Optical device

Abstract

An optical device (2) for expanding input light and outputting expanded light, the optical device comprising: a waveguide (22); an input optical element (21) configured to receive light (41) incident on a first side of the waveguide and comprising an input reflective surface configured to reflect the received light into the waveguide; an intermediate diffractive optical element (24) configured to receive light in the waveguide from a first direction and to provide expansion of the received light in a second direction perpendicular to the first direction; and an output optical element (23) comprising an output reflective surface configured to reflect the expanded light out of the waveguide towards a viewer. The waveguide is configured to guide light along an optical path from the input optical element to the intermediate diffractive optical element and from the intermediate diffractive optical element to the output optical element.

Description

Technical Field

[0001] This invention relates to waveguides for near-eye displays, such as augmented reality displays or virtual reality displays. In such displays, a light source provides an image that extends through the waveguide and is coupled outward toward the viewer. Background Technology

[0002] Augmented reality displays allow users to view their surroundings as well as projected images. In military or transportation applications, projected images can be overlaid on the real world as perceived by the user. Other applications for these displays include video games and wearable devices such as glasses. Any augmented reality display can simply be used as a virtual reality display by overlaying a view of the real world onto it.

[0003] Figure 1 shows an example of a normal augmented reality setup in the form of wearable glasses 40.

[0004] In a typical augmented reality setup, a transparent display screen 44 is positioned in front of the user, allowing the user to continue viewing the physical world. The transparent display screen 44 may include a screen for each of the user's eyes. The display screen is typically a glass waveguide, with a projector positioned on one side. Light from the projector is coupled into the waveguide via a diffraction grating (input grating 42). The projected light undergoes total internal reflection within the waveguide. The light is then coupled out of the waveguide via another diffraction grating (output grating), allowing the user to observe the light. The projector can provide information and / or images that enhance the user's view of the physical world.

[0005] There are challenges in producing widescreen augmented reality or virtual reality displays because light from the input projector needs to be provided across the entire width of the display (if augmented reality is desired across the entire width). One solution is to provide a single input projector and optics that can extend the field of view across the width of the display.

[0006] However, in the normal setting using the output grating, it is difficult to obtain both high efficiency and high uniformity due to the continuous characteristics of pupil replication provided by the output grating.

[0007] Therefore, it is desirable to provide a more efficient and / or uniform waveguide optics device for augmented reality displays or virtual reality displays. Summary of the Invention

[0008] According to a first aspect, this disclosure provides an optical device for amplifying input light and outputting amplified light, the optical device comprising: a waveguide; an input optical element configured to receive light incident on a first side of the waveguide and including an input reflective surface configured to reflect the received light into the waveguide; an intermediate diffraction optical element configured to receive light in the waveguide from a first direction and provide amplification of the received light in a second direction perpendicular to the first direction; and an output optical element including an output reflective surface configured to reflect the amplified light toward a viewer out of the waveguide.

[0009] The waveguide is configured to guide light along optical paths from the input optics to the intermediate diffraction element and from the intermediate diffraction element to the output optics. The optical path may be directly between the optics or may include one or more additional elements or light redirection.

[0010] By providing an optical device having a reflective input element, a reflective output element, and an intermediate diffractive optical element, the optical device is able to extend light without suffering the efficiency and uniformity losses associated with the output grating. The intermediate diffractive optical element is configured to extend light perpendicular to the propagation direction in the waveguide.

[0011] Optionally, the output optics are spaced apart from the input optics in the first direction. An intermediate diffractive optics receives light from the input optics and couples the extended light toward the output optics. This provides a simple linear arrangement that can be easily constructed.

[0012] Optionally, the output optics are configured to reflect light out of the waveguide via a first side. In a more specific example, the input reflecting surface may optionally be geometrically similar to the output reflecting surface. Alternatively, the output optics may be configured to reflect light out of the waveguide via a second side opposite to the first side.

[0013] In other words, the optical device can be configured to output light on the same side as the side in the light receiving device, or on the side opposite to the side in the light receiving device. This means that the optical device can be adapted to a variety of different applications while achieving the advantages of the present invention.

