CMOS vs CCD wars: The battle is won!
The CCD was the be-all and end-all in imaging. This was the chip that was sensitive to light and colour and was used in 99% of cameras. Invented in the late '60s it has since then, been dominant in imaging devices until only very recently. The alternative to the CCD is the CMOS sensor. Also invented in the late '60s but it took a lot longer to evolve and become a viable alternative in serious camera applications.
For years, the mantra on CCD was that it is more sensitive than CMOS and that it had a global shutter - where all the pixels on the chip are active at
once - unlike it's poor relation, CMOS which worked by making each line of pixels active one by one. The result of this was distortion if something in the image was moving, or the camera moved. CMOS sensors with global shutter were available but only with limited resolution and this was the status quo for some years. But CCD seemed to reach the zenith of it's development some time ago. Plus, CCD is expensive to build, uses a lot of power and requires a lot of supporting electronics. The first image here shows all the work the CMOS image sensor does before the image is made available.
CMOS is the apprentice that has become the master
Now times have changed and CMOS is the apprentice that has become the master. Recent developments in CMOS architecture have meant a dramatic improvement of the technology and now we have CMOS imaging sensors that have a global shutter, low power consumption and pixel counts that are overtaking CCD. Now we have multi-megapixel CMOS sensors with global shutter, low power and high sensitivity. So the CMOS is here to stay and we're saying goodbye to CCD in all but the most specialist of applications.
CMOS Sensor Comparison
Here's a current appraisal of the popular CMOS sensors that have become available in the last 5 years or so. Quantum Efficiency is how effective the sensor is at converting photons into image data. So we've used this as an indicator of performance in the comparison chart below (520nm is in the green wavelength). This number shouldn't be read as a marks out of 10 for the sensor, it's just one performance reading of a whole set of specifications that should be taken into account. For example, some of these sensors have fantastic performance in the infrared range at 850nm) - something that CCD isn't good at.
|Sensor Manufacturer||Sensor||Released||Optical Format||Megapixels||Pixel Pitch||Shutter||Frame Rate||QE @ ~525nm||Available Cameras|
|OnSemi||Vita 1300||Dec '09||1/2"||1.3||4.8μm||Global||150fps||62%||PL-D721|
|OnSemi||Vita 2000||Nov '10||2/3"||2.3||4.8μm||Global||93fps||53%||PL-D722|
|OnSemi||Vita 5000||Nov '10||1"||5.3||4.8μm||Global||75fps||53%||PL-D725|
This table displays the enhanced performance that CMOS sensors offer over CCD, particularly with regard to frame rate and more recently sensitivity. The latest Sony sensors exceed the performance of the CCD that was the imaging standard for so long.
PixeLINK - The CMOS Camera Specialist
Our camera principles have incorporated the new sensors in their cameras. PixeLINK have a very flexible camera platform that gives them the ability to exploit the sensors to their maximum without any penalty caused by bandwidth limitations. For this reason, they have majored in USB3 Vision as this gives a large bandwidth improvement over Gigabit ethernet.