CN115933290A - Miniature projection system and near-to-eye display device - Google Patents

Abstract

The invention discloses a micro projection system and a near-eye display device, which are used for projecting a non-self-luminous image arranged on an image source surface to a projection surface, and comprise: the device comprises a first prism, a second prism and a PBS prism; the illumination light is emitted into the PBS prism, reflected by the polarization beam splitting surface, transmitted in the second prism and the first prism, emitted from the incident surface and emitted to the image source surface; the image light is configured to be linearly polarized light of which the polarization direction is changed after the illumination light is reflected by the image source surface, enters the first prism through the incident surface, is reflected by the second surface, is reflected by the third surface or other surfaces adjacent to the third surface, then penetrates through the second prism, enters the PBS prism, penetrates through the polarization splitting surface, and then is emitted from the PBS prism to the projection surface. According to the micro projection system, the imaging light path and the illumination light path share the first prism, the second prism and the PBS prism, so that the light path is folded, and the size of the projection system is greatly reduced.

Description

Miniature projection system and near-to-eye display device

Technical Field

The invention relates to a miniature projection system, and also relates to a near-eye display device using the miniature projection system.

Background

As the concept of Virtual Reality (VR) and Augmented Reality (AR) has been proposed, the market of near-eye display devices based on VR or AR modes has been greatly developed. Among the hardware implementations applying AR or VR technology, near-Eye display (NED) is the most efficient implementation that can bring the best experience to the user. Since the near-eye display needs to be worn on the head of a person, it is important to have a small size and a good display effect.

The waveguide system is a representative of a light and thin scheme in the current near-eye display scheme, and the thickness of the waveguide is light and thin and is generally within 3 mm; the waveguide needs to be matched with a projection system for use, however, the volume of the existing projection system is usually large, and the size of the projection system directly restricts the whole volume of the display module.

Disclosure of Invention

The invention aims to provide a micro projection system.

Another object of the present invention is to provide a near-eye display device using the micro projection system.

In order to achieve the technical purpose, the invention adopts the following technical scheme:

according to a first aspect of embodiments of the present invention, there is provided a miniature projection system for projecting a non-self-luminous image disposed on an image source surface toward a projection surface, comprising:

the first prism comprises an incidence surface close to the image source surface, a second surface close to the projection surface and a third surface far away from the projection surface;

a second prism disposed between the first prism and the projection surface;

a PBS prism disposed between the second prism and the projection surface; a polarization beam splitting surface is arranged in the PBS prism;

the illumination light is linearly polarized light, is emitted into the PBS prism, reflected by the polarization beam splitting surface, emitted to the second prism, then transmitted in the second prism and the first prism, emitted from the incident surface and emitted to the image source surface

The image light is configured to be linearly polarized light, the polarization direction of which is changed after the illumination light is reflected by the image source surface, enters the first prism through the incident surface, is reflected by the second surface, is reflected by the third surface or other surfaces adjacent to the third surface, penetrates through the second prism and enters the PBS prism, and the image light penetrates through the polarization splitting surface, is emitted from the PBS prism and is emitted to the projection surface.

According to a preferred embodiment of the present invention, preferably, the first prism and the second prism are wedge prisms with a gap therebetween.

Preferably, the first prism and the second prism are free-form surface prisms; an incident angle when the image light is emitted from the incident surface to the second surface satisfies a total reflection condition.

According to still another preferred embodiment of the present invention, preferably, the first prism and the second prism are triangular prisms, a polarization splitting film is disposed between the first prism and the second prism, and the first prism and the second prism are adhered to form another PBS prism.

Preferably, the second surface of the first prism is provided with a 1/4 wave plate; a first curved surface reflector is arranged on the second surface side;

the second prism has a fourth surface opposite to the incident surface; the fourth surface is provided with a 1/4 wave plate; and a second curved surface reflector is arranged on the fourth surface side.

Preferably, a first lens group is disposed between the first curved mirror and the first prism; and a second lens group is arranged between the second curved reflector and the second prism.

Preferably, the first curved reflector is realized by attaching a total reflection film to the surface of the first lens group far away from the first prism; the second curved reflector is realized by attaching a total reflection film on the surface of the second lens group far away from the second prism.

