Device and method for expanding the field of view of an optical waveguide

Abstract

The present invention relates to a device and method for expanding the field of view of an optical waveguide. The device comprises a waveguide plate, an input coupling prism, an array reflective film, and an optical wedge. The central ray of the incident light passes through the input coupling prism and enters the waveguide plate to become the central field of view ray. The array reflective film is arranged inside the waveguide plate. The angle between the array reflective film and the total reflection surface of the waveguide plate is i By changing the angle of the coupling prism, the included angle between the central field light and the vertical line of the total reflection surface of the waveguide plate is β >2 i ; The optical wedge is arranged at the total reflection surface of the waveguide plate; the optical wedge is used to make the light in the central field of view perpendicular to the total reflection surface of the waveguide plate when entering the human eye, which is in line with the viewing habits of the human eye.

Description

Technical Field

[0001] The present invention relates to the field of augmented reality (AR) technology, and in particular to a device and method for expanding the field of view of an optical waveguide. Background Art

[0002] The following content only represents the background technology known to the inventors and is not the prior art that is readily available to the public.

[0003] In the AR field, field of view (FOV) is a crucial parameter affecting the performance of AR glasses. For today's optical waveguide modules, to ensure that the central FOV of the optical machine remains central after passing through the waveguide and entering the human eye, the angle between the incident central FOV light and the perpendicular to the waveguide's total reflection surface is equal to twice the angle between the waveguide array's reflection surface and the total reflection surface. This ensures that the central FOV of the optical machine exits vertically after passing through the waveguide. This limits the angular range within which the waveguide can be applied, due to the waveguide's total reflection conditions.

[0004] like Figure 1 As shown, the angle between the central field of view of the incident light 4 (central field of view light) and the vertical line of the total reflection surface of the waveguide plate is (2 i ) is the angle between the array reflective film 3 in the waveguide and the total reflection surface (5, 6) of the waveguide ( i ) times; at this time, the direction of the central field of view light exiting the waveguide is perpendicular to the total reflection surface of the waveguide. i When fixed, assuming that the refractive index of the waveguide is n1, the angle range of the incident light in the waveguide is F1=2 due to the total reflection condition. [2 i -arcsin(1 / n1)]. Figure 1 In the figure, reference numeral 2 denotes a coupling prism. Summary of the Invention

[0005] The present invention aims to provide a device and method for expanding the field of view of an optical waveguide. The technical problem to be solved is how to expand the field of view of an AR optical module while ensuring that the outgoing light in the central field of view is perpendicular to the total reflection surface of the waveguide, which conforms to the viewing habits of the human eye.

[0006] The purpose of the present invention is to solve the shortcomings of the prior art and provide a device for expanding the field of view of an optical waveguide, comprising a waveguide plate, a coupling prism, an array reflective film and an optical wedge; the center line of the incident light passes through the coupling prism and enters the waveguide plate to become the central field of view light; the array reflective film is arranged inside the waveguide plate; the angle between the array reflective film and the total reflection surface of the waveguide plate is i By changing the angle of the coupling prism, the included angle between the central field light and the vertical line of the total reflection surface of the waveguide plate isβ >2 i ; The optical wedge is arranged at the total reflection surface of the waveguide plate; the optical wedge is used to make the light in the central field of view perpendicular to the total reflection surface of the waveguide plate when entering the human eye, which is in line with the viewing habits of the human eye.

[0007] Preferably, assuming that the refractive index of the waveguide is n1, the angle range of the incident light in the waveguide that satisfies the total reflection condition is F2=2 [ β -arcsin(1 / n1)].

[0008] Preferably, a predetermined gap is left between the optical wedge and the waveguide plate to ensure total reflection of the waveguide plate.

[0009] Preferably, assuming that the total length of the array reflective film of the waveguide plate is L1, the length of the optical wedge is greater than L2, and the optical wedge covers the length range of L1; wherein L2>L1.

[0010] Further preferably, the wedge angle of the optical wedge is recorded as f , assuming that the refractive index of the wedge is n2, then f =(n2-1) arcsin[n1 sin(2 β -4 i )].

[0011] Further preferably, assuming that the minimum thickness of the optical wedge is h1, the maximum thickness of the optical wedge h=h1+L2 tan f .

