Thermal Security Cameras for Surveillance Purposes

The development and adoption of thermal imaging technology has been driven by the desire to see in complete darkness or through smoke or fog. Thermal imaging cameras are an essential part of security programs specifically in the security and surveillance sector. They perform terrifically when it comes to protecting assets and prevent vandalism, terrorism or random aggressive assaults.

A scene's heat signature is the definition of the term "Thermal imaging". Technically it translates to the 8 um to 14 um, or long wavelength infrared energy (LWIR), that it discharges into a data or visual footage that can be interpreted by a processor. Thermal imaging is the technology of choice for imaging in the dark or other difficult environmental conditions due to the fact that the thermal energy of a scene is largely independent of reflected light and because it can travel through many obscurants. Believe it or not there is a great demand for this thermal imaging technology in markets such as consumer applications, firefighting, law enforcement, surveillance, homeland security, as well as industrial purposes.

Particularly, in the surveillance and security markets, merging a traditional video camera with a thermal imaging camera is an added benefit of providing good imaging abilities in bad weather situations when traditional cameras are unable to perform adequately.

Near-infrared radiation as well as visible light, to which modern day commercial video cameras and their imaging sensors are receptive, has spectral elements that are between 0.4 to 1.1 microns. Adding on, the wavelengths of the thermal energy of interest lie between 15 and 7.5 microns. The last therefore go unnoticed.

According to an administrator at J.P. Freeman Laboratories, until recently, the only camera device that preformed adequately at these thermal wavelengths utilized cameras with cryogenically-cooled imagers and carried a price of between five thousand and fifty thousand US dollars. For that reason their use is limited to military or very complicated industrial deployments that can afford the expensive price of the device.

Before we can make thermal imaging cameras universally deployable there are several characteristics that have to be fulfilled.

Decreased price and easiness of Production

This equipment must be producible for a small price even in modest amounts. Carrying out this vision is only possible with high yields and liberal exploitation of technology and manufacturing platforms established for other high-volume, high-tech businesses.

Ease of measurability

Resolution, sensitivity and other parameters are some of the factors that decide the needs of various other applications. In order for product variety to be provided without excessive development time or expense any universally deployable technology must be easily testable and measurable.

Decreased Power Requirements

 The majority of thermal imaging cameras must be portable small, as well as lightweight. In the present day and age, the batteries utilized to power the system restrict size and weight amount. And as a result smaller batteries are required to make cameras smaller, lighter and more widely usable due to the lower power consumption.

High quality image and footage

A thermal imaging technology that is universally deployed must have the capability of producing images of sufficient quality for the applications in which it is utilized.

Investigating the Microbolometer Technology

The Microbolometer sensor is the most common form of thermal imaging technology available today. Vanadium oxide (VOx) or amorphous silicon (aSi) processes are the main components that are used in building the Microbolometers. Depending on resolution, performance and feature set, the typical prices for microbolometer-based cameras range from eight thousand to twenty thousand US dollars.

The pixels of Microbolometer are sophisticated. The actual shape of the pixel looks like a table with two legs that separate it from a substrate and read out incorporated circuit underneath. The "table" forms a complete circuit with the underlying electronics due to the fact that it is made of VOx or other electrically-conductive material. The electrical resistances of the table top materials change when incident LWIR energy strikes it. Greater change in resistance is caused by more incident radiation. Through passing a current through the device the change in resistance can be probed. Furthermore, modification in temperature can be read out as electronic signs and utilized to produce a picture. The main reason that the pixel design becomes complicated is due to the fact that the legs must both thermally segregate the pixel (to be able to produce a response) and create electricity (in order for the response can be investigated). It is not clear-cut to generate both results with a single blueprint.

Several elements make up a complete microbolometer camera engine including: optics, the microbolometer sensor, which consists of a sensing pixel array, back-end electronics read-out incorporated circuit (ROIC) as well as vacuum package.

The microbolometer detector is made using a micro-electro-mechanical system (MEMS) procedure, which is the usual in a custom foundry with dedicated VOx processing ability.

To start with, a custom ROIC wafer is created. This includes complex circuitry that is needed to deduce the thermally-induced resistance types. After that, pixel arrays are deposited on this wafer piece. Let us not forget to mention that a typical pixel design usually is fairly complex and can demand more than 30 mask layers when the underlying CMOS layers are incorporated. As soon as the pixel arrays have been put down, the wafer is diced into separate dies, which are yielded and vacuum packed to generate a finished microbolometer detector. The detector is then incorporated into control and processing electronic systems. In addition LWIR optics are also installed. The entire engine is standardized for performance over ambient temperature and is then ready to be purchased by customers.

Assessment of the microbolometer construction, supplies and manufacturing procedure renders it clear why this technology is unable to carry out the requirements of universal installation.

Not a very price. The average price of Microbolometer based cameras is greater than seven thousand us dollars per device. They are built in dedicated custom foundries and their highly complicated, multi-mask step designs result in decreased outcomes. In addition, failed devices include the price of custom ROIC electronic units. Furthermore, Expensive die-level packaging is necessary because VOx can not be uncovered to the high temperatures required for low-cost wafer scale wrapping.

Not easily measurable. The phase period for new microbolometer designs costs millions of dollars and takes several years.

Restricted reduced power

The finest microbolometer designs takes up close to 2W for normal procedures.

