Patent Application
20250138477
The present invention relates to a display device of an eyeball-mounted type, a contact lens, and a driving method for driving the display device.
Non-Patent Document 1 describes that “The laser backlight emits vertically polarized laser light to illuminate the phase-only SLM. The phase-only SLM modulates the phase of the vertically polarized light and do not modulate the phase of the horizontally polarized light. The vertically polarized light is modulated to produce wavefront for the image generation. The polarizer transmits the horizontally polarized light from outer scenery, which is not modulated by the SLM.” (2 PROPOSED SYSTEM).
Non-Patent Document 1: J. Sano, S. Liu, Y Nagahama, and Y Takaki, “Contact Lens Display Based on Holography,” The 26th International Display Workshops (IDW '19), Sapporo, Hokkaido, Japan, 28 Nov. 2019.
A first aspect of the present invention provides a display device of an eyeball-mounted type. The display device may include a backlight that emits spatially coherent light which converges within a predetermined region. The display device may include a spatial light modulator which forms a hologram pattern, and generates a reconstructed image corresponding to the hologram pattern by spatially modulating a phase of the light entering from the backlight.
The backlight may have a convexly curved shape or a flat shape.
The spatial light modulator may have a convexly curved shape or a flat shape.
The backlight and the spatial light modulator may have a convexly curved shape to follow a user's cornea when the display device is attached to a user's eyeball.
The backlight and the spatial light modulator may cover an entirety of a user's cornea when the display device is attached to a user's eyeball.
The display device may further include a polarizer. The backlight may be transparent. The spatial light modulator may modulate the phase of the light entering from the backlight and does not modulate a phase of the light component of external light, which is transmitted through the polarizer.
The backlight may have a waveguide, a thin film diffraction grating provided in the waveguide, and a light source that emits the light into the waveguide.
The thin film diffraction grating may converge the light within the predetermined region by diffracting the light emitted into the waveguide from the light source.
The thin film diffraction grating may include at least any of a nanostructured diffraction grating or a hologram optical element.
An optical coupling efficiency of the thin film diffraction grating may be lower when closer to a position where the light from the light source enters into the waveguide.
The light source may include a plurality of light sources, the backlight may have a plurality of light sources, and the plurality of light sources may emit the light from positions different from each other in a periphery of the waveguide into the waveguide.
The light source may be a laser or an LED.
A second aspect of the present invention provides a contact lens including any above-described display device, and a lens substrate enclosing the display device.
A third aspect of the present invention provides a driving method for driving a display device of an eyeball-mounted type with a backlight and a spatial light modulator. The driving method may include emitting a spatially coherent light which converges within a predetermined region by the backlight. The driving method may include forming a hologram pattern and generating a reconstructed image corresponding to the hologram pattern by spatially modulating a phase of the light entering from the backlight, by the spatial light modulator.
Note that the summary clause does not necessarily describe all necessary features of the embodiments of the present invention. The present invention may also be a sub-combination of the features described above.
Hereinafter, the present invention will be described through embodiments of the invention, but the following embodiments do not limit the invention according to the claims. In addition, not all of the combinations of features described in the embodiments are essential to the solution of the invention.
The contact lens 10 according to the present embodiment includes a display device of an eyeball-mounted type 100 and a lens substrate 12. An outer shape of the contact lens 10 is similar to a common contact lens.
The display device 100 is a display using a holography technology, configured to form a hologram pattern, and generate a corresponding reconstructed image as a virtual image in a position away from the display device 100. The position is sufficiently far away from the display device 100 to the external side, for example, from a few centimeters to infinity, so that the user's eyeball 30 wearing the contact lens 10 can focus on it. When the user's eyeball 30 focuses on the virtual image, an image 50 of the virtual image is formed on a retina 37 of the eyeball 30. Further, the display device 100 transmits some components of light from the external world. This allows the user wearing the contact lens 10 to simultaneously observe the reconstructed image generated by the display device 100 and the external world.
The display device 100 uses spatially coherent light that converges within a predetermined region, as an illuminating light for generating the reconstructed image. When compared to using an entirely flat spatial light modulator using a plane wave as the illuminating light, the display device 100 enlarges a field of view, and forms a larger image 50 on the retina 37 of the eyeball 30.
The lens substrate 12 has a transparent, circular plate-shaped body and forms a contour of the contact lens 10. In the present application, being transparent refers to being transparent at least for a visible wavelength region, excluding unavoidable absorption for a particular wavelength, unless otherwise specified. The lens substrate 12 encloses the display device 100. Therefore, the display device 100 is not exposed to the outside nor contacts the user's eyeball 30 wearing the contact lens 10. Further, the lens substrate 12 may have a lens power or may not have a lens power. When referring to the display device 100 in the following descriptions, it may refer to the display device 100 alone or may refer to the display device 100 enclosed in the lens substrate 12, i.e. the contact lens 10.
