CN110632760A

CN110632760A - Light beam expansion optical structure

Info

Publication number: CN110632760A
Application number: CN201910934854.XA
Authority: CN
Inventors: 鲍鹏飞
Original assignee: Parallel Reality (hangzhou) Technology Co Ltd
Current assignee: Parallel Reality (hangzhou) Technology Co Ltd
Priority date: 2019-09-29
Filing date: 2019-09-29
Publication date: 2019-12-31

Abstract

The invention discloses a light beam expansion optical structure, which comprises a lens array consisting of a plurality of superposed micro lenses and triangular prisms positioned at two ends of the lens array, wherein each micro lens is of a parallelogram structure, the surfaces of the two parallel micro lenses of each micro lens are respectively plated with a film layer with the reflectivity of 10% -90%, and the optical surfaces of the films plated by each micro lens and the triangular prisms are sequentially superposed and glued to form the optical structure. The light beam expanding optical structure realizes the return of the light path, and increases the effective optical path of the optical system in a limited space, thereby reducing the mechanical length of the whole system.

Description

Light beam expansion optical structure

Technical Field

The invention relates to the field of near-to-eye optics, in particular to a light beam expansion optical structure.

Background

In the design and construction process of the light path, one beam of light is often required to be expanded into an optical structure of multiple beams of parallel light, so that the function of adding the light beam is realized, and the purpose of building the light path or expanding the light path is achieved. The core device for solving the optical problem is a beam splitter, and the optical device is commonly used in an interferometer and is usually composed of a metal film or a dielectric film to realize the semi-reflection function of a light beam. However, a single beam splitter is difficult to expand light into multiple parallel beams, and the loss of the luminous flux after beam splitting is serious, so that the practical application is greatly limited. When the transflective film system is applied to a near-eye optical system, miniaturization and weight reduction of the optical element are required for the near-eye optical system, and therefore, a small optical focal length is required to ensure that the total length of the optical element is within 15mm, but a small focal length causes large aberration. Therefore, an optical structure that can expand the light beam and increase the exit pupil of the optical system is desired.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a light beam expansion optical structure, thereby realizing the function of optical amplification, enlarging the exit pupil of an optical system and having small volume.

The purpose of the invention is realized by the following technical scheme:

a light beam expansion optical structure is characterized by comprising a lens array and triangular prisms, wherein the lens array is composed of a plurality of superposed micro lenses, the triangular prisms are positioned at two ends of the lens array, each micro lens is of a parallelogram structure, the surfaces of the two parallel micro lenses of each micro lens are plated with film layers with reflectivity of 10% -90%, and the optical surfaces of the films plated by each micro lens and the triangular prisms are sequentially superposed and glued to form the optical structure.

Further, the film layer is a semi-transparent semi-reflective film.

Furthermore, the optical structure is formed by superposing a plurality of optical structure units in a plane two-dimensional space, and each optical structure unit comprises a lens array formed by a plurality of superposed micro lenses and triangular prisms positioned at two ends of the lens array, so that the beam expanding range is enlarged.

Furthermore, the optical structure is formed by superposing a plurality of optical structure units in a three-dimensional space, and each optical structure unit comprises a lens array formed by a plurality of superposed micro lenses and triangular prisms positioned at two ends of the lens array, so that the beam expanding range is enlarged.

The invention has the following beneficial effects:

according to the invention, the transmission and reflection of light rays are realized through the film layer on the micro lens, and the overlapping structure of the micro lens is combined, so that the expansion function of light beams is realized, and the exit pupil of the optical system is increased. Larger Eye Box can be obtained by applying the method in a VR system.

The light beam expanding optical structure realizes the return of the light path, and increases the effective optical path of the optical system in a limited space, thereby reducing the mechanical length of the whole system.

