RU2740065C1 - Augmented reality device based on holographic optical waveguide - Google Patents

Abstract

FIELD: optics.

SUBSTANCE: device relates to the field of optical instruments and can be used as a base for optical devices for generating a dynamic image of augmented reality. Device uses an optical element - a holographic optical waveguide, which is a two-dimensional optical waveguide with a holographic optical element (lens) deposited on the surface. Image is formed by modulation of the displayed beam by an array of a liquid crystal matrix. Formed image is focused into the centre of the pupil of the eye and then projected on the back side of the eye retina of the observer.

EFFECT: invention provides compactness of form factor and high technical parameters (field of view, resolution, contrast, multi-colour, multiple viewing).

13 cl, 16 dwg

Description

The technical field to which the invention relates

The device belongs to the field of optical devices and can be used as a basis for optical devices for forming a dynamic image of augmented reality, for example, in such areas as geolocation services, navigation systems, training programs, visualization systems in medicine, game applications, design systems, virtual advertising ...

State of the art

Augmented (AR) and virtual (VR) reality systems have been developing intensively over the past 20 years. Unlike virtual reality, which allows you to completely immerse the user in the digital world, AR has a better ability to perceive the real world. AR allows the user to view in real time the stream of generated digital information and an image of the environment. AR systems are now widely used in the aviation industry. The operation of such devices is based on the use of an optical element capable of simultaneously displaying the stream of the generated digital image and having a high transmittance of visible light necessary for observing the environment.

From the prior art patent US 8477425 B2 is known, which discloses an interactive optical system, which is attached to the user's head and provides the ability to display a digital image while maintaining the ability to view the environment. The main element of the device (optical system) is a partially reflective, partially transmissive optical element, which is a beam splitting plate located in front of the user's eye. A system consisting of a polarizing filter and non-collimated red, blue and green (RGB) LEDs is used as light sources. The image is formed using a liquid crystal (LCoS) matrix with polarizing films. The generated image, passing through the lens system, falls on a partially reflective, partially transmissive optical element, and then redirects to a semitransparent curved surface, which returns the generated image to the observer's field of view. Since the main optical element partially transmits the incident light radiation, the user can view the environment. Since the system uses a single LCoS, it is necessary to use backlight time-division multiplexing to provide a color image.

This solution has several disadvantages. A complex optical system, including a large number of passive optical elements, leads to a decrease in the resolution of the generated image, which can reach 800 × 480. In addition, the use of a large number of polarization units and semitransparent optical elements leads to a significant decrease in the intensity of light generated at the beginning of the optical path, which leads to a decrease in the energy efficiency of the entire device. The separation of the source of the generated image (LCoS) matrix and the main partially reflecting, partially transmitting optical element leads to an increase in the overall system dimensions, which also negatively affects the consumer properties of this solution.

The publication WO 2014/068482 A1 discloses the construction of augmented reality glasses capable of superimposing information and images on the field of view without overlapping it. Augmented reality glasses contain a frame that supports the lens of the glasses, and a miniature display is associated with the frame, configured to project an image in a given direction. The image formed by the projection system hits a mirror, which redirects the beam to the area of the lens of the glasses. According to the solution, the optical system contains an element including two lenses connected so that one of the respective surfaces is treated with a reflective surface coating. The reflective coating is designed to reflect a narrow band of the visible spectrum with a characteristic spectral width of 20-30 nm. The use of such a two-component lens makes it possible to form part of the lens of the glasses in the form of an inclined flat mirror, which leads to the possibility of redirecting the reflected image to the user's viewing area. The invention supports the ability to adjust the glasses to the physical characteristics of the user's vision.

This solution has several disadvantages. Thus, low image contrast leads to the need to use a partially transmissive coating only in a limited area of the field of view. Field of View (FOV) is limited to 60 °. In addition, the use of a coating with a narrow spectral selectivity leads to the possibility of generating only a monochromatic image, and the separation of the image generating element and the two-component lens leads to a significant increase in the overall system dimensions.

From US Pat. No. 9,910,283 B2 a light guide with a plurality of built-in partially reflective surfaces is known for an augmented reality system. This system is a type of head-up display (HUD), which is compact due to the use of the waveguide principle. The first reflective surface is illuminated by a collimated display coming from a light source located behind the device. The reflective surface transforms the formed image into a waveguide, in which the beam continues to propagate through total internal reflection (waveguide principle). After several reflections from parallel surfaces of the waveguide, the captured light waves reach an array of selectively translucent and semi-reflective surfaces that redirect the light waves from the substrate towards the viewer's eye. To reduce the effects of re-reflection of a propagating beam at the boundaries of reflecting surfaces, the possibility of using anisotropic optical films (an array of thin parallel conductors) is considered. This technology achieves an angle of view larger than the standard HUD system while maintaining a thin viewing lens.

This solution has the following disadvantages. Due to the use of translucent re-reflective surfaces, the image coming from the real world is darkened, while insufficient visibility of the environment leads to a limitation of the areas of use of this device. Partial flashing of the generated image on each semi-reflective element leads to a decrease in the intensity of light propagating along the waveguide, which requires correct correction of the reflection coefficient for each region of the waveguide. In addition, in the known device, the image is generated before it is introduced into the waveguide, which leads to the use of a circuit with the separation of the image source and the viewing area, and, accordingly, to an increase in the size of the device. Fourthly, to form a high-quality image with high contrast and high resolution, it is necessary to use multilayer structures.

