Small-size single-layer full-color AR optical waveguide based on LCoS optical machine

Abstract

The invention discloses a small-size single-layer full-color AR optical waveguide based on LCoS, the AR optical waveguide structure comprises an LCoS optical engine, a parallel plate, a coupling-in gradual change period polarization body holographic lens and a two-dimensional coupling-out polarization body holographic grating, and the LCoS is connected with the parallel plate in an optical gluing mode; the gradient period polarization holographic lens is coupled to achieve the effect of light collimation and light deflection coupling, and the wavelength bandwidth is expanded to the visible light range through variable period processing. The two-dimensional coupling-out polarization body holographic grating is used for expanding light rays to two directions, and the pupil expanding effect is achieved. According to the structure, the problem that an LCoS light machine depends on a projection lens, and the size is too large is solved, and the single-layer full-color AR optical waveguide under the small size is achieved.

Description

Technical Field

[0001] The present invention relates to the field of augmented reality, and in particular to a small-area single-layer full-color AR optical waveguide based on an LCoS optical machine. Background Art

[0002] Augmented Reality, hereinafter referred to as AR, is a display technology that "seamlessly" integrates virtual information with the real world, and "enhances" the real world through computer image rendering, human-computer interaction, three-dimensional space modeling and other technologies, which are difficult to experience in a certain time and space range in the real world, such as visual, auditory, taste, and tactile information. The basic functions and requirements of the augmented reality display system are realized, but at the same time there are obvious defects such as small display field of view, small exit pupil, large volume and weight, which affect consumers' display experience and wearing comfort.

[0003] With the continuous development of AR technology, microdisplays have become the best solution for realizing high-performance displays required for portable devices. The main microdisplays currently include: digital display processing technology, micro light-emitting diodes, organic light-emitting diodes, and liquid crystal on silicon (LCoS). Among them, LCoS has outstanding performance in color accuracy and resolution compared with other technologies, and is suitable for AR devices that require high image quality, but it is relatively large in size.

[0004] For AR optical waveguide imaging systems, the performance of coupling elements directly affects the system efficiency and imaging quality of optical waveguide near-eye display systems. Volume holographic grating (Holographic Volume Grating), hereinafter referred to as VHG, is coupled based on volume grating Bragg diffraction, which can achieve high-efficiency single-order diffraction. In addition, the response bandwidth of VHG is relatively narrow, which makes it more transparent to the external ambient light field, which meets the needs of AR applications, but the narrow response bandwidth also brings problems such as smaller field of view and color performance. The new polarization volume holographic grating (Polarization Volume Grating), hereinafter referred to as PVG, can produce efficient single-order Bragg diffraction under the body effect in terms of diffraction characteristics, just like VHG, thereby ensuring the optical coupling efficiency and image transmission quality of the waveguide system. In addition, PVG has the advantage of a response bandwidth far greater than that of traditional VHG, and also exhibits the Pacharatnam-Berry (PB) phase polarization response characteristics that VHG does not have, enabling it to achieve a lens effect by modulating the phase. Summary of the invention

[0005] Purpose of the invention: To solve the problem that the LCoS optical machine relies on a projection lens that is too large, a small-volume single-layer full-color AR optical waveguide based on LCoS is proposed, which can realize a single-layer full-color AR optical waveguide in a small volume.

[0006] Technical solution: A small-volume single-layer full-color AR optical waveguide based on LCoS, including an LCoS light engine, a parallel plate, a coupled-in gradient periodic polarizer holographic lens, and a two-dimensional coupled-out polarizer holographic grating; the parallel plate plays the role of total internal reflection light transmission; the light emitted by the LCoS light engine is incident on the coupled-in gradient periodic polarizer holographic lens through the parallel plate, and the coupled-in gradient periodic polarizer holographic lens plays the effect of light collimation and light deflection coupling, and after variable period processing, the wavelength bandwidth of the light is expanded to the visible light range; the light emitted by the coupled-in gradient periodic polarizer holographic lens is incident on the two-dimensional coupled-out polarizer holographic grating through the parallel plate, and the two-dimensional coupled-out polarizer holographic grating is used to expand the light in two directions, thereby achieving the effect of pupil expansion.

[0007] Preferably, the parallel plate is located between the LCoS light engine and the in-coupled gradient period polarization holographic lens and the two-dimensional out-coupled polarization holographic grating.

[0008] Preferably, the LCoS light engine is connected to the parallel plate by optical bonding.

[0009] Preferably, the gradient period polarizer holographic lens is a diffractive optical element with continuously changing lateral and longitudinal periods, wherein the lateral period variation is a function of position, ensuring that the spherical phase of the incident wave is modulated into a plane wave, and the longitudinal period is modulated by the diffraction of the mask during the curing process to widen the Bragg diffraction wavelength bandwidth of the polarizer holographic lens.

