A projection multi-view 3D imaging device

Abstract

The present disclosure relates to projection multi-view 3D imaging device. The device comprises at least one projector configured to form an image in a corresponding viewing zone, wherein each of the at least one projector is separated from the geometric center of the corresponding viewing zone in a vertical plane relative to the viewer's eyes, and is located outside the corresponding viewing zone, a screen unit having at least one of a spatial scattering distribution function and a spatial reflection distribution function.

Description

A PROJECTION MULTI-VIEW 3D IMAGING DEVICE

[0001] The present disclosure relates to projection-type devices for forming a multi-view three-dimensional (3D) image, for example, an autostereoscopic or holographic image for one or more users or viewers, and can be used for educational, advertising and entertainment purposes for home and public use, such as cinemas, museums, educational institutions where there is a need to generate large holographic images.

[0002] There are a variety of imaging means in the art that provide multi-view stereoscopic 3D images in certain viewing zone, both with auxiliary means for viewing such as wearable devices, for example stereo glasses and without wearable devices, to maximize viewer immersion experience.

[0003] However, known stereoscopic imaging devices have some limitations for obtaining high-quality 3D images.

[0004] The objective of the present disclosure is to solve the following problems of holographic / autostereoscopic imaging devices known from the related art.

[0005] It is known for the skilled person in the art that for comfortably viewing a high-quality 3D image (holographic / autostereoscopic 3D image), the viewing zone may be large enough in the vertical direction of the screen, for example ≥ 20 degrees, and with low scattering in the horizontal direction of the screen, for example ≤1 degree, to eliminate overlap of viewing zones / crosstalk of viewing zones formed for each eye, and provide high image contrast, without image doubling while maintaining high efficiency of the generated image, i.e. the amount of light falling from the projector into the formed viewing zone, for example ≥ 50%.

[0006] The known retroreflective films include, for example, retroflectors based on glass beads, reflective films (see Fig. 1A) that use glass beads or spherical lenses as reflective elements, and reflective films that use retro-reflective microprisms as reflective elements(see, Fig. 1B). Light in such reflective (retro-reflective) films undergoes scattering at the interface between materials and at defects in the volume (inside) of the material caused by technological errors, which causes very high light scattering at the exit from the film, which makes it impossible to qualitatively separate the viewing zones for each eye for the 3D image formation.

[0007] Moreover, resolution of the generated 3D image degrades with a conventional retroreflectors at trying of extend viewing zone in vertical direction by a vertical diffuser (optical light-scattering element) that scatters light in the vertical direction.

[0008] Thus, in the known 3D imaging devices, there is very often overlap between the viewing zones for the right eye (R) and the left eye (L) of the viewer (1), which causes doubling and degradation of the contrast of the 3D image (see Fig. 1C).

[0009] The known 3D imaging devices in a configuration in which the projector (2) is not fixed above the head of the viewer 1 i.e. placed at a distance from the viewer's head 1 and stereo glasses are not used, they have significant light scattering in the vertical direction of the viewing zone. Therefore, part of the light in the vertical direction does not fall into the useful viewing zone, and the viewing zone for the left eye of the viewer is designated as L, and for the right eye as R, and the screen comprising a retroreflector is designated as 120. This device configuration has low efficiency in the vertical direction, see Fig. 2A.

[0010] If it is necessary to generate a 3D image on a large screen 120, when the projector 2 is not fixed above the viewer's head 1, but is located at a distance from it, and stereo glasses are not provided in the configuration of the 3D imaging device, this leads to distortion (curvature) of the viewing zone, and the viewing zone for the left eye of the viewer designated as L, and for the right eye as R. Due to this aberration, the viewing zone becomes blurred / curved in the horizontal direction, and part of the field of view does not fall into the viewer's pupil . Thus, only part of the whole image can be seen (see Fig. 2B).

[0011] In addition, the inventors made an analysis of particular performance parameters of flagship solutions in the market and of the present disclosure, which clearly demonstrated the advantage of the projection multi-view 3D imaging device.

[0012] Main performance characteristics chosen for analysis include: 1) approaches, 2) the presence of auxiliary means for viewing (stereo glasses), 3) the possibility of vertical separation of the projector from the viewer's head, 4) efficiency in the viewing zone, 5) field of view.

[0013] The present disclosure may comprises the following:

[0014] 1) the device comprises: a highly efficient one-dimensional retroreflector (1D RR), an optical light-scattering element, a redirecting optical element and a compensation block,

[0015] 2) auxiliary means for viewing, such as glasses, are not used

[0016] 3) the possibility of a large vertical separation of the projector from the viewer's head is possible (up to <85 degrees in angular measure),

[0017] 4) high efficiency of the device,

[0018] 5) large field of view, for example, 40, 60, 120, etc. degrees.

[0019] The present disclosure relates to projection-type device for generating a multi-view color autostereoscopic / holographic three-dimensional (3D) image, where holographic / autostereoscopic scene / image is generated by forming one or more viewing zones (windows) without the use of wearable devices, and by using at least two projectors to generate an autostereoscopic image or at least one projector to generate a holographic image and a new screen with controlled / directed scattering.

[0020] In this case, the present disclosure provides the following advantages:

[0021] - the ability to observe an autostereoscopic / holographic 3D image without the use of auxiliary means for vieweing, for example, stereo glasses;

[0022] - formation of narrow and separated viewing zones provided by reduced diffusion / scattering horizontally of the screen to prevent image doubling and degradation of 3D image contrast;

[0023] - correction / minimization of manufacturing defects of the retroreflector;

[0024] - the ability to control / limit diffusion / scattering along the vertical direction of the screen;

[0025] - the ability to correct aberrations of the viewing zone.

[0026] Thus, the object of the present disclosure is to provide a multi-view 3D imaging device that provides a multi-view 3D image in a specific viewing zone without the use of additional wearable devices to maximize the viewer's immersive experience. Proposed is a screen unit that is capable of spatial control of the BRDF / BSDF (Bidirectional Scattering Distribution Function (BSDF) and / or Bidirectional Reflectivity Distribution Function (BRDF)), and is also capable of highly efficiently forming aberration-free viewing zones of the projected 3D image.

[0027] According to an aspect of the present disclosure, a projection multi-view 3D imaging device is provided, the device comprises:

[0028] at least one projector (2) configured to form an image in a corresponding viewing zone, wherein each of the at least one projector is separated from the geometric center of the corresponding viewing zone in a vertical plane relative to the viewer's eyes, and is located outside the corresponding viewing zone, and

[0029] a screen unit (SU) having at least one of a spatial scattering distribution function and a spatial reflection distribution function, and configured to form at least one viewing zone of the generated image.

[0030] The screen unit may comprise a retroreflector (3) , and an optical light-scattering element (4).

[0031] The retroreflector may be a reflective film and is configured in the form of a set of one-dimensional rectangular prisms elongated in the vertical direction relative to the eyes of the viewer and having a reflective coating on the prism faces.

[0032] The optical light-scattering element may be located next to the retroreflector along the direction of light emitted from at least one projector, and is configured to scatter light reflected from the retroreflector in the vertical direction relative to the viewer's eyes.

[0033] The screen unit may further comprise a redirecting optical element (5) and a compensation block, optically coupled with at least one projector and with at least one pupil of the viewer's eyes.

[0034] The redirecting optical element may have at least one of the spatial scattering distribution function and the spatial reflection distribution function, and is configured to redirect light, when the light is reflected from the retroreflector and passing through the optical light-scattering element, to the area of at least one viewing zone in which the viewer's eye is located, in the use of the device.

[0035] The redirecting optical element may be made with an offset optical axis relative to the optical axis of the device, and have zero optical power in the horizontal direction and a predetermined optical power (OP) in the vertical direction relative to the viewer's eyes, which is inversely proportional to the distance from the screen unit to the at least one corresponding viewing zone.

[0036] The compensation block is configured to compensate a distortion of at least one corresponding viewing zone in the horizontal direction.

[0037] The compensation block may comprise a first compensation element (7), and a second compensation element (6).

[0038] The first compensation element may be located next to the redirecting optical element along the direction of light emitted from at least one projector and have zero optical power in the vertical direction in relation to the viewer's eyes, and negative optical power in the horizontal direction in relation to the eyes of the viewer.

[0039] The second compensation element may be located between the retroreflector and the optical light-scattering element along the direction of light emitted from at least one projector and have by zero optical power in the vertical direction in relation to the viewer's eyes and positive optical power in the horizontal direction in relation to the viewer's eyes.

[0040] The retroreflector configured in the form of a set of one-dimensional rectangular prisms elongated in the vertical direction with a reflective coating on the faces of the prisms, may additionally contain an absorbing coating on the edges at the tops and / or bottoms of the prisms to provide reflection of light from at least one projector without loss of light scattering in the horizontal direction relative to the viewer's eyes, caused by the light scattering on the edges of the prisms at the tops and / or bottoms, and the scattering and absorption of light inside the prism material.

[0041] Tthe first compensation element having zero optical power in the vertical direction and negative optical power in the horizontal direction may be an optical element selected from: a holographic lens, a diffraction lens, a Fresnel lens, a geometric phase lens, a metalens, and the second compensation element having zero optical power in the vertical direction relative to the eyes of the viewer and positive optical power in the horizontal direction relative to the eyes of the viewer, is an optical element selected from: a holographic lens, a diffraction lens, a Fresnel lens, a geometric phase lens, a metalens.

[0042] According to an embodiment of the present disclosure of the projection multi-view 3D imaging device, the redirecting optical element is configured such that it allows each of at least one projector to be separated from the geometric center of at least one corresponding viewing zone in a vertical plane relative to the viewer's eyes, and each of the at least one projector to be placed above and / or below the viewing zone.

[0043] In addition, the device may include a light source configured to direct light to the screen unit and integrated into each of the at least one projector.

[0044] According to the another embodiment of the present disclosure, the projection multi-view 3D imaging device further comprises a switchable lens line optically coupled to at least one projector to form at least one viewing zone.

[0045] Moreover, each switchable lens of the switchable lens array may be an objective lens configured to transfer an image formed by at least one projector to the screen unit to form at least one viewing zone.

[0046] The projection multi-view 3D imaging device further may comprise a tracking device configured to track the position of at least one of the user's head, eyes, pupils, and connectable to at least one projector and the switchable lens array, respectively.

[0047] The projection multi-view 3D imaging device also may comprise a control unit connected to at least one projector, the tracking device, and the switchable lens line, and configured to control at least one projector, the tracking device, and the switchable lens array.

