Let it be shopping, entertainment, or security, technological advancements have changed the way of life across the globe. The developments render a better environment and safe living conditions. The thermal imaging camera is such an invention that offers better surveillance capabilities, thereby providing improved security to a home, office, or industrial establishment.

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As with any other thing, a thermal imaging camera also has advantages and disadvantages. An elaborate understanding of the same will be helpful to make the right choice.

Advantages of Thermal Imaging Camera

Let’s have a look at the advantages of thermal imaging cameras.

Thermal Imaging Camera Delivers More Efficient Surveillance Scenario

Sensitive installations, houses, offices, factories, or industrial areas can use thermal imaging cameras at any corner of the property effectively. It doesn’t require lighting at all, since it captures the heat radiated from living beings. This operational peculiarity helps in installing the camera hidden from public eyes.

Weatherproof Device

It will not be impacted by wind, moisture, rain, or heat. Manufactured to withstand adverse climatic scenarios, the thermal camera will give the same quality of image irrespective of weather.

Capture Even Distant Images

Distant images will not be clear in visible-light cameras. The thermal imaging cameras capture the heat radiated from the body; therefore, it will indicate even distant living beings and their movements.

Maintenance-friendly

Thermal imaging cameras will not require frequent preventive or corrective maintenance.

Cost-effective Option

The comparatively higher initial cost may be a cause of concern for many. You may note that the longevity, performance and weatherproof aspects make thermal imaging cameras a cost-effective option.

Distinctive Images

You can easily differentiate an animal from a human being, which is essential in surveillance requirements. On the other hand, it may be difficult to distinguish between an animal and man, during bad light conditions, in the case of a visible light camera.

Functions Equally Well in Any Time of the Day

Be it day or night, the thermal imaging camera will perform with equal accuracy.

Disadvantages of Thermal Imaging Camera

The thermal imaging camera has been developed after in-depth studies and analysis. Moreover, all the available technical components have been integrated, to obtain the best result. Therefore, thermal imaging cameras are superior to visible light cameras. Nonetheless, the thermal imaging camera has a few disadvantages.

Initial procurement and Installation Cost is Higher than Visible Light Camera

The manufacturing of thermal imaging cameras necessitates exorbitantly priced components. Furthermore, it undergoes a systematic, yet complicated, production process to integrate the parts. The uniquely designed and developed components make the overall production cost higher. As a result, initial procurement and installation will turn dearly. 

Features of Intruders will not be Registered

Thermal imaging cameras will not provide real images of the individuals. It is highly used in defence establishments, wherein they have a special team to monitor unauthorized activities and capture the intruders at the same time. While one uses it at a residence to prevent theft or such unlawful activities, the image of the burglar or intruder is necessary to identify and nab him/ her. Thermal imaging cameras may not be of much use in areas where round the clock security is not available.

Limitations of Infrared

A thermal imaging camera uses infrared rays for capturing living beings. Unlike normal light, infrared rays cannot pass through glass or water. It will simply reflect upon hitting glass or water. This is a serious limitation whilst using this camera for surveillance in certain areas including highways. The camera will not be able to detect the individuals inside a vehicle.

Using Thermal Camera in Pandemic Scenario

Since the camera captures a person’s (a living being’s) body temperature, the surveillance may turn into a complex issue during pandemic conditions. It may not detect a person, who has a reduced body temperature due to the consumption of paracetamol or any other medicines. You may note that miscreants can try this method during normal conditions also.

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After analyzing the aforementioned advantages and disadvantages, you might have understood that a proper inspection of the area of use, assessment of the requirements, evaluation of possible threats, and end-use are vital in deciding upon a thermal camera and visible light camera.

Choose to buy visible light or thermal imaging cameras only from a reputed manufacturer, once you have identified the right option. Constant support from the manufacturer will be essential in installation, implementing modifications, and advising on the updation of formulated preventive maintenance policies.

It would be beneficial for you if you can discuss the requirements, available budget and other relevant factors with professionals. Guidance from experts will be of paramount value to choose and install the right type of surveillance camera at your premise. Providing highly secure and robust solutions for the cabling and communication requirement, Norden Communication caters to all the major sectors such as Telecommunication, Building, Finance, IT, Health, Education, Tourism and Government sector.

The Correct Material for Infrared (IR) Applications

Introduction to Infrared | Importance of the Correct Material | Choose the Correct Material | Infrared Comparison

Introduction to Infrared (IR)

Infrared (IR) radiation is characterized by wavelengths ranging from 0.750 -μm (750 - nm). Due to limitations on detector range, IR radiation is often divided into three smaller regions: 0.750 - 3μm, 3 - 30μm, and 30 - μm – defined as near-infrared (NIR), mid-wave infrared (MWIR), and far-infrared (FIR), respectively (Figure 1). Infrared products are used extensively in a variety of applications ranging from the detection of IR signals in thermal imaging to element identification in IR spectroscopy. As the need for IR applications grows and technology advances, manufacturers have begun to utilize IR materials in the design of plano-optics (i.e. windows, mirrors, polarizers, beamsplitters, prisms), spherical lenses (i.e. plano-concave/convex, double-concave/convex, meniscus), aspheric lenses (parabolic, hyperbolic, hybrid), achromatic lenses, and assemblies (i.e. imaging lenses, laser beam expanders, eyepieces, objectives). These IR materials, or substrates, vary in their physical characteristics. As a result, knowing the benefits of each allows one to select the correct material for any IR application.

The Importance of Using the Correct Material

Since infrared light is comprised of longer wavelengths than visible light, the two regions behave differently when propagating through the same optical medium. Some materials can be used for either IR or visible applications, most notably fused silica, BK7 and sapphire; however, the performance of an optical system can be optimized by using materials better suited to the task at hand. To understand this concept, consider transmission, index of refraction, dispersion and gradient index. For more in-depth information on specifications and properties, view Optical Glass.

