Different substances have their own 'fingerprint spectrum', and hyperspectral remote sensing technology can accurately capture this important information and improve human eye and remote sensing capabilities.

I have seen the audience of the documentary 'I am in the Forbidden City to repair cultural relics' may have an impression on the following scenes: the technician uses an instrument to scan the ancient calligraphy and painting, and after the scanning information is professionally processed, the cultural relics repair expert can find the invisible information on the calligraphy and painting. Even the painting techniques and the pigments used at the time can be analyzed.

This magical instrument is a hyperspectral scanner developed by the Institute of Remote Sensing and Digital Earth of the Chinese Academy of Sciences (hereinafter referred to as the Institute of Remote Sensing Earth of the Chinese Academy of Sciences). Why is hyperspectral remote sensing so powerful? What other applications besides artifact detection and repair? What is the level of research and development in China in the field of hyperspectral remote sensing?

Using hyperspectral technology to extract the pigment information of ancient paintings, and calculate the origin of the pigments, so that the pigments can be accurately selected during the restoration.

The light that people see in their daily lives is a complex color of light composed of a plurality of colors, which is monochromatic light after being split by a prism or the like. The pattern in which these monochromatic lights are sequentially arranged at different wavelengths (or frequencies) is the spectrum.

Spectral analysis is an important way for humans to use the light to perceive the world. Different elements and their compounds on the earth have their own unique spectral characteristics, and the spectrum is therefore regarded as the 'fingerprint' of the distinguishing substance. If the optical imaging of the naked eye can see the shape and size of the substance, spectral analysis can obtain the composition information of the substance.

In order to obtain more abundant and detailed material composition information, in addition to improving the performance of the spectroscopic system, it is also possible to improve the spectroscopic method and presentation mode. Hyperspectral remote sensing is such an idea. Zhang Lifu, director of the Hyperspectral Remote Sensing Laboratory of the Institute of Remote Sensing Earth, Chinese Academy of Sciences, said that hyperspectral remote sensing is characterized by continuous imaging in the spectral range from visible to short-wave infrared. Traditional color cameras can only record images of three channels of red, green and blue. The bandwidth of a channel is very wide, and the number of channels recorded by hyperspectral imaging can reach hundreds, and the spectral channel is narrow and the resolution is very high. The spectral detection range far exceeds the human eye's perception range, and it can detect people. A large amount of information that cannot be seen by the eye, raising people's awareness of nature and matter.

Because of the rich information available in a very narrow spectral band, the information obtained by hyperspectral technology has a high resolution and can even distinguish the molecular and atomic structure of the observed material, which is not achieved by ordinary optical remote sensing.

How to use high-spectral technology to identify and repair ancient calligraphy and painting? In the laboratory of the Hyperspectral Earth Laboratory of the Institute of Remote Sensing Earth, Chinese Academy of Sciences, Zhang Lifu drew a picture and explained the principle of hyperspectral remote sensing imaging for reporters: hyperspectral instruments scan the surface of the painting and extract the spectral data of each point on the image; because of the high spectrum The feature of continuous imaging is to obtain images of hundreds of different wavelengths of the target. These images are superimposed to form an image cube in three dimensions, and the values of hundreds of digital images corresponding to each pixel are connected. A spectral curve.

'The spectral information reflected by different substances and even different ages is also different, that is, there is a 'fingerprint' spectrum that belongs to it. If the composition information of two objects is the same, the curve obtained should basically match; if a curve The local part has large fluctuations, and it can be estimated that there are abnormalities.' Zhang Lifu said.

For example, the collection of the Forbidden City, 'The Eight Diagrams of the Emperor of the Chongqing Emperor', depicts the real life of the birthday of the Emperor of Emperor Qianlong of the Qianlong Emperor's 80th birthday. After more than 250 years, it was very broken, and there was a defect in the face. There are even molds. To restore the original style, it is necessary to understand the pigments used at the time of repairing the painting. The hyperspectral research team of the Institute of Remote Sensing Earth of the Chinese Academy of Sciences scanned the ancient paints with a hyperspectral scanner and extracted the information of ancient paints, thus deducing the types of mineral materials used in the original paintings. Depending on the spectral curve of the different pigment origins, the scientific staff can even reverse the origin of the pigment – this provides a basis for repairing the selection of precision pigments.

Zhang Lifu said that most of the materials used in Chinese ancient paintings and calligraphy are enamel and paper. The texture is thin and thin, and it is easy to break and fade in the age. Hyperspectral analysis technology does not damage the ontology of cultural relics. It can help the restoration experts understand the pigment composition and painting techniques of ancient paintings and paintings, and even discover the potential disease information of painting and calligraphy early.

