This PDF file contains the front matter associated with SPIE Proceedings Volume 12608, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

All-optical ultrasound imaging has emerged as paradigm that is well-suited to highly miniaturized applications. With this technique, ultrasound is both generated and received using light, allowing the use of optical fibres for device fabrication. Ultrasound generation typically requires multimode light delivery to provide the pulse energies needed for high pressure generation. Whilst ultrasound reception typically requires single mode light delivery to provide high sensitivity. This means that devices have typically comprised two optical fibres, one multimode for ultrasound generation and one single mode for ultrasound reception. Recently, we demonstrated an all-optical ultrasound imaging device based on a single dual-clad optical fibre. In this work, we build on our previous study and demonstrate rotational imaging with this device. Two copper wire phantoms were imaged, and the wire were well-resolved, demonstrating a signal-to-noise >20 dB. The presented device and system are well-suited for use in minimally invasive and intravascular imaging applications and future work will focus on translating the device.

In this work, an innovative noninvasive nickel wire-gated FET glucose sensor with and without graphene film as an intermediate layer was investigated. According to the redox reactions between nickel nanowires and glucose molecules in weak alkaline solutions, electron exchange occurs when Ni (III) reacts with glucose to form Ni (II) and glucolactone. However, the generated electrons are usually neutralized prematurely due to material defects. This study investigates the electrical effects of using graphene as an intermediate layer between Ni nanowires and gate metal. Compared with the glucose FET sensor using nickel nanowires alone as the gate metal, due to the good electrical conductivity of the graphene film under the nickel nanowires in the gate area, the electrons generated by the nickel nanowires catalyzing glucose molecules can quickly dispersed on the metal surface via the graphene film, which will enhance the change of the gate potential, and the sensitivity of the FET glucose detector is further improved. This experiment shows that the detection limit of a transistor-based glucose detector with a nickel nanowire gate is 551.2 μM and 51 nM, respectively, without and with graphene as an intermediate layer.

The proposed mid-infrared passive spectroscopic imager could measure blood glucose levels of internal bodies from a distance. In this report, we distinguished blood vessel areas and interstitial fluid areas in accordance with time-response differences. Freestyle Libre measures blood glucose levels in interstitial fluid. Thus, the measured value has time delay around 10 min compared with the conventional blood collection type. In accordance with correlation coefficients of radiation value, whose wavelength was 9.65μm, we identified these two areas at every pixel.

We had already reported that blood glucose levels of internal bodies were able to be measured by the proposed mid-infrared (LWIR: 8-14μm) passive spectroscopic imager from a distance. The mid-infrared passive spectroscopic imager, whose sensitivity is very high because of the proposed multi-slit array technology, is able to detect and analyze radiations from body heats. Expanding the wavelength region to 3 to 20μm will realize the measurement of lactic acids and ketone bodies. Lactic acid levels, whose emission peak are 5.65μm etc., are an indicator of fatigue. Ketone bodies, whose emission peak are 4.65μm etc., are an indicator of metabolic effects of dieting. On the other hand, transmission type lens requires AR(Anti-reflection) coating whose band pass is theoretically narrow around 8 to 14μm. But our passive spectroscopic imager is able to be constructed by the wavelength-independent reflection optics. In this report, we mentioned the broad band, whose wavelength was 3 to 20μm, reflective optics spectroscopic imager using free-form mirror lens units (provided by NALUX Co., Ltd.) with a micro-bolometer array sensor.

We propose a new low coherence digital in-line holographic microscope (DIHM) system to accurately obtain the three-dimensional (3D) position of the nanoparticle. The two low coherence digital in-line holograms of the nanoparticle are recorded with two respective illumination angles of the light source. The reconstruction process is carried out with two holograms at different distances to calculate the diffraction images. The 3D position of the nanoparticle can be determined by the diffraction distance where two diffraction images of the nanoparticle form the smallest overlap area. The method can be employed to accurately track the position of the nanoparticles without pre-preparation nanoparticle pattern and also not depending on the structure of the nanoparticle.

Real-time physiological monitoring is a real challenge due to physical activity to directly disturb photoplethysmography (PPG) based physiological monitoring. Opto-physiological monitoring (OPM) to evolute Beer-Lambert driven PPG, has been well generating a new multi-wavelength optoelectronic patch sensor (mOEPS) to overcome drawbacks of present PPG sensors causing from gravity, balance, skin tone, thermoregulation, and contact force that are highly conducted with hemodynamic processes. A specific configuration of mOEPS has been well defined to enable OPM engineering realization and to generate a multi-spectral imaging of various opto-physiological variations. Together bespoke electronics with embedded algorithms of minimum residual (MR) signal processing, mOEPS delivers a high standard physiological monitoring and assessment in real time and at any time. One physical activity protocols engaged with 12 subjects have been implemented with mOEPS system together with its real time MR. The MA-free pulsatile signals obtained through mOEPS system enables to calculate HR and respiration rate (RR) to 1.44 beat/min and 2.85 breath/min respectively for in-house datasets. Oxygen saturation (SpO₂%) levels calculated from MR are consistent with the expected values of ≥ 95% and the Pearson correlation (R) for HR and RR are 0.99 and 0.91 respectively. The outcomes demonstrate mOEPS system is capable of real-time and anytime physiological monitoring at physical states. The coming mOEPS validation against golden standards will be performed to prove a prospective wearable system for clinical grade monitoring and assessment in a continuous physiological status.

