These 0.5” (12.7 mm) diameter silicon nitride balls are Grade 5, the best quality available as a
commodity item. The balls are round to 125 nm with a surface finish of 1.25 nm rms. They are
near diffraction-limited convex mirrors with a reflectivity of about 11%, more than enough for
most applications with the PSM. As with the steel balls, they are ideal for use with the PSM in
transferring optical to mechanical datums, and vice versa to better than 1 µm. They are superior
to steel balls in that they are virtually indestructible and resist stains, corrosion, and fingerprints.
The silicon nitride balls are non-magnetic, so they do not work with magnetic nests without
clamping unless the kinematic support is moderately centered under the ball.
We generally have these in stock, but occasionally there is an extended lead time.