Micromap 570 3D Surface Profiler (Micromap
Corperation)
The Micromap 570 3D surface profiler
(shown above) is a microscope-based instrument that utilizes visible
light interferometry to measure the surface finish (i.e. surface
roughness) of optical surfaces. A CCD detector mounted on the
microscope is used to measure an area (on the order of a few mm x
mm, which is dependent on the microscope objective used) with a
height resolution of approximately 0.03 nm.
Four different objectives are currently available: 5X, 10X, 20X,
and 50X, which enable us to cover a wide range of spatial samplings
(0.0002-1.25 mm) and spatial frequencies (0.0004-2.5
mm-1).
Three measurement modes are available in software -
smooth phase mode (interferometry phase measurement), wave mode
(white light interferometry phase scan) and focus mode (interferometry
focus scan). Smooth phase mode is ideal for very smooth surfaces
(0.02 - 100) nm Sq roughness, but is limited to a maximum height
measurement of 4 mm (focus depth). Wave
mode is ideal for smooth surfaces with steps (maximum height
measurement of 150 mm). Focus mode is
ideal for rough surface textures and weak surface reflections
(maximum height measurement of 150 mm).
Above is shown the 3D surface profile of a smooth
mirror, taken using a 10X objective with the Micromap 570. This was
taken in "smooth phase" mode using filtered white light (550 nm with
a 25 nm filter bandwidth). The image represents approximately
0.5 x 0.5 mm2 of the mirror.
This mirror surface has the following surface texture parameters
- a root-mean-square surface roughness of 3.132 angstroms RMS (Sq),
an average surface roughness of 2.481 angstroms (Sa), and a maximum
peak to valley height over the sample of 37.34 angstroms (St).
Numerous striations are clearly visible in this image - they
result from the lapping and polishing steps that occur in
manufacturing the mirror, before the mirror is coated.