[0048] In addition, in the projection multi-view 3D imaging device, the retroreflector is configured such that the reflection of the light emitted from at least one projector occurs on the outer surface of the retroreflector, formed by the set of rectangular prisms, and which is the first surface along the direction of the light emitted from at least one projector without loss of light scattering in the horizontal direction relative to the viewer' eyes, and the period (p) of the retroreflector is the distance between the vertices of adjacent prisms and, taking into account the angular resolution of the viewer's eye, must satisfy the following expression:

[0049] (Expression 1)

[0050] where ω is the angular resolution of the eye, L is the distance from the screen unit to the viewer, λ is the maximum wavelength from the range of operating wavelengths of the projector, W is the width of the viewing zone.

[0051] In this case, the operating wavelength range of at least one projector may be from 400 nm to 700 nm.

[0052] Besides, in the projection multi-view 3D imaging device, the optical light-scattering element may be a holographic diffuser and / or a diffuser made of frosted glass with the ability to scatter light in the vertical direction relative to the viewer's eye or is a diffraction grating of an arbitrary type, where a change of the grating period (p1, p2,.. pN), ensuresthe formation of an expanded viewing zone in the vertical direction.

[0053] In addition, the light-scattering optical element may be one of: a holographic lens array, a geometric phase lens array, a metalens array which are capable of light scattering in the vertical direction, or 2D lens array comprising a set of lenses arranged along the X and Y axes, with the ability to light scattering in the vertical direction, and, if necessary, in the horizontal direction.

[0054] In the projection multi-view 3D imaging device, the redirecting optical element may have an off-axis parameter (OA), which determines the displacement of the optical axis of the redirecting optical element from the optical axis of the device, which is given by the following relationship:

[0055] OA~T / 2,

[0056] where OA is the off-axis parameter of the redirecting optical element, T is the distance from the light source, which is at least one projector, to the viewer's eye.

[0057] In this case, the redirecting optical element may be an optical element selected from: a holographic lens, a diffraction lens, a Fresnel lens, a geometric phase lens, a metalens.

[0058] In the projection multi-view 3D imaging device, at least one of the optical elements of the screen unit: the retroreflector, the optical light-scattering element, the optical redirecting element, the first and second compensation elements, is configured with the possibility of applying, optionally, a filter coating to filter out unwanted radiation for the operation of the device; a reflective coating to increase the reflectance of the surfaces of optical elements, an antireflective coating to increase the transmittance of the surfaces of optical elements.

[0059] The projection multi-view 3D imaging device according to one embodiment is configured to generate an autostereoscopic image and comprises at least two stereoscopic projectors.

[0060] The projection multi-view 3D imaging device according to one embodiment is configured to generate a holographic 3D image and comprises one holographic projector.

[0061] The above and other features and advantages of the present present disclosure are explained in the following description illustrated by drawings, in which:

[0062] Fig. 1A is a diagram of total internal reflection (TIR) of light passing through a retroreflective film where glass beads or spherical lenses are used as reflective elements according to the related art.

[0063] Fig. 1B is a diagram of total internal reflection (TIR) of light passing through a retroreflective film, where retroreflective microprisms are used as reflective elements according to the related art.

[0064] Fig. 1C is a schematic representation of the overlapping of viewing zones for the left (L) and right eye (R) when using the retroreflective film according to Figs. 1A, 1B according to the related art.

[0065] Fig. 2A shows a diagram of the formation of a 3D image on a screen in a configuration in which the projector is placed at a distance from the viewer's head and stereo glasses are not used according to the related art.

[0066] Fig. 2B shows a diagram of the formation of a 3D image on a large screen in a configuration in which the projector is placed at a distance from the viewer's head and stereo glasses are not used according to the related art.

[0067] Fig. 2C is a schematic side view (Y-Z plane) of the configuration of a 3D imaging device with a light source and a set of projectors positioned in close proximity to the viewing zones and the viewer's head 1 when forming 3D image according to the related art.

[0068] Fig. 2D is a schematic top view (X-Z plane) of the configuration of a 3D imaging device with overlapped viewing zones when the light source and a set of projectors are located in close proximity to the viewing zones and the viewer's head 1 when forming 3D image according to the related art.

[0069] Fig. 3A is a schematic representation of a cross-section of retroreflective film including an array of one-dimensional triangular prisms with a reflective coating on the side faces of the prism and absorbing coatings on the edges, where the arrows indicate the rays reflected from the side faces of the prism, and the crossed out arrows indicate the rays absorbed by the areas of the prism with the applied absorbing coating.

[0070] Fig. 3B is a schematic side view (Y-Z plane) of the configuration of a 3D imaging device according to the present disclosure, with at least one projector and a light source arranged (in the context of the present disclosure, the light source and the projector are combined in the projector and are hereinafter referred to as the projector) at a distance from the corresponding viewing zone and the viewer's head.

[0071] Fig. 3C is a schematic top view (X-Z plane) of the configuration of a multi-view 3D imaging device according to the present disclosure, with separated viewing zones with at least two projectors positioned at a distance from the corresponding viewing zones and the viewer's head.

[0072] Fig. 4A is a schematic side view (Y-Z plane) of a ray propagation scheme in a multi-view 3D imaging device, where H is the height of the viewing zone.

[0073] Fig. 4B is a top view (X-Z plane) of the ray propagation scheme in a multi-view 3D imaging device, where L is the distance from the screen to the viewer, W is the width of the viewing zone for the right and left eyes, respectively.

[0074] Fig. 5A is an embodiment of realization of a retroreflector without an absorbing coating, made in the form of a one-dimensional set of rectangular prisms elongated vertically.

[0075] Fig. 5B is an embodiment of realization of 2D retroreflector including a two-dimensional set of prisms with or without an absorbing coating.

[0076] Fig. 5C is an embodiment of realization of 1D retroreflector including 1D set of rectangular total internal reflection (TIR) prisms elongated vertically.

[0077] Fig. 5D is an embodiment of realization of 1D glass beads-type retroreflector that uses glass beads or spherical lenses as reflective elements.

[0078] Fig. 6A is a schematic diagram of the arrangement of an optical light-diffusing element with the ability to scatter light in the vertical direction relative to the eye of the viewer 1, where the optical light-diffusing element (VD), located next to the retroreflector (1D RR), is an array of one-dimensional (1D) lenticular lenses.

[0079] Fig. 6B is a schematic diagram of an arrangement of an optical light-diffusing element (VD1) configured to scatter light in a vertical direction relative to the eye of an viewer 1, where the optical light-diffusing element (VD1) located next to a retroreflector (1D RR) is an array two-dimensional (2D) lens elements, including a set of lenses distributed along the X and Y axes, and provides light scattering in two directions.

[0080] Fig. 6C is a schematic diagram of an arrangement of an optical light-diffusing element (VD) configured to scatter light in a vertical direction relative to the eye of an viewer 1, where the optical light-diffusing element VD located next to a retroreflector (1D RR) is one-dimensional (1D ) diffuser, such as a holographic diffuser, and a diffuser made of frosted glass.

[0081] Fig. 6D is a schematic diagram of the arrangement of an optical light-diffusing element (VD), configured to scatter light in a vertical direction relative to the eye of the viewer 1, where the optical light-diffusing element VD, located next to the retroreflector (1D RR), is a diffraction grating of an arbitrary type.

[0082] Fig. 7A is a schematic side view (Y-Z plane) of the ray propagation scheme of a multi-view 3D imaging device according to the related art.

[0083] Fig. 7B is a schematic side view (Y-Z plane) of the ray propagation scheme in a multi-view 3D imaging device, including a retroreflector, an optical light-scattering element and a redirecting optical element according to an embodiment of realization of the present disclosure.

[0084] Fig. 7C is a schematic top view (X-Z plane) of a ray propagation scheme in a multi-view 3D imaging device including a retroreflector, an optical light-scattering element, a redirecting optical element, and two projectors according to an embodiment of realization of the present disclosure.

[0085] Fig. 7D is a schematic side view (Y-Z plane) of the ray propagation scheme in a multi-view 3D imaging device, including a retroreflector and a redirecting optical element according to an embodiment of realization of the present disclosure.

[0086] Fig. 8A shows a light intensity distribution map for the multi-view 3D imaging device without a redirecting optical element.

[0087] Fig. 8B shows a light intensity distribution map for the multi-view 3D imaging device with a redirecting optical element according to the embodiment of realization of the present disclosure.

[0088] Fig. 9A is a top view (X-Z plane) of a ray propagation scheme in the multi-view 3D imaging device including a screen unit including a retroreflector, an optical light-scattering element, and a redirecting optical element according to the embodiment of realization of the present disclosure.

[0089] Fig. 9B is a diagram of rays entering the eye's pupil as they propagate in the multi-view 3D imaging device according to Fig. 9A.

[0090] Fig. 9C is a top view (X-Z plane) of a ray propagation scheme in a multi-view 3D imaging device including a screen including a retroreflector, an optical light-scattering element, a redirecting optical element, and a compensation block according to an embodiment of realization of the present disclosure.

[0091] Fig. 9D is a diagram of rays entering the eye's pupil as they propagate in the multi-view 3D imaging device according to Fig. 9C.

[0092] Fig. 10A is a top view (X-Z plane) of a ray propagation scheme in the multi-view 3D imaging device that provides widescreen 3D imaging on a large screen according to the embodiment of realization of the present disclosure.

[0093] Fig. 10B is a diagram of rays entering the eye's pupil as they propagate in the multi-view 3D imaging device of Fig. 10A.

[0094] Fig. 11A shows a light intensity distribution map for the multi-view of 3D imaging device without a compensation block, obtained on the detector.

[0095] Fig. 11B is a cross-sectional graph of the light intensity distribution map according to Fig. 11A, where the X-axis is the detector coordinate value along the X-axis, and the Y-axis is the intensity value (I).

[0096] Fig. 11C shows a light intensity distribution map for the 3D imaging device with a compensation block, obtained on the detector.

[0097] Fig. 11D is a cross-sectional graph of the light intensity distribution map according to Fig. 11C, where the X-axis is the detector coordinate values along the X-axis, and the Y-axis is the intensity values (I).

[0098] Fig. 12A is a schematic representation of a ray propagation scheme in the 3D imaging device with a curved screen according to the embodiment of realization of the present disclosure.

[0099] Fig. 12B is a schematic representation of a ray propagation scheme in the multi-view 3D imaging device with a switchable lens line according to the embodiment of realization of the present disclosure.

[0100] All documents mentioned in this application form an integral part of the description of the application, i.e. their disclosures are hereby incorporated by reference in their entirety.

[0101] References to elements in the singular are to be understood to include elements in the plural and vice versa, unless otherwise expressly stated or the context clearly indicates.