A fairly limited sensitivity

Big pixel microbolometer layouts have established enough sensitivity for current deployments, but future potential may be restricted for smaller pixel sizes. A 2.5 percent change in signal per change in temperature represents the best possible response for VOx microbolometers.

Universal Deployment and its fundamental principle

In order to make universal deployment of thermal imaging a reality, a new technology with significant changes in underlying design, materials and manufacturing procedures is required. Optical thermal imaging is that aspired technology. For that reason, RedShift Systems Corp. has established the Thermal Light ValveTM, (TLV) which is a passive, optical component that makes optical thermal imaging a possibility.

The reality of the matter is that optical thermal imaging does not rely on the modification of resistance to measure changes in temperature. As an alternative to that, optical thermal imaging technologies depend on changes in optical properties when exposed to changes in temperature. As an alternative to electronic read out, these modifications are optically read out, through utilizing electronics of standard digital camera.

Not to mention that each pixel acts as a passive wavelength transformer. The TLV receives and absorbs the image of the Long-wave length infrared radiation from the scene. After that, it heats up particular thermal pixels on the range in direct association with the thermal signature of the sight. Based upon the thermal energy incident on each, the minimum reflective wavelengths of the pixels changes location. In order to probe the temperature of the pixels across the TLV a narrow-band near-infrared light source (NIR) is put to use. Depending on the pixel temperature the NIR probe signal is then reflected off the TLV in varying quantities onto the CMOS imager device. The strength of the light received by the CMOS imager device is consequently modulated by the heat signature of the site.

A thermal picture is captured through measuring the pixel-to-pixel deviation in transmission of the NIR probe signal using CMOS imager equipment.

On the other hand a Fabry-Perot structure constitutes the TLV tunable optical filter. This equipment is essentially an amorphous silicon and silicon nitride thin films, which have been put to use extensively for loads of years in solar cells and flat-panel projectors and monitors. These resources are set down using plasma enhanced, chemical vapor deposition, which has the ability to produce uniform, dense materials in high-volume deployment surroundings. The optical thickness of the cavity (which is the wavelength a product of physical thickness and index of refraction) is the one that decides the optical filter's minimum reflective. Furthermore, RedShift achieves tunability through altering the refraction index. A high thermo-optic coefficient (which is defined as the change of index of refraction per degree of temperature change) characterizes the materials.

The procedure shows that temperature induced changes in optical materials can be used to produce thermal pictures, but it does not address the issue of whether optical thermal imaging is better than microbolometers in terms of universal installations.

A number of important differences from the microbolometer should be kept in mind:

• The detection range is not an electronic apparatus. It is merely a passive layer of optical thin films on a glassy layer. This significantly simplifies packaging and manufacturing.
• Furthermore, the detection range is produced in a standard MEMS foundry, taking advantage of foundry economies of scale to considerably decrease manufacturing cost over that obtainable with custom fabrication settings.
• One must also realize that, the readout circuit in the optical thermal imaging device is not physically coupled to the detection range, nor is it a custom establishment. It is essentially made up of off-the-shelf parts, such as CMOS sensors and laser diodes, which can be sourced from consumer camera applications and high volume optical mouse and independently controlled from the detection range. This reduces development cycle time, increases yield as well as reduces cost.

The variations are vital. The variations in the two procedures make optical thermal imaging and TLV cameras far more fitting for global deployments.

An apparent Low cost. An optical thermal imaging-based camera will be obtainable for less than three thousand US dollars in low volumes and will rapidly decrease in price over time and quantity. The detection range (which in this case is the TLV) is produced in standard semiconductor foundries so no capital investment is needed. The TLV necessitates simply four mask steps to manufacture. This translates to the fact that it is less costly to produce and has much higher results. On the other hand, the ROIC is not yielded with the range. The TLV can be packaged through utilizing wafer scale procedures, which considerably reduces the expenses of packaging and wrapping. The ROIC is almost made up entirely of inexpensive off-the-shelf components such as CMOS sensors and optical mouse lasers that are sourced globally and manufactured in enormously high amounts.

Adding on, it is also easily measurable. New products will be released on a time scale consistent with consumer products through the utilization of optical thermal imaging. Due to the fact that the pixel's thermal isolation does not also have to be electrically conductive, the design is much easier and can be easily measured. All that is required for new designs is a change in sensor component.

Adding on, it uses lower amounts of power. The majority of optical thermal imaging engines will usually use up well under 1W of power. Not to mention that the TLV is passive and it consumes no power at all. Also, the back-end electronics are almost the same as a digital camera unit.

Furthermore it is a very high potential of producing Good quality images. The majority of the thermo-optic materials used in Optical Thermal Imaging is very sensitive to temperature fluctuations. In addition, the percent alteration in signal for a one-degree change in temperature is up to twenty times higher in optical thermal imaging than in microbolometers apparatuses.

After reading all of this information it is more than obviously that a major technological shift is fundamentally required in order to satisfy the strong demand for thermal imaging technology. A great deal of industry sectors and governmental departments can greatly benefit from a technology that makes thermal imaging cameras reasonably priced, and this will increase security and safety for all the parties associated with it.

Surveillance Thermal Security Cameras technology imaging wavelength infrared energy (LWIR), data visual footage traditional sensors are receptive, high-tech Power High quality Microbolometer sensor amorphous silicon (aSi) Vanadium oxide (VOx) electronic read-out incorporated circuit (ROIC) micro-electro-mechanical system (MEMS) CMOS installation Thermal Light ValveTM, (TLV)