CN116400500A

CN116400500A - Optical waveguide structure and head-mounted display device

Info

Publication number: CN116400500A
Application number: CN202111618079.0A
Authority: CN
Inventors: 刘立川; 程鑫; 吾晓; 饶轶
Original assignee: Goertek Inc
Current assignee: Goertek Inc
Priority date: 2021-12-27
Filing date: 2021-12-27
Publication date: 2023-07-07

Abstract

The invention discloses an optical waveguide structure and head-mounted display equipment, wherein the optical waveguide structure comprises a waveguide substrate, a coupling-in grating and two coupling-out gratings, and the coupling-in grating is arranged on one surface of the waveguide substrate; the two coupling-out gratings are arranged side by side on the surface of the waveguide substrate, provided with the coupling-in gratings, and are arranged at intervals with the coupling-in gratings; the light received by the coupling-in gratings is respectively emitted to the two coupling-out gratings after passing through the waveguide substrate, and the light of one coupling-out grating is emitted to image after passing through the other coupling-out grating. According to the technical scheme, the two coupling-out gratings are arranged, so that the surface utilization rate of the optical waveguide structure is improved, and the efficient and compact optical waveguide structure is realized.

Description

Optical waveguide structure and head-mounted display device

Technical Field

The invention relates to the technical field of diffraction optical devices, in particular to an optical waveguide structure and head-mounted display equipment.

Background

AR (Augmented Reality ) display is a technique that calculates the position and angle of camera images in real time and adds corresponding image, video, 3d models, the goal of which is to fit the virtual world around the real world and interact on the screen.

AR displays are typically viewed by the human eye after incident light is emitted from an image source, reflected and refracted by an optical waveguide. For better viewing of the presented image by the human eye, the exit pupil of the AR product is large enough, and it is known that the optical waveguide usually has three or more grating areas, such as light in-coupling, light out-pupil, light out-coupling, etc., which are devices capable of expanding the pupil.

However, in the existing optical waveguide structure, three functional areas of optical coupling-in, optical pupil expansion and optical coupling-out are independently distributed, and finally, only a small part of the coupled area is formed, the effective image display area occupies a small proportion of the whole optical waveguide area, and both light propagation and pupil expansion are unidirectionally asymmetric, so that the displayed image is also asymmetric in brightness.

Disclosure of Invention

Based on this, for low surface utilization of the optical waveguide element, it is necessary to provide an optical waveguide structure and a head-mounted display device, which aim to improve the area ratio of the effective image display area in the entire optical waveguide device by having both the pupil expansion and the coupling-out functions of the two grating areas, thereby realizing an efficient and compact optical waveguide structure.

In order to achieve the above object, an optical waveguide structure according to the present invention includes:

a waveguide substrate;

the coupling grating is arranged on one surface of the waveguide substrate; a kind of electronic device with high-pressure air-conditioning system

The two coupling-out gratings are arranged on the surface of the waveguide substrate, on which the coupling-in gratings are arranged, side by side and are arranged at intervals with the coupling-in gratings;

the light received by the coupling-in gratings is respectively emitted to the two coupling-out gratings after passing through the waveguide substrate, and the light of one coupling-out grating is emitted to image after passing through the other coupling-out grating.

Optionally, a perpendicular bisector in the arrangement direction of the two coupling-out gratings passes through the middle of the coupling-in gratings.

Optionally, the cross section of each coupling-out grating is rectangular, the length direction of each coupling-out grating is consistent with the extending direction of the waveguide substrate, and the two coupling-out gratings are arranged side by side in the width direction of the coupling-out gratings.

Optionally, the couplingThe grating vector of the incident grating is k _in A grating vector of the coupled grating is k ₁ The included angle between the coupled light and the horizontal plane is ρ ₁ The other coupled grating has a grating vector k ₂ The included angle between the coupled light and the horizontal plane is ρ ₂ Wherein, |k _in |＝2*|k ₂ |cosρ ₂ 。

Optionally, the cross section of each coupling-out grating includes a rectangular portion and a trapezoidal portion, the trapezoidal portion is disposed at one end of the rectangular portion, which is close to the coupling-in grating, the upper bottoms of the trapezoidal portions of the two coupling-out gratings face the coupling-in grating, and the two opposite waists of the trapezoidal portions are in fit with each other.

