Device for enlarging the pupil area and display comprising same

Abstract

Provided are a device configured to expand an exit pupil region of a visual optical device and a display including the same, the device including a diffraction grating configured to output a plurality of diffracted beams of a plurality of diffraction orders by diffracting an incident beam, and a waveguide provided on the diffraction grating and configured to form an exit pupil based on first diffracted beams among the plurality of diffracted beams output from the diffraction grating and an exit pupil level based on second diffracted beams among the plurality of diffracted beams output from the diffraction grating.

Description

TECHNICAL FIELD

[0001] Example embodiments of the present disclosure relate to an optical device for enlarging an eye box of a visual optical device and a display including the same. BACKGROUND

[0002] Lenses of visual optical devices such as augmented reality (AR) devices, eyepieces, and optical devices (microscopes, telescopes, sights, etc.) have been significantly improved. The most important characteristic parameters of such visual optical devices are the size of a field of view (FoV) and the size of an eye box. According to an analysis of the prior art, it is difficult to impart a wide field of view (e.g., about 60° or more) and a large eye box (e.g., about 3 mm or more) to a visual optical device while guaranteeing a required image quality or resolution (e.g., a resolution equal to about 1 arcmin, not greater than the angular resolution limit of the eye). Known devices for enlarging an eye box are not universal due to the use of complex elements therein. However, an eye box enlarging device needs to be designed individually for each visual optical device.

[0003] In the prior art, an exit pupil expander can include a waveguide in which light (radiation) can be incident on and can propagate in the waveguide while being output from the waveguide through a diffractive element. The above-described exit pupil expander can enlarge a field of view without using a material having a high refractive index. However, the field of view enlarged by the exit pupil expander has a relatively small width (the horizontal dimension of the field of view is limited), and the exit pupil expander has a complex structure with a large overall size. In addition, since light propagates a large distance in the waveguide of such an exit pupil expander, significant energy loss occurs. Furthermore, since various diffractive elements are used in such an exit pupil expander to receive and output light, the diffraction efficiency, uniformity, and brightness of the resulting image can be limited.

[0004] A substrate-guided beam expander of the prior art can be a waveguide device configured to provide light within a field of view by using a semi-transparent mirror. The size of the exit pupil is related to the geometric parameters of the expander, specifically, to the thickness of the waveguide and the number of mirror elements. A disadvantage of such an expander is that the waveguide has a significant thickness, and thus the expander has a significantly increased size and a complex design. In addition, even when such an expander is used, a sufficient field of view cannot be obtained. SUMMARY

[0005] One or more example embodiments provide a device capable of enlarging an eye box to provide a wide exit pupil area while maintaining a wide field of view, high diffraction efficiency, and image uniformity and brightness of a visual optical device.

[0006] One or more example embodiments also provide a small and versatile device for expanding an exit pupil area with reduced energy loss of incident light.

[0007] One or more example embodiments also provide a device for expanding an exit pupil area applicable to various visual optical devices.

[0008] Additional aspects will be set forth in part in the description which follows, and, in part, will be apparent from the description, or can be learned by practice of example embodiments.

[0009] According to an aspect of an example embodiment, there is provided a device configured to expand an exit pupil area of a visual optical device, the device including: a diffraction grating configured to output a plurality of diffracted light beams of a plurality of diffraction orders by diffracting an incident light beam; and a waveguide provided on the diffraction grating, the waveguide configured to form an exit pupil based on a first diffracted light beam among the plurality of diffracted light beams output from the diffraction grating and an exit pupil order based on a second diffracted light beam among the plurality of diffracted light beams output from the diffraction grating.

[0010] The waveguide can be further configured to form the exit pupil based on outputting the first diffracted light beam output from the diffraction grating without total internal reflection.

[0011] The waveguide can be further configured to form at least one exit pupil order based on the second diffracted light beam output from the diffraction grating, the second diffracted light beam being totally internally reflected at least once and output from the waveguide.

[0012] The waveguide can be further configured to return the second diffracted light beam to the diffraction grating by totally internally reflecting the second diffracted light beam, the diffraction grating can be further configured to diffract the returned second diffracted light beam into a plurality of diffracted light beams, and the waveguide can be further configured to form the exit pupil order based on outputting some of the plurality of diffracted light beams obtained by diffracting the returned second diffracted light beam and reflecting the remaining diffracted light beams of the plurality of diffracted light beams, which are not output, back to the diffraction grating.

[0013] The waveguide can include a first surface on which the diffraction grating is provided and a second surface opposite the first surface and configured to output the first diffracted light beam to an outside of the waveguide.

[0014] The waveguide can be further configured to additionally form the exit pupil order until all of the diffracted light beams incident on the second surface are totally internally reflected.

[0015] A number of the exit pupil orders can be proportional to a number of times that the diffracted light beams of the plurality of diffracted light beams incident on the second surface pass through the second surface.

[0016] A distance between the exit pupil orders can be proportional to a thickness of the waveguide.

[0017] The distance between the exit pupil stages can be inversely proportional to the refractive index of the waveguide.

[0018] The first diffracted beams can include 0th order diffracted beams, and the second diffracted beams can include at least one of +1st order diffracted beams and -1st order diffracted beams.

[0019] The waveguide can be further configured to form the first exit pupil stage based on the +1st order diffracted beams and form the second exit pupil stage based on the -1st order diffracted beams.

[0020] The waveguide can be further configured to form the first exit pupil stage and the second exit pupil stage in different directions with respect to an exit pupil provided between the first exit pupil stage and the second exit pupil stage.

[0021] The diffraction grating can be further configured to diffract light beams incident at a predetermined aperture angle or less.

[0022] The aperture angle can be greater than a visual angle of the visual optical device.

[0023] The waveguide can be a first waveguide, and the device can further include a second waveguide provided on the diffraction grating and configured to totally internally reflect light output from the diffraction grating.

[0024] The diffraction grating can be provided between the first waveguide and the second waveguide.

[0025] The diffraction grating can include a first diffraction region configured to diffract light beams incident within a range of a first aperture angle or less, and a second diffraction region configured to diffract light beams incident within a range greater than the first aperture angle but less than or equal to a second aperture angle, wherein the waveguide further includes a first waveguide configured to form an exit pupil stage based on diffracted beams output from the first diffraction region, and a second waveguide configured to form an exit pupil stage based on diffracted beams output from the second diffraction region.

[0026] The diffraction grating, the first waveguide, and the second waveguide can be sequentially provided in a propagation direction of the incident light beams.

[0027] The waveguide can include a curved waveguide.

[0028] The diffraction grating can include a Bragg diffraction grating.

[0029] According to another aspect of an example embodiment, there is provided a display comprising a visual optical device configured to output a light beam having a given angle of view and a device configured to expand an exit pupil area of the visual optical device, the device comprising: a diffraction grating configured to output a plurality of diffracted light beams of a plurality of diffraction orders by diffracting an incident light beam; and a waveguide provided on the diffraction grating, the waveguide being configured to form an exit pupil based on a first diffracted light beam among the plurality of diffracted light beams being output from the diffraction grating and to form an exit pupil order based on a second diffracted light beam among the plurality of diffracted light beams being output from the diffraction grating and being totally internally reflected at least once in the waveguide.

[0030] The display can be a near-eye display.

[0031] According to another aspect of an example embodiment, there is provided a device for expanding an exit pupil area of a visual optical device, the device comprising: a diffraction grating configured to output a plurality of diffracted light beams of a plurality of diffraction orders by diffracting an incident light beam; and a waveguide provided on the diffraction grating, the waveguide being configured to form an exit pupil based on a first diffracted light beam among the plurality of diffracted light beams being output from the diffraction grating without total internal reflection and to form at least one exit pupil order based on a second diffracted light beam among the plurality of diffracted light beams being output from the diffraction grating and being totally internally reflected at least once in the waveguide.

