KR102162994B1 - Ned polarization system for wavelength pass-through - Google Patents

Abstract

A system and method are disclosed for homogenizing the color distribution of light propagating from a light source to an eye box in a near-eye display (NED). In an example of the system and method, an optical element comprising two or more waveguides optimized for different colors in the visible spectrum is used. The optical element includes one or more polarization state generators that control polarization of light incident on the waveguide to promote coupling of the light to the matched waveguide while inhibiting coupling with the unmatched waveguide. Include more.

Description

Polarization system and method for wavelength pass control for near-eye display {NED POLARIZATION SYSTEM FOR WAVELENGTH PASS-THROUGH}

The present invention relates to a near-eye display, and more particularly, to a polarization system and method for controlling a wavelength pass for a near-eye display.

Near-Eye Display (Near-Eye Display or Near-to-Eye Display, hereinafter referred to as NED) unit is used to display a mixture of real objects and virtual images in a physical environment. Such a NED unit includes a light engine that generates an image, and an optical element having some transmittance and some reflectivity. Specifically, the optical element has transmittance so that light from the outside of the NED unit can reach the wearer's eyes, while having some reflectivity so that light from the light engine can reach the wearer's eyes. In addition, the optical element may include a plurality of diffracting optical elements (DOE) or holograms positioned within a planar waveguide for diffracting the image from the microdisplay to the wearer's eye. have.

In practice, the NED unit may include a stack structure in which a plurality of waveguides each assigned to a predetermined wavelength component are stacked. In particular, each of the plurality of waveguides can be matched or optimized to couple with a predetermined wavelength component with high efficiency by controlling the aspect of the DOE in the waveguide. By optimizing the different DOEs to different colors of the visible light spectrum, it becomes possible for the NED unit to display full color.

However, in the waveguide stack structure, a wavelength component matched with a waveguide located at a relatively far distance (ie, far from the light engine) passes through the waveguide located at a relatively short distance. In this case, there may be a case in which the wavelength component matched with the far waveguide does not pass through the waveguide located at the near distance as it is but is coupled to the waveguide at the corresponding distance. This may reduce the brightness of light reaching the wearer's eyes, make the color uneven, and result in deterioration of the quality of the reproduced virtual image.

The present invention has been devised to solve the above problem, and is to control the NED unit to be coupled to the originally matched waveguide when different wavelength bands pass through the waveguide.

Embodiments of the present invention relate to a system and method for selectively changing polarization states of different wavelength bands when different wavelength bands pass through a waveguide in a NED unit. The DOE on or inside the waveguide is sensitive to polarization. By changing the polarization of the wavelength band to a state in which the DOE on the waveguide becomes less sensitive, the wavelength band can pass through the DOE with little or no attenuation. The polarization of the wavelength band is controlled so that the light is in a state of coupling to the desired waveguide through the DOE before entering the waveguide.

According to an embodiment of the present invention, a method for displaying an image includes: (a) receiving light including at least a first wavelength band and a second wavelength band, from a light source, at least a first waveguide and a second waveguide. And projecting the first waveguide and the second waveguide to an optical element having at least one optical grating, and (b) a first wavelength band incident on the first waveguide, the first wave Polarization of the first wavelength band incident on the first waveguide is determined to be further coupled to the first waveguide than a wavelength band other than the first wavelength band among a plurality of wavelength bands incident on the guide. Controlling to be different from polarization of a wavelength different from the first wavelength band among the plurality of wavelength bands incident on the waveguide, and (c) a second wavelength band incident on the second waveguide, the second waveguide Polarization of the second wavelength band incident on the second waveguide is determined to be more coupled to the second waveguide than a wavelength band other than the second wavelength band among a plurality of wavelength bands incident on the second waveguide. An image display method is provided which includes controlling polarization of a wavelength band different from that of the second wavelength band among the plurality of wavelength bands incident on a guide.

According to another embodiment of the present invention, as a method for displaying an image, (a) light including n (where n is 2 or more) wavelength bands, m (however, m is 2 or more) Projecting light from a light source including a waveguide to an optical device, and (b) one or a plurality of wavelength bands among the n wavelength bands, each of which is associated with any one of the m waveguides. Including passing through a polarization state generator, in projecting the light of (a), the i-th (however, i is 1 or more and n or less) wavelength band is the j-th (however, j is 1 or more and m or less) ) Matched to a waveguide, and allowing the one or more wavelength bands of the (b) to pass through the plurality of polarization state generators, the plurality of polarization state generators, wherein the one or more The polarization of the wavelength band is controlled so that the coupling of the i th wavelength band to the j th waveguide is promoted, while the rest of the wavelength band passing through the j th waveguide is inhibited from coupling to the j th waveguide. An image display method is provided.

According to another embodiment of the present invention, an optical element for transmitting light from a light source to an eye box, comprising: a first optical grating for receiving light from the light source and coupling with a first portion of the light. A second waveguide including a first waveguide and a second optical grating for receiving light from the light source and coupling with the second portion of the light, and positioned between the light source and the first waveguide, the second waveguide A first polarization state generator configured to change the polarization of the first portion of the light to be coupled with the first waveguide, and the light is positioned between the light source and the second waveguide, and the light is coupled to the first waveguide. An optical element is provided that includes a second polarization state generator that changes the polarization of the second portion.

