CN111880304A - Optical pupil expanding device, display device and method for outputting light beam and displaying image - Google Patents

Abstract

An optical pupil expanding device and a display device and methods of outputting light beams and displaying images thereof, comprising a waveguide plate (1), the waveguide plate (1) comprising a first optically diffractive entrance pupil unit (10), diffracting an input light beam (200) to form a first transmitted light (11) and a second transmitted light (12); a second optical diffractive pupil expanding unit (20) which diffracts the first transmitted light (11) to form third transmitted light (13); a third optical diffractive pupil expanding unit (30) which diffracts the second light guide (12) to form a fourth light guide (14); a fourth optical diffractive exit pupil unit (40) which diffracts the third transmitted light (13) to form first output light (130) and diffracts the fourth transmitted light (14) to form second output light (140); the overlapping region of the fourth optically diffractive exit pupil element (40) and the third optically diffractive pupil element (30) is REG 1A. The overlapping region REG1A does not directly diffract light diffracted by the entrance pupil unit, achieving the lowest crosstalk while reducing the overall pupil expansion device area.

Description

Optical pupil expanding device, display device and method for outputting light beam and displaying image

Technical Field

The invention relates to an optical pupil expanding device, a display device, an output light beam and a method for displaying an image, which are mainly used in a virtual display device.

Background

Referring to fig. 1, a prior art pupil expanding device EPE0 comprises a waveguide plate SUB01, which in turn comprises a diffractive entrance pupil element DOE01, a diffractive pupil expanding element DOE02 and a diffractive exit pupil element 30. One input light beam 200 is expanded by multiple diffractions in the pupil expanding device EPE0, and finally the light beam 300 is output. The in-coupling pupil unit DOE01 diffracts the input light 200 into the first guided light 11 by diffraction. The first transmitted light 11 is diffracted by the pupil expanding unit DOE02 to form expanded transmitted light B3. The diffused transmitted light B3 is diffracted out as light 300 by the diffractive exit pupil unit 30.

The pupil expanding device EPE0 may expand the light beam in both directions SX and SY. The width of the output beam 300 is much larger than the width of the input beam 200. The pupil expanding device EPE0 may be used to expand the viewing pupil of the virtual display device to facilitate a larger comfortable viewing position (large eyebox) for the EYE1 relative to the viewing position of the virtual display device. The EYE1 of the observer can see the finished virtual image within the viewing position of the output beam. The output light may include one or more output beams, where each output beam may correspond to a different image location of the displayed virtual image. The pupil expansion device may also be referred to as e.g. an expansion device, an expansion means, etc.

The intensity of the conducted light (B1, B3) propagating in the waveguide plate SUB01 decreases as its propagation path length in the pupil expanding device EPE01 increases. At the same time, the transmitted light undergoes a very large number of independent diffractions in the pupil expanding element DOE02, the number of diffractions being proportional to the distance traveled. The output intensity of the most distant (leftmost) corner region CRA may be low due to the long optical path from the entrance pupil element DOE01 to said corner region CRA. Moreover, the pupil expanding unit DOE02 further reduces the intensity of the exiting light.

Therefore, the intensity of the output light in the farthest corner region CRA of the diffractive exit pupil element DOE03 may be much lower than the intensity of the output light at the center POS3c of the diffractive exit pupil element DOE 03. The spatial intensity distribution of the output light which ultimately results in the pupil expanding device EPE0 in figure 1 may be non-uniform.

In addition, since the pupil expanding device EPE0 only passes through the diffractive entrance pupil unit DOE01, the diffractive exit pupil unit DOE02 and the diffractive exit pupil unit DOE03 to form a single conduction channel composed of the conduction light (B1, B3), the angle of the output light beam OUT1 finally emitted from the diffractive exit pupil unit DOE03 is limited, the EYE1 cannot obtain a larger field of view angle (FOV), and color cast or dark areas may occur at the corners of the image.

Disclosure of Invention

The present invention proposes a new pupil expanding device, a method of expanding light beams, a display device, and a method for displaying an image for expanding a field of view angle (FOV), improving uniformity of output light, and compressing a waveguide area.

According to the general principle, the present invention proposes an optical beam pupil expanding device (100) comprising a waveguide plate (1), characterized in that said waveguide plate (1) comprises: a first optical diffractive entrance pupil unit (10) for diffracting an input light beam (200) to form first and second transmitted light (11, 12); a second optical diffractive pupil expanding unit (20) for diffracting the first transmitted light (11) to form a third transmitted light (13); a third optically diffractive pupil expanding unit (30) for diffracting the second light transmission (12) to form a fourth light transmission (14); and a fourth optically diffractive exit pupil unit (40) for diffracting the third light (13) to form the first output light (130) and the fourth light (14) to form the second output light (140); wherein the first light-conducting light (11) propagates in a first direction (DIR1) and the second light-conducting light (12) propagates in a second direction (DIR 2); the angle formed between the first direction (DIR1) and the second direction (DIR2) is 12, said 12 being between 45 ° and 135 °; wherein the fourth optically diffractive exit pupil unit (40) comprises one or more regions (REG0, REG1A), the overlapping region of the fourth optically diffractive exit pupil unit (40) and the third optically diffractive pupil unit (30) being REG 1A; the superposition of the first output light (130) and the second output light (140) results in an output light beam 300.

