Papers by Keyword: Optical Glass

Abstract: The problematic issues connected with the optical details deformations that arise during the temperature tests of cemented assemblies are considered. Climatic tests of optical devices after assembly result in a change of technical product characteristics. The research problem is to define how N and ∆N of surfaces of cemented optical assemblies are changing after the temperature testing. The research objects are plane convex lenses fabricated of LK7 (LZOS) glass brand and plane concave lenses - of TF7 (LZOS). Before cementing, the bounded surfaces cleaning by the hydromechanical method in the clean room has been purged. The temperature testing of samples is held at 22, 50 and 65 °C. The effect of temperature on a surface deformation of cemented optical assemblies is experimentally established. The comparison of effect of optical cements OK72FT₅ and OK72FT₁₅ on the optical surfaces deformation is carried out. In this paper we have compared the results of shape accuracy of the external surfaces of optical assemblies and the flat surfaces. Interferograms of lenses after heat treatment of optical assemblies are presented. It is determined that the cement polymerization temperature equals or higher than the test temperature.

Abstract: Ductile removal behavior of hard and brittle material in the process of machining has always been a sticking topic. A series of nanoscratch tests of K9 glass were conducted with Berkovich probe on nanoindenter XP to investigate the ductile removal process, material deformation and crack damage. It was found that the scratches surface was free from crack damage in the range of the selected scratching parameters and excellent machinability of K9 glass was obtained. The observation also showed that the stable chips were distributed on the sides of the scratches and the deformation of chips was much larger than that obtained in the conventional machining. Meanwhile, a pile-up phenomenon was obvious and the residual depth of scratches was decreased with the increasing of scratch velocity under the same normal load condition.

Abstract: Mie scattering theory is used in this paper to analyze the forward scattered light intensity distribution of an air bubble in the subsurface of optical glass, shining by a monochrome laser with a wavelength of 632.8um. The scattering process can be classified as uncorrelated single scattering .according to the properties of optical media. The finite difference time domain (FDTD) software is used to establish a 3-d simulation model to calculate for forward scattered intensity distribution of different sized air bubbles. Moreover, according to the relationship between Mie scattering intensity pattern and the size of bubbles, the size of bubbles are figured out with the help of neural network algorithm. The errors are lower than 10%. The simulation results can improve the precision of defects detection in optical glass.

Abstract: Most optical glasses are in recent years being manufactured by diamond turning processes which has certainly modernized the field of production of optics. Confines of diamond turning for both form and surface finish accuracy have not been reached, yet. In advent of contemporary technology, high precision finishing techniques are of great concern and the need of present industrialized-scenario. This paper presents the development of a small rotary multi-jet abrasive fluid jet polishing tool for use in polishing of optical glasses. The newly designed and manufactured tool has relative angular speed with respect to the spindle of machining centre and is capable of polishing at micro levels. The paper also investigates the optimal polishing parameters for selected, crown optical glass based on experiments conducted using Taguchi’s experimental method. According to the possible number of control factors L₁₈ orthogonal array was used. ANOVA analysis was carried out to determine the main factors which would affect the surface roughness significantly. Consequently, a 2.5 μm size of Al₂O₃ abrasive, 10wt% abrasive concentration, 40 rpm of polishing head rotation, 6 numbers of nozzles, 6 kg/cm² of fluid pressure, 45minuet of polishing time and 40% of step over have been found to be the optimal parameters. It was observed that about 97.22% improvements on surface roughness; Ra, from 0.360 μm to 0.010 μm has been achieved using the optimal parameters. In addition to this; rotation of polishing head, applied fluid pressure and polishing time were found to have significant effect on surface roughness improvement.