[0032] The first diffracted light beam can be a 0thorder diffracted light beam output from the diffraction grating and the second diffracted light beam can be a +1storder or -1storder diffracted light beam output from the diffraction grating, which is totally internally reflected in the waveguide and diffracted by the diffraction grating as a 0thorder light beam. BRIEF DESCRIPTION OF DRAWINGS

[0033] The above and / or other aspects, features and advantages of certain example embodiments will be more apparent from the following description taken in conjunction with the following drawings, in which:

[0034] Figure 1 A telecentric ray path is shown in an object space;

[0035] Figure 2A An exit pupil expander for expanding an eyebox is shown according to an example embodiment;

[0036] Figure 2B Propagation of light in an exit pupil expander for expanding an eyebox is shown according to an example embodiment;

[0037] Figure 2C An exit pupil expander for use with a visual optical device is shown according to an example embodiment;

[0038] Figure 2D An exit pupil expander operating in a reflection mode is shown according to an example embodiment;

[0039] Figure 3 is a perspective view showing a display using an exit pupil expander according to an example embodiment;

[0040] Figure 4A shows a combination device operating in a transmissive mode according to an example embodiment and an exit pupil expander;

[0041] Figure 4B shows a relationship between a combination device operating in a reflective mode according to an example embodiment and an exit pupil expander;

[0042] Figure 5 is a view schematically showing an exit pupil expander including a one-dimensional diffraction grating according to an example embodiment;

[0043] Figure 6 is a view schematically showing an exit pupil expander including a two-dimensional diffraction grating according to an example embodiment;

[0044] Figure 7 shows an exit pupil expander according to another example embodiment;

[0045] Figure 8A shows an eyebox including a plurality of exit pupil stages distributed discretely;

[0046] Figure 8B shows an exit pupil stage formed by an exit pupil expander according to an example embodiment;

[0047] Figure 9 shows a flat exit pupil expander forming a spot according to an example embodiment;

[0048] Figure 10 shows a curved exit pupil expander according to an example embodiment; and

[0049] Figure 11 shows an exit pupil expander including a plurality of waveguides according to another example embodiment. DETAILED DESCRIPTION

[0050] Reference will now be made in detail to the example embodiments, which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. The example embodiments can have different forms and should not be construed as being limited to the description set forth herein. Accordingly, the example embodiments are described below by referring to the drawings, to explain aspects. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. Expressions such as "at least one of," when preceding the term "comprising," "including," "containing," "characterized by," or "comprised of," "including," "containing," "characterized by," or "comprised of," modifies the term following it and does not modify the phrase following it. For example, the expression "at least one of a, b, and c" should be understood as including only a, only b, only c, both a and b, both a and c, both b and c, or all of a, b, and c.

[0051] Hereinafter, example embodiments will be described with reference to the accompanying drawings. The example embodiments described herein are merely for the purpose of illustration and various modifications can be made thereto. In the drawings, like reference numerals refer to like elements throughout, and the size of elements can be exaggerated for the purpose of illustration.

[0052] In the following description, when an element is referred to as "on" another element, it can be directly on the other element while being in contact with the other element, or can be above the other element without being in contact with the other element.

[0053] Although the terms "first" and "second" are used to describe various elements, the terms are used only to distinguish one element from another element. The terms do not limit the elements to having different materials or structures.

[0054] Unless otherwise mentioned, the singular forms "a," "an," and "the" can include plural forms. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0055] An element mentioned with a definite article or a demonstrative pronoun can be interpreted as the element or elements, even if it has a singular form.

[0056] Unless explicitly described in an order or contrary, the operations of the method can be performed in a suitable order. In addition, example or exemplary terms such as "such as" and "etc." are used for the purpose of description and are not intended to limit the scope of the inventive concept unless limited by the claims.

[0057] According to the example embodiments, a small device that expands an eye movement range (also referred to as "exit pupil area") by using a waveguide and a diffraction grating for receiving or outputting light, such as a diffractive optical element (DOE) or a holographic optical element (HOE), can be provided.

[0058] The device according to the example embodiment can be used to expand an eyebox of a visual optical device such as an eyepiece of an optical device. The eyepiece of an optical device is an element configured to face an eye of a viewer and can be a part of an optical device such as a viewfinder, a range finder, a binocular, a microscope, or a telescope designed for a viewer to view an image formed by a lens or a primary mirror of the optical device.

[0059] The device for expanding an eyebox according to the example embodiment can be applied to an augmented reality (AR) device provided with an image combining device that combines an environmental image with an image formed by using an internal display of a visual optical device or a HOE / DOE.

[0060] The device for expanding an eyebox according to the example embodiment (hereinafter referred to as an "exit pupil expander") can be compact and versatile. Here, compactness and versatility are determined only by a diffraction grating as an element for receiving and outputting light, and a waveguide used in the proposed device does not need to be a high-quality waveguide.

[0061] The exit pupil expander according to an example embodiment can have a small overall size. That is, the device according to the example embodiment can not change the overall size of a visual optical device and thus can be used for various optical devices.

[0062] The exit pupil of a visual optical device is an area for a viewer to view an image. In other words, the exit pupil is a paraxial image of an aperture stop in an image space, and the paraxial image can be formed by a next part of the visual optical device in a direct course of a light ray. These terms are well recognized in the field of optics. The main feature of the exit pupil of a visual optical device is that the entire image field is at a certain point in the visual optical device.

[0063] Increasing (expanding) the exit pupil of a visual optical device can include increasing the size (or the number) of the exit pupil without increasing the longitudinal size of the visual optical device. The size of the exit pupil of a classical optical system can be increased, but in this case, the longitudinal size of the visual optical device can also be increased. The use of a waveguide optical system in a visual optical device makes it possible to increase the size of the exit pupil of the visual optical device without increasing the size of the visual optical device.

[0064] The eyebox can be an area into which a pupil of a human eye can enter when the eye pupil moves, and can be an exit pupil area including the exit pupil.

[0065] The field of view can refer to an angular space that the eye can see in the case where the pupil and the head are fixed. When the field of view is large, the eye can see most of the object space. However, when the pupil of the eye moves, for example, several millimeters to the side, the field of view can be blocked to some extent, and the field of view can decrease. This is because the eye movement range of the visual optical device is small, so that when the pupil of the eye moves, the eye movement range cannot perfectly match the pupil of the eye or can not match the pupil of the eye at all.

[0066] The diffraction efficiency can be a characteristic of the diffraction grating and can be measured in percentage or decimal fraction as a ratio of energy contained in one of the diffraction orders to energy incident on the diffraction grating.

[0067] Figure 1 A telecentric ray path in the object space is shown. As shown in Figure 1 The light beam output from the ordinary visual optical device 100 can form an exit pupil.

[0068] The size of the field of view FoV of the visual optical device 100 can be determined according to Equation 1 below.

[0069] [Equation 1]

[0070]

[0071] Here, S refers to the size of the object (unit: mm), F refers to the focal length of the lens included in the visual optical device 100 (unit: mm), and FoV refers to the size of the field of view (unit: degree).

[0072] The size E of the exit pupil of the visual optical device 100 can be determined by Equation 2 below.

[0073] [Equation 2]

[0074]

[0075] Here, E refers to the size of the exit pupil (mm), Le refers to the exit pupil distance (eye-relief distance) from the visual optical device 100 to the pupil 1a of the eye 1 (mm), and D refers to the diameter of the transparent lens included in the visual optical device 100 (mm).

