Hermann's wire test for camera precession/wobble

[hherde]

Developing a test to see if there is a wobble or precession in the camera when it is mounted to the XYZ stage which is moving. The test should determine if the camera remains parallel to the stage during all motion, or demonstrates some kind of wobble.

[sciollalab]

Hermann Wellenstein wellenst@brandeis.edu on 27 April 2017

Hi Hannah,

Ideally the wire should run close to the (future) sensor surfaces at the positions #1 and #2. (Perhaps a 2nd // wire at #3 and #4).

First take images of a short (straight) piece of wire and find the best illumination (glow in the dark or white tape?) and the best analysis. (You might need 1cm below the wire for the tape so the core might have to be removed.)

As you will need a 10N tension, the wire should be clamped outside the assembly frame at one end and 1kg should hang over the table edge on the other end. If there are no mounting holes you can clamp alu blocks with large C-clamps.

Please take photos of the ends of the assembly frame. Is there a shop drawing of the assembly frame?

I looks to me that the two small end-brackets are higher than the top of the core and perhaps, for now, the wire should be imaged with a z just above those brackets. Just outside the core (but inside the frame) the wire should be pushed up with cylinders so that the sag is due to L = 1.5m.

If that frame ever goes back into the shop perhaps holes can be drilled into the end-pieces so that the wire is just above the core.

I will send you a sketch once I have more details.

-Hermann

[sciollalab]

Hannah Herde on 27 April 2017

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Hi Hermann,

Thanks for the reply.

I don't know what positions 1 and 2 are in your message. I also don't know what you mean by end brackets.

The assembly frame containing the stave comes from Queen Mary in the UK. It does not have mounting holes, and it does not get mounted on the granite table. It just holds the stave. The ends are solid. I don't know about shop drawings for it -- I suppose the UK must have them. However, if we clamp things onto the frame, it will not be flat. This is why I indicated the rails (which are fixed to the granite table) in my image. Do you have a plan based on the rails?

[sciollalab]

Hermann again on 27 April

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Hannah,

I don't know what positions 1 and 2 are in your message. I also don't know what you mean by end brackets.

1 and #2 are the positions you take your data. You go clockwise from #1 to #2 and x increases. #3 and #4 are at a more negative y. That is what I understood from Laura.

End brackets: (photo of the end of the stave assembly frame)

How much space between end brackets and core?

The assembly frame containing the stave comes from Queen Mary in the UK. It does not have mounting holes, and it does not get mounted on the granite table.

What keeps the frame in position as the temp changes? One end should be bolted down.

(The frame expands ~33µm per °C. With ∆T = 3°C the position is unknown to 100µm.)

It just holds the stave. The ends are solid.

How high (±.5mm) are the end brackets above the core?

I don't know about shop drawings for it -- I suppose the UK must have them. However, if we clamp things onto the frame, it will not be flat.

I do not plan to clamp to the frame, only to the granite!

This is why I indicated the rails (which are fixed to the granite table) in my image. Do you have a plan based on the rails?

Can you take some photos of the ends?