Optionally, the maximum included angle between the light rays emitted by the coupling-in grating to the two coupling-out gratings is ω, and the base angle of the trapezoid part is pi/2- ω/2.

Optionally, the cross section of the incoupling grating is circular.

Optionally, the thickness of the waveguide substrate is d, the total reflection angle is a, the distance between two adjacent coupled light rays of the coupling-out grating is t, and t=2dtan_a;

the radius of the coupling-in grating is r, the center distance of the pupils of two adjacent coupling-out light rays of the coupling-out grating is s, and the included angle between the coupling-out light rays of the coupling-out grating and the horizontal plane is ρ ₁ ，s＝2r/tanρ ₁ ；

Wherein t is less than s.

Optionally, the thickness d of the waveguide substrate ranges from greater than 0.2mm to less than or equal to 2mm.

Optionally, the coupling grating is a surface relief grating, a holographic volume grating, a polarizer grating, or a two-dimensional grating;

and/or the coupling-out grating is a surface relief grating, a holographic volume grating, a polarizer grating or a two-dimensional grating.

In order to achieve the above object, the present invention further proposes a head-mounted display device comprising an image source and an optical waveguide structure as described above, the optical waveguide structure being located on the light exit side of the image source.

According to the technical scheme provided by the invention, the optical waveguide structure comprises a waveguide substrate, and the coupling-in grating and two coupling-out gratings which are arranged on the waveguide substrate, wherein the two coupling-out gratings are arranged side by side and are arranged at intervals with the coupling-in grating, so that the two coupling-in gratings can both receive emergent rays of the coupling-in grating, and the coupling-in grating which is firstly shot can be used as a pupil expanding foundation of the coupling-in grating which is shot later. Therefore, the two coupling-out gratings can emit imaging light after passing through the pupil expansion, compared with the existing coupling-out grating structure which only occupies a small part, the area of a limited waveguide substrate can be efficiently utilized, the effective image area is increased, and the high-efficiency compact optical waveguide structure is realized. Meanwhile, as two identical coupling-out gratings are arranged, the uniformity of the brightness of the image represented by the light rays emitted by the two coupling-out gratings is improved.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to the structures shown in these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a cross-sectional view of one embodiment of an optical waveguide structure of the present invention;

FIG. 2 is a ray propagation path diagram of the optical waveguide structure shown in FIG. 1;

FIG. 3 is a graph of a k-space vector analysis of the optical waveguide structure of FIG. 1;

FIG. 4 is a transverse cross-sectional view of another embodiment of an optical waveguide structure of the present invention;

FIG. 5 is a k-space vector analysis diagram of the optical waveguide structure of FIG. 4;

FIG. 6 is a longitudinal cross-sectional view of a further embodiment of an optical waveguide structure of the present invention;

FIG. 7 is a pupil diagram of a light outcoupling structure according to another embodiment of the present invention;

FIG. 8 is a graph showing the distribution of coupled light at different waveguide substrate thicknesses in the optical waveguide structure of FIG. 7;

fig. 9 is a schematic diagram of a simulation image of the optical waveguide structure shown in fig. 7.

Reference numerals illustrate:

reference numerals	Name of the name	Reference numerals	Name of the name
				100	Optical waveguide structure	30	Coupling out grating
10	Waveguide substrate	31	Trapezoid part
				20	Coupling in grating	32	Rectangular portion

The achievement of the objects, functional features and advantages of the present invention will be further described with reference to the accompanying drawings, in conjunction with the embodiments.

Detailed Description

The following description of the embodiments of the present invention will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

It should be noted that all directional indicators (such as up, down, left, right, front, and rear … …) in the embodiments of the present invention are merely used to explain the relative positional relationship, movement, etc. between the components in a particular posture (as shown in the drawings), and if the particular posture is changed, the directional indicator is changed accordingly.

Furthermore, descriptions such as those referred to as "first," "second," and the like, are provided for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implying an order of magnitude of the indicated technical features in the present disclosure. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In the description of the present invention, the meaning of "plurality" means at least two, for example, two, three, etc., unless specifically defined otherwise.

In the present invention, unless specifically stated and limited otherwise, the terms "connected," "affixed," and the like are to be construed broadly, and for example, "affixed" may be a fixed connection, a removable connection, or an integral body; can be mechanically or electrically connected; either directly or indirectly, through intermediaries, or both, may be in communication with each other or in interaction with each other, unless expressly defined otherwise. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.