[0102] In this application, the statement of limits of values is not intended to be limiting, but is intended to apply individually to any and all values falling within the limits, unless otherwise stated in this application, and each individual value within such limits is included in the specification as if it was individually provided in this application.

[0103] The words "about", "approximately" or similar numerical values may be understood by skilled person in the art to indicate the deviation at which satisfactory performance in the intended application is achieved. Likewise, words referring to an approximate value, such as "approximately" or "substantially", when used in relation to physical characteristics, may be understood by the skilled person in the art to express the limits of deviation that will provide satisfactory performance for its intended use, operation, intended purpose or the like.

[0104] The ranges of values and / or numbers provided in this application are by way of example only and are not intended to limit the scope of the described embodiments of realization. When limits of values are given, they are intended to include each value within the limits as if they were presented individually, unless otherwise specifically stated. The use of any or all examples, or an introductory word before an example (for example, such or the like) provided in this application is intended only to better highlight the embodiments and is not intended to limit the scope of the embodiments. Nothing in the specification may be construed as indicating that any unstated element is essential to the practice of the embodiments realization.

[0105] Within the scope of the present disclosure, the following used concepts and terms shall be interpreted as they are defined by the inventors:

[0106] An autostereoscopic projection 3D imaging system may be a system that forms an autostereoscopic image that causes the illusion of volume, that is, a feeling of relief and extension in depth due to the features of binocular vision without the use of additional wearable devices. In this autostereoscopic system a stereo pair of images is projected onto the screen.

[0107] A stereo pair is a pair of flat images of the same object (scene), with differences between the images intended to create a volume effect.

[0108] A holographic projection 3D imaging system may be a system that forms a 3D image by reconstructing the wavefront of the displayed object (scene). In the holographic system, a holographic image is projected onto a screen.

[0109] In the present disclosure, the direction of the horizontal axis (X-axis) may be parallel to the line segment connecting the centers of the pupils of the viewer's eyes; the direction of the vertical axis (Y-axis) may be orthogonal to the direction of the horizontal axis.

[0110] As used herein, reference to a direction in the vertical or horizontal direction means a direction along the vertical or horizontal axis, respectively.

[0111] A horizontal plane, as used herein, means the plane in which the horizontal axis lies.

[0112] The vertical plane, as used herein, means the plane in which the vertical axis lies.

[0113] A diffraction optical element (DOE) may be a diffractive microstructure that performs amplitude-phase modulation of transmitted or reflected radiation(light).

[0114] Holographic optical element (HOE) may be a diffractive optical element manufactured by light wave interference methods.

[0115] It may be noted that both the diffraction optical element (DOE) and the holographic optical element (HOE) are based on essentially the same physical principle, that is, both types of these optical elements can essentially be classified as diffraction optical elements. The difference between them is that diffraction optical elements are called optical elements in which diffraction occurs on the surface relief, and holographic optical elements are called gratings in which diffraction occurs within the material due to a local change in its optical properties.

[0116] Field of view may be the angle between two rays passing through the center of the entrance pupil of the objective lens (lens) to the most distant displayed points of the object from the optical axis in object space.

[0117] Viewing zone (window) may bean area of space in which the eye's pupil can observe the corresponding image of a stereo pair or holographic image.

[0118] Useful viewing zone - in the context of the present disclosure, may be the area selected from the viewing zone in which the user's head is most likely to be located when using the device.

[0119] Dead viewing zone - in the context of the present disclosure, may be the area selected from the viewing zone in which the user's head is least likely to be located when using the device.

[0120] Field of view angle may be the angle between the optical axis and the ray passing through the point of the object in the field of view.

[0121] Recording material may be a substance used to record holograms (the full wavefront of an object / image / scene).

[0122] Within the framework of this description, the terms "recording material", "holographic material" are used as equivalent synonyms.

[0123] Imaging device efficiency, in the context of the present disclosure, may be the ratio of the amount of light (radiation) emitted by the projector to the amount of radiation entering the useful viewing zone.

[0124] Next, the main design solutions of the present disclosure will be described, which can be divided into:

[0125] Key Point 1, Key Point 2 and Key Point 3.

[0126] Key point 1 - providing a highly efficient one-dimensional (1D) retroreflector with low scattering in the range from 0 to 1 degree, while horizontally the rays are reflected in the same direction in which they fall on the retroreflector, and vertically the rays are reflected as from a regular mirror. In this case, the scattering of the retroreflector in the horizontal direction is no more than one degree. According to Key Point 1, the present disclosure also provides an optical light-scattering element (diffuser), configured to scatter light along a vertical axis, which together with a retroreflector constitute a screen unit (hereinafter referred to as a screen). In this case, the optical light-scattering element is configured to form a viewing zone in the vertical plane in order to prevent the eyes from fixing in a certain location (vertically).

[0127] Key Point 2: providing an optical element that has a spatially distributed scattering function and transfers the light from the entire viewing zone to the useful viewing zone, significantly increasing the device efficiency.

[0128] Key point 3: using an optical element with negative field curvature, which operates as a compensation element and provides compensation for distortion (aberration) of viewing zones to form a wide picture (image).

[0129] The above key points provide the following effects of the present disclosure:

[0130] - formation of a 3D image without the use of auxiliary viewing means (stereo glasses),

[0131] - providing narrow, for example, 1 degree, and separated viewing zones for each viewer's eye,

[0132] - providing a high 3D image quality,

[0133] - providing a large size of the formed 3D image. The diagonal angular size of the formed image can be, for example, 40, 60, 120, etc. degrees.

[0134] Next, we will dwell in more detail on Key Point 1, i.e. consider the formation of a retroreflector with low scattering in the horizontal direction and an optical light-scattering element.

[0135] As previously described with reference to Figs. 1A, 1B, and 1C, known are various types of retroreflectors in the related art, such as glass beads-type retroreflective films 100(see Fig. 1A), which use glass beads or spherical lenses 101 as reflective elements and reflective films 110 in which retroreflective microprisms 111 are used as reflective elements (see Fig. 1B). The light in such reflective (retroreflective) films undergoes many reflections and refractions at the interfaces, which causes very high light scattering at the exit from the film. In addition, light scattering is often caused by defects in the material from which the reflector is made, for example, the presence of bubbles or microparticles. In addition, scattering is often caused by manufacturer errors, for example, when manufacturing retroreflectors in the form of a microprism array, the angle at the tops and bottoms of the prisms (see Fig. 1B) should ideally be 90 degrees, which is very difficult to achieve with available optical surface processing technologies, so the peaks and valleys have some slight rounding, which causes light scattering and widening the viewing zone. All of the above problems with related art retroreflectors cause the following problems in the known 3D imaging devices:

[0136] - overlapping viewing zones,

[0137] - poor 3D image quality (occurrence of crosstalks, ghosting,

[0138] - large scattering, which is more than 2 degrees in the horizontal direction of the screen,

[0139] - low contrast and low efficiency of the generated 3D image,

[0140] - viewing zones are located in close proximity to the projector (there is no vertical separation (along the Y axis).

[0141] Fig. 2C is a schematic side view (Y-Z plane) of the configuration of a 3D imaging device with the location of viewing zones (VZ), a light source and at least one projector (2) in close proximity to the viewer's head 1, and a 1D retroreflector (1D RR ) according to the related art. In this configuration, the projectors and the light source (in the present disclosure, the light source and the projector are combined in the projector and are referred to hereinafter as the projector) are located near the viewer's head.

[0142] Fig. 2D is a schematic top view (X-Z plane) of the configuration of a 3D imaging device with viewing zones (VZ), a light source, and at least one projector 2 in close proximity to the viewer's head 1, the device also includes a 1D retroreflector (1D RR) as a screen, as well as an optical light diffusing element (VD) according to the related art.

[0143] Figure 2D shows an overlap of viewing zones (VZ) when projectors 2 are positioned next to the viewer' s head 1, as result a 3D image is formed, and the formed 3D image has low resolution and poor quality.

[0144] The present disclosure is aimed at eliminating the above problems, for this purpose, the authors of the present disclosure proposed the design of a retroreflector which formed from a non-transparent one-dimensional (1D) 90-degree prism array with mirror side faces, using reflection from the outer surface of the side face of at least one prism from the prism array, excluding the light rays from entering inside prism material. In this case, the edges (prisms) at the top and bottoms of each prism from the prism array are covered with an absorbing coating, which prevents light from scattering on them. This ensures the smallest width of one viewing zone and a clear vertical boundary of the viewing zone, which ensures smooth transitions between multi-view 3D image without noticeable breaks and / or steps, while eliminates their overlapping.

[0145] This embodiment of realization of the retroreflector in the projection multi-view 3D imaging device according to the present disclosure makes a significant contribution to the following effects provided by the 3D imaging device:

[0146] - providing multi-view 3D images without the use of additional wearable devices, for example, stereo glasses,

[0147] - no viewing zones overlapping,

[0148] - high signal-to-noise ratio (SNR) (for example, 10, 15, 20 and above), low ghosts / cross-talks,

[0149] - high 3D image quality (high contrast and resolution of the generated 3D image),

[0150] - separated viewing zones with a wide field of view (FOV) in the vertical direction.

[0151] In this case, Fig. 3A schematically shows a cross-section of a retroreflective film 30including one-dimensional triangular prism array 10 in which prisms 15 are arranged, where arrows A indicate light rays reflected from the side faces 15a of the prisms 15, and crossed out arrows B indicate rays absorbed by areas 11 and 12 of the prisms 15 coated with an absorbing coating.

[0152] In Fig. 3B is a schematic side view (Y-Z plane) of a multi-view 3D imaging device 20 according to the present disclosure with the arrangement of viewing zones (VZ), at least one projector 2 including a light source 2a(in this embodiment, two projectors are presented) at a distance from the viewing zone VZ and viewer's head 1. In this case, the multi-view 3D imaging device 20 also contains a screen unit SUincluding a one-dimensional retroreflector (1D RR) 3 and an optical light-scattering element 4 configured to scatter light rays along the vertical axis.

[0153] Fig. 3C schematically shows a top view (X-Z plane) of the multi-view 3D imaging device 20 according to the present disclosure with the location of viewing zones (VZ), the at least one projector 2 including the light source 2a(in this embodiment, two projectors are presented) at a distance from the viewing zone and the viewer's head 1. In this case, the device 20 also contains a screen unit SU including a one-dimensional retroreflector (1D RR) 3 and an optical light-scattering element (VD)4, configured to scatter light rays along the vertical axis.

[0154] Figure 3C demonstrates the separation of viewing zones (VZ) when two projectors 2 are positioned at a distance from the viewing zones VZ and the viewer's head 1, resulting in a 3D image that has high resolution and high quality, as seen in Fig. 3C.

