Convex Mirror Research Articles

Hybrid Refractive and Diffractive Testing Method for Free-Form Convex Mirror in High-Resolution Remote-Sensing Cameras

The development of high-resolution and large field of view remote-sensing cameras is inextricably linked to the application of free-form mirrors. The free-form mirror offers higher design of freedom and is more effective at correcting aberrations in optical systems. The surface shape error of a free-form mirror directly affects the imaging quality of remote-sensing cameras. Consequently, a high-precision free-form mirror detection method is of paramount importance. For the convex free-form surface mirror with a large aperture, a hybrid refractive and diffractive testing method combining computer-generated holography (CGH) and spherical mirrors for high-precision null test is proposed in this paper. When comparing the effect of error and the detection sensitivity of different designs, the results showed that the influence of the system error is reduced by about 42% and the sensitivity is increased by more than 2.6 times. The proposed method can achieve higher testing accuracy and represents an effective and feasible approach for the surface shape detection method.

A novel phase measuring deflectometry based on polar coordinate

Phase measuring deflectometry (PMD) is a method measure the surface of a mirror. However, when measuring convex mirrors, Cartesian coordinate fringes experience extreme compression. To address this issue, this paper proposes a novel PMD based on polar coordinate. This new method defines two linearly independent phase modulation directions, using the orthogonal basis of polar coordinate. It establishes polar coordinate fringes with rotational symmetry and radial pre-modulation, effectively reducing the impact of extreme compression at the edges. To correct the phase errors in polar coordinate fringes, a phase error compensation algorithm based on greyscale gradient is introduced. The algorithm calculates the influence factor of the eight connected domains around the error points to be compensated, utilising the phase grey gradient. The wavefront gradient data obtained through polar coordinate fringes are radial and tangential. Hence, a surface reconstruction method is proposed based on the Zernike partial derivative polynomial based on polar coordinate. In this method, the tangential partial derivatives and radial partial derivatives of the first 36 terms of Zernike in polar coordinate to construct Gram matrix equations. As a result, linearly independent Zernike recovery coefficients are obtained from coupled aliasing gradient data. Compared to the Cartesian coordinate system, the proposed method significantly reduces the fitting coefficient errors. Experimental measurements of convex mirrors with radii of curvature of 200 mm and 100 mm were conducted. The results demonstrate that compared to traditional PMD, this technique not only effectively suppresses extreme compression and increases the measurement area but also improves measurement accuracy by six times.

Coaxial panoramic 3D-DIC system for full inner surface deformation measurement

A coaxial panoramic three-dimensional digital image correlation (3D-DIC) system was developed for full 360o inner surface deformation measurement. The panoramic observation was realized by using a convex mirror. Two cameras were arranged coaxially to ensure the largest overlapping observation area. After the coordinate transformation and correlation calculation, the 3D displacement and strain distributions were reconstructed. The principles of the system were presented in detail, and the internal morphology and deformation of pipes subjected to compression loading were described to verify the effectiveness, practicality, and accuracy of the proposed system.

LOW VISION IN RETINITIS PIGMENTOSA: HOW TO ENHANCE FUNCTIONAL VISION IN PSEUDOPHAKIC PATIENT

Introduction : Retinitis Pigmentosa (RP) could lead to various visual impairments, including decreased visual acuity, poor dark adaptation, decreased contrast sensitivity, poor color vision, visual field constriction, leading to low vision (LV). LV in RP decreases patient’s quality of life (QoL) and Independence. We aim to report a successful case of LV management in a bilateral pseudophakic patient with RP.
 Case Illustration : A 33-year-old man came with progressively blurred vision in both eyes (BE) that worsen 6 months ago. Ophthalmologic examination revealed his uncorrected visual acuity for right eye (RE) and left Eye (LE) was 6/60 and 4/60. The patient had cataract surgeries and IOLs implantation on BE in 2021. Funduscopic examination revealed the bone spicule appearance, blood vessel attenuation, and waxy disc pallor on BE. Humphrey's examination showed a peripheral visual field defect. Decreased contrast sensitivity and poor color vision were also found.
 Discussion : The patient was managed by LV aids and rehabilitation. Spectacle clarified distant and near vision with best corrected visual acuity (BCVA) 6/21 and 0.8 M on BE, photochromic lenses aided in adapting to various lighting levels and as a UV protection, and the addition of illumination and color contrast enhancement improved vision in dim light. A convex mirror to be used as a field- enhancement spotting tool. Rehabilitation enhances his head tracking, scanning, and habitual spotting skills. Improvement of QoL has been recorded using LVQoL questionnaires.
 Conclusion : LV management are vary based on an individual’s level of functional vision and personal preferences. Optimal LV management could enhance patient QoL and Independence.