[0076] As shown in Equation 1 and Equation 2, when the exit pupil expander according to an example embodiment is not applied to the visual optical device 100, the size E of the exit pupil can not be limited by the field of view FoV, and the field of view FoV can be limited by the focal length F of the visual optical device 100 and the size S of the object. The larger the area of the object space (e.g., an object) that a user wants to view, the larger the field of view FoV. However, as devices such as AR glasses become smaller, the focal length F of the lens included in the visual optical device 100 needs to be smaller.

[0077] According to Equation 1 and Equation 2, there is generally an inverse relationship between the size of the field of view FoV and the size E of the exit pupil. In the visual optical device 100, it is difficult to increase both the size of the field of view FoV and the size E of the exit pupil without using additional elements. The device for expanding the eyebox according to an example embodiment is more versatile and compact.

[0078] Figure 2A An exit pupil expander 200 for expanding the eyebox according to an example embodiment is shown. As shown, the exit pupil expander 200 can include a waveguide 230 and a diffraction grating 210. When the exit pupil expander 200 uses the diffraction grating 210, there are only diffraction orders in the waveguide 230, and there are no diffraction orders in free space. Figure 2A

[0079] The diffraction grating 210 can be designed according to a specific incidence angle of light incident on the diffraction grating 210. The incidence angle can be determined by the aperture angle of the visual optical device 100 (i.e., the viewing angle of the visual optical device 100). For example, light is output from the visual optical device 100 at a specific angle with respect to the optical axis, and can be incident on the diffraction grating 210 at the same angle as the specific angle.

[0080] The diffraction grating 210 of the exit pupil expander 200 can be designed so that light incident on the diffraction grating 210 can be diffracted into three diffraction orders "0", "+1", and "-1". The diffraction orders can propagate into the waveguide 230.

[0081] The period of the diffraction grating 210 satisfying the above conditions is shown in Equation 3 below.

[0082] [Equation 3]

[0083]

[0084] Here, n1 refers to the refractive index of the medium in front of the exit pupil expander 200, for example, the refractive index of air, n2 refers to the refractive index of the waveguide 230, M refers to the number of diffraction orders, and d refers to the grating period.

[0085] ​Further, θ refers to the angle of incidence of light, that is, θ1 refers to the angle of incidence of light from air into the diffraction grating 210, and θ2 refers to a diffraction angle representing the angle at which the Mth order diffracted beam travels into the waveguide 230 from the diffraction grating 210.

[0086] Further, λ refers to the wavelength of light incident on the diffraction grating 210, and T refers to the frequency of the diffraction grating 210, which can be represented by the reciprocal of the grating period, i.e., T = 1 / d. When d is given in millimeters (mm), T can be given in dashes / mm.

[0087] The diffraction grating 210 can be designed to expand the eyebox according to Equation 3. The parameters of the diffraction grating 210 can be determined according to the specific operation to be performed by the diffraction grating 210. The parameters of the diffraction grating 210 can include the period of the diffraction grating 210, which is constant or variable, the relief depth, the profile type (stroke), the stroke direction, etc. According to an example embodiment, the specific operation to be performed by the diffraction grating 210 is to expand the eyebox.

[0088] The parameters of the diffraction grating 210 can vary according to the angle of incidence of the light beams incident on the diffraction grating 210 from the visual optics device 100, the material of the waveguide 230 on which the diffraction grating 210 is disposed, and the target size of the eyebox.

[0089] The operation of the diffraction grating 210 can be determined as follows.

[0090] When the diffraction grating 210 is in the hologram recording mode, the operation of the diffraction grating 210 can be determined by the ratio of the spatial arrangement of the recording sources to the radiant power of the recording sources.

[0091] When the diffraction grating 210 is in the photolithography recording mode, the operation of the diffraction grating 210 can be determined by the structure of the diffraction grating 210 determined by modeling and calculation.

[0092] According to preliminary theory and computer modeling, it can be proven that when the parameters of the diffraction grating 210 and the parameters of the waveguide 230 match each other, the combination of these parameters can act to expand the eyebox.

[0093] That is, in the exit pupil expander 200, the parameters of the diffraction grating 210 can be designed to produce only three diffraction orders "0", "+1", and "-1". The light diffracted into diffraction orders other than "0" can be reflected at least once by the surface of the waveguide 230 under the condition of total internal reflection (TIR) and can propagate in the waveguide 230. The 0th order diffracted beam ("0" order diffracted light) can be refracted at the interface between the waveguide 230 and air and output from the exit pupil expander 200 without total internal reflection.

[0094] A key element of the exit pupil expander 200 can be a waveguide 230, which can allow incident light to propagate in a waveguide mode. The waveguide mode can refer to a mode in which "+1" and "-1" order diffracted beams are incident on an interface between the waveguide 230 and air at an angle equal to or greater than a total reflection angle for total reflection. There is a relationship between parameters of the waveguide 230 and operation of the waveguide 230.

[0095] In an example embodiment, the waveguide 230 can have a small thickness so that light output from the waveguide 230 can be uniform, and in this case, the light can be uniform at an eyebox as an enlarged exit pupil area. For example, the thickness of the waveguide 230 can be about 3 mm or less.

[0096] Accordingly, the parameters of the waveguide 230 and the parameters of the diffraction grating 210 can be matched to each other to obtain characteristics for enlarging the exit pupil area.

[0097] The diffraction grating 210 can be manufactured by a method well known in the art. For example, a relief diffraction grating can be manufactured as the diffraction grating 210 using a mask or a nanoimprint method, or a holographic diffraction grating can be manufactured as the diffraction grating 210 by an interference pattern recording method.

[0098] The diffraction grating 210 obtained by such a manufacturing or recording method can be applied to a planar and non-planar waveguide. In general, the diffraction grating 210 can be applied to the waveguide 230 when the exit pupil expander 200 is manufactured. The parameters of the diffraction grating 210 can be matched to the parameters of the waveguide 230 during the manufacturing process to increase light incident on the exit pupil expander 200 without changing characteristics of the light rays.

[0099] The diffraction grating 210 can be formed on the waveguide 230 by using a substrate coated with a photosensitive material. For example, the substrate can be mainly used as the waveguide 230, and the diffraction grating 210 having a material and thickness for enlarging the eyebox can be formed on the substrate. The parameters of the substrate can be matched to the parameters of the diffraction grating 210.

[0100] The diffraction grating 210 of a thin film type can be formed by forming a diffraction grating on a photoresist material, and then copying and transferring the diffraction grating to a photosensitive polymer. The diffraction grating 210 of a thin film type can be applied to the waveguide 230. In this case, the parameters of the waveguide 230 and the parameters of the diffraction grating 210 can be matched to each other as described above to enlarge the eyebox.

[0101] When the pupil expander 200 is manufactured, the pupil expander 200 can be designed according to a specific incident angle determined by an aperture angle of the visual optical device 100. Even when the aperture angle of the visual optical device 100 is not equal to the aperture angle of the pupil expander 200, the pupil expander 200 can be integrated into the visual optical device 100 and can operate more precisely on the condition that the aperture angle of the visual optical device 100 is equal to or smaller than the aperture angle of the pupil expander 200. This means that the pupil expander 200 for expanding an eyebox according to an example embodiment has versatility. For example, the pupil expander 200 can have an angle range for precise operation, and the angle range can be determined by an exit aperture angle of the visual optical device 100.

