WO2020217217A1

WO2020217217A1 - An open light field volumetric device for displaying flows of fluctuating and stereoscopic 3d images and method thereof

Info

Publication number: WO2020217217A1
Application number: PCT/IB2020/053878
Authority: WO
Inventors: Enrico BENASSI; Giovanni TREGNAGHI
Original assignee: 3dIVE Srl
Current assignee: 3dIVE Srl
Priority date: 2019-04-24
Filing date: 2020-04-24
Publication date: 2020-10-29
Anticipated expiration: 2021-10-24
Also published as: IT201900006344A1

Abstract

The invention describes a light field volumetric device comprising an emitting means (1) for emitting a main beam (MB) of light rays (R1i) in first directions (d1i); a reflection system (50) provided with a single system aperture (AP), wherein said reflection system (50) is coupled to an emitting means (1), and, in turn, comprising a first concave reflecting means (10) and a second concave reflecting means (20) structured as continuous surfaces without holes; wherein said first concave reflecting means (10) is mounted with respect to said second concave reflecting means (20) with concavities (C_10; C_20) facing one another and coaxial; wherein the foci (F1,F2) of the first concave reflecting means (10) and of the second concave reflecting means (20) lie on a straight line that defines the azimuth axis (A-A) of the reflection system (50); wherein said first concave reflecting means (10;110) and said second concave reflecting means (20;120) intersect along an open intersection curve (C_int_AP); wherein, by intersecting along the open intersection curve (C_int_AP), the first concave reflecting means (10) and the second concave reflecting means (20) determine a conformation of the single system aperture (AP); wherein the first concave reflecting means (10) and the second concave reflecting means (20) are structured so that at least the main beam of light rays (R1i), which are reflected by the second concave reflecting means (20), exits from the reflection system (50) along the third directions (d3i1M) through the single system aperture (AP); wherein an image (IMM) generated as a function of the main beam (MB) of light rays (R1i) is perceived by an observer, located at a variable viewing distance (∆h) along a reference direction (dir_M), with respect to said second concave reflecting means (20), and a regulator (30) adapted to set said reference direction (dir_M), defined as a function of said directrices (DIR_L,DIR_R) and of said third main directions (d3i), to determine an overlap measurement (OVL) of said areas (AL,AR).

Description

“AN OPEN LIGHT FIELD VOLUMETRIC DEVICE FOR DISPLAYING FLOWS OF FLUCTUATING AND STEREOSCOPIC 3D IMAGES AND

METHOD THEREOF”

DESCRIPTION

FIELD OF APPLICATION

The present invention relates to an open light field volumetric device.

In particular, the invention relates to an open light field volumetric device for displaying flows of fluctuating and stereoscopic 3D images projected at a considerable distance from the device without optical interferences.

The present invention further relates to a method of displaying flows of fluctuating and stereoscopic 3D images projected at a considerable distance from the device without optical interferences.

In other words, the present invention relates to an open volumetric device/method that enables a display of 3D image flows without requiring any display support, starting from 2D images at a considerable distance from the device without optical interferences.

PRIOR ART

A first drawback of systems for projecting images generated by a display, wherein such systems use parabolic mirrors or mirrors of another type to reconstruct images in space, is that such reconstructed images are small in size compared to the size of the projection system.

This drawback severely limits viewing by an observer who is not in the immediate vicinity of the projection system.

A second drawback of such image projection systems is tied to the distance of the image reconstruction area from the projection system, which is always minimal. In other words, the reconstruction of the projected image always takes place near the projection system, typically just above the system.

As the purpose of these projection systems is to enable an observer to perceive an image projected by the system and reconstructed in a certain point in space, this constitutes a considerable limitation. A third drawback in the above-mentioned systems consists in the projection, together with the main image, of optical interferences, i.e. other unwanted images, which are defined as“ghost” images.

The“ghost” images that are formed in the neighbourhood of the viewing area disturb the observer’s perception of the images.

In order to eliminate“ghost” images, it has been proposed to limit the area usable for the projection of the images by creating closed systems provided with a small aperture from which the images come out; this embodiment is shown in the as yet unpublished international application PCT/IB2018/058365 of the same applicant.

Unfortunately, this configuration greatly limits the field of view that the system in itself would allow, thus considerably reducing the size of the image that is projected.

In other words, systems are adopted which are very large compared to the projected images and completely closed, with the exception of a small aperture that is at most 25% of the linear dimensions of the entire system. With this configuration it is possible to project images that can cover at most 25% of the dimensions of the entire system.

However, even with this completely closed configuration with a small usable aperture, the problem of“ghost” images is only marginally overcome.

In addition, the aforesaid first and second drawbacks, namely, that the reconstructed images are small or very close to the display, are not overcome.

A fourth drawback regards the viewing point of the system for an observer. This viewing point is one alone, in a predetermined position, typically above the system.

In other words, as the area of image reconstruction is small in size and located near the aperture of the system, just above the system itself, the possibility for an observer to perceive the image reconstructed in space is extremely limited. An observer cannot perceive the image when standing in front of the system, or if the angle of observation is below the system; an observer can perceive the image only if the observation point is above the system aperture.

The main object of the present invention is to provide an open volumetric device with a high reconstruction efficiency and which is capable, therefore, of overcoming the above-described drawbacks.

In particular, one object of the present invention is to provide an open volumetric device capable of reconstructing images that are large in size compared to the prior art.

In particular, one object of the present invention is to provide an open volumetric device capable of reconstructing images at a distance from the emitter device, and not only in proximity thereto.

In particular, one object of the present invention is to provide an open volumetric device free of optical interferences, i.e. by eliminating ghost images or rendering them uninfluential.

In particular, one object of the present invention is to provide an open volumetric device wherein the observer can be positioned in front of the system aperture.