Publication US 2019/0324274 A1 discloses a technology for performing an augmented reality system based on a film with a locally modulated transparency. The adjustable transparency system includes an adjustable transparency layer and a projection system. The projection system includes an ultraviolet (UV) laser source and a micromirror array (MEMS), which together generate the required image. The image is then projected onto a layer with modulated transparency (photochromic layer) applied to a spectacle lens. The projected beam locally changes the transparency of the film, which leads to the formation of an image on the surface of the film. The generated image is a mask for light from the environment, thus forming an image in the area of the observer's eye.

This solution has several disadvantages. Since the image is formed directly in the area of the spectacle lens, the image will be available to the observer only with close focusing of the eye, respectively, joint observation of the generated image and the view of the surrounding world, which is more than 2 m distant, is not possible. Using a UV source to modulate transparency makes it impossible to generate a multicolor image. The influence of UV radiation from external sources of the environment leads to background modulation of the photochromic layer and a strong deterioration in the contrast of the displayed image. The use of a photochromic film with a strong dependence of the optical properties on the ambient temperature leads to a significant limitation of the functionality of the device (in a limited temperature range of ± 10 degrees).

US Pat. No. 9846307 B2 discloses a method and a compact device for displaying an image on the retina of a human eye using a display built into glasses. The system is based on VRD (virtual retinal display) technology. Small lasers or LEDs are used as a radiation source. From them, the radiation hits the dynamic MEMS element. For each position of the scanning mirror, a pixel on the retina can be generated by raster scanning. After the dynamic system, the beam hits a volumetric holographic optical element (HOE) located in the area of the spectacle lens. The HOE element has two main functions: it allows light from the environment to pass unimpeded, providing normal vision for the user, and it also redirects the scanned light from the projector to the user's eye to display an image passing through the center of the pupil of the eye, and is projected onto the back of the retina. HOE is manufactured using holographic technology. Using multiple HOE layers, recorded at different wavelengths and superimposed on each other, produces a multi-color image.

This solution has the following disadvantages. VRD technology requires precise positioning of the pupil of the eye and the projection system, so the user sees the generated image only when the eyes are fixed. It also leads to the need to adjust the entire system to the physical characteristics of an individual observer (interpupillary distance and the position of the glasses transfer). The use of a single reflector in the dynamic MEMS element for progressive scanning results in low resolution of the generated image and overlapping of the finite elements of the scan array.

WO 2019132474 A1 discloses a virtual and augmented reality system with point mirrors. The initial image is formed by a display located away from the projection system of the image of the observer's viewing area (bow of glasses). The generated image, passing through the lens system, is projected onto point mirrors located in the volume of the spectacle lens. Point mirrors are made with the possibility of redirecting the light rays that form the virtual image to the optical element with the expansion of the field of view, which, in turn, redirects the light rays that form the virtual image to the user's eye area. As a result, the formed image is projected onto the back side of the retina, passing through the center of the pupil of the observer's eye. In some embodiments, the widening optical element may be semi-transparent. In many embodiments, to achieve a wide field of view, the optic expanding the field of view has a larger lateral dimension than the pupil of the human eye when viewed from the user's point of view. When using the AR system, opaque point mirrors are not visible to the user, since they are not in focus of the gaze, and their size is much smaller than the pupil of the human eye.

This solution has the following disadvantages. To focus the generated image on a point mirror, it is necessary to use spectacle lenses with a thickness of more than 5 mm, which leads to an increase in the characteristic dimensions of the final system. In this case, projecting an image through the center of the pupil of the observer's eye requires precise adjustment of the position of the projection system. When using a configuration with multiple view areas, it is not possible to "smooth" transition between adjacent areas. The thickness of the spectacle lens sets the finiteness of the viewing field of view (FOV), which reduces the area of registration of the generated image and the image of the environment.

US publication 20170235143 A1 discloses an augmented reality system based on a waveguide display with a two-dimensional scanner. This system is small in size compared to similar systems based on HUD technology. The source assembly includes a set of coherent or quasi-coherent light sources. One or more precursors can emit light at different wavelengths. The optical system includes one or more optical elements that focus and collimate the light received from the source. The optical system also includes one or more scanning mirrors (eg MEMS) that scan the light received from the focusing lens. From the scanning system, the beam enters the area of the optical waveguide display. The display includes an introduction area and an image output area, which are realized by means of diffraction gratings. The period of the input diffraction grating is selected for the possibility of radiation propagation along the waveguide through total internal reflection. After the propagation of the radiation introduced through the entrance area, the image is expanded and flashed towards the user's eye. The pitch of the output diffraction grating is selected so as to force the incident image light to leave the output region.

This solution has the following disadvantages. Mirror size and frequency of movement are two fundamental limits for resolution. In the far field, the size of the mirror determines the scattering angle of the diffraction of the scanned laser beam. US Pat. No. 9,753,297 B2 describes an exit pupil dilator optical device that can be used in an augmented reality system. The optical device is an optical waveguide with diffraction gratings applied to the regions, which are different in period and directivity.

