Chapter 3.1: Cameras - CCTV Technology Fundamentals

Posted by Arowosegbe Olawale in General

Cameras are a crucial part of any CCTV setup. The increasing variety of uses for CCTV cameras and the rapid pace at which technology is advancing make it difficult to find the ideal camera for any given purpose. There are many variables that can impact a system's performance beyond what is specified in the vendor's data sheets. Accurately selecting a camera calls for expert-level familiarity with the camera, the application, the underlying architecture, and the host environment.

The three fundamental components of any CCTV camera are:

• Image sensor: Light (photons) are transformed into electronic signals by the image sensor; 
• Lens: light reflected from the subject is collected by the lens and focused on the image sensor; and 
• Image processing circuitry: the image processing circuitry organizes, optimizes, and transmits video signals.

The optimal CCTV camera will be determined by the system's operational environment and the way in which the cameras will be integrated. You can learn more about which camera is right for you based on your responses to the following questions:

• What kind of picture quality are you hoping to achieve?
• How big of a view do you need?
• Is there enough light?
• Is it an indoor or outdoor camera?
• Will there be constant surveillance of the footage?
• Can you tell me how the video will be sent? 
• Will the camera be subjected to harsh environments?

Cameras come in many forms, each optimized for a different set of circumstances; however, they can be broadly classified as either fixed or pan-tilt-zoom (PTZ). Motor-driven PTZ cameras can instantly adjust their field of view by panning left and right, tilting up and down, and zooming in and out, while fixed cameras are designed to keep a steady gaze on a single point. To achieve the desired level of surveillance, it is common practice to employ a mix of fixed and pan-tilt-zoom (PTZ) cameras. 

3.1.1 Fixed Cameras

The field of view (FOV) of a fixed camera is fixed, meaning that it only ever records footage from a single location. These cameras have a wide range of applications and can be installed both openly and discreetly. Mounting options for fixed cameras are as diverse as the sizes of the cameras themselves (e.g., inside cabinets or control panels, or on poles, fence lines, or roofs).

Connecting fixed cameras to an ESS allows for the evaluation of ESS alarms. Cameras can be set up to monitor a locked gate and only start recording when an alarm is triggered. Because there are fewer moving parts, fixed cameras are typically more cost-effective than PTZ cameras.

3.1.2 PTZ Cameras

PTZ cameras are available in a wide range of sizes and forms, making them suitable for a wide range of indoor and outdoor applications. The field of view (FOV) of a PTZ camera can be adjusted by adjusting the focal length of the lens, in addition to the camera's ability to pan and tilt on two axes. As a result, unlike fixed cameras, PTZ cameras allow for greater maneuverability in capturing and viewing images in real time. Pan-Tilt-Zoom (PTZ) cameras can be scanned either manually or automatically to get the best possible footage.

The operator can adjust the camera's direction and focus on a specific area of interest (such as a suspicious bag, a person's face, or a license plate) in manual mode.

Another useful feature of PTZ cameras is the ability to program them to automatically pan and tilt over large areas that would be impossible to monitor with a single stationary camera. It is possible to set up a sequence of predetermined positions to cycle through different perspectives at various intervals. You can set up a PTZ camera to automatically pan and tilt 10 times per minute to cover more ground in the area under surveillance.

3.1.3 Video Surveillance Cameras

Video surveillance cameras can send data in one of two ways:

Network Cameras: Network cameras are able to transmit video and audio over IP networks, such as the Internet, and can be viewed and recorded from a distance. High-definition (HD) versions of network cameras are also on the market.

Analog Cameras: It's true that digital network cameras are becoming more popular, but there's still a demand for analog cameras. The expense of upgrading and switching to a new transmission method could be to blame. High-resolution analog camera options expand their usefulness for surveillance applications. The coaxial cable these cameras use to connect has additional cyber security benefits because it would require physical access to compromise.

3.1.4 Day/Night Cameras

Day/night cameras are convenient because they can adapt to a variety of settings. When it's daytime, these cameras record in color, but when nighttime rolls around, they switch to black and white for the best possible image quality. For automatic removal of the infrared-cut filter and monochrome mode, the camera uses an analysis of the current image or a photoelectric sensor.

3.1.5 Low-Light or Night Vision Cameras

Low-light or night vision cameras are used to take photos in pitch black conditions.