SUMMARY OF THE INVENTION

In a first aspect of the invention, these and other objects are achieved by an open light field volumetric device for displaying images or flows of fluctuating and stereoscopic 3D images according to what is described in claim 1.

Advantageous aspects are described in the dependent claims.

In a second aspect of the invention, these and other objects are achieved by a method of displaying images or flows of fluctuating and stereoscopic 3D images according to what is described in claim 15.

Advantageous aspects are described in the dependent claims.

The invention can be implemented in the following applications, wherein the device of the invention can be one of the following: a device for projecting in air three-dimensional images dedicated to remote communication and to videoconferences;

a device for projecting in air fluctuating 3D images of furnishings; a device for the virtual 3D enlarged projection in air of a two- dimensional monitor;

a device for the projection of images in air of the contents of the display of a smartphone and external projection of the keyboard;

a 3D display for smartphones, tablets and personal computers; virtual monitors and/or televisions in three dimensions;

a device for projecting in air 3D images of data relative to the on board instruments of automobiles, aircraft and means of transport in general;

a device for realising signage by means of the projection of 3D images;

a device for projecting in air images of maps and directions relative to guided navigation systems;

a device for CAD applications for projecting fluctuating 3D images in air;

a device for“Entertainment” and for exhibitions, shows and virtual art and that is capable of projecting virtual 3D images;

a device dedicated to design (for example automotive design) and that is capable of projecting three-dimensional images in air;

a device for realising 3D holographic shop windows and displays; a device for 3D Movie Theatres or Virtual Theatres with the projection of images in three dimensions suspended in air;

in general, devices for projecting fluctuating 3D images in air;

a device for the three-dimensional displaying of images originating from a telescope;

a device for the three-dimensional displaying of images originating from a microscope; in general, devices for the three-dimensional displaying of images originating from optical instruments;

a device for the three-dimensional displaying of images originating from diagnostic instruments such as, by way of non-limiting example, radiographic images and other types of images used in the medical and health sectors;

a device for projecting three-dimensional images used for training and for corrective/rehabilitative applications;

optoelectronic devices based on dynamic synthetic holography.

The invention achieves the following technical effects:

- reconstruction of the image in an area of space distant from the projection device;

- reconstruction of large-sized images that correspond to the open side of the projection device;

- elimination of“ghost” images;

- the point of viewing the flow of images can be frontal, or above or below the projection device.

In general, the open volumetric device of the invention is capable of converting images, or a flow of images of any 2D display, into a fluctuating three-dimensional stereoscopic image perceivable as such by an observer without any supplemental viewing instrument, and perceivable as an image of considerable size, clearly visible also at a distance from the device and without optical interferences.

The aforementioned technical effects/advantages and other technical effects/advantages of the invention will emerge in greater detail from the description, provided below, of example embodiments illustrated by way of non-limiting example with reference to the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a first general schematic view of the device of the invention. Figure 2 is a second general schematic view of the device of the invention. Figure 3 shows details of the reflections that occur in the device of figures 1 and 2.

Figure 3A is a side sectional view along a directrix B-B of the device of the preceding figures.

Figure 3B is a side sectional view along a directrix B-B of the device of figures 1 and 2 in one embodiment of the invention.

Figure 3C is a side sectional view along a directrix B-B of the device of figures 1 and 2 in a variant embodiment of the invention.

Figure 4 is a schematic view of optical reflections determined by the device according to the invention.

Figures 5A, 5B show details of the embodiment of figures 3B and 3C.

Figure 6 shows sections of two parabolic mirrors of the device of the invention.

DETAILED DESCRIPTION

As will be described in detail in the following mathematical explanation, the invention allows determining the path of an image point inside the projection device and then in the space outside the device. In other words, it allows determining the position of the image point in space at every instant.

Given the image point projected by the emitting means, it is thus possible to determine the point of reflection on the first reflecting means and on the second reflecting means and therefore, after the second reflection, the position of the point in space.

By analysing the path of various image points we can therefore determine the areas subtended by an image emitted by the emitting means on the first reflecting means and on the second reflecting means and the various points of reconstruction of the image in space.

This enables the creation of a projection device wherein only the parts of the reflecting means corresponding to the area in which the image originating from the emitting means is reflected are inserted as portions of mirrors in the device.

In other words, it enables the size of the reflecting means and thus the size of the device to be reduced. It is possible to create devices of considerably reduced size compared to the prior art.

The reduction of the device mirrors also allows the area of the aperture AP of the device to be increased to completely different values, enormously greater than in prior art systems, as described below.

Increasing the area of the aperture AP of the device enables the size of the images projected to be increased correspondingly.

In other words, we are able to obtain considerably larger images relative to the size of the device compared to the prior art.

By appropriately shaping the mirror portions, it is also possible to compensate for any anamorphoses of the images introduced by the projection device itself, due to its intrinsic characteristics as a system with curved mirrors.

In the preferred embodiments of the invention, the emitting means is placed at the distal end of a neighbourhood of the focus of the paraboloid that enables the projection of images by the device.

In a first aspect of the invention, with general reference to figures 1 and 2, an open light field volumetric device for displaying images or flows of fluctuating and stereoscopic 3D images is shown.

With general reference to figure 1 , the device of the invention comprises an emitting means 1.

The emitting means 1 preferably comprises at least one among a monitor, a display, a projector or the like.

In particular, the emitting means 1 is also shown in figures 3B and 3C in one embodiment of the invention.

The device of the invention further comprises a reflection system 50 coupled to the emitting means 1.

According to the invention, the emitting means 1 is contained in the reflection system 50.

According to the invention, the emitting means 1 is offset relative to an azimuth axis A-A of the reflection system 50, as will be described in greater depth below.

According to the invention, the reflection system 50 is provided with a single system aperture AP.