We propose a new single-shot highly accurate digital holography technique using a single image sensor. The signal light passes through a rhombic low pass filter optical element, and the optical axis of the reference light is slightly tilted. The interference fringe of the signal and reference light is captured by the image sensor. In the computer, the signal intensity only used in the calculation process is calculated by the original three-step algorithm that can cancel the effect of a linear signal phase in adjacent pixels. The Fourier plane of the signal component obtained by subtracting the signal and reference intensity consists of the real and imaginary parts of the signal light inside and outside the rhombic region, respectively. The complex amplitude consisting of the real and imaginary parts is the reconstruction image of signal light that passed the rhombic low pass filter. The complex amplitude includes noise, so the additional process of the noise suppression is applied and improves measurement accuracy. After the process, the final reconstruction image is obtained. To confirm the operation principle, numerical analysis is conducted. In numerical analysis, the SNRs of the reconstructed intensity and phase in this method were 9.34 and 4.18 dB higher than the two-step parallel method, respectively, and 12.12 and 6.21 dB higher than Fourier fringe analysis, respectively.

Parkinson's disease is a progressive neurodegenerative disease that leads to decreased secretion of nigrostriatal dopamine, which inhibits the activity of the brain's motor cortex, Deep brain stimulation (DBS) is currently the best treatment for patients who do not respond well to drug therapy. The subthalamic nucleus (STN) is the target area for the implanting deep brain electrical stimulation electrodes. Currently, the surgical navigation for DBS depends on pre-operative CT/MRI and intra-operative MER (microelectrode recording) to know whether the electrode has reached the target area, but MER only has non-directional signals. In this project, we developed Optical Coherence Tomography-guided DBS (OCTgDBS) technology, which can obtain real-time, high-resolution images from miniature pig brain, which can assist in the accuracy of navigation and positioning during DBS surgery. Finally, postoperative CT/MRI was used as the basis for positioning in the brain. The results demonstrate that the OCT has a potential to be optical guidance system for DBS.

We developed a one-shot passive Fourier spectrometer to integrate with wearable devices for non-invasive blood glucose measurements. The apparatus was designed with a N.A. of 0.77 for passive spectroscopy of the living body. The field curvature due to the increased N.A. was improved by combining an imaging lens with a phase shifter. Because the apparatus was configured with two lenses, the transmission was high and the optical axis length was 14 mm. In addition, the apparatus was equipped with a multi-slit to prevent loss of interference sharpness. The multi-slit was designed with 5 lines with aperture patterns that enabled the detection of glucose. We measured a blackbody to evaluate the apparatus.

The use of prior knowledge is important for effective phase retrieval in biological imaging using coherent light. We design a new algorithm based on alternating direction method of multipliers (ADMM), where physical constraints in the imaging system are used as prior knowledge. Experimental results where we apply the method on a masked coherent diffractive imaging (CDI) system show the efficiency of our algorithm.

The objective of this study is to visualize tooth hardness by mid-infrared passive spectroscopic imaging with an imaging type 2D Fourier spectrometer. Radiated light in the mid-infrared region (wavelength of approximately 10 μm) is radiated from the surface of an object with a radiation intensity that depends on the temperature of the object. Our proposed device has a multi-slit grating that prevents the cancellation of bright spots. The multi-slit grating enables an inexpensive uncooled microbolometer array sensor to acquire two-dimensional spectral information from the radiated light of the measured target without external irradiation. Because the intrinsic vibration of the molecule itself is detected in this case, the spectral characteristics are the radiation spectra due to the intrinsic vibration peak. Wavelengths that can be confirmed as absorption in active spectroscopy can be confirmed as radiation in passive spectroscopy, resulting in a negative-positive relationship. First, we measured bovine teeth with our spectrometer. A radiation peak assigned to hydroxyapatite, the main component of teeth, was detected. Next, to obtain the relationship between the tooth hardness and spectrum, the micro-Vickers hardness of the tooth surface was measured. By peak deconvolution, we found a negative correlation between the hardness and peak area ratio of the crystalline and amorphous hydroxyapatite phases. The results of this study will be used in the future for non-invasive and simple risk prediction of caries formation.

