Optical Profilometry Lab

Within this lab we house several instruments for performing metrology on optical surfaces; we measure optical elements for figure and form as well as RMS surface roughness. The three main tools used in this lab are the Form Talysurf, the RTH Talystep, and the WYCO Topo 2D.

The Form Talysurf:

Talysurf
The Talysurf is a long trace surface contact profilometer
Measurement length
Measurement speed
0.5-120 mm
0.5 mm/s
Range 4.0 mm with diamond stylus
8.0 mm with ball stylus
Resolution 10 nm with 60 mm nominal length stylus
20 nm with 120 mm nominal length stylus
40 nm with 240 mm nominal length stylus
Table of operating Parameters

Stylus contact surface profiles can be performed on a range of optical elements covering many types of surfaces, from Fresnel lenses to toroidal components. New paradigm optics with high order surfaces and lens arrays for computational imaging can be measured using this instrument. The data can be analyzed using Matlab or MathCAD. As well, the actual surface can be put into predictive models for performance validation and overall optical system verification.

Comparison
Comparison of a diamond turned Fresnell surface to the theory using the talysurf.
Typical stylus profile of optical surface
Typical stylus profile of optical surface.

The Talystep:

Rank Taylor Hobson Talystep
Rank Taylor Hobson Talystep

The Rank Precision Industries Talystep provides an electromechanical method for measuring RMS roughness and thin film thickness, measuring surface roughness down to 4 Angstroms RMS; using our 0.1 micron probe tip. Operationally, vertical movement of the stylus is detected by an inductance transducer and the electrical signal is amplified. The stylus can be traversed at three different speeds and the vertical stylus force can be varied, usually kept at 1-2 mg. Several of our staff have been trained by Dr. Jean Bennett, a former CAO employee, and continue to maintain the high finesse procedures required for operating this delicate instrument when measuring angstrom level RMS surfaces.

Typical output
Typical output from the Talystep.

The WYKO Topo 3D:

This is our main non-contact surface profile instrument. The measurements are accomplished through phase measurement interferometry. This instrument has a 2 angstrom vertical resolution and a 1 micron lateral resolution you can obtain both 2D and 3D plots, which are then transferred to the Matlab or Mathcad for further analysis. We typically measure or calculate slope, curvature, power spectrum and autocovariance with this instrument.

Our WYKO Topo 3D
Typical 2D contour plot1
Typical 2D contour plot2
Typical 2D contour plots from the WYKO profilometer
Typical 3D plot1
Typical 3D plot2
Typical 3D plots