1) The first region is configured to connect the first light beam component to the device, the first light beam component having a wavelength in the first spectral range;

2) The second region is configured to attach a second light beam component to the device, the second light beam component having a wavelength in a second spectral range different from the first spectral range;

3) The third region is configured to expand the first component of the light beam in the first dimension to create an expanded first component;

4) The fourth region is expandable in the second dimension of the expanded first component to create an additional expanded first component and is configured to output the additional expanded first light beam component from the device;

5) The fifth region is configured to expand the second component of the light beam in the second dimension to create an expanded second component;

6) The sixth region is expandable in the first dimension of the expanded second component to create an additional expanded second component and is configured to output the additional expanded second component from the device collinear with the additional expanded first light beam component.

The system of regions allows you to enter the generated image into the optical waveguide, as well as output the image in the direction of the observer's eye.

This solution has the following disadvantages. The image is displayed only from one area, the other areas perform the functions of forming and expanding the image. This approach leads to a significant increase in the size of the device. The use of diffraction gratings with a period comparable to the wavelength of the visible light range leads to the appearance of an iridescent coloration of the spectacle lens surface when illuminated by external light sources. In addition, the technology used is distinguished by the need for high positioning accuracy of the manufactured diffractive elements with a viewing area.

Closest to the claimed device is a multi-pixel retinal display system (MPBRD) disclosed in US patent 9250445 B2. The main element of the device is a matrix with micro-holes that redirect and limit the beam divergence. The image is generated using a standard 2D LCD or OLED display. A volumetric layer installed between the display and the observer collimates light into a narrow, low-divergence beam and redirects it to the observer's pupil. The bulk layer consists of micro-holes with a characteristic size of 100 microns and having different directions with a characteristic ratio of thickness to hole diameter of 1: 100. This ratio can lead to very small angular divergence of the transmitted light. The orientation of the holes is selected in such a way as to provide a pixel-by-pixel projection of the image through the center of the pupil onto the back side of the retina of the observer's eye. In other configurations of the device, microfibers may be used instead of micro-holes, oriented appropriately, which allows unobstructed observation of the environment through the device.

This solution has the following disadvantages. The high aspect ratio of hole or fiber diameter to thickness results in the ability to display in only one fixed position of the eye, which greatly complicates its use. In order to be able to combine the digital generated image with the image of the environment, it is necessary to use, at the initial stages of the beam, displays (OLED or LCD), which have a low transparency coefficient, which generally leads to a decrease in the visibility of the environment.

Brief essence of the claimed invention

Thus, from the prior art, two main methods of superimposing a digital image on the image of the surrounding world can be distinguished: the first is diffractive waveguides and HUD technologies, the second is VRD-based technologies. At the same time, devices that implement the first method can be characterized by high resolution, but a small viewing area and not a compact end device. Devices that implement the second method are characterized by a wide viewing field and a compact form factor, but are significantly inferior in image resolution and multicolor. Thus, the prior art does not know a device that has both high resolution and multicolor, and a large viewing field and compact design.

The technical problem solved by the claimed invention consists in the need to overcome the disadvantages inherent in known analogs and the prototype by creating an augmented reality device having, on the one hand, the design and weight and dimensions characteristic of traditional glasses for correcting vision, and, on the other hand with such optimal technical characteristics as: viewing angle, multicolor, resolution, contrast of the generated image. The system being developed can be used as a basis for optical devices for forming a dynamic image of augmented reality, which is in demand in such areas as geolocation services, navigation systems, training programs, visualization systems in medicine, game applications, design systems, virtual advertising. The technical result achieved when using the claimed invention is to increase the viewing field of the device up to 100 ° in combination with a resolution of> 1280 × 720, high contrast of the generated image and small thickness of the viewing element, which in turn leads to a decrease in the form factor of the entire device ...

The claimed device also has the following technical advantages:

• Resolution: ≥1280 × 720.

• Field of View (FOV): ≥100 °.

• Alignment of image source and viewing area.

• Thickness: ≤4 mm.

• Multicolor.

• Multi-viewing.

• Transmittance: ≥70%.

The claimed technical result is achieved by the fact that in an augmented reality device designed to project the generated image onto the back side of the retina of a person through the center of his pupil, which includes an optical circuit equipped with means for attaching to a person's head, and a means for introducing radiation into the optical circuit, according to the technical solution ,

- the optical scheme, geometrically representing a plate with lateral edges, includes at least one transparent multilayer optical element made of the following adjacent layers: an outer layer made in the form of a stepped planar optical waveguide, an inner layer facing the human eye , formed in the form of a liquid crystal matrix equipped with a polarizing filter, and an intermediate layer located between the said layers with a dense, excluding the formation of an air gap, adjoining the outer layer, made in the form of a film, which is a holographic optical element,

- and the system for introducing radiation includes at least one source of monochromatic radiation located outside the multilayer optical element, made with the possibility of introducing radiation into the optical waveguide through the side edges of the plate of the optical circuit.

