Thermal Imaging for Low Emissivity UAV Detection

Optical system for far-infrared cameras that provides good imaging quality, compact size, thermal stability, and ease of manufacture. The system uses a combination of sulfur lenses and a metalens. The sulfur lenses correct low-order aberrations, while the metalens corrects high-order aberrations and off-axis aberrations. The metalens can be stacked layers of unit cells. An aperture slot can be placed near the metalens to control light intake.

Source

A joint imaging system for efficient and rapid collection of visible light and thermal infrared images using an unmanned aerial vehicle (UAV) platform. The system enables effective spatial registration and pixel-level fusion of the images to obtain thermal infrared images with texture details. The UAV carries two cameras, one visible light and one thermal infrared, with offset angles. This allows simultaneous imaging of the same scene from different angles. The images are then fused by scaling and aligning them based on offset vectors. This provides high-quality thermal images with texture details for applications like 3D modeling.

Source

Thermal imager for satellites, aircraft, and UAVs that achieves high-resolution thermal imaging without active cooling. The imager employs an array of thermopile-based IC chips, each with a dedicated wavelength filter, to capture thermal radiation in multiple spectral bands. By synchronizing the sampling of adjacent rows of IC chips, the imager enables stereoscopic imaging and spectral subtraction to infer atmospheric properties and surface temperature. The design eliminates the need for active cooling, enabling compact and power-efficient thermal imaging systems for small platforms.

Source

A joint imaging system for unmanned aerial vehicles (UAVs) that integrates visible light and thermal infrared cameras to enable simultaneous collection of high-resolution images from multiple angles. The system employs a novel image enhancement fusion method that synchronizes and registers the thermal and visible light images in real-time, enabling effective pixel-level fusion and accurate feature point recognition. This enables efficient and rapid collection of high-quality images for 3D modeling and other applications.

Source

Unmanned aerial vehicle-based thermal anomaly detection system for buildings, enabling efficient and comprehensive thermal imaging of structural defects. The system employs a UAV equipped with thermal cameras and visible light sensors to capture thermal and visible images of building structures. The UAV performs systematic flight patterns around the structure, defining thermal boundaries and identifying temperature anomalies through pixel analysis. The system calculates heat loss rates before and after anomaly detection, providing a comprehensive understanding of building thermal performance.

Source

Infrared thermal imaging temperature measurement method and device for unmanned aerial vehicles (UAVs) that addresses the issue of temperature instability in thermal imaging detectors. The method involves acquiring data from the thermal imaging assembly, including operating temperature and original gray value images, and determining temperature values for different sub-regions using calibration data and the acquired data. The device includes an acquisition module for acquiring the data and a determination module for determining the temperature values. The method also includes calibration steps to generate calibration information for the thermal imaging assembly.

Source

A lens assembly for thermal infrared imaging comprising a substrate, a functional layer with sub-wavelength microstructures, and an imaging layer with non-periodic microstructures. The functional layer provides anti-reflection and hydrophobic properties while the imaging layer focuses infrared light onto a thermal sensor. The lens assembly enables compact, weather-resistant thermal imaging devices with improved environmental adaptability.

Source

Non-contact temperature measurement device and method that corrects temperature measurement errors caused by object emissivity and camera-object distance using multiple infrared cameras with different wavelength bands. The device estimates pixel correspondence between images captured by cameras with the same wavelength band, estimates camera-object distance based on the correspondence, and corrects temperature measurements using images captured by cameras with different wavelength bands.

Source

A drone-based inspection system that can fly, hover, and navigate around structures to perform the inspection in an efficient/fast manner can considerably reduce inspection time. Active thermography is a well-known non-destructive testing method for inspection. However, using it on a drone is challenging due to the drone needing to carry an appropriate heat source, batteries or tethering system to power the heat source and to provide adequate flight time. This complicates the inspection process and can restrict the amount of thermal energy that can be applied to the inspected structure. Another challenge with drone-based active infrared thermography (DBAIT) is that, unlike traditional active thermography inspection in which, the source is either stationary or moving in a precisely controlled manner, the drone and the heat source are subjected to undesired dynamic motion. This paper presents the results of experiments performed to compare potential heat sources that can be retrofitted onboard a drone to conduct active thermographic inspection.