We propose a method to realize parallel two-step phase-shifting digital holography with a single exposure. In the proposed method, the intensity distribution of the reference wave is derived from a single hologram recorded by parallel four-step phase-shifting digital holography. By using the derived intensity distribution of the reference wave, the numerical processing used in two-step phase-shifting digital holography is applied to each pair of two phase-shifted holograms derived from the single hologram. We numerically verified that the proposed method can obtain the complex amplitude of an object wave with a single exposure. In addition, we found that the proposed method can improve the quality of the amplitude image in comparison to parallel four-step phase-shifting digital holography.

Optical coherence elastography (OCE) is a promising and efficient technique to investigate the mechanical properties of biological tissues. We demonstrate an elastographic platform by imaging surface wave propagation on tissue phantoms using reflection-mode holographic imaging.

For straight perm, the microscopic mechanism is still unclear, especially for changes in the secondary structure of the protein of the hair. Expecting to find a better condition for the straight perm treatment, we made the research on grey hair using the Raman imaging technique and principal component analysis (PCA). We succeeded to detect changes in different secondary structures such as β-turn and α-helix and to visualize their distributions.

Raman research on black colored hair has been limitedly reported, because (i) the laser incident frequently burns and destroys the hair; (ii) Raman bands of melanin are much larger and broader, overlapped with the other hair originated Raman signals, which stopped Raman hair analysis. Here, we realized a versatile bio-Raman hair analysis including black colored hair system, (i) by fabricating a semi ultrathin cross section with the thickness of 500 nm of black hair using an ultramicrotome; (ii) by separating the signal of melanin from that of other hair components using the automatic background removal method that recently we developed.

We used mid-infrared passive spectroscopic imaging to monitor the composition of components during the fermentation of sake, and to measure the infrared emission peak of glucose of a fruit (Muscat grapes). Monitoring the composition of sake components during fermentation requires the separate analysis of the liquid and gaseous components. In this report, we propose a measurement method for monitoring the liquid and gas components during the sake fermentation process. The proposed method was used to analyze two-dimensional spectral data obtained on site at a sake brewing plant, and the results on the absorption coefficient of ethanol and the luminous intensity of glucose were confirmed by FTIR. Measurements the infrared emission peak of glucose of fruit were also made using passive spectroscopic imaging.

The scalp-cortex correlation (SCC) is important for the brain activity measurements by functional near-infrared spectroscopy. A physical head surface model was manufactured to accurately determine the probe positions mounted on the probe holder attached to the head. The coordinates of the probe positions measured in the physical space were mapped to the surface of the virtual head model. The light propagation in the virtual head model was calculated to obtain the spatial sensitivity profile and normalized partial optical path length for the evaluation of the SCC.

We have developed the method for image detection of thrombus in artificial blood flow using laser light scattering patterns. We experimentally discuss the spatial and temporal intensity change in light scattering patterns in relation to the degree of formation of thrombus under illumination of a laser diode. Experimental results show the feasibility of the present method for in vitro monitoring of the growth of thrombus in artificial blood flow.

Glioblastoma (GBM) is the most aggressive malignant primary brain tumor[1]. Effective treatments on the early-stage glioblastoma may improve its poor survival rate and poor prognosis[2]. In this pilot study, a low copy number of nucleic acid detection system using a high-throughput microfluidic droplet imaging device was developed to achieve the specific nucleic acid detection of extracellular vesicles (EVs). Our aim is to realize an inexpensive liquid biopsy tool for the early detection of GBM using human plasma and cerebrospinal fluid (CSF). Our results demonstrate that: (a) the fabricated microfluidic chip (10 mm × 25 mm) can produce more than 25,000 droplets within 3 minutes. The average volume of generated droplets is 0.043 nanoliter (nL); (b) the entire droplet image can be acquired within 15 seconds without using the conventional stitching technique; (c) additionally, we automated the droplet image processing to determine the absolute copy number and concentration of nucleic acid samples. This portable IoT-integrated digital droplet nucleic acid sensing system provide an inexpensive and affordable optical biopsy screening tool for the early diagnosis and treatment surveillance of brain tumors. Our work can be applied into other diseases, such as colorectal cancer, pancreatic cancer and breast cancer.

Digital droplet analysis divides a liquid biopsy sample into twenty-five thousand of nanoliter beads. Specific molecular recognition and amplification reactions are spaced into each droplet. To achieve sensitive molecular detection, we need to group droplets by different fluorescent colors and count the number of sorted beads. To expedite the entire molecular omic data analysis, we use Roboflow to label positive/negative droplets, and train the labeled images through several YOLOv5 models. We are developing and integrating an efficient droplet identification method into a point-of-use Raspberry Pi bead imaging device for counting the copy number of specific gene expression in biofluids. We particularly focus on the specific gene expression on extracellular vesicles of a malignant brain tumor.

