Hirotsugu Yamamoto

Hirotsugu Yamamoto
Utsunomiya University · Division for Advanced Research

About

327
Publications
17,322
Reads
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1,713
Citations
Citations since 2017
146 Research Items
907 Citations
2017201820192020202120222023050100150
2017201820192020202120222023050100150
2017201820192020202120222023050100150
2017201820192020202120222023050100150

Publications

Publications (327)
Article
This paper proposes a method to improve the modulation transfer function (MTF) of aerial images by combining an aerial imaging optical system by retro-reflection with conjugated two transparent spheres. In the proposed optical system, the transparent spheres collimate the light incident on the retro-reflector to improve the resolution by making the...
Article
We propose a pre-processing method of source image to reduce blur of aerial image that is formed with aerial imaging by retro-reflection (AIRR). In the AIRR optical system, anisotropic blurring occurs due to the influence of diffraction on the surface of the optical element. In this experiment, we measured the point spread function with multiple re...
Article
Full-text available
We propose multiple aerial imaging system by use of two beam splitters in the optical system of aerial imaging by retro-reflection (AIRR). The AIRR optical system consists of a light source, a beam splitter, and a retro-reflector. Use of two-layered beam splitters enables us to show multiple aerial signs to drivers in multiple driving lanes. The pu...
Article
By combining an aerial display, user tracking system, and virtual reality (VR) space, we realized an aerial interface for providing both an immersive user experience and real-time communication with people outside the device. We developed a simple application for detecting user contact and changing the color of an object to measure the latency of o...
Article
We propose a method to realize video calling with an aerial display using a camera that has a direct view of the speaker's face, but which is not visible to the speaker. Because the aerial display uses p-AIRR (polarization-modulated aerial imaging by retro-reflection), we show that it is possible to take advantage of the polarization encoding of th...
Article
In the AIRR optical system that combines transparent spheres, the MTF due to quasi‐parallelization is greatly improve according to the placement distance of the transparent spheres. Due to the effect of aberration, the MTF reaches its maximum when the sphere is placed outside its Paraxial approximate focal length.
Article
We propose a pre-processing method of source image to reduce blur of aerial image that is formed with aerial imaging by retro-reflection (AIRR). The image blur in the AIRR optical system depends on the optical elements and the incident angle. In this paper, the point spread function (PSF) was measured by changing the optical arrangements and the re...
Article
This paper evaluates the spatial distortion of aerial image and proposes a novel optical design to utilize the distortion as visual expression. Our optical system is based on aerial imaging by retro-reflection (AIRR). Using acrylic plate as beam splitter, a clear aerial image can be obtained at low cost. However, when upsizing the device, there is...
Article
AIRR (Aerial imaging by retro-reflection) can form a large aerial image in mid-air for digital signage. Resolution of the aerial image formed with AIRR is determined mainly by the retro-reflector, which is one of its components. However, increasing the resolution of aerial images by increasing the density of retro-reflective elements poses physical...
Article
This paper proposes a novel steganography method to show an aerial image that is formed with aerial imaging by retro-reflection by use of dual transparent balls made of acrylic resin. Our optical system forms a floating image screen in front of an acrylic ball that is placed on a beam splitter. We have confirmed our proposed optical system by perfo...
Article
We have utilized single-pixel imaging and deep-learning to solve the privacy-preserving problem in gesture recognition for interactive display. Silhouette images of hand gestures were acquired by use of a display panel as an illumination. Reconstructions of gesture images have been performed by numerical experiments on single-pixel imaging by chang...
Article
We have developed a new high-speed driving circuit of a multi-color LED panel by the use of FPGA for subjective super-resolution display. In the subjective super-resolution display, the coded display image is switched and displayed at high speed. The viewer makes an unconscious correction by fixational eye movement and perceives the resolution high...
Article
Phase imaging without a phase wrapping ambiguity is required for wide-axial-range 3D imaging in the fields of surface topography measurement and biomedical imaging. Although multicascade-linked synthetic-wavelength digital holography (MCL-SW-DH) using an optical frequency synthesizer (OFS) is a promising method to meet this requirement, the slow sw...
Article
We have realized a novel optical system to form a large aerial image in front of a full-color LED panel that is covered with retro-reflector. The retro-reflector has square apertures through which lights from the LED pixels pass. Our optical system is based on aerial imaging by retro-reflection (AIRR). The aerial image formed with AIRR is visible o...
Article
This paper proposes a novel optical system to form an aerial image over a transparent sphere. The proposed optical system is composed of two transparent acrylic spheres in the light path of the aerial imaging by retro-reflection (AIRR) device. The first sphere collects the diverging light rays from a light-source display. The second sphere converge...
