Forum > General discussions > Rumours > SE plans to impove K750 in July/August

Posted: 2005-05-27 23:52

This message was posted from a S700

Posted: 2005-05-27 23:58

This message was posted from a S700

Posted: 2005-05-29 21:14

• Both CMOS and CCD imagers are manufactured in a silicon foundry
  
• Developed in the 1970s and 1980s specifically for imaging applications, CCD technology and fabrication processes were optimized for the best possible optical properties and image quality. The technology continues to improve and is still the choice in applications where image quality is the primary requirement or market share factor.
  
• This (the CCD) architecture produces a low-noise, high-performance imager. That optimization, however, makes integrating other electronics onto the silicon impractical. In addition, operating the CCD requires application of several clock signals, clock levels, and bias voltages, complicating system integration and increasing power consumption, overall system size, and cost.
  
• A CMOS imager, on the other hand, is made with standard silicon processes in high-volume foundries. Peripheral electronics, such as digital logic, clock drivers, or analog-to-digital converters, can be readily integrated with the same fabrication process.
  
• This architecture allows the signals from the entire array, from subsections, or even from a single pixel to be readout by a simple X-Y addressing technique—something a CCD can’t do.
  
• The biggest opportunities for CMOS sensors lie in new product categories for which they are uniquely suited. Keys to their success are
  
  
  
  • Lower power usage
    
  • Integration of additional circuitry on-chip
    
  • Lower system cost
    
  
  Such features make CMOS sensors ideal for mobile, multifunction products ...
  
• CCDs have been mass-produced for over 25 years whereas CMOS technology has only just begun the mass production phase. Rapid adoption was also hindered because some early implementations of these devices were disappointing: they delivered poor imaging performance and poor image quality.
  
• ... the current sensor market divides itself into two areas: the high-performance, low-volume branch, and the low-cost, high-volume branch. In the high-performance branch are applications that will continue to be dominated by CCD technology, but CMOS technology will find market share too, especially for lower cost or more portable versions of these products. The second area is where most of the CMOS activity will be. Here, in many applications CCD sensors will be replaced with CMOS sensors. These could include some security applications, biometrics and most consumer digital cameras.
  
• Most of the growth, though, will likely come from products that can employ imaging technology—automotive, computer video, optical mice, imaging phones, toys, bar code readers and a host of hybrid products that can now include imaging. These kinds of products will require millions of CMOS sensors.
  

• CCD (charge coupled device)
  
• CMOS (complementary metal oxide semiconductor)
  
• CCDs and CMOS imagers have unique strengths and weaknesses that make them appropriate to different applications. Neither is categorically superior to the other ...
  
• In a CCD sensor, every pixel's charge is transferred through a very limited number (often one) of output nodes to be converted to voltage, buffered, and sent off-chip as an analog signal. All of the pixel can be devoted to light capture, and the output's uniformity (a key factor in image quality) is high.
  
• In a CMOS sensor, each pixel has its own charge-to-voltage conversion, and the sensor often also includes digitization circuits, so that the chip outputs digital bits. These other functions reduce the area available for light capture, and with each pixel doing its own conversion, uniformity is lower. But the chip requires less off-chip circuitry for basic operation.
  
• CCDs have been the dominant solid-state imagers since the 1970s, primarily because CCDs gave far superior images with the fabrication technology available.
  
• Only recently has semiconductor fabrication advanced to the point that CMOS image sensors can be useful and cost-effective in some mid-performance imaging applications.
  
• CCDs offer superior image performance (as measured in quantum efficiency and noise), and flexibility at the expense of system size. They continue to rule in the applications that demand the highest image quality, such as most industrial, scientific, and medical applications.
  
• CMOS imagers offer more integration (more functions on the chip), lower power dissipation (at the chip level), and smaller system size at the expense of image quality and flexibility. They are well-suited to high-volume, space-constrained applications where image quality is not paramount, such as security cameras, PC peripherals, toys, fax machines, and some automotive applications.
  
• CMOS cameras may require fewer components and less power, but they may also require post-processing circuits to compensate for the lower image quality.
  
• The money and attention concentrated on CMOS imagers means that their performance will continue to improve, eventually blurring the line between CCD and CMOS image quality.
  
• ... for the forseeable future, CCDs and CMOS will remain complementary. Each can provide benefits that the other cannot.
  

• All CCD cameras use interpolation to create images. For example, a 3 megapixel digital camera only has 750,000 red, 750,000 blue, and 1.5 million green pixels, but the camera's on-board processor generates a 3 million pixel RGB color image by interpolating the data from each neighboring pixel.
  
• CMOS sensors have several advantages over CCDs. They use only 1/5 to 1/10 as much power as CCDs, making them a good choice for battery-powered cameras. CMOS sensors are made using the same techniques and equipment as more familiar CMOS circuits like CPUs and RAM memory, so they cost less to produce than CCDs, which require specialized fabrication equipment.
  
• Each pixel in a CMOS sensor has its own amplifier circuit, so the signal amplification is performed before the image is scanned.
  
• ... CMOS sensors often contain additional image processing circuitry (including analog-to-digital converters and JPEG compression processors) directly on the chip, making it easier and faster to retrieve and process the picture information. This results in a lower chip count, increased reliability, reduced power consumption, and a more compact design.
  
• A key problem in older CMOS sensors was that some pixels often had more or less sensitivity than their neighbors. This unevenness translates into noise.
  

• ... CMOS components are fabricated in mainstream silicon foundries, resulting in significant cost reductions, process line improvements, and a higher level of circuit integration on the chip.
  This on-chip circuitry enables CMOS image sensors to achieve a significant advantage in functionality over CCDs. The result? A more compact system that decreases defects, increases reliability and reduces the need for peripheral support chip packaging and assembly, further reducing cost.
  
• Stated simply, CMOS sensors consume much less power than that of similar CCD sensors—at least 10 times less, in fact. This advantage is particularly important for applications such as digital cameras, PC videocameras, laptop computers, cellular phones and toys.
  
• Unlike CMOS components, CCD systems require multiple 5-15 V power supply levels and voltage regulators for operation. CMOS typically uses a single, 3.3 volt (or 5 volt supply), increasing power supply efficiency.
  
• With CMOS, signal processing can be integrated directly on the chip.
  
• Higher yields and less susceptibility to defects make CMOS a lower cost technology than CCD for image sensors. Fewer parts, a smaller form factor, and higher reliability in the end product system mean cost savings to the systems manufacturer.
  
• CCDs rely on a process that can leak charge to adjacent pixels when the CCD register overflows; thus bright lights “bloom” and cause unwanted streaks in the image. CMOS architecture is inherently less sensitive to this effect.
  
• In addition, smear—caused by charge transfer in the CCD under illumination—is non-existent with CMOS.