Holographic waveguide

Abstract

This invention discloses a holographic waveguide comprising: a light guiding unit configured to guide light; a first holographic optical element disposed on one or another surface of the light guiding unit and configured to diffract input light; a second holographic optical element disposed on either the first or the second surface and configured to receive light diffracted by the first holographic optical element and to guide a portion of the received light to the other of the first or the second surface; a third holographic optical element disposed on the surface and configured to receive light diffracted by the second holographic optical element and to guide light; and a fourth holographic optical element configured to receive light diffracted by the third holographic optical element and to allow light to be output from the light guiding unit.

Description

[Technical Field] This invention relates to a holographic waveguide. [Previous Technology] Figure 1 is a schematic view of a typical vehicle head-up display (HUD) system. A typical vehicle head-up display (HUD) system 10 may include: a display 1 that generates and outputs images; and an optical system 2 that guides images toward the vehicle's windshield. The optical system 2 uses multiple mirrors 3 and 4 as shown in Figure 1 to reduce the overall size of the head-up display (HUD) system 10 while ensuring the optical path between the display 1 and the windshield. Although multiple mirrors 3 and 4 are used as described above, the total volume of the head-up display (HUD) system 10 is limited to about 10 liters due to the need to ensure the distance between the display 1 and the multiple mirrors 3 and 4. In this head-up display (HUD) system, it is difficult to form a wide eye motion box (EMB), which is the area where the driver can visually recognize the image through the windshield. Therefore, considering the visual axis of the driver's pupils and the viewing angle of the image, the driver needs to inconveniently and directly adjust the angle between multiple mirrors 3 and 4 to ensure that the image reaches a limited area of ​​the windshield. Furthermore, in prior art, to extend the eye movement box, a first waveguide is used to extend the incident light vertically, and then a second waveguide is used to extend the incident light horizontally; that is, two waveguides are used to extend the incident light both vertically and horizontally. However, using two waveguides presents limitations in terms of structural size reduction. Moreover, the two waveguides need to be precisely configured so that light emitted from the first waveguide is incident at the appropriate position on the second waveguide. Therefore, precision is required in the manufacturing process, leading to increased manufacturing costs and time. The prior art described above is technical information that the inventor already possesses for deriving embodiments of the present invention or technical information obtained during the process of deriving embodiments of the present invention. Before the filing of the application for embodiments of the present invention, it cannot be said that the prior art is publicly known technology disclosed to the general public. [Summary of the Invention] Technical issues The embodiments of the present invention are intended to provide a holographic waveguide applicable to head-up displays. The problems to be solved by this invention are not limited to those described above, and other unmentioned problems will be clearly understood by those skilled in the art from the following description. Technical solutions According to an embodiment of the present invention, a holographic waveguide is provided, comprising: a light guiding unit configured to guide light; a first holographic optical element disposed on one or another surface of the light guiding unit such that light output from a light source is input to and guided on the light guiding unit and configured to diffract the input light; a second holographic optical element disposed on either one of the surfaces of the light guiding unit and configured to receive light diffracted by the first holographic optical element and guided via the light guiding unit, and configured to guide a portion of the received light to the other of the surfaces of the light guiding unit by diffraction; a third holographic optical element disposed on a surface opposite to the surface of the light guiding unit on which the second holographic optical element is disposed, and configured to receive light diffracted by the second holographic optical element and configured to guide the received light to a region on the light guiding unit by diffraction, said region being different from the regions on which the first and second holographic optical elements are disposed; and a fourth holographic optical element configured to receive light diffracted by the third holographic optical element and configured to allow the received light to be output from the light guiding unit by diffraction. In this embodiment, each of the first holographic optical element and the second holographic optical element may include a pattern in which high-refractive-index portions and low-refractive-index portions are alternately arranged along a first direction, and each of the third holographic optical element and the fourth holographic optical element may include a pattern in which high-refractive-index portions and low-refractive-index portions are alternately arranged along a second direction perpendicular to the first direction. In this embodiment, the second holographic optical element can be configured such that the diffraction efficiency of its pattern is increased along the first direction. In this embodiment, the third holographic optical element can be configured such that the diffraction efficiency of its pattern is substantially uniform in the region along the first direction. In this embodiment, the fourth holographic optical element can be configured such that the diffraction efficiency of its pattern is increased along the second direction. In this embodiment, the phase retardation film can be placed between the second holographic optical element and the third holographic optical element. In this embodiment, the phase retardation film can be placed between the light guide unit and the third holographic optical element. Beneficial effects The holographic waveguide according to an embodiment of the present invention can help reduce the size of head-up displays. In addition, holographic waveguides have the advantage of being able to display images while maintaining high brightness.

Implementation Method

Claims

1. A holographic waveguide, comprising: Optical guide unit, configured to guide light; A first holographic optical element is disposed on one or the other surface of the light guide unit such that light emitted from a light source enters the light guide unit and is guided thereon, and is configured to diffract the input light; a second holographic optical element is disposed on either the first or the other surface of the light guide unit, and is configured to receive light diffracted by the first holographic optical element and guided through the light guide unit, and is configured to guide a portion of the received light to the other of the first or the other surface of the light guide unit by diffraction; a third holographic optical element is disposed on a surface opposite to the surface of the light guide unit on which the second holographic optical element is disposed, and is configured to receive light diffracted by the second holographic optical element and is configured to guide the received light to a region on the light guide unit different from the regions on which the first and second holographic optical elements are disposed; A fourth holographic optical element is disposed on either one of the surfaces of the light guide unit and the other surface, configured to receive light diffracted by the third holographic optical element and configured to allow the received light to be output from the light guide unit by diffraction, wherein each of the first and second holographic optical elements comprises a pattern in which high-refractive-index portions and low-refractive-index portions are alternately arranged along a first direction, and each of the third and fourth holographic optical elements comprises a pattern in which high-refractive-index portions and low-refractive-index portions are alternately arranged along a second direction perpendicular to the first direction.

2. The holographic waveguide as claimed in claim 1, wherein the second holographic optical element is configured such that the diffraction efficiency of its pattern is increased along the first direction.

3. The holographic waveguide as claimed in claim 1, wherein the third holographic optical element is configured such that the diffraction efficiency of its pattern is substantially uniform along the first direction within the region.

4. The holographic waveguide as claimed in claim 1, wherein the fourth holographic optical element is configured such that the diffraction efficiency of its pattern is increased along the second direction.

5. The holographic waveguide as claimed in claim 1, wherein a phase retardation film is disposed between the second holographic optical element and the third holographic optical element.

6. The holographic waveguide as claimed in claim 5, wherein the phase retardation film is disposed between the optical guide unit and the third holographic optical element.

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