China raindrop underwater photography

1, fire method and understanding of fire

In ancient China, the tool for making fire was called "incense", which was divided into golden incense and woody incense. The golden elephant takes the fire of the sun, and the wooden elephant takes the fire of the wood. According to Chinese ancient books, "Auspicious" and "Yangxiang" (actually a kind of concave mirror, made of metal, so collectively called "Jinxiang") were used to make fire. In ancient times, people always carried firearms with them when marching or hunting. In the Book of Rites, there are records of "Pei Zuo Jin Xiang" and "You Pei Mu Xiang", indicating that the fire was made with Jin Xiang on sunny days and with Mu Xiang on cloudy days. It is a pioneer of mankind to concentrate solar energy with optical instruments. When it comes to making fire, ancient people made it with homemade ancient lenses. In the 2nd century BC, some people used ice as a lens to gather sunlight to make a fire. There is such a record in Tang Wenjing Series and Huainan Wanbi Book: "Cutting the ice to make the circle, lifting it to the sun, and inheriting its shadow with Ai, it must be fire." We often say that fire and water are incompatible, but it is a wonderful creation to make an ice lens to make a fire. Glasses made of ice can't be kept for a long time, so glasses or glasses are used as lenses.

"Hua Yan Jing" Bodhisattva asked Ming Pinlu "Diligent Bodhisattva answered praise: those who drill the fire, rest for a few times, then go out, the fire stops, and those who slack off are also. If people hold the pearl of the sun, they will not bear the shadow of things, and the fire will not be obtained in the end. "

2. Pinhole imaging and shadow understanding

In the 4th century BC, Mohist school did pinhole imaging experiment, and gave an analysis and explanation. It is clearly written in the Mohist book: "When the scenery arrives (falls), it will end in the afternoon, and if it lasts for a long time, it will end." The "noon" here is where the cave is. This passage shows that the pinhole is an inverted image because there is a point ("end") at the pinhole that is the intersection of light, and the size of the image has nothing to do with the position of this intersection. It can also be clearly seen from here that the ancients have realized that light travels in a straight line, so they often use "shooting" to describe that light travels in a straight line. Shen Kuo in the Northern Song Dynasty also described the experiment of linear propagation of light and pinhole imaging in Meng Qian Bi Tan. First of all, he directly observed the flight in the air, and the shadow on the ground followed, consistent with the direction of the flight. Then make a small hole in the paper window, so that the shadow flying from the window appears on the paper screen in the room, and explain the observed result with the principle of direct light: "East shadow west, west shadow east." Mohist school uses the linear propagation property of light to discuss the relationship between light source, object and projection. In the Book of Mohism, it is written: "If the scenery does not move, it will change." "Light, scene book. If so, then do your best. " Explain that the shadow is motionless. If the shadow moves, it is because the light source or object moves, so that the original shadow disappears and new shadows are constantly generated. Where the projection is made, if there is light, the shadow will disappear. If the shadow exists, it means that the object has not moved. As long as the object does not move, the shadow will always exist in its original place. Mohism also explained umbra and penumbra. There is such a record in the Book of Mohism: "It is important to respect the second." "The second scene, light editing. One, light one. Light, scenery. " It means that an object has two kinds of projections (umbra and penumbra), which means that it is the result of repeated irradiation by two light sources at the same time ("the speaker" and "the lamp holder"). One projection means that it is only irradiated by one light source, and emphasizes the relationship between the light source and the projection ("the light source is also a scene"). In connection with this, Mohism also discussed the size and change of shadow according to the change of the relative position of the object and the light source, as well as the difference of the size of the object and the light source itself.

3. Understanding of mirrors

Mozi also systematically studied the imaging principles of concave mirror, convex mirror and plane mirror, and found the existence of concave mirror focus. For example, the Mohist school made an in-depth observation and study of concave mirror, which was clearly recorded in the Mohist Complete Book. "Looking down, the scenery is small and easy, and the big one is right, saying outside and inside." "Low" is a deep depression; If you put it in the middle, the image you get is bigger and more upright than the object. Although he still confuses the center and focus of the ball, these experiments are the earliest optical experiments in the world and have great scientific significance. Needham once compared Mozi optics with ancient Greek optics, pointing out that Mozi's optical research was "earlier than any Greece we know" and "India can't compare with it".