Drawings

FIG. 1 is a light path diagram of a single microstructure;

FIG. 2 is a schematic optical path diagram of a beam expanding optical structure of the present invention;

FIG. 3 is a schematic diagram of an optical path of an embodiment of the beam expanding optical structure of the present invention;

FIG. 4 is a schematic optical path diagram of a second embodiment of a beam expanding optical structure according to the present invention;

FIG. 5 is a schematic diagram of a third overall structure of an embodiment of a beam expanding optical structure according to the present invention;

FIG. 6 is a schematic diagram of a portion of a third embodiment of a beam expanding optical structure according to the present invention.

Detailed Description

The present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments, and the objects and effects of the present invention will become more apparent, it being understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

As shown in fig. 1, for a single microstructure, fig. 1 is an incident light beam, 21 is a first microlens surface, 22 is a second microlens surface, 31 is a first partial outgoing light beam, 32 is a second partial outgoing light beam, and 41 is a third partial outgoing light beam. The first microlens surface 21 and the second microlens surface 22 are coated with a film with a certain reflectivity, wherein the reflectivity is 0.5, namely the transmissivity is 0.5, and the film system is characterized by semi-transparency and semi-reflectivity. An incident beam 1 vertically enters the single microstructure, a first part of emergent light 31 is provided after being transmitted by the first micro-lens surface 21, a second part of emergent light 32 is provided after the reflected light is reflected by the second micro-lens surface 22, and two beams of

light beams

31 and 32 which are parallel to each other are obtained through the parallelogram microstructure.

As shown in fig. 2, the optical surfaces of the microstructure in fig. 1 plated with the reflective film are stacked and glued to obtain the optical structure with expanded light beam. To maintain structural integrity, the upper and lower surfaces are glued with triangular prisms, respectively. The structure can realize beam expansion, and the number of expanded beams is related to the number of micro-parallelograms. The optical structure comprises a lens array consisting of a plurality of superposed micro lenses and triangular prisms positioned at two ends of the lens array, each micro lens is of a parallelogram structure, the surfaces of the two parallel micro lenses of each micro lens are coated with film layers with the reflectivity of 10% -90%, and the optical surfaces of the coated micro lenses and the triangular prisms are sequentially superposed and glued to form the optical structure.

Further, in consideration of the light intensity distribution of the outgoing light, the following formula can be derived:

I₁＝I₀·t

I_N＝I₀·(1-t)²·t^N-2 N＝2，3，4，5...

in the formula I₀For incident light intensity, t is the transmittance of the reflective film on the surface of the microstructure, I₁For the intensity of the transmitted light after the incident light passes through the surface of the microstructure, I_NThe incident light is reflected for N times to obtain the light intensity.

Therefore, the light intensity of the expanded light is exponentially attenuated, and the attenuation coefficient is related to the transmissivity t. Greater transmission, undeflected I₁Occupies a large light intensity, resulting in a weak overall light intensity of the deflected light beam. The smaller the transmittance, the more rapidly the luminous intensity attenuates with the increase of the deflected beam, and the beam expansion effect is insignificant. Therefore, a film layer having a reflectance of 50% is selected as a preferable example.

To ensure the beam expansion effect, the embodiment uses a collimated parallel light source.

FIG. 3 is a schematic diagram of an optical path of an embodiment of the beam expanding optical structure of the present invention. In fig. 3, 1 is an incident light beam, 201, 202, 203, 204, 205, 206 are first, second, third, fourth, fifth, sixth microlens surfaces, respectively, 31, 32, 33, 34, 35, 36, 41 are first, second, third, fourth, fifth, sixth, and seventh emergent light beams, respectively. One or more microlens surfaces are arranged between the third microlens surface 203 and the fourth microlens surface 204, and one or more partial emergent lights are arranged between the third partial emergent light 33 and the fourth partial emergent light 34. The surface of each micro lens is plated with a film layer with certain reflectivity, and the reflectivity is 0.5. An incident beam 1 vertically enters the single microstructure, and has a first part of emergent light 31 after being transmitted through the first microlens surface 201, and has a second part of emergent light 32 after being reflected by the second microlens surface 202. And by analogy, first partial emergent light 31, second partial emergent light 32, fourth partial emergent light 33, fifth partial emergent light 34, sixth partial emergent light 35, sixth partial emergent light 36 and seventh partial emergent light 41 are generated respectively, wherein one or more partial emergent light exists between the third partial emergent light 33 and the fourth partial emergent light 34. Thus, a plurality of mutually parallel beams is obtained through the parallelogram-shaped microstructure.