Further, the overlapping region (REG1A) of the fourth optically diffractive exit pupil unit (40) and the third optically diffractive exit pupil unit (30) does not diffract the second guided light (12) out of the waveguide plate (1); the overlap region (REG1A) occupies 0% to 20% of the area of the third optically diffractive pupil-expanding element 30.

Further, the overlapping region (REG1A) forms a first output light (130) by diffracting the third guided light (13), while forming a second output light (140) by diffracting the fourth guided light (14), and forms a combined output light (300) by superimposing the first output light (130) and the second output light (140).

Further, the first transmitted light (11) does not interact with the third and fourth optically diffractive pupil cells 30,40, the second transmitted light (12) does not interact with the second optically diffractive pupil cell 20; the diffractive effect of the fourth optically diffractive exit pupil unit 40 on the transmitted light 12 is negligible.

Further, the image information carried by the first output light 130 has a different or complementary missing corner and color uniformity than the image information carried by the second output light 140.

The invention also proposes a display device (500) comprising the aforementioned beam expanding pupil apparatus (100) and further comprising an optical engine (400) forming a primary image and converting the primary image into a plurality of said input light beams (200), said beam expanding pupil apparatus expanding said input light beams (200) by diffraction to form said output light beams (300).

The invention also proposes a method for providing an output light beam (300) using the aforementioned pupil expansion device (100).

The invention also proposes a method for displaying an image using the aforementioned pupil expansion device (100).

The scope of protection sought for the various embodiments of the invention is defined by the independent claims. The embodiments described in this patent, if any, that do not fall within the scope of the independent claims are to be construed as examples to facilitate the understanding of the various embodiments of the invention.

The pupil expanding device comprises two pupil expanding units and an overlapping area for increasing the field angle FOV of the output light and optimizing the uniformity of the spatial intensity distribution of the output light. The pupil expanding device may decompose the input light to propagate through two main paths to the output exit pupil unit. When the light beams of the two main paths are finally output and superposed together, the total field angle FOV can be increased, and the non-uniform intensity distribution of the light on each path can be compensated. In order to reduce the area of the total pupil expanding device, the exit pupil unit and one of the pupil expanding units may be combined together by an overlapping region. The overlapping area may be a special area of the diffractive pupil expanding element. The overlapping area only diffracts the light beam output by the pupil expanding unit and does not output or act on the light beam directly diffracted by the entrance pupil unit, so that the function of the whole exit pupil is ensured to be complete and the function of the overlapped pupil expanding area is not influenced.

In an embodiment, the overlapping region may have two diffractive features, including a first diffractive feature to diffract the transmitted light received from the second pupil expanding unit and a second diffractive feature of the overlapping region to diffract the transmitted light received from the second pupil expanding unit. The overlapping region does not have a characteristic of directly diffracting the light diffracted by the entrance pupil unit, or has negligible diffraction efficiency for the light diffracted by the entrance pupil unit. This achieves a minimum of crosstalk while reducing the total pupil device area.

Drawings

In the following examples, several variations will be described in more detail with reference to the accompanying drawings

Figure 1 is a schematic diagram of a prior art optical pupil expansion device;

figure 2 is a front view of the pupil expanding device of the present invention, including the location of the two main paths of light and the overlapping region; figure 3 shows a front view of the pupil expansion device with an overlapping area of 0% according to the invention;

figure 4 shows a three-dimensional view of the pupil expanding device;

figure 5 shows a cross-sectional side view of the pupil expanding device;

fig. 6 shows, by way of example, two images with different unfilled corners are selected through two main paths on an image and are superimposed to obtain an effect diagram of completing the FOV and better uniformity;

figure 7 is a front view of the pupil expanding device of the present invention with detailed structural markings.

Detailed Description

Referring to fig. 2 and 4, the pupil expanding device 100 includes a planar waveguide plate 11 with good flatness, which in turn includes a first optically diffractive entrance pupil unit 10, a second optically diffractive exit pupil unit 20, a third optically diffractive exit pupil unit 30 and a fourth optically diffractive exit pupil unit 40.

The entrance pupil unit 10 may receive the input light beam 200 and the exit pupil unit 40 may provide an expanded output light beam 300 such that the length and width of the output light beam 300 are greater than the length and width of the input light beam 200.

The pupil expanding device 100 may expand the light beam 200 in two dimensions (e.g. in the horizontal direction SX and in the vertical direction SY). The expansion process may also be referred to as exit pupil expansion, ray expansion, and the like. The pupil expanding device 100 may be referred to as a beam expander or an exit pupil expander, etc.

The first unit 10 may be used as a coupling unit. The first optically diffractive entrance pupil unit 10 may form the first and second light transmission lights 11 and 12 by diffracting the input light 200. The first light-conducting light 11 and the second light-conducting light 12 may propagate within the planar waveguide plate 1. The first and second light-conducting light 11, 12 may be confined to the planar waveguide plate 1 for total internal reflection (total internal reflection).