Shen Kuo measured the focal length of concave mirror in Northern Song Dynasty. He put his finger in front of concave mirror, observed the imaging situation, and found that the image changed with the distance between his finger and the mirror. It is recorded in Meng Qian's pen talk: "Yang Xiang's face is sunken, and it is right to take photos with one finger. If he is far away, he can't see anything." After that, you will fall down. " Explain that when the finger approaches concave mirror, it seems to be upright and gradually moves away from somewhere (near the focus), then "nothing can be seen", that is, there is no image (like at infinity); After moving this distance, it's like a handstand. This experiment not only expresses the imaging principle of concave mirror, but also is a rough method to measure the focal length of concave mirror.

Mohism also studied convex lenses. The Mohist Classic wrote: "Jiantuan, Jing Yi. It is said that the punishment is very strong. " The "Sword Group" is concave mirror, also known as the Group Mirror. "Scene 1" shows that there is only one kind of convex mirror imaging. The homonym of "punishment" refers to an object, which is always bigger than an image. Our ancestors made use of the characteristic that plane mirrors can reflect light, and combined many plane mirrors, and achieved interesting results. For example, Zhuangzi Tianxiapian's related annotation "Zhuangzi's Correction" records: "Take the shadow as a mirror, then the shadow as a mirror, and take the surface as a mirror, then the ghost is infinite." Such a device has received the effect of "taking photos in front of the mirror and taking photos in the back, and the flowers set each other off". It is recorded in the series "Jian" and "Huainan Bay Wall Book": "You can see your neighbors with a big mirror and a basin under it." It shows that someone made the earliest open-tube "periscope" a long time ago, and you can watch the outdoor scenery through the partition wall.

In addition, the transparent mirror invented in Han dynasty can reflect beautiful images on the back of bronze mirror, which is a great invention of ancient optics in China and is still concerned by Chinese and foreign scholars.

4. Understanding of rainbows

Rainbow is an atmospheric optical phenomenon. Since the 6th century, we have had a correct understanding of ancient rainbows in China. Kong Ying Da (574-648) in the early Tang Dynasty summed up the causes of rainbows. He believed that "if the clouds are thin and the sun leaks, raindrops in the sun will produce rainbows." It is clearly pointed out that the rainbow has three conditions, namely, cloud, sun and "sunshine and raindrops". Shen Kuo also made a detailed study on this and made a field trip. In Meng Qian Bitan's Notes, he wrote: "It's another new rain, see the rainbow in front of the account." In view of the view of the same post, both ends of the rainbow are hanging in the stream. It makes people cross the stream, facing each other across the rainbow, a few feet apart, such as the gap in the middle, which can be seen from west to east; Gaixihong also. If you look at something standing in a stream, you will be caught by the sun and see nothing. "It is pointed out that the position of the rainbow and the sun is only relative. The rainbow in the evening can be seen in the east, but the sun can't. After the ground rainbow is known, it can be made manually. In the mid-8th century, there was an experiment in the Tang Dynasty: "The water sprayed from the back of the sun looks like a rainbow", which means that water droplets sprayed from the back of the sun can see a scene similar to a rainbow.

5. Eight pieces of Mohist optics

Mo Zhai (about 478 BC-392 BC) was the founder of Mohism. Politicians and scientists in the Warring States period. He and his disciples studied and summarized the experience of the eight methods according to the optical knowledge recognized by the ancient working people in practice, and recorded it in the Mohist Classic. They say this is one of the best parts of Mohist classics. Eight optical rods are directly related to some problems in optical applications.

