CN113189683B

CN113189683B - Geometric phase lens

Info

Publication number: CN113189683B
Application number: CN202110394762.4A
Authority: CN
Inventors: 李晓春
Original assignee: Changsha Lubang Photonics Technology Co ltd
Current assignee: Changsha Lubang Photonics Technology Co ltd
Priority date: 2021-04-13
Filing date: 2021-04-13
Publication date: 2023-03-31
Anticipated expiration: 2041-04-13
Also published as: CN113189683A

Abstract

The invention relates to the technical field of optics, and discloses a geometric phase lens which is used for forming a plurality of focuses based on incident beams with any specific wavelength at the same time. The geometric phase lens disclosed by the invention is used for carrying out geometric phase modulation on incident light based on polarization state change by respectively controlling the change of the long axis direction of the birefringent material corresponding to each ring taking an optical axis as a circle center so as to realize light beam diffraction and deflection; wherein at least one ring borders a first region adjoining the inside with a second region adjoining the outside; the first area and the second area are both equal to a convex lens which converges non-zero same-order diffracted beams with a real focus, and the focal length of the first area and the focal length of the second area are distributed at different positions of the optical axis.

Description

Geometric phase lens

Technical Field

The invention relates to the technical field of optics, in particular to a geometric phase lens.

Background

The lens can be widely applied to various fields such as security, vehicles, digital cameras, lasers, optical instruments and the like, and along with the continuous development of the market, the lens technology is more and more widely applied.

The conventional lens is a refractor manufactured according to the law of refraction of light, and is an optical element which is made of transparent substances (such as glass, crystal and the like) and has a part of a spherical surface, and includes a plastic lens and a glass lens. The refracting surface is a transparent body consisting of two spherical parts or a spherical part and a plane. For example:

convex lens: the middle is thick, the edge is thin, and the structure is double convex, plano-convex and concave-convex; concave lens: the middle is thin, the edge is thick, and the three types of the concave-convex, the plano-concave and the convex-concave are provided.

In some of the new lenses, liquid crystals or liquid crystal polymers are used in part. For example, CN1367398a discloses a continuous zooming fresnel lens, and CN1702487a discloses a method for manufacturing an electrically controlled zooming optical imaging system. Such lenses all achieve zooming by applying different voltages at different times; but cannot form multiple focal points at the same time based on an incident beam of any particular wavelength; from the conventional wisdom, it goes against the wisdom of those skilled in the art that forming multiple focal points at the same time based on an incident beam of any particular wavelength with a single lens is more difficult.

However, in application scenarios such as laser cutting, the cutting surface formed by the single focus often easily causes the final curved surface structure with an arc-shaped section, which may cause a gap in the assembly process of the cut object, thereby affecting the overall performance of the cut object, such as the cutting and assembly accuracy.

Disclosure of Invention

The invention aims to disclose a geometric phase lens which can form a plurality of focuses based on incident beams with any specific wavelength at the same time.

In order to achieve the purpose, the invention discloses a geometric phase lens, which is used for carrying out geometric phase modulation based on polarization state change on incident light by respectively controlling the change of the long axis direction of a birefringent material corresponding to each ring taking an optical axis as a circle center so as to realize light beam diffraction and deflection;

wherein at least one ring borders a first region adjoining the inside with a second region adjoining the outside; the first area and the second area are equal to a convex lens, the real focus of the convex lens converges non-zero diffracted light beams of the same order, and the focal length of the first area and the focal length of the second area are distributed at different positions of the optical axis.

Optionally, in the present invention, in the first region, with the optical axis as a center of a circle, along a radial direction, a long axis direction of the birefringent material between adjacent rings continuously and periodically changes, with a change from 0 to 180 degrees in the long axis direction as a change period, and a change rate is in positive correlation with a radius, so that a diffraction angle corresponding to a same diffraction order of each ring increases with an increase in the ring radius; similarly, in the second region, the optical axis is taken as the center of a circle, the long axis direction of the birefringent material between adjacent rings continuously and periodically changes along the radial direction, the long axis direction changes from 0 to 180 degrees as a change period, and the change rate is in positive correlation with the radius, so that the diffraction angle corresponding to the same diffraction order of each ring increases along with the increase of the ring radius; wherein a rate of change in a long axis direction in the first region is different from a rate of change in a long axis direction corresponding to the second region.

Preferably, the first and second regions diverge corresponding opposite-order diffracted beams based on a virtual focus when converging non-zero same-order diffracted beams.

Optionally, when the +1 diffraction order beam diverges based on the virtual focus, the-1 diffraction order beam converges based on the real focus; or when the-1 diffraction order beam diverges based on the virtual focus, the +1 diffraction order beam converges based on the real focus.

