A mixing-type monolithic waveguide lens and a three-dimensional display device

Abstract

The present invention provides a frequency mixing type single-chip waveguide lens and a three-dimensional display device. The frequency mixing type single-chip waveguide lens includes a waveguide and an incident functional region and an output functional region located on the upper surface or the lower surface of the waveguide, wherein: an incident peak-shaped diffraction grating structure for coupling an external image optical signal into the waveguide is arranged in the incident functional region, and the incident peak-shaped diffraction grating structure is formed by overlapping multiple groups of incident diffraction gratings, and each incident diffraction grating correspondingly couples an image optical signal of a different wavelength; an output peak-shaped diffraction grating structure for coupling the image optical signal transmitted in the waveguide out of the waveguide is arranged in the output functional region, and the output peak-shaped diffraction grating structure is formed by overlapping multiple groups of output diffraction gratings, and each output diffraction grating correspondingly couples an image optical signal of a different wavelength. The present invention realizes color display of a single-chip waveguide lens, ensures the compactness of the display device in terms of structure, reduces optical loss at the same time, and improves the display effect.

Description

Technical Field

[0001] The present invention relates to virtual reality display technology, and particularly to a mixing type single-chip waveguide lens and a three-dimensional display device. Background Art

[0002] With the development of virtual reality and augmented reality technologies, near-eye display devices have developed rapidly, such as Google Glass of Google and HoloLens of Microsoft. Near-eye display of augmented reality is a technology that images a light field in the real space and can simultaneously take into account virtual and real operations. The waveguide display system uses the total reflection principle to achieve light wave transmission, combines diffraction elements, and realizes the directional conduction of light, and then guides the image light to the human eye so that the user can see the projected image.

[0003] Traditional optical waveguide lenses can only achieve the coupling of the image light of a single wavelength band. Therefore, in order to achieve color virtual display imaging, multiple optical waveguide lenses need to be stacked together to form a diffraction element. The display device constructed by using such a diffraction element has a large weight and volume, and a relatively high manufacturing cost. In addition, since a large optical loss will occur at the junction of adjacent optical waveguide lenses for the image light signal, the final display effect is reduced.

[0004] In view of the defects of traditional optical waveguide lenses, the applicant has invested a large amount of R & D resources in order to achieve color display of a single-chip waveguide lens. Prior to this, the applicant disclosed a single-chip holographic diffraction waveguide lens in a Chinese patent application with the publication number of CN106773057A. A plurality of structural unit pixels are arranged in the functional area thereof, and each structural unit pixel includes a plurality of structural sub-unit pixels for coupling different primary color image lights. The display device constructed by using such a single-chip holographic diffraction waveguide lens can achieve color display. However, since each structural sub-unit pixel is tiled in the functional area, the waveguide area occupied by the functional area is too large, reducing the display effect. In addition, the spatial multiplexing of pixel tiling has extremely high requirements for the modulation of gratings corresponding to respective light rays, and it is easy to generate diffraction crosstalk between light rays. Summary of the Invention

[0005] In order to solve the above technical problems, a first aspect of the present invention provides a mixing type single-chip waveguide lens, which can achieve synchronous coupling of image light signals of multiple different wavelengths to achieve color display. The specific technical solution is as follows:

[0006] A mixing type single-chip waveguide lens, characterized in that it includes:

[0007] A waveguide;

[0008] A functional region with transparent optical and waveguide bending functions located on the upper or lower surface of the waveguide, the functional region at least includes:

[0009] An incident functional region, in which an incident peak-shaped diffraction grating structure for coupling an external image optical signal into the waveguide is provided, and the incident peak-shaped diffraction grating structure is formed by overlapping multiple groups of incident diffraction gratings, and each group of the incident diffraction gratings corresponds to coupling an image optical signal of a specific wavelength;

[0010] An output functional region, in which an output peak-shaped diffraction grating structure for coupling the image optical signal transmitted in the waveguide out of the waveguide is provided, and the output peak-shaped diffraction grating structure is formed by overlapping multiple groups of output diffraction gratings corresponding to the multiple groups of incident diffraction gratings, and each group of the output diffraction gratings corresponds to coupling an image optical signal of a specific wavelength out of the waveguide.