The emitting means 1 is configured to: transmit a main beam MB of light rays R1 i in first main directions d1 iM.

In particular, with specific reference to figure 1 , the first main directions d1 iM comprise respective directions d1 1 M,d12M,d13M,d14M of light rays comprised in the main beam MB.

According to the invention, the beam of light rays R1 i represents a two- dimensional image flow.

According to the invention, the reflection system 50 comprises a first concave reflecting means 10 and a second concave reflecting means 20, both structured as continuous surfaces without holes.

In a preferred embodiment of the invention, the first reflecting means 10 and the second reflecting means 20 are made as portions of a paraboloid. The first concave reflecting means 10 is configured to: receive the main beam MB of light rays R1 i and reflect it in second main directions d2iM obtained at least as a function of the first main directions d1 iM and of a first conformation Confl of the first concave reflecting means 10.

According to the invention, the first main transmission directions d1 iM are definite as a function of:

- a point of light P₀ in a Cartesian space, located on the emitting means 1 within the reflection system 50 from which the main beam MB is emitted;

- a main angulation w of the main beam MB exiting from the emitting means 1 , wherein the angulation is defined with respect to a reference plane P on which an open curve C_INT_AP of intersection of the first concave reflecting means 10 with the second concave reflecting means 20 lies, as described below.

In particular, as shown in figures 5A and 5B, which refer to the embodiment shown in figures 3B and 3C, the value of the main angulation of the main beam MB is w = 90°. In particular, the conformation Confl , Conf 2 comprises one or more among concavity, opacity, roughness, colour, etc.

In a preferred embodiment of the invention, the conformation Confl , Conf2 coincides with a concavity C_10, C_20 of the concave reflecting means 10.

In general, according to the invention, the conformation Confl , Conf2 comprises a first conformation Confl and a second conformation Conf2. The conformations are expressed in terms of a portion of the reflecting means definite as a function of:

- the focal length f of the concave reflecting means;

- a distance c between the first concave reflecting means 10 and the second concave reflecting means 20.

According to the invention, the first concave reflecting means 10 is mounted with respect to the second concave reflecting means 20 with respective concavities C_10, C_20 facing one another and coaxial.

In particular, the first concave reflecting means 1 0 is mounted above the second concave reflecting means 20 with the respective concavities C_10, C_20 facing one another and coaxial.

Preferably, the first 10 and second 20 reflecting means are identical.

Preferably, the first 10 and second 20 reflecting means comprise mirrors. Preferably, the mirrors can be Fresnel mirrors or other types of mirrors adapted to contain the dimensions of the reflection system 50.

Preferably, the mirrors can be adaptive mirrors, or in general mirrors with a variable focus.

Preferably, the first 10 and second 20 reflecting means comprise paraboloids or portions thereof.

Indicating the positioning of a point of light P₀(x₀,y₀,z₀) and a second point P₁ (x₁ ,y₁,z₁) on the emitter we will analyse, in the explanation that follows, the path of such points inside and then outside the device.

Sections P₁ and P₂ of the concave reflecting means, defined as a function of the focal length f and of the distance c are defined hereinbelow in the general case of complete facing paraboloids (Fig. 6), although portions of facing paraboloids are considered in the invention (fig.3A).

Let P₁ and P₂ be the sections of two identical concave parabolic mirrors with a focal length f > 0, which are coaxial, facing and located at a vertex- to-vertex distance equal to

so that the focus of one is near the vertex of the other; for the sake of clarity, Fig. 6 shows the sections of complete circular paraboloids, whereas the paraboloid portions of fig.3A are considered in the real case.

Let us introduce the orthogonal Cartesian system Oxyz, so that O coincides with the vertex V2 and the x-axis coincides with the axis of symmetry of the mirrors.

For the calculation of the first main directions d1 iM, i.e. for the tracing of the rays exiting from the emitting means 1 , the following mathematical explanation applies, with reference to figure 4, wherein:

P₀ º (₀ y₀ z₀)^T is the positioning of a point of light in the Cartesian space (within the reflecting system) and e º (0 1 tan w ^T is the direction of the light ray, we define the value of the parameter:

where ^T0 ^(P0)represents the straight line portion (from t=0 to t= ^T0 ^(P0)) defining the beam exiting from the emitting means 1 and which terminates on the first concave reflecting means 10.

where:

We thus have:

The formula (154) expresses the second main directions d2iM along which the main ray MB, incident upon the first concave reflecting means 10, is reflected by the first concave reflecting means 10.

The reflection system 50 further comprises a second concave reflecting means 20 configured to receive the main beam MB of light rays R1 i along the second main directions d2iM and reflect it in third main directions d3iM obtained at least as a function of the second main directions d2iM and of a second conformation Conf2 of the second concave reflecting means 20.

As may be deduced from what has been disclosed thus far, the main beam MB is reflected in the third directions d3iM, moving away from the second reflecting means 20.

In other words, the third directions d3iM define the direction of the main beam MB through which the image represented by the beam is projected, which, after subsequent transformations, will determine a three- dimensional image IMM.

In particular, for the calculation of the third main directions d3iM, starting from equation (154), the following mathematical explanation applies:

We then define the value of the parameter: which represents the straight line portion (from

defining the beam exiting from the first concave reflecting means 10 and which terminates on the second concave reflecting means 20.

where:

We thus have:

The formula (159) expresses the third main directions d3iM along which the ray, incident upon the first concave reflecting means 10, reflected thereby and then incident upon the second concave reflecting means 20, is reflected by the latter.

Let us then define the value of the parameter

which represents the straight line portion (from

) defining the beam exiting from the second concave reflecting means 20 and which terminates on the inner surface S of the paraboloid that will be considered for the reflection.

