Large Concave Mirror Research Articles

Current status and plan of development of Nd:YAG laser Thomson scattering system in Heliotron J

An Nd:YAG Thomson Scattering system has been developed in Heliotron J. The Thomson scattering system is used for an investigation of an improved confinement physics such as the edge transport barrier (H-mode) or the internal transport barrier of the helical plasma. The system has 25 spatial points with ∼10 mm resolution. Two high repetition Nd:YAG lasers (> 500mJ@50 Hz) realize the measurement of the time evolution of the plasma profile with 10 ms time intervals. The scattered light is collected with a large concave mirror (D=800 mm) with a solid angle of ∼80–100 mstr. The laser beam is injected from obliquely downward to upward, and obliquely backscattered light is detected. A multi-path Thomson scattering system is under development to measure anisotropic electron velocity distribution and to increase the accuracy of the density and temperature profiles. First, we have applied a double-path Thomson scattering system using a Faraday rotator to the Heliotron J. The clear backward and forward scattered lights are successfully detected. Now the system is upgraded to a multi-path system using a pockels cell. The final goal of the development is the system that has two pockels cells to separate the backward and forward scattered lights.

Leonardo da Vinci’s design for the construction of burning mirrors

The use of burning mirrors has been an issue for Leonardo since his apprenticeship under Andrea Verrocchio (1468–70). From about 1508 he dealt more closely with the theoretical prerequisites of reflection. In his Codex Arundel and on numerous sheets of the Codex Atlanticus we find more than 200 designs belonging to the subject. Afterwards (1513–15), in the service of Giuliano de’ Medici, he planned the process-steps for the production of large concave mirrors. He set great expectations on this technology (ms. G). In this stage he complains about lack of support by two German craftsmen and encrypts his notes in cipher. Several times he remembers the problems of soldering, which his teacher Verocchio had met while soldering the spherical segments on the lantern of Florence cathedral. Numerous are the drawings of precise grinding and polishing machines for the production of mirrors. Leonardo finds a solution to avoid shading if the receptor of the solar rays obstructed the front of a mirror. Burning mirrors should heat fishponds or dyeing tubs, and they would save fire-wood during lime-burning. In the service of Giuliano, commander-in-chief of the papal army, Leonardo may well have trusted in the legend of Archimedes destructing Roman ships by burning mirrors.

광선추적을 사용한 나사산 표면결함 검사용 환형 광학계 개발

This study aims to develop a vision inspection system for screw threads. To inspect external defects in screw threads, the vision inspection system was developed using front light illumination from which bright images can be obtained. The front light system, however, requires multiple side images for inspection of the entire thread surface, which can be performed by omnidirectional optics. In this study, an omnidirectional optical system was designed to obtain annular images of screw threads using an image sensor and two reflection mirrors; one large concave mirror and one small convex mirror. Optical simulations using backward and forward ray tracing were performed to determine the dimensional parameters of the proposed optical system, so that an annular image of the screw threads could be obtained with high quality and resolution. Microscale surface defects on the screw threads could be successfully detected using the developed annular inspection system.

Present Status of the Nd:YAG Thomson Scattering System Development for Time Evolution Measurement of Plasma Profile on Heliotron J

A new high repetition rate Nd:YAG Thomson scattering system is developed for the Heliotron J helical device. A main purpose of installing the new system is the temporal evolution measurement of a plasma profile for improved confinement physics such as the edge transport barrier (H-mode) or the internal transport barrier of the helical plasma. The system has 25 spatial points with ∼10 mm resolution. Two high repetition Nd:YAG lasers (> 550 mJ@50 Hz) realize the measurement of the time evolution of the plasma profile with ∼10 ms time intervals. Scattered light is collected by a large concave mirror (D = 800 mm, f/2.25) with a solid angle of ∼100 mstr and transferred to interference filter polychromators by optical fiber bundles in a staircase form. The signal is amplified by newly designed fast preamplifiers with DC and AC output, which reduces the low frequency background noise. The signals are digitized with a multi-event QDC, fast gated integrators. The data acquisition is performed by a VME-based system operated by the CINOS.

Design of a new high repetition rate Nd:YAG Thomson scattering system for Heliotron J

A new high repetition rate Nd:YAG Thomson scattering system has been designed for the Heliotron J helical device. The main purpose of installing the new Thomson scattering system is an investigation of an improved confinement physics such as the edge transport barrier (H-mode) or the internal transport barrier of the helical plasma. The system has 25 spatial points with ∼10 mm resolution. Two high repetition Nd:YAG lasers (>550 mJ at 50 Hz) realize the measurement of the time evolution of the plasma profile with 10 ms time interval. Scattered light is collected with a large concave mirror (D=800 mm, f/2.25) with a solid angle of ∼100 msr. The laser beam is injected from obliquely downward to upward, and obliquely backscattered light is detected (scattering angle is 20°). Model simulation of the polychromator shows the measurable electron temperature and density range are from 10 eV to 10 keV, >5×10(18) m(-3) within 3% error for the temperature measurement, respectively.