[0011] Further, the incident diffraction grating and the output diffraction grating are formed by exposure of a light beam group composed of two plane waves.

[0012] Further, the incident peak-shaped diffraction grating structure and the output peak-shaped diffraction grating structure are respectively formed by multiple single light beam group exposures, and each single light beam group exposure corresponds to forming a group of incident diffraction gratings or a group of output diffraction gratings.

[0013] Further, the incident peak-shaped diffraction grating structure and the output peak-shaped diffraction grating structure are respectively formed by one multi-light beam group exposure. During the exposure process, each light beam group corresponds to forming a group of incident diffraction gratings or output diffraction gratings.

[0014] Further, the functional region further includes a relay functional region located on the upper or lower surface of the waveguide, and a relay diffraction grating structure for changing the propagation direction of the light beam in the waveguide lens is provided in the relay functional region.

[0015] Further, the incident diffraction grating and the output diffraction grating are wavelength-selective oblique gratings, volume gratings or blazed gratings

[0016] Further, the frequency mixing type single-chip waveguide lens is used to regulate the three primary color image optical signals, wherein: the incident peak-shaped diffraction grating structure is formed by overlapping three groups of incident diffraction gratings, and the three groups of incident diffraction gratings respectively couple the red light image optical signal, the blue light image optical signal and the green light image optical signal into the waveguide at different angles; the output peak-shaped diffraction grating structure is formed by overlapping three groups of output diffraction gratings, and the three groups of output diffraction gratings respectively couple the red light image optical signal, the blue light image optical signal and the green light image optical signal out of the waveguide

[0017] Further, each functional region includes a plurality of structural unit pixels, and each structural unit pixel can couple red light image optical signals, blue light image optical signals, and green light image optical signals.

[0018] The second aspect of the present invention provides a three-dimensional display device capable of realizing color three-dimensional virtual imaging, and its specific technical solution is as follows:

[0019] A three-dimensional display device, which includes:

[0020] A micro-projection device;

[0021] A frequency mixing single-chip waveguide lens, and the frequency mixing single-chip waveguide lens is the frequency mixing single-chip waveguide lens provided in the first aspect of the present invention.

[0022] Further, the number of the micro-projection devices is two, and they are respectively arranged corresponding to the frequency mixing single-chip waveguide lenses of the corresponding left and right eyes.

[0023] Compared with the prior art, the frequency mixing single-chip waveguide lens and the three-dimensional display device provided by the present invention have the following technical effects:

[0024] 1. It realizes color display by a single-chip waveguide lens unit, thereby ensuring the compactness of the display device in structure, reducing light loss, and improving the display effect.

[0025] 2. Based on spatial multiplexing, the diffraction grating structure in the functional region is a peak-shaped diffraction grating structure formed by overlapping multiple groups of diffraction gratings, which reduces the diffraction crosstalk between light rays and improves the display effect of the display device. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic cross-sectional structure diagram of a three-dimensional display device of the present invention in an embodiment;

[0027] Figure 2 It is a schematic cross-sectional structure diagram of the frequency mixing single-chip waveguide lens of the present invention in an embodiment;

[0028] Figure 3 It is a schematic partial enlarged structure diagram of the coupled-in peak-shaped diffraction grating structure in the incident functional region of the invention in an embodiment;

[0029] Figure 4 It is a schematic partial enlarged structure diagram of the coupled-out peak-shaped diffraction grating structure in the outgoing functional region of the invention in an embodiment;

[0030] Figure 5 It is a schematic plan structure diagram of the frequency mixing single-chip waveguide lens of the present invention in an embodiment;

[0031] Figure 6Schematic plan view of the mixing-type monolithic waveguide lens according to another embodiment of the present invention;

[0032] Figures 7A - 7D Schematic diagram of the exposure principle for forming the coupling-in peak-shaped diffraction grating structure by single-beam group exposure three times in one embodiment;

[0033] Figures 8A - 8B Schematic diagram of the exposure principle for forming the coupling-in peak-shaped diffraction grating structure by three-beam group exposure once in another embodiment;

[0034] Figure 9 Schematic plan view of the structural unit pixel of the incident functional area of the present invention. Detailed implementation manners

[0035] To make the above objects, features and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific implementation manners.