In addition, the technical solutions of the embodiments of the present invention may be combined with each other, but it is necessary to be based on the fact that those skilled in the art can implement the technical solutions, and when the technical solutions are contradictory or cannot be implemented, the combination of the technical solutions should be considered as not existing, and not falling within the scope of protection claimed by the present invention.

In the conventional diffractive optical waveguide structure, an independent coupling-in grating and an independent coupling-out grating are generally arranged, the coupling-out grating occupies only a small part, the waveguide area is not fully utilized, and the brightness of an image formed by the coupling-out grating positioned at one side is asymmetric. Therefore, the invention provides the optical waveguide structure, and the two grating areas have the functions of pupil expansion and coupling-out, so that the optical waveguide structure is efficient and compact.

Referring to fig. 1, in an embodiment of the present invention, an optical waveguide structure 100 includes a waveguide substrate 10, an in-coupling grating 20, and two out-coupling gratings 30, wherein the in-coupling grating 20 is disposed on a surface of the waveguide substrate 10; the two coupling-out gratings 30 are arranged on the surface of the waveguide substrate 10, on which the coupling-in gratings 20 are arranged, in parallel, and are arranged at intervals with the coupling-in gratings 20; the light received by the coupling-in grating 20 is emitted to the two coupling-out gratings 30 after passing through the waveguide substrate 10, and the light of one coupling-out grating 30 is emitted to be imaged after passing through the other coupling-out grating 30.

In the present embodiment, the optical waveguide structure 100 is applied to the AR display field, for example, the optical waveguide structure 100 is applied to AR glasses. The waveguide substrate 10, also called a dielectric optical waveguide, is generally planar and has a coupling-in region for receiving incident light and a coupling-out region for projecting the incident light out, and the incident light is incident through the coupling-in region, transmitted within the waveguide substrate 10, and exits from the coupling-out region. Of course, in other embodiments, the waveguide substrate 10 may be configured in a cylindrical shape, and may be designed according to the desired product. The material of the waveguide substrate 10 may be a loop resin or other organic material, or may be an inorganic material such as heavy flint glass, and is not limited thereto.

It can be known that the transmission of the incident light in the waveguide substrate 10 needs to satisfy two conditions, namely, the light is emitted from the optically dense medium to the optically sparse medium, the refractive index of the medium inside the waveguide substrate 10 is greater than that of the medium outside, that is, the refractive index of the waveguide substrate 10 needs to be greater than 1 (the refractive index of air is 1); the other is that the incident angle of the light is larger than the critical angle.

For this purpose, the optical waveguide substrate 10 further includes a coupling grating, and the coupling grating 20 is disposed on the surface of the waveguide substrate 10 and located in the coupling region for coupling the light into the waveguide substrate 10. The coupling-in grating 20 can change the incident angle of the incident light into the waveguide substrate 10, so that the incident angle is greater than or equal to the critical angle, and the light can be totally reflected in the waveguide substrate 10, thereby completing the transmission of the light. The coupling-in grating 20 may be applied as a separate optical element to the coupling-in region, or the structure of the coupling-in grating 20 may be formed in the coupling-in region of the waveguide substrate 10.

The out-coupling grating 30 is located in the out-coupling region, and similarly, the out-coupling grating 30 may be applied to the out-coupling region as a separate optical element, or the structure of the out-coupling grating 30 may be formed in the out-coupling region of the waveguide substrate 10. When the light beam coupled into the waveguide substrate 10 by the coupling-in grating 20 is emitted to the coupling-out grating 30, the incident angle is deflected again, for example, the incident angle is smaller than the critical angle of total reflection, and the incident light beam is transmitted to the waveguide substrate 10, so that the incident light beam exits to form a display image and is acquired by human eyes.

