Mixed-style homemade cage birds
Humans are able to temporarily store the images they see, and after the images disappear, the previous images will still temporarily remain in front of their eyes. This is the basic principle of the animation that moves, which is known as 'persistence of vision'.
Because the image of the bird will temporarily remain in our field of vision, when the card turns to the side of the birdcage, the image of the bird will overlap on the birdcage, looking like the bird is trapped in the cage! The principle of television screen image is actually composed of 30 continuous independent faces per second! They were originally separate frames. The image tube continuously sends one after another, and because of the human visual persistence phenomenon, it looks like a continuous moving picture, which is the reason why television can recreate actions. And visual persistence is a very brief memory produced when our eyes look at anything. By remembering these memories together, we will see the action and produce the illusion of "continuous picture", which is visual persistence! For example, when you turn off the light in the room and spin the flashlight quickly, you will see a halo, which is also a phenomenon of visual persistence.