[0036] As Figure 1 shown, a mixing-type monolithic waveguide lens 2 is used for preparing a mixing-type monolithic waveguide three-dimensional display device. The mixing-type monolithic waveguide lens 2 includes:

[0037] A waveguide 21;

[0038] A functional area with an optical diffraction function located on the upper surface or the lower surface of the waveguide 21 ( Figure 2 In this case, if the surface where the image optical signal is incident is defined as the upper surface and the surface where it exits is defined as the lower surface, then Figure 2 In the embodiment, two functional areas are provided on the upper surface of the waveguide 21).

[0039] In some embodiments, as Figure 2 and Figure 5 shown, the functional area includes an incident functional area 22 and an exit functional area 23, where:

[0040] In the incident functional area 22, a coupling-in peak-shaped diffraction grating structure for coupling an external image optical signal to the waveguide 21 is provided. The coupling-in peak-shaped diffraction grating structure is formed by overlapping multiple groups of coupling-in diffraction gratings, and each group of coupling-in diffraction gratings corresponds to coupling in an image optical signal of a specific wavelength (or color).

[0041] In the exit functional area 23, a coupling-out peak-shaped diffraction grating structure for coupling the image optical signal transmitted in the waveguide out of the waveguide 21 is provided. The coupling-out peak-shaped diffraction grating structure is formed by overlapping multiple groups of coupling-out diffraction gratings corresponding to the multiple groups of coupling-in diffraction gratings, and each group of coupling-out diffraction gratings corresponds to coupling out an image optical signal of a specific wavelength (or color).

[0042] Here, it should be noted that the image optical signal of a specific wavelength mentioned in the present invention, where the "specific wavelength" refers to a certain wavelength range. For example, for the red image light, its wavelength range is 610 - 650 nm. Therefore, when we mention the wavelength of the red image light, it means its wavelength is 610 - 650 nm, rather than a specific point value. In addition, as is well known to those of ordinary skill in the art, the current color display device is at least in a three - primary - color mode. Therefore, the "multiple groups" of the multiple groups of coupled - in diffraction gratings and multiple groups of coupled - out diffraction gratings mentioned in the present invention can be understood as three groups or more.

[0043] As for the specific number of the coupled - in diffraction gratings included in the coupled - in peak - shaped diffraction grating structure and the specific number of the coupled - out diffraction gratings included in the coupled - out peak - shaped diffraction grating structure, they can be set according to the specific primary - color mode of the color three - dimensional display device constructed thereby. For example, in a three - primary - color (red, green, blue) display device, the coupled - in peak - shaped diffraction grating structure and the coupled - out peak - shaped diffraction grating structure each include three groups of diffraction gratings, while in a four - primary - color display system, the coupled - in peak - shaped diffraction grating structure and the coupled - out peak - shaped diffraction grating structure each include four groups of diffraction gratings, and so on.

[0044] Taking the three - primary - color display as an example, as Figure 3 shown, the coupled - in peak - shaped diffraction grating structure is formed by overlapping three groups of coupled - in diffraction gratings, namely the first coupled - in diffraction grating 221, the second coupled - in diffraction grating 222, and the third coupled - in diffraction grating 223, where: the structure of the first coupled - in diffraction grating 221 matches the wavelength of the red image light, and it is used to couple the red image light into the waveguide 21; the structure of the second coupled - in diffraction grating 222 matches the wavelength of the green image light, and it is used to couple the green image light into the waveguide 21; the structure of the third coupled - in diffraction grating 223 matches the wavelength of the blue image light, and it is used to couple the blue image light into the waveguide 21. Correspondingly, as Figure 4 shown, the coupled - out peak - shaped diffraction grating structure is formed by overlapping three groups of coupled - out diffraction gratings.

[0045] Since the peak - shaped diffraction grating structure is formed by overlapping the coupled - in diffraction gratings, it contains multiple different amplitude and phase information. After the red, green, and blue image lights are incident on the peak - shaped diffraction grating structure simultaneously, they are respectively adjusted at different diffraction angles, thus avoiding crosstalk between the light rays and ultimately improving the display effect.

[0046] The structure of the diffraction grating described here includes parameters such as the grating period. As is well known to those skilled in the art, by adaptively setting parameters such as the period of the diffraction grating, the regulation of the optical signal of a specific wavelength (color) can be achieved, and the optical signal outside the specific wavelength range will be blocked by the diffraction grating (or cannot pass through the diffraction grating). The diffraction grating can be a tilted grating, a volume grating, a blazed grating, etc.