Preferably, the micro projection system further comprises:

a microdisplay for providing image light to the first prism; the micro display screen reflects light and changes the polarization direction of linearly polarized light;

and the illumination light source is used for providing illumination light for the PBS prism, and a wire polarizer is arranged between the illumination light source and the PBS prism.

Preferably, an illumination dodging collimation system is further arranged between the illumination light source and the PBS prism.

According to a second aspect of the embodiments of the present invention, there is provided a near-eye display device, including the above miniature projection system, and further including a waveguide system, where a coupling end of the waveguide system is disposed at a position of a projection surface of the miniature projection system.

The invention discloses a miniature projection system and near-to-eye display equipment, which comprise an imaging system and an illumination system which share a first prism, a second prism and a PBS prism, wherein image light enters the first prism through an incident surface, is reflected by the second surface, is reflected by a third surface or other surfaces adjacent to the third surface, penetrates through the second surface, then enters the PBS prism after penetrating through the second prism, and is emitted from the PBS prism after penetrating through a polarization beam splitting surface and then is emitted to a projection surface; the illumination light enters the PBS prism, is reflected by the polarization splitting surface, then enters the second prism, propagates through the second prism and the first prism, and exits from the entrance surface. According to the micro projection system, the imaging light path and the illumination light path share the first prism, the second prism and the PBS prism, so that the light path is folded, and the size of the projection system is greatly reduced.

Drawings

FIG. 1 is a schematic diagram of the overall optical path of a micro projection system according to a first embodiment;

FIG. 2 is a schematic diagram of an imaging optical path in a micro-projection system according to a first embodiment;

FIG. 3 is an optical path diagram of a part of components in an imaging optical path in the first embodiment;

FIG. 4 is a schematic diagram of the illumination path in a micro-projection system according to a first embodiment;

FIG. 5 is a schematic diagram of a near-eye display device constructed by adapting a waveguide system for use with the miniature projection system of the first embodiment;

FIG. 6 is a schematic diagram of the overall optical path of a micro projection system in a second embodiment;

FIG. 7 is an optical diagram of a part of components in an imaging optical path in a second embodiment;

FIG. 8 is a schematic diagram of the illumination path in a micro-projection system according to a second embodiment;

fig. 9 is a schematic diagram of an imaging optical path in a micro projection system in a second embodiment.

Detailed Description

The technical solution of the present invention is further described in detail with reference to the accompanying drawings and specific embodiments. It is to be understood that the described embodiments are merely a few embodiments of the invention, and not all embodiments. It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.

The invention discloses a miniature projection system and a near-eye display device using the miniature projection system and a waveguide system. The miniature projection system is used for projecting a non-self-luminous image placed on an image source surface to a projection surface, and comprises an illumination system and an imaging system, wherein the illumination system is used for providing illumination light to the image source surface, and the illumination light is linearly polarized light; the imaging system is used for outputting image light from the image source surface to the projection surface, and the image light is configured into linearly polarized light with the polarization direction converted after the illumination light is reflected by the image source surface; the imaging system and the illumination system share the first prism, the second prism and the PBS prism, so that the light path is folded, and the volume of the projection system is greatly reduced.

First embodiment

As shown in fig. 1 to 4, the micro projection system provided in this embodiment includes a micro display screen 108, an LED light source 201, a PBS prism 102, a second prism 104, and a first prism 105, wherein a surface on which the display screen 108 is located is an image source surface 203, and a surface on which the diaphragm 109 is located is a projection surface; the imaging system is composed of a micro display 108, a first prism 105, a second prism 104, a PBS prism 102 and auxiliary lenses 107, 106 and 101; the illumination light path consists of an illumination light source 201, an illumination dodging collimation system 202, a PBS prism 102, a second prism 104, a first prism 105 and auxiliary lenses 204, 106 and 107; the imaging system and the illumination system share the first prism 105, the second prism 104, the PBS prism 102, and the like.

Specifically, the micro display screen 108 is a non-self-luminous display screen such as a liquid Crystal on silicon (Li qui Crystal on si i con, LCOS) or a digital micromirror device (Di ial Mi cromirror Devi ce S, DMD). The microdisplay 108 may reflect light while changing the polarization direction of the linearly polarized light.

