CN117192790A - Achromatic vortex superlens and optical waveguide optical module for realizing edge enhancement imaging - Google Patents
Achromatic vortex superlens and optical waveguide optical module for realizing edge enhancement imaging Download PDFInfo
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Abstract
The invention provides an achromatic vortex super lens for realizing edge enhancement imaging and an optical waveguide optical module, and relates to the technical field of optical lenses; the basic array comprises a plurality of nano-pillars with the same height; any nano-pillar meets the unique dispersion phase requirement, and the phase regulation quantity at the center of the circular substrate is smaller than that at the edge of the circular substrate; the image light rays are changed into vortex light beams after being emitted from the achromatic vortex super lens; the vortex beam can highlight edges of the image where the gray values of adjacent areas differ by more than a first preset value. The invention realizes focusing and achromatizing functions by utilizing the vortex superlens, so that human eyes receive more realistic scenes; meanwhile, the edge enhancement can be carried out on the image, so that the identification of different object types and the delineation of the distribution range are facilitated; and the display device can display the actual scene more clearly, improve the transmittance of the optical waveguide and enable the transmittance to reach more than 90%.
Description
Technical Field
The invention relates to the technical field of optical lenses, in particular to an achromatic vortex superlens for realizing edge enhancement imaging and an optical waveguide optical module.
Background
In recent years, with development of micro-displays, advanced optics and hardware and software technologies, AR (Augmented Reality )/VR (Virtual Reality) display products have also been better applied:
AR is a technique that combines computer-generated virtual information with real-world scenes. By using AR technology, a user can see virtual elements in real scenes, for example, AR applications in fields of games, advertising, education, medical treatment, etc. AR technology typically requires the use of cameras and displays, etc. to present virtual information.
VR is a technique that creates a virtual environment through computer simulation, allowing users to feel that they are sitting in. VR technology typically requires the use of head mounted displays, handles, and the like, as well as specialized virtual reality software to present the virtual environment. VR technology has applications in gaming, education, military, medical, etc.
AR/VR display products are highly dependent on the quality of the optical waveguide optical module, which projects visual information to a location very close to the human eye covering the user's full angular field of view, however, this proximity to the human eye also amplifies display defects that are often undetectable by the user when viewing at a distance. These subtle display anomalies include: the image has blurred edges, low transmittance, large chromatic aberration and the like.
Disclosure of Invention
The invention provides an achromatic vortex super lens for realizing edge enhancement imaging and an optical waveguide optical module, which are used for solving the technical problems of blurred image edges, low transmittance and large chromatic aberration in the prior art.
The invention provides an achromatic vortex superlens for realizing edge enhancement imaging, comprising: a circular base and a base array; the circular substrate comprises a first side and a second side, and the basic array is arranged on the second side of the circular substrate; the basic array comprises a plurality of nano-pillars; the heights of all the nano columns are the same; any nano-pillar meets the unique dispersion phase requirement, and the phase regulation quantity at the center of the circular substrate is smaller than that at the edge of the circular substrate; the image light rays are emitted from the first side of the circular substrate and then become vortex light beams; the vortex beam can highlight the edges of the adjacent areas in the image, wherein the gray value difference of the edges is larger than a first preset value;
wherein the electric field strength E (ω) of the achromatic vortex superlens is expressed as:
；
wherein,the number of annular zones of the achromatic vortex super lens is represented; />Representing the first calculated from the achromatic vortex superlens centeriRadius displacement of the respective endless belts; />Representing the first calculated from the achromatic vortex superlens centeri-1 radial displacement of the annulus; />Representing the operating frequency; />Representing the amplitude of the scattered electric field; />Represent the firstiA basic focal phase profile of the respective zones;erepresenting a phase distribution; />Represent the firstiThe electric field strength of the individual zones; />Representing the radial displacement calculated from the achromatic vortex superlens center, +.>Indicating the operating wavelength;
lens equation for achromatic vortex superlensExpressed as:
；
the method comprises the steps of carrying out a first treatment on the surface of the Wherein,representing a basic focus phase profile; />Representing the dispersive phase at which achromatism is achieved; />Representing the radial displacement calculated from the achromatic vortex superlens center; />Indicating the operating wavelength +.>Representing the maximum wavelength among the operating wavelengths; />Representing the focal length of the achromatic vortex superlens; />Representing the deflection angle; />Indicating vortex phase offset;
；the method comprises the steps of carrying out a first treatment on the surface of the Wherein (1)>Representing a horizontal displacement calculated from the achromatic vortex superlens center; />Representing the vertical displacement calculated from the achromatic vortex superlens center; />Indicating the vortex phase offset.
