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Summary Pit-bearing snakes (vipers, pythons, and boas) have the extraordinary ability to “see” and accurately locate their prey and predators in total darkness. These animals use the infrared radiation emanating from objects that are warmer relative to the background environment to form a thermal image. Although enormous progress has been made to identify the key physiological features that enable the infrared vision of these snakes and a few other animals, the precise thermoelectric transduction mechanism that mediates the conversion of infrared heat to processable electrical signals has remained elusive. In this work, we quantitatively outline how cells in the snake's pit membrane organ act as apparent pyroelectric materials and convert infrared radiation into electrical signals. Despite the exceptional simplicity of our proposed mechanism and model, we are able to explain many central experimental results pertaining to the transduction process.

1) Background: The aim of this study is to present the results of experiments in which surface electromyography (sEMG) and thermal imaging were used to assess the muscle activation during gait and to verify the hypothesis that there is a relationship in the case of low fatigue level between sEMG-measured muscle activation, assessed in the frequency domain, and thermal factors calculated as minimum, maximum, kurtosis, mean, median, and mode from the area of interest. 2) Methods: Comparison of activity calculated from the recorded sEMG data for rectus femoris (RF), biceps femoris, tibialis anterior, and gastrocnemius medialis (GM) with thermal data obtained from the infrared vision. 3) Results: Data of 14 healthy volunteers obtained during 10 min of treadmill gait are presented and analyzed. The analysis revealed statistically significant linear correlations for RF (five moderate relationships) and GM (one good relationship) and moderate nonlinear correlations for all examined muscles. Also, a detailed protocol for precise, repeatable thermal examination is presented. 4) Conclusions: Estimated moderate linear and nonlinear correlations between thermal and electromyographic parameters are found for low level of muscle fatigue, which suggests that the presented method is useful in the analysis of muscle activation with the use of a thermal imaging as a complement to sEMG.

The conservation of artworks is playing an increasingly important role in society today. Non-destructive investigation can provide the potential to identify deterioration as early as possible. In this research, transmission mid-wave infrared (MWIR) vision and air-coupled ultrasound (ACU) were used to investigate two paintings on canvas made from different textile support materials. An X-ray technique was used in the work for validation. It was found that the transmission mode can probe deeper and the differences in absorption due to the different textile support materials can be distinguished. This paper summarises advantages of the transmission inspection mode and compares and analyses images from the two techniques from a physical point of view.

We examine in this work the desirability and preferences of people with visual impairments for assistive vision, i.e., vision rehabilitation and enhancement, delivered by smart eyewear devices. We present results from a vignette experiment with N = 17 participants with visual impairments, who reported their preferences regarding 32 hypothetical scenarios that we formulated for assistive vision, e.g., long-distance vision, peripheral vision, highly sensitive perception of colors, thermal vision, night vision, and others. Our results show higher desirability (average score of 4.21 out of 5) for assistive vision scenarios addressing rehabilitation of lost vision functions compared to scenarios that propose Augmented Reality-based enhancements of human vision (3.76) or visual perception in other regions of the electromagnetic spectrum, such as thermal or infrared vision (3.36). To understand these results, we conduct a second vignette study involving N = 178 participants without visual impairments, for which we report lower desirability for vision augmentation (3.44/5) compared to participants with visual impairments (3.75/5). We discuss implications of our results for augmented and mediated vision delivered by smart eyewear devices.

Infrared (IR) spectral imaging sensing is a powerful visual technique for industrial material recognition in robot vision systems. However, the imaging sensing data have issues of random noise and band overlap. Resolution enhancement is usually the first step in the preprocessing procedure of industrial robot vision sensing. In this article, we develop a resolution-enhancement algorithm with total variation (TV) constraints for the degraded Fourier transform IR (FTIR) spectrum due to overlap and noise degradation in the robot vision sensing. The kernel function is calculated using the spectrometer imaging systems and Fourier optical theory. The proposed model not only can remove noises effectively but also can estimate the kernel function because of the adaptive TV as constraint regularization. This model is examined by a set of simulated FTIR spectra with the Poisson noises and a series of real FTIR spectra. The proposed model is compared with the other state-of-the-art methods in terms of performance. Experimental results demonstrate that the proposed approach can split the overlap band effectively while the spectral structure details are retained satisfactorily. The enhanced high-resolution imaging spectrum data can raise the robot vision sensing accuracy in industrial intelligent systems.

