High resolution lenses for machine vision — standard and custom lens design

Differences Between CCD and CMOS Technologies

High Resolution Lenses for machine vision, instrumentation, inspection and vibration-sensitive applications. Standard and custom hi-res lens assemblies.

ccd & cmos

CCD & CMOS Lenses

There are many applications in which CCD (charge coupled device) and CMOS (complementary metal oxide semiconductor) image sensors are compatible, but to believe that the technologies are interchangeable is like comparing apples and oranges; they are both fruits, but are vastly different. CCD and CMOS are robust technologies used to capture images digitally and each brings with it its own unique benefits and limitations.

The technologies that incorporate CMOS and CCD both capture and convert light into an electric charge, which is processed into an electronic signal. When using a CCD sensor, the pixels’ charges are transferred through a small number of output nodes; CMOS sensors allow each pixel to have its own charge-to-voltage conversion rate. The CMOS sensor also can include amplifiers, noise-correction and digitization circuits. Because of the complexity of information being manipulated in a CMOS sensor, the pixels are not as high quality or clear. CCD sensors take the information and convert it to voltage, buffer it and send it out as an analog signal. The pixel information captured in a CCD sensor allows for its capture into light and this leads to a more uniform output and a higher quality image.

For close to a half a century CCD and CMOS imagers have been in use. In the early stages CCD took the lead as the more robust imager because of the superior images it provided. The CMOS technology required a more uniform and smaller image in order to provide a high quality output image. In the last 20 years CMOS imagers gained a foothold because of the developments in lithography designers. Lithographers appreciate that CMOS imagers use less power than CCD imagers and they also had a camera-on-a-chip integration.

Excellent imaging performance can be achieved from both CCD and CMOS imagers, but the quality depends on the initial design of the chips. CCD imagers have made performance benchmarks in industrial applications, photographic and scientific settings. Integration and functionality are the notable distinctions of CMOS imagers because it offers “lower power dissipation” and has the ability to capture images in smaller system sizes than CCD imagers.

While there is no clear-cut division on the applications, it is noted that the designers of CMOS technologies target their efforts on achieving high image qualities while the designers of CCD technologies focus their efforts on lowering power requirements and pixel sizes. What this can mean in the consumer market is that CCDs are able to be used in low-cost, lower power cell phone cameras while you will see CMOS sensors in use in the high performance and industrial fields even though there are many crossover fields of application and usages.