[0102] For example, the pupil expander 200 can be designed for a visual optical device 100 having an aperture angle of about 60° (i.e., a viewing angle of about 60°). In this case, the pupil expander 200 can even be used for a visual optical device having an aperture angle of less than about 60° (e.g., about 40°). However, the pupil expander 200 having an aperture angle of about 60° can not function abnormally for a visual optical device having an aperture angle (viewing angle) greater than about 60°. For example, the pupil expander 200 having an aperture angle of about 60° can not be used for a visual optical device 100 having an aperture angle greater than about 60°.

[0103] Figure 2B propagation of light in the pupil expander 200 for expanding an eyebox according to an example embodiment is shown, Figure 2C A pupil expander 200 for use with a visual optical device 100 according to an example embodiment is shown.

[0104] Referring to Figure 2B and Figure 2C A light beam output from the visual optical device 100 to the diffraction grating 210 can travel in three directions, for example, can be diffracted into three diffraction orders. That is, "0", "+1", and "-1" order diffracted light beams can propagate in the waveguide 230 toward the second surface 234 of the waveguide 230 opposite to the first surface 232 of the waveguide 230 on which the diffraction grating 210 is formed. In Figure 2B and Figure 2C Narrow parallel light beams (a) and (b) and narrow parallel light beams α and β incident on the diffraction grating 210 are shown in

[0105] The "0" order diffracted light beam incident on the second surface 234 of the waveguide 230 can pass through the second surface 234 and completely exit the waveguide 230 without being totally reflected, because the "0" order diffracted light beam does not satisfy the total internal reflection (TIR) condition. The "0" order diffracted light rays from the parallel light beams α and β can be as Figure 2CAs shown, all of these are collected at the pupil of eye 1, and can be... Figure 2C As shown, the exit pupil 7 is formed within the eye movement range B.

[0106] The +1 and -1 order diffracted beams incident on the second surface 234 of waveguide 230 can be totally internally reflected back to diffraction grating 210 via the interior of waveguide 230 because the +1 and -1 order diffracted beams satisfy the total internal reflection condition. When diffracted by diffraction grating 210 and / or totally reflected by the second surface 234, the +1 and -1 order diffracted beams can be deflected by a specific angle. The +1 and -1 order diffracted beams can then be incident on diffraction grating 210 again at the deflected angle.

[0107] Each of the "+1" and "-1" order diffracted beams can be further divided into multiple diffracting orders by the diffraction grating 210. Since the diffraction grating 210 divides the incident beam into three diffracting orders as described above, each of the "+1" and "-1" order diffracted beams can be further diffracted by the diffraction grating 210 into diffracting orders "0", "+1" and "-1".

[0108] The "0" order diffracted beam in the secondary diffracted beam can leave the waveguide 230, and the "+1" and "-1" order diffracted beams in the secondary diffracted beam can propagate in the waveguide 230 after being deflected at a specific angle.

[0109] The +1 and -1 order diffracted beams can be incident on the diffraction grating 210 again at a deflected angle. Then, according to the characteristics of the diffraction grating 210, the +1 and -1 order diffracted beams can be diffracted by the diffraction grating 210. The diffraction grating 210 can repeatedly diffract the incident beam until the beam is incident at a specific angle or greater, and the waveguide 230 can output the beam incident at an angle less than the specific angle and can totally reflect the beam incident at an angle equal to or greater than that specific angle.

[0110] For example, a +1 order diffracted beam from diffraction grating 210 is totally reflected back to diffraction grating 210 by the second surface 234 of waveguide 230. Each of the +1 order diffracted beams is diffracted by diffraction grating 210 into diffraction orders "0", "+1", and "-1", and then the "0" order diffracted beam can be output from waveguide 230 because the "0" order diffracted beam does not satisfy the total internal reflection condition of the second surface 234 of waveguide 230. The light output from waveguide 230 can form a first exit pupil order 8a, which can be an exit pupil formed by light diffracted at least twice by diffraction grating 210 and then output from waveguide 230.

[0111] The +1 and -1 order diffracted beams reflected by the second surface 234 of waveguide 230 are again incident on diffraction grating 210 and diffracted a third time. The 0th order diffracted beam in the third diffracted beam passes through the second surface 234 of waveguide 230 and can form an additional exit pupil order. The additional exit pupil order can be formed in a region adjacent to the first exit pupil order 8a in a direction away from the exit pupil 7.

[0112] Similar to a +1st order diffracted beam, a portion of a -1st order diffracted beam can form a second exit pupil order 8b after repeatedly undergoing total internal reflection, diffraction, refraction, and transmission. The second exit pupil order 8b can be formed at a position relative to the first exit pupil order 8a, based on the exit pupil 7.

[0113] The remaining portion of the -1st order diffracted beam can form additional exit pupil orders after repeated total internal reflection, diffraction, refraction, and transmission. These additional exit pupil orders formed by the remaining portion of the -1st order diffracted beam can be formed in a region adjacent to the second exit pupil order 8b in a direction away from exit pupil 7. The formation of these additional exit pupil orders can increase the number of second exit pupil orders 8b. The number of exit pupil orders can be proportional to the number of times the diffracted beam incident on the second surface 234 passes through the second surface 234.

[0114] Furthermore, due to the nature of the propagation mode of waveguide 230, optical interactions may occur between diffraction grating 210 and waveguide 230, so the light output from waveguide 230 can correctly correspond to the incident light. For example, the waveform of the light at the exit end of exit pupil expander 200 can be the same as the waveform of the light at the entrance end of exit pupil expander 200.

[0115] like Figure 3 As shown, eye movement range B (represented by circles for clarity) may include exit pupil 7 and multiple exit pupil levels 8 (see reference). Figure 2B The plurality of exit pupil levels 8 includes exit pupil level 8a and exit pupil level 8b. The number of exit pupil levels 8 can vary according to the needs of the visual optics device 100.

[0116] The number of exit pupil levels 8 can be selected based on the number of exit pupils 7 obtained by using the visual optics device 100 without the exit pupil expander 200 and the number of exit pupils 7 required for the proper operation of the visual optics device 100.

[0117] The number of exit pupil levels 8 required to expand the eye-tracking range B can be determined by changing the parameters of the diffraction grating 210 and the waveguide 230 (e.g., the parameters used to expand the eye-tracking range B).

[0118] The number of exit pupil levels 8 corresponding to the degree of increase of the exit pupil level 8 can be controlled by the thickness of the waveguide 230 and the diffraction angle. For example, the number of exit pupil levels 8 can increase as the thickness of the waveguide 230 decreases and the diffraction angle decreases. The distance between the exit pupil levels 8 can be determined by the thickness and the material of the waveguide 230. For example, the distance between the exit pupil levels 8 can decrease as the thickness of the waveguide 230 decreases and can increase as the refractive index of the waveguide 230 increases. The emission intensity of each exit pupil level 8 for expanding the eyebox B can depend on the diffraction intensity of the diffraction grating 210. For example, the emission intensity of each exit pupil level 8 can be proportional to the diffraction intensity of the diffraction grating 210. When properly designed for expanding the eyebox B, the exit pupil expander 200 can form a predetermined number of exit pupil levels 8. Thus, the degree of expansion can be controlled in the process of manufacturing the exit pupil expander 200.

[0119] The material of the waveguide 230 included in the exit pupil expander 200 can include, for example, optical colorless glass, and the refractive index of the waveguide 230 can be selected according to the number of exit pupil levels 8 required. For example, the higher the refractive index of the waveguide 230 formed of, for example, flint glass, the greater the angle of total internal reflection in the waveguide 230, so that the exit pupil levels 8 can be disposed farther apart from each other. In addition, the smaller the refractive index of the waveguide 230 formed of, for example, crown glass, the smaller the angle of total internal reflection in the waveguide 230, so that the exit pupil levels 8 can be disposed closer to each other.

