CN114839765A

CN114839765A - Optical pupil expanding device with large field angle, display device and method

Info

Publication number: CN114839765A
Application number: CN202210226531.7A
Authority: CN
Inventors: 蒋厚强; 塔帕尼·卡列沃·利沃拉; 朱以胜
Original assignee: Shenzhen Guangzhou Semiconductor Technology Co ltd
Current assignee: Shenzhen Guangzhou Semiconductor Technology Co ltd
Priority date: 2022-03-09
Filing date: 2022-03-09
Publication date: 2022-08-02
Also published as: WO2023169502A1

Abstract

The invention discloses an optical pupil expanding device with a large field angle, a display device and a method, comprising a waveguide plate, wherein the waveguide plate comprises: an entrance pupil unit that forms first transmitted light by diffracting input light, a light splitting unit that forms second transmitted light by diffracting the first transmitted light, a first pupil expanding unit that forms third transmitted light by diffracting the second transmitted light, a second pupil expanding unit that forms fourth transmitted light by diffracting the first transmitted light, and an exit pupil unit that forms first output light by diffracting the third transmitted light and forms second output light by diffracting the fourth transmitted light, the exit pupil unit combining the first output light and the second output light to form combined output light; the light splitting unit and the first pupil expanding unit have the same first grating period, and the second pupil expanding unit and the first pupil expanding unit have different second grating periods.

Description

Optical pupil expanding device with large field angle, display device and method

Technical Field

The invention relates to an optical pupil expanding device with a large field angle, a display device and a method, which can be used in a virtual display device.

Background

Referring to fig. 1, the pupil expanding device EPE0 comprises a waveguide plate SUB01, which in turn comprises a diffractive entrance pupil unit DOE01, a diffractive pupil expanding unit DOE02 and a diffractive exit pupil unit DOE 03. One input light IN1 is expanded by multiple diffraction IN the pupil expanding device EPE0, and finally outputs light OUT 1.

Input light IN1 is emitted by optical engine ENG 1. The optical engine ENG1 may be comprised of a micro display DISP1 and collimating optics LNS 1.

The diffractive entrance pupil unit DOE01 diffracts the input light IN1 into first transmitted light B1 by diffraction. The first light guiding light B1 is diffracted by a diffractive pupil expanding unit DOE02 to form expanded second light guiding light B2. The expanded second light guiding B2 is diffracted by the diffractive exit pupil unit DOE03 as output light OUT 1.

The pupil expanding device EPE0 may expand the light beam in both directions SX and SY. The width of output light OUT1 is much larger than the width of input light IN 1. 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 comprise one or more output beams, where each output beam may correspond to a different image location of the displayed virtual image VIMG 1. The pupil expansion device may also be referred to as, for example, a pupil expansion unit, a pupil expansion device, or the like.

The virtual image VIMG1 has an angular amplitude LIM 1. Fig. 1 shows a way of displaying a full-color virtual image VIMG1 by using the pupil expanding device EPE0, and the total reflection condition of the waveguide plate SUB01 cannot be satisfied during transmission due to the corner rays of the virtual image VIMG1 corresponding to red and blue. Therefore, the corner of the virtual image VIMG1 appears to lack red or blue.

The CN112817153A solution provides a pupil-expanding device to solve the problem that the corner of the virtual image VIMG1 is lack of red or blue, but the incident light needs to be further improved because by splitting the entrance pupil into two semicircles, a path is coupled in only from one of the semicircles for a single color complete image to be transmitted (the other path cannot transmit or can only partially transmit the color image), and the image energy of the single path is only from the coupling-in area of a half circle, which is too small.

Disclosure of Invention

The present invention proposes a new pupil expanding device, and at the same time a method of expanding light beams, and at the same time a display device, and a method for displaying an image, which may provide a larger field of view angle (FOV).

According to its configuration, the invention proposes an optical pupil expansion device (EPE1), the key parts of which are as follows:

waveguide plate (SUB1), comprising:

an entrance pupil unit (DOE1) that diffracts the input light (IN1) by the entrance pupil unit (DOE1) to form first transmitted light (B1B);

a light splitting unit (DOEbs) for diffracting the first light-conducting light (B1B) by the light splitting unit (DOEbs) to form a second light-conducting light (B1a) for enhancing energy input of the first light-conducting light (B1B) and the second light-conducting light (B1 a);

a first pupil expanding unit (DOE2a) that forms a third light-guiding light (B2a) by diffracting the second light-guiding light (B1 a);

a second pupil expanding unit (DOE2B) that forms a fourth light-transmitting light (B2B) by diffracting the first light-transmitting light (B1B); and

an exit pupil unit (DOE3) for forming a first output light (OB3a) by diffracting the third transmitted light (B2a) and for forming a second output light (OB3B) by diffracting the fourth transmitted light (B2B);

wherein the exit pupil unit (DOE3) combines the first output light (OB3a) and the second output light (OB3b) forming a combined output light (OUT 1); wherein the first pupil expanding unit (DOE2a) has a first grating period (d1a) for forming the third light guiding light (B2a), and the second pupil expanding unit (DOE2B) has a different second grating period (d1B) for forming the fourth light guiding light (B2B).

Other embodiments are defined in the claims.

The scope of protection sought for the various embodiments of the invention is defined by the independent claims. The embodiments described in the present invention, if any, which do not belong to the scope of the independent claims are to be interpreted as examples to facilitate the understanding of the various embodiments of the invention.

The pupil expanding device may be used to display a color image, wherein the display width of the color image is increased. The color image may be an RGB image, comprising red (R) light, green (G) light, and blue (B) light.

Increasing the width of the displayed image may result in leakage of blue and/or red light at the corner points of the displayed image. In other words, red or blue light, which is formed by the entrance pupil unit of the pupil expanding device, cannot be confined entirely within the waveguide plate by total internal reflection.

The pupil expansion device can be designed to contain two different light paths in order to overcome the limitation of the waveguide plate for different colors of light in the corresponding propagation directions when transmitting a wide image.

The pupil expanding device may divide the light coupled in through the entrance pupil unit by the light splitting unit to propagate to the exit pupil unit through the first path and through the second path, respectively. The first path may be realized from the light splitting unit to the exit pupil unit by the first pupil expanding unit. The second path may be realized from the light splitting unit to the exit pupil unit through a second pupil expanding unit. By optimizing the first path for propagating blue light at a corner point, while by optimizing the second path for propagating red light at a corner point. Thus, the pupil expanding device can cause the red and blue colors of the displayed image to be displayed normally at all corner points. The corner red light may be conducted through at least one path, and the corner blue light may be conducted through at least one path.

When optimization and an increase in the angular amplitude of the displayed image are required, the first path may have red light loss at the corner points of the displayed image and the second path may have blue light loss at the corner points of the displayed image. However, the red light propagating along the second path may at least partially compensate for the loss of red light from the first path. The blue light propagating along the first path may at least partially compensate for the loss of blue light from the second path.