Here, two out-coupling gratings 30 are disposed, and two out-coupling regions are disposed on the corresponding waveguide substrate 10, where the two out-coupling gratings 30 are disposed side by side, and can receive the light transmitted by the in-coupling grating 20 at the same time. The shape of the two coupling-out gratings 30 is not limited, and may be rectangular parallelepiped, square, or the like. After the incident light is coupled into the waveguide substrate 10 by the coupling-in grating 20, the incident light is transmitted to the position of the coupling-out grating 30 through total reflection of the waveguide substrate 10, after the grating direction of the coupling-out grating 30 is designed, the light which enters one coupling-out grating 30 first passes through pupil expansion and turning and then enters the other coupling-out grating 30, after pupil expansion is completed in the coupling-out grating 30, the coupling-out of the image is completed, and the human eye is reached. Similarly, light that enters the other out-coupling grating 30 will be emitted as described above. The light rays can generate new light rays after passing through the pupil expansion, the new light rays can continue to propagate and expand the pupil and circulate continuously, and the final image fills the whole exit pupil after expanding the pupil, so that the human eyes can see the image in a large area, and the display effect is improved.

In the technical solution provided in the present invention, the optical waveguide structure 100 includes a waveguide substrate 10, and an in-coupling grating 20 and two out-coupling gratings 30 disposed on the waveguide substrate 10, and by disposing two out-coupling gratings 30 disposed side by side and spaced apart from the in-coupling grating 20, both can receive the outgoing light of the in-coupling grating 20, and the first-incident in-coupling grating 20 can be used as the pupil expanding base of the last-incident in-coupling grating 20. In this way, the two coupling-out gratings 30 can both emit imaging light after passing through the pupil expansion, and compared with the existing structure in which the coupling-out gratings 30 occupy only a small part, the area of the limited waveguide substrate 10 can be efficiently utilized, the effective image area is increased, and the high-efficiency compact optical waveguide structure 100 is realized. Meanwhile, as the two identical coupling-out gratings 30 are arranged, the uniformity of the brightness of the image represented by the light rays emitted by the two coupling-out gratings is also improved.

With continued reference to fig. 1, alternatively, a perpendicular bisector in the arrangement direction of the two coupling-out gratings 30 passes through the middle of the coupling-in grating 20.

In this embodiment, the coupling-in gratings 20 are disposed on the middle vertical lines in the arrangement direction of the two coupling-out gratings 30, so that the probability that the light coupled by the coupling-in gratings 20 is emitted to the two coupling-out gratings 30 is equal, the brightness of the light emitted from each coupling-out grating 30 is the same, the brightness of the image observed by human eyes is symmetrically distributed, and the display effect is effectively improved.

Alternatively, the cross section of each of the coupling-out gratings 30 is rectangular, the length direction of each of the coupling-out gratings 30 is consistent with the extending direction of the waveguide substrate 10, and the two coupling-out gratings 30 are arranged side by side in the width direction thereof.

In this embodiment, the cross-sectional shape of the coupling-out grating 30 may be set to be rectangular, which is convenient for processing. Of course, the surface of the coupling-out grating 30 is provided with a microstructure for changing the incident angle of the light, which will not be described herein. The microstructure settings of the two coupling-out gratings 30 may be different, and specifically, the alignment direction of the gratings and the size of the gratings may be symmetrically arranged with respect to the perpendicular bisector of the arrangement of the gratings. The length direction of each coupling-out grating 30 is set to be consistent with the extending direction of the waveguide substrate 10, so that the occupancy rate of the coupling-out grating 30 on the waveguide substrate 10 is larger, the surface utilization rate of the waveguide substrate 10 is further improved, meanwhile, after the incident light is transmitted to the coupling-out grating 30, the space for spreading and expanding pupils to the right is larger, and the efficient and compact optical waveguide structure 100 is further realized.

Referring to fig. 2, when the optical waveguide structure 100 is used for image transmission, light is input from the coupling grating 20 on the left side, enters the waveguide substrate 10, propagates rightward, satisfies the total reflection condition of the light in the propagation process, continuously reflects up and down in the waveguide substrate 10, is coupled out above the coupling grating 30, and finally converges to the human eye, and can be seen that the width of the output light is significantly larger than that of the input light, which proves that the optical waveguide structure 100 provided by the present embodiment can expand the pupil (increase the beam caliber) while coupling out the image.