According to the achromatic vortex super lens for realizing edge enhancement imaging, the distances between the centers of adjacent nano-columns are equal.
According to the achromatic vortex super lens for realizing edge enhancement imaging, the height of the nano column is 50nm to 1000nm; the maximum length of the cross section graph of the nano column is in the range of 10nm to 200nm; the maximum width of the cross section pattern of the nano-pillars is in the range of 10nm to 200nm.
According to the achromatic vortex super lens for realizing edge enhancement imaging, the cross section pattern of the nano column is one of a circle, an ellipse, a triangle, a quadrangle and a hexagon.
The present invention also provides an optical waveguide optical module comprising: the image light source, the first circular polarizer, the second circular polarizer, the diffraction optical waveguide and the achromatic vortex super lens for realizing edge enhancement imaging; the diffraction optical waveguide comprises a coupling-in grating, a slab waveguide and a coupling-out grating; the image light source is used for providing image light carrying image information; after passing through the first circular polarizer, the achromatic vortex super lens and the second circular polarizer in sequence, the image light is coupled into the slab waveguide from the coupling-in grating, and the coupling-out grating is used for coupling out the image light conducted in the slab waveguide.
According to the optical waveguide optical module provided by the invention, the first circular polarizer is a left-handed circular polarizer, and the second circular polarizer is a right-handed circular polarizer; alternatively, the first circular polarizer is a right-handed circular polarizer, and the second circular polarizer is a left-handed circular polarizer.
According to the optical waveguide optical module provided by the invention, the first circular polarizer is a left-handed circular polarizer, and the first circular polarizer comprises a first linear polarizer and a first quarter wave plate; the second circular polarizer is a right-handed circular polarizer, and comprises a second linear polarizer and a second quarter-wave plate; the image light passes through the first linear polarizer, the first quarter wave plate, the achromatic vortex super lens, the second quarter wave plate and the second linear polarizer in sequence.
According to the optical waveguide optical module provided by the invention, the coupling-in grating and the coupling-out grating are decoupling super-structured surface gratings.
The invention provides an achromatic vortex super lens for realizing edge enhancement imaging and an optical waveguide optical module, wherein the achromatic vortex super lens for realizing edge enhancement imaging comprises a circular substrate and a basic array; the circular substrate comprises a first side and a second side, and the basic array is arranged on the second side of the circular substrate; the basic array comprises a plurality of nano-pillars; the heights of all the nano columns are the same; any nano-pillar meets the unique dispersion phase requirement, and the phase regulation quantity at the center of the circular substrate is smaller than that at the edge of the circular substrate; the image light rays are emitted from the first side of the circular substrate and become vortex light beams after being emitted from the second side of the circular substrate; the vortex beam is a beam with annular light intensity distribution, determined orbital angular momentum and spiral wave front structure; the beam center of the vortex beam has a phase singular point in the transmission process, so that the vortex beam can highlight edges of adjacent areas in the image, wherein the gray values of the edges differ by more than a first preset value. Through the mode, the vortex super lens is used for realizing focusing and achromatizing functions, so that human eyes can receive more real scenes; meanwhile, the edge enhancement can be carried out on the image, the definition of the image is improved, and the identification of different object types and the delineation of the distribution range of the object types are facilitated; the image after edge enhancement can display the real scene more clearly, and the transmittance of the optical waveguide is improved, so that the transmittance reaches more than 90%.