As shown in fig. 3, the first prism 105 includes an incident surface S6 close to the image source surface 203, a second surface S4 close to the projection surface, and a third surface S5 far from the projection surface. The first prism 105 is a wedge prism or a triangular prism, and a wedge prism is used in this embodiment. Wherein, the incident surface S6, the second surface S4, and the third surface S5 of the first prism 105 have a spherical surface, an aspherical surface, or a free-form surface; preferably, the incident surface S6 of the first prism 105 is an aspherical surface or a free-form surface, and the surface types of the second surface S4 and the third surface S5 are free-form surfaces, so that the system aberration is corrected. The surface of the third surface S5 is provided with a total reflection film. The image light emitted from the micro display 108 enters the first prism 105 through the incident surface S6, the incident angle reaching the second surface S4 for the first time satisfies the total reflection condition, the image light reaches the third surface S5 and is reflected to the second surface S4 after being totally reflected by the second surface S4, and at this time, the image light reaches the second prism 104 through the second surface S4 without satisfying the total reflection condition.

Between the first prism 105 and the micro display screen 108, a lens group including a positive lens 107 and a negative lens 106 is further provided for adjusting the power and magnification of the imaging system. The lens group may also be a positive-negative cemented lens, which is not limited herein.

And a second prism 104 disposed between the first prism 105 and the projection surface 109. The second prism 104 is a wedge prism or a triangular prism, and a wedge prism is used in this embodiment. A gap exists between the second prism 104 and the first prism 105 to ensure the total reflection effect of the second surface S4. The second prism 104 includes a surface S3 adjacent to the first prism, a surface S1 facing the projection surface, and a non-optical surface S2 between S3 and S1, and the surface types of the surface S3 adjacent to the first prism 105 and the surface S1 facing the projection surface may be a spherical surface, an aspherical surface, or a free-form surface. Wherein the surface shape of the surface S3 close to the first prism is consistent with that of the second surface S4, and preferably, the gap between the two is less than 1mm.

The PBS prism 102 is disposed between the second prism 104 and the projection surface 109; the PBS prism 102 is provided with a polarization splitting surface 103, which may be a plated splitting film layer or a film-attached splitting film layer. The film system is characterized by transmitting P polarized light and reflecting S polarized light. In this embodiment, the image light reaching the polarization splitting plane 103 is P-type polarized light, and the image light passes through the polarization splitting plane 103 and is directed to the projection plane 109.

A plano-convex lens 101 is provided on the side of the PBS prism 102 facing the projection surface 109, and the plane of the plano-convex lens 101 is attached to the surface of the PBS prism 102.

Fig. 2 is a schematic diagram of an imaging optical path of the micro projection system. In the imaging process, linearly polarized light is emitted from the micro display screen 108, refracted by the lenses 107 and 106 and enters the wedge prism 105 through the incident surface S6; at this time, a schematic light propagation diagram inside the wedge prism 105 is shown in fig. 3, because an air gap exists between the surface S3 of the wedge prism 104 and the second surface S4 of the wedge prism 105, light is incident to the third surface S5 after being totally reflected on the surface S4, a total reflection film is plated or attached to the surface of the third surface S5, the light is incident to the second surface S4 again after being reflected on the third surface S5, and at this time, the light no longer satisfies the total reflection condition, and is emitted from the second surface S4 and enters the wedge prism 104; after passing through the surface S3 adjacent to the first prism 105 and the surface S1 facing the projection surface, the image light exits the wedge prism 104 and enters the PBS prism 102; at this time, the polarization state of the image light satisfies the transmission polarization state of the beam splitter prism, and the image light transmits through the polarization splitting surface 103, and then passes through the lens 101 to reach the stop position 109 of the image light, that is, the position of the projection surface.

This experimental example provides a set of optically relevant parameters according to the system described above, see tables 1 and 2.

