Yao-chun Shen

• PhD
• Professor at University of Liverpool

Purpose To investigate central Bowman’s layer thickness (BT) in relation to central corneal thickness (CCT) and curvature, and epithelial thickness in healthy and disease corneas. Methods Patients with keratoconus (KC), corneal dystrophies (CD) and healthy controls (HC) were included. Linnik and Mirau versions of an ultra-high axial resolution lin...

Background Alzheimer’s disease (AD) is a major healthcare challenge, with existing diagnostics being costly/infeasible. This study explores retinal biomarkers from optical coherence tomography (OCT) and OCT angiography (OCTA) as a cost-effective and non-invasive solution to differentiate AD, mild cognitive impairment (MCI), and healthy controls (HC...

The applications of Optical Coherence Tomography (OCT) systems have been extensively explored in clinical settings and have attracted growing interest in other fields. Factors such as speed and cost are often prioritized over high resolution and power efficiency in industrial applications. Modern OCT systems typically operate at speeds between 20k-...

Optical coherence tomography (OCT) is a nonintrusive optical imaging method offering micrometer-scale spatial resolution, enabling the generation of internal structural cross-sectional images. Since the first OCT was invented in the early 1990s, its utilization has become prevalent in the field of ophthalmology and has become one of the golden stan...

Optical Coherence Tomography (OCT) is a growing family of biophotonic imaging techniques, but in the literature there is a lack of easy-to-use tools to universally directly evaluate a device’s theoretical performance for a given metric. Modern computing tools mean that direct numerical modeling can, from first principles, simulate the performance m...

Purpose To investigate the central thickness of Bowman’s layer in patients with keratoconus, healthy cornea and other corneal conditions in relation to corneal curvature and, epithelial and total corneal thickness in health, keratoconus (KC) and Fuchs’ endothelial corneal dystrophy (FED). Methods Patients with keratoconus, FED and other dystrophie...

We provide a full solution for creating 3D models using a 100k Hz A-line rate line-field OCT system. The generated models have a 50-fold reduction of data size and can be exported for AR/VR and 3D printing.

For OCM to replace IVCM as a screening tool for DPN, the equivalent nerve en-face projection needs to be displayed in real time. Here we show it can be done with a moderate spec CPU.

Background Traditional methods for diagnosing dementia are costly, time-consuming, and somewhat invasive. Since the retina shares significant anatomical similarities with the brain, retinal abnormalities detected via optical coherence tomography (OCT) and OCT angiography (OCTA) have been studied as a potential non-invasive diagnostic tool for neuro...

Fourier domain optical coherence tomography (FD-OCT) is a well-established imaging technique that provides high-resolution internal structure images of an object at a fast speed. Modern FD-OCT systems typically operate at speeds of 40,000–100,000 A-scans/s, but are priced at least tens of thousands of pounds. In this study, we demonstrate a line-fi...

Unlabelled: *Correspondence, Stephen Kaye: s.b.kaye@liverpool.ac.uk PURPOSE: To assess the accuracy, repeatability, and performance limits of in vivo Mirau ultrahigh axial resolution (UHR) line field spectral domain (LF-SD) optical coherence tomography (OCT) for the clinical in vivo measurement of Bowman's layer thickness in subjects with and with...

Cerebral malaria (CM) remains a significant global health challenge with high morbidity and mortality. Malarial retinopathy has been shown to be diagnostically and prognostically significant in the assessment of CM. The major mechanism of death in paediatric CM is brain swelling. Long term morbidity is typically characterised by neurological and ne...

3D objects with integrated electronics are produced using an additive manufacturing approach relying on multiphoton fabrication (direct laser writing, (DLW)). Conducting polymer‐based structures (with micrometer‐millimeter scale features) are printed within exemplar matrices, including an elastomer (polydimethylsiloxane, (PDMS)) have been widely in...

It is particularly important to make quality evaluation for paint spraying process. This work presented an efficient method based on wavelet packet energy for terahertz non-destructive evaluation of organic protective paint. The wavelet packet energy analysis algorithm was summarized. Various coating structures were experimentally investigated usin...

