Considering CMOS for security and surveillance

Sunday, June 1, 2003

Once the darling of the digital imaging industry, CCD is now being rivaled by its ugly duckling-turned-swan counterpart - CMOS.

CMOS image sensors are taking the digital imaging market by storm, as the technology gains ground on the better-known CCD technology. Much of CMOS’ growth stems from its ability to enable lower power consumption, sophisticated imaging and the development of low-cost, “smart” imaging devices. As systems integrators and OEMs work to utilize the most advanced surveillance imaging products in security lineups - including migrating from analog systems to digital technology that runs on installed Ethernet networks - there are a number of benefits to using CMOS image sensors in surveillance equipment. These benefits include the ability to build truly wireless surveillance devices, effective digital conversion, superior image quality and cost savings. And, these key differentiators are all crucial factors in driving the overall direction of the industry towards “smart” surveillance cameras, which will free up network bandwidth and network administrators’ time and save money.

The low power consumption derived from CMOS image sensors is a major technological advancement with numerous positive implications.

One of the reasons that wireless technology is not yet as prevalent as some had predicted is that, to be truly wireless, a surveillance camera cannot have a wired power source. CMOS image sensors, which consume less than 1/100 of the power of CCD sensors, allow systems integrators to employ truly wireless security technologies and integrate imaging into a broader range of security products and systems.

Digital or Analog?

The impact of the shift to digital surveillance will be tremendous and is not unlike the major changes occurring in the recording industry today. Although security customers will reap many rewards from going digital, conversion is not always fast or smooth; resulting in a network camera market that is growing but still fairly small. For example, digital video recorders are widely accepted and utilized by systems integrators, but the actual cameras monitoring such public spaces as bank lobbies or convenience stories remain analog. To realize the true value of digital technology, everything from the video to the storage to the network must be digital. CMOS sensors can help speed this conversion because they do not require processing to convert from analog to digital. This means that the transformation from analog to digital is not only less expensive, but also results in purer digital images and better data integrity.

Recent heightened security concerns and the pervasive use of security cameras in public spaces, coupled with the increased use of biometrics, render overall image quality a crucial factor in effective surveillance. Unfortunately, typical security cameras suffer from shadow in scenes that have a mix of bright and dim lighting.

The camera may show detail in the bright areas or the shaded areas, but not both simultaneously. In order for security personnel to provide effective protection, they must be able to see what is happening everywhere within a camera’s field of view. This lack of information leads to the loss of overall security and, therefore, protection failure.

Certain CMOS imagers can overcome this obstacle because only CMOS - not CCD - offers wide dynamic range. Wide dynamic range is the ability of video cameras to show details in both the bright and dim areas of an image at the same time, just as the eye would see them. With a built-in programming feature, wide dynamic range also offers more flexible control over the CMOS imager, a value-added feature that CCD sensors simply cannot provide. Wide dynamic range gives security and surveillance OEMs and large systems integrators the ability to install cameras with mixed lighting security settings.

This leads me to the end of my discussion as well as the final direction of the industry - toward “smart” surveillance cameras. Smart cameras are required in today’s digital world because precious network bandwidth should only be consumed by video when it is required. In other words, the camera must decide when to send video.

CMOS imagers with wide dynamic range enable this intelligence because they provide the crisp, digital details required by sophisticated motion detection, face recognition and other image analysis applications. These applications can be built directly into wide dynamic range cameras, enabling real-time triggering of video transmission.

Cameras that do not have CMOS’ imaging capabilities such as wide dynamic range, will send a constant stream to the web server, thus taking up bandwidth with unnecessary images, giving your network administrator a massive headache. A smart camera is making real-time decisions, and sending images out only when they are needed. Your web server will not be bogged down with unneeded images; your overall level of protection will be more effective and your network administrator will thank you.

Dan Ostrower is director of product marketing at SMaL Camera Technologies. He can be reached at