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The successful surgery of chronic otitis media (COM) is challenging; this depends on the surgeon's knowledge of the optical visibility of surgical microscopes. Herein, we reported the utilization of intra-surgical optical coherence tomography (OCT) system to effectively guide the surgery of COM based on augmented reality with cross-sectional images. The intra-surgical spectral-domain OCT system with a center wavelength of 846 nm was capable of obtaining non-invasive, high-resolution, and high-speed visualizations with an axial resolution of 8 ${{\bf \mu }}$ m, lateral resolution of 30 ${{\bf \mu }}$ m, and an extended working distance of 280 mm. Three patients with COM were involved in this research. The lesion conditions of the temporal bone were observed with computed tomography pre-operatively. Furthermore, pure-tone audiogram examinations were performed to evaluate pre and post-surgical conditions. The results revealed that the averaged air-bone gap of 500 Hz, 1 kHz, 2 kHz, and 4 kHz in all cases improved to 61%. Thus, the research proves that the experimental procedure can be beneficial and clinically applicable with the developed intra-surgical OCT system for future otolaryngological assessments.

The primary optimization of the imaging speed of optical coherence tomography (OCT) has been keenly studied. In order to overcome the major speed limitation of spectral-domain OCT (SD-OCT), we developed an ultrahigh-speed SD-OCT system, with an A-scan rate of up to 1 MHz, using the method of space–time-division multiplexing (STDM). Multicameras comprising a single spectrometer were implemented in the developed ultrahigh-speed STDM method to eliminate the dead time of operation, whereas STDM was simultaneously employed to enable wide-range scanning measurements at a high speed. By successfully integrating the developed STDM method with GPU parallel processing, 8 vol/s for an image range of $250\times 250\times2048$ pixels ( $9\times 4.5\times 5$ mm) was achieved, with an adjustable volume rate according to the required scanning speed and range. The examined STDM-OCT results of the customized optical thin film confirmed its feasibility for various fields that require rapid and wide-field scanning.

The accurate screening of otitis media (OM) lies in clarifying the numerous confounding and quantitative factors that are discovered during primary inspections. Increased awareness about bacterial biofilms and inflammation has allowed researchers to develop a better understanding of the bacterial infections that occur in the middle ear. In this study, four live guinea pigs were inoculated with Streptococcus pneumonia to induce OM-related inflammatory changes. Since optical techniques have been effectively used for diagnosis in medicine, low-coherence interferometry-based optical coherence tomography (OCT) was employed for depth-resolved high-resolution data screening. Multiple locations of the tympanic membrane (TM), mastoid mucosa, and round window membrane were examined to assess inflammatory changes. We performed qualitative assessments and thickness quantifications and investigated the variations due to adverse inflammatory affects. The findings of the present study provide a better understanding of S. pneumonia bacteria caused inflammatory changes in middle ear and it further provides a fundamental platform for future clinical utility.

Optical polarizing thin film is an optical filter enables light waves of a specific polarization pass through while blocking light waves of other polarizations. Optical polarizing thin films control the brightness of back-light unit for LCD (liquid crystal display) panel, which is essential to produce LCD modules. Defect inspection of polarizing thin films is an important feature during the manufacturing process that is helpful to improve the product quality. In the current study, an automated defect inspection algorithm is introduced and incorporated with a well-known non-destructive and non-contact optical inspection method called spectral domain optical coherence tomography (SD-OCT) to pre-identify defective sub-surface as well as top-surface locations of optical polarizing thin films Polarizing thin films employed in this study consist of 6 layers. The tomographic information, layer information, and defective locations were sufficiently identified through the SD-OCT system owing high-axial resolution. The acquired results indicate the possible application of the proposed system in optical polarizing thin films for the quality assurance.

Optical fiber is widely used in optical coherence tomography (OCT) to propagate light precisely with low attenuation and low dispersion. However, the total optical path length within the optical fiber varies in accordance with changes of the temperature. This leads changes in the total optical travel path of the interfering signals and results in shifting of OCT image position to an unintended depth pixel value. In this paper, we presented the temperature-based automatic path length compensating method in OCT to limit the external temperature effect and control the image position in micro-scale without manual movement of optical components. By utilizing developed hardware and software of automatic temperature control system, the external temperature of optical fiber is precisely regulated that evokes thermal expansion and finally changes the physical length of fiber, which is main mechanism of temperature-based path length compensating method. The effectiveness of the presented method was verified by two-dimensional OCT images of mirror and in vivo retina. The obtained results confirmed the path length variance due to temperature change is computable and can be regulated in real-time for whole pixel range of OCT image. Therefore, the proposed temperature-based path length compensating method can be used as an alternative method to precisely control the position of OCT image, while eliminating the effect of external temperature and apply to effectively configuring compact optical systems.

Dental crowns are used to restore decayed or chipped teeth, where their surfaces play a key role in this restoration process, as they affect the fitting and stable bonding of the prostheses. The surface texture of crowns can interfere with this restoration process, therefore the measurement of their inner surface roughness is very important but difficult to achieve using conventional imaging methods. In this study, the inner surfaces of dental crowns were three-dimensionally (3D) visualized using swept-source optical coherence tomography (SS-OCT) system. Nine crowns were fabricated with a commercial 3D printer using three different hatching methods (one-way, cross, and 30° angle counter-clockwise) and three different build direction angles (0°, 45°, and 90°). In addition, an image processing algorithm was developed, which uses morphological filtering, boundary detection, and a high-pass frequency filtering technique, to quantitatively evaluate the inner surface roughness of the dental crowns cross-sections with the depth-of-focus set to match two different regions. The averaged smoothness of fabricated crown was effectively produced using the cross-hatching and the build direction angle of 90° by the respective process. Thus, the results confirm the potential use of this methodology to determine the best parameters to use in 3D fabrication for improving the effectiveness and stability of dental prostheses.