In this paper, a new application of the optical mouse sensor is presented. The optical mouse is used as a main low-cost infrared vision system of a new proposal of a head-mounted human-computer interaction (HCI) device controlled by eye movements. The default optical mouse sensor lens and illumination source are replaced in order to improve its field of view and capture entire eye images. A complementary 8-bit microcontroller is used to acquire and process these images with two optimized algorithms to detect forced eye blinks and pupil displacements which are translated to computer pointer actions. This proposal introduces an inexpensive and approachable plug and play (PnP) device for people with severe disability in the upper extremities, neck, and head. The presented pointing device performs standard computer mouse actions with no extra software required. It uses the human interface device (HID) standard class of the universal serial bus (USB) increasing its compatibility for most computer platforms. This new device approach is aimed at improving comfortability and portability of the current commercial devices with simple installation and calibration. Several performance tests were done with different volunteer users obtaining an average pupil detection error of 0.34 pixels with a successful detection in 82.6% of all mouse events requested by means of pupil tracking. This research was funded by Indra, Accessibility Chair, 2017. This research also was supported by the Government of Catalonia (Comissionat per a Universitats i Recerca, Departament d’Innovació, Universitats i Empresa) and the European Social Fund.

Two-photon vision arises from the perception of pulsed infrared (IR) laser light as color corresponding to approximately half of the laser wavelength. The physical process responsible for two-photon vision in rods has been delineated and verified experimentally only recently. Here, we sought to determine whether IR light can also be perceived by mammalian cone photoreceptors via a similar activation mechanism. To investigate selectively mammalian cone signaling in mice, we used animals with disabled rod signal transduction. We found that, contrary to the expected progressive sensitivity decrease based on the one-photon cone visual pigment spectral template, the sensitivity of mouse cone photoreceptors decreases only up to 800 nm and then increases at 900 nm and 1000 nm. Similarly, in experiments with the parafoveal region of macaque retinas, we found that the spectral sensitivity of primate cones diverged above the predicted one-photon spectral sensitivity template beyond 800 nm. In both cases, efficient detection of IR light was dependent on minimizing the dispersion of the ultrashort light pulses, indicating a non-linear two-photon activation process. Together, our studies demonstrate that mammalian cones can be activated by near IR light by a nonlinear two-photon excitation. Our results pave the way for the creation of a two-photon IR-based ophthalmoscope for the simultaneous imaging and functional testing of human retinas as a novel tool for the diagnosis and treatment of a wide range of visual disorders.

The Advanced Gas Cooled Reactors (AGRs) are a vital component of the UK's electricity supply system. Their continued reliable operation is supported by safety cases that include assessments of their seismic resilience to their ultimate lifetimes. These assessments are developed via a complex programme of numerical simulations, physical modelling and shaking table testing. A quarter sized physical model representing a single layer of an AGR graphite core was developed at the University of Bristol (UOB) to test the dynamic response for various core array configurations and seismic excitations. The dynamic displacement response is significant, as displaced components may cause local or general distortions that could theoretically affect the channel shapes and the keying system of an AGR core, with implications on the fundamental functions of the reactor. This paper presents a computer vision approach for component displacement mapping. An infrared vision system and a high-resolution video system were employed to track all the components in the model core during a seismic event. The systems have proven to be fit for purpose, being able to map the position of the array components at a resolution of 0.1 mm and to reveal features of response that are useful for understanding the core dynamics. The employed hardware and tracking algorithms are general in nature, hence they are transferrable to other case studies involving multi-body assemblies under dynamic loading.