[0155] Next, we will consider in more detail the operation of the retroreflector according to the present disclosure with reference to Fig. 3A, 4A and 4B.

[0156] Fig. 4A is a side view (Y-Z plane) of a ray propagation scheme in the multi-view 3D imaging device 20, where H is the height of the viewing zone.

[0157] Fig. 4B is a top view (X-Z plane) of the ray propagation scheme in the multi-view 3D imaging device 20, where L is the distance from the screen unit SU to the viewer 1, W is the width of the viewing zone for the right and left eyes, respectively. In the X-Z plane, as shown in Fig. 4B, the position in X-axis of the viewer's head (eyes) 1 may coincide with the position in X-axis of the projectors 2. The distances from the screen unit SU to the viewer 1 and from the projector(s)2 to the viewer 1 may be equal.

[0158] In the context of the present disclosure, one or more projectors 2 may be considered as a light source. In this case, for the generation of a holographic 3D image, at least one projector 2 may be provided, and for the generation of an autostereoscopic image, at least two projectors 2 may be provided, each of which forms an image for one viewing zone for the corresponding eye, right or left. The projectors 2 may be placed in the same vertical plane, but in different horizontal planes from the plane in which the viewing zone is located, in particular above or below the viewing zone (VZ), see, Fig.4A. The image formed by each of at least two projectors 2 falls at an angle onto the screen unit SUincluding the retroreflector 3 and the optical light-scattering element 4, configured to scatter light along a vertical axis, which together form the screen unit SU.

[0159] The retroreflector 3 may be non-transparent film including a one-dimensional (with horizontal periodicity) rectangular prism set (array), elongated vertically, with a reflective coating on the faces of the prisms and an absorbing coating on the edges at the tops and bottoms of the prisms. Reflection occurs on the outer surface of the retroreflector 3, formed by a rectangular prism set, and being the first surface along the path of rays from the projector 2 to the screen unit SU including the retroreflector 3 and the optical light-scattering element 4, without losses due to light scattering on the edges of the prisms at the tops and bottoms, and without scattering and absorption of the light inside the prism material. Thus, the retroreflection occurs in the horizontal direction with high efficiency and low scattering into the viewing zones (VZ). In addition, taking into account the diffraction and angular resolution of the eye, the pitch or (period) (p) of the retroreflector, see Fig. 3A must correspond to the following expression:

[0160] (Expression 1)

[0161] where ω is the angular resolution of the eye, L is the distance from the screen unit to the viewer, λ is the maximum wavelength from the range of operating wavelengths of the projector, W is the width of the viewing zone.

[0162] It may be noted that the wavelength range at which the projector 2 operates is the visible range of electromagnetic radiation (400nm -700nm).

[0163] It may be noted that the number of rectangular prisms in a set or array of prisms is determined by the size of the screen, which is selected based on the area of use: home or public cinema, divided by the period (p) of the retroreflector 3.

[0164] It may be noted that the light ray directed from the projector 2 falls on the one-dimensional retroreflector 3 at a certain angle, and is reflected horizontally in the same direction in which it falls on the reflector, and vertically the light ray is reflected as from an ordinary mirror. In this case, a viewing zone is not formed in the vertical direction, and with a fixed position of the viewer's eye, only a small part of the image will be visible. To form the viewing zone in the vertical direction in which the viewer's eye will see the full image (when located inside the viewing zone), the optical light-scattering element 4 may be included in the screen design by the authors of the present disclosure, and it scatters each light ray from each point of the screen in the vertical direction, thus forming a viewing zone. The effect of realization of the screen of the 3D imaging device according to the present disclosure is as follows:

[0165] providing low scattering along the horizontal axis of the screen; providing elongated viewing zone along the vertical axis; not overlapping the viewing zones for the viewer's left and right eyes. Thin (un-scattered) and large vertical viewing zone, high signal-to-noise ratio, low crosstalks.

[0166] Next, we will consider embodiments of retroreflectors that can be used in the 3D imaging device according to the present disclosure.

[0167] According to the examplary embodiment of realization, the retroreflector 3 is made with a reflective coating on the faces of the prisms, but without the absorbing coating, see Fig. 5A, and is a one-dimensional set (array) of rectangular prisms elongated vertically. In this case, the light ray directed from the projector falls on the retroreflector according to the present disclosure at a certain angle, and horizontally, essentially without loss, is reflected in the same direction in which it falls on the retroreflector 3, and vertically the light ray is reflected as from an ordinary mirror. Thus, the light ray directed from the projector is almost completely reflected from the outer surface of the prism without going into the prism material, which provides a significant reduction in the degree of scattering in the horizontal direction of the retroreflector 3 according to the present disclosure, compared to the solutions known from the related art.

[0168] However, the production of such optical elements requires high manufacturing precision, which is not always possible to achieve in real production. To eliminate even minimal defects at the tops and bottoms of the prisms that arise as a result of manufacturing errors, the authors of the present disclosure further propose to apply an absorbing coating on the edges at the tops and / or bottoms of the prisms; in this case, scattering from the tops and bottoms may be practically completely eliminated.

[0169] As a retroreflector, according to another embodiment of realization according to Fig. 5B, a 2D retroreflector including a two-dimensional set of prisms with or without an absorbing coating can be used.

[0170] The 2D retroreflector is widely known in the relevant field of technology:https: / ru.wikipedia.org / wiki / %D0%A3%D0%B3%D0%BE%D0%BB%D0%BA%D0%BE%D0%B2%D1%8B%D0%B9_%D0%BE%D1%82%D1%80%D0%B0%D0%B6%D0%B0%D1%82%D0%B5%D0%BB%D1%8C

[0171] This type of retroreflector is characterized by retroreflection along two axes (unlike 1D reflector) and the use of this type of retroreflector in a display will result in a fixed and small viewing zone with high brightness. Due to retroreflection along two axes, the position of the center of the formed viewing zone will coincide with the center of the projector lens. In the embodiments of a 2D retroreflector known from the prior art, it is impossible to separate the center of the formed viewing zone from the center of the projector lens. In addition, for increasing / expanding the viewing zone of the display with a 2D retroreflector, a different type of diffuser is required compared to the present disclosure.

[0172] According to another embodiment of realization with reference to Fig. 5C, the retroreflector is a one-dimensional set of rectangular total internal reflection (TIR) prisms elongated vertically. In this case, the light ray from the projector penetrates at a certain angle into the inside of the prism and undergoes refraction and reflection there. In this case, horizontally the rays are reflected in the same direction in which they fall on the retroreflector, and vertically the rays are reflected as from an ordinary mirror and then exit the prism. This type of retroreflector is characterized by quite significant scattering and dispersion resulting from the light propagation through the prism material, in addition to scattering from defects in the prism's manufacturing. At the same time, the production of this TIR retroreflector is high-tech.

[0173] As a retroreflector, according to another embodiment of realization (Fig. 5D), a glass beads-type retroreflector may be used, which uses glass beads or spherical lenses as reflective elements. The light ray from the projector penetrates at a certain angle into the ball, undergoes reflection and refraction there, and leaves the ball at the same angle (2D-retroreflection, along two axes like a 2D retroreflector, consisting of a two-dimensional set of prisms), while the ball surface is partially covered with reflective / mirror coating from which the light ray is reflected. This type of retroreflector is easy to manufacture and provides a fixed, small viewing zone with high brightness. However, with this design of the retroreflector, a large scattering of the rays occurs, which causes an overlap of viewing zones for the left and right eyes of the viewer. Due to retroreflection along two axes, the position of the center of the formed viewing zone will coincide with the center of the projector lens and, with embodiments of a glass beads-type retroreflector known from the retated art: https: / ru.wikipedia.org / wiki / %D0%9A%D0%B0%D1%82%D0%B0%D1%84%D0%BE%D1%82,

[0174] it is impossible to separate the center of the formed viewing zone from the center of the projector lens. In addition, for increasing / expanding the viewing zone of a display with the glass beads-type retroreflector, a different type of diffuser is required, compared to the present disclosure.

[0175] Thus, the embodiments of realization of the retroreflectors described with reference to Figs. 5B-5D have a number of disadvantages that significantly deteriorate the quality of the generated 3D image, while the design of the screen with a one-dimensional retroreflector with a reflective coating on the outer faces of the prisms and an absorbing coating on the edges at the tops and the bottoms of the prisms, according to the present disclosure, eliminates all of the above disadvantages of known retroreflectors.

[0176] Next, with reference to figures 6A-6D, possible embodiments of realization of the optical light-scattering elements used in the present disclosure will be shown.

[0177] Known are various types of optical elements used as light-scattering elements (diffusers), the diffusers typically provide the formation of light beams with a specific scattering pattern. The objective of the present disclosure is to provide, using the optical light-scattering element, the scattering of light rays reflected from a retroreflector in the vertical direction, thus ensuring the creation of the required scattering pattern in accordance with the position of the viewer's eye and the required size of the viewing zone.

[0178] Fig. 6A is a schematic diagram of the arrangement of an optical light-scattering element in relation to the eye of an viewer 1, where the optical light-scattering (diffusing) element (VD), configured to scatter light rays in the vertical direction, and located next to the retroreflector (1D RR), is an one-dimensional (1D) lenticular lens array. In this case, a holographic lenses array, a diffraction lens array, a lens array, a GPL(lenses with a geometric phase)array, and a metalens array can be used as optical light-scattering elements.

[0179] The use of one-dimensional (1D) optical elements as an optical light-scattering element in a 3D imaging device provides increased flexibility in system design due to the variability (the ability to use a variety of optical elements) in the choice of optical elements and ensures the formation of an extended viewing zone in the vertical plane. FIG. 6B is a schematic diagram of an arrangement of an optical light-scattering (diffusing) element (VD) configured to scatter light in a vertical direction relative to the viewer's eye 1, where the optical light-scattering element (diffuser) (VD) located adjacent to the retroreflector (1D RR) is an array of two-dimensional (2D) lens elements including a set of lenses distributed along the X and Y axes, providing light scattering in two directions. In this case, a holographic lenses array, a diffraction lens array, a lens array, a GPL(lenses with a geometric phase)array, and a metalens array can be used as optical light-scattering elements.

[0180] The use of two-dimensional (2D) optical elements as an optical light-scattering element in a 3D imaging device provides increased flexibility in system design and provides an extended viewing zone in the horizontal (if necessary) and vertical planes.

