PoE (Power over Ethernet)

Power over Ethernet (PoE) is a mechanism for supplying power to network devices over the same cabling used to carry network traffic. In this technology no infrastructure upgrade is necessary.
A digital security camera normally requires two connections to be made when it is installed:

A network connection, in order to be able to communicate with video recording and display equipment and a power connection, to deliver the electrical power the camera needs to operate. However, if the camera is PoE-enabled, only the network connection needs to be made, as it will receive its electrical power from this cable as well and this enables the elimination of a separate cable solely for power use.

Cisco was one of those manufacturers that began including PoE capability within its switches in 2000.

Advantage of the Ethernet cable
• The challenge during installation is to calculate the total power consumption required so it is less than the power budget of the switch. The total power consumption requirement of all equipment that will be connected to a specific switch on a network needs to be calculated to ensure sufficient power is available per switch.

 • Without being tethered to an electrical outlet, devices such as IP cameras and wireless access points can be located wherever they are needed most and repositioned easily if required.

 • POE power comes from a central and universally compatible source, rather than a collection of distributed wall adapters.

 • Having power available on the network means that installation and distribution of network connections is simple and effective.

 • Wifi and Bluetooth APs and RFID readers are commonly PoE-compatible, to allow remote location away from AC outlets, and relocation following site surveys.

 • Unlike standards such as Universal Serial Bus which also power devices over the data cables, PoE allows long cable lengths.

 • Simply connect other network devices to the switch as normal and the switch will detect whether they are PoE-compatible and enable power automatically.

There are several standardized or ad-hoc systems which pass electrical power along with data on Ethernet cabling. Two of them have been standardized by IEEE 802.3: standard IEEE 802.3af and new prepared standard IEEE 802.3at.

In addition to standardizing existing practice for spare-pair and common-mode data pair power transmission, the IEEE PoE standards provide for signaling between the power source equipment (PSE) and powered device (PD). Up to a theoretical 51 watts is available for a device, depending on the version of the standard in use and the vendor of the hardware.

A midspan (or PoE injector) is used to add PoE capability to regular non-PoE network links. Upgrading each network connection to PoE is as simple as patching it through the midspan, and as with POE switches, power injection is controlled and automatic. It is also possible to upgrade powered devices, such as IP cameras, to PoE by using a PoE splitter.

The following chart shows the power consumption at both the PSE and the PD.

Class Usage Power Level Output at the Power Sourcing Equipment (PSE) Maximum Power Levels at the Powered Device (PD)

PoE Applications

Wide Dynamic Range (WDR)

The challenge that often arises with video security systems is the inability of standard network cameras to capture clear video in situations where there is a significant variance in lighting levels within a single scene.

In surveillance, Wide Dynamic Range (WDR) is intended to provide clear and useful images/video even under backlighting, where the intensity of illumination varies a lot—namely when there are very bright and very dark areas simultaneously in the camera’s field of view. Hence WDR allows system to correct for the intense back light surrounding a subject and thus elevates the ability to distinguish features and shapes on the subject.

There are many areas and conditions, both inside and outside, where video surveillance cameras with WDR should be installed:

• A store or an office that has a lot of windows.

• Inside parking garages, tunnels, train stations and another transportation centers where people and vehicles enter or exit.

• Environments with intense light reflection, like office buildings, shopping malls, locations with water features or areas that are prone to water puddles.

There are two basic techniques that are generally used to provide WDR: multi-frame imaging and non-linear sensors.

Multi-frame imaging – In this technique the camera captures multiple frames of the field-of-view; each frame having a different dynamic range. The camera then combines the frames to produce one improved WDR frame.

Non-linear sensors – These are typically logarithmic sensors, where the sensitivity of the sensor at different illumination levels varies, enabling the capture of a wide dynamic range image in a single frame.

So the performance of a WDR camera is very dependent on the sensitivity of its sensor and the processing ability of its DSP, in combination with its iris type and shutter speed.

WDR cameras are becoming increasingly popular as being able to tell colors apart at night is important for identifying suspects and culprits.  The professional WDR security camera can be used to provide surveillance of areas that have a wide range of lighting conditions. This technology is used in famous security camera brand like Sony, Axis, RedLeaf and JVC.

Camera Sensors

Over the years, the security cameras are improved. Housings have gone from the behemoths of the 1970s and ’80s to the compact versions we see today. Images have gotten more obvious and have changed from black and white to color. However what has driven these remarkable changes? The cameras can’t get smaller unless the components inside the camera get smaller and use less power. Video can’t improve unless the image sensors and processors work better. An image sensor is the piece of camera that captures the light hitting the camera lens and turns it into electrical signals.