The lateral faces of the optical scheme can be provided with a reflective coating and made inclined at an angle of 30 ° to 60 ° to the surface of the plate, while the radiation source is placed to ensure that radiation is introduced into the optical waveguide at a normal angle to the surface of the multilayer optical element with subsequent re-reflection from the lateral face optical circuit. On a part of the surface of the multilayer optical element, a diffraction mask with a period of 100-2000 nm can be applied, while the radiation source is placed so that radiation can be introduced into the optical waveguide through the diffraction mask. In another case, the side faces of the optical scheme plate can be made inclined at an angle of 45 ° -60 ° or rounded with a radius of curvature of 0.1 ... 10 mm, providing focusing by the lateral face, while the radiation source is placed so that radiation can be introduced into the optical waveguide through the specified edge. Additionally, the planar optical waveguide can be provided with protective polymer coatings applied to both its surfaces, while the refractive index of the polymer coating is lower than the refractive index in the waveguide core. The optical scheme can be made of at least two multilayer optical elements closely adjacent to each other, having different operating wavelengths and / or different operating orientations. The holographic optical element has a variable diffraction coefficient of 10-95%, which increases with distance from the region where the radiation is introduced into the multilayer optical element. The device can be provided with means for adjusting the position of the displayed image relative to the human eye, as well as an eye tracking system installed in the means for attaching the device to the human head. A multilayer optical element can be made of layers with a total transmittance of at least 50% and has a thickness of no more than 1 mm. The liquid crystal matrix is a dynamic monochrome matrix consisting of a layer of liquid crystals controlled by thin film transistors. A frame with bows can be used as a means of attaching to a person's head.

The technical result is also achieved through the implementation of a method of manufacturing a holographic optical element, which is intended for use in the claimed device of augmented reality according to claim 1 of the claims, according to which a photosensitive film with a thickness of 10 ... 200 microns and an area of at least 1 sq. cm is placed on one of the side faces of a triangular optical prism with a refractive index of the prism material 1.2-1.5, radiation from a coherent source is directed to the specified prism, while part of the radiation, which is a reference beam, is introduced through one side face of the prism, ensuring its complete internal reflections at the boundary of the film with air, and a part of the radiation, which is an object beam, is directed to the outer surface of the film through a recordable optical element by its location in the path of radiation propagation, and then the reference and object beams interfere in the film region, as a result of which a holographic recording is obtained. images of the object in the film.

Brief Description of Drawings

The claimed invention is illustrated by the following drawings, where

FIG. 1 schematically shows the device of a holographic optical waveguide and the principle of operation of an electro-optical element that superimposes the generated image on the image of the environment.

FIG. 2a-b shows the recording schemes of a holographic optical element (lens): a - direct recording, b - recording using a prism.

FIG. 3 shows the structure of the regions of the holographic optical element.

FIG. Figures 4a-d show the possible options for introducing illumination radiation into the optical waveguide: (a) reflection from the boundary, (b) based on a diffraction grating, (c) direct entry through an inclined facet, (d) entry through the end of a complex shape.

FIG. 5a-b shows the methods of realizing a multicolor image: a - the use of several layers of holographic optical elements, b - the use of illumination from different faces.

FIG. 6 schematically shows the use of several holographic optical elements to create a multi-viewing image (for different orientations of the observer's eye).

FIG. 7a-c schematically shows the use of different orientations of the illumination to create a multi-viewing image (for different orientations of the observer's eye): a - direct image, b - displacement of the focus position in the direction of light propagation along the waveguide, c - displacement of the focus position in the perpendicular direction of light propagation along the waveguide ...

FIG. 8a-b shows the adjustment of the focal spot of augmented reality glasses to the physiological characteristics of the observer: a - degrees of freedom for adjusting the interpupillary distance and position height; b - degree of freedom for adjusting the bow with temples.

FIG. 9 to 10 show photographs of the result of using the claimed device. Superposition of a monochromatic image (letters and numbers) on the image of the environment. The image was detected using a digital camera that simulates the human eye.

The holographic optical element used in the claimed invention can be obtained by holographic recording of the image of the optical element in the volume of the photosensitive layer in the circuits shown in FIG. 2. In this case, the recorded holographic optical element must have a different diffraction coefficient. FIG. 3, necessary for uniform emission of radiation from different areas. The emission of radiation occurs from a two-dimensional optical waveguide, the radiation in which propagates through total internal reflection. The introduction of radiation into the waveguide can be carried out in various ways, shown in FIG. 4. By combining several layers or different orientations of the illumination in conjunction with the system for tracking the position of the pupil of the eye, it is possible to achieve a multi-color (Fig. 5) and multi-view (Fig. 6, Fig. 7) image. For more correct operation of the device, it is necessary to initially adjust the system to the physiological characteristics of the user's eyes. The adjustment levels are shown in FIG. 8.

