I am working on figuring my 10 inch F5 plate glass blank and I have a few observations. I was using the Ronchi test for surface figure and I still have some work to do to get the surface smooth but am very close based on the sessions I have done so for. It shows my mirror is within the 1/4 wave figure based on the Ronchi criteria so I went to the knife edge test to get a better read. I am using the Stallafane design of slitless moving tester and total movement for the 5 zones I am testing is a total of .108 inches and the central 2 zones require a very small move. I can get a pretty good parabolic shadow at the 70% and edge zone but the central zone does not pop out like I would like to see. Also the "expert eye" required to distinguish between the gray scale values is much harder than I thought it would be. I was concerned that my testing technic was weak so I put a commercial 8 inch f6.25 on the stand which has given me decent performance and I was not impressed with the shadow results I saw. Actually my mirror gave closer to the desired shadow results than the commercial mirror but the commercial mirror was smoother in surface smoothness. Actually it was very smooth. I realize now that I need to put some serious time into using this tester and recording data. Those of you experts who can read this test to the 1/10 or 1/20 wave have my greatest respect.
Can anyone point me to a web page or a software program which simulates knife edge results so that I can sharpen my skills. Also any suggestions which would improve my testing methods would be appreciated. I am going to redesign my tester this week to use a dial indicator and make the lateral and knife edge movement smoother so I can set it and study without worrying about any drift. Also I am going to get a better testing tunnel set up so that all drafts are reduced and I am sitting at a more comfortable level. Does it matter if you resetup the tester and stand for every test because right now my testing area is not in a secure location and I have to breakdown and resetup for every test.
Thanks again for the help. I feel a great mirror is right around the corner.
)
Dave H.
Dave
Can anyone point me to a web page or a software program which simulates knife edge results so that I can sharpen my skills. Also any suggestions which would improve my testing methods would be appreciated. I am going to redesign my tester this week to use a dial indicator and make the lateral and knife edge movement smoother so I can set it and study without worrying about any drift. Also I am going to get a better testing tunnel set up so that all drafts are reduced and I am sitting at a more comfortable level. Does it matter if you resetup the tester and stand for every test because right now my testing area is not in a secure location and I have to breakdown and resetup for every test.
Thanks again for the help. I feel a great mirror is right around the corner.
)Dave H.
Dave