[0181] FIG. 6C is a schematic diagram of an arrangement of an optical light-scattering element in relation to the viewer's eye 1, wherein the optical light-scattering element (VD) located next to a retroreflector (1D RR) is a one-dimensional (1D) diffuser. In this case, a holographic diffuser and a diffuser made of frosted glass can be used as optical light-scattering elements. Peculiarities of the above diffusers are widely known from the prior art and are disclosed in detail in the following publication:https: / www.rp-photonics.com / diffusers.html

[0182] The use of an optical light-scattering element, i.e. a one-dimensional (1D) diffuser provides the formation of an extended viewing zone in the vertical direction.

[0183] Fig. 6D is a schematic diagram of the arrangement of the optical light-scattering element in relation to the viewer's eye 1, where the optical light-scattering element (VD), located next to the retroreflector (1D RR), is a diffraction grating of any kind with variable period (p1, p2, ...,pN)allows to form viewing zone with required size.

[0184] The use of a diffraction grating as an optical light- scattering element provides an extended viewing zone in the vertical direction and provides increased flexibility in system design.

[0185] Peculiarities of various diffuser designs in various optical systems, as well as methods for their selection depending on the required parameters, are disclosed in the following publication:https: / www.edmundoptics.com / knowledge-center / application-notes / optics / diffuser-selection-guide /

[0186] Next, we will dwell in more detail on Key Point 2, which is based on providing an optical element that has a spatially distributed scattering function, and ensures the transfer of light from the entire viewing zone to the useful viewing zone, significantly increasing the efficiency of the device.

[0187] Peculiarities of the implementation of Key Point 2 will be further described with reference to Figures 7A, 7B, 7C, 7D.

[0188] FIG. 7A is a schematic side view (Y-Z plane) of the ray propagation scheme of a known 3D imaging device. The device includes: a retroreflector 121, an optical light-scattering element 122 configured to scatter light rays in the vertical direction, as well as at least one projector 2, which is fixed at a distance from the viewer's head 1. However, this device does not use any additional wearable devices, such as glasses. As can be seen in scheme of Fig. 7A, the light rays emitted from the projector 2 fall on the retroreflector 121 and are reflected vertically from the retroreflector 121 as from an ordinary mirror, then all the rays reflected from the retroreflector 121 fall on the optical light-scattering element 122, which ensures the scattering of the light rays in the vertical direction, which forms a long (highly scattering) viewing zone, as a result, only a small part of the rays enters the viewer's pupil 1. In this case, in the horizontal direction, these rays are reflected from the retroreflector 121 in the same direction in which they fall on it and, when passing through the optical light-scattering element 122, do not change their direction (are not scattered in the horizontal plane).

[0189] Since Fig. 7A is a view in the Y-Z plane, light rays reflected from the retroreflector in the horizontal direction are not visible in the vertical plane. At the same time, because light is scattered in vertical direction over a large (long) viewing zone by an optical light-scattering element, its density (correlates with the brightness of the image) in the useful viewing zone is low. In this case the dead viewing zones are formed that is an area in which the pupil of the eye can observe the corresponding image of a stereo pair or a holographic image, but the probability of the pupil of the viewer's eye falling into this area is close to zero. Thus, as clearly seen in Fig. 7A, the image formed in accordance with this scheme has low brightness and low projection efficiency due to light loss in the dead viewing zone.

[0190] Fig. 7B is a schematic side view (Y-Z plane) of the light ray propagation scheme in a multi-view 3D imaging device 20 according to the present disclosure, which includes a retroreflector 3, an optical light-scattering element 4 configured to scatter light in the vertical direction, and at least one projector 2 located at a distance from the head of the user(viewer) 1, and a redirecting optical element 5, essentially performing the function of a light condenser with an offset optical axis relative to the optical axis of the multi-view 3D imaging device. The redirecting optical element 5 is configured such that it has zero optical power in the horizontal direction and a predetermined optical power in the vertical direction. For example, in the case of a personal gaming monitor, when the distance from the user's head to the screen is small, for example, 0.5 m, the optical power is equal to 2 diopters. In the case of a home cinema, when the distance from the user's head to the screen is more significant, for example, 2 meters, the optical power of the redirecting element 5 is equal to 0.5 diopters. Similarly, for a public cinema where the distance is large, for example 10 meters, the optical power is 0.1 diopter. The inclusion of a redirecting optical element with zero optical power in the horizontal direction and a predetermined optical power in the vertical direction in the optical scheme of the device ensures the redirection of light rays entering the dead viewing zone when reflected from the retroreflector 3 and passing through the optical light-scattering element 4 into the useful viewing zone. It may be noted that in the context of this description, an indication of the horizontal direction implies a direction along the horizontal axis (X-axis), which is parallel to the segment connecting the centers of the pupils of the viewer's eyes; and indicating a vertical direction implies a vertical axis direction (Y axis) that is orthogonal to the horizontal axis direction. In this case, L is the distance from the screen, including a retroreflector 3 and an optical light-scattering element 4, to the viewer, and T is the distance from the light source, which is at least one projector 2, to the viewer's eye 1.

[0191] Thus, as is clearly seen in Fig. 7B, with such a screen design, greater flexibility is achieved in configuring the a multi-view 3D imaging device with different locations of projectors, the device is compact and has high efficiency in the useful viewing zone that allows to generate a clear and bright 3D image without using additional means for viewing, such as stereo glasses, while ensuring a high signal-to-noise ratio.

[0192] Fig. 7C schematically shows a top view (X-Z plane) of the ray propagation scheme in the multi-view 3D imaging device, according to the present disclosure, which comprises a retroreflector 3, an optical light-scattering element 4, configured to scatter light in the vertical direction, as well as at least one projector 2 (in this scheme there are 2 projectors), located at a distance from the viewer's head 1 (not visible in the X-Z plane), and a redirecting optical element 5, essentially performing the function of a light condenser with an offset optical axis relative to the optical axis of the multi-view 3D imaging device, where L is the distance from the screen to the viewer, which coincides with the projectors 2 in the top view.

[0193] Fig. 7D schematically shows a side view (Y-Z plane) of the ray propagation scheme in the multi-view 3D imaging device according to the present disclosure, in which, for clarity of the function of the redirecting optical element 5, the optical light-scattering element 4 is omitted from the scheme, where L is the distance from the screen, including a retroreflector 3 and an optical light-scattering element 4 (not shown), to the viewer 1, T is the distance from the light source, which is at least one projector 2, to the viewer's eye 1. It may be noted that in the multi-view 3D imaging device according to the present disclosure with reference to Fig. 7D:

[0194] 1) one or more projectors 2 also act as a light source and, according to the present disclosure, are placed in the same vertical plane in which the useful viewing zone (VZ) is located, but in different horizontal planes, in particular above or below the useful viewing zone (VZ) at a distance T. Each of the at least one projector 2 produces an image for one viewing zone for the corresponding eye, right or left;

[0195] 2) the light emitted by each of at least one projector 2 falls at an angle onto a screen including a retroreflector 3 and an optical light-scattering element 4, configured to scatter light along the vertical axis, as well as a redirecting optical element 5, and the above mentioned elements together form the screen;

[0196] 3) retroreflector 3 is an non-transparent film including a one-dimensional (with horizontal periodicity) set (array) of rectangular prisms, elongated vertically with a reflective coating on the faces of the prisms and an absorbing coating on the edges at the tops and bottoms of the prisms. Reflection occurs on the outer surface of the retroreflector 3, formed by a set of rectangular prisms, which is the first surface along the path of light rays from the projector 2 to the screen without losses due to light scattering on the edges at the tops and bottoms of the prisms, without scattering and absorption of light inside the prism material. Thus, retroreflection occurs in the horizontal direction with high efficiency and low scattering into the viewing zones (VZ). In addition, taking into account the diffraction and angular resolution of the eye, the pitch or (period) (p) of the retroreflector, see Fig. 3A must satisfy to the following expression:

[0197] (Expression 1)

[0198] where ω is the angular resolution of the eye, L is the distance from the screen unit to the viewer, λ is the maximum wavelength from the range of operating wavelengths of the projector, W is the width of the viewing zone.

[0199] It may be noted that the light ray directed from the projector 2 falls on the one-dimensional retroreflector 3 at a certain angle and is reflected at the same angle. For forming the viewing zone in the vertical direction in which the viewer's eye will see the full image (when located inside the viewing zone), the authors of the present disclosure included an optical light-scattering element 4 in the screen design, which scatters each light ray from each point of the screen in the vertical direction, thus forming a viewing zone;

[0200] 4) the redirecting optical element 5 performs the function of a light condenser and is an optical element with an offset optical axis relative to the optical axis of the 3D imaging device. The redirecting optical element 5 is configured in such a way that it has zero optical power in the horizontal direction and a predetermined optical power (OP) in the vertical direction, which is inversely proportional to the distance to the viewing zone (VZ), i.e. OP~(1 / L) (2),

[0201] where OP is the optical power, L is the distance from the screen unit to the viewer 1 (m). The off-axis parameter (OA) of the redirecting element 5 may be twice smaller than distance from the light source , i.e. projector 2 to the geometric center of the useful viewing zone (VZ). It may be noted that the size of the useful viewing zone and its geometric center relative to the optical axis of the multi-view 3D imaging device depends (determine) on the area of use of the 3D imaging device, for example, a home / public cinema.

[0202] In addition, the off-axis parameter of the redirecting element 5 is set as follows:

[0203] OA~T / 2 (3),

[0204] where OA is the off-axis parameter of the redirecting element 5, T is the distance from the light source, which is at least one projector 2, to the viewer's eye 1.

[0205] It may be noted that OA (off-axis parameter of the redirecting element) is the distance between the optical axis of the redirecting element 5 (see AXIS in Fig. 7D) and the optical axis of the multi-view 3D imaging device. The expression was obtained by the authors of the present disclosure from considerations of geometric optics.

[0206] Thus, the inclusion of a redirecting optical element 5 in the configuration of the multi-view 3D imaging device makes it possible to concentrate the light reflected from the retroreflector in the useful viewing zone, which increases the brightness of the generated image for the viewer.

[0207] Figures 8A, 8B show a light intensity distribution map for a multi-view 3D imaging device with a redirecting optical element (Fig.8B) and without a redirecting optical element (Fig. 8A), obtained on a detector in the form of a square, 300Х300 mm in size ( -150:+150), located at a distance of 500 mm from the screen (including a retroreflector 3, a diffuser 4, a redirecting optical element 5), while the angle between the optical axis of the projector and the optical axis of the screen is 40 degrees. In this case, the values along the X, Y axes in Figs. 8A, 8B represent the coordinates of the detector, and the light intensity scales (I) near to the detector show the intensity of any point and its corresponding position on the detector, i.e. the intensity distribution.

