Invisible Wavelengths Research Articles

Wavefront imaging of a biological sample using DMD-based single-pixel phase-shifting interferometric techniques: An experimental comparison

Single-pixel wavefront imaging (SWI) is an innovative technique for simultaneously measuring the amplitude and phase of an unknown field, which is particularly important for wavefront imaging in invisible wavelengths and under low light conditions. However, most of the existing SWI techniques are still in the technical development stage. Here, we provide a comprehensive analysis and comparison of the SWI methods using DMD-based single-pixel multi-step phase-shifting interferometric techniques. Through experimental demonstrations, we first compare the performances of the techniques using the Hadamard basis, Fourier basis, and discrete cosine transform (DCT) basis. Further, the performances of the Hadamard basis-based SWI (HSWI) technique using phase-shifting interferometry with the different reference strategies are investigated while the binary grating, Lee, and super-pixel methods are applied to control the DMD for realizing the necessary complex amplitude modulations there. Experimental results suggest the grating-phase-shifting-based HSWI performs best, in which one can use the checkerboard reference for the maximum field of view or select the peripheral reference for a better imaging resolution; and it can do 2 fps wavefront imaging of the sample at 10 % downsampling rate with a resolution of 128 × 128 pixels. Our work provides researchers with a guideline to choose a suitable SWI technique for their applications.

Clinical effects of combined red and infrared wavelengths in the treatment of local injuries caused by Bothrops leucurus snake venom

Aimto evaluate the effects of visible and invisible wavelengths, individually and combined, on local edematogenic activity, serum and muscle enzymes, and clinical response in mice inoculated with B. leucurus snake venom. Methods: 112 male mice were inoculated with diluted B. leucurus snake venom in the right gastrocnemius muscle, the same volume of saline solution was applied in the contralateral muscle. The animals were divided into four groups, one control and three treated with: 1) red laser (λ = 660 nm), 2) infrared laser (λ = 808 nm) and 3) red laser (λ = 660 nm) + infrared (λ = 808 nm). Each group was subdivided into four subgroups, according to the duration of treatment application (applications every 24 h over evaluation times of up to 144 h). A diode laser was used (0.1 W, CW, 1J/point, DE: 10 J/cm2). Results: the treatments prevented the loss of the proprioception reflex, accelerated the reestablishment of the damaged area, and reduced claudication, local hemorrhage, and edematogenic activity caused by bothropic venom. Both wavelengths reduced serum concentrations of creatine kinase (CK) and aspartate aminotransferase (AST) and increased muscle concentration of CK. The combined wavelengths caused a significant reduction in serum enzyme concentrations and a better clinical response when compared to the isolated treatments. Conclusion: Laser photobiomodulation proved to be effective in the treatment of the disorders evaluated and the interaction between red and infrared wavelengths potentiated the therapy effects.

Antitumor Effects of Deep Ultraviolet Irradiation for Pancreatic Cancer.

Deep ultraviolet (DUV) light spans within the 250 nm to 350 nm invisible wavelength range. Although it strongly damages various cells, the efficacy of DUV irradiation on pancreatic cancer cells has never been clarified. The purpose of this study was to reveal the antitumor effects of DUV irradiation on pancreatic cancer cells. Human pancreatic cancer cell lines were eradicated with DUV or ultraviolet A (UVA) for 5 s. Several angiogenesis-related proteins were studied in cancer cells after DUV irradiation using a protein antibody array. A subcutaneous xenograft model was established by inoculation of pancreatic cancer cells into mice. Tumors in this model were irradiated with DUV or UVA once or twice for two weeks. Tumor volumes in these groups (DUV×1: one irradiation, DUV×2: two irradiations, and untreated) were analyzed one week after the second irradiation. DUV irradiation significantly changed the cytomorphology of pancreatic cancer cells. In addition, DUV irradiation induced apoptosis on pancreatic cancer cells more strongly than UVA irradiation and no irradiation. Interestingly, lower expression of thrombospondin 1 (TSP1) and tissue inhibitor of metalloproteinase 1 (TIMP1) was identified after DUV treatment. The tumor volume in the DUV-treated groups (DUV×1 and DUV×2) was smaller than that in the untreated group. Further investigations are required to reveal the precise mechanisms of the antitumor effects of DUV irradiation and to facilitate its clinical application as a new therapy for pancreatic cancer. Overall, DUV irradiation can be potentially used as a therapeutic option of pancreatic malignancy.

