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Understanding 3D TV Technology

Understanding 3D TVs

For those who are less acquainted with home theater offerings in general, we can imagine how perplexing it is to experience the bevy of 3D televisions out there. Whatever happened to the days when TVs were all alike? Why are there different types of glasses accompanying these 3D screens? Can this TV work with other brands' AV equipment? If you find yourself asking similar questions along the way, then this guide is for you. Let us begin by providing you with a little insight on the two major 3D technology before we touch on the various pros and cons of owning a 3D set.  

The Active 3D Faction

Essentially, a large majority of so-called active 3D televisions utilize the alternate-frame sequencing methodology. In other words, the TV's onscreen images are transmitted to the viewer in alternate sequences. For example, a dedicate frame is designated for the left eye, while the subsequent frame is meant for the right eye. For this to work, active-shutter glasses are required to be worn by the user. These lenses are filled with liquid crystals which turn dark when a voltage is applied. For instance, the left lens is darkened when the right picture frame reaches the right eye, and vice versa for the left eye. These glasses also contain a receiver, which works in tandem with the TV's emitter to coordinate the shuttering lenses with the alternating frames. Each lens shutters on and off at about 50 or 60 times a second, which also explains why an active 3D TV needs to have a minimum of 120Hz (2 x 60Hz) refresh rate. Sony, Samsung and Panasonic are some of the main players in this group.


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The Passive 3D Camp

Unveiled this year, LG's passive Cinema 3D series is undoubtedly the biggest competitor to the active 3D TV troops since its inception. Based on its FPR (Film Patterned Retarder) technology, LG's latest suite of Cinema 3D televisions involve a special circular polarizing film applied unto the panel, designed to transmit simultaneous left and right eye images to the viewer. A pair of polarized lenses then filters the images accordingly. While this process may sound similar to their active-shutter rival, both technologies are actually quite different in the way a 3D picture is transmitted to the viewer.

Instead of transmitting one frame for each eye, a single frame is shared between both eyes. In other words, interlaced within each frame are left and right eye fields.This effectively halves the resolution for each eye as well, and also results in a "CRT effect" when viewed up close due to the visible horizontal lines. So how do the Cinema 3D televisions create a stereoscopic effect? To put it simply, each of these left and right eye fields actually consists of segmented odd and even "scans" respectively (see diagram below). The job of the polarized glasses, on the other hand, is to filter these scans such that the left eye only sees the left lines, and vice versa for the right eye. The brain then combines both fields to form a stereoscopic image.