The two paths share a common entrance pupil unit, and the display image frame is usually rectangular, for example 16: 9, the angular width of the three colors of the image is smaller in the short side direction than in the long side direction, and the total angular width of the short side direction is smaller after the three colors of the image are subjected to grating dispersion widening, so that it is still possible to design the grating period and direction of the entrance pupil unit, so that the red light and the blue light at the corner points of the image can be limited in the waveguide plate after the image passes through the entrance pupil unit, and the first light transmission is formed.

The light splitting unit is used for partially separating light of one or two colors, such as blue light and green light, and forming second transmission light, the propagation direction of the second transmission light is different from that of the first transmission light, and the light of angular falling points of the blue light and the green light can be limited in the waveguide plate by designing the grating period and the direction of the light splitting unit. The first light-transmitting light can partially pass through the light-splitting unit, and the propagation direction is not influenced. Therefore, the image light in the waveguide forms two propagation paths after passing through the light splitting unit.

The two paths together may at least partially compensate for color deviations of corner points of the displayed image. The two paths may reduce or avoid color errors at corner points of a wide color display image. The two paths may improve the color uniformity of a wide color display image.

The exit pupil unit may form the first output light by diffracting the third transmitted light propagating along the first path. The diffracted third conducted light is from the first pupil expanding unit. The exit pupil unit may form the second output light by diffracting fourth transmitted light that propagates along the second path. The diffracted fourth conducted light is from the second pupil expanding unit. The first output light may spatially overlap with the second output light. By combining the first output light with the second output light, a combined output light is formed at the exit pupil unit.

The exit pupil unit may contain first diffractive features to diffract the transmitted light received from the first pupil expanding unit. The exit pupil unit may contain second diffractive features to diffract the transmitted light received from the second pupil expanding unit. The first diffractive feature may have a fourth grating period and the second diffractive feature may have a different fifth grating period. The fourth grating period may be selected to ensure that the blue guided light at the corner points is confined within the waveguide plate. The fifth grating period may be chosen to ensure that the red guided light at the corner points is confined within the waveguide plate. The first diffractive feature may have a first direction and the second diffractive feature may have a different second direction. The first diffractive feature may have a very low or negligible out-coupling pupil efficiency for light received from the second pupil expanding unit. The second diffractive feature may be very low or negligible for the coupled-out pupil efficiency of the light received from the first pupil expanding unit.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

Figure 1 is a schematic diagram of a conventional pupil expansion device 20;

FIGS. 2 a-2 e are three-dimensional views illustrating examples of incident light rays formed using an optical engine;

FIG. 2f is an example of a display process for representing a virtual image in a three-dimensional view;

FIG. 2g is an example of horizontal angular amplitude (angular width) of a virtual image;

FIG. 2h is an example of pitch angle amplitude (angular height) of a virtual image;

figure 3a is an example of a front view of a pupil expanding device providing two different paths for the entrance pupil rays;

figure 3b is a schematic diagram of the R channel energy in RGB of a conventional pupil expansion device;

figure 3c is a schematic diagram of the G channel energy in RGB of the conventional pupil expanding device;

figure 3d is a schematic diagram of the B channel energy in RGB of a conventional pupil expansion device;

figure 3e is a schematic diagram of the R channel energy in RGB of the pupil expanding device of figure 3 a;

figure 3f is a schematic diagram of the G channel energy in RGB of the pupil expanding device of figure 3 a;

figure 3g is a diagram of the B channel energies in RGB for the pupil expanding device of figure 3 a;

figure 4a shows an example of a display device comprising a pupil expanding device in a three-dimensional view;

figure 4b shows an example of a display device comprising a pupil expanding device in a cross-sectional view;

figure 5a is an example of a vector diagram of the blue light wave vector propagating along the first path of the pupil expanding device in an embodiment of the present invention;

figure 5b is an example of a vector diagram of the red light wave vector propagating along the first path of the pupil expanding device in an embodiment of the present invention,

FIG. 5c is an exemplary vector diagram of the blue light wave vectors of the image corner points in an embodiment of the present invention;

FIG. 5d is an exemplary vector diagram of the blue light wave vectors of the corner points of the image in an embodiment of the present invention;

FIG. 5e is an exemplary vector diagram of the red wave vectors of the image corner points in an embodiment of the present invention;

FIG. 5f is an exemplary vector diagram of the red wave vectors of the image corner points in an embodiment of the present invention;

FIG. 5g is a diagram of a first guided light formed by coupling an input optical beam into a waveguide plate, where the first guided light has a tilt angle near the critical angle for total internal reflection, according to an embodiment of the present invention;

FIG. 5h shows an embodiment of the present invention where a first guided light is formed by coupling an input light beam into a waveguide plate, where the first guided light is tilted at an angle close to 90 degrees;

FIG. 5i is a diagram illustrating a relationship between a wave vector angle of the first light guiding and a wave vector angle of the input light according to an embodiment of the present invention;

figure 6a is an example of a vector diagram of the blue light wave vector propagating along the second path of the pupil expanding device in an embodiment of the present invention;

figure 6b is an example of a vector diagram of the red light wave vectors propagating along the second path of the pupil expanding device in an embodiment of the present invention;

FIG. 6c is an exemplary vector diagram of the blue light wave vectors of the image corner points in an embodiment of the present invention;

fig. 6d is a vector diagram example of the blue light wave vector of the image corner point in the embodiment of the present invention.

Detailed Description

As shown in fig. 2a to 2e, the optical engine ENG1 may be composed of a display DISP1 and collimating optics LNS 1. The display DISP1 may be arranged to display an input image IMG 0. The display DISP1 may also be referred to as a microdisplay or microdisplay. The display DISP1 may also be referred to as a spatial intensity modulator. The input image IMG0 may also be referred to as an image source.

The input image IMG0 may include a center point P0 and four corner points P1, P2, P3, P4. P1 may represent the top left corner drop point. P2 may represent the upper right corner drop point. P3 may represent the lower left corner drop point. P4 may represent the lower right corner drop point. The input image IMG0 may contain graphical characters such as "F", "G", and "H".

The input image IMG0 may be a color image. The input image IMG0 may be, for example, an RGB image, which may contain a red partial image, a green partial image, and a blue partial image. Each image point may provide, for example, red, green and/or blue light. The red beam of light may have a red color, e.g., a wavelength of 650nm, and the green beam of light may have a green color, e.g., a wavelength of 510 nm. The light of the blue beam may have a blue color, e.g. a wavelength of 470 nm. In particular, the light at the corner points of the color image IMG0 may include red and blue light.

The optical engine ENG1 may provide input light IN1, which may comprise a plurality of substantially collimated light beams (B0). Each red light beam may travel in a different direction and may correspond to a different point of the input image IMG 0. For example, the red beam B0 _P1，R May correspond to an image point P1 and at a wave-vector k0 _P1，R Is propagated in the direction of (a).

Furthermore, blue light beam B0 _P1，B May correspond to the same image point P1 and at wave vector k0 _P1，B Is propagated in the direction of (a).