[0014] Optionally, the input optics are configured to reflect light into the waveguide over a range of angles relative to the plane of the waveguide. This has the effect that the received light is extended parallel to its direction of motion within the waveguide, and combined with the extension in the intermediate diffractive optics, provides a two-dimensional extension. Similarly, the waveguide can be configured to receive input light with an angular field of view and extend the received light in its direction of motion by a first extension factor through total internal reflection.

[0015] By additionally configuring the waveguide to extend the light in the first direction via total internal reflection, the device is able to extend the light independently in two vertical directions without suffering the efficiency loss associated with the output grating.

[0016] Optionally, the intermediate diffractive optical element is configured to spread the received light in a second direction with a second spreading factor, the second spreading factor being a predetermined multiple of the first spreading factor.

[0017] By defining a predetermined ratio between the spread factors in two vertical directions, the aspect ratio of the spread light can be controlled without modifying the light source.

[0018] Optionally, the intermediate diffractive optical element includes a first grating oriented at a third angle to the light received from the input optical element to provide first and second diffraction within the intermediate diffractive optical element, thereby coupling the light toward the output optical element. The first diffraction couples the light from the input optical element toward the first grating at a fourth angle, such that second diffraction is provided at a plurality of spaced-apart locations in the intermediate diffractive optical structure to provide light propagation. The second diffraction couples the light toward the output diffractive optical structure.

[0019] Gratings provide a simple way to realize the function of intermediate diffractive optical elements. Gratings can be etched or deposited on the surface of a waveguide, for example.

[0020] Optionally, the intermediate diffractive optical element further includes a second grating oriented at a fifth angle to the light received from the input optical element to provide third and fourth diffraction within the intermediate diffractive optical element, thereby coupling the light toward the output optical element. The third diffraction couples the light from the input optical element toward the second diffraction feature at a fourth angle, such that a fourth diffraction is provided at a plurality of spaced-apart locations in the intermediate diffractive optical structure, thereby providing one-dimensional extension of the light, wherein the fourth diffraction couples the light toward the output diffractive optical structure.

[0021] By using two gratings, the optical device can be configured to produce a bright output light that is symmetrical about the center of the output light in a second direction.

[0022] Alternatively, the first and third angles are substantially equal and opposite. By using equal and opposite angles, the two gratings can be constructed with a simple method to provide symmetrical extension in the second direction.

[0023] Optionally, the first angle is +(45+Δ)° and the third angle is -(45+Δ)°, where Δ is non-zero. The parameter Δ can be controlled to modify the spread factor of the light spread in the second direction.

[0024] Optionally, the first and second gratings are physically spaced apart on the waveguide. By separating the gratings, the first and second gratings can be set as basic gratings on a single surface of the waveguide, thereby simplifying the construction.

[0025] Optionally, the first and second gratings overlap at least partially in the waveguide as a pair of intersecting gratings. By overlapping the gratings, the size of the intermediate diffractive optical element can be reduced, and the size of the entire optical device can be reduced.

[0026] Optionally, the first and second gratings are disposed on opposite surfaces of the waveguide. By disposing the gratings on opposite surfaces, the size of the optical device can be reduced while still enabling the production of intermediate diffractive optical elements using simple techniques.

[0027] Optionally, the first grating and the second grating are arranged in substantially the same plane in the waveguide. By arranging the gratings in substantially the same plane, it can be ensured that light interacts with both gratings simultaneously, thus ensuring that the propagation in the second direction is necessarily symmetrical.

[0028] Alternatively, a photonic crystal is used to provide the first and second gratings. By using a photonic crystal, the gratings are embedded in the waveguide and protected from external damage.

[0029] According to a second aspect, this disclosure provides an optical system comprising: an optical device according to the first aspect; and a projector arranged to project light toward an input optical element of the optical device.

[0030] This optical system offers improved efficiency compared to optical systems that use output gratings to couple light out of the waveguide.

[0031] Alternatively, the projector is configured to project light into the angular field of view of the input optics.

