Real-time measurement of microscopic surface shape using high-speed cameras with continuously scanning interference microscopy

Currently the use of white light interference microscopy for measuring static 3D surface shape typically involves the "snapshot" approach, comprising the pressing of a button and waiting for the 3D "photo". For a standard image acquisition rate of 25 to 60 i/s, the time to result can vary from a few seconds to a few minutes, depending on the depth. Deeper and larger area structures such as those of MOEMS micro-systems can take many minutes. In this work we develop the concept of real time 3D measurement (4D) of non-periodic movement by means of high speed image acquisition and processing. A dedicated high speed CCD camera and FPGA (1 million gates) imaging board processes images 512x512 pixels in size (10 bits) at a rate of 250 i/s, and displays 3D images at up to 5 i/s. A second system based on a CMOS camera has also been tested at acquisition rates of 1017 i/s, but in this case with post processing. The move from "snapshot" to "video" leads to several advantages, such as easier system optimization, higher speed measurement and new applications in the areas of the analysis of moving parts, surface chemical reactions and fragile materials.

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