According to the present invention, in the near-eye display unit, the color distribution of light transmitted from the light source to the wearer's eyes can be made uniform.

1 is a diagram illustrating exemplary components of an embodiment of a system for displaying a virtual environment to one or a plurality of users.
2 is a perspective view of an embodiment of the NED unit worn on the head.
3 is a partial side view of an embodiment of the NED unit worn on the head.
4 is a cross-sectional view of an optical element of a NED unit including a waveguide having a plurality of diffraction gratings.
5 is a partially enlarged view of a surface relief diffraction grating structure.
6 is a partial side view of an embodiment of an NED unit worn on the head, including an optical element having a plurality of waveguides.
7 is a diagram showing an incident surface of light incident on a diffraction grating.
8 is a cross-sectional view of a first embodiment of an imaging optical system in an NED unit including a plurality of waveguides and a polarization state generator for changing polarization of a wavelength band passing through the waveguides.
9 is a cross-sectional view of a second embodiment of an imaging optical system in an NED unit including a plurality of waveguides and a polarization state generator for changing polarization of a wavelength band passing through the waveguides.
10 is a flowchart showing the operation of the optical system according to the first embodiment shown in FIG. 8.
11 is a flowchart showing the operation of the optical system according to the second embodiment shown in FIG. 9.
12 is a cross-sectional view of a third embodiment of an imaging optical system in an NED unit including a plurality of waveguides and a polarization state generator for changing polarization of a wavelength band passing through the waveguides.
13 is a cross-sectional view of a fourth embodiment of an imaging optical system in an NED unit including a plurality of waveguides and a polarization state generator for changing polarization of a wavelength band passing through the waveguides.
14 is a cross-sectional view showing a wavelength band transmitted through a pair of waveguides without controlling polarization.
15 is a cross-sectional view showing a wavelength band transmitted through a pair of waveguides with polarization controlled according to an embodiment of the present invention.
16 is a graph showing coupling efficiency in the wavelength band of FIGS. 14 to 15.

Hereinafter, embodiments according to the present invention will be described with reference to FIGS. 1 to 16. 1 to 16 are diagrams generally related to an imaging optical system for selectively changing a polarization state of another wavelength band when a wavelength band passes through a waveguide in the NED unit. The DOE on the waveguide is sensitive to light polarization. Therefore, by selectively controlling the polarization of the wavelength band entering the DOE on the waveguide, the wavelength band matching the waveguide can be coupled with the DOE with high efficiency. On the other hand, unmatched wavelength bands may pass through unaffected waveguides and DOEs largely or entirely. One example using DOE is described herein, but it is understood that the waveguide may include DOE, holograms, surface relief gratings, or other types of periodic structures of optical elements. This structure may be referred to as an “optical grating”.

In the following embodiment, the NED unit may be a head-worn (head-worn) display unit used in a complex reality system. However, embodiments of the NED unit and the imaging optical system contained therein can be used in a variety of other optical applications, such as optical couplers and other optical modulator devices. The drawings are provided for an understanding of the current technology and may not be drawn to scale.

1 shows an example of a NED unit 2 as a head worn display used in the realism system 10. The NED unit 2 can be worn as glasses including lenses that are transparent enough to be able to see the actual object 27 in the field of view (FOV) of the user through the display element. The NED unit 2 also provides the ability to project a virtual image 21 with the user's FOV so that the virtual image can also appear with real objects. Although not essential for the present invention, the mixed reality system can automatically track where the user is looking so that the system can determine to insert a virtual image into the user's FOV. Once the system knows where to project the virtual image, the image is projected using a display element.

1 shows each user 18a, 18b, 18c wearing a head-worn NED unit 2. In one embodiment, the head-wearing NED unit 2 in the shape of glasses is worn on the user's head so that the user can see through the display and have a real and direct view of the space in front of the user. More details of the head worn NED unit 2 are provided below.

The NED unit 2 can provide signals to the processing unit 4 and the hub computing device 12 and receive signals from the processing unit 4 and the hub computing device 12. The NED unit 2, the processing unit 4 and the hub computing device 12 may cooperate to determine what is the FOV of each user 18, the virtual image that should be provided within the FOV, and how it should be represented. The hub computing device 12 also includes a capture device 20 that captures image data from a portion of the scene within its FOV. The hub computing device 12 may also be connected to the audio-visual device 16 and the speaker 25 that can provide games and application images and sounds. Details regarding the process unit 4, the hub computing device 12, the capture device 20, the audio-visual device 16, and the speaker 25 are, for example, "Low-Latency Fusing of Virtual and Real Content". It is disclosed in US Patent Application Publication No. 2012/0105473 published on May 3, 2012 titled, the entirety of which is incorporated herein by reference.

