WO2023234505A1

WO2023234505A1 - Projection-type augmented reality optical device miniaturized through polarization adjustment

Info

Publication number: WO2023234505A1
Application number: PCT/KR2022/020184
Authority: WO
Inventors: 염지운; 최광순; 손예슬
Original assignee: 한국전자기술연구원
Priority date: 2022-05-31
Filing date: 2022-12-13
Publication date: 2023-12-07
Also published as: KR20230166468A

Abstract

A projection-type augmented reality optical device miniaturized through polarization adjustment is provided. The augmented reality device according to an embodiment of the present invention comprises a projector that generates and projects an image, an optical path folding portion that folds an optical path for the image projected by the projector, through polarization adjustment, a scattering layer that scatters an image emitted from the optical path folding portion, and an image combiner that combines the image scattered by the scattering layer, with external light incident from the real world. Accordingly, an augmented reality image may be provided to a general user with a compact device, thereby eliminating the user discomfort and implementing an ergonomic design.

Description

Projection-type augmented reality optical device miniaturized through polarization adjustment

The present invention relates to augmented reality technology, and more specifically, to a projection-type augmented reality optical device that provides an augmented reality image while worn by a person.

Augmented reality optical devices using laser projection can expand the viewing area by using a scattering layer such as a separate diffuser for the projected virtual image to secure a sufficient eye box.

However, in order for the projected image to be correctly focused on the scattering layer and to secure a sufficient image size, a sufficient separation distance between the projection system and the scattering layer must be secured, which has the limitation of making the entire optical system very long.

This dilutes the advantages of laser projection-based optical devices that enable compact structures, so it is necessary to develop technology that can reduce the overall optical path while securing the viewing area.

The present invention was devised to solve the above problems, and the purpose of the present invention is to increase the allowable area where images can be observed in the pupil direct-projection augmented reality device by expanding the beam width of the light beam bundle, while maintaining the entire optical path. The aim is to provide a projection-type augmented reality optical device that reduces system size and reduces system size.

An augmented reality device according to an embodiment of the present invention for achieving the above object includes a projector that generates and projects an image; an optical path folding unit that folds the optical path for the image projected from the projector through polarization adjustment; A scattering layer that scatters the image emitted from the optical path folding unit; It includes an image combiner that combines the image scattered from the scattering layer with external light incident from the real world.

And the scattering layer can transmit the image projected from the projector and transmit it to the optical path folding unit, and scatter the image emitted from the optical path folding unit and reflect it to the image combiner.

The scattering layer may be an element that transmits the image in the first polarization state projected from the projector and scatters and reflects the image changed to the second polarization state by the optical path folding unit.

The optical path folding unit transmits the image in the first polarization state transmitted from the scattering layer, converts it into an image in the third polarization state, and transmits it to the polarization mirror, and transmits the image in the fourth polarization state transmitted from the polarization mirror to the image in the second polarization state. A converter that converts the polarization state and transmits it to the scattering layer; and a polarization mirror that reflects the image in the third polarization state transmitted from the converter to the converter and converts it into an image in the fourth polarization state.

The distance between the projector and the scattering layer may be shorter than the distance between the projector and the scattering layer when the augmented reality device does not have an optical path folding unit.

The scattering layer may have a planar shape. The scattering layer may have an approximate free-form shape by connecting each point where the parallel light bundle emitted from the eye position passes through the image combiner and comes into focus with a curved line.

A method of providing augmented reality according to another embodiment of the present invention includes the steps of generating and projecting an image by a projector; A step of folding, by an optical path folding unit, an optical path for an image projected from a projector through polarization adjustment; A scattering layer scattering the image emitted from the optical path folding unit; The image combiner includes a step of combining the image scattered from the scattering layer with external light incident from the real world.

As described above, according to embodiments of the present invention, the entire optical path can be folded by adding only film-type optical element layers without a separate complex and thick composite optical element, making it a compact device for general users. Augmented reality images can be provided, eliminating user discomfort and implementing an ergonomic design.

1 is a structural diagram of a projection-type augmented reality optical device to which the present invention is applicable;

Figure 2 is a structural diagram of a projection-type augmented reality optical device according to an embodiment of the present invention;

Figure 3 is a diagram showing the change in polarization state by each element, and

Figure 4 is a diagram illustrating a polarization selective scattering layer of a free-form surface.

Hereinafter, the present invention will be described in more detail with reference to the drawings.

A holographic lens is a transparent and thin optical element produced by recording the interference pattern of two light waves (reference beam and signal beam) coming from different directions on a recording medium (e.g. photopolymer, photorefractive polymer, silver halide, etc.). Even in film form, it has the advantage of being able to replace the function of a specific optical device.

The interference pattern recorded within the device forms a periodically repeating volume grating within the holographic recording medium, and when the incident beam at the later reproduction stage satisfies the Bragg condition of the volume grating, It has the advantage of forming a thin and light optical element by performing the function of outputting a reproduction beam through a diffraction phenomenon.

