Beamsplitter Patented????

[P3D Gabriel Jacob <jacob@xxxxxxxxxxxxxx>]

I never could understand how the Viewmagic viewer can have a patent.
Now I run across something similiar, where a patent was issued on
July 2, 1996 on basically a beamsplitter or stereo-adaptor.
The twist on this one, and am still not sure how it's implemented, is
that it has focus-related convergence compensation. Basically seems
to me, to mean adjustable outside mirrors. Now can come of the more
knowledgable P3D members explain how a patent was issued on this.
You can find more info on this, with a diagram at
http://www.lightlink.com/~bbm/zan1.html
Below is the text from the web page.

Gabriel

>>Stereographic photography is the method of producing images which are
apparently three dimensional by recording separate left- and right-eye
images. The viewer reconstructs the 3-D image by viewing the two separate
2-D images simultaneously. Stereographic photography has been known since
at least the late 19th century, when stereo viewers were a popular parlor
accessory.=20

Such stereo views have historically been created with two lenses on a
single camera, spaced apart by approximately the inter-ocular distance
of a human head. The Stereo Realist series of 35mm still cameras, popular
in the 1950's, are an example of this kind of imaging. Left and right
views were recorded simultaneously through two lens/shutter sets on
alternate frames of the 35mm film. The later Nimslo system used four
lenses for essentially the same approach.=20

Stereo movies appeared in the 1950's. The images were typically created
either using two synchronized cameras, or a two-lens system on a single
camera. Similarly, the various Stereo TV systems have typically used two
cameras (see Lipton, et al, US Patent 4,583,117) or a single camera with
two lenses (Lipton, et al, US Patent 4,523,226).=20

All of the multiple-camera systems have severe drawbacks, in the added=20
complexity and cost of duplicating the complete camera system and the
synchronization of the two separate images (this is especially a problem
in film (non-video) applications). In addition, the use of two separate
lenses (whether on one camera or two) introduces problems of synchronizing
focus and view.=20

The need for solving this latter problem is real, but not addressed by
prior art devices. Simply mounting two cameras side-by-side will allow=20
the taking of the left- and right-eye images, and the cameras can be
focused on whatever the subject is (although follow-focus of moving objects
is problematic). However, there is more to stereoscopic vision than simply
having two eyes. A simple experiment will demonstrate the problem. If one
holds up a finger at arms length, and brings it closer and closer to the
face, it becomes apparent that your eyes do more than merely focus on the
finger as it approaches. You also aim each eye independently, becoming more
and more "cross-eyed" as the finger nears the face. Without this adaptation,
most 3-D films tended to induce discomfort as the apparent image distance
to the view changed, since the camera views would not shift as one's
instinct might expect.=20

The invention comprises an adapter having a set of four mirrors in two
pairs located in front of a camera lens. The centers of the four mirrors
are all aligned on a common centerline, with the outer two mirrors facing
generally outward along the optical axis of the lens and the inner two
mirrors facing generally inward into the lens. The centers of the outer
two mirrors are spaced apart by an appropriate interocular distance.
The two inside mirrors are together large enough to cover the complete
viewing area of the lens, each taking half of the lens viewing area.
The two outside mirrors are bigger than the inside pair and large enough
to cover the viewing area of the inside pair to avoid viewing area
reduction.=20

The convergence of the two outer mirrors is adjustable by swiveling them
simultaneously and equally about their centerlines with a ganging mechanism.
The two center mirrors may be fixed, or could be adjustable by being
swiveled so that one side of each remains in tight contact with the other
along the optical axis of the camera lens, and each makes a 45=B0 or lesser
angle to the optical axis.=20

The actuating mechanism for the outer mirrors is connected to a ring that
fits tight around the focusing ring of the lens, so a change in focus=20
automatically leads to readjustment of the convergence of the images. The
whole assembly is to be housed in a dust and light proof housing that
mounts onto the lens.=20

The apparatus of the invention is also useful in stereo photogrammetry.<<=20


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