[0120] The above-described light propagation principle can be observed from each narrow light beam incident on the exit pupil expander 200, for example, the first parallel light beam (a) and the second parallel light beam (b) in Figure 2C and α and β in Figure 2C .

[0121] The exit pupil expander 200 can be insensitive to the distance from the visual optical device 100, such as the offset distance var as shown in Figure 2C . The offset distance var can not affect the incidence angle of light traveling from the visual optical device 100 onto the exit pupil expander 200 configured to expand the eyebox B. For example, the incidence angle of light onto the exit pupil expander 200 depends on the exit angle of light from the visual optical device 100. The visual optical device 100 integrated with the exit pupil expander 200 can form an image from the best viewing distance to infinity.

[0122] The degree of rotation about the optical axis 9 does not affect the incidence angle onto the diffraction grating 210. The parameters of the exit pupil expander 200 are designed according to the incidence angle onto the exit pupil expander 200 determined by the visual optical device 100, and the incidence angle onto the exit pupil expander 200 is sufficient within the aperture angle of the visual optical device 100, for example, within the viewing angle of the visual optical device 100.

[0123] Generally, the eyebox B can be enlarged, increased, and / or repeated as shown. Figure 2C An image of an object can be formed by the vision optical device 100, such as an AR device, a microscope eyepiece, a telescope, or a scope, and then can be transmitted to the eye 1 in which the image is formed on the retina. For example, light reflected from an object passes through the vision optical device 100 and enters the pupil 1a in which the light is focused on the retina 1.

[0124] To enlarge the eyebox B output from the vision optical device 100, the exit pupil expander 200 can be disposed along a path of the light on an exit side of the vision optical device 100, and the exit pupil expander 200 can split the light beam into at least two light beams that can each form an exit pupil 7 and an exit pupil stage 8. Thus, the exit pupil 7 output from the vision optical device 100 can be increased (enlarged) to form the eyebox B.

[0125] The exit pupil expander 200 can be used with an optical device configured to form an image in a range from an optimal viewing distance to infinity, such as the vision optical device 100.

[0126] In the waveguide mode, a loss of light propagating in the waveguide 230 can be very small. Thus, in an example embodiment, since the exit pupil expander 200 includes the diffractive grating 210 for receiving and outputting light and the waveguide 230 used in the waveguide mode, the exit pupil expander 200 can result in substantially no loss of light. For example, all of the light output from the vision optical device 100 can be in the form of the exit pupil stage 8 forming the eyebox B.

[0127] Further, since the eye 1 is an optical receiver, the vision optical device 100 can emit parallel light. The parallel light entering the eye 1 is focused by the lens of the eye 1, which can be a converging lens, and thus the user can clearly see the object. When non-parallel light is output from the vision optical device 100, the image formed on the retina of the eye 1 can be blurred. The image can be formed before or after the retina, not on the retina. The light output from the vision optical device 100 in the form of parallel light can be in the form of parallel light even after passing through the exit pupil expander 200 provided according to an example embodiment.

[0128] The exit pupil expander 200 can be applied to the vision optical device 100 using single-spectrum light and multi-spectrum light to form a color image. The reason is that the diffractive grating 210 is used to input and output light to and from the waveguide 230, and the waveguide 230 satisfies the waveguide mode. Thus, the light beam incident on the exit pupil expander 200 can be output from the exit pupil expander 200 as a plurality of light beams without a change in its optical characteristics, and the exit pupil 7 and the plurality of exit pupil stages 8 can be formed by the plurality of light beams.

[0129] Exit pupil dilator 200 can be like Figure 2D The diagram shows operation in transmission mode, but it is not limited to this. For example, the exit pupil dilator 200 can also operate in reflection mode.

[0130] Figure 2D An exit pupil expander 200 operating in reflection mode according to an example embodiment is shown.

[0131] like Figure 2C As shown, a light beam (e.g., a parallel beam) from the visual optics device 100 can be incident on a second surface 234 of the waveguide 230, which corresponds to a first surface 232 of the waveguide 230 on which a reflection diffraction grating 210 is formed.

[0132] A parallel beam can be refracted in waveguide 230 and incident obliquely on reflection diffraction grating 210.

[0133] A parallel beam can be diffracted into three diffraction orders “0”, “+1” and “-1” by the reflective diffraction grating 210, and then propagated in three directions in the waveguide 230.

[0134] A zero-order diffracted beam (e.g., a portion of a parallel beam diffracted once) propagating in waveguide 230 and incident on the second surface 234 does not satisfy the total internal reflection condition and can therefore be output from waveguide 230 through the second surface 234 without being totally reflected by the second surface 234.

[0135] The "0" order diffracted beam can be collected in a portion of the pupil region of eye 1 and can form exit pupil 7 in eye movement range B, similar to the operation in transmission mode.

[0136] The +1 and -1 order diffracted beams satisfy the total internal reflection condition of the second surface 234, and therefore can be totally reflected by the second surface 234 and propagate in the waveguide 230, as described in the description of the exit pupil expander 200 operating in transmission mode.

[0137] The +1 and -1 order diffracted beams are again incident on the reflective diffraction grating 210, and each of the +1 and -1 order diffracted beams is diffracted into diffraction orders +1, 0, and -1. The 0 order diffracted beam, as a secondary diffracted beam, is output from the waveguide 230 through the second surface 234 and forms the exit pupil order 8, while the other beams propagate again in the waveguide 230.

[0138] A beam propagating in waveguide 230 can be repeatedly diffracted, transmitted, totally reflected and refracted until the beam is incident on the reflective diffraction grating 210 at an incident angle at which the beam is not diffracted by the reflective diffraction grating 210, and then the beam can additionally form an exit pupil order 8.

[0139] Similarly to the operation of the pupil expander 200 in the transmission mode, the eyebox B formed by the pupil expander 200 operated in the reflection mode is formed by the exit pupil 7 and a set of pupil stages 8. As mentioned above, the number of stages of the exit pupil 7 can be arbitrary. For example, the number of stages of the exit pupil 7 can be equal to the number required by the visual optical system to which the pupil expander 200 is applied, and the degree of increase of the pupil stages 8 can be determined by the parameters of the pupil expander 200, for example, the parameters of the reflective diffraction grating 210 and the parameters of the waveguide 230.

[0140] As mentioned above, the principle of propagation of light in the pupil expander 200 in which the reflective diffraction grating 210 is used for expanding the eyebox B is similar to the principle of propagation of light in the pupil expander 200 in which the transmissive diffraction grating 210 is used. The difference is the orientation of the pupil expander 200 relative to the optical axis.

[0141] In the case where the pupil expander 200 is operated in the transmission mode, light can first propagate through the transmissive diffraction grating 210, and the eyebox B can be formed behind the pupil expander 200 as shown in Figure 2D In the case where the pupil expander 200 is operated in the reflection mode, light can first be incident on the waveguide 230 and can be refracted in the waveguide 230, and then can be incident on the reflective diffraction grating 210. The eyebox B can be formed in front of the pupil expander 200 as shown in Figure 3 In the case where the pupil expander 200 is operated in the reflection mode, light can first be incident on the waveguide 230 and can be refracted in the waveguide 230, and then can be incident on the reflective diffraction grating 210. The eyebox B can be formed in front of the pupil expander 200 as shown in

[0142] The field of view of the visual optical system of the visual optical device 100 in which the pupil expander 200 is applied is measured together with the field of view of the visual optical system of the visual optical device 100 in which the pupil expander 200 is not applied. As a result of the measurement, the field of view of the visual optical system to which the pupil expander 200 is applied is equal to or greater than about 5 times the field of view of the visual optical system without the pupil expander 200.

