Who discovered pinhole imaging?

Mozi

The principle of pinhole imaging was first discovered by Mozi. His differential calculus principles are also earlier than those in the West. Therefore, he is called the Democritus of the East by the Western scientific community.

Mozi first discussed the relationship between light and shadow. He carefully observed the changing rules of the images of moving objects, and

put forward the proposition that "the scenery never moves". In other words, when viewed from the surface, the shadow of a moving object is also moving with the object. In fact, this is an illusion. Because when the position of a moving object moves, the image it formed the moment before

has disappeared, and the image formed after its displacement is a newly formed one, not the original one

The image moves to a new position. If the original image does not disappear, it will always exist in its original location.

This is impossible. Therefore, the movement of the images you see is just the continuous alternation of new and old images with the movement of objects. It is not the movement of the images themselves. This proposition of Mozi was later inherited by famous scholars, and from this he put forward the proposition that "the shadow of a flying bird has not yet moved".

Subsequently, Mozi discussed the issue of umbra and secondary shadow of objects. He pointed out that if the light source is not a point light source, due to the repeated illumination of the light emitted from various points, the object will produce umbra and secondary shadow; if the light source is a point light source , then only the umbra appears.

Then, Mozi conducted experiments on small hole imaging. He clearly pointed out that light propagates in straight lines, and the image formed by an object passing through a small hole is an inverted image. This is because when light passes through an object and then passes through the small hole, due to the straight line propagation of light, the upper part of the object is imaged below, and the lower part of the object is imaged above, so the image formed is an inverted image. He also discussed

the relationship between the size of the image and the tilt of the object and the distance of the light source. He pointed out that if the object is tilted or the light source is far away, the shadow will be long and thin.

If the object is straight or the light source is close, the shadow will be long and thin. The shadow is short and thick. If it is reflected light, the shadow is formed between the object and the light source.

What is particularly valuable is that Mozi conducted quite systematic research on plane mirrors, concave mirrors, convex mirrors, etc., and

came up with a series of basic principles of geometric optics. He pointed out that plane mirrors form images that are the same size and symmetrical at near and far, but are inverted from left to right. If two or more plane mirrors illuminate each other, repeated reflections will occur, forming countless images. The image of a concave mirror forms a positive image within the "middle". The image formed far away from the "middle" is large. The image formed close to the "middle" is small. The image formed at the "middle" is the same as that of the "middle". Objects are the same size; outside the "middle", they form an inverted image, with the "middle" near like a big image and the "middle" far away like a small. A convex mirror only forms an erect image, with a large near image and a small far image.

The "center" here is the center of the spherical mirror. Although Mozi was not able to distinguish the difference between the center of the sphere and the focus,

he confused the center of the sphere with the focus, but his conclusion is consistent with the imaging principle of modern spherical mirrors. Still basically consistent.

Mozi also studied the propagation of sound and found that wells and poppies can amplify sound, and he used them skillfully

. He once taught his students that when defending a city, in order to prevent the enemy from digging tunnels to attack the city, wells were dug every thirty feet

and large opiums were placed in the wells. The mouths of the opiums were stretched with thin cowhide to allow hearing. Good people lie on the grass and listen to monitor whether the enemy is digging tunnels and where they are digging, so as to be prepared to defend against the enemy.

Although Mozi could not understand the mechanism of sound vibration at that time, this method of defending against enemies contains rich scientific connotations