The display device 100 includes a backlight 110 and a spatial light modulator 120. As one example, the display device 100 according to the present embodiment further includes a polarizer 130 and a driving unit 140. The display device 100 of the present embodiment is configured so that the polarizer 130, the backlight 110, and the spatial light modulator 120 line up in this order from the external side when attached to the user's eyeball 30.
The backlight 110 emits spatially coherent light that converges within the predetermined region described above. The spatially coherent light that converges within the predetermined region is, for example, directed toward a center of an entrance pupil in an entire optical system created by the eyeball 30. The light may be a spherical wave.
The backlight 110 according to the present embodiment has a convexly curved shape as one example. This allows the backlight 110 to follow a user's cornea 31 when the display device 100 is attached to the user's eyeball 30. It becomes easier for the backlight 110 to converge light in the vicinity of the center of a crystalline lens 35 of the eyeball 30 similarly to the cornea 31, by being formed to follow the cornea 31. In this case, the backlight 110 may be designed so that the center of curvature of the backlight 110 or a converging position of the light emitted by the backlight 110 coincides with the center of curvature of the cornea 31. In the specification of the present application, when it is described that any configuration of the display device 100 has a convexly curved shape, the convex surface is intended to be directed toward the external side when the display device 100 is attached to the user's eyeball 30.
As a suitable example when the backlight 110 has a convexly curved shape, the backlight 110 covers an entirety of the user's cornea 31 when the display device 100 is attached to the user's eyeball 30. In this case, the spatial light modulator 120 may generate a reconstructed image for the user's full field of view. As another example, the backlight 110 may only cover a part of the user's cornea 31. In this case, the backlight 110 may only cover, for example, an annular region concentric with the contact lens 10.
The backlight 110 according to the present embodiment is transparent as one example. For example, the backlight 110 can be nearly transparent because it diffracts some of wavelength components of the external light and transmits most of the wavelength components other than the some of the wavelength components without a diffraction effect.
The backlight 110 according to the present embodiment includes, as one example, a waveguide 111, a thin film diffraction grating 113 provided in the waveguide 111, and a light source 115 that emits the spatially coherent light into the waveguide 111. A thickness of the waveguide 111 is, for example, approximately 0.1 mm. The waveguide 111 may form a contour of the backlight 110, i.e. may have a convexly curved shape. Inside the waveguide 111, light emitted by the light source 115 propagates with total reflection.
The thin film diffraction grating 113 converges the light within the predetermined region described above by diffracting the light emitted into the waveguide 111 from the light source 115. The thin film diffraction grating 113 may include at least any of a nanostructured diffraction grating or a hologram optical element.
As one example, the thin film diffraction grating 113 is provided in the waveguide 111 so that it is positioned on the external side or the opposite side of the waveguide 111 when the contact lens 10 is attached to the user's eyeball 30. The thin film diffraction grating 113 may be formed integrally with the waveguide 111 or may be formed into a film shape and adhered to a surface of the waveguide 111.
The spatially coherent light with a particular wavelength, which is the linearly polarized light polarized toward the particular direction, is emitted by the light source 115 into the waveguide 111. The particular wavelength is the same as the wavelength of the light used during the calculation of the hologram pattern formed by the display device 100, and for example, may be a wavelength of a visible wavelength range or may be a wavelength of an infrared wavelength range. The thin film diffraction grating 113 diffracts the light with the particular wavelength toward a direction orthogonal to a wavefront converging within the predetermined region. Note that the thin film diffraction grating 113 transmits light with a wavelength other than the particular wavelength without the diffraction effect.
An optical coupling efficiency of the thin film diffraction grating 113 is preferably lower when closer to an incident position of the light into the waveguide 111 from the light source 115. Light intensity of the light emitted from the backlight 110 can be made uniform by forming the thin film diffraction grating 113 so that the optical coupling efficiency of the thin film diffraction grating 113, i.e. a diffraction efficiency indicating an efficiency of converting incident light into diffracted light, becomes lower when a distance from the light source 115 is shorter.
For the same purpose, the backlight 110 has a plurality of light sources 115, and the plurality of light sources 115 may emit light into the waveguide 111 from positions different from each other in a periphery of the waveguide 111.
The light source 115 emits at least the spatially coherent light. The light source 115 may be, for example, a semiconductor laser, and emit spatially and temporally coherent laser light. The light source 115 may be, for example, an LED, and emit spatially coherent light.
The spatial light modulator 120 forms the hologram pattern. The spatial light modulator 120 is, for example, a transmissive liquid crystal element, and forms a two-dimensional hologram pattern according to a voltage value applied to a matrix electrode connected to the liquid crystal layer. A thickness of the spatial light modulator 120 with such a configuration is, for example, approximately 10 μm. Because the lens substrate 12 of the contact lens 10 is required to permeate oxygen, an encapsulant or the like is preferably used in the spatial light modulator 120 which is a liquid crystal element to prevent oxygen from affecting the liquid crystal itself.