Of the input light IN1, the blue light beam B0 corresponding to the first corner point P1 of the input image IMG0 _P1，B Propagation direction k0 _P1，B The red light beam B0 corresponding to the first angle point P1 can be parallel _P1，R Propagation direction k0 _P1，R 。

The second corner point P2 of the input image IMG0 corresponds to the input light IN1Blue light beam B0 _P2，B Propagation direction k0 _P2，B The red light beam B0 corresponding to the second corner point P2 can be parallel _P2，R Propagation direction k0 _P2，R 。

Red light beam B0 _P2，R May correspond to an image point P2 and at a wave-vector k0 _P2，R Is propagated in the direction of (a). Red light beam B0 _P3，R May correspond to an image point P3 and at a wave-vector k0 _P3，R Is propagated in the direction of (a). Red light beam B0 _P4，R May correspond to an image point P4 and at a wave-vector k0 _P4，R Is propagated in the direction of (a). Red light beam B0 _P0，R May correspond to the central image point P0 and at the wave-vector k0 _P0，R Is propagated in the direction of (a).

The wave vector (k) of light can be defined as a vector having a propagation direction of said light and having an amplitude given by 2 pi/lambda, where in is the wavelength of said light.

Referring to fig. 2f, output light OUT1 (i.e., combined output light OUT1) may comprise a plurality of output beams, which may correspond to displayed virtual image VIMG 1. Each output beam may correspond to a point of the image. For example, at the wave vector k3 _P0，R May correspond to point P0' of the virtual image VIMG 1. Wave vector k3 _P1，R May correspond to point P1' of the virtual image VIMG 1. Along wave vector k3 _P2，R May correspond to point P2' of the virtual image VIMG 1. Wave vector k3 _P3，R May correspond to point P3' of the virtual image VIMG 1. Wave vector k3 _P4，R May correspond to point P4' of the virtual image VIMG 1.

The pupil expanding device EPE1 may form the output light OUT1 by expanding the exit pupil of the optical engine ENG 1. Output light OUT1 may include a plurality of output beams that correspond to a displayed virtual image VIMG 1. The output light beam OUT1 may be illuminated on the observer's EYE1 so that the observer can see the displayed virtual image VIMG 1.

The virtual image VIMG1 may be displayed with a center point P0 ' and four corner drop points P1 ', P2 ', P3 ', P4 '. The input light IN1 may include a plurality of light beams corresponding to points P0, P1, P2, P3, P4 of the input image IMG 0. The pupil expanding device EPE1 may form a point P0' of the displayed virtual image VIMG1 by diffracting and guiding light from the point P0 of the input image IMG 0. The pupil expanding device EPE1 may form points P1 ', P2', P3 ', P4' by diffracting and transmitting light from the points P1, P2, P3, P4, respectively.

The pupil expanding device EPE1 may form an output light OUT1 comprised by the wave vector k3 _P0，R ，k3 _P1，R ， k3 _P2，R ，k3 _P3，R ，k3 _P4，R Etc. in specified different directions.

The red light beam corresponding to the point P0' of the displayed virtual image VIMG1 has a wave vector k3 _P0，R . The red light beam corresponding to the point P1' of the virtual image VIMG1 has a wave vector k3 _P1，R . The red light beam corresponding to the point P2' of the virtual image VIMG1 has a wave vector k3 _P2，R . The red light beam corresponding to the point P3' of the virtual image VIMG1 has a wave vector k3 _P3，R . The red light beam corresponding to the point P4' of the virtual image VIMG1 has a wave vector k3 _P4，R 。

The pupil expanding unit EPE1 may be designed such that the wave vector k3 _P1，R With the wave-vector k0 of the red beam at the point P1 IN the input light IN1 _P1，R Parallel. Wave vector k3 _P0，R May intersect the wave vector k0 of the point P0 IN the input light IN1 _P0，R Parallel. Wave vector k3 _P2，R May intersect the wave vector k0 of the point P2 IN the input light IN1 _P2，R Parallel. Wave vector k3 _P3，R May intersect the wave vector k0 of the point P3 IN the input light IN1 _P3，R Parallel. Wave vector k3 _P4，R May intersect the wave vector k0 of the point P4 IN the input light IN1 _P4R Parallel.

In fig. 2g and 2h, the virtual image VIMG1 is shown having an angular width Δ

And an angular height Δ θ.

The displayed virtual image VIMG1 may have, for example, the left side of the virtual image VIMG1A first corner point P1 'on the side, and a second corner point P2' on the right side of the virtual image VIMG1, for example. The angular width of the virtual image VIMG1 may be equal to the wave vector k3 of the corner point P1', P2 _P1，R ，k3 _P2，R The horizontal included angle therebetween.

The displayed virtual image VIMG1 may have an upper corner point P1 'and a lower corner point P3'. The angular height Δ θ of the virtual image VIMG1 may be equal to the wave vector k3 of the corner point P1', P3 _P1，R ，k3 _P3，R The vertical included angle therebetween.

The two paths of the pupil expanding device EPE1 may allow displaying a wide color virtual image VIMG 1. The two paths of the pupil expanding device EPE1 may allow the display to have an expanded angular width Δ

The color virtual image VIMG 1.

Passing azimuth

And θ to specify the direction of the wave vector. The angle may represent the angle between the wave vector and the reference plane REF 1. The reference plane REF1 may be defined as the plane of the directions SZ and SY. The angle θ may represent the angle between the wave vector and the reference plane REF 2. The reference plane REF2 may be defined as the plane of the directions SZ and SX.

Referring to fig. 3a, the pupil expanding device EPE1 may comprise a substantially planar waveguide plate SUB1, the waveguide plate SUB1 in turn comprising an entrance pupil unit DOE1, a beam splitting unit DOEbs, a first pupil expanding unit DOE2a, a second pupil expanding unit DOE2b and an exit pupil unit DOE 3. The grating elements used may be on the first surface or on the second surface of the waveguide plate SUB 1.

The entrance pupil unit DOE1 may receive the input light IN1, while the exit pupil unit DOE3 may provide the output light OUT 1. The input light IN1 may comprise multiple light beams propagating IN different directions. Output light OUT1 may include a plurality of expanded light beams formed by light beams (B0) IN input light IN 1.

Width w of output light OUT1 _OUT May be larger than the width w of the input light IN1 _IN1 . The pupil expanding device EPE1 may expand the input light IN1 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 pupil expansion. The pupil expanding device EPE1 may be referred to as a beam pupil expanding device or an exit pupil expanding device.

The entrance pupil unit DOE1 may form the first light-transmitting light B1B by diffracting the input light IN1, and the light splitting unit DOEbs may form the second light-transmitting light B1a by diffracting the first light-transmitting light B1B. The first light guiding light B1B and the second light guiding light B1a may propagate within a planar waveguide plate SUB 1. The first light guiding light B1B and the second light guiding light B1a may be confined within the waveguide plate SUB1 by total internal reflection.