As shown in FIG. 1, the augmented reality device using a holographic element and laser projection diffracts the image light bundle emitted from the projection system 10 at an image combiner (30) located in front of the user's eyes to position the image at the user's pupil. It consists of an optical structure that provides

This technology has the advantage of being able to provide a high-transparency-based image without a complicated optical structure, but in order to secure a sufficient eye-box, the laser projected image is diffused per pixel by scattering it in the scattering layer 20. You must be able to secure a sufficient angle.

In order to ensure sufficient image size and correct focus for the laser projected image on the scattering layer 20, a projection distance of several tens of mm is typically required on the back of the scattering layer 20.

The image light projected from the laser projector 10 must satisfy the minimum projection distance (d) required to secure a sufficient image size before being scattered in the scattering layer 20.

Therefore, the total length of the entire system requires a value greater than or equal to the additional projection distance (d) in addition to the space between the scattering layer (20) and the image combiner (30). This has the side effect of making the projection portion of the entire augmented reality optical device very long, which is a major problem in implementing an augmented reality device with a compact design.

Accordingly, an embodiment of the present invention presents a method of miniaturizing a projection-type augmented reality optical device through polarization adjustment. In other words, a miniaturized augmented reality optical device is implemented by increasing the overall optical path through polarization adjustment.

Figure 2 is a diagram showing the structure of a projection-type augmented reality optical device according to an embodiment of the present invention. In the projection-type augmented reality optical device according to an embodiment of the present invention, a polarization-based optical path folding optical layer is added, and the scattering layer is replaced with an optical element capable of selectively responding to polarization.

For this purpose, the projection-type augmented reality optical device according to an embodiment of the present invention includes a laser projector 110, a polarization selective scattering layer 120, a quarter wave retarder (QWR) 130, and a polarization selective mirror 140, as shown in FIG. 2. ) and an image combiner 150.

The polarization selective scattering layer 120, QWR 130, and polarization selective mirror 140 reduce the physical size of the entire augmented reality optical device system while satisfying the length of the optical path, enabling simplification of the system. .

The laser projector 110 generates and projects a virtual image that will constitute augmented reality. Unlike the existing laser projector 10 shown in FIG. 1, the laser projector 110 is disposed close to the rear of the polarization selective scattering layer 120 without a sufficient separation distance.

That is, the separation distance between the laser projector 110 and the polarization selective scattering layer 120 is the distance between the projector 10 and the scattering layer 20 of the augmented reality device that uses the general scattering layer 20 and does not have the

configurations

130 and 140 for optical path folding. ) can be implemented shorter than the separation distance between them.

The polarization selective scattering layer 120 transmits the image light projected from the laser projector 110 and transmits it to the optical

path folding units

130 and 140, and scatters the image light emitted from the optical

path folding units

130 and 140 to produce an image. It reflects toward the coupler 150.

The image combiner 150 is a holographic lens designed to combine image light reflected from the polarization selective scattering layer 120 and external light incident from the real world and project the image directly into the user's pupil.

The optical

path folding units

130 and 140 are configured to fold the optical path for the image light projected from the laser projector 110.

To this end, the QWR (130) transmits the image light transmitted from the polarization-selective scattering layer 120 to the polarization-selective mirror 140, and transmits the image light reflected from the polarization-selective mirror 140 to the polarization-selective scattering layer. Forward to (120).

The polarization-selective mirror 140 reflects the image light transmitted through the QWR 130 and makes it re-incident into the polarization-selective scattering layer 130.

The optical path of the image light emitted from the laser projector 110 is configured as follows.

Laser projector (110) → Polarization selective scattering layer (120) → QWR (130) → Polarization selective mirror (140) → QWR (130) → Polarization selective scattering layer (120) → Image combiner (150)

In order to configure the optical path as above, the polarization selective scattering layer 120 is composed of an element capable of inducing a polarization selective scattering reaction. As shown in FIG. 3, the polarization selective scattering layer 120 transmits the vertical linear polarization state 210, which is the polarization state of the image light emitted from the laser projector 110, without separate scattering. On the other hand, the image light in the vertical linear polarization state 210 and the optically independent (orthogonal) horizontal linear polarization state 220 transmitted through the QWR 130 is scattered without transmission.

The QWR (130) is a conversion element that converts the linearly polarized state and the circularly polarized state into each other. Therefore, as shown in FIG. 3, the QWR 130 transmits the image light in the vertical linear polarization state 210 passing through the polarization selective scattering layer 120 and converts it to the right circular polarization state 310, and uses a polarization selective mirror ( The image light in the left circular polarization state 320 reflected from 140) is transmitted and converted to the horizontal linear polarization state 220.