Large-scale product inspection is an important aspect in thin film industry to identify defects with a high precision. Although vision line scan camera (VLSC)-based inspection has been frequently implemented, it is limited to surface inspections. Therefore, to overcome the conventional drawbacks, there is a need to extend inspection capabilities to internal structures. Considering that VLSC systems have access to rich information, such as color and texture, high-resolution real-time multimodal optical synchronization between VLSC and dual spectral domain optical coherence tomography (SD-OCT) systems was developed with a laboratory customized in-built automated defect-tracking algorithm for optical thin films (OTFs). Distinguishable differences in the color and texture of the bezel area were precisely determined by the VLSC. Detailed OCT assessments were conducted to verify the detection of previously unobtainable border regions and micrometer-range sub-surface defects. To enhance the accuracy of the method, VLSC images were aided for the precise surface defect identification using OCT and the image acquisition, signal processing, image analysis, and classification of both techniques were simultaneously processed in real-time for industrial applicability. The results demonstrate that the proposed method is capable of detecting and enumerating total number of defects in OTF samples with exceptional resolution and in a cost-effective manner facilitating wide area inspection for OTF samples.

We demonstrated a preliminary research to investigate the feasible in vivo utilization of swept-source optical coherence tomography (SS-OCT) system with 1310 nm wavelength band to obtain morphological visualizations and human gingival sulcus depth measurements. Apart from the cross-sectional analysis, pixel intensity based OCT image classification algorithm is developed to identify the depth of gingival sulcus quantitatively. A total of 43 sites from the periodontal tissues of five healthy individuals were imaged in vivo by using the OCT system. Two periodontal tissues were right and left maxillary central incisors, while the other four periodontal tissues were left and right mandibular central incisors and later incisors. The developed classification algorithm could measure the gingival sulcus depths, which are 1.15 ± 0.21 mm of the maxilla and 1.06 ± 0.27 mm of the mandible. The averaged total depths obtained by the system was 1.10 ± 0.26 mm. Hence, the gingival sulcus depth could be quantitatively measured by using the swept-source OCT system with the developed image classification algorithm as well as revealing a structural visualization, which ultimately confirmed the potential applicability for gingival sulcus depth real-time assessment.

On-field in situ inspection of Marssonina coronaria infected apple blotch for apple leaf specimens was demonstrated using compact backpack-type optical coherence tomography (OCT). Simultaneously, the acquired OCT results were precisely matched with a widely used agricultural plant pathogen inspection technique called loop-mediated isothermal amplification (LAMP) to confirm on-field applicability of the compact backpack-type OCT. Specimens were examined for 8 weeks. Automated Amplitude-scan (A-scan) depth profiling and post-processed infected tissue boundary detection from acquired OCT images were performed to investigate the increase in the internal layer gaps of the leaf specimens resulting from the disease. Clearly identifiable morphological difference between healthy and infected-suspected specimens was observed through the OCT images, which were well correlated with LAMP results. OCT-LAMP correlations and confirmed feasibility study results conclude that the compact backpack-type OCT diagnosing modality can be effective and extensively applicable for various novel agricultural discoveries.

In the past decade, there has been an increase in the development of sensitive, high-resolution, non-invasive diagnostic methods for periodontic diseases. Optical coherence tomography (OCT) has attracted considerable attention in clinical settings. In this paper, a reliable, robust algorithm for the detection of gingival sulcus in 2D OCT cross-sectional images is proposed. Previously, the measurement of gingival sulcus in OCT images has been performed by manual identification using two-dimensional (2D) cross-sectional images. The automated detection of gingival sulcus continuity in 2D OCT images may help medical practitioners to assess important features of gingival tissues. The Sobel and canny operators have mainly been used for boundary and edge detection in OCT images. However, these algorithms are highly sensitive to noise and speckle in OCT images. To overcome these limitations, we propose an algorithm for the quantitative depth measurement of the human gingival sulcus, based on averaged intensity difference. In this paper, we utilized two commercially-available swept-source OCT systems operating at center wavelengths of 1310 and 1060 nm to image gingival sulcus of human samples in vivo. The images were processed using three algorithms: canny, Sobel, and averaged intensity difference.

An internal and marginal fit between prosthesis and abutment is an important factor of the durability of dental prosthesis. In this paper, we have proposed the use of swept-source optical coherence tomography (OCT) as a novel application for non-ionized and high-resolution measurements of internal and marginal discrepancies at anatomically critical four points, such as occlusal, angle, axial, and margin during prosthesis attachment. A tooth model was fabricated by a 3D printing technique, and the dental prosthesis was designed using dental CAD software. The cross-sectional images along with intensity peak profile analysis of the sample were acquired using the OCT system for measurements of fit. The demonstrated qualitative and quantitative evaluations can be well-utilized for assessment of the internal and marginal fit of dental prosthesis.