The term "conducting" may denote that light propagates within the planar waveguide plate SUB1, thereby confining the light beam within the waveguide plate by Total Internal Reflection (TIR). The term "guide" may mean the same meaning as the term "waveguide".

The light splitting unit DOEbs may split the light into two different paths, which propagate to the exit pupil unit DOE3 via the first and second pupil expanding units DOE2a and DOE2b, respectively. The entrance pupil unit DOE1 passes through the beam splitting unit DOEbs by optical coupling, through the first pupil expanding unit DOE2a and finally to the exit pupil unit DOE 3. It is also possible to enter the pupil unit DOE1 by optical coupling, through DOEbs, through the second pupil expanding unit DOE2b and finally to the exit pupil unit DOE 3. The pupil expanding device EPE1 may provide a first path from the entrance pupil unit DOE1, via the beam splitting unit DOEbs, to the first pupil expanding unit DOE2a, and to the exit pupil unit DOE 3. The pupil expanding device EPE1 may provide a second path from the entrance pupil unit DOE1, via the beam splitting unit DOEbs, to the second pupil expanding unit DOE2b, and to the exit pupil unit DOE 3.

The second guided light B1a may propagate from the light splitting unit DOEbs to the first pupil expanding unit DOE2a mainly along the first direction DIR1 a. The first pupil expanding unit DOE2a may form the third light guiding light B2a by diffracting the second light guiding light B1 a. The lateral dimensions of the third light-conducting light B2a may be larger than the corresponding lateral dimensions of the input light IN 1. The third conducted light B2a may also be referred to as expanded conducted light B2 a.

The expanded conducted light B2a may propagate from the first pupil expanding unit DOE2a to the exit pupil unit DOE 3. The expanded conducted light B2a may be confined within the waveguide plate SUB1 by total internal reflection.

The exit pupil unit DOE3 may form the first output light OB3a by diffracting the expanded transmitted light B2 a.

The first light guiding light B1B may propagate from the entrance pupil unit DOE1 via the beam splitting unit DOEbs to the second pupil expanding unit DOE2B mainly along the second direction DIR 1B. The second pupil expanding unit DOE2B may form the fourth light guiding light B2B by diffracting the first light guiding light B1B. The lateral dimensions of the fourth light-conducting B2a may be larger than the corresponding lateral dimensions of the input light IN 1. The fourth conducted light B2B may also be referred to as expanded conducted light B2B.

The expanded conducted light B2B may propagate from the second pupil expanding unit DOE2B to the exit pupil unit DOE 3. The expanded conducted light B2B may be confined within the waveguide plate SUB1 by total internal reflection. The exit pupil unit DOE3 may form the second output light OB3B by diffracting the expanded transmitted light B2B.

The exit pupil unit DOE3 may diffract the third guiding light B2a received from the first expanding pupil unit DOE2a, while the exit pupil unit DOE3 may diffract the fourth guiding light B2B received from the second expanding pupil unit DOE 2B.

The first direction DIR1a may represent an average propagation direction of the second guided light B1 a. The first direction DIR1a may also represent the central axis of propagation of the second guided light B1 a.

The second direction DIR1B may represent the average propagation direction of the first light-conducting B1B. The second direction DIR1B may also represent the central axis of propagation of the first light-conducting light B1B.

An angle γ between the first direction DIR1a and the second direction DIR1b _ab And may be in the range of 60 deg. to 120 deg..

Expanded conducted light B2a may propagate in a third direction DIR2a, which may be substantially parallel to second direction DIR 1B. Expanded conducted light B2B may propagate in fourth direction DIR2B, which may be substantially parallel to first direction DIR1 a.

The waveguide plate SUB1 may contain one or more optical isolation units ISO1 to prevent direct optical coupling between the first and second pupil expanding units DOE2a, DOE2 b. The optical isolation unit ISO1 may be realized by depositing a (black) absorbing material on the surface of the waveguide plate, or (and) by adding a (black) absorbing material into the area of the waveguide plate, or (and) by forming one or more openings in the waveguide plate.

SX, SY and SZ are orthogonal directions. The waveguide plate SUB1 may be parallel to the plane defined by SX and SY.

Fig. 3 b-3 d are energy output simulation images of the exit pupil RGB of the pupil expanding device in CN112817153A, and fig. 3 e-3 g are energy output simulation images of the exit pupil RGB of the pupil expanding device of fig. 3 a. The simulated image represents the relative intensity of the image of the region by color, and the corresponding color internal standard number is the relative average value of the energy per unit area of the color region.

In the R channel, the mean energy per unit area of the R channel simulation image of CN112817153A shown in figure 3b is between 1.0 and 4.0, the mean energy per unit area of the R channel simulation image of the pupil expanding device of figure 3a is between 3.0 and 10.0, and the simulation energy of the pupil expanding device of figure 3a in the R channel is larger than that of CN 112817153A.

In the G channel, the mean energy per unit area of the G channel simulation image of CN112817153A shown in figure 3c is between 1.0 and 4.0, the mean energy per unit area of the R channel simulation image of the pupil expanding device of figure 3a is between 6.0 and 16.0, and the simulation energy of the pupil expanding device of figure 3a in the G channel is larger than that of CN 112817153A.

In the B channel, the mean energy per unit area of the B channel simulated image of CN112817153A shown in figure 3d is between 1.0 and 4.0, the mean energy per unit area of the R channel simulated image of the pupil expanding device of figure 3a is between 2.0 and 13.0, and the simulated energy of the pupil expanding device of figure 3a in the B channel is larger than that of CN 112817153A.

The pupil expanding device of figure 3a thus has a more energetic effect on the diffraction intensity of the incident light in the exit pupil cell DOE3 than the pupil expanding device in CN112817153A has a better display effect.

Referring to fig. 4a to 4b, the pupil expanding device EPE1 may form the output light OUT1 by diffracting and guiding the input light IN1 obtained from the optical engine ENG 1. The display device 500 may comprise an optical engine ENG1 and a pupil expanding device EPE 1.

The input light IN1 may comprise multiple light beams propagating IN different directions. Each beam of input light IN1 may correspond to a different point of the input image IMG 0. Output light OUT1 may comprise multiple light beams propagating in different directions. Each beam of output light OUT1 may correspond to a different point of the displayed virtual image VIMG 1. The pupil expanding unit EPE1 may form the output light OUT1 from the input light IN1 such that the direction and intensity of the light beam of the output light OUT1 corresponds to the point of the input image IMG 0.

The beam of input light IN1 may correspond to a single image point (P0) of the displayed image. The pupil expanding device EPE1 may form an output light beam from a light beam from the input light IN1 such that the direction k3 of the output light beam _P0，R Parallel to the direction k0 of the beam of the respective input light IN1 _P0，R 。

Display device 500 may include optical engine ENG1 to form a primary image IMG0 (i.e., input image IMG0) and to convert primary image IMG0 into a plurality of light beams of input light IN 1. The light of the optical engine ENG1 may be coupled in from the entrance pupil unit DOE1 of the pupil expanding device EPE 1. The input light IN1 may be coupled IN from the entrance pupil unit DOE1 of the pupil expanding device EPE 1. The display apparatus 500 may be a display device for displaying a virtual image. The display device 500 may also be a myopic eye optical apparatus.

