What is stereoscopic impression?

We humans and most animals have two eyes and two ears. Through these organs, we can feel the existence of three-dimensional space and our position in this three-dimensional space. In fact, we feel the "three-dimensional sense" all the time in life! Because we always see the world with two eyes and listen to the world with two ears. In ancient Greece, Euclid had found that the images seen by human left and right eyes were different, and there was parallax between them, which was the main reason why people could gain insight into three-dimensional space, the source of stereoscopic impression and the basic principle of three-dimensional imaging technology. -In terms of vision. Although we only saw one scene, our eyes saw different images. Because the left eye and the right eye form a visual angle with respect to the scene, the difference of visual angles causes the left eye and the right eye to see two different images forever. These two different images are transmitted to our brain through the left and right eyes, and the brain makes us feel "distance" and "depth" after judging this difference. The same is true of hearing (two ears hear different sounds, not stereo). From this difference, we can judge where the sound comes from and how far it is. It is precisely because of two different feelings that we perceive the existence of three-dimensional space and our position in this space, and we will have a three-dimensional sense. -So, one-eyed people can't perceive the space world? No, one-eyed people can also feel three-dimensional space. Careful observation reveals that Cyclops often shakes his head to see things, because he regards one eye as two eyes, and the other eye is "moving to see". He is actively looking for different perspectives and feeling different images. So that your brain can judge "distance" and "depth". In addition, he also used some optical principles of "near the big and far from the small" and some common sense of life to assist in judgment. But he can't feel the stimulation of two different images at the same time like a normal person, but there is a time difference. So he knows the existence and location of space, but he can't feel the real stereoscopic vision. You can do a simple experiment: stand a wine bottle on a table half a meter away, close one eye and don't shake your head, so it is difficult for you to insert chopsticks into the wine bottle at once, shake your head to see clearly and then insert it accurately. If you open your eyes at ordinary times, it will be easy. -If our brain wants to produce stereoscopic effect, it must be stimulated by two different pictures at the same time. The traditional single photo is to save a three-dimensional scene in a flat picture, and two eyes look at this flat picture. No matter how you look at it, the left and right eyes will always see the same picture, and there can be no difference in perspective. You can't appreciate the three-dimensional sense of the scene in the photo. Any stereoscopic image is composed of two images with different perspectives, both of which are double images. Only when the left and right eyes see different double pictures will they have a three-dimensional sense. "Stereo photography" is to save two images of a scene from left and right perspectives through two photos.