FR2785396A1 - Three dimensional image viewer has casing with spaced Fresnel lenses and whit light projectors onto screen - Google Patents

Abstract

The three dimensional image viewer has a casing (1) with two Fresnel lenses forming an objective, a diaphragm and a screen (5) forming a Fresnel lens. The image of an object emerges across the screen when it is illuminated by white light projectors (6,7) across holographic diffusers. The lenses are physically thin with a gap (D) allowing spatial filtering of the light.

Description

 The present invention relates to an optical device for viewing 3-dimensional images, visible in natural relief in front of a screen, without special glasses or prostheses.

Technical area
Optical processes allowing the formation of real 3-dimensional images, for direct natural vision.

State of the art
There are relief viewer devices on the market.

For some, it is a simple conjugation where an object is placed at 2 F behind a lens with large aperture. The resulting image thus "floats" at 2 F in front of this lens perceived as a screen by observers.

For others, these are more sophisticated optical architectures in which several lenses or mirrors process the formation of the image.

Here are some current problems: -In these devices, the geometric aberrations and especially that of
sphericality, distort the resulting images.

-The viewing angles of the image (and therefore, the solid angle presented of the object)
are very limited or even zero.

-The weight of these devices is often high due to the technology of
mirrors or the mass of lenses.

Description of the device
The device according to the invention overcomes these drawbacks.

 Figure 1 shows the device according to the invention.

 According to a first characteristic, it indeed comprises a case (1) incorporating 2 Fresnel lenses (2,3) forming a lens, a diaphragm (4) and a screen (5) made up of a Fresnel lens.

An object (10) is placed at a distance between 1 and 2 F from the objective resulting from the lenses (2,3), F being the effective focal length of the objective.

The variation of this distance acts on the emergence of the image (11) which will appear totally real or partially virtual through the screen (5).

 The screen (5) is placed upstream of the image (11) formed by the objective.

White light projectors (6,7) illuminate the object (10) through diffusers (8,9) whose function is to reduce the effects of specular-- reflections of the object, as well as ensuring in image (11) regular brightness.

The diffusion function is provided by holographic diffusers
(8,9) which allows a high light output, avoiding the use of
too powerful light projectors (6,7) which bring constraints
thermal.

 This also allows a closer distance between the light projector and the diffuser, which reduces the overall size.

All the lenses (2,3,5) are Fresnels and consist of light synthetic materials, like acrylic, by way of nonlimiting example.

The lenses (2,3) have an opening greater than F / 0, 5 and thus act as thick lenses, while being physically thin, which allows the distance D; performing a first spatial filtering of the flow
luminous carrying the image and limiting the geometric aberrations.

The diaphragm (4) completes the spatial filtering function and moreover, by its
adjustable position (A) between the lens (2,3) and the screen (5) does not reduce
the angle of view of the resulting image.

 Figure 2 shows a variant of this device.

 The device according to the variant is in the form of a terminal (12) the center of the screen (5) of which is at eye level with the observing public.

The deflection mirror (13) makes it possible to express the device vertically, reducing the size on the ground.

The enclosure (15) incorporates the object (10), its support (16), the projectors
white light (6,7), diffusers (8,9), and the Fresnel lens (2).

The support (16) of the object is adjustable in height and allows to adjust
the emergence of the image (11) through the screen (5).

 This enclosure (15) moves vertically by a system of slides, by way of nonlimiting example.

 This possibility of vertical translation ensures the adjustment of the distance D.

The support (14) of the diaphragm (4) moves vertically by a system of slides, by way of nonlimiting example; to set the distance A.

The device according to the invention and its variant, is particularly intended for the fields of leisure, exhibitions and advertising.

Claims (5)

 CLAIMS 1) Optical device for viewing 3-dimensional images, visible in natural relief in front of a screen, without special glasses or prostheses, characterized in that it comprises a housing (1) incorporating several Fresnel lenses (2, 3), a diaphragm (4), a screen (5), several white light projectors (6,7), several diffusers (8,9), as well as an object (10). 2) Device according to claim 1 characterized in that the scattering function is provided by holographic diffusers having a high light output and a possibility of close-range operation of light sources (6,7). 3) Device according to claim 1 characterized in that all the lenses (2,3,5) are Fresnel and made of light synthetic materials.  4) Device according to claim 1 characterized in that by varying the distance (D), a first spatial filtering of the light flux carrying the image and a limitation of the geometric aberrations are carried out. 5) Device according to claim 1 or claim 4 characterized in that by varying the distance (A), the position of the diaphragm (4) is adjusted and thus the spatial filtering function is completed.