October 22, 2019

Automotive CMOS sensors – Why it’s better than CCD sensors

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The public and industrial sector have witnessed a sudden dip in prices of digital imaging solutions in the current market. Some believe the decline of production and demand from the public caused the introduction of lower priced components of the camera itself such as the image sensors. 

The introduction of CMOS (Complementary Metal-Oxide Semiconductor) image sensors has shaken the film and camera industry because of its lower cost of production and better performance when used compared to its predecessor (Charge-Coupled Device) sensors which are in older cameras. 

As both follow the same technology in theory—which is to convert light into electrons, the advanced technology today has dramatically improved the game in durability, quality, and price. 

CCDs use a particular manufacturing process that creates the ability to transport charges across the chip without distortion which leads to a high-quality sensor in terms of fidelity and light sensitivity. Alternatively, CMOS chips use traditional manufacturing processes to create the chip, similar to the production of microprocessors. The differences in production observe the quality of the images and video footages produced by these sensors. 

Historically, CMOS sensors were known for being significantly less efficient when it comes to converting incoming light. As a rule in photography, light plays an integral part in taking photos. However, thanks to the advanced technology today, this is no longer the case. Improvements such as on-board micro-lens arrays on chips ensure that today’s CMOS sensors achieve the same or even better sensitivity than CCD sensors, despite the comparison. 

CMOS sensors produced in the market today allow for considerably higher frame rates which dramatically improves the quality of clips and photographs. Combined with improved sensitivity and the latest global shutter technology, it’s now possible to capture a rapid sequence of images without sacrificing the quality. 

CMOS sensors often have a higher full well capacity or saturation capacity. The full well capacity is the maximum number of electrons per pixel, whereby the ratio between the full well capacity and the sensitivity threshold defines the dynamic range that the sensor can cover. While a CCD sensor offers a better sensitivity threshold, the CMOS sensor makes up for it in its dynamic performance through its superior saturation capacity. Ultimately, CMOS and CCD sensors perform at almost equal dynamics levels. 

Noise Distortion
CCD sensors guarantee that very little to low-noise images. CMOS sensors, on the other hand, are more susceptible to noise but can still provide quality image output given the right amount of light. 

Light sensitivity
Each pixel on a CMOS sensor has several transistors located adjacent to it, the light sensitivity of a CMOS chip tends to be lower due to the number of photons hitting the chip’s transistors instead of the photodiode. However, this should not be an issue for automotive application where headlights and taillights usually help the camera sensor pick up images. 

Battery consumption
CMOS traditionally consumes less power compared to CDD as it’s a low-power sensor. CCDs consume as much as 100 times more energy than an equivalent CMOS sensor. 

Ease of production and fabrication
CMOS chips are fabricated on almost any standard silicon production line, so they tend to be extremely inexpensive compared to CCD sensors. However, this means there are many knocks offs available in the market as well. Although CCD sensors are harder to produce, it is consequently more expensive. 

CCDs used in cameras that focus on high-quality images with higher pixels have excellent light sensitivity. CMOS, while known in the past for being less efficient, have made drastic improvements in technology which has made it 

SOURCE: https://www.ovt.com/blog/automotive-cmos-sensors-why-its-better-than-ccd-sensors

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