Drawings
In order to more clearly illustrate the invention or the technical solutions of the prior art, the following description will briefly explain the drawings used in the embodiments or the description of the prior art, and it is obvious that the drawings in the following description are some embodiments of the invention, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of one embodiment of an achromatic vortex superlens implementing edge-enhanced imaging according to the present invention;
FIG. 2 is a schematic side view of one embodiment of an achromatic vortex superlens implementing edge-enhanced imaging according to the present invention;
FIG. 3 is a schematic top view of one embodiment of the distribution of nanopillars in an achromatic vortex superlens of the present invention;
FIG. 4 is an analytical schematic of an edge enhanced contrast embodiment of the achromatic vortex superlens of the present invention;
FIG. 5 is a schematic illustration of the effect of an edge enhanced contrast embodiment of the achromatic vortex superlens of the present invention;
FIG. 6 is a schematic diagram of an embodiment of an optical waveguide module according to the present invention;
fig. 7 is a schematic structural diagram of another embodiment of the optical waveguide module of the present invention.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings, and it is apparent that the described embodiments are some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Referring to fig. 1-2, fig. 1 is a schematic structural diagram of an embodiment of an achromatic vortex super lens for implementing edge enhanced imaging according to the present invention, and fig. 2 is a schematic side view of an embodiment of an achromatic vortex super lens for implementing edge enhanced imaging according to the present invention.
In this embodiment, an achromatic vortex superlens that implements edge-enhanced imaging includes a circular base 210 and a base array 220.
The circular substrate 210 includes a first side and a second side, and the base array 220 is disposed on the second side of the circular substrate 210; the base array 220 includes a plurality of nano-pillars therein; the heights of all the nanopillars are the same. The number of nano-pillars in the base array 220 may be determined according to practical situations, and is not limited herein.
Any one of the nanopillars meets the unique dispersion phase requirement, with the amount of phase modulation at the center of the circular substrate being less than the amount of phase modulation at the edges of the circular substrate.
Common achromatic superlenses typically compensate for chromatic dispersion by locally engineered superatomic waveguide modes (or resonance modes) to achieve broadband achromatic superlenses. However, the diameter size of such achromatic superlenses is tens of microns because of the limited group delay that can be achieved with superatoms, limiting their practical application. The traditional optical lens has chromatic aberration, and imaging performance is limited. Chromatic aberration of refractive lenses results from the intrinsic dispersion of the material, which can result in longer wavelengths being focused at longer focal lengths. In comparison, diffractive lenses (e.g., fresnel lenses) have more than 10 times the focusing properties of dispersive lenses. Such severe chromaticity is mainly due to phase discontinuity at the region boundaries. For shorter wavelengths, it results in a longer focal length. The shape factor and chromatic aberration of conventional optical lenses are difficult to reduce simultaneously.
Therefore, in this embodiment, the annular band structure of the fresnel lens is used on the achromatic vortex super lens, and the chromatic dispersion is compensated by using the inverse relation between the focal length and the wavelength, so that a general design principle is proposed to realize the achromatic vortex super lens with large area and multiple wavelengths. By using the design principles of the above formulas, an achromatic vortex superlens for edge enhanced imaging is provided.
In particular, the electric field strength of an achromatic vortex superlensE（ω) Expressed as:
；
wherein,the number of annular zones of the achromatic vortex super lens is represented; />Representing the first calculated from the achromatic vortex superlens centeriRadius displacement of the respective endless belts; />Representing the first calculated from the achromatic vortex superlens centeri-1 radial displacement of the annulus; />Representing the operating frequency; />Representing the amplitude of the scattered electric field; />Represent the firstiA basic focal phase profile of the respective zones;erepresenting a phase distribution; />Represent the firstiThe electric field strength of the individual zones; />Representing the radial displacement calculated from the achromatic vortex superlens center, +.>Indicating the operating wavelength.
Wherein,represent the firsti-1 annulus and the firstiThe juncture of the endless belts is discontinuous; electric field at focal spotE（ω) By interference of electric fields in the respective zones>And interference of the electric fields of N different zones +.>And (5) determining.
The achromatism principle in this embodiment belongs to the achromatism of the diffraction element, i.e. the fresnel zone form. The achromatic vortex superlens in this embodiment needs to have each nano-pillar on the lens achieve a phase correspondence, namely: each nanopillar requires a unique dispersion relationship.