Terahertz (THz) technology has firmly established itself as an effective sensing and nondestructive testing technique for the detection of substances and physico-chemical evaluation of materials and structural systems since its first emergence almost three decades ago. To date, both the effectiveness and accuracy of this technology have been extens...

The line field (LF) design choice for the lateral image formation mechanism (lateral format) has historically been a fraction of the whole optical coherence tomography (OCT) field. However, as the OCT technology develops, the parallelised acquisition of LF-OCT formats (LF-time domain (TD)-OCT, LF-spectral domain (SD)-OCT, LF-swept source (SS)-OCT)...

Reliable and contactless measurements of vital signs, such as respiration and heart rate, are still unmet needs in clinical and home settings. Mm-wave radar and video-based technologies are promising, but currently, the signal processing-based vital sign extraction methods are prone to body motion disruptions or illumination variations in the surro...

Terahertz (THz) technology is probably best known to the public as a powerful tool for imaging, since it has been applied in security and medical scanning, resulting in numerous impressive images that would be unobtainable using other technologies. With the roll-out of 5G mobile networks, research into 6G wireless communications is heating up. It i...

Purpose: The purpose of this study was to assess the accuracy, repeatability, and performance limits of in vivo Mirau ultrahigh axial resolution (UHR) line field spectral domain (LF-SD) optical coherence tomography (OCT) for the measurement of Bowman's and epithelial thickness, and to provide a reference range of these values for healthy corneas....

Seed germination and uniform plant stand in the field are the most critical crop growth stages determining the final yield. Pea (Pisum sativum L.) seeds production is often hampered due to the seed dormancy caused by the hard seed coat. Such effect is mainly attributed to poor or uneven germination and unsynchronised seedling emergence. Understandi...

In-line terahertz pulsed imaging has been utilized to measure the film coating thickness of individual tablets during the coating process in a production-scale pan coater. A criteria-based waveform selection algorithm (WSA) was developed to select terahertz signals reflected from the surface of coating tablets and determine the coating thickness. S...

Reliable and contactless measurements of vital signs, such as respiration and heart rate, are still an unmet need in clinical and home settings. Mm-wave radar and video-based technologies are promising, but currently, the signal processing-based vital sign extraction methods are prone to body motion disruptions or illumination variations in the sur...

The repetitive electrical-thermal-mechanical deformation causes bonding wires failures that can damage whole power electronic modules. The LF-OCT can measure electrical-thermal-mechanical deformation on a bonding wire's loop, which can help the reliability analysis of bonding wires.

Terahertz metamaterial sensing (TMS) is a new interdisciplinary technology. A TMS system employs terahertz waves as the pumping source, these then interact with the sample and carry the substance information, e.g., refractive index, absorption spectra. These properties are relevant to the molecular rotation and vibration states produced by a surfac...

Echocardiography is an essential diagnostic method to assess cardiac functions. However, manually labelling the left ventricle region on echocardiography images is time-consuming and subject to observer bias. Therefore, it is vital to develop a high-performance and efficient automatic assessment tool. Inspired by the success of the transformer stru...

Mm-wave radar and video-based technologies have shown potentials for contactless detection of vital signs. However, state-of-the-art signal processing based vital sign extraction methods are prone to disruptions, such as motion corruption. In this work, we propose a novel graph-based segmentation algorithm for improved accuracy and robustness. We a...

As a non-destructive method, spectral-domain optical coherence tomography (OCT) has already been adapted to study seed samples. SD-OCT provides a set of capabilities in terms of millimetre-scale penetration depth, high-speed acquisition, and resolution typically in the range of ten microns. It has been therefore gaining popularity in this specific...

We proposed a tunable terahertz (THz) broadband absorber using monolayer MoS2 patterned with subwavelength Ring-Cross array. The combination of MoS2 micro-ring and MoS2 micro-cross exhibits excellent broadband absorption properties which can be continuously tuned by controlling the bias voltage to regulate the carrier concentration of MoS2. Detaile...