Unidirectional Invisibility in PT-Symmetric Cantor Photonic Crystals

In this paper, we investigate the nonreciprocity of reflection in parity-time−symmetric (PT-symmetric) Cantor photonic crystals (PCs). Two one-dimensional PCs abiding by the Cantor sequence are PT-symmetric about the center. The PT symmetry and defect cavities in Cantor PCs can induce optical fractal states which are transmission modes. Subsequently, the left and right reflectionless states are located on both sides of a transmission peak. The invisible effect depends on the incident direction and the invisible wavelength can be modulated by the gain–loss factor. This study has potential applications in tunable optical reflectors and invisible cloaks.

Visible and Online Detection of Near‐Infrared Optical Vortices via Nonlinear Photonic Crystals

AbstractNear‐infrared (NIR) optical vortices (OVs), which carry specific orbital angular momentum, are believed to greatly increase the capacity of conventional optical communication systems. However, due to the equipment limits in invisible wavelengths, NIR OVs detection remains a great difficulty. Here, the up‐conversion imaging technology is exploited to circumvent using NIR detectors. A lithium niobate crystal with its quadratic susceptibility modulated by a specially designed Dammann vortex grating is fabricated to realize the frequency conversion—from NIR to the visible region—while converting multiplexed OVs to Gaussian modes in specific multichannels. During the detection process, the most of energies of the detected OVs are preserved, which can be considered as online detection. Additionally, at least 400 nm applicable wavelength range of this method is experimentally demonstrated, as well as up to 25 independent detection channels. Compared with existing solutions, this scheme enables a large‐broadband wavelength, low energy loss, and multiprocessing channels platform for visible detection of NIR OVs, showing great potential to be applied in optical communication systems.

High-efficiency single-pixel imaging using discrete Hartley transform

Single-pixel imaging technology is popular with invisible wavelengths and low light environments. However, the time-consuming steps hindered the development of single-pixel imaging technology. To improve imaging efficiency, a high-efficiency one-step single-pixel imaging method based on the discrete Hartley transform is proposed. The proposed method does not require a large number of fringe patterns and only requires a real-number calculation. The number of fringe patterns required for the proposed method is only half of that required for the four-step phase-shift Fourier method at the same sampling rate. Although a one-step method, it also uses the idea of differential measurements and adds upsampling processing strategies, which simultaneously improve the signal-to-noise ratio of the recovered image. The simulation shows that the peak signal-to-noise ratio and structural similarity index of the recovered target scene exceed 20 dB and 80%, respectively, when the sampling rate is 30%. Only 20 164 patterns are needed to reconstruct a (256 × 256)-pixel image. After defocusing the gray stripe pattern into a binary pattern, it only takes milliseconds to project these patterns into the target. It can be seen that the experimental results of the proposed method are significantly better than those of the two-step phase-shift method under dramatical noise interference. With the rapid development of advanced equipment, this method will represent significant progress in the real-time reconstruction of single-pixel imaging.

Programmable spatially variant single-pixel imaging based on compressive sensing

Single-pixel camera is developed to mitigate the constraints faced by the conventional cameras especially in invisible wavelengths and low light conditions. Nyquist–Shannon theorem requires as many measurements as the image pixels to reconstruct images flawlessly. In practice, obtaining more measurements increases the cost and acquisition time, which are the major drawbacks of single-pixel imaging (SPI). Therefore, compressive sensing was proposed to enable image reconstruction with fewer measurements. We present a design of sensing patterns to obtain image information by utilizing spatially variant resolution (SVR) technique in SPI. The proposed method reduces the measurements by prioritizing the resolution in the region of interest (ROI). It successfully achieves the programmable imaging concept where multiresolution adaptively optimizes the balance between the image quality and the measurements number. Results show that SVR images can be reconstructed from significantly fewer measurements yet able to achieve better image quality than uniform resolution images. In addition, the SVR images can be further enhanced by integrating the dynamic supersampling technique. Consequently, the concerns of image quality, long acquisition, and processing time can be addressed. The proposed method potentially benefits imaging applications where the target ROI is prioritized over the background and most importantly it requires fewer measurements.

