Two-dimensional pupil-expanding waveguide optical module

Abstract

A two-dimensional pupil-expanding waveguide optical module relates to the field of optical waveguides and comprises an image source, a waveguide element, a coupling-in element, a turning element and a coupling-out element. The turning element comprises a top grating and a bottom grating; the top grating is arranged on the upper surface of the waveguide element, and the bottom grating, the coupling-in element and the coupling-out element are arranged on the lower surface of the waveguide element; light emitted by the image source is subjected to total reflection in the waveguide element after being diffracted by the coupling-in element; after at least two times of total reflection in the waveguide, the light is diffracted by the top grating and is vertically emitted to the bottom grating, so that expansion in the first direction is realized; the light emitted from the top layer grating is emitted to the other direction after vertically emitting to the bottom layer grating, so that the turning of the light is realized; and the light emitted by the bottom grating is reflected totally at least once in the waveguide element, is diffracted by the coupling-out element and then is emitted to human eyes, so that expansion in a second direction is realized. According to the utility model, the two-dimensional pupil expansion of the image light is realized, the volumes of the coupling element and the projection light machine are reduced, and the manufacturing difficulty of the waveguide element is simplified.

Description

TECHNICAL FIELD

[0001] The utility model relates to the field of optical waveguide, especially two -dimensional pupil dilation waveguide optical module. BACKGROUND

[0002] At present, the diffraction optical waveguide technology has the advantages of large exit pupil, large field of view, light, compact, high transmittance, and is one of the devices with the most large-scale application prospects in the augmented reality head-mounted display device.

[0003] For the augmented reality head-mounted display system, mainly by micro display, collimating mirror group, diffraction optical waveguide, system circuit is composed, wherein the diffraction waveguide is by the coupling-in element, waveguide base, coupling-out grating is constituted. The diffraction waveguide is used in the display device field, and the most remarkable advantage is that the exit pupil expansion function can be realized, the trade-off relationship between the size of the traditional optical display device, the size of the exit pupil and the field of view is effectively solved, so that the display effect of small volume and large exit pupil is realized.

[0004] The diffraction optical waveguide several common pupil dilation schemes have the "L" type and "Y" type waveguide structure, and each has advantages and disadvantages in preparation difficulty and imaging quality. Two kinds of waveguide structures at least contain three different gratings, which are simply summarized as in-coupling grating, relay grating and out-coupling grating, in order to eliminate the dispersion caused by each grating, the sum of the K vectors of the three gratings must be zero, which requires strict control of the exposure angle in the grating preparation process, which will greatly increase the preparation difficulty. For waveguide display, two-dimensional pupil dilation waveguide can greatly improve the exit pupil size, thereby improving the display performance of the waveguide. Therefore, under the premise of not increasing the system volume and realizing high-quality imaging effect, how to reduce the preparation difficulty of two-dimensional pupil dilation waveguide is urgent to be solved. SUMMARY

[0005] The utility model discloses a two -dimensional pupil dilation waveguide optical module, realizes two -dimensional pupil dilation of image light through coupling-in element, waveguide element, by the turning element of two layers of gratings integrated and coupling-out element, reduces the volume of coupling-in element and projection light machine, simplifies the manufacturing difficulty of waveguide element.

[0006] In order to achieve the above object, the utility model adopts the following technical scheme:

[0007] A two-dimensional pupil expanding waveguide optical module, comprising an image source, a waveguide element, a coupling-in element, a turning element and a coupling-out element; the turning element comprises a top grating and a bottom grating; the top grating is arranged on the upper surface of the waveguide element, and the bottom grating is arranged on the lower surface of the waveguide element and below the top grating; the coupling-in element and the coupling-out element are arranged on the lower surface of the waveguide element, and the coupling-in element is arranged on the same side of the bottom grating, and the coupling-out element is arranged on the other side of the waveguide element in parallel with the bottom grating; wherein the light emitted by the image source is diffracted by the coupling-in element and totally reflected in the waveguide element; after at least twice of total reflection in the waveguide, the light is diffracted by the top grating of the turning element and vertically shot to the bottom grating, so as to realize expansion in the first direction; the light emitted by the top grating is vertically shot to the bottom grating and then shot to another direction, so as to realize turning of the light; the light emitted by the bottom grating is diffracted by the coupling-out element after at least once of total reflection in the waveguide element, and then shot to the human eye, so as to realize expansion in the second direction.