Fourier transform infrared (FTIR) imaging spectrometers are often corrupted by the problems of band overlap and random noise during the infrared spectrum acquisition process. Such noise would degrade the quality of the acquired infrared spectrum, limiting the precision of the subsequent processing. In this paper, we present a novel blind reconstruction method with wavelet transform regularizations for infrared spectrum obtained from the aging instrument. Inspired by the finding that the wavelet coefficient distribution of the clean spectrum is sparser than that of the degraded spectrum, a blind reconstruction model for infrared spectrum is proposed in this paper to regularize the distribution of the degraded spectrum by total variation regularization. This method outperforms when suppressing random noise and preserving the spectral structure details. In addition, an effective optimization scheme is introduced in overcoming the issue of formulated optimization. The instrument response function and latent spectrum can be simultaneously estimated through the proposed method that can efficiently mitigate the effects caused by instrument degradation. Finally, extensive experiments on simulated and real noisy infrared spectra are carried out to demonstrate the superiority of the proposed method over the existing state-of-the-art ones. Thus, the reconstructed spectrum will better serve the feature extraction and educational robot infrared vision sensing in industrial applications.

This work features an important structural engineering project that provides experimental and numerical predictions to support the safety cases of the Advanced Gas-cooled Reactors (AGRs) in the United Kingdom (UK). The AGR core columns must remain vertical within tight tolerances so that the control rods and the fuel stringers have a secure and unimpeded travel in and out the channels. This paper presents the design, development and testing of bespoke techniques for column interface measurements which feed into the channel shape calculations of a quarter size physical model of an AGR core, developed at the University of Bristol (UOB). The results will play a vital part in the characterization of the core’s dynamic behaviour and will feed into the seismic resilience assessments of the AGRs.

Pulsed near-infrared (NIR) light sources can be successfully applied for both imaging and functional testing of the human eye, as published recently1. These two groups of applications have different requirements. For imaging applications, the most preferable is invisible scanning beam while efficiently visible stimulating beam is preferable for functional testing applications. The functional testing of human eye using NIR laser beams is possible due to two-photon vision (2PV) phenomenon. 2PV enables perception of pulsed near-infrared laser light as color corresponding to approximately half of the laser wavelength2. This study aims to characterize two-photon vision thresholds for various pulse lengths from a solid- state sub-picosecond laser (λc = 1043.3 nm, Frep = 62.65 MHz), either of 253 fs duration or elongated by Martinez- type stretcher to 2 ps, and fiber-optic picosecond laser (λc = 1028.4 nm, Frep = 19.19 MHz, p = 12.2 ps).

In this chapter, we study the outcomes of simultaneous localization and mapping algorithms from a 3D infrared vision sensor. Also, provided for discussion is the limitation of vision-based and other sensory-based indoor navigation and object tracking methods. At the receiver end, we measure the Received Signal Strength Index (RSSI) of a wireless node which indicates how effectively the device can capture a signal from an access point through a value that effectively indicates whether one has enough signal strength. RSSI is a simple process of location estimation and, when available, ensures that no additional hardware is needed at individual network nodes. It is difficult to estimate the position in an indoor environment directly from the RSSI values.

Infrared imaging is a crucial technique in a multitude of applications, including night vision, autonomous vehicles navigation, optical tomography, and food quality control. Conventional infrared imaging technologies, however, require the use of materials like narrow-band gap semiconductors which are sensitive to thermal noise and often require cryogenic cooling. Here, we demonstrate a compact all-optical alternative to perform infrared imaging in a metasurface composed of GaAs semiconductor nanoantennas, using a nonlinear wave-mixing process. We experimentally show the up-conversion of short-wave infrared wavelengths via the coherent parametric process of sum-frequency generation. In this process, an infrared image of a target is mixed inside the metasurface with a strong pump beam, translating the image from infrared to the visible in a nanoscale ultra-thin imaging device. Our results open up new opportunities for the development of compact infrared imaging devices with applications in infrared vision and life sciences., Comment: 32 pages, 13 figures

