Lens Telescope Research Articles

Exact solution of telescopic aplanatic lens and catadioptric optical systems

Exact solution of telescopic aplanatic lens and catadioptric optical systems

Dual-channel aperture-splitting snapshot spectral imaging detection system

The contemporary spectral imaging detection systems commonly employed, such as pushbroom and stare systems, often necessitate motion-based imaging mechanisms such as scanning motors. This reliance on motion renders the imaging process vulnerable to platform vibrations, resulting in intricate post-image correction procedures and precluding dynamic target detection. Consequently, the advent of snapshot spectral imaging detection systems has ensued. Currently, there are significant challenges in the miniaturization design and rapid data acquisition aspects of snapshot spectral imaging systems. In this study, linear variable filters were employed as spectral components, and, through optical system simulation and design, the design of the nonspherical monolithic lens system and telescope system in the dual-channel aperture-splitting snapshot spectral imaging detection system were separately completed. The spectral range covered 400–1000 nm, with a spectral resolution of 27.3 nm, and each channel had a spatial sampling of 409×409 pixels. Additionally, based on the optical system design results, the system structure design and assembly were completed. Performance testing and preliminary spectral image fusion research were conducted on the assembled prototype. The instrument demonstrated excellent spectral imaging performance, thereby enhancing the efficiency of spectral imaging detection in snapshot spectral imaging.

INFORMATION SYSTEM FOR MULTI-VECTOR RAYTRACING IN ELLIPSOIDAL REFLECTORS

Due to two focuses, ellipsoidal reflectors are unique reflective optical elements that allow conjugate imaging in two focal planes within their inner cavity. Such reflectors are used in various devices, such as lens telescopes, to achieve high resolution. They have found applications in microscope optical systems to increase the depth of field. They are used in scientific instruments, such as laser systems, to ensure the laser beam's high accuracy and stability. Despite their advantages, the non-spherical shape of ellipsoidal reflectors also introduces drawbacks in the form of errors arising from raytracing on the side surface. It complicates aberration analysis and necessitates specialized software for multi-vector ray tracing. Considering the deviations in the coordinates of the intersections between rays and the second focal plane allows for optimizing the reflector design to achieve maximum efficiency. Therefore, this work aims to enhance the efficiency of the aberration analysis of ellipsoidal reflectors by developing principles and informational tools for multi-vector ray tracing.
 The article presents the results of developing an information system for multi-vector analysis in ellipsoidal reflectors. The developed multi-vector algorithm enables selecting tracing modes, tuning launch parameters, and setting the step size for launching rays. The specialized software features for single- and multi-vector raytracing in an ellipsoidal reflector are presented. The side surface of the ellipsoid is the object under study. The software provides the capability to realize different methods of multi-vector ray tracing, such as radius-based, diameter-based, and partial radius-based, for different types of tasks, thereby expanding the possibilities for visualizing the simulation results.
 Based on the multi-vector aberration analysis of the side surface of the ellipsoidal reflector, the center coordinates and root mean square deviations were obtained for different reflection acts when changing the zenith angle of tracing. The influence of zenith angles on coordinate variations was assessed, which can be realized in selecting parameters for ellipsoidal reflectors and designing the optical system of photometers for various purposes. It can also aid in developing additional means to compensate for aberrations or modify the reflector's side surface shape.

Kinematically engaged yoke system for segmented lens-based space telescope integration and testing

One of the most profound and philosophically captivating foci of modern astronomy is the study of Earth-like exoplanets in the search for life in the Universe. The paradigm-shifting investigation described here calls for a new type of scalable space telescope that redefines the available light-collecting area in space. The Nautilus Space Observatory, enabled by multiple-order diffractive optics (the MODE lens), is ushering in the advent of large space telescope lenses designed to search for biosignatures on a thousand exo-earths. The Kinematically Engaged Yoke System (KEYS) was developed to align a segmented version of the MODE lens. A technology demonstration prototype of KEYS was built and tested using scanning white light interferometry and deflectometry. A deflectometry system was also developed to monitor the closed-loop alignment of the segmented MODE lens during its UV (i.e., Ultraviolet) curing.

Progress and future prospect of the CRAFFT project for the next generation UHECR observatory

The next generation of ultra-high energy cosmic ray observations will require large detector arrays to achieve large statistics. In order to realize next-generation large-scale detector arrays, the Cosmic Ray Air Fluorescence Fresnel lens Telescope (CRAFFT) project is developing a low-cost simple fluorescence detector (FD). The simple structure of the CRAFFT detector will reduce the cost to about 1/10 of the current FD. We also aim to realize a fully automated observation system. A prototype of the CRAFFT detector has been successfully used to detect cosmic ray air showers. Since the spatial resolution of the simple FD is rougher than that of the current FD, we are developing a new air shower reconstruction method using the waveform fitting method. In this presentation, we report the performance of the CRAFFT detector, detector optimization, and future prospect.