Whole-directional scanning methodology is required to observe distinctive features of an entire physical structure with a three dimensional (3D) visualization. However, the implementation of whole-directional scanning is challenging for conventional optical coherence tomography (OCT), which scans a limited portion of the sample by utilizing unidirectional and bidirectional scanning methods. Therefore, in this paper an integrated quad-scanner (QS) strategy-based OCT method was implemented to obtain the whole-directional volumetry of a sample by employing four scanning arms installed around the sample. The simultaneous and sequential image acquisition capabilities are the conceptual key points of the proposed QS-OCT method, and were implemented using four precisely aligned scanning arms and applied in a complementary way according to the experimental criteria. To assess the feasibility of obtaining whole-directional morphological structures, a roll of Scotch tape, an ex vivo mouse heart, and kidney specimens were imaged and independently obtained tissue images at different directions were delicately merged to compose the 3D volume data set. The results revealed the potential merits of QS-OCT-based whole-directional imaging, which can be a favorable inspection method for various discoveries that require the dynamic coordinates of the whole physical structure.

Nail beautification is a widely applied gender independent practice. Excessive nail beautifications and nail-arts have a direct impact on the nail structure and can cause nail disorders. Therefore, the assessment of post-progressive nail-art effects on the nail is essential to maintain optimal nail health and to avoid any undesirable disorders. In this study, in vivo nails were examined in control stage, with a nail-art stage, and after removing the nail-art stage using a 1310 nm spectral-domain optical coherence tomography (SD-OCT) system. The acquired cross-sectional OCT images were analyzed by a laboratory customized signal processing algorithm to obtain scattered intensity profiling assessments that could reveal the effects of nail beautification on the nail plate. The formation and progression of cracks on the nail plate surface were detected as an effect of nail beautification after 72 h of nail-art removal. Changes in backscattered light intensity and nail plate thickness of control and art-removed nails were quantitatively compared. The results revealed the potential feasibility of the developed OCT-based inspection procedure to diagnose post-progressive nail-art effects on in vivo nail plate, which can be helpful to prevent nail plate damages during art removal through real-time monitoring of the boundary between the nail plate and nail-art. Besides nail-art effects, the developed method can also be used for the investigation of nail plate abnormalities by examining the inconsistency of internal and external nail plate structure, which can be diagnosed with both qualitative and quantitative assessments from a clinical perspective.

A bacterium in bacterial colony is a basal component of bacterial studies and is therefore of considerable importance. The morphological characteristics of a single colony have been widely used as the standard to identify diverse bacterial species. However, the conventional methods for obtaining morphological information, such as microscopic techniques, cannot provide tomographic views. This study utilizes spectral-domain optical coherence tomography (SD-OCT) to observe both external and internal structures for single colonies. OCT imaging provided a clear top (projection) and lateral (cross-sectional) images, which can identify distinct features in the fifteen different bacterial species examined. Through the acquired OCT images, the elevation type in each genus was confirmed, and the quantitative measurements for morphology including a diameter, height, and elevation angle were achieved. Moreover, the OCT raw data was used to build three-dimensional images to observe outer appearances in all direction. As a result, the averaged angles of 7.92°, 14.40°, 6.78°, and 11.92° of the genus Hymenobacter, Spirosoma, Bacillus, and Deinococcus, respectively, were calculated. In conclusion, we have demonstrated that OCT is a highly feasible, non-invasive method for the identification of bacterial species, providing detailed morphological and visual information. It thus has strong potential for applications in bacteriology, as well as biomedical and food sciences.

Depth-visualizing sensitivity can be degraded due to imperfect optical alignment and non-equidistant distribution of optical signals in the pixel array, which requires a measurement of the re-sampling process. To enhance this depth-visualizing sensitivity, reference and sample arm-channeled spectra corresponding to different depths using mirrors were obtained to calibrate the spectrum sampling prior to Fourier transformation. During the process, eight interferogram patterns corresponding to point spread function (PSF) signals at eight optical path length differences were acquired. To calibrate the spectrum, generated intensity points of the original interferogram were re-indexed towards a maximum intensity range, and these interferogram re-indexing points were employed to generate a new lookup table. The entire software-based process consists of eight consecutive steps. Experimental results revealed that the proposed method can achieve images with a high depth-visualizing sensitivity. Furthermore, the results validate the proposed method as a rapidly performable spectral calibration technique, and the real-time images acquired using our technique confirm the simplicity and applicability of the method to existing optical coherence tomography (OCT) systems. The sensitivity roll-off prior to the spectral calibration was measured as 28 dB and it was halved after the calibration process.

The aim of this research was to visualize and measure the human gingival sulcus in vivo using the swept-source optical coherence tomography system based on 1310 nm wavelength source with the developed classification algorithm of gingival sulcus. Apart from the algorithm based examination procedure, the OCT cross-sectional images were involved in A-scan depth profile analysis to illustrate the intensity fluctuation of teeth and the periodontal tissue structures to clarify the end point of gingival sulcus. The quantitative measurement was assessed with 1.10 ± 0.26 mm. Thus, the swept-source optical coherence tomography system could be used to perform the gingival sulcus imaging.

The main goal of this study is to develop an ultra-compact optical coherence tomography (OCT) system operated by a single-board computer to enhance its on-field applicability with superior user-friendliness and minimized system complexity. The conceptual breakthrough of this demonstration is the development of an OCT using a simple Raspberry Pi single-board computer architecture (RB-OCT) that works in a similar manner as the conventional OCT systems. The unique feature of the developed all-in-one RB-OCT system is the versatile ultra-compactness, comprising all key components of an OCT system. To further enhance the miniaturization, the micro-electro-mechanical system (MEMS) scanning unit, the entire optical configuration, and signal generating amplifier circuits were custom made to be compatible with Raspberry Pi single-board computer architecture. The dimensions of the developed system are 228 mm width, 168 mm length, and 107 mm depth with an approximate weight of 2 kg, including an image display. The software interface was developed using C++ based on Debian OS and configured using parallel programming with multi-threading. In vivo skin, ex vivo mouse cochlea, and fresh onion peels were used to evaluate the performance of the proposed system. Based on the feasibility study, this new type of single-board architecture OCT has potential merits over conventional OCT systems to be applied as a primary imaging device in various fields.

