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Exploding the myths of digital microscopy: Is CCD always better than CMOS?

CMOS sensors are very attractive and have such an excellent price-performance ratio that virtually any device today can be equipped with the ability to image – and give any microscope, scientific instrument or medical device a significant competitive advantage. The ability to visualize samples – whether central to the analysis or an apparent “nice to have” feature – can lead to desirable new applications, quality assurance and experimental design.

, Stefan Seidlein
Biological imaging has evolved from a passive observational collector of descriptive pictures to a keen, versatile and quantitative analytical tool. Microscopic images of tissues and cells provide the basis for characterization and measurements of disease progression, live cell imaging, automated diagnostics, and a host of other activities in the life science and medical diagnostic laboratory. Digital microscopes thus play a crucial role in the signal pathway between the biological sample of interest and the eyes of the scientist.

CCD compared to CMOS sensors

Whether one is measuring fluorescence, performing in vitro molecular diagnostics or developing new drugs, analytical bioimaging requires a high-quality digital imaging system to resolve tiny but crucial details.

For many years, the charge-coupled device (CCD) has been the best imaging sensor scientists could choose for their microscopes. A CCD sensor consists of a two-dimensional grid of metal-oxide-semiconductor capacitors. Like miniaturized rain buckets, the capacitors collect incoming photons and convert them into electrical current, which is sequentially read out and reassembled into a picture.

However, a newer technology called the complementary metal-oxide-semiconductor (CMOS) sensor, also known as the active-pixel sensor, has emerged in the microscope optics marketplace. The pixels in a CMOS sensor are slightly more complicated than those in a CCD, because each pixel contains not just a photodiode, but also a set of tiny transistors to amplify the light-generated electrical signal and pass it along for processing.

The advantages of CMOS sensors, however, outweigh the added complexity of the individual pixels. CMOS sensors are faster than their CCD counterparts, which allows for higher video frame rates. CMOS imagers provide higher dynamic range and require less current and voltage to operate. The active pixels also have a higher quantum efficiency – a measure of how well the device converts photons to electrons – than their passive cousins.

The end of the line for CCD?

Tech companies are advancing CMOS imaging technology, whereas the development of CCDs has stalled. One global supplier of CCD sensors stopped manufacturing CCDs years ago, and another CCD source has announced that it will ship its last CCD imagers in the near future. Companies that make such decisions usually halt product development years before the end of the product cycle. The entire industry is switching over to CMOS and active pixels, and manufacturers of devices that produce digital images, from ordinary cameras to the most advanced bioimaging systems, must adapt to the newer technology.

Fortunately, the market’s embrace of CMOS means that end users of imaging systems, including the overall biophotonic market, can benefit from ongoing improvements to the technology. The image quality of today’s CMOS sensors exceeds that of CCD sensors and will only get better.

When should digital microscope systems upgrade their components from CCD to CMOS sensors? They should make the move when they want faster video frame rates, or when they need less image noise or background interference, or they desire longer battery life for mobile digital imaging out in the field. In other words, CMOS can open up a whole new world of microscope imaging performance at lower cost.

The JENOPTIK SYIONS® miniaturized digital microscope subsystem consists of inter-compatible modules including smart sensors that work together seamlessly no matter what the final application is. Jenoptik’s technical team has years of experience with CMOS technology and light microscopy. Jenoptik can help customers choose the right image sensors with the pixel size that perfectly matches to light source, optics and electronics in order to achieve the optimum performance regarding resolution, signal-to-noise ratio, dynamic range and other specifications according to their application.

CMOS performance will continue to improve

It is fully possible to upgrade the existing architecture of a digital microscope with a miniaturized imaging system, taking up less space than the previous generation. Just like the progression of smartphone imaging devices, miniaturized microscopes will only improve in terms of performance, size and versatility of application as sensors become better, smarter, more economical and smaller. And that will mean a clear competitive advantage for biomedical imaging companies that adopt this technology sooner.

Stefan Seidlein

About Stefan Seidlein

Stefan Seidlein has been working for Jenoptik since 2000 in various positions in the field of Digital Imaging. As product manager, he currently focuses on the light microscope camera product portfolio and brings his entire digital imaging competence and experience to projects. As a graduated technician with a focus on energy technology and process automation, he is fascinated by digitalization and the many opportunities it offers both individuals and Jenoptik.

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