AO American Optical EPIStar

baby steps with EPIStar

Initial stylus image capture employs a 10x epi microscope objective with darkfield illumination
and Olympus NFK 3.3x projection ocular into a Canon EOS sensor.
To hold the stylus at ~45 degrees, the cartridge was mounted in a headshell
with no finger lift and clamped at the bayonet connector using a clothespin:
Although it facilitates sorting spacing between camera sensor and objectives, a bellows is not necessary;
extension tubes suffice, with more length yielding greater magnification.
The resulting image has decent resolution, but poor contrast.

This microscope has short working distance objectives;
the 20x objective would not clear this stylus' plastic grip at this angle.
90 degree shots will clear but require image stacking;
whether objective darkfield illumination will then highlight stylus wear spots remains to be seen.

EPIStar contrast

To investigate low contrast, Ray Parkhurst suggested removing the camera and looking down into the tube.

Internal surfaces were not reflecting appreciable light,
but a small bright spot and dim blob are seen in the optic at the bottom of the eye tube.

Lacking ground glass, wax paper was laid over the camera adapter:
The dim blob is revealed as the projected stylus.
The bright spot appears less focused than when viewed directly and,
depending on viewing angle, more or less distinct from the projected stylus image.

Removing the microscope head and looking down into the arm reveals a bright spot centered in an epi illuminator lens in a port off to one side as well as a less bright spot on the lower lip of that port. That very bright area below the epi lens is the brightfield mirror.

An A.O. #3002 image erector spaces the head further from the epi illuminator
and slightly improved contrast, despite adding magnifying optics in the path:

EPIStar 10X with EF-S 55-250mm STM

Infinity objectives can be used with a camera lens focused @ infinity,
in this case, a Reichert EPIStar 10x
with Canon EF-S 55-250mm STM zoomed to 250mm.
This is an example of camera telephoto as tube lens.

To prevent this zoom from collapsing to 55mm,
the camera body needs support.
Fortunately, focus is internal. Some observations:

• EPIStar darkfield illumination wants alignment
• Kenko 1.4x TELEPLUS HD DGX reportedly works with this lens,
  but Kenko TELEPLUS PRO 300 does not.
  About 50% more focal length is wanted to eliminate vignette:
  
  
  
• monochromatic illumination or fully corrected objective is wanted.  
  
  1:1 crop of focus near center