As light passes through your camera lens, it hits the image sensor. The sensor is made up for many little photosites (each photosite becomes a pixel in the video resolution), and the amount of light on each individual photosite determines how much light will be in each pixel of video. The light/dark sections of each pixel make up a cohesive image in the final video.

Image sensors for IP cameras are typically categorized into two main technologies: charge-coupled devices (CCD), complementary metal oxide semiconductor (CMOS). Both CCD sensor and CMOS sensor are actually using same kind of sensor called Photo diode. Even though analog CCD sensors are an old technology (around for over 30 years), requiring complex implementation systems and costly manufacturing processes, they are still the most common image sensor used in the security industry.

In CCD sensors, signal readout is an analog voltage, which is then converted to digital signals using additional, high-speed electronic components. Image quality is affected because signals are converted of analog to digital far away from the capture’s original point. CMOS image sensors utilize newer technology to record better HD resolution and fast-moving activity, and are found in the majority of IP new cameras.

CCD

CCD sensors generally record more resolution than CMOS sensors. Even though a CCD sensor has to spend more time and energy converting each pixel than an equivalent CMOS sensor, it can hold more across its surface. The noise level on a CCD sensor is inherently less than that on a CMOS sensor of the same size. In CCD sensor, colors tend to be more saturated and vibrant in contrast to those that are taken through a CMOS sensor.

CMOS

Each CMOS pixel is packaged with the circuitry to convert it to digital signal, thus each sensor takes up more space. CMOS sensor is become idle under 10 lux. The clutter on CMOS sensors reduces the light sensitivity of the chip. CMOS sensors have 10 times more fix pattern noise then CCD sensors.

CMOS sensor very useful for fast frame camera, the speed of frame can be as high as 400 ~2000 frame/sec. Early CMOS sensors were based on standard technology already extensively applied in memory chips inside PCs, for example modern CMOS sensors use a more specialized technology and the quality of the sensors is rapidly increasing. CMOS sensors also have a faster readout (which is advantageous when high-resolution images are need), lower power dissipation at the chip level.

Smart IR Camera

As mentioned in “Day and night network cameras” post, in order to see at night or in other situations in which there are low levels of visible light, IR security cameras capture clear images. Such cameras use infrared LED arrays to augment the available ambient lighting.

Sometimes, customers can make the mistake of purchasing an IR camera that does not fit their application because they do not know the size of their coverage area and overexposure is happened. For instance, a person’s face will be “whited out” so that no features can be recognized, making the images captured unusable for identification purposes. This can easily happen for an infrared camera with a 65 foot IR range, but the camera is monitoring an area where people can approach the camera at a much closer distance (5 to 10 feet for example).

Smart IR is a technology was invented to adjusts the intensity of the camera’s infrared LEDs to compensate for overexpose problem. These cameras automatically (combination of hardware and software) adjust the intensity of their built in infrared LEDs to compensate for objects within close distances to the camera lens.

Applications which would greatly benefit from Smart IR include high traffic areas where subjects move towards and away from the camera such as:

• Store fronts
• Gated access points
• Home entry and exit points

Many infrared cameras like VIVOTEK, RedLeaf and Hikvision that are available today include this technology, but not all do, so check your camera’s specification.

Day and Night Network Cameras

Regular, color network cameras are available which delivers color images during the day. But when daylight fades, cameras sense the lower light levels. There are a variety of techniques to improve image quality in condition of poor light.

Camera with IR filter

In this camera, the end user can see picture in total darkness at the distance of infrared emission produced by LEDs. A day and night camera can have infrared LEDs mounted surrounding the lens. These LEDs can emit their own light anywhere from 20 meters all the way up to 70 meters and beyond.

During day time, when the filter is put in place, it filters the wavelengths, improving the quality of the image by showing only the “visible” light, removing the “infrared” light from the spectrum.

When the camera is in night mode (light diminishes below a certain level), the IR-cut filter is removed by a small motor, allowing the camera’s light sensitivity to reach down to 0.001 lux or lower. In this mode, the camera starts recording in black and white.

Remember that a camera’s infrared capabilities are, for the great majority of applications, be used for less than half the day.

Digital day/night cameras

Digital day/night cameras (or electronic day/night cameras) are also available, which electronically adjust colors during the day, instead of using an infrared filter. Once it becomes dark, the camera digitally switches to black and white. Checking the LUX rating is the best way to see how digital day/night cameras are performed.  Without the need for a physical filter, digital day/night technology can also be leveraged for smaller form factors. Day/Night recording is available on dome, fixed dome, bullet, box, and PTZ security cameras.