[0143] In addition, since light propagates in the waveguide 230 of the pupil expander 200 for a relatively short distance, loss of light energy can be reduced.

[0144] The high diffraction efficiency of the pupil expander 200 allows light to uniformly fill in the eyebox B.

[0145] Figure 3 is a perspective view showing a display using the pupil expander 200 according to an example embodiment. Figure 1 The display shown can be an AR device of the near-eye display type.

[0146] Light emitted from an image source F (e.g., an internal display) can enter a combining device 300, which combines an environmental image with an image formed by the image source F. The combining device 300 can correspond to a reference. Figure 2B , Figure 3 The visual optical device 100 is described above. The combination device 300 can redirect light to the exit pupil expander 200 to form the size of the AR field of view and expand the eye movement range B.

[0147] The exit pupil expander 200 can increase the eye movement range B of the AR device as described above. From various regions of the exit pupil expander 200 (e.g.) Figure 4A The light output from (a), (b), (c), and (d) can be redirected to eye 1 at various angles. The light output from the exit pupil expander 200 can completely and uniformly fill the eye movement range B, including exit pupil 7 and exit pupil level 8. This is because light propagates from the AR device through the exit pupil expander 200. In this case, the exit pupil expander 200 for the AR device can use a two-dimensional diffraction grating 210, and the eye movement range B can be two-dimensional. For example, the eye movement range B can extend in the same plane in two directions perpendicular to each other.

[0148] When the combination device 300 includes holographic optical elements, the combination device 300 may have a small eye movement range B. To increase the eye movement range B of the combination device 300, an exit pupil dilator 200 according to an example embodiment can be used.

[0149] Figure 4A The diagram shows a combination device 300 and an exit pupil dilator 200 operating in transmission mode according to an example embodiment. Figure 4B The combined device 300 and exit pupil expander 200 shown can be integrated into an AR device that serves as a display. The AR device can be glasses-type. The combined device 300 can be a holographic optical element. The image can be formed behind the combined device 300, that is, on the side opposite to the illuminated side of the combined device 300. The exit pupil expander 200 can be arranged behind the combined device 300 closer to the eye 1. For example, the combined device 300 can be arranged between the exit pupil expander 200 and the eye 1.

[0150] Light emitted from image source F can be incident on the combining device 300, and the viewing angle of the combining device 300 can be formed by oblique parallel light. Light output from the combining device 300 can be incident on the exit pupil expander 200, and an exit pupil and multiple exit pupil stages can be formed as described above. Light output from the exit pupil expander 200 can propagate through the combining device 300 without interacting with it. That is, the combining device 300 can correspond to the exit pupil and exit pupil stages without affecting the propagation of light output from the exit pupil expander 200.

[0151] Figure 5 The relationship between the combination device 300 operating in a reflection mode and the exit pupil expander 200 according to an example embodiment is illustrated. For example, the image generated by the combination device 300 can be formed in front of the combination device 300 on the same side as the image source F. In this case, the exit pupil expander 200 can also be arranged in front of the combination device 300, and thus the exit pupil expander 200 to the eye 1 can be closer than the combination device 300 to the eye 1. In addition, the combination device 300 can form a viewing angle, and the exit pupil expander 200 can expand the eyebox B by forming an additional exit pupil level 8.

[0152] The exit pupil expander 200 can be relatively compact and can be more easily integrated into an AR device without a substantial increase in the overall size and weight of the AR device.

[0153] Figure 5 A view schematically illustrating the exit pupil expander 200 including a one-dimensional diffraction grating 210 according to an example embodiment is illustrated. As Figure 6 As illustrated, when the exit pupil expander 200 includes the one-dimensional diffraction grating 210, the light emitted from the vision optical device 100 can be incident on the exit pupil expander 200 and diffracted by the exit pupil expander 200. The light propagating from the vision optical device 100 and the light diffracted by the exit pupil expander 200 can be on the same plane.

[0154] As described above, the "0"th order diffracted beam can pass through the exit pupil expander 200, and the "+1"th and "-1"th order diffracted beams can propagate along the Y-axis direction and return to the one-dimensional diffraction grating 210 due to total reflection in the waveguide 230 of the exit pupil expander 200, at which each of the "+1"th and "-1"th order diffracted beams can be diffracted into the diffraction orders "0", "+1", and "-1".

[0155] The "0"th order diffracted beam among the twice diffracted beams can not satisfy the total reflection condition, and thus can pass through the waveguide 230 to form an exit pupil level. As described above, the light can be output from the exit pupil expander 200 after experiencing diffraction, total reflection, refraction, etc. in the exit pupil expander 200, and then an additional exit pupil level can be formed in the Y-axis direction. For example, the exit pupil region can be expanded in only one direction.

[0156] A two-dimensional diffraction grating can form the exit pupil level 8 in two orthogonal directions. Figure 6 A view schematically illustrating the exit pupil expander 200 including a two-dimensional diffraction grating 210 according to an example embodiment is illustrated. As Figure 7As shown, when the exit pupil expander 200 includes the two-dimensional diffraction grating 210, the light emitted from the vision optical device 100 can be incident on the exit pupil expander 200 and diffracted by the exit pupil expander 200 in two directions along the X-axis and the Y-axis. The two-dimensional diffraction grating 210 has the same principle of operation as the one-dimensional diffraction grating 210, but the two-dimensional diffraction grating 210 can expand the eyebox B in two directions. For example, the eyebox B can extend to two coordinates.

[0157] Figure 7 An exit pupil expander 200 according to another example embodiment is shown. As Figure 8A shown, the diffraction grating 210 can be located inside the waveguide 230. For example, the exit pupil expander 200 can include a first waveguide 230a, a second waveguide 230b, and the diffraction grating 210 disposed between the first waveguide 230a and the second waveguide 230b. The two ends of the diffraction grating 210 can be in contact with the first waveguide 230a and the second waveguide 230b, respectively. The light incident on the diffraction grating 210 through the first waveguide 230a can be split into two parts.

[0158] One part of the light incident on the diffraction grating 210 can be transmitted through the diffraction grating 210 while being diffracted by the diffraction grating 210 and can propagate in the first waveguide 230a. The light propagating in the first waveguide 230a is light of diffraction orders “0”, “+1”, and “-1”, and the “0” order diffracted light passes through the first waveguide 230a and forms an exit pupil. The “+1” and “-1” order diffracted light can repeatedly undergo total reflection, refraction, diffraction, transmission, etc. and can form additional exit pupil levels.

[0159] Another part of the light incident on the diffraction grating 210 can be reflected by the diffraction grating 210 while being diffracted by the diffraction grating 210 and can propagate in the second waveguide 230b. The diffracted light propagating in the second waveguide 230b can be totally internally reflected in the second waveguide 230b and then incident on the diffraction grating 210 again. One part of the light can pass through the diffraction grating 210, and the remaining part of the light can be reflected by the diffraction grating 210.

[0160] The part of the light passing through the diffraction grating 210 can propagate in the first waveguide 230a and can form additional exit pupil levels. The remaining part of the light reflected by the diffraction grating 210 into the second waveguide 230b can propagate into the first waveguide 230a while repeatedly undergoing total reflection, diffraction, etc. Due to the first waveguide 230a, the light can be uniformly distributed to the exit pupil levels.

[0161] Figure 8A An eyebox B including a plurality of exit pupil levels discretely distributed is shown. The light output from the vision optical device can form a plurality of exit pupils 7. As Figure 8BAs shown, the exit pupils 7 formed by the visual optics device can be unevenly and discretely distributed in the eyebox B. Therefore, a blind area 10 can be formed in the eyebox B, and since no exit pupil level is formed in the blind area 10, the user can not see the image when the user’s eye is at the blind area 10.