[0032] By projecting onto the angular field of view, the optical device can extend the light in the first direction even when the input reflective surface is a flat surface, thereby simplifying the construction of the optical device. Attached Figure Description

[0033] Figure 1 is a schematic diagram of an augmented reality system;

[0034] Figure 2A and Figure 2B This is a schematic diagram of the optical system according to the present invention;

[0035] Figure 3 This is a schematic side view of the optical device according to the present invention;

[0036] Figure 4 This is a schematic top view of the optical device according to the present invention;

[0037] Figure 5 This is a schematic diagram of the intermediate diffractive optical element;

[0038] Figure 6 This is a schematic top view of the alternative optical device according to the present invention;

[0039] Figure 7 This is a schematic top view of another alternative optical device according to the present invention. Detailed Implementation

[0040] Figure 2A and Figure 2B This is a schematic diagram of an optical system according to the invention that can be used, for example, in an augmented reality display or a virtual reality display, in which the x and z directions are marked for comparison with subsequent diagrams. Figure 2A and Figure 2B The optical system can be used, for example, in eyeglasses similar to eyeglasses 40 in Figure 1.

[0041] In the optical system, light 41 is projected from the projector 1 onto the optical device 2. The optical device 2 amplifies the received light 41 and outputs the amplified light 42 toward the user's eye 3.

[0042] Projector 1 can be oriented towards the same side of optical device 2 as the eye 3, such as... Figure 2A As shown, or the projector 1 can be oriented towards the side of the optical device 2 opposite to the eye 3, such as... Figure 2B As shown.

[0043] The optical device 2 is a planar structure having a waveguide 22 oriented along the x-axis. An input optical element 21 is configured to couple light into the waveguide 22, and an output optical element 23 is configured to couple light out of the waveguide 22.

[0044] Both the input optical element 21 and the output optical element 23 include their own reflective surfaces, preferably non-dispersive surfaces. Light incident on the optical device 2 at the input optical element is reflected on the input reflective surface and enters the waveguide 22. Light from the waveguide 22 is reflected on the output reflective surface and exits the optical device 2.

[0045] In this embodiment, the reflective surface is a flat surface with its surface normal in the xz plane and at a corresponding angle relative to the x-axis. and Arrangement.

[0046] exist Figure 2A In the example, it is preferable that the direction of light passing through the optical device is reflected along the z-axis between the input and output. To achieve this, Figure 2A Angle marked in the middle and The equal orientation of the reflective surfaces results in a mirror-like orientation.

[0047] exist Figure 2B In the example, it is preferable to maintain the direction of light passing through the optical device. To achieve this, Figure 2B Angle marked in the middle and The equal orientation of the output reflective surfaces results in a parallel orientation (i.e., the output reflective surface is rotated 180 degrees relative to the input reflective surface in the xz plane).

[0048] Figure 3 It is a side view that includes the x-axis and z-axis. Figure 2A A schematic cross-sectional view of the optical device 2 configuration is shown, and the light passing through the optical device 2 is also shown.

[0049] The light incident on the optical device 2 at the input optical element 21 has an angular range (also known as the field of view FOV) θ FOV,in Internal extension. For example, the projector 1 used with the optical device 2 can be a wide planar source or a curved source that extends across the field of view. In a planar light source, an electrical time delay can be used to simulate a curved source, or the frame rate and / or shutter speed can be kept slow enough that time correction is not required.

[0050] As a result of the field of view, the light reflected into the waveguide has an angular range relative to the plane of the waveguide. When light propagates within the optical device, it undergoes total internal reflection within waveguide 22, and the angular range within the waveguide is fixed at the maximum angle θ relative to the x-axis. max With respect to the minimum angle θ of the x-axis min However, due to this angular divergence, the linear spread of light increases as the light propagates within waveguide 22. This can be seen as the lengths of the reflection regions R1 to R5 increase, indicating the position where each ray of light undergoes its nth reflection within waveguide 22. Therefore, when the light reaches the output optics 23, it undergoes linear spread in the x-direction. However, because and The angle range θ of the light output from optical device 2 is equal. FOV,out With θ FOV,in same.