Finally, we have:

The vector

defines the geometric location of the points in space that identify the portion of surface S (fig.4) of the system aperture AP, i.e. the surface defined in the exit directions d3iM from the reflection system 50.

When evaluated along the perimeter of the surface of the emitting means

1 corresponding to the projected image, the vector allows

describing the portion of mirrors indispensable for the formation of the image outside the device to be described.

As may also be observed from Fig. 4, this window, which indicates the minimum optimal aperture and coincides with the surface So, has a shape that exhibits a certain complexity.

From this it will then be possible to derive (negatively) an essential portion of mirrors usable for the projection of the image, care being taken to render non-reflective or eliminate completely from the design of the device the surface portions comprised between the actual window and the theoretically evaluated mixtilinear trapezoid in order to reduce possible spurious reflections.

Based on how it is described and obtained, the device will be“maximally open”, i.e. from what has been mathematically demonstrated, the device consists solely of two portions of a paraboloid (responsible for the first and second reflections) adapted to obtain the effect of reconstruction of the image in space.

In the real case, to which the preferred embodiment of the present invention relates, the aperture AP is defined in all of the space with the exception of the paraboloid portions 10 and 20 described.

The image IMM emitted by the emitting means, reflected twice, respectively by the first 10 and second 20 emitting means, and exiting through the surface S, that is, through the aperture AP, according to formula 162, is reconstructed in space at a distance from the reflection system 50. The distance at which the image is reconstructed is obtained as follows: let us consider the second point of the emitter Pi(xi,y-i,zi), not coinciding with Po(xo,yo,zo), and let us repeat the same mathematical explanation as described above for the point Po(xo,yo,zo). At this point, where we intend to calculate by how much the image “comes out”, it is possible to quantitatively determine this effect by determining the distance from the surface of second reflection of the point of intersection of the rays in the second reflection exiting from the device and originated by the light points of the emitter ^P0 and ^P1. The position of said point is determined by the specification of the parameter t as follows:

Given this value of the parameter it is possible to identify the point in space of the intersection of the two rays:

Now we want to calculate the distance of this point relative to the lower mirror along the straight line defined as the axis of the rotated-translated visual cone. The equation of said axis results from the rotation-translation of the initial axis of the cone, which coincided with the z axis of the Cartesian reference system.

The translation vector

will be such as to include the aforesaid point in the transformed axis. Analogously to the previous explanation of the conical surface, we define point K as the point of intersection

Following the same procedure as proposed for the conical surface, once K has been identified it will be possible to evaluate the norm

the quantification of which provides the determination of the“coming out” of the image

At the conclusion of the explanation, the technical effect achieved is that the main image exits from the device through the aperture AP according to what is expressed by formula 162 at a distance that can be calculated as the quantification of the norm described.

The first concave reflecting means 10 and the second concave reflecting means 20 comprise respective foci F1 and F2.

According to the invention, as shown in figure 1 , the foci F1 , F2 respectively of the first concave reflecting means 10 and of the second concave reflecting means 20 lie on a straight line that defines the azimuth axis A-A (fig.3) of the reflection system 50.

With particular reference to figure 1 , according to the invention the first concave reflecting means 10 and the second concave reflecting means 20 intersect along an open intersection curve C_int_AP lying on a reference plane P that is perpendicular to the aforesaid azimuth axis A-A of the reflection system 50.

The first concave reflecting means 10 and the second concave reflecting means 20, by intersecting along the open intersection curve C_int_AP, determine a conformation of the single system aperture AP.

In a preferred embodiment of the invention, the first reflecting means 10 and the second reflecting means 20 are made as a portion of a paraboloid defined between the distal point of the neighbourhood that allows the projection of the image outside the device, which gives rise to the reconstruction of the image in space and the open curve C_INT_AP.

The first concave reflecting means 10 and the second concave reflecting means 20 are thus structured so that:

at least the main beam of light rays R1 i, reflected by the second concave reflecting means 20, exits from the reflection system 50 along the third directions d3iM through the single system aperture AP;

- wherein an image IMM generated as a function of the main beam of light rays R1 i is perceived by an observer, located at a variable viewing distance Dh with respect to the second concave reflecting means 20, when the observer looks towards the second concave reflecting means 20 along two visual cones CL,CR having respective directrices DIR_L,DIR_R.

In particular, with reference to figure 2, the vertices VL, VR of the two cones CL,CR coincide with the observation points WL,WR of the observer,

In particular, the vertices VL, VR of the two cones CL,CR coincide with the observation points WL,QR of the observer, wherein the observation points WL,WR have a mean observation point WM and a predefined distance DW, as shown in figure 2.

According to the invention, the cones CL,CR intersect the second concave reflecting means 20 along respective distinct curves KL KR having respective areas AL,AR.

In particular, the curves KL,KR are the curves obtained by the intersection of the lateral surfaces of the cones CL,CR with the surfaces of the second concave reflecting means 20.

In particular, the areas AL,AR are the areas delimited by the curves KL,KR on the second concave reflecting means 20.

According to the invention, the variable viewing distance Dh is variable between a first distance h1 and a second distance h2 along a reference direction dir_M, defined below.

According to the invention, hi corresponds to the distance between the fluctuation point F and the centre of gravity of the area OVL. According to the invention, h2 corresponds to the distance between the point in which the image IMM is no longer perceived by an observer, when the observer looks towards the second concave reflecting means 20, along the two visual cones CL,CR having respective directrices DIR_L,DIR_R, and the centre of gravity of the area OVL.

According to the invention, the reference direction dir_M is defined as a function of the directrices DIR_L, DIR_R and of the third directions d3i.

The reference direction dir_M is defined as a function of the point of intersection of the directrices P_INT and of the mean observation point WM.

