Abstract: A delay mirror 1 includes a base 2, and an optical multilayer film 4 formed on a surface R of the base 2. The value of a group delay in a first wavelength band according to the optical multilayer film 4 is different from the value of the group delay in the second wavelength band according to the optical multilayer film 4, and the value of a group delay dispersion in the first wavelength band according to the optical multilayer film 4 and the value of the group delay dispersion in the second wavelength band according to the optical multilayer film 4 are each not less than ?100 fs2 and not greater than 100 fs2. Further, the delay mirror system includes a delay mirror movement mechanism which moves the delay mirror 1 such that the number of times of reflection is changed.

Abstract: In the optical product bending prediction method according to the present invention, bending ? of a substrate having a film is predicted by a computer performing calculation (steps S11 to S13) of the following Expressions (A1), (B1), etc., in which a and Td are set as fitting parameters and have been optimized in each coating condition using a plurality of samples. Here, ?int is intrinsic stress, Ef is a Young's modulus of a multilayer film, vf is a Poisson's ratio of the multilayer film, ?f is a linear coefficient expansion of the multilayer film, ?s is a linear coefficient expansion of the substrate, T is a room temperature, d is a film thickness, b is a substrate thickness, l is a radius of the substrate, Es is a Young's modulus of the substrate, and vs is a Poisson's ratio of the substrate.