In this study, the industrial inspection of optical thin film on touch screen panels was demonstrated using line field spectral domain optical coherence tomography. The conventional Fourier domain optical coherence tomography system requires a single scanner for two-dimensional cross-sectional images and two scanners for volumetric images. Our developed line field spectral domain optical coherence tomography has the advantage of needing only a single scanner for volumetric images, while two-dimensional cross-sectional images are obtained by the parallel acquisition of an illuminated line on a sample using an area camera. Further, the image acquisition speed was enhanced by implementing a high speed camera (340 frames per seconds) with improved quantum efficiency at near infrared region enabling two-fold frame rate. Cross-sectional and volumetric images were acquired to detect the internal sublayer defects in the optical thin films, which are difficult to observe using visual or machine vision-based inspection methods. The developed pseudo code for defect identification in optical thin films was well-utilized here for the defect inspection. The system characterization is demonstrated using United State Air Force (USAF) resolution target. The results indicate the possible application of the proposed system in touch screen panel inspection for the quality assurance of products at the consumer end.

Laser transmission welding offers significant benefits over conventional welding techniques enabling single-stage rapid plastic joining. The quality of laser transmission welded products is commonly assessed by measuring the weld penetration depth, hardened weld boundary, and inspecting the formation of porosity. However, the existing methods of verification are inevitably accompanied by destruction of the specimen. Thus, non-destructive quality assessment methods for laser transmission welding have gained attention recently. Here, we demonstrated an extended industrial application of 860 nm wavelength-based spectral domain optical coherence tomography for the non-destructive inspection of the aforementioned quality parameters of laser transmission welded industrial plastic materials, i.e., polycarbonate and acrylonitrile butadiene styrene copolymer. The acquired cross-sectional resolution and volumetric and intensity profiles sufficiently contributed to the quality assessment procedure, revealing the weld boundary and porosity formation, and thus confirming the potential applicability of optical coherence tomography for the quality inspection of laser transmission welded products.

Mice and rats are rodent specimens commonly used in multidisciplinary research. Specifically, vasculature imaging of rodents has been widely performed in preclinical studies using various techniques, such as computed tomography, magnetic resonance imaging, and ultrasound imaging. Photoacoustic CT (PACT) is a noninvasive, nonionizing optical imaging technique derived from photoacoustic tomography and benefits from using intrinsic endogenous contrast agents to produce three-dimensional volumetric data from images. In this study, a commercial PACT device was employed to assess the cervicothoracic vasculature of mouse and rat specimens, which has rarely been examined using PACT, under two conditions with depilation and skin incision. Various blood vessels, including the common carotid artery, internal/external jugular veins, cranial vena cava, internal thoracic vein, and mammary, were identified in the acquired PACT images. The difference between the depilated and skin-incised specimens also revealed the presence of branches from certain blood vessels and specific anatomical features such as the manubrium of the sternum. This study presents detailed PACT images observing the cervicothoracic vasculature of rodent specimens and is expected to be used as a reference for various preclinical experiments on mice and rats.

The aim of this study was to quantitatively assess the residual adhesive on orthodontic ceramic bracket-removed dental surface. In orthodontic process, ceramic bracket was repeated debonding physically, then the adhesive remained on the dental surface. The residual adhesive caused a lack of adhesive strength between dental and ceramic bracket. Since commonly used adhesive in orthodontics is translucent, residual adhesive is hard to be detected with conventional microscopes. Therefore, 1310 nm center wavelength swept-source OCT system based on laboratory customized image processing algorithm was used for the precise detection of residual adhesive on tooth surface. The algorithm separates residual adhesive from dental surface by comparing the height of adjacent B-scan images, while providing color-scaled images emphasizing the thickness information of residual adhesive. Finally, the acquired results were compared with microscopic and adhesive remnant index scoring gold standards, while the comparison confirmed the potential merits and the improvements of the proposed method over gold standards.

The large-scale liquid-crystal display (LCD) industry requires an accurate inspection system for identifying defects, as the LCD quality can be drastically degraded because of defects. In particular, the refractive index of LCD panels can be changed by internal micrometer-range substances, which form as a result of defectiveness and the insufficient solidification of industrial liquid resins. Intrinsically, the defect inspection of the raw materials must be performed prior to the LCD manufacturing process. Thus, optical coherence tomography (OCT) based automated fluid-inspection (AFI) methodology was introduced to demarcate and enumerate the defects in industrial liquid resins and the final product (LCD smartphone). The accuracy of the method was enhanced by implementing an intensity-detection algorithm. Subsequently, the optimal solidification rates of liquid resins were investigated using a fluorescence sensor-based ultraviolet hardening method to prevent the formation of defects between the internal layers of the LCD panel. Therefore, AFI can be implemented as an effective and cost-saving method in the smartphone industry for improving the quality of the final product.