Referring to fig. 3 in combination, optionally, the grating vector of the coupling-in grating 20 is k _in A grating vector of the coupling-out grating 30 is k ₁ The included angle between the coupled light and the horizontal plane is ρ ₁ The other out-coupling grating 30 has a grating vector k ₂ The included angle between the coupled light and the horizontal plane is ρ ₂ Wherein, |k _in |＝2*|k ₂ |cosρ ₂ 。

In order to further analyze the diffraction effect of the optical waveguide structure 100, a K-space analysis grating direction and period is established, the K-space vector diagram is formed by two concentric circles, an outer circle is defined as a maximum angle that can be transmitted at the waveguide substrate 10, an inner circle is defined as a total reflection angle of light at the waveguide substrate 10, a square represents an image, and the length and width of the image are represented by the light angle in the figure. The grating vector represents the alignment direction and period size of the grating, and the period coupled into the grating 20 is set to p _ic Wherein one of the outcoupling gratings 30 has a period p ₁ The period of the other out-coupling grating 30 is p ₂ Then k ₁ ＝2π/p ₁ ，k ₂ ＝2π/p ₂ ，k _in ＝2π/p _ic The grating vectors shown in the figure form an equilateral triangle with 60 deg. each. Of course, in other embodiments, the grating vector only needs to form any isosceles triangle, ensuring that the formula |k is satisfied _in |＝2*|k ₂ |cosρ ₂ Therefore, the coupled light rays can be ensured to enter human eyes, and image imaging is realized.

Referring to fig. 4, optionally, the cross section of each of the coupling-out gratings 30 includes a rectangular portion 32 and a trapezoidal portion 31, the trapezoidal portion 31 is disposed at one end of the rectangular portion 32 near the coupling-in grating 20, the upper bottoms of the trapezoidal portions 31 of the two coupling-out gratings 30 face the coupling-in grating 20, and the opposite waists of the two trapezoidal portions 31 are disposed in a fitting manner.

In this embodiment, the shape of the coupling-out grating 30 is set to include a rectangular portion 32 and a trapezoid portion 31, the trapezoid is a right trapezoid, and the two right-angled waists are attached to each other, and the two hypotenuse waists are attached to each other and are away from each other, that is, when the cross section of the coupling-out grating 30 in the above embodiment is rectangular, the two vertex angles facing the coupling-in grating 20 are cut off, so as to form a hypotenuse, and the hypotenuse serves as the waist of the trapezoid portion 31, so that incident light can expand the pupil when entering the coupling-out grating 30, unnecessary light energy loss at the vertex angle of the square can be reduced, and the light utilization rate can be improved.

Referring to fig. 4 and 5, alternatively, the maximum included angle between the light beams emitted from the coupling-in grating 20 to the two coupling-out gratings 30 is ω, and the base angle of the trapezoid portion 31 is pi/2- ω/2.

Similarly, the vector of the coupling-out grating 30 with the trapezoid part 31 can be analyzed through a k-space vector diagram, the basic coordinate parameter identification of the k-space is unchanged, the light rays are coupled into the waveguide substrate 10 and then propagate to the right, and a certain included angle is formed between the light rays and the origin of coordinates when the light rays reach the coupling-out grating 30. When the origin is connected to the vertices of two square durations, i.e. the angle between the two most marginal rays when the coupling-in grating 20 is directed to the coupling-out grating 30, and the maximum angle is set to ω, the angle between each ray and the abscissa is ω/2, and when the image size is larger and the angle of view is larger, ω is also larger. The base angle of the trapezoid part 31 is set to pi/2-omega/2, so that when the coupling-out grating 30 is designed, corresponding modification can be performed according to the requirement of the image size, so as to improve the coupling efficiency of light rays.

Optionally, the cross-section of the incoupling grating 20 is circular.

In this embodiment, the cross section of the coupling-in grating 20 is selected to be circular, and of course, the surface of the coupling-in grating 20 is also provided with a plurality of micro-light structures arranged in an array to deflect the incident angle of the incident light. The cross section of the coupling-in grating is circular, so that the coupled light can be more uniformly emitted to the two coupling-out gratings 30, and the uniformity of the brightness of the light coupled out by the two coupling-out gratings 30 is further improved. Of course, in other embodiments, the cross-section of the incoupling grating 20 may also be rectangular, polygonal, or of other irregular shapes, etc.

Referring to fig. 6, under normal conditions, during the transmission process of the same light in the optical waveguide structure 100, due to the diffraction time difference, coupled-out light with a certain distance is formed during the coupling-out, the distance between two adjacent coupled-out light is related to the thickness of the waveguide substrate 10 and the total reflection angle thereof, the thickness of the waveguide substrate 10 is d, the total reflection angle is a, and the distance between two adjacent coupled-out light of the coupling-out grating 30 is t, where t=2dtan_a is known in the figure.