The center of the achromatic vortex superlens is the center of the circular base. As can be appreciated, the amount of phase modulation is small at the center of the achromatic vortex superlens; and the phase adjustment amount is larger at the edge of the achromatic vortex superlens. It should be noted that, when the center zone of the fresnel element is wider at the center of the achromatic vortex superlens, the difficulty of multi-wavelength matching is still acceptable, and each wavelength can realize phase adjustment, but when the structure is extended outwards, the zone width gradually narrows as the zone is extended outwards, so that the phase transformation speed is also increased, finally, the multi-wavelength matching is difficult, and the structural profile of each wavelength is difficult to realize when the phase adjustment point is matched. Therefore, the radius value range of the achromatic vortex superlens is less than or equal to 3mm, and preferably, the radius value range of the achromatic vortex superlens is 2 mm-2.5 mm.
Chromatic dispersion is a dependence of focal length on optical wavelength, and in imaging systems, chromatic dispersion can lead to degradation of image quality, and superlenses are diffraction lenses which can be considered to have only one diffraction order, and in this embodiment, achromatic vortex superlenses are combined with a nanopillar dispersive phase design so that each place of the achromatic vortex superlens satisfies phase dispersion (phase as a function of wavelength).
When the light source is applied, image light rays are emitted from the first side of the circular substrate, and the image light rays are emitted from the second side of the circular substrate and then become vortex light beams; compared to a light beam after passing through a normal lens, a vortex light beam has an orbital angular momentum in addition to a spin angular momentum. I.e. a vortex beam is a beam having a circular intensity distribution, defining an orbital angular momentum and a helical wavefront structure.
In the transmission process, the beam center of the vortex beam has a phase singular point, the light intensity at the singular point is zero, and the vortex beam has no heating effect and no diffraction effect; the vortex beam can highlight edges of the image where the gray values of adjacent areas differ by more than a first preset value. Wherein the gray value may be represented as a luminance value or a hue.
The highlighting may be performed by enhancing the display of the edge region of the object in the image and/or by weakening the display of the center region of the object in the image.
Therefore, the vortex light beam can highlight and emphasize the edge with larger difference of brightness value (or tone) of the adjacent area (or pixel) of the image (or image) (namely, the boundary line of the image tone mutation or ground feature type), and the image after the edge enhancement can more clearly display the boundary of different object types or phenomena or the trace of the linear image so as to facilitate the identification of different object types and the delineation of the distribution range thereof; the image after the edge enhancement can more clearly display the actual scene, and the transmittance of the optical waveguide is improved, so that the transmittance reaches more than 90%.
The circular substrate 210 and the underlying array 220 are all dielectric materials, such as gallium nitride, silicon dioxide, and the like. The materials of the circular base 210 and the base array 220 may or may not be the same.
The dimension parameters of the nanopillars include nanopillar height and nanopillar cross-sectional dimensions. The dimension parameter of the nano column is designed according to the phase requirement of the achromatic vortex super lens corresponding to the position of the nano column. In this embodiment, the heights of all the nanopillars are the same. The size of the cross section of the nanopillar at different positions in the achromatic vortex superlens may be different, i.e. different sizes of nanopillar are included in the chromatic vortex superlens.
Alternatively, the cross-sectional pattern of the nano-pillars is one of a circle, an ellipse, a triangle, a quadrangle, and a hexagon, and one skilled in the art can select a suitable nano-pillar pattern according to the specific situation. Preferably, the cross-sectional pattern of the nanopillars may be square in view of the difficulty of the process manufacturing.
Optionally, the height of the nano-pillars is in the range of 50nm to 1000nm; the maximum length of the cross section graph of the nano column is in the range of 10nm to 200nm; the maximum width of the cross section pattern of the nano-pillars is in the range of 10nm to 200nm.
As shown in fig. 2, three sizes of nano-pillars are included in the base array 220, namely, a first nano-pillar 221, a second nano-pillar 222, and a third nano-pillar 223. Wherein the height h1 of the first nano-pillars, the height h2 of the second nano-pillars and the height h3 of the third nano-pillars are equal, i.e. h1=h2=h3. The width w1 of the first nano-pillars, the width w2 of the second nano-pillars and the width w3 of the third nano-pillars are not equal, i.e. w1+.w2+.w3.
