If you intend to know about the definition of a CMOS Camera for your application, then the knowledge about the image sensor technology is a must. An image sensor basically is a medium of detecting and conveying imaging information. Broadly, two types of image sensor technologies are available in the market today.
- CCD Sensors
- CMOS Sensors
The debate about the relative advantages of CMOS verses CCD sensors is still elusive. With the technological evolution, the market values what is technically as well as commercially viable with different changing requirements. Depending on the tailored requirements of various imaging applications, some are best served by CMOS and some by CCDs. In the succeeding paragraphs, we will highlight key differences including the technical trade-offs of both technologies.
A digital camera constituting CMOS sensor technology is called CMOS camera. The word CMOS implies Complementary Metal Oxide Semiconductor also known as Active Pixel Sensors (APS). In the recent decade, CMOS cameras evolved rapidly due to their ease of use. This integrated circuit chip technology offers flexibility in reducing costs. It comprises of an array of pixel sections containing a separate light sensor and active amplifier for each pixel. CMOS sensor contains its functioning parts on a single circuit allowing the user to convert real-time situations into a digital image. The components critical for pixel sensors operation are located on the CMOS sensor i.e. analog-to-digital converter and digital controller. The required components and circuitry are integrated into the sensor thus offering faster speeds and low power consumption without compromising on high image performance.
What is a CCD Camera?
On the contrary, a digital camera utilizing CCD sensor technology is called CCD camera. The term CCD stands for Charged Coupling Devices. It comprises of an array of pixel sections with extra circuitry to create an analog voltage signal out of the captured data. The CCD sensors comprise of two key parts i.e. a pixel array and a color filter. The color filter processes the light coming through the lens before it reaches the pixel sensor array. The pixel sensor array then captures the light intensity data from the filtered light, and converts it into an analog voltage signal before it is further processed by other chips present on an external circuit board. A special manufacturing process is adopted for these sensors for producing excellent distortion-free images by converting images from analog light signals into digital pixels. Each cell of a CCD sensor acts as an analog device, which gains a small electrical charge when light strikes the chip generating high-quality images.
Is CMOS or CCD Better?
In a CCD Camera, the output uniformity is quite high which represents a key factor in attaining image quality. Few output nodes transfer each pixel charge for conversion into a voltage signal and sent off chip as an analog signal. All pixels in these cameras capture light thus helpful in generating image uniformity. In a CMOS camera, the output uniformity is low as each pixel is involved in its own charge to voltage conversion. The sensors in these cameras output digital bits as it includes its own amplifiers, digitization circuits and noise correction. These added functions reduce the light capturing area due to design complexity. In these cameras, the overall bandwidth is high conforming high speeds.
Both CMOS and CCD cameras are widely used in digital world and have their own weaknesses and strengths. Both technologies comprise of a pixel array which converts light photons striking the pixel sensor into electrons by using photoelectric effect. In CMOS sensors, each pixel section converts electrons into a voltage signal, while in CCDs the electrons are first transferred to an output node before conversion into a voltage signal. Moreover, CMOS sensor also include other circuitries on the chip i.e. analog-to-digital converter, built-in amplifier, noise-corrector and digital controller. Unlike CMOS sensors, CCD sensors comprise of an external circuit board to perform noise correction and analog-to-digital conversion functions.
CMOS cameras constitute added features which reduces off chip circuitry i.e. each pixel array performing its own voltage conversion lowers the uniformity, generates more noise and reducing the area for capturing light required for the operation. However, in CCD sensors there is no extra circuitry to hamper capturing of light and output uniformity is relatively high but they require extra off chip circuitry for proper operation. Industrial cameras requiring highest image quality make CCDs an ideal choice due to their low temporal noise and high quantum efficiency. However, if designed properly both CMOS and CCD sensors can generate excellent imaging performance.
Until recently, it was speculated that CMOS sensors stand much lower in costs than CCDs as they utilize existing mainstream memory chips i.e. standard silicon production line and stand low on power consumption thus extending the battery life of a CMOS camera. While it was believed that CCD sensors are more advanced and expensive as they necessitate special manufacturing process requiring more electronic circuitry consuming up to 100 times more power than CMOS sensors.
Practically, a custom CCD sensor is far less costly than a custom CMOS sensor as it requires more circuitry and deep submicron masks for better performance. Although, the development costs of a new CMOS sensors can be higher but if produced in high volumes economies of scale can be achieved. Another important element to consider is supply security in the long term i.e. to choose a reliable producer instead of focusing on better value preposition.
Before the evolution of CMOS cameras, CCD (Charged Coupling Devices) sensors were used in digital cameras to attain noise-free and distortion-free imaging. CCD sensors offered slow data processing speed and required more power consumption as analog-to-digital conversion takes place outside the sensor thus consuming more time. The cutting-edge CMOS camera advantages over CCD cameras constitute low power consumption and smaller system use. While analog component technology allows CCD sensors to produce high-quality images with low noise under low light conditions due to their high sensitivity and are preferred for most of the industrial applications.
It’s not an easy task to choose a camera for industry varied requirements with radical technological changes. The most important facet of any camera is its speed and noise to generate high-quality imaging. Initially, CCD cameras became dominant as they were based on fabrication technology offering far superior images. However, the invention of CMOS technology engendered new hopes due to its attractive deliverable offering based on low fabrication costs, low power consumption and on-chip integration. However, the process adoption has taken far more time and money for delivering high image quality.
CMOS technology has joined CCDs as mainstream technology and Emergent Vision Technologies (EVT) among renowned camera manufacturers has successfully adopted CMOS technology for providing superior customer satisfaction. For generating high-end imagery experience EVT unveiled its 50 MP 10 GigE camera series. The camera technology in this series uses latest Sony Pregius Global Shutter CMOS image sensors for adhering to crisp image details for machine vision applications. These cameras further employ 10 GigE interfaces for exceptional performance in terms of speed, cost and resolution. Thus, EVT is committed to provide ultimate invaluable imaging experience by combining technology with over 40 years of expertise in providing application solutions. Their cameras enable multi-camera synchronization in a unified manner for onward processing and storage with a classic IT hardware for fast video transmission. In a nutshell, both CMOS cameras and CCD cameras are now used interchangeably making them unique in their own way for varied industrial applications.