Production method and measurement method

A method for measuring a surface shape of an optical element in a predetermined measurement environment, wherein the optical element comprises a main body with a substrate and a reflective surface, and wherein at least one cooling channel for receiving a coolant is formed in the substrate,

• the method comprising:
• a) recording a cooling channel pressure,
• b) recording a measurement environment pressure,
• c) determining an actual pressure difference based on the cooling channel pressure and the measurement environment pressure,
• d) comparing the actual pressure difference with a predetermined target pressure difference,
• e) monitoring for a deviation between the actual pressure difference and the target pressure difference, wherein, if a deviation greater than a predetermined limit value is detected, the cooling channel pressure is adapted in such a way that the deviation becomes less than or equal to the predetermined limit value, and
• f) measuring the surface shape if the deviation is less than or equal to the predetermined limit value.