Re: PHOTO-3D digest 1359

[P3D Neil Harrington <nharrington@xxxxxxxxxxxxx>]

Peter Homer writes:

>In reply to Neil Harringtons query about digest 1355 William Carter
>mentioned the 1677 microscope in response to my request for further
>information about his mention of SL3D being around in the 1600,s. I

[ . . . ]

>  However even if it was of the beamsplitting binocular type some of them
>at least are capable of giving a stereo image even though this is not the
>intention. I have already mentioned on this list three methods I found in a

Peter, I'm sorry to say I haven't seen the earlier message you describe.
I'm pretty new to this list.  I did start reading the archived messages from
the beginning, but realizing it would take me a LONG time to catch up that
way, have moved up to the more recent archives, and still haven't nearly
caught up.  So I know I've missed a lot of very interesting messages up to
the present time.

>book using red/ green filters in the filter tray and eyepieces or crossed
>polaroids to preserve true colour or "D" caps in the eyepieces .The authors
>explanation was that this enabled the left and right images to be seperated
>to their respective eyepieces. 

I am having a LOT of trouble trying to understand this!  The D-cap method I
assume means obscuring opposite halves of the eyepieces, but I can't see how
that can produce 3-D.

[ . . . ]

>  So I tried the anaglyph method again this time with quite large specimens
>of chalk dust on a slide uncovered . This time it worked although it was
>actualy pseudoscopic until I changed the filters around ,but when I removed
>them to check the effect it was still stereoscopic although the filters did
>enhance the effect a bit . The effect of the filters was more pronounced by
>the way they could reverse the relief. 

Could you describe the arrangement of the filters at the subject end a
little more clearly?

> I have since obtained an old book "The Microscope" by Conrad Beck where he
>mentions that some people doubt that beamspliter binoculars can give a
>stereo image but adds. "Those who have used such a microscope dont retain
>any such doubt and the explanation is quite satisfactory". This explanation
>is essentialy the same as the other book but requires a diagram so I cant
>reproduce it here.

I sure wish it were possible for you to do so!  I'll have to check the local
libraries and see what I can find, though I don't hold much hope for finding
Beck's book if it is very old.

[ . . . ]

>My own feeling is that because the beamsplitter is a Swan cube consisting
>of two right angle prisms together to  make the cube . The seperation is at
>least partly dependant  on "Total Internal Reflection" the reflected rays
>having to be beyond the "Critical Angle" which for air seperated cubes
>would be about 43 degreees . This means that the beamsplitting is angle
>dependant so that a small stereo seperation is also introduced .

At the very least that's an intriguing idea, though I must say I'm still
having an awfully hard time trying to understand how it could work.  Thanks
for the fascinating information and the sources.



------------------------------