Supplemental Digital Content is Available in the Text. Infrared light two-photon excitation provides a new parameter for testing visual function, one that can be used in the detection and monitoring of ocular abnormality. Diabetic retinopathy significantly impairs retinal sensitivity to infrared light., Purpose: Human photoreceptors are sensitive to infrared light (IR). This sensitivity can be used as a novel indicator of retinal function. Diabetic retinopathy patients were assessed using in vivo two-photon excitation and compared their scotopic IR threshold with that of healthy patients. Methods: Sixty-two participants, 28 healthy and 34 with diabetic retinopathy, underwent a comprehensive eye examination, where visual acuity and contrast sensitivity were assessed. Infrared thresholds were measured in the fovea and parafovea following 30-minute dark adaptation. A two-photon excitation device was used with integrated pulsed laser light (1,045 nm) for sensitivity testing and scanning laser ophthalmoscopy for fundus imaging. Results: The mean Snellen visual acuity of diabetic patients (6/7.7) was worse than that of the healthy patients (6/5.5), which was significantly different (P < 0.001). Disease patients had decreased contrast sensitivity, especially at 6 and 18 cycles/degree. The mean retinal sensitivity to IR light in eyes with diabetic retinopathy (11.6 ± 2.0 dB) was significantly (P < 0.001) lower than that in normal eyes (15.5 ± 1.3 dB). Conclusion: Compared with healthy control subjects, the IR light sensitivity of diabetic patients was significantly impaired. Two-photon measurements can be used in the assessment of retinal disease, but further studies are needed to validate IR light stimulation in various stages of diabetic retinopathy.

In traditional lens design Often only the empirical design of the appearance of the mechanical structure is carried out, and the strength check and modal analysis for the lens in a complex vibration environment are carried less often. The structural rationality cannot be well evaluated in the increasingly complex lens industrial application environment. This article designs the mechanical structure of a zoomable infrared vision lens and carries out finite element stress analysis for the structural dangerous parts. It is pointed out that stress singularity should be paid attention to when performing finite element stress analysis. If necessary, rounding should be added at the sharp corners where stress singularity occurs, and local mesh subdivision can be performed to effectively eliminate stress singularity. Therefore, to achieve convergence result. In addition, the modal analysis of the lens structure is carried out in this paper, and the first 6 modes are extracted. The stress and modal analysis results show that the lens can maintain sufficient structural strength and stability in a complex vibration environment.

Thermal illusion device, which can change an arbitrary object into another one when observed from an infrared vision, recently has attracted considerable attention amongst a series of innovative thermal phenomena by resorting to the unique thermal metamaterial. To enhance the illusion deceptiveness, current thermal illusion devices mostly change the location or shape of the target, but seldom deal with the number of heat signatures. In this paper, we develop a general formula to enhance the illusion deceptiveness by splitting the thermal target to appear like thermal bilocation with twinborn distinct heat signatures. The exhaustive design process based on transformation thermodynamics is rigorously introduced in order to realize thermal bilocation. Simulative and experimental results agree well with each other and validate the conception of thermal bilocation. Additionally, the influence of three structure parameters on the bilocation effects has been considered for further optimization. Our device can thermally camouflage the original target with twinborn signatures at different locations, improving the deceptiveness greatly compared with only moving or reshaping. The present thermal bilocation not only can fortify the performance of thermal camouflage, but also can stimulate the extension of illusion thermodynamics to further physical applications.

In mining operation, the longitudinal tear detection of conveyor belt is of great significance to safety production. A novel method, named Dual Band Infrared Detection (DBID), is proposed to detect the longitudinal tear of conveyor belts in this paper. The DBID method is based on the collaboration of mid-infrared and long infrared vision. The DBID sensor device captures the lower surface images of conveyor belt. The feature of tear or scratch and tearing precursor can be extracted by analyzation of captured images. The DBID method is verified by experiments and practice, including the capturing of dual band infrared images (mid-infrared and long infrared images), image preprocessing, and tear detection. The DBID method is not only unlimited by visual condition, but also much more accurate and reliable compared with the Integrative Binocular Vision Detection (IBVD) method presented before which meets the requirement of real-time online detection.

Ultra-wideband (UWB) has broad application prospects in the field of indoor localization. In order to make up for the shortcomings of ultra-wideband that is easily affected by the environment, a positioning method based on the fusion of infrared vision and ultra-wideband is proposed. Infrared vision assists locating by identifying artificial landmarks attached to the ceiling. UWB uses an adaptive weight positioning algorithm to improve the positioning accuracy of the edge of the UWB positioning coverage area. Extended Kalman filter (EKF) is used to fuse the real-time location information of the two. Finally, the intelligent mobile vehicle-mounted platform is used to collect infrared images and UWB ranging information in the indoor environment to verify the fusion method. Experimental results show that the fusion positioning method is better than any positioning method, has the advantages of low cost, real-time performance, and robustness, and can achieve centimeter-level positioning accuracy.