Article
We measure the image resolution of aerial images formed with an AIRR (aerial imaging by retro-reflection) system. Using three different types of retro-reflectors inside the AIRR system, we measure the aerial image modulation transfer function (MTF) via the slanted knife edge method, showing that the resolution of depends on the angle of incidence o...
Article
To realize a triple-views aerial image floating in the center of the passages that can be displayed in front of an user and passed through, we propose a novel display device using aerial imaging with retro-reflection with polarization. We confirmed that our device can form aerial images in the center of the intersection of three passages and can di...
Article
Image resolution is one of the most important performance specifications of aerial display techniques. However, there is no standard method for evaluating the aerial image resolution. In this paper, we propose a method for measuring the modulation transfer function (MTF) of an aerial imaging system based on the slanted knife edge method. We hypothe...
Article
In this article, we obtain precise theoretical expressions and various experimental dependences of the perceived depth in an arc 3D display and find that they coincide. We also propose two liquid-crystal (LC) active devices that can switch arc 3D images on and off by changing either the amplitude or frequency of a high applied voltage and clarify t...
Article
We have proposed and developed an “edge-based depth-fused 3D (DFD) display” in order to solve four problems in conventional DFD displays for many applications. (1) Obscure double imaging and an inappropriate luminance distribution may appear outside the overlap area due to adjusting the ratio of the luminances between the two overlapping images, wh...
Article
This paper proposes a novel aerial 3D display that forms an aerial image augmented in the real space with DS3D (directional scattering 3D) display. The aerial image is formed with AIRR (aerial imaging by retro‐reflection) in see‐through structure. We have demonstrated presenting the position of the aerial image to observers in an easy‐to‐understand...
Article
Several kinds of micro optics array have been developed to form aerial images in the mid‐air, and we propose evaluation methods for imaging performance of the optical system using the micro optics array. To evaluate the influence caused by aperture limitation of micro optics array and diffraction, the MTF measurement method using a knife edge has b...
Article
Full-text available
Dual-comb microscopy (DCM), based on a combination of dual-comb spectroscopy (DCS) with two-dimensional spectral encoding (2D-SE), is a promising method for scan-less confocal laser microscopy giving an amplitude and phase image contrast with the confocality. However, signal loss in a 2D-SE optical system hampers increase in image acquisition rate...
Preprint
Fluorescence lifetime imaging microscopy (FLIM) is a powerful tool for quantitative fluorescence imaging because fluorescence lifetime is independent of concentration of fluorescent molecules or excitation/detection efficiency and is robust to photobleaching. However, since FLIM is based on point-to-point measurements, mechanical scanning of a foca...
Preprint
Dual-comb microscopy (DCM), based on a combination of dual-comb spectroscopy (DCS) with two-dimensional spectral encoding (2D-SE), is a promising method for scan-less confocal laser microscopy giving an amplitude and phase image contrast with the confocality. However, signal loss in a 2D-SE optical system hampers increase in image acquisition rate...
Conference Paper
Fluorescence lifetime imaging microscopy (FLIM) is useful for life science; however, mechanical scanning of focal point hampers rapid imaging. In this article, we demonstrated scanless full-filed FLIM imaging by 2D spectral encoding and dual-comb heterodyne-beating. OCIS codes: (170.3650) Lifetime-based sensing; (180.2520) Fluorescence microscopy,...
Conference Paper
This paper proposes an optical system to form multiple aerial images from a light source by use of infinity mirror optics and aerial imaging by retro-reflection. We analyse viewing angle of the multiple aerial images.
Article
We construct a full-field phase-shifting terahertz digital holography (PS-THz-DH) system by use of a THz quantum cascade laser and an uncooled, 2D micro-bolometer array. The PS-THz-DH enables us to separate the necessary diffraction-order image from unnecessary diffraction-order images without the need for spatial Fourier filtering, leading to supp...
Article
We propose a method to realize a subjective super-resolution on a high-speed LED display, which dynamically shows a set of four neighboring pixels on every LED pixel. We have experimentally confirmed the subjective super-resolution effect. This paper proposes a subjective super-resolution hypothesis in human visual system and reports simulation res...
Article
We proposed a refractive index (RI) sensing method with temperature compensation by using an optical frequency comb (OFC) sensing cavity including a multimode-interference (MMI) fiber, namely, the MMI-OFC sensing cavity. The MMI-OFC sensing cavity enables simultaneous measurement of material-dependent RI and sample temperature by decoding from the...
Article
We propose a novel optical setup to project a flat plane onto a spherical surface. Our proposed method employs putting a curved mirror in the optical path of the projection optics. The curved mirror is placed at the initial image plane formed by a relay lens. This initial image is then re-imaged at the spherical surface. Thus, our optical setup ena...
Article
Full-text available