In some embodiments, to exclude the phase influence of the nano-pillar arrangement period on the chromatic aberration-eliminating vortex superlens, the distances between the centers of adjacent nano-pillars may be set to be equal. With continued reference to fig. 2, the distance between two adjacent first nano-pillars 221 is d1, the distance between two adjacent first nano-pillars 221 and second nano-pillars 222 is d2, and the distance between two adjacent second nano-pillars 222 and third nano-pillars 223 is d3, i.e., d1=d2=d3.
To better illustrate the period of distribution of nanopillars and the dimensional parameters of nanopillars in an achromatic vortex superlens, reference is made to fig. 3, which is a schematic top view of an embodiment of nanopillar distribution in an achromatic vortex superlens of the present invention. The cross-sectional dimensions of the nanopillars and the distribution period can be seen from fig. 3.
In this embodiment, three sizes of nanopillars are included, and the cross sections of the three sizes of nanopillars are three squares with unequal side lengths. The nano-pillars are divided into a first nano-pillar, a second nano-pillar and a third nano-pillar according to the size of the side length.
Wherein A1, A2 are the centers of two first nano-pillars, B1, B2 are the centers of two second nano-pillars, and C1, C2 are the centers of two third nano-pillars. L1 is a distance between the first nanopillar center A1 and the first nanopillar center A2, L2 is a distance between the first nanopillar center A1 and the second nanopillar center B1, L3 is a distance between the second nanopillar center B1 and the second nanopillar center B2, L4 is a distance between the second nanopillar center B2 and the third nanopillar center C1, and L5 is a distance between the third nanopillar center C1 and the third nanopillar center C2.
In this embodiment, the distances between centers of all adjacent nanopillars are equal, i.e., l1=l2=l3=l4=l5. The dimensions of the nanopillar cross-section do not affect the distance between the centers of adjacent nanopillars.
Note that, adjacent nanopillars in this embodiment refer to being adjacent in the horizontal direction and being adjacent in the vertical direction.
Such a vortex superlens can operate efficiently for monochromatic focusing or imaging. Determining the focal length of the vortex superlens can calculate the corresponding phase profile. When the vortex superlens is operated at other wavelengths, its focal length will refer to this variation as a chromatic aberration effect. To operate in multiple or continuous wavelengths, one of the effective methods of solving the problem uses chromatic aberration integrated resonant elements (IRUs) in the continuous bandwidth to obtain the phase, in particular, the lens equation of an achromatic vortex superlensExpressed as:
；
；
wherein,representing a basic focus phase profile; />Representing the dispersive phase at which achromatism is achieved;representing the radial displacement calculated from the achromatic vortex superlens center; />Indicating the operating wavelength +.>Representing the maximum wavelength among the operating wavelengths; />Representing the focal length of the achromatic vortex superlens; />Representing the deflection angle; />Indicating the vortex phase offset.
The lens equationThe method can be used for designing the nano column phases at different positions in the achromatic vortex super lens. Lens equation>Is divided into two parts, and the designed working frequency band is->Comprises->To->. To achieve achromatism @>Representing the basic focus phase profile, and +.>Correlation; IRU can provide different phase compensation for various wavelengths, and the method is realized through PB phase design>Is provided.
In some embodiments, the basic focus phase profileCan be expressed as:
；
；
wherein,representing a horizontal displacement calculated from the achromatic vortex superlens center; />Representing the vertical displacement calculated from the achromatic vortex superlens center; />Indicating the vortex phase offset. />Representing the topological charge number of the vortex beam.
Referring to fig. 4-5, fig. 4 is an analytical schematic of an embodiment of the invention for edge enhancement contrast of an achromatic superlens, and fig. 5 is an effect schematic of an embodiment of the invention for edge enhancement contrast of an achromatic superlens.
The broken line as shown in fig. 4 is data of the achromatic vortex superlens of the present embodiment, and the solid line is data of a normal lens. It can be seen that the light image passing through the common lens has three peaks, and the analysis is performed by the pixel positions 280-340, and the common lens only includes one peak corresponding to the region, which represents that the display of the center of the object in the light image is enhanced; in the achromatic vortex superlens of the embodiment, one wave crest is divided into two small wave crests, the middle of the wave crest is sunken, the display representing the center of an object is weakened, and the display of the edge of the object is strengthened, so that the achromatic vortex superlens can realize the effect of edge enhancement.