Analytical Formulas for Refractive Indices of a Telescopic GRIN Lens for Aperture Magnification

In this letter, we derive a new closed-form analytical formula for the refractive index of a telescopic lens based on inhomogeneous graded index (GRIN) material. The telescopic lens is composed of two cylindrical confocal GRIN lenses, one divergent and one convergent. The scope of the telescopic lens is to magnify the aperture of a flat antenna placed at the first interface of the divergent-convergent lens doublet. This telescopic GRIN lens is useful for reusing already available medium-gain arrays and bring them to a high-gain, occupying a reduced volume as compared to traditional lenses or multireflector systems. The formulation used here is based on the solution of a regularized ray-congruence integral equation recently introduced by the authors, and applied in a previous work to treat convergent cylindrical GRIN lenses. The formulation is extended here to the case of a telescopic lens leading to analytical formulas for the two inhomogenous refractive indexes that involve five independent parameters; these parameters are eventually optimized to get the maximum gain boost.

Low Vision and Driving

Driving an automobile is an important option for community mobility. Functional vision is a major consideration for safe driving, and age-related vision impairment may result in the loss of driving independence. Clinicians and older drivers would benefit from understanding current options for driving with low vision, including state laws, use of adaptive equipment, low-vision rehabilitation, and driver rehabilitation. This article reviews the concept of a bioptic telescopic lens system for driving with low vision, including an example of a collaborative interdisciplinary bioptic driving training program developed by the Pennsylvania Department of Transportation in conjunction with clinical experts.

System of Imaging Photometers for Upper Atmospheric Phenomena Study in the Arctic Region

A Pulsating Aurora Imaging Photometers Stereoscopic System (PAIPS) is suggested and described in the paper. The system is based on two lens telescopes with a matrix of multianode photomultiplier tubes as photodetectors placed in two high latitude observatories of the Polar Geophysical Institute. Telescopes provide simultaneous observations of a large volume of the atmosphere at altitudes in the range 50–100 km with high temporal resolution (up to 2.5 μs) and a spatial resolution of about 2 km. This is a novel system for pulsating aurora study aimed to determine the energies of precipitating electrons responsible for the pulsating aurora occurrence. The system can be used for other atmospheric phenomena studies: meteors, transient luminous events, etc. One telescope has been operating since September 2021 and has measured a variety of optical phenomena.

Nanocracks in nature and industry.

Nanocracks in nature and industry.

Method for Increasing of Lens Gluing Technological Process Efficiency and a Reliable Evaluation of Output Controlled Parameters

The use of glued lens components in optical devices improves the image quality of telescopic and photographic lenses or inverting systems by eliminating a number of aberrations, and also reduces light losses in the optical system of the device. The traditional production process of lenses gluing involves the sequential execution of a set of technological operations and takes a significant period of time. The purpose of the research was to improve the accuracy and productivity of the technological process of lenses gluing by improving the optical system of the control and measuring device and automating the operation of lenses optical axes combining by introducing an electronic reference system and mechanisms for micro-movements of optical parts.A technique is proposed for centering of two and three-component optical blocks by an autocollimation flare which provides a matching accuracy of less than 0.5 μm. The possibility of constructive modernization of the classic ST-41 autocollimation microscope with parallel separation of the displayed output information in the visual and television channels is shown. An automated system for controlling of the process of convergence of autocollimation points in the device is proposed. Using software methods an electronic grid template is formed on the monitor screen, onto which images of autocollimation points are projected. The decentering value 2Δe is determined and a corrective control voltage is applied to three stepper motors and pushers for transverse movement of the glued optical part.Specialized software has been developed for automatically bringing the position of the autocollimating crosshair to the center of the measuring scale of the grid based on a combination of two methods of “least squares” and “successive approximation”. Compliance with a number of technological transitions and the accompanying control of geometric parameters make it possible to achieve greater accuracy in determining the eccentricity of the crosshairs of the aligned optical axes of the glued lenses.

Nautilus: The advent of large lens-based space telescopes

One of the most profound and philosophically captivating foci of modern astronomy is studies of Earth-like exoplanets in search of life in the Universe. The paradigm-shifting investigation described here calls for a new type of space telescope that redefines the available light-collecting area in space, far beyond what is currently possible with the 6.5 m diameter James Webb Space Telescope. The Nautilus Space Observatory, which is enabled by multiple-order diffractive optics, is ushering in the advent of large space telescope lenses designed to search for biosignatures on a thousand exo-earths.