Positions in the drawings indicate:

1. Optical waveguide

2. Parallel beam

3. Photopolymer layer with a written image of a holographic optical element

4.LCD - matrix

5. Polarizing filter

6. Protective polymer layer

7. Center of the pupil of the human eye

8. The back side of the retina of the human eye

9. Light from the image of the environment

10. Glass substrate

11. Rectangular prism

12. Recordable optical element (lens)

13. Object bundle

14. Reference beam

15. Holographic film with different diffraction coefficients

16. Holographic film with different diffraction coefficients

17. Holographic film with different diffraction coefficients

18. Reflective coating

19. Beveled angle at the base of a plane-parallel optical waveguide

20. Diffraction grating

21. Point source of illumination

22. The edge of the optical waveguide made in the form of a convex surface

23. Holographic optical element recorded for the red range

24. Holographic optical element recorded for the blue range

25. Holographic optical element recorded for the green range

26. Three-color backlight

27. Side face of a plane-parallel optical waveguide

28. Holographic optical element recorded for position A

29. Holographic optical element recorded for position B

30. Holographic optical element recorded for position C

31. Active pixels for the selected position

32. Eye tracking system

33. Focus spot

34. Focus spots when viewing with two eyes

35. Interpupillary distance adjustment system

36. Means for attaching to a person's head (temples of glasses)

37. System of adjustment of temples

38. The side region of the system in which the control electronic part is located, which is a unit that controls the LCD matrix to provide an augmented reality image.

Implementation of the invention

The claimed device can be implemented in the form of a structure that is as close as possible in shape and dimensions to the design of conventional glasses for vision correction. In this case, the frame with arches act as a means of attaching the optical circuit to the human head. The optical scheme is one or more closely spaced multilayer optical elements, in the limiting case, closely spaced. In this case, when using several optical elements, they are selected with the provision of different operating wavelengths and different viewing areas. The use of several elements allows to achieve advanced functional properties: multicolor and multi-viewing. Each multilayer optical element is a transparent two-dimensional optical waveguide coated with a polymer layer with the image of a holographic optical element. Geometrically, the element is made in the form of a plate, predominantly of a prismatic shape, while the side edges of such a plate can be made beveled at an angle necessary to establish parallel illumination radiation with subsequent propagation along the waveguide, or rounded inclined edges, which allows you to simultaneously convert the radiation of a point source into parallel beam with the subsequent introduction of radiation into the waveguide. The multilayer optical element is formed by the following layers (starting from the one farthest from the observer's eye):

• the outer layer, facing away from the human eye, is a plane-parallel plate made of glass or optically transparent polymer with modified edges necessary to introduce illumination radiation (optical waveguide);

• the intermediate layer following the waveguide towards the eye is a photopolymer transparent film with a holographic recorded image of the required optical element (lens);

• the inner layer, which is a liquid crystal (LC) -matrix equipped with a polymer film with polarization filtration;

The main element of the device being developed is a multilayer optical element containing an optical stepped planar waveguide installed in the area of the spectacle lens. Such a waveguide is a glass plate 1-5 mm thick with a roughness of at least 7 surface cleanliness class. The lateral faces of the plate are modified so that it is possible to introduce illumination radiation with subsequent propagation of the beam in the waveguide through total internal reflection. The establishment can be provided in several ways: by placing a diffraction grating near the side face (Fig.4b), polishing the side face at a fixed angle, followed by applying a reflective layer (Fig.4a) or direct illumination of the side face (Fig.4c), a combination of the above is also possible. ways of establishment (Fig. 4d). Coherent or non-coherent sources with a given polarization can be used as a backlight source. Together with the source, various configurations of passive optical elements can be used to obtain parallel and polarized radiation directed into the waveguide. A holographic optical element (HOE) written in a photosensitive polymer layer with a characteristic thickness of about 15 μm is used to redirect radiation from the optical waveguide towards the observer's eye. A focusing element with a focal length of f = 10-500 mm is used as a recordable HOE. HOE recording can be performed in a direct scheme (Denisyuk's method (Leith EN, Upatnieks J. Journ. Opt. Soc. Amer., V. 54, 1295, 1964)) or by placing a photosensitive film on the surface of an optical element (prism), in which one of the beams can propagate through total internal reflection. A highly coherent laser source is used as a radiation source for recording. The recorded film can be transferred to the prepared surface of a two-dimensional optical waveguide by re-sticking. To ensure the propagation of the light beam through the waveguide without losses, the deposition of protective polymer layers with thicknesses of the order of 50 μm with a refractive index lower than the refractive index of the central part of the planar waveguide can be used. When radiation propagates through a two-dimensional waveguide with a deposited film, in the volume of which HOE is recorded, diffraction of the beam occurs in the volume of the film, which leads to partial emission of radiation in the direction specified during HOE recording (working area). Since the intensity decreases with each act of emission of radiation from the waveguide, this can lead to inhomogeneous illumination when using HOE with a constant diffraction coefficient (the ratio of the intensity of the diffracted beam to the intensity of the initial beam). To eliminate this disadvantage, HOE can be used with variable diffraction coefficients for each individual illumination region from 10% to 95%. Thus, the collimated polarized radiation is redirected from the waveguide surface. To generate an image, a liquid-crystal monochromatic matrix is installed along the beam path, which makes it possible to obtain modulation of polarized illumination. The generated image is projected onto the back of the viewer's retina. In this case, the projection of the image is carried out through the center of the pupil of the observer's eye, which makes it possible to exclude the dynamics of self-focusing of the eye. The projected image appears distant to the observer at infinity at any focus of the eye (far or near). Since for the correct display of the image it is necessary to precisely match the HOE focus with the center of the observer's pupil, the developed device provides a system for adjusting to the physical characteristics of the observer by arranging adjusting mechanisms and mechanisms for attaching to the head in the frame of the device.