Low-light cameras are optimized for use in environments with some amount of natural or artificial light, such as dimly lit restaurants, outdoor street lamps, or the night sky illuminated by the moon.

Near-infrared (NIR) and infrared (IR) cameras with infrared (IR) illuminators are the most common types of night vision cameras used in CCTV systems. The operator can see in the dark with these devices because they were made for that purpose. The effectiveness of an IR illuminator and other camera components, such as the lens and sensor, determines how far away in the dark a CCTV camera can see objects. These light sources can produce infrared light at wavelengths beyond the range of human vision.

Whether a camera sends an image in color or monochrome (varying tones of a single color) is largely determined by its image sensor. Color cameras use filters on the image sensor's individual light sensitive elements to limit that element to specific color wavelengths, whereas monochrome cameras record images using light in NIR wavelengths outside the range of human perception (i.e. spectroscopic). Without these filters, a monochrome sensor would only be able to detect and transmit light intensity; these filters allow the sensor to detect and transmit color as well.

It is common practice to use color cameras during the day or in well-lit areas of the night. Precision in color reproduction is useful in a wide variety of contexts. It is possible to select and evaluate cameras and optics with greater precision thanks to the information provided by color reference charts. CCTV technicians and installers frequently consult such charts when evaluating image color. The effectiveness of a system can also be evaluated with the aid of waveform generators and vector scopes. Keep in mind the importance of accurate color reproduction on your video monitor.

When used in low light or total darkness, monochrome cameras produce images with greater detail than the naked eye can detect. Because visible and infrared light have different planes of focus, daytime monochrome images may be lacking in contrast and detail if shot with a color camera. Monochrome image sensors are typically constructed from silicon and germanium, two materials with distinct spectral responses. So, the image sensors can function well in the infrared spectrum.

3.1.6 Thermal Imaging Cameras

Figure 3-1. Image from Thermal Camera

A thermal imaging camera's ability to see in low light or through smoke or fog makes it useful in a variety of operational settings. Infrared or heat radiation is undetectable to the naked eye, but can be captured by thermal imaging cameras. These cameras can currently detect a temperature difference as small as 0.1 °F. While thermal imagers are useless for seeing through transparent materials like glass or water, they can provide a picture through thin gases like smoke or fog.

The contrast of thermal images can be enhanced by the built-in image processing of many modern cameras. This results in sharper, clearer images with enhanced feature definition. For nighttime surveillance in low-light conditions, thermal cameras are frequently installed in gyro-stabilized, pan-and-tilt devices, as well as on boats and helicopters. They can also be purchased as portable, hand-held units with integrated displays for use in safety, security, and first responder settings. Since thermal cameras' image sensors can degrade over time, it's important to check in with the manufacturer to learn about expected performance characteristics and to plan for the expense of regular maintenance and replacement.

3.1.7 Miniature or Covert Cameras

There are situations where a CCTV system would benefit from the addition of covert, miniature cameras. These cameras typically aren't built to withstand the elements, so an additional housing may be necessary for outdoor use. These cameras are typically battery-operated and may feature in-built transmitters to offer a convenient, portable wireless option. Companies can pick from a wide variety of mini and covert cameras to meet their specific needs.

3.1.8 Optional Camera Features

The operational environment dictates the specific features that should be included in a CCTV camera. The following are examples of some of these shared characteristics: 

Auto Scan -Some pan, tilt, and zoom (PTZ) cameras can be set to perform automated actions. One method of performing this sweep, known as a "auto scan," is to set the scanner to run on a perpetual loop.

Preset: A preset is a specific lens position and camera orientation that can be programmed into a pan-tilt-zoom camera and then moved to at regular intervals or in response to events. When an intrusion alarm is triggered, a camera, for instance, can be set to automatically display the surveillance area's most valuable assets or focus on the access point that triggered the alarm.

Privacy Masking: Cameras equipped with privacy masking features can obscure specific areas of a video feed to prevent unwanted attention. To prevent intruders from seeing inside an apartment building, PTZ cameras can be used to monitor the parking lot outside. As a function of the setup of the system (whether software or hardware), this can be difficult to implement and expensive to maintain. 

Slip Ring: With a slip ring, the signal and control cable for a pan-tilt-zoom camera can be turned without kinking. Light beams can be used to transmit the image optically through the slip ring, or a sliding brush contact on the base ring can create an electrical path. To a greater or lesser extent, contamination and temperature changes will affect the performance of a slip ring.

