Automotive CMOS Sensors – Why It’s Better than CCD Sensors?

CMOS Sensors

After the introduction of the CMOS or the Complementary Metal-Oxide Semiconductor in the market, the prices of imaging sensors in both the public and industrial sectors dropped, effectively succeeding the expensive CCD or Charge-Coupled Device image sensors. The speculation was that the high price of the CCD led to the decrease of public demand and production subsequently paved the way for the CMOS.

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The CMOS image sensors shook both the film and camera industries because of its plethora of advantages to its predecessor, the CCD image sensors. Newer cameras employ the CMOS sensors resulting in cheaper cameras introduced to the market.

Automotive image sensors made use of CCD sensors before, but after the introduction of the CMOS sensors, many shifted to use the latter. Since both sensors are the same technology that converts light into electrons, advanced technology found on CMOS improved the game in terms of durability, quality, and, a common deciding factor, price.

The CMOS sensor is better than the CCD thanks to its low price, excellent light sensitivity, minimal noise distortion, battery consumption, and ease of production and fabrication.

The CCD image sensors are made through a particular manufacturing process that allows the transportation of charges across the chip without distortion. The process results in a high-quality sensor with excellent fidelity and sensitivity. Since a specialized process is required for the CCD, the price is significantly higher than its cheaper successor.

CMOS image sensors have a more traditional manufacturing process compared to the CCD. The production of CMOS sensors is similar to that of microprocessors, and they can even be produced in almost any standard silicon production line. The ease of manufacture and fabrication makes the CMOS inexpensive. The process, though, means a difference in the quality of images and videos captured compared to those of the CCD. Having a traditional method for production allows the CMOS to have a lower price compared to its predecessor.

Historically, the CMOS sensor had problems with converting incoming light thanks to the difference in the manufacturing process with the CCD. The CCD’s process allowed it greater fidelity and light sensitivity than the earlier versions of CMOS sensors. Advanced technology, though, let the CMOS achieve equal to better fidelity and sensitivity compared to CCDs thanks to the introduction of onboard micro-lens arrays on chips. The improvements on the CMOS allowed the matter of light playing an integral part in photography to not be the case anymore.

CMOS sensors also have several transistors adjacent to each of its pixels which results in lower light sensitivity thanks to the number of photons hitting the transistors instead of the photodiodes. Headlights and taillights, however, usually help the camera sensor pick up images making the CMOS’s application in automotive a non-issue.

One more result of the different manufacturing process is that the CMOS sensors are more susceptible to noise than the CCD sensors, but the higher full well capacity of the CMOS allows it to capture quality images despite the noise as long as there is enough light.

The CCD produces images with lower noise compared to the CMOS because of its light sensitivity. The ratio between the saturation capacity and the sensitivity threshold defines the dynamic range a sensor can cover. The CCD possesses a better sensitivity threshold, but the CMOS has superior saturation capacity resulting in a comparable performance between the two in the dynamics range.

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CCDs consume a hundred percent more energy than CMOS as well. The CMOS is more energy efficient and implementing them would result in a camera with lower power consumption. Conserving energy means a longer operational time for any camera using the CMOS sensor than the CCD and lesser fuel consumption for cars installed with CMOS sensors.

Thanks to its traditional manufacturing process, the CMOS is far easier to produce than the CCD resulting in a more abundant supply of sensors that can meet public demand. The CCD’s particular manufacturing process meant that its production is by no means simple making it harder to produce and resulting in a higher price.

Current CMOS sensors, more advanced compared to earlier versions, allow for higher frame rates which improve the quality of images and videos — combining the CMOS’s improved sensitivity and the latest shutter technology results in the possibility of capturing images rapidly, even in a sequence, without sacrificing the output’s quality.

There is no doubt that CCDs in cameras achieve capturing high-quality images through its excellent light sensitivity, but its expensive nature decreased the demand for imaging solutions in the first place which was revived by the inexpensive CMOS.

The low price of the CMOS, its comparable performance with the CCD, its dynamic nature, lower battery consumption, and the ease of production, and the various technological advancements resulted in the CMOS becoming a top choice for many car manufacturers.

Omnivision’s infographic contains information about why CMOS sensors are better than CCD sensors in the automotive application.

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