The pupil expanding device EPE1 may propagate the content of the virtual image from the optical engine ENG1 in front of the EYE1 of the user. The pupil expanding device EPE1 may expand the viewing pupil, thereby expanding the eyebox.

The optical engine ENG1 may contain a micro display DISP1 to generate the main image IMG 0. The microdisplay DISP1 may comprise a two-dimensional array of light-emitting pixels. The display DISP1 may generate, for example, a main image IMG0 with a resolution of 1280 × 720. The display DISP1 may produce, for example, a main image IMG0 at a resolution of 1920 × 1080(Full HD)). The display DISP1 may produce, for example, a main image IMG0 at a resolution of 3840 × 2160(4 KUHD). The primary image IMG0 may include a plurality of image points P0, P1, P2, …. Optical engine ENG1 may include collimating optics LNS1 to form a collimator lens with each collimator lens formed as a collimator lensThe individual image pixels differ in light beam. Optical engine ENG1 may include collimating optics LNS1 to form a substantially collimated beam of light from image point P0. The light beam corresponding to image point P0 may be at wave vector k0 _P0，R Propagating in the specified direction. The light beams corresponding to different image points P1 may be oriented in the direction k0 _P0，R Different directions k0 _P1，R And (5) spreading.

The optical engine ENG1 may provide a plurality of light beams corresponding to the generated primary image IMG 0. One or more light beams provided by the optical engine ENG1 may be coupled into the pupil expanding device EPE1 and serve as input light IN 1.

Optical engine ENG1 may comprise, for example, one or more Light Emitting Diodes (LEDs). The display DISP1 may comprise one or more microdisplay imagers, such as Liquid Crystal On Silicon (LCOS), Liquid Crystal Display (LCD), Digital Micromirror Device (DMD).

The exit pupil unit DOE3 may form the first output light OB3a by diffracting the third transmitted light B2a received from the first pupil unit DOE2 a. The exit pupil unit DOE3 may form the second output light OB3B by diffracting the fourth transmitted light B2B received by the second pupil expanding unit DOE 2B. By combining the first output light OB3a with the second output light OB3b, a combined output light OUT1 may be formed at the exit pupil unit DOE 3.

The pupil expanding device EPE1 may be arranged such that the direction of light of a given image point (e.g. P0) in the first output light OB3a is parallel to the direction of light of a given image point (P0) in the second output light OB3 b. Thus, combining the first output light OB3a with the second output light OB3b may form a combined light beam corresponding to a given image point (P0).

Each cell DOE1, DOEbs, DOE2a, DOE2b, DOE3 may comprise one or more diffraction gratings, with the diffractive functionality described above.

The diffraction period (d) and the direction (β) of the diffraction grating of the optical elements DOE1, DOEbs, DOE2a, DOE2b, DOE3 may be selected such that the direction of each beam of output light OUT1 may be parallel to the direction of the corresponding beam of input light IN 1.

The grating period (d) and direction (beta) of the grating vector may suffice,for a predetermined integer m ₁ ，m _bs ，m _2a ， m _3a Vector sum m ₁ V ₁ +m _bs V _bs +m _2a V _2a +m _3a V _3a A condition of zero. V ₁ The grating vector of the entrance pupil element DOE1 is represented. V _bs Representing the grating vector of the spectroscopic unit DOEbs. V _2a The grating vector of the first pupil expanding element DOE2a is represented. V _3a The grating vector of the exit pupil element DOE3 is indicated. The values of these predetermined integers are typically +1 or-1.

The grating period (d) and direction (beta) of the grating vector can satisfy that m ₁ ，m _2b ，m _3b Vector sum m ₁ V ₁ +m _2b V _2b +m _3b V _3b A condition of zero. V ₁ The grating vector of the entrance pupil element DOE1 is represented. V _2b The grating vector of the first pupil expanding element DOE2b is represented. V _3b The grating vector of the exit pupil element DOE3 is indicated. The values of these predetermined integers are typically +1 or-1.

The waveguide plate may have a thickness t _SUB1 . The waveguide plate comprises a planar waveguide core portion. In an embodiment, the waveguide plate SUB1 may optionally comprise, for example, one or more cladding layers, one or more protective layers and/or one or more mechanical support layers. Thickness t _SUB1 May refer to the thickness of the planar waveguide core portion of the waveguide plate SUB 1.

The pupil expanding device EPE1 can expand the light beam in two directions: in the direction SX and in the direction SY. The width (IN the SX direction) of the output light OUT1 may be greater than the width of the input light IN1, and the height (IN the SY direction) of the output light OUT1 may be greater than the height of the input light IN 1.

The pupil expanding device EPE1 may be arranged to expand the viewing pupil of the virtual display device 500 to facilitate the positioning of the EYE1 relative to the display device 500. In the case where output light OUT1 is incident on the EYE1 of the viewer, the viewer can see the displayed virtual image VIMG 1. Output light OUT1 may include one or more output light beams, where each output light beam may correspond to a different image point (P0 ', P1') of displayed virtual image VIMG 1. Optical engineThe ENG1 may include a microdisplay DISP1 for displaying the primary image IMG 0. The optical engine ENG1 and the pupil expanding device EPE1 may be arranged to convert the primary image IMG0 into a plurality of input light beams (e.g., B0) _P0，R ，B0 _P1，R ，B0 _P2，R ，B0 _P3，R ，B0 _P4，R ，..，B0 _P0，B ， B0 _P1，B ，B0 _P2，B ，B0 _P3，B ，B0 _P4，B ) Output light OUT1 is formed by expanding the input light beam. For example, symbol B0 _P2，R An input light beam may be represented which corresponds to the image point P2 and has a red color (R). For example, symbol B0 _P2，B An input light beam may be represented that corresponds to the image point P2 and has a blue color (B). The input light beams may together constitute input light IN 1. Input light IN1 may include multiple input light beams (e.g., B0P0, R, B0P1, R, B0P2, R, B0P3, R, B0P4, R.. B0P0, B0P1, B0P2, B0P3, B0P4, B.).

Output light OUT1 may include multiple output light beams, each of which may form a different image point (P0 ', P1') of virtual image VIMG 1. The primary image IMG0 may be represented, for example, as graphics and/or text. The main image IMG0 may be represented as, for example, a video. The optical engine ENG1 and the pupil expanding device EPE1 may be arranged to display the virtual image VIMG1 such that each image point (P0 ', P1') of the virtual image VIMG1 corresponds to a different image point on the primary image IMG 0.

The waveguide plate SUB1 may have a first major surface SRF1 and a second major surface SRF 2. First major surface SRF1, second major surface SRF2 may be substantially parallel to a plane defined by directions SX and SY.

