HyDra: A novel hydrodynamic polishing tool for high quality optical surfaces

2005 ◽  
Author(s):  
Benjamin Martinez ◽  
Manuel Nunez ◽  
Esteban Luna ◽  
Luis Salas ◽  
Irene Cruz-Gonzalez ◽  
...  
Keyword(s):  
High Quality ◽  
Optical Surfaces ◽  
Polishing Tool

scholarly journals Refractive vs Reflective Correctors

1984 ◽  
Vol 79 ◽  
pp. 549-567
Author(s):  
E.H. Richardson ◽  
C.L. Morbey
Keyword(s):  
Good Combination ◽  
The Other ◽  
Stray Light ◽  
High Quality ◽  
Optical Surfaces ◽  
Other Hand

SummaryImproved designs of refractive correctors produce excellent images with fast telescopes such as those with an F/1.5 prime focus and F/3.5 secondary focus. The fields are flat and there is compensation for the chromatic effect caused by windows. Disadvantages of such correctors are that stray light is produced at the optical surfaces, the elements must be supported at their edges, prerequisite high quality glass is available in only limited sizes, and all wavelengths are not transmitted.Reflective correctors, on the other hand, can produce diffraction limited images at all wavelengths and the mirrors can be supported across their backs as well as at their edges. Disadvantages are that the images are degraded by any substantial window (such as a detector faceplate), there is more central obstruction, and the correctors are sometimes very large and heavy.Except, perhaps, for a specialized telescope, such as one devoted to multi-object slit spectroscopy using fibres, the refractive corrector is preferable at fast foci.A good combination is a Ritchey-Chretien (R-C) telescope with refractive correctors at the fast prime and secondary foci, and a reflective corrector-magnifier for the slow infrared focus.

Study on Polishing Characteristics of Pyramidal Structured Polishing Pad

2019 ◽  
Vol 13 (2) ◽  
pp. 237-245
Author(s):  
Ryunosuke Sato ◽  
Yoshio Ichida ◽  
◽  
Keyword(s):  
Steady State ◽  
Wear Rate ◽  
Removal Rate ◽  
High Quality ◽  
Abrasive Grains ◽  
Polishing Pad ◽  
Finished Surface ◽  
Polishing Tool ◽  
Polishing Pressure

We conducted a polishing test to clarify the change in polishing characteristics resulting from the wear of a pyramidal-structured polishing tool, and discuss the polishing mechanism unique to the pyramidal-structured polishing pad. When the pyramidal-structured polishing pad is used for polishing, there exists an initial polishing stage in which the removal rate is high but the finished surface is rough; followed by a steady-state polishing stage in which the wear rate is low, removal rate is stable, and a high-quality finish is obtained. The true polishing pressure is constant in the steady-state polishing stage regardless of the nominal polishing pressure, although it differs with workpiece hardness. Polishing was carried out using the pyramidal-structured polishing pad containing 6 μm alumina abrasive grains for 90 min without any scorching or clogging. This resulted in finished surfaces of 0.4 μmRzand 0.07 μmRzfor oxygen-free copper and S45C, respectively.

Distortion of removal function based on the local asphericity of aspheric surface and the viscoelasticity of polishing tool in computer-controlled optical surfacing

2017 ◽  
Vol 232 (7) ◽  
pp. 1135-1145 ◽  
Author(s):  
Xianhua Chen ◽  
Bo Zhong ◽  
Jian Wang ◽  
Hongzhong Huang ◽  
Wenhui Deng ◽  
...  
Keyword(s):  
Contact Region ◽  
Influence Factors ◽  
Least Square Method ◽  
Least Square ◽  
Experimental Result ◽  
Aspheric Surface ◽  
Optical Surfaces ◽  
Computer Controlled Optical Surfacing ◽  
Computer Controlled ◽  
Polishing Tool

In the process of large aspheric optical surfaces fabrication, the distortion of the removal function is a big problem that affects the producing efficiency and accuracy, due to the misfit between the tool and the aspheric surface in the contact region. Consequently, this paper aims to find out the influence factors and the distortion rule of aspheric removal function in the computer-controlled optical surfacing. Firstly, based on the analysis of the sub-aperture polishing technology for the large aspheric optical surfaces, the local asphericity of aspheric surface and the viscoelasticity of polishing tool are supposed to be the main sources. After that, a method to calculate the local asphericity considering the misfit between the tool and the aspheric surface is proposed based on the least square method, and the viscoelasticity of the polishing tool is obtained through viscoelastic experiment. Subsequently, combining the results of the local asphericity of aspheric surface and the viscoelasticity of polishing tool, the prediction of the distortion rule of aspheric removal function is presented. Finally, the comparative experiment is carried out, and the removal function on different regions of the aspheric surface is obtained. The experimental result indicated that the distortion of the removal function is consistent with the theoretical result. Through this study, the distortion rule of aspheric removal function in the computer-controlled optical surfacing with pitch tool is finally mastered, which provides a theoretical guidance for the computer-controlled optical surfacing process optimization.

