We have talked a lot on our blog about the change over in the industrial vision market from CCD to CMOS image sensors. Here are some of our thoughts on where image sensor technology will continue to go as well as the supporting image processing, optics, and interfaces.
Where is CMOS going?
Looking back on this year so far it is clear that CMOS is the image sensor technology of today and the future. The announcement from Sony to discontinue CCD manufacturing to invest more in CMOS further supports this – the latest CMOS image sensors outperform their CCD sensors that have been a benchmark for the last decade. CMOS always had the advantage of higher speeds, offering a higher level of integration, and lower power to enable smaller cameras. Now with the image quality improvements, the benefits of both technologies are combined in CMOS. The latest CMOS image sensors are outperforming CCD in all aspects, including dark current, uniformity, and read noise where CCD previously had the advantage. As a note, it is not all CMOS image sensors performing better than all CCD image sensors. It is just the highest end CMOS image sensors with state-of-the-art processing including advanced global shutter that offer the lower noise, higher dynamic range, etc.
Driven by the consumer market, there has been a constant drive towards smaller pixels to get high resolutions in small packages and lower costs. The industry has now reached 1 um pixels, which is expected to be the limit. Focus has now shifted to further improve performance and increase functionality.
Smaller pixels are of interest for industrial applications too: one of the benefits of smaller pixels in industrial applications is the ability to get more pixels in the same optical format. This means that possibly you can use the same optics if the MTF works out, and you can definitely increase resolution with the same system outline. With the performance improvements in CMOS as well, this enable inspection and metrology systems to measure smaller structures and more complex structures.
While today’s pixel sizes are 4.5 to 5.5 um (industrial cameras – much smaller in the consumer/ cell phone market). In 2-3 years, industrial sensors will have pixel sizes of 2.8 to 3.5 um. Though some applications may benefit from even smaller pixels, we anticipate this will be the end of the pixel size race for industrial sensors because smaller pixels will need expensive optics. Also, it will be difficult to have smaller pixels with Global Shutter functionality.
CCD is a mature technology that will continue have a place in certain applications, such as those requiring the extra sensitivity of EMCCD. The high-end CMOS image advances rely on volume production. For lower version programs such as those using very large array sensors, CCDs can also be more cost-effective.
Improvements in Image Processing
With the quality of the image sensors increasing, camera manufacturers can spend less time and energy on sensor related correction. This allows for further decrease of size and costs for mainstream cameras.
For metrology, medical, and rugged cameras, more image processing and functionality can be added while keeping the camera outline the same. This gives the camera designer/manufacturer space to add this other processing such as color processing, image enhancement, digital zoom, rotation, and even more. We see even higher levels of integration and more capacity with processing still to come.