5-ALA (5-aminolevulinic acid) administration for positioning tumor tissues in craniotomy is growing since the FDA approval has already passed in June 2017 [1]. This may also open a path to the convenient single extracellular vesicle (EV) analysis in liquid biopsy for tracking and analyzing the tumor-derived EVs with PPIX expression, the middle byproduct upon the oral intake of 5-ALA. 5-ALA-based fluorescence is due to preferential accumulation of the fluorophore protoporphyrin-IX (PpIX) in the malignant glioma tissue. Single EV analysis has become technically feasible and promising in studies of early cancer diagnosis and clinical translational medicine applications [2]. It can minimize the heterogenous issue between EVs once capturing a group of low percentage biomarker-positive EVs. There is a need to scale up and implement an easy-to-use single EV analysis platform to be organized into the routine practices of current research and clinical laboratories to enable early cancer diagnostics. We are combining the 5-ALA dyed EV samples with single EV detection method to establish a more efficient and precise approach for patient’s early cancer diagnosis.

Development of liquid biopsies for non-invasive tumor characterization techniques shows a great promise for real-time monitoring of tumor recurrence, progression, and treatment response. To better assess the various tumor evolution, cellular heterogeneity, consequent drug-resistance mechanisms, it is critical to screen specific proteins and nucleic acids from biofluid-derived extracellular vesicles (EVs). We are developing a rapid integrated ultra-sensitive digital bead-based sensor enabling evaluation of molecular profiling of EVs in glioblastoma (GBM). The tumor relevant nucleic acid information in EVs is enriched by antibody-specific magnetic beads and amplified by reverse transcription recombinase polymerase amplification using the CRISPR/Cas13a system with around twenty-five thousand droplets. Detection results are analyzed by a miniaturized portable imaging device. The niches of our developing technique include: (a) the streamlined sample preparation process and miniaturized detection system enable the sensitive detection of important mRNAs, EGFR, EGFRvIII, IDH1wt, IDH1 R132H and GAPDH, in EVs within 1.5 hours; (b) the fluorescent signal-to-noise ratio (SNR) in each micrometer sized droplet is significantly enhanced via using a simple Cas13a assay and triggering greater than 104 turnovers of fluorescent reporters on a high-throughput microfluidic chip; (c) real-time image data are transferred to a cloud-based server and classified using several trained YOLOv5 models; (d) the RNAomics results are displayed on the Raspberry Pi touchscreen. This approach improves the speed of GBM diagnosis and treatment decision-making in using liquid biopsy.

A volumetric beam shaping is applied to sophisticated and functional laser processing. It is performed with a computer-generated hologram displayed on a liquid-crystal spatial light modulator. The design parameters are optimized.

Light-sheet microscopy enables rapid 3D imaging of biological samples. Its field-of-view can be extended ten-fold by relying on propagation-invariant Airy beams. However, such beams propagate on a parabolic trajectory. By consequence, a light-sheet formed by Airy beams is not planar, thus warping the images. Here, we demonstrate a planar Airy light-sheet that does not rely on digital image restoration techniques for two-photon microscopy.

In mathematically the method of tomographic image reconstruction from projection can be formulated by the Fredholm integral equation of the first kind. It is necessary to solve the equation. But it is difficult in general to seek the strict solution. By discretizing the image reconstruction problem, we applied Image Space Reconstruction Algorithm (ISRA) to the problem and evaluated the image quality. We computed the normalized mean square error (NMSE) in reconstructed image. We have showed that the error decreases with increasing the number of detectors, views and iterations. Also, we have showed the effect of the relaxation parameter and the noise to the reconstructed image.

In this paper, we discuss use of polarization correlations, particularly Stokes parameters (SPs) correlations, in the design and development of new holographic methods.

We developed a lens-less vascular endoscope that uses local wavefront control to observe the inside of narrow blood vessels and vessels with a small radius of curvature. The endoscope uses a spatial phase modulator to control beam scanning by manipulating the local wavefront of the laser beam. To achieve beam focusing, the spatial phase modulator requires many phase patterns. To increase the number of focusing beam patterns, this study used 1-bit (binary) control for each cell value of the spatial phase modulator. The study experimentally investigated the characteristics of the focusing beam, including the beam pattern and the spatial resolution associated with beam scanning.

Saturated-excitation (SAX) microscopy can provide theoretically unlimited improvement of spatial resolution in laser scanning microscopy. However, in practice, the signal-to-noise ratio (SNR) limits its capability. In this research, we introduced image scanning microscopy (ISM) into SAX microscopy to improve the SNR.

Spectral reflectance in human skin tissue has been studied through Monte Carlo simulation using the nine-layered skin tissue model. It is important to estimate the penetration depth of detected light affected by absorption and scattering to know the condition of human skin. In this study, we estimated the depth of penetration of photons in the visible wavelength range that propagate inside skin tissue and are detected at different positions in the vicinity of the illuminated area by using Monte Carlo simulation.