Claude Chamber

Proto-photographic and proto-cinematic technologies are an unending source of inspiration for a visual artist. We want to consider the case of an eighteenth-century optical device, the Claude mirror, as a starting point for an artistic collaboration.
 The Claude mirror is a small black convex mirror named after the painter Claude Lorrain and used by late eighteenth-century and early nineteenth-century painters and travellers for viewing landscapes. The dark mirror surface produces an image with a limited tonal range, allowing the viewer to look at the environment as if it were a painting. A famous Thomas Gainsborough drawing shows a man seated on a bank with a sketchbook on his lap and holding an oval mirror propped against a tree branch (Gainsborough, 1750-55).
 In spring 2019, in a flash of joint inspiration, we conceived a method of combining aspects of our artistic processes: Salla’s moving image and Laura’s printmaking practice. For 18 months, we captured photographic time-lapse sequences of everyday views from the backyards of our studios, residencies, and homes as reflections on the surface of copper plates installed in the environment (Myllylä and Vainikka, 2021). In the resulting installation, titled Claude Chamber, we projected the video sequences on the gallery space, reflected via the same mirror surfaces, and the projected images became distorted and spatial.
 We were intrigued by this optical device, in which characteristics of photography and printmaking meet. One can think of a Claude glass as a predecessor of the camera viewfinder, an early photographic gesture. It can also be viewed as a printing plate, a matrix reflecting a view. In a traditional printing plate, the image is attached or fastens itself onto the surface of the plate; in our installation, the image is transient and moving.

Mixed compensation for the testing of large convex aspheres

Since the testing of convex mirrors often requires a compensator with a larger aperture than the mirror under test, this is undoubtedly a trade-off not worth pursuing. Moreover, for surfaces with higher levels of asphericity, it further escalates the challenges in testing. In this study, high-accuracy testing of large convex aspheric surfaces with rotary symmetry was achieved via a method that combines sub-aperture stitching and Computer-Generated Holograms (CGH) compensation testing. Applying the methodology outlined in this study, practical testing was conducted on a large-aperture convex aspheric mirror with a diameter of 538 mm. The outcomes demonstrated that the center testing data and the outer ring testing data were stitched by the stitching algorithm to obtain the surface error of the full-aperture. The results were compared to those of Luphoscan and compensation testing, with a residual Root Mean Square (RMS) less than λ/20 (λ = 632.8 nm). Finally, the error analysis of the entire testing process showed that the accuracy was better than λ/50. The results demonstrate that the method can achieve highly accurate test of large convex aspheric surfaces.

Smart Turns: Revolutionizing Road Safety

Abstract: A technological replacement for traditional convex mirrors at blind curves and T-junctions is presented in the abstract of this research article. The suggested system makes use of ultrasonic proximity sensors to see oncoming cars and sends timely notifications to drivers on both sides of the turn. The technology also computes and shows the oncoming vehicle's speed. A typical signal system or direct roadside projection of the alerts are both options provided by the system. This approach facilitates safer navigation at blind bends and T-junctions by using proximity sensors to measure vehicle speed and improve driver awareness. Our method improves accuracy, range, and reliability in vehicle detection and alerting by overcoming the limitations of convex mirrors. This technology improves safer driving by enhancing driver awareness and reducing accidents.

