CCD Versus CMOS

CCD Versus CMOS

Mobotix, said CEO Ralf Hinkel, uses CMOS because it provides lower power consumption, faster reaction and technical advantages. "CMOS sensors without auto iris, digital contrast enhancement and configurable exposure measurement zones guarantee optimal exposure control," Hinkel said. "Most cameras with mechanical auto iris more or less shut down when they are confronted with backlight. As a result, darker areas become even darker and faces unrecognizable."


While frequent attempts to brighten images electronically using backlight are taken, in Hinkel's view, the results are unsatisfactory since the auto-iris lens is closed. Mobotix, he stressed, has taken a completely different approach to solve the problem. "The CMOS sensors used in Mobotix cameras need no mechanical auto iris. Instead, they expose electronically from 1/8,000 second to one second. This means that Mobotix cameras have no moving shutter parts that fail or freeze during winter."


Moreover, Hinkel explained that without the auto iris, the camera can electronically choose what to see. Exposure windows are easily configured and they inform the automatic exposure control which areas of images to lighten.


Likewise, Grandeye CEO Alexa McCulloch believes that CMOS is the future. "While more expensive CCD sensors have historically offered significantly higher quality than CMOS sensors, the latter have made great strides in image quality, consume less power and require less circuitry. For these reasons, Grandeye network cameras feature CMOS sensors, which enable our smaller form factor cameras."


In the opinion of Oh Tee Lee, Regional Director, South Asia Pacific, Axis Communications, CMOS is "up and coming," and being used a lot in mobile phones, smart phones and PDAs. "CMOS sensors emit less heat and use smaller batteries, while CCDs need much larger batteries. When you use products with CCD sensors, it is immediately obvious that they are hotter to the touch. CMOS sensors also enable much smaller products. As the technology improves and becomes less expensive, CMOS will be more widely adopted."


According to Lee, many Axis products already feature CMOS progressive scan. "Very few megapixel cameras are using CCDs as they require a layer of film to insulate the camera from heat. CMOS also allows windowing, which cannot be done with CCD sensors," he said.


While CCD technology is more mature, said Paul Bodell, Chief Marketing Officer of IQinVision, not much is available for use with multimegapixel cameras. CMOS, on the other hand, is "reliable and affordable."

Injecting a word of caution was Hidenori Taguchi, Manager of the Product Planning Department at Sony Corp. "While things are changing," he explained, "CCDs retain advantages in terms of sensitivity."


Lee agreed. "Today, CCD sensors are more widely used because they have been around for a long time. Most camera manufacturers like Sony, Cannon and Panasonic use them." CCD sensors, he continued, are much better for use in low-light environments and provide background compensation and wide dynamic range.

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