Usefulness of Autofluorescence Video-Monitoring to Enhanced Localization of Parathyroid Glands

Background and Objectives Near-infrared (NIR) fluorescence photo imaging provides real time parathyroid anatomy enhancement. Moreover, autofluorescence enables intraoperative virtual reality parathyroid exploration of the optical characteristics of the parathyroid gland. This study was performed to demonstrate the new technique of visualizing the parathyroid gland using video-guided autofluorescence during thyroid and parathyroid surgery and to evaluate the outcomes. This is the first study that introduces the video-monitoring technique for intraoperative parathyroid mapping.Subjects and Method A total of 26 patients underwent 18 total thyroidectomies and 8 hemithyroidectomies in 2016. Fifty-six parathyroid glands were enrolled in this study. Surgery was performed by NIR video-monitoring via thyroid lateral side dissection to find the parathyroid tissues and extract the thyroid glands. With the operation room light turned on, the parathyroid glands were identified by the video-guided autofluorescence detection technique carried out in 3 stages (P1, P2, and P3), which are imaging with surgeon’s eyes before parathyroids exposure (P1), after identification (P2), and in extracted specimen (P3).Results The parathryoid autofluorescence could be video-monitored in real time by our NIR camera system with the indoor room light turned on. Of the total 56 parathyroids, 52 were detected by fluorescence. Of these, the location of 43 glands were predicted by using the high signal in a before-exposure state and the glands were confirmed as containing parathyroid tissues [in P1, sensitivity=82.69%, positive predictive value (PPV)=100.00%]. Of the nine glands that did not show high signals in P1, seven glands visually showed fluorescence signals (in P1 and P2, sensitivity=96.15%, PPV=100.00%). One of the two glands that showed high signals in the extracted tissue was identified as parathyroid, but the other one was proved not by histologic examination by despite high intensity fluorescence signal (in P1-P3, sensitivity=100.00%, PPV=98.08%). The accuracy of video-guided parathyroid mapping in P1, P2, and P3 were 83.93%, 96.43%, and 96.43%, respectively.Conclusion This is the first study that demonstrates the parathyroid gland autofluorescence as a real-time video-monitoring technique and shows that it could be applied to real surgery. Although parathyroid autofluorescence is a phenomenon seen in the invisible wavelength, our data suggest that the operator can see the parathyroid fluorescent signal in real time on the video-monitor. This technique could help the operator to predict the gland location and preserve them safely.

Proof-of-principle experimental demonstration of quantum secure imaging based on quantum key distribution

We present a quantum secure imaging (QSI) scheme based on the phase encoding and weak+vacuum decoy-state BB84 protocol of quantum key distribution (QKD). It allows us to implement a computational ghost imaging (CGI) system with more simplified equipment and reconstructed algorithm by using a digital micro-mirror device (DMD) to preset the specific spatial distribution of the light intensity. What is more, the quantum bit error rate (QBER) and the secure key rate analytical functions of QKD are used to see through the intercept-resend jamming attacks and ensure the authenticity of the imaging information. In the experiment, we obtained the image of the object quickly and efficiently by measuring the signal photon counts with a single-photon detector (SPD), and achieved a secure key rate of 571.0 bps and a secure QBER of 3.99%, which is well below the lower bound of QBER of 14.51%. Besides, our imaging system uses a laser with invisible wavelength of 1550 nm, whose intensity is as low as single-photon, that can realize weak-light imaging and is immune to the stray light or air turbulence, thus it will become a better choice for quantum security radar against intercept-resend jamming attacks.

Discrete cosine single-pixel microscopic compressive imaging via fast binary modulation

Single-pixel imaging technology has significant imaging advantages in the invisible wavelength and low light environment. Considering the energy compressive characteristic of discrete cosine spectrum, a single-pixel microscopic compressive imaging method based on the two-dimensional discrete cosine transform is proposed. In this method, a digital micro-mirror device is used for high-speed binary differential modulation of discrete cosine basis patterns; and the zigzag sorting is adopted to perform the under-sampling. The discrete cosine spectrum is generated by calculating the weighted sum of the light intensities measured by a single-pixel detector, and the object is reconstructed by two-dimensional inverse discrete cosine transform. The proposed method is verified by both computational simulations and laboratory experiments. The effects of different sampling rates, binary quantization level and compressive sampling modes on imaging results are discussed. The results show that the proposed method can realize high quality and high efficiency imaging. The method is suitable for microscopic imaging applications.