Bonding wires are one of the most failure-prone component of power electronics modules (PEMs), and silicone gel is usually employed to encase bonding wires. To study the deformation of silicone gel-encased bonding wires, in this paper we report the use of line-field optical coherence tomography (LF-OCT) technique to precisely measure the electrical...

For any single anterior chamber cross-sectional (tomographic) imaging method, there is a practical compromise between image size and image resolution. In order to obtain large field-of-view cross-sectional images of the whole anterior chamber and high-resolution cross-sectional images of the fine corneal layers, measurements by multiple devices are...

Complementary split-ring resonator (CSRR) metasurfaces present interesting applications in terahertz biosensing. Indium tin oxide (ITO) is an essential optoelectronic material because of its optical transparency, high conductivity, and good stability. In this letter, we innovatively suggest that ITO-based CSRR metasurfaces can excite multi-peaks re...

We report a broadband terahertz time-domain spectroscopy (THz-TDS) which enables twenty vibrational modes of adenosine nucleoside to be resolved in a wide frequency range of 1–20 THz. The observed spectroscopic features of adenosine are in good agreement with the published spectra obtained using Fourier transform infrared spectroscopy (FTIR) and Ra...

We proposed a method for driving metal nanoparticles in the focal field by cylindrical metalens with phase gradient. It was found that the introduced gradient phase would not affect the formation of the focal line, where metal nanoparticles can be trapped. While being driven along the direction with the phase gradient, Ag nanoparticles with differe...

Terahertz (THz) plasmonic sensors has been regarded as exciting advances in biomedical engineering, due to their real-time, label-free, and ultrasensitive monitoring features. But actually, its widespread application remains impeded by poor modulation properties of operating frequency, single amplitude characterization method, and limited to low-lo...

Terahertz radiation (0.1 THz-10 THz) has attracted tremendous attention because of its miraculous properties, which have inspired broad applications in communication, imaging, astrosurveillance, and national defense applications, especially in sensing and diagnosis. In the last ten years or so, terahertz sensing and diagnosis have become a very dyn...

We report a broadband terahertz time-domain spectroscopy (THz-TDS) which enables twenty vibrational modes of adenosine nucleoside to be resolved in a wide frequency range of 1-20 THz. The observed spectroscopic features of adenosine are in good agreement with the published spectra obtained using Fourier Transform Infrared Spectroscopy (FTIR) and Ra...

This paper reports the development of a new technique, free space line field spectral domain optical coherence reflectometry (LF-SD-OCR), which is able to produce tomographic like (quasi) images. Furthermore, the capabilities and cost benefits of the technique are demonstrated by constructing a handheld LF-SD-OCR device. For glossy paint systems an...

Terahertz pulsed imaging (TPI) was introduced approximately fifteen years ago and has attracted a lot of interest in the pharmaceutical industry as a fast, non-destructive modality for quantifying film coatings on pharmaceutical dosage forms. In this topical review, we look back at the use of TPI for analysing pharmaceutical film coatings, highligh...

We report a high-resistivity silicon (HR-Si) prism coupled terahertz (THz) spoof surface plasmon polaritons (SSPPs) on flat subwavelength metasurface. Using a high refractive index prism as an external coupler, a more tightly confined SSPPs mode can be excited in a smaller resonant cavity, leading to strong light-matter interaction. Besides, theore...

A highly reliable three-dimensional network structure joint was fabricated based on Cu/Ni/Sn powder with double-layer coatings and transient liquid phase bonding (TLPB) technology for high temperature application. The Cu/Ni/Sn joint is characterized by Cu metal particles embedded in the matrix of (Cu,Ni) 6 Sn 5 /Ni 3 Sn 4 intermetallic compounds (I...

We experimentally demonstrated a corrugated metallic metasurface based tunable perfect absorber for terahertz (THz) frequencies in a total internal reflection geometry. The absorbance is strongly depend on the central layer of this three-layer absorber, which provides a feasible approach to tune the absorption. In particular, there exist an optimal...

Based on the focusing feature of a metalens, we numerically studied its application in optical manipulation of Rayleigh particles. Three types of metalenses—point focusing, line focusing, and line focusing with phase gradient—were designed. Simulation results using the finite-difference time-domain method showed that the incident optical beams coul...