Preferably, the geometric phase lens is in a flat plate structure.

Preferably, the geometric phase lens is further configured to: the incident left-handed circularly polarized light is deflected into emergent right-handed circularly polarized light, and/or the incident right-handed circularly polarized light is deflected into emergent left-handed circularly polarized light, and/or the incident unpolarized natural light is diffracted into left-handed circularly polarized light and right-handed circularly polarized light with opposite diffraction angles.

The invention has the following beneficial effects:

1. breaking from the conventional wisdom, a geometric phase lens is disclosed that is capable of forming multiple focal points at the same time based on an incident beam of any particular wavelength (which typically has a spot size equal to the cross-section of the geometric phase lens).

2. When the geometric phase lens based on the invention is applied to the light path of laser cutting, the light energy can be distributed in different longitudinal depths through multiple intersection points (for example, at least three real focuses which are uniformly distributed on the optical axis), so that a smoother cutting surface can be formed and the cutting efficiency can be improved.

The present invention will be described in further detail below with reference to the accompanying drawings.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:

fig. 1 is a partial structural schematic diagram of a geometric phase lens according to a preferred embodiment of the present invention.

Detailed Description

The embodiments of the invention will be described in detail below with reference to the drawings, but the invention can be implemented in many different ways as defined and covered by the claims.

Example 1

The present embodiment discloses a geometric phase lens, which performs geometric phase modulation based on polarization state change on incident light by respectively controlling the change of the long axis direction of a birefringent material corresponding to each ring with an optical axis as the center of a circle, so as to implement light beam diffraction and deflection. Wherein at least one ring borders a first region adjoining the inside with a second region adjoining the outside; the first area and the second area are both equal to a convex lens which converges non-zero same-order diffracted beams with a real focus, and the focal length of the first area and the focal length of the second area are distributed at different positions of the optical axis.

As shown in fig. 1, the geometric phase lens includes two concentric demarcation rings, a demarcation ring 1 demarcates a zone a from a zone B, and a demarcation ring 2 demarcates a zone B from a zone C. It is worth mentioning that: the ring is preferably a virtual ring which carries out different orientations on liquid crystal molecules based on a micro-nano structure; as a degradation realization, the skilled person can also splice the regions by gluing or other means after the regions are individually manufactured during the manufacturing process.

In this embodiment, in the first region, the optical axis is used as a center of a circle, the long axis direction of the birefringent material between adjacent rings continuously and periodically changes along the radial direction, the long axis direction changes from 0 to 180 degrees as a change period, and the change rate and the radius are positively correlated, so that the diffraction angle corresponding to the same diffraction order of each ring increases with the increase of the ring radius; in the second region, the optical axis is taken as the circle center, the long axis direction of the birefringent material between adjacent rings continuously and periodically changes along the radius direction, the long axis direction changes from 0 to 180 degrees as a change period, and the change rate is in positive correlation with the radius, so that the diffraction angle corresponding to the same diffraction order of each ring increases along with the increase of the radius of the ring; wherein a rate of change in a long axis direction in the first region is different from a rate of change in a long axis direction corresponding to the second region.

In this embodiment, assuming that the long axis direction angle is a, the radius is r, and the fast axis direction change rate is: da/dr.

Corresponding to fig. 1, there are several virtual rings for orientation according to the molecular arrangement gradient rule in the areas A, B and part C; and the main difference between the regions is that the rate of change in the direction of the long axis is different.

It is worth mentioning that: the "ring" described in the present embodiment does not represent the geometric phase lens in an actual product, but is necessarily a symmetrical ring structure, and is merely a description of the evolution rule of the internal structure of the geometric phase lens along the radius direction. In the actual product delivery or the operation processes of grinding or other processing treatment and the like for adapting the lens frame, the change of the external shape can be flexibly changed into other structural forms such as square, oval and the like. Similarly, the geometric phase lens may be provided with a corresponding substrate for easy assembly, and the shape of the combination is preferably a flat plate structure, or other special structures which do not change the light path but are aesthetic; such modifications, which are readily imaginable to those skilled in the art, are not intended to limit the scope of the invention.

In this embodiment, when the first region and the second region converge the non-zero diffracted light beams of the same order, the corresponding diffracted light beams of the opposite order diverge based on the virtual focus. For example: each region A, B and C, when converging on +1 order diffracted beams, typically also diverges-1 order diffracted beams. So that the geometric phase lens of the embodiment is equivalent to the conventional lens in terms of optical performance of virtual focus and real focus. However, compared with the conventional lens, the geometric phase lens of the embodiment can be thinner and thinner, has higher light transmittance and more precisely matches with the requirements of users.