Polarization selective mirror 140 converts the circularly polarized state. Specifically, as shown in FIG. 3, the polarization selective mirror 140 reflects image light in a right-handed circularly polarized state 310 that passes through the QWR 130 and converts it into a left-handed circularly polarized state 320.

Accordingly, the image light in the vertical linear polarization state 210 emitted from the laser projector 110 is converted to the right-circular polarization state 310 by the QWR 130 after passing through the polarization selective scattering layer 120, and is converted to the polarization selective scattering layer 120. It is converted to the left circular polarization state 320 in the mirror 140, and converted to the horizontal linear polarization state 220 in the QWR 130, then scattered in the polarization selective scattering layer 120 and reflected to the image combiner 150.

Meanwhile, the polarization state of each device shown in FIG. 3 is merely an example. Of course, as long as the vertical/horizontal linear polarization state and the right/left circular polarization state are mutually orthogonal, a structure with the same function can be created by applying a different polarization pair as shown.

On the other hand, the light source of the laser projector 110 usually emits linearly polarized light due to a gain medium for lasing. Therefore, the laser projector 110 has the advantage that it can be applied even without separate polarization filtering in optical path folding using polarization, and the light loss due to polarization adjustment and passing through a linear polarizer is very small, so the advantage can be maximized. You can.

If the light source of the laser projector 110 has un-polarized characteristics, it is required to install a separate polarization filtering element on the front of the laser projector 110.

On the other hand, since the polarization selective scattering layer 120 has flexibility in a film-like form and has few restrictions on the shape of the implementation, the polarization selective scattering layer 120 is used to reduce aberrations of the image combiner 150, that is, the holographic lens. It is possible to manufacture and laminate in the form of a free curved surface rather than a simple flat surface.

Figure 4 shows such an example, and the aberration problem (a problem in which the focusing position of each pixel is not arranged linearly) occurring in the holographic lens 150 can be solved by introducing the scattering layer 125 in the form of a free-form surface. The free-form shape of the scattering layer 125 can be obtained by approximating each point where the parallel light bundle emitted from the eye position passes through the image combiner 150 and comes into focus with a curved line.

So far, a projection-type augmented reality optical device miniaturized through polarization adjustment has been described in detail with preferred embodiments.

In the above embodiment, a laser projection and scattering layer are provided for a wearable imaging device that uses a divergent holographic optical element as an image combiner, but a miniaturized image is provided by applying separate polarization adjustment and polarization-based optical path folding technology. The device was presented.

As a result, the entire optical path can be folded by adding only film-type optical element layers without the need for a separate complex and thick composite optical element, thereby eliminating user discomfort by providing images to general users with a compact device. , it is possible to implement an augmented reality device with an ergonomic design.

In addition, although preferred embodiments of the present invention have been shown and described above, the present invention is not limited to the specific embodiments described above, and can be used in the technical field to which the invention pertains without departing from the gist of the present invention as claimed in the claims. Of course, various modifications can be made by those skilled in the art, and these modifications should not be understood individually from the technical idea or perspective of the present invention.

Claims

A projector that generates and projects images;

an optical path folding unit that folds the optical path for the image projected from the projector through polarization adjustment;

A scattering layer that scatters the image emitted from the optical path folding unit;

An augmented reality device comprising an image combiner that combines the image scattered from the scattering layer with external light incident from the real world.
In claim 1,

The scattering layer is

The image projected from the projector is transmitted to the optical path folding unit,

An augmented reality device characterized by scattering the image emitted from the optical path folding unit and reflecting it to the image combiner.
In claim 2,

The scattering layer is

An augmented reality device characterized by an element that transmits the image in the first polarization state projected from the projector and scatters and reflects the image changed to the second polarization state by the optical path folding unit.
In claim 3,

The optical path folding part,

The image in the first polarization state transmitted from the scattering layer is transmitted and converted into an image in the third polarization state and transmitted to the polarization mirror, and the image in the fourth polarization state transmitted from the polarization mirror is transmitted and converted to the second polarization state. A transducer delivering to the scattering layer; and

An augmented reality device comprising a polarization mirror that reflects the image in the third polarization state transmitted from the converter to the converter and converts it into an image in the fourth polarization state.
In claim 1,

The distance between the projector and the scattering layer is,

An augmented reality device characterized in that the distance between the projector and the scattering layer is shorter than the distance between the projector and the scattering layer when the augmented reality device does not have an optical path folding part.
In claim 1,

The scattering layer is

An augmented reality device characterized in that it has a flat form.
In claim 1,

The scattering layer is

An augmented reality device characterized in that a bundle of parallel light emitted from the eyeball passes through an image combiner and connects each point of focus with a curved line, forming a nice free-form shape.
A projector generating and projecting an image;

A step of folding, by an optical path folding unit, an optical path for an image projected from a projector through polarization adjustment;

A scattering layer scattering the image emitted from the optical path folding unit;

A method for providing augmented reality comprising: an image combiner combining images scattered from a scattering layer and external light incident from the real world.