[0162] According to an example embodiment, the exit pupil expander can form and increase the exit pupil levels. The resolution of the eyebox B corresponding to the number of exit pupil levels increased by the exit pupil expander can vary according to two parameters: the diffraction angle of the diffraction grating (e.g. the angle at which light is incident on the waveguide 230) and the thickness and material of the waveguide (e.g. the total internal reflection angle).

[0163] The number of total reflections in the waveguide and the degree of discontinuity of the exit pupil levels can be adjusted by combining these two parameters. For example, the smaller the diffraction angle of the diffraction grating 210 or the smaller the total internal reflection angle of the waveguide, the higher the resolution of the eyebox B.

[0164] Figure 8B An exit pupil level 8 formed by the exit pupil expander according to an example embodiment is shown. According to an example embodiment, the exit pupil expander can increase the exit pupil levels 8 by diffraction, transmission, refraction, total reflection, etc. The exit pupil levels 8 can be formed such that the exit pupil levels 8 can at least partially overlap each other. Referring to Figure 9 As the number of exit pupil levels 8 increases and the eyebox B is filled with exit pupil levels 8, the discreteness of the eyebox B can decrease, and the eyebox B can be more uniform.

[0165] In addition, for the uniformity of the image, the light energy can be more uniform in the exit pupils 7 and the exit pupil levels 8. Without the exit pupil expander 8, the eye 1 can see a very bright image at one location and a very weak image at another location.

[0166] By optimizing the parameters of the diffraction grating, the uniformity of the light energy in the exit pupils 7 and the exit pupil levels 8 can be guaranteed. To this end, during manufacturing, the period of the diffraction grating 210 can be selected so that the light at the entrance point of the exit pupil expander can match the light at the exit point of the exit pupil expander. In addition, the relief height of the diffraction grating can be selected so that the exit pupils 7 and the exit pupil levels 8 can have uniform brightness and the same size. The exit pupil expander can have an angular range for precise operation. The angular range can be equal to or greater than the viewing angle of the visual optics device, e.g. the aperture angle of the visual optics device.

[0167] For example, when the exit pupil expander according to an example embodiment is designed to operate in a range of aperture angles of about 60° or less, the exit pupil expander can be used with a visual optical device having a viewing angle in a range of less than about 60° (e.g., 40°). However, the exit pupil expander cannot be used with a visual optical device having a viewing angle greater than about 60°, because the exit pupil expander can not operate normally.

[0168] When the exit pupil expander includes a planar waveguide, any type of diffraction grating can be applied to the planar waveguide. However, in this case, the flat exit pupil expander 200 can generally be used for a visual optical device having a small field of view.

[0169] Figure 9 An exit pupil expander 200 forming a flare according to an example embodiment is illustrated.

[0170] As Figure 9 illustrated, light beams providing different viewing angles can be incident on the exit pupil expander 200. For example, a first light beam such as an image can be incident on the exit pupil expander 200 with a first viewing angle θ1, and a second light beam such as a flare can be incident on the exit pupil expander 200 with a second viewing angle θ2. Further, an aperture angle of the exit pupil expander 200 can be equal to the first viewing angle θ1. When the first light beam is incident on the exit pupil expander 200, the exit pupil expander 200 can form an exit pupil 7 and a plurality of exit pupil levels 8 in an eyebox B by using the first light beam.

[0171] Further, when the second light beam is incident on the exit pupil expander 200 with the second viewing angle θ2 greater than the aperture angle (e.g., the first viewing angle θ1) of the exit pupil expander 200, the exit pupil expander 200 can not form the exit pupil levels 8 using the second light beam. Accordingly, as Figure 10 illustrated, the exit pupil expander 200 can form a rainbow flare in the eyebox B. Although the second light beam generated by an additional light source (e.g., a street light, a car headlight, etc.) can be displayed through the visual optical device 100, the second light beam can be diffracted by the diffraction grating 210 of the exit pupil expander 200 but can not be increased by the waveguide 230 of the exit pupil expander 200, such that the second light beam can be displayed in the form of a spectrum (e.g., a rainbow). This phenomenon can be observed when the exit pupil expander 200 is used in AR glasses having a small eyebox.

[0172] Figure 10 A curved exit pupil expander 200 according to an example embodiment is illustrated.

[0173] Due to a change in shape of the curved exit pupil expander 200, the curved exit pupil expander 200 can be implemented to operate only in a specific aperture angle. That is, a curvature of the curved exit pupil expander 200 can be designed to select an aperture angle.

[0174] The curved exit pupil expander 200 can include a curved diffraction grating 210 and a curved waveguide 230, as shown. Figure 11 A first light beam incident on the curved exit pupil expander 200 within a first aperture angle θ1may be in a direction perpendicular to the curved exit pupil expander 200. This is because the curved exit pupil expander 200 has a curvature variable or adjustable within a range of parameters (e.g., a desired aperture angle) that is a range that can be set by a visual optical device designed for use.

[0175] The first light beam incident within the first aperture angle θ1may be diffracted by the curved diffraction grating 210, and the curved waveguide 230 can form an exit pupil and an exit pupil stage using the diffracted light beams to expand an eyebox B. However, a second light beam incident at a second aperture angle θ2larger than the first aperture angle θ1may not form the eyebox B. Although the curved diffraction grating 210 diffracts the second light beam incident at the second aperture angle θ2, the diffracted light beams are not output from the curved waveguide 230 after being totally reflected in the curved waveguide 230.

[0176] When the curved exit pupil expander 200 uses the curved waveguide 230, a Bragg diffraction grating can be used as the curved diffraction grating 210. The Bragg diffraction grating can have a high diffraction efficiency. In addition, the Bragg diffraction grating can be selective with respect to an incident angle and a wavelength of light.

[0177] When the Bragg diffraction grating aims to increase the efficiency of light incident at a specific angle with a range of viewing angles of a visual optical device, the Bragg diffraction grating can also be used in a planar waveguide or a flat exit pupil expander. Accordingly, light perpendicularly incident on the Bragg diffraction grating can be output with a relatively small energy loss, and light obliquely incident on the Bragg diffraction grating can be output with a relatively large energy loss.

[0178] When a volume Bragg grating is used as the curved diffraction grating 210, the efficiency of light incident at a specific angle from a visual optical device can be further improved.

[0179] The curved exit pupil expander 200 of the example embodiment can be integrated into a visual optical device having a large viewing angle. A flat exit pupil expander has a limitation with respect to an incident angle of light for expanding an eyebox. Accordingly, when a viewing angle of a visual optical device exceeds a limit of an aperture angle of a flat exit pupil expander, the flat exit pupil expander can not properly expand an eyebox. However, since the curved exit pupil expander 200 can thereby increase or adjust an aperture angle according to its curvature, the curved exit pupil expander 200 can even be applied to a visual optical device having a large viewing angle.

[0180] In addition, a plurality of waveguides can be used to increase an aperture angle of a flat exit pupil expander.Figure 11 An exit pupil expander including a plurality of waveguides according to another example embodiment is illustrated. As ​ illustrated, a region of the diffraction grating 210 can be designed to diffract a first light beam incident in a range of a first aperture angle θ1, and a remaining region of the diffraction grating 210 can be designed to diffract light incident in a range of a second aperture angle θ2 larger than the first aperture angle θ1. Parameters of the diffraction grating 210 can be designed according to the aperture angles.

