Microelectronic solutions for digital photography
Microelectronic solutions for digital photography

Start this free course now. Just create an account and sign in. Enrol and complete the course for a free statement of participation or digital badge if available.

Free course

Microelectronic solutions for digital photography

3.2 CMOS detectors

The rival technology for CCDs is loosely called CMOS. That's not, at first sight, descriptive of the way the devices function, but it does identify the kind of production line that can be used to make them. You should recall that CMOS is the basis of mass memory. The commercial convenience of being able to produce imaging chips on a memory line has played a part in opening up the market for digital imaging, in cameras, mobile phones, remote monitoring systems, etc.

The image capture array is essentially the same as in CCDs, but instead of marching the data out through a single amplifier, CMOS amplifiers are built into each pixel, completing the conversion from charge to voltage locally. A CMOS amplifier is made from MOS transistors and so their inclusion is entirely compatible with the processing technology required for the light-capture components. However, a significant fraction of array space is given over to this local data handling, so again microlenses are incorporated to compensate for the loss of capture area. Figure 9 shows a diagram of a CMOS imager.

Figure 9
Figure 9 CMOS imager schematic

A disadvantage for the CMOS array is that each pixel uses a different charge-to-voltage amplifier, so there is additional statistical variation between pixels, as compared with CCDs. On the other hand, data can be drawn out of the array in parallel: a CMOS array can be interrogated row by row, as discussed in connection with CMOS memory. So, there is a trade-off between quality and speed.


Take your learning further

Making the decision to study can be a big step, which is why you'll want a trusted University. The Open University has 50 years’ experience delivering flexible learning and 170,000 students are studying with us right now. Take a look at all Open University courses.

If you are new to University-level study, we offer two introductory routes to our qualifications. You could either choose to start with an Access module, or a module which allows you to count your previous learning towards an Open University qualification. Read our guide on Where to take your learning next for more information.

Not ready for formal University study? Then browse over 1000 free courses on OpenLearn and sign up to our newsletter to hear about new free courses as they are released.

Every year, thousands of students decide to study with The Open University. With over 120 qualifications, we’ve got the right course for you.

Request an Open University prospectus371