The characteristics of optics polished with a polyurethane pad

Abstract

The effect of polishing an optical workpiece with a polyurethane pad was studied in this paper, including material removal rate, surface roughness and subsurface damage. Usually, optical polishing pitch is applied to polish optical workpieces, but the material removal rate (MRR) of pitch is quite low, and polyurethane foam is thus substituted for polishing pitch. With the polyurethane pad a much higher MRR was obtained. Surface roughness and subsurface damage of workpieces were also examined. We were gratified to find that there was almost no subsurface damage in the workpieces manufactured with pad polishing and surface roughness was comparable to the result of pitch polishing. Finally, a hypothesis was proposed in an attempt to explain the result that workpieces were defect-free.

Producing fused silica optics with high UV-damage resistance to nanosecond pulsed lasers

“…Fused silica optical components are usually finished by various polishing techniques where polishing compound is used to polish out the surface of fused silica with loose abrasive polishing [6][7][8] and/or bound-abrasive polishing [9][10][11]. Although the techniques employed to polish an optics may differ, the mechanism is similar that a polishing layer (Beilby layer) is almost inevitably left on the finished optics [4,5,12].…”

“…Although the techniques employed to polish an optics may differ, the mechanism is similar that a polishing layer (Beilby layer) is almost inevitably left on the finished optics [4,5,12]. For instance, the conventional pitch or pad polishing may form a layer that contains abundant Ce because of the widespread use of ceria as polishing compound in optical shop floor [6,7]. Some metallic elements such as Ce, Fe are considered to absorb laser light in UV spectra, potentially resulting in elevated temperature and finally mechanical damage in localized region [13].…”

“…It seems that the polishing layer (in terms of Ce depth into the surface of fused silica) is greater in the fused silica polished by pitch lap than those by polyurethane pad. The reason is presumably reckoned as the more chemically active pitch during the polishing of fused silica which result in thicker polishing layer [7]. Slightly etching will sharply reduce the concentration of Ce as well as other metallic impurities (Fe, Al, etc.)…”

Fundamental performance of Magnetic Compound Fluid (MCF) wheel in ultra-fine surface finishing of optical glass

“…In the manufacturing process of optical devices, optical glass is generally polished with a loose abrasive to eliminate breaks, cracks and damaged layers on the work surface caused by the previous process, which is typically grinding. However, to achieve the desired surface quality, the conventional loose-abrasive technique is time-consuming and therefore costly [1,2]. The causes are mainly the difficulties in maintaining an effective amount of the abrasive slurry and a uniform distribution of abrasive particles in the polishing area.…”

“…(2) and (3) for an outer diameter (D) of 39 mm, an inner diameter (d) of 19 mm, a width (B) of 7 mm and a clearance of 0.5 mm (a distance of 20 mm from the center of the magnet). Figure 16 shows the distribution of the magnetic field strength across the width of the wheel (in the X-axis).…”