Corneal transplantation by full‐thickness penetrating keratoplasty with human donor tissue is a widely accepted treatment for damaged or diseased corneas. Although corneal transplantation has a high success rate, a shortage of high‐quality donor tissue is a considerable limitation. Therefore, bioengineered corneas could be an effective solution for this limitation, and a decellularized extracellular matrix comprises a promising scaffold for their fabrication. In this study, three‐dimensional bioprinted decellularized collagen sheets were implanted into the stromal layer of the cornea of five rabbits. We performed in vivo noninvasive monitoring of the rabbit corneas using swept‐source optical coherence tomography (OCT) after implanting the collagen sheets. Anterior segment OCT images and averaged amplitude‐scans were acquired biweekly to monitor corneal thickness after implantation for 1 month. The averaged cornea thickness in the control images was 430.3 ± 5.9 μm, while the averaged thickness after corneal implantation was 598.5 ± 11.8 μm and 564.5 ± 12.5 μm at 2 and 4 weeks, respectively. The corneal thickness reduction of 34 μm confirmed the biocompatibility through the image analysis of the depth‐intensity profile base. Moreover, hematoxylin and eosin staining supported the biocompatibility evaluation of the bioprinted decellularized collagen sheet implantation. Hence, the developed bioprinted decellularized collagen sheets could become an alternative solution to human corneal donor tissue, and the proposed image analysis procedure could be beneficial to confirm the success of the surgery., Three‐dimensional bioprinted decellularized collagen sheets were implanted into the stromal layer of the cornea of five rabbits. After implanting the collagen sheets, the rabbit corneas were monitored biweekly in vivo with a swept‐source optical coherence tomography system to assess the biocompatibility of the bioprinted implantation for 1 month through corneal thickness measurements. The small variation in the averaged corneal thickness along with evidence from hematoxylin and eosin‐stained histology images shows the potential use of the biocompatible collagen sheet.

Non-invasive investigation of rice leaf specimens to characterize the morphological formation and particular structural information that is beneficial for agricultural perspective was demonstrated using a low coherence interferometric method called swept source optical coherence tomography (SS-OCT). The acquired results non-invasively revealed morphological properties of rice leaf, such as bulliform cells, aerenchyma, parenchyma, and collenchyma layer, and vascular bundle. Beside aforementioned morphologic characteristics, several leaf characteristics associated with cytological mechanisms of leaf rolling (leaf inclination) were examined for the pre-identification of inevitable necrosis and atrophy of leaf tissues by evaluating acute angle information, such as angular characteristics of the external bi-directional angles between the lower epidermis layer and lower mid-vein, and internal angle of lower mid-vein. To further assist the pre-identification, acquired cross-sections were employed to enumerate the small veins of each leaf specimen. Since mutants enlarge leaf angles due to increased cell division in the adaxial epidermis, healthy and abnormal leaf specimens were morphologically and quantitatively compared. Therefore, the results of the method can be used in agriculture, and SS-OCT shows potential as a rigorous investigation method for selecting mutant infected rice leaf specimens rapidly and non-destructively compared to destructive and time consuming gold-standard methods with a lack of precision.

Ixodidae tick, also known as a hard tick, is one of the major vectors of various tick-borne diseases. Studying its anatomy is the fundamental approach for diverse acarological studies and the key to understanding tick morphology. However, the conventional methods of observing internal organs rely primarily on dissection, which damages specimens irrecoverably. In this study, we developed an optical coherence tomography (OCT) system to non-invasively investigate the morphological characteristics of the hard tick. Herein, OCT imaging was conducted by the developed spectral-domain OCT (SD-OCT) system with two different objective lenses. The developed system provides an axial resolution (in the air) of 6.2 µm and a maximum lateral resolution of 2.46 µm as an objective lens with a high numerical aperture (NA) and 10× magnification was employed. Using the developed SD-OCT system, internal organs of tick specimens, such as salivary glands, midgut, genital orifice, and ovary, were identified without inflicting damage. The study suggests the feasibility of the optical coherence imaging for the acarological study of the fundamental morphological inspection and for possible future studies, such as verifying the potential morphological differences among virus transmitted hard tick specimens.

A dual-path handheld system is proposed for cornea and retina imaging using spectral domain optical coherence tomography. The handheld sample arm is designed to acquire two images simultaneously. Both eyes of a person can be imaged at the same time to obtain the images of the cornea of one eye and the retina of the other eye. Cornea, retina, and optic disc images are acquired with the proposed sample arm. Experimental results demonstrate the usefulness of this system for imaging of different eye segments. This system reduces the time required for imaging of the two eyes and is cost effective.

The pathological and physiological defects in various types of fruits lead to large amounts of economical waste. It is well recognized that internal fruit defects due to pathological infections and physiological disorders can be effectively visualized at an initial stage of the disease using a well-known bio-photonic detection method called optical coherence tomography (OCT). This work investigates the use of OCT for identifying the morphological variations of anthracnose (bitter rot) disease infected and physiologically disordered Diospyros kaki (Asian Persimmon) fruits. An experiment was conducted using fruit samples that were carefully selected from persimmon orchards. Depth-resolved images with a high axial resolution were acquired using 850-nm-based spectral-domain OCT (SD-OCT) system. The obtained exemplary high-resolution two-dimensional and volumetric three-dimensional images revealed complementary morphological differences between healthy and defected samples. Moreover, the obtained depth-profile analysis results confirmed the disappearance of the healthy cell layers among the healthy-infected boundary regions. Thus, the proposed method has the potential to increase the diagnostic accuracy of the OCT technique used in agricultural plantations.