[0208] At the same time, the efficiency of the device, i.e. the amount of light falling from the projector into the formed viewing zone in case of the presence of a redirecting optical element is 51.3%, and without the redirecting optical element is only 22.8%, which proves the advantage of the multi-view 3D imaging device.

[0209] Next, the embodiments of the realization of the redirecting optical elements will be presented.

[0210] Optical elements that collect rays reflected from the retroreflector 3 and direct them to the useful viewing zone (VZ) can be used as redirecting optical elements.

[0211] In one of the embodiment of realization 1), the redirecting elements can be: holographic lenses, diffraction lenses, Fresnel lenses, geometric phase lenses, metalenses, diffraction gratings.

[0212] The inclusion of redirecting optical elements in accordance with the above-mentioned embodiment 1) in the multi-view 3D imaging device allows to increase flexibility in the multi-view 3D imaging device design due to the variability (the possibility of using a variety of optical elements) in the choice of optical elements. In one embodiment of the realization 2) the redirecting optical elements may be active redirecting elements or deflectors. Examples of active redirecting elements are disclosed in the publication: https: / en.wikipedia.org / wiki / Acousto-optic_modulator

[0213] The inclusion of active redirecting elements of the above-mentioned embodiment of realization 2) in the multi-view 3D imaging device allows to actively control the redirection of light into the viewing zone, but at the same time, the production of such optical elements is difficult due to large-scale active optical elements, which requires more advanced technologies to achieve high accuracy when manufacturing.

[0214] In yet another embodiment of realization 3) the redirecting optical elements may be a combination of optical elements with different properties. The inventors are considering the possibility to conjunct functions of different optical elements into one optical element, for example, combining a diffuser, configured to diffuse light in the vertical direction, and a redirecting optical element into a redirecting element with the additional function of light diffusion in the vertical direction.

[0215] The inclusion of redirecting optical elements with combined functions in the multi-view 3D imaging device, for example, with a diffuser function according to the embodiment of realization 3) reduces the number of elements making up the device and significantly reduces the thickness of the device, but at the same time, optical elements with combined functions are more complex in themselves, which requires more advanced technologies.

[0216] In another embodiment of realization 4) the function of the redirecting optical element is performed by a screen (screen unit), which has curvature in the vertical direction (not shown), and can fully or partially perform the function of redirection of light when it reflected from the retroreflector 3 and passing through the optical light-scattering element 4, into the viewing zone VZ, in which the viewer's head is located when using the device. This function of redirection of light is at least partially performed due to the curvature of the components that make up the screen unit: a retroreflector, an optical light-scattering element configured to scatter light reflected from the retroreflector in the vertical direction relative to the viewer's eye, in a vertical plane. In this case, when the redirection function is partially performed due to the curvature of the constituent optical components of the screen unit, the redirecting element is still present in the device design, but has a different (smaller in magnitude) optical power in the corresponding plane, i.e. the plane in which the redirecting optical element redirects light according to the examplary embodiment of the realization of the present disclosure, and different off-axis parameter value, compared with the specified parameters of the redirecting optical element in the embodiment of the realization with a flat screen unit according to the examplary embodiment of realization of the present disclosure, see Fig. 7B.

[0217] The inclusion of redirecting optical elements of complex shape in the multi-view 3D imaging device according to embodiment of realization 4) is characterized by a new ergonomic design, which allows to turn the viewer's head less when viewing the generated image and the effect of complete immersion (immersion effect), which is usually used in planetariums (images are viewed on a round roof), and, at the same time, is complicated by the presence of difficult-to-manufacture optical elements in the device, which requires more advances production technologies.

[0218] It may be noted that solutions with a curved screen of display are known in the prior art and are intended to improve display ergonomics and user immersion, see, for example, the publication: https: / insights.samsung.com / 2022 / 11 / 16 / how-a-curved-monitor-brings-ergonomic-benefits-and-productivity-2 /

[0219] In yet another embodiment of realization 5), the redirecting optical elements have additional optical coatings for various purposes, for example: antireflective coatings to increase the light transmittance of the surfaces of the optical elements that transmit light, reflective coatings to increase the reflectance of surfaces that reflect light and filter coatings to filter unwanted light for device operation, as well as beam splitter coatings. The specified coatings are used depending on the required tasks.

[0220] The inclusion of redirecting optical elements with the coatings in the multi-view 3D imaging device according to embodiment of realization 5) allows increasing flexibility during designing the multi-view 3D imaging device, due to the fact that a number of optical coatings have specific properties and allow working with light in very diverse way. Thanks to this property of optical coatings, skilled person can select the required specified parameters of the designed multi-view 3D imaging device from a wide range of options, i.e. there is greater flexibility in choosing the required parameters. At the same time, the described redirecting elements with coatings have a great complexity in themselves, which requires more advanced production technologies to eliminate the occurrence of parasitic optical effects from additional optical elements.

[0221] The key point 3 of the present disclosure is to provide an optical element with negative field curvature, which serves as a compensation element that compensates the distortion of viewing zones to form a wide picture (image).

[0222] Figure 9A shows a top view (X-Z plane) of the ray propagation scheme in a multi-view 3D imaging device, according to the present disclosure, which uses a screen unit that consists of a retroreflector 3, an optical light-scattering element 4 configured to scatter rays in the vertical direction, and redirecting optical element 5, while the device in accordance with this embodiment comprises two projectors 2 (see Fig. 9A), while the pupils of viewer's eyes are located in the same vertical plane, but in different horizontal planes with the projectors 2, L is the distance from the light source to the screen unit, in this case, the function of the light source is performed by projectors, and the screen including a retroreflector 3, an optical light-scattering element 4 and a redirecting optical element 5.

[0223] At the same time, if it is necessary to form a wide-format 3D image on a large screen, for example, in cinemas, museums, educational institutions, there is a distortion (aberration) of the viewing zone as a result of which not whole of the projected image enters the eye's pupil, and part of the generated 3D image along its edges in the horizontal direction is lost. Due to the described aberration, the viewing zone becomes blurred / curved in the horizontal direction, and part of the field of view does not fall into the viewer's pupil, and crosstalks between the viewing zones may occur, and thus, the user (viewer) will see only part of the 3D image which may contain additional ghost images.

[0224] Fig. 9B schematically shows a diagram of rays entering the eye's pupil, where it is clearly seen that the central ray, indicated by dots in Fig. 9A and incident on the center of the screen and reflected from it in the same direction, enters the viewer's pupil, see Fig. 9B, where the central, dotted, straight line passes through the eye's pupil, and the rays propagating along the edges (rays indicated by solid and dashed lines), see Fig. 9A, do not enter the eye's pupil, see curved lines (solid and dashed lines) in Fig. 9B and the edges of the image in the horizontal direction do not fall into the eye's pupil, which is further illustrated by the figure of a man, the image of which is cut off at the edges.

[0225] The inventors have tried to eliminate these disadvantages of the embodiments of realization according to Fig. 9A and Fig. 9B and included in the device a compensation block with negative field curvature, which compensates the distortion of viewing zone to form a wide picture (image), see Fig. 9C, which shows a top view (X-Z plane) of the ray propagation scheme in the multi-view 3D imaging device, according to the present disclosure, where a screen unit is used, which consists of a retroreflector 3, an optical light-scattering element 4, configured to scatter light in the vertical direction, a redirecting optical element 5, and a compensation block including the first (7) and second (6) compensation optical elements, and further the device comprises two projectors 2 (see Fig. 9C).

[0226] It may be noted that the pupils of the viewer's eye are located in the same vertical plane, but in different horizontal planes with the projectors 2, L is the distance from the light source to the screen unit, in this case the role of the light source is played by projectors, and the screen unit consists of a retroreflector 3, an optical light-scattering element 4, redirecting optical element 5 and compensation block (compensation elements 6,7).

[0227] Moreover, if it is necessary to form a wide-format 3D image on a large screen, for example, in cinemas, museums, educational institutions, due to the inclusion of compensation elements in the device, the entire projected image enters the eye's pupil, and thus, in Fig. 9D, where it is schematically shown diagram of the rays entering the eye's pupil, it is clearly seen that the central and side rays, indicated by dots, solid or dasched lines in Fig. 9C, enter the pupil of the viewer's eye, see Fig. 9D, which is further illustrated by the figure of a person, the image of which is presented clearly and is completely observable.

[0228] The inclusion of optical compensation elements in the device provides the following effects: no image loss, no crosstalks, no need to use additional viewing means such as stereo glasses, obtaining a clear and bright 3D image.

[0229] With reference to Fig. 10A, the operation of a multi-view 3D imaging device will be described, which provides a wide-format 3D image on a large screen, for example, in cinemas, museums, educational institutions if it has a compensation block.

[0230] 1) one or more projectors 2 according to the present disclosure are placed in the same vertical plane in which the useful viewing zone (VZ) is located, but in a different horizontal plane, in particular above or below the useful viewing zone (VZ). Each of the at least one projector 2 produces an image for one viewing zone for the corresponding eye, right or left.

[0231] 2) the light emitted by each of at least one projector 2 falls at an angle onto a screen unit including a retroreflector 3 and an optical light-scattering element 4, configured to direct the radiation along the vertical axis, a redirecting optical element 5, a compensation block (6, 7), the above elements together form the screen unit.

[0232] 3) retroreflector 3 may be an opaque film comprising a one-dimensional (with horizontal periodicity) set (array) of rectangular prisms, elongated vertically with a reflective coating on the faces of the prisms and an absorbing coating on the edges at the tops and bottoms of the prisms. Reflection occurs on the outer surface of the retroreflector 3, formed by a set of rectangular prisms, which is the first surface along the path of rays from the projector 2 to the screen without losses due to light scattering on the edges of the prisms at the tops and bottoms, without scattering and absorption of light inside the prism material. Thus, in the horizontal direction, retroreflection occurs with high efficiency and low scattering into the viewing zones (VZ). In addition, taking into account diffraction and angular resolution of the eye, the pitch or (period)(p) of the retroreflector, see Fig. 3A must satisfy to the following expression:

[0233] (Expression 1)

[0234] where ω is the angular resolution of the eye, L is the distance from the screen unit to the viewer, λ is the maximum wavelength from the range of operating wavelengths of the projector, W is the width of the viewing zone.

[0235] It may be noted that the light ray directed from the projector 2 falls on the one-dimensional retroreflector 3 at a certain angle and is reflected at the same angle. To form the viewing zone in the vertical direction in which the viewer's eye will see the full image (when located inside the viewing zone), an optical light-scattering element 4 is included in the screen design by the authors of the present disclosure, it scatters each light ray from each point of the screen in the vertical direction, thus forming a viewing zone;

[0236] 4) Compensation block may comprise the first compensation element 7 and the second compensation element 6. The first compensation element 7 may have zero optical power in the vertical direction and negative optical power in the horizontal direction, thus, the first compensation element 7 may have a negative field curvature, which is used for compensating the curvature of the viewing zone by the inventors, and the entire wide field of view will be directed towards the viewer's eye.

