Patent ID: 7466427

Claim:
A vibration-resistant interferometer apparatus comprising: a light source emitting a luminous flux; a light divider configured to divide the luminous flux into two divided luminous fluxes; an optical detouring component configured to detour each of said two divided luminous fluxes into respective optical paths that have different optical path lengths relative to each other; an optical recombining component configured to recombine said two divided luminous fluxes into one luminous flux to form an irradiating luminous flux; and means for producing interference fringes through optical interference between a first luminous flux obtained by reflecting said irradiating luminous flux at a reference surface and a second luminous flux obtained by transmitting said irradiating luminous flux through said reference surface and then reflecting at a sample surface, and then recombining said first luminous flux and said second luminous flux such that the axis of said first luminous flux and the axis of said second luminous flux substantially coincide with one another, wherein said light source is a low-coherence light source for which said luminous flux, emitted from said light source, has a coherence length shorter than twice the optical distance between said reference surface and said sample surface, or a wavelength-modulated light source adjusted such that the coherence length is equivalent to the coherence length possessed by such a low-coherence light source when an image of said interference fringes is captured by an imaging element, said irradiating luminous flux is obtained by reflecting a first divided luminous flux out of said two divided luminous fluxes from a second reference surface that is held such that the relative positional relationship thereof with said reference surface does not change, and reflecting a second divided luminous flux out of said two divided luminous fluxes from a secondary sample surface that is held such that the relative positional relationship thereof with said sample surface does not change and faces in the same direction as said sample surface, and then recombining said first divided luminous flux and said second divided luminous flux via said optical recombining component into said one luminous flux such that the axis of said first divided luminous flux and the axis of said second divided luminous flux substantially coincide with one another, and a position of the secondary sample surface is set such that an optical path length difference between the optical path taken by said first divided luminous flux from the light divider to the secondary reference surface and back to the optical recombining component and the optical path taken by said second divided luminous flux from the light divider to the secondary sample surface and back to the optical recombining component is twice an optical path length between the reference surface and the sample surface.