The geometrical characteristics of dental implants, such as thread depth and width, facing angle, pitch, and surface roughness, are important to assess their stability and osseointegration after implant surgery. Herein, we demonstrate the potential use of depth-resolved swept-source optical coherence tomography (SS-OCT) to assess the structural quality of widely used dental implants. The implemented SS-OCT system was centered at a wavelength of 1300 nm with a 100 nm full-width at half-maximum. Four dental implants with different structural formations fabricated using either titanium or ceramic were visualized. Qualitative assessments were performed using boundary flattening with an amplitude-profiling algorithm to emphasize and compare the thread depths, surface roughness, and inner structures of the experimental samples. Cross-sectional and volumetric OCT data clearly revealed the depth, width, and pitch of the dental implants, and especially, the quantitative assessment of axial and lateral thread depth unobtainable using conventional inspection methods was successfully conducted. The depth of thread was measured using a depth-directional intensity profile. In conclusion, the high-resolution SS-OCT system could be utilized to improve the quality assurance of dental implant products through multi-plane assessment.

Significant technical and optical advances are required for intraoperative optical coherence tomography (OCT) to be utilized during otological surgeries. Integrating OCT with surgical microscopy makes it possible to evaluate soft tissue in real-time and at a high resolution. Herein, we describe an augmented-reality, intraoperative OCT/microscope system with an extended working distance of 280 mm, providing more space for surgical manipulation than conventional techniques. We initially performed ex vivo experiments to evaluate system performance. In addition, we validated the system by performing preliminary clinical assessments of tympanomastoidectomy outcomes in six patients with chronic otitis media. The system evaluated residual inflammation in the region-of-interest of the mastoid bone. Most importantly, the system intraoperatively revealed the connection between the graft and the remnant tympanic membrane. The extended working distance allows otological surgeons to evaluate the status of both the mastoid bone and tympanic membrane during manipulation, affording full intraoperative imaging.

An index-regulation technique functionalized by numerical sampling for direct calibration of the non-linear wavenumber (k)-domain to a linear domain in spectral domain optical coherence tomography (SD-OCT) is proposed. The objective of the developed method is to facilitate high-resolution identification of microstructures in biomedical imaging. Subjective optical alignments caused by nonlinear sampling of interferograms in the k-domain tend to hinder depth-dependent signal-to-noise ratios (SNR) and axial resolution in SD-OCT. Moreover, the optical-laser-dependent k-domain requires constant recalibrated in accordance with each laser transition, thereby necessitating either hardware or heavy software compensations. As the key feature of the proposed method, a relatively simple software-based k-domain mask calibration technique was developed to enable real-time linear sampling of k-domain interpolations whilst facilitating image observation through use of an index-regulation technique. Moreover, it has been confirmed that dispersion can be simultaneously compensated with noise residuals generated using the proposed technique, and that use of complex numerical or hardware techniques are no longer required. Observed results, such as fall-off, SNR, and axial resolution clearly exhibit the direct impact of the proposed technique, which could help investigators rapidly achieve optical-laser-independent high-quality SD-OCT images.

The tremendous advances achieved in the biophotonics technologies have intensified the necessity for non-invasive modalities that can characterize diverse biological materials with increased sensitivity and resolution. Optical coherence tomography (OCT) is one of the techniques that has been applied for biological applications in medicine and agriculture to identify structural properties. Herein, we report the successful incorporation of OCT for the identification of morphological changes that occur as a result of the bitter rot disease, through continuous detection of structural changes. Detailed inner morphological structural changes occurring in fruit specimens were precisely analyzed as a function of the disease incubation period using OCT. The conducted histological correlation and quantitative three-dimensional evaluations provide a robust platform for further discoveries related to plant materials. The results highlight the initial identification of bitter rot progression on apple specimens owing to the non-invasive inspection capability of OCT. Therefore, we expect that the proposed method will enable immediate sensitivity improvements in the inspection of plant diseases for postharvest utility.

The non-destructive classification of plant materials using optical inspection techniques has been gaining much recent attention in the field of agriculture research. Among them, a near-infrared (NIR) imaging method called optical coherence tomography (OCT) has become a well-known agricultural inspection tool since the last decade. Here we investigated the non-destructive identification capability of OCT to classify diversely stained (with various staining agents) Capsicum annuum seed specimens of different cultivars. A swept source (SS-OCT) system with a spectral band of 1310 nm was used to image unstained control C. annuum seeds along with diversely stained Capsicum seeds, belonging to different cultivar varieties, such as C. annuum cv. PR Ppareum, C. annuum cv. PR Yeol, and C. annuum cv. Asia Jeombo. The obtained cross-sectional images were further analyzed for the changes in the intensity of back-scattered light (resulting due to dye pigment material and internal morphological variations) using a depth scan profiling technique to identify the difference among each seed category. The graphically acquired depth scan profiling results revealed that the control specimens exhibit less back-scattered light intensity in depth scan profiles when compared to the stained seed specimens. Furthermore, a significant back-scattered light intensity difference among each different cultivar group can be identified as well. Thus, the potential capability of OCT based depth scan profiling technique for non-destructive classification of diversely stained C. annum seed specimens of different cultivars can be sufficiently confirmed through the proposed scheme. Hence, when compared to conventional seed sorting techniques, OCT can offer multipurpose advantages by performing sorting of seeds in respective to the dye staining and provides internal structural images non-destructively.