[0047] It can be seen that the diffraction grating structure in the functional region of the frequency-mixing monolithic waveguide lens 2 of the present invention is formed by overlapping multiple diffraction gratings with different structures, and each group of diffraction gratings can correspondingly couple an image optical signal of a specific wavelength. Based on this structure, the present invention realizes color three-dimensional display of a monolithic waveguide, thereby greatly reducing the volume, weight and cost of the three-dimensional display device and improving the display effect.

[0048] Compared with the monolithic holographic diffraction waveguide lens in the Chinese patent application with the publication number CN106773057A in the background art, in the frequency-mixing monolithic waveguide lens of the present invention, the diffraction grating structure in its functional region is formed by overlapping multiple diffraction gratings, reducing the possibility of diffraction crosstalk between light rays and further improving the display effect.

[0049] Preferably, as Figure 6 shown, the functional region further includes a relay functional region 24, and a relay diffraction grating structure for changing the propagation direction of the image optical signal in the waveguide lens is provided in the relay functional region 24. The relay functional region 24 changes the direction of the image optical signal transmitted from the incident functional region 22 and the waveguide 21 and then conducts it to the exit functional region 23 through the waveguide 21, thereby extending the waveguide transmission distance, realizing further magnification of the image, and improving the display effect.

[0050] In some preferred embodiments, the functional region is generally set as a pixel structure. As Figure 9 shown, taking the incident functional region 22 as an example, the incident functional region 22 includes a plurality of structural unit pixels, and an incident peak-shaped diffraction grating structure formed by overlapping a first coupling diffraction grating 221, a second coupling diffraction grating 222 and a third coupling diffraction grating 223 is provided in each structural unit pixel. Therefore, each structural unit pixel can couple a red light image optical signal, a blue light image optical signal and a green light image optical signal.

[0051] Figure 1 FIG. is a schematic cross-sectional structure diagram of a three-dimensional display device constructed by using the frequency-mixing monolithic waveguide lens 2 in some embodiments, and this three-dimensional display device is used to realize three-primary color imaging. Figure 1 In the embodiments, each functional region is provided on the light-incident surface of the waveguide 21, that is, on the upper surface of the waveguide 21.

[0052] Combined with Figures 2 to 4, Image light is emitted from the micro - projection device 1 and irradiates the incident functional area 22 of the waveguide 21. At this time, the three primary - color lights in the image light are split. Among them: the red image - light signal is coupled into the waveguide 21 through the first coupling diffraction grating 221, and the diffracted light satisfies the requirement of total internal reflection in the waveguide; the green image - light signal is coupled into the waveguide 21 through the second coupling diffraction grating 222, and the diffracted light satisfies the requirement of total internal reflection in the waveguide; the blue image - light signal is coupled into the waveguide 21 through the third coupling diffraction grating 223, and the diffracted light satisfies the requirement of total internal reflection in the waveguide.

[0053] It can be seen that after being split by the three - coupling diffraction grating in the incident functional area 22, three non - interfering optical - signal transmission channels are formed in the waveguide 21, thereby realizing the synchronous and non - interfering transmission of the red image - light signal, the green image - light signal, and the blue image - light signal. After being coupled out by the coupled - out peak - shaped diffraction grating structure, they are focused onto the human eye.

[0054] When constructing a three - dimensional display device, generally, two sets of micro - projection devices 1 and two mixed - frequency single - chip waveguide lenses 2 are included, corresponding to the left - eye and right - eye displays respectively.

[0055] Considering from the preparation process, it can be seen that to obtain the mixed - frequency single - chip waveguide lens 2 of the present invention, the key problem is how to prepare a diffraction grating structure formed by overlapping multiple groups of diffraction gratings.

[0056] As is well known to those of ordinary skill in the art, at present, generally two plane waves are used to prepare a diffraction grating on a waveguide through an interference exposure process. According to the basic theory of the grating, the period of the prepared diffraction grating satisfies the following quantitative relationship with the angle between the two plane waves and the wavelength:

[0057] Among them, d is the period of the diffraction grating, θrec is the angle between the two plane waves, and λrec is the optical wavelength of the plane wave.

