Thermal Imaging: How Infrared Technology Work?

Thermal Imaging: Beyond the Visible Spectrum

Thermal Imaging is a technology that detects infrared radiation to create images based on temperature variations. It enables visualization of heat patterns in objects and environments, commonly used for applications in surveillance, medical diagnostics, building inspections, and wildlife monitoring.
3D Image from Thermal Imaging

Overview

In the realm of technology, where innovation is a constant companion, thermal imaging has emerged as a powerful tool with applications spanning various industries. From military and defense to healthcare, construction, and even consumer electronics, thermal imaging has found its way into diverse fields. In this article by Academic Block, we will explore the intricacies of thermal imaging, exploring its principles, applications, advancements, and the future possibilities it holds.

Understanding Thermal Imaging

1. Principles of Thermal Imaging

At the core of thermal imaging lies the detection and interpretation of infrared radiation emitted by objects. All objects with a temperature above absolute zero emit thermal radiation. This radiation, commonly referred to as infrared radiation, is invisible to the human eye but can be detected by thermal imaging devices.

Thermal cameras utilize special sensors, often based on microbolometers, to capture the infrared radiation emitted by objects. These sensors convert the detected radiation into electrical signals, which are then processed to create an image. The resulting thermal image represents variations in temperature, with warmer areas appearing brighter or different in color than cooler ones.

2. Types of Thermal Imaging Devices

There are various types of thermal imaging devices designed for specific applications. Some common types include:

  • Uncooled Thermal Cameras: These cameras use microbolometer arrays that do not require cooling. They are more compact, energy-efficient, and cost-effective compared to their cooled counterparts.

  • Cooled Thermal Cameras: Cooled cameras employ a cooling mechanism, often using cryogenic substances, to enhance the sensitivity of the sensors. They are typically more expensive and bulky but offer higher image quality, making them suitable for advanced applications.

  • Infrared Thermography Devices: Infrared thermography is a technique that uses thermal cameras to visualize temperature differences on surfaces. This method is widely used in preventive maintenance, building inspections, and medical diagnostics.

3.Father of thermal imaging

Sir William Herschel, an astronomer and scientist from the 18th century is often attributed as the "father of thermal imaging". Herschel is best known for his discovery of the planet Uranus in 1781, but he also made significant contributions to the understanding of infrared radiation.

In 1800, Herschel conducted an experiment using a prism to split sunlight into its constituent colors and then placed thermometers in different colors to measure the temperature. He observed an increase in temperature beyond the red end of the spectrum, where no visible light was present. This led him to the discovery of infrared radiation, which is not visible to the human eye but can be detected as heat. Herschel's work laid the foundation for the development of thermal imaging technology.

It is important to note that, while Herschel played a crucial role in the foundational understanding of thermal phenomena, the credit for the entire development of thermal imaging technology goes to a collective effort of numerous individuals over the years.

Mathematical equations behind the Thermal Imaging

The mathematical equations behind thermal imaging involve principles from radiometry and the Planck radiation law. These equations help to describe the relationship between temperature and the intensity of thermal radiation emitted by objects. Additionally, there are equations related to the sensors and optics used in thermal imaging devices. Let's explore some of the fundamental equations involved:

  1. Planck's Law of Radiation: Planck's law describes the spectral radiance (intensity per unit area per unit solid angle per unit wavelength) of a black body at thermodynamic temperature T. The equation is given by:

    B(λ,T) = (2hc2 / λ5) [1 / ehc/λkT −1] ;

    Where:

    • B(λ,T) is the spectral radiance.

    • h is Planck's constant.

    • c is the speed of light.

    • λ is the wavelength of radiation.

    • k is the Boltzmann constant.

    • T is the temperature in Kelvin.

    This equation helps to understand the distribution of thermal radiation across different wavelengths for a given temperature.

  2. Stefan-Boltzmann Law: The Stefan-Boltzmann law provides the total power radiated per unit surface area of a black body and is given by:

    P = σ⋅A⋅T4 ;

    Where:

    • P is the total power.

    • σ is the Stefan-Boltzmann constant.

    • A is the surface area.

    • T is the temperature in Kelvin.

    This equation quantifies how the total emitted power increases with the fourth power of temperature.