The precise identification of intra-cochlear microstructures is an essential otorhinolaryngological requirement to diagnose the progression of cochlea related diseases. Thus, we demonstrated an experimental procedure to investigate the most optimal wavelength range, which can enhance the visualization of ex vivo intra-cochlear microstructures using multiple wavelengths (i.e., 860 nm, 1060 nm, and 1300 nm) based optical coherence tomography (OCT) systems. The high-resolution tomograms, volumetric, and quantitative evaluations obtained from Basilar membrane, organ of Corti, and scala vestibule regions revealed complementary comparisons between the aforementioned three distinct wavelengths based OCT systems. Compared to 860 nm and 1300 nm wavelengths, 1060 nm wavelength OCT was discovered to be an appropriate wavelength range verifying the simultaneously obtainable high-resolution and reasonable depth range visualization of intra-cochlear microstructures. Therefore, the implementation of 1060 nm OCT can minimize the necessity of two distinct OCT systems. Moreover, the results suggest that the performed qualitative and quantitative analysis procedure can be used as a powerful tool to explore further anatomical structures of the cochlea for future studies in otorhinolaryngology.

Reconstruction of volumetric images of biological and industrial samples has become an essential requirement in medical and industrial fields. The acquisition of three dimensional volumetric images in optical coherence tomography (OCT) is mainly based on reflection of light from sample interfaces. In OCT technology, multiply acquired two dimensional images are rendered together using a software based calibration technique to generate the volumetric image. In this work, we demonstrate the importance of the volumetric imaging capability of OCT technology along with the simultaneous visualization of internal sections in all three X-, Y-, and Z- directions. The volumetric analysis and the enface images were acquired from various biological (agricultural) and industrial materials. Therefore, the proposed study demonstrates the importance and the valuable applicability of OCT based volumetric imaging technique for diverse biological and industrial applications.

The study of mosquitoes and analysis of their behavior are of crucial importance in the on-going efforts to control the alarming increase in mosquito-borne diseases. Furthermore, a non-destructive and real-time imaging technique to study the anatomical features of mosquito specimens can greatly aid the study of mosquitoes. In this study, we demonstrate the three-dimensional imaging capabilities of optical coherence tomography (OCT) for structural analysis of Anopheles sinensis mosquitoes. The anatomical features of An. sinensis head, thorax, and abdominal regions, along with the morphology of internal structures, such as foregut, midgut, and hindgut, were studied using OCT imaging. Two-dimensional and three-dimensional OCT images, used in conjunction with histological images, proved useful for anatomical analysis of mosquito specimens. By presenting this work as an initial study, we demonstrate the applicability of OCT for future mosquito-related entomological research, and also in identifying changes in mosquito anatomical structure.

In this study, Optical coherence tomography (OCT) is demonstrated as a plausible optical tool for in vivo detection of plant seeds and its morphological changes during growth. The experiment was carried out on Capsicum annuum seeds that were treated with different molar concentrations of NaCl to investigate the most optimal concentration for the seed growth. The monitoring process was carried out for 9 consecutive days. The in vivo 2D OCT images of the treated seeds were obtained and compared with seeds that were grown with sterile distilled water. The obtained results confirm the feasibility of using OCT for the proposed application. Normalized A-scan analysis method is utilized for supporting the concluded results.

The conventional Fourier domain optical coherence tomography system requires single scanner for two dimensional cross-sectional image and two scanners for volumetric image. Parallel spectral domain optical coherence tomography has advantage of single scanner for volumetric image, while two dimensional cross-sectional images are obtained by parallel acquisition of illuminated line on sample using area camera. In this study, the industrial inspection of optical thin film on touch screen panels was demonstrated using parallel spectral domain optical coherence tomography. The cross-sectional and volumetric images were acquired to detect the internal sub layer defects in optical thin film which are difficult to observe using visual or machine vision based inspection methods. The results indicate the possible application of the proposed system in touch screen panels inspection for quality assurance of product at consumer end.

A dual illumination system is proposed for cornea and retina imaging using spectral domain optical coherence tomography (SD-OCT). The system is designed to acquire cornea and retina imaging with dual illumination with limited optics and using a single spectrometer. The beam propagation for cornea and retina imaging in dual illumination enables to acquire the images of different segments. This approach will reduce the imaging time for separate corneal and retinal imaging. The in vivo imaging of both the cornea and retina of a health volunteer shows the feasibility of the system for clinical applications

This note points out additional funding that was not added to Appl. Opt.56, D108 (2017)APOPAI0003-693510.1364/AO.56.00D108.

Here we describe the possible application of optical coherence tomography (OCT) to inspect Marssonina coronaria infected apple blotch disease of in situ apple leaves. To fulfill the in situ field inspection requirement, we developed a compact wearable OCT system. For the confirmation of OCT results, simultaneous experiment was performed in realtime using loop-mediated isothermal amplification (LAMP), which is frequently used in agriculture. LAMP method was developed as an alternative approach for the inspection of disease. We performed field inspection for 30 consecutive days, and all the acquired results from both OCT and lamp were compared to confirm the correlation. A clear identification between healthy specimens, apparently healthy but infected specimens, and infected specimens could be obtained through the real-time OCT images, and the correlation between OCT and lamp results was confirmed through the obtained realtime lamp results. Based on this feasibility study, we conclude that the combination of both these diagnosing modalities can be effective for various novel agricultural discoveries.

We developed a compact, wearable diagnostic imaging modality employing optical coherence tomography for in situ plant leaf quality assessments. This system is capable of diagnosing infected leaves at the initial disease stages. Our system is a versatile backpack-type imaging modality with a compact spectrometer, miniature computer, rechargeable power source, and handheld inspection probe. This method enhances real-time in situ specimen inspection through direct implementation of the imaging modality in a plantation. To evaluate the initial performance, field experiments were conducted in apple, pear, and persimmon plantations. Based on the obtained results, we can conclude that the developed imaging modality can be considered as a promising, efficient, convenient, and fast in situ inspection technique for various agricultural fields, which minimizes the limitations of complex tabletop inspection modalities.