To form several viewing areas, several HOEs can be used, recorded in one photosensitive film or several films and then superimposed on each other, oriented for different positions of the observer's pupil. Also, changing the position of the focus (working orientation) can be implemented by changing the angle of introduction of radiation into the waveguide.

To form a color image, an intermediate layer can be used, consisting of several layers of a photosensitive film, the recording of a holographic element into which is made at different wavelengths. It is also possible to record one holographic film for several wavelengths with corresponding different illumination orientations. The restoration of the required length in such a film occurs only with a certain orientation of the backlight (at which the recording was carried out).

The implementation of such an augmented reality system will significantly reduce its form factor while maintaining high technical parameters. The compactness of the device is ensured by the lack of separation between the image generation element and the image display element. In the device under development, a multilayer optical element (spectacle lens) serves as both a source of illumination radiation, an image generator, and a projection system. At the same time, the technical parameters of the device also correspond to a high level. Thus, the viewing field of view is 110 degrees, which corresponds to the maximum angle for the human eye. The image resolution is determined by the resolution of the LCD matrix and can reach 2048 * 1080. In the case of using a matrix with an average pixel size of 30 microns, the resolution is 1280 × 720. Multi-viewing and multicolor performance is achieved by varying the orientation of the backlight or by combining several optical elements.

The device under development is made in the form of glasses for vision correction. The handling of the claimed device is similar to the handling of wearable glasses. The device can be in two modes: off (passive) and working (active). In passive mode, no digital image generation occurs and the user can observe an image of the environment without interference. When the operating mode is active, the backlight is switched on and the LCD matrix works dynamically, which leads to the effect of superimposing a digital picture on the image of the environment. For the user, the generated image is remote to infinity, and its focus does not depend on the focus of the eye (the image is always clear for any focusing of the observer's eye).

FIG. 1 shows a diagram and principle of operation of an augmented reality device based on a holographic optical waveguide. The drawing shows the structure of the spectacle lens and eye in cross section. The main element of a spectacle lens is an optical waveguide (1), in the volume of which a parallel beam (2) propagates due to total internal reflection at the interface between the waveguide and the holographic optical element. When radiation propagates, radiation diffraction occurs in the volume of the holographic optical element (3) and the beam is redirected towards the observer's eye. Moreover, radiation (2) may not be monochromatic and weakly coherent, the holographic optical element serves as a wavelength selector. Diffraction with the desired geometry of the emitted beam occurs only in a narrow spectral range, excellent spectral components are not emitted or emitted, but without creating the desired beam geometry. Further, the emitted radiation is modulated using a liquid crystal matrix (LCD). If the radiation propagated through the waveguide has a fixed polarization, then using the LCD matrix (4) and the polarizer (5) it is possible to obtain the modulation of the emitted radiation. Next, the generated image is focused to the center of the pupil of the eye (7) and then projected on the back of the retina of the observer's eye (8). Since the spectacle lens consists of transparent and translucent elements, it is possible to freely observe the image of the environment through this optical element (9). For mechanical protection and to reduce the loss of radiation propagated through the waveguide, additional films (6) with a refractive index lower than the refractive index of the main optical waveguide can be used, which will make it possible to achieve complete internal reflection at the waveguide boundary - a protective film.

FIG. 2 shows the recording schemes of the holographic optical element. The recording is carried out by a coherent laser source. The beam is divided into object (13) and reference (14) beams. The object beam passes through the required recordable optical element - a convex lens (12), with a focal length of f = 40 mm, and is projected onto a photosensitive holographic plate (3), remote from the lens by a double focal length. The reference beam is projected onto the photosensitive plate at a fixed angle, which corresponds to the angle of total internal reflection of the beam propagating in the waveguide during reconstruction. Recording of a holographic lens can be carried out both with direct recording (a), by gluing the film onto a flat surface (10), and with total internal reflection (b), by gluing the film onto the surface of an optical prism (11).

FIG. 3 demonstrates the need to create a holographic optical element with different diffraction coefficients for each separate region (15), (16), (17). When the beam (2) propagates in the volume of the optical waveguide (1) and the holographic film with the image of the optical lens applied to it, the intensity of the propagating radiation decreases after each act of diffraction. A decrease in intensity during propagation of radiation leads to inhomogeneity of the illumination of the generated image. To create an element with different areas of diffraction, the method of partial illumination of areas or a method that includes the possibility of varying the power of the beams in the arms (object and reference beams) can be used.

FIG. 4 shows various schemes for introducing radiation into an optical waveguide. To introduce radiation into the waveguide, the following methods can be used: (a) - one of the faces of the spectacle lens is a tilted surface with applied reflective material (18), the projected light is reflected from this face and then propagates due to total internal reflection; (b) - the use of a diffraction grating (20), one of the orders of which can propagate along the waveguide; (c) - direct introduction through the end, made at a fixed angle to the larger surface of the waveguide (19), at which radiation propagates; (d) - the use of complex surfaces (22) that can convert the radiation of a point source (21) into a parallel beam of light. The last scheme corresponds to the greatest compactness of the entire device.