[0051] The spread factor of light 42 relative to input light 41 in the x-direction depends on the path length of the light in waveguide 22. Therefore, the spread factor in the x-direction can be increased by lengthening waveguide 22 and decreased by shortening it. Alternatively, it can be decreased relative to the x-axis. and This increases the spread factor, causing light to propagate at a larger angle relative to the x-direction and increasing the path length, and vice versa.

[0052] like Figure 3 As shown, the area of ​​the input reflecting surface used to reflect the input light is smaller than the area of ​​the output reflecting surface used to reflect the output light. Therefore, although Figure 3 The input and output optical elements shown have the same dimensions, but the input optical element 21 can typically be smaller than the output optical element 23. More specifically, the ratio of the length of the reflecting surface in the xz plane shown can be the same as the spread factor of the optical device 2 in the xz plane.

[0053] Furthermore, the optical device 2 extends the light along the y-direction, perpendicular to the x-direction, between the input optical element 21 and the output optical element 23. The extension in the y-direction is independent of the extension in the x-direction. More specifically, when the extension in the x-direction is reflection extension, the extension in the y-direction is diffraction extension. The optical device 2 can be configured such that a first extension factor for reflection extension is a predetermined multiple of a second extension factor for diffraction extension, the first extension factor depending on the waveguide length, while the second extension factor is controlled as described below.

[0054] Figure 4 The optical device 2 according to the embodiment is schematically shown in a top view, which shows the xy plane perpendicular to the previously shown xz plane.

[0055] like Figure 4 As shown, the optical device 2 includes an intermediate diffractive optical element 24, which has a width w in the x-axis direction. grating Light 43, propagating from input optics 21 toward output optics 23, interacts with intermediate diffractive optics 24 as it passes through them. This interaction provides an extension of light 43 in the y-direction perpendicular to the aforementioned x-direction of reflection extension, and the extended light 45 couples toward output optics 23 to exit the waveguide toward the viewer.

[0056] exist Figure 5 The interaction is shown in more detail below. Figure 5 The intermediate diffractive optical element 24 is shown schematically.

[0057] like Figure 5As shown, in this embodiment, the intermediate diffractive optical element 24 is a linear grating with a periodic pattern of parallel lines 241. The lines 241 are oriented at an angle ψ (in this case +45°) to the x-axis, which is the direction from which light is received from the input optical element 21. When light 43 encounters the intermediate diffractive optical element 24, it undergoes a first diffraction, becoming first-order and turning by 90°. The diffracted light 44 propagates in the y-direction and is trapped within the waveguide 22 by total internal reflection. The diffracted light 44 interacts with the intermediate diffractive optical element 24 again at multiple points along its length, and at each point of interaction, the light is either diffracted or not. In the case of diffraction, a second diffraction by the intermediate diffractive optical element 24 causes the light to turn by 90° again, such that light 45 couples towards the output optical element 23 in a direction parallel to the x-axis. The undiffracted light continues to propagate within the waveguide 22 to interact with the intermediate diffractive optical element 24 at another point. In this way, the intermediate diffractive optical element 24 provides a one-dimensional extension of light along the y-axis. Light 45 propagating from the intermediate diffractive optical element 24 toward the output optical element 23 is diffracted twice within the intermediate diffractive optical element 24, and rotated 90° twice. The two diffractions within the intermediate diffractive optical element 24 interact equally and oppositely, making them self-conjugated, and the optical effects introduced by the first diffraction are canceled out by the second diffraction.

[0058] The diffraction-based extension in the y-direction described above is probabilistic, and the more time light spends in the intermediate diffractive optical element 24 (the longer the path length), the more the light can be expected to extend. Therefore, the extension can be increased by changing the width w of the intermediate diffractive optical element 24 in the x-axis direction. grating To control the spread factor of light passing through the optical device in the y-direction.

