In this blog post, we’ll take a step-by-step look at everything from the principles of human stereoscopic vision to the latest glasses-free 3D display technologies and how they work.
“Wow, what a thrilling game! How do you watch Girls’ Generation?”
“We watch them in 3D!”
Anyone who used to watch TV regularly will remember the 3D TV commercial where Girls’ Generation appeared wearing 3D glasses and said, “We’re watching in 3D!” Back then, the fact that you could see stereoscopic images just by wearing glasses felt truly amazing. But technology has advanced even further. Now, displays have emerged that allow you to enjoy 3D images without wearing glasses. How exactly is this technology possible? To understand this, let’s first take a step-by-step look at the basic principles of 3D displays.
First, let’s explore why we perceive depth when looking at objects. For example, imagine placing a box on the floor and moving from side to side while looking at it. The box looks slightly different when viewed from the left than when viewed from the right. Similarly, when we look at an object with both eyes, there are subtle differences between the images received by the left and right eyes. Our brain compares and analyzes these two images to determine how far away or how close an object is, thereby creating a sense of depth.
Now, let’s imagine a situation where there is actually nothing on the floor. Instead, what would happen if we showed only the image seen by the left eye to the left eye, and only the image seen by the right eye to the right eye? Our brain would perceive that a box is actually placed at that location. In other words, a virtual 3D image is created. Thus, the core principle of 3D displays lies in delivering different images to each eye.
The remaining question is, “How can we show different images to each eye?” This challenge has been addressed for a long time, and the first widely adopted solution was the use of glasses. Glasses are made using two special lenses that allow only specific types of light to pass through, and the screen displays two images simultaneously. As a result, each eye sees only the image intended for it, creating a sense of depth. A prime example is the 3D display that uses polarization, a technology still widely used in many movie theaters today.
However, with recent advancements in 3D display technology, it has become possible to view 3D images without glasses. Among these glasses-free 3D technologies, the most representative method is the parallax barrier. This technology became widely known through its application in handheld game consoles such as the “Nintendo 3DS” and has since served as the foundation for various display technologies. The basic principle is the same as explained earlier: delivering different images to each eye. So, how was it possible to implement this principle without glasses?
The term “Parallax Barrier” can be roughly translated as “parallax screen.” In other words, it refers to a device that selectively blocks light to utilize the parallax that occurs between the two eyes. The specific method is as follows: The numerous pixels that make up the screen are divided into odd-numbered pixels (R) and even-numbered pixels (L) based on the vertical direction. This divides the screen into vertical stripes. The odd-numbered pixels display the image (R) intended for the right eye, while the even-numbered pixels display the image (L) intended for the left eye.
Next, a very thin black barrier is placed in front of the screen at regular intervals. In practice, rather than a simple barrier, an LCD panel capable of being turned on and off is used. This barrier is designed to block the pixels intended for the right eye from being seen by the left eye, and vice versa. As a result, the left eye sees only the left image and the right eye sees only the right image, allowing the viewer to perceive a sense of depth without needing special glasses.
This technology does have its limitations. To achieve the sharpest 3D effect, the user must view the screen from a specific position and distance. The technology developed to address this issue is called the Tracking Barrier. “Tracking” refers to the technology that tracks the user’s position in real time. As explained earlier, since the barriers used in the parallax barrier are LCD panels, their black and transparent areas can be freely adjusted. By having a camera at the top of the screen track the user’s eye position in real time and continuously adjust the shape of the barrier, the display can maintain an appropriate 3D image even as the user moves.
Furthermore, this user-tracking technology can be easily combined with eye-tracking technology. By recognizing the user’s gaze, the system not only makes objects on the screen appear to pop out but also dynamically adjusts the image in real time so that, as the user moves, they can naturally see not only the front view but also the side view of the object. This technology is evolving alongside various next-generation display technologies today, such as augmented reality (AR), virtual reality (VR), mixed reality (MR), and spatial computing.
So far, we’ve explored everything from the basic principles of 3D displays to the latest glasses-free 3D display technologies. Technologies that were once thought to be possible only in movies have now become a reality and continue to advance. Future 3D displays are expected to provide even more natural spatial representation and a higher level of immersion, finding applications in a wide range of fields. Someday, we may enter an era where we can naturally enjoy stereoscopic images and spatial experiences in our daily lives—ones that are almost indistinguishable from reality, just as we’ve seen in movies.
