Demystifying the working principle of VR helmet, it works like this.

A lens, some sensors, and other things, how do they "tune" you into a wonderful new world?

VR may look a bit like black magic, but in fact, each helmet is a well-designed product, a fusion of cutting-edge technology and whimsy, designed to let you forget all the trivial things, focus on the screen. In the VR world. The following is an exploded introduction to how the helmet works. Together, these components provide a compelling VR experience.

lens

Secret! The original VR helmet works like this.

The lens is one of the most important elements. The lens is designed to fool your eyes and make you think that there is a vast space in front of you, not a two-inch flat display. To do this, the lens needs to focus the light, making you feel like the display is at an infinite distance.

Many helmets use a special Fresnel lens that achieves the same effect as a large curved lens by using a thin, circular prism array. These lenses are also used to magnify the helmet's built-in display, allowing the image to take up your entire view so you don't notice the edges of the screen.

Display

High-performance displays are another important factor in making VR convincing. They must have enough pixel density to display a clear image and be fast enough so that the moving picture in VR is smooth and smooth.

Both HTC Vive and Oculus use two 1080x1200 displays, one for each eye, which can display images at 90 frames per second - providing users with smooth, smooth motion and a wide viewing angle of 110 degrees. Can cover a large part of your field of vision.

The high-end helmet also uses a dual screen to provide a stereoscopic 3D effect similar to the Nintendo 3DS. Each screen displays a slightly offset image of each eye, and our brain automatically "bonds" them together into an image, creating a depth-related illusion in the process.

The Samsung Gear VR uses the smartphone as a display, sacrificing visibility and graphics fidelity in order to maintain low cost and "wireless" effects. In this case, the work of creating a stereoscopic image is done by two replaceable lenses.

Focus debugging

Because the distance between the center of each of the two pupils (that is, the distance you need to measure when you go to the glasses) is different, the position of the lens in the helmet must be adjustable to fit our distance. Provide the correct stereoscopic 3D effect.

Secret! The original VR helmet works like this.

The Oculus Rift also uses a hybrid Fresnel lens with a variable focus level that you can adjust to achieve the best position by moving the helmet up or down.

position sensor

In order to display an accurate picture, the helmet must track your head movement with sub-millimeter accuracy as you look around. This is done with a variety of built-in sensors. With all the data provided by these sensors, the helmet can achieve true “six degrees of freedom” and the tracking helmet can follow any movement made by the head. (Note: The object has six degrees of freedom in space, that is, the degree of freedom of movement along the three orthogonal coordinate axes of x, y, and z and the degree of freedom of rotation around the three coordinate axes.)

Magnetometers measure the Earth's magnetic field, so always know which direction "Magnetic North" is in. This ensures that it points in the right direction and prevents "offset" errors - that is, when the helmet thinks it is moving in one direction, it is actually moving in the other direction.

Accelerometers have several uses, one is to detect gravity and let the helmet know which direction is above. The smartphone automatically converts the horizontal and vertical screens, relying on the accelerometer. And as its name suggests, it can measure acceleration along an axis, so it can provide useful data to let the helmet know the speed at which an object moves.

Gyroscopes can track small offsets along an axis (such as when you tilt your head or nod slightly) to provide more accurate object rotation information.

Instead of using a more advanced infrared tracking method, the Samsung Gear VR uses an Inertial Measurement Unit (IMU), an all-in-one device that combines a magnetometer, accelerometer and gyroscope. Unlike most smartphones, this IMU is specifically designed to reduce hysteresis and improve head tracking performance.

Infrared tracking

Both the Oculus Rift and the HTC Vive use infrared lasers to track the movement of the helmet, but each has its own method.

Oculus uses a Constella TIon infrared camera on the desk to track the infrared emitters in front of and behind the Oculus Rift helmet. If you use the Oculus Touch controller, you will need to have an additional camera to avoid confusion when tracking the infrared light on the helmet and controller. Each sensor is tracked separately, and the computer collects all the information to render the image so that the image is correct from any angle at any time. All of this almost always needs to be done immediately, which means that the coordinates of each infrared sensor are captured and processed immediately, and the image is displayed immediately, with almost no lag.

HTC Vive uses the "Lighthouse" infrared emitter, which is placed in the corner of the game space to quickly launch a laser and sweep across the room. The infrared sensor on the Vive captures it and measures its position in a space. This system works like Oculus, but in essence it uses the "lighthouse" as the launcher, the helmet as the camera, and the character just reverses.

Companion system

In addition to the "Beacon" infrared tracking system, the Vive helmet also has a front camera that uses a "companion" system to help detect if you are away from the boundaries of the game space. So if you're about to hit a wall or furniture, Vive can subtly send you a visual cue to let you know you've reached the edge of VR space.

Controller

Both Rift and Vive have wireless motion controllers that allow you to interact with objects in 3D space to enhance immersion.

Like a helmet, each controller is equipped with a magnetometer, accelerometer and gyroscope, and an infrared sensor to track sub-millimeter accuracy of motion.

Audio

Many helmets have built-in headphones that can produce 3D audio. This allows the game to add audio prompts relative to your location so that you can hear sounds that appear to come from behind, above, or even below.

Hidden microphones give game developers more choices and add more immersive features to the game. Using a microphone, the game can detect the amount of noise you produce in a stealth game, or use it as a way to communicate in VR.

Wire

While some VR devices (such as the Samsung Gear VR) are completely wireless, both Vive and Rift require wires to connect the helmet to the computer to transfer data and power, allowing the display to display high-definition images at 90 frames per second. If you're sitting in a helmet and gamepad, there's nothing wrong with it, but when you're walking around indoors, the wire can actually get in the way.

computer

The real thing that VR is such a black magic is actually in the computer. All location tracking data is sent to the computer, entered into the game, and then it renders the image and sends it to the helmet for display.

For the Samsung Gear VR and other wireless VR helmets, the computer is placed inside the helmet. For example, on the Gear VR, the smartphone not only plays the role of the display, but also assumes the task of the processor. (Kathy participates in the compilation)

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