Wherein the term "conducting" may mean that the light propagates inside the planar waveguide 1, the light rays being confined inside the planar waveguide 1 by Total Internal Reflection (TIR). The term "waveguide" may be the same as the term "optical waveguide".

The first light-conducting light 11 and the second light-conducting light 12 may have the same wavelength λ 0. The first unit 10 may couple the input light 200 to two different paths, i.e. through a first main path and a second main path, respectively, to the diffractive exit pupil unit 40.

The light passing through the first optically diffractive entrance pupil unit 10 can be coupled to the exit pupil unit 40 through the second optically diffractive pupil expanding unit 20. The pupil expanding device 100 may provide a first main path from the first optically diffractive entrance pupil unit 10 through the second optically diffractive exit pupil unit 20 to the fourth optically diffractive exit pupil unit 40.

The first optically diffractive entrance pupil unit 10 can also couple light rays to the exit pupil unit 40 through the third optically diffractive pupil unit 30. The pupil expanding device 100 may provide a second main path from the first optically diffractive entrance pupil unit 10 through the third optically diffractive exit pupil unit 30 to the fourth optically diffractive exit pupil unit 40.

The second optically diffractive pupil expanding unit 20 may function as a diffractive pupil expanding unit. First the first light-conducting light 11 may be conducted from the first diffractive entrance pupil unit 10 to the second optically diffractive pupil unit 20, this direction being the first direction DIR 1. The second optically diffractive pupil expanding unit 20 may form the expanded third transmitted light 13 by diffracting the first transmitted light 11. The expanded transmitted light 13 may propagate from the second diffractive pupil expanding unit 20 to the exit pupil unit 40. The expanded guided light 13 may be confined to propagate in the waveguide plate 1 by total internal reflection. In the present embodiment, the second diffractive pupil expanding unit 20 can distribute the transmitted light 13 nearly uniformly to the entire area of the third diffractive exit pupil unit 30.

The fourth optically diffractive exit pupil unit 40 can be used as a diffractive exit pupil unit. As shown in fig. 4, the exit pupil unit 40 may diffract the expanded transmitted light 13 to form output light 130.

The third optically diffractive pupil expanding unit 30 may function as a diffractive pupil expanding unit. First the second guiding light 12 may be conducted from the first diffractive entrance pupil unit 10 to the third optically diffractive exit pupil unit 30, which is the second direction DIR 2. The third optically diffractive pupil expanding unit 30 may form the expanded fourth light guide 14 by diffracting the second light guide 12. The expanded guided light 14 may propagate from the third optically diffractive pupil expanding unit 30 to the fourth optically diffractive exit pupil unit 40. The extended guided light 14 may be confined to propagate in the waveguide plate 1 by total internal reflection. In the present embodiment, the diffractive pupil expanding unit 30 can distribute the guided light 14 nearly uniformly to the entire area of the fourth optically diffractive exit pupil unit 40.

The overlapping region of the third optically diffractive pupil expanding unit 30 and the fourth optically diffractive exit pupil unit 40 is REG1A, which serves to reduce the area of the overall pupil expanding device to the left and right. The overlapping region REG1A may be a special region of the third diffractive pupil-expanding element 30, occupying 0% to 20% of the area size of the third optically diffractive pupil-expanding element 30, where 0% is the case shown in fig. 3, i.e. there is no overlapping region. The overlapping region REG1A diffracts only the light beams 13 and 14 output from the second and third diffractive pupil-expanding units 20 and 30, and does not output or act on the light beams 11 and 12 directly diffracted by the first diffractive entrance pupil unit 10, thereby ensuring that the entire exit pupil functions properly and the function of the overlapping pupil-expanding region is not affected.

In an embodiment, the overlapping region REG1A may have two diffractive features, including a first diffractive feature to diffract the transmitted light 13 received from the second optically diffractive pupil expanding unit 20, and a second diffractive feature of the overlapping region to diffract the transmitted light 14 received from the third optically diffractive pupil expanding unit 30. The overlap region REG1A has no characteristic of directly diffracting the light rays 11 and 12 diffracted by the first diffractive entrance pupil unit 10, or has negligible diffraction efficiency for the light rays diffracted by the first diffractive entrance pupil unit 10. This achieves a minimum of crosstalk while reducing the total pupil device area.

The first direction DIR1 represents the average direction of propagation of the guided light 11. The direction DIR1 may also represent the central axis of propagation of the guided light 11.

The second direction DIR2 represents the average direction of propagation of the guided light 12. The direction DIR2 may also represent the central axis of propagation of the guided light 12.

The angle γ 12 is the angle between the first direction DIR1 and the second direction DIR2, and may be in the range of 45 ° to 135 °.