The grating period (d) of the diffraction grating and the direction (β) of the diffraction features of the diffraction grating may be determined by the grating vector V of the diffraction grating. The diffraction grating contains a plurality of diffraction features (F) that can be used as diffraction lines. The diffractive features may be, for example, tiny ridges or grooves. The diffractive features may also be, for example, microscopic protrusions (or depressions), wherein adjacent protrusions (or depressions) may act as diffraction lines. The grating vector V may be defined as a vector having a direction perpendicular to the diffraction lines of the diffraction grating and an amplitude given by 2 pi/d, where d is the grating period.

The entrance pupil unit DOE1 may have a grating vector V ₁ . The beam splitting unit DOEbs may have a grating vector V _bs . The first pupil expanding element DOE2a may have a grating vector V _2a . The second pupil expanding element DOE2b may have a grating vector V _2b . The exit pupil element DOE3 may have a grating vector V _3a ，V _3b 。

Raster vector V ₁ Having a direction beta ₁ And a size of 2 pi/d ₁ . Raster vector V _bs Having a direction beta _bs And a size of 2 pi/d _bs . Raster vector V _2a Having a direction beta _2a Sum amplitude of 2 pi/d _2a . Raster vector V _2b Having a direction beta _2b And a size of 2 pi/d _2b . Raster vector V _3a Having a direction beta _3a Sum amplitude of 2 pi/d _3a . Raster vector V _3b Having a direction beta _3b Sum amplitude of 2 pi/d _3b . The direction (β) of the grating vector may be defined as the angle between the grating vector and a reference direction (e.g. direction SX).

The grating period (d) and the direction (β) of the diffraction grating of the optical elements DOE1, DOEbs, DOE2a, DOE3 may be chosen such that the propagation direction (k 3) of the light of the central point P0 in the first output light OB3a is such that it is the direction of propagation of the light of the central point P0 _P0，R ) The propagation direction of light (k 0) parallel to the center point P0 IN the input light IN1 _P0，R )。

The grating period (d) and the direction (β) of the diffraction grating of the optical units DOE1, DOE2b, DOE3 may be selected such that the propagation direction (k 3) of the light of the central point P0 of the second output light OB3b is _P0，R ) The propagation direction of light from the center point P0 IN the input light IN1 (k 0) _P0，R ) Parallel.

The diffraction periods (d) and the directions (β) of the diffraction gratings of the optical units DOE1, DOE2a, DOE2b, DOE3 may be selected such that the propagation direction (k 3) of the light at the central point P0 of the combined output light OUT1 is _P0，R ) The propagation direction of light from the center point P0 IN the input light IN1 (k 0) _P0，R ) Parallel.

Raster vector V of light splitting unit DOEbs _bs With the grating vector V of the entrance pupil element DOE1 ₁ Between the directions ofThe included angle may be, for example, in the range of 60 ° to 120 °.

Grating period d of the first pupil expanding cell DOE2a _2a The grating period d, which may be different from the second pupil expanding cell DOE2b _2b To optimize the first path for a first color and the second path for a second, different color.

First grating period d of the exit pupil element DOE3 _3a The second grating period d, which may be different from that of the exit pupil element DOE3 _3b To optimize the first path for a first color and the second path for a second, different color.

The exit pupil unit DOE3 may have a first grating vector V _3a To couple the expanded third guided light B2a out of the waveguide plate SUB 1. The exit pupil unit DOE3 may have a second grating vector V _3b To couple the expanded fourth guided light B2B out of the waveguide plate SUB 1. The exit pupil unit DOE3 may have a diffractive feature F3a to provide a grating G3a with a grating period d3a and a direction β 3a (with respect to the reference direction SX). The exit pupil unit DOE3 may have a diffractive feature F3b to provide a grating G3b with a grating period d3b and a direction β 3b (relative to the reference direction SX). The exit pupil element DOE3 may be realized by a crossed grating or two linear gratings. A first linear grating G3a with diffractive features F3a may be implemented on a first major surface (e.g., SRF1) of the waveguide plate SUB1, and a second linear grating G3b with diffractive features F3b may be implemented on a second major surface (e.g., SRF2) of the waveguide plate SUB 1.

The entrance pupil cell DOE1 may have a width w ₁ And height h ₁ . The first pupil expanding cell DOE2a may have a width w _2a And height h _2a . The second pupil expanding cell DOE2b may have a width w _2b And height h _2a . The exit pupil cell DOE3 may have a width w ₃ And height h ₃ 。

The width may represent a dimension in the direction SX and the height may represent a dimension in the direction SY. The exit pupil cell DOE3 may be, for example, substantially rectangular. The edges of the exit pupil cell DOE3 may, for example, be along the directions SX and SY.

Width w of the pupil expanding element DOE2a _2a May be substantially larger than the width w of the entrance pupil cell DOE1 ₁ . The width of the expanded third light guiding B2a may be substantially larger than the width w of the entrance pupil unit DOE1 ₁ 。

The waveguide plate SUB1 may comprise or consist essentially of a transparent solid material. The waveguide plate SUB1 may comprise, for example, glass, polycarbonate or Polymethylmethacrylate (PMMA). The diffractive optical elements DOE1, DOEbs, DOE2a, DOE2b, DOE3 may be formed by, for example, molding, embossing and/or etching. The unit DOE1, DOEbs, DOE2a, DOE2b, DOE3 may be realized by, for example, one or more surface diffraction gratings or by one or more volume diffraction gratings.

The spatial distribution of the diffraction efficiency can be arbitrarily adjusted, for example by selecting the local height of the microscopic diffractive features F. Therefore, the height of the microscopic diffractive features F of the exit pupil element DOE3 may be selected to further homogenize the intensity distribution of the output light OUT 1.

Fig. 5a shows, by way of example, a wave vector of blue light propagating along a first path in the waveguide plate SUB 1. The wave vector of the input light IN1 may be within the region BOX0 of the wave vector space defined by the initial wave vectors kx and ky. Each angle of the region BOX0 may represent a wave vector of light at a corner point of the input image IMG 0.

The wavevector of the first light-conducting B1B may be within the region BOX1 a.

The wavevector of the second guided light B1a may be within the region BOX1 a.

The wave vector of the third guided light B2a may be re-within the region BOX2 a.

The wavevector of first output light OB3a may be within region BOX 3.

The entrance pupil unit DOE1 may form the first light guiding light B1B by diffracting the input light IN 1. By passing the grating vector m of the entrance pupil element DOE1 ₁ V ₁ Which adds to the wave vector of the input light IN1 to represent diffraction. By dividing the raster vector m ₁ V ₁ The wavevector of the first light-transmitting light B1B is determined by adding to the wavevector of the input light IN 1. The wavevector of the second guided light B1a may be determined by combining the grating vector m _bs V _bs Is determined in addition to the wavevector of the first light-guiding B1B. Third light transmission light BThe wave vector of 2a can be obtained by transforming a grating vector m _2a V _2a Is determined by adding to the wave vector of the second guided light B1 a. By applying a raster vector m _3a V _3a The wavevector added to the second light guide B2a determines the wavevector of the first output light OB3 a.