  3. Radiance and Temperature Relationship: The relationship between radiance, temperature, and emissivity (ε) can be expressed as:

    E(λ,T) = ε ⋅ B(λ,T) ;

    Where:

    • E(λ,T) is the emitted radiance.

    • ε is the emissivity, representing the efficiency of an object in emitting thermal radiation.

    This equation is crucial in understanding how thermal cameras capture the emitted radiation from objects based on their temperatures and emissivity.

  4. Response of Thermal Imaging Sensors: The response of thermal imaging sensors, such as microbolometers, is often characterized by their responsivity (R) and thermal time constant (τ). The relationship between radiant power (P), responsivity, and temperature difference (ΔT) can be expressed as:

    P=R⋅ΔT;

    Additionally, the time response of the sensor can be described by:

    T(t) = T0 + (T(t0) − T0) ⋅ e−t/τ ;

    Where:

    • T(t) is the temperature at time tt.

    • T0 is the initial temperature.

    • τ is the thermal time constant.

    These equations help model the behavior of thermal sensors and their response to changes in temperature.

In thermal imaging, these mathematical principles guide the design of sensors, the interpretation of thermal images, and the understanding of the relationship between temperature and emitted radiation. Advanced signal processing and image analysis techniques further contribute to the extraction of meaningful information from thermal images.

Applications of Thermal Imaging

1. Military and Defense

One of the earliest adopters of thermal imaging technology was the military. Thermal cameras proved invaluable for night vision, target identification, and surveillance. The ability to detect heat signatures in complete darkness provided a significant tactical advantage. Modern military applications include the integration of thermal imaging into surveillance drones, enhancing situational awareness and reconnaissance capabilities.

2. Medical Imaging

In the field of healthcare, thermal imaging has found applications in medical diagnostics and research. Thermography, a non-invasive imaging technique, is used to detect abnormalities in body temperature distribution. This is particularly useful in early detection of diseases such as breast cancer, where temperature variations in tissues can indicate potential health issues.

3. Building Inspections and Maintenance

Thermal imaging is widely employed in building inspections to identify issues such as heat loss, electrical faults, and insulation deficiencies. Infrared thermography allows inspectors to visualize temperature variations on building surfaces, providing insights into potential problems that may not be apparent through visual inspections alone. This aids in proactive maintenance and energy efficiency improvements.

4. Law Enforcement and Search and Rescue

Law enforcement agencies leverage thermal imaging for various purposes, including surveillance, suspect detection, and search and rescue operations. The ability to identify individuals or objects based on their heat signatures is especially beneficial in challenging environments, such as dense forests or urban areas, where traditional visibility may be limited.

5. Wildlife Monitoring

Biologists and conservationists use thermal imaging to study and monitor wildlife behavior. The technology enables researchers to observe animals in their natural habitats without disturbing them. It is particularly useful for nocturnal species or those living in dense vegetation, where visual observation may be challenging.

6. Firefighting

In firefighting applications, thermal imaging cameras assist firefighters in locating hotspots, victims, and potential hazards in smoke-filled environments. These cameras can "see through" smoke, providing a crucial tool for improving situational awareness and enhancing the safety and effectiveness of firefighting efforts.

Advancements in Thermal Imaging Technology

1. Resolution Enhancement

Advancements in sensor technology have led to significant improvements in the resolution of thermal imaging cameras. Higher resolutions allow for more detailed and accurate thermal images, enabling users to discern finer temperature variations and identify smaller objects.

2. Integration with Other Technologies

Thermal imaging is increasingly being integrated with other technologies to enhance its capabilities. For example, combining thermal imaging with artificial intelligence (AI) algorithms enables automated object recognition and tracking. This integration is particularly useful in security and surveillance applications.

3. Miniaturization and Portability

Modern thermal imaging devices are becoming more compact and portable, making them accessible to a broader range of users. Miniaturization has paved the way for the integration of thermal cameras into smartphones and consumer electronics, opening up new possibilities for everyday applications.

4. Cost Reduction

As technology advances and production processes improve, the cost of thermal imaging devices has decreased. This cost reduction has contributed to the widespread adoption of thermal imaging across various industries, from large enterprises to individual consumers.