According to the invention, the second reflecting means 20, with non- limiting reference to figure 2, is configured to: reflect the beam of light rays R1 i along the third directions d3i in the neighbourhood of the image fluctuation point F along the reference direction DIR_M.

The fluctuation point F and the mean observation point WM are located at a reciprocal viewing distance d defined as a function of the image fluctuation point F.

The fluctuation point F is calculated at a fluctuation distance

from the second reflecting means 20, in particular from a point y, intersection between the straight line DIR_M and the second reflecting means 20 within the overlap surface OVL.

In particular, the positioning distance Dh is the distance calculated along the straight line DIR_M between the point WM and the point y; i.e.

d.

According to the invention, the fluctuation distance

is in a third functional relationship with the conformations Conf_1 , Conf_2 and the first

directions d1 i.

In the real application, the following relationships apply:

- d has a minimum value (~ 25 cm) dictated by human anatomy and physiology;

- Dh has a minimum value dictated by: - d (how the eye works)

-

(how the device is made)

- OVL (how the brain works).

According to the invention, the device further comprises a regulator 30 adapted to set the reference direction dir_M, defined as a function of the directrices DIR_L,DIR_R and of the third directions d3i, in order to determine an overlap measurement OVL of the areas AL,AR, thereby realising a visual effect of the image IMM) as a three-dimensional image, fluctuating and stereoscopic in a neighbourhood of the image fluctuation point F for the observer located at the variable viewing distance Dh.

According to the invention, the regulator 30 is predisposed to regulate a position of the reflection system 50.

The regulator is preferably one among a mechanical, electromechanical, pneumatic and electromagnetic regulator

The adjustment of the position preferably takes place relative to a support means 60 of the reflection system 50, adapted to support the reflection system 50.

The technical effect achieved is a visual effect of the image IMM as a three-dimensional image, fluctuating and stereoscopic in the neighbourhood of an image fluctuation point F for the observer located within the variable viewing distance Dh.

In the embodiment of the invention, the emitting means 1 is set perpendicularly to the plane containing the curve of intersection of the first and second concave reflecting means and projects images in the opposite direction to the azimuth axis. There are two reflections of the image: one that we call the main reflection by the first reflecting means and one that we call the“ghost” reflection by the second reflecting means.

The main reflection is due to the first reflecting means, which will reflect the image coming from the emitting means towards the second reflecting means, which will reflect it towards the outside of the device, i.e. towards the area of reconstruction of the image. The“ghost” reflection is the reflection generated by the second reflecting means; this reflection consists of the single reflection of the second reflecting means directly towards the outside of the device and the image due to this reflection is upside-down relative to the primary image, which instead undergoes a double reflection.

The main reflection is the reflection that enables the image to be reconstructed in the space outside the device, whereas the “ghost” reflection generates the“ghost” image, whose presence near the area of reconstruction of the main image disturbs the viewing thereof by an observer.

In other words we will have the main image reconstructed in space and near the upside-down“ghost” image caused by the direct reflection of the second reflecting means (figure 3).

In the case of the “ghost” reflection, the mathematical explanation is analogous to the one described above, stopped at the first reflection because after the first reflection the image exits from the device and creates the interference defined as“ghost” image in the viewing area of an observer.

In this case as well, the mathematical explanation allows defining the area subtended by the image on the second reflecting means responsible for the reflection of the“ghost” image.

By eliminating the part of the second reflecting means responsible for the “ghost” image or by covering it with an absorber we eliminate the“ghost” image and thus the interference created by that image in the viewing area of an observer.

Let us now consider the areas subtended on the reflecting means by the main reflection and by the“ghost” reflection. The areas subtended on the first and second reflecting means by the main reflection are located in the part of the device between the distal end of the neighbourhood of the focus of the paraboloid that enables the projection of images by the device and the curve c_int_AP (see figure 3), the“ghost” reflection is located on the second reflecting means in proximity to the emitting means (see figure 3).

Considering the positions of the areas subtended on the mirrors by the main reflection and by the“ghost” reflection it is possible to drastically reduce the dimensions of the device to solely the areas subtended by the main reflection. It is then possible to eliminate the “ghost” reflection, located on the second reflecting means in proximity to the emitting means, by eliminating the part of the second reflecting means responsible for the “ghost” reflection.

In other words in this embodiment, the device will be composed only of the parts of the first and second reflecting means that enable the main reflection of the image.

This makes it possible to obtain, as the device aperture AP, all of the space with the exception of the two portions of the reflecting means that enable the main reflection of the image.

With specific reference to figure 3, the emitting means 1 is responsible not only for the transmission of the main beam MB, but also for the transmission of a spurious beam GB (ghost beam).

In particular, the emitting means 1 is configured to: transmit the spurious beam GB of light rays R2i in first spurious directions d1 iG towards the second concave reflecting means 20.

The first spurious directions d1 iG are defined as a function of

- a point of light P0 in the Cartesian space located on the emitting means 1 within the reflection system 50 from which the spurious beam GB is emitted;

- a spurious beam angulation w G of the spurious beam GB, exiting from the emitting means 1 , with respect to the reference plane P.

In particular, for the calculation of the first spurious directions d1 iG, i.e. for tracing the spurious beam GB exiting from the emitting means 1 , the mathematical explanation previously expressed for the main beam MB, stopped at the first reflection, applies. Figures 3B and 3C show a side sectional view of the open volumetric device of the invention, in the embodiment described, along the directrix B- B.

In this embodiment, the emitting means 1 are such that the angle w = 90°. In other words, the emitting means 1 is vertical relative to the reference plane P.

According to the invention, the emitting means 1 is provided at a proximal limit Lp, relative to the second concave reflecting means 20, of the neighbourhood l_F2 of the focus F2 of the second concave reflecting means 20.

The neighbourhood l_F2 corresponds to the maximum area within which the image emitting means 1 can be located in order that the images IMM are reconstructed outside the reflection system 50 at a distance.

