DISPOSITIF POUR REPRESENTER DES IMAGES EN MOUVEMENT DANS DES PLANS SITUES L'UN DERRIERE L'AUTRE

DEVICE FOR REPRESENTING MOVING IMAGES IN PLANES LOCATED ONE BEHIND THE OTHER

Abrégé français

L'invention concerne un dispositif pour représenter deux images en mouvement. A cet effet, deux générateurs d'images (14, 16) sont agencés de façon à former un angle de 90· l'un par rapport à l'autre et sont orientés dans la direction d'une lame séparatrice (22). Un miroir concave (24) et une lentille de Fresnel (26) se situent des côtés de la lame séparatrice (22) opposés aux générateurs d'images (14, 16). Un observateur voit deux images flottant librement dans l'espace l'une derrière l'autre. Ces images peuvent être par exemple un film publicitaire et le logo d'une entreprise.

Abrégé anglais

A device is disclosed for representing two moving images. For that purpose,
two image generators (14, 16) are arranged at a 90~ angle to one another and
are oriented towards a beam splitter (22). A concave mirror (24) and a Fresnel
lens (26) are located at the sides of the beam splitter (22) opposite to the
image generators (14, 16). An observer sees two images floating freely in
space one behind the other. The images may for example be a publicity film and
a corporation logo.

Revendications

CLAIMS
1. A device for representing two moving images in two planes
disposed one behind the other having two image generators, a beam splitter
disposed at an acute angle in the optical path of the two image generators,
and using a concave mirror, characterised in that the two image generators
(14, 16) are at an angle of 90° relative to each other, the beam splitter(22) faces with its one side towards the first and the second image
generators (14, 16) and is at an angle of 45° to the longitudinal centre
lines thereof, a concave mirror (24) is disposed on the side of the beam
splitter (22), which is remote from the second image generator (16), in the
optical path of said image generator (16), and a Fresnel lens (26) is
disposed on the side of the beam splitter (22), which is remote from the
first and second image generators (14, 16), in the common optical path of
the two image generators (14, 16).
2. A device as set forth in claim 1 characterised in that the
first image generator (14) shows the image which is in the rear plane from
the point of view of an observer.
3. A device as set forth in claim 1 or claim 2 characterised in
that the second image generator (16) shows the image which is in the front
plane from the point of view of an observer.
4. A device as set forth in one of claims 1 to 3 characterised in
that the beam splitter (22) has a transparency of 50%.
5. A device as set forth in claim 4 characterised in that the
beam splitter (22) has an edge length of 50 x 50 cm.

6. A device as set forth in one of claims 1 to 5 characterised in
that the two image generators (14, 16) are of a rectangular shape and have
a diagonal of 6 to 76 cm.
7. A device as set forth in one of claims 1 to 6 characterised in
that the concave mirror (24) has an immersion depth of 4 to 18 cm.
8. A device as set forth in one of claims 1 to 7 characterised
in that the Fresnel lens (26) has a focal length of 6 to 20 cm.

Description

CA 02239816 1998-06-19
WO 98/18114 PCT/EP97/05834
DEVICE FOR REPRESENTING MOVING IMAGES IN PLANES DISPOSED
5ONE BEHIND THE OTHER
The invention concerns a device for representing two moving images
in two planes disposed one behind the other, having two image generators, a
beam splitter disposed at an acute angle in the optical path of the two
image generators, and using a concave mirror.
A device which represents an image floating freely in space so that
it appears to the observer as a virtual image is known (DE-U 295 15 955).
That device has in a hollow cylinder at least one image generator, in the
optical path of which a beam splitter extends at 45~. In the side of the
beam splitter which is remote from the image generator the hollow cylinder
has a viewing window. For an observer who is in front of the viewing
window the image appears to lie behind the beam splitter. The observer
sees only that single image. Generally this is a moving image which is
comparable to a film. The known device makes use of the physical principle
that any automobile driver experiences on the windshield of his vehicle.
An article which is lying on the storage surface in front of the windshield
is reflected therein in such a fashion that - as viewed in the direction of
travel - it appears to the automobile driver to be lying in front of the
windshield. In the known device the article to be represented is projected
by the image generator onto the beam splitter which corresponds to the
windshield and it is then reflected in the beam splitter in such a way that
it appears to the observer to be disposed behind the beam splitter. The
article appears as a virtual image. The observer does not see the
reflection effect at the beam splitter. He only sees the article floating
30freely in space. Also known is a device (DE 195 29 936 A1), which imparts
to the observer a real image and a virtual image of an article. That
device includes a beam splitter, a screen acting as a mirror and a
partially reflecting, light-transmissive plate. The real image appears to