Transmission

The foremost attribute defining any material is transmission. Transmission is a measure of throughput and is given as a percentage of the incident light. IR materials are usually opaque in the visible while visible materials are usually opaque in the IR; in other words, they exhibit nearly 0% transmission in those wavelength regions. For example, consider silicon, which transmits IR but not visible light (Figure 2).

Index of Refraction

While it is mainly transmission that classifies a material as either an IR or visible material, another important attribute is index of refraction $ \small{ \left( n_d \right) } $. Index of refraction is the ratio of the speed of light in a vacuum to the speed of light within a given material. It is a means of quantifying the effect of light "slowing down" as it enters a high index medium from a low index medium. It is also indicative of how much light is refracted when obliquely encountering a surface, where more light is refracted as $ \small{n_d} $ increases (Figure 3).

The index of refraction ranges from approximately 1.45 - 2 for visible materials and 1.38 - 4 for IR materials. In many cases, index of refraction and density share a positive correlation, meaning IR materials can be heavier than visible materials; however, a higher index of refraction also implies diffraction-limited performance can be achieved with fewer lens elements – reducing overall system weight and cost.

Dispersion

Dispersion is a measure of how much the index of refraction of a material changes with respect to wavelength. It also determines the separation of wavelengths known as chromatic aberration. Quantitatively, dispersion is inversely given by the Abbe number $ \small{ \left( v_d \right) } $, which is a function of the refractive index of a material at the f (486.1nm), d (587.6nm), and c (656.3nm) wavelengths (Equation 1).

Materials with an Abbe number greater than 55 (less dispersive) are considered crown materials and those with an Abbe number less than 50 (more dispersive) are considered flint materials. The Abbe number for visible materials ranges from 20 - 80, while the Abbe number for IR materials ranges from 20 - .

Index Gradient

The index of refraction of a medium varies as the temperature changes. This index gradient $ \left( \tfrac{\text{d} n}{\text{d} T} \right) $ can be problematic when operating in unstable environments, especially if the system is designed to operate for one value of n. Unfortunately, IR materials are typically characterized by larger values of $ \tfrac{\text{d} n}{\text{d} T} $ than visible materials (compare N-BK7, which can be used in the visible, to germanium, which only transmits in the IR in the Key Material Attributes table in Infrared Comparison).

How to Choose the Correct Material

When choosing the correct IR material, there are three simple points to consider. Though the selection process is easier because there is a much smaller practical selection of materials for use in the infrared compared to the visible, these materials also tend to be more expensive due to fabrication and material costs.

1. Thermal Properties – Frequently, optical materials are placed in environments where they are subjected to varying temperatures. Additionally, a common concern with IR applications is their tendency to produce a large amount of heat. A material's index gradient and coefficient of thermal expansion (CTE) should be evaluated to ensure the user is met with the desired performance. CTE is the rate at which a material expands or contracts given a change in temperature. For example, germanium has a very high index gradient, possibly degrading optical performance if used in a thermally volatile setting.
2. Transmission – Different applications operate within different regions of the IR spectrum. Certain IR substrates perform better depending on the wavelength at hand (Figure 4). For example, if the system is meant to operate in the MWIR, germanium is a better choice than sapphire, which works well in the NIR.
3. Index of Refraction – IR materials vary in terms of index of refraction far more than visible materials do, allowing for more variation in system design. Unlike visible materials (such as N-BK7) that work well throughout the entire visible spectrum, IR materials are often limited to a small band within the IR spectrum, especially when anti-reflection coatings are applied.

Infrared Comparison

Although dozens of IR materials exist, only a handful is predominantly used within the optics, imaging, and photonics industries to manufacture off-the-shelf components. Calcium fluoride, fused silica, germanium, magnesium fluoride, N-BK7, potassium bromide, sapphire, silicon, sodium chloride, zinc selenide and zinc sulfide each have their own unique attributes that distinguish them from each other, in addition to making them suitable for specific applications. The following tables provide a comparison of some commonly used substrates.

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Key IR Material Attributes Name Index of Refraction, $$ \small{ \left( n_d \right)} $$ Abbe Number, $$\small{ \left( v_d \right)}$$ Density CTE $$\pmb{\frac{\text{d}\textit{n}}{\text{d}\textit{T}}} $$ Knoop Hardness $$ \left[ \tfrac{\text{g}}{\text{cm}^3} \right] $$ $$ \left[ \times \tfrac{10^{-6}}{^{\text{o}} \text{C}} \right] $$ $$ \left[ \times \tfrac{10^{-6}}{^{\text{o}} \text{C}} \right] $$ $$ \left[ \tfrac{\text{kg}_f}{\text{mm}^2}\right] $$ Calcium Fluoride (CaF2) 1.434 95.1 3.18 18.85 -10.6 158.3 Fused Silica (FS) 1.458 67.80 2.2 0.55 11.9 500 Germanium (Ge) 4.003 N/A 5.33 6.1 396 780 Magnesium Fluoride (MgF2) 1.413 106.2 3.18 13.7 1.7 415 N-BK7 1.517 64.2 2.46 7.1 2.4 610 Potassium Bromide (KBr) 1.527 33.6 2.75 43 -40.8 7 Sapphire 1.768 72.2 3.97 5.3 13.1 Silicon (Si) 3.422 N/A 2.33 2.55 160 Sodium Chloride (NaCl) 1.491 42.9 2.17 44 -40.8 18.2 Zinc Selenide (ZnSe) 2.403 N/A 5.27 7.1 61 120 Zinc Sulfide (ZnS) 2.631 N/A 5.27 7.6 38.7 120