On-Machine 구면기준 Shack-Hartmann 장치를 이용한 대형 반사경의 가공 정밀도 연구

A spherical surface referenced Shack-Hartmann method is studied for inspecting machining accuracy of large concave mirror. This method is so strong to the vibration environment for using as an on-machine inspection system during polishing process of large optics comparing with the interferometry. The measuring uncertainty of the system is shown as less than p-v 150 nm. On-machine measured surface profile data with this method is used for feed back control of the polishing time or depth to improve the surface profile accuracy of large concave mirror. Also, the spherical surface referenced Shack-Hartmann method is useful for measuring aspheric such as parabolic or hyperbolic surface profile, comparing that the interferometry needs a special null lens, which is to be a reference and difficult to fabricate.

A variable-focal-length telescope

A special additional optical system (AOS) to develop any telescope into a zoom or a variable-focal-length telescope (variotelescope) is proposed. This system permits the telescope optics and detector (charge-couped device) to be matched in order to obtain the best resolution. An analysis of the resolution of the system consisting of the ‘V-telescope and detector’ is performed, and it is shown that the best way to match the optics and detector is to change the focal length, that is to change the image scale. The proposed AOS consists of two spherical mirrors: a large concave mirror and a small convex mirror. The AOS is illustrated by means of figures and tables.

System for projection of a three-dimensional, moving virtual target for studies of eye-hand coordination

Eye-hand tracking of moving visual objects in three-dimensional (3D) space is common in the behavioral repertoire of primates. However, behavioral and/or neurophysiological studies of this function are lacking mainly because devices do not exist that allow its investigation. We describe a device by which a spot of light can be presented in the immediate extrapersonal space of a subject and can be moved in various trajectories in 3D space. The target is a real image of a circular aperture produced by a system consisting of a light source, aperture, filters, several lenses and fold mirros, and a large concave mirror to focus the final real image. Rapid, computer-controlled movement of the image is obtained by tilting a gimbal-mounted guide mirror (for x and y motion) and by translating a lens (for motion in the z direction). A second configuration of the system allows movement of a 3D image in the 3D space. Hand motion is monitored by means of a sonic, 3D, position-measurement system.

Automated Measurement of Strabismic Deviations Using a Remote Haploscope and an Infrared Television-Based Eye Tracker

A large concave mirror used in a specular display arrangement provides a remote mirror haploscope having superimposed visual fields subtending 50° × 50° at a viewing distance of 80 cm. Strabismic d...

Parabolic mirror made by the rotation method: its fabrication and defects

One possible method of making a large screen display is to use a virtual image system with a large concave mirror. A concave mirror with a high quality surface can be made inexpensively. A resin, such as an epoxy resin which hardens at room temperatures, is formed into the parabolic shape by a rotating dish. A mirror with a 920-mm diam and a 1150-mm focal length is made, which has sufficiently good characteristics for a virtual image display system. The fabrication and defects of mirrors made by this method are described.

Large concave mirror for indirect ophthalmoscopy.

Large concave mirror for indirect ophthalmoscopy.

Optical Effect of Flexure in Vertically Mounted Precision Mirrors

Under their own weight, large concave mirrors, such as used in telescopes and various research equipment, may elastically bend beyond tolerable limits. The problem of preventing harmful mirror deformations arises in full severity when gravity has a substantial component in the direction of the optical axis. The less serious case of gravity acting perpendicular to the optical axis has been dismissed by one author as harmless for mirror sizes up to 120 inches. However, disfigurations observed on much smaller vertically mounted mirrors are definitely traceable to elastic flexure by gravity. This paper briefly discusses the elastic deformation of an upright solid disk with a concave front surface and a plane back, supported along its edge by a distribution of radial forces which originate in the contact areas between disk and mount. The loss of image definition through flexure is related to the Fourier coefficients of the edge-pressure distribution in an explicit form simple enough as to permit the analysis of various types of mounts, as well as the synthesis of optimum mounting conditions. Numerical values and graphs are presented from which the optical effect can be appraised for different mirror shapes. The results are compared with observations made in practical tests.

Alice Through the (Convex) Looking Glass

OH, wad some power the giftie gi’e usTo see oursels as others see us,It wad frae mony a blunder free us,And foolish notion;in which case it is probable that wars would cease. During the last few years we have had glimpses of ourselves through the spectacles of the Central Powers; occasionally through the telescopes of the French, the Italians, or the Russians, and in the near future we are likely to get a good many pictures of ourselves as we appear to the last-named people. We are apt to think that our own view of ourselves is the only true view, and all other images are in error just as they differ from our own standard. Naturally other nations adopt the same course, and we are free to believe that in many cases their vision of themselves is far more at fault than our own self image. In this respect a study of Alice and her standards might be not without profit to the nations. When we want to see ourselves, or, at least, our faces, we usually employ a mirror, and what we see depends very much on the mirror we use. Sir George Greenhill was the first professor of Applied Mathematics at the Eoyal Indian Civil Engineering College, Coopers’ Hill. He told us that at the end of the first session a reception was held and the science departments were on view. A young lady entering the physical laboratory and seeing an inverted image of herself in a large concave mirror naively remarked to her companion, “They have hung that looking glass upside down.” But those who fixed the mirror were not to blame, as the lady would have discovered had she advanced past the centre of the curvature. The reply of modern mathematics to the prayer of Eobert Burns is the Theory of Relativity I have some doubt whether Burns would have appreciated the answer. As a rule, we use a plane mirror to inspect ourselves. This reverses certain spatial relations which can be expressed best, perhaps, by stating that it presents a right-handed screw as a left-handed screw and vice versû, or changes a wine screw into a beer screw, as Clerk Maxwell would say, referring to the tendrils of the vine and the hop.