Difference between CCD and CMOS image
CMOS:
CCD:
Layman version:
Digital cameras have become extremely common as the prices have come down. One of the drivers behind the falling prices has been the introduction of CMOS image sensors. CMOS sensors are much less expensive to manufacture than CCD sensors.
Both CCD (charge-coupled device) and CMOS (complimentary metal-oxide semiconductor) image sensors start at the same point -- they have to convert light into electrons. If you have read the article How Solar Cells Work, you understand one technology that is used to perform the conversion. One simplified way to think about the sensor used in a digital camera (or camcorder) is to think of it as having a 2-D array of thousands or millions of tiny solar cells, each of which transforms the light from one small portion of the image into electrons. Both CCD and CMOS devices perform this task using a variety of technologies.
CCD chip:
The next step is to read the value (accumulated charge) of each cell in the image. In a CCD device, the charge is actually transported across the chip and read at one corner of the array. An analog-to-digital converter turns each pixel's value into a digital value. In most CMOS devices, there are several transistors at each pixel that amplify and move the charge using more traditional wires. The CMOS approach is more flexible because each pixel can be read individually.
CCDs use a special manufacturing process to create the ability to transport charge across the chip without distortion. This process leads to very high-quality sensors in terms of fidelity and light sensitivity. CMOS chips, on the other hand, use traditional manufacturing processes to create the chip -- the same processes used to make most microprocessors. Because of the manufacturing differences, there have been some noticeable differences between CCD and CMOS sensors.
* CCD sensors, as mentioned above, create high-quality, low-noise images. CMOS sensors, traditionally, are more susceptible to noise.
* Because each pixel on a CMOS sensor has several transistors located next to it, the light sensitivity of a CMOS chip tends to be lower. Many of the photons hitting the chip hit the transistors instead of the photodiode.
* CMOS traditionally consumes little power. Implementing a sensor in CMOS yields a low-power sensor.
* CCDs use a process that consumes lots of power. CCDs consume as much as 100 times more power than an equivalent CMOS sensor.
* CMOS chips can be fabricated on just about any standard silicon production line, so they tend to be extremely inexpensive compared to CCD sensors.
* CCD sensors have been mass produced for a longer period of time, so they are more mature. They tend to have higher quality and more pixels.
Based on these differences, you can see that CCDs tend to be used in cameras that focus on high-quality images with lots of pixels and excellent light sensitivity. CMOS sensors traditionally have lower quality, lower resolution and lower sensitivity. CMOS sensors are just now improving to the point where they reach near parity with CCD devices in some applications. CMOS cameras are usually less expensive and have great battery life.
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Background info - History- More in depth tech:
The difference between CCD and CMOS
1970 is a landmark year for image processing industry; the United States Bell Labs invented the CCD. After 20 years, people use it to create the digital cameras; image-processing industries is pushed into a new field. Digital camera without film and rinse, can repeat shooting and immediate adjustment; Imaging can be copied without limit and not reduced quality, facilitate the permanent preservation and can be used for electronic transmission and processing. Its birth to the image processing industry has brought a revolution.
Later, it was discovered that a kind of processing chip in the computer system can be used as digital camera sensitive sensors or CMOS, featuring mass production and low-cost that is businessmen pursuit. Industry analysis believes that it in the near future may replace CCD, but now they still coexist. Many people believe that: "Intelligent sensors, particularly CCD, is the extremely core components, is the heart of digital cameras. "This is not true: Intelligent sensor, or CCD, its function is to capture light and converted them to electronic signals through lens, CCD is not so much the heart, as it is eyes for the cameras. In researching cameras, the CCD or CMOS sensor photosensitive though is a very important component, determine a large extent the pixel camera, However, CCD / CMOS chip do not take the dominant position of the cost, the more sophisticated areas, the more prominent this character.
From a view of technical point, CCD and CMOS have four different aspects:
1. Data readout method
The charge stored by CCD charge-coupled device, need the control of synchronous signal to read after being translated. Charge transfer and information read and output need work with clock control circuit and three different power resources. The whole circuit is much more complex. CMOS photoelectric sensors directly generated electronic signal after conversion, the signal is very simple to read.
2. Speed
CCD charge-coupled device output the information under the control of clock control circuit; the speed of output is slow. While the CMOS can capture the signal and output it at the same time, process the image data of each unit in the meanwhile. Of course, the speed is faster than CCD’s.
3. Power source and electricity consumption
CCD needs three power sources to support its work; the consumption of electricity is serious. CMOS only need one power source and the consumption is small, maybe equivalent to 1/8 to 1/10 of CCD. Therefore, CMOS has a real advantage in saving energy.
4. Image quality
Because CCD is begin made in early days, its technology is maturity, and adopt PN or SiO2 to reduce the noise, so the image quality is better than CMOS. But in recent years, with the development of the noise eliminating technology, CMOS will get much better image quality.
Besides, the internal and external structures of them are different.
1. The internal structure (itself structure)
The each image point of CCD consists of one Photodiodes and one charge storage zoon next to charge storage and under its control. Photodiodes convert the photons into electron and the relationship between the numbers of electron and intensity of light is direct ratio, when read these charge, the data moved into the ISA Server. The image generated from this structure has the merits of low noise and high function, but need clock signal and Technology for Deflective Pressure to produce CCD, so that the whole system is complex , increase the consumption of electricity and cost.
CMOS’s electronic components can be integrated at the one process period, such as Digital Logic Circuit, Clock Driver and the ADC. It likes storage and each image point includes one Photodiodes, one charge or voltages convert unit, one reset and others. It can read the signal by simple X-Y addressing technology,
2.external structure (the application of the products)
CCD charge-coupled device output the information under the control of clock control circuit; the speed of output is slow. While the CMOS can capture the signal and output it at the same time, process the image data of each unit in the meanwhile. Of course, the speed is faster than CCD’s.
CMOS can combine all of components of digital camera into one chip, including photosensitive element, picture amplifier, signal readout circuit, image signal processor and controller and among others. Only one chip can carry out many functions, so the whole cost of it is low.
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