The technical effect achieved is thus the reconstruction of the images IMM at a distance from the reflection system 50.

The calculation of the distance is performed by considering the distance from the second reflection surface, as previously described in the mathematical explanation.

In a variant of the second embodiment of the invention, the reflection system 50 comprises within it an absorber of ghost images A functionally coupled to the emitting means 1 predisposed to absorb the spurious beam of light rays R2i along the first spurious directions d1 iG.

The absorber A will be arranged in proximity to the second concave reflecting means 20 along the first spurious directions d1 iG.

The location of the points representing the absorber A is the one that cancels out the beam along the direction n₀(P₀), i.e. it cancels out the beam at the first reflection in equation 152.

In a second aspect, the invention discloses a method of displaying of images or flows of fluctuating and stereoscopic 3D images.

The method according to the invention comprises the steps of:

predisposing emitting means 1 , predisposing a reflection system 50 provided with a single system aperture AP coupled to said emitting means 1 and comprising first concave reflecting means 10 and second concave reflecting means 20;

- predisposing said first concave reflecting means 10 structured as continuous surfaces without holes;

- predisposing said second concave reflecting means 20 structured as continuous surfaces without holes;

- predisposing said first concave reflecting means 10 mounted, with respect to said second concave reflecting means 20, with concavities C_10, C_20 facing one another and coaxial;

- predisposing foci F1 ,F2 of said first concave reflecting means 10 and of said second concave reflecting means 20 lying on a straight line that defines the azimuth axis A-A of the reflection system 50;

- intersecting said first concave reflecting means 10 and said second concave reflecting means 20 along an open intersection curve C_int_AP lying on a reference plane P that is perpendicular to the azimuth axis A-A of the reflection system 50, wherein, by intersecting along said open intersection curve C_int_AP, said first concave reflecting means 10 and said second concave reflecting means 20 determine a conformation of said single system aperture AP;

- on the part of said emitting means 1 , transmitting a main beam MB of light rays R1 i representing a two-dimensional image flow, in first main directions d1 iM;

- on the part of first concave reflecting means 10, receiving at least said main beam MB of light rays R1 i and reflecting at least said main beam MB of light rays R1 i in second main directions d2iM obtained as a function of said first main directions d1 iM and of a first conformation Confl of the first concave reflecting means 10;

- on the part of second concave reflecting means 20, receiving at least said main beam of light rays R1 i along said second directions d2i1 M and reflecting at least said beam in third main directions d3i1 M obtained as a function of said second main directions d2i1 M and of a second conformation Conf2 of the second concave reflecting means 20;

- structurally predisposing said first concave reflecting means 10 and said second concave reflecting means 20 so that:

at least said main beam of light rays R1 i, which are reflected by the second concave reflecting means 20, exits from said reflection system 50 along said third directions d3i1 M through said single system aperture AP;

- wherein an image IMM generated as a function of the main beam of light rays R1 i is perceived by an observer, located at a variable viewing distance Dh with respect to said second concave reflecting means 20, when the observer looks towards said second concave reflecting means 20 along two visual cones CL,CR having respective directrices DIR_L,DIR_R;

- wherein said variable viewing distance Dh is variable between a first distance h1 and a second distance h2 along a reference direction dir_M,

- wherein vertices VL,VR of the two cones CL,CR coincide with the observation points WL,WR of the observer,

- wherein said cones CL,CR intersect said second concave reflecting means 20 along respective distinct curves KL,KR having respective areas AL,AR;

- wherein the device further comprises:

a regulator 30 adapted to set said reference direction dir_M, which is defined as a function of said directrices DIR_L,DIR_R and of said third main directions d3iM, to determine an overlap measurement OVL of said areas AL,AR, thus realising a visual effect of said image IMM as a three- dimensional image, fluctuating and stereoscopic in the neighbourhood of a fluctuation point F for said observer located at said variable viewing distance Dh.

In a third aspect, the invention describes a television for projecting flows of fluctuating and stereoscopic 3D images comprising:

a receiving means for receiving a digital television signal TV_Sn; an open light field volumetric device for displaying flows of fluctuating and stereoscopic 3D images, as previously described, and configured to receive the digital television signal TV_Sn.

According to the invention, the emitting means 1 is configured to:

• receive an input signal INPUT defined as a function of the digital television signal TV_Sn;

• emit a main beam of light rays R1 iM representing a two-dimensional image flow, the images being defined as a function of the input signal INPUT;

wherein the light field volumetric display device is configured to realise a visual effect of a three-dimensional image IMM, fluctuating and stereoscopic about said fluctuation point (F) for said observer located at a variable viewing distance Dh.

In a fourth aspect, the invention describes an application for an open light field volumetric device for displaying images or flows of fluctuating and stereoscopic 3D images wherein said device is one of the following:

a device for projecting in air three-dimensional images dedicated to remote communication and to videoconferences;

a device for projecting in air 3D images of data relative to the on- board instruments of automobiles, aircraft and means of transport in general;

a device for realising signage by means of the projection of 3D images; a device for projecting in air images of maps and directions relative to guided navigation systems;

a device for CAD applications for projecting fluctuating 3D images in air;

in general, devices for projecting fluctuating 3D images in air;

a device for the three-dimensional displaying of images originating from a microscope;

in general, devices for the three-dimensional displaying of images originating from optical instruments;

a device for the three-dimensional displaying of images originating from diagnostic instruments such as, by way of non-limiting example, radiographic images and other types of images used in the medical and health sector;

optoelectronic devices based on dynamic synthetic holography.