The fourth optically diffractive exit pupil unit 40 may include an overlap region REG1A and a basic region REG 0. The overlapping region REG1A has been described in the foregoing. The basic region REG0 forms the first output light 130 by diffracting the third transmitted light 13, while the basic region REG0 forms the second output light 140 by diffracting the fourth transmitted light 14. The direction of first diffracted output light 130 and second diffracted output light 140 are in line, with the direction DIR 0'. The overlapping region REG1A diffracts only the light beams 13 and 14 output from the second and third diffractive pupil-expanding units 20 and 30, and does not output or act on the light beams 11 and 12 directly diffracted by the first diffractive entrance pupil unit 10, thereby ensuring that the entire exit pupil functions properly and does not affect the function of the overlapping pupil-expanding region. This achieves a minimum of crosstalk while reducing the total pupil device area.

The first diffracted output light 130 and the second diffracted output light 140 are superposed to obtain an output light beam 300, and the direction DIR0' of the output light beam 300 is parallel to the direction DIR0 of the input light beam 200.

The expanded conducted light 13 may propagate in a third direction, DIR3, DIR 3. The expanded guided light 14 may propagate in a fourth direction DIR 4.

The first main path represents an optical path from the first optically diffractive entrance pupil unit 10 to the fourth optically diffractive exit pupil unit 40 via the second optically diffractive pupil expanding unit 20.

The second main path represents the optical path from the entrance pupil unit 10 to the exit pupil unit 40 via the pupil expanding unit 20. SX, SY, and SZ represent orthogonal directions. The waveguide plate 1 is parallel to the plane defined by the directions SX and SY.

POS1b indicates the center position of the overlapping region REG1A, with the overlapping region REG1A at the corner regions of the exit pupil cell 40. POS1a may indicate the center position of the exit pupil unit 40. In an embodiment, when the guided light is transmitted directly to POS1b or overlap region REG1A in the 12 direction, the light is not diffracted out, but continues to be transmitted to region REG1 by total internal reflection and is diffracted into guided light 14.

Referring to fig. 4, the pupil expanding device 100 comprises two main paths to increase and optimize the uniformity of the spatial intensity distribution and the larger field of view angle FOV of the output light beam 300. For example, the point POS1b in the overlapping region REG1A can receive the light from the light conducting wires 13 and 14 at the same time, and the two light beams can be superimposed by controlling the efficiency of the two light beams, for example, if the intensity of the light conducting wire 13 is small, the light conducting wire 14 can be increased, or if the intensity of the light conducting wire 14 is small, the light conducting wire 13 can be increased. Thereby achieving a better spatial intensity distribution and a larger field of view angle FOV.

The pupil expanding device 100 may optimize the output light beam 300 such that the light intensity (IPOS1a) of the output light beam 300 at a first lateral position (POS1a) is substantially equal to the intensity (IPOS1b) of the output light beam 300 at a second lateral position (POS1 b). The relative difference (IPOS1b-IPOS1a)/IPOS1b needs to be less than 30%, preferably less than 10%. The first lateral position POS1a is in the center of the exit pupil unit 40. The second lateral position POS1b is at the corner of the exit pupil unit 40.

The input light beam 200 has a propagation direction DIR 0. The input light beam 200 may correspond to a point on the display image. The pupil expansion device 100 may convert light of the input light beam 200 into the output light beam 300 such that the output light beam 300 has a propagation direction DIR 0'. After the light input beam 200 is converted into the output beam 300 by the pupil expansion device 100, the direction DIR0' is parallel to the direction DIR 0. The period (d) and direction (β) of the individual diffraction gratings of the cells 10, 20, 30,40 are carefully designed so that the direction DIR0' of the output light beam 300 is parallel to the direction DIR0 of the input light beam 200.

Referring to fig. 5, the display device 500 comprises the pupil expanding device 100 and one optical light engine 400. The display device 500 comprises an optical engine 400, the optical engine 400 providing a primary image 401 and converting the primary image 401 into a plurality of input light beams 200. The light emitted by the optical engine 400 is incident into the first optically diffractive entrance pupil unit 10 of the pupil expanding device 100. The plurality of light beams 200 of input light are diffracted by the first optically diffractive entrance pupil unit 10 into the extended pupil device 100. The display device 500 is a display device for displaying virtual images, or a near-eye optical display device.

The pupil expanding device 100 may conduct the virtual image content from the optical engine 400 in front of the EYE1 of the user. The pupil dilation device 100 may expand the viewing pupil, thereby enlarging the eyebox.

The optical engine 400 may include a micro display 402 to produce a primary image 401. The micro-display 402 may include a two-dimensional array of light-emitting pixels. The display 402 may be a main image 401 generated, for example, at a resolution of 1920 × 1080 (full high definition). The display 402 may generate a main image 401, for example at a resolution of 3840 × 2160(4 khud). The primary image 401 may include a plurality of image points P0, P1. The optical engine 400 may include collimating optics 403 to form a different beam than each image pixel. The light beam from image point P0 of light passes through collimating optics 403 of optical engine 400 to form a substantially collimated light beam. The beam propagation direction corresponding to image point P0 is propagation direction DIR 0. The direction of beam propagation for different image points P1 is different from direction DIR 0. The engine 400 may provide a plurality of light beams corresponding to the generated primary image 401. One or more light beams provided by the optical engine 400 may be coupled to the expander 100 as input light 200.