BND1 denotes a first boundary for satisfying the Total Internal Reflection (TIR) criterion in waveguide plate SUB 1. BND2 denotes the second boundary of the largest wave vector in the waveguide plate SUB 1. The maximum wave vector may be determined by the refractive index of the waveguide plate. Light can be waveguided in the waveguide plate SUB1 only when the wave vector of the light is in the region ZONE1 between the first boundary BND1 and the second boundary BND 2. If the wave vector of the light is outside the ZONE1, the light may leak out of the waveguide plate or not propagate at all.

The grating period d1 of the entrance pupil unit DOE1 may be selected such that all wavevectors of the first light conducting B1B of all colors are within the region ZONE1 defined by the boundaries BND1, BND 2.

The grating period d of the light splitting unit DOEbs can be selected _bs So that, for example, all wavevectors of the blue second light guiding light B1a are within the region ZONE1 defined by the boundaries BND1, BND 2.

Fig. 5b shows by way of example a wave vector of red light propagating along a first path within waveguide plate SUB 1.

Now, if the grating period d of the entrance pupil element DOE1 has been selected _1a So that all wavevectors of the blue first light-conducting B1a are within the ZONE1, the wavevectors of the red light at certain corner points may lie outside the ZONE 1. In other words, the waveguide plate SUB1 cannot confine or conduct red light of certain corner points of the input image IMG 0.

The wave vector falling within the subregion FAIL1 of the region BOX1a corresponds to a case where the input unit DOE1 cannot form the guided light by diffracting the input light. In other words, the diffraction equation does not have a correct practical solution for the wave vectors present in the sub-region FAIL1 of the region BOX1 a. Thus, in case the wave-vector of the guided light is outside the ZONE1, it is not possible to couple red light into the waveguide plate for some image points.

In the case where the wavevector of the guided light is outside the ZONE1, leakage of red light may limit the angular width of the displayed virtual image VIMG1 for certain (other) image points.

Thus, the boundaries BND1, BND2 of the ZONE1 may limit the angular width (Δ) of the displayed virtual image VIMG1

) Forming a wave-vector outside the ZONE1 may mean light leaking from the waveguide plate or light coupling failure.

k _x Denotes the direction in wave-vector space, where the direction k _x Parallel to the direction SX of the physical space. k is a radical of _y Denotes the direction in wave vector space, where k _y The direction is parallel to the SY direction of the real space. Symbol k _z (not shown in the figure) denotes the direction in wave-vector space, where the direction k _z Parallel to the direction SZ of the real space. Wave vector k may have a direction k _x ，k _y And k _z The component (c) above.

Fig. 5c and 5d show, by way of example, the wave vectors of the blue light at image points (P0, P1, P2, P3, P4) in the wave vector space.

Fig. 5e and 5f give, by way of example, the wave vectors of red light at image points (P0, P1, P2, P3, P4) in the wave vector space.

FIG. 5g shows, in a cross-sectional side view, coupling of input light into a waveguide plate to form first guided light, wherein the first guided light has an inclination angle

Near the critical angle for total internal reflection of SUB1

The case of fig. 5g corresponds to the operation near the first boundary BND1 of the ZONE 1.

FIG. 5h shows, in a cross-sectional side view, the coupling of input light into a waveguide plate to form first guided light, wherein the first guided light has an inclination angle

Approximately 90 degrees. The situation of fig. 5h may correspond to operation near the second boundary BND2 of ZONE 1.

The curve CRV1 in FIG. 5i gives the tilt angle of the wave-vector k1 of the first light-conducting B1a

Input angle with wave vector k0 of input light B0

Functional relationship between them. Angle of inclination

The wavevector and the angle between the direction SZ and the reference plane REF1 defined by SY can be expressed. By using diffraction equations, the angle can be input

The tilt angle is calculated from the grating period of the entrance pupil element DOE1 and the refractive index of the waveguide plate SUB1

First angle limitation

May correspond to the tilt angle of the first light-conducting light

Equal to the critical angle for total internal reflection

The case (1). Second angle limitation

May correspond to the tilt angle of the first light-conducting light

Equal to 90 degrees.

Fig. 6a gives by way of example a wave vector diagram of blue light propagating along a second path within the waveguide plate SUB 1. The second path may be, for example, a counterclockwise path.

Fig. 6b shows by way of example a wave vector diagram of red light propagating along a second path within the waveguide plate SUB 1.

Fig. 6c and 6d show by way of example the wave vectors of the blue light at image points (P0, P1, P2, P3, P4) in the wave vector space.

The grating period d2B of the second pupil expanding unit DOE2B may be selected such that, for example, all wavevectors of the red fourth light guiding light B2B are within the ZONE1 defined by the boundaries BND1, BND 2.

Now, if the grating period d of the second pupil expanding element DOE2b has been selected _2b So that all wavevectors of the fourth light-guiding B2B for red are within the ZONE1, the wavevectors of the blue light for some corner points may lie outside the ZONE 1. In other words, the waveguide plate SUB1 cannot confine blue light at certain corner points of the input image IMG 0. The leakage of blue light may limit the angular width of the displayed virtual image VIMG 1. The wave vector falling in the sub-region LEAK1 of the region BOX2b represents light that is not confined within the waveguide plate by total internal reflection.

However, the pupil expanding device EPE1 may be arranged to provide a first path and a second path. The first path may provide a full width of the blue virtual image VIMG1

The second path may provide the full width of the red virtual image VIMG1

Thus, the pupil expanding device EPE1 may be arranged to display images having a full width

The color virtual image VIMG 1.

Thus, the pupil expanding device EPE1 may be arranged to display a color virtual map in red and blueLike all corner points (P1, P2, P3, P4) of VIMG1, wherein the color virtual image VIMG1 has full width of the full color

Therefore, the angular width of the color virtual image VIMG1 displayed by using the two paths

May be substantially larger than the maximum angular width (LIM1, predetermined limit) of other pupil expanding devices (EPE0) that do not use the second path.

The pupil expanding device EPE1 with two paths may be arranged to display a color virtual image VIMG1 with an expanded angular width

The first path may be set to limit the blue component of the input image while allowing leakage of red light at one or more corner points of the input image. The second path may be arranged to limit the red component of the input image while allowing leakage of blue light at one or more corner points of the input image.

The display apparatus 500 may be a virtual reality device 500. The display apparatus 500 may be an augmented reality device 500. The display apparatus 500 may be a near-eye device. The display apparatus 500 may be a wearable device, for example, an earphone. The display device 500 may comprise, for example, a headband through which the display device 500 may be worn on the user's head. During operation of the display device 500, the exit pupil unit DOE3 may be positioned in front of the user's left EYE1 or right EYE 1. Display device 500 may project output light OUT1 into the user's EYE 1. In one embodiment, the display device 500 may include two optical engines ENG1 and/or two pupil expanding devices EPE1 to display a stereoscopic image. In the augmented reality device 500, the viewer may see real objects and/or environments through the pupil expanding device EPE1 in addition to the displayed virtual image. The optical engine ENG1 may be arranged to generate still images and/or video. The optical engine ENG1 may generate a real primary image IMG0 from the digital image. The optical engine ENG1 may receive one or more digital images from an internet server or a smartphone. The display device 500 may be a smart phone. The displayed image may be viewed by a person, and may also be viewed by an animal or machine (possibly including, for example, a camera).