Almost every IP camera on the market now has some form of day/night feature, from basic image optimization technologies such as the Panasonic BL-C101 and the Sony SNC-CH110, to advanced, day/night functionality in models like the Axis P1347, the RedLeaf RLC-DF2035 and the RedLeaf RLC-BF2422.

Image Scanning Technique

There are two basic ways in which video images can be read or displayed on display screens: interlaced scan and progressive scan.

Interlaced scan

“Interlaced” means the lines that combine the picture on your TV screen are drawn in an alternating method. It means, interlaced video scans the display twice, one contains only the odd lines and other contains only the even lines, to complete a single frame.

The interlaced image rendering method was used in the 1980s, the 1990s saw a growing demand for better resolutions. While this interlaced scanning worked well for older, analog screens, it was not ideal for the new standard of electronic display sets that use a Liquid Crystal Display (LCD).

Analog cameras can use the interlaced scanning technique for transferring images over a coaxial cable and for displaying them on analog screens.

The interlacing technique creates artifacts or distortions as a result of missing data; they are not very important on an interlaced screen. But on larger screens particularly, an irritating flickering effect can sometimes become apparent.

Progressive scan

Progressive scanning is much simpler than interlaced scanning: each line is scanned consecutively until a complete frame is drawn. Computer displays and many recent HD televisions use progressive scanning. While HD was introduced, more and more image creating devices were built with the ability to create superb images applying progressive scanning.

This method of image processing keeps the capture and sending of the complete image together thus producing higher quality and clearer video with sharper motion details and virtually no distortion, zippering, or flickering as they are refreshed at a faster frequency.

 

Megapixel Cameras

Megapixel cameras will bring great changes to the video security business. These cameras can be used in one of two ways: they can enable users to see greater details in a higher resolution image, that would be helpful in identifying people and objects, or they can be used to cover a larger field of view and lower the camera number. These two differences between the VGA and megapixel cameras are determined as follows:

The standard VGA resolution camera supplies a pixel of array of 640×480 that is about 0.3 megapixels. In facial recognition application, VGA cameras could cover a five feet field of view, but a 2 megapixel camera can cover a field of 11 feet and a 3 megapixel camera covers almost 15 feet.

Megapixel cameras use CMOS sensors which require a low operating current. In CMOS cameras, each frame is exposed from top to bottom in a rolling motion. Traditional video uses a series of odd and even lines scanning, called interlacing, to display each video frame, resulting in the blurred or jagged edges of moving objects but each frame in megapixel cameras, eliminate this effect and use progressive scanning.

High resolution cameras transmit greater amounts of data and this additional data takes longer for the camera to process and needs network bandwidth and storage space for recordings, although this can be compensated by using the H.264 video compression standard.

These cameras often deliver low quality images in low light condition, and the automatic gain control used to compensate this situation additional noise. A megapixel compatible lens should be used to ensure that images provide consistently high contrast and high resolution from the center of the lens all the way to the edge. Without using the proper lens, the advantage of the higher resolution camera will be lost in condition that most require megapixel performance.

Right now, the lower frame rates provided by megapixel cameras, but in the future megapixel cameras will offer the same frame rates we’ve expect from standard video.

Advantages of IP Cameras

The fact is that traditional CCTV cameras have reached the end of their evolution and companies switch to HD cameras and dedicated network video recorders (NVRs) for all their video surveillance needs.

Here are 6 causes to select between the analog cameras and IP security cameras.

Image quality

Image quality is clearly one of the most important features of any camera. In a fully digital IP surveillance system, images from a network camera are immediately converted into a digital stream before transmission and they stay digital with no unnecessary transformation and no image degradation due to distance traveled over a network.

High resolution

IP security cameras offer sharp, crisp video images, as compared to analog systems. Moreover, digital images can be more easily stored and recovered and provided better resolution, expanded surveillance environments, and more detailed images.

Ease of installation

IP cameras provide a high level of integration with other equipment and functions, making it a continually developing system. On the other hand, an analog system rarely has an open interface for easy integration with other systems and applications.

Scalability

Network based IP cameras can be located anywhere they are needed, at any time, and they can share the same wired or wireless network that’s already in use for communicating data. And also they have ability to add to an existing analog cameras system.

In an IP cameras system, any number of network video products can be added to the system without significant or costly changes to the network substructure.

Remote accessibility

One important of IP camera’s feature is the ability to access and view video files from any location in the world. With network video, users can access individual cameras from within their local network, or over the internet.

Power over Ethernet (POE)

Increasing reliability and providing substantial savings, Power over Ethernet (PoE) enables IP cameras to receive power from the very same Ethernet cable that transports the video and audio data.