[0181] The first waveguide 230c forms an exit pupil and an exit pupil stage by using a first light beam incident in a range of the first aperture angle θ1, and the second waveguide 230d can form an exit pupil and an exit pupil stage by using a second light beam incident in a range of the first aperture angle θ1 to the second aperture angle θ2. For example, a plurality of waveguides 230 can be used to widen a viewing angle.

[0182] As described above, according to one or more of the above example embodiments, the exit pupil expander 200 can be applied to various visual optical devices 100 as a small and convenient additional element for expanding an eyebox B of the visual optical device 100.

[0183] The exit pupil expander 200 described above can be general-purpose and can have a compact and slim design and have a high diffraction efficiency.

[0184] The exit pupil expander 200 each can expand the eyebox B while maintaining a field of view of the visual optical device 100.

[0185] The exit pupil expander 200 can guarantee uniformity and brightness of an image formed in an exit pupil region.

[0186] The exit pupil expander 200 can be applied to an image formed using a plurality of spectrums.

[0187] Although the display and the exit pupil expander have been described with reference to the accompanying drawings according to example embodiments, the embodiments are only examples, and those of ordinary skill in the art will understand that various modifications and other equivalent embodiments can be made thereto without departing from the spirit and scope of the present disclosure. Although many items have been set forth in the above description, these are merely specific examples and should not be construed as limiting the scope of the disclosure. The scope and spirit of the disclosure should not be limited by the descriptions of the embodiments, but should be defined by the appended claims.

[0188] It should be understood that the example implementations described herein should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each example implementation should typically be considered as being applicable in other similar implementations where appropriate. While example implementations have been described with reference to the figures, it will be apparent to those of ordinary skill in the art that various changes in form and details could be made without departing from the spirit and scope of the claims.

[0189] This application claims priority to Russian Patent Application No. 2019136751, filed November 15, 2019, in the Russian Federation Office for Intellectual Property, and Korean Patent Application No. 10-2020-0067855, filed June 4, 2020, in the Korean Intellectual Property Office, the disclosures of which are incorporated by reference herein in their entireties.

Claims

1. A device configured to expand an exit pupil area of a visual optical device, the device comprising: a diffraction grating configured to output a plurality of diffracted beams of a plurality of diffraction orders by diffracting an incident beam of light; and a waveguide provided on the diffraction grating, the waveguide configured to form an exit pupil based on a first diffracted beam of the plurality of diffracted beams output from the diffraction grating and to form an exit pupil order based on a second diffracted beam of the plurality of diffracted beams output from the diffraction grating, wherein the first diffracted beam comprises a 0th order diffracted beam, wherein the second diffracted beam comprises at least one of a +1st order diffracted beam and a -1st order diffracted beam, wherein the waveguide is further configured to form a first exit pupil order based on the +1st order diffracted beam and to form a second exit pupil order based on the -1st order diffracted beam, wherein the waveguide is configured to form the exit pupil by outputting the 0th order diffracted beam of the first diffracted beam without additional diffraction and to form the exit pupil order by total internal reflecting the second diffracted beam on the waveguide and diffracting the second diffracted beam at least once on the diffraction grating and then outputting the 0th order diffracted beam of the totally internally reflected and diffracted second diffracted beam.

2. The device of claim 1, wherein the waveguide is further configured to form the exit pupil by outputting the first diffracted beam output from the diffraction grating without total internal reflection.

3. The device of claim 1, wherein the waveguide is further configured to form at least one exit pupil order by totally internally reflecting the second diffracted beam output from the diffraction grating at least once and then outputting the second diffracted beam.

4. The device of claim 3, wherein the waveguide is further configured to return the second diffracted beam to the diffraction grating by totally internally reflecting the second diffracted beam, wherein the diffraction grating is further configured to diffract the returned second diffracted beam into a plurality of diffracted beams, and wherein the waveguide is further configured to form the exit pupil order by outputting some of the plurality of diffracted beams obtained by diffracting the returned second diffracted beam and reflecting the remaining diffracted beams of the plurality of diffracted beams that are not output back to the diffraction grating.

5. The device of claim 1, wherein the waveguide comprises: a first surface on which the diffraction grating is provided; and a second surface opposite to the first surface and configured to output the first diffracted beam to an outside of the waveguide.

6. The device of claim 5, wherein the waveguide is further configured to additionally form exit pupil orders until all diffracted beams incident on the second surface are totally internally reflected.

7. The device of claim 5, wherein a number of the exit pupil orders is proportional to a number of times diffracted beams of the plurality of diffracted beams incident on the second surface pass through the second surface.

8. The device of claim 5, wherein a distance between the exit pupil orders is proportional to a thickness of the waveguide.

9. The device of claim 5, wherein a distance between the exit pupil orders is inversely proportional to a refractive index of the waveguide. ​ 10. The device of claim 1, wherein the waveguide is further configured to form the first and second exit pupil levels in different directions with respect to the exit pupil provided between the first and second exit pupil levels.

11. The device of claim 1, wherein the diffraction grating is further configured to diffract light beams incident at a predetermined aperture angle or less.

12. The device of claim 11, wherein the aperture angle is greater than a viewing angle of the visual optical arrangement.

13. The device of claim 1, wherein the waveguide is a first waveguide, and the device further comprises: a second waveguide provided on the diffraction grating and configured to totally internally reflect light output from the diffraction grating.

14. The device of claim 13, wherein the diffraction grating is provided between the first and second waveguides.

15. The device of claim 1, wherein at least one of the +1 order diffracted light beam and -1 order diffracted light beam is totally internally reflected in the waveguide and diffracted by the diffraction grating as a 0 order light beam.

16. The device of claim 1, wherein the diffraction grating comprises: a first diffraction region configured to diffract light beams incident within a first aperture angle or less; and a second diffraction region configured to diffract light beams incident within a range greater than the first aperture angle but less than or equal to a second aperture angle, wherein the waveguide further comprises: a first waveguide configured to form an exit pupil level based on diffracted light beams output from the first diffraction region; and a second waveguide configured to form an exit pupil level based on diffracted light beams output from the second diffraction region.

17. The device of claim 16, wherein the diffraction grating, the first waveguide, and the second waveguide are sequentially provided in a propagation direction of the incident light beams.

18. The device of claim 1, wherein the waveguide comprises a curved waveguide.

19. The device of claim 1, wherein the diffraction grating comprises a Bragg diffraction grating.

20. A display comprising: a visual optical arrangement configured to output light beams having a given viewing angle; and a device configured to expand an exit pupil area of the visual optical arrangement, the device comprising: a diffraction grating configured to output a plurality of diffracted light beams of a plurality of diffraction orders by diffracting incident light beams; and a waveguide provided on the diffraction grating, the waveguide configured to form an exit pupil based on first diffracted light beams among the plurality of diffracted light beams output from the diffraction grating, and to form an exit pupil level based on second diffracted light beams among the plurality of diffracted light beams output from the diffraction grating, wherein the first diffracted light beams comprise 0 order diffracted light beams, wherein the second diffracted light beams comprise at least one of +1 order diffracted light beams and -1 order diffracted light beams, wherein the waveguide is further configured to form a first exit pupil level based on the +1 order diffracted light beams, and to form a second exit pupil level based on the -1 order diffracted light beams, ​ ​ ​ wherein the waveguide is configured to form the exit pupil by outputting a 0th order diffracted beam of the first diffracted beam without additional diffraction, and to form the exit pupil order by total internal reflecting on the waveguide and diffracting on the diffraction grating at least once the second diffracted beam and then outputting a 0th order diffracted beam of the totally internally reflected and diffracted second diffracted beam.

21. The display of claim 20, wherein the display is a near-eye display.

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