Re: Digital Media Associates 3D display

[P3D Andrew Woods <andrew@xxxxxxxxxxxxxxxxxxxxx>]

As Jan Gjessing mentioned, I saw a three dimensional display by
Digital Media Associates in February 1996.  I was in San Jose
at the time for the Stereoscopic Displays and Applications
conference.

The display is not stereoscopic but does generate a very
striking three dimensional display which is very eye catching
and would be very useful for advertising purposes.
Below is my guess of the internal optical system.

                        --
                       |  | <--- television (screen facing down)
                      /    \
person               /  TV  \
   _                 --------
  / \                       /     \ <---concave mirror
  | OO ----->   .   .   .  / .  .  \
  \_/                     /       . \
   |                     /           \
  / \                   /       .     |
       beamsplitter -> /              |
                              .       |
                                      |
                       |    .
                       |
                       |  .         __
                       |           /  \ <---  object to be imaged
    concave mirror -->  \ .  .   . \__/ 
                         \
                          \
                           \

A pair of concave mirrors produce a form of optical relay
which produce a virtual image of an object which is placed at the
other end of the optical relay system.  The image of the object
appears to float out the front of the display.

If the object which is placed at the end of the optical relay is
three dimensional, the image will be three dimensional.  But if, for
example, a CRT is placed at the end of the optical relay, the image seen
by the viewer will be as flat as the image on the face of the CRT.

I haven't discussed the purpose of the TV and beamsplitter yet.
This allows a background image to be placed behind the image which
is projected out the front of the display.  When I saw the display,
a statue head was floating in front of the display and behind the
statue head was a star field.  To achieve this, the statue head
would be placed at the bottom of the display (where I have labeled
"object to be imaged") and the star field would be displayed on the
TV screen.

As I mentioned, this display is not stereoscopic in the usual usage of
the term.  It does however produce a very striking display and no
viewing apparatus are needed.  The display has severe limitations on
the type of three dimensional image it can generate and would be
unsuitable for stereoscopic teleoperation and most forms of stereoscopic
display.  I can see the display being very useful in advertising.
If placed at the front window of a shop for instance, it would 
quickly catch people's attention due to the image appearing to
float outside the window.  

I believe the optical layout of this system to be similar to that
used in the SEGA video game called (I think) "time traveller".

Regards,
Andrew Woods.



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