What is Head-mounted displays (HMDs)?

A head-mounted display is a screen you wear on your head that tricks your eyes into seeing a world inside a box while letting you see what is happening outside it.

Imagine holding two tiny television screens right in front of your face, very close to your eyes. Because they are so near, they look huge, like movie posters standing tall at the end of a long hallway. This device does exactly that, but instead of just showing pictures, it moves with your head.

The display sits comfortably on top of your nose or over your eyes like thick glasses. Inside, there are OLED screens (which make colors pop and look bright). The lenses in the headset focus those tiny screens so they appear far away.

You might have played with a paper card game called Pepper’s Ghost where a hidden image appears in a mirror. HMDs use a similar trick but digitally. When you turn your head left, the image on the screen turns with you. This is because special sensors inside measure how fast and which way your head moves.

The secret is binocular vision. Your two eyes see slightly different pictures. The headset shows one picture to your left eye and a slightly shifted picture to your right eye. Your brain smashes them together to create depth, making it feel like you are actually in the game or movie, not just watching it from far away.

It is like wearing a helmet made of computer screens that follows every nod and shake of your head, turning your bedroom floor into any place in the universe.