High-spectrum technology can be used to detect pesticide residues in fruits and vegetables, and smog may be detected at any time in the future.

Hyperspectral's ability to 'eyes' is not only to help identify and repair artifacts. Because it can present details that are invisible to the human eye and distinguish substances with different components, the technology has broad application value in the fields of national defense military, precision agriculture, water environment monitoring, and geology and mineral exploration.

In the laboratory of the Hyperspectral Laboratory of the Institute of Remote Sensing Earth, Chinese Academy of Sciences, Zhang Lifu showed a green radish to reporters. From the surface, the leaves of this pot of green radish have nothing special, but after the 'eyes' of the hyperspectral instrument, a white area is displayed on the electronic screen. 'There are a few plastic leaves in the green radish, which are almost hard to find with the naked eye, but because of the great difference in spectral information from normal leaves, they can't hide the hyperspectral ‘eyes,’” Zhang Lifu said.

Using this principle, hyperspectral can also be used in the detection of pesticide residues in fruits and vegetables. Whether there are residual pesticides or pesticide residues, there will be subtle differences in the spectral characteristics. By analyzing these differences, professionals can make scientific judgments.

Zhang Lifu said that compared with traditional food safety sampling and testing methods, hyperspectral technology detection has the advantages of no contact and no damage, which can greatly improve the detection efficiency. In addition, according to the different growth dates or the origin of the spectrum characteristics of fruits and vegetables are different, hyperspectral technology can also be used to detect the freshness of fruits and vegetables, traceability of origin.

According to Zhang Lifu, based on the principle of hyperspectral, researchers are currently developing hyperspectral detection applications for smartphones. He hopes that in the future, mobile phones will have hyperspectral detection capabilities. Combined with cloud computing and big data, people can quickly detect food safety problems with their mobile phones anytime, anywhere. In this way, farmers can use mobile phones to detect information on pests and diseases of fruits and vegetables, and send the data to the cloud. Based on this information, researchers can predict where pests and diseases may occur.

“From the detection of pesticide residues in fruits and vegetables to the detection of heavy metals in cosmetics, the monitoring of environmental pollution such as water and soil, and the medical detection of teeth and skin, there is a great imagination in the application of hyperspectral technology.” Zhang Lifu said that different air particles reflect different spectra. In the future, people can even monitor smog in a timely and accurate manner through mobile phones.

Hyperspectral technology belongs to the category of remote sensing technology. Usually, when people refer to remote sensing, they often associate with satellite remote sensing, aerial remote sensing, etc., and think that remote sensing is not directly related to the daily life of ordinary people, but it is not. Among the 3S technologies (Geographic Information System, Global Positioning System, Remote Sensing), the first two “S” have been closely related to people's lives. People have been widely used in mobile phones. What is missing is the third “S” and the lives of ordinary people. Linked up. The application of hyperspectral remote sensing technology indicates that remote sensing technology is entering people's lives. 'What we are doing is to make hyperspectral remote sensing technology fly into the homes of ordinary people. The combination of remote sensing and smart phones will make ‘remote sensing’ everywhere,” said Zhang Lifu.

China is in an international leading position in hyperspectral remote sensing research

The huge application prospect makes hyperspectral remote sensing technology the frontier field of remote sensing technology in the world.

According to experts, China is in a leading position in the field of hyperspectral remote sensing research.

In the 1990s, the Institute of Remote Sensing Applications of the Chinese Academy of Sciences and the Shanghai Institute of Technical Physics collaborated to develop a series of aeronautical hyperspectral sensors and traveled to Japan, Australia, Malaysia and other countries for international cooperation for local environment, agriculture, oceans, geology, etc. Field research provides important data and is highly valued.

Zhang Lifu said that due to the support of scientific research funding, China's hyperspectral research at the beginning of this century was slow to develop. In recent years, China has increased its support for hyperspectral data, and researchers have also achieved a series of results. He introduced that China is at the forefront of international research in hyperspectral basic research and information data accumulation. At the same time, researchers continue to expand the application of hyperspectral applications, in the field of imaging spectral and spectral image simulation, hyperspectral image intelligent processing and information extraction. A series of international leading research has been made in many aspects such as the development of new application fields.

'China has a strong accumulation in hyperspectral technology, but some key components of spectroscopic instruments still need to be imported, which affects the autonomy of the application of hyperspectral technology in China to a certain extent.' Zhang Lifu said that there are shortcomings in the manufacture of high-end scientific instruments and equipment. It is related to China's overall low level in materials science and manufacturing technology. He called on more and different researchers in China to participate in the research and development of hyperspectral, improve the manufacturing capacity of spectroscopic instruments, and make China a powerful country in hyperspectral research. .

(Source: Machine Network)