Today we made some progress on the Tape sensor. We made and tested two prototypes: the 4 fibers all 1mm PMMA fiber, and the 4 fiber one glass 125/62.5 MM delivery and 3 PMMA 1mm collectors.
a stereo microscope was used for visualization and optical alignment
first version, flat tip glass fiber version
In both cases a green laser was used. The picture below shows, from left to right, the laser, a lens, and the fiber.
second version, round tip
In both cases, a flat mirror on a gimbal was used to simulate the operation of the device. The gimbal was placed on a XY stage.
The the case of the flat tip version the results obtained were only sightly better than in the case of the 4 fibers all PMMA prototype. We also noticed that the light coming out of the glass fiber was not very gaussian, almost resembles a flat top, with a lot of speckles.
We moves right a way to the second version, with the round tip, since the results were not encouraging.
The advantage of the round tip is that it makes the exit cone of the glass fiber smaller, and increases the sensitivity of the device. This was confirmed by observing the light out of the round tip of the fiber using a white piece of paper. We used a fiber splicer modified by Jonathan to process the tip of the fiber.
on the computer screen, the 125 micron diameter glass fiber
between the two electrodes, waiting to get zapped
fiber getting zapped on the same screen, you can see the plasma
between the two electrodes. this plasma melts the glass
the kind of shapes we can get, a much smaller sphere was created
in the case of the fiber used in the tested device, see picture above
The video below shows the results obtained. Angle steps of 0.02 degrees were made while the signal was recorded. The signal plotted was intensity of one fiber minus intensity of another fiber. The test was performed on a single axis. We can clearly see that we have a resolution of at least 0.02 degrees. This can be greatly improved by doing some signal conditioning on the electronic board.