As shown in fig. 5, the optical image includes a solid object "89", and after the optical image is processed by the achromatic superlens, the optical image becomes a hollow object "89", the display effect in the center thereof is reduced, and the display effect in the edge thereof is enhanced.
The achromatic vortex super lens for realizing edge enhancement imaging comprises a circular substrate and a basic array; the circular substrate comprises a first side and a second side, and the basic array is arranged on the second side of the circular substrate; the basic array comprises a plurality of nano-pillars; the heights of all the nano columns are the same; any nano-pillar meets the unique dispersion phase requirement, and the phase regulation quantity at the center of the circular substrate is smaller than that at the edge of the circular substrate; the image light rays are emitted from the first side of the circular substrate and become vortex light beams after being emitted from the second side of the circular substrate; the vortex beam is a beam with annular light intensity distribution, determined orbital angular momentum and spiral wave front structure; the beam center of the vortex beam has a phase singular point in the transmission process; the vortex beam can highlight edges of the image where the gray values of adjacent areas differ by more than a first preset value. By means of the mode, the vortex super-lens is used for achieving focusing and achromatizing functions, and therefore human eyes can receive more actual scenes; meanwhile, the edge enhancement can be carried out on the image, the definition of the image is improved, and the identification of different object types and the delineation of the distribution range of the object types are facilitated; the image after edge enhancement can display the real scene more clearly, and the transmittance of the optical waveguide is improved, so that the transmittance reaches more than 90%.
On the other hand, the invention also provides an optical waveguide optical module. Referring to fig. 6, fig. 6 is a schematic structural diagram of an optical waveguide module according to an embodiment of the present invention, in which the optical waveguide module includes an image light source 610, a first circular polarizer 620, a second circular polarizer 630, a diffraction optical waveguide, and the above-mentioned achromatic vortex super lens 650 for implementing edge-enhanced imaging.
Since the optical waveguide optical module of the present embodiment includes the above-described achromatic vortex superlens for realizing edge-enhanced imaging, the optical waveguide optical module of the present embodiment has technical effects similar to those of the achromatic vortex superlens for realizing edge-enhanced imaging in the above-described embodiment. And the optical waveguide optical module can realize independent projection of two polarization multiplexing stereoscopic images through modulating circularly polarized light.
Specifically, the diffractive optical waveguide includes an in-coupling grating 641, a slab waveguide 642, and an out-coupling grating 643; the image light source 610 is used for providing image light carrying image information; after the image light passes through the first circular polarizer 620, the achromatic vortex superlens 650 and the second circular polarizer 630 in sequence, the image light is coupled into the slab waveguide 642 from the coupling-in grating 641, and the coupling-out grating 643 is used for coupling out the image light conducted in the slab waveguide 642.
The optical waveguide optical module may be an AR optical module or a VR optical module.
The image light source may be an image source based on DLP (Digital Light Processing ) technology, among others. The DLP technology is to process the binary digits of the image signal and then project the light, so that the provided light can carry specific image information.
In some embodiments, the image information may include color information, and thus the colors of the image light may include green, blue, and red. Specifically, light emitted by an image light source is filtered into one of three colors of red, green and blue through a rotating color wheel, then an image with a certain color is formed through reflection of a unique DMD chip, and finally a plurality of pictures with different time and different colors are overlapped together, so that a color picture is formed by utilizing the persistence effect of human eyes.
A slab waveguide refers to a waveguide having a slab structure that guides waves in only one direction. Alternatively, transparent dielectric layers with high refractive index can be prepared on some substrates or embedded in two underlayers. For example, a thin neodymium-doped YAG layer may be fabricated on an undoped YAG layer having a lower refractive index, resulting in a slab waveguide.
The coupling-out grating couples out diffracted light from the coupling-in grating and conducted in total reflection within the slab waveguide to human eye imaging while extending the exit pupil in both directions.
