Building the Interferometer’s Platform

 

Hello Again,

 

When I first got the interferometer all put together, I was eager to “Play” with it!  Not having a proper platform to set it on, I clamped it to one of my Robo-Foucault platforms.  While I was able to image some fringes, it was exceptionally difficult! 

 

When setting up for interferometry, you need to align the two focal points (one from the reference element, and the second from the optic being tested) at one point in Space!  Not an easy challenge, as once you have everything close, you need to be able to twist/tilt in fine increments to get the fringe lines to form properly.

 

I realized what I needed was a Mount with 5 degrees of freedom, each being very accurately positioned, AND the whole thing needed to be very STURDY.  Here’s what I ended up creating:

 

 

 

Yup, more of my favorite building materials

  1. “Medium Density Fiber board”
  2. ¼-20 threaded rod
  3.  Drywall Screws

 

However I did add some new materials to the list.

  1. Ball Bearing Cabinet Drawer Rails
  2. Tiny roller Bearings
  3. And Lots of Brazing together of components J

 

Let’s go over the above image step by step, I’ll throw in some links to more detailed images of each section as I go, but if your eager to look around NOW, head over to this folder:

http://lerch.no-ip.com/atm/Inter/5Deg_Platform/

 

OK, starting at the top, and working our way down:

  1. The cutout in the top board is where the Camera will be mounted (in its own 6 degree mount..)
  2. Top Left of the image is the handle to control Longitudinal travel adjustment
  3. Below this, and facing you are the two handle’s that control:
    1. When turned together, slide the interferometer Left/Right
    2. When turned independently, they “Rotate” the interferometer Left/Right
    3. This part of the platform stage is built from Cabinet Drawer rails
    4. Here’s a link to several images showing additional detail:

                                                              i.      http://lerch.no-ip.com/atm/Inter/5Deg_Platform/Dsc03969.jpg (118Kb)

                                                            ii.      http://lerch.no-ip.com/atm/Inter/5Deg_Platform/Dsc03967.jpg (84Kb)

                                                          iii.      http://lerch.no-ip.com/atm/Inter/5Deg_Platform/Dsc03963.jpg (94Kb)

  1. OK, so far we have 3 of the 5 degrees of freedom, now for the remaining two.
    1. In the center “Section” you’ll see a handle on the left
    2. On the bottom “Section” you’ll see a Handle on the right
    3. When turned together, we get Vertical Travel
    4. When Turned independently, we tilt forward/backwards along the optical axis
    5. Below are some links to an animation showing the vertical travel method

                                                              i.      http://lerch.no-ip.com/atm/Inter/5Deg_Platform/In_Motion.avi (520KB AVI file)

                                                            ii.      http://lerch.no-ip.com/atm/Inter/5Deg_Platform/In_Motion.gif (1.8MB Gif File, Same as above!)

                                                          iii.      http://lerch.no-ip.com/atm/Inter/5Deg_Platform/Animation%20Stills/ (still images from above)

    1. This method of travel is the result of several sleepless nights of “Day Dreaming”, I have no idea what to call it, but it works surprisingly well J
    2. Below are some additional links to images showing the details of the vertical travel stages

                                                              i.      http://lerch.no-ip.com/atm/Inter/5Deg_Platform/Dsc03966.jpg (80Kb)

1.      The handle turns the threaded rod

2.      The threaded rod pulls the “Long Nut” forward

3.      The “Long Nut” is supported by the “mini Wheelie bars”

4.      As the nut moves forward, the hinge is forced to swivel

5.      As the hinge swivels, it forces the platform to raise

                                                            ii.      http://lerch.no-ip.com/atm/Inter/5Deg_Platform/Dsc03962.jpg (100KB)

 

Well, I guess that pretty much sums up the mount.  Surprisingly this mount is rather steady while making adjustments.  One rather welcomed side effect of its overall girth, is the rear-ward adjustments of Tilt and Twist are so far away from the focal point of the interferometer I get an amazing amount of fine resolution.  Consequently, controlling the number of fringes formed, and the position of the fringes in the interferograms is surprisingly easy!

 

Take Care,

James Lerch