Claims

1 . An open light field volumetric device for displaying images or flows of fluctuating and stereoscopic 3D images comprising:

- an emitting means (1 ) configured to transmit a main beam (MB) of light rays (R1 i) representing a two-dimensional image flow, in first main directions (d1 iM);

a reflection system (50) provided with a single system aperture (AP), wherein said reflection system (50) is coupled to said emitting means (1 ) and, in turn, comprises:

- a first concave reflecting means (10) structured as continuous surfaces without holes, and predisposed to receive at least said main beam (MB) of light rays (R1 i) and reflect at least said main beam (MB) of light rays (R1 i) in second main directions (d2iM), said second main directions (d2iM) being obtained as a function of said first main directions (d1 iM) and of a first conformation (Confl ) of the first concave reflecting means (10);

- a second concave reflecting means (20) structured as continuous surfaces without holes, and predisposed to receive at least said main beam of light rays (R1 i) along said second directions (d2i1 M) and reflect at least said beam in third main directions (d3i1 M), said third main directions (d3i1 iM) being obtained as a function of said second main directions (d2i1 M) and of a second conformation (Conf2) of the second concave reflecting means (20);

- wherein said first concave reflecting means (10) is mounted, with respect to said second concave reflecting means (20), with concavities (C_10; C_20) facing one another and coaxial;

- wherein said first concave reflecting means (10) and said second concave reflecting means (20) comprise respective foci (F1 ;F2);

- wherein said foci (F1 ; F2) of said first concave reflecting means (10) and of said second concave reflecting means (20) lie on a straight line that defines an azimuth axis (A-A) of the reflection system (50);

- wherein said first concave reflecting means (10) and said second concave reflecting means (20) intersect along an open intersection curve (C_int_AP) lying on a reference plane (P) that is perpendicular to said azimuth axis ( A-A) of the reflection system (50),

- wherein, by intersecting along said open intersection curve (C_int_AP), said first concave reflecting means (10) and said second concave reflecting means (20) determine a conformation of said single system aperture (AP);

- wherein said first concave reflecting means (10) and said second concave reflecting means (20) are structured so that:

at least said main beam of light rays (R1 i), which are reflected by the second concave reflecting means (20), exits from said reflection system (50) along said third directions (d3i1 M) through said single system aperture (AP);

- wherein an image (IMM) generated as a function of the main beam of light rays (R1 i) is perceived by an observer, located at a variable viewing distance (Dh) with respect to said second concave reflecting means (20), when the observer looks towards said second concave reflecting means (20) along two visual cones (CL; CR) having respective directrices (DIR_L; DIR_R);

- wherein said variable viewing distance (Dh) is variable between a first distance (h1 ) and a second distance (h2) along a reference direction (dir_M),

- wherein vertices (VL; VR) of the two cones (CL; CR) coincide with the observation points (WL; WR) of the observer,

- wherein said cones (CL; CR) intersect said second concave reflecting means (20) along respective distinct curves (KL; KR) having respective areas (AL; AR);

- wherein the device further comprises:

a regulator (30) adapted to set said reference direction (dir_M), which is defined as a function of said directrices (DIR_L; DIR_R) and of said third main directions (d3iM), to determine an overlap measurement (OVL) of said areas (AL; AR), thus realising a visual effect of said image (IMM) as a three-dimensional image, fluctuating and stereoscopic in the neighbourhood of a fluctuation point (F) for said observer located at said variable viewing distance (Dh).

2. The open light field volumetric device according to claim 1 , wherein said emitting means (1 ) is configured to transmit said main beam (MB) of light rays (R1 i) in said first main transmitting directions (d1 iM), wherein:

said first main transmitting directions (d1 iM) are defined as a function of:

- a point of light (P₀) in the Cartesian space located on said emitting means (1 ) within said reflection system (50) from which said main beam (MB) is emitted.

- a main angulation (w) of said main beam (MB), exiting from said emitting means (1 ), wherein the main angulation (w) is defined with respect to a reference plane (P) on which said open intersection curve (C_INT_AP) lies said first and second conformations (Conf1 ; Conf2) are defined as a function of:

- a focal distance (f) of said concave reflecting means (10; 20)

- a distance (c) between said first concave reflecting means (10) and said second concave reflecting means (20).

3. The open light field volumetric device according to claim 2, wherein said emitting means (1 ) is such that said angulation (w) is 90°.

4. The open light field volumetric device according to claim 3, wherein said emitting means (1 ) is arranged at a proximal limit (Lp), with respect to said second concave reflecting means (20), in a neighbourhood (l_F2) of the focus (F2) of said second concave reflecting means (20).

5. The open light field volumetric device according to claim 1 or 2, wherein said emitting means (1 ) is configured to transmit a spurious beam (GB) of light rays (R2i) in a first spurious direction (d1 iG) towards said second concave reflecting means (20), wherein said first spurious direction (d1 iG) is defined as a function of

- a point of light (P₀) in the Cartesian space located on said emitting means (1 ) within said reflection system (50) from which said spurious beam (GB) is emitted

- a spurious beam angulation (wG) of said spurious beam (GB), exiting from said emitting means (1 ), wherein the spurious beam angulation ( wG) is defined with respect to a reference plane (P) on which said open intersection curve (C_INT_AP) lies

said first and second conformations (Conf1 ; Conf2) are defined as a function of:

- a focal distance (f) of said concave reflecting means (10; 20)

6. The open light field volumetric device according to claim 5, wherein said reflection system (50) comprises therewithin an absorber of ghost images (A) that is functionally coupled to said emitting means (1 ) and predisposed to absorb said spurious beam of light rays (R2i) along said first spurious direction.

7. The open light field volumetric device according to claim 6, wherein said absorber of ghost images (A) is arranged in proximity to said second concave reflecting means (20) along said first spurious directions (d1 iG).

8. The open light field volumetric device according to any one of the preceding claims, wherein vertices (VL; VR) of the two cones (CL; CR) coincide with the observation points (WL; WR) of the observer, said observation points (WL; WR) having a mean observation point (WM) and a predefined distance (DW).

