How many kinds of camera sensors?
According to the category of light-sensitive devices to points, now on the market for the majority of the camera lens for the CCD and CMOS two kinds, of which the CCD (Charge Coupled Device, charge coupled components) because of the higher price is more used in the camera, image scanning aspects of the high-end technology components, CMOS (Complementary Metal Oxide Semiconductor, additional metal oxide semiconductor components) are mostly used in some low-end video products.
The digital cameras sold in the market are basically CMOS cameras. In the use of CMOS as a light-sensitive components of the product, through the use of image light source automatic gain reinforcement technology, automatic brightness, white balance control technology, color saturation, contrast, edge enhancement and gamma correction and other advanced image control technology, fully comparable to the effect of CCD cameras. Restricted by market conditions and market development and other circumstances, the camera using CCD image sensor manufacturers are few, mainly due to the impact of the high cost of using CCD image sensors.
Expanded Information
Image sensor image sensor is the use of photoelectric devices photoelectric conversion function. The light-sensitive surface of the light image will be converted into a corresponding proportion with the image of the light into the relationship between the electrical signal. Compared with the photodiode, phototransistor and other "point" light-sensitive components, the image sensor is the light received on the surface of the light image, divided into many small units, which will be converted into usable electrical signals of a functional device. Image sensors are categorized into photoconductive camera tubes and solid-state image sensors. Compared with photoconductive camera tubes, solid-state image sensors are characterized by small size, light weight, high integration, high resolution, low power consumption, long life, and low price. Therefore, they are widely used in various industries.
CCD
CCD is used in photography and video of high-end technology components, CMOS is used in lower image quality products, its advantage is that the manufacturing cost is lower than the CCD, power consumption is also much lower, which is the market many products using the USB interface without the need for external power supply and the reason for the cheap price. Although technically different, but CCD and CMOS performance gap between the two is not very large, just CMOS camera on the light source requirements to be higher, but the problem has been basically resolved. CCD component size is more than 1/3 inch or 1/4 inch, in the same resolution, it is desirable to choose a larger size of the component is good. The image sensor is also called the light-sensitive element.
Applications
An image sensor? , or photoreceptor, is a device that converts an optical image into an electronic signal, and it is widely used in digital cameras and other electronic optical devices. Early image sensors used analog signals, such as a camera tube (video camera tube). With the rapid development of digital technology, semiconductor manufacturing technology, and networking, the market and the industry are facing the arrival of the era of great integration of video, audio-visual, and communications across various platforms, outlining the beauty of human daily life in the future.
With its application in daily life, digital camera products undoubtedly belong to the speed of its development can be described as rapid change. In just a few years, digital cameras have grown from hundreds of thousands of pixels to 4, 5 million pixels or even higher. Not only in the developed countries of Europe and the United States, digital cameras have occupied a large market, is in the development of China, the digital camera market is also growing at an alarming rate, therefore, its key components - image sensor products have become the current and future industry concerns, attracting a large number of manufacturers to invest.
To distinguish by product category, image sensor products are mainly divided into CCD, CMOS and CIS sensors. This article will mainly introduce the CCD and CMOS sensor technology and industrial development status.
History
The light-sensitive device is the most core component of the industrial camera, the image sensor has CMOS and CCD two kinds of. CCD unique process, with good low-light effect, high signal-to-noise ratio, a strong sense of permeability, color reproduction ability, etc., in the transportation, medical and other high-end fields are widely used. Because of its imaging advantages, in a long time will continue to be used, but at the same time due to its high cost, power consumption also restricts the space of its market development.
CCD and CMOS in different application scenarios have their own advantages, but with the continuous improvement of CMOS process and technology, as well as high-end CMOS prices continue to decline, I believe that in the future development of high-definition cameras in the security industry, CMOS will occupy an increasingly important position.
CCD (Charged Coupled Device) was successfully developed in 1969 in Bell Labs, and then by the Japanese companies began mass production, its development history has been nearly 30 more than. CCD can be divided into line (Linear) and surface (Area) two kinds of, which is used in the linear image scanner and fax machine, and the surface type is mainly used in the digital camera (DSC), camcorder (DSC), digital camera (DSC), digital camera (DSC), digital camera (DSC), digital camera (DSC), digital camera (DSC), digital camera (DSC) and digital camera (DSC). CCDs can be divided into two types: Linear and Area, with Linear being used in image scanners and fax machines, and Area being used in digital cameras (DSC), videocassette recorders, and surveillance cameras.