The spatial light modulator 120 generates the reconstructed image corresponding to the hologram pattern by spatially modulating a phase of the spatially coherent light entering from the backlight 110. As described above, the spatially coherent light entering from the backlight 110 is the linearly polarized light polarized toward the particular direction. The spatial light modulator 120 modulates the phase of the spatially coherent light entering from the backlight 110 and does not modulate the phase of light components, which is transmitted through the polarizer 130, of the external light.
The spatial light modulator 120 two-dimensionally modulates the phase of light, and controls the wavefront of the light, only regarding the light polarized to the particular direction. The spatial light modulator 120 transmits light and does not modulate the phase of light regarding the light polarized toward a direction orthogonal to the particular direction. The spatial light modulator 120 does not modulate an amplitude of light. More specifically, when the spatial light modulator 120 transmits light, some light absorption occurs, but it is nearly uniform spatially, so the amplitude of the light is hardly spatially modulated.
When the display device 100 is attached to the user's eyeball 30 and the eyeball 30 focuses on the reconstructed image, the spatial light modulator 120 forms the image 50 of the reconstructed image described above on the retina 37 of the eyeball 30.
As one example, the spatial light modulator 120 according to the present embodiment has a convexly curved shape. This allows the spatial light modulator 120 to follow the user's cornea 31 when the display device 100 is attached to the user's eyeball 30. In this case, the spatial light modulator 120 may be designed so that the center of curvature of the spatial light modulator 120 coincides with the center of curvature of the cornea 31.
As a suitable example when the spatial light modulator 120 has a convexly curved shape, the spatial light modulator 120 covers the entirety of the user's cornea 31 when the display device 100 is attached to the user's eyeball 30. Since the spatial light modulator 120 and the backlight 110 cover the entirety of the user's cornea 31, the light emitted from the backlight 110 and modulated by the spatial light modulator 120 can be converged at a maximum field of view regarding the entire optical system comprised of the cornea 31, the iris 33 and the crystalline lens 35, etc. of the user's eyeball 30. This allows the display device 100 to transmit the light converged at the maximum field of view through the crystalline lens 35 to be projected on the retina 37 of the eyeball 30 at the maximum field of view, thereby generating the reconstructed image for the full view of the user.
As one example, the spatial light modulator 120 may have a pixel pitch of approximately 3 to 5 μm. When the pixel pitch reduces, a diffraction angle of light which diffracts at each point of the spatial light modulator 120 widens. Extent of light in the crystalline lens 35 of the eyeball 30 gives an effective entrance pupil diameter in an image formation system of the eyeball 30. In the image formation system of the eyeball 30, when the entrance pupil diameter widens, a depth of field, which is a depth range in which the image is in focus, decreases. Therefore, the depth of field of the reconstructed image displayed three-dimensionally on the display device 100 can be narrowed by reducing the pixel pitch of the spatial light modulator 120, making it possible to display the reconstructed image in a particular position in the depth direction. That is, the display device 100 can show a three-dimensional image sharply in a particular position and show the three-dimensional image in a blurred state in a position in front or back of the particular position to the user wearing the display device 100 by reducing the pixel pitch of the spatial light modulator 120.
The polarizer 130 controls the polarization of light. As described above, the polarizer 130 transmits a component, which is polarized toward the particular direction, of the external light and blocks a component, which is polarized toward the direction orthogonal to the particular direction, of the external light. The particular direction is orthogonal to the direction in which the phase experiences spatial modulation in the spatial light modulator 120. In other words, orientations, etc. of the polarizer 130 and the spatial light modulator 120 are designed respectively, so that the phase of the light component transmitted through the polarizer 130 is not modulated spatially in the spatial light modulator 120. A thickness of the polarizer 130 is, for example, several μm to several tens of μm.
The driving unit 140 drives the display device 100. The driving unit 140 may include a memory, a controller, a battery and so on. The memory, controller, battery, etc. of the driving unit 140 may be implemented as an integrated unit or implemented as multiple units.
For example, the driving unit 140 stores information of a voltage value corresponding to each of one or more hologram patterns. The driving unit 140 is connected electrically to the light source 115 of the backlight 110 and the spatial light modulator 120, and controls them. For example, the driving unit 140 controls light emitted from the light source 115 by controlling electrical power supplied to the light source 115. The driving unit 140 controls the hologram pattern formed in the spatial light modulator 120 by controlling the voltage applied to the matrix electrode of the spatial light modulator 120 based on the information of the voltage value corresponding to each of the one or more hologram patterns. The driving unit 140 may control the position in the depth direction for three-dimensionally displaying the reconstructed image corresponding to the hologram pattern by controlling the voltage applied to the matrix electrode of the spatial light modulator 120.