Optionally, the in-coupling grating and the out-coupling grating are both decoupled super-structured surface gratings. The decoupling super-structured surface grating can lead the phase of the image light rays to be suddenly changed when the image light rays are reflected or transmitted on the surface of the image light rays, has surface effect, the phase of the image light rays is unevenly distributed, and the image light rays are guided to a direction of oblique emergence when the phase of the image light rays is changed along with the gradient change of a certain direction.
The decoupling super-structured surface grating can efficiently couple and press image light onto the slab waveguide, and reconstruct the wavefront of the image light. The decoupling super-structured surface grating can realize the focusing function of a common lens on one hand, generate parallel light, generate vortex rotation on the other hand, and further realize edge enhancement.
Alternatively, the first circular polarizer may be a left-handed circular polarizer and the second circular polarizer may be a right-handed circular polarizer.
Alternatively, the first circular polarizer may be a right-handed circular polarizer, and the second circular polarizer may be a left-handed circular polarizer.
In some embodiments, the first circular polarizer is a left-handed circular polarizer, and the first circular polarizer comprises a first linear polarizer and a first quarter-wave plate; the second circular polarizer is a right-handed circular polarizer, and comprises a second linear polarizer and a second quarter-wave plate; the image light passes through the first linear polarizer, the first quarter wave plate, the achromatic vortex super lens, the second quarter wave plate and the second linear polarizer in sequence.
Referring to fig. 7, fig. 7 is a schematic structural diagram of another embodiment of an optical waveguide module according to the present invention. As shown in fig. 7, the optical waveguide optical module includes an image light source 710, a first circular polarizer 720, a second circular polarizer 730, a diffractive optical waveguide, and an achromatic vortex superlens 750 described above that implements edge-enhanced imaging.
Specifically, the diffractive optical waveguide includes an in-coupling grating 741, a slab waveguide 742, and an out-coupling grating 743; the first circular polarizer 720 includes a first linear polarizer 721 and a first quarter-wave plate 722, and the first linear polarizer 721 and the first quarter-wave plate 722 are integrated as a left-handed circular polarizer.
The second circular polarizer 730 includes a second linear polarizer 731 and a second quarter-wave plate 732, and the second linear polarizer 731 and the second quarter-wave plate 732 are integrated as a right-handed circular polarizer.
The red, green and blue three-color image light provided by the image light source sequentially passes through the first linear polarizer 721, the first quarter wave plate 722, the achromatic vortex super lens 750, the second quarter wave plate 732 and the second linear polarizer 731, and then enters the slab waveguide 742 through the coupling-in grating 741, and the image light conducted by total reflection in the slab waveguide 742 is emitted after passing through the coupling-out grating 743.
With continued reference to FIG. 7, the distance between the coupling-out grating 743 and the eye box 760 is the exit pupil distance L, and the size of the Field of view (FOV) determines the Field of view of the optical waveguide optical module.
In summary, the achromatic vortex superlens and the optical waveguide optical module for realizing edge enhanced imaging of the embodiment comprise a circular substrate and a basic array; the circular substrate comprises a first side and a second side, and the basic array is arranged on the second side of the circular substrate; the basic array comprises a plurality of nano-pillars; the heights of all the nano columns are the same; any nano-pillar meets the unique dispersion phase requirement, and the phase regulation quantity at the center of the circular substrate is smaller than that at the edge of the circular substrate; the image light rays are emitted from the first side of the circular substrate and become vortex light beams after being emitted from the second side of the circular substrate; the vortex beam is a beam with annular light intensity distribution, determined orbital angular momentum and spiral wave front structure; the beam center of the vortex beam has a phase singular point in the transmission process; the vortex beam can highlight edges of the image where the gray values of adjacent areas differ by more than a first preset value. By means of the mode, the vortex super-lens is used for achieving focusing and achromatizing functions, and therefore human eyes can receive more actual scenes; meanwhile, the edge enhancement can be carried out on the image, the definition of the image is improved, and the identification of different object types and the delineation of the distribution range of the object types are facilitated; the image after edge enhancement can display the real scene more clearly, and the transmittance of the optical waveguide is improved, so that the transmittance reaches more than 90%.