Final Words

In this article by Academic Block, we have seen that the thermal imaging has evolved from a niche technology to a versatile tool with applications across diverse industries. From military and healthcare to construction and consumer electronics, the ability to visualize thermal information has opened up new possibilities for innovation and problem-solving. As technology continues to advance, the future of thermal imaging holds exciting prospects, with potential breakthroughs in healthcare, autonomous systems, and environmental monitoring. However, addressing challenges related to data privacy and ethical considerations will be crucial in ensuring the responsible and beneficial use of thermal imaging technology in the years to come. Please provide your comments below, it will help us in improving this article. Thanks for reading!

This Article will answer your questions like:

+ What is thermal imaging and how does it capture infrared radiation? >

Thermal imaging is a technology that captures infrared (IR) radiation emitted by objects to create images based on temperature variations. Thermal cameras detect heat emitted in the infrared spectrum (longer wavelengths than visible light) and convert this data into visible images called thermograms. This allows visualization of temperature differences in the scene, revealing hot spots and cold areas. The cameras measure infrared radiation using sensors sensitive to IR wavelengths, converting heat signatures into electrical signals processed to generate thermal images. Applications include night vision, building diagnostics, and industrial monitoring where detecting thermal anomalies is critical.

+ How are thermal cameras used to visualize temperature variations? >

Thermal cameras visualize temperature variations by detecting infrared radiation emitted by objects. They convert IR radiation into thermal images (thermograms) that display varying colors or shades representing different temperatures. Cooler temperatures appear as blue or purple, while warmer temperatures appear as yellow, orange, or red. This capability allows users to identify temperature gradients, heat leaks, or abnormalities in equipment, structures, or living organisms. Thermal cameras are widely used in firefighting, law enforcement, and scientific research for non-contact temperature measurement and environmental monitoring.

+ What is the basic principle of thermal imaging? >

The basic principle of thermal imaging involves detecting infrared radiation emitted by objects due to their temperature. Thermal cameras convert this radiation into electronic signals, which are processed to create visible images representing temperature variations. This technology is widely used in applications such as surveillance, building inspections, and medical diagnostics, allowing for non-invasive assessment of thermal characteristics.

+ What is thermography used for? >

Thermography is employed to detect thermal anomalies in various applications, including electrical inspections, medical diagnostics, and building assessments. It allows for non-contact monitoring of temperature variations, which can indicate equipment failures or potential hazards. In medicine, thermography aids in diagnosing conditions related to vascular health and inflammation, offering a valuable tool for early detection and preventative care.

+ How does thermal imaging differ from visible light photography? >

Thermal imaging differs from visible light photography in that it captures infrared radiation emitted by objects rather than visible light reflected off them. While traditional photography relies on light visible to the human eye, thermal imaging uses sensors sensitive to infrared wavelengths to detect heat emitted by objects. This enables visualization of temperature differences rather than physical appearance, making it useful in environments with low visibility or where detecting heat signatures is critical, such as firefighting, search and rescue, and building diagnostics.

+ What types of thermal radiation are detected by thermal cameras? >

Thermal cameras detect infrared radiation emitted by objects, which varies depending on their temperature. Objects emit thermal radiation across the infrared spectrum, typically ranging from around 9,000 to 14,000 nanometers (9 to 14 micrometers). This range corresponds to the heat emitted by objects at normal temperatures, allowing thermal cameras to capture thermal images based on these emissions. Different materials and surfaces emit infrared radiation differently due to their emissivity and temperature, affecting how thermal cameras interpret and display temperature variations in thermographic images.

+ What is the use of a thermal imager? >

A thermal imager is used to visualize heat patterns and temperature variations in objects. It finds applications in diverse fields including electrical inspections, predictive maintenance, and building diagnostics. By revealing heat leaks, hotspots, and insulation deficiencies, thermal imagers enable proactive measures to enhance safety and efficiency. Additionally, they are invaluable in medical settings for diagnosing conditions related to blood flow and inflammation.

+ What is an example of thermal imaging? >

An example of thermal imaging is its use in electrical inspections. Technicians employ thermal cameras to identify overheating components in electrical panels and equipment, which can indicate potential failures. This non-invasive method allows for early detection of issues, improving safety and preventing costly downtime. Additionally, thermal imaging is utilized in building inspections to locate heat leaks and assess insulation effectiveness, contributing to energy efficiency efforts.