9. The open light field volumetric device according to claim 8, wherein said regulator (30) is configured to set said reference direction (dir_M), as a function of the point of intersection (P_INT) of the directrices (DIR_L; DIR_R) and of said mean observation point (WM).

10. The open light field volumetric device according to any one of the preceding claims, wherein said fluctuation point (F) is positioned along said reference direction (DIR_M), wherein said fluctuation point (F) and said mean observation point (WM) are arranged at a reciprocal viewing distance (d) defined as a function of said fluctuation point (F), wherein said fluctuation point (F) is calculated at a fluctuation distance from

said second reflecting means (20).

11. The open light field volumetric device according to claim 10, wherein said fluctuation distance

is in a functional relation with said

conformations (Conf_1 ; Conf_2) and said first directions (d1 iM).

12. The open light field volumetric device according to any one of the preceding claims, wherein said regulator (30) is predisposed to adjust a position of said reflection system (50).

13. The open light field volumetric device according to claim 12, wherein said regulator comprises a mechanical, electromechanical, pneumatic or electromagnetic regulator.

14. A television for projecting flows of fluctuating and stereoscopic 3D images, comprising:

receiving means for receiving a digital television signal (TV_Sn);

an open light field volumetric device for displaying flows of fluctuating and stereoscopic 3D images, according to any one of claims 1 to 13, and configured to receive said digital television signal (TV_Sn), and wherein said emitting means (1 ) is configured to:

- receive an input signal (INPUT) defined as a function of the digital televisual signal (TV_Sn);

- emit a main beam of light rays (R1 im) representing a two- dimensional image flow, the images being defined as a function of said input signal (INPUT);

wherein the light field volumetric display device is configured to realise a visual effect of a three-dimensional image (IMM), fluctuating and stereoscopic about said fluctuation point (F) for said observer located at a variable viewing distance (Dh).

15. An application for an open light field volumetric device for displaying flows of fluctuating and stereoscopic 3D images wherein said device is one of the following:

a device for projecting in air fluctuating 3D images of furnishings; - a device for the virtual 3D enlarged projection in air of a two- dimensional monitor;

a 3D display for smartphones, tablets and personal computers; - virtual monitors and/or televisions in three dimensions;

a device for realising signage by means of the projection of 3D images;

a device for CAD applications for projecting fluctuating 3D images in air;

- a device for“Entertainment” and for exhibitions, shows and virtual art and that is capable of projecting virtual 3D images;

a device dedicated to design and that is capable of projecting three- dimensional images in air;

a device for realising 3D holographic shop windows and displays; - a device for 3D Movie Theatres or Virtual Theatres with the projection of images in three dimensions suspended in air;

in general, devices for projecting fluctuating 3D images in air;

- a device for the three-dimensional displaying of images originating from a microscope; in general, devices for the three-dimensional displaying of images originating from optical instruments;

optoelectronic devices based on dynamic synthetic holography.

16. A method of displaying images or flows of fluctuating and stereoscopic 3D images comprising the steps of:

predisposing emitting means (1 ),

predisposing a reflection system (50) provided with a single system aperture (AP), coupled to said emitting means (1 ) and comprising first concave reflecting means (10) and second concave reflecting means (20);

- predisposing said first concave reflecting means (10) structured as continuous surfaces without holes;

- predisposing said second concave reflecting means (20) structured as continuous surfaces without holes;

- predisposing said first concave reflecting means (10) mounted, with respect to said second concave reflecting means (20), with concavities (C_10; C_20) facing one another and coaxial;

- predisposing foci (F1 ; F2) of said first concave reflecting means (10) and of said second concave reflecting means (20) lying on a straight line that defines the azimuth axis (A-A) of the reflection system (50; 150);

- intersecting said first concave reflecting means (10) and said second concave reflecting means (20) along an open intersection curve (C_int_AP) lying on a reference plane (P) that is perpendicular to the azimuth axis (A-A) of the reflection system (50), wherein, by intersecting along said open intersection curve (C_int_AP), said first concave reflecting means (10) and said second concave reflecting means (20) determine a conformation of said single system aperture (AP);

- on the part of said emitting means (1 ), transmitting a main beam (MB) of light rays (R1 i) representing a two-dimensional image flow, in first main directions (d1 iM);

- on the part of said first concave reflecting means (10), receiving at least said main beam (MB) of light rays (R1 i) and reflecting at least said main beam (MB) of light rays (R1 i) in second main directions (d2iM), said second main directions (d2iM) being obtained as a function of said first main directions (d1 iM) and of a first conformation (Confl ) of the first concave reflecting means (10);

- on the part of said second concave reflecting means (20), receiving at least said main beam of light rays (R1 i) along said second directions (d2i1 M) and reflecting at least said beam in third main directions (d3i1 M), said third main directions (d3i1 iM) being obtained as a function of said second main directions (d2i1 M) and of a second conformation (Conf2) of the second concave reflecting means (20);

- structurally predisposing said first concave reflecting means (10) and said second concave reflecting means (20) so that:

- wherein said variable viewing distance (Dh) is variable between a first distance (hi ) and a second distance (h2) along a reference direction (dirJM), - wherein vertices (VL; VR) of the two cones (CL; CR) coincide with the observation points (WL; WR) of the observer,

- further predisposing:

a regulator (30) adapted to set said reference direction (dir_M), which is defined as a function of said directrices (DIR_L; DIR_R) and of said third main directions (d3iM), to determine an overlap measurement (OVL) of said areas (AL; AR), thus realising a visual effect of said image (IMM) as a three-dimensional image, fluctuating and stereoscopic about a fluctuation point (F) for said observer located at said variable viewing distance (Δh).