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CMOS CCTV: An Introduction
The world of CMOS CCTV security cameras and surveillance systems is expanding like never before. These cameras today come in a wide variety in terms of features and hardware. Look at the security cameras’ inside. You can find a structure of reflective photodiodes that build a component called an image sensor.
It has one of the two types of image sensors – CMOS or CCD based on your security camera specifications. They are different kinds of photodiodes and work much like one another. They are responsible for the conversion of light into electrons to create an image that can be displayed.
In this guide, we talk about the progressive scan CMOS and try to understand how it works for the image sensor. We also discuss how CCD and CMOS CCTV differ from each other and which one is better.
What is Progressive Scan CMOS?
CMOS or Complementary Metal-Oxide Semiconductor image sensors use symmetrical pairs of p and n-type metal oxide semiconductor transistors to execute logic functions for the security system or camera. Progressive image scanning technology is used extensively in CMOS security cameras. It enables the camera to provide a wide range of advantages to users.
Progressive Scan is also called a slow scan. It is a sequential scanning technology associated with the image sensor to display, transmit, and store moving images. Traditionally, most video signal formats used the interlace scanning method. It is used in standard-definition TVs, CRT-based computer monitors, and analog CCTV cameras. It was introduced to overcome the limitations of bandwidth in analog broadcasting structures.
Interlace scanning works by scanning half an image in a frame quickly enough to go unnoticed by the human eye. However, as it displays half frame in one scan, it suffers from blurring and tearing, resulting in low image quality compared to progressive scanning. A progressive scan works differently. It displays all the image lines in full on a frame and doesn’t separate them into halves.
The main advantage of this type of scanning comes in the form of clarity of the picture, particularly when it is about capturing a moving object. A progressive scan CMOS reduces the effects of blurring and tearing found in traditional interlace technology as used in analog CCTV cameras. That makes CMOS image sensors ideal for cameras used in security applications.
When you pause your security system’s recordings, the images of moving objects appear much clearer when a progressive scan CMOS is used. Moreover, it delivers a much better result when scaling to higher resolutions as compared to interlaced video.
CMOS CCTV or CCD CCTV – Which is Better?
Security cameras can be either CCD (charged-coupled device) or CMOS that we have discussed above. But which of the two image sensor types is better for CCTV? Let us try to understand the differences and find out which one outperforms the other.
CMOS CCTV Pros and Cons
CMOS CCTV cameras mainly use progressive scan technology to deliver a plethora of benefits in terms of performance and quality.
• Great color
• High resolution
• Lower power consumption
• Fast frame rate
• Moderate sensitivity
• High noise
CCD CCTV Pros and Cons
CCD cameras contain p-doped metal-oxide-semiconductor capacitors to represent pixels. Cameras with these image sensors have an excellent WDR (wide dynamic range), so they perform better in low-light conditions. CCD cameras are less likely to be affected by vibration problems as compared to CMOS CCTV.
CMOS cameras use a rolling shutter that exposes them from top to bottom. On the other hand, CCD security cameras use a global shutter that exposes the entire sensor simultaneously. These cameras are thus less vulnerable to vibration.
• High sensitivity
• High performance in low light conditions
• Low noise
• Good WDR
• High definition
• Less susceptibility to vibration
• Slow frame rate
• High power consumption
CCD Vs. CMOS Image Sensor – Which is Better?
People have a lot of questions about CCD and CMOS image sensors for CCTV cameras. Let us discuss some important things you need to know about these image sensors to decide which is better.
Power Consumption and Frame Rate
When it comes to frame rate for a CCTV, the CMOS image sensor is definitely the winner. That is because CMOS can convert the photoelectric signal into a digital signal directly. The frame rate and processing speed are fast as compared to CCD sensors. For CCD, analog to digital conversion often takes place outside the sensors. It thus takes longer to generate videos and images.
CMOS CCTV image sensors can easily integrate different types of applications on a versatile chip. These sensors on the security cameras also need lower bandwidth. On the other hand, CCD CCTV image sensors need interior circuits and external components to perform amplification and conversion to a digital signal. That is why this type of camera encounters problems like overheating.
Overall, CCTV cameras with CMOS image sensors provide a higher frame rate with lower power consumption than CCD CCTV image sensors. CMOS cameras are therefore most cost-effective and affordable than CCD security cameras.
CCD sensor cameras are generally known to offer a higher resolution of images and videos. But the technological development has enabled CMOS CCTV cameras to provide an image quality at par with CCD image sensors when used in surveillance systems. For example, CCTV cameras with CMOS image sensors can deliver clearer pictures when equipped with an optical zoom feature.
Low-Light Sensitivity and Noise
When CCD image sensors are used in surveillance systems, they move charged cells across the chip and are less vulnerable to distortion. That means this type of camera has a higher sensitivity to light and generates much less noise than CMOS CCTV. Quantum Efficiency is a measure of how efficiently the camera sensor converts photons to a digital signal. Higher this measure, the more sensitive the image sensor is.
CCD cameras were known to provide better performance in low-light or night conditions. Today, CMOS CCTV cameras are capable enough to outperform CCD in terms of sensitivity. That is why it is difficult to say which of the two performs better in low-light conditions.
As you can see from the above comparison, both CMOS and CCD image sensors CCTV cameras have their advantages and limitations. There is no definite answer to which of the two is better. The answer comes down to your application with the security system. Here are some useful tips you can consider:
– Choose security cameras with CCD image sensors when you aim to monitor locations in dark or low-light environments.
– For covert environments, CMOS CCTV cameras are the right choice. This type of image sensor makes the cameras compact in size as their dimension is small.
– CMOS CCTV cameras are ideal when your internet connection is not so good. Cameras with CMOS image sensors offer a faster frame rate that doesn’t take up much bandwidth. That means you don’t suffer from a lot of internet loss.
What is a 1.3 CMOS CCTV Camera?
The size of the image sensor is an essential consideration for CCTV camera performance. An image sensor is generally the eye of a security camera. It captures the light hitting the lens of the camera and converts it into an electronic signal. That is how the CCTV camera enables you to view the image or video when you access it.
You might have checked the specification of your CCTV camera to find something like 1/3″ 4 MP CMOS. This type of description is for the measure of the camera’s image sensor format. This specification is about the shape and size of the image sensor that decides the angle of viewing for the security camera.
Sensor size is often described in inches as an optical format. There are three common CCTV camera image sensor formats available in the market – 1/3, ½, and 2/3. A 2/3-inch image sensor can target long-range in low-light conditions. A ½-inch security camera image sensor is the perfect format for security cameras as the sensitivity is quite acceptable.
A 1/3-inch CMOS image sensor offers a good low light performance, highly desirable in CCTV cameras. When used with progressive scan CMOS, it also delivers a high frame rate that adds to the image’s quality.