[0010] Preferably, the rotation angle of the liquid crystal molecules of the gradient periodic polarizer holographic lens under the linear gradient pitch distribution in the y direction is calculated by the following formula:

[0011]

[0012] where Λ x is the period length in the transverse direction, d is the thickness of the polarization volume holographic grating material, Λ y0 and Λ y1 They are respectively the lengths corresponding to the longitudinal rotation period of the liquid crystal near the orientation layer and the other surface of the polarizer holographic grating; the longitudinal period is the length from Λ y0 Linear change to Λ y1 .

[0013] Preferably, the diffraction wavelength bandwidth of the gradient pitch distribution of the gradient period polarizer holographic lens and the polarizer holographic grating under the uniform pitch distribution structure is 400-700nm, and the gradient pitch variation range is Λy0 ~Λ y1 The larger it is, the wider the wavelength bandwidth will become.

[0014] Preferably, the two-dimensional out-coupled polarizer holographic grating is two layers of liquid crystal with opposite rotation directions, wherein the left-handed cholesteric liquid crystal responds to left-handed circularly polarized light and diffracts it in one direction, and the right-handed cholesteric liquid crystal responds to right-handed circularly polarized light and diffracts it in another direction, thereby achieving the effect of two-dimensional pupil expansion with a single grating.

[0015] The present invention also provides an AR optical display system, comprising an LCoS display and the above-mentioned small-volume single-layer full-color AR optical waveguide.

[0016] Beneficial effects: The small-volume single-layer full-color AR optical waveguide of the present invention achieves the effect of light collimation and light deflection coupling by coupling into a gradient period polarizer holographic lens, and expands its wavelength bandwidth to the visible light range by variable period processing; the light is expanded in two directions by two-dimensional out-coupling polarizer holographic grating, achieving the effect of pupil expansion. The present invention solves the problem that the LCoS optical machine relies on the large volume of the projection lens, and realizes a single-layer full-color AR optical waveguide in a small volume. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of a small-volume single-layer full-color AR optical waveguide structure based on an LCoS optical machine provided in an embodiment of the present invention;

[0018] Figure 2 This is a schematic diagram of a small-volume single-layer full-color AR optical waveguide gradient periodic polarizer holographic lens micro-nano structure based on an LCoS optical machine provided in an embodiment of the present invention;

[0019] Figure 3 Schematic diagram of wavelength bandwidth of a small-volume single-layer full-color AR optical waveguide gradient periodic polarizer holographic lens based on an LCoS optical machine provided in an embodiment of the present invention;

[0020] Figure 4 It is a schematic diagram of the position of a two-dimensional out-coupling grating of a small-volume single-layer full-color AR optical waveguide based on an LCoS optical engine provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0021] The specific implementation of the present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be noted that the embodiments and features in the embodiments of the present invention can be combined with each other without conflict.

[0022] like Figure 1As shown, it is a schematic diagram of a small-volume single-layer full-color AR optical waveguide structure provided by an embodiment of the present invention, which includes an LCoS optical engine 1, a parallel plate 2, an in-coupled gradient periodic polarizer holographic lens 3, and a two-dimensional out-coupled polarizer holographic grating 4. Among them, the LCoS optical engine 1 is connected to the parallel plate 2 by optical bonding; the in-coupled gradient periodic polarizer holographic lens 3 plays the role of light collimation and light deflection coupling, and its wavelength bandwidth is extended to the visible light range after variable period processing; the two-dimensional out-coupled polarizer holographic grating 4 is used to expand the light in two directions, which plays the role of pupil expansion.

[0023] The parallel plate 2 is located between the LCoS light engine 1 and the in-coupled gradient periodic polarization holographic lens 3 and the two-dimensional out-coupled polarization holographic grating 4 .

[0024] The LCoS optical engine 1 is attached to the parallel plate 2. The parallel plate plays a role in total internal reflection light transmission. The parallel plate and the in-out coupling grating together form an optical waveguide.

[0025] like Figure 2 As shown, it is a schematic diagram of the micro-nano structure of a small-volume single-layer full-color AR optical waveguide gradient period polarizer holographic lens provided by an embodiment of the present invention. 200nm~400nm, 100nm~200nm are the lateral periods at different positions respectively; 1μm~20μm is the thickness range of the polarizer holographic lens. The gradient period polarizer holographic lens 3 is a diffractive optical element with continuous changes in lateral and longitudinal periods. Its lateral period change is a function of position, ensuring that the spherical phase of the incident wave is modulated into a plane wave, and its longitudinal period is modulated by the diffraction of the mask during the curing process to widen the Bragg diffraction wavelength bandwidth of the polarizer holographic lens.

