Optical profilometry

For a long time the classical interferometry was the only optical displacement measuring method and the targets needed to be specularly reflective. By the end of the seventies the first triangulation based measuring systems appeared on the market. They used expensive and delicate gas lasers. Parallel there were a few applications using light diffraction, e.g. fast scales. More promising seemed at that time the development of shadow casting methods.

At Microtecnic 1986 the first autofocusing devices were shown and shortly thereafter the first 3D measurement stations appeared. The white light interferometry started at the beginning of the ninetees and is meanwhile wide-spread.

Since 2011 BMT has been offering exclusively an area measuring sensor utilising the digital holographic principle. It offers a range of several mm and at the same time a high resolution.

The current market for displacement measurement and surface profilometry is now as before dominated by stylus based instruments both for roughness and coordinate measuring devices. It is rewarding and makes sense to further develop the tactile instruments and make use of the technological progess. All optical methods used for microstructure profilometry suffer from artefacts as described by the laws of nature for the light propagation. Often one can only achieve the results as expected by certain customers by massive filering of the data.

Indeed there are numerous applications for optical measurement techniques only in especially in electronics and optics where high resolution and fast data acquisition are requested. Also for the measurement of honing structures in combustion engine production an optical measurement is about to become the industry standard for the area honing structure assessment.

Area measuring devices like short coherence interferometry, confocal microscopy and stripe projection are being supplemented by pointwise measuring sensors having working principles like chromatic abberation, autofocus or triangulation. These can favourably be used to scan large object areas. The higher data point density at large areas with respect to camera based instruments are traded of by a correspndingly long measurement time.

Commercially available optical measurement devices feature at best a lateral resolution of approx. 0.5 µm which is given by the diffration limit. A considerably higher resolution upto atomic dimensions is achieved by using an AFM. Even more sophisticated than when dealing with optical scanning is here the differentiation of the true surface profile and scanning artefacts.

BMT offers all important interferometric measurement methods, namely Mirau, Michelson, Linnik and, brandnew, digital holography. Our measurement stations offer apart from the state-of-the-art technical features custum friendly and innovative supplements like automated sample tilt, autofocus, multiple light exposure runs to enhance the measurement efficiency, monochromatic and white light illumination and numerous mathematical evaluation procedures in order to provide the maximum benefit for our customers.

All technical data and features on this website are not binding and subject to change without notice.