Some problems of objective-prism spectra classification

1966 ◽  
Vol 24 ◽  
pp. 51-52
Author(s):  
E. K. Kharadze ◽  
R. A. Bartaya
Keyword(s):  
Short Wave ◽  
High Quality ◽  
Stellar Spectra ◽  
Objective Prism

The unique 70-cm meniscus-type telescope of the Abastumani Astrophysical Observatory supplied with two objective prisms and the seeing conditions characteristic at Mount Kanobili (Abastumani) permit us to obtain stellar spectra of a high quality. No additional design to improve the “climate” immediately around the telescope itself is being applied. The dispersions and photographic magnitude limits are 160 and 660Å/mm, and 12–13, respectively. The short-wave end of spectra reaches 3500–3400Å.

A non-cyanide method of electropolishing silver

1978 ◽  
Vol 36 (1) ◽  
pp. 146-147
Author(s):  
R. L. Lyles ◽  
S. J. Rothman ◽  
W. Jäger
Keyword(s):  
Electron Microscopy ◽  
Sulphuric Acid ◽  
Methyl Alcohol ◽  
Health Hazards ◽  
Silver Alloy ◽  
High Quality ◽  
Silver Alloys ◽  
Free Sample ◽  
Specimen Quality ◽  
Standard Techniques

Standard techniques of electropolishing silver and silver alloys for electron microscopy in most instances have relied on various CN recipes. These methods have been characteristically unsatisfactory due to difficulties in obtaining large electron transparent areas, reproducible results, adequate solution lifetimes, and contamination free sample surfaces. In addition, there are the inherent health hazards associated with the use of CN solutions. Various attempts to develop noncyanic methods of electropolishing specimens for electron microscopy have not been successful in that the specimen quality problems encountered with the CN solutions have also existed in the previously proposed non-cyanic methods.The technique we describe allows us to jet polish high quality silver and silver alloy microscope specimens with consistant reproducibility and without the use of CN salts.The solution is similar to that suggested by Myschoyaev et al. It consists, in order of mixing, 115ml glacial actic acid (CH3CO2H, specific wt 1.04 g/ml), 43ml sulphuric acid (H2SO4, specific wt. g/ml), 350 ml anhydrous methyl alcohol, and 77 g thiourea (NH2CSNH2).

A High Resolution Scanning Microscope

1968 ◽  
Vol 26 ◽  
pp. 356-357
Author(s):  
A. V. Crewe ◽  
J. Wall ◽  
L. M. Welter
Keyword(s):  
High Resolution ◽  
Field Emission ◽  
Spherical Aberration ◽  
Focal Length ◽  
Spot Size ◽  
Emission Source ◽  
Field Of View ◽  
Scanning Microscope ◽  
Magnetic Lens ◽  
High Quality

A scanning microscope using a field emission source has been described elsewhere. This microscope has now been improved by replacing the single magnetic lens with a high quality lens of the type described by Ruska. This lens has a focal length of 1 mm and a spherical aberration coefficient of 0.5 mm. The final spot size, and therefore the microscope resolution, is limited by the aberration of this lens to about 6 Å.The lens has been constructed very carefully, maintaining a tolerance of + 1 μ on all critical surfaces. The gun is prealigned on the lens to form a compact unit. The only mechanical adjustments are those which control the specimen and the tip positions. The microscope can be used in two modes. With the lens off and the gun focused on the specimen, the resolution is 250 Å over an undistorted field of view of 2 mm. With the lens on,the resolution is 20 Å or better over a field of view of 40 microns. The magnification can be accurately varied by attenuating the raster current.

Quantitative defect studies in semiconductor TEM samples prepared by low angle ion milling

1995 ◽  
Vol 53 ◽  
pp. 512-513
Author(s):  
L. Mulestagno ◽  
J.C. Holzer ◽  
P. Fraundorf
Keyword(s):  
Sample Preparation ◽  
Milling Time ◽  
High Density ◽  
Low Density ◽  
Ion Milling ◽  
High Quality ◽  
Variable Angle ◽  
Major Disadvantage ◽  
Induced Defects

Due to the wealth of information, both analytical and structural that can be obtained from it TEM always has been a favorite tool for the analysis of process-induced defects in semiconductor wafers. The only major disadvantage has always been, that the volume under study in the TEM is relatively small, making it difficult to locate low density defects, and sample preparation is a somewhat lengthy procedure. This problem has been somewhat alleviated by the availability of efficient low angle milling.Using a PIPS® variable angle ion -mill, manufactured by Gatan, we have been consistently obtaining planar specimens with a high quality thin area in excess of 5 × 104 μm2 in about half an hour (milling time), which has made it possible to locate defects at lower densities, or, for defects of relatively high density, obtain information which is statistically more significant (table 1).

Sign in / Sign up

Export Citation Format

Share Document