+ How is thermal imaging used in medical diagnostics and veterinary care? >

Thermal imaging is used in medical diagnostics and veterinary care to assess blood flow, inflammation, and abnormal temperature patterns indicative of underlying health conditions. In medicine, thermal cameras aid in early detection of vascular disorders, nerve injuries, and musculoskeletal injuries by visualizing temperature changes on the body's surface. In veterinary care, thermal imaging identifies injuries, infections, and circulatory problems in animals, supporting diagnostic evaluations and treatment planning without invasive procedures. This non-contact imaging technique provides valuable insights into physiological processes, facilitating timely intervention and improved patient outcomes in human and veterinary healthcare.

+ What are the advantages of using thermal imaging for surveillance and security? >

Thermal imaging offers advantages for surveillance and security by detecting intruders, monitoring perimeter activity, and enhancing situational awareness in low-light or obscured environments. Thermal cameras detect heat signatures emitted by people, animals, or vehicles, distinguishing them from the background and providing clear visibility at night or in adverse weather conditions. This capability improves threat detection, facilitates rapid response to security breaches, and enhances operational effectiveness for military, law enforcement, and critical infrastructure protection. Thermal imaging's non-reliance on visible light and ability to detect concealed threats make it indispensable in security applications requiring continuous monitoring and proactive threat mitigation.

+ What can thermal imaging detect? >

Thermal imaging can detect temperature variations in objects, making it valuable for identifying issues in various fields. It is widely used to spot electrical faults, monitor equipment heat levels, and assess building insulation efficiency. Additionally, thermal imaging can detect human and animal presence, making it useful in security and wildlife monitoring. In medicine, it helps visualize inflammation and blood flow, providing insights into various health conditions and assisting in diagnostics.

+ How is data from thermal imaging processed and analyzed? >

Data from thermal imaging is processed and analyzed using specialized software that converts thermal signals into visual images or numerical data. Image processing algorithms enhance contrast, remove noise, and adjust temperature scales to improve image quality and accuracy. Analytical tools measure temperature gradients, identify hotspots, and quantify temperature variations across a scene or object. Advanced thermal analysis includes trend monitoring, anomaly detection, and integration with geographic information systems (GIS) for mapping temperature data. This processed information guides decision-making in building diagnostics, industrial inspections, medical evaluations, and security operations, optimizing resource allocation and facilitating preventive maintenance strategies.

+ What are the limitations and factors affecting thermal imaging accuracy? >

Thermal imaging accuracy is influenced by factors such as environmental conditions (temperature, humidity), emissivity variations of materials, distance from the target, and sensor resolution. Atmospheric conditions, including fog, rain, or smoke, can attenuate infrared radiation and affect image clarity. Material properties, surface finishes, and angle of incidence impact emissivity and thermal contrast, influencing temperature measurement accuracy. Sensor quality, calibration, and thermal drift can introduce measurement errors and affect consistency in thermal imaging results. Understanding these factors is essential for interpreting thermal data correctly and optimizing the reliability of thermal imaging systems across diverse applications.

+ Can you use thermal imaging for hunting? >

Yes, thermal imaging can be effectively used for hunting. It enables hunters to detect animals based on their heat signatures, even in complete darkness or adverse weather conditions. This technology enhances situational awareness and safety, allowing for more efficient tracking and identification of game. Moreover, it minimizes disturbance to wildlife, promoting ethical hunting practices. However, it's essential to follow local regulations regarding the use of thermal imaging in hunting.

+ How does thermal imaging integrate with unmanned aerial vehicles (UAVs) and drones? >

Thermal imaging integrates with unmanned aerial vehicles (UAVs) and drones to provide aerial thermal surveys for applications in agriculture, infrastructure inspection, and search and rescue operations. Mounted thermal cameras on UAVs capture aerial views of landscapes, buildings, or disaster zones, detecting heat signatures and thermal anomalies from above. This aerial perspective enhances coverage and accessibility in large or hazardous areas, allowing rapid assessment of vegetation health, energy loss in buildings, or locating survivors in emergencies. Real-time thermal data streaming from UAVs supports decision-making, enhances operational efficiency, and expands capabilities in remote sensing and environmental monitoring.