A degraded fluorescence image passing through a weak diffuser is improved by the acquisition of fluorescence wavefront information and phase retrieval. The amplitude and phase distributions of the fluorescent light wave are obtained using the transport of intensity equation. After calculating back-propagation to the diffuser surface from the recording plane, phase retrieval is applied for improving the image quality. Experiments using fluorescent beads examined at different recording plane showed the effectiveness of the proposed method.

Phase-shifting digital holography is performed with a burst imaging method. The measurement error was analytically and experimentally estimated for objects without and with movements.

A photoacoustic imaging system detecting ultrasound generated by pulse-modulated mid-infrared light irradiation is proposed and developed. Based on the spectra obtained with this method, we used SVM to derive the optimal combination of two wavelengths for separating muscle and fat, and achieved imaging using this combination.

Transmission matrix is one of the methods to focus light through scattering media. To measure complex transmission matrix, four-step phase shifting is often used. Here we propose co-axial configuration method to derive phase distribution of output field. In the proposed method, ordinary and extraordinary polarization states are used as a reference wave and an object wave. This method utilizes the maximum projection area of a spatial light modulator (SLM), hence, improves the focusing power.

We have developed a high-speed 3D color planar lightwave circuit digital holographic microscope (PLC-DHM) by applying our new thermo-optical phase control method and switching the three-wavelength laser. In this study, we experimentally demonstrate that this high-speed 3D color PLC-DHM successfully captures the cell structure of mammalian skeletal muscle with a thickness of 40 um and discuss its effectiveness for application in live cell imaging.

Optical coherence tomography (OCT) is a noninvasive, high-speed, and label-free imaging technique, providing 2D and 3D depth-resolved structures of biological tissue. In this study, we utilized a portable OCT system for in vivo studies of skin diseases and the evaluation of laser treatment outcome. A handheld probe with a light weight of 210 g is implemented for scanning arbitrary skin locations. To acquire en-face images at various skin depths, a segmentation algorithm was developed to identify skin surface and the boundary between the epidermis and dermis layers. According to the segmentation algorithm, skin parameters can be estimated including the thickness of stratum corneum, the thickness of epidermis, pore/hair follicle diameter, collagen concentration, and skin roughness. Moreover, the OCT images and skin parameters are used for clinical studies of skin diseases such as rosacea and psoriasis. In addition, the proposed method is utilized for observation and evaluation of laser treatment outcome in vivo. The results illustrate that such a portable OCT system could be potential for clinical diagnoses of skin diseases and laser treatment.

Chromophore estimation is vital in diagnosing structural and functional aspects of skin tissue. Diffuse reflectance spectroscopy aids the non-invasive determination of tissue chromophores. Here we present a finite element model of tissue diffuse reflectance for constructing a look-up table (LUT) with multiple source-to-detector separations, which can be used for the quantitative estimation of skin tissue melanin and haemoglobin content and was verified using in-vitro skin tissue phantoms. The statistical analysis demonstrated the applicability of the developed LUT and the inverse algorithm for chromophore estimation from skin layers.

Fluorescence microscopy is a common method to observe the structural features of biological samples. Conventional tunable lenses are usually used to axially scan the volumetric samples for obtaining fluorescence optical sectioning images. However, they suffer from spherical aberration and distortions. In this work, we propose a compact imaging system with optical sectioning capability based on Moiré metalens which consists of two complementary phase metasurfaces to perform fluorescence bio-imaging applications in visible regions. The focal length of system can be tuned from 10 mm to 125 mm at the wavelength of 532 nm by changing mutual angles between two metasurfaces. In addition, the speckle illumination HiLo microscope is used to reduce the effect of out-of-focus light scattering. To demonstrate the optical sectioning capability of our system, the labeled beads as well as ex vivo mice intestine tissue samples are imaged. The presented design of varifocal metalens is anticipated to realize important applications in fluorescence microscopy and endoscopy.

We have developed a system that separates and measures the optical properties of skin, i.e., the surface reflection, diffuse reflection, and sub-surface scattering components of the skin. This system includes two polarization filters that separate light from the skin into a surface reflection component image and a diffuse reflection component image. Furthermore, by using a projector as a light source and irradiating the skin using a high-frequency binary illumination pattern, the sub-surface scattering component image alone can be separated and generated. Using the proposed system, we performed a survey of 154 Japanese women aged from their 20s to their 70s and analyzed age-related changes in the optical properties of their skin. The results revealed the following. First, the luminance value Y of the surface reflection from the cheek and its standard deviation within the analysis area increase with age. Second, the Y value of diffuse reflection from the skin decreases with age. Third, the amount of light in the sub-surface scattering components also decreases with age. The proposed system is expected to have a wide range of applications in the medical and cosmetic fields.