[0058] Therefore, after selecting the optical wavelengths of the two plane waves, by setting the angle between the two plane waves, a diffraction grating with a corresponding period can be obtained to meet the regulation of the primary - color lights with different wavelengths.

[0059] In the embodiments of the present invention, the two - plane - wave interference exposure process in the prior art is still used to prepare the diffraction grating in the functional area. Taking the regulation of the three - primary - color image - light signals as an example, below, taking the preparation process of the coupled - out peak - shaped diffraction grating structure as an example, it is introduced in detail how to prepare a diffraction grating structure formed by overlapping three groups of diffraction gratings through the exposure process.

[0060] As Figures 7A - 7DAs shown, in the first type of embodiments, the coupled-in peak-shaped diffraction grating structure is formed by three consecutive single-beam group exposures, that is: the exposure light source only includes a beam group composed of two plane waves. Specifically:

[0061] The first single-beam group exposure: As Figure 7A , according to the wavelength of the plane wave and the periodic structure of the third coupled-in diffraction grating 213 to be prepared, the included angle between the two plane waves is adjusted to θ1, and the adjusted two plane waves are used to perform the first exposure operation on the incident functional region 22 on the optical waveguide 21 to prepare the third coupled-in diffraction grating 223, which is used to realize the coupling-in of the blue image optical signal.

[0062] The second single-beam group exposure: As Figure 7B , according to the wavelength of the plane wave and the periodic structure of the second coupled-in diffraction grating 212 to be prepared, the included angle between the two plane waves is adjusted to θ2, and the adjusted two plane waves are used to perform the second exposure operation on the incident functional region 22 on the optical waveguide 21 to prepare the second coupled-in diffraction grating 222, which is used to realize the coupling-in of the green image optical signal.

[0063] The third single-beam group exposure: As Figure 7C , according to the wavelength of the plane wave and the period of the first coupled-in diffraction grating 221 to be prepared, the included angle between the two plane waves is adjusted to θ3, and the adjusted two plane waves are used to perform the third exposure operation on the incident functional region 22 on the optical waveguide 21 to prepare the first coupled-in diffraction grating 221, which is used to realize the coupling-in of the red image optical signal.

[0064] After three consecutive single-beam group exposures before and after, as Figure 7D , a coupled-in peak-shaped diffraction grating structure formed by the overlapping of three groups of diffraction gratings is formed in the incident functional region 22.

[0065] In a specific embodiment, the wavelength of the plane wave is set to 532 nm, and the calculated included angles between the two plane waves are: θ1 = 166°, θ2 = 120°, θ3 = 93°.

[0066] Of course, in some other embodiments, the three groups of coupled-in diffraction gratings can also be prepared according to other exposure sequences. For example, the first single-beam group exposure is used to prepare the first coupled-in diffraction grating 221, the second single-beam group exposure is used to prepare the second coupled-in diffraction grating 222, and the third single-beam group exposure is used to prepare the third coupled-in diffraction grating 223.

[0067] As Figures 8A - 8BAs shown, in the second type of embodiment, the coupled-in peak-shaped diffraction grating structure can be formed by a single three-beam group exposure, that is: the exposure light source includes three beam groups, namely the first beam group a, the second beam group c, and the third beam group d. Each beam group includes two plane waves. Specifically:

[0068] As Figure 8A , referring to the first type of embodiment above, the included angle between the two plane waves in the first beam group a is adjusted to θ1, the included angle between the two plane waves in the second beam group b is adjusted to θ2, and the included angle between the two plane waves in the third beam group c is adjusted to θ3. The adjusted three beam groups are used to expose the incident functional region 22 on the optical waveguide 21, so as to synchronously fabricate the first coupled-in diffraction grating 221, the second coupled-in diffraction grating 222, and the third coupled-in diffraction grating 223 that overlap each other in the incident functional region 22, that is, the Figure 8B shown coupled-in peak-shaped diffraction grating structure is formed.

[0069] In a specific embodiment, the wavelength of each plane wave is set to 532 nm, and the included angles between the two plane waves in each beam group are respectively: θ1 = 166°, θ2 = 120°, θ3 = 93°. During the exposure, the first beam group a realizes the fabrication of the third coupled-in diffraction grating 223, the second beam group b realizes the fabrication of the second coupled-in diffraction grating 222, and the third beam group c realizes the fabrication of the first coupled-in diffraction grating 221.