Features
In general, CCD sensors have the following advantages:
High Resolution
(High Resolution): The size of the image point is in the μm level, which allows for the sensing and recognizing of fine objects, and improves the quality of the image. From 1-inch, 1/2-inch, 2/3-inch, 1/4-inch to the introduction of 1/9-inch, the number of pixels from more than 100,000 increased to 4 to 5 million pixels;
Low Noise
(Low Noise) High Sensitivity: CCD has a very low readout noise and dark current noise, so improve the signal-to-noise ratio (SNR), but also has a high degree of sensitivity, the very low luminosity of the incident light can be detected. Incident light can also be detected, the signal will not be masked, so that the application of the CCD is more independent of the weather constraints;
Wide dynamic range
(High Dynamic Range): Simultaneous detection and resolution of strong and weak light, to improve the use of the system environment range, not due to the large differences in brightness caused by the phenomenon of signal contrast.
Good linear characteristic curve
(Linearity): the incident light source intensity and the output signal size into a good proportional relationship, the object information will not be lost, reduce the cost of signal compensation processing;
High Quantum Efficiency: very weak incident light irradiation can be recorded. Recorded, if with the image intensifier tube and projector, even in the dark of the night distant scene can still be detected;
Large Field of View: The use of semiconductor technology has been able to manufacture large-area CCD chip, and the size of the traditional film equivalent to the 35mm CCD has begun to be applied to digital cameras, becoming the key to replace the professional favorable optical camera components.
Broad Spectral Response (Broad Spectral Response): can detect a wide range of wavelengths of light, increasing the flexibility of the system, expanding the application areas of the system;
Low Image Distortion (Low Image Distortion): the use of the CCD sensor, the image processing will not have distortion.
Small size and light weight
CCDs are small and lightweight, so they can be easily installed on satellites and various navigation systems;
Low_electricity
Unaffected by strong electromagnetic fields;
Good charge transfer efficiency
The efficiency factor affects the signal-to-noise ratio, and the efficiency factor affects the signal-to-noise ratio.
The efficiency factor affects the signal-to-noise ratio and resolution, if the charge transfer efficiency is not good, the image will become blurred;
Mass production, stable quality, sturdy, not easy to aging, easy to use and easy to maintain.
According to In-Stat's research report on global image sensors in 2001, the top seven manufacturers in the CCD industry are all Japanese manufacturers, accounting for 98.5% of the global market share, and in terms of technological development, the more distinctive major manufacturers should be Sony, Philips and Kodak.
CMOS
Features
CMOS sensors using general semiconductor circuits most commonly used in the CMOS process, has a high degree of integration, low power consumption, speed, low cost and other characteristics, the last few years in the wide dynamic, low illumination aspects of the development of a rapid. CMOS that is, the complementary metal-oxide semiconductor, is mainly the use of silicon and germanium made of two elements Semiconductor, through the CMOS on the negatively charged and positively charged transistors to achieve the basic functions. The current generated by these two complementary effects can be recorded and interpreted as an image by the processing chip.
In analog cameras and SD network cameras, CCD is the most widely used, has long been dominant in the market. CCD is characterized by high sensitivity, but the response speed is low, is not suitable for high-resolution progressive scanning used in high-definition surveillance cameras, so into the era of high-definition monitoring, CMOS is gradually recognized, high-definition surveillance cameras CMOS sensors are commonly used.
The main advantage of CMOS over CCD is that it is very energy efficient. Unlike CCDs, which are composed of diodes, CMOS circuits consume almost no static electricity. This makes the power consumption of CMOS is only about 1/3 of the ordinary CCD, CMOS is an important issue in the processing of fast-converting images, due to the current change too often and overheating, dark current suppression is not much of a problem, if the suppression is not good, it is very easy to noise.
Have developed 720P and 1080P dedicated back-illuminated CMOS devices, its sensitivity performance has been close to the CCD. Compared to surface-illuminated CMOS sensors, back-illuminated CMOS has a great advantage in sensitivity (S/N), significantly improving the shooting effect under low-light conditions, so shooting in low-light environments can significantly reduce noise.