Multispectral Recovery of a Fragment of Richard FitzRalph's Summa de Questionibus Armenorum from University of Rochester, D.460 1000-03

Multispectral imaging—the process of obtaining image data from a range of both visible and invisible wavelengths—is a new frontier in medieval studies, raising the possibility of recovering damaged or palimpsested texts that have been illegible for centuries. In this paper we show the remarkable results of applying this technology to University of X, MS D.460 1000-003, a previously unidentified single-folio fragment that was gifted to the university in 1968. Formerly used as a limp vellum binding for a seventeenth-century volume, the text has become so worn that it is all but completely unreadable to the naked eye. The fragment has consequently received little scholarly attention prior to our investigation. Our team recovered nearly all of the lost text and identified the fragment as an excerpt from Richard FitzRalph's Summa de Questionibus Armenorum. Although this text survives in 45 other manuscripts and fragments, our discovery is highly significant because the Rochester fragment is the only copy of any of FitzRalph's works in a non-European collection. Moreover, the fragment, whose handwriting dates to no later than 1370, may be the oldest extant copy of the Summa by at least half a decade. We present the process of this discovery, our conclusions about the text, and the potential for multispectral imaging to unlock new information hidden in known but understudied fragments held in archival collections around the world.

A Review of Image Processing Techniques Common in Human and Plant Disease Diagnosis

Image processing has been extensively used in various (human, animal, plant) disease diagnosis approaches, assisting experts to select the right treatment. It has been applied to both images captured from cameras of visible light and from equipment that captures information in invisible wavelengths (magnetic/ultrasonic sensors, microscopes, etc.). In most of the referenced diagnosis applications, the image is enhanced by various filtering methods and segmentation follows isolating the regions of interest. Classification of the input image is performed at the final stage. The disease diagnosis approaches based on these steps and the common methods are described. The features extracted from a plant/skin disease diagnosis framework developed by the author are used here to demonstrate various techniques adopted in the literature. The various metrics along with the available experimental conditions and results presented in the referenced approaches are also discussed. The accuracy achieved in the diagnosis methods that are based on image processing is often higher than 90%. The motivation for this review is to highlight the most common and efficient methods that have been employed in various disease diagnosis approaches and suggest how they can be used in similar or different applications.

Unidirectional invisibility andPTsymmetry with graphene

We investigate the reflectionlessness and invisibility properties in the transverse electric (TE) mode solution of a linear homogeneous optical system which comprises the $\mathcal{PT}$-symmetric structures covered by graphene sheets. We derive analytic expressions, indicate roles of each parameter governing optical system with graphene and justify that optimal conditions of these parameters give rise to broadband and wide angle invisibility. Presence of graphene turns out to shift the invisible wavelength range and to reduce the required gain amount considerably, based on its chemical potential and temperature. We substantiate that our results yield broadband reflectionless and invisible configurations for realistic materials of small refractive indices, usually around $\eta = 1$, and of small thickness sizes with graphene sheets of rather small temperatures and chemical potentials. Finally, we demonstrate that pure $\mathcal{PT}$-symmetric graphene yields invisibility at small temperatures and chemical potentials.

The Invisible Universe

With our own eyes we can see the night sky of the stars, planets and the Milky Way, the arena of pre-telescopic astronomy. Modern optical telescopes have opened up the universe of galaxies and we are familiar with the superb images of the Hubble Space Telescope. But with the invisible wavelengths of radio, infrared and X-ray, a very different universe comes into view. The astronomy of the invisible wavelengths was inaugurated by William Herschel in 1800 but developed very slowly over the next 160 years. The past fifty years have seen an explosion in our understanding of this strange world.

The Invisible Universe

With our own eyes we can see the night sky of the stars, planets and the Milky Way, the arena of pre-telescopic astronomy. Modern optical telescopes have opened up the universe of galaxies and we are familiar with the superb images of the Hubble Space Telescope. But with the invisible wavelengths of radio, infrared and X-ray, a very different universe comes into view. The astronomy of the invisible wavelengths was inaugurated by William Herschel in 1800 but developed very slowly over the next 160 years. The past fifty years have seen an explosion in our understanding of this strange world.

Beamlike photon pairs entangled by a2×2fiber

Polarization-entangled photon pairs have been widely used as a light source of quantum communication. The polarization-entangled photon pairs are generally obtained at the crossing points of the light cones that are generated from a type-II nonlinear crystal. However, it is hard to pick up the photon pairs coming out from the crossing points because of their invisible wavelength and low intensity. In our previous work, we succeeded in generating polarization-entangled photon pairs by overlapping two light paths for the photon-pair generation. The photon pairs could be entangled in all of the generated photon pairs without clipping the crossing points, even with some difficulty in its alignment to overlap the two light paths. In this paper, we have developed an optical system which generates polarization-entangled photon pairs using a beamlike photon pair, without the difficulty in alignment. The measured results show that the photon pairs generated in the system are entangled in their polarizations.

