Testing results for the optic labeled “B”

Hello again,

 

I’m going to break this page into several sections as follows:

 

  1. General Synopsis of the test results
  2. Impression of the optical surface and performance predictions
  3. Detailed Robo Foucault results and images
  4. Detailed Interferometry results and images

 

Section #1     Synopsis

 

  1. Optical Diameter = 202mm (7.9”)
  2. Radius of Curvature = 2040mm (80.3”)
  3. Focal Ratio = F/5.05
  4. 15 Zone Robo Foucault Knife edge results: (@550nm)
    1. Axis 1 Horizontal

                                                              i.      P-V Wave Front Error = 1/14.2

                                                            ii.      Surface RMS Error = 6nm

                                                          iii.      Strehl Ratio = 0.981

                                                           iv.      Near perfect correction, best fit conic = -1

    1. Axis 2 Horizontal

                                                              i.      P-V Wave Front Error = 1/30

                                                            ii.      Surface RMS Error = 2.9nm

                                                          iii.      Strehl Ratio = 0.996

                                                           iv.      Slightly over corrected, best fit conic constant = -1.019

  1. Reduction of 16 fringe image interferometric data (@550nm)
    1. P-V Wave Front Error = 1/2.63
    2. Surface RMS Error = 15.58nm
    3. Strehl Ratio = 0.881
    4. Over Corrected, best fit conic constant = -1.105
    5. ** Interferometric testing is somewhat suspect on this optic ** See the detailed interferometry results for more information.

 

 

Section #2 Impression of the optical surface and performance predictions

  1. This optic was fabricated from an unusual substrate.  While I’m not certain of the composition, it is obviously not Pyrex nor Plate Glass as it was very crystal clear with a white tint on the fine ground edge.  If I had to guess the substrate is either a Crown or Flint originally intended for an achromatic lens.  I mention this for two reasons
    1. The substrate was rather thin, at 19mm thick and appears to flex rather easily (perhaps more so than plate glass)
    2. While testing with the interferometer, no matter the orientation, I had a fixed amount of test stand induced primary astigmatism that did not rotate with the optic.
  2. With that being said, lets move onto some sample surface images J
    1. Green Circle indicates a camera defect, not a surface defect!
  3. As seen in the sample images, the surface of this optic is rather smooth, with only a slight amount of micro ripple, and the occasional sleek (seen in the second image, bottom left corner near the edge.
  4. In addition this optic show a near perfect edge!  I offer a hearty “Well Done” to the optician!
  5. If this optic can be properly supported in an adequate mirror cell, I expect this optic to be an excellent performer.  Even the suspect interferometry indicates the optic is diffraction limited, combined with the smooth surface and excellent edge, I see no reason why this optic shouldn’t exceed 50 power per inch and provide excellent contrast and detail!

 

 

Section #3 Detailed Robo Foucault results and images

 

  1. Below are the screen captures of the 15 zone Robo Foucault results as reduced by FigureXP
    1. Axis 1 Horizontal
    3. Axis 2 Horizontal
  2. The results can also be download as one of three file types:
    1. A Figure file for use in Figure45 or FigureXP
      1. Axis 1 Horizontal
      2. Axis 2 Horizontal
    2. A Sixtests file for use in Jim Burrows’ Sixtest reduction program
      1. Axis 1 Horizontal
      2. Axis 2 Horizontal
    3. A plain text file for entry into any Foucault data reduction program
      1. Axis 1 Horizontal
      2. Axis 2 Horizontal
  3. In addition to the numerical results, you can also browse or download the generated knife edge images obtained during each test
    1. Axis 1 Horizontal
      1. Browse Images
      2. Download Images (20Meg Zip File)
    2. Axis 2 Horizontal
      1. Browse Images
      2. Download Images (20Meg Zip File)

 

Section #4 Detailed Interferometry Reports and Images

 

  1. Intereferometry on this optic was rather difficult.  The difficulty arouse from the inability to support the optic in the test stand with out introducing astigmatism.  Normally I don’t see much test stand induced astigmatism, but on this optic there was a rather large amount.  I can only  suppose that the thinness of the substrate and possible the material composition of the substrate lent its self to bending easier than other optics of its size that I’ve tested.  In any event, the astigmatism didn’t rotate with the optic, instead it stayed in the same relative location.  It appears that the method of rotating the optic between tests, de-rotating the images, then reducing the data seems to have removed the test stand induced aberrations, but I’m still a little suspect of the results.  Oh Well…
  2. Here is the final interferometry on this optic, from a total of 16 interferograms over two test orientations:
  4. I have the original interferograms available for either browsing or downloading
    1. Axis 1 Horizontal Interferograms

                                                              i.      Browse Axis 1 horizontal Images

                                                            ii.      Download Axis 1 Horizontal images (3.7Meg zip file)

    1. Axis 2 Horizontal Interferograms

                                                              i.      Browse Axis 2 Horizontal Images

                                                            ii.      Download Axis 2 Horizontal Images (3.8 Meg zip file)

    1. Axis 2 Horizontal and ROTATED to match axis 1’s orientation!

                                                              i.      Browse Axis 2 rotated Images

                                                            ii.      Download Axis 2 rotated images

 

 

This completes my analysis of Mirror B.  Any questions or comments are welcomed!

 

James Lerch

jlerch@tampabay.rr.com

http://lerch.no-ip.com/atm