A highly reliable three-dimensional network structure joint was fabricated based on Cu@Ni@Sn core-shell powder and transient liquid phase bonding (TLPB) technology for high temperature application. Cu@Ni@Sn joint is characterized by Cu metal particles embedded in the matrix of (Cu,Ni)6Sn5/Ni3Sn4 intermetallics (IMCs), low level of voiding is achiev...

Optical coherence tomography (OCT) has recently been demonstrated as a powerful tool to image through pharmaceutical film coatings. Majority of the existing systems can, however, resolve film coatings for thickness greater than 10 µm. Here we report on an ultra-high-resolution (UHR) OCT system, with 1 µm axial and 1.6 µm lateral resolutions, which...

In the laundry industry, colorimetry is a common way to evaluate the stain removal efficiency of detergents and cleaning products. For ease of visualization, the soiling agent is treated with a dye before measurement. However, it effectively measures the dye removal rather than stain removal, and it cannot provide depth-resolved information of the...

There has been a lot of interest in accurately characterising corneal biomechanical properties under intraocular pressure (IOP) to help better understand ocular pathologies that are associated with elevated IOP. This study investigates the novel use of Line-Field Optical Coherence Tomography (LF-OCT) as an elastographic tool for accurately measurin...

Both the instantaneous rotational speed (IRS) and vibration of a rotating shaft are key information for condition monitoring and faults diagnosis of rotary machinery. Instead of using a rotational speed encoder and a displacement sensor to measure the IRS and the vibration of a rotating shaft, a non-projection fringe pattern and vision-based system...

Faults may be generated in power networks as a result of bad weather, human activities or some other factors. The complex structure of power network adds to the difficulty of fault location (FL). This paper presents a novel FL scheme by utilizing the information of the time differences of arrival (TDOAs) of modal traveling waves (MTWs) asynchronous...

A novel approach was presented to enhance the capability of resolving thin coating layers using terahertz pulsed imaging (TPI) based on a neural network-based hybrid signal procession method, which is of great significance for in-line painting applications. In the present work, Terahertz detected signals were obtained by numerical simulation using...

The phase behavior of the reflected terahertz radiation (THz) under surface plasmon resonance (SPR) supported by doped graphene has been comprehensively investigated. For a TM–polarized wave, the dependence of the phase on the angle of incidence has a region with an abrupt jump–like change. We found in particular that the resonance phase dependence...

Optical coherence tomography (OCT) has recently attracted a lot of interest in the pharmaceutical manufacturing industry as a fast, contactless and non-destructive modality for quantifying thin film coatings on pharmaceutical dosage forms, which cannot be resolved easily with other techniques. In this topical review, we present an overview of the r...

In medical imaging, high-resolution can be crucial for identifying pathologies and subtle changes in tissue structure. However, in many scenarios, achieving high image resolution can be limited by physics or available technology. In this paper, we aim to develop an automatic and fast approach to increasing the resolution of Optical Coherence Tomogr...

In recent years, terahertz in-line sensing has been used to monitor the film coating thickness of individual pharmaceutical tablets during the coating process. In the previous work, the in-line measurements were verified against off-line measurements of samples from the same population. Here, we report on our recent progress to further verify the v...

We proposed a terahertz (THz) surface plasmon resonance (SPR) sensor with Kretschmann coupling configuration with buffer layer covered substrate containing doped monolayer graphene (MLG) directly deposited onto the coupling prism. The performance of the SPR sensor in terms of detection accuracy, sensitivity and figure of merit (FOM) were investigat...

Optical coherence tomography (OCT) can monitor human donor corneas non-invasively during the de-swelling process following storage for corneal transplantation, but currently only resultant thickness as a function of time is extracted. To visualize and quantify the mechanism of de-swelling, we present a method exploiting the nanometer sensitivity of...

Blur is a significant problem in medical imaging which can hinder diagnosis and prevent further automated or manual processing. The problem of restoring an image from blur degradation remains a challenging task in image processing. Semi-blind deblurring is a useful technique which may be developed to restore the underlying sharp image given some as...