The term "k-vector" may be the same as the term "wave vector".

It will be clear to a person skilled in the art that modifications and variations of the device and the method according to the invention are conceivable. The figures are schematic. The particular embodiments described above with reference to the drawings are illustrative only and not meant to limit the scope of the invention, which is defined by the appended claims.

Claims

1. An optical pupil expanding device (EPE1) comprising a waveguide plate (SUB1) which in turn comprises:

an entrance pupil unit (DOE1) that forms first transmitted light (B1B) by diffracting input light (IN 1);

a light splitting unit (DOEbs) forming a second light-conducting light (B1a) by diffracting the first light-conducting light (B1B) for enhancing energy input of the first light-conducting light (B1B) and the second light-conducting light (B1 a);

a second pupil expanding unit (DOE2B) that forms a fourth transmitted light (B2B) by diffracting the first transmitted light (B1B), and forms a first output light (OB3a) by diffracting the third transmitted light (B2a), and forms an exit pupil unit (DOE3) of the second output light (OB3B) by diffracting the fourth transmitted light (B2B);

wherein the exit pupil unit (DOE3) is arranged to form a combined output light (OUT1) by combining the first output light (OB3a) with the second output light (OB3 b);

wherein the beam splitting cell (DOEbs) has the same first grating period (d1a) as the first mydriatic cell (DOE2a), and the second mydriatic cell (DOE2b) has a different second grating period (d1b) than the first mydriatic cell (DOE2 a).

2. The optical pupil device according to claim 1, characterized in that the light-splitting cell (DOEbs) has a third grating period which is different from the first grating period (d1 a).

3. The optical pupil device according to claim 1 or 2, characterized IN that the input light (IN1) corresponds to an input image (IMG0) and the width of the input image (IMG0)

Greater than a predetermined limit (LIM1), the units being arranged to provide:

red light (B1a) corresponding to a first corner point (P1) of an input image (IMG0) _P1,R )

Wherein the grating vectors (m) of the cells (DOE1, DOEBs, DOE2a, DOE2b, DOE3) are selected ₁ V ₁ ，m _bs V _bs ，m _2a V _2a ，m _2b V _2b ，m _3a V _3a ，m _3b V _3b ) So as to:

red light of the first angle landing point (P1) is directed from the entrance pupil unit (DOE1) to the exit pupil unit (DOE3) by the second pupil expanding unit (DOE2b), and red light of the first angle landing point (P1) is not directed from the entrance pupil unit (DOE1) to the exit pupil unit (DOE3) by the first pupil expanding unit (DOE2 a).

4. The optical pupil expanding device of claim 1 or 2, characterized IN that the input light (IN1) corresponds to an input image (IMG0) and the width of the input image (IMG0)

Above a predetermined limit (LIM1), the units (DOE1) being arranged to provide:

red light (B1a) corresponding to a first corner point (P1) of an input image (IMG0) _P1,R )；

Blue light (B1a) corresponding to a second corner point (P2) of the input image (IMG0) _P1,B )；

red light of the first corner point (P1) is directed from the entrance pupil unit (DOE1) to the exit pupil unit (DOE3) by the second pupil expanding unit (DOE2 b);

red light of the first corner point (P1) is not directed from the entrance pupil unit (DOE1) to the exit pupil unit (DOE3) by the first pupil expanding unit (DOE2 a);

blue light of the second corner point (P2) is directed from the entrance pupil unit (DOE1) to the exit pupil unit (DOE3) by the first pupil expanding unit (DOE2a), and blue light of the second corner point (P2) is not directed from the entrance pupil unit (DOE1) to the exit pupil unit (DOE3) by the second pupil expanding unit (DOE2 b).

5. Optical pupil expansion device according to claim 1 or 2,

the first light-guiding light (B1B) contains light (B1bP0) corresponding to a center point (P0) of the input image (IMG 0);

the second light guide (B1a) contains light (B1aP0) corresponding to a center point (P0) of the input image (IMG 0);

the third light guide (B2a) contains light (B2aP0) corresponding to a center point (P0) of the input image (IMG 0);

the fourth light guide (B2B) contains light (B2bP0) corresponding to a center point (P0) of the input image (IMG 0);

wherein the exit pupil unit (DOE3) is arranged to:

forming a first output light beam (OB3a) by diffracting a light beam corresponding to a center point (P0) of the input image (IMG0), forming a second output light beam (OB3b) by diffracting a light beam corresponding to a center point (P0) of the input image (IMG0),

wherein the first output light beam (OB3a) and the second output light beam (OB3b) propagate in a direction (k0P0) corresponding to the center point (P0).

6. The optical pupil expanding device according to claim 1 or 2, characterized IN that the entrance pupil unit (DOE1) is arranged to diffract input light (IN1) such that the first light guiding light (B1B) contains light of a central point (P0) of an input image (IMG0), the light splitting unit (DOEBs) is arranged to diffract the first light guiding light (B1B) such that the second light guiding light (B1a) contains light of a central point (P0) of an input image (IMG0),

wherein the exit pupil unit (DOE3) is arranged to diffract the third transmitted light (B2a) received by the first pupil expanding unit (DOE2a) such that the first output light (OB3a) comprises light of a central point (P0) of the input image (IMG0),

wherein the exit pupil unit (DOE3) is arranged to diffract the fourth transmitted light (B2B) received by the second pupil expanding unit (DOE2B) such that the second output light (OB3B) comprises light of a central point (P0) of the input image (IMG0),

wherein the light of the central point (P0) in the first output light (OB3a) propagates in the axial direction (k3, P0), wherein the light of the central point (P0) in the second output light (OB3b) propagates in the same axial direction (k3, P0).

7. The optical pupil expanding device according to claim 1 or 2, characterized by comprising one or more optically isolating units (ISO1) to prevent direct optical coupling between the first (DOE2a) and the second (DOE2b) pupil expanding unit.

8. A display device (500) comprising an optical engine (ENG1) to form an input image (IMG0) and to convert the input image (IMG0) into a plurality of input beams of input light (IN1), the display device (500) comprising an optical pupil expanding device (EPE1) according to any one of claims 1 to 7 to expand the input beams of input light (IN1) by diffraction to form an output beam of combined output light (OUT 1).

9. A method, characterized in that it comprises using an optical pupil expansion device (EPE1) according to any one of claims 1 to 7 to provide a combined output light (OUT 1).

10. A method, characterized in that it comprises displaying a virtual image (VIMG1) using an optical pupil expanding device (EPE1) according to any one of claims 1 to 7.