2 and 3 are a perspective view and a side view of the head worn NED unit (2). 3 shows the right side of a head worn NED unit 2 comprising part of a device with temples 102 and nose rest 104. Part of the frame of the head worn NED unit 2 surrounds the display (including one or more lenses). The display includes a light guide optical element 115, a see-through lens 116, and a see-through lens 118. In one embodiment, the light guiding optical element 115 is behind the see-through lens 116 and aligned with the see-through lens 116 and the see-through lens 118 is behind the light guiding optical element 115 and aligned with the light guiding optical element 115. . The see-through lenses 116 and 118 are standard lenses used for eyeglasses (including the case of no prescription), and can be by prescription. The light guide optical element 115 transmits artificial light to the eye. Further details of the light guide optical element 115 are provided below.

(In one embodiment) An image source including an optical engine such as a microdisplay 120 for projecting a virtual image and a lens 122 for directing an image from the microdisplay 120 to the light guide optical element 115 is a temple ( 102) or mounted inside. In one embodiment, lens 122 is a collimate lens. The micro display 120 projects an image through the lens 122.

There are other image generation techniques that can be used to implement the micro display 120. For example, the microdisplay 120 may be implemented using a transmissive projection technique in which a light source is modulated by a white light backlight optically active material. These techniques are generally implemented using LCD-type displays with strong backlights and high light energy density. The micro-display 120 may also be implemented using a reflection technique in which external light is reflected and optically controlled by an active material. The lighting is dimmed from the front by either a white source or an RGB source, depending on the technology. Digital Light Processing (DLP), Liquid Crystal On Silicon (LCOS) and Mirasol display technologies from Qualcomm are examples of efficient, reflective technologies in which most of the energy is reflected from the modulation structure. And can be used in this system. Additionally, micro-display 120 may be implemented using emission techniques in which light is generated by the display. For example, Micro Vision's PicoP™ display engine emits a micro-mirror steered laser signal that acts as a direct beam (eg laser) on the eye or on a small screen that acts as a transmissive element.

The light guide optical element (or optical element) 115 may transmit light from the microdisplay 120 to the eye box 13. The eye box 130 is a two-dimensional area, and is a two-dimensional area through which light passes when leaving the optical element 115, and is located in front of the eyes 132 of a user wearing the head-worn NED unit 2. The optical element 115 also allows light from the front of the head-worn NED unit 2 to be transmitted to the eye box 130 through the light guide optical element 115, as shown by arrow 142. do. This allows the user to have a direct view of the space in front of the head worn NED unit 2 in addition to receiving a virtual image from the micro display 120.

3 shows a half of the head worn NED unit 2. The overall head worn display device may include other optical elements 115, other micro-displays 120, and other lenses 122. When the head-worn NED unit 2 has two optical elements 115, each eye has a micro-display 120 of each eye capable of displaying the same image for both eyes or a different image for both eyes. I can. In another embodiment, there may be an optical element 115 that reflects light from a single micro-display 120 to both eyes.

Further details of the light guide optical element 115 will be described with reference to FIGS. 4 to 13. In general, the optical element 115 includes two or more waveguides in which one optical element 115 is stacked on another optical element 115 to form an optical train. One waveguide 140 is shown in FIG. 4. In other embodiments, the waveguide 140 may be formed from a thin planar sheet of glass, although it may be formed of plastic or other material. The waveguide 140 includes two or more diffraction gratings, such as an input diffraction grating 144 that couples light rays into the waveguide 140 and an emission diffraction grating 148 that diffracts light rays outside the waveguide 140. can do. The gratings 144 and 148 are shown as transmission type diffraction gratings inside the lower surface 150a of the substrate 150 or attached to the lower surface 150a of the substrate 150. A reflective diffraction grating attached to the opposite surface of the substrate 150 may be used in other embodiments.

4 shows the total internal reflection of the wavelength band λ ₁ coupled to the inside or outside of the waveguide 140. The wavelength band as used herein may consist of one or more wavelengths, for example in the visible spectrum. 4 is a simplified diagram of a single wavelength band in a system in which the second and higher diffraction orders do not appear. Although not shown in FIG. 4, the optical element 115 may further include a polarization state generator in front of the waveguide and between the waveguides, as described below.

The wavelength band λ ₁ from the micro display 120 is collimated through the lens 122 and coupled to the substrate 150 by the input diffraction grating 144 at the incident angle θ ₁ . The input grating diffraction 144 redirects the wavelength band through the diffraction angle θ ₂ . The refractive index N ₂ , the incident angle θ _1, and the diffraction angle θ ₂ are provided so that the wavelength band λ ₁ is total internal reflection in the substrate 150. The wavelength band λ ₁ is reflected from the surface of the substrate 150 until it reaches the emission diffraction grating 148, and the wavelength band λ ₁ is diffracted from the substrate 150 toward the eye box 130. The details of the waveguide such as the waveguide 140 are disclosed as an example in “Compact Head-Up Display”, US Patent No. 4,711,512 issued on December 8, 1987, and the whole is incorporated by reference in this application. do.