It is the most common phenomenon in nature that luminous bodies illuminate objects to form shadows, and it is also an issue that photographers are interested in in artistic modeling. This is the beginning of the optical exposition in the Mohist Classic. The first and second rules of "Eight Light Rules" are: essence: essence migration. Say "in" instead. Say: Jing Liang, Jing died. If you are here, do it and have a rest. (Part I) Classic: Jinger. This is very important. Say: scenery, two lamps, editing, one lamp. A lamp is also a scene. (Article 2)

The main idea is the cause of shadow. Where there is light, there is no shadow; If there is a shadow, it is that the light is blocked by an object. Furthermore, if the light source, the object and the bearing surface are relatively static, the position of the shadow is relatively fixed. When two light sources illuminate an object at the same time, two "penumbras" will be produced with a "umbra" in the middle. A light source illuminates only one shadow. These two articles reflect the simplest understanding of optical phenomena of the ancients. There is also a noteworthy, direct discussion of pinhole imaging principle. The original text is: scene: the scene arrives, and there is an ending in the afternoon; With Jing Chang, it's over. It is said that if people in Jingguang shine, the people below are also tall, and the people above are also tall. The foot is covered with light, so the scenery is above, and it is covered with light for the first time, so the scenery is below. There is an end and light in the distance, so it is also in the scene library. (Article 3)

The main idea is that the shadow inversion is because the light beams converge into a beam at the pinhole, and "noon" refers to the point where the two beams intersect, that is, the pinhole. Light travels in a straight line like an arrow. The light from below is imaged at the top through a small hole, and the light from above is imaged at the bottom. The last sentence "There is light in the distance" is interpreted by modern scholars as similar to the concepts of object distance and image distance in photographic optics. This can explain why photographers come in and out of the camera now. The fifth article discusses the relationship between the intensity of light. The conclusion is that the distance between illuminators determines the intensity of light. Similar to the modern photometric concept. Four or six articles explain the phenomenon of plane mirror reflection.

China ancient smelting technology is very developed. Secondly, the manufacturing technology of bronze mirrors. According to written records and archaeological discoveries, bronze mirrors at that time not only had flat mirrors, but also were made into convex mirrors or concave mirror and concave mirror, which were called Yangsui in ancient times, which was a tool for people to focus fire by using sunlight. In ancient times, there was no official position in charge of Yang Sui. Book of Rites, Volume 70, Qiu Guan Four Mouths, records: "Four Declarations (Sound Fire. The name of the ancient official position) took the husband's hand and took the open flame to the sky. " Zheng Xuan in the Eastern Han Dynasty noted: "Fu Sui, Yang Sui also." It should be pointed out that concave mirror plays an important role in modern applied photographic optics. The recent emergence of catadioptric photographic lenses further proves this point. The ancients have realized that when an object is placed outside the center of the ball, it will get a smaller reflection than the object. When an object is in the center of a sphere, it gets an upright image larger than the object. That is to say, as the saying goes, "learning to be excellent is an official, and the scenery is small and easy, which is a big blow." Say it outside and say it inside. To sum up, it can be inferred that people have understood: 1. Linear propagation of light; 2. The causes and changing rules of shadows; 3. The principle of pinhole imaging; 4. In pinhole camera imaging, the size of objects and images depends on the relationship between object distance and image distance; 5. The concept of similar magnification; 6. The special significance of the front focus of concave mirror for spherical center imaging. Eight optical articles in Mohist Scriptures reflect the outstanding contributions of Chinese people in scientific research in the pre-Qin period. Due to the limitation of knowledge level, it is obviously one-sided and incomplete from today's perspective. Although the content of Mo Jing is abstruse and difficult to understand, the annotations of various academic circles are basically the same, and the content itself is beyond doubt. After the formation of Mohism, China's "Theory of Gezhi" was opened up, which inspired future generations to study photographic optics.