Blood pressure is an important index to measure the function of human cardiovascular system. In order to solve the problem of non-invasive continuous measurement of blood pressure in electronic sphygmomanometer, a noninvasive blood pressure measurement method based on EEMD (ensemble empirical mode decomposition) and ANN (artificial neural networks)...

Automotive coating systems are designed to protect vehicle bodies from corrosion and enhance their aesthetic value. The number, size and orientation of small metallic flakes in the base coat of the paint has a significant effect on the appearance of automotive bodies. It is important for quality assurance (QA) to be able to measure the properties o...

As the urban population is increasing, more and more cars are circulating in the city to search for parking spaces which contributes to the global problem of traffic congestion. To alleviate the parking problems, smart parking systems must be implemented. In this paper, the background on parking problems is introduced and relevant algorithms, syste...

Optical coherence tomography (OCT) has recently been demonstrated to measure the film coating thickness of pharmaceutical tablets and pellets directly. The results enable the analysis of inter- and intra-tablet coating variability at an off-line and in-line setting. To date, only a few coating formulations have been tried and there is very little i...

The measurement of the thicknesses of layers is important for the quality assurance of industrial coating systems. Current measurement techniques only provide a limited amount of information. Here, we show that spectral domain Line Field (LF) Optical Coherence Tomography (OCT) is able to return to the user a cross sectional B-Scan image in a single...

Spectral domain optical coherence tomography (SD-OCT) has recently attracted a lot of interest in the pharmaceutical industry as a fast and non-destructive modality for direct quantification of thin film coatings that cannot easily be resolved with other techniques. While previous studies with SD-OCT have estimated the intra-tablet coating uniformi...

We present in-line coating thickness measurements acquired simultaneously using two independent sensing modalities: terahertz pulsed imaging (TPI) and optical coherence tomography (OCT). Both techniques are sufficiently fast to resolve the coating thickness of individual pharmaceutical tablets in-situ during the film coating operation and both tech...

We have experimentally observed the steady rotation of a mesoscopic size metallic particle trimer that is optically trapped by tightly focused circularly polarized optical vortex. Our theoretical analysis suggests that a large proportion of the radial scattering force pushes the metallic particles together, whilst the remaining portion provides the...

We present in-line coating thickness measurements acquired simultaneously using two independent sensing modalities: terahertz pulsed imaging (TPI) and optical coherence tomography (OCT). Both techniques are sufficiently fast to resolve the coating thickness of individual pharmaceutical tablets in-situ during the film coating operation and both tech...

A novel spinning disk approach is reported, to achieve video-rate compressive imaging at infrared (IR) and terahertz (THz) frequencies. It uses a 200-mm-diameter circular stainless steel disk with a number of chemically etched 2-mm-diameter holes as a spatial light modulator (SLM). The authors demonstrate that this mechanical SLM is well suited for...

Spectral domain optical coherence tomography (SD-OCT) has recently attracted a lot of interest in the pharmaceutical industry as a fast and non-destructive modality for direct quantification of thin film coatings that cannot easily be resolved with other techniques. While previous studies with SD-OCT have estimated the intra-tablet coating uniformi...

Parking in major cities, particularly with dense traffic, directly effects the traffic flow and people's life. In this paper, we introduce a new smart parking system that is based on intelligent resource allocation, reservation, and pricing. The proposed system solves the current parking problems by offering guaranteed parking reservations with the...

Terahertz imaging based on compressed sensing concept provides an opportunity for high-efficient terahertz imaging solution. In this paper we will first provide a general overview of terahertz imaging technology, and then focus specifically on the experimental implementations of high speed and high-resolution terahertz imaging based on compressed s...

We proposed a vertically-oriented dimer structure based on focused plasmonic trapping of metallic nanoparticle. Quantitative FDTD calculations and qualitative analysis by simplified dipole approximation revealed that localized surface plasmon coupling dominates in the plasmon hybridization, and the vertically-oriented dimer can effectively make use...