5 is a surface forming part of a transmission type diffraction grating, such as an input diffraction grating 144 and/or an emission diffraction grating 148 (FIG. 5 shows a diffraction grating 144 that diffracts light into the substrate 150) It is a partial enlarged view showing an example of the relief grid 154. The surface relief grating 154 may have an inclined profile with period p, but the grating may have other profiles, such as squares and teeth, in other embodiments. As mentioned, the input diffraction grating 144 and the exit diffraction grating 148 may be reflective in other embodiments.

Waveguides can be matched or optimized for specific wavelength bands. The relationship is determined according to the lattice equation of Equation 1 below.

[Equation 1]

mλ = p(n ₁ sinθ ₁ + n ₂ sinθ ₂ )

Here, m is the diffraction order, λ is the wavelength band matched with the waveguide/diffraction grating, p is the grating period, n ₁ is the refractive index of the incident medium, n ₂ is the refractive index of the waveguide 140, θ ₁ is the incident angle, θ ₂ means diffraction angles, respectively.

By varying parameters such as the grating period p and the reflectance n ₂ of the substrate 150, the specific waveguide 140 including the input diffraction grating 144 and the emission diffraction grating 148 may be matched to a specific wavelength band. That is, a specific wavelength band may be coupled to the matched waveguide 140 having a higher coupling efficiency than other wavelength bands. In addition, Rigorous Coupled Wave Theory (RCWT) is used to optimize the profile parameters of the grating 154 (Fig. 5) to improve the performance of the waveguide such as angular bandwidth, diffraction efficiency and polarization. It can be improved (described later).

4 shows a single waveguide 140 for a specific wavelength band through diffraction gratings 144 and 148. In an embodiment according to the present invention, the optical element 115 may include two or more waveguides 140 described with respect to FIG. 4 which are shown layered together in an optical train. The waveguides 140 in each of these waveguide optical elements 115 may be matched to different wavelength bands. For example, as illustrated in FIG. 6, there may be four waveguides 140 ₁ , 140 ₂ , 140 ₃ , and 140 ₄ layered on top of each other. Providing more than four layers may be impractical, but including more than four layers of optical elements can be easily derived. Light of different wavelengths, e.g. purple light at a wavelength of about 400 nm, indigo light at about 445 nm, blue light at about 475 nm, green light at about 510 nm, yellow light at about 570 nm, orange at about 590 nm It can be optimized for light, and/or light comprising about 650 nm red light.

Waveguides (140 ₁ , 140 ₂ , 140 ₃ , 140 ₄ ) can be provided in any order, and one or more waveguides (140 ₁ , 140 ₂ , 140 ₃ , 140 ₄ ) match other wavelengths than those presented above. Can be. For example, the single waveguide 140 may be matched to a wavelength band covering wavelengths of different colors in the visible light spectrum.

Within the stack of stacked waveguides, the emission wavelength band matched with the distal waveguide in the stack passes through all proximal waveguides in the stack. For example, in the embodiment of FIG. 6, the wavelength band λ ₁ from the microdisplay 120 that matches the most distal waveguide 140 ₁ passes through the proximal waveguides 140 ₂ and 140 ₄ . As described in the background art, a problem with the conventional stack of stacked waveguides is that the wavelength band that tends to couple into the distal waveguide also partially couples into the proximal waveguide, reaching the eyebox 130. It degrades the color of the image.

It is a property of the diffraction grating in the waveguide 140 that the diffraction gratings are sensitive to polarization in the wavelength band passing through. Therefore, the wavelength band in the first polarization can be coupled with one or more waveguide layers through which it passes, but the same wavelength band in the second polarization different from the first polarization passes through one or more waveguide layers without coupling. can do. According to an aspect of the present invention, the polarization of the wavelength band of light is controlled to be coupled to the inside of the matched waveguide while passing through another unmatched waveguide. Thus, in the example of Figure 5, the wavelength λ _1, the waveguide (140 ₁₎ that match into a wavelength band λ ₁ the wave guide (140 ₁₎ coupled in a ring to the previous wave guide (140 _2, 140 ₄ ), its polarization is controlled to pass through.

Referring to FIG. 7, the polarization of light incident on the diffraction gratings 144 and 148 may be defined by the direction of its electromagnetic field with respect to the incidence plane P _i . The plane (P _i ) can be defined by the grating normal vector (GN) and the propagation vector (PV) from the irradiation light source. The propagation vector (PV) is the projection of the K-vector of light on the waveguides 144 and 148. The grating vector GV is a vector in the plane of the diffraction gratings 144 and 148 that defines the direction of the grating line. The term "E state" as used herein refers to a polarization state in which the electric field component of the wavelength band is zero along the grating vector (GV). As used herein, the term "M state" refers to a polarization state in which the magnetic field component is zero along the grating vector (GV).

In the example described below, the polarization of the wavelength band incident on the diffraction gratings of the various waveguides 140 is controlled and changed between the E-state and the M-state. In one embodiment, the wavelength band of the M state incident and polarized to the diffraction grating passes through the diffraction grating, whereas the wavelength band of the E state incident and polarized to the diffraction grating is coupled into a waveguide including the diffraction grating. .