[0059] Additionally, the spread factor in the y-direction can be controlled by changing the angle ψ. More specifically, the angle ψ represents the direction of first-order diffraction in the grating. If ψ is small, the direction of the diffracted light 44 is similar to the direction of the received light 43, and the light spends less time and spreads less in the intermediate diffractive optical element 24. On the other hand, if ψ is greater than 45° relative to the x-axis, the diffracted light 44 travels backward relative to the x-axis and spends more time and spreads more in the intermediate diffractive optical element 24. In a preferred embodiment, the angle ψ is close to 45°, and the deviation from ψ is between 0° and ±10°.

[0060] The spacing between lines 241 can be chosen to maximize the chance of first-order diffraction. This chance depends on the wavelength of the light, therefore the spread factor in the y-direction is partially wavelength-dependent. For visible light applications, the spacing can be chosen to match the wavelength of green light in the waveguide.

[0061] Back Figure 4 As can be seen, when ψ is positive, the expansion in the y-direction only occurs in the positive y-direction. Therefore, in this example, the center of the output optical element 23 is shifted in the positive y-direction relative to the center of the input optical element 21. This has a drawback because first-order diffraction in the grating is less likely than transmission (zero-order diffraction), so the brightest part of the output light 42 is off-center in the y-direction.

[0062] Figure 6 This is a schematic top view of the alternative optical device 2, wherein the centers of the input optical element 21 and the output optical element 23 are aligned in the y-direction, and the extended light output from the optical device 2 can be symmetrically bright on the y-axis.

[0063] exist Figure 6 In the process, the diffractive optical element includes a first grating 24 and a second grating 25. Each of the first grating 24 and the second grating 25 can be similar to the one described above. Figure 5 The gratings are described. However, for one grating, the angle ψ is positive, while for the other grating, the angle ψ is negative, such that the gratings provide expansion in opposite directions along the y-axis. The first and second gratings preferably provide equal expansion factors.

[0064] Figure 7 This is a schematic top view of another alternative optical device 2, wherein the centers of the input optical element 21 and the output optical element 23 are aligned in the y-direction, and the extended light output from the optical device 2 can be symmetrically bright on the y-axis.

[0065] exist Figure 7 In the diagram, the diffractive optical element comprises a pair of intersecting gratings 26 in the xy plane. The intersecting gratings 26 can be substantially similar to... Figure 6 A first grating 24 and a second grating 25 are provided, wherein the gratings are disposed on two opposing surfaces of the waveguide 22, wherein the opposing surfaces are opposite to each other in the z-direction. Alternatively, the cross grating 26 may be a single structure on one surface of the waveguide 22, or it may be a single structure extending along the z-direction of the waveguide 22. For example, the cross grating 26 may take the form of a photonic crystal with a triangular lattice, as described in WO 2016 / 020643 A1.

[0066] In the above embodiment, the spread of light in the x-direction by total internal reflection requires the input light to be distributed across an angular field of view. However, in another embodiment, parallel light in a planar field of view can be spread along the x-axis. More specifically, the input and output reflecting surfaces can be corresponding curved surfaces (e.g., parabolic surfaces), or a series of flat surfaces arranged to approximate curved surfaces, such that the light has an angular directional distribution as it passes through the waveguide, but is parallel when entering the optical device at the input optics and when leaving the optical device at the output optics. The relative focal length of the curved surfaces can be configured according to the desired spread factor in the x-direction. Figure 8 A portion of an optical device according to the invention is schematically shown, having an input optical element designed to receive parallel light. In an embodiment where the reflective surface is curved, when the projector and user... Figure 2A In the arrangement shown, the output reflective surface can be oriented as a reflection of the input reflective surface in the yz plane, and when the projector and user... Figure 2B In the arrangement shown, the output reflective surface can be oriented as a rotation of the input reflective surface in the xz plane.

[0067] By independently controlling the spread factors in the y-direction and x-direction using the aforementioned independent reflection and diffraction mechanisms, the optical device 2 can be configured to provide an output light aspect ratio that differs from the predetermined rectangular spread of the input light. This means that the design of the projector 1 is not constrained by the desired aspect ratio of the light 42 projected toward the user's eye 3.