Abstract: As the needs of optical glasses are on the rise, the precision on shape, form, surface qualities and the scaling down of sizes are rising, too. The standards and surface finish of reference mirrors used in measuring appliances are crucial; hence, enhancement of the surface finish is indispensable in manufacturing industries. This paper proposes a self-propelled multi jet polishing technique for ultra precision polishing process in which bladeless Tesla turbine was used as a prime mover. The turbine is characterized by high swirling velocity at the outlet; therefore, high kinetic energy in the course of away from the turbine was used as polishing energy. Simulation of the flow of the field of turbine blades using computational fluid dynamics software (CFD) has also been presented. With a newly designed and manufactured polishing tool, this paper investigates the optimal polishing parameters for surface roughness improvement of crown optical glasses using Taguchis experimental approach; signal-to-nose (S/N) ratio and ANOVA analysis was also carried out to determine the effect of main factors on the surface roughness. Consequently, a 2.5μm size of Al₂O₃ abrasive, 10wt% abrasive concentration, 80rpm of polishing head, 6 numbers of nozzles, 6 kg/cm² of pressure, and 45min. of polishing time have been found to be the optimal parameters. It was observed that about 94.44% improvements on surface roughness; Ra, from 0.360μm to 0.020μm has been achieved using the optimal parameters. In addition to this; angular speed of polishing head, pressure and polishing time were found to have significant effect on surface roughness improvement.

Abstract: For the technology of diamond cutting of optical glass, the machinability of glass is poor, which hindering the practical application of this technology. In order to investigate and ameliorate the machinability of glass, and achieve optical parts with the satisfied surface quality and dimensional accuracy, this paper first conducted SF6 indentation experiment by Vickers microhardness instrument, and then the scratching tests with increasing depths of cut were conducted on glass SF6 to evaluate the influence of the cutting fluid properties on the machinability of glass. Based on this, turning tests were carried out, and the surface quality of SF6 was assessed based on the detections of the machined surfaces roughness. Experimental results indicated that compared with the process of dry cutting, the machinability of glass SF6 can be improved by using the cutting fluid

Abstract: In diamond cutting of optical glasses, the magnitude of critical depth of cut for brittle-ductile transition is an important factor affecting the machinability of the work material in terms of production rate and surface quality. In this work, scratching tests with increasing depths of cut were conducted on glass BK7 to evaluate the influence of the cutting fluid properties on the critical depth of cut. Boric acid solutions of different concentrations were selected as cutting fluids in the tests. The resulting scratches were examined utilizing a white light interferometer and the values of the critical depth of cut were determined based on the observations of the micro-morphology of the scratch surfaces produced. Experimental results indicated that compared with the process without cutting fluid action, the critical depth of cut in diamond cutting of glass BK7 can be increased by using boric acid solution as the cutting fluid.

Abstract: For the technology of diamond cutting of optical glass, the machinability of glass is poor, which hindering the practical application of this technology. In order to investigate and ameliorate the machinability of glass, and achieve optical parts with the satisfied surface quality and dimensional accuracy, this paper first conducted SF6 indentation experiment by Vickers microhardness instrument, and then the scratching tests with increasing depths of cut were conducted on glass SF6 to evaluate the influence of the cutting fluid properties on the machinability of glass. Based on this, turning tests were carried out, and the surface quality of SF6 was assessed based on the detections of the machined surfaces roughness. Experimental results indicated that compared with the process of dry cutting, the machinability of glass SF6 can be improved by using the cutting fluid.

Abstract: In diamond cutting of optical glasses, the magnitude of critical depth of cut for brittle-ductile transition is an important factor affecting the machinability of the work material in terms of production rate and surface quality. In this work, scratching tests with increasing depths of cut were conducted on glass BK7 to evaluate the influence of the cutting fluid properties on the critical depth of cut. Boric acid solutions of different concentrations were selected as cutting fluids in the tests. The resulting scratches were examined utilizing a white light interferometer and the values of the critical depth of cut were determined based on the observations of the micro-morphology of the scratch surfaces produced. Experimental results indicated that compared with the process without cutting fluid action, the critical depth of cut in diamond cutting of glass BK7 can be increased by using boric acid solution as the cutting fluid.

Abstract: The mechanism of ultrasonic assisted grinding is presented. Single factor experiment method was used to conduct experiments in order to reveal the effect of different grinding parameters (including feed rate, spindle speed, grinding depth) on surface roughness and grinding force of optical glass in ultrasonic assisted grinding and conventional grinding. The experiment data wss analyzed and it shows that the surface roughness and tangential grinding force decrease while the axial grinding force increase in ultrasonic assisted grinding process than that in conventional grinding process.