The following examples describe the current technology in terms of controlling the polarization conditions of the E-state and M-state, but the wavelength band passes through the waveguide in the first polarization state, but the wavelength band is coupled with the waveguide in the second polarization state. It will be appreciated that other polarization states may be used to ring. Other examples of the first and second polarization states are left and right polarizations of the wavelength passing through the waveguide 140. Further, the following describes polarized light in one of the two states, but it should be considered that the polarized light can occupy more than one state. In this embodiment, at least one state couples within the waveguide, while at least one other state passes without coupling.

An exemplary embodiment will be described with reference to FIGS. 8 to 9 showing an optical element 115 composed of two waveguides 140. FIG. 12 described below shows an example of an embodiment of an optical element 115 in which the optical element 115 may be composed of n waveguides. n may be another number of the waveguide. The first embodiment will be described with reference to the flow charts of FIGS. 8 and 10. 8 shows a pair of waveguides 140 ₁ and 140 ₂ . In step 300, separate wavelength bands λ ₁ and λ ₂ are emitted from the micro display 120 and collimated through the lens 122. The waveguides are arranged so that light from the microdisplay 120 first passes through the waveguide 140 ₂ and then passes through the waveguide 140 ₁ .

The waveguides 140 ₁ and 140 ₂ may each be matched to two different wavelength bands emitted from the micro display 120. For example, the waveguide 140 ₁ may be tuned to red light, and the wave guide 140 ₂ may be tuned to blue and green light. In further embodiments, the waveguides 140 ₁ and 140 ₂ may be matched to different wavelength bands of one or more wavelengths of visible light.

In this embodiment, the light emitted from the micro-display 120 may be unpolarized light or E-state polarized light. Before entering the first waveguide 140 ₂ , both wavelength bands λ ₁ and λ ₂ pass through a polarization state generator (PSG). PSG (160, including PSGs to be described later) is a polarization retarder or wavelength that can shift the phase of a specific wavelength band between two vertical polarization states while preventing light of other wavelengths from being affected. It may be a known polarization state generator such as a waveplate.

PSG (160) may be formed in the optical element 115, a wave guide (140 ₂₎ of the birefringent thin sheet material which may be attached in front of the diffraction grating 144 of the substrate 150 in the inside (thin plate). When a diffraction grating type reflection, PSG (160) may be in front of the diffraction grating 144 of the wave guide (140 ₂₎ to be integrated to the substrate 150 of the wave guide (140 _2). The PSG 160 (including PSGs to be described later) may occupy the same footprint as the waveguide 140 and may be smaller or larger in embodiments. If smaller, the PSG 160 may be positioned at least above the input diffraction grating 114. For example, the PSG 160 may be formed of a polymer film retarder, a birefringent crystal retarder, a liquid crystal retarder, or a combination thereof. PSG 160 may be constructed of other materials in additional embodiments. For example, PSG (160, including PSGs to be described later) may be manufactured by Meadowlark Optics, Inc., Frederick, CO, USA.

In step 304, the PSG 160 may be configured to change the polarization of the wavelength band λ ₁ from the E state to the M state. The PSG 160 may prevent the intensity and direction of the wavelength band λ ₁ from being affected. The PSG 160 also prevents the polarization, intensity, and direction of the wavelength band λ ₂ from being affected, so that the wavelength band λ ₂ may pass directly without any change or change at all.

As described above, in embodiments, non-contiguous wavelengths from micro-display 120 may not be polarized. In this embodiment, the PSG 160 may modulate the wavelength band λ ₁ into the M state as described above, and the second PSG (not shown) may modulate the wavelength band λ ₂ into the E state.

As described above, while the M-state polarized light is not coupled to the waveguide 140 (or is coupled to a smaller extent), the E-state polarized light may be coupled to the waveguide 140. . Thus, in a subsequent state change through the PSG (160), step 308, E state polarized wavelength λ ₂ has a wave guide (140 ₂₎ being coupled in, is captured in the wave guide (140 ₂₎ Waveguide ( 140 ₂ ) is transmitted to the eye box 130 outside.

The M state polarized wavelength band λ ₁ passes substantially or completely through the waveguide 140 ₁ without coupling or attenuation. Wave guide (140 ₁₎ to the coupling of the wavelength bands λ ₁ within a wavelength band λ ₁ is the second PSG (162) prior to entering the wave guide (140 ₂₎ after leaving the wave guide (140 ₁₎ Must pass.

The PSG 162 may be formed of the same material as the PSG 160, but may be configured to modulate the polarization of the wavelength band λ ₁ from the M state to the E state in step 310. The PSG 162 may be formed to be between the waveguide 140 ₁ and the waveguide 140 ₂ in the optical element 115. In other cases, the PSG 162 is formed after the diffraction grating 144 in the substrate 150 of the waveguide 140 ₂ , or the diffraction grating 144 in the substrate 150 of the waveguide 140 ₁ It can also be formed before ).

After the phase change through the PSG 162, in step 314, the wavelength band λ ₁ may be coupled to the captured waveguide 140 ₁ as described above, or the eye box 130 outside the waveguide 140 ₁ It can also be sent to. In this way, while maintaining the color quality of the wavelength transmitted through the optical element 115, light of different wavelengths from the microdisplay 120 may be transmitted using the waveguide 140.