Motion Detection: Built-in motion detectors in cameras can be set to sound an alert whenever there is motion within the field of view. The alarm can be set to either begin recording or contact a human operator. There is a risk of false alarms from motion detectors if there is any natural motion in the area.

Backlight Compensation (BLC): Some cameras have built-in BLC features to compensate for dim lighting. By boosting the brightness of the foreground, BLC can improve the contrast of images with a very bright background. Using BLC, security guards can make out individual features of a person walking in front of a well-lit window, for instance.

Digital Noise Reduction (DNR): For taking clear photos even in dim light, many modern cameras have a function called digital noise reduction (DNR). DNR filters out the pixelated, grainy spots of video noise, also called "raster." Because of this, the picture is now more vivid, clear, and simple to understand. Since there is less fluff in the video, the need for storage space can be cut down if digital noise is reduced.

Mobile Compatibility: Video can be viewed remotely on mobile devices like smartphones, tablets, and laptops with the help of this application. Some remote viewing techniques call for specialized camera software or hardware, while others let you connect directly to a camera through a preconfigured application (PC). 

3.1.9 Types of Image Sensors

CCTV cameras usually employ either charge-coupled device (CCD) or complementary metal oxide semiconductor (CMOS) image sensor technology. The pixel is the smallest component of an electronic image. No matter the sensor type, the resolution, light sensitivity, and spectral responses are all engineered through the number, size, and filtering of the pixels.

3.1.9.1 Charge-Coupled Device Sensors

Midway through the 1980s, CCD image sensor cameras began appearing in the CCTV market, and today, these cameras account for the vast majority of sales of both daytime and nighttime infrared (NIR) cameras. When compared to the tubes utilized by early video cameras, CCD technology provides numerous benefits. CCD image sensors are more compact, cooler to the touch, and less likely to produce blooming in captured images. When a bright object within the field of view (FOV) overwhelms the camera's image sensor, a phenomenon known as "blooming" occurs. A CCD camera can be used for anywhere between five and twenty-five years.

CCDs are made up of a grid of pixels that, depending on how much light they're exposed to, send out different electrical signals. This electrical signal is converted from analog to digital on a different chip. The camera's internal processing of this digital data is transmitted to the rest of the CCTV system. In order to transmit the processed signal, some cameras perform a conversion to analog video.

CCTV cameras use a special kind of CCD whose surface looks like a bird's-eye view of a perfectly organized metropolis. Rooftops stand for light sensors, and the roads are the electronic control and timing mechanisms. The sensitivity to light and the resolution of the CCD are both dependent on the density of the city's rooftops (sensor elements) in relation to the density of its streets (circuits). The sensitivity and detail captured by a camera improve as their sensor's surface area grows. Reduced sensitivity and coarser resolution are the results of a smaller fraction. Additionally, some companies provide CCDs with a lens capability for sensor elements to gather more light and increase sensitivity.

CCDs are not only sensitive to visible light but also to near-infrared. The spectral response of a sensor can be altered by changing the chemistry of certain components or by using filtering technologies. Infrared-cut filters, so-called because they are designed to reduce or eliminate IR light, can be placed in front of a color camera's sensors to boost image quality. These filters are unnecessary for the near-IR applications of monochrome cameras. Since monochrome cameras use both visible and NIR light to create an image, the daytime image may be less clear than the nighttime one.

Three CCDs are used in some cameras to achieve higher resolution. White light entering the lens is dispersed into the three primary colors by a prism in this setup. Next, the vector output is calculated and combined by three monochrome CCDs, each of which is filtered to receive a different color, yielding a high-resolution photograph. Even cameras with three CMOS sensors can benefit from these same ideas.

3.1.9.2 CMOS Sensors

However, CMOS sensors are widely used in devices like network cameras, PC peripherals, and smartphones, while CCD sensors are typically reserved for applications that demand superior image quality. This is because CMOS sensors consume less power and are cheaper to produce than CCDs.

 

Individual pixels can be addressed in CMOS sensors, which is not the case with CCD ones. Each pixel's charge is interpreted and transmitted as a binary digit. This method lessens the burden on the transmission path by eliminating the need for extra processing. Since more of a CMOS sensor's chip can be used for its processing circuits, it consumes less power than a CCD.