TABLE 1 parameters of optical surfaces in an imaging system provided by a first embodiment

TABLE 2 decentration data (relative to the projection plane 109) for the optical surfaces of the wedge prisms 104 and 105

	X eccentricity	Y eccentricity	Z eccentricity	Alpha tilt
					S1	0	0	7.5403	0
S3	0	1.293456	8.51253	27.36136
					S5	0	0.491254	11.68895	-9.96077
S6	0	4.212386	9.747441	79.00855

The miniature projection system provided by the present invention includes an illumination system for providing illumination light to the image source plane 203. The lighting system is schematically shown in fig. 4, and includes an illumination light source and an illumination dodging collimation system, where the illumination light source is an LED light source 201, the LED light source 201 is a self-luminous high-brightness LED lamp, the illumination dodging collimation system is an optional element, and includes a collimation element, a filter element, and a dodging element, the collimation element may be an optical element having a function of receiving a ray angle, such as a lens group or a TIR lens, and the dodging element may be a differential optical device, such as a micro lens array or a light rod. A lens 204 and a linear polarizer are arranged on the surface of one side, facing the illumination light source, of the PBS prism; the polarization state of the illumination light entering the PBS prism 102 meets the reflection polarization state of the beam splitter prism 102, and the illumination light is reflected from the beam splitter surface 102 and then is incident on the micro display screen 108 through the second prism 104, the first prism 105, the lens 106 and the lens 107 based on the reversible principle of the light path; the micro display screen 108 emits light in a reflective manner, and emits image light with display information along an imaging light path to enter the stop position 109, wherein after the light is reflected by the micro display screen 108, the polarization state of the light is changed by 90 degrees, and the changed polarization state can penetrate through the polarization splitting film 103 and cannot be reflected.

Fig. 5 is an optical schematic diagram of a near-eye display device comprising a micro projection system adaptive waveguide system according to the present invention. The coupling end of the waveguide system 20 is disposed at the projection plane of the micro projection system 10, so that the image light enters the waveguide system 20 through the coupling end, is totally reflected for multiple times, is finally coupled out by the coupling-out element, and is emitted to the human eye. The waveguide system may be a geometric waveguide, a diffractive waveguide, or other optical system with a pupil expanding feature.

Here, typical data of the micro projection system provided by the above embodiment is given, the angle of view is 40 °, and the optical volume is 13mm × 15mm × 8mm, which is about 1.56cc. Therefore, the miniature projection system is small in size, the thickness of the whole near-eye display device can be reduced, and the near-eye display device can be made into a glasses shape.

Second embodiment

As shown in fig. 6 to fig. 9, the micro projection system provided by the present embodiment includes a micro display screen 316, an LED light source 308, a PBS prism 302, a second PBS prism 312 composed of a second prism and a first prism, a first curved reflector 315, a second curved reflector 309, a uniform illumination collimation system, and other auxiliary lenses. Wherein, the surface where the light-emitting surface of the display screen 316 is located is an image source surface, and the surface where the diaphragm 304 is located is a projection surface; the imaging system consists of a micro display 316, a second PBS prism 312 consisting of a first prism and a second prism, a first curved mirror 315, a PBS prism 302 and lenses 304, 313 and 314; the illumination light path is composed of an illumination light source 308, an illumination relay system, a PBS prism 302, a second PBS prism 312 composed of a second prism and a first prism, a second curved reflector 309 and other lenses 303, 310 and 311; the imaging system and the illumination system share a PBS prism 302 and a second PBS prism 312 comprised of a first prism and a second prism.

Specifically, the micro display screen 316 is a non-self-luminous display screen such as a liquid Crystal on silicon (Li qui Crystal on si i con, LCOS) or a digital micromirror device (Di ial Mi cromirror Devi ce S, DMD). The microdisplay 316 reflects light while changing the polarization of the linearly polarized light.

In this embodiment, the first prism and the second prism are triangular prisms, and a polarization splitting film 319 is provided between the first prism and the second prism, and the film system is characterized by transmitting P-polarized light and reflecting S-polarized light; the first prism and the second prism are glued to form a second PBS prism 312.

As shown in fig. 7, in the PBS prism 312, a triangular prism close to the projection plane 304 is defined as a second prism 312B, a triangular prism far from the projection plane 304 is defined as a first prism 312A, a plane of the first prism 312A facing the micro display 316 is defined as an incident plane S6, a plane of the first prism 312A close to the second prism 312B is defined as a second plane S4, and a plane of the first prism 312A far from the second prism 312B is defined as a third plane S5; the surface of the second prism 312B facing the incident surface S6 is a fourth surface S2. Each surface of the first prism 312A and the second prism 312B is a flat surface.

As shown in fig. 6 and 8, a quarter wave plate 321 is attached to the third surface S5 of the first prism 312A, and a lens 313, a lens 314, and a first curved mirror 315 are provided outside the third surface S5 to correct the aberration of the imaging system.