Laser Output Performance and Temporal Quality Enhancement at the J-KAREN-P Petawatt Laser Facility

We described the output performance and temporal quality enhancement of the J-KAREN-P petawatt laser facility. After wavefront correction using a deformable mirror, focusing with an f/1.3 off-axis parabolic mirror delivered a peak intensity of 1022 W/cm2 at 0.3 PW power levels. Technologies to improve the temporal contrast were investigated and tested. The origins of pre-pulses generated by post-pulses were identified and the elimination of most pre-pulses by removal of the post-pulses with wedged optics was achieved. A cascaded femtosecond optical parametric amplifier based on the utilization of the idler pulse rather than the signal pulse was developed for the complete elimination of the remaining pre-pulses. The orders of magnitude enhancement of the pedestal before the main pulse were obtained by using a higher surface quality of the convex mirror in the Öffner stretcher. A single plasma mirror was installed in the J-KAREN-P laser beam line for further contrast improvement of three orders of magnitude. The above developments indicate, although it has not been directly measured, the contrast can be as high as approximately 1015 up to 40 ps before the main pulse. We also showed an overview of the digital transformation (DX) of the system, enabling remote and automated operation of the J-KAREN-P laser facility.

A Vicarious Technique for Understanding and Diagnosing Hyperspectral Spatial Misregistration.

Pushbroom hyperspectral imaging (HSI) systems intrinsically measure our surroundings by leveraging 1D spatial imaging, where each pixel contains a unique spectrum of the observed materials. Spatial misregistration is an important property of HSI systems because it defines the spectral integrity of spatial pixels and requires characterization. The IEEE P4001 Standards Association committee has defined laboratory-based methods to test the ultimate limit of HSI systems but negates any impacts from mounting and flying the instruments on airborne platforms such as unmanned aerial vehicles (UAV's) or drones. Our study was designed to demonstrate a novel vicarious technique using convex mirrors to bridge the gap between laboratory and field-based HSI performance testing with a focus on extracting hyperspectral spatial misregistration. A fast and simple extraction technique is proposed for estimating the sampled Point Spread Function's width, along with keystone, as a function of wavelength for understanding the key contributors to hyperspectral spatial misregistration. With the ease of deploying convex mirrors, off-axis spatial misregistration is assessed and compared with on-axis behavior, where the best performance is often observed. In addition, convex mirrors provide an easy methodology to exploit ortho-rectification errors related to fixed pushbroom HSI systems, which we will show. The techniques discussed in this study are not limited to drone-based systems but can be easily applied to other airborne or satellite-based systems.

Long-wavelength infrared zoom system using tunable concave and convex mirrors

We propose and demonstrate a long-wavelength infrared (LWIR) zoom system with focus tunable mirrors. The designed system consists of two focus tunable mirrors, four static lenses, and a detector. The zoom magnification can be changed by altering the focal length of the two mirrors through a control of the radius of the surface curvature of the mirrors. The shape of the mirrors can be concave or convex, which means that the focal length can vary from negative to positive. The fixed-focus lenses are designed to correct the aberrations of the tunable mirrors and are made of a material with good transparency at LWIR. Following the above design, an LWIR zoom system with the characteristic of being concave or convex is realized for the first time, and its results demonstrate 2x magnification and speeds up to 5 Hz. The proposed zoom system is free from mechanical moving parts and has potential as a low-cost LWIR system with high-speed zoom.

Development of a Low-Cost Michaelson Interferometer with Convex Mirrors for Qualitative Experiments

Development of a Low-Cost Michaelson Interferometer with Convex Mirrors for Qualitative Experiments

Research on Omnidirectional Stereo Measurement Using Convex Mirrors and Vertical Disparity

We propose an omnidirectional measurement method without blind spots by using a convex mirror, which in principle does not cause chromatic aberration, and by using vertical disparity by installing cameras at the top and bottom of the image. In recent years, there has been significant research in the fields of autonomous cars and robots. In these fields, three-dimensional measurements of the surrounding environment have become indispensable. Depth sensing with cameras is one of the most important sensors for recognizing the surrounding environment. Previous studies have attempted to measure a wide range of areas using fisheye and full spherical panoramic cameras. However, these approaches have limitations such as blind spots and the need for multiple cameras to measure all directions. Therefore, this paper describes a stereo camera system that uses a device capable of taking an omnidirectional image with a single shot, enabling omnidirectional measurement with only two cameras. This achievement was challenging to attain with conventional stereo cameras. The results of experiments confirmed an improvement in accuracy of up to 37.4% compared to previous studies. In addition, the system succeeded in generating depth image that can recognize distances in all directions in a single frame, demonstrating the possibility of omnidirectional measurement with two cameras.

