyph), Passively Polarized (either linear or circular), or Active Shutter.
Color Key, or anaglyph, glassed rely on the two separate images being keyed in two different colors. The glasses worn have a different color filter for each eye (usually red and blue) which allow only the correct color for that eye’s binocular image to pass to the retina. This is the method used in many 3D presentations from the 1950s into the 1980s, comic books, and even some recent 3D TV presentations. Color rendition and resolution suffer greatly.
Passively Polarized and Active Shutter glasses both rely on full-color and full-resolutions binocular images, so color rendition and resolution suffer far less than anaglyph presentations. With Passively Polarized glasses presentations, the light of each eye’s image is polarized at a different angle using an active polarizer in front of the projection lens. The glasses worn then have polarized lenses with each eye polarized at a different complementary angle, allowing only the light of each eye’s respective image to pass to the retina. This presentation method is most common in commercial theaters, theme park attractions, and professional/industrial applications.
Active shutter glasses work much in the same was as passively polarized glassed. Instead of relying on polarization of the image and lenses, the lenses themselves use active shutters (liquid crystal) that flip on and off to allow each eye to see the correct image in sequence. The timing of the shutters is synced using either radio (bluetooth or proprietary RF signals) or optical/visual cues from somewhere on the image screen or infrared emitters. This presentation method was used extensively for early IMAX 3D film presentation and will represent the vast majority home 3D implementations.
4.) Are there any systems that do not require glasses?
There are systems that do not require glasses, referred to as Autostereoscopic displays. These displays are limited in size, resolution, and require users to stand or sit at very specific viewing locations. These limitations have this technology being adapted mainly for 3D signage and advertising.
That’s all for today. Next week we’ll be diving deeper into 3D in the home, and specifically the technical and equipment requirements.
Stephen Hopkins is chief technology editor for EH Publishing. He writes product reviews, features, and focuses heavily on 3D TV, iPhone and iPad apps, and digital content.