+ What recent advancements have been made in thermal imaging technology? >

Recent advancements in thermal imaging technology include improved sensor resolutions, enhanced image processing algorithms, and integration with artificial intelligence (AI) for automated analysis and anomaly detection. High-definition thermal cameras offer higher pixel densities and sensitivity, providing clearer and more detailed thermal images. Advanced image enhancement techniques reduce noise and improve image clarity in challenging conditions. AI-driven thermal analytics enable real-time object detection, tracking, and classification based on thermal signatures, enhancing surveillance and security applications. Miniaturization of thermal sensors and integration with mobile devices expand accessibility and versatility in personal thermal imaging solutions, supporting diverse applications from consumer electronics to industrial automation and smart city infrastructure.

List the hardware and software required for Thermal Imaging

Hardware:

  1. Uncooled Thermal Cameras: These cameras use microbolometer sensors that do not require cryogenic cooling. They are suitable for a wide range of applications, including consumer devices.
  2. Cooled Thermal Cameras: These cameras use a cooling mechanism to enhance sensitivity, making them suitable for more demanding applications where higher image quality is required.
  3. Infrared Sensors: Microbolometers or other infrared sensors are the core components of thermal cameras, converting infrared radiation into electrical signals.
  4. Optics: Lenses and optical components are essential for focusing and capturing thermal radiation effectively.
  5. Signal Processing Unit: A dedicated unit or chip processes the electrical signals from the thermal sensors, converting them into digital data.
  6. Display: A display, such as an LCD or OLED screen, is necessary for visualizing thermal images. Some systems may also include augmented reality (AR) displays.
  7. Power Supply: Thermal imaging devices require a power source, which can be provided by batteries or external power systems.
  8. Thermal Imaging Software: Dedicated software embedded in the thermal imaging device for real-time processing, analysis, and display of thermal data.
  9. Cooling Systems (for Cooled Cameras): Cooled thermal cameras may require a cooling system, often using cryogenic substances, to maintain optimal sensor performance.

Software:

  1. Operating System: The thermal imaging device will run on an operating system, such as embedded systems or specialized OS for thermal cameras.
  2. Firmware: The software embedded in the hardware to control the functionality of the thermal imaging device.
  3. Image Processing Software: Algorithms for enhancing, filtering, and processing thermal images to improve image quality and extract relevant information.
  4. User Interface Software: Software for user interaction, allowing users to control settings, analyze images, and navigate menus.
  5. Calibration Software: Software for sensor calibration to ensure accurate temperature measurements and image consistency.
  6. Analysis and Measurement Tools: Software tools for performing temperature measurements, region of interest (ROI) analysis, and other quantitative assessments.

Future Prospects and Challenges

Healthcare Innovations: In the healthcare sector, ongoing research aims to expand the applications of thermal imaging in disease detection and monitoring. The development of more sophisticated algorithms and the integration of thermal imaging with other medical imaging modalities hold promise for enhancing diagnostic capabilities.

Autonomous Vehicles: Thermal imaging is being explored as a complementary technology for autonomous vehicles. The ability to detect pedestrians and obstacles based on their thermal signatures could improve safety, especially in low-visibility conditions such as fog or darkness.

Environmental Monitoring: Thermal imaging is finding applications in environmental monitoring, including the study of climate change, wildlife conservation, and agriculture. Monitoring temperature variations in ecosystems provides valuable data for understanding and mitigating the impact of environmental changes.

Data Privacy and Ethical Considerations: As thermal imaging becomes more pervasive, concerns about data privacy and ethical considerations arise. Balancing the benefits of thermal imaging with the potential for misuse and invasion of privacy requires careful attention and the development of appropriate regulations and guidelines.

Facts on Thermal Imaging

Infrared Spectrum: Thermal imaging operates in the infrared spectrum, specifically in the long-wave infrared (LWIR) or far-infrared region. This spectrum ranges from approximately 9,000 nanometers to 14,000 nanometers.

Temperature Sensitivity: Thermal cameras can detect temperature differences as small as 0.01 degrees Celsius (or 0.02 degrees Fahrenheit), making them highly sensitive to variations in thermal radiation.

Human Detection in Darkness: Thermal imaging is widely used for night vision applications, allowing the detection of humans and animals in complete darkness based on their heat signatures.

No Need for Illumination: Unlike visible light cameras, thermal cameras do not rely on external light sources. They can capture images in total darkness because they detect emitted infrared radiation rather than reflected light.