Power-scaled CW Alexandrite lasers

We present several strategies for increasing the output laser power of near-diffraction limited continuous-wave Alexandrite lasers pumped by fibre-coupled red laser diodes. Laser mode size control using a convex mirror with the varying thermal lens is shown to be an efficient method for generating record levels of output power from a diode-pumped Alexandrite laser. 8.6 W is obtained with M^{2}<1.1 and an optical efficiency of 27%. 735–790 nm wavelength tuning is demonstrated with > {2.5},hbox {W} and a record dual-wavelength output power of 4.2 W. In a ring-cavity geometry, 5.1 W is obtained with M^{2}<1.1 showing promising potential for multi-watt single-longitudinal-mode operation. Detailed laser cavity modelling including thermal lens analysis is also provided.

A Before-and-After Study of a Collision Risk Detecting and Warning System on Local Roads

Local roads have numerous blind spots caused by complex geometry, obstacles, and narrow width. Thus, conventional proactive countermeasures, such as passive traffic signs and convex mirrors, have not always been effective in preventing local road collisions. In this paper, we present a novel proactive two-step approach for traffic safety on local roads, comprised of detection of pedestrian-to-vehicle and vehicle-to-vehicle collision risks and warning systems. First, using video surveillance and radars to eliminate blind spots, the system detects road objects, predicts their trajectories and reachable areas, and identifies a potential risk situation. Second, it provides road users such as vehicles and pedestrians with warnings through LED variable message signs, which allows them to react effectively in risky situations. We have applied the system to two local road sites in South Korea, including a university campus in Seoul City and an apartment complex in Daejeon City. The detecting system has been validated using a confusion matrix. We have assessed the warning effect through a before-and-after study and found that the proposed system contributed to the improvement of traffic safety at the case study site in that traffic conflicts decreased by 55–62%.

Self-Representation in John Ashbery's Poem Self Portrait in A Convex Mirror

Self-Representation in John Ashbery's Poem Self Portrait in A Convex Mirror

Portrait in a Convex Mirror: Seeing Dickinson in Contemporary Spanish-Language Poetry

Abstract: In the Spanish-speaking world, there are four primary ways in which authors have sought, like Thomas Wentworth Higginson, to take Emily Dickinson by the hand as they try to understand her, eager to communicate her strength to others who are distant from her in space and time and language. Listed in order of closeness and level of interpretation, these four methods or interactions are translation, conversation or dedication, reinterpretation, and influence. This essay studies examples of each and in tracing these varieties of literary transmission explores an important facet of what Dickinson meant when she spoke of circumference.

Versatile Tunable Microresonator for the Light-Matter Interaction Studying in the Strong-Coupling Mode

The interaction between an ensemble of molecules and an electromagnetic field in a highly limited volume makes it possible to control the properties of a substance and, therefore, is an exceptionally promising area of research. The most common way to achieve weak or strong light-matter coupling is to place an ensemble of molecules in a micron-sized resonator. In such a system,the interaction of light with matter appears in the form of a change in the spectral response of the system, which depends on the strength of the coupling between the ensemble of molecules and the modes of the resonator. Currently, there is no general and user-friendly approach that allows studying a lot of different samples in a wide optical range using the same resonator setup. The present paper describes the design of a device that makes it possible to overcome this disadvantage, speed up and facilitate the study of the light-matter interaction, and also obtain weak and strong light-matter coupling modes for a large number of samples in the UV, visible, and IR regions of the optical spectrum. The device developed here is based on the tunable unstable λ/2 Fabry-Perot microresonator, consisting of flat and convex mirrors, which satisfy the condition of plane-parallelism at least at one point of the curved mirror and can significantly reduce the mode volume. The device was used to study the effect of the strong-coupling regime on the fluorescent properties of the Rhodamine 6G (R6G) dye embedded in a boron nitride nanoparticles matrix. It was found that the use of boron nitride (h-BN) as a carrier matrix has an orienting effect on the dye molecules, that results in an increase of the light-matter coupling strength at a lower resonator mode energy required. Keywords: microspectroscopy, optical microresonator, strong coupling, boron nitride.