Induction thermography has been applied as an emerging non-destructive testing and evaluation technique for a wide range of conductive materials. The infrared vision sensing acquired image sequences contain valuable information in both spatial and time domain. However, automatic and precisely extracting defect pattern from thermal video remains a challenge. In order to accurately find anomalous patterns for defect detection and further quantitative nondestructive evaluation, we propose an automatic relevance determination approach with adaptive variational Bayes for sub-group sparse decomposition. A subset of scale parameters is driven to a small low bound in the inference, with the pruning the corresponding spurious components. In addition, an internal sub-sparse grouping as well as adaptive fine-tuned is built into the proposed algorithm to control the sparsity. Experimental tests on both artificially and nature defects and comparisons with other methods have been conducted to verify the efficacy of the proposed method.

Pit-bearing snakes (vipers, pythons, and boas) have the extraordinary ability to "see" and accurately locate their prey and predators in total darkness. These animals use the infrared radiation emanating from objects, that are warmer relative to the background environment, to form a thermal image. While enormous progress has been made to identify the key physiological features that enable the infrared vision of these snakes and a few other animals, the precise thermo-electric transduction mechanism that mediates the conversion of infrared heat to processable electrical signals has remained elusive. In principle, the presence of a pyroelectric material would explain many of the idiosyncratic features of the snakes' infrared vision. However, pyroelectricity is a rare material property and restricted to a small set of hard crystalline materials not found in any of the animals with infrared vision. In this work, we quantitatively outline how cells in the snake's pit membrane organ may convert infrared radiation into electrical signals. Despite the exceptional simplicity of our proposed mechanism and model, we are able to explain many of central experimental results pertaining to the transduction process.

This paper presents an application for hand-based movements using two Recurrent Complex-Valued Neural Networks (RCVNN) in real-time. The proposed system identifies hand-based movements using two angles of human arm model acquired by the infrared vision time of flight depth system integrated in Kinect v2. The results of the experiments compare the performance of the RCVNN with the inverse kinematic. Finally, this topology helps us to identify hand-based movements avoiding singularities.

Fog is a major reason behind road accidents and road side causalities as it reduces visibility, limits contrast and distorts perception. This paper presents some concepts for maturing of a scheme which will be able to increase clearity in winter and foggy conditions using the light rays and heat properties. Various type of foggy environments, their effects on visibility range and remedial measures are discussed. We proposed the Infrared Vision (IV) for fog detection systems to improve object visibility in dense fog.

In order to improve the effectiveness and reliability of unmanned aerial vehicles (UAVs) automatic navigation and inspection for large photovoltaic (PV) power plants, a strategy of navigation and inspection based on infrared vision was proposed, according to the arrangement characteristics of PV strings. In order to implement the strategy, a PV strings recognition and localization algorithm combining color features and shape features was proposed to obtain information that can be used for navigation. At the same time, a navigation strategy based on the location of PV strings was presented for PV strings inspection. Experiments clearly demonstrated the adaptability and real-time of the proposed method, which makes a contribution to the automatic navigation and inspection for large PV power plants.

Infrared vision system uses infrared lens to collect radiation and focus the object onto the detector. Information such as pixel and temperature distribution could be captured and displayed as images. Infrared optics are the “eyes” of the vision system. The need of broadband, compact, low cost are driven by increasing commercial applications such as UAV, autonomous driving and smart phone. This paper presents our latest development in infrared optics design for broadband application and optics manufacturing based on Chalcogenide glasses for potential mass production. New optics design makes a single lens to achieve dual wavelength band (MWIR and LWIR) switchable. The aspheric lens and diffractive optical element (DOE) configuration are investigated to realize the broadband and compact lens design. In LWIR regime, several detector manufacturers have demonstrated both cooled and uncooled technologies with pixel size down to 12μm. It sets new standard for size, weight, power and performance in terms of resolution. Chalcogenide material is gradually taking over Germanium in broad IR regime. It performs especially well in the 8 to 12μm range, because of its lowest absorption and dispersion in LWIR. The low dn/dT of the Chalcogenide makes lens athermalization much simpler by removing required mechanical compensation complexity. The Chalcogenide series of glasses can be processed by molding. As compare to the polished/machined glass lens which take more than 1 hour for each piece, the molding process time will be reduced to 5 mins.