Additional embodiments will be described with reference to the flowcharts of FIGS. 9 and 11. In step 320, non-contiguous wavelengths of light are emitted from the micro-display 120, pass through the lens 122, and collimate. Then, the collimated light is passed through the first wave guide (140 _2). The waveguides 140 ₂ and 140 ₁ may be optimized for two different wavelength bands λ ₁ and λ ₂ , corresponding to discontinuous wavelengths emitted from the microdisplay 120 as described above. In this embodiment, light of all wavelengths emitted from the microdisplay 120 may not be polarized or may be M-state polarized. Before entering the first waveguide 140 ₂ , both wavelength bands λ ₁ and λ ₂ pass through the PSG 166.

The PSG 166 may be formed of the same material and size as the PSG 160, but may be configured to change the polarization of the wavelength band λ ₂ from the M state to the E state in step 324. The PSG 166 may prevent the intensity and direction of the wavelength band λ ₂ from being affected. The PSG 166 may prevent the polarization, intensity, and direction of the wavelength band λ ₁ from being affected, so that the wavelength band λ ₁ may pass directly without change.

When the light from the micro-display 120 is not polarized, the PSG 166 may modulate the wavelength band λ ₂ to the E state as described above, and the second PSG (not shown) changes the wavelength band λ ₁ to M It can also be modulated to state.

After the state change through the PSG 166, the E-state modulated wavelength band λ ₂ is coupled in the waveguide 140 _{2 in} which the tooth is captured as described above, and the eye box outside the waveguide 140 ₂ ( 130).

The M state polarized wavelength band λ ₁ may substantially or completely pass through the waveguide 140 ₁ without coupling or attenuation. Wave guide (140 ₁₎ to the coupling of the wavelength bands λ ₁ within a wavelength band λ ₁ is the second PSG (168) prior to entering the wave guide (140 ₂₎ after leaving the wave guide (140 ₁₎ Must pass. The PSG 168 may be the same as the PSG 162 in FIG. 8, and may also modulate the wavelength band λ ₁ from the M state to the E state in step 334. Thereafter, in step 338, the wavelength band λ ₁ may be coupled to the captured waveguide 140 ₁ as described above, or may be transmitted back to the eye box 130 outside the waveguide 140 ₁ .

When using a system in which PSGs are placed before and between the waveguides, as described above, various number of wavelength bands are polarized, passing through unmatched waveguides, and as much as possible within the matched waveguides. It can also be coupled with almost maximum strength. The system of PSGs can ensure that the polarization of the wavelength band close to the unmatched waveguide is already in the M state condition, which causes the unmatched waveguide to pass through unaffected. In other cases, the polarization of the wavelength band that is close to the unmatched waveguide may be in the E state condition, so after passing through the PSG to be modulated to the M state, the unmatched waveguide may pass through unaffected. . These wavelength bands may remain in the M state condition until the matching waveguide is reached thereafter, and when the waveguide matching it is reached, it passes through the PSG to be modulated to the E state, and the matching waveguide is Can be coupled.

An example including n wavelength bands and waveguides will be described below with reference to FIG. 13. The example of FIG. 13 shows a wavelength band and a waveguide in which n is 4 or more, but an additional example may include three wavelength bands and a waveguide.

Discontinuous wavelength bands λ1, λ _2, λ _3,… λ _n is emitted from the micro-display 120, passes through the lens 122, and collimates. In one example, light of all wavelengths from the micro display 120 may be polarized to the M state. In this case, this embodiment may include the PSG 170 ₁ as described above, or may be configured to modulate the polarization of λ ₁ to the E state while the remaining wavelength bands are polarized to the M state. In an additional embodiment, the wavelength band emitted from the micro-display 120 may or may not have a different polarization. In this further embodiment, one or more of the PSG is (are integrated into or wave guides (140 ₁₎₎ in front of the waveguide _{(140: 1)} may be located, and thus, the waveguide after passing through one or more PSG (140 ₁₎ When entering the input diffraction grating 144 of, the wavelength band λ ₁ is polarized in the E state, and the wavelength band λ ₂ to λ _n is polarized in the M state.

Thereafter, the E-state polarized wavelength band λ ₁ may be coupled to the captured waveguide 140 ₁ as described above, or may be transmitted back to the eye box 130 outside the waveguide 140 ₁ . . The remaining M-state polarized wavelength bands λ ₂ to λ _n substantially or completely pass through the waveguide 140 ₁ without coupling or attenuation.

Next, the remaining wavelength range λ ₂ to λ _n to pass the ₂ PSG (170 2), and claim ₂ PSG (170 2) the remaining wavelength band and modulating the wavelength λ ₂ to the E state λ ₃ to λ _n is Make sure it is not substantially or completely affected.

Then, E state polarized wavelength λ ₂ may be coupled to a wave guide (140 _{2) The} teeth are captured as described above, a wave guide (140 ₂₎ outside the eye box 130 to be sent back to the have. M state polarized remaining wavelength λ ₃ to λ _n is passed through a substantially or completely wave guide (140 _2), without coupling or attenuation.

