CCD versus CMOS, or should it now be CMOS vs. CCD?

Okay so we just talked about how you may not have to make a choice between a CCD or CMOS image sensor. However, since that is not the case at the moment (examples expected in 2015) what to do if you need to make an industrial camera selection now?

There has been a continued improvement in CMOS and increased use in CMOS image sensors over CCD in machine vision and global security applications. This will be an ongoing trend.

Let’s look at where CMOS is right now. In the 2 years since we last examined this topic there have been a lot of changes.

For many years CCD image sensors had the advantages over CMOS including a perfect global shutter, the lowest dark current, better Qe in the NIR, good MTF…basically better overall image quality.

In the last few years (fueled by investments in the consumer market), there have been dramatic improvements in sensitivity of CMOS image sensors – most importantly Qe and read noise.

CCD technology is mature and very good, but does not have much room to get better – it is reaching the technology limits. For instance, the current state of the art is read noise of 9 electrons. There is some focus on improvements in Qe in the NIR. CCD still maintains an advantage in terms of dark current as CCD has very predictable dark current behavior at high temperatures. CCD has a perfect global shutter, but the gap is closing.

Over the last few years CMOS image sensors have been introduced into the market with much better global shutter technology and more recently in combination with dramatic improvements in read noise and dark current related shot noise performance.

The latest CMOS technology brought a much more complex pixel with correlated double sampling (CDS) for excellent image quality and a better global shutter.

CMOS cameras have been taking over for CCD in many traditional machine vision applications such as inspection and positioning. CMOS cameras are now leading in new applications such as CMOSIS-based cameras in biometrics: http://www.azosensors.com/Article.aspx?ArticleID=448

This does not mean CCD is dead, and there are still many applications that can benefit from CCD cameras. In machine vision applications with constant illumination and short integration times, CCD may be a better choice. There are also many machine vision applications where a perfect global shutter is required such as measuring the liquid level in a moving container or monitoring a fast chemical reaction.

In traffic applications, an accurate global shutter is needed to handle moving objects, 60 fps is fast enough, and the stability in temperature extremes is required.

*Likely to change to CMOS soon

CCD-based cameras are still relevant, but they are starting to become ideal only for niche applications.

In this article we have excluded the advanced scientific CMOS, EBCMOS, EMCCD, and other image sensor technology that have much better scientific performance but also require complex cooling capabilities.

CCD vs CMOS increased CCD use in machine vision

CCD versus CMOS in traffic applications

CCD vs CMOS image sensors for machine vision, defense, and traffic applications