The driving unit 140 is, for example, configured to accumulate electrical power. The driving unit 140 may be powered wirelessly from an external power supply, and in this case, the driving unit 140 may include an antenna for receiving power. Note that the driving unit 140 may be arranged on an outer peripheral side of the lens substrate 12 so that the driving unit 140 is not located inside the user's field of view when the display device 100 is attached to the user's eyeball 30.
The display device 100 of the contact lens 10 performs preparing including acquiring the information of the voltage value required to control the hologram pattern formed by the spatial light modulator 120 and the display position in the depth direction for three-dimensionally displaying the reconstructed image corresponding to the hologram pattern (step S101). The display device 100 stores the information in advance. As one example, the hologram pattern and the display position may be designated by the user.
The display device 100 performs emitting the spatially coherent light that is converged, by the backlight 110, within the predetermined region (step S102). As a specific example, the light source 115 of the backlight 110 emits the coherent light, which is a spherical wave of linearly polarized light, into the waveguide 111 having a spherical shape. For example, the coherent light emitted into the waveguide 111 and propagating with total reflection inside the waveguide 111 is diffracted, by the thin film diffraction grating 113 provided in the waveguide 111, toward a direction perpendicular to the wavefront of the spherical wave converged within the predetermined region, for example, within the region in the vicinity of the center of the crystalline lens 35 when the display device 100 is attached to the user's eyeball 30, and is emitted toward a side of the spatial light modulator 120. Since the optical coupling efficiency of the thin film diffraction grating 113 decreases as closer to the incident position of the light from the light source 115 into the waveguide 111, the intensity of the light emitted from each point on the side of the spatial light modulator 120 of the waveguide 111 is uniform.
The display device 100 performs, by the spatial light modulator 120, forming the hologram pattern and generating the reconstructed image corresponding to the hologram pattern by spatially modulating the phase of the spatially coherent light entering from the backlight 110 (step S103), and ends the flow. The hologram pattern formed in step S103, and the display position in the depth direction of the generated reconstructed image correspond to the information acquired in the preparing in step S101. When the display device 100 which underwent the flow in
On the other hand, the display device 100 according to the present embodiment generates the reconstructed image corresponding to the hologram pattern by emitting the spatially coherent light that converges within the predetermined region and spatially modulating the phase of the light with the hologram pattern. With the display device 100 having the configuration, as shown in
In the descriptions of the embodiments above, the light source 115 has been a semiconductor laser or an LED as an example. Particularly when using laser as the light source 115, laser light can generate the reconstructed image corresponding to the hologram pattern more accurately without blurring, because it has high spatial and temporal coherence. In this manner, the backlight 110 may emit the laser light or may emit LED light as the spatially coherent light.
In the descriptions of embodiments above, the display device 100 is described as a configuration that has a convexly curved shape so as to follow the cornea 31 of the user's eyeball 30. Alternatively, the display device 100 may have a flat shape when emitting a spherical wave from the backlight 110. For example, the contact lens 10 according to another embodiment may include a display device 200 in a flat shape, and emit a spherical wave from the backlight 110.
In the descriptions of embodiments above, the display device 100 is described as having a configuration including the driving unit 140. Alternatively, the display device 100 may be controlled, without the function of a memory or controller in the driving unit 140, wirelessly by an external control device. In this case, the control device may have the functions of a memory and controller in the driving unit 140. The control device may be a smartphone held by the user, or a wearable device, etc. attached to the user.
While the present invention has been described by way of the embodiments, the technical scope of the present invention is not limited to the above-described embodiments. It is apparent to persons skilled in the art that various alterations or improvements can be made to the above-described embodiments. It is also apparent from the described scope of the claims that the embodiments added with such alterations or improvements can be included the technical scope of the present invention.
The operations, procedures, steps, stages, or the like of each process performed by a device, system, program, and method shown in the claims, embodiments, or diagrams can be performed in any order as long as the order is not indicated by “prior to,” “before,” or the like and as long as the output from a previous process is not used in a later process. Even if the process flow is described using phrases such as “first” or “next” in the claims, embodiments, or diagrams, it does not necessarily mean that the process must be performed in this order.
10: contact lens; 12: lens substrate; 20: contact lens; 21: spatial light modulator; 30: eyeball; 31: cornea; 33: iris; 35: crystalline lens; 37: retina; 50: image; 100, 200: display device; 110: backlight; 111: waveguide; 113: thin film diffraction grating; 115: light source; 120: spatial light modulator; 130: polarizer; 140: driving unit.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-020433 | Feb 2022 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2023/000689 | 1/12/2023 | WO |