Detection and Analysis of the Intestinal Ischemia Using Visible and Invisible Hyperspectral Imaging

Intestinal ischemia, or inadequate blood flow to the intestine, is caused by a variety of disorders and conditions. The quickness with which the problem is brought to medical attention for diagnosis and treatment has great effects on the outcome of ischemic injury. Recently, hyperspectral sensors have advanced and emerged as compact imaging tools that can be utilized in medical diagnostics. Hyperspectral imaging provides a powerful tool for noninvasive tissue analyses. In this paper, the hyperspectral camera, with visible and invisible wavelengths, has been evaluated for detection and analysis of intestinal ischemia during surgeries. This technique can help the surgeon to quickly find ischemic tissues. Two cameras, a visible-to-near-infrared camera (400-1000 nm) and an infrared camera (900-1700 nm) were used to capture the hyperspectral images. Vessels supplying an intestinal segment of a pig were clamped to simulate ischemic conditions. A key wavelength range that provides the best differentiation between normal and ischemic intestine was determined from all wavelengths that potentially reduces the amount of data collected in subsequent work. The data were classified using two filters that were designed to discriminate the ischemic intestinal regions.

Electrical and optical properties of inorganic complexes C36H76N2O9ClNa and C14H12N2O4TeBr2

The electrical properties of some inorganic samples were studied as functions of temperature and the results were analyzed. These samples activation energies were calculated from the electrical conductivity measurements. Also, a detailed study of optical absorption is presented. The optical absorption spectra are measured in the UV + invisible wavelength range 200‐1100 nm. The absorption coefficient and value optical energy gaps were determined from the absorption spectra. The complex C36H76N2O9ClNa is characterized by direct optical absorption with an optical edge at 4.49 eV. However, the complex C14H12N2O4TeBr2 is characterized by indirect optical absorption with an optical edge at 1.45 eV, and a nearby

半導体レーザ光学系の光軸測定法

An optical axis determination method for semiconductor laser systems of invisible wave length, e. g. 1.3, 1.5 μm, has been proposed. A semiconductor laser module with a microlens shaped by the surface tension of melted glass is discussed. The optical axis of the system is determined as follows. At first, the axis of the lens is searched from interference fringes made by reflecting He-Ne laser visible light. This axis is then used as the reference axis. Next, the electromotive current in the semiconductor laser is measured by illuminating the semiconductor laser with a He-Ne laser light from the opposite direction against the laser emission. At the same time, the angle of the illuminating laser light is continuously changed by means of an f·θ lens. The illuminating laser light axis which corresponds to the desired optical axis is found when the maximum electromotive current is obtained. The spacial orientated axis is determined by independently measuring the maximum currents along two directions orthogonal to each other.

Lasers in rectosigmoid cancers: factors affecting immediate and long-term results

Surgical segmental resection offers the best chance of cure in patients with rectosigmoid cancer. It is also the most effective form of palliation of local symptoms. Unfortunately, it can cause excessive morbidity and mortality in patients who have severe concomitant medical illness. For these patients, alternative methods of removing cancer are being studied for efficacy and risk. One important method of destroying rectosigmoid cancer uses laser energy. Laser is an acronym for light amplification of stimulated emission of radiation. The energy is monochromatic, coherent and collimated. It can be delivered through a quartz fibre passed down the instrument channel of an endoscope to focus the beam on a well demarcated area of tissue. At an appropriate intensity, laser energy creates heat in the tissue resulting in cell death at moderate temperatures and tissue vaporization at higher temperatures. The amount of heating depends on the wavelength, the irradiance, the pulse sequence and the spot size. The goal in laser ablation of cancer is to destroy the cancer cells while avoiding deeper injury to the intestinal wall which could result in perforation. The two most commonly used lasers for gastrointestinal tumour ablation are the argon laser and the Nd:YAG laser. The argon laser emits several wavelengths from 4W514 nm which is in the blue-green range of the visible light spectrum. Absorption is high in tissue and this results in superficial destruction without deeper injury. It is most useful in destroying smaller amounts of tissue with a high degree of precision. The Nd:YAG laser has an invisible wavelength of 1064nm and is poorly absorbed. There is much more penetration and diffusion of heat with the Nd:YAG laser than with the argon laser. The Nd:YAG laser is therefore more useful for destroying larger intraluminal areas of tumour. Rectosigmoid cancers which invade only superficially into the submucosa