[0237] It may be noted that field curvature is an optical aberration of optical systems, see, for example: https: / en.wikipedia.org / wiki / Petzval_field_curvature, which they usually try to eliminate in optical systems. By contrast, the shape of the first compensation element 7 with a negative field curvature is used for compensating the curvature of the field of view in accordance with the present disclosure.

[0238] Due to the negative optical power in the horizontal direction of the first compensation element 7, the rays related to the edges of the image have large angles of incidence on the retroreflector 3, so some of them cannot be reflected from the retroreflector in the same direction, so some of the light and image may be lost. To convert these larger angles into smaller ones that will be reflected correctly, i.e. horizontally in the same direction in which they fell on the reflector, and vertically as from a conventional mirror, and with high efficiency, the second compensation element 6 is used, which has zero optical power in the vertical direction and positive optical power in the horizontal direction.

[0239] Thus, light from the projector 2 in a certain range of angles falls on the first compensation element 7, the light rays passing in the center of the field of view pass without changes through the redirecting optical element 5, the optical light-scattering element 4 and fall on the retroreflector 3, then are reflected from it in the same direction horizontally, and the light rays again pass through the optical light-scattering element 4, where they are scattered in the vertical direction, and the redirecting optical element 5, where they are redirected from the dead viewing zones to the useful one and enter the viewer's pupil, see the rays indicated by dots in Fig. 10A. In this case, the rays (rays indicated by solid or dasched lines) related to the edges of the image pass through the first compensation element 7, which has a negative optical power in the horizontal direction, and exit the first compensation element 7 at large angles, then the rays pass through the redirecting element 5 and optical light-scattering element 4, practically without changing the direction of light propagation, and fall on the second compensation element 6, which has zero optical power in the vertical direction and positive optical power horizontally and is designed in such a way that rays at large angles are converted into smaller angles and then fall on the retroreflector 3, and they are reflected from it in the same direction horizontally and as from a conventional mirror in the vertical direction, pass through the second compensation element 6, and upon exiting from the second compensation element 6 the rays at small angles are converted into large angles and then fall on the optical light-scattering element 4, which scatters light in the vertical direction, then rays fall on the redirecting optical element 5, which ensures the redirection of rays falling into the dead viewing zones into the useful viewing zone, and then pass through the first compensation element 7, while the rays passing in the center of the first compensation element 7, pass through unchanged, and edge rays at large angles are converted to smaller angles and enter the useful viewing zone without distortion.

[0240] Fig. 10B shows a diagram of rays entering the eye's pupil, where it is clearly seen that the central and edge rays, indicated by dots, solid or dasched lines in Fig. 10A, enter the viewer's pupil.

[0241] Fig. 11A shows a light intensity distribution map for a 3D imaging device without a compensation block, obtained on a detector in the form of a square, 300Х300 mm in size (- 150:+150), located at a distance of 500 mm from the screen unit (comprising a retroreflector 3, optical light-scattering element 4, redirecting optical element 5), while the angle between the optical axis of the projector and the optical axis of the screen unit is 40 degrees. In this case, the values along the X, Y axes in Fig. 11A represent the detector coordinates, and the light intensity scale (I) next to the detector shows the intensity of any point and its position on the detector, i.e. the intensity distribution.

[0242] Fig. 11B is a cross-sectional graph of the light intensity distribution map according to Fig. 11A, where the X-axis is the detector coordinate values along the X-axis, and the Y-axis is the intensity values (I).

[0243] In this case, the width of the viewing zone provided by the 3D imaging device without a compensation block is 15 mm, i.e. not the entire image falls into the pupil of the viewer's eye (the pupil of the viewer's eye is 2-5 mm depending on the lighting).

[0244] Fig. 11C shows a light intensity distribution map for a multi-view 3D imaging device with a compensation block obtained on a detector in the form of a square, 300Х300 mm in size (-150: +150), located at a distance of 500 mm from the screen unit (comprising a retroreflector 3, optical light-scattering element 4, redirecting optical element 5), and the angle between the optical axis of the projector and the optical axis of the screen unit is 40 degrees. In this case, the values along the X, Y axes in Fig. 11C represent the detector coordinates, and the light intensity scale (I) next to the detector shows the intensity of any point and its position on the detector, i.e. the intensity distribution.

[0245] Fig. 11D is a cross-sectional graph of the light intensity distribution map according to Fig. 11C, where the X-axis is the detector coordinate values along the X-axis, and the Y-axis is the intensity values (I).

[0246] In this case, the width of the viewing zone provided by the 3D imaging device with a compensation block is 4 mm, i.e. the entire image enters the pupil of the viewer's eye.

[0247] Thus, the presence of a compensation block in the device helps to eliminate distortions and aberrations in the viewing zone for horizontal fields, i.e. in the horizontal direction, see Figs. 10A, 10B, where it is clearly illustrated that the viewing zones are deformed along the horizontal direction, and as can be clearly seen in Fig. 10B the entire image falls into the viewer's eye.

[0248] Further, embodiments of realization of compensation elements will be presented.

[0249] Various optical elements 1) can be used as compensation elements, such as cylindrical lenses, Fresnel lenses, diffraction lenses, holographic lenses, geometric phase lenses, liquid crystal lenses, metalenses.

[0250] The inclusion of compensation elements of the above embodiment 1) in the multi-view 3D imaging device simplifies the manufacture of the device, since it is possible to use commercially produced optical elements; these optical elements are suitable for any device configurations.

[0251] In one of embodiments, namely embodiment 2), the compensation elements may be active liquid crystal (LC) lenses. Examples of active LC lenses are disclosed in the publication: https: / www.researchgate.net / publication / 258813376_Electrically_Tunable_Liquid_Crystal_Lenses_and_Applications

[0252] The inclusion of active LC lenses of the above embodiment 2) in the multi-view 3D imaging device allows actively correcting the distortion of the viewing zone, but at the same time, the production of such optical elements is complicated by the large dimensions of these elements, which requires more advanced production technologies to achieve high precision in manufacturing.

[0253] In yet another embodiment 3), the compensation elements can be a combination of the properties of various optical elements in one element. The inventors are considering the possibility of combining various functions of optical elements in a single optical element, for example, combining an optical light-scattering element configured to scatter a light in the vertical direction and a compensation element into a compensation element with an additional function of light scattering in the vertical direction.

[0254] The inclusion of compensation elements with combined functions in the multi-view 3D imaging device, for example, with the function of an optical light-scattering element according to embodiment 3) reduces the number of elements make up the device and significantly reduces the thickness of the device, but at the same time, optical elements with combined functions are more complex in themselves, which requires more advanced production technologies.

[0255] In another embodiment 4), the function of compensation elements is performed by a screen (screen unit), which has curvature in the horizontal direction. In Fig. 12A, is represented an embodiment of a curved screen of the multi-view 3D imaging device according to the present disclosure, comprising a retroreflector 3, an optical light-scattering element 4 and a redirecting optical element 5; Fig. 12A also schematically shows one projector, although the number of projectors can be 2 or more depending on the number of the formed viewing zones(VZ). In this embodiment of realization, the compensation function of distortion of the viewing zone in the horizontal direction is fully or partially performed due to the curvature of the components that make up the screen unit: retroreflector 3, optical light-diffusing element 4, configured to scatter light reflected from the retroreflector 3 in the vertical direction relative to the viewer's eye, redirecting the optical element 5 in the horizontal plane. In this case, when the compensation function is partially performed due to the curvature of the constituent optical components of the screen, the compensation block (the first and second compensation elements 7, 6) are still presented in the device design, but have a different (smaller in magnitude) optical power in the corresponding directions.

[0256] The inclusion of a screen unit with a compensation element function in the multi-view 3D imaging device according to the present disclosure of the embodiment 4) has a new ergonomic design, which allows to turn viewer's head less in viewing the formed image and by the effect of complete immersion (immersion effect), which is usually used in planetariums (images are viewed on a round roof). However, in some cases of using display technology (too small distance or too large distance from the screen to the user or viewer), the screen curvature may be too large (the screen will be a hemisphere), which is already inconvenient, not ergonomic, and not aesthetically pleasing. In addition, the presence of optical elements of complex shape that form a curved screen is due to the difficulties of screen manufacturing, which requires more advanced production technologies.

[0257] In another embodiment 5), the compensation elements have additional optical coatings for various purposes, for example: anti-reflective coatings to increase the transmittance of the surfaces of optical elements that transmit radiation, reflective coatings to increase the reflectance of surfaces that reflect radiation, filter coatings to filter out unwanted radiation for the operation of the device, as well as beam splitting coatings. The specified coatings are used depending on the required tasks.

[0258] The inclusion of compensation elements with coatings in the multi-view 3D imaging device according to the present disclosure of the embodiment 5) allows increasing flexibility when designing the multi-view 3D imaging device, due to the fact that a number of optical coatings have specific properties and allow very diverse work with light. Due to this property of optical coatings, the skilled person in the art can select the required specific parameters of the 3D imaging device being designed from a wide range of options i.e., there is greater flexibility in choosing the required parameters. At the same time, the described compensation elements with coatings are more complex in themselves, which requires more advanced production technologies.

[0259] Further, it will be considered possible options for the arrangement of projectors used in the projection multi-view 3D imaging device according to the present disclosure, in which the 3D image is an autostereoscopic or holographic image.

[0260] A. Obtaining an autostereoscopic image.

[0261] It may be noted that the generated 3D image can be obtained with a use of a block of projectors that project views of the 3D image / scene onto the screen and form viewing zones of the autostereoscopic image, causing the illusion of volume, that is, a feeling of relief and extension in depth due to the peculiarities of binocular vision, for the user or viewer, who placed the eye's pupils in the corresponding viewing zones, without the use of additional wearable devices.

[0262] For the autostereoscopic projection method, at least two traditional projectors known from the prior art are used: https: / en.wikipedia.org / wiki / Projector, that are located at a distance corresponding to the intraocular distance of the user at a certain distance to the screen, i.e. depending on the purpose of the system (home / public cinema), and where, each of the projectors creates a viewing zone, in which the user's eye will see one 2D image.

[0263] B. Obtaining a holographic image

[0264] A holographic projection device produces the 3D image by reconstructing a wavefront of the displayed object (scene), in which the holographic image is projected onto the screen.