When the cross section of the coupling-in grating is circular, in order to increase the pupil density of the optical waveguide structure 100, the thickness of the waveguide substrate 10 and the radius of the coupling-in grating 20 need to be strictly set. Optionally, the radius of the coupling-in grating 20 is r, the center distance of the pupils of two adjacent coupling-out light rays of the coupling-out grating 30 is s, and the included angle between the coupling-out light rays of the coupling-out grating 30 and the horizontal plane is ρ ₁ ，s＝2r/tanρ ₁ The method comprises the steps of carrying out a first treatment on the surface of the Wherein t is less than s.

In this embodiment, when the cross section of the coupling-in grating 20 is circular, the pupil of the coupled-out light is two semicircles, as shown in fig. 7, and the radius of the coupling-in grating 20 determines the size of the semicircles, and the thickness of the waveguide substrate 10 determines the distance between two adjacent semicircles. For better pupil expansion effect and imaging effect, the position relation of the pupil is shown as the figure, two semi-circles adjacent from top to bottom are overlapped, the semi-circles adjacent from left to right are just welted, the circle center distance of the two semi-circles is s, then s=2r/tan ρ ₁ And the radius of the coupling-in grating and the direction ρ of the coupling-out grating 30 ₁ And (5) correlation. In order to make two light partsThe value of t is smaller than the value of s when the two images overlap, so that the image effect can be met, the pupil expansion effect and the imaging effect are improved, and the formula d < r/(tan rho) can be obtained ₁ tan a), i.e., the thickness of the waveguide substrate 10, needs to satisfy the above formula.

Alternatively, the thickness d of the waveguide substrate 10 may range from greater than 0.2mm to 1mm.

It will be appreciated that the thickness of the waveguide substrate 10 is not too great, which is required to satisfy the above equation, and of course, is not too thin to ensure a certain structural strength basis. Therefore, the thickness range of the waveguide substrate 10 is set to be 1mm or less, for example, 0.2mm, 0.4mm, 0.6mm, 0.7mm, 0.8mm, 1mm, etc., so that a good pupil expansion and imaging effect can be achieved on the basis of having a certain structural strength. Of course, in other embodiments, the thickness of the waveguide substrate 10 may be enlarged to 2mm.

The solution of the above embodiment is also verified in a specific experiment, please refer to fig. 8, where the thickness of the waveguide substrate 10 is set to be 1.6mm, 1mm, and 0.7mm respectively under the condition that the radius of the coupling-in grating 20 is fixed, so as to obtain a corresponding distribution diagram of the coupled-out light, where the abscissa and the ordinate represent coordinate points of the coupled-out light respectively. As can be seen, at d of 1.6mm, the semi-circular pupils are spaced farther apart from each other, leaving a large number of voids. When d is 1mm, the semi-circular pupils are just close to each other, a small part of gaps are reserved, when d is 0.7mm, the pupils are overlapped with each other, the coupling-out area is completely covered, and no gaps exist.

And according to the above formula, in one embodiment, the radius r of the coupling-in grating 20 is set to be 2mm, a=50°, ρ ₁ When=60°, d is less than 0.97, which corresponds to the above range.

Referring to fig. 9, according to experiments for simulating input and output images, the optical waveguide structure 100 of the above embodiment can ensure that the input images are completely output to human eyes, and the brightness distribution can be seen that the brightness of the images is symmetrically distributed, which is beneficial to improving the uniformity of the images.

Optionally, the incoupling grating 20 is a surface relief grating, a holographic volume grating, a polarizer volume grating, or a two-dimensional grating;

and/or the out-coupling grating 30 is a surface relief grating, a holographic volume grating, a polarizer volume grating or a two-dimensional grating.

In this embodiment, the coupling-in grating 20 may be a holographic volume grating, which has a high light coupling efficiency and can couple more light into the waveguide substrate 10. Specifically, the coupling-in grating 20 may be a transmission type holographic volume grating or a reflection type holographic volume grating, which is not limited herein. Of course, in other embodiments, the incoupling grating 20 may be a surface relief grating, a polarizer grating, a two-dimensional grating, or the like.

Alternatively, when the coupling-in grating 20 is any one of the gratings, the coupling-out grating 30 may be a surface relief grating, which has a larger refractive index difference than air, so that a larger deflection angle of the light is obtained. Of course, in other embodiments, the out-coupling grating 30 may be a polarizer grating, a two-dimensional grating, or a holographic grating.