[0012] The present invention also provides a method for expanding the field of view of an optical waveguide, comprising the following steps:

[0013] The first step is to change the angle of the coupling prism so that the angle between the central field light and the vertical line of the total reflection surface of the waveguide plate is β >2 i When the angle between the array reflective film and the total reflection surface of the waveguide plate is i When fixed, assuming that the refractive index of the waveguide is n1, the angle range of the incident light in the waveguide that meets the total reflection condition is F2=2 [ β -arcsin(1 / n1)]; the field of view of the waveguide is increased;

[0014] The second step is to add an optical wedge at the total reflection surface of the waveguide plate; the optical wedge is used to make the light in the central field of view perpendicular to the total reflection surface of the waveguide plate when entering the human eye, which is in line with the viewing habits of the human eye.

[0015] Beneficial effects

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The device and method for expanding the field of view of an optical waveguide described in the present invention adopt a method in which the angle between the incident central field of view light and the perpendicular line of the total reflection surface of the waveguide plate in the waveguide plate is greater than twice the angle between the waveguide plate array reflection surface and the total reflection surface. At this time, the center of the field of view is offset in the direction of increasing the incident angle in the waveguide plate, thereby increasing the field of view angle transmitted in the waveguide plate, thereby expanding the field of view of the AR optical module; an optical wedge is added outside the waveguide plate to ensure that the outgoing light of the central field of view is perpendicular to the total reflection surface of the waveguide plate, which is in line with the viewing habits of the human eye. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings are used to provide a further understanding of the technical solution of the present invention and constitute a part of the specification. Together with the specific embodiments of the present application, they are used to explain the technical solution of the present invention and do not constitute a limitation on the technical solution of the present invention.

[0019] Figure 1 This is a schematic diagram of a common arrangement of waveguide plates in the background art.

[0020] Figure 2 It is a schematic structural diagram of the device for expanding the field of view of an optical waveguide according to the present invention. DETAILED DESCRIPTION

[0021] The present invention is described in more detail below to facilitate understanding of the present invention.

[0022] like Figure 2 As shown, the device for expanding the field of view of an optical waveguide according to the present invention comprises a waveguide plate 1, a coupling prism 2, an array reflective film 3, and an optical wedge 7; the incident light passes through the coupling prism 2 and enters the waveguide plate 1 to become the central field of view light 4; the array reflective film 3 is arranged inside the waveguide plate 1; the angle between the array reflective film 3 and the total reflection surface of the waveguide plate 1 is i By changing the angle of the coupling prism, the angle between the central field light 4 and the vertical line of the total reflection surface of the waveguide plate is β >2 i .

[0023] In this way, when i When fixed, assuming that the refractive index of the waveguide is n1, the angle range of the incident light in the waveguide that meets the total reflection condition is F2=2 [ β -arcsin(1 / n1)]= F1+2( β -2 i)>F1; Obviously, the field of view of the waveguide increases.

[0024] When the light in the central field of view exits the waveguide using the aforementioned method, it is not perpendicular to the total reflection surface of the waveguide, which is not in line with the human eye's viewing habits. Therefore, an optical wedge 7 is added at the total reflection surface 5 where the light exits the waveguide. Assuming that the total length of the array reflective film 3 of the waveguide is L1, the length of the optical wedge should be greater than L2 and cover the length range of L1. In addition, a certain gap is left between the optical wedge and the waveguide (to make the structure as compact as possible, the actual gap reference value is between 0 and 0.3 mm) to ensure total reflection of the waveguide. The wedge angle of the optical wedge is recorded as f , assuming the refractive index of the wedge is n2, then f =(n2-1) arcsin[n1 sin(2 β -4 i )]; Based on the consideration of processing technology, assuming that the minimum thickness of the optical wedge is h1, the maximum thickness of the optical wedge h=h1+L2 tan f In this way, after passing through the optical wedge, the light in the central field of view is perpendicular to the total reflection surface of the waveguide when entering the human eye, which is in line with the viewing habits of the human eye.

[0025] In actual operation, in order to ensure the lightness of the product, L2 is as small as possible while ensuring that it can cover the length of L1. For reference: the center positions of L1 and L2 coincide, and 0 <L2-L1<2mm。

[0026] The present invention also provides a method for expanding the field of view of an optical waveguide, comprising the following steps:

[0027] The first step is to change the angle of the coupling prism so that the angle between the central field light 4 and the vertical line of the total reflection surface of the waveguide is β >2 i When the angle between the array reflective film 3 and the total reflection surface of the waveguide plate 1 is i When fixed, assuming that the refractive index of the waveguide is n1, the angle range of the incident light in the waveguide that meets the total reflection condition is F2=2 [ β -arcsin(1 / n1)]; the field of view of the waveguide is increased;

[0028] The second step is to add an optical wedge 7 at the total reflection surface 5 of the waveguide plate; the optical wedge is used to make the light in the central field of view perpendicular to the total reflection surface of the waveguide plate when entering the human eye, which is in line with the viewing habits of the human eye.