[0026] like Figure 3 As shown, it is a schematic diagram of the wavelength bandwidth of a small-volume single-layer full-color AR optical waveguide gradient periodic polarizer holographic lens provided by an embodiment of the present invention. The diffraction wavelength bandwidth of the polarizer holographic grating under the gradient pitch distribution of the gradient periodic polarizer holographic lens 3 and the uniform pitch distribution structure is 400-700nm, and the larger the gradient pitch variation range (Λy0-Λy1), the wider the wavelength bandwidth will become. The rotation angle of the liquid crystal molecules of the gradient periodic polarizer holographic lens 3 under the linear gradient pitch distribution in the y direction can be calculated by the following formula:

[0027]

[0028] Where Λx is the period length along the transverse direction (x direction), d is the thickness of the polarizer holographic grating material, Λy0 and Λy1 are the lengths corresponding to the longitudinal rotation period of the liquid crystal near the orientation layer and the other surface of the polarizer holographic grating. At this time, the longitudinal period is no longer a constant value, but changes linearly from Λy0 to Λy1 in space.

[0029] like Figure 4 As shown, it is a schematic diagram of the position of the two-dimensional out-coupling grating of a small-volume single-layer full-color AR optical waveguide provided by an embodiment of the present invention. The left side of the schematic diagram shows the LCoS light engine 5 and the coupled-in gradient periodic polarizer holographic lens 6, and the right side of the schematic diagram shows the two-dimensional out-coupling polarizer holographic grating 7 and the parallel plate 8. The two-dimensional out-coupling polarizer holographic grating 7 is two layers of liquid crystal with opposite rotation directions, in which the left-handed cholesteric liquid crystal responds to the left-handed circularly polarized light and diffracts it in one direction, and the right-handed cholesteric liquid crystal responds to the right-handed circularly polarized light and diffracts it in another direction, so as to achieve the effect of a single grating to achieve two-dimensional pupil expansion.

[0030] The present invention also provides an AR optical display system, comprising an LCoS display and the above-mentioned small-volume single-layer full-color AR optical waveguide.

Claims

1. A small volume single-layer full-color AR optical waveguide based on LCoS, characterized in that: It includes an LCoS light engine, a parallel plate, an in-coupled gradient periodic polarizer holographic lens, and a two-dimensional out-coupled polarizer holographic grating; the parallel plate plays the role of total internal reflection light transmission; the light emitted by the LCoS light engine is incident on the in-coupled gradient periodic polarizer holographic lens via the parallel plate, the in-coupled gradient periodic polarizer holographic lens plays the effect of light collimation and light deflection coupling, and the wavelength bandwidth of the light is extended to the visible light range after variable period processing; the light emitted by the in-coupled gradient periodic polarizer holographic lens is incident on the two-dimensional out-coupled polarizer holographic grating via the parallel plate, the two-dimensional out-coupled polarizer holographic grating is used to expand the light in two directions, playing the effect of pupil expansion.

2. The small-volume single-layer full-color AR optical waveguide according to claim 1, characterized in that: The parallel plate is located between the LCoS light engine, the coupled-in gradient period polarization holographic lens, and the two-dimensional coupled-out polarization holographic grating.

3. The small-volume single-layer full-color AR optical waveguide according to claim 1, characterized in that: The LCoS light engine is connected to the parallel plate in an optical bonding manner.

4. The small-volume single-layer full-color AR optical waveguide according to claim 1, characterized in that: The gradient period polarizer holographic lens is a diffractive optical element with continuously changing lateral and longitudinal periods, wherein the lateral period variation is a function of position, ensuring that the spherical phase of the incident wave is modulated into a plane wave, and the longitudinal period is modulated by the diffraction of the mask during the curing process, so as to widen the Bragg diffraction wavelength bandwidth of the polarizer holographic lens.

5. The small-volume single-layer full-color AR optical waveguide according to claim 1, characterized in that: The rotation angle of the liquid crystal molecules of the gradient periodic polarizer holographic lens under the linear gradient pitch distribution in the y direction is calculated by the following formula: where Λ x is the period length in the transverse direction, d is the thickness of the polarization volume holographic grating material, Λ y0 and Λ y1 They are respectively the lengths corresponding to the longitudinal rotation period of the liquid crystal near the orientation layer and the other surface of the polarizer holographic grating; the longitudinal period is the length from Λ y0 Linear change to Λ y1 .

6. The small-volume single-layer full-color AR optical waveguide according to claim 5, characterized in that: The diffraction wavelength bandwidth of the gradient pitch distribution of the gradient periodic polarizer holographic lens and the polarizer holographic grating under the uniform pitch distribution structure is 400-700nm, and the gradient pitch variation range is Λ y0 ~Λ y1 The larger it is, the wider the wavelength bandwidth will become.

7. The small-volume single-layer full-color AR optical waveguide according to claim 1, characterized in that: The two-dimensional out-coupling polarizer holographic grating is two layers of liquid crystal with opposite rotation directions, wherein the left-handed cholesteric liquid crystal responds to left-handed circularly polarized light and diffracts it in one direction, and the right-handed cholesteric liquid crystal responds to right-handed circularly polarized light and diffracts it in another direction, thereby achieving the effect of two-dimensional pupil expansion with a single grating.

8. An AR optical display system, characterized in that: The invention comprises an LCoS display and a small-volume single-layer full-color AR optical waveguide as described in any one of claims 1 to 7.

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