Development of a dual-display handheld optical coherence tomography (OCT) system for retina and optic-nerve-head diagnosis beyond the volunteer motion constraints is reported. The developed system is portable and easily movable, containing the compact portable OCT system that includes the handheld probe and computer. Eye posterior chambers were diagnosed using the handheld probe, and the probe could be fixed to the bench-top cradle depending on the volunteers’ physical condition. The images obtained using this handheld probe were displayed in real time on the computer monitor and on a small secondary built-in monitor; the displayed images were saved using the handheld probe’s built-in button. Large-scale signal-processing procedures such as k-domain linearization, fast Fourier transform (FFT), and log-scaling signal processing can be rapidly applied using graphics-processing-unit (GPU) accelerated processing rather than central-processing-unit (CPU) processing. The Labview-based system resolution is 1,024 × 512 pixels, and the frame rate is 56 frames/s, useful for real-time display. The 3D images of the posterior chambers including the retina, optic-nerve head, blood vessels, and optic nerve were composed using real-time displayed images with 500 × 500 × 500 pixel resolution. A handheld and bench-top hybrid mode with a dual-display handheld OCT was developed to overcome the drawbacks of the conventional method.

The initial detection of dental caries is an essential biomedical requirement to barricade the progression of caries and tooth demineralization. The objective of this study is to introduce an optical frequency-domain imaging technique based quantitative evaluation method to calculate the volume and thickness of enamel residual, and a quantification method was developed to evaluate the total intensity fluctuation in depth direction owing to carious lesions, which can be favorable to identify the progression of dental caries in advance. The cross-sectional images of the ex vivo tooth samples were acquired using 1.3 mu m spectral domain optical coherence tomography system (SD-OCT). Moreover, the advantages of the proposed method over the conventional dental inspection methods were compared to highlight the potential capability of OCT. As a consequence, the threshold parameters obtained through the developed method can be used as an efficient investigating technique for the initial detection of demineralization.

We have developed an ultra wide-field of view Optical Coherence Tomography(OCT) which has capability to 2D and 3D views of cross-sectional structure of in vivo human retina. Conventional OCT has a limitation in visualizing the entire retina due to a reduced field of view. We designed an optical setup to significantly improve the lateral scanning range to be more than 20 mm. The entire human retinal structure in 2D and 3D was reported in this paper with the developed OCT system. Also, we empirically searched an optimized image size for real time visualization by analyzing variation of the frame rate with different lateral scan points. The size was concluded to be pixels which took 9 seconds for visualization.

A method for depth enhancement is presented using a bidirectional imaging modality for spectral domain optical coherence tomography (SD-OCT). Two precisely aligned sample arms along with two reference arms were utilized in the optical configuration to scan the samples. Using exemplary images of the optical resolution target, Scotch tape, a silicon sheet with two needles, and a leaf, we demonstrated how the developed bidirectional SD-OCT imaging method increases the ability to characterize depth-enhanced images. The results of the developed system were validated by comparing the images with the standard OCT configuration (single-sample arm setup). Given the advantages of higher resolution and the ability to visualize deep morphological structures, this method can be utilized to increase the depth dependent fall-off in samples with limited thickness. Thus, the proposed bidirectional imaging modality is apt for cross-sectional imaging of entire samples, which has the potential capability to improve the diagnostic ability.

We have demonstrated the application of optical coherence tomography (OCT) in diagnosis of growth and spread of the gray leaf spot disease inCapsicum annuumleaf caused by the fungusStemphylium lycopersici. Using 2D cross-sectional and 3D volumetric images of OCT,in vivostudy of layer differences between fungus infected leaves and healthy leaves was observed with distinctive features. We observed that the internal layers of the disease-affected parts of the leaf seem to merge forming a single thick layer. The obtained OCT results verify the noninvasive diagnosis ability of fungal growth and spread inCapsicum annuumleaves and the applicability of this methodology for other plant diseases.

An application of spectral domain optical coherence tomography (SD-OCT) was demonstrated for a fast industrial inspection of an optical thin film panel. An optical thin film sample similar to a liquid crystal display (LCD) panel was examined. Two identical SD-OCT systems were utilized for parallel scanning of a complete sample in half time. Dual OCT inspection heads were utilized for transverse (fast) scanning, while a stable linear motorized translational stage was used for lateral (slow) scanning. The cross-sectional and volumetric images of an optical thin film sample were acquired to detect the defects in glass and other layers that are difficult to observe using visual inspection methods. The rapid inspection enabled by this setup led to the early detection of product defects on the manufacturing line, resulting in a significant improvement in the quality assurance of industrial products.

We demonstrate that optical coherence tomography (OCT) is a plausible optical tool for in vivo detection of plant seeds and its morphological changes during growth. To investigate the direct impact of salt stress on seed germination, the experiment was conducted using Capsicum annuum seeds that were treated with different molar concentrations of NaCl. To determine the optimal concentration for the seed growth, the seeds were monitored for nine consecutive days. In vivo two-dimensional OCT images of the treated seeds were obtained and compared with the images of seeds that were grown using sterile distilled water. The obtained results confirm the feasibility of using OCT for the proposed application. Normalized depth profile analysis was utilized to support the conclusions.