Method of manufacturing an optical element

A method of manufacturing an optical element having an optical surface of a predetermined shape, the method comprising:

• machining a substrate having a main surface extending beyond an outline of an optical surface of the main surface, such that the substrate has a first thickness in a height direction transverse to the main surface and within a complete interior of the outline of the optical surface, and such that the substrate has a second thickness in the height direction and within a removable portion of the main surface disposed outside of the outline of the optical surface, wherein a ratio of the first thickness over the second thickness is greater than 3;
• performing a first processing of the main surface such that differences between a shape of the main surface and the predetermined shape are below a predetermined first tolerance within the interior of the outline of the optical surface;
• performing a second processing of the main surface, wherein the second processing includes polishing the main surface such that the differences between the shape of the main surface and the predetermined shape are below a predetermined second tolerance of 1 nm rms at a spatial wavelength in a spatial wavelength range from about 100 nm to about 1 mm and within the interior of the outline of the optical surface;
• and
• performing a third processing of the substrate including removing the removable portion of the substrate to reduce a distance between a periphery of the optical surface and a periphery of the main surface of the substrate.