As shown in fig. 6 and 9, a quarter wave plate 320 is attached to the fourth surface S2 of the second prism 312B, and a lens 311, a lens 312, and a second curved mirror 309 are provided outside the fourth surface S2 to correct the aberration of the illumination system.

In this embodiment, the parameters of the lenses 311, 312 provided outside the third face S5 and the parameters of the lenses 313, 314 provided outside the fourth face S2 are the same. Lens 311 and lens 312 are preferably positive-negative cemented lenses.

In this embodiment, the parameters of the second curved mirror 309 and the first curved mirror 315 are the same, and the first curved mirror 315 and the second curved mirror 309 are separate mirrors. In other embodiments, the parameters of the first curved mirror 315 and the second curved mirror 309 may be different, and the first curved mirror 315 and the second curved mirror 309 may also be implemented by attaching a total reflection film on the surfaces of the lens 314 and the lens 310 farthest from the PBS prism 312.

PBS prism 302 is disposed between second PBS prism 312 and projection surface 304. The PBS prism 302 is provided with a polarization beam splitting surface 318, which may be a coated beam splitting film layer or a film-attached beam splitting film. The film system is characterized by P polarized light transmission and S polarized light reflection.

On the side of the PBS prism 302 facing the projection plane 304, a plano-convex lens 301 is provided, and the plane of the plano-convex lens 301 is attached to the surface of the PBS prism 302.

In this embodiment, the illumination system comprises an illumination source and an illumination dodging collimation system; wherein the illumination source 308 is an LED light source, the illumination dodging system is an optional element, and comprises a TIR lens 307, a dichroic sheet 306 and a micro-lens array 305, the TIR lens 307 is a collimating element, the dichroic sheet 306 is a filtering element, and the micro-lens array 305 is a dodging element.

In the illumination system, a plano-convex lens 303 is further included, a plane of the plano-convex lens 303 is pasted on a surface of the PBS prism 302 facing the illumination light source 308, and a linear polarizer 317 (see fig. 8) is further provided on the surface of the PBS prism 302 facing the illumination light source, thereby converting the illumination light into linearly polarized light.

The present embodiment provides a set of optically relevant parameters according to the system described above. The lens 301 and the lens 303 are glass spherical lenses, and the lens 301 and the lens 303 are glued on the adjacent surface of the same PBS prism 302; the lens 310 and the lens 311 are spherical lenses, the lens 310 and the lens 311 form a positive-negative cemented lens, and the second curved mirror 309 is an aspherical mirror; the lens 313 and the lens 314 are spherical lenses, the lens 313 and the lens 314 form a positive-negative cemented lens, and the first curved reflector 315 is an aspheric reflector; lens 315 is an aspheric mirror; the optical parameters of the lens 313, the lens 314, the lens 310 and the lens 311 are the same, and the optical parameters of the first curved mirror 315 and the second curved mirror 309 are the same. Specific parameters of the optical lens or prism are shown in tables 3 and 4.

TABLE 3 parameters of optical surfaces in a micro-projection system provided in a second embodiment

TABLE 4 optical parameters of aspheric curved mirror 315

In this embodiment, the light path diagram of the illumination system is shown in fig. 8, the illumination light is emitted by an LED light source 308, because the divergence angle of the LED light source is large, the light needs to be collimated by a TIR lens 307, the light passes through a relay system 306 to perform a filtering function, and the light passes through a microlens array 305 to perform a beam splitting and dodging function; after passing through the lens 303, the light enters the prisms 302, 302 and 303, is plane-cemented, and is glued by an intermediate linear polarizer 317, so that the light emitted by the LED can be formed into S-polarized light, and the light is converted into S-polarized light, enters the PBS polarizing film 318, is reflected, exits the PBS prism 302, and enters the second prism 312B; the image light is reflected by the polarization splitting film 319 between the first prism 312A and the second prism 312B; a 1/4 wave plate 320 is attached to the fourth surface S2 of the second prism 312B, S-polarized light of the illumination light passing through the 1/4 wave plate 320 is converted into left-hand polarized light, the illumination light emitted from the PBS prism 312 enters the cemented lens group 311, 310 downward, enters 309 after being reflected by the aspheric mirror, and then enters 310, 311 again, the reflected light is converted into right-hand polarized light, the polarized light passes through the 1/4 wave plate 320 again and then is converted into P-polarized light, and the P-polarized light is incident on the PBS polarizing film 319, and then is transmitted and incident on the LCOS panel 316.