Wave-optical study of the Einstein cross formed by a quadrupole gravitational lens

We study imaging of point sources with a quadrupole gravitational lens while focusing on the formation and evolution of the Einstein cross formed on the image sensor of an imaging telescope. We use a new type of a diffraction integral that we developed to study generic, opaque, weakly aspherical gravitational lenses. To evaluate this integral, we use the method of stationary phase that yields a quartic equation with respect to a Cartesian projection of the observer's position vector with respect to the vector of the impact parameter. The resulting quartic equation can be solved analytically using the method first published by Cardano in 1545. We find that the resulting solution provides a good approximation of the electromagnetic (EM) field almost everywhere in the image plane, yielding the well-known astroid caustic of the quadrupole lens. The sole exception is the immediate vicinity of the caustic boundary, where a numerical treatment of the diffraction integral yields better results. We also convolve the quartic solution for the EM field on the image plane with the point-spread function of a thin lens imaging telescope. By doing so, we are able to explore the direct relationship between the algebraic properties of the quartic solution for the EM field, the geometry of the astroid caustic, and the geometry and shape of the resulting Einstein-cross that appear on the image plane of the thin lens telescope. The new quartic solution leads to significant improvements in numerical modeling as evaluation of this solution is computationally far less expensive than a direct numerical treatment of the new diffraction integral. In the case of the solar gravitational lens (SGL), the new results drastically improve the speed of numerical simulations related to sensitivity analysis performed in the context of high-resolution imaging of exoplanets.

Status and prospects of the CRAFFT project for the next generation UHECR observation

Recent observations by TA and Auger have advanced our understanding of ultra-high energy cosmic rays, but their origin is still unclear. As a future approach, it will be effective to obtain the directional energy spectra and compositional distributions by observing even larger statistics, and there are active discussions on future large-scale experiments. In order to realize such a huge observation area, the Cosmic Ray Air Fluorescence Fresnel lens Telescope (CRAFFT) project has started to develop a cost-effective fluorescence telescope with Fresnel lenses. We have succeeded in observing cosmic ray induced air showers by simultaneous observations with TA using prototype telescope. We are currently working on the development of an event reconstruction method using waveforms, optimization of the focal plane, development of a calibration system, and development of an autonomous observation system for future large-scale deployment. The current status and future prospects of the CRAFFT project are discussed.

Multi‐actuator control with modal switching and different disturbance for scanning imaging motion compensation

Scanning imaging can be used to obtain wide field-of-view, high-resolution remote-sensing images with a telescope lens. However, the motion between the image and the sensor causes blurring during scanning, which reduces the image quality. In this paper, a motion compensation method based on multi-actuator control with modal switching is proposed. In this method, the tracking controller realizes scanning and compensation; the cooperative controller reduces the relative motion that causes motion blur, and modal switching solves the travel limitation of the linear actuator. Further, to improve the control performance, an adaptive sliding mode controller is proposed and combined with a disturbance observer. The stability theorems for multi-actuator and modal switching are studied. Experimental results show that the accuracy, robustness, and frame rate of the proposed method improved compared with those of traditional methods. Compared with the non-cooperative structure using a PD controller, the root mean square error is reduced by 76.61 % .

Innovative Technologies To Improve Low Vision

According to WHO data from 2015 – globally 36 million people are blind, 253 million are visually impaired, 55% of whom are women. The creator of modern optical aids for the visually impaired is the famous American scientist William Feinbloom. The special devices to support the low vision are mainly divided into non-optical, optical and electronic. Of interest are the special magnifying devices for surgical implantation in the anterior segment of the eye – mini-telescopes. They apply the concept of enlarging the image on the retina, using a combination of minus and plus lenses as a magnifying glass. A new generation lens “Eyemax mono” is also a technological achievement. It is intended for monocular or binocular implantation in patients with AMD. An innovation is the use of a contact lens for visual rehabilitation – Contact Telescopic Lens. It is a solid gas-permeable scleral contact lens. The Argus II prosthesis is the first epiretinal prosthesis that restores vision in patients with Retinitis Pigmentosa. „Artificial intelligence“ glasses are too expensive. OrCam MyEye can read all printed texts, in addition, the device detects and recognizes objects and people, and recently has software in Bulgarian. In Bulgaria there is no integrated approach to the problem of the visually impaired. Most people with severe visual impairments, unlike complete blindness, have residual useful vision.

Title-Optical Forceps: The Real Boon for Surgeon, Residents and Patients with Foreign Body Aspiration.

