With the move from standard resolution to HD for full motion video in global security applications to improve detection, recognition, and identification capabilities, there is then the question of what HD image sensor and camera are the best.
In 2011, we had looked at the advantages of CCD versus CMOS image sensors in defense and global security cameras. CMOS has long offered the advantage of higher frame rates, but had lagged behind in image quality. Of course over the last four years there have been many improvements in image sensors, especially with CMOS image sensors in low light and global shutter performance. As we have noted, the big change over from CCD to CMOS is happening now in industrial markets so what about in defense and security applications?
If we consider the special requirements in the global security market that are most important, we can help determine which technology is the best fit, such as:
Because the daylight cameras are often used to cover the lowlight gap in 24/7 systems, the sensitivity of the camera in lower light conditions is necessary. The quantum efficiency, QE, divided by the read noise gives the overall sensitivity of the sensor, or the minimum amount of light you can see. In general, CMOS image sensors have a higher QE in the NIR due to their design structure, and now the latest sensors also have lower read noise providing better sensitivity than CCD image sensors at all wavelengths. Here is a graph we previously shared of the sensitivity data of the latest generation high-performance image sensors. For a graph of the data from 2011, click here.
QE/Dark Noise versus Wavelength
Performance in Harsh Outdoor Conditions
Cameras with either type of sensor can be ruggedized to perform in high shock and vibration environments. The effects from high temperatures are different, though. With previous generations, the noise in CCD image sensors was much less at higher temperatures. This is no longer true, and the sensitivity advantage of CMOS image sensors remains at higher temperatures without any additional camera functionality or cooling (see above graph).
Available products and complementary products
CCD cameras have long been used in industrial and global security cameras so there are many different resolution and pixel combinations. There are also many options in high quality optics that meet the full MTF. Many of these lenses can still be used with CMOS cameras as more and more resolution and pixel pitch combinations are becoming available.
Because of the level of integration, CMOS sensors allow for lower power camera designs. This can be very important for systems that need to run on batteries in the field.
Small Size, Weight
Fewer parts are required in a CMOS-based camera allowing for a smaller, lighter outline. There are a large number of systems in the field using small, analog cameras. Smaller and lighter cameras allow for higher resolution, digital cameras to fit within the envelope of existing systems
So, CMOS is taking over for CCD in the industrial and machine vision market, and this is also now happening in the defense market but perhaps will take a little longer with the additional changes of going to HD and moving from analog to digital.
 When we talk about CCDs, we are referring to Interline Technology CCDs – the type most commonly used in machine vision and military systems.