As shown in fig. 9, the optical path diagram of the imaging system is that after the illumination light is reflected by the LCOS 316, the polarization state is converted from P-type polarization into S-type polarization, the image light is reflected by the PBS polarizing film 319, passes through the 1/4 wave plate 321, penetrates through the gluing prism set, passes through the 1/4 wave plate again after being reflected by the aspheric mirror 315, the S-type polarization is converted into P-type polarization, and the image light passes through the two PBS prisms and then exits from the stop position 304.

In summary, according to the micro projection system and the near-eye display device provided by the invention, the imaging light path and the illumination light path share a plurality of elements such as the first prism, the second prism and the PBS prism, so that the illumination light path and the imaging light path are folded for many times, the volume of the projection system is greatly reduced, the miniaturization of the projection system is realized, and the volume of the near-eye display device is finally reduced.

The micro projection system and the near-eye display device provided by the invention are explained in detail above. It will be apparent to those skilled in the art that any obvious modifications thereof can be made without departing from the spirit of the invention, which infringes the patent right of the invention and bears the corresponding legal responsibility.

Claims (10)

1. A miniature projection system for projecting a non-self-luminous image disposed on an image source surface onto a projection surface, comprising:

the first prism comprises an incidence plane close to the image source surface, a second plane close to the projection plane and a third plane far away from the projection plane;

a second prism disposed between the first prism and the projection surface;

a PBS prism disposed between the second prism and the projection surface; a polarization beam splitting surface is arranged in the PBS prism;

the illumination light is linearly polarized light, is emitted into the PBS prism, is reflected by the polarization beam splitting surface, is emitted to the second prism, is transmitted in the second prism and the first prism, is emitted from the incident surface and is emitted to the image source surface;

the image light is configured to be linearly polarized light of which the polarization direction is changed after the illumination light is reflected by the image source surface, enters the first prism through the incident surface, is reflected by the second surface, is reflected by the third surface or other surfaces adjacent to the third surface, penetrates through the second prism and enters the PBS prism, and after penetrating through the polarization light splitting surface, the image light is emitted from the PBS prism and is emitted to the projection surface.

2. The miniature projection system of claim 1, wherein:

the first prism and the second prism are wedge prisms with a gap therebetween.

3. The miniature projection system of claim 2, wherein:

the first prism and the second prism are free-form surface prisms; an incident angle when the image light is emitted from the incident surface to the second surface satisfies a total reflection condition.

4. The miniature projection system of claim 1, wherein:

the first prism and the second prism are triangular prisms, a polarization beam splitting film is arranged between the first prism and the second prism, and the first prism and the second prism are adhered to form another PBS prism.

5. The miniature projection system of claim 4, wherein:

the second surface of the first prism is provided with a 1/4 wave plate; a first curved surface reflector is arranged on the second surface side;

the second prism has a fourth surface opposite to the incident surface; the fourth surface is provided with a 1/4 wave plate; and a second curved surface reflector is arranged on the fourth surface side.

6. The miniature projection system of claim 5, wherein:

a first lens group is arranged between the first curved reflector and the first prism;

and a second lens group is arranged between the second curved reflector and the second prism.

7. The miniature projection system of claim 6, wherein:

the first curved reflector is realized by attaching a total reflection film on the surface of the first lens group far away from the first prism;

the second curved reflector is realized by attaching a total reflection film on the surface of the second lens group far away from the second prism.

8. The miniature projection system of claim 2 or 4, further comprising:

a microdisplay for providing image light to the first prism; the micro display screen reflects light and changes the polarization direction of linearly polarized light;

and the illumination light source is used for providing illumination light for the PBS prism, and a wire polarizer is arranged between the illumination light source and the PBS prism.

9. The miniature projection system of claim 8, wherein:

and an illumination uniform light collimation system is also arranged between the illumination light source and the PBS prism.

10. A near-eye display device comprising a miniature projection system according to any of claims 1-9, further comprising a waveguide system, the coupled-in end of the waveguide system being arranged at the location of the projection surface of the miniature projection system.

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