How to realize 3D? Analysis of the principle of 3D TV stereoscopic imaging

3D stereo imaging technology is not a new thing. In terms of time, 3D stereo imaging technology has appeared as early as the middle of the last century, which is longer than the current mainstream flat-panel display technologies such as LCD and plasma.

As the first decade of the 21st century came to an end, the flat-panel home appliance industry, without much warning, began to enter the "3D stereo" trend. Starting from the CES exhibition in the United States in early 2010, various home appliance brands have launched TVs with 3D stereo display functions, including mainstream LCD TVs and plasma TVs. The sizes of 3D products have basically covered the mainstream and complete range from 42 inches to a maximum of 150 inches. The prelude to the advent of the 3D TV era has begun to slowly start.

However, unlike the 3D stereo imaging technology that appeared decades ago, today's 3D TVs rely on high-definition and high-quality hardware and use the latest technical means to immediately promote the "Full HD Flicker-free 3D Stereo" brand. So what methods do today's 3D TVs use to achieve the so-called "Full HD Flicker-free" stereo images?

Chromatic 3D has a long history and the most shortcomings

First, let’s take a look at the earliest and easiest to implement 3D stereoscopic imaging technology: chromatic aberration 3D imaging technology.

From a technical perspective, chromatic aberration 3D stereoscopic imaging is a relatively simple method. This type of 3D imaging can be achieved with a simple pair of red and blue (or red and green) glasses, and the hardware cost is only a few yuan. There is no need for additional upgrades to the display device, and any existing display device can display directly.

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The principle of chromatic aberration 3D stereo imaging technology is to print two images taken from different perspectives in two different colors on the same screen. If we don't wear glasses, we can only see a blurred image with overlapping colors. But after wearing glasses, the different colored lenses of the left and right eyes filter the corresponding colors respectively, and only the red image passes through the red lens and the blue passes through the blue lens. Finally, the different images seen by the two eyes overlap in the human brain to produce a three-dimensional effect.

The principle of chromatic aberration 3D stereo imaging is simple, and the 3D depth effect it can achieve is quite good. However, the chromatic separation method used will cause serious visual impairment to the viewer, and the comfort is always unsatisfactory. At the same time, the color reproduction effect of the picture has always been at a low level, which makes it difficult for it to become the mainstream of 3D stereo display technology.

Polarized 3D cinema is not easy to achieve in mainstream families

Before the emergence of 3D TVs, 3D cinemas have actually been in our lives for a long time. The most common 3D cinema technology is polarized 3D technology.

Polarized 3D technology mainly uses polarized light separation technology to achieve 3D stereoscopic imaging. When viewers wear polarized glasses, the left and right lenses filter out light with different polarization directions respectively, thus achieving the separation of the left and right eye images.

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There are two main ways to implement it in theaters: dual-machine 3D and single-machine 3D. Dual-machine 3D is mostly used in IMAX 3D theaters. It uses two projectors to transmit left and right eye images with different polarization directions. Single-machine 3D is relatively simple. It mainly uses a head-up lens and a fast-switching polarizer to switch the left and right eye images at high speed, and finally separates the left and right eye images through polarized glasses.

The cost of polarized 3D systems is not high, and 3D glasses are easy to make and buy, but there are certain limitations, especially for home users. If they rely on polarized 3D TVs, they will have to face the problem of resolution loss. For example, to achieve full HD 3D images, the physical resolution of the TV must reach 2 times full HD. Otherwise, if the 3D system is made with existing HD flat-panel TVs, the resolution can only hover within the standard definition specification.

Since chromatic aberration 3D and polarized 3D have obvious shortcomings, active shutter 3D imaging technology has come to the fore for home users.

Active shutter 3D has obvious advantages

The principle of shutter 3D technology is not complicated. It is to switch on and off the shutter-type 3D glasses in turn to control the images entering the left and right eyes respectively, thereby forming a 3D stereoscopic effect in the viewer's brain.

The key to the shutter 3D solution lies in the signal source and display device. First, the signal source needs to have twice the number of frames of the 2D image (one frame for each eye), and secondly, the display device needs to have high-speed image refresh capability. For example, a 720/50P 3D signal only requires a TV with a 50HZ image refresh rate per second in the 2D era, but under a 3D signal, it needs to have a 100HZ image refresh rate.

At present, all mainstream 3D TV manufacturers have adopted this solution. The reason why this solution is so popular is that it can maintain the resolution of FULL HD; secondly, the refresh rate of current flat-panel TVs has already reached 200Hz or even 400Hz, which is more than enough to handle 1080/60P 3D signals.

The shutter 3D solution has a very good clarity index, and most TVs have high-speed refresh capabilities. In fact, the 3D images seen by consumers on each side of the glasses have a refresh rate higher than 60Hz, which means that there will be no obvious flicker. Therefore, this solution is currently the most widely used.

However, this method also has its disadvantages, that is, the cost of 3D glasses is relatively high. Since the lenses need to be turned on and off in turn to separate the left and right eye images, the glasses also need to be powered. For a large family, buying 3D glasses is also a considerable expense.