Metrology

WAVEFRONT PHASE


Wooptix WFP is capable of achieving spatial resolutions orders of magnitude higher than conventional wave front sensors.


By measuring the reflected light from a surface we can provide a detailed elevation map of the surface, with the advantage of needing only one shot (no scanning needed) and high levels of accuracy and precision.

Wooptix WFP Working principle:

Imagine we send a narrow light beam to a surface at a particular angle, if the surface is flat, the reflected light will always fall in the same position of the sensor. If the surface slope differs from the perfect flatteness, the reflected light ray will fall in a different part of the sensor. The difference in distance from the two positions is proportional to the local surface slope.

This is the “Triangulation Reflection Method”, a well known metrology method. The disadvantage is that only gives one data point at one time, meaning that, to measure a surface needs some robot arm, or translation stage to scan all the surface area.

Wooptix WFP solution is also based in measuring displacements of light rays, but there is no need of scanning, since we can measure large areas in one shot. Basically we launch a bunch of light rays against a surface and capture the reflected light. As in the “Triangulation Reflection Method”, the deflection of each light ray gives the local slope of the surface.

It can be seen that the main difficult here is the identification of each light ray path to estimate the surface slope. It is easy when there is only 1, but when launching millions of light rays it becomes much more complicated.

Next figure, shows the image captured from a defect in a car paint sample and its reconstructed surface map. Note the heights on the surface map are in meters, that means the central bump height is about 12 microns!

Other applications