Digital holography microscopy (DHM) is a quantitative phase imaging technique that is useful to observe transparent samples. The diffraction grating is most widely employed in the common-path DHM (CP-DHM) to allow the object beams and reference beams to be separated at a small angle and propagate almost along the same optical path. However, the conventional thin grating's intrinsic multiple diffraction orders cause CP-DHM to suffer a significant power loss. To address this issue, we propose a volume holographic-based CP-DHM that utilizes the single diffraction order characteristics of volume grating. The two beams in CP-DHM can be generated by volume holograms with low power loss and ease. Our method is advantageous as compared to the other closely related methods, and it is expected to increase the applications of common-path DHM systems.

Assessments of the burn depth is very important for shorter healing time, fewer infection, better functional and aesthetic result and reduce hospital stay. We investigated a red-green-blue camera-based diffuse reflectance imaging for monitoring of oxygenated hemoglobin (HbO), deoxygenated hemoglobin (HbR), methemoglobin (metHb), tissue oxygen saturation (StO₂) and methemoglobin saturation (StMet) in superficial dermal burn (SDB), deep dermal burn (DDB) and non-burned skin in rats. The canonical discriminant analysis with the concentrations and saturations of hemoglobin derivatives showed good separation between SDB, DDB, and non-burned skin.

Light sheet fluorescence microscopy (LSFM) is one of the leading technique for high resolution imaging. To image mouse lungs, optical sectioning and high-speed image acquisition are required. In addition, light scattering, reflection, and attenuation limit the application of light sheet microscopy in the visible region to imaging small and transparent animals and organisms. In this work, we present a light sheet microscope that works in the NIR-II wavelength range and demonstrate deep mouse lung imaging. We utilized light with excitation at 532 nm and detection in the NIR-II range of approximately 1450 nm. Our method is expected to find important applications for deep tissue imaging.

Fluorescence from cells excited by deep-ultraviolet (DUV) light is known as autofluorescence and intrinsic properties of cells. Therefore, the imaging of the distribution of autofluorescence of biological specimen enables us to promote tissue histology and cell biology. This fluorescence is, however, very weak, which prevents the development of autofluorescence imaging. The present work utilizes the surface plasmon resonance (SPR) on aluminum surfaces to enhance the fluorescence signals for highly sensitive imaging of living cells without staining. Aluminum is promising material for the excitation of SPR in the DUV region (DUV-SPR) due to their negative permittivity. DUV-SPR was excited with Kretschmann configuration using a sapphire prism. The DUV-SPR excitation of Al thin film through a sapphire prism was investigated theoretically and experimentally. For living biological specimen, i.e. water-immersed specimens, a high refractive index of the sapphire is suitable for the observation. The autofluorescence intensity through DUV-SPR is increased ~3-fold. Results from this work provide an effective technique for highly sensitive label-free observation of living biological specimens.

Two-photon holographic microscopy (TPHM) is a powerful technique for stimulating biological cells three-dimensionally. TPHM requires an imaging technique to detect fluorescence lights from the three-dimensionally distributed cells. In this study, parallel phase-shifting incoherent digital holography is applied to TPHM. Owing to the parallel phase-shifting method, the lights from the cells are detected with the frame rate of an image sensor. The feasibility of the proposed method is experimentally verified.

A photothermal deflection spectroscopy system detecting heat generated by mid-infrared laser as a change in the refractive index of prism was realized using a small prism and a simple probe optical path. The effectiveness of this method is confirmed by measurement of glucose solution and human fingertip.

We developed spontaneous Raman microscopy using Bandit algorithm to realize fast diagnosis of the existence of anomalies or not with guaranteeing accuracy. The algorithm evaluates obtained Raman spectra during measurement to judge if the diagnosis is completed with ensuring an allowance error rate that users decided and also to generate optimal illumination patterns for the next irradiation which are optimized to accelerate the detection of anomaly. We present our simulation and experimental studies to show that our system can accelerate more than a few tens times faster than line-scanning Raman microscopy which requires full scanning over all pixels.

The objective of this study was to establish a scattering imaging method that uses non-negative matrix factorization (NMF) to remove the effects of scattering from images taken of scattered light and to recover the original object information. In addition, fluorescence imaging by two-photon excitation using random pattern illumination was newly tackled. Fluorescent beads are emitted by two-photon excitation with random pattern illumination, and the scattered light is captured and reconstruction is implemented using memory effect, non-negative matrix factorization and correlation calculation.

