Do not know the original so VR headlight lens working principle analysis

In order to make the display effect of fixed size head more stable in VR, the lens mode adopted by several mainstream VR head displays is designed based on Fresnel lens.For example, the HTC Vive has a built-in Fresnel lens, while the Oculus Rift CV1 has a built-in hybrid Fresnel lens.And what is a Fresnel lens?

FRESNEL lens is based on the principle invented by French light physicist FRESNEL, and can be manufactured in different processing methods.It was first used in navigation lighthouses in 1800, and has been used ever since.Its composition is the surface processing into circles from small to large, from shallow to deep concentric circles, from the profile looks like a sawtooth.The top arc line of each saw tooth is composed of an arc of the same size.You can also design it as a zigzag and a vertical row.To understand how Fresnel lenses work, we cite an illustration on Yivian's website.

If the eye gazes into the distance, the gaze point is infinite.That means the light is parallel and the lens is at rest.

If an object is close to your eye like this little fly, and you keep looking at it, the lens bends and the parallel state of light breaks.To keep looking at the fly, all the single light coming from the fly needs to be focused on a single point in the eye.

If the fly gets too close, the lens isn't elastic enough to bend and the eye loses focus.

That's why a special lens is needed to correct the Angle of the lens's light source and re-read by the eye.

Because the light beams hit the lens from different angles, it feels as if the eye is far away from the object, when in fact it is not.

In order to make the headlens thinner and lighter, Fresnel lenses are used in some of the headlenses.The lens has the same curvature as an ordinary lens, but has threads of varying sizes on one side.

But using a Fresnel lens means you have to make some sacrifices.You can make a multi-threaded lens so that you can see a clearer image.But light cannot focus on a point, and the curvature is always incorrect.

Alternatively, you can use a Fresnel lens with fewer threads to help focus the beam and improve contrast, but the sharpness of the image is impaired.However, VR head display equipment can realize effective image display effect in a short distance by using the characteristics of Fresnel lens, which is also the basic working principle of lens in the mainstream VR head display.