While megapixel camera products based on CMOS technology have deficiencies in low-light environments and signal-to-noise processing, this does not fundamentally affect its application prospects. And the relevant international companies are making greater efforts to solve these two problems, I believe that in the near future, the effect of CMOS will be more and more close to the effect of CCD, and CMOS equipment prices will be lower than CCD equipment.
Security industry using CMOS more than CCD has become an indisputable fact, although the same size of the CCD sensor resolution is better than the CMOS sensor, but if you do not take into account the size of the limitations of the CMOS in the amount of rate of the advantages of the large size of the photographic raw materials can be effectively overcome the difficulties in the manufacture of the original, so that the CMOS in a higher resolution will be more advantageous. In addition, CMOS response speed is faster than CCD, so it is more suitable for high-definition monitoring of large data volume characteristics.
History
Compared with CCD, CMOS has the advantages of small size, consumes less than 1/10 of the power of CCD, and sells at a price 1/3 cheaper than that of CCD.
Compared to CCD products, CMOS is a standard process that can utilize existing semiconductor equipment without the need for additional investment in equipment, and the quality can progress with the advancement of semiconductor technology. At the same time, the global fab CMOS production line more, later mass production is also conducive to cost reduction. In addition, the biggest advantage of CMOS sensors is that they have a high degree of system integration.
Theoretically, all the functions required by the image sensor, such as vertical displacement, horizontal displacement register, timing control, CDS, ADC, etc., can be placed on a chip integrated, and even all the wafers, including the back-end chip (Back-end Chip), Flash RAM (Flash RAM), etc., can be integrated into a single chip (SYSTEM-ON-CHIP), to achieve a single chip (SYSTEM-ON-CHIP), and to achieve a single chip (SYSTEM-ON-CHIP), and to achieve a single chip (SYSTEM-ON-CHIP).
Auto Sync with Cloud
No manual interaction required for cloud services.
Because of this, into the R & D, production of more manufacturers, the United States has more than 30, Europe 7, Japan about 8, South Korea 1, Taiwan has eight. The global leader in the position of the manufacturer is Agilent (HP), its market share of 51%, ST (VLSI Vision) accounted for 16%, Omni Vision accounted for 13%, Hyundai accounted for 8%, Photobit accounted for about 5%, the five combined market share of 93%.
According to In-Stat statistics, global sales of CMOS sensors are expected to exceed $1.8 billion by 2004, and CMOS will grow rapidly at a compound annual growth rate of 62%, gradually encroaching on the application areas of CCD devices. Especially in 2013 the rapid development of cell phone applications, CMOS image sensor-based camera module will occupy more than 80% of its application market.
Market
CMOS image sensor belongs to the emerging product market, its market share changes are not as constant as the mature industry, for example, in 1999, the CMOS market, according to the proportion of shipments ranked in order of Agilent, OmniVision, STM and Hyundai, its market share of 24%, 22%, 14% and 14%, of which STM is a European manufacturer, Hyundai is a Korean manufacturer; but only after a year after the market competition, Agilent and OmniVision shipment ranking order is still divided into one and two, and market share were raised to 37.7% and 30.8%, while STM fell to the fourth, the market share slipped significantly to 4.8%.
As for Hyundai, the market share is only 2.1%, but Photobi's growth in 2000 is worth mentioning, with its global market share growing rapidly to 13.7%, ranking third in the world. These three manufacturers accounted for 82.2% of global shipments. From this, we can analyze that the concentration of vendors in this industry is quite dense, so by observing the dynamics and development of the above three vendors, we can see the direction of the future development of the licensing industry and technology.
Agilent's main products are the second-generation CIF (352*288) HDCS-1020 and the second-generation VGA (640*480) HDCS-2020, which are mainly used in digital cameras, mobile phones, PDAs, PC Cameras, and other emerging information appliances. Agilent in 2000, another successful strategy is and Logitech and Microsoft, the two companies strategic alliance, into the optical mouse product area, but this is a very low-end CMOS products, and not to capture images.
So when we did the global statistics on image sensors, we didn't include this number, but this move shows Agilent's intention to use CMOS technology as the basis for its plans to move into optical components.
