Miroir et substrat de miroir à rapport de forme élevé, et procédé et moyen pour produire un tel substrat de miroir

L'invention concerne de manière générale un miroir et un substrat de miroir, notamment un miroir et un substrat de miroir ayant un rapport de forme élevé, et un procédé et un moyen pour produire ceux-ci. Figure pour l'abrégé : Fig 1 A mirror, a mirror substrate, a method for producing are provided. The mirror substrate is made of a material having a coefficient of mean linear thermal expansion of less than or equal to 1*10−6/K. The mirror substrate includes at least one feature selected from a group consisting of: a ratio of a lateral dimension to a maximum thickness of at least 100, a ratio of the lateral dimension to the maximum thickness of at least 150, a ratio of the lateral dimension to the maximum thickness of at least 200, a ratio of the lateral dimension to the maximum thickness of at least 300, a weight per unit area of 100 kg/m2 or less, a weight per unit area of 50 kg/m2 or less, a weight per unit area of 30 kg/m2 or less, a weight per unit area of 15 kg/m2 or less, a mirror surface with a roughness (Ra) of at most 3.5 μm, and a mirror surface with a roughness (Ra) of less than 1.2 μm.