Универсальный перестраиваемый микрорезонатор для исследования взаимодействия света с веществом в ржиме сильной связи

The interaction between an ensemble of molecules and an electromagnetic field in a highly limited volume makes it possible to control the properties of a substance and, therefore, is an exceptionally promising area of research. The most common way to achieve weak or strong light-matter coupling is to place an ensemble of molecules in a micron-sized resonator. In such a system,the interaction of light with matter appears in the form of a change in the spectral response of the system, which depends on the strength of the coupling between the ensemble of molecules and the modes of the resonator. Currently, there is no general and user-friendly approach that allows studying a lot of different samples in a wide optical range using the same resonator setup. The present paper describes the design of a device that makes it possible to overcome this disadvantage, speed up and facilitate the study of the light-matter interaction, and also obtain weak and strong light-matter coupling modes for a large number of samples in the UV, visible, and IR regions of the optical spectrum. The device developed here is based on the tunable unstable λ/2 Fabry-Perot microresonator, consisting of flat and convex mirrors, which satisfy the condition of plane-parallelism at least at one point of the curved mirror and can significantly reduce the mode volume. The device was used to study the effect of the strong-coupling regime on the fluorescent properties of the Rhodamine 6G (R6G) dye embedded in a boron nitride nanoparticles matrix. It was found that the use of boron nitride (h-BN) as a carrier matrix has an orienting effect on the dye molecules, that results in an increase of the light-matter coupling strength at a lower resonator mode energy required.

Polynomial color compensation model with neural network solver for color-coded fringe patterns in phase-measuring deflectometry

The total image display/projection and image acquisition time in a projector-based phase-measuring deflectometry (PMD) measurement is reduced when color-coded fringe patterns are used since only a single image of the fringe pattern is sufficient to extract phase information using the phase-stepping method. This benefit is, however, offset by the difficulty in resolving various sources of color intensity errors of the fringe patterns in the camera view, such as uneven illumination, color imbalance, color crosstalk, and deviation of color intensity response of the camera and the projector from the calibrated color targets. Thus, a polynomial color compensation model is proposed in this study to compensate for color intensity errors. The model coefficients were estimated using the relationship between the captured and targeted color intensities, which are sequences of monochromatic 8-bit red, green, and blue (RGB) images for projection. The model was applied to modify the color intensities of the generated fringe patterns before projection. The modified color fringe patterns were then used for PMD measurement on spherical concave and convex mirrors. Based on the experimental results, the root-mean-squared (RMS) color intensity errors in R, G, and B channels were reduced by 33.3%, 58.3%, and 36.4%, respectively, after conducting the polynomial color compensation. The RMS phase errors in the fringe patterns were reduced by 71.9%. The RMS height errors and the radius percentage errors of the reconstructed concave and convex heightmaps were 1.87 μm (0.12%) and 1.55 μm (0.17%), respectively. The performance of the proposed polynomial color compensation model in reducing color intensity errors of the captured fringe patterns for accurate PMD measurement was demonstrated successfully.

Aktivitas Pembelajaran Berbasis Proyek Terintegrasi dalam Pendekatan STEM: Pemanfaatan Cardboard bekas dalam Mendesain VR (Virtual Reality) Berdasarkan Konsep Pembiasan Cahaya pada Lensa Cembung Sebagai Media Proyeksi Video 3D untuk Meningkatkan Metaliterasi Siswa

After the Covid-19 pandemic, students are used to online learning, namely learning using gadgets. It is a fact that more students use their gadgets to play online games than educational sites. In playing online games students feel they are in a game that seems real. It's not uncommon for gamers to buy a VR box to play 3D games more realistically. VR or Virtual Reality is a medium of interaction between humans and computers that makes users feel that they are in a computer environment. The aim of this research is to make VR with the right and cheaper materials, namely used cardboard and plastic bottles. The results of this study are Virtual Reality to improve students' metalliteracy abilities. Metalliteration ability is very important in the industrial era 4.0. Metalliteracy is a comprehensive framework of thinking that goes beyond other literacy with the main literacy being technology and information literacy. This metalliteracy ability is still relatively new, therefore, in this study a project-based learning model that is integrated with the STEM (Science, Technology, Engineering, Mathematics) approach is applied to improve students' metalliteracy abilities by presenting STEM problem solving in learning. The STEM problem raised in this study is the use of used cardboard in making VR (virtual reality). Shiva made VR based on the concept of light refraction in convex mirrors, then PjBL and STEM tools were developed in learning to increase student metalliteracy by calculating the surface area of geometric shapes. The results of the research are in the form of learning activities in the form of table descriptions of 1-6 stages of learning activities.