6. Discovery of optical refraction phenomenon

The Mohist Classics did not discuss the refraction phenomenon of light propagating in different media, because the manufacturing conditions at that time could not provide ideal transparent glass, and the refraction phenomenon was directly related to the theoretical basis of lens imaging. In BC 139, Liu An, the king of Huainan in the Western Han Dynasty, presided over the compilation of Huainan Wanbi Book. In addition to repeating the statement that "Yang Yang sees the sun, he must make a fire", there is also a record of using ice as a lens: "Cut the ice to make a circle, stick to it, and make a fire with Ai." According to Xijing Diary, when Emperor Wu of the Han Dynasty (140-87 BC), he knew to use white glass to fold sunlight into a dark room to make it daytime. According to the Chronicle of Lin Zhicheng in Qing Dynasty, during the Northern Wei Dynasty (386-58 1), merchants in the western regions made artificial colored glass from ores. I once made a house that could accommodate 100 people, and it was surrounded by artificial glass to make the indoor light color clear. As late as the Song Dynasty, Liu Qi's Leisure Diary also talked about the case of focusing sunlight and illuminating darkness with crystal refraction.

Shen Kuo (1031-1095), a great scientist in the Northern Song Dynasty, further analyzed and explained the pinhole imaging theory and concave mirror in his book Meng Qian Bi Tan, and achieved new results. He explained with vivid metaphor that pinhole imaging is the result of light passing through "obstacles" (pinholes) to form beams. Since then, due to the coincidence of objective conditions in daily life, people have observed the phenomenon of pinhole imaging many times, which has aroused widespread concern, especially by scholars of all ages, and is often recorded in ancient books. Tao's famous note "Dropping out of Farming" in Yuan Dynasty said: "The Huqiu Pavilion in Pingjiang has a certain understanding of the version. When the day is clear, the shadow of the temple will be borne by a large piece of white paper, and the shape of the temple will win. Please note here. But above and below, this inherent image is tolerant, not illusory. " He added: "There are four pagodas in Songjiang City ... Xia's home is in the east of the four pagodas, but there is a tower shadow in the small room, which is five inches long and hangs upside down on the western wall. I don't know where it came from However, it is not often, or sometimes it is unclear.

In Ming Dynasty, Dong Liu and Yu Yi mentioned the pinhole imaging of Tianning Temple in Beijing in A Brief Introduction to the Scenery of the Imperial Capital, and made some explanations. The original text is "tower reflection, in the underground palace." In Japan, the door in the middle of the temple was closed, the entrance door was open that day, and the tower was completely reflected on the stone. People used to say: shadows enter from the sky, but things in the air hinder them. If it is blocked, the shadow beam will fall. ..... Today, the image hanging in the mirror passes through the side mirror and turns upside down, and the sunlight pours in. The light is on again, there are thirteen floors. The light spreads again and again, and the object is very small ... "Cihui Temple is a temple in Beijing during the Ming and Qing Dynasties, and it is also a historical site, famous for its reflection, which attracts tourists.

The phenomenon of "pinhole imaging" has attracted more and more people's interest. In order to further study, Zhao Youqin, a scientist in Yuan Dynasty, designed a considerable optical experiment. He used the whole house as a laboratory. Dig a round well with different shades in two rooms separated from each other. There are small holes in the wellhead, the roof of the movable shed is used as a screen, and thousands of candles are used as illuminators. Through the pre-designed experimental scheme, the following conclusions are drawn: when the pinhole is enlarged to a considerable size, it is impossible to image; When the pinhole is quite small, the image on the screen has the same shape as the light source, but the direction is opposite; "Illumination" is inversely proportional to distance.

Zhao Youqin wrote a paper about the process and result of this experiment, which is called "A Small Scene" and included in his natural science anthology "A New Book of Leather Elephants". This book was later included in the large-scale book Yongle Dadian compiled in the Ming Dynasty. Zhao Youqin's experiment used thousands of waxes as illuminants, which shows that he has realized that images are composed of many light spots in the sense of photography. Its experimental field can be said to be the largest black box. At that time, the academic level of Zhao Youqin's paper Scenes of Xiao Kun was leading in the world.