Source

Athermalized lens systems and methods for infrared imaging that maintain focus across temperature changes. The systems employ a combination of thermal compensation techniques, including active focus adjustment and passive mechanical athermalization, to counteract thermal expansion and refractive index changes in the lens elements. The lens elements are specifically designed with materials having tailored coefficients of thermal expansion to achieve optimal thermal compensation.

Source

Thermal infrared imaging mechanism and electronic equipment that enhances the field of view of thermal infrared cameras by using a diffractive optical element array to collect and concentrate thermal infrared light onto a photosensitive unit. The diffractive optical element array is positioned in a vacuum chamber adjacent to the photosensitive unit, and the thermal infrared light is diffracted and focused onto the photosensitive unit, increasing the amount of light collected and enabling a wider field of view.

Source

Thermal imaging system that achieves higher resolution than its micro mirror array by measuring multiple frames with sub-pixel offsets during each frame generation cycle, leveraging high-speed optical image sensors to capture detailed thermal radiation distributions.

Source

Infrared sensor with improved detection accuracy, comprising a substrate, a sensor element with a thermoelectric conversion section and a light receiving section separated by a hollow support, and an amplifier with a switchable input terminal. The sensor element's hollow support structure enhances thermal insulation and reduces thermal time constant, while the switchable input terminal enables mode switching between noise measurement and infrared detection modes. The sensor's design minimizes signal leakage and crosstalk between pixels, enabling high-speed and high-sensitivity infrared detection.

Source

To measure low-temperature thermal fields, we have developed a single-element cooled thermal imaging camera for a spectral range of 8{\div}14 {\mu}m with an internal shutter for radiometric calibration. To improve the accuracy of measuring the temperature of cold objects, we used a shutter with a combined emissivity as an internal reference source of radiation at the input of the device optical unit. With this aim a small mirror was fixed in the center on its surface covered black, thereby ensuring an efficient reflection of radiation in a wide spectral range of wavelengths. When processing the signal for each pixel of the thermal image, the differential value of the detector response to the shutter blackened and mirror areas was used as a reference. A relative measurement error of 3 percent was obtained for the studied objects with a temperature of -150 {\deg}C. The device was successfully used for remote study of thermal field dynamics during freeze-thawing of biological tissues in vivo.

Source

Due to the limitations and costs of thermal sensors, unmanned aerial vehicle (UAV) platforms often equip with high-resolution (HR) visible imaging and low-resolution (LR) thermal imaging cameras for all-day monitoring capability. Existing works generate the high-resolution thermal UAV images by either super-resolution (SR) from high-resolution visible and low-resolution thermal images or modality conversion (MC) from high-resolution visible images. However, the modality gap between visible and thermal sources might degrade the generation quality. We observe that the MC task is beneficial in addressing the cross-modal gap in the SR task, while the SR task can provide the condition of thermal information to boost the MC task. Moreover, these two tasks have the same output and can thus be carried out simultaneously without any additional annotation. Based on this observation, we propose a collaborative enhancement network (CENet), which performs thermal UAV image SR and visible image MC in a joint manner, for high-resolution thermal UAV image generation. In particular, we design a mutua... Read More

Source

With the advancement of drone technology, object detection from the perspective of drones has found extensive applications in various fields, including surveillance, search operations, and reconnaissance tasks. Currently, most drones in the market are equipped with visible light imagers, while some high-end drones are equipped with infrared imaging detectors capable of performing infrared object detection tasks. Infrared imaging utilizes a passive imaging mode, enabling it to detect thermal radiation emitted by objects. As a result, it offers the distinct advantage of continuous operation without being restricted by daylight conditions. In comparison to visible imaging, infrared imaging uses longer wavelengths and possesses a certain level of penetration capability through clouds and smoke. Consequently, infrared object detection represents a significant research area within the field of object detection. However, detecting infrared objects, especially small ones, remains challenging due to the complexity of background information, lower resolution compared to visible images, and the... Read More

Source

A two-point correction method for infrared images that improves image quality by mitigating temperature-induced degradation. The method uses a blackbody with a temperature matching the lens temperature and a second blackbody with a higher temperature to generate correction parameters. These parameters are obtained through a fitting process and are used to accurately calculate corrected gray values, eliminating the "pot lid" effect caused by non-uniformity.