The optical engine 400 may include, for example, one or more Light Emitting Diodes (LEDs). The display 402 may include, for example, one or more microdisplay imagers, such as Liquid Crystal On Silicon (LCOS), Liquid Crystal Display (LCD), Digital Micromirror Display (DMD), Micro-LED display, or the like.

The basic region (REG0) of the fourth optically diffractive exit pupil unit 40 diffracts the transmitted light 13 transmitted from the pupil expanding unit 20 by the second optical diffraction to emit the first output light 130, and diffracts the transmitted light 14 transmitted from the pupil expanding unit 30 by the third optical diffraction to emit the second output light 140, and the first output light 130 and the second output light 140 are superimposed on each other to form the output light 300. The overlapping region REG1A has the same function, and emits the first output light 130 by diffracting the transmitted light 13 transmitted from the pupil expanding unit 20 by the second diffraction, and emits the second output light 140 by diffracting the transmitted light 14 transmitted from the pupil expanding unit 30, and the first output light 130 and the second output light 140 are superimposed on each other to form the output light 300, and the overlapping region REG1A does not diffract or neglect the diffraction efficiency of the transmitted light 11 and the transmitted light 12.

The direction of propagation of said first output beam component 130 is the direction DIR0', and the direction of propagation of the second output beam component 140 is the same as 130, also the direction DIR 0'. The pupil expansion device 100 can make the direction DIRA 'parallel to the direction DIR0' by the design and control of the grating, so that the first output light 130 and the second output light 140 correspond to the same incident light beam 200 and also correspond to the same point on the image (e.g. P0). Output beam 300 may be formed from input beam 200 such that direction DIR0' is parallel to direction DIR0 of input beam 200.

Each cell 10, 20, 30,40 may contain one or more diffraction gratings as described.

The grating period (d), grating direction (β) and grating vector (V) of the optical unit 10, 20, 30,40 are programmable, by which the directions of the first output light 130 and the second output light 140 are parallel, all in the direction DIR 0'.

By designing the grating period (d), grating direction (β) and grating vector (V) it is achieved that the sum of the grating vectors of the cells 10, 20 and of the region REG0 is zero.

By designing the grating period (d), the grating direction (β) and the grating vector (V) it is achieved that the sum of the grating vector of the cell 10, the grating vector of 20 and the grating vector of the region REG1A is zero.

By designing the grating period (d), the grating direction (β) and the grating vector (V) it is achieved that the sum of the grating vector of the cell 10, the grating vector of the cell 30 and the grating vector of the region REG0 is zero.

By designing the grating period (d), the grating direction (β) and the grating vector (V), it is achieved that the sum of the grating vectors of the cells 10, the grating vectors of the cells 30, and the grating vectors of the regions REGA is zero.

The thickness of the waveguide plate is t 1. The waveguide plate comprises a planar waveguide core. In an embodiment, the waveguide plate 1 may optionally comprise, for example, one or more plating layers, one or more protective layers, and/or one or more mechanical support layers. t1 refers to the thickness of the core portion of the waveguide plate 1.

The pupil expanding device 100 may expand the light beam in both directions SX and SY. The width of the output light beam 300 (in direction SX) may be greater than the width of the input light beam, and the height of the output light beam 300 (along direction SY) may be greater than the height of the input light beam 200.

The pupil expanding apparatus 100 may expand the viewing pupil of the virtual display device 500 to facilitate the positioning of the EYE1 to achieve a large viewing range. An observer of a person to the virtual display device 500 can see a virtual image VIMG1 incident at the position of EYE1 of the observer at the position of the output light 300. The output light 300 may comprise one or more output light beams, characterized in that each output light beam may correspond to a different image point (P0', P1') of the virtual image. The engine 400 includes a microdisplay to display a primary image 401. The optical engine 400 and the pupil expanding device 100 may convert the main image 401 into a display virtual image VIMG1 having a plurality of input light beams, and by forming the output light beams 300, each output light beam may form a different image point (P0', P1') of the virtual image VIMG1, since a plurality of input and output light beams may be comprised from the input light beam 200 to the output light 300. The main image 401 may be a graphic, text or video. The optical engine 400 and the pupil expanding device 100 may display the virtual image VIMG1 such that each image point (P0', P1') of the virtual image VIMG1 corresponds to a different image point of the main image 401.

Fig. 6 shows that the effect of increasing the field angle FOV and improving the uniformity of the output light is achieved by superimposing the first output light 130 with the second output light 140 to form a combined output light 300.

The first main path represents the optical path from the entrance pupil unit 10 via the pupil expanding unit 20 to the exit pupil unit 40, and the image information VIMG1 carried by the output 130 may be the missing corner image information DA1, or the corner image information DA2, or the corner image information DA3, or the corner image information DA 4. The second main path represents the optical path from the entrance pupil unit 10 via the pupil expanding unit 30 to the exit pupil unit 40, and the image information VIMG1 carried by the output 140 may be corner image information DA1, or corner image information DA2, or corner image information DA3, or corner image information DA4, which is different from the image VIMG1 of 130. The image complementation of different corners realizes the functions of increasing the view field angle and improving the uniformity of output light.