CA 02239816 1998-06-19
the observer in front of that plate and the virtual image appears behind
it.
The inventor set himself the object of providing a device which
represents two different moving images in two planes which are disposed one
behind the other. Taking the known device as described in the opening part
of this specification as his basic starting point, that object is attained
in accordance with the invention in that the two image generators are
disposed at an angle of 90~ relative to each other. the beam splitter faces
with its one side towards the first image generator and the second image
generator and is at an angle of 45~ relative to the longitudinal centre
lines thereof, a concave mirror is disposed on the side of the beam
splitter which is remote from the second image generator in the optical
path of that image generator and a Fresnel lens is disposed on the side of
the beam splitter which is remote from the first and second image
generators in the common optical path of both image generators. The
observer views by way of the Fresnel lens and the beam splitter onto the
so-called first image generator. It is disposed directly in the field of
view of the observer in the so-called rear plane. Depending on the use of
the device that image generator shows for example a teaching or
instructional film or also an advertising film. The so-called second image
generator projects its image through the beam splitter onto the concave
mirror. It projects it back onto the beam splitter which after rotation
through 90~ reflects it onto the Fresnel lens and thus the observer. It
appears to the observer as a virtual image floating freely in space in
front of the Fresnel lens. Depending on the use of the device the second
image generator shows for example a teacher or instructor when dealing with
a teaching or instructional film or a corporate logo when dealing with an
advertising film, the teacher or instructor or the corporate logo
respectively then appearing in the foreground in front of the film in the
background. The observer thus experiences the rare spectacle that he sees
a film in the background as in the state of the art and in front of that
background, in the foreground, a virtual image, floating freely in space.

CA 02239816 1998-06-19
That virtual image is produced by the co-operation of the beam splitter
the concave mirror and the Fresnel lens. The dimensions and optical data
of the beam splitter. the concave mirror and the Fresnel lens can be
matched to each other in such a way that the observer sees the virtual
S image in a large angular range of up to 60~. In other words the observer
can move towards the left and the right in front of the device and
continuously sees the virtual image.
As stated the first image generator shows the image which is in the
rear plane from the point of view of the observer and the second image
generator shows the image which is in the front plane from the point of
view of the observer.
The beam splitter desirably involves a transparency or light
transmission ratio of 50%. It may be a pane of glass. In the above-
described known device the beam splitter comprises a sheet which is
stretched taut. The use of a pane of glass which is less expensive is
sufficient for the purposes according to the invention. The beam splitter
has an edge length of 50 x 50 cm.
The two image generators are desirably of a rectangular shape with a
diagonal of 6 to 76 cm. They involve television picture tubes or normal
monitors. They can be controlled in any way. They are desirably digital
in operation.
The concave mirror advantageously involves an immersion depth of 4
to 18 cm. The Fresnel lens desirably involves a focal length of 6 to 20
cm.
The invention will now be further described by means of the example
of the embodiment diagrammatically illustrated in the drawing.
The device includes a housing 12 and therein the first image
generator 14 and the second image generator 16. The first image generator
14 is actuated by a control device or a memory 18 and the second image
generator 16 is actuated by a control device or a memory 20. A beam
splitter 22 is disposed in the optical path of the two image generators 14
and 16. The concave mirror 24 is disposed above the beam splitter 22 and

CA 02239816 1998-06-19
at the top side of the housing 12. The Fresnel lens 26 is disposed in
front of the beam splitter 22 or, when viewing the Figure, to the left of
the beam splitter 22. The virtual image 28 occurs floating freely in space
in front of the Fresnel lens 26 or, when looking at the Figure, to the left
of the Fresnel lens 26.
The observer is positioned in front of the Fresnel lens 26 or, when
looking at the Figure, to the left thereof. The view of the observer goes
directly to the first image generator 14 by way of the Fresnel lens 26 and
the beam splitter 22. The observer sees the image of the first image
generator 14 in the plane thereof or in the background. The Fresnel lens
26 or the beam splitter 22 do not adversely affect the view onto the first
image generator 14. The situation is different with the image produced by
the second image generator 16. That image appears to the observer as a
virtual image 28 in front of the Fresnel lens 26, in a condition of
floating freely in space.
In addition to the fact that the device represents two moving images
in two planes which are disposed one behind the other, the observer also
experiences an illusion. The illusion is that the virtual image 28 is
floating freely in space. A projection screen, a picture screen or the
like is not to be seen nor can it be touched with a hand. The observer can
equally not touch the virtual image.

Dessin représentatif