Source

Building heat loss quantification using image analysis to improve building thermal performance and energy usage optimization. The system captures images of buildings using drones, detects objects like roofs and windows, estimates their temperatures, and calculates the heat transfer coefficient (U-value) based on the temperatures. This data-driven approach leverages deep learning, clustering, and thermal imaging to quantify heat loss for building efficiency improvements. The technique reduces uncertainties related to weather conditions, image capture, and object detection to provide accurate building analytics.

Source

A nanoscale bolometer for infrared imaging that operates near the thermodynamic limit. The device features a thin suspended membrane structure with subwavelength antenna for radiation absorption, and a thermometer for temperature measurement. By nanostructuring the membrane and support beams, the device achieves a radiative thermal conductance that approaches the fundamental limit, enabling a 10-30× increase in specific detectivity compared to commercial microbolometers.

Source

An uncooled infrared camera that reduces noise in captured images by using a black body section to cover a portion of the detector, extracting noise from the covered area, and removing it from the entire image. The camera can further improve temperature estimation by rotating a polarizer and estimating a temperature model based on the detected temperatures and rotation angles.

Source

A system and method for contactless temperature measurement of subjects using a visible spectrum camera and thermal image sensor. The system registers visible and thermal images onto a common coordinate system, identifies regions of interest (ROIs) for each subject, and determines their temperatures. A reference object with unknown emissivity is used to compensate for ambient temperature variations, enabling accurate temperature measurement in changing environments.

Source

A thermal imaging module with integrated lens assembly and shutter mechanism for improved accuracy and reduced size. The lens assembly includes a mounting part and extension part with a base plate, forming a cavity for the infrared detector. The detector is fixed facing the lens, and a correction shutter assembly is integrated into the lens barrel to provide non-uniformity correction. The shutter mechanism enables switching between normal operation and calibration modes.

Source

Aerial thermography is both a challenging and rewarding field of study, combining two distinct areas of expertiseUAV piloting and thermographyinto a single planned mission. As such, it often requires a diverse team with expertise in flight operations, thermal data collection, mapping, imagery post-processing, and data management. As the cost of acquiring UAVs and thermal cameras continues to rapidly drop, this technology is quickly undergoing further democratization and widespread use. While an effort has been made in this chapter to cover both breadth of thermal applications and the depth of a particular use case, the applications of this technology are nearly limitless. The reader is encouraged to seek out additional resourcesa wealth of training and research materials are published each year by camera manufacturers such as FLIR (www.flir.com) and Workswell (www.drone-thermal-camera.com). Standards such as those published by the American Society for Testing and Materials (ASTM, www.astm.org) are also an excellent resource for those interested in learning more about this exciting... Read More

Source

A broad range of imaging and sensing technologies in the infrared require large field-of-view (FoV) operation. To achieve this, traditional refractive systems often employ multiple elements to compensate for aberrations, which leads to excess size, weight, and cost. For many applications, including night vision eye-wear, air-borne surveillance, and autonomous navigation for unmanned aerial vehicles, size and weight are highly constrained. Sub-wavelength diffractive optics, also known as meta-optics, can dramatically reduce the size, weight, and cost of these imaging systems, as meta-optics are significantly thinner and lighter than traditional refractive lenses. Here, we demonstrate 80 FoV thermal imaging in the long-wavelength infrared regime (8-12 m) using an all-silicon meta-optic with an entrance aperture and lens focal length of 1 cm.

Source

A temperature measurement device that improves accuracy by calibrating object temperature measurements against a known blackbody reference. The device includes an infrared thermal imaging camera, a blackbody radiator, and a processor that calculates object temperature based on the blackbody's specified temperature and the camera's measurement of the blackbody's surface temperature.

