Re Re digest 281

[P3D Peter Homer <P.J.Homer@xxxxxxxxxxxxxxxxx>]

To answer Ronald J Becks question I was talking about a microscope with one
objective in digest 281 a bi-ocular microscope if that is the correct term
(I dont recall ever coming across it before these discussions) rather than
binocular. Bi-ocular does seem to be a better term as binoculars themselves
do have two objectives . In digest 281 I was recounting my observations I a
not shure I know why filters should improve the stereo effect or for that
matter why it should be there in the first place but I know of a couple of
theories one of which is my own. To start with Conrad Beck (no relation I
suppose?) he takes an example of a fine blade of material placed on end as
the object all the light from the left hand of which that enters the
objective at all can only enter the left hand side and vice versa. He says
that if the light from the lens can be geometricaly divided and passed to
one eye at A and the other at B , a perfect stereoscopic picture will
result ,as though the eyes were looking on both sides of a card held in
font of them in the" well known experiment on binocular vision. (Actualy I
do not know this experiment that well althouh I have come across it in a
book somewhere.) Because a microscope inverts the image he says that the
light from the right hand side must pass to the left eye and vice versa. At
this point you realy need a diagram of the optical path of a microscope
preferably a binocular. The eye ring is the point where the rays from
opposite sides come together and then converge again and if the opposite
halves   could be blocked of from each eye instead of both reaching each
eye you should get a stereo image. He suggest "D" shaped diaphragms at the
eye ring (Ramsden circle) a method I have seen previously although in a
more recent book along with the anaglyph and polaroid method. But he
dissmises it as impractical because they would have to be in the eye very
close to the pupils and the eyelids and eyelashes make things worse.
 Instead he suggests that the interocular be set slightly wide or narrow to
cut of the edges of the eye rings giving stereoscopic or pseudoscopic
relief. With what he terms the "new" microscopes the eye tubes are raked
outwards and you only have to move you slightly back an forth to get the
effect. Perhaps this design feature did not continue though as our older
Watson system 70,s are like this not the Kyowas.
 I am not convinced myself that this is needed to get a stereo image and if
any thing it just enhances it again and it is not very comfortable to view
like this for long periods. The use of coloured or polaroid filters behind
the objective or in the condenser code the images allowing them to be
seperated by appropriate filters in the eyepieces which can then be set to
the normal comfortable interocular. The above was Becks theory not mine and
I am not to convinced by it why for instance if both halves of the stereo
pair are normaly present in both eyepieces dont we get a double image ?.
 William Carter expressed suprise that I thought the images lacked stereo "
snap crackle and pop" I dont think I said that I believe it was Allan Woods
I see stereo without the filters and they enhance it . After all this does
any one awasnt to hear my theory as to why it works?.       P.J.Homer



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End of PHOTO-3D Digest 2183
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