In order to realize the effect of two-dimensional beam expansion, the microstructures can be superposed. FIG. 4 is a schematic diagram of the second optical path of the beam expanding optical structure according to the present invention. In FIG. 4, 1 is the incident light, and 31-36 and 41-43 are the partial emergent light. 20 is a first microstructure, 21 is a second microstructure, and 22 is a third microstructure. Wherein one or more micro-surfaces are provided between the third micro-surface 203 and the fourth micro-surface 204 and one or more micro-structures are provided between the second microstructure 21 and the third microstructure 22. The surface of each micro lens is plated with a film layer with certain reflectivity, and the reflectivity is 0.5. An incident light beam 1 vertically enters the first microstructure 20, and after being transmitted through the first microlens surface 201, a first part of emergent light is transmitted, and finally reaches the microstructure 22 through the second microstructure 21 and the like, and finally is emitted as part of emergent light 31. The reflected light from the first microlens surface 201 is reflected by the second microlens surface 202, then passes through the second microstructure 21, and finally reaches the microstructure 22, and finally exits a part of the emergent light 32. By analogy, partial outgoing light beams 31-36 and 41-43 are generated, respectively. One or more partial outgoing light beams are arranged between the partial outgoing light beam 33 and the partial outgoing light beam 34, and between the partial outgoing light beam 42 and the partial outgoing light beam 43. Thus, the microstructure achieves a two-dimensional beam expanding effect.

To further optimize the second embodiment, fig. 5 is a schematic diagram of a third overall structure of the beam expanding optical structure according to the present invention. The square structure can be divided into four parts according to diagonal lines, and the micro-structures of each part are symmetrically distributed. A schematic structural view of a part of it is shown in fig. 6. When light incident on the center of the square enters the portion of the structure, an expansion is formed along the direction in which the microstructures are superimposed, as shown in example one. Therefore, as long as the incident light enters the central position shown in fig. 5 and enters the four microstructures, a two-dimensional beam expanding effect can be achieved. This structure reduces the mechanical length in the optical axis direction, compared to the second embodiment.

The array formed by the micro lenses can be superposed in multiple dimensions, so that the beam expanding range is enlarged. The overlay scheme includes, but is not limited to, the above embodiments.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and although the invention has been described in detail with reference to the foregoing examples, it will be apparent to those skilled in the art that various changes in the form and details of the embodiments may be made and equivalents may be substituted for elements thereof. All modifications, equivalents and the like which come within the spirit and principle of the invention are intended to be included within the scope of the invention.

Claims

1. A light beam expansion optical structure is characterized by comprising a lens array and triangular prisms, wherein the lens array is composed of a plurality of superposed micro lenses, the triangular prisms are positioned at two ends of the lens array, each micro lens is of a parallelogram structure, the surfaces of the two parallel micro lenses of each micro lens are plated with film layers with reflectivity of 10% -90%, and the optical surfaces of the films plated by each micro lens and the triangular prisms are sequentially superposed and glued to form the optical structure.

2. The beam expanding optical structure of claim 1, wherein said film layer is a transflective film or the like.

3. The structure of claim 1 or 2, wherein the optical structure is a superposition of a plurality of optical structure units in a planar two-dimensional space, each optical structure unit comprises a lens array formed by a plurality of superposed microlenses and triangular prisms located at two ends of the lens array, so as to increase the beam expanding range.

4. A beam expanding optical structure according to claim 1 or 3, wherein the optical structure is a stack of a plurality of optical structure units in three-dimensional space, each optical structure unit comprises a lens array formed by a plurality of stacked microlenses and triangular prisms located at two ends of the lens array, thereby increasing the beam expanding range.