Source

A system and method for measuring the thermal performance of building envelope surfaces using an unmanned aerial vehicle (UAV). The system includes a UAV equipped with sensors for measuring air velocity, temperature, and infrared radiation at specific points on the building surface. The sensors are positioned using an extendable arm to achieve precise measurements, and the data is transmitted to a remote base station for analysis. The system enables rapid and non-intrusive measurement of building envelope surfaces, particularly those that are difficult or impossible to access manually, such as high-rise windows and roofs.

Source

Thermal vision-based devices are nowadays used in a number of industries, ranging from the automotive industry, surveillance, navigation, fire detection, and rescue missions to precision agriculture. This work describes the development of a low-cost imaging device based on thermographic technology. The proposed device uses a miniature microbolometer module, a 32-bit ARM microcontroller, and a high-accuracy ambient temperature sensor. The developed device is capable of enhancing RAW high dynamic thermal readings obtained from the sensor using a computationally efficient image enhancement algorithm and presenting its visual result on the integrated OLED display. The choice of microcontroller, rather than the alternative System on Chip (SoC), offers almost instantaneous power uptime and extremely low power consumption while providing real-time imaging of an environment. The implemented image enhancement algorithm employs the modified histogram equalization, where the ambient temperature sensor helps the algorithm enhance both background objects near ambient temperature and foreground ob... Read More

Source

A thermal imaging system that automatically determines emissivity values for objects in a scene using a visible light imager and machine learning algorithms, enabling accurate temperature measurements without manual input or predefined emissivity values. The system analyzes visible light images to identify objects and their materials, then associates thermal pixels with corresponding emissivity values to generate radiometric images with accurate temperature readings.

Source

Infrared thermography techniques (IRT) are increasingly being applied in non-invasive structural defect detection and building inspection, as they provide accurate surface temperature (ST) and ST contrast (Delta-T) information. The common optional or off-the-shelf installation, of both low- and high-resolution thermal cameras, on commercial UAS further facilitates the application of IRT by enabling aerial imaging for building envelope surveys. The software used in photogrammetry is currently accurate and easy to use. The increasing computational capacity of the hardware allows three-dimensional models to be obtained from conventional photography, thermal, or even multispectral imagery with very short processing times, further improving the possibilities of analysing buildings and structures. Therefore, in this study, which is an extension of a previous work, the analysis of the envelope of a wine cellar, using manual thermal cameras, as well as cameras installed on board an Unmanned Aerial System (UAS), will be presented. Since the resolution of thermal images is much lower than that... Read More

Source

A system for generating and processing multi-modal image streams from thermal, spectral, and panchromatic sensors, where the sensors are synchronized to capture images concurrently. The system processes the synchronized images to generate a digital surface model, estimate pixel conditions, and identify distressed plants or irrigation leaks. The system can also estimate temperatures and count distinct objects in the scene.

Source

Method for generating an infrared image from an RGB-IR sensor that extracts infrared data from both IR and color pixels without losing resolution. The method determines a local color-related ratio for each color pixel based on adjacent IR pixel values, estimates an infrared portion value from the color pixel value using the ratio, and combines these values with IR pixel values to generate a high-resolution infrared image.

Source

The use of small unmanned aerial vehicles (UAVs) equipped with an infrared (IR) camera has created opportunities for qualitative and quantitative thermal assessments of building envelopes. However, it is currently unclear how successful this method is at quantifying heat losses through the building envelope. The inconsistency in findings indicates that sources of error that affect the accuracy of surface temperature measurements are not well understood by thermographers and that recommendations to minimize the errors in aerial thermography measurements have yet to be determined. In this study, laboratory and field experiments were conducted to investigate the scientific reasons for discrepancies between aerial (i.e. dynamic) and conventional stationary infrared thermography (IRT) observations. A set of practical approaches were presented to minimize the sources of error in UAV-IRT measurement. The results of field experiments showed a non-linear and dramatic variation of measured surface temperature during flight, where the deviations of results between dynamic and stationary thermog... Read More

