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RE: [atm_free] Re: High Intermdeiate zone MOT, and targeted work on the higher segm

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  • Jerry
    Getting close. I leave my lap and mirror together at all times when not testing. I have not seen imprinting of the lap on the mirror. Once when making a lens I
    Message 1 of 35 , May 1, 2012
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      Getting close.

       

      I leave my lap and mirror together at all times when not testing. I have not seen imprinting of the lap on the mirror.

      Once when making a lens I used a pitch lap to support the relatively thin lens while I polished the other side. The lens taped in position and was in contact with the supporting lap for the entire polishing time on the opposite side. I could see an imprint of the supporting lap on the glass. I believe it was from slight movements against the supporting lap as I worked. I suppose it could have been chemical etching. Some types of glass might be more susceptible to etching. It didn’t take long to remove it.

      Yours does not show in the OF analysis. I would think that it can’t be but a few nm deep.  

       

      Your pitch lap shows signs of

       

      It looks like you might reach your goal with just a little more work.

       

      I think you could do one more turn with the 115 mm long MOT COC stroke to get the high zone down a little more. Only one turn this time.

      The correction would decrease a little more.

       

      Then if you want to make a bold step to see if you can reach your goal you could add some correction with

      1 turn MOT large W with 3 or 4 forward and back strokes across the mirror in one direction, do the increment of rotation stroke a W back across the other direction. If it is easier for you can center the disk for the rotation increment and then move the disk to the side to work another W across again in the same direction each time. Do this about 12 positions around the mirror.

       

      And then 1 turn TOT large W with 3 strokes across the W.  Same as with the MOT stroke do only 1 W across at each of about 12 positions.

       

      I think that will get it done, Strehl about .874  :)   If not it should be real close.

       

      Jerry

       

      From: atm_free@yahoogroups.com [mailto:atm_free@yahoogroups.com] On Behalf Of madhukar
      Sent: Tuesday, May 01, 2012 12:21 AM
      To: atm_free@yahoogroups.com
      Subject: [atm_free] Re: High Intermdeiate zone MOT, and targeted work on the higher segm

       



      Hi jerry,

       

      I have uploaded the latest OF report  and the picture of the lap. This time I also rotated the mirror by 180 to take average.

       

      I think I am very close to my goal of Strehl between .85 and .9. But I have got a different problem this time. I had the lap on top of my mirror for last 24 hours. I thought it will give me a very good fit between the two before doing the last few rounds of polishing. But the Ronchi today shows that the lap has got imprinted on my mirror! Since I take Ronchi at zero offset everyday, I know that it happened last night only.

       

      I am surprised how the lap pattern can get imprinted by just keeping it on top for around 30 hours. Have you seen this earlier? I will try the smoothing stroke from your video tonight and see. I guess it will change the conic also but not by much. 

       

       

      - Madhukar

       


      --- In atm_free@yahoogroups.com, "Jerry" <wa4guu@...> wrote:
      >
      > Hello Madhukar,
      >
      > Whatever stoke length you used :) it looks like it did ok.
      >
      >
      >
      > Stroke length is described as the total length of the forward and back
      > movement, from the position nearest you to the position farther away from
      > you.
      >
      > Total stroke length to effect the 1/3 D stroke for your mirror is about 90
      > mm.
      >
      >
      >
      > The peak of the intermediate zone is at about the 85mm r from the center of
      > the mirror. A stroke length of 115 mm stroke will put the edge of the lap at
      > that zone at the full forward and full back positions of the strokes. If
      > your average stroke length is 115 mm you will get more work on the high
      > zone. Other stroke lengths will work too, but this should be most
      > effective.
      >
      >
      >
      > Some 1/3 D, 4/10D and some ½ D, (90 mm, 115 mm and 140 mm), 1 turn of each
      > should work well.
      >
      > MOT or TOT will work, but MOT is probably a better choice to avoid more
      > astigmatism.
      >
      >
      >
      > Jerry
      >

      _,_._,___

    • madhukar
      Hi Vladimir, The pattern remained even after a round of polishing. So as Jerry commented, they are probably in the glass. Regards, - Madhuhkar
      Message 35 of 35 , May 2, 2012
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        Hi Vladimir,

        The pattern remained even after a round of polishing. So as Jerry commented, they are probably in the glass.


        Regards,

        - Madhuhkar


        --- In atm_free@yahoogroups.com, "Vladimir" <vladimir.galogaza1@...> wrote:
        >
        > Madhukar,
        >
        > >Now that I looked at the pictures second time, I feel they are not lap
        > >imprints as the patterns are not exactly square.
        >
        > I also doubt that imprints are real. In my opinion they could be CeO that
        > was squeezed in channels of the lap left on to the mirror for a prolong time.
        > If this is a case they should go away with few strokes which may not be true
        > for real imprints (indentations).
        > What was your experience with disappearance of "imprints" after you have
        > continued with figuring?
        >
        > Regards
        > Vladimir.
        >
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