Introduction to the Microsurf, Photomap and Zoomsurf Profilers

PhotoMap is based on the Peak Fringe Scanning Microscopy principle. It measures, without contact and with high accuracy, the micro-relief of a surface and quantifies its roughness-undulation by means of a statistical analysis.
The vertical nanometric displacement is controlled by computer and the interferometric data is automatically computed to render 3D imaging of the topography. With this technique a complete 3x2.5 mm can be taken in less than 30seconde with very high resolution. The instrument can also be used to measure the thickness of translucent layers or films.

Detailed principle of operation :
A Michelson interferometer splits the beam emitted by the source (So) into two " half-beams ". One half-beam is reflected on the reference mirror (M), the other on the sample. The beam splitter (Sp) transmits both reflected beams to the camera target (C) through the lens (L). The intensity I(d) measured on the camera target, varies as a function of the path difference (d) between 1 and 2. The I(d) signal (fringes pattern (F)) is maximum for d = 0.

Non-contact Accuracy

The method could be summarized by considering that the interferences generates a horizontal light plane (P). This light plane (P) is used as a probe. A vertical displacement (Z) of the measured surface makes the latter cross up the probe plane. The successive intersections between the probe plane and the sample are the relief level curves (isophots). The acquisition system keeps the coordinates (x,y,z) of all the points making the isophots and interpolates from one level curve to another so as to get a better measurement resolution.

The displacement of the measured surface along (Z) is servo-controlled by capacitive sensors. The principle of the capacitance-based technology, well known for its high accuracies, is the following : the measured capacity is conversely proportional to the desired distance. The positioning is better than 1 nm.

The CCD target (782 x 582 pixels) carries out simultaneously the measurement of all the points on the measured surface. There is no need to mechanical scanning along the x and y axes. This allows for small areas to be scanned with very high resolutions very quickly.