From the above description of the embodiments, it will be apparent to those skilled in the art that the embodiments may be implemented by means of software plus necessary general hardware platforms, or of course may be implemented by means of hardware. Based on this understanding, the foregoing technical solution may be embodied essentially or in a part contributing to the prior art in the form of a software product, which may be stored in a computer readable storage medium, such as ROM/RAM, a magnetic disk, an optical disk, etc., including several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute the method described in the respective embodiments or some parts of the embodiments.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims (8)
1. An achromatic vortex superlens for edge enhanced imaging, comprising: a circular base and a base array; the circular substrate includes a first side and a second side, the base array being disposed on the second side of the circular substrate; the basic array comprises a plurality of nano-pillars; the heights of all the nano columns are the same; any nano column meets the unique dispersion phase requirement; the amount of phase modulation at the center of the circular base is less than the amount of phase modulation at the edges of the circular base;
the image light is emitted from the second side of the circular substrate and then becomes a vortex light beam; the vortex light beam can highlight and emphasize edges of adjacent areas in the image, wherein the gray value difference of the edges is larger than a first preset value;
electric field strength of the achromatic vortex superlensExpressed as:
；
wherein,representing the number of zones of the achromatic vortex superlens; />Representing the first calculated from the achromatic vortex superlens centeriRadius displacement of the respective endless belts; />Representing the first calculated from the achromatic vortex superlens centeri-1 radial displacement of the annulus; />Representing the operating frequency; />Representing the amplitude of the scattered electric field; />Represent the firstiA basic focal phase profile of the respective zones;erepresenting a phase distribution; />Represent the firstiThe electric field strength of the individual zones; />Representing the radial displacement calculated from the achromatic vortex superlens center, +.>Indicating the operating wavelength;
lens equation for the achromatic vortex superlensExpressed as:
；
；
wherein,representing a basic focus phase profile; />Representing the dispersive phase at which achromatism is achieved;representing the maximum wavelength among the operating wavelengths; />Representing a focal length of the achromatic vortex superlens; />Representing the deflection angle;indicating vortex phase offset;
；
；
wherein,representing a calculated horizontal displacement from the achromatic vortex superlens center; />Representing a vertical displacement calculated from the achromatic vortex superlens center; />Indicating the vortex phase offset.
2. The achromatic vortex superlens for edge-enhanced imaging according to claim 1, wherein the distances between centers of adjacent nanopillars are equal.
3. The achromatic vortex superlens for edge-enhanced imaging according to claim 1, wherein the height of the nanopillars is in the range of 50nm to 1000nm; the maximum length of the cross section graph of the nano column is in the range of 10nm to 200nm; the maximum width of the cross section pattern of the nano column is in the range of 10nm to 200nm.
4. The achromatic vortex superlens for edge-enhanced imaging according to claim 1, wherein the cross-sectional pattern of the nanopillars is one of circular, elliptical, triangular, quadrilateral, and hexagonal.
5. An optical waveguide module, comprising: an image light source, a first circular polarizer, a second circular polarizer, a diffractive optical waveguide, and an achromatic vortex super lens implementing edge-enhanced imaging as recited in any of claims 1-4; the diffraction optical waveguide comprises a coupling-in grating, a slab waveguide and a coupling-out grating;
the image light source is used for providing image light carrying image information; after passing through the first circular polarizer, the achromatic vortex super lens and the second circular polarizer in sequence, the image light is coupled into the slab waveguide from the coupling-in grating, and the coupling-out grating is used for coupling out the image light conducted in the slab waveguide.
6. The optical waveguide module according to claim 5, wherein,
the first circular polarizer is a left-handed circular polarizer, and the second circular polarizer is a right-handed circular polarizer; or, the first circular polarizer is a right-handed circular polarizer, and the second circular polarizer is a left-handed circular polarizer.
7. The optical waveguide module according to claim 6, wherein,
the first circular polarizer is a left-handed circular polarizer, and comprises a first linear polarizer and a first quarter-wave plate; the second circular polarizer is a right-handed circular polarizer, and comprises a second linear polarizer and a second quarter-wave plate;
the image light passes through the first linear polarizer, the first quarter wave plate, the achromatic vortex superlens, the second quarter wave plate and the second linear polarizer in sequence.
8. The optical waveguide module according to any one of claims 5 to 7, wherein,
the coupling-in grating and the coupling-out grating are decoupling super-structured surface gratings.
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