We propose a novel laser-scanning optical microscopy employing optical-frequency-comb (OFC) lasers. Laser-scanning OFC microscopy enables unique spectroscopic imaging by analyzing an interferogram of OFC. The interferogram has a lot of information involved in light such as amplitude, phase, polarization, frequency, and time of flight information. Thus, multimodal imaging is expected to become possible with only a single measurement by using these various light information. We provide a proof-of-principle demonstration of laser-scanning OFC microscopy in a variety of applications, such as spectroscopic amplitude, phase, polarization, and time of flight imaging. Our approach would be a useful and powerful tool for microscopic observation.

Laser irradiation of gold nanoparticles in water causes deformation of the gold nanoparticles and heating of the surrounding water, resulting in a change in refractive index. With sufficient heating, the water vaporizes and micro bubbles are generated. We are attempting to observe a series of physical processes using pump/probe digital holography. First, we developed the holographic observation system for the behavior of gold nanoparticles heated by a continuous wave near-infrared laser on a millisecond time scale.

This paper presents fluorescence probes that can be identified using the excitation spectrum of a Förster resonance energy transfer (FRET) network. By using the excitation spectrum, it is not required to measure spectral information at every imaging point, and fluorescence imaging systems can be simplified. We investigated the property of the probe by numerical calculation. The results show that a variety of excitation spectra can be synthesized by changing the arrangement of the fluorophores used in the FRET network. We also confirmed that the composition ratio of probes can be estimated by measuring the excitation spectrum. The knowledge will be helpful not only for molecular sensing/imaging but also for FRET-based computing and other applications.

We investigated a method to perform measurements of tissue oxygen saturation (StO₂) in real-time, using a digital red– green–blue (RGB) camera. Concentrations of oxygenated hemoglobin (C_HbO) and deoxygenated hemoglobin (C_HbR) were estimated from videos of the human face using a method based on a tissue-like light transport model of the skin. StO₂ was calculated from the values of C_HbO and C_HbR. In vivo experiments with human volunteers while varying the fraction of inspired oxygen were performed to evaluate the comparability of the proposed method with a commercially available device for StO₂ measurement.

Micro-electro-mechanical system (MEMS) scanner has the potential to be used in the optical coherence tomography (OCT) imaging system due to fabrication friendliness, and miniature architecture size. The function of feedback control circuits provides the output signal to be fed back to the scanner enabling correcting the drive waveform in real-time to conquer the limitation of scanning stability of the MEMS scanner. In this study, we have developed a swept-source optical coherence tomography (SS-OCT) system configuration of a dual-axis MEMS scanner, switchable operated between open-loop and closed-loop driving modes, to investigate the scanning stability of the MEMS scanner by analyzing the scanning trajectories detected by the position sensitive device (PSD) sensor at frame rates of 50 and 250 Hz. Preliminary results of the quantitative analysis are presented in this paper.

We overexpressed fluorescence-tagged receptors (MOP-CFP & NOP-YFP) by transiently transfecting HEK 293 cells and then measured the variations in fluorescent signals in single-particle tracking (SPT) and fluorescence resonance energy transfer (FRET) by two-photon fluorescence microscopy to explore the cellular localization of μ-opioid (MOP) and nociceptin/orphanin FQ (NOP) receptors regulated by opioids.

A new endoscope structure called chip-on-tip is designed to reach both miniaturization and affordability beyond the conventional rigid endoscope. Hence, the precision glass molding process as a replicative manufacturing method can be integrated into the endoscopes production chain and deliver the optics with not only high quality but also reasonable cost under large production volume.

A diffraction-limited condition limits the spatial resolution of the imaging schemes. In this paper, we discuss incoherent illumination and imaging in terms of the second-order correlation to improve the resolution and reconstruction quality. A comparison of performance based on conventional imaging in free space, the average intensity of the speckles with incoherent illumination, and the intensity correlation of the imaged speckles is discussed and examined by simulation tests of these three cases. Simulation results for imaging in two cases viz. conventional imaging and with second-order correlation measurement are presented and discussed. The approach can be used to enhance the quality of reconstruction in quantitative imaging and microscopy.

Fluorescence microscopy is an essential technique in biomedical research because it can reveal morphological details of complex organisms. Over the past few decades, the spatial resolution of fluorescence microscopy has dramatically improved with super-resolution techniques, contributing significantly to the evolution of life science. On the other hand, temporal resolution (imaging speed) has been overlooked, and its applications have been limited. Therefore, we are developing high-speed fluorescence microscopy techniques to open up new frontiers in life science. Here, we will introduce our recently developed high-speed fluorescence microscopy techniques and their applications to imaging flow cytometry and 3D imaging. We will also discuss the future of high-speed fluorescence imaging that will lead to integrating photonics, informatics, and life science.