FIG. 5 shows how to create a three-color image. The first (a) relates to a method using three holographic optical elements (23), (24), (25) recorded for three wavelengths. When monochromatic or mixed radiation propagates (26), for each holographic optical element, diffraction with the required geometry occurs only at the wavelength at which the recording took place. The second (b) includes a method based on one holographic element, in the volume of which three optical elements for three different wavelengths are recorded. When this element is illuminated at various orientations of the illumination, the required wavelength is illuminated only with the correct orientation (27), at which the element was originally recorded.

FIG. 6 shows a method for displaying an image for different positions of the pupil of the eye. The standard system only allows projecting for one fixed eye position. But the eye is a dynamic system, so when the pupil deviates from the focus formed by the holographic lens, the projection is distorted or overlapped. Thus, it is necessary to create several viewing positions at which the image will be visible. A scheme with the separation of viewing positions can be used by recording a holographic optical lens for a fixed eye position, and a combination of several layers (28), (29), (30) allows obtaining several viewing positions a, b, c for different orientations of the observer's gaze. Thus, for the propagating beam (2), a layer (28) is illuminated in the direction a, and the modulation of the pixels (31) allows obtaining its own image for the selected direction.

FIG. 7 shows a diagram of the projection of the image in different positions of the orientation of the eye. A camera (32) is used to track the position of the eye (pupil). Then the signal from the camera is transmitted to the modulator, which changes the orientation of the incoming beam (2) relative to the stationary optical waveguide (1). When the orientation of the incoming beam is changed, the focus spot (33) shifts over the waveguide region (1). (A) - corresponds to the normal position of the input beam; (B) - corresponds to the inclination of the incoming beam in the direction of the beam propagation in the waveguide; (B) - corresponds to the inclination of the incoming beam along the perpendicular direction of the beam propagation in the waveguide.

FIG. 8 shows the possible adjustment ratios for adjusting the displayed image in the direction of the viewing eye. Depending on the physiological characteristics of the user, it is not possible to create a universal system. For accurate display of the image and for the passage of the focused beam through the center of the pupil, adjustment is necessary according to the parameters of the user. So on one of the projections (a) degrees (34) allow you to adjust the interpupillary distance (33), and the degree (35) allows you to adjust the horizon of vision. On the other projection (b), the degree (37) allows you to adjust the distance between the temple (36) and the control unit (38).

FIG. 9-10 demonstrates the operation of an augmented reality device based on a holographic optical waveguide with monochromatic illumination at a wavelength of 650 nm. The image (text and numbers) is generated in the area of the optical waveguide. The resulting image is projected through a lens system onto a digital camera matrix, which is a model of the observer's retina. Since the viewing area has transparency, it is possible to observe the environment together with the overlaid digital image.

Examples of specific implementation

Example 1

A functional prototype of the proposed device has been made. A stepped planar optical waveguide is made in the form of a plate having the following characteristic dimensions: 35 mm (H) × 35 mm (W), characteristic thickness (side edge) 4 mm, glass polishing roughness class not lower than 7. One of the lateral edges of the plate is polished at an angle of 45 ° to the base.

The holographic optical element was recorded in Bayfol HX-200 photopolymer film with a thickness of 16 μm. The recording was carried out by analogy with Denisyuk's scheme: from a coherent source (a laser diode with a power of 20 mW and an operating wavelength of 650 nm), the beam was expanded to a characteristic size of 50 mm and then divided into two using a beam splitter, one of the beams (reference) using mirrors were redirected to the photopolymer film at an angle of incidence of 45 °, and the other (object) passed through the recorded optical element (plano-convex lens with a focal length of F = 20 mm) and was projected onto the region of the polymer film, while the recorded optical element was installed at a distance of twice focus. As a result of the interference of coherent beams in the volume of the photopolymer film, the image of the holographic optical element is recorded.

The recorded film with the lens image (holographic optical element) was transferred to the surface of the planar waveguide. A liquid-crystal monochrome matrix with a resolution of 64 × 80 was superimposed on top of the resulting design. A system consisting of a low-power laser diode with an operating wavelength of 650 nm and a plano-convex lens providing the formation of a parallel expanded beam was used as the source of the induced radiation. The formed beam was directed under the normal to the lateral face of the planar waveguide. The generated image was projected onto the back of the observer's retina. To ensure accurate alignment of the focus of the HOE and the pupil of the eye, a system was used to adjust the position of the viewing area relative to the eye using 5 adjustment screws. The attachment of the system to the user's head was carried out through the use of an independently designed and 3D printed eyeglass arch.

Example 1 shows the fundamental feasibility of the proposed device in a compact geometry with a device thickness of 4 mm, due to the alignment of the viewing area with the augmented reality image generation area.

