Surface measurement is an important part of metrology, covering many industries, including ceramics, pharmaceuticals, surface bonding, laser micromachining, optical design, material science, biotechnology, coatings and nanotechnology. In order to exploit these opportunities, the Photonics Cluster has a Stil optical profiling system that enables surface profiling measurements to an accuracy of 10 nanometres. This sensor works on the principle of extended field confocal imaging.

The Stil system uses the principle of chromatic aberration to sense the position of the sample in the field of view. Simply put, the focus of every lens is slightly flawed as the red through to the blue wavelengths of light focus in different vertical planes. If the sensor illuminates a sample with white light, it can use the reflected wavelength to determine the height of the surface that it is measuring. This system has nanometre resolution in the Z plane, and 0.1 micron resolution in the X and Y planes. This allows measurement of:

• Form and texture
• Dimensional metrology
• Surface topography
• Roughness parameters
• Profile analysis
• Film thickness

The thickness of transparent samples can also be measured as long as the refractive index of the material is known. Our system has three different sensors, with different depths of field and different resolutions.