Referring to fig. 7, each cell 10, 20, 30,40 may include one or more diffraction gratings for diffracting light. For example, cell 10 may include one or more gratings G1. For example, the cell 20 may include one or more gratings G2. For example, cell 40 may include a grating G4. For example, the base region REG0 may include one or more gratings G4. For example, the overlap region REG1A may include one or more gratings G4A.

A diffraction grating is generally described by a grating period (d), a grating direction (β), and a grating vector (V). In addition, the diffraction grating also includes a plurality of diffractive features (F) that can also be used to design and manipulate the diffracted light. The diffractive properties may be, for example, microscopic ridges or grooves, microscopic protrusions (or depressions), wherein adjacent rows of protrusions (or depressions) may serve as diffraction lines. The grating vector (V) is defined as a vector having a direction perpendicular to the diffraction lines of the diffraction grating and a magnitude of pi/d, where d is the grating period.

The diffractive entrance pupil unit 10 has grating vectors V11, V12. The diffractive pupil expanding element 20 has a grating vector V21. The diffractive pupil expanding element 30 has a grating vector V31. The fourth optically diffractive exit pupil unit 40 has a grating vector V41. The basic region REG0 has raster vectors V41 and V42. The overlap region REG1A has grating vectors V41A, V42A. The grating vector V11 has a direction β 11 and a magnitude of 2 π/d 11. The grating vector V12 has a direction β 12 and a magnitude of 2 π/d 12. The grating vector V21 has a direction β 21 and a magnitude of 2 π/d 21. The grating vector V31 has a direction β 31 and a magnitude of 2 π/d 31. The grating vector V41 has a direction β 41 and a magnitude of 2 π/d 41. The grating vector V42 has a direction β 42 and a magnitude of 2 π/d 42. The grating vector V41A has a direction β 41A and a magnitude of 2 π/d 41A. The grating vector V42A has a direction β 42A and a magnitude of 2 π/d 42A. The grating vector V41 substantially coincides with the grating vector V41A, and the grating vector V42 substantially coincides with the grating vector V42A.

The grating period (d) and the orientation (β) of the grating vector V of the optical elements 10, 20, 30,40 may be chosen such that the first output beam component 130 is parallel to the direction DIR0' of the second output beam component 140.

The angle between the directions of the grating vectors V12, V11 of the first optically diffractive entrance pupil unit 10 may for example be in the range of 45 ° to 135 °. The grating period d12 of the cell 10 may be substantially equal to the grating period d 11. The grating period d12 of the cell 10 may also be equal to the grating period d 11.

The grating period (d) and direction (β) of the grating vectors (V11, V21, V41) may be designed such that, for example, the sum of the vectors of the grating vectors (V11, V21, V41) of the cells 10, 20, 40 is zero. In particular, by means of the detailed design of the grating periods d11, d21, d41 and the directions β 11, β 21, β 41, the grating vectors V11, V21, V41 are controlled such that the vector sum of the grating vectors V11, V21, V41 is zero.

The grating period (d) and direction (β) of the grating vectors (V12, V31, V42) may be designed such that, for example, the sum of the vectors of the grating vectors (V12, V31, V42) of the cells 10, 30,40 is zero. In particular, by means of the detailed design of the grating periods d12, d31, d42 and the directions β 12, β 31, β 42, the grating vectors V12, V31, V42 are controlled such that the vector sum of the grating vectors V12, V31, V42 is zero.

The grating period (d) and direction (β) of the grating vectors (V11, V21, V41A) may be designed such that, for example, the sum of the vectors of the grating vectors (V11, V21, V41A) of the cells 10, 20, 40 is zero. Specifically, by detailed design of the grating periods d11, d21, d41A and the directions β 11, β 21, β 41A, the grating vectors V11, V21, V41A are controlled such that the vector sum of the grating vectors V11, V21, V41A is zero.

The grating period (d) and direction (β) of the grating vectors (V12, V31, V42A) may be designed such that, for example, the sum of the vectors of the grating vectors (V12, V31, V42A) of the cells 10, 30,40 is zero. Specifically, by detailed design of the grating periods d12, d31, d42A and the directions β 12, β 31, β 42A, the grating vectors V12, V31, V42A are controlled so that the vector sum of the grating vectors V12, V31, V42A is zero.