Teleoperation has a wide range of applications that have been under development over the past two decades. Previous researches have focused on the control design of teleoperation machine systems to deal with obstacles such as time-delayed stability and transparency. Recent researches have shown that the inclusion of human closed-loop dynamics in control design can improve the performance of robot telemanipulation. The complexity of human behavior arises from the uncertainty of both human physiology and psychology; hence, the investigation can benefit from empirical studies. This study develops a type of statistical learning method to model and evaluate human stochastic closed-loop behavior, which is considered as a hand motion during the direct incremental control process of master-slave teleoperation. The hand trajectory is empirically considered as having a binary linear regression relationship with the error and error rate between the demanded and simulated teleoperator trajectories, while random movements with zero error and error rate are discovered. Hand movement tracking is achieved using a multi-leap-motion sensor (MLM), which is a markerless and natural infrared vision-based manner for motion capture. The established behavior model and statistical learning results reveal certain human properties of operational activities including visual perception, decision making, and robot telemanipulation. The properties indicate some probable system enhancements for future work.

The object of the work is a character of the Madonna con Bambino (XIII–XV century) mural painting (Fontecchio – L’Aquila, Italy). It was analyzed by different nondestructive testing (NDT) techniques: electronic speckle pattern interferometry (ESPI), ultraviolet (UV) imaging and infrared vision. In addition, three micro-samplings were collected on suspected areas after examination of the signal strength variations over the raw thermograms. On the latter, the images’ quality was enhanced by applying advanced processing techniques. Micro-samplings were also analyzed by scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared (FTIR) and μ-Raman spectroscopy. Splitting, subsurface cracks and under-/over-paintings were detected by this integrated method.

Two-photon absorption occurring in photoreceptors of human eye is responsible for perception of pulsed infrared laser beams. Color of perceived light corresponds to about half of wavelength of stimulating beam. This recently discovered phenomenon is called two-photon vision. However it is yet not clear how such phenomena could impact an ophthalmic diagnosis and therefore further studies are required. In this paper we present the system that enables future psychophysical experiments to extend knowledge about two-photon vision and its diagnostic value by identifying differences between two-photon and single-photon vision. Full Text: PDF References D. A. Atchison, G. Smith, Optics of the human eye (Butterworth-Heinemann 2000) CrossRef G. Palczewska et al. "Human infrared vision is triggered by two-photon chromophore isomerization", Proceedings of the National Academy of Sciences 111, 1428 (2014). CrossRef P. Artal, S. Manzanera, K. Komar, A. Gambin-Regadera, M. Wojtkowski, "Visual acuity in two-photon infrared vision", Optica 4, 1488 (2017). CrossRef K. Komar et al. "Posterior Eye Shape Measurement With Retinal OCT Compared to MRI", Investigative Ophthalmology & Visual Science 57, 196 (2016). CrossRef K. Komar et al. "Two-photon visual sensitivity of human cones - a psychophysical study", Investigative Ophthalmology & Visual Science 59, 4049 (2018). DirectLink S. A. Burns,R.H. Webb, Handbook of optics 28 (New York, McGraw Hill 1994) DirectLink R. W. Nygaard, T. E. Frumkes, "Calibration of the retinal illuminance provided by maxwellian views", Vision Research (1982) CrossRef P. Melillo et al. "Pupillometric analysis for assessment of gene therapy in Leber Congenital Amaurosis patients", Biomedical engineering online 11, 40 (2012) CrossRef P. A. Stanley, A. K. Davies, "The effect of field of view size on steady-state pupil diameter", Ophthalmic and Physiological Optics, 15, 601 (1995) CrossRef S. Mathot, "Pupil mimicry is the result of brightness perception of the iris and pupil" Journal of Cognition 1 (2018) CrossRef M. M. Thomas, T. D. Lamb, "Light adaptation and dark adaptation of human rod photoreceptors measured from the a‐wave of the electroretinogram", The Journal of physiology 518, 479 (1999) CrossRef

