The invention relates to a sub-aperture polishing tool, comprising a support member including an attachment feature for attachment to a sub-aperture polishing machine. At an end of the support member is a polishing head comprising: a base structure attached to or integral with the support member, the base structure being arranged to provide a non-flat surface. The polishing head also comprises an outer shell, at least part of the outer surface of which defines the working surface of the polishing tool, the outer shell being affixed to the base structure so as to enclose a cavity between the outer shell and the non-flat surface. A viscoelastic material filling the cavity, located between the outer shell and the base structure.

A method for manufacturing an ophthalmic device, comprising a polishing step to polish a surface comprising at least one unpolished zone, the at least one unpolished zone is a zone intended not to be polished. The polishing step comprises covering during which a protective cover is provided on the surface so as to cover the at least one unpolished zone; polishing at least a part of the surface and removing the protective cover.

A polishing pad or button for ophthalmic lenses has a flexible cover and a substantially rigid base. The cover has cutouts in a gyre or spiral pattern that may be eccentric from the geometric center of the button. The cutouts may enhance distribution of a polishing fluid across the working surface of the button as the button is moved across a lens. The base may have an undercut around its periphery, which may cause the button to attain a domed shape for conformance to a concave, convex, or saddleback lens surface as the button is pressed against the lens. The button may be used in a conventional lens polishing apparatus.

A spiral magnetorheological polishing method for mid-frequency error control is provided, relating to the technical field of optical polishing. The method includes: scanning along a polishing path by using a magnetorheological polishing method, and removing a material in a spiral manner with a polishing tool to achieve spiral magnetorheological polishing of a workpiece. An angle between a scanning direction and a workpiece material removal direction is changed in real time during scanning, to alter a spatial posture of a removal function on a polishing surface in a spiral manner, thereby reducing mid-frequency errors. The method further includes: during scanning, randomly changing a processing line spacing in real time to further achieve suppression of mid-frequency ripple errors. A scanning strategy employs raster scanning processing; when the scanning strategy employs raster scanning processing, the processing line spacing is a raster scanning spacing.