[0265] In this case, the generated 3D image can be obtained using a holographic projector block, which projects a holographic image / scene onto the screen and forms viewing zones for the holographic image, i.e. in each of the viewing zones the user, who placed the eye's pupils in the corresponding viewing zone, will see the full reconstructed wavefront from a real object scene, which contains all the features of a 3D object scene, without the use of additional wearable devices.

[0266] In this case, at least one known holographic projector is used:

[0267] https: / sciencing.com / holographic-projectors-work-12226294.html,

[0268] which creates one viewing zone in which the user's eye will see the full reconstructed wavefront from the real object / scenes.

[0269] According to an embodiment of the present disclosure, the projection multi-view 3D imaging device, additionally comprises a switchable lens line (switchable lens array), i.e. a set of spatially spaced lenses, representing objective lenses, with the ability to direct light from a light source into any lens of the switchable lens line. It may be noted that the light source is a projector without the objective lens.

[0270] In addition, very often for various purposes it is necessary to increase the number of viewing zones, but to implement this task it is necessary to increase the number of projectors, which is expensive. To maintain the number of projectors with a minimum configuration (1-2), the applicants propose to use the switchable lens line (objective lenses) optically coupled with at least one projector to form two or more viewing zones. Thus, the number of generated viewing zones is increasing while maintaining the same number of projectors. In Fig. 12B is a diagram of a multi-view 3D imaging device according to the present disclosure, wherein the switchable lens line 8 is optically coupled to at least one projector 2 to form two or more viewing zones (VZ).

[0271] It may be noted that the switchable lens line contains at least two lenses.

[0272] In this case, the switchable lens of the switchable lens line 8 is the lens configured to transfer the image generated by at least one projector 2 to the screen unit (3+4+5+6+7) to form at least one viewing zone VZ. In this case, the screen unit contains a retroreflector 3, an optical light-scattering element 4, a redirecting optical element 5 and a compensation block (6,7), optically coupled with at least one projector 2 and with at least one viewer's pupil.

[0273] In this case, the device additionally comprises a tracking device 9, configured to track the position of at least one of the user's eyes or pupils and ensure that the image is output to the corresponding viewing zone. These tracking devices (trackers) are known from the prior art, see, for example, the publication: https: / ru.wikipedia.org / wiki / TrackIR

[0274] The tracking device 9 may be configured to connect with at least one projector 2 and a switchable lens line 8. In this embodiment, the light emitted from the light source, in this case, the light source is the projector 2, has the ability to fall on any lens of the switchable lens line 8, the each lens will transfer the light onto the screen, which will form the viewing zone VZ. Thus, an increase in the number of zones is achieved with the same number of light sources, the function of which is performed by projector 2.

[0275] In addition, the device is also provided with a control unit (not shown) connected to at least one projector 2, a tracking device 9 and a switchable lens line 8 to provide control of each of these units and ensure synchronization of the operation of these units. For example, in this embodiment of realization, the tracking device 9 for tracking the user's head position transmits the coordinates of the user's head position to the control unit, and the control unit, based on the received data (coordinates), outputs an image corresponding, for example, to an angle, view of a 3D object or scene based on the position of the user's head, into the projector 2 and sends a signal to the switchable lens line 8 to activate the lens (objective lens) corresponding to the coordinates of the position of the user's head, and accordingly, other lenses in the switchable lens line 8 are not activated, while the activated lens (objective lens) transfers light from the projector 2 to the screen unit (3+4+5+6+7), which forms the viewing zone VZ corresponding to the current coordinates of the user's head position.

[0276] In a examplary embodiment of realization, the projectors are separated from the geometric center of the corresponding viewing zone in a vertical plane, and are located outside the corresponding viewing zone, namely above or below the viewing zone. This projector arrangement is user-friendly, providing the user freedom in the location of the projection system and is compact. With this projector arrangement, it is possible to use a tracking device 9 to determine the exact position of the user's head or eyes (pupils).

[0277] Various types of light sources.

[0278] The following light sources for the projection multi-view 3D imaging device can be used: digital micromirror display (DMD), liquid crystal on silicon (LCOS) display, laser projectors, LEDs, liquid crystal display (LCD), digital micromirror projection display (DLP) etc.

[0279] Further, in another embodiment of realization, all optical elements of the screen unit of the device according to the present disclosure have additional optical coatings for various purposes, for example: anti-reflective coatings to increase the transmittance of the surfaces of optical elements that transmit light, reflective coatings to increase the reflectance of surfaces that reflect light, filter coatings to filter unwanted light for device operation, as well as beam splitting coatings. The specified coatings are used depending on the required tasks.

[0280] The inclusion of coated optical elements in the projection multi-view 3D imaging device allows to increase flexibility in designing the multi-view 3D imaging device, due to the fact that a number of optical coatings have specific properties and allow working with light in very diverse way. Due to this property of optical coatings, the skilled person can select the required specified parameters of the designed multi-view 3D imaging device from a wide range of options, i.e. there is greater flexibility in choosing the required parameters. At the same time, the described optical elements with coatings are more complex in themselves, which requires more advanced production technologies.

[0281] A projection multi-view 3D imaging device, such as autostereoscopic or holographic images for one or more users, can be used for educational, advertising and entertainment purposes at home, as well as in public places, for example, cinemas, museums, educational institutions, where there is a need to generate multi-view, color 3D images.

Claims

1.A projection multi-view 3D imaging device, comprising:at least one projector (2), configured to form an image in a corresponding viewing zone, wherein each of the at least one projector is separated from the geometric center of the corresponding viewing zone in a vertical plane relative to the viewer's eyes, and is located outside the corresponding viewing zone,a screen unit (SU), having at least one of a spatial scattering distribution function and a spatial reflection distribution function, and configured to form at least one viewing zone of the generated image,wherein the screen unit comprises a retroreflector (3), and an optical light-scattering element(4), the retroreflector is a reflective film, and is configured in the form of a set of one-dimensional rectangular prisms, elongated in the vertical direction relative to the viewer' s eyes, and having a reflective coating on the prism faces,the optical light-scattering element is located next to the retroreflector along the direction of light emitted from the at least one projector, and is configured to scatter light reflected from the retroreflector in the vertical direction relative to the viewer's eyes.2.The device according to claim 1, wherein the screen unit further comprises a redirecting optical element 5 and a compensation block, optically coupled with at least one projector and with at least one pupil of the viewer's eyes, andthe redirecting optical element has at least one of the spatial scattering distribution function and the spatial reflection distribution function, and is configured to redirect light, when the light is reflected from the retroreflector and passing through the optical light-scattering element, to the area of at least one viewing zone in which the viewer's eye is located, in the use of the device.3.The device according to claim 2, wherein the redirecting optical element is made with an offset optical axis relative to the optical axis of the device, and has zero optical power in the horizontal direction and a predetermined optical power (OP) in the vertical direction relative to the viewer's eyes, which is inversely proportional to the distance from the screen unit to the at least one corresponding viewing zone,the compensation block is configured to compensate a distortion of at least one corresponding viewing zone in the horizontal direction,wherein the compensation block comprises a first compensation element 7, and a second compensation element 6,the first compensation element is located next to the redirecting optical element along the direction of light emitted from at least one projector and has zero optical power in the vertical direction in relation to the viewer's eyes and negative optical power in the horizontal direction in relation to the viewer's eyes,the second compensation element is located between the retroreflector and the optical light-scattering element along the direction of light emitted from at least one projector and has zero optical power in the vertical direction in relation to the viewer's eyes and positive optical power in the horizontal direction in relation to the viewer's eyes.4.The device according to claim 1, wherein the retroreflector configured in the form of the set of one-dimensional rectangular prisms elongated in the vertical direction with a reflective coating on the faces of the prisms, additionally comprises an absorbing coating on the edges at the tops and / or bottoms of the prisms to provide a reflection of the light from at least one projector without loss of light scattering in the horizontal direction relative to the viewer's eyes, caused by the light scattering on the edges of the prisms at the tops and / or bottoms, and the scattering and the absorption of light within the prism material.5.The device according to claim 3, wherein the first compensation element, having zero optical power in the vertical direction and negative optical power in the horizontal direction, is an optical element selected from: a holographic lens, a diffraction lens, a Fresnel lens, a geometric phase lens, a meta lens.6.The device according to claim 3, wherein the second compensation element, having zero optical power in the vertical direction relative to the viewer's eyes and positive optical power in the horizontal direction relative to the viewer's eyes, is an optical element selected from: a holographic lens, a diffraction lens, Fresnel lenses, geometric phase lenses, metalens.7.The device according to claim 1, wherein the redirecting optical element is configured in such a way that it allows each of the at least one projector to be separated from the geometric center of at least one corresponding viewing zone in the vertical plane relative to the viewer's eyes, and each of the at least one projector to be placed above and / or below the viewing zone.8.The device according to claim 1, further comprises a switchable lens line optically coupled to at least one projector to form at least one viewing zone, andwherein the switchable lens of the switchable lens line is an objective lens configured to transfer an image generated by at least one projector to a screen unit to form at least one viewing zone.9.The device according to claim 8, further comprises a tracking device configured to track the position of at least one of the viewer's eyes / pupils.10.The device according to any one of claims 1-9, further comprises a control unit connected to at least one projector, the tracking device, and the switchable lens line, andwherein the control unit is configured to control at least one projector, the tracking device, and the switchable lens line.11.The device according to claim 1, wherein the retroreflector is made such that the period (p) of the retroreflector is the distance between the vertices of adjacent prisms and, taking into account the angular resolution of the viewer's eye, must satisfy the following expression:where ω is the angular resolution of the eye, L is the distance from the screen unit to the viewer, λ is the maximum wavelength from the range of operating wavelengths of the projector, W is the width of the viewing zone.12.The device according to claim 1, wherein the optical light-scattering element is a diffraction grating of an arbitrary type, where a change of the grating period (p1,p2,..pN), ensuresthe formation of an expanded viewing zone in the vertical direction.13.The device according to claim 2, wherein the redirecting optical element has an off-axis parameter (OA), which determines the displacement of the optical axis of the optical redirecting element from the optical axis of the device, which is given by the following relationship:OA~T / 2,where OA is the off-axis parameter of the redirecting optical element, T is the distance from the light source, which is at least one projector, to the viewer's eye.14.The device of claim 2, wherein the redirecting optical element is an optical element selected from: a holographic lens, a diffraction lens, a Fresnel lens, a geometric phase lens, a metalens.15.The device according to claims 1-14, wherein at least one of the retroreflector, and the optical light-scattering element comprises a filter coating to filter out unwanted radiation for the operation of the device; a reflective coatingand an antireflective coating.

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