[0068] In the example above, the input optics reflect light toward the output optics, and the light passes through the intermediate diffractive optics before reaching the output optics. However, in other examples, the optics do not need to be arranged in a straight line. For example, the optical device may include one or more internal reflecting elements configured to redirect light in the xy plane of the waveguide. Such internal reflecting elements can be used to provide one or more bends in the optical path taken by the light within the waveguide. In such an example, the aforementioned extension in the x-direction is defined as an extension parallel to the direction of light movement in the waveguide, and the aforementioned extension in the y-direction is defined as an extension perpendicular to the direction of light movement incident on the intermediate diffractive optics.

[0069] In some embodiments, multiple optical devices as described above can be stacked. Each optical device can be configured to optimally spread different optical frequencies. By using a beam splitter as the input optical element 21 and the output optical element 23, light can pass through multiple stacked optical devices.

Claims

1. An optical device for amplifying input light and outputting amplified light, the optical device comprising: waveguide; An input optical element is configured to receive light incident on a first side of the waveguide and includes an input reflective surface configured to reflect the received light into the waveguide; An intermediate diffractive optical element is configured to receive light in the waveguide from a first direction and to provide an extension of the received light in a second direction perpendicular to the first direction; as well as An output optical element includes an output reflective surface configured to reflect the extended light toward a viewer out of the waveguide. The waveguide is configured to guide light along optical paths from the input optical element to the intermediate diffractive optical element and from the intermediate diffractive optical element to the output optical element. The input reflective surface and the output reflective surface are parabolic surfaces.

2. The optical device according to claim 1, wherein, The output optical element is configured to reflect light out of the waveguide through the first side.

3. The optical device according to any of the preceding claims, wherein, The input optical element is configured to reflect light into the waveguide at a range of angles relative to the plane of the waveguide, such that the received light is expanded by a first expansion factor parallel to its direction of motion within the waveguide.

4. The optical device according to claim 3, wherein, The intermediate diffractive optical element is configured to spread the received light in the second direction with a second spreading factor, the second spreading factor being a predetermined multiple of the first spreading factor.

5. The optical device according to claim 1, wherein, The intermediate diffractive optical element includes a first grating oriented at a third angle to light received from the input optical element to provide first and second diffraction within the intermediate diffractive optical element, thereby coupling light toward the output optical element. The first diffraction couples light from the input optical element toward the first grating at a fourth angle, such that the second diffraction is provided at a plurality of spaced-apart locations within the intermediate diffractive optical element to provide light propagation. The second diffraction couples light toward the output diffractive optical structure.

6. The optical device according to claim 5, wherein, The intermediate diffractive optical element further includes a second grating oriented at a fifth angle to the light received from the input optical element to provide third and fourth diffraction within the intermediate diffractive optical element, thereby coupling light toward the output optical element. The third diffraction couples light from the input optical element toward the second diffraction feature at a fourth angle, such that the fourth diffraction is provided at multiple spaced locations within the intermediate diffractive optical element, thereby providing one-dimensional light extension. The fourth diffraction couples light toward the output diffractive optical structure.

7. The optical device according to claim 6, wherein, The third angle is a positive angle ψ, and the fifth angle is a negative angle ψ.

8. The optical device according to claim 7, wherein, The angle ψ is close to 45°, and the deviation is between 0° and ±10°.

9. The optical device according to any one of claims 6 to 8, wherein, The first grating and the second grating are physically spaced apart on the waveguide.

10. The optical device according to any one of claims 6 to 8, wherein, The first grating and the second grating overlap each other at least partially in the waveguide as a pair of intersecting gratings.

11. The optical device according to claim 10, wherein, The first grating and the second grating are disposed on opposite surfaces of the waveguide.

12. The optical device according to claim 10, wherein, The first grating and the second grating are disposed in substantially the same plane in the waveguide.

13. The optical device according to claim 10, wherein, The first grating and the second grating are provided using photonic crystals.

14. An optical system comprising: The optical device according to any of the preceding claims, and A projector, which is arranged to project light toward the input optical element of the optical device.

15. The optical system according to claim 14, wherein, The projector is configured to project light onto the angular field of view of the input optics.

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