The first optically diffractive entrance pupil unit 10 may have a first grating vector V11 to form a first light-transmitted light 11 along direction DIR1 and a second grating vector V12 to form a second light-transmitted light 12 along direction DIR 2. The first cell 10 may have a first diffractive feature F11, having a first grating period d11 and a first orientation β 11 (with respect to the reference direction SX). The first cell 10 may have a second diffractive feature F12 with a second grating period d12 and a second orientation β 12 (with respect to the reference direction SX). The first optically diffractive entrance pupil unit 10 may be, for example, a grating as shown in the figure, realized by a crossed grating or by two linear gratings. A first linear grating with features F11 may be arranged on a first side of the slab 1 (e.g. on the input side SRF 1) and a second linear grating with features F12 may be arranged on a second side of the waveguide slab 1 (e.g. on the output side SRF 2), or both two-dimensional gratings arranged with the same side surface SRF1 or surface SRF 2. The features of the diffraction grating may be, for example, microscopic ridges or microscopic protrusions.

A grating having a single grating feature may be disposed on surface SRF1 or surface SRF2, a grating having two or more grating features may be disposed on surface SRF1 or surface SRF2, respectively, or on one of the surfaces in the form of a two-or multi-dimensional grating. The gratings are described herein.

The second cell 20 may have a first grating vector V21 to diffract the first light-transmitted light 11 into a third light-transmitted light B3. The grating G2 of the second cell 20 may have a diffraction signature F21 with a grating period d21 and an orientation β 21 (with respect to the reference direction SX).

The third optically diffractive pupil expanding unit 30 may have a first grating vector V31 to diffract the second light guide 12 into the fourth light guide 14. The grating G3 of the third optically diffractive pupil unit 30 may have a diffractive feature F31 with a grating period d31 and an orientation β 31 (with respect to the reference direction SX).

The base region REG0 of the fourth optically diffractive exit pupil unit 40 may have a first grating vector V41 to diffract the third light guiding light B3 to form the output light beam 130 and to diffract the fourth light guiding light 14 to form the output light beam 140. The fourth optically diffractive exit pupil unit 40 may have a first diffractive feature F41 with a first grating period d41 and a first orientation β 41 (with respect to the reference direction SX). The fourth optically diffractive exit pupil unit 40 may have a second diffractive feature F42 with a second grating period d42 and a second orientation β 42 (with respect to the reference direction SX). The fourth optically diffractive exit pupil unit 40 may be, for example, a grating as shown in the figure, realized by a crossed grating or by two linear gratings. A first linear grating with features F41 may be arranged on a first side of the slab 1 (e.g. on the input side SRF 1) and a second linear grating with features F42 may be arranged on a second side of the waveguide slab 1 (e.g. on the output side SRF 2), or both two-dimensional gratings arranged with the same side surface SRF1 or surface SRF 2. The features of the diffraction grating may be, for example, microscopic ridges or microscopic protrusions.

The overlap region REG1A may have a first grating vector V41A to diffract the third conductive light B3 to form the output beam 130 and to diffract the fourth conductive light B4 to form the output beam 140. The overlap region REG1A may have a first diffraction signature F41A with a first grating period d41A and a first orientation β 41A (with respect to the reference direction SX). The overlap region REG1A may have a second diffraction signature F42A, with a second grating period d42A and a second orientation β 42A (with respect to the reference direction SX). The overlap region REG1A may be, for example, a grating as shown in the figures implemented by a crossed grating or by two linear gratings. A first linear grating with features F41A may be arranged on a first side of the slab 1 (e.g. on the input side SRF 1) and a second linear grating with features F42 may be arranged on a second side of the waveguide slab 1 (e.g. on the output side SRF 2), or both arranged as two-dimensional gratings again of the same side surface SRF1 or surface SRF 2. The features of the diffraction grating may be, for example, microscopic ridges or microscopic protrusions. The overlapping region REG1A almost coincides with the region REG0 structure. However, the REG1A region may not diffract the light 12 directly by design, or the diffraction efficiency may be less than 10% or less.

The overlap region REG1A may have a high outcoupling efficiency for diffractively coupling the guided light B3 and B4 out of the waveguide plate 1.

The cells 10, 20, 30,40 may be positioned and sized such that the first light-conducting light (11) does not interact with the cells 30 and 40 and the second light-conducting light (12) does not interact with the cell 20. Although some of the light-conducting 12 interacts with the cells 40, the effect of the interaction is negligible by the grating design.

The first cell 10 may have a width w1 and a height h 1. The second cell 20 may have a width w2 and a height h 2. The third optically diffractive pupil expanding unit 30 may have a width w3 and a height h 3. The fourth optically diffractive exit pupil unit 40 may have a width w4 and a height h 4. The width indicates the dimension in the direction SX, and the height indicates the dimension in the direction SY. The exit pupil unit 40 may be rectangular. The edges of the diffractive exit pupil unit 40 are along the directions SX and SY, respectively.

The width w2 of the pupil expanding unit 20 is much larger than the width w1 of the entrance pupil unit 10. The width of the expanded conducted light beam B3 is much greater than the width of the input light beam 200. The height h3 of the pupil expanding unit 30 is much larger than the height h1 of the entrance pupil unit 10. The width of the expanded conducted optical beam 14 is much greater than the height of the input optical beam 200.

POS1a represents the center point of the diffractive exit pupil unit 40. The position POS1b may be the corner region REG1A of the exit pupil unit 40. The horizontal distance between the positions POS1a, POS1b may be, for example, around 40% of the width w4 of the diffractive exit pupil unit 40.