OmniVision's main products include _CIF (352 x 288), VGA (640 x 480), SVGA (800 x 600) and SXGA (1280 x 1024). 1.3-megapixel grade CMOS image sensors developed by Omnivision are being used by the industry in a large number of digital cameras. The industry generally believes that megapixels are a watershed for the use of CMOS and CCDs, and the success of CMOS in crossing over into this market is a good indication of the degree of penetration of CMOS technology development into the market, which will probably replace CCDs as a non-remaining application for low and mid-range imaging products in the future.
Omnivision in May 2001 to develop the CIF (352 x 288) level of CMOS sensors, which is characterized by low _ electricity, the target market positioning in the cell phone, its product development strategy and the major research and survey institutions coincide, in the cell phone market, CMOS modules of the camera module has become the most large number of products for mobile communication applications.
Photobit achieved greater success in 2000. 2001 Photobit took the lead in developing the PB-0330 product model CMOS image sensor, this product features a single chip logic to digital inverter, it is the second generation of 1/4-inch VGA (640 x 480), and also introduced PB-0111 product model CMOS image sensor, which is a second generation 1/5-inch CIF (352 x 288).
Photobit launched these two products mainly for digital cameras and PC Camera digital products, and OmniVision CIF (352 x 288) positioning in the mobile phone market to differentiate between its CIF (352 x 288) and VGA (640 x 480) two different levels of resolution of the image sensor, the sales range is intended to cover the low and mid-range of the market. The scope is intended to cover both the low and mid-range market.
Development
In 2013, the industry developed a new CMOS image sensor technology, C3D, which is best characterized by the uniformity of pixel response, redefining imager performance (i.e., including overall system performance) and improving the standard performance of CMOS image sensors in terms of uniformity and dark current.
Early in 2014, Foveon Corporation publicly demonstrated its latest development, Foveon X3 technology, which immediately drew significant industry attention.Foveon X3 is the world's first image sensor array that captures all the colors in a single pixel. Traditional photocoupling devices can only sense light intensity, not color information, and need to sense color information through color filters, which we call Bayer filters. Foveon X3, on the other hand, senses color through different depths on a pixel, with the top layer sensing blue, the second layer sensing green, and the third layer sensing red.
It is based on the absorption effect of silicon on different wavelengths of light to achieve one pixel to sense all the color information, and there is already a CMOS image sensor that uses this technology, and its application product is the "Sigma SD9" digital camera.
This innovative technology provides sharper images and better colors than previous image sensors, and the X3 is the first to detect colors through a built-in silicon photoelectric sensor.
The Foveon X3's technology is a great breakthrough for traditional semiconductor photoreceptor technology, and has the effect of overturning the traditional technology, so I believe that the Foveon X3 has a very good future.
In terms of high-resolution pixel products, a few days ago, Taiwan's sharp vision technology has led the industry batch launch of 2.1 megapixel CMOS image sensors, and there has been a U.S. and Taiwan's optical lens factory, will be launched in the third quarter of this CMOS sensor combined with the lens of the module, the CMOS application has begun to be applied in the 2 megapixel digital camera products.
Contrast
CCDs offer excellent image quality, noise immunity and flexibility in camera design. Despite the increased size and complexity of the system due to the addition of external circuitry, there is more flexibility in circuit design to maximize the performance of some of the special concerns of a CCD camera.CCDs are better suited for applications that require very high camera performance and less stringent cost control, such as astronomy, high-definition medical X-ray imaging, and other scientific applications that require long exposure times and stringent requirements for image noise.
CMOS is an image sensor that can be produced by applying contemporary large-scale semiconductor integrated circuit production processes, featuring high yield, high integration, low power consumption, low price, etc. CMOS technology is the technology that many image sensor semiconductor research and development companies around the world are trying to use to replace CCDs. After years of effort, as an image sensor, CMOS has overcome many of the early shortcomings, the development of the image quality can be in the image quality of the CCD technology to compete with the level.
CMOS level makes them more suitable for applications requiring small space, small size, low power consumption and image noise and quality requirements are not particularly high occasions. For example, most industrial inspection applications with auxiliary light illumination, security and safety applications, and most consumer commercial digital camera applications.
Technical Parameters
It is very important to understand the imaging principles and main parameters of CCD and CMOS chips for product selection. Similarly, the performance of the same chip may vary with different designs of cameras.
