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Concave Surface Figure Measurement

• Concave measurement setup (vertical mount shown)

Use a transmission sphere on the interferometer to bend the Minifiz output beam into a spherical wavefront for the evaluation of spherical surfaces and lenses. With this arrangement of optics, examine a concave spherical surface for surface figure and irregularity, that is, its deviation from a hypothetical best-fitting sphere, by placing its center of curvature at the point of focus of the transmission sphere.

Radius of curvature can be determined with some additional accessories. Check the sphericity page for an illustration of this process.

Adjustment of the surface under test is typically provided by a 3-axis mount.

Using phase shifting, the interferometer acquires data about surface height variations. Note that concave surface measurements of this type effectively remove the spherical surface figure, and 'see' the curved surface as virtually flat. This then allows an analysis of the test surface's departure from sphericity, by showing local shape variations.

Suggested Accessories: Phase Shifting Interferometer; Transmission sphere; Mount, 3-axis (tip-tilt); Self-centering element holder.

Below are links for other interferometer setups, for measuring different kinds of surface figures. 

Convex optical measurements

Interferometer setups

Flatness measurements of optics

Products related to this application:

MiniFIZ

Transmission Spheres

Related applications

Concave optics measurement

Measuring sphericity and radius of curvature

Flatness measurements