Diffractive optical element for a test interferometer

A calibration method for calibrating a diffractive optical element comprising diffractive shape measuring structures arranged on a used surface of the diffractive optical element and each configured to generate a test wave when the diffractive optical element is arranged in a test interferometer configured for measuring a shape of an optical surface, wherein the test wave is arranged to irradiate the optical surface to be measured, comprising:

• arranging the diffractive optical element in a measuring device and measuring test fields arranged at a plurality of locations of the used surface and each having test structures having a profile line extending transversely with respect to the used surface, for ascertaining a plurality of profile properties of the test structures relating to the profile line, wherein the profile properties comprise a flank angle of the profile line of the test structures, a profile depth of the test structures and a depth of a microtrench which occurs in a bottom region of a trench-shaped profile of the test structures, and
• determining, from the profile properties ascertained, a calibration value for calibrating the shape measuring structures during the measurement of the optical surface.

A method for producing diffractive optical elements for a test interferometer for measuring a shape of an optical surface, comprising:

• producing the diffractive optical elements with in each case diffractive shape measuring structures arranged on a used surface of the respective diffractive optical element and configured to generate a test wave for irradiating the optical surface to be measured when the respective diffractive optical element is arranged in the test interferometer, wherein at least one test field is arranged at one location of the used surface of each of the diffractive optical elements instead of the diffractive shape measuring structures such that the at least one test field is surrounded by a plurality of the diffractive shape measuring structures, and
• monitoring a production process stability by measuring the test fields of the diffractive optical elements.