Dual-comb spectroscopy (DCS) is useful for gas spectroscopy due to the high potential of optical frequency comb (OFC). However, fast Fourier transform (FFT) calculation of a huge amount of temporal data spends significantly longer time than the acquisition time of an interferogram. In this article, we demonstrate frequency-domain DCS by a combinati...
Preprint
Full-text available
We proposed a refractive index (RI) sensing method with temperature compensation by using an optical frequency comb (OFC) sensing cavity employing a multimode-interference (MMI) fiber, namely, the MMI-OFC sensing cavity. The MMI-OFC sensing cavity enables simultaneous measurement of material-dependent RI and sample temperature by decoding from the...
Article
Full-text available
A fiber-coupled photoconductive antenna (PCA) is a powerful tool for portable terahertz (THz) systems using a compact 1550-nm mode-locked Er:fiber laser with a fiber output port. However, a low-temperature-grown GaAs (LTG-GaAs) PCA could not be used for this purpose due to the need for wavelength conversion of the 1550-nm light, regardless of the g...
Preprint
Dual-comb spectroscopy (DCS) is useful for gas spectroscopy due to high potential of optical frequency comb (OFC). However, fast Fourier transform (FFT) calculation of a huge amount of temporal data spends significantly longer time than the acquisition time of an interferogram. In this article, we demonstrate frequency-domain DCS by a combination o...
Presentation
1. We propose a method to realize a subjective super-resolution on a high-speed LED display, which dynamically shows a set of four neighboring pixels on every LED pixel of the coarse LED panel. 2. The subjective super-resolution effect was confirmed experimentally using a variable frame rate high speed LED display system[2]. 3. This paper propose...
Article
We have realized an omnidirectional aerial display for behavioral experiments. The omnidirectional aerial image is formed using a beam splitter with a cone shape. When an aerial image is shown to medaka and betta fish, they react following the aerial image. Furthermore, we propose a method for changing the position of the aerial image by increasing...
Article
Full-text available
We propose a novel ultrasonic wave sensing method employing an optical-frequency-comb (OFC) cavity, namely, an OFC sensing cavity-based ultrasonic wave sensor. We confirm the fundamental characteristics of the OFC sensing cavity-based ultrasonic wave sensor by using an ultrasonic wave transducer and realize the frequency response of up to 13 MHz wi...
Conference Paper
We combine dual-comb microscopy and post-amplification technique for rapid acquisition of confocal amplitude and phase images. The proposed method significantly improves signal-to-noise ratio in the rapid scan-less imaging.
Conference Paper
Line-by-line spectral shaping of a 10-GHz optical frequency comb (OFC) is used for cascade-linked multi-synthetic-wavelength digital holography. The proposed method enables the real-time 3D shape measurement with wide axial dynamic range.
Conference Paper
We combined dual-comb microscopy and post-amplification technique for rapid acquisition of confocal amplitude and phase images. This combination enables us to improve SNR in both images while achieving rapid image acquisition.
Conference Paper
Aerial imaging by retro-reflection (AIRR) is an aerial-image-forming technique by use of a retro-reflector [1]. Our previous study proposed a novel steganography that utilizes AIRR and two clear spheres in the same size. The proposed technique used one of the clear spheres as a key to form an aerial image that was formed with AIRR [2].
Conference Paper
Aerial displays are expected to be the next-generation information screens for like digital signage. Aerial imaging by retro-reflection (AIRR) [1] has proposed as one of the image-forming methods. AIRR can form a translucent image through which users can observe the reflected image while observing aerial image.
Conference Paper
Full-text available
We propose a novel super-resolution display technique by use of spatiotemporal coding. When for neighboring image data are displayed dynamically on a coarse LED panel, the resolution becomes higher than the conventional LED display. We examined the cognitive mechanism in the human visual system to explain this experiment result.
Conference Paper
In this paper, the image photographed by the light field camera is reconstructed by the light field display, and projected in the air by Fresnel lens and an aerial imaging by retro-reflection (AIRR) technique. This allows you to face the 3D aerial image of the user in another location and perform a realistic conversation.
Article
We have realized a new type of three-dimensional (3D) aerial image. The aerial image is an image that exists in the mid-air and can be observed without using 3D glasses. We utilized aerial imaging by retro-reflection (AIRR) to form the aerial image. Conventionally, the formed aerial image is a two-dimensional (2D) image. To give depth information,...
Conference Paper
We propose a method to represent a super-resolution image on a coarse LED panel. Our proposed method dynamically shows a set of four neighboring image data whereby only one element emits light. The experiment shows that the proposed method results in a higher resolution and is perceived more smoothly in human visual system than the conventional sta...
Article
Full-text available
Digital holography (DH) is a promising method for non-contact surface topography because the reconstructed phase image can visualize the nanometer unevenness in a sample. However, the axial range of this method is limited to the range of the optical wavelength due to the phase wrapping ambiguity. Although the use of two different wavelengths of lig...