Talking about Digital Imaging (4) - Electronic Image Sensor

Brief introduction to search data, the original electronic image can be traced back to 1873, when scientists Joseph May and Willoughby Smith discovered that Selenium crystal can produce light Current, the beginning of the development of electronic imaging. Since then, there have been organizations and scholars studying electronic images one after another, among which important inventions are television systems, Photomultiplier Tubes (PMTs) and Electronic Couplers (CCDs).

Figure 1: Electronic image sensors are very common. For many office and home electronics products, PMTs and CCDs are very successful electronic image sensors (also known as optical sensors). The former is the invention of the fifties and the latter is the seventies. The invention can be applied to a variety of products, such as astronomical telescopes, satellites (there are foreign companies providing satellite digital photo services, shooting anywhere in the world, about HK$3), thermometers, analyzers, fax machines and scanning Instrument, etc., CCD can also be applied to small products such as digital cameras and camcorders. In 1998, two new types of electronic image sensors, CMOS (Complementary metal Oxide Semiconductor) and CIS (Contact lmage Sensor), also appeared. Then introduce their technical and commercial applications.

Electronic image sensor
(Electronic Image Sensor)
The previously used Observatory’s astronomical telescope used film to capture images. Later, electronic image sensors replaced film, which not only saved the printing process and could be immediately displayed on the screen, but also had much better sensitometric performance than the film. After the computer was connected, it could be used digitally. Technology improves image quality. From the fifties to the present, electronic image sensors have been widely used in commercial applications. For example, the satellite digital photographs and the astronomical telescopes used to photograph the universe from the ground were used in the early days, and digital photographs were used by young people in shopping malls in daily life. machine. Of course, the most common applications are fax machines, scanners, digital cameras and camcorders.

PMT--from the fifties. In the development to the present, it is the earliest electronic sensor, and it is also the best (quality) technology. The structure is like a small cylindrical light bulb (see photo). It has a diameter of about one inch and a length of about two inches. Built-in multiple electrodes, the incoming light is converted into a powerful electronic signal, and even very weak light can accurately capture, which is better than other sensors. PMT is often used in printing, publishing industry scanners and engineering analyzers. The PMT scanner has a maximum sensing density of D4.2, which means it can capture very dark image parts. PMT is very durable and generally has a white to 100,000 operating hours.
Figure 3: Single-line CCD wafers for monochrome scanners (color scanners use three-line CCD wafers, while digital cameras or camcorders use planar () two-dimensional CCD wafers).

CCD--invented by Bell Labs in the United States in 1969, is similar to computer chip CMOS technology. Like CMOS, it can be used as computer memory and logic operation chip. Of course, DRAM is more suitable for electronic memory. The most popular applications are non-scanners, digital cameras and camcorders, but the most notable representative is the installation of four large CCD chips in the BTC (Big Throughput Camera) at the American Observatory of Andas in South America and Chile (see Figure 5). Inside the telescope, it can shoot 35MB of data at a time, greatly aiding astronomy research. The CCD has lower photosensitivity and quality than PMT, but in recent years, CCD technology has progressed, and its maximum density can reach D4.0, which is slightly lower than the highest sensing window of PMT. The size of the CCD. Usually only one ordinary coin is as big, of course there are some extra large (see Figure 4) or small. The CCD is as durable as the PMT.

Figure 4: Tony Tyson, a Bell Labs researcher, uses the CCD on his hands for astronomical research. Copyright of Bell Labs, Lucent Technologies Figure 5: A four-metre-long BTC astronomical telescope in the InterAmerican Observatory in Das, Chile. Copyright of Bell Labs, Lucent Technologies Figure 6: Cosmic puzzles taken by the BTC astronomical telescope.
Copyright of Bell Labs, Lucent Technologies

CMOS--This technology has been developed for decades. It can be said that there are digital computers because CPU and memory are composed of CMOS. However, it was only applied to electronic sensors or digital cameras in 1998. It can also be applied to camcorders. The advantage of CMOS is that the structure is simpler than CCD. With a smaller crystal and lower voltage, the manufacturing cost is lower than that of CCD. CMOS also has its disadvantages, that is, its technology is not yet mature, its quality is generally lower than that of CCD, and its resolution is generally relatively poor. However, there are data showing that the technology of CMOS (which may not be provided in this document) will progress and will surpass CCD.

CIS - Because of the structural relationship, CIS technology is usually used only for scanners. The sensor is CMOS. The CIS scanner fixes the light source, the focusing lens and the sensor together in a housing. It does not have to be warm-up, so it starts faster than the CCD scanner. With this design, the size of the CIS scanner is smaller than that of the CCD scanner, and the manufacturing cost is also reduced. However, the C1S technology is not yet mature and generates relatively large noises. Therefore, it is currently worse than CCD quality.

Conclusion PMT, CCD, CMOS, and CIS are currently popular electronic image sensors. The manufacture of PMT CCDs is relatively complicated and costly. A sensor needs several tens to hundreds of dollars, but its quality is also better. PMT has the highest quality. The professional drum scanner uses PMT technology, but its size and structure are not suitable for portable or small products. The CCD, CMOS and CIS are small and can be used in small products. At present, most of the electronic imaging products use CCDs. We hope that there will be more products of other electronic imaging technologies (for example, CMOS or better sensors) in the near future so that consumers can have more choices.

reference
Http://Telescope/Docs/ccd1.htm
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Http://SCANNERS/ccdvcis.html
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