In order to achieve the above object, the present invention further proposes a head-mounted display device (not shown) comprising an image source and the optical waveguide structure 100 as described above, the optical waveguide structure 100 being located on the light-emitting side of the image source. Since the optical waveguide structure 100 of the head-mounted display device of the present invention refers to the structure of the optical waveguide structure 100 of the above embodiment, the beneficial effects brought by the above embodiment are not described again.

In this embodiment, the head-mounted display device may be AR glasses or MR glasses, which includes an image source that provides incident light to the optical waveguide structure 100, and when the incident light is incident to the optical waveguide structure 100 from an air medium, the incident light first passes through diffraction of the coupling-in grating 20, then enters the waveguide substrate 10, passes through total reflection transmission, then passes out of the coupling-out grating 30, and is injected into the human eye. Of course, the head-mounted display device may also be a near-eye display (NEd), a head-mounted display (HMd), a head-up display (HUd), or the like.

In an embodiment, in order to receive the image source as much as possible, the coupling-in grating 20 is disposed opposite to the image source, that is, the image source coincides with the projection of the coupling-in grating 20 on the waveguide substrate 10, so that it can be ensured that the incident light is received by the coupling-in grating 20, and the light transmission efficiency is improved.

Optionally, the image source includes a light source, optionally a LEd light source, and a display panel, which provides a light source for the display panel, and incident light is formed after passing through the display panel and directed to the light waveguide structure 100. The display panel may be one of a liquid crystal on silicon display module (Liquid Crystal on Silicon, LCOS), a transmissive liquid crystal display module (LCd), a digital light processing display module (digital Light Processing, dLP), and a laser scan (Laser Beam Scanning, LBS).

The foregoing description of the preferred embodiments of the present invention should not be construed as limiting the scope of the invention, but rather should be understood to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the following description and drawings or any application directly or indirectly to other relevant art(s).

Claims

1. An optical waveguide structure, characterized in that the optical waveguide structure comprises:

a waveguide substrate;

2. The optical waveguide structure of claim 1, wherein a perpendicular bisector in the direction of arrangement of the two out-coupling gratings passes through a middle portion of the in-coupling gratings.

3. The optical waveguide structure of claim 2, wherein each of the coupling-out gratings has a rectangular cross section, a length direction of each of the coupling-out gratings is identical to an extending direction of the waveguide substrate, and the two coupling-out gratings are arranged side by side in a width direction thereof.

4. The optical waveguide structure of claim 3 wherein the grating vector of the incoupling grating is k _in A grating vector of the coupled grating is k ₁ The included angle between the coupled light and the horizontal plane is ρ ₁ The other coupled grating has a grating vector k ₂ The included angle between the coupled light and the horizontal plane is ρ ₂ Wherein, |k _in |＝2*|k ₂ |cosρ ₂ 。

5. The optical waveguide structure of claim 2, wherein the cross section of each of the coupling-out gratings comprises a rectangular portion and a trapezoid portion, the trapezoid portion is disposed at one end of the rectangular portion near the coupling-in grating, the upper bottoms of the trapezoid portions of the two coupling-out gratings face the coupling-in grating, and the opposite waists of the two trapezoid portions are in fit with each other.

6. The optical waveguide structure of claim 5 wherein the maximum angle between the light rays of the coupling-in grating directed to the two coupling-out gratings in the horizontal plane is ω, and the base angle of the trapezoid is pi/2- ω/2.

7. The optical waveguide structure of any of claims 2 to 6 wherein the cross-section of the incoupling grating is circular.

8. The optical waveguide structure of claim 7, wherein the waveguide substrate has a thickness d and a total reflection angle a, and a distance between two adjacent coupled light rays of the coupling-out grating is t, t=2dtan_a;

Wherein t is less than s.

9. The optical waveguide structure of claim 7 wherein the waveguide substrate has a thickness d in the range of greater than 0.2mm and less than or equal to 2mm.

10. The optical waveguide structure of claim 1 wherein the incoupling grating is a surface relief grating, a holographic volume grating, a polarizer volume grating, or a two-dimensional grating;

11. A head-mounted display device comprising an image source and the optical waveguide structure of any one of claims 1 to 10, the optical waveguide structure being located on the light exit side of the image source.