[0029] The present invention's device and method for expanding the field of view of an optical waveguide employs a method in which the angle between the incident central field of view light and the perpendicular to the waveguide's total reflection surface within the waveguide is greater than twice the angle between the waveguide array's reflection surface and the total reflection surface. This shifts the center of the field of view toward a direction that increases the angle of incidence within the waveguide, thereby increasing the angle of the field of view transmitted within the waveguide and thus expanding the field of view of the AR optical module. An optical wedge is added to the outside of the waveguide to ensure that the outgoing light from the central field of view is perpendicular to the waveguide's total reflection surface, which conforms to the human eye's viewing habits.

[0030] The preferred embodiments of the present invention are described above, but they are not intended to limit the present invention. Those skilled in the art may make improvements and changes to the embodiments disclosed herein without departing from the scope and spirit of the present invention.

Claims

1. A device for expanding the field of view of an optical waveguide, characterized in that: The device for expanding the field of view of the optical waveguide includes a waveguide plate, a coupling prism, an array reflective film and an optical wedge; the central ray of the incident light passes through the coupling prism and enters the waveguide plate to become the central field of view ray; the array reflective film is arranged inside the waveguide plate; the angle between the array reflective film and the total reflection surface of the waveguide plate is θ By changing the angle of the coupling prism, the included angle between the central field light and the vertical line of the total reflection surface of the waveguide plate is β >2 θ ; The refractive index of the waveguide is n1, then the angle range of the incident light in the waveguide that satisfies the total reflection condition is F2=2 [ β -arcsin(1 / n1)]; the optical wedge is arranged at the total reflection surface of the waveguide plate; the optical wedge is used to make the light of the central field of view perpendicular to the total reflection surface of the waveguide plate when entering the human eye, which is in line with the viewing habits of the human eye.

2. The device for expanding the field of view of an optical waveguide according to claim 1, characterized in that: A gap is provided between the optical wedge and the waveguide plate to ensure total reflection of the waveguide plate.

3. The device for expanding the field of view of an optical waveguide according to claim 1, wherein: The total length of the array reflective film of the waveguide plate is L1, the length of the optical wedge is greater than L2, and the optical wedge covers the length range of L1; wherein L2>L1.

4. The device for expanding the field of view of an optical waveguide according to claim 1, wherein: The wedge angle of the optical wedge is recorded as φ , assuming that the refractive index of the wedge is n2, then φ =(n2-1) arcsin[n1 sin(2 β -4 θ )].

5. The device for expanding the field of view of an optical waveguide according to claim 3, wherein: When the minimum thickness of the optical wedge is h1, the maximum thickness of the optical wedge is h=h1+L2 tan φ .

6. The method for expanding the field of view of an optical waveguide according to any one of claims 1 to 5, characterized in that: The method for expanding the field of view of an optical waveguide comprises the following steps: The first step is to change the angle of the coupling prism so that the angle between the central field light and the vertical line of the total reflection surface of the waveguide plate is β >2 θ When the angle between the array reflective film and the total reflection surface of the waveguide plate is θ When the refractive index of the waveguide is fixed, n1, the angle range of the incident light in the waveguide that satisfies the total reflection condition is F2=2 [ β -arcsin(1 / n1)]; the field of view of the waveguide is increased; The second step is to add an optical wedge at the total reflection surface of the waveguide plate; the optical wedge is used to make the light in the central field of view perpendicular to the total reflection surface of the waveguide plate when entering the human eye, which is in line with the viewing habits of the human eye.

7. The method for expanding the field of view of an optical waveguide according to claim 6, wherein: A gap is provided between the optical wedge and the waveguide plate to ensure total reflection of the waveguide plate.

8. The method for expanding the field of view of an optical waveguide according to claim 6, wherein: The total length of the array reflective film of the waveguide plate is L1, the length of the optical wedge is greater than L2, and the optical wedge covers the length range of L1; wherein L2>L1.

9. The method for expanding the field of view of an optical waveguide according to claim 6, wherein: The wedge angle of the optical wedge is recorded as φ , the refractive index of the wedge is n2, then φ =(n2-1) arcsin[n1 sin(2 β -4 θ )]; when the minimum thickness of the optical wedge is h1, the maximum thickness of the optical wedge is h=h1+L2 tan φ .

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