The main parameters of the CCD and CMOS are the following:
1, the pixel size?
Pixel size refers to the actual physical size of each pixel on the chip pixel array, the usual size including 14um, 10um, 9um , 7um , 6.45um , 3.75um and so on. The pixel size reflects the chip's ability to respond to light to some extent. The larger the pixel size, the more photons it can receive, and the more charge it can generate under the same light conditions and exposure time. For low-light imaging, the pixel size is a characterization of the chip's sensitivity.
2. Sensitivity?
Sensitivity is one of the important parameters of the chip, it has two physical meaning. One refers to the photoelectric conversion ability of the optical device, with the same meaning as the response rate. That is, the chip's sensitivity refers to a certain spectral range, the unit exposure of the output signal voltage (current), the unit can be nanoampere / lux nA / Lux, volts / watt (V / W), volts / lux (V / Lux), volts / lumens (V / lm). The other refers to the radiant power (or illuminance) to earth that the device can sense, in the same sense as detection rate,. The unit can be expressed in watts (W) or lux (Lux).
3, bad points?
Because of the limitations of the manufacturing process, for sensors with millions of pixel points, all the pixels are good situation is almost unlikely, the number of bad points refers to the number of bad points in the chip (can not be effectively imaged pixel or the corresponding inconsistency is greater than the parameter allowable range of pixels), the number of bad points is an important parameter of the chip to measure the quality of the parameter.
4, spectral response
Spectral response refers to the chip's ability to respond to different wavelengths of light, usually given by the spectral response curve.
From the product technology development trend, whether it is CCD or CMOS, its volume miniaturization and high pixel count is still the industry's active research and development goals. Because the pixel size is small, the higher the resolution of the image product, the better the clarity, the smaller the volume, its application is more extensive.
From the above two kinds of image sensor resolution, the future will have a few years to 1.3 megapixels to 2 megapixels as the boundary, above the application field, will still be the mainstream CCD, under the product, will begin to CMOS sensors as the mainstream. Industry analysis of the end of 2014 to the beginning of 2015, there will be 3 megapixel CMOS market, predicting that the CMOS market applications beyond the timing of the CCD is generally in 2004-2005.
State of the Art
The image sensor's visual ratio is now a given using High Definition (HD) resolution of 1080p, and camera designs are evolving toward using smaller optical formats, resulting in the need for smaller pixel structures to reduce overall system costs without compromising image performance or light sensitivity.
CCD image sensors are gradually becoming the mainstream of image sensors due to their high sensitivity and low noise. However, due to process reasons, the sensitive components and signal processing circuits can not be integrated on the same chip, resulting in a large volume of cameras assembled by the CCD image sensor, high power consumption.
CMOS image sensor with its small size, low power consumption in the image sensor market is unique. However, the initial CMOS image sensors on the market have not been able to get rid of the shortcomings of low light sensitivity and low image resolution, and the image quality is not comparable to that of CCD image sensors.
If the light sensitivity of CMOS image sensors is increased by 5 to 10 times, and the noise is further reduced, the image quality of CMOS image sensors can reach or slightly exceed the level of CCD image sensors, and at the same time maintain the advantages of small size, light weight, low power consumption, high degree of integration, and low price, CMOS image sensors will replace CCD image sensors, and develop better performance. Sensors, and develop a better efficacy.
The development of next-generation image systems has grown tremendously due to the use of CMOS image sensors, and the cost of production has been reduced with the formation of economies of scale. CMOS image sensors now offer picture quality comparable to that of CCD image sensors, thanks in large part to improvements in image sensor chip design, as well as sub-micron and deep-sub-micron designs that have added new functionality within the pixel.
In reality, a CMOS image sensor is more of an image system. A typical CMOS image sensor typically consists of an image sensor core (which multiplexes discrete signal levels to a single output, much like a CCD image sensor), all of the timing logic, a single clock, and on-chip programmable features such as gain adjustments, integration times, windows, and analog-to-digital converters.
In fact, when a designer buys a CMOS image sensor, he gets a full system including image array logic registers, memory, timing pulse generators and converters. Integrating the entire image system on a single chip not only reduces power consumption, but also offers the advantages of lighter weight, reduced footprint, and lower overall price compared to traditional CCD image systems.
Source: Baidu Encyclopedia-Image Sensor