This procedure is repeated for each remaining waveguide. Each of the wavelength bands may be polarized to pass through an unmatched waveguide until a matching waveguide is reached, or may be polarized to couple to a matched waveguide when a matching waveguide is reached. End wavelength λ _n is passed through the wave guide (140 ₁₎ to the waveguide (140 _n-1) the total to reach the waveguide (140 _n). Before passing through the waveguide 140 _n , the wavelength band λ _n passes through the PSG 170 _n and is polarized to a state capable of being coupled to the waveguide 140 _n .

Other implementations of PSGs may be provided in which a wavelength band matching a waveguide is polarized and coupled to the waveguide while the other wavelength band is polarized to pass through the waveguide. In this case, light having different wavelengths may pass through the optical element 115 using a waveguide and PSG as described above, while maintaining color quality of all wavelengths passing through the corresponding optical element 115.

The wavelength band passes through each of the proximal waveguides on the way to the eye box 130 after being coupled and leaving the distal waveguide. As described above with respect to FIG. 4, each of the waveguides 140 includes an emission diffraction grating 148 that couples light already present in the waveguide out of the waveguide. The emission diffraction grating 148 may allow the incident wavelength band returning from the distal waveguide to pass widely or completely straight through without coupling. However, it may happen that the light rays from the distal waveguide are at least partially coupled to the proximal waveguide on their way to the eye box 130.

For example, in a further embodiment, in addition to providing PSGs for the input diffraction grating 144 for controlling the coupling of light from the microdisplay 120 within each waveguide, an emission diffraction grating PSGs may also be provided for 148. The exit grating PSGs can prevent light from the distal waveguide from being coupled within the proximal waveguide on the way to the eye box 130. One such embodiment is shown in FIG. 13. In this embodiment, the wavelength bands λ ₁ to λ _n are coupled to their matched waveguides while passing through the unmatched waveguides as described above. When the wavelength band is emitted from the matched waveguide, the polarization passes through the proximal waveguide without coupling after being changed again from the E state to the M state by the PSGs 180 ₁ to 180 _n do. In this embodiment, the PSG 180 ₁ , which is the last PSG before the eye box, to present to the user's eye 132 through the eye box 130, the wavelength bands λ ₁ to λ _n in various desired manners. Polarized.

In some of the embodiments described above, E-state polarized wavelengths are described as allowing them to couple within their matched waveguide and M-state polarized wavelengths passing through an unmatched waveguide without attenuating. However, instead of full coupling/full pass, it is also possible to cause both E-state and M-state polarized wavelengths to be partially coupled to the waveguide they are incident on. However, by the use of PSGs as described above, the coupling efficiency of the E-state polarization wavelength may be increased compared to the coupling efficiency of the M-state polarization wavelength.

14 to 16 will be described. Each of FIGS. 14 and 15 shows an edge view of a wavelength band λ incident on a pair of waveguides 140 ₁ and 140 ₂ . The wavelength band λ matches the waveguide 140 ₂ , but first passes through the waveguide 140 ₁ . In FIG. 15, the polarization of the wavelength band is controlled using the PSG 160, whereas in FIG. 14, the PSG is not used, except that FIG. 14 and FIG. 15 are the same.

In Fig. 14, the input wavelength band is incident on the diffraction grating 144 in the unmatched waveguide 140 ₁ at an angle of incidence of θ ₁ . The uncontrolled wavelength band may have E-state polarization, and thus, a portion λ _1c may be coupled to the waveguide 140 ₁ . The second part λ _{1m is} diffracted with a second order diffraction (not shown, there may be additional grating order diffraction). Rest λ _1t is transmitted through a wave guide (140 ₁₎ is entered in this way it matches the wave guide (140 _2). As a relatively large element of the wavelength band λ coupled with the waveguide 140 ₁ , a smaller portion λ _2c is left to be coupled to the waveguide 140 ₂ .

Conversely, in FIG. 15, the same wavelength band λ is polarized to the M state prior to entering the waveguide 140 ₁ (eg, by a PSG not shown). As indicated, a relatively small portion λ _1c of the wavelength band is coupled to the waveguide 140 ₁ . In this way, the portion λ _1t passing through the waveguide 140 ₁ increases. Between the waveguide 140 ₁ and the waveguide 140 ₂ , the polarization of the wavelength band is changed from the M state to the E state by the PSG 160. As a result, E-polarized state wavelength λ has its match the wave guide (140 ₂₎ coupled λ relatively large portion _2c to be within.

16 is a graph showing coupling efficiency according to an in-coupling incident angle. Here, the coupling efficiency is defined as the ratio (expressed as a number between 0 and 1) of the intensity of the wavelength band emitted from the light source and the intensity of the wavelength coupled in the matched waveguide. This example uses the red light (650 nm) shown in Figs. 14 and 15 as a wavelength that matches the wave guide (140 _2). The graph also shows the second wavelength band of green light (540 nm). The green wavelength band is not shown in FIGS. 14 and 15, but is matched to and coupled to the first waveguide 140 ₁ . The lattice spacing of the diffraction grating (144 ₁₎ for a first wave guide (140 ₁₎ is 450 nm and the lattice spacing of the second wave guide (140 ₂₎ the diffraction grating (144 ₂₎ is about 550 nm.

