About mechanical stability using Vialux DMDs

We have been using DMDs from Vialux for a few years now, and I already published few posts about different effects that need to be taken into account when working with such devices (in particular aberrations and diffraction effects). One more trivial, but potentially troublesome, effect is due to vibrations, that come from the FPGA board and transmitted through the rigid flat cables. In this quick post, I show the damaging effect of vibrations and how to easily get rid of them, at least partially.

In our experiment, we measure the complex field at the output of multimode fibers using off-axis holography. We noticed some instabilities of the fringes as shown in Fig. 1.

 

Figure 1. Fringes recording without isolation.

After investigation, it turned out that the sources of the instabilities were vibrations coming from the FPGA board, that has a fan. Since the board is linked to the DMD chip via a rigid flat cable, those vibrations were directly transmitted to the DMD, resulting in angle fluctuations.

To get rid of these vibrations, a quick and dirty solution turned out to be quite effective; we simply clamped the cable using some foam to absorb the vibrations and isolate the DMD from the board. Fig 2. and Fig 3. shows how it looks like for a DMD working in the horizontal position and at 45 degrees.