[0008] The angle between the light emitted by the coupling-in element and the lower surface of the waveguide element is greater than the critical reflection angle of the base body of the waveguide element; and the angle between the light emitted by the bottom grating of the turning element and the upper surface of the waveguide element is greater than the critical reflection angle of the base body of the waveguide element.

[0009] The top grating and the bottom grating are diffraction gratings or volume holographic gratings.

[0010] The size of the top grating is equivalent to that of the bottom grating.

[0011] The coupling-in element and the coupling-out element are diffraction gratings or volume holographic gratings.

[0012] The area of the coupling-in element is smaller than that of the coupling-out grating.

[0013] Compared with the prior art, the technical scheme of the utility model has the beneficial effects that:

[0014] The two-dimensional pupil expanding waveguide optical module provided by the utility model realizes two-dimensional pupil expansion of image light through the coupling-in element, the waveguide element, the turning element integrated by the top grating and the bottom grating and the coupling-out element, and a larger exit pupil can be obtained. On the one hand, the volume of the waveguide and the projection light machine is reduced; on the other hand, the difficulty of the manufacturing process of the two-dimensional pupil expanding waveguide is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 It is a structural schematic view of the utility model; wherein the coupling-in element 2, the coupling-out element 4 and the bottom grating 32 are located on the lower surface of the waveguide element 1, and the top grating 31 is located on the upper surface of the waveguide element 1;

[0016] Figure 2 It is a one-dimensional expansion schematic view of the light beam of the utility model;

[0017] Figure 3 The two-dimensional light beam expansion is achieved.

[0018] Figure 4 The vector light beam expansion is achieved.

[0019] The reference signs: waveguide element 1, coupling-in element 2, turning element 3, coupling-out element 4, light ray cluster one 5, light ray cluster two 6, top layer grating 31, bottom layer grating 32. DETAILED DESCRIPTION

[0020] In order to make the technical problems, technical solutions and beneficial effects of the utility model clearer and more understandable, the utility model will be further described in detail in combination with the drawings and embodiments.

[0021] Embodiment 1

[0022] As Figure 1 The two-dimensional pupil expansion waveguide optical module comprises an image source, a waveguide element 1, a coupling-in element 2, a turning element 3 and a coupling-out element 4; the turning element 3 comprises a top layer grating 31 and a bottom layer grating 32.

[0023] The waveguide element 1 comprises an upper surface close to the human eye and a lower surface away from the human eye; the top layer grating 31 is arranged on the upper surface of the waveguide element 1, the bottom layer grating 32 is arranged on the lower surface of the waveguide element 1, and the bottom layer grating 32 is arranged directly below the top layer grating 31, and the size of the top layer grating 31 and the bottom layer grating 32 is equal; the coupling-in element 2 is arranged on the lower surface of the waveguide element 1 and on the same side as the bottom layer grating 32, and the other side of the lower surface of the waveguide element 1 is provided with a coupling-out element 4 parallel to the bottom layer grating 32.

[0024] The light emitted by the image source is diffracted by the coupling-in element 2 and then totally reflected in the waveguide element 1; after at least two times of total reflection in the waveguide element 1, the light is diffracted by the top layer grating 31 of the turning element 3 and then vertically shot to the bottom layer grating 32, so that the expansion in the first direction is realized; the light is diffracted by the bottom layer grating 32 and then shot to another direction, so that the turning of the light ray is realized; the light shot by the bottom layer grating 32 is totally reflected at least once in the waveguide element 1 and then diffracted by the coupling-out element 4 and shot to the human eye, so that the expansion in the second direction is realized.