This work presents a robotized line-scan thermography (LST) modality for the inspection of two paintings on canvas, which are the mock-ups of a famous oil painting, titled Portrait of the Painter’s Mother. Two widely used image post-processing methods were applied on the acquired LST thermal sequences. X-ray radiography was used to anticipate the thermal inspection results. It was concluded that LST is an effective technique for artwork inspection, and it can additionally provide a higher image contrast if compared to classical flash thermography technique. Consequently, the corresponding physical analysis was conducted. Overall, this work appears useful to investigate the feasibility of LST technique for large-scale artwork in-line inspection.

Dielectric metasurfaces have recently shown to be an excellent candidate for efficient frequency mixing at the nanoscale due to the excitation of Mie resonances. Among various dielectric materials, GaAs-based nanostructures have been reported to have high-efficiency of second-order nonlinear processes due to their high quadratic nonlinear susceptibility. Efficient frequency up-conversion can thereby be realised in GaAs-based metasurfaces through the process of sum-frequency generation (SFG), thereby opening new opportunities for nonlinear imaging and infrared vision not possible before. Here we demonstrate for the first time, infrared imaging based on nonlinear mixing of an infrared image with a pump beam in a GaAs resonant metasurface. The nonlinear mixing process generates visible images (Fig. 1a), which can be time resolved with femtosecond resolution and can be observed on a conventional CMOS sensor. Our results open new opportunities for the development of compact night-vision devices operating at room temperature and have multiple applications in defense and life sciences.

This paper proposes an intelligent inspection system based on infrared vision for Automated Fiber Placement. It can improve composite materials production quality and production efficiency, shorten process design time, and reduce material waste. The system can realize the defect recognition and defect measurement, which can be used in intelligent decision-making, optimization of multi-parameters and quality traceability. Experiments are conducted to verify the feasibility and effectiveness of the presented system.

© 2019, Springer Nature Limited. The injection of rare-earth-doped upconversion nanoparticles into the eyes of mice allows them to visualize near-infrared light with a wavelength of ~1 μm.

In this work, the potentialities of the infrared vision to explore sub-superficial defects in polychromatic statues were investigated. In particular, it was possible to understand how the reflector effect of the exterior golden layers could be minimized, applying advanced statistical algorithms to thermal images. Since this noble metal is present as external coating in both artworks, an in-depth discussion concerning its physicochemical properties is also added. In this context, the principal component thermography technique and, the more recent, partial least squares thermography technique were used on three different datasets recorded, providing long thermal stimuli. The main images were compared both to phasegrams and to the thermographic signal reconstruction results in order to have a clear outline of the situation to be debated. The effects of view factors on the radiation transfer linked to the specular reflections from the surface did not falsely highlight certain features inadvertently. Indeed, the raw thermograms were analyzed one by one. Reflectograms were used to pinpoint emissivity variations due to, e.g., possible repainting. The paper concludes that, as it is possible to understand from a physical point of view, the near-infrared reflectography technique is able to examine the state of conservation of the upper layers in cultural heritage objects, while the infrared thermography technique explores them more in-depth. The thesis statement is based on the thermal and nonthermal parts of the infrared region, therefore, indicating what can be detected by heating the surface and what can be visualized by illuminating the surface, bearing in mind the nature of the external coating.

The aim of this work is to evaluate the potentiality of a multi-technique nondestructive approach for characterizing the state of conservation of precious bookbindings. In particular, the bookbinding of an ancient book dating back nineteenth century was inspected by infrared thermography, near-infrared reflectography and transmittography, digital speckle photography, holographic interferometry, and proton magnetic resonance relaxometry. Data were processed by different and innovative methodologies, among which, a calibration procedure of the camera for correlation analyses based on specklegrams. The results were compared, showing a promising synergy for the diagnostic purposes, on the basis of the relationship between structure, properties, and uses of the analyzed materials.