Example 2:

We used a two-dimensional optical waveguide made of a plane-parallel plate made of optically clear glass 4 mm thick. Insert geometry: square with two adjacent beveled ends. With an angle of 45 ° at the base, selected to initiate the illumination radiation with subsequent propagation along the waveguide. A polymer film with an image of a convex lens with a focal length F = 20 mm, recorded for perpendicular polarization orientations of the illumination for wavelengths of 450 nm and 650 nm, was transferred to the surface of the waveguide. The recording was carried out sequentially: first, a lens image was recorded at 450 nm in horizontal polarization of the illumination, then the sample was rotated by 90 ° and the recording was made at a wavelength of 650 nm. A liquid crystal matrix with a polarization filter and a resolution of 64 × 80 was superimposed over the optical waveguide with the deposited holographic film. To create the illumination, two parallel light beams with wavelengths of 450 nm and 650 nm were formed, which were introduced through adjacent faces. The generation of a color image was carried out sequentially by turning on the red and turning off the blue backlight and vice versa. The frequency of the generated image was on the order of 50 Hz, which was sufficient to observe a two-color image.

Thus, example 2 demonstrated the possibility of creating a contrasting color image using the proposed device.

Example 3:

A sample of a multilayer optical element was used as in Example 1. Illumination was performed with an expanded parallel beam with a dynamic change in the angle of the illumination. The angle varied from -30 ° to 30 ° relative to the normal to the surface of the beveled face of the waveguide. As a result, the position of the focusing spot was changed (shifted) along the waveguide surface in the range from -5 mm to 5 mm. That is, the possibility of capturing the working area up to 10 mm inclusive is shown.

Since the average radial size of the retina is about 11 mm, with a blind spot of about 1.5 mm, Example 3 implements imaging within the maximum viewing angle and for various positions (working orientations) of the eye.

In conclusion, the achievement of the technical result was demonstrated - a small thickness of the optical circuit (Examples 1-3), the implementation of multicolor of the generated image (Example 2), the viewing field of the device covers the field of view of the eye, high resolution is achievable through the use of a liquid crystal matrix with high resolution.

Claims (15)

1. An augmented reality device designed to project the generated image onto the back side of the retina of a person through the center of his pupil, which includes an optical circuit equipped with means of attachment to the human head, and a means for introducing radiation into the optical circuit, characterized in that - the optical scheme, geometrically representing a plate with side edges, includes at least one transparent multilayer optical element made of the following adjacent layers: an outer layer made in the form of a stepped planar optical waveguide, an inner layer facing the human eye, formed in the form of a liquid crystal matrix equipped with a polarizing filter, and an intermediate layer placed between the said layers with a dense, excluding the formation of an air gap, adjoining the outer layer, made in the form of a film, which is a holographic optical element, - and the system for introducing radiation includes at least one source of monochromatic radiation, located outside the multilayer optical element, made with the possibility of introducing radiation into the optical waveguide through the lateral edges of the plate of the optical scheme. 2. The device according to claim 1, characterized in that the lateral faces of the optical circuit are provided with a reflective coating and are made inclined at an angle of 30 to 60 ° to the surface of the plate, while the radiation source is placed to ensure that radiation is introduced into the optical waveguide at a normal angle to the surface multilayer optical element with subsequent re-reflection from the side face of the optical circuit. 3. The device according to claim 1, characterized in that a diffraction mask with a period of 100-2000 nm is applied to a part of the surface of the multilayer optical element, and the radiation source is placed so that radiation can be introduced into the optical waveguide through the diffraction mask. 4. The device according to claim 1, characterized in that the lateral edges of the optical scheme are made inclined at an angle of 45-60 ° or rounded with a radius of curvature of 0.1 ... 10 mm, providing focusing by the lateral edge, while the radiation source is placed so that radiation can be introduced into optical waveguide through the specified face. 5. The device according to claim 1, characterized in that the planar optical waveguide is additionally equipped with protective polymer coatings applied to both its surfaces, while the refractive index of the polymer coating is less than the refractive index in the waveguide core. 6. The device according to claim 1, characterized in that the optical circuit includes at least two multilayer optical elements closely adjacent to each other, having different operating wavelengths and / or different operating orientations. 7. The device according to claim 1, characterized in that the holographic optical element has a variable diffraction coefficient of 10-95%, which increases with distance from the region where the radiation is introduced into the multilayer optical element. 8. The device according to claim 1, characterized in that it is provided with means for adjusting the position of the displayed image relative to the human eye. 9. The device according to claim 1, characterized in that it is provided with an eye tracking system installed in the means for attaching the device to the human head. 10. The device according to claim 1, characterized in that the multilayer optical element is made of layers with a total transmittance of at least 50% and has a thickness of not more than 1 mm. 11. The device according to claim 1, characterized in that the liquid crystal matrix is a dynamic monochrome matrix consisting of a layer of liquid crystals controlled by thin-film transistors. 12. A device according to claim 1, characterized in that a frame with bows can be used as a means of attachment to a person's head. 13. A method of manufacturing a holographic optical element intended for use in an augmented reality device according to claim 1, characterized in that the photosensitive film with a thickness of 10 ... 200 μm and an area of at least 1 sq. cm is placed on one of the side faces of a triangular optical prism with a refractive index of the prism material 1.2-1.5, radiation from a coherent source is directed to the specified prism, while part of the radiation, which is a reference beam, is introduced through one side face of the prism, ensuring its complete internal reflections at the boundary of the film with air, and a part of the radiation, which is an object beam, is directed to the outer surface of the film through a recordable optical element by its location in the path of radiation propagation, and then the reference and object beams interfere in the film region, as a result of which a holographic recording is obtained. images of the object in the film.

Images