[0025] As Figures 2 to 4As shown, the light emitted by the light source hits the coupling-in element 2, and then propagates in the +Y direction in the waveguide element 1 at a propagation angle satisfying the total reflection condition, and reaches the top grating 31 of the turning element 3 after at least two times of total reflection. After reaching the top grating 31, part of the light is diffracted, and the other part of the light continues to propagate under the total reflection condition and is diffracted after reaching the top grating 31. The light beam is continuously diffracted and replicated to form the light cluster I 5 during the propagation, thereby realizing one-dimensional exit pupil expansion in the +Y direction. The light cluster I 5 formed by the diffraction of the top grating 31 of the turning element 3 is vertically incident on the bottom grating 32, and then propagates in the +X direction in the waveguide under the total reflection condition, and reaches the coupling-out element 4 after at least one time of total reflection. After reaching the coupling-out element 4, part of the light is diffracted out of the waveguide, and the other part of the light continues to propagate under the total reflection condition. The light beam is continuously replicated and expanded in the +X direction during the process, and finally forms the light cluster II 6 that can be incident on the human eye or other optical systems, thereby realizing two-dimensional exit pupil expansion of the image light.

[0026] In the embodiment, the waveguide element 1 of the two-dimensional exit pupil expansion waveguide optical module is an optical glass or resin with a refractive index of 1.3-2.2 and has a rectangular shape. The coupling-in element 2 and the coupling-out element 4 can be a diffraction grating or a volume holographic grating, etc. Each top grating 31 of the turning element 3 has a predetermined diffraction efficiency, and the diffraction efficiencies of the plurality of gratings gradually decrease from the end of the incident coupling-in element 2 to the other end of the waveguide element 1, thereby realizing uniform expansion of the image light in the +Y direction. Each coupling-out grating of the coupling-out element 4 also has a predetermined diffraction efficiency, and the diffraction efficiencies of the plurality of gratings gradually decrease from the end of the turning element 3 to the other end of the waveguide element 1, thereby realizing uniform expansion of the image light in the +X direction, and further realizing uniform expansion of the light in two-dimensional directions.

[0027] In the preparation, the coupling-in element 2 corresponds to the coupling-out element 4, the top grating 31 of the turning element 3 corresponds to the bottom grating 32, has similar processing parameters, and can use similar processing technology, thereby reducing the cost and manufacturing difficulty of the waveguide element.

[0028] In summary, the two-dimensional exit pupil expansion waveguide optical module provided by the utility model realizes two-dimensional exit pupil expansion of the image light through the coupling-in element, the waveguide element, the turning element integrated by the upper and lower gratings, and the coupling-out element, reduces the volume of the coupling-in element and the projection light machine, and simultaneously simplifies the manufacturing difficulty of the waveguide element.

Claims

1. A two-dimensional pupil-expanding waveguide optical module, characterized in that: It includes a waveguide element, a coupling element, a transition element, and a coupling element; the transition element includes a top grating and a bottom grating; the top grating is disposed on the upper surface of the waveguide element, and the bottom grating is disposed on the lower surface of the waveguide element and located below the top grating; the coupling element and the coupling element are disposed on the lower surface of the waveguide element, with the coupling element and the bottom grating disposed on the same side, and the coupling element and the bottom grating disposed parallel to each other on the other side of the waveguide element.

2. The two-dimensional pupil-expanding waveguide optical module as described in claim 1, characterized in that: The angle between the emitted light from the coupling element and the lower surface of the waveguide element is greater than the critical reflection angle of the waveguide element substrate; the angle between the emitted light from the bottom grating of the transition element and the upper surface of the waveguide element is greater than the critical reflection angle of the waveguide element substrate.

3. The two-dimensional pupil-expanding waveguide optical module as described in claim 1, characterized in that: The top and bottom gratings are diffraction gratings or volume holographic gratings.

4. The two-dimensional pupil-expanding waveguide optical module as described in claim 1, characterized in that: The top and bottom gratings are of similar size.

5. A two-dimensional pupil-expanding waveguide optical module as described in claim 1, characterized in that: The coupling element and coupling element are diffraction gratings or volume holographic gratings.

6. The two-dimensional pupil-expanding waveguide optical module as described in claim 1, characterized in that: The area of ​​the coupled element is smaller than the area of ​​the coupled-out grating.

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