In micro-nano optics, based on the existence of many relevant definitions (including the definition of positive and negative diffracted beams) of non-uniform standards, the skilled person can easily think: when the +1 diffraction order beam diverges based on the virtual focus, the-1 diffraction order beam converges based on the real focus; or when the-1 diffraction order beam diverges based on the virtual focus, the +1 diffraction order beam converges based on the real focus.

Preferably, the geometric phase lens of the present embodiment is further configured to:

deflecting the incident left circularly polarized light into emergent right circularly polarized light;

deflecting the incident right-handed circularly polarized light into emergent left-handed circularly polarized light;

incident unpolarized natural light is diffracted into left-handed circularly polarized light and right-handed circularly polarized light with opposite diffraction angles. Wherein, the left-handed circularly polarized light and the right-handed circularly polarized light respectively correspond to positive and negative diffraction orders; for example: when the +1 st order diffracted beam is left circularly polarized light based on virtual focus divergence, then the-1 st order diffracted beam is right circularly polarized light based on real focus convergence. The distribution of the real focal point and the virtual focal point is similar to that of the traditional lens, and the distances between the two sides of the lens are equal.

It should be noted that the above-mentioned different deflections of the light beam according to the polarization states are generally functions that the flat lens has at the same time, and therefore, depending on the usage scenarios, the functions presented by the flat lens may be any one of the functions, or any two of the functions, or both of them.

Based on the functions, the geometric phase lens of the embodiment can be widely applied to the light path of laser cutting. Preferably, at least three real focal points uniformly distributed on the optical axis form a cutting surface. Therefore, the light energy can be distributed in different longitudinal depths, so that a smoother cutting surface can be formed and the cutting efficiency can be improved.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A geometric phase lens, through controlling the major axis direction change of birefringent material that every ring corresponds to with optical axis as centre of a circle separately, in order to carry on the geometric phase modulation based on change of polarization state to the incident light, realize the light beam diffraction and deflect;

wherein at least one ring borders a first region adjoining the inside with a second region adjoining the outside; the first area and the second area are both equal to a convex lens and converge non-zero same-order diffracted light beams through a real focus, and the real focus of the first area and the real focus of the second area are positioned on the same side of the geometric phase lens and distributed at different positions of the optical axis;

in the first region, the optical axis is taken as the center of a circle, the long axis direction of the birefringent material between adjacent rings continuously and periodically changes along the radius direction, the long axis direction changes from 0 to 180 degrees as a change period, and the change rate is in positive correlation with the radius, so that the diffraction angle corresponding to the same diffraction order of each ring increases along with the increase of the radius of the ring;

in the second region, the optical axis is taken as the center of a circle, the long axis direction of the birefringent material between adjacent rings is continuously and periodically changed along the radius direction, the long axis direction is changed from 0 to 180 degrees as a change period, and the change rate is in positive correlation with the radius, so that the diffraction angle corresponding to the same diffraction order of each ring is increased along with the increase of the radius of the ring;

the change rate of the long axis direction in the first area is different from the change rate of the long axis direction corresponding to the second area, so that the focal length corresponding to the first area is not equal to the focal length corresponding to the second area.

2. The geometric phase lens of claim 1, wherein the first and second regions diverge corresponding opposite order diffracted beams based on a virtual focus when converging non-zero same order diffracted beams.

3. The geometric phase lens of claim 2, wherein when the +1 diffraction order beam diverges based on the virtual focus, the-1 diffraction order beam converges based on the real focus; or

When the-1 diffraction order beam diverges based on the virtual focus, the +1 diffraction order beam converges based on the real focus.

4. The geometric phase lens of claim 1, wherein the geometric phase lens is a flat plate structure.

5. The geometric phase lens of any of claims 1 to 4, further configured to: the method comprises the steps of deflecting incident left circularly polarized light into emergent right circularly polarized light, and/or deflecting the incident right circularly polarized light into emergent left circularly polarized light, and/or diffracting incident unpolarized natural light into left circularly polarized light and right circularly polarized light with opposite diffraction angles.

6. The geometric phase lens according to any of claims 1 to 4, wherein the geometric phase lens is applied in the optical path of laser cutting.

7. The geometric phase lens of claim 6, wherein at least three real focal points evenly distributed on the optical axis form a cut surface.

8. The geometric phase lens of claim 7, wherein the geometric phase lens is applied in the optical path of laser cutting.

9. A geometric phase lens according to claim 5, wherein at least three real focal points evenly distributed on the optical axis form a cut surface.