Applications in Medicine: Infrared thermography, a form of thermal imaging, is used in medical diagnostics to detect abnormalities in body temperature distribution. It is non-invasive and can aid in early detection of certain medical conditions.

Military and Defense: Thermal imaging has been extensively used in military and defense for applications such as night vision, target acquisition, surveillance, and camouflage detection.

Construction and Building Inspections: In the construction industry, thermal imaging is employed for building inspections to identify issues like insulation gaps, water leaks, and structural defects by visualizing temperature variations on surfaces.

Wildlife Monitoring: Thermal imaging is a valuable tool for wildlife biologists and conservationists. It allows for non-intrusive observation of animals in their natural habitats, especially during nocturnal activities.

Firefighting and Search and Rescue: Thermal cameras aid firefighters in locating hotspots, victims, and potential hazards in smoke-filled environments. They are also used in search and rescue operations to find individuals in challenging conditions.

Limitations in Transparent Materials: Thermal imaging is limited in its ability to see through transparent materials such as glass. This is because these materials do not emit or absorb infrared radiation in the same way opaque materials do.

Emissivity Considerations: The accuracy of temperature measurements in thermal imaging is influenced by the emissivity of materials. Emissivity is a material property that describes how efficiently an object emits thermal radiation.

Advancements in Miniaturization: Technological advancements have led to the miniaturization of thermal imaging devices, enabling their integration into consumer electronics such as smartphones and wearable gadgets.

Privacy and Ethical Concerns: The use of thermal imaging technology has raised concerns about privacy, as it can be used to capture sensitive information, including human activities, without consent. Striking a balance between the benefits and potential misuse is an ongoing challenge.

Integration with Artificial Intelligence: Modern thermal imaging systems often integrate artificial intelligence (AI) algorithms for automated object recognition, tracking, and analysis, enhancing their capabilities in various applications.

Environmental Monitoring: Thermal imaging is employed in environmental monitoring, helping scientists study climate change, monitor volcanic activity, and assess the health of ecosystems by analyzing temperature variations.

Academic References on Thermal Imaging

Books:

  1. Palmer, D. A. (2005). Thermal Imaging Techniques to Survey and Monitor Animals in the Wild: A Methodology. Springer.
  2. Smith, J. B., & Brown, K. L. (2018). Infrared Technology: Applications to Electro-Optics, Photonic Devices, and Sensors. CRC Press.
  3. Gupta, R., & Singh, V. (2016). Principles of Infrared Thermal Imaging: A Practical Guide to Thermal Camera Use. CRC Press.
  4. Jones, E. F., & White, T. P. (2013). Thermal Imaging Techniques in Materials Science and Engineering. Woodhead Publishing.

Journal Articles:

  1. Johnson, M. R., & Rodriguez, A. S. (2017). Applications of Infrared Thermography in Structural Health Monitoring: A Review. Journal of Nondestructive Evaluation, 36 (3), 45-60.
  2. Wang, Y., & Li, Z. (2019). Recent Advances in Uncooled Infrared Detectors. Journal of Infrared, Millimeter, and Terahertz Waves, 40 (2), 123-145.
  3. Brown, A. N., & Robinson, C. D. (2014). Advances in Infrared Imaging for Diagnostic Medicine. Journal of Medical Imaging, 21 (4), 287-302.
  4. Lee, S., & Kim, H. (2018). A Comprehensive Survey of Infrared Thermography Applications in Building Science. Energy and Buildings, 167 , 263-281.
  5. Martinez, L., & Chen, J. (2017). Recent Developments in Microbolometer Technologies for Infrared Imaging. Sensors, 17 (5), 1109.
  6. Smith, R. W., & Patel, A. (2020). Applications of Infrared Thermography in Agriculture: A Review. Computers and Electronics in Agriculture, 178 , 105739.
  7. Turner, T., & Wilson, J. (2015). Infrared Thermography for Wildlife Ecology: What We Know and What We Need to Know. Wildlife Society Bulletin, 39 (2), 402-413.
  8. Wang, Q., & Smith, P. L. (2019). Recent Advances in Uncooled Infrared Photodetectors. IEEE Journal of Selected Topics in Quantum Electronics, 25 (1), 1-14.
  9. Zhang, H., & Kim, T. (2016). Thermal Imaging in Robotics: A Review. Robotics and Autonomous Systems, 75 , 406-416

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