We proposed the mid-infrared passive spectroscopic imager for non-invasive blood glucose sensors from a distance. As is well known as thermography, radiation lights whose central wavelength is around 10μm are emitted from body heat. Because radiation lights are derived from resonance frequencies due to intrinsic molecular vibrations, the passive spectroscopy are able to detect emission peaks at 9.25 and 9.65μm of glucose. We constructed false color images of emission intensities at 9.65μm from human arms. And we got high correlation coefficients of glucose levels between conventional blood glucose sensors and the passive spectroscopy. We are expanding applications of the passive spectroscopic imaging to medical diagnosis like testing for malaria infected erythrocyte and amyloid β in brains etc.

Non-interferometric optical diffraction tomography based on intensity-only measurement is plagued by low-frequency missing problems due to the difficulty of meeting matched illumination. We present two methods to address this challenging issue, which are called transport of intensity diffraction tomography with non-interferometric synthetic aperture and transport-of-intensity Fourier ptychographic diffraction tomography.

In this talk, I will discuss diffractive optical networks designed by deep learning to all-optically implement various complex functions as the input light diffracts through spatially-engineered surfaces. These diffractive processors designed by deep learning have various applications, e.g., all-optical image analysis, feature detection, object classification, computational imaging and seeing through diffusers, also enabling task-specific camera designs and new optical components for spatial, spectral and temporal beam shaping and spatially-controlled wavelength division multiplexing. These deep learning-designed diffractive systems can broadly impact (1) all-optical statistical inference engines, (2) computational camera and microscope designs and (3) inverse design of optical systems that are task-specific. In this talk, I will give examples of each group, enabling transformative capabilities for various applications of interest, e.g., autonomous systems, defense/security, telecommunications as well as biomedical imaging and sensing.

Neuromodulation is a technology for reversibly modulating neural activity by applying artificial stimuli to an organism. Electrical and magnetic stimulation technologies have been employed in clinical practices, especially for brain disorders including motor and mood disorders. Ultrasound stimulation has theoretically superior spatial and time resolution to electrical and magnetic stimulation. Even cell-type specific non-invasive neuromodulation is possible with an emerging technology with mechano-sensitive ion channels. Here we briefly mention the current situation of ultrasound neuromodulation and the neuromodulation of the autonomic nervous system. An application of the ultrasound neuromodulation of an organ controlled by the autonomic nervous system (such as the cardiovascular system) is then discussed.

Behavior is a consequence of computation in a neural circuit composed of massive millisecond neural firings that undergo in 4D space. We recently found that the nematode Caenorhabditis elegans exhibits collective pattern formations. To examine the neural computation mechanism in this collective behavior, we are developing a new light-field microscopy. Light-field microscopy is a computational imaging technology that enables scan-less, single-shot acquisition of a 3D volumetric image by postprocessing 2D camera snapshots recorded via a microlens array. Here, we show C. elegans collective behavior and high-resolution light-field microscopy. We performed single-shot 4D brain-wide imaging of a freely behaving C. elegans with high temporal resolution and 3D volumetric imaging of mouse hippocampus amyloid plaques. Finally, we also combined high-resolution light-field microscopy with a quantum sensor, and demonstrated an ultrasensitive 4D physical parameter sensing in Hela cells and in vivo.

Optical bioimaging and optogenetics have recently made it possible to control brain functions. However, these methods have limitations, such as the inability to regulate neural activity with a high spatiotemporal resolution. To address this limitation, we have developed microscope for biological applications by integrating optogenetics and digital holographic technology. This provides precise spatiotemporal information about neural activity.

Raman scattering is known to offer a label-free imaging contrast with chemical bond specificity. However, the scattering cross section of Raman interaction is extremely weak. In order to boost Raman signal strength for high-speed imaging, coherent Raman interaction and electronic pre-resonance enhancement are two potential strategies. For coherent Raman scattering, two lasers with one fixed frequency and one tunable frequency, serving as pump and Stokes beams, are necessary to match the vibrational frequencies of specific molecules or chemical bonds. On the other hand, to achieve electronic pre-resonance, it is required to tune both pump and Stokes laser frequencies simultaneously. In this work, we develop a multi-plate continuum (MPC) source that delivers octave-spanning bandwidth (600-1300 nm) and high spectral energy density (~1 nJ/cm^-1 ). This source not only enables coherent Raman enhancement with spectroscopic interrogation across the entire Raman active region (0-4000 cm^-1), but also provides additional two orders of magnitude enhanced signal strength through electronic pre-resonance. The imaging modalities of stimulated Raman scattering (SRS) and coherent anti-Stokes Raman scattering (CARS) are both demonstrated with the MPC light source, on a fixed Drosophila brain tissue. We envision that utilizing MPC light source will substantially enhance the sensitivity and specificity of SRS by implementing electronic pre-resonance and spectral multiplexing via accessing three or more coherent wavelengths.

We study effects of long-term transcranial infrared light stimulation on cognitive functions of the elders. The fraction of photon energy penetrating to the brain is estimated noninvasively to enable the optimization of light source parameters.