Non-contact surface gaging

Non-contact surface gaging

October 4, 2018

Marposs Corp
Quality/Metrology Surface Finish

Auburn Hills, Michigan – Marposs introduces Confocal, a non-contact measuring system which enables fast, high-resolution distance and thickness gaging of surfaces including solid, transparent, and polished mirror surfaces such as glass, plastic, or silicon wafers. Featuring a 4mm optical sensor within the measuring probe, the accuracy is precise, enabling the identification of very small aberrations in shape, air gap, or paint finish.

The measuring probe placement can be adjusted to achieve very high accuracy. For example, a measuring range of 0.4mm provides 0.055µm accuracy whereas a measuring range of 12mm provides about 0.750µm accuracy. Example applications include:

• Detection of metal burrs in holes

• Measurement of air gaps between two pieces of glass being assembled into a windshield

• Thickness measurement of transparent finishing paint on a glass surface

• Diameter measurement of plastic insulin syringe fingers

Marposs offers the solution with different sensor models and either a DIN rail controller for combination with a PC or a stand-alone unit with an integrated 7" display screen.

The Confocal solution is based on the confocal chromatic measuring principle, where white light is split into different spectra using lenses focused on an object through a multi-lens optical system. The lenses are arranged to create and send a chromatically aberrated beam to the target. The target reflects the optical beam back to the probe where it transmits the reflected optical beam to a spectrometer. The reflected optical beam is comprised of rays coming from the outside surface of the object being measured and from the internal surfaces that the beam can reach.

The reflected light intensity is at a maximum for the wavelengths focused on the surfaces. Electronic processing can then determine the intralayer thickness values of the target, or the distance from the probe to the outside surface and to the intralayer surfaces of the target.