CMOS image sensor (CIS) advancements enabling big growth in Smartphone camera, machine vision, medical imaging and security applications

Innovations in CMOS image sensor (CIS) technology continue to enhance digital imaging landscape. While the demand has been driven by smartphone makers, leveraging enhanced photo-taking capabilities to differentiate their devices from the competition, there is also a growing market for applications in the automotive, security, medical, and manufacturing sectors. Smartphone camera technology is growing in leaps and bounds in the past couple of years and continues to be a major point to differentiate their products.  Image sensors are found at the heart of every camera system and convert incoming light into electronic signals.

At its most fundamental level, CIS technology is tasked with converting light from the camera lens into digital data to create a picture of what’s in view. When light energy in the visible light wavelength range of 400 to 700 nm is condensed on the photodiode (PD) of the silicon substrate, the silicon surface of a CMOS image sensor receives the light energy to form an electron-hole pair. The electron generated in this process is converted into voltage through floating diffusion (FD) and then into digital data through an analog-to-digital converter (ADC). The data is sent to a processor to create a digital description, usually an image, of what’s in view.

Depending on the image sensor used, cameras are termed charge-coupled devices (CCDs), electron-multiplying CCDs (EMCCDs), or complementary metal-oxide-semiconductor (sCMOS) devices. Both CMOS sensors and CCD sensors are semiconductors; each type of integrated circuit has integrated pixels for light—and therefore image—capture.  CCD-based cameras, however, often require some form of analog-to-digital (ADC) conversion circuitry. This addition increases the camera’s overall footprint, which may be critical when housing lack needed real estate.

As the name suggests, CMOS image sensors are fabricated in standard CMOS technology and can be made at a very low cost.  Most integrated circuits including computing and communication chips are however made in CMOS processes. This is a major advantage because it allows us to integrate the sensor with other analog and digital circuits required for an imaging system including digital signal processing functions like image stabilization, image compression, multi-resolution imaging, wireless control, color encoding, etc. An integrated solution allows us to reduce power consumption and improve the readout speed. More importantly, however, with a larger number of integrated circuits being manufactured in these processes, the average cost of individual chips made in these processes is significantly lower than that of CCDs

The CMOS image sensor has been the revolutionary technology for smartphones that through smaller pixels, higher sensitivity and lower noise at a decreased cost has resulted in cameras that produce fast and high-quality images. CMOS cameras, therefore have been rapidly gaining in popularity because of their ability to provide improved performance in speed, field of view, dynamic range, and image quality.

The enhanced image sensors have also benefitted machine vision, medical imaging and security applications. Therefore, instead of merely capturing an image for viewing by the human eye, CIS technology is now capturing data to power a host of new use cases from autonomous vehicles and virtual reality (VR) to next-generation medical imaging and high-tech surveillance systems.