Fang Yizhi, a scientist in the late Ming and early Qing Dynasties, was called Man Gong. 1611——1671), and in his book "Physics", he also described the pinhole imaging experiment that he personally did: "The house leaks when it rains all night, and the sun is like a disc. Taste it with paper, stab a small hole, and let the sun turn into stone, just like its point; The hand gradually moves higher and higher, and the light is gradually greater than the stone; Hit four or five points and shine on the spot, four or five points are light and shadow; The hand moves higher and higher, and photosynthesis is one, but the shadow of four or five can't be recovered. " It shows that Fang Yizhi's experiment is an exploration of pinhole imaging conditions and the regularity of specific factors affecting image size.

7. lens black box

The invention and application of photography can not be separated from the black box. Although pinhole camera can image, just like Zhao Youqin's experimental results, it has a fatal shortcoming, that is, it can't solve the contradiction between brightness and clarity of the image. Therefore, the appearance of lens black box makes optical application technology take a big step forward. During the European Renaissance, the lens camera was widely used by painters, but it was only used as an auxiliary tool for painting. In the late Ming and early Qing dynasties, some western missionaries came to China, which promoted cultural exchanges between China and the West. Subsequently, some optical instruments began to be introduced into China. Firstly, various lenses, including glasses and magnifying glasses, are introduced. In the Qing Dynasty, Zhao Yi said in "Examination of Yu Cong": "There were no glasses in ancient times, but there were them in the Ming Dynasty, originally from the western regions." After the Qing Dynasty, an industry of manufacturing glass by modern methods appeared in Guangdong Province, which provided material conditions for China to grind optical lenses.

Sun, who made optical instruments in the early Qing Dynasty, was a master of grinding lenses in China. Sun, the word, and the word Spencer. People from Wuxian County, Jiangsu Province. Born in the early years of Chongzhen, he died in the reign of Kangxi, and only lived for 33 years. His father Zhiru is a magistrate in Zhangzhou, Fujian. Sun Qiu Yun was very clever when he was a child. 13 years old studying in Wujiang County School. Shortly after his father died, his family collapsed, and he supported his mother by selling herbs. He likes to study machinery and make his own clocks. When he was young, he became a famous lens manufacturer. According to historical records: "In the past, Qiu Yun, the son of Tiger Hill, had 72 kinds of goggles, such as blinding goggles, sight-seeing goggles and children's goggles. There are also telephoto mirrors, fire mirrors, end-capacity mirrors, light-taking mirrors, sunset mirrors and microscopes ... "He is also the author of" The History of Mirrors ",but it is a pity that it has been lost. It is proved that there were domestic photographic lenses (so-called "photographic lenses") at that time, and some optical instruments assembled with photographic lenses appeared, among which movie lights were one.

The so-called "shadow lamp" is a slide projector or a magnifying glass for photography. In fact, as early as the third century BC, the ancient book Han Feizi recorded a story of an ancient people showing slides. Zhou Jun hired a man to paint for him, and it was finished in three years. When you look at it, you need to build a high wall, open a small hole in the wall and insert "?" (equivalent to a slide show), you can only watch it when there is sunshine. "Everything is in the shape of dragons, snakes, beasts, chariots and horses." Unfortunately, this pinhole projector has not been developed and improved.

Lu Gu (Tieqing), a scholar in Qing Dynasty, recorded the movie lanterns that were circulated among the people at that time. He said: "Its laws are all passed down from western countries in Europe, and Huqiu people can do it today. In the scene of the lamp shadow, a tall paper box was used, an oil lamp was stored in the belly, and seven or eight stems were burned. Its flame is suitable for the hole in the front. The hole and the box protrude by one inch to form a hexagon, so it is necessary to overlap one side of the lens. This is a psychic ear ... with glass embedded, the opera is painted backwards ... The shadow is absorbed into the powder wall. The farther the box is, the bigger the light is, but the light in the room goes out, and its shadow begins to be clear ... "Interestingly, the article mentioned that" overlapping lens is needed ",which means that" compound lens "was used, and this is precisely the period when black-box was popular in Europe, and compound lens marked the advanced optical technology level in the world.