The waveguide plate 1 may be composed of a transparent solid material. The waveguide plate 1 may be made of, for example, glass, polycarbonate, or polymethyl methacrylate (PMMA). The diffractive optical element 10, 20, 30,40 may be formed, for example, by molding, embossing and/or etching, holographic exposure, etc. The cells 10, 20, 30,40 may be realized, for example, by one or more surface diffraction gratings or by one or more volume holographic diffraction gratings.

In one embodiment, the input light 200 may be substantially monochromatic or a different input wavelength λ 0. All light beams 200, 11, 12, 13, 14, 300, 130, 140 may have the same wavelength λ 0.

The spatial distribution of the diffraction efficiency can only be controlled by selecting the local parameters of the microscopic diffraction features F. The uniformity of the intensity distribution of the output light 300 can be further improved by controlling the parameters of the microscopic diffraction features F of the exit pupil unit 40.

The display device 500 may be a virtual reality apparatus 500 or an augmented reality device 500. The display device 500 may be a near-eye device or may be a wearable device, such as an earpiece. The device 500 may be used, for example, in a headband, through which the device 500 may be worn on the head of a user. In use, the diffractive exit pupil element 304 of the device 500 is placed in front of the user's left EYE1 or right EYE 1. Apparatus 500 may project output light 300 into the EYE1 of the user. In one embodiment, the apparatus 500 may include two engines 400 and/or two pupil expanding devices 100 to display a stereoscopic image. With the augmented reality device 500, the viewer can see not only the virtual image displayed by the pupil expanding device 100, but also real objects and/or environments. The engine 400 may generate still images and/or video. The engine 400 may generate a real main image 401 from the digital image. The engine 400 may receive one or more digital images from an internet server or from a smartphone. The device 500 may be a smartphone. The displayed image may be visible to a person, but may also be viewed, for example, by an animal or machine (which may include, for example, a camera).

Modifications and variations of the apparatus and method according to the invention may be apparent to those skilled in the art. The figures are schematic representations, and the specific embodiments described above in connection with the accompanying drawings are illustrative only and not meant to limit the scope of the invention, which is defined by the appended claims.

Claims (8)

1. An optical pupil expanding device (100) comprising a waveguide plate (1), characterized in that the waveguide plate (1) comprises:

a first optical diffractive entrance pupil unit (10) for diffracting an input light beam (200) to form first and second transmitted light (11, 12);

a second optical diffractive pupil expanding unit (20) for diffracting the first transmitted light (11) to form a third transmitted light (13);

a third optically diffractive pupil expanding unit (30) for diffracting the second light transmission (12) to form a fourth light transmission (14); and the number of the first and second groups,

a fourth optically diffractive exit pupil unit (40) for diffracting the third light guide (13) to form a first output light (130) and diffracting the fourth light guide (14) to form a second output light (140);

wherein the first light-conducting light (11) propagates in a first direction (DIR1) and the second light-conducting light (12) propagates in a second direction (DIR 2); the angle formed between the first direction (DIR1) and the second direction (DIR2) is γ 12, said γ 12 being between 45 ° and 135 °;

wherein the fourth optically diffractive exit pupil unit (40) comprises one or more regions (REG0, REG1A), the overlapping region of the fourth optically diffractive exit pupil unit (40) and the third optically diffractive pupil unit (30) being REG 1A;

the superposition of the first output light (130) and the second output light (140) results in an output light beam 300.

2. The apparatus according to claim 1, wherein the overlapping region (REG1A) of the fourth optically diffractive exit pupil unit (40) and the third optically diffractive exit pupil unit (30) does not diffract the second guided light (12) out of the waveguide plate (1); the overlap region (REG1A) occupies 0% to 20% of the area of the third optically diffractive pupil-expanding element 30.

3. The apparatus of claim 2, wherein the overlap region (REG1A) forms the first output light (130) by diffracting the third guided light (13), while forming the second output light (140) by diffracting the fourth guided light (14), and forms the combined output light (300) by superimposing the first output light (130) with the second output light (140).

4. The apparatus of claim 3, the first transmitted light (11) not interacting with the third and fourth optically diffractive pupil expanding units 30,40, the second transmitted light (12) not interacting with the second optically diffractive pupil expanding unit 20; the diffractive effect of the fourth optically diffractive exit pupil unit 40 on the transmitted light 12 is negligible.

5. A device as claimed in any one of claims 1 to 4, the image information carried by the first output light 130 having a different or complementary angular and colour uniformity to that carried by the second output light 140.

6. A display device (500) comprising the beam expanding pupil device (100) of any one of claims 1 to 5, characterized in that: further comprising an optical engine (400) for forming a primary image and converting the primary image into a plurality of said input optical beams (200), said beam expanding pupil device expanding said input optical beams (200) by diffraction to form said output optical beams (300).

7. Method of providing an output light beam (300) using the pupil expanding device (100) of any of claims 1 to 5.

8. Method of displaying an image using the pupil expansion device (100) of any of claims 1 to 6.

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