Source

Emissivity is a crucial parameter for a quantitative thermography measurement. It influences measured temperature using an infrared camera. Typically, the emissivity is handled by infrared camera software but often for more complex taskse.g., setting and controlling the emissivity of individual pixelsa custom-made solution must be created. This can be especially beneficial for active thermography measurement and dynamic building inspection by infrared thermography as many surfaces of interest with different emissivity occur in thermographic data. In literature, one technique for suppressing emissivity occurs most oftenthe technique used by infrared camera manufacturers. Nonetheless, two other techniques are marginally mentioned. The most complex technique is the one used by infrared camera manufacturers, which allows many parameters to be set, but it is difficult to incorporate it into own solution. In contrast, the second one can be adapted easily, and it uses the relationship between emissivity and the fourth power of temperatures. The third one is a scarcely used technique that... Read More

Source

A low-cost thermographic camera system that generates thermal images using a single IR sensor and position determination means. The system determines temperature values for partially overlapping fields of view, calculates temperature differences, and uses these values to determine temperatures for non-overlapping areas. This approach enables thermal imaging with a single sensor, eliminating the need for multiple sensors and associated costs.

Source

A multi-channel catadioptric setup for recording infrared images with high resolution and compact design. The setup comprises multiple optical correction elements, detectors, and mirror elements arranged in a segmented configuration to capture a wide field of view. The system enables high-intensity optics with reduced structure height and complexity, making it suitable for applications such as automotive thermal imaging, surveillance, and multi-spectral imaging.

Source

Imaging device and movable platform that can defog or deice light-transmitting components like camera lenses to prevent fogging and icing that can impair image quality. The imaging device inside the platform has a heating element to warm the lens surface temperature above the dew point to prevent fogging. If fogging or icing already occurs, the heating element can melt the ice or steam off the lens. This ensures clear images even in cold, humid conditions.

Source

A thermal imaging system that reduces the effects of undesired reflected infrared radiation, comprising an integrated dewar cooler assembly (IDCA) with a temperature-controlled thermal imager, and an external optical element with a curved surface that receives infrared radiation emitted by the thermal imager and reflects it in a uniform distribution over the thermal imager's field of view.

Source

Uncooled infrared focal plane detector for accurate temperature measurement in infrared imaging applications. The detector has two imaging areas with independently adjustable responsivity. By measuring radiation in both areas, it calculates the net radiation from the target object while accounting for internal detector radiation. This compensates for temperature-induced radiation changes inside the detector that can affect accuracy. The method provides adaptability to internal temperature rise, ambient changes, and wind.

Source

Infrared image sensor with improved temperature measurement range and accuracy without mode switching. The sensor has an array with multiple types of photosensitive pixels with different sensitivities. This allows the sensor to have both wider temperature measurement range and higher accuracy compared to conventional sensors with fixed pixel sensitivity. The different pixel types enable more flexible tradeoffs between range, accuracy, and image quality. It eliminates the need for mode switching during use.

Source

Abstract Thermography is commonly used for auditing buildings. Classical manual terrestrial thermography records images of individual buildings at a short distance. When auditing a large number of buildings (e.g. whole city districts) this approach reaches its limits. Using drones with thermographic cameras allows images to be recorded automatically from different angles, with faster speed and without violating property rights. However, an airborne camera has a significantly greater distance and more varied angles to a building compared to terrestrial thermography. To investigate the influence of these factors for building auditing, we perform a study evaluating seven different drone settings of varying flight speed, angle, and altitude. A comparison is drawn to manually recorded terrestrial thermographic images. While we find that a flight speed between 1m/s and 3m/s does not influence the thermographic quality, high flight altitudes and steep viewing angles lead to a significant reduction of visible details, contrast, and to falsified temperatures. A flight altitude of 12m over bui... Read More

Source

Micro-bolometer for infrared imaging with reduced thermal capacity and improved signal-to-noise ratio. The bolometer features a membrane with a thermometric material that occupies less than 40% of the membrane's surface area, while recesses are formed in the absorbing material and dielectric layers in areas devoid of thermometric material. This design enables significant reduction of thermal capacity without compromising absorption, enabling faster response times and improved image quality.

Source

A thin-film infrared (IR) imaging device comprising an array of pixels, each pixel comprising a plasmonic absorber layer and a metalens layer. The plasmonic absorber layer is configured to absorb and convert IR radiation to an electrical signal, while the metalens layer focuses IR radiation onto the absorber layer. The device enables compact, wearable IR imaging with a wide field of view, suitable for applications such as night vision, thermal imaging, and spectroscopy.