Management of aspirated foreign bodies in children becomes very challenging in absence of most appropriate instruments. Rigid bronchoscopy has evolved in the long course of history. The advent of Hopkins rod telescope and optical forceps has enhanced the efficacy as well as the safety of removing tracheobronchial foreign bodies. Total 36 children of age less than 16year with confirmed diagnosis of airway F.B. were included in the study. Two types of forceps were used: (1)Optical forceps combined with Hopkins rod lens telescope[n = 25] (2)Standard forceps [n = 11]. Most common age group was 1-5year [n = 26] with male preponderance [n = 20]. Most common site was right bronchus in 13 cases (RMB-11, RBI-1, RLLB-1) followed by Left main bronchus in 11 cases, trachea in 10 cases, bilateral bronchus and sub-glottis each in 1 case. Vegetative F.B. were found in majority of cases [n = 26]. Mean grasping attempt, Mean bronchoscopic insertion and Mean time taken from insertion of forceps to removal of F.B. were less in optical forceps as compared to standard forceps with significant p-value. Optical forceps have advantage of high resolution & magnified view of airway, spring action in handle and better tactile sensation. These helps in correctly identifying the type, size and site of tracheobronchial foreign body. Precise grasping attempts with optical forceps reduces the chances of complications. Optical forceps have given the new dimension to the Rigid Bronchoscopy and proved to be the real boon for surgeons, residents and patients with F.B. aspiration.

Compact Optical Systems for Space Applications

Some optical schemes of lenses for spacecraft developed by the author are considered. The main optical characteristics of telescope lenses of various architectures are compared. We propose compact solutions of mirror, lens-mirror, and lens systems with maximum available angular resolutions and other parameters. Examples of calculating the optical systems of lenses used for various tasks both in the field of astronomy and in the field of remote sensing of the Earth and other planets are given. The example of onboard computer system is discussed. Practical recommendations on the development and use of telescope lenses are given.

The UV Atmosphere (MINI-EUSO) Experiment: A Wide-Field-of-View Lens Telescope on Board the ISS

The UV Atmosphere (MINI-EUSO) Experiment: A Wide-Field-of-View Lens Telescope on Board the ISS

A Review of Tracheal Bronchus in Universiti Kebangsaan Malaysia Medical Centre (UKMMC).

Tracheal bronchus (TB) is a rare congenital anomaly described as a abnormal bronchus that originates directly from the trachea above the carina directed towards the upper lung lobe. We analysed all paediatric rigid endoscopies of the airway from January 2015 until August 2020 to determine the incidence and characteristic of TB. In total, 68 rigid endoscopic airway examination record from children aged 0 to 12years were analyzed. Endoscopic examination was performed from supraglottic region to carina using a 0 degree Hopkins rod lens telescope. Patients with a TB were identified and the site of TB origin was noted. Data of the identified patients was reviewed for the presence of preoperative airway findings such as stridor, upper lobe pneumonia, other congenital anomalies, intraoperative findings and complications and postoperative general condition outcome. TB was detected in 8 (11.8%) of 68 airway endoscopic examinations. 6 children (75%) were syndromic. 5 patients (62.5%) has congenital malacic airway and 2 patients (25%) has congenital tracheal stenosis. All TB originated from the right lateral wall of the trachea. All children had stridor unrelated to TB as presentation and 4 (50%) of children had preoperative upper lobe pneumonia. Tracheal bronchus is not a rare finding and is highly associated with syndromes and other airway anomalies. Although children with TB can be asymptomatic, upper lobe pneumonia is a common presentation. TB should be included in the differential diagnosis in patients with recurrent right upper lobe pneumonia or collapse and patients with unexplained oxygenation problem during endotracheal intubation, particularly in children with syndromes or other congenital anomalies.

Thermal stress cleaving of glass-based X-ray telescope lenses by heated wire to eliminate microdefects

Abstract The satellite borne X-ray telescope (XRT) is a key technical tool for studying major astronomical problems in the universe. During the fabrication of ultra-thin glass lenses for XRTs, conventional glass cutting technologies yield micro-cracks along the cut surface or micro-damage on the surfaces of the glass normal to the cut. These micro-defects will cause the lenses to be damaged by the strong vibration and jerk of the launch process. In this paper, we seek to resolve this issue by developing a non-destructive cutting technique for glass lenses. Specifically, in this study we propose a heated wire thermal stress cleaving method. We derived the principal parameters affecting the thermal stress fracture behavior of lenses and furthermore calculated the relationship between the length of the initial crack and the minimum temperature. Experimental studies are performed to investigate the process parameters that affect the propagation of a crack in the telescope lens during the thermal stress cleaving process. In particular, we have successfully achieved thermal stress cleaving of a 0.3mm thick lenses with a surface roughness Ra of less than 0.5nm. When assessed in a satellite launch vibration test with a maximum accelerations amplitudes of 5g and 6g in the Y- and Z-directions, respectively, no crack propagation or damage was observed on the surface of the obtained telescope lenses. The study lays a foundation for the manufacture of glass-based XRT.