As shown in the graph of Fig. 16, due to the fact that the green wavelength is coupled to the matched waveguide without having to pass through another waveguide, the curve 184 in the green wavelength band has the highest coupling efficiency over 90%. Represents. The curve 186 of the red wavelength band of Fig. 15 coupled to the waveguide using the polarization control according to the present invention shows a coupling efficiency of about 88%. The curve 188 of the red wavelength band of FIG. 14 in which the polarization control is not used shows a low coupling efficiency, which is lower than 70%. Accordingly, the PSGs of the present invention can prevent coupling of light to an unmatched waveguide, and enable coupling of light to a matched waveguide.

While the claimed subject matter has been described in language specific to structural features and/or methodological behavior, the subject matter defined in the appended claims is not necessarily limited to the specific features or behavior described above. The specific features and actions described above are described in an exemplary form in implementing the claims. It is intended that the scope of the invention be defined by the claims appended hereto.

Claims (10)

As a method for displaying an image on a near-eye display (NED),
(a) light including at least a first wavelength band and a second wavelength band, from a light source, including at least a first waveguide and a second waveguide, and each of the first waveguide and the second waveguide is at least one Projecting onto an optical element having an optical grating of,
(b) The polarization of the second wavelength band incident on the first waveguide is determined by the first polarization state generator so that the second wavelength band does not couple within the first waveguide during a first time. Changing from state 1 to state 2,
(c) Polarization of the first wavelength band incident on the first waveguide is applied to the first waveguide so that the first wavelength band couples more than the first wavelength band within the first waveguide. Controlling to be different from the polarization of the second wavelength band incident on the waveguide,
(d) by a second polarization state generator, polarization of the second wavelength band incident on the second waveguide so that the second wavelength band is coupled within the second waveguide during a second time period is converted to the second Including the step of changing from the state to the first state,
The controlling of the polarization of the first wavelength band to be different from the polarization of the second wavelength band may include the polarization of the first wavelength band incident on the first waveguide and the first wavelength band according to a grating vector. Including the step of changing from polarized light in which the magnetic field component of is zero, to polarized light in which the electric field component of the first wavelength band according to the grating vector becomes zero,
Wherein the second polarization state generator is between the first wave guide and the second wave guide. A method for displaying an image on a near-eye display (NED). The method of claim 1,
The controlling of the polarization of the first wavelength band to be different from the polarization of the second wavelength band comprises changing the polarization of the first wavelength band incident on the first waveguide. Method for displaying images on (NED). The method of claim 1, wherein the controlling of the polarization of the first wavelength band to be different from the polarization of the second wavelength band comprises: polarization of the first wavelength band incident on the first waveguide in a first state. And changing to a second state, wherein the first wavelength band is more coupled in the second state compared to the first state within the first waveguide. How to display. delete The method of claim 1, wherein the light further includes a third wavelength band, and the method comprises: polarization of the second wavelength band incident on the second waveguide, and the second wavelength band according to the grating vector The polarization of the second wavelength band is different from the polarization of the third wavelength band by changing the polarization in which the magnetic field component becomes zero and the electric field component in the second wavelength band according to the grating vector becomes zero. The method for displaying an image on a near-eye display (NED) further comprising the step of controlling, wherein the third wavelength band has polarization in which a magnetic field component of the third wavelength band according to the grating vector becomes zero. The method of claim 1, wherein projecting light including a first wavelength band from a display to an optical element comprises projecting light in which the first and second wavelength bands are composed of light from a visible spectrum. A method for displaying an image on a near-eye display (NED). The method of claim 1, wherein the at least first and second waveguides comprise four waveguides. In a method for displaying an image on a near-eye display (NED),
(a) projecting light from a light source to an optical device, wherein the light includes a plurality of wavelength bands, the optical device includes a plurality of waveguides, and one of the plurality of wavelength bands is Projecting light onto an optical element that matches one of the plurality of waveguides,
(b) passing the wavelength band through a plurality of polarization state generators, wherein each polarization state generator is associated with one of the plurality of waveguides, and the plurality of polarization state generators are configured for a first time period. , Changing from the first state to a second state passing through one or more waveguides, and for a second time, the matched waveguide facilitates coupling of the wavelength band in the matched waveguide from the second state The step of passing the wavelength band to control the polarization of the passing wavelength band to change back to the first state that delays coupling of the remaining wavelength bands passing through
Including,
The controlling of the polarization of the wavelength band passing through is the polarization of the wavelength band, from polarization in which the magnetic field component of the wavelength band according to the grating vector becomes zero, and the electric field component of the wavelength band according to the grating vector becomes zero. Including the step of changing to polarized light,
Wherein the plurality of polarization state generators are between the plurality of waveguides. A method for displaying an image on a near-eye display (NED). delete delete

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