Source

Infrared filter for thermal imaging applications, comprising a silicon substrate with a metallic reticulated structure having multiple holes for transmitting infrared light, and a thermal infrared sensing device incorporating the filter to detect infrared radiation while maintaining vacuum integrity.

Source

Thermal imaging system for unmanned aerial vehicles (UAVs) that improves accuracy and reliability by compensating for atmospheric interference and adjusting operation based on regulatory limits. The system uses the UAV's sensors to determine its location and if it's in restricted areas. It also accounts for factors like air temperature and reflected background radiation to adjust the thermal imaging data for more accurate readings.

Source

System and method for determining a thermal image using a bolometric detector array with a base body, where the system includes a processor unit and a signal interface, and the method involves detecting infrared radiation, generating measurement signals, determining body heat, predicting temperature values compensated for time delay, correcting for measurement errors, and generating a thermal image.

Source

A photonic sensor pixel for imaging applications, comprising a thermally isolated micro-platform with one or more photonic sensing structures that provide a signal responsive to absorbed incident radiation within a broad wavelength range or selected limited wavelength bands. The micro-platform is supported by nanowires and may include a Peltier thermoelectric cooler for temperature control. The photonic sensing structures can be type II superlattice phototransistors, pyroelectric sensors, or thin-film bolometers, and can be operated in a variety of configurations to enhance sensitivity and reduce noise.

Source

Abstract. Thermal remote sensing from unmanned aerial vehicles is a slowly but steadily growing field of application. New hyperspectral systems operating in the thermal infrared are deployable on such systems and are also usable for ground based monitoring, such as in mining applications. Temperature/emissivity retrieval methods have to be adapted for these new situations. This contribution presents an extension of the Drone Atmospheric Correction method (DROACOR) for thermal infrared imaging spectroscopy. The method includes an implementation of the semi-automatic normalized emissivity mapping (NEM) method for temperature/ emissivity separation. Furthermore, an extension of the method for correction of low emissivity targets, appearing as cold targets in the temperature mapping is introduced. Two examples of DROACOR-thermal processing are presented for a nadir looking drone based and a horizontal ground based data acquisitions are shown. The resulting spectral emissivitiy distributions and temperature mappings are plausible. They are well comparable to spectral library references a... Read More

Source

A system for remote and passive mapping of physical objects in space, comprising a multi-sensor package providing depth, surface, and heat mapping. The system combines visual and infrared data to generate 3D maps of objects, with thermal data used to identify internal thermal sources and anomalies. The system enables autonomous analysis, characterization, and navigation of objects in space, with applications in satellite operations, space exploration, and environmental monitoring.

Source

Infrared imaging device with improved temperature compensation, comprising an infrared imaging sensor, a substrate temperature sensor, a temperature drift compensation amount calculation unit, a function generation unit, and a timing control unit. The device calculates temperature drift compensation amounts based on substrate temperature changes and generates a function to calculate these amounts using substrate temperature as an independent variable. The function is generated using data from the imaging sensor and substrate temperature sensor during substrate energization, and is refined using additional data from the imaging sensor after function generation.

Source

It is necessary to establish the relative performance of established optical flow approaches in airborne scenarios with thermal cameras. This study investigated the performance of a dense optical flow algorithm on 14 bit radiometric images of the ground. While sparse techniques that rely on feature matching techniques perform very well with airborne thermal data in high-contrast thermal conditions, these techniques suffer in low-contrast scenes, where there are fewer detectable and distinct features in the image. On the other hand, some dense optical flow algorithms are highly amenable to parallel processing approaches compared to those that rely on tracking and feature detection. A Long-Wave Infrared (LWIR) micro-sensor and a PX4Flow optical sensor were mounted looking downwards on a drone. We compared the optical flow signals of a representative dense optical flow technique, the Image Interpolation Algorithm (I2A), to the Lucas-Kanade (LK) algorithm in OpenCV and the visible light optical flow results from the PX4Flow in both X and Y displacements. The I2A to LK was found to be gen... Read More

Source