[0070] It can be seen that compared with the three single-beam group exposures in the first type of embodiment, the single three-beam group exposure in the second type of embodiment can complete the fabrication of the coupled-in peak-shaped diffraction grating structure through a single exposure, which significantly improves the grating fabrication efficiency.

[0071] The above has described the present invention in sufficient detail with a certain degree of particularity. Those of ordinary skill in the art should understand that the description in the embodiments is only exemplary, and all changes made without departing from the true spirit and scope of the present invention should fall within the protection scope of the present invention. The scope of protection required by the present invention is defined by the claims described, rather than by the above description in the embodiments.

Claims

1. A mixing type monolithic waveguide lens, characterized in that It includes: A waveguide; A functional region with an optical diffraction function located on the upper or lower surface of the waveguide, and the functional region at least includes: An incident functional region, in which an incident peak-shaped diffraction grating structure for coupling an external image optical signal into the waveguide is provided, and the incident peak-shaped diffraction grating structure is formed by overlapping multiple groups of incident diffraction gratings, and each group of the incident diffraction gratings corresponds to coupling an image optical signal of a specific wavelength; An output functional region, in which an output peak-shaped diffraction grating structure for coupling the image optical signal transmitted in the waveguide out of the waveguide is provided, and the output peak-shaped diffraction grating structure is formed by overlapping multiple groups of output diffraction gratings corresponding to the multiple groups of incident diffraction gratings, and each group of the output diffraction gratings corresponds to coupling an image optical signal of a specific wavelength.

2. The frequency mixing type monolithic waveguide lens according to claim 1, characterized in that The incident diffraction grating and the output diffraction grating are formed by exposure with a beam group composed of two plane waves.

3. The frequency mixing type monolithic waveguide lens according to claim 2, wherein The incident peak-shaped diffraction grating structure and the output peak-shaped diffraction grating structure are respectively formed by multiple single-beam group exposures, and each single-beam group exposure corresponds to forming a group of incident diffraction gratings or a group of output diffraction gratings.

4. The frequency mixing type monolithic waveguide lens according to claim 2, wherein The incident peak-shaped diffraction grating structure and the output peak-shaped diffraction grating structure are respectively formed by one multi-beam group exposure. During the exposure process, each beam group corresponds to forming a group of incident diffraction gratings or output diffraction gratings.

5. The frequency mixing type monolithic waveguide lens according to claim 1, characterized in that, The functional region further includes a relay functional region located on the upper or lower surface of the waveguide, and a relay diffraction grating structure for changing the propagation direction of the image optical signal in the waveguide is provided in the relay functional region.

6. The frequency mixing type monolithic waveguide lens according to claim 1, characterized in that, The incident diffraction grating and the output diffraction grating are wavelength-selective oblique gratings, volume gratings or blazed gratings.

7. The frequency mixing type monolithic waveguide lens according to claim 1, characterized in that, It is used for regulating the three primary color image optical signals, wherein: The incident peak-shaped diffraction grating structure is formed by overlapping three groups of incident diffraction gratings, and the three groups of incident diffraction gratings respectively couple the red light image optical signal, the blue light image optical signal and the green light image optical signal into the waveguide at different angles; The output peak-shaped diffraction grating structure is formed by overlapping three groups of output diffraction gratings, and the three groups of output diffraction gratings respectively couple the red light image optical signal, the blue light image optical signal and the green light image optical signal out of the waveguide.

8. The frequency mixing type monolithic waveguide lens according to claim 7, wherein, Each functional region includes a plurality of structural unit pixels, and each structural unit pixel can couple the red light image optical signal, the blue light image optical signal and the green light image optical signal.

9. A three-dimensional display device, characterized in that: It includes: A micro-projection device; A frequency-mixing single-chip waveguide lens, and the frequency-mixing single-chip waveguide lens is the frequency-mixing single-chip waveguide lens according to any one of claims 1 to 8.

10. The three-dimensional display device according to claim 9, wherein: The number of the micro-projection devices is two, and they are respectively arranged corresponding to the frequency-mixing single-chip waveguide lenses for the left and right eyes.

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