having stability problems with table March 13 2004 at 12:06 AM
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its mostly on long exposers and cars go by in front of my house
mine is a steal door on soribitfoam cinder blocks and intertubs...put on the garage floor
i use lots of magnets and vices
do i need to add more weight to the table?
is it the more weight the less noise?
i wounder if some of the movement is coming from laser
March 13 2004, 1:08 AM
its a dpss 2 beam 457 and has a fan on the back end.....and i have it ob a cinder block clip down on a work bench....maybe i need to make a sold stand from the floor by stacking Cinder blocks and bolting down laser to cinders
Re: i wounder if some of the movement is coming from laser
March 13 2004, 2:31 AM
You are only required to have stability after the beamsplitter. If you are doing single beam work then you only need stability after the beam passes the plate as this is your beamsplitter.
How are you determining that your table is unstable? Interferometer, bad holograms, guessing?
Colin's spot on. If you're doing single beam work make a plate holder that is rigidly connected to an object holder. Turn the two into one object and securely fasten the object and plate to this.
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If someone says it can't be done but they haven't tried it, don't believe them. http://www.dragonseye.com/Holography
i set up a interferometer....the fringes dance every few seconds ......i tap the table the laser is on and the fringes blure ..... and tap the optical table... they blur.....i stomp on the flower and it barly afects it
im geting coherence at the plate...(reflections in the plate) and also i do get trasmission.... but the movement must be to great for the reflection holo...
i set up a interferometer....the fringes dance every few seconds ......i tap the table the laser is on and the fringes blure ..... and tap the optical table... they blur.....i stomp on the flower and it barly afects it
Do the fringes "dance every few seconds" in the same way as they do when you tap on the table or stomp on the floor or is it more of a quick movement that settles just as quickly?
If you can stomp on the floor and "barely" affect the fringes I would expect the same to be true if you tap the table the laser is on. I would guess there is a problem with your laser changing modes. Is that possible with your type?
im geting coherence at the plate...(reflections in the plate)
I'm not sure what this sentence means.
and also i do get trasmission....
Do you get bright transmission holograms or dim ones?
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If someone says it can't be done but they haven't tried it, don't believe them. http://www.dragonseye.com/Holography
Do the fringes "dance every few seconds" in the same way as they do when you tap on the table or stomp on the floor or is it more of a quick movement that settles just as quickly?
they settle quickly
If you can stomp on the floor and "barely" affect the fringes I would expect the same to be true if you tap the table the laser is on. I would guess there is a problem with your laser changing modes. Is that possible with your type?
the table that the laser is on is not as solid...it does have some give in it .......when i try to prop up the table with steel bars to ...the fridges stable a bit more
I'm getting coherence at the plate...(reflections in the plate)
I'm not sure what this sentence means.
when i do a single beam .. the reflection of the light in the plate....and the light being reflected from the edge of the plate...
and also i do get trasmission....
Do you get bright transmission holograms or dim ones?
have to check that more
Yes, this laser can mode hop if not designed to avoid it. I have been talking to a laser designer in China of these lasers and they can not guarentee me stability over time. The linewidth apears to be narrow instantaniously (sounds like the red diodes). I am very excited to learn more about this and await Danny's results eagerly.
Danny, I would advise that you set up an interfermoter for a wekk or so and check the fringes very carefully. I watch a new laser for about 10 hours before I decide what it is doing. Make sure to watch it for at least 2 hours in one sitting. A hard thing for sure. Mode hops will show when the fringes jump. Or blur out then come back when the ground is very quiet. Until you know more about your blue laser I would advise you to work with the compass as we know it is stable.
As long as you have the BLD model and not the DSD model the laser should not be a problem. How are you dealing with the two beams? Are you combining them for dumping one?
found out that it is low noise (cars, foots stopping) is where the noise is coming from......the friges recover fast......but is their more i can do to filter out noise.....without moving to the desert
i use 4 layers of bubble rap...and its made the fringes much more stable... i can now see the real fine fringes... where before they didnt show up at all
i use cinder blocks+bubble rap+plywood+intertube+plywood+sorbifom+steel door
You could add another layer to your table. Legs, inner tubes, heavy weight (marble etc) another layer of inner tubes, then the final surface. It would be real bouncy to work on, but it would cut your vibrations from the floor by roughly 3/4, depending on the exact materials...
Danny, As long as the one end of the table remains spatially registered to the other end of the table your stablility will be greatly enhanced. In other words I believe that that actual steel top is bowing with the vibrations, that is it is not rigid enough.
How thick is the steel?
Does it have cross supports like "I" beams along its length?
its a steel door....not quite shure how the inside webing is........it dosnt seem to give (or have play) when i put magnetic stands on it......i have in proved the stabilty buy putting bubble rap on all foour legs
One would think that a steel door would be very rigid as the manufacturer would not want it to twist and thus not fit in the jam anymore.
Danny, a steel door sound like a very good idea. I did a quick search on Google and found steel doors that are honeycomb core with insulation within the honeycomb core. Very interesting and novel table top. You are very resourceful.
I was driving home yesterday and thinking about your door and I thought of the following. The door may be very light with respect to its size. A good passive table (inner tube, sorbithane, bubble wrap) should be very heavy. The heavier the better. If the table is light then not all frequencies of vibration will effectively be dampened. Others may elaborate on what I mean. I try to visualize what is happening in my mind. Envision a light, very light 2 x 2 tabletop on a single inner tube. Now introduce a rapid shake (high frequency) at the base of the inner tube and envision what the top does. It moves with the shakes. Now envision a very, very heavy tabletop on that same inner tube and introduce the same rapid shake. Since the top is so heavy it does not have enough time to move in between shakes. It is more stable. The key is Inertia - The tendency of matter to remain at rest if at rest or to remain in motion in a straight line if in motion. The more mass the matter has that is at rest the more tendency it has to want to remain at rest.
So what is my point? If you are still having some stability problems, try to evenly add weight to your table top.
My table is 4 x 8 and 12 inches thick of sand. It is very massive. I recently covered the sand with contractor grade (very thick) trash bags duct taped together. There is not much